Nanodiamonds and Its Applications

Abstract

One of the most futuristic and unique carbon materials which is formed from detonation method is nanodiamond. Nanodiamonds below 100 nm size popularly known as attracting crystal or ultrafine dispersed diamonds (UDD) have exceptional optical, mechanical, and biological properties. The structure of nanodiamonds resembles diamond structure. Due to the peerless properties, Nanodiamonds make itself potential to several applications. Nanodiamonds became demand in medical field. Currently, Nanodiamonds acquired substantial recognition in all areas particularly nanomedicine. This chapter opens a detailed review about the evolution of Nanodiamonds, their properties, applications and future perspectives in research. Researchers are still doing their studies on nanodiamonds to make an effective tool in various sectors.

1. Introduction

The narration of discovery of Nanodiamonds is highly interpreted by the inventor V.V. Danilenko. Over a period of two decades, Nanodiamonds accidently produced three times by Russian scientists through explosion. Initially, Nanodiamonds developed as single diamond particles (having diameter 4–5 nm). Later on Nanodiamonds used as an alternative for semiconductor quantum dots for biomedical imaging. Subsequently, Nanodiamonds used as magnetic sensors, composites, biomolecules and drugs, surface chemistry, other areas in medicines also. At the end of twentieth century, Nanodiamonds or ultrafine-dispersed diamonds (UDD) originated through an ignition of larger masses [1]. Nanotubes, fullerene, 3D, 2D, 1D nanosheets composed of carbon materials captivate young researchers toward wide range of applications. Recently Nanodiamonds (NDs) which is also carbon based material fascinating the world of science. Nanodiamonds is basically composed of carbon having sp³ hybridization possess elevated chemical and physical properties [2].

Nanodiamonds can be produced through different process namely diamond microcrystals, high pressure high temperature (HPHT), chemical vapor deposition (CVD), laser ablation, detonation technique, autoclave synthesis, electron irradiation of carbon onions, chlorination of carbides, and ultrasound cavitation. Laser ablation, detonation technique, and high energy ball milling of diamond by HPHT methods were using economically. We require large quantities of Nanodiamonds for research and application level studies. In this chapter we are discussing about Nanodiamonds, production of Nanodiamonds, its structure and properties, applications in major areas.

2. Nanodiamonds

2.1 Structure of the Nanodiamond

Diamonds are known as the hardest material and transparent electrical insulator. The structure can be studied in detail by separating the complex structure of Nanodiamond into three ways namely core, an intermediate and the surface layer. Nanodiamonds consists of carbon atoms which are sp³ hybridized and all form distinctive large crystals. The core of the Nanodiamonds (size approximately range from 2 to 3 nm) looks similar to the diamond structure (sp³ C-atoms), but the surface be like graphite (sp² C-atoms) having hanging bonds edges with functional groups. The inner core holds about major percentage of carbon. The middle sheet which is usually examined as nonhomogeneous translational carbon shell (lesser than 1 nm width). The innermost facet of the shell is detached with onion like carbon rings and the coating composed of graphitic monolayer carbon. The most frequent Nanodiamond outer layer models are (1) a layer of sp² carbon atoms which are amorphous in nature and (2) a sheet which is graphitic sp² nature in the form of fullerene, known as “Bucky Diamond” (Figure 1) [3].

Figure 1.

Structure of the nanodiamond.

The most distinguishable feature of the Nanodiamond is its core which is distinct from other carbon materials. The high refractive index of the core creates Nanodiamonds useful in polymer coatings and sunscreen as it robust light scattering. Diamonds are non-conducting material with an optical bandgap of 5.5 eV which shows lucidity from ultraviolet to infrared regions. Still their optical properties can be changed by instituting the dopants or imperfections. Chemical elements like (a) boron introduced as dopant will change its lattice thereby boost electrical conductivity applicable in thin film electronics, (b) nitrogen as a dopant increases the vacancy site inside the lattice improve the fluorescence properties and also used in quantum computing, (c) tritium an allotrope of hydrogen introduced in diamond lattice is applicable in biodistribution application and biolabelling [3].

2.2 Properties of Nanodiamonds

The properties of the nanomaterials depend on their size. In Nanodiamonds also, depending on the size the properties vary. When the size of the cluster changes, the discrete electronic energy levels become visible at the edges of the bands. As a result the band gap increases as a consequence of separation of frontier orbitals’ energy which follows the quantum confinement effect. Quantum confinement will occur when the diameter of the Nanodiamond becomes trivial say 2–3 nm thereby structure variation possible (Bucky diamonds or fullerene structure). When the diameter of the cluster of Nanodiamond increases, the surface carbon atoms reduces and hence the characteristics of the Nanodiamonds improves. During the development of the dangling bonds on the outer layer of the Nanodiamond accords the stabilization of the material. The surface terminations have influence on the stabilization of carbon compounds drained the center of attention to several studies. For good functionalization and surface termination, the surface of the Nanodiamond can be enhanced with the organic functional groups. These groups can be easily identified by FTIR studies.

The surface functionalization and size studies make Nanodiamonds a potential material in drug delivery, biomolecule conjugation, uploading sorbent molecules, catalytic application and polymer matrix. At room temperature, the nitrogen vacancies in Nanodiamonds provide red emission spectrum and visible emission spectrum. Nanodiamonds also favors the fluorescent properties empowers the nanoelectrometry, nano-magnetometry, etc. Nanodiamonds can tune their magnetic and optical properties by adjusting the surface chemistry of the material.

Nanodiamonds have high hardness, thermal conductivity, biocompatibility, Young’s modulus, chemical stability, high electrical resistivity, resilience to a dictatorial setting. Nanodiamonds are known for their exceptional mechanical and optical qualities, as well as their large surface areas and tunable surface topologies. They’re also nontoxic, making them ideal for biological applications [4]. The most featured properties are fluorescence and biocompatibility which are depicted below.

2.2.1 Fluorescence

Introducing a nitrogen vacancy in the lattice is known as NV center or nitrogen vacancy center which dominance the fluorescence properties in Nanodiamonds. A nitrogen vacancy is created by bombarding elevated particles and vacuum annealing between 600 and 800°C. During the irradiation vacancy will form at the centers and during annealing the vacancies will emigrated and confined by the nitrogen atoms. During this process two types of vacancy center forms namely negatively charged nitrogen vacancy and neutral nitrogen vacancy center. In addition, both vacancy centers will have distinct emission spectra. Among these, peculiarity falls into negatively charged nitrogen vacancy center as it has a spin S = 1 ground level results in spin polarization through optical pumping and controlled by electromagnetic resonance. The spin coherence time for this vacancy center is quite long. Nitrogen vacancy became highly capable for bioimaging, magnetic sensing, and fluorescence resonance high energy transfer.

Under high temperature and pressure synthesis, blazing photo luminescent Nanodiamonds can be produced in materials later squeeze down to nano sized particles. The concentration of NV imperfections developed from electron irradiation, does not depend upon the size of the Nanocrystals but they can decrease the size of the Nanodiamonds as the electrons might get pin down at the surface.

Recent studies picturizes the interest on imaging applications from nitrogen vacancy centers. In a bare Nanodiamond (~5 nm) developed from trinitrotoluene (TNT) and hexagon precursor, the intermittent luminescence is emanated from nitrogen vacancy center is reported [5]. Nanodiamonds which are considered larger (>20 nm) grown from TNT, graphite precursors show the presence of stable luminescence [6]. When fluorophores are linked or adsorbed with Nanodiamond fluorescent particles are formed. This fluorophore linked Nanodiamond can pass through different cell chambers (variable pH) without changing the cell feasibility [7]. When octadecylamine is covalently linked with carboxylic acid on a nanodiamond surface a bright blue fluorescent Nanodiamond is produced and reported [8].

2.2.2 Biocompatibility of Nanodiamonds

Diamond is known as a non-toxic material. The toxicity of Nanodiamonds is investigated through in-vivo as well as in-vitro studies. Both studies scrutinize the characteristics of a cell feasibility, cell mechanism and behavior. Through in-vitro cytotoxicity, carbon nanomaterials like nanotubes (single as well as multi walled), carbon black the toxicity were studied. They also examined with Nanodiamonds. The studies concluded the carboxyl nanotubes are more toxic rather than Nanodiamonds as carboxyl Nanodiamonds shows relatively less toxicity [9].

In human beings, in-vivo toxicity is deeply developed with the help of animal models. By the detonation techniques Nanodiamonds are formed in a powder form (low density) which will be easily spread in the environment. The respiratory tracking is much more efficient in human beings to study the toxicity. To know more about the tracking of the toxicity intratracheal instillation can be selected. Nanodiamonds controlled by intratracheal instillation is examined by biomedical measurement is diffused into spleen, liver, heart and bones [10]. The interaction of nanomaterials introducing to living system is monitored through adsorption, distribution, metabolism and excretion process (ADME process). As nanomaterials are very small, it is arduous to spot the interaction through a microscopic method. One of the most promising technique for good reliability, high sensitivity, and easy detection is radionuclide tracer technique. Gallium, Indium, Copper are used for labeling carbon nanoparticles. Rhenium Nanodiamonds are appropriate Nanodiamonds used for experimental research.

3. Synthesis of Nanodiamonds

Nanodiamonds can be synthesized using different techniques and also artificial synthesis also available nowadays. Diamonds are allotropes of carbon. Diamonds are natural and found in the Earth’s mantle having high temperature and pressure. Once a diamond phase is formed, there is a chance to move to graphitic phase. In order to prevent this phase, it has to undergo a high energy barrier phase transition that will overcome the change of sp² to sp³ which makes diamond in a metastable phase. Several techniques for the synthesis of Nanodiamonds are depicting here. The most common methods are CVD, detonation technique, laser ablation and HPHT methods (Figure 2).

Figure 2.

Synthesis of Nanodiamonds.

3.1 Chemical vapor deposition technique (CVD)

This method is among the most used thin film coating methods, and it was utilized to make nanocrystalline diamond layer. More specifically, carbon atoms are deposited during the breakdown of a gaseous mixture and carbon-containing molecules, most commonly methane CH₄ (excess hydrogen). The gas phase decomposes into radicals like H• and CH3•, which are required for diamond formation, via a heated filament or microwave plasma. A continuous ND film is created on a membrane, usually a thin layer of silicon covered with a μm powder that functions as a nanodiamond deposition seed. Depending on the relative concentration of CH₄/H₂, the size of the coils wrapping the film ranges from 10 microns to a few nanometers.

Microcrystalline diamonds are formed by a low concentration of CH₄, while a large quantity of CH₄/H₂ lowers particle size to the order of 10 of nm at 15% CH₄/H₂. After the hydrogen is absorbed by H• radicals, the carbon atoms on topmost of the diamond seeds are left with their bonds dangling. The CH₃ molecules are then used to fill these bonds. New carbon can be caught together and finally bound in a diamond chains when this process occurs in two nearby regions [11].

3.2 Detonation technique

The most popular method of producing high dosages of ND is detonation synthesis, which involves bursting an explosion mix of substances composed of in a metallic chamber under a mixture of nitrogen, water and carbon dioxide. The diamond fragments effect is afterwards recorded in the chambers [12]. Explosive molecules serve as a carbon supply while also providing energy through fusion method. The following are the several stages of detonation synthesis:

1. Explosions cause panic waves.

2. The decomposition of an explosive substance.

3. Temperature and pressure build rapidly in the room made up of steel to reach point A, called as C-J point (Chapman-Jouguet point).

4. Blasting products begin to increase as pressure and temperature decrease.

5. Carbon nanocluster formation.

6. As crystal growth proceeds, the temperature and pressure drop lower than point C-J, resulting in the generation of liquid nanodroplets from the synthesis of carbon nanoclusters.

7. Assembled Nanodiamonds are gathered from the room’s floor and walls.

A reduction in pressure under the diamond-graphite measuring line can affect diamond development through graphite production, hence precise control of room pressure is necessary during the detonation process. The diamond shaft is the result of the blasting strategy, which is made up of 75% NDs (sized 4–5 nm) and the rest of carbon or fossil fuels. Only explosive NDs (length 3.5–6 nm) have already been widely sold among the many forms of UNCDs. Different cooling media, the blasting method produces a carbon production of 4–10% of the explosives weight. The blasting procedure begins with the use of a connection. The complex is the source of many metallic contaminants found in the blast.

The room’s walls are covered in dirt (including such metal and other metals). The diamond powder that results is made up of NDs with a mean size of 4–5 nm. These diamonds nanoparticles are commonly arranged in clusters of a few hundreds of nanometers to micrometers in size. The nucleus of the sp³ carbon atom is put together in a three dimensional cubic lattice in each diamond particle, which explains the NDs’ special properties. Contaminants could be found (i) within the ND aggregates or (ii) on the ND’s exterior surface. In many of their applications, disassembling the ND levels is required to eliminate any trapped contaminants. Exploding ND combos with random explosives should be the focus of future research. Artificial explosives are used to clarify the assembling method and certify effective headed over the ND particle sizes that result. Explosive NDs with a magnitude of 2.8 nm are produced by using explosives particles (as thin as 40 nm) [13].

3.3 HPHT and high energy ball milling

HPHT is a really appealing method of preserving ND fluorescent Nanodiamonds through electron radiation and subsequent high pressure high temperature microdiamond integration. The incorporation of irradiation and removal of mature HPHT diamonds for the creation of NV center in the diamond lattice are the two primary processes in this approach. The N₂ melts the molten metal in the HPHT reactor and is then injected into the diamond for subsequent crystal formation. For thermos-kinetic reasons, the changed atoms of N₂ remain isolated inside the diamond crystal and are bonded to neighboring atoms in a diamond sequence.

Strong particles drive carbon atoms out of their regular lattice positions upon irradiation by elevated fragments such as neutrons, ions, photons or electrons, creating voids (V) in the diamond line. Annealing, which is usually done at 800°C below vacuum, aids in the transferring of spaces to N₂ atoms, resulting in the formation of N-vacancy centers. By choosing the right time and acceleration separator, separated nanodiamond sizes created for the HPHT technique via ultracentrifugation can be modified (from 4 to 25 nm). Using nitrogen-rich type Ib diamond powders, it is able to enhance the percentage of N-void centers in Nanodiamonds. As a result of decreased spin contamination within and surrounding the nanocrystal, the HPHT technique can create NDs of ultra-small fluorescent NDs with substantially longer durations of infidelity [14].

3.4 Laser ablation (LA)

With the invention of the ruby laser, the era of laser ablation commenced. In 1987, employing rising pulsing laser beams of water interfaces, to mix nanoparticles (iron oxide) LA was utilized. PLAL (Pulsed laser ablation in liquids) is quickly becoming one of the most popular ways to test pure liquids. Carbon powder is used to physically generate nanodiamonds in areas of contact with solids, liquids, or solids. The PLAL approach merges the advantages of pulse laser deposition with soft chemical lines to generate nanoparticles in the nature of stable colloidal suspensions. This approach entails the laser treatment of an object immersed in a liquid (either one solitary piece of material or crushed powder) (e.g., ether, ethanol, acetone and its compounds). It can combine plasma expansion and contraction with the delivery of specific conditions (such as pressure and temperature) via atomic fluids and liquids. The strength of the laser generated on the target surface is usually greater than 108 W/cm², resulting in the target object being released and evaporation. In comparison to carbon wafers or crystal graphite wafers, microcrystalline graphite is often favored as a target. Plasma plume sealing happens after laser plume collision and consequent coagulation cooling to facilitate the production of crystalline nanodiamond. Shock wave and extinguishing operations can be employed to provide suitable conditions for nanodiamond production. The features of effect NDs can be altered by a number of factors, including (a) laser uncontrollable compulsion, laser intensity, and excitation wavelength; (b) solvent; and (c) system temperature and pressure [15]. PLAL is a method that has the potential to be cost-effective. The capillary influence of the curvature of a nanoscale crystalline nucleus on the nucleation and development of nanocrystals is explained using a kinetic way of theory [16].

3.5 Nanodiamond purification method

Nanodiamond integration frequently includes performance and after process procedures designed at purification residues. To deal with two of the most prevalent and most common pollutants, some types of carbon (particularly graphitic) and associated metals and oxides, a number of approaches have been devised. The overall purpose of carbon emissions refining is to discharge selective oxidation by characterized sp² carbon reactivity in comparison to sp³ carbon in the diamond phase. Sustaining a maximum temperature of 400–430°C was used to select sp² carbon [17]. In the situation of PLAL NDs, where metal contamination is avoided but the fraction of sp² carbon is so high that it becomes a main reaction product, this approach provides a simple and effective solution. The most extensively utilized processes are liquid-phase oxidation reactions. Strong acids are typically used in these processes, which have the additional benefit of removing certain metal-based contaminants. Perchloric acid, concentrated nitric acid, sulfuric acid, hydrochloric acid coupled with nitric acid, and hydrogen fluoride are some examples. Because these therapies demand temperatures between 80 and 200°C, additional equipment is required, adding to the complexity and cost. However, particularly in detonation methods, when metal-based contaminants are included in substantial levels, this is important due to the equipment used in such processes, such as metal blasting rooms [18].

4. Applications of Nanodiamonds

The controlled explosive detonation of carbon-containing explosives is used to produce diamond soot on a wide scale. Manufacturers of ND preludes are actively centering on cost cutting of producing ND sediments by repurposing obsolete devices. There are several methods for producing ND particles with a high sp³ content from Nanodiamond fragment. These integrate acid treatment of selected sp² carbon oxidation in the exploding diamond assistance and detonation release of Nanodiamond sediment in high amount of oxygen environment. In the recent several years, there has been a surge in the use of NDs. The amount of Nanodiamond combinations (e.g., Nanodiamond with graphene, Nanodiamond with polymer, Nanodiamond with metal) confirmed to contain several alluring features such as magnified strength, resistance influence, and heat resistance is particularly impressive.

4.1 Photovoltaic devices

Nanodiamonds compounds have received notable observation in DSSCs (dye-sensitive solar cells). A spectral sensitivity of diamond areas with natural dyes containing-photocurrent of ca. 120 nA/cm² under visible light is being reported [19]. The link between the diamond (electron donor) and receiver levels was created using oligothiophene and Suzuki (complete). In addition, photocurrent hire of around 4–6 mA/cm² was measured in boron-doped NDs using the same arrangement. Polymer dye-functionalized polycrystalline B-doped Nanodiamonds provide a high density of the current image when used as electrodes in dye sensitized solar cells in a liquid electrolyte solution [20]. The photovoltaic devices which are based on B-doped diamonds shows good current density and open circuit voltage thereby indicating that Nanodiamonds might be used as solar photo-electrodes. Utilizing NDs as optical scatterers in DSSCs enhanced performance significantly at a greater current density. Furthermore, power conversion efficiency has also increased while comparing with pure TiO₂ photo-electrodes [21]. As a result, diamond-based composite materials could be utilized in flat panel displays and solar utensils (Figure 3).

Figure 3.

Applications of Nanodiamonds.

4.2 Thin film electronics

Because of their unusual physical and mechanical features, ND-reinforced polymers have recently received a lot of attention. A translucent and bendable fluorinated polymer nanohybrid film with high heat resistance and improved mechanical properties was created using a dissipated ND organo-modified Nanodiamond refill. The existence of tiny lamellae in a fluorinated polymers resulted in the formation of a dense amorphous phase with high brightness. The outer layer of NDs must be covered to ensure structural stability. Electrostatic interactions involving Nanodiamonds and the membrane, regardless of the substrate’s structure and shape, are critical for ND replication and similarity. Detonation ND seeds are a good alternative to silicon or glass substrates for CVD diamond films [22]. The effects of bulk ND particles on polymer nano- and micro-fibers had studied [23]. Comparing with polyamide 11, the electrospun nanofibers with elevated Nanodiamonds on these substances (polymer) was assembled into tiny layers results in high mechanical properties. Furthermore, lens in Nanodiamond films are a key matter that cause unacceptable degeneration of Nanodiamond film structures like thermal conductivity, bright light, Young’s modulus, and piezoresistivity [24]. Carbon/carbide interlayer formation, substrate scratch, improved nucleation bias, and electrostatic seeds carrying ND colloid have all been developed for the manufacture of ND films without pinhole ultra-thin ND. Among all of these strategies, the implantation method has demonstrated considerable benefits regarding delivering homogeneous high density and nucleation sites via optimized electrostatic interactions between ND particles and substrate. In a wide range of situations, these reflective coatings even provide UV protection and scratch resistance, particularly in systems which need a unique mix of dielectric, thermal, and mechanical qualities. Based on layer and layer production procedures, detonation Nanodiamond dispersions and ployvinylalcohol were utilized as 3D printing novels for materials of various shapes. In the consumer electronics business, this three dimensional printing of ND-based polymer compounds leaves the panel open to the creation of tiny solids with complicated forms [25]. Due to the high N-incorporated UNCD feature, ND films additionally include field output elements (i.e., 10 V/mm open field) in addition to these uses. The goal of the research was to pinpoint the precise position (e.g., grain characteristics) of field retrieval in the same nanodiamond environment. The prerequisite for a high temperature of substrate growth (>800°C) in order to support the n-doping type process is a fundamental restriction of these ND films [26].

4.3 Energy storage devices

The popularity for relatively speaking high power and energy density values, as well as good cycle life, has grown massively in the field of energy storage to assist the fast expanding businesses of mobile and adaptable digital equipment, e-mobility, and machine tools, and also the growing economies of power grid applications. Due to their flexible applicability, conductivity, surface area, aspect rations, stability, electrochemical potential windows are relatively high in Nanodiamonds which will make this material a desirable choice in energy storage systems. The advancement of ND-based electrode materials has been hastened by the discovery of effective methods for growth of Nanodiamond on conducting layers under sub-atmospheric environments. The Nanodiamond’s nature can be changed by using an acceptor type doping substance (boron). Boron-doped diamond electrodes are extremely stable over a long range of operating potentials, even in water. HPHT, PECVD, and ion-implantation procedures are commonly used to dope NDs, with PECVD being the favored method for device construction as it allows both n and p-type Nanodiamonds to manage impurity concentrations [27]. In comparison with carbon containing electrodes or metals, Nanodiamond electrodes (conducting) doped substantially with boron have several interesting properties. Moreover, oxidized Nanodiamond electrodes has a higher capacitive current than hydrogen terminated Nanodiamond electrodes [28]. Surface functionalization of NDs can also be used to boost the ion-storage capacity of Nanodiamond-based electrodes by introducing extra pseudo-capacitive processes [29]. Different techniques, like as plasma and electrochemical treatments, can be used to terminate the surface of NDs with H₂, O₂, or OH groups, allowing for adjustable aqueous and due to the hydrophobic water sorption in anti-adherent scalpels and self-cleaning protective coatings [30]. In other words, the electrical characteristics of ND/electrolyte interfaces can be changed by aligning the energies of interaction levels properly. As a result, NDs have been used in energy-related applications as electrodes.

4.4 Electrochemical sensors

Recently, research has focused on the utilization of NDs to construct new electrochemical nerves for applications like as drug detection, gas monitoring, genetic sequence diagnostics, etc. The high level of electrochemical reaction accuracy, photo-stability and resolution is one of the most important parameters in any sensory system. NDs are a good choice for the sensitivity of electrochemicals because of have unique features, such as durability, chemical resistance, biocompatibility, spin break, fluorescence, and catalytic structures [31]. Different conversion approaches have been developed to improve the sensory function of NDs, including turning NDs into self-assembled monolayers, oxygen plasmas, liquid chemical procedures, metal catalysis and so on. Modified NDs provide optimal melting, as well as special binding to targeted sensory analysts. Using square-wave voltammetry, a sensor (electrochemical) based on scattered Nanodiamonds with glassy carbon electrode (GCE) was reported on pyrazinamide (PZA) sensors [32]. In a typical way, carbon black nanoparticles modified-NDs are constructed to monitor based electrochemical transmitter using cyclic voltammetry, which produces a dopamine sensor with a detection limit of 0.06 mM [33].

4.5 Drug delivery

Biocompatibility, the capacity to hold a wide scope of treatments, water dissipation, and reliability are all requirements for a drug delivery platform. It is also vital to consider the possibility of tailored therapy, which might be used in conjunction with images. A combination of Nanodiamond with Duxorubin (drug used in cancer treatment) were now used for the treatment in lung cancer, breast cancer, and also it reduced the circulation half time of Nanodiamond Duxorubin complexes [34].

Nanodiamonds are covered with polyethylenimine 800 (PEI800), which has been researched for delivering nucleic acids in addition to delivering tiny molecules. These studies indicated a 70-fold improvement in GFP plasmid transfection efficiency while keeping PEI800’s minimal maintenance hazardous properties [35]. In body circumstances, the administration of ND-PEI800 of siRNA suppressing GFP expression was more efficient than lipofectamine (a widely utilized delivery platform). Other loads have been delivered, including combinations of medicines, proteins, tiny molecules in acidic conditions (common in tumors), and cancer-specific siRNA. Although nanodiamonds have mostly been studied as prospective injectable therapeutic agents for broad drug administration, sheets of parylene–nanodiamond composites have been shown to be effective for localized release of drug for durations ranging from 2 days to 1 month.

4.6 Other applications

NDs can provide a suitable foundation for improving the utilization of drug carriers to cure skin cancer because of their great biocompatibility. The inclusion of NDs to beauty products can also allow active compounds to perform to their full capacity due to their high adsorption rate. NDs are able to transport more active chemicals and dive deeper into the skin layers than standard formulations. The higher moisture content capacity of NDs keeps the skin moisturized for longer, in addition to being fully and quickly absorbed by the skin. NDs may also help with healing process and can be used to dress wounds. Because NDs have an elevated surface chemistry that can be modified to aid carry genes and impact cell entrance, ND-based gene delivery systems for healing process seem appealing. Gene transfer is being researched in wound healing to overcome the limited availability of growth factors to the injury site. As an example, Bovine collagen is a biocompatible matrix that acts as a cofactor for tissue repair and serves as a supportive gene therapy vector [36].

A fast-emerging area of research is nanodiamond nanocomposite/polymer with improved thermal and mechanical properties. The nanocomposites that are quickly developing with distributed nanodiamonds were created utilizing a variety of processes, and they are promising for future applications (aeronautical, automotive, membranes, coatings, lubricants). Microelectromechanical systems (MEMS), quantum coherent devices, quantum computing have used nitrogen doped detonation ND nanocomposite. Scanning electron microscopy (SEM), Raman scattering spectroscopy cyclic voltammetry measurements and electrochemical response were used to investigate nanocrystalline diamond nanocomposite. These materials also contain boron doped nanodiamond. Because of its biocompatibility and bioresorbability, nanocomposite has been used to transport medicines and physiologically active compounds. The ability to transport a wide range of treatments is part of the drug delivery podium. In the desired medium, dispersibility and scalability are important. These materials have the potential to be used in bioimaging [37].

The medical applications of a Nanodiamond include imaging (MRI image, fluorescent Nanodiamonds,), tissue engineering (dental applications, bone tissue engineering, skin tissue engineering), drug delivery (cytotoxic drugs, anti-tubercular drugs, anti-diabetic drugs), binding biomolecules (siRNA, β-galacsidase, lysozyme proteins, poly-phenolic compounds). Modified Nanodiamonds can be used as a nucleic acid complexion platform and as a gene delivery vectors. Despite its unique properties, the idea of improving its compatibility with various solvents and polymers has not been fully investigated. Furthermore, it has been difficult to distribute NDs in a mixture for successful application in the biomedical field until now, thus future research should look into particle complexes for this reason [38].

Some fluorescent molecules have been observed to bind to the NDs for transport, including proteins, antibodies, growth hormones, siRNA and DNA molecules. These are applied in many areas like cancer treatment, targeted drug transportation, protein separation and purification by appropriately modifying NDs. This lays a solid platform for the future development of NDs and their potential clinical application. NDs’ biocompatibility and toxicity should be tested on a variety of cell types. More study is needed to understand the potential ramifications on the design of biocompatible Nanodiamonds in order to fulfill the demands of safe nanomedical applications [39].

NDs could be used in a variety of medical and biological applications, including biosensor components, targeted drug delivery, biocompatible composited and implants, and strong solid supports for synthesis of peptides. However, three main applications of NDs have been reported: protein immobilization, fluorescent markers for cell imaging, and medication administration (Table 1) [2].

Name of the material	Brief description on the area	Reference
Nanodiamonds	Skin treatment, wound healing	[36]
Boron doped Nanodiamond	Transport medicines, physiologically active compounds and bioimaging	[37]
Modified Nanodiamonds	Nucleic acid complexion platform and gene delivery vectors	[38]
Fluorescent molecules with Nanodiamonds	Targeted drug transportation, cancer treatment, protein separation	[39]

Table 1.

Other applications of Nanodiamonds.

5. Conclusion

Nanodiamonds obtained more attention from the researchers and young scientists in science and technology. Nanodiamonds protrude as an eccentric in several areas. The size and shape of the independent Nanodiamonds are solely responsible for the reproducibility and reliability of Nanodiamond-based products. Without structural or microstructural deterioration, semi or doped ND electrodes can perform successfully in harsh solution conditions. Diamond-based energy-saving machines’ ideal performance, which is dependent on their huge window with specific high strength, also has tremendous promise for broad usage in the storage technology community in the near future. Nanodiamond is an essential structural material in addition to being a good functional material. As a structured material, nanodiamond, for instance, has a wide range of uses, including in the oil and gas, semiconductor, and development sectors for tool surface modification, grinding, and polishing. The numerous applications for Nanodiamonds will continue to drive research ahead. Nanodiamonds’ structure and surface chemistry will be better understood, which will lead to even more uses.