Open access peer-reviewed chapter

Graphene Oxide-Based Nanohybrids as Pesticide Biosensors: Latest Developments

Written By

Navin Kumar Mogha

Submitted: March 27th, 2020 Reviewed: August 3rd, 2020 Published: August 26th, 2020

DOI: 10.5772/intechopen.93538

Chapter metrics overview

781 Chapter Downloads

View Full Metrics

Abstract

Graphene is the most significant two-dimensional nanomaterial with sp2 hybridized carbon atoms in a honeycomb arrangement with an extremely high surface area, excellent electrical properties, high mechanical strength, and advantageous optical properties and is relatively easy to functionalize and mass produce. Various inorganic nanoparticles incorporated with graphene, such as gold, silver, and palladium nanoparticles are brought into sharp focus due to their catalytic, optical, electronic, and quantized charging/discharging properties. Graphene oxide-based nanohybrids are particularly well suited for biosensing applications and catalysis. Consequently, this area of research has grown to represent one of the largest classes within the scope of materials science and is rapidly becoming a key area in nanoscience and nanotechnology offering significant potential in the development of advanced materials in multiple and diverse applications. Here in this present chapter, synthesis, characterization of graphene oxide, and their nanohybrids are discussed thoroughly with their application in the field of pesticide biosensors. This chapter will help in a further understanding of graphene-based nanohybrids as a biosensing platform for their future applications in a sustainable environment.

Keywords

  • graphene oxide
  • pesticides
  • biosensors
  • nanohybrids
  • nanoparticles
  • chemical reduction

1. Introduction

The prevalence of harmful and toxic chemical compounds in the environment has become a serious issue in recent decades [1]. Contamination of foodstuffs, drinking water, and air with hazardous pollutants and other foreign substances are real and a direct threat to human health, whereas the accumulation of such contaminants in the human body and environment may lead to long-lasting, severe, and harmful effects after primary exposure [2]. Chemicals such as pesticides, plastic, lead, methylmercury, polychlorinated biphenyls, arsenic, toluene, rubber, and paper [3] play a key role in the economic growth of countries to fulfill their development objectives [4]. The term “pesticide” is defined as any chemical entity, which has the ability to kill the various kinds of pests including rodents, insects, fungi, weeds, etc. and henceforth categorized accordingly as rodenticides, insecticides, fungicides, and herbicides [5]. However, based on chemical composition, pesticides can be classified into five main groups as organochlorines, organophosphorus (OP), carbamates, pyrethrin, and pyrethroids compound. The unnecessary consumption of those agrochemicals has undesirable effects on the ecosystem, including a decreased population of beneficial insects as well as risks to vulnerable species and bird habitats. Pesticide pollution is becoming one of the most severe challenges of common public health around the globe because of their particular application in the agriculture sector to assure crop yield and productivity [6]. In some cases, acute poisoning may occur because of inappropriate handling that ultimately causes adverse health effects because of long-term and low-level exposures. The widespread diffusion of such toxic chemicals adversely affects a great part of the population. A large number of people, categorized by different patterns, ages, and degrees of exposure, are at increased risk to the adverse effects of these chemicals. Workers who are involved in the manufacturing and application of pesticides are at a considerable risk of exposure, which typically occurs among specific users in public health. In the agricultural sector, farmers may get direct exposure to pesticides during spraying across the agricultural fields [7, 8]. In the general population, individuals may be at a risk of pesticide exposure on a daily basis in food and drinking water or to pesticide drift in domestic areas adjacent to spraying areas [9]. Given their hazardous effect on human health and the environment, the prime concern should be of their rapid and reliable detection by a convenient method. Although various laboratory-based analytical methods such as colorimetry, capillary electrophoresis (CE), thin-layer chromatography (TLC), gas-liquid chromatography(GLC), high-performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), and enzyme-linked immunosorbent assays (ELISA) have been employed so far, but these suffer from one and the other drawback such as the use of expensive instrumentation, time-consuming process, and requirement of trained personnel [5]. Therefore, there is a dire need to develop sensitive, rapid, economically feasible, and easy-to-use methods for the detection of these compounds in the environment. Such efficient detection methods could be developed using biosensors that are used in a variety of applications for prompt and accurate detection of different analytes such as biomolecules and chemical compounds [10]. Various nanomaterials are generally categorized into nanoparticles, nanotubes, and nanocomposites, which can be generally employed for the diagnosis, degradation, and adsorption of chemical pesticides. Carbon nanomaterials or nanoparticles (NPs) have specific characteristics, including a high surface-to-volume ratio, good electrical conductivity, catalytic action, and beneficial biocompatibility and can be simply modified with functional groups, which has made them be often used in pesticide biosensors to boost analytical efficiency [11].

It is well known that graphite and diamond are its most common allotropic form of carbon found in nature. Graphite, which is found as a natural mineral, consists of sp2 hybridized carbon atomic layers that are stacked collectively through weak attraction forces such as van der Waals forces. Single-layer out of these carbon atomic layers are packed in a two-dimensional honeycomb structure called as “graphene” termed coined by Boehm et al. [12]. It remains almost impossible to isolate graphene monolayer for several decades before Geim and Novoselov [13] who reported a scotch tape method or micromechanical cleavage method for the isolation of graphene monolayer from silicon oxide substrate. Discovery of graphene monolayer awarded Geim and Novoselov the Nobel Prize in Physics “for groundbreaking experiments regarding the two-dimensional material graphene”.

Graphene, which consists of a one-atom-thick planar sheet comprising an sp2-bonded carbon structure with exceptionally high crystal and electronic quality, is a novel material that has emerged as a rapidly rising star in the field of material science [14, 15].

Research-based on graphene oxide (GO) and graphene is an established interdisciplinary field associated with different disciplines such as physics, chemistry, material sciences, and nanotechnology with still a lot of emerging ideas to be developed. The result of working experience on other carbon allotropes leads to rapid discoveries of exceptional electronic, optical, and mechanical properties of graphene. In particular, its extraordinary charge carrier mobilities, thermal, and electrical conductivity, collective with high transparency and mechanical strength make graphene a suitable material for biosensing applications.

These exceptional physicochemical properties indicate its potential for delivering new tactics and critical developments in electrochemical sciences. For instance, a large number of analytic molecules can be attached to the large surface of electrically conductive graphene sheets leading to the development of the highly sensitive miniaturized device. Direct electron transfer between graphene and redox species creates new prospects for sensing applications. Consequently, graphene has lately fascinated the attention of the scientific community worldwide.

1.1 Graphene and graphene oxide

GO is considered as a precursor for obtaining graphene via chemical or thermal reduction methods. It consists of single-layer graphite oxide, having various oxygen-containing groups, whose structure has been proposed through several models over the years [16, 17, 18, 19, 20]. Oxygen functional groups have been identified as typically in the form of hydroxyl, epoxy groups and carboxy, carbonyl, phenol, lactone, quinone on the basal plane, and at the sheet edges, respectively [21, 22, 23]. However, due to ambiguity pertaining to the nature and distribution of the oxygen-containing functional groups (Figure 1) [24, 25], its nonstoichiometric atomic composition, and the absence of adequately sensitive analytical techniques for GO characterization, its precise structure cannot be fully elucidated. The difference between GO and pristine graphene is as a result oxygenated groups present in GO which affect its electronic, mechanical, and electrochemical properties. Hence, they account for the differences between GO and pristine graphene [26]. The covalent oxygenated functional groups in GO give rise to remarkable structure defects, which are associated with some loss in its electrical conductivity [27], limiting the direct application of GO in electrically active materials and devices. In contrast, these functional groups can also be proved advantageous for exploiting GO in numerous other applications. The presence of polar oxygen-containing moieties gives GO a hydrophilic character making it dispersible in many solvents particularly in water [24, 28, 29]. Subsequent stable GO suspension can be used for preparing thin conducting films using spin coating, drop-casting, or spraying methods [23] for further to be used as electrodes.

Figure 1.

A schematic illustration of methods for the preparation of graphene, GO, and rGO by means of mechanical cleavage, exfoliation, CVD, and reduction methods including chemical, thermal, and electrochemical methods from graphite. Reprinted with permission from Ref. [25], Published by Elsevier.

Furthermore, well-known chemistry strategies can be used for the functionalization of GO using oxygen-containing groups as a site for chemical modification, which subsequently can be exploited for immobilization of various electroactive species via covalent or noncovalent bonds different application in sensing or catalysis. Thus, the physicochemical properties of GO can be tuned very easily by engineering its chemical composition [21, 30, 31].

Hydroxyl, epoxy, and carboxyl groups present in GO are covalently bonded to the carbon atom with sp3 hybridization are termed as oxidized region, disrupting the extended sp2 conjugated network of honeycomb lattice in graphene, which can be viewed as an unoxidized region [32, 33]. sp3 hybridized carbon clusters with oxygen-containing groups are uniformly but randomly distributed either above or below the GO plane [34]. Various microscopic and spectroscopic techniques have been employed for an in-depth analysis of the structure of GO. For instance, atomic force microscopy (AFM) provides the apparent thickness of the single-layer GO sheet beside the number of layers present [33, 35, 36, 37].

In contrast, conductive AFM demonstrates electrical defects found in GO [38]. Lately, one of the significant breakthroughs in determining the structure of GO, high-resolution transmission electron microscopy (HRTEM) has been employed for direct imaging of lattice atoms and topological defects present in single layer of GO [39, 40, 41]. Erickson et al. [39] identified specific atomic scale topographies of the GO monolayers, consisting of three major portions viz. holes, graphitic regions, and high-contrast disordered regions having approximate area percentages of 2, 16, and 82%, respectively.

According to the author, excessive oxidation and sheet exfoliation lead to the release of CO and CO2 consequently forming holes in GO. They also proposed that graphitic regions are a result of incomplete oxidation of basal plane having the preserved honeycomb structure of graphene, whereas the disordered region is rich in oxygen functionalities, such as hydroxyl, epoxides, and carbonyls with no order between them.

The chemical composition of GO and its oxygenated functionalities have been recognized through various spectroscopic techniques, which include solid-state nuclear magnetic resonance (SSNMR) [42, 43, 44], X-ray absorption near-edge spectroscopy (XANES) [45, 46, 47, 48, 49], Raman spectroscopy [45, 46, 47, 48, 49], X-ray photoelectron spectroscopy (XPS) [49] and Fourier transform infrared spectroscopy (FT-IR) [47, 50, 51]. Three main peaks around 60, 70, and 130 ppm are assigned to carbon atoms bonding to the epoxy group, hydroxyl group, and graphitic sp2 carbon, respectively [44], can be seen in a typical solid-state 13C magic-angle spinning NMR spectra of GO. Furthermore, three small additional peaks were also found at about 101, 167, and 191 ppm tentatively attributed to lactol, the ester carbonyl, and the ketone groups, correspondingly. XANES is another powerful tool for GO characterization, which provides information related to the degree of bond hybridization in mixed sp2/sp3-bonded carbon, the specific bonding arrangements of functional atoms, and graphitic crystal structure’s degree of alignment inside GO [49].

Besides, Raman and FTIR spectroscopy data support the presence of oxygenated species in GO and its degree of oxidation. Raman spectrum of a GO displays two characteristic bands namely a D-band at ∼1340 cm−1 and G-band at ∼1580 cm−1 [52]. The G-band is a distinctive peak of all sp2-hybridized carbon networks and due to first-order scattering from the doubly degenerate E2g phonon modes of graphite whereas the D peak originates from structural imperfections and disorders produced by the addition of oxygenated groups on the carbon basal plane [52, 53, 54]. Hence, the intensity ratio of the D- and G-bands (Id/Ig) points to the oxidation degree, disorders, and the size of sp2 ring clusters in a matrix of sp3- and sp2-bonded carbon [53]. A significant decrease in Id/Ig ratio was observed after thermal reduction, indicating a considerable regaining of conjugation in the graphitic structure after the defunctionalization of GO [45]. Functional groups can be recognized by the use of FT-IR spectroscopy and in the case of GO, it has reinforced the presence of hydroxyl (broad peak at 3050–3800 cm−1), carbonyl (1750–1850 cm−1), carboxyl (1650–1750 cm−1), C═C (1500–1600 cm−1), and ether or epoxide (1000–1280 cm−1) groups [43, 47, 50].

Specific 2D structure and the presence of oxygenated functionalities are responsible for excellent properties of GO, which include electronic, optical, thermal, mechanical, and electrochemical properties along with chemical reactivity. Electronic properties like conductivity of GO sheets are dependent on its chemical and atomic structure; in particular, the degree of oxidation arises from disorders due to substantial sp3 carbon. Generally, pristine GO films are insulating in nature with an energy gap in electron density of states, [55] as well as sheet resistance (Rs) about 1012 Ω sq.−1 or higher [56]. This inherent insulating nature of GO is strongly associated with the amount of sp3 C▬O bonding, which acts as transport barriers, leading to the lack or interruption of penetrating pathways among the sp2 carbon clusters. However, reduction of GO, whether chemical or thermal assists the transport of carriers, [57] helps to bring Rs down to several orders of magnitude and transforming the material into a semiconductor or finally into graphene-like material [58, 59, 60]. Reduced GO has conductivity up to ∼1000 S/m, [61] and activation energy as 32 ± 5 kcal/mol, estimated by the use of resistivity and temperature-programmed desorption (TPD) measurements [62]. Additionally, GO exhibits unique optical properties photoluminescence (PL) [63] occurring near-UV-to-blue visible (vis) to near-infrared (IR) wavelength range. Applications of this property have been sought in biosensing, fluorescence tags, and optoelectronic applications [64, 65].

GO also demonstrates excellent electrocatalytic properties [66, 67, 68], such as the electrocatalytic activity of GO toward oxygen reduction and certain biomolecules [66], oxidation of hydrazine by reduced GO [67]. In addition to this, GO is capable of showing high electrochemical capacitance for application in ultracapacitors [68, 69]. As compared to carbon nanotubes, reduced GO exhibit higher electrochemical capacitance and cycling durability, wherever specific capacitance for reduced GO and carbon nanotubes was found to be ∼165 and ∼86 F/g, respectively [68].

The chemical reactivity of GO can be attributed to the presence of oxygenated functionalities and its disordered structure with defects. The reduction is the most important chemical reaction of GO, and it has been reduced by employing various approaches such as hydrazine, [70] sodium borohydride, [71] or hydroquinone, [72] in the liquid phase and the vapor phase using hydrazine/hydrogen [33, 52] or just by thermal annealing [52] or by using electrochemical techniques [73]. Chemical functionalization is another important chemical reaction involving GO, which includes the addition of other chemical groups to GO employing different chemical reactions. Oxygenated functionalities over GO surface play a very important role in its chemical reactions. Hence, it becomes an ideal approach to selectively chemical functionalize GO by utilizing reactions on these functionalities. Typically, covalent functionalization of GO can be realized using small molecules and polymers via activation, amidation, or esterification of either hydroxyls or carboxyl groups through coupling reactions [74, 75, 76]. For example, GO was made soluble in organic solvents by rendering a coupling reaction with octadecylamine via amide formation, where carboxyl functionalities of GO were first activated by SOCl2 [74]. Ring-opening reactions can be used to functionalize epoxy groups by nucleophilic attack at α-carbon by the amine [77]. For example, octadecylamine attachment to GO surface [57], attachment of an amine group-containing ionic liquid through ring-opening reaction with epoxy groups on GO [77] making chemically functionalized GO more soluble in water as well as other organic solvents.

Noncovalent functionalization of GO is also known in addition to covalent modifications. Noncovalent modification of GO can be accomplished by various forces and interactions including hydrogen bonding, van der Walls interaction, π-π stacking, cation-π interaction [78, 79]. Doxorubicin hydrochloride (Dox)/GO hybrid was synthesized through noncovalent interactions using π-π stacking and hydrophobic interactions between the sp2 carbon matrix and quinone functionality of Dox as primary noncovalent interactions. Additionally, strong hydrogen bonding between hydroxyl and amine groups of Dox with hydroxyl and carboxyl groups of GO also helps in covalent modification [78].

The usefulness of GO can be estimated from this fact that along with its applications in electronics and displays, it can also act as a carbocatalyst for assisting hydration and oxidation reactions [80, 81, 82]. GO can be used as a catalyst for oxidation of alcohols and alkenes besides hydration of alkynes into aldehydes and ketones [80]. Furthermore, GO has a broad range of oxidation reaction, for example, it can oxidize olefins to diones, methylbenzene to aldehydes as well as other dehydrogenations [83].

Advertisement

2. Graphene oxide-based nanohybrids

GO and reduced GO (rGO) themselves have many advantageous properties, but a substantial amount of work is being done to utilize these materials in combination with other nanomaterials such as nanoparticles or polymers. Based on their morphologies, graphene oxide/nanoparticle nanohybrids can be roughly divided into two classes: first where nanoparticles are grown or decorated upon sheets of GO and second, nanoparticles are wrapped in GO sheets. Particularly in the first type, graphene/nanoparticle nanohybrid can be synthesized by combining GO or rGO with different nanoparticles such as metal nanoparticles, metal oxide nanoparticles, quantum dots, or silica nanoparticles depending upon the application desired. A unique combination of the nanoparticles and GO/rGO makes a novel synergistic nanomaterial with enhanced and diverse properties. For example, decorated metal or metal oxide nanoparticles over GO surface modify the local electronic structure and hence the charge transfer behavior of graphene [84] resulting in improved catalytic behavior of this nanocomposite. Alternatively, enhancement in sensitivity and selectivity has been observed in sensors derived from the combination of graphene material and nanoparticles having good conductivity and catalytic behavior [85, 86].

Similarly, in graphene oxide/polymer nanohybrids, surface functionalities present on GO surface groups can assist the combination of GO with polymers or synthesis of the polymer by different polymerization techniques [87, 88]. A typical modification strategy includes covalent bonding, that is, “Grafting to” and “Grafting from” approaches, whereas noncovalent modification includes π-π stacking, electrostatic interaction, and hydrogen bonding [89, 90, 91]. Similarly, fabrication strategies of graphene oxide/polymer nanohybrids synthesis include in situ polymerization, melt compounding, latex blending, solution mixing, and electro polymerization [92, 93].

Advertisement

3. Synthetic methodologies for graphene oxide/nanoparticle nanohybrids

Graphene oxide/nanoparticle nanohybrids in which GO/rGO sheets are decorated with nanoparticles having dimensions ranging from few nanometers to a couple of hundred nanometers [94] can be attained by attaching different types of nanoparticles to the surface of GO sheets either by in situ method or by ex situ method. In situ method comprises growing nanoparticles on the surface of GO; however, in the case of ex situ method, pre-synthesized nanoparticles are immobilized over the surface of GO. The presence of defects and oxygenated functionalities makes GO an encouraging templates for the attachment, nucleation, and growth numerous metal (e.g., Au [87, 95], Ag [96], Pt [97], etc.) and metal oxide nanoparticles (e.g., Fe3O4 [98], TiO2 [99], ZnO [100], SnO2 [101], Cu2O [102, 103], MnO2 [104], NiO [105, 106], La2O3, [107, 108], etc.). Subsequent graphene oxide/nanoparticle nanohybrid offers several unique and beneficial properties for various applications depending on individual characteristics showed by nanoparticles immobilized upon GO.

The following section includes the different methods for the preparation of graphene oxide/nanoparticles nanocomposites, for example, chemical reduction, hydrothermal route, and electrochemical method or ex situ synthesis, while primarily focusing on individual characteristics and advantages of each technique correlated to the properties of resulting graphene oxide/nanoparticle nanohybrids.

3.1 Chemical reduction method

Graphene oxide/metal nanoparticle nanohybrids are mostly synthesized by chemical reduction of their metal salt precursors such as HAuCl4, AgNO3, and K2PtCl4 utilizing reducing agents such as sodium citrate, ethylene glycol or polyethylene glycol, and sodium borohydride [96, 109], positively charged metallic salts get nucleated on negatively charged functional groups of GO which results in the growth of metal nanoparticles on its surface, while reducing GO to rGO, preserving the excellent electrical properties of rGO. Moreover, the density of metal nanoparticles can also be controlled by tuning the density of oxygenated functionalities on GO.

Chemical reduction technique is the most basic method for the preparation of Graphene oxide/noble metal nanoparticle nanohybrids. In particular, gold (AuNP) and silver nanoparticles (AgNPs) are among the most comprehensively studied nanomaterials with a wide range of biomedical applications such as diagnostics, imaging, drug delivery [110]. High biocompatibility and surface plasmon resonance are some of the very unique properties of noble nanoparticles making them of particular interest. These properties can be tuned to desired values according to the shape and size of the nanoparticles [111]. Furthermore, graphene oxide/noble metal nanoparticle nanohybrids are able to show SERS in addition to enhanced catalytic activity [112]. Reduced graphene oxide/AuNPs are the most common and utilized nanocomposites, which can be prepared by mixing HAuCl4 with GO and sodium citrate, followed by reduction using NaBH4 to form AuNPs while reducing GO to rGO [113, 114]. Similarly, instead of using HAuCl4, AgNO3 is used for reduced graphene oxide/AgNPs composite synthesis [112, 114]. In a similar way, reduced graphene oxide/platinum nanoparticle or reduced graphene oxide/palladium nanoparticle nanohybrids are formed by mixing graphene oxide with chloroplatinic acid (H2PtCl6) or tetrachloropalladic acid (H2PdCl4), followed by reduction with ethylene glycol or any other reducing agent.

3.2 Hydrothermal methods

Another very common method for synthesizing inorganic nanoparticles is the hydrothermal method. This method gives nanoparticles with high crystallinity and narrow size distribution over graphene oxide. Moreover, there is no need for postannealing or calcination for reduced graphene oxide/metal nanoparticle nanohybrids. In general, the growth of nanocrystals is induced by high temperature and pressure, which is also responsible for the conversion of GO to rGO during the process. However, in most cases reducing agents are also added to make sure a complete reduction of GO [115].

The most common nanohybrids synthesized by the hydrothermal method are reduced graphene oxide/ metal oxide nanoparticle nanohybrids which include ZnO [116], TiO2 [117], Fe3O4 [118], SnO2 [119], etc.

Reduced graphene oxide/metal oxide nanoparticle hybrids illustrate their specific properties such as higher capacitance, which depends upon nanoparticle size, shape, and crystallinity; also, it helps in the suppression of restacking and agglomeration in graphene oxide sheets. Furthermore, these nanocomposites also exhibit enhancement in electron conductivity, high surface area as compared to GO or graphene, also shortened route for ion transfer, which in all responsible for their higher electrochemical activity. For instance, reduced graphene oxide/SnO2 nanosphere nanohybrid exhibited significantly enhanced formaldehyde sensing performance compared to the pristine SnO2 nanospheres [119]. Alternatively, reduced graphene oxide/magnetic nanoparticle nanohybrid has been prepared using FeCl3 as an iron source and ethylene glycol as a reducing agent [120]. Resulting nanohybrid displayed outstanding electrical conductivity as well as magnetic properties. Similarly, chalcogenide quantum dots, for example, CdS [121], ZnS [122], Cu2S [123], and MoS2 [124], etc. have been successfully immobilized on graphene oxide exploiting hydrothermal methods.

3.3 Electrochemical deposition method

The electrochemical deposition method is a very simple, low cost, fast, easy to miniaturize, highly stable, reproducible, and green technique for preparation of graphene oxide/nanoparticle composite [125]. The advantage of this technique is that the size and shape of the nanoparticles to be deposited can be precisely controlled using varying the conditions of electrochemical deposition. Electrochemical deposition methods have been established for the fabrication of a vast variety of graphene oxide/metal nanoparticle composites for noble metals like Au, [126] using cyclic voltammetry (CV), which helped in fabricating an electrode for the determination of trace amount As(III) employing square wave anodic stripping voltammetry, Ag, [127] for carrying out the oxidation of different amino acids such as glycine, alanine, leucine, aspartic and glutamic acids using cyclic voltammetry and amperometric techniques. Similarly for Pt [128], Pt nanoparticles embedded rGO on glassy carbon electrode are utilized to carry out electrooxidation of formic acid. Generally, a typical electrochemical deposition experiment is consisting of three basic steps, that is, assembly of graphene oxide sheets on the electrode, graphene oxide-coated electrode immersion in an electrolytic solution of selected metal precursors, and potential applied across electrodes. A majority of research has concentrated on using electrochemical deposition methods for synthesizing graphene oxide/metal nanoparticle composite, but there are some reports for preparation of graphene oxide/metal oxide nanoparticle composite synthesis by the same technique. For instance, Cl-doped n-type Cu2O nanoparticles with a direct band gap of ca. 2.0 eV [128] have been deposited on rGO electrodes with a subsequent carrier concentration of up to 1 × 1020 cm−3 [129].

3.4 Graphene oxide/encapsulated nanoparticles

Flexible and 2D sheet-like structure of graphene oxide and its derivatives help in wrapping or encapsulating nanoparticles in the range from 100 nm to few micrometers.

GO and rGO sheets are most commonly used for nanoparticle encapsulation due to their hydrophilic nature and ease of fabrication. Noncovalent bonds are responsible for this type of encapsulation; for instance, modification of nanoparticle surface with a positive charge is used for electrostatic interaction with negatively charged GO [130, 131]. Encapsulation of a variety of nanomaterials, for example, polymer, inorganic nanoparticles, metal, and metal oxide nanoparticles, can be achieved by controlling the cracked size of GO and rGO, thus obtained composite offer enhanced properties and additional advantages. For example, enhancement in electrical, optical, and electrochemical properties has been observed for graphene oxide encapsulated nanoparticles, also suppression of aggregation of small nanoparticles [132, 133]. Moreover, leaching of nanoparticles is reduced in graphene oxide encapsulated nanoparticles due to the high amount of contact between GO and nanoparticles, making them more stable. Several reports have revealed the encapsulation of metal oxide nanoparticles with graphene oxide. For example, rGO encapsulated cobalt oxide nanoparticles have shown a very high reversible capacity (1000 mAh g−1) over 130 cycles, much more than the normal cobalt oxide nanoparticles used for capacitors [131]. Moreover, rGO encapsulated Co3O4 nanofibers-based sensor exhibited an excellent sensitivity with a fast response and recovery to different concentrations of ammonia from 5 to 100 ppm at room temperature [134]. Furthermore, a nonenzymatic electrochemical sensor based on 3D porous phase graphene oxide sheets encapsulated chalcopyrite (GOS@CuFeS2) nanocomposite is reported for the detection of methyl paraoxon [135]. Encapsulation of nonconducting silicon oxide nanoparticles within conducting rGO can be used as the “bridging-material” in a field-effect transistor-based biosensor [130, 136]. Similarly, Si nanoparticles encapsulated with rGO via electrostatic interaction using APTES has also been reported [137, 138], resulting in less destruction and aggregation of SiNPs as compared to pristine nanoparticles. It also exhibited a high reversible capacity of 902 mAh g−1 after 100 cycles at 300 mA g−1 when used as the electrode.

Advertisement

4. Graphene oxide-based nanohybrids as pesticide biosensors

An analytical device that utilizes a biological sensing element to detect a specific analyte molecule or family of the analytical molecule is called as biosensor. Biosensors can seek applications in diverse fields such as food safety, environmental monitoring, and biomedical field. Generally, biosensors are consisting of two basic parts: first receptor, any organic or inorganic material that interacts with analytes. The second part, a transducer, which converts a recognition event, happened between analyte and receptor, into a measurable signal. Evaluation of biosensor ‘s performance is measured by its sensitivity to target, linear range, the limit of detection, dynamic ranges, reproducibility, precision in response, and selectivity [139]. Other parameters that are also important include the sensor’s response time, ease of use, portability, storage, and operational stability. Graphene oxide/nanoparticle nanohybrids are known to be well suited for application in biosensing because of the rise of new advantageous properties due to the combination of graphene oxide and nanoparticles. Here, in this section, a detailed aspect of graphene oxide nanohybrid-based biosensors, specifically electrochemical biosensors are discussed.

Electrochemical sensors are the largest group of sensors for detecting or analyzing various molecules by directly converting biological recognition event into an electrical signal. A typical electrochemical biosensor is composed of a three-electrode system with a working electrode consisting of a biological recognition element, counter electrode, and reference electrode separated by suitable electrolytes. Based on their biological recognition process, electrochemical biosensors can be divided into two main groups: first, affinity-based sensors, and second, catalytic sensors. The basic principle of working in affinity biosensors is the measurable electric signal that arises due to the interaction of the biological component like an antibody, enzyme, nucleic acid, or a receptor and target molecules. Whereas in catalytic sensors, incorporated nanoparticles or enzymes recognize the analyte molecules and produce an electroactive species by catalysis. The electrical signal produced by the electroactive species is then correlated to the concentration of the target analyte molecule. Commonly used techniques in electrochemical biosensing include different forms of voltammetry (e.g., cyclic, linear sweep, differential, square wave, etc.) and amperometry [139].

The large surface area of graphene oxide nanohybrids is beneficial for the immobilization of biomolecules to use it as a platform for biosensing material. Furthermore, the synergistic effect of graphene oxide also enhances achievable sensitivities and measurable ranges. Most commonly biomolecule immobilized biosensors utilize enzymes, antibodies, and DNA as biomolecules.

Lately, enzyme immobilized GO nanohybrids-based biosensors have fascinated a lot for the detection of various kinds of analytes. The most common example is the determination of glucose, which has an important role in the diagnosis and therapy of diabetes. Apart from glucose oxidase based biosensors, other enzyme-based biosensors are also known with high sensitivity and selectivity, which includes biosensors based on alcohol dehydrogenase [140], microperoxidase [141], horseradish peroxidase [142], tyrosinase [143], urease [144], and acetylcholinesterase [145]. Acetylcholinesterase (AChE) is a catalytic enzyme present in the central nervous system, which catalyzes the hydrolysis of acetylcholine and choline esters. Its catalytic ability is severely affected by the presence of different types of organophosphorus and carbamate pesticides even in trace amounts. AChE can be easily immobilized on the surface of graphene oxide-based nanohybrids which offer a large surface area and abundant active sites so that they can be used for developing AChE inhibition-based biosensors [146].

Although a lot of work has already been reported on graphene-based biosensors; however, due to novel microbes and diseases associated with them, excess use of toxicants in food and feed products, nonjudicial use of pesticide and day by day disintegrating environmental conditions urgently need tools for detection of such chemicals and biologicals, and hence, more rapid and urgent requirement for the development of biosensors arises In the past 2 years, countless new graphene oxide nanohybrids-based biosensors are reported. For example, Yao et al. [147] reported an electrochemical biosensor based on the inhibition of AChE, using a gold nanocage/graphene oxide-chitosan nanocomposite-modified screen-printed carbon electrode for detection of chlorpyrifos (Figure 2). Where the biosensor showed good electrocatalytic activity for the oxidation of enzymatically produced thiocholine and detected chlorpyrifos concentrations as low as 3 ng L−1.

Figure 2.

(a) A schematic diagram of the construction process of AChE biosensor based on screen-printed electrodes, (b) and (c) DPV behavior, and percent inhibition obtained by biosensor in the presence of chlorpyrifos. Reprinted with permission from ref. [147], published by the Royal Society of Chemistry (RSC) on behalf of the Centre National de la Recherche Scientifique (CNRS) and the RSC.

Similarly, Bao et al. [148] developed a biosensor for malathion detection based on three-dimensional graphene-copper oxide nanoflowers nanocomposites electrode, and the group was able to obtain a wide linear relationship to malathion concentration ranging from 3 pM to 46.665 nM with a theoretical limit of detection at 0.92 pM. Moreover, Cui et al. reported a very stable electrochemical AChE biosensor for detection of dichlorvos by adsorption of AChE on chitosan, TiO2 sol-gel, and rGO-based many fold matrix, with the linear range varying from 0.036 μM to 22.6 μM, limit of detection of 29 nM and total time for detection about 25 min. Furthermore, electrochemical acetylcholinesterase biosensor based on the silver nanowire, graphene, TiO2 sol-gel, chitosan, and acetylcholinesterase is fabricated by Zhang et al. [149] (Figure 3).

Figure 3.

(a) Schematic illustration of the AChE based biosensor and its working mechanism to ATCl.(b) and (c) SEM images of Gra/AgNWs/SiO2 nanohybrids, where large graphene sheet is enhancing the connection with AgNWs in (b) with small graphene pieces further improving the performance of biosensor (in red rectangle shown in (c)), while (d) and (e) represent the inhibition of AChE in presence of DDVP using the biosensors. Reprinted with permission from ref [149], Published by The Royal Society of Chemistry.

On a similar note, Zhang et al. [150] developed a highly sensitive AChE amperometric biosensor based on conjugated polymer and Ag-rGO-NH2 nanocomposite. Group used a slightly different method for electrode fabrication where authors first electrochemically polymerized 4, 7-di (furan-2-yl) benzothiadiazole on electrode surface followed by deposition of Ag-rGO-NH2 nanocomposite. The biosensor is found to be biocompatible with high efficiency having the linear range from 0.099 to 9.9 μg L−1 0.032 μg L−1 for malathion and 0.001 μg L−1 for trichlorfon. Moreover, Mogha et al. [151] developed a biosensor for the detection of Chlorpyrifos using rGO supported Zirconium Oxide immobilized AChE (Figure 4). The group is able to detect the Chlorpyrifos in two linear ranges first from 10−13 to 10−9 M, whereas the second linear range was observed between 10−9 and 10−4 M.

Figure 4.

An illustration of rGO supported Zirconium Oxide immobilized AChE nanohybrid as a biosensing platform for chlorpyrifos detection. Reprinted with permission from Ref. [151], published by Elsevier.

Aghaie et al. [152] developed a nonenzymatic biosensor for the detection of paraoxon ethyl. A graphene-based NiFe bimetallic phosphosulfide nanocomposite biosensor is fabricated, where square wave voltammetric is used as a detection technique. The linear range for the detection of paraoxon methyl is found to be 12.3–10,000 nmol L−1 and limit of detection as 3.7 nmol L−1.

Furthermore, a group of Hondred et al. [153] (Figure 5) utilized salt impregnated inkjet maskless lithography for preparation of 3D porous architectured graphene for application in biosensing of paraoxon and supercapacitor. The as developed biosensor showed a wide linear range from 10 to 500 nM, low limit of detection of 0.6 nM with high sensitivity of 12.4 nA nM−1; moreover as a supercapacitor, it demonstrates a high energy density of 0.25 mW h cm−3 at a power density of 0.3 W cm−3. Similarly, another AChE biosensor is developed based on a film of gold nanoparticles/three-dimensional graphene, by Dong et al. [154], for methyl parathion and malathion detection in a linear range from 1.0 × 10−10 to 1.0 × 10−6 g L−1, having limits of detection as 2.78 × 10−11 g L−1 and 2.17 × 10−11 g L−1.

Figure 5.

(a) Schematic diagram of AChE biosensor portraying the functionalization approach for pesticide detection using EDC/NHS. (b) AChE pesticides biosensor characterization with photograph, activity, sensitivity, and comparison between salt impregnated inkjet maskless lithography (SIIML) and inkjet maskless lithography (IML)-based biosensors. Reprinted with permission from Ref. [153], published by The Royal Society of Chemistry.

Some more examples of biosensors based on graphene oxide nanohybrids for the detection of different types of pesticides such as methyl parathion [155, 156, 157, 158], carbofuran [155, 157, 159], chlorpyrifos [156], imidacloprid [160], phoxim with graphene/GCE [161], poly(3-methylthiophene)/nitrogen-doped graphene [162], and carboxylic chitosan /silver nanoclusters-rGO [163], paraoxon and chlorpyrifos with TiO2-GO/UiO-66 composite [164], carbaryl with MWCNTs/GO nanoribbons [165], carbaryl and chlorpyrifos with AgNPs-CGR/NF composite [166], chlorpyrifos and carbofuran with ZnONPs-CGR/NF composite [167], carbaryl and monocrotophos with ionic liquid-functionalized graphene /gelatin [168], monocrotophos with Prussian blue nanocubes [169], malathion and carbaryl with rGO-AuNP/β-cyclodextrin/Prussian blue-CS nanocomposites [170], fenitrothion with cerium oxide nanoparticle-decorated rGO [171], diuron with rGO-AuNPs [172], paraoxon-ethyl with rGO-AuNPs/polypyrrole [173], carbaryl with Graphene/polyaniline nanohybrid [174], carbaryl with an electrochemically induced porous GO network [175], and methyl parathion and malathion with plant esterase—Chit/AuNPs-graphene nanosheets [176].

Advertisement

5. Conclusion and future aspects

Graphene oxide is an attractive material that has gathered ever accumulative interest from the scientific community over the past several years. Owing to its extraordinary properties, graphene oxide and its derivatives are already being exploited in a wide variety of applications comprising electronics, energy, biosensors, catalysis, green chemistry, etc. Though, in the last decade, the relentless search for new opportunities benefiting from graphene oxide has led to the introduction and evolution of graphene oxide-based nanohybrids, which combine matchless and beneficial properties of nanomaterials/nanotechnology with those of graphene oxide to yield valuable and synergistic effects.

In this chapter, we have discussed the brief history of graphene oxide and graphene, emphasizing the structural details of graphene oxide and excellent properties associated with it. Graphene oxide-based nanohybrids show the synergistic effect of having properties of both graphene oxide as well as other constituting material whether nanoparticle or polymer. Synthetic mythologies of graphene oxide-based nanohybrids have also been discussed here in this chapter, in particular, graphene oxide/nanoparticle nanohybrids. Finally, applications of graphene oxide-based nanohybrids were presented in the field of biosensors and catalysis. In the case of biosensors, the main emphasis was given to the largest class of biosensors, that is, electrochemical biosensors, which consist of mainly enzyme biosensors and electrochemical DNA sensors, but some cases of other electrochemical sensors were also demonstrate. Applications of these graphene oxide-based hybrids in catalysis were also discussed emphasizing their use as an organic reaction catalyst, photocatalysts for the degradation of environmentally harmful molecules.

In conclusion, we have highlighted the properties of graphene oxide-based nanohybrids wherein these nanostructures can bring excellent synergistic advantages to a wide variety of biosensing applications. While promising, the field of graphene oxide-based nanohybrids is still not completely exhausted and several intriguing issues must be resolved before its maximum potential can be achieved. Besides, we envision that the evolution of this technology will result in the use of graphene oxide-based nanohybrids in a much wider range of applications by employing high quality and large-scale fabrication of these materials to minimize the cost leading to their commercialization. We also hope that this chapter has motivated attention from various disciplines that will gain benefits from the expansion of graphene oxide-based nanohybrids development for applications in numerous other fields of interest.

Advertisement

Acknowledgments

The author is heartily thankful to the Director, Shriram Institute for Industrial Research and Monica Singh, In-charge, Pesticide Laboratory for unconditional help and support.

References

  1. 1. Bao LJ, Wei YL, Yao Y, Ruan QQ , Zeng EY. Global trends of research on emerging contaminants in the environment and humans: A literature assimilation. Environmental Science and Pollution Research. 2015;22:1635-1643. DOI: 10.1007/s11356-014-3404-8
  2. 2. Gavrilescu M, Demnerová K, Aamand J, Agathos S, Fava F. Emerging pollutants in the environment: Present and future challenges in biomonitoring, ecological risks and bioremediation. New Biotechnology. 2015;32:147-156. DOI: 10.1016/j.nbt.2014.01.001
  3. 3. Grandjean P, Landrigan PJ. Neurobehavioural effects of developmental toxicity. Lancet Neurology. 2014;13:330-338. DOI: 10.1016/S1474-4422(13)70278-3
  4. 4. Moser F, Dondi F. Environmental protection between chemical practice and applied ethics: A critical review. Toxicological and Environmental Chemistry. 2016;98:1026-1042. DOI: 10.1080/02772248.2015.1025786
  5. 5. Pundir CS, Malik A, Preety. Bio-sensing of organophosphorus pesticides: A review. Biosensors & Bioelectronics. 2019;140:111348. DOI: 10.1016/j.bios.2019.111348
  6. 6. Liu M, Khan A, Wang Z, Liu Y, Yang G, Deng Y, et al. Aptasensors for pesticide detection. Biosensors & Bioelectronics. 2019;130:174-184. DOI: 10.1016/j.bios.2019.01.006
  7. 7. Damalas CA, Koutroubas SD. Farmers’ exposure to pesticides: Toxicity types and ways of prevention. Toxics. 2016;4:1. DOI: 10.3390/toxics4010001
  8. 8. Ye M, Beach J, Martin JW, Senthilselvan A. Occupational pesticide exposures and respiratory health. International Journal of Environmental Research and Public Health. 2013;10:6442-6471. DOI: 10.3390/ijerph10126442
  9. 9. Damalas CA, Eleftherohorinos IG. Pesticide exposure, safety issues, and risk assessment indicators. International Journal of Environmental Research and Public Health. 2011;8:1402-1419. DOI: 10.3390/ijerph8051402
  10. 10. Kaur N, Prabhakar N. Current scenario in organophosphates detection using electrochemical biosensors. TrAC, Trends in Analytical Chemistry. 2017;92:62-85. DOI: 10.1016/j.trac.2017.04.012
  11. 11. Xia N, Gao Y. Carbon nanostructures for development of acetylcholinesterase electrochemical biosensors for determination of pesticides. International Journal of Electrochemical Science. 2015;10:713-724
  12. 12. Boehm HP, Setton R, Stumpp E. Nomenclature and terminology of graphite intercalation compounds (IUPAC recommendations 1994). Pure and Applied Chemistry. 1994;66:1893-1901. DOI: 10.1351/pac199466091893
  13. 13. Novoselov KS, Geim AK, Morozov SV, Jiang D, Zhang Y, Dubonos SV, et al. Electric field effect in atomically thin carbon films. Science. 2004;306:666-669. DOI: 10.1126/science.1102896
  14. 14. Novoselov KS, Geim AK, Morozov SV, Jiang D, Katsnelson MI, Grigorieva IV, et al. Two-dimensional gas of massless dirac fermions in graphene. Nature. 2005;438:197-200. DOI: 10.1038/nature04233
  15. 15. Lau CN, Bao W, Velasco J. Properties of suspended graphene membranes. Materials Today. 2012;15:238-245. DOI: 10.1016/S1369-7021(12)70114-1
  16. 16. Ruoff R. Calling all chemists. Nature Nanotechnology. 2008;3:10-11. DOI: 10.1038/nnano.2007.432
  17. 17. Dreyer DR, Park S, Bielawski CW, Ruoff RS. The chemistry of graphene oxide. Chemical Society Reviews. 2010;39:228-240. DOI: 10.1039/B917103G
  18. 18. Lerf A, He H, Forster M, Klinowski J. Structure of graphite oxide revisited ‖. The Journal of Physical Chemistry. B. 1998;102:4477-4482. DOI: 10.1021/jp9731821
  19. 19. Szabó T, Berkesi O, Forgó P, Josepovits K, Sanakis Y, Petridis D, et al. Evolution of surface functional groups in a series of progressively oxidized graphite oxides evolution of surface functional groups in a series of progressively oxidized graphite oxides. Chemistry of Materials. 2006;18:2740-2749. DOI: 10.1021/cm060258
  20. 20. Gao W, Alemany LB, Ci L, Ajayan PM. New insights into the structure and reduction of graphite oxide. Nature Chemistry. 2009;1:403-408. DOI: 10.1038/nchem.281
  21. 21. Eda G, Chhowalla M. Chemically derived Graphene oxide: Towards large-area thin-film electronics and optoelectronics. Advanced Materials. 2010;22:2392-2415. DOI: 10.1002/adma.200903689
  22. 22. Li X, Zhang G, Bai X, Sun X, Wang X, Wang E, et al. Highly conducting graphene sheets and Langmuir–Blodgett films. Nature Nanotechnology. 2008;3:538-542. DOI: 10.1038/nnano.2008.210
  23. 23. Kim F, Cote LJ, Huang J. Graphene oxide: Surface activity and two-dimensional assembly. Advanced Materials. 2010;22:1954-1958. DOI: 10.1002/adma.200903932
  24. 24. Compton OC, Nguyen ST. Graphene oxide, highly reduced graphene oxide, and Graphene: Versatile building blocks for carbon-based materials. Small. 2010;6:711-723. DOI: 10.1002/smll.200901934
  25. 25. Filip J, Tkac J. Is graphene worth using in biofuel cells? Electrochimica Acta. 2014;136:340-354. DOI: 10.1016/j.electacta.2014.05.119
  26. 26. Gómez-Navarro C, Meyer JC, Sundaram RS, Chuvilin A, Kurasch S, Burghard M, et al. Atomic structure of reduced graphene oxide. Nano Letters. 2010;10:1144-1148. DOI: 10.1021/nl9031617
  27. 27. Mkhoyan KA, Contryman AW, Silcox J, Stewart DA, Eda G, Mattevi C, et al. Atomic and electronic structure of graphene-oxide. Nano Letters. 2009;9:1058-1063. DOI: 10.1021/nl8034256
  28. 28. Bissessur R, Scully SF. Intercalation of solid polymer electrolytes into graphite oxide. Solid State Ionics. 2007;178:877-882. DOI: 10.1016/j.ssi.2007.02.030
  29. 29. Paredes JI, Villar-Rodil S, Martínez-Alonso A, Tascón JMD. Graphene oxide dispersions in organic solvents. Langmuir. 2008;24:10560-10564. DOI: 10.1021/la801744a
  30. 30. Mattevi C, Eda G, Agnoli S, Miller S, Mkhoyan KA, Celik O, et al. Evolution of electrical, chemical, and structural properties of transparent and conducting chemically derived graphene thin films. Advanced Functional Materials. 2009;19:2577-2583. DOI: 10.1002/adfm.200900166
  31. 31. Eda G, Fanchini G, Chhowalla M. Large-area ultrathin films of reduced graphene oxide as a transparent and flexible electronic material. Nature Nanotechnology. 2008;3:270-274. DOI: 10.1038/nnano.2008.83
  32. 32. Eda G, Mattevi C, Yamaguchi H, Kim H, Chhowalla M. Insulator to semimetal transition in graphene oxide. Journal of Physical Chemistry C. 2009;113:15768-15771. DOI: 10.1021/jp9051402
  33. 33. Gómez-Navarro C, Weitz RT, Bittner AM, Scolari M, Mews A, Burghard M, et al. Electronic transport properties of individual chemically reduced graphene oxide sheets. Nano Letters. 2007;7:3499-3503. DOI: 10.1021/nl072090c
  34. 34. Schniepp HC, Li JL, McAllister MJ, Sai H, Herrera-Alonson M, Adamson DH, et al. Functionalized single graphene sheets derived from splitting graphite oxide. The Journal of Physical Chemistry. B. 2006;110:8535-8539. DOI: 10.1021/jp060936f
  35. 35. Stankovich S, Dikin DA, Piner RD, Kohlhaas KA, Kleinhammes A, Jia Y, et al. Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide. Carbon N Y. 2007;45:1558-1565. DOI: 10.1016/j.carbon.2007.02.034
  36. 36. Cote LJ, Kim F, Huang J. Langmuir−Blodgett assembly of graphite oxide single layers. Journal of the American Chemical Society. 2009;131:1043-1049. DOI: 10.1021/ja806262m
  37. 37. Paredes JI, Villar-Rodil S, Solís-Fernández P, Martínez-Alonso A, Tascón JMD. Atomic force and scanning tunneling microscopy imaging of graphene nanosheets derived from graphite oxide. Langmuir. 2009;25:5957-5968. DOI: 10.1021/la804216z
  38. 38. Mativetsky JM, Treossi E, Orgiu E, Melucci M, Veronese GP, Samorì P, et al. Local current mapping and patterning of reduced graphene oxide. Journal of the American Chemical Society. 2010;132:14130-14136. DOI: 10.1021/ja104567f
  39. 39. Erickson K, Erni R, Lee Z, Alem N, Gannett W, Zettl A. Determination of the local chemical structure of graphene oxide and reduced graphene oxide. Advanced Materials. 2010;22:4467-4472. DOI: 10.1002/adma.201000732
  40. 40. Pantelic RS, Meyer JC, Kaiser U, Baumeister W, Plitzko JM. Graphene oxide: A substrate for optimizing preparations of frozen-hydrated samples. Journal of Structural Biology. 2010;170:152-156. DOI: 10.1016/j.jsb.2009.12.020
  41. 41. Pacilé D, Meyer JC, Fraile Rodríguez A, Papagno M, Gómez-Navarro C, Sundaram RS, et al. Electronic properties and atomic structure of graphene oxide membranes. Carbon N Y. 2011;49:966-972. DOI: 10.1016/j.carbon.2010.09.063
  42. 42. Casabianca LB, Shaibat MA, Cai WW, Park S, Piner R, Ruoff RS, et al. NMR-based structural modeling of graphite oxide using multidimensional 13C solid-state NMR and ab initio chemical shift calculations. Journal of the American Chemical Society. 2010;132:5672-5676. DOI: 10.1021/ja9030243
  43. 43. Si Y, Samulski ET. Synthesis of water soluble graphene. Nano Letters. 2008;8:1679-1682. DOI: 10.1021/nl080604h
  44. 44. Cai W, Piner RD, Stadermann FJ, Park S, Shaibat MA, Ishii Y, et al. Synthesis and solid-state NMR structural characterization of 13C-labeled graphite oxide. Science. 2008;321:1815-1817. DOI: 10.1126/science.1162369
  45. 45. Lee V, Whittaker L, Jaye C, Baroudi KM, Fischer DA, Banerjee S. Large-area chemically medified graphene films: Electrophoretic deposition and characterization by soft X-ray absorption spectroscopy. Chemistry of Materials. 2009;21:3905-3916. DOI: 10.1021/cm901554p
  46. 46. Saxena S, Tyson TA, Negusse E. Investigation of the local structure of graphene oxide. Journal of Physical Chemistry Letters. 2010;1:3433-3437. DOI: 10.1021/jz1014339
  47. 47. Lee DW, De Los Santos VL, Seo JW, Felix LL, Bustamante DA, Cole JM, et al. The structure of graphite oxide: Investigation of its surface chemical groups. The Journal of Physical Chemistry. B. 2010;114:5723-5728. DOI: 10.1021/jp1002275
  48. 48. Saxena S, Tyson TA, Shukla S, Negusse E, Chen H, Bai J. Investigation of structural and electronic properties of graphene oxide. Applied Physics Letters. 2011;99:013104. DOI: 10.1063/1.3607305
  49. 49. Ganguly A, Sharma S, Papakonstantinou P, Hamilton J. Probing the thermal deoxygenation of graphene oxide using high-resolution in situ X-ray-based spectroscopies. Journal of Physical Chemistry C. 2011;115:17009-17019. DOI: 10.1021/jp203741y
  50. 50. Bagri A, Mattevi C, Acik M, Chabal YJ, Chhowalla M, Shenoy VB. Structural evolution during the reduction of chemically derived graphene oxide. Nature Chemistry. 2010;2:581-587. DOI: 10.1038/nchem.686
  51. 51. Acik M, Lee G, Mattevi C, Pirkle A, Wallace RM, Chhowalla M, et al. The role of oxygen during thermal reduction of graphene oxide studied by infrared absorption spectroscopy. Journal of Physical Chemistry C. 2011;115:19761-19781. DOI: 10.1021/jp2052618
  52. 52. Yang D, Velamakanni A, Bozoklu G, Park S, Stoller M, Piner RD, et al. Chemical analysis of graphene oxide films after heat and chemical treatments by X-ray photoelectron and micro-Raman spectroscopy. Carbon N Y. 2009;47:145-152. DOI: 10.1016/j.carbon.2008.09.045
  53. 53. Pimenta MA, Dresselhaus G, Dresselhaus MS, Cançado LG, Jorio A, Saito R. Studying disorder in graphite-based systems by Raman spectroscopy. Physical Chemistry Chemical Physics. 2007;9:1276-1291. DOI: 10.1039/b613962k
  54. 54. Dresselhaus MS, Dresselhaus G, Hofmann M. Raman spectroscopy as a probe of graphene and carbon nanotubes. Philosophical Transactions of the Royal Society A - Mathematical Physical and Engineering Sciences. 2008;366:231-236. DOI: 10.1098/rsta.2007.2155
  55. 55. Boukhvalov DW, Katsnelson MI. Modeling of graphite oxide. Journal of the American Chemical Society. 2008;130:10697-10701. DOI: 10.1021/ja8021686
  56. 56. Becerril HA, Mao J, Liu Z, Stoltenberg RM, Bao Z, Chen Y. Evaluation of solution-processed reduced graphene oxide films as transparent conductors. ACS Nano. 2008;2:463-470. DOI: 10.1021/nn700375n
  57. 57. Wang S, Chia PJ, Chua LL, Zhao LH, Png RQ , Sivaramakrishnan S, et al. Band-like transport in surface-functionalized highly solution-processable graphene nanosheets. Advanced Materials. 2008;20:3440-3446. DOI: 10.1002/adma.200800279
  58. 58. Du X, Skachko I, Barker A, Andrei EY. Approaching ballistic transport in suspended graphene. Nature Nanotechnology. 2008;3:491-495. DOI: 10.1038/nnano.2008.199
  59. 59. López V, Sundaram RS, Gómez-Navarro C, Olea D, Burghard M, Gómez-Herrero J, et al. Chemical vapor deposition repair of graphene oxide: A route to highly conductive graphene monolayers. Advanced Materials. 2009;21:4683-4686. DOI: 10.1002/adma.200901582
  60. 60. Lee G, Kim KS, Cho K. Theoretical study of the electron transport in graphene with vacancy and residual oxygen defects after high-temperature reduction. Journal of Physical Chemistry C. 2011;115:9719-9725. DOI: 10.1021/jp111841w
  61. 61. Li D, Müller MB, Gilje S, Kaner RB, Wallace GG. Processable aqueous dispersions of graphene nanosheets. Nature Nanotechnology. 2008;3:101-105. DOI: 10.1038/nnano.2007.451
  62. 62. Jung I, Field DA, Clark NJ, Zhu Y, Yang D, Piner RD, et al. Reduction kinetics of graphene oxide determined by electrical transport measurements and temperature programmed desorption. Journal of Physical Chemistry C. 2009;113:18480-18486. DOI: 10.1021/jp904396j
  63. 63. Loh KP, Bao Q , Eda G, Chhowalla M. Graphene oxide as a chemically tunable platform for optical applications. Nature Chemistry. 2010;2:1015-1024. DOI: 10.1038/nchem.907
  64. 64. Eda G, Lin YY, Mattevi C, Yamaguchi H, Chen HA, Chen IS, et al. Blue photoluminescence from chemically derived graphene oxide. Advanced Materials. 2010;22:505-509. DOI: 10.1002/adma.200901996
  65. 65. Liu F, Choi JY, Seo TS. Graphene oxide arrays for detecting specific DNA hybridization by fluorescence resonance energy transfer. Biosensors & Bioelectronics. 2010;25:2361-2365. DOI: 10.1016/j.bios.2010.02.022
  66. 66. Tang L, Wang Y, Li Y, Feng H, Lu J, Li J. Preparation, structure, and electrochemical properties of reduced graphene sheet films. Advanced Functional Materials. 2009;19:2782-2789. DOI: 10.1002/adfm.200900377
  67. 67. Wang Y, Wan Y, Zhang D. Reduced graphene sheets modified glassy carbon electrode for electrocatalytic oxidation of hydrazine in alkaline media. Electrochemistry Communications. 2010;12:187-190. DOI: 10.1016/j.elecom.2009.11.019
  68. 68. Shao Y, Wang J, Engelhard M, Wang C, Lin Y. Facile and controllable electrochemical reduction of graphene oxide and its applications. Journal of Materials Chemistry. 2010;20:743-748. DOI: 10.1039/b917975e
  69. 69. Wang DW, Li F, Wu ZS, Ren W, Cheng HM. Electrochemical interfacial capacitance in multilayer graphene sheets: Dependence on number of stacking layers. Electrochemistry Communications. 2009;11:1729-1732. DOI: 10.1016/j.elecom.2009.06.034
  70. 70. Park S, An J, Potts JR, Velamakanni A, Murali S, Ruoff RS. Hydrazine-reduction of graphite- and graphene oxide. Carbon N Y. 2011;49:3019-3023. DOI: 10.1016/j.carbon.2011.02.071
  71. 71. Shin HJ, Kim KK, Benayad A, Yoon SM, Park HK, Jung IS, et al. Efficient reduction of graphite oxide by sodium borohydride and its effect on electrical conductance. Advanced Functional Materials. 2009;19:1987-1992. DOI: 10.1002/adfm.200900167
  72. 72. Guoxiu W, Juan Y, Jinsoo P, Xinglong G, Bei W, Hao L, et al. Facile synthesis and characterization of graphene nanosheets. Journal of Physical Chemistry C. 2008;112:8192-8195. DOI: 10.1021/jp710931h
  73. 73. Ramesha GK, Sampath NS. Electrochemical reduction of oriented graphene oxide films: An in situ Raman spectroelectrochemical study. Journal of Physical Chemistry C. 2009;113:7985-7989. DOI: 10.1021/jp811377n
  74. 74. Niyogi S, Bekyarova E, Itkis ME, McWilliams JL, Hamon MA, Haddon RC. Solution properties of graphite and graphene. Journal of the American Chemical Society. 2006;128:7720-7721. DOI: 10.1021/ja060680r
  75. 75. Liu ZB, Xu YF, Zhang XY, Zhang XL, Chen YS, Tian JG. Porphyrin and fullerene covalently functionalized graphene hybrid materials with large nonlinear optical properties. The Journal of Physical Chemistry. B. 2009;113:9681-9686. DOI: 10.1021/jp9004357
  76. 76. Fang M, Wang K, Lu H, Yang Y, Nutt S. Covalent polymer functionalization of graphene nanosheets and mechanical properties of composites. Journal of Materials Chemistry. 2009;19:7098-7105. DOI: 10.1039/b908220d
  77. 77. Yang H, Shan C, Li F, Han D, Zhang Q , Niu L. Covalent functionalization of polydisperse chemically-converted graphene sheets with amine-terminated ionic liquid. Chemical Communications. 2009:3880-3882. DOI: 10.1039/b905085j
  78. 78. Yang X, Zhang X, Liu Z, Ma Y, Huang Y, Chen Y. High-efficiency loading and controlled release of doxorubicin hydrochloride on graphene oxide. Journal of Physical Chemistry C. 2008;112:17554-17558. DOI: 10.1021/jp806751k
  79. 79. Lu CH, Yang HH, Zhu CL, Chen X, Chen GN. A graphene platform for sensing biomolecules. Angewandte Chemie, International Edition. 2009;48:4785-4787. DOI: 10.1002/anie.200901479
  80. 80. Dreyer DR, Jia HP, Bielawski CW. Graphene oxide: A convenient carbocatalyst for facilitating oxidation and hydration reactions. Angewandte Chemie, International Edition. 2010;49:6813-6816. DOI: 10.1002/anie.201002160
  81. 81. Dreyer DR, Jarvis KA, Ferreira PJ, Bielawski CW. Graphite oxide as a dehydrative polymerization catalyst: A one-step synthesis of carbon-reinforced poly(phenylene methylene) composites. Macromolecules. 2011;44:7659-7667. DOI: 10.1021/ma201306x
  82. 82. Dreyer DR, Jarvis KA, Ferreira PJ, Bielawski CW. Graphite oxide as a carbocatalyst for the preparation of fullerene-reinforced polyester and polyamide nanocomposites. Polymer Chemistry. 2012;3:757-766. DOI: 10.1039/c2py00545j
  83. 83. Jia HP, Dreyer DR, Bielawski CW. C-H oxidation using graphite oxide. Tetrahedron. 2011;67:4431-4434. DOI: 10.1016/j.tet.2011.02.065
  84. 84. Shah B, Yin PT, Ghoshal S, Lee KB. Multimodal magnetic core-shell nanoparticles for effective stem-cell differentiation and imaging. Angewandte Chemie, International Edition. 2013;52:6190-6195. DOI: 10.1002/anie.201302245
  85. 85. Tjoa V, Jun W, Dravid V, Mhaisalkar S, Mathews N. Hybrid graphene-metal nanoparticle systems: Electronic properties and gas interaction. Journal of Materials Chemistry. 2011;21:15593-15599. DOI: 10.1039/c1jm12676h
  86. 86. Artiles MS, Rout CS, Fisher TS. Graphene-based hybrid materials and devices for biosensing. Advanced Drug Delivery Reviews. 2011;63:1352-1360. DOI: 10.1016/j.addr.2011.07.005
  87. 87. Mogha NK, Gosain S, Masram DT. Gold nanoworms immobilized graphene oxide polymer brush nanohybrid for catalytic degradation studies of organic dyes. Applied Surface Science. 2017;396:1427-1434. DOI: 10.1016/j.apsusc.2016.11.182
  88. 88. Mogha NK, Gosain S, Masram DT. Lanthanum oxide nanoparticles immobilized reduced graphene oxide polymer brush nanohybrid for environmental vitiation of organic dyes. Arabian Journal of Chemistry. 2020;13:1367-1376. DOI: 10.1016/j.arabjc.2017.11.008
  89. 89. Zhang M, Li Y, Su Z, Wei G. Recent advances in the synthesis and applications of graphene-polymer nanocomposites. Polymer Chemistry. 2015;6:6107-6124. DOI: 10.1039/c5py00777a
  90. 90. Ye YS, Chen YN, Wang JS, Rick J, Huang YJ, Chang FC, et al. Versatile grafting approaches to functionalizing individually dispersed graphene nanosheets using RAFT polymerization and click chemistry. Chemistry of Materials. 2012;24:2987-2997. DOI: 10.1021/cm301345r
  91. 91. Chen Y, Zhang S, Liu X, Pei Q , Qian J, Zhuang Q , et al. Preparation of solution-processable reduced graphene oxide/polybenzoxazole nanocomposites with improved dielectric properties. Macromolecules. 2015;48:365-372. DOI: 10.1021/ma502326v
  92. 92. Yuan B, Bao C, Song L, Hong N, Liew KM, Hu Y. Preparation of functionalized graphene oxide/polypropylene nanocomposite with significantly improved thermal stability and studies on the crystallization behavior and mechanical properties. Chemical Engineering Journal. 2014;237:411-420. DOI: 10.1016/j.cej.2013.10.030
  93. 93. Hu H, Zhang G, Xiao L, Wang H, Zhang Q , Zhao Z. Preparation and electrical conductivity of graphene/ultrahigh molecular weight polyethylene composites with a segregated structure. Carbon N Y. 2012;50:4596-4599. DOI: 10.1016/j.carbon.2012.05.045
  94. 94. Kong BS, Geng J, Jung HT. Layer-by-layer assembly of graphene and gold nanoparticles by vacuum filtration and spontaneous reduction of gold ions. Chemical Communications. 2009:2174-2176. DOI: 10.1039/b821920f
  95. 95. Hong W, Bai H, Xu Y, Yao Z, Gu Z, Shi G. Preparation of gold nanoparticle/graphene composites with controlled weight contents and their application in biosensors. Journal of Physical Chemistry C. 2010;114:1822-1826. DOI: 10.1021/jp9101724
  96. 96. Tien HW, Huang YL, Yang SY, Wang JY, Ma CCM. The production of graphene nanosheets decorated with silver nanoparticles for use in transparent, conductive films. Carbon N Y. 2011;49:1550-1560. DOI: 10.1016/j.carbon.2010.12.022
  97. 97. Qiu JD, Wang GC, Liang RP, Xia XH, Yu HW. Controllable deposition of platinum nanoparticles on graphene as an electrocatalyst for direct methanol fuel cells. Journal of Physical Chemistry C. 2011;115:15639-15645. DOI: 10.1021/jp200580u
  98. 98. Lin J, Raji ARO, Nan K, Peng Z, Yan Z, Samuel ELG, et al. Iron oxide nanoparticle and graphene nanoribbon composite as an anode material for high-performance li-ion batteries. Advanced Functional Materials. 2014;24:2044-2048. DOI: 10.1002/adfm.201303023
  99. 99. Liang Y, Wang H, Casalongue HS, Chen Z, Dai H. TiO2 Nanocrystals grown on graphene as advanced photocatalytic hybrid materials. Nano Research. 2010;3:701-705. DOI: 10.1007/s12274-010-0033-5
  100. 100. Son DI, Kwon BW, Park DH, Seo WS, Yi Y, Angadi B, et al. Emissive ZnO-graphene quantum dots for white-light-emitting diodes. Nature Nanotechnology. 2012;7:465-471. DOI: 10.1038/nnano.2012.71
  101. 101. Lin J, Peng Z, Xiang C, Ruan G, Yan Z, Natelson D, et al. Graphene nanoribbon and nanostructured SnO2 composite anodes for lithium ion batteries. ACS Nano. 2013;7:6001-6006. DOI: 10.1021/nn4016899
  102. 102. Deng S, Tjoa V, Fan HM, Tan HR, Sayle DC, Olivo M, et al. Reduced graphene oxide conjugated Cu2O nanowire mesocrystals for high-performance NO2 gas sensor. Journal of the American Chemical Society. 2012;134:4905-4917. DOI: 10.1021/ja211683m
  103. 103. Subodh MNK, Chaudhary K, Kumar G, Masram DT. Fur-imine-functionalized graphene oxide-immobilized copper oxide nanoparticle catalyst for the synthesis of xanthene derivatives. ACS Omega. 2018;3:16377-16385. DOI: 10.1021/acsomega.8b01781
  104. 104. He Y, Chen W, Li X, Zhang Z, Fu J, Zhao C, et al. Freestanding three-dimensional graphene/MnO2 composite networks as ultralight and flexible supercapacitor electrodes. ACS Nano. 2013;7:174-182. DOI: 10.1021/nn304833s
  105. 105. Zhou G, Wang DW, Yin LC, Li N, Li F, Cheng HM. Oxygen bridges between nio nanosheets and graphene for improvement of lithium storage. ACS Nano. 2012;6:3214-3223. DOI: 10.1021/nn300098m
  106. 106. Kumar G, Mogha NK, Kumar M, Subodh MDT. NiO nanocomposites/rGO as a heterogeneous catalyst for imidazole scaffolds with applications in inhibiting the DNA binding activity. Dalton Transactions. 2020;49:1963-1974. DOI: 10.1039/c9dt04416g
  107. 107. Mogha NK, Kirti S, Masram DT. La2O3/reduced graphene oxide nanocomposite: A highly efficient, reusable heterogeneous catalyst for the synthesis of biologically important bis(indolyl)methanes under solvent free conditions. Journal of Nanoscience and Nanotechnology. 2017;17:2508-2514. DOI: 10.1166/jnn.2017.13441
  108. 108. Mogha NK, Sahu V, Sharma M, Sharma RK, Masram DT. Sensitive and reliable ascorbic acid sensing by lanthanum oxide/reduced graphene oxide nanocomposite. Applied Biochemistry and Biotechnology. 2014;174:1010-1020. DOI: 10.1007/s12010-014-0986-z
  109. 109. Chen Y, Li Y, Sun D, Tian D, Zhang J, Zhu JJ. Fabrication of gold nanoparticles on bilayer graphene for glucose electrochemical biosensing. Journal of Materials Chemistry. 2011;21:7604-7611. DOI: 10.1039/c1jm10293a
  110. 110. Jain PK, Huang X, El-Sayed IH, El-Sayed MA. Noble metals on the nanoscale: Optical and photothermal properties and some applications in imaging, sensing, biology, and medicine. Accounts of Chemical Research. 2008;41:1578-1586. DOI: 10.1021/ar7002804
  111. 111. Eustis S, El-Sayed MA. Why gold nanoparticles are more precious than pretty gold: Noble metal surface plasmon resonance and its enhancement of the radiative and nonradiative properties of nanocrystals of different shapes. Chemical Society Reviews. 2006;35:209-217. DOI: 10.1039/b514191e
  112. 112. Naqvi TK, Srivastava AK, Kulkarni MM, Siddiqui AM, Dwivedi PK. Silver nanoparticles decorated reduced graphene oxide (rGO) SERS sensor for multiple analytes. Applied Surface Science. 2019;478:887-895. DOI: 10.1016/j.apsusc.2019.02.026
  113. 113. Zhang H, Hines D, Akins DL. Synthesis of a nanocomposite composed of reduced graphene oxide and gold nanoparticles. Dalton Transactions. 2014;43:2670-2675. DOI: 10.1039/c3dt52573b
  114. 114. Darabdhara G, Das MR, Singh SP, Rengan AK, Szunerits S, Boukherroub R. Ag and Au nanoparticles/reduced graphene oxide composite materials: Synthesis and application in diagnostics and therapeutics. Advances in Colloid and Interface Science. 2019;271:101991. DOI: 10.1016/j.cis.2019.101991
  115. 115. Zhou Y, Bao Q , Tang LAL, Zhong Y, Loh KP. Hydrothermal dehydration for the “green” reduction of exfoliated graphene oxide to graphene and demonstration of tunable optical limiting properties. Chemistry of Materials. 2009;21:2950-2956. DOI: 10.1021/cm9006603
  116. 116. Liu WM, Li J, Zhang HY. Reduced graphene oxide modified zinc oxide composites synergistic photocatalytic activity under visible light irradiation. Optik (Stuttg). 2020;207:163778. DOI: 10.1016/j.ijleo.2019.163778
  117. 117. Kusiak-Nejman E, Wanag A, Kapica-Kozar J, Kowalczyk Ł, Zgrzebnicki M, Tryba B, et al. Methylene blue decomposition on TiO2/reduced graphene oxide hybrid photocatalysts obtained by a two-step hydrothermal and calcination synthesis. Catalysis Today. 2019. DOI: 10.1016/j.cattod.2019.04.078
  118. 118. Frindy S, Sillanpää M. Synthesis and application of novel α-Fe2O3/graphene for visible-light enhanced photocatalytic degradation of RhB. Materials and Design. 2020;188:108461. DOI: 10.1016/j.matdes.2019.108461
  119. 119. Hu J, Chen M, Rong Q , Zhang Y, Wang H, Zhang D, et al. Formaldehyde sensing performance of reduced graphene oxide-wrapped hollow SnO2 nanospheres composites. Sensors and Actuators B: Chemical. 2020;307:127584. DOI: 10.1016/j.snb.2019.127584
  120. 120. Ren L, Huang S, Fan W, Liu T. One-step preparation of hierarchical superparamagnetic iron oxide/graphene composites via hydrothermal method. Applied Surface Science. 2011;258:1132-1138. DOI: 10.1016/j.apsusc.2011.09.049
  121. 121. Indhumathy M, Prakasam A. A one pot hydrothermal stimulated CdS-reduced graphene oxide (CdS/rGO) hybrid nanocomposite for high performance photovoltaic applications. Journal of Materials Science: Materials in Electronics. 2019;30:15444-15451. DOI: 10.1007/s10854-019-01920-x
  122. 122. Wang SX, Maimaiti H, Xu B, Awati A, Bin ZG, Dan CY. Synthesis and visible-light photocatalytic N2/H2O to ammonia of ZnS nanoparticles supported by petroleum pitch-based graphene oxide. Applied Surface Science. 2019;493:514-524. DOI: 10.1016/j.apsusc.2019.06.287
  123. 123. Zhang X, Duan L, Zhang X, Li X, Lü W. Preparation of Cu2S@rGO hybrid composites as anode materials for enhanced electrochemical properties of lithium ion battery. Journal of Alloys and Compounds. 2020;816:152539. DOI: 10.1016/j.jallcom.2019.152539
  124. 124. Hou X, Wang Z, Fan G, Ji H, Yi S, Li T, et al. Hierarchical three-dimensional MOS2/GO hybrid nanostructures for triethylamine-sensing applications with high sensitivity and selectivity. Sensors and Actuators B: Chemical. 2020;317:128236. DOI: 10.1016/j.snb.2020.128236
  125. 125. Bijani S, Martínez L, Gabás M, Dalchiele EA, Ramos-Barrado JR. Low-temperature electrodeposition of Cu2O thin films: Modulation of micro-nanostructure by modifying the applied potential and electrolytic bath pH. Journal of Physical Chemistry C. 2009;113:19482-19487. DOI: 10.1021/jp905952a
  126. 126. Zhao G, Liu G. Electrochemical deposition of gold nanoparticles on reduced graphene oxide by fast scan cyclic voltammetry for the sensitive determination of As(III). Nanomaterials. 2019;9:41. DOI: 10.3390/nano9010041
  127. 127. Azevedo VHR, da Silva JL, Stradiotto NR. Silver oxide nanoparticles in reduced graphene oxide modified electrode for amino acids electrocatalytic oxidation. Journal of Electroanalytical Chemistry. 2019;845:57-65. DOI: 10.1016/j.jelechem.2019.05.037
  128. 128. Saravanan G, Mohan S. Pt nanoparticles embedded on reduced graphite oxide with excellent electrocatalytic properties. Applied Surface Science. 2016;386:96-102. DOI: 10.1016/j.apsusc.2016.05.152
  129. 129. Wu S, Yin Z, He Q , Lu G, Zhou X, Zhang H. Electrochemical deposition of Cl-doped n-type Cu2O on reduced graphene oxide electrodes. Journal of Materials Chemistry. 2011;21:3467-3470. DOI: 10.1039/c0jm02267e
  130. 130. Myung S, Solanki A, Kim C, Park J, Kim KS, Lee KB. Graphene-encapsulated nanoparticle-based biosensor for the selective detection of cancer biomarkers. Advanced Materials. 2011;23:2221-2225. DOI: 10.1002/adma.201100014
  131. 131. Yang S, Feng X, Ivanovici S, Müllen K. Fabrication of graphene-encapsulated oxide nanoparticles: Towards high-performance anode materials for lithium storage. Angewandte Chemie, International Edition. 2010;49:8408-8411. DOI: 10.1002/anie.201003485
  132. 132. Liu J, Li Y, Li Y, Li J, Deng Z. Noncovalent DNA decorations of graphene oxide and reduced graphene oxide toward water-soluble metal-carbon hybrid nanostructures via self-assembly. Journal of Materials Chemistry. 2010;20:900-906. DOI: 10.1039/b917752c
  133. 133. Lee JK, Smith KB, Hayner CM, Kung HH. Silicon nanoparticles-graphene paper composites for Li ion battery anodes. Chemical Communications. 2010;46:2025-2027. DOI: 10.1039/b919738a
  134. 134. Feng Q , Li X, Wang J, Gaskov AM. Reduced graphene oxide (rGO) encapsulated Co3O4 composite nanofibers for highly selective ammonia sensors. Sensors and Actuators B: Chemical. 2016;222:864-870. DOI: 10.1016/j.snb.2015.09.021
  135. 135. Rajaji U, Murugan K, Chen SM, Govindasamy M, Chen TW, Lin PH, et al. Graphene oxide encapsulated 3D porous chalcopyrite (CuFeS2) nanocomposite as an emerging electrocatalyst for agro-hazardous (methyl paraoxon) detection in vegetables. Composites. Part B, Engineering. 2019;160:268-276. DOI: 10.1016/j.compositesb.2018.10.042
  136. 136. Myung S, Yin PT, Kim C, Park J, Solanki A, Reyes PI, et al. Label-free polypeptide-based enzyme detection using a graphene-nanoparticle hybrid sensor. Advanced Materials. 2012;24:6081-6087. DOI: 10.1002/adma.201202961
  137. 137. Zhou M, Cai T, Pu F, Chen H, Wang Z, Zhang H, et al. Graphene/carbon-coated si nanoparticle hybrids as high-performance anode materials for li-ion batteries. ACS Applied Materials & Interfaces. 2013;5:3449-3455. DOI: 10.1021/am400521n
  138. 138. Tanaka Y, Shimizu K, Akashi K, Onda K, Uesugi Y, Ishijima T, et al. High rate synthesis of graphene-encapsulated silicon nanoparticles using pulse-modulated induction thermal plasmas with intermittent feedstock feeding. Japanese Journal of Applied Physics. 2020;59:SHHE07. DOI: 10.35848/1347-4065/ab71db
  139. 139. Ronkainen NJ, Halsall HB, Heineman WR. Electrochemical biosensors. Chemical Society Reviews. 2010;39:1747-1763. DOI: 10.1039/b714449k
  140. 140. Pilas J, Selmer T, Keusgen M, Schöning MJ. Screen-printed carbon electrodes modified with graphene oxide for the design of a reagent-free NAD+-dependent biosensor array. Analytical Chemistry. 2019;91:15293-15299. DOI: 10.1021/acs.analchem.9b04481
  141. 141. Xu M, Shen Y, Wang L, Gong C, Chen S. A novel H2O2 biosensor based on the composite of MP-11 encapasulated in PCN-333 (Al)-graphene oxide. International Journal of Electrochemical Science. 2017;12:10390-10401. DOI: 10.20964/2017.11.45
  142. 142. López Marzo AM, Mayorga-Martinez CC, Pumera M. 3D-printed graphene direct electron transfer enzyme biosensors. Biosensors & Bioelectronics. 2020;151:111980. DOI: 10.1016/j.bios.2019.111980
  143. 143. Hashim HS, Fen YW, Omar NAS, Daniyal WMEMM, Saleviter S, Abdullah J. Structural, optical and potential sensing properties of tyrosinase immobilized graphene oxide thin film on gold surface. Optik (Stuttg). 2020;212:164786. DOI: 10.1016/j.ijleo.2020.164786
  144. 144. Chou JC, Wu CY, Liao YH, Lai CH, Yan SJ, Wu YX, et al. Enzymatic urea sensor based on graphene oxide/titanium dioxide films modified by urease-magnetic beads. IEEE Transactions on Nanotechnology. 2019;18:336-344. DOI: 10.1109/TNANO.2019.2907225
  145. 145. Fenoy GE, Marmisollé WA, Azzaroni O, Knoll W. Acetylcholine biosensor based on the electrochemical functionalization of graphene field-effect transistors. Biosensors & Bioelectronics. 2020;148:111796. DOI: 10.1016/j.bios.2019.111796
  146. 146. Krishnan SK, Singh E, Singh P, Meyyappan M, Nalwa HS. A review on graphene-based nanocomposites for electrochemical and fluorescent biosensors. RSC Advances. 2019;9:8778-8781. DOI: 10.1039/c8ra09577a
  147. 147. Yao Y, Wang G, Chu G, An X, Guo Y, Sun X. The development of a novel biosensor based on gold nanocages/graphene oxide-chitosan modified acetylcholinesterase for organophosphorus pesticide detection. New Journal of Chemistry. 2019;43:13816-13826. DOI: 10.1039/c9nj02556a
  148. 148. Bao J, Huang T, Wang Z, Yang H, Geng X, Xu G, et al. 3D graphene/copper oxide nano-flowers based acetylcholinesterase biosensor for sensitive detection of organophosphate pesticides. Sensors and Actuators B: Chemical. 2019;279:95-101. DOI: 10.1016/j.snb.2018.09.118
  149. 149. Zhang J, Wang B, Li Y, Shu W, Hu H, Yang L. An acetylcholinesterase biosensor with high stability and sensitivity based on silver nanowire-graphene-TiO2 for the detection of organophosphate pesticides. RSC Advances. 2019;9:25248-25256. DOI: 10.1039/c9ra02140j
  150. 150. Zhang P, Sun T, Rong S, Zeng D, Yu H, Zhang Z, et al. A sensitive amperometric AChE-biosensor for organophosphate pesticides detection based on conjugated polymer and Ag-rGO-NH2 nanocomposite. Bioelectrochemistry. 2019;127:163-170. DOI: 10.1016/j.bioelechem.2019.02.003
  151. 151. Mogha NK, Sahu V, Sharma M, Sharma RK, Masram DT. Biocompatible ZrO2- reduced graphene oxide immobilized AChE biosensor for chlorpyrifos detection. Materials and Design. 2016;111:312-320. DOI: 10.1016/j.matdes.2016.09.019
  152. 152. Aghaie A, Khanmohammadi A, Hajian A, Schmid U, Bagheri H. Nonenzymatic electrochemical determination of paraoxon ethyl in water and fruits by graphene-based NiFe bimetallic phosphosulfide nanocomposite as a superior sensing layer. Food Analytical Methods. 2019;12:1545-1555. DOI: 10.1007/s12161-019-01486-8
  153. 153. Hondred JA, Medintz IL, Claussen JC. Enhanced electrochemical biosensor and supercapacitor with 3D porous architectured graphene via salt impregnated inkjet maskless lithography. Nanoscale Horizons. 2019;4:735-746. DOI: 10.1039/c8nh00377g
  154. 154. Dong P, Jiang B, Zheng J. A novel acetylcholinesterase biosensor based on gold nanoparticles obtained by electroless plating on three-dimensional graphene for detecting organophosphorus pesticides in water and vegetable samples. Analytical Methods. 2019;11:2428-2434. DOI: 10.1039/c9ay00549h
  155. 155. Yang L, Wang G, Liu Y. An acetylcholinesterase biosensor based on platinum nanoparticles- carboxylic graphene-nafion-modified electrode for detection of pesticides. Analytical Biochemistry. 2013;437:144-149. DOI: 10.1016/j.ab.2013.03.004
  156. 156. Yang L, Wang G, Liu Y, Wang M. Development of a biosensor based on immobilization of acetylcholinesterase on NiO nanoparticles–carboxylic graphene–nafion modified electrode for detection of pesticides. Talanta. 2013;113:135-141. DOI: 10.1016/j.talanta.2013.03.025
  157. 157. Yang L, Zhou Q , Wang G, Yang Y. Acetylcholinesterase biosensor based on SnO2 nanoparticles-carboxylic graphene-nafion modified electrode for detection of pesticides. Biosensors & Bioelectronics. 2013;49:25-31. DOI: 10.1016/j.bios.2013.04.037
  158. 158. Jeyapragasam T, Saraswathi R, Chen SM, Chen TW. Acetylcholinesterase biosensor for the detection of methyl parathion at an electrochemically reduced graphene oxide-nafion modified glassy carbon electrode. International Journal of Electrochemical Science. 2017;12:4768-4781. DOI: 10.20964/2017.06.77
  159. 159. Tan X, Hu Q , Wu J, Li X, Li P, Yu H, et al. Electrochemical sensor based on molecularly imprinted polymer reduced graphene oxide and gold nanoparticles modified electrode for detection of carbofuran. Sensors and Actuators B: Chemical. 2015;220:216-221. DOI: 10.1016/j.snb.2015.05.048
  160. 160. Zhang M, Zhao HT, Xie TJ, Yang X, Dong AJ, Zhang H, et al. Molecularly imprinted polymer on graphene surface for selective and sensitive electrochemical sensing imidacloprid. Sensors and Actuators B: Chemical. 2017;252:991-1002. DOI: 10.1016/j.snb.2017.04.159
  161. 161. Chao M, Chen M. Electrochemical determination of Phoxim in food samples employing a Graphene-modified glassy carbon electrode. Food Analytical Methods. 2014;7:1729-1736. DOI: 10.1007/s12161-014-9813-y
  162. 162. Wu L, Lei W, Han Z, Zhang Y, Xia M, Hao Q. A novel non-enzyme amperometric platform based on poly(3-methylthiophene)/nitrogen doped graphene modified electrode for determination of trace amounts of pesticide phoxim. Sensors and Actuators B: Chemical. 2015;206:495-501. DOI: 10.1016/j.snb.2014.09.098
  163. 163. Zheng Y, Wang A, Lin H, Fu L, Cai W. A sensitive electrochemical sensor for direct phoxim detection based on an electrodeposited reduced graphene oxide-gold nanocomposite. RSC Advances. 2015;5:15425-15430. DOI: 10.1039/c4ra15872e
  164. 164. Karimian N, Fakhri H, Amidi S, Hajian A, Arduini F, Bagheri H. A novel sensing layer based on metal-organic framework UiO-66 modified with TiO2-graphene oxide: Application to rapid, sensitive and simultaneous determination of paraoxon and chlorpyrifos. New Journal of Chemistry. 2019;43:2600-2609. DOI: 10.1039/c8nj06208k
  165. 165. Liu Q , Fei A, Huan J, Mao H, Wang K. Effective amperometric biosensor for carbaryl detection based on covalent immobilization acetylcholinesterase on multiwall carbon nanotubes/graphene oxide nanoribbons nanostructure. Journal of Electroanalytical Chemistry. 2015;740:8-13. DOI: 10.1016/j.jelechem.2014.12.037
  166. 166. Liu Y, Wang G, Li C, Zhou Q , Wang M, Yang L. A novel acetylcholinesterase biosensor based on carboxylic graphene coated with silver nanoparticles for pesticide detection. Materials Science and Engineering: C. 2014;35:253-258. DOI: 10.1016/j.msec.2013.10.036
  167. 167. Wang G, Tan X, Zhou Q , Liu Y, Wang M, Yang L. Synthesis of highly dispersed zinc oxide nanoparticles on carboxylic graphene for development a sensitive acetylcholinesterase biosensor. Sensors and Actuators B: Chemical. 2014;190:730-736. DOI: 10.1016/j.snb.2013.09.042
  168. 168. Zheng Y, Liu Z, Jing Y, Li J, Zhan H. An acetylcholinesterase biosensor based on ionic liquid functionalized graphene-gelatin-modified electrode for sensitive detection of pesticides. Sensors and Actuators B: Chemical. 2015;210:389-397. DOI: 10.1016/j.snb.2015.01.003
  169. 169. Zhang L, Zhang A, Du D, Lin Y. Biosensor based on Prussian blue nanocubes/reduced graphene oxide nanocomposite for detection of organophosphorus pesticides. Nanoscale. 2012;4:4674-4679. DOI: 10.1039/c2nr30976a
  170. 170. Zhao H, Ji X, Wang B, Wang N, Li X, Ni R, et al. An ultra-sensitive acetylcholinesterase biosensor based on reduced graphene oxide-Au nanoparticles-β-cyclodextrin/Prussian blue-chitosan nanocomposites for organophosphorus pesticides detection. Biosensors & Bioelectronics. 2015;65:23-30. DOI: 10.1016/j.bios.2014.10.007
  171. 171. Ensafi AA, Noroozi R, Zandi-Atashbar N, Rezaei B. Cerium (IV) oxide decorated on reduced graphene oxide, a selective and sensitive electrochemical sensor for fenitrothion determination. Sensors actuators B Chem. 2017;245:980-987. DOI: 10.1016/j.snb.2017.01.186
  172. 172. Shams N, Lim HN, Hajian R, Yusof NA, Abdullah J, Sulaiman Y, et al. A promising electrochemical sensor based on Au nanoparticles decorated reduced graphene oxide for selective detection of herbicide diuron in natural waters. Journal of Applied Electrochemistry. 2016;46:655-666. DOI: 10.1007/s10800-016-0950-4
  173. 173. Yang Y, Asiri AM, Du D, Lin Y. Acetylcholinesterase biosensor based on a gold nanoparticle-polypyrrole-reduced graphene oxide nanocomposite modified electrode for the amperometric detection of organophosphorus pesticides. Analyst. 2014;139:3055-3060. DOI: 10.1039/c4an00068d
  174. 174. Li Y, Zhang Y, Han G, Xiao Y, Li M, Zhou W. An acetylcholinesterase biosensor based on graphene/polyaniline composite film for detection of pesticides. Chinese Journal of Chemistry. 2016;34:82-88. DOI: 10.1002/cjoc.201500747
  175. 175. Li Y, Shi L, Han G, Xiao Y, Zhou W. Electrochemical biosensing of carbaryl based on acetylcholinesterase immobilized onto electrochemically inducing porous graphene oxide network. Sensors and Actuators B: Chemical. 2017;238:945-953. DOI: 10.1016/j.snb.2016.07.152
  176. 176. Bao J, Hou C, Chen M, Li J, Huo D, Yang M, et al. Plant esterase-chitosan/gold nanoparticles-graphene nanosheet composite-based biosensor for the ultrasensitive detection of organophosphate pesticides. Journal of Agricultural and Food Chemistry. 2015;63:10319-10326. DOI: 10.1021/acs.jafc.5b03971

Written By

Navin Kumar Mogha

Submitted: March 27th, 2020 Reviewed: August 3rd, 2020 Published: August 26th, 2020