Green Engineering of Iron and Iron Oxides by Different Plant Extract

Abstract

Green synthesis has emerged as a promising and eco-friendly approach for the synthesis of nanoparticles, including iron and iron oxide nanoparticles. This method utilizes plant extracts, microorganisms, or other natural resources as reducing and stabilizing agents instead of toxic chemicals to produce nanoparticles with desired properties. One advantage of green synthesis is the ability to control the size, shape, and crystalline structure of the nanoparticles, which can be analyzed using techniques such as powder X-ray diffraction (XRD). The two variable oxidation states (+2 and + 3) provide an opportunity for multiple products with different designing and crystallite structures. Iron and Iron oxide nanoparticles are both important for biological and photochemical activities. The method for green synthesis decides what kind of particles will one get and for what activity it is suitable. Iron nanoparticles are more suitable for biological activities like antibacterial, antimicrobial, anti-cancerous, and iron oxide for photoelectrical like band gap studies, conduction and photo-catalysis.

1. Introduction

Nanochemistry is a branch of chemistry that focuses on the synthesis, characterization, and manipulation of nanoparticles and nanomaterials. Over the past few years, the field of nanoscience and technology has gained increasing importance in research and development areas. Nanoparticles and nanomaterials have diverse properties that can be tuned to meet specific requirements, making them useful in various applications, such as electronics, energy storage devices, and drug delivery systems. Nanoparticles can also be used for environmental remediation, water treatment, and catalysis, among others [1].

Iron is hard and brittle metal, as the fourth most abundant element in the earth’s crust; it makes up the majority of the planet’s core by weight. Researchers believe that iron has been used by humanity for about 5000 years. The most commonly found sources of iron are the minerals magnetite and hematite. However, smaller quantities of iron can also be derived from the minerals siderite, taconite, and limonite. It contains four fundamental structures, alpha, beta, gamma, and delta, where particles join under various circumstances [2].

Ferrites are categorized into four groups: alpha (attractive), beta, gamma, and omega. The symbol for iron in the periodic table is Fe, which has a nuclear weight of 55.845 and a nuclear number of 26 with a thickness of 7.874 g/cm³. Iron has high melting and boiling point of 1538 and 2862°C, respectively, making it a useful material for applications where high temperatures are involved, such as in the manufacturing of steel or in metallurgical processes. There are 33 different isotopes in existence, but only four of them are stable. The most well-known is iron-56, which has a usual overflow of 91.75% [2].

Iron has been the subject of several recent scientific efforts due to its lithophilicity and chalcophilicity, which result in the production of minerals such as pyrite (FeS₂), magnetite (Fe₃O₄), hematite (Fe₂O₃), siderite (FeCO₃), and others. Ferritin, a type of protein that stores iron in the body, also contains iron oxide (Fe₃O₄). Magnetite, in particular, has garnered significant attention in recent years. It is not uncommon to find magnetite in the Magnesian area of Asia Minor, where it occurs in two forms: reduced ferrous iron species and oxidized ferric iron. This intriguing chemical has the potential to be employed in a range of applications and exhibits a variety of unique properties. The features of magnetite vary according to the mix methods, and the size of the material (from bulk to nanoscale), the structure of magnetite was originally determined in 1995 using X-ray diffraction (Figure 1). When magnetite was initially identified in the region, its structure was first discovered using X-ray diffraction. Magnetite is naturally ferromagnetic and has an inverted spinal structure as a result of the alternating lattices of iron (II) and iron (III). The fact that it includes both divalent and trivalent iron sets it apart from other iron oxide [2].

Figure 1.

Graphical abstract of green synthesis.

2. Classification of iron and iron oxide nanoparticles

Fe₂O₃ is primarily used in the fields of sensors, coatings, UV radiation blocking, and coloring. Fe₂O₃ nanoparticles are also ideal for exploring nanoparticle polymorphism, magnetic transition, and structural phase transition.

• Alpha Fe₂O₃ is an antiferromagnetic material with hexagonal structure corundum, its magnetic momentum is extremely low, and at 1 emu/cc, the transition is seen in alpha Fe₂O₃. The alpha structure exhibits mild ferromagnetism in the transition above 260 K, whereas it exhibits anti-ferromagnetism below 960 K. This is a low-temperature transition, and it is dependent on the size of the particles.

• The beta Fe₂O₃ is a material that is paramagnetic and has a cubic structure.

• The gamma polymer is a ferromagnetic molecule with a cubic spinal structure. At room temperature, it has a magnetic moment of 430 emu/cc.

• The orthorhombic structure of the epsilon exhibits ferromagnetic molecules (Figure 2) [2].

Figure 2.

Formation and transformation of iron and iron oxides nanoparticles [3].

2.1 Benefits of green synthesis

The following advantages of green/biological synthesis (Figure 3) methods are comparable to those of frequently used physical and chemical synthesis protocols:

1. A method that is safe for the environment and uses no toxic substances.

2. By acting as a capping and reducing agent, the active biological component, which may include an enzyme, lowers the total cost of the manufacturing process.

3. Even during mass manufacturing and external experimental circumstances like high energy, small nanoparticles can be created [4].

Figure 3.

Diversity of green synthesis.

3. Synthesis methodology of nanoparticles

Mostly two synthesis methods are used in the procedures, which are following

• Wet chemistry method

• Nonwet chemistry methods.

Precipitation, co-precipitation, hydrothermal, reduction, solvothermal, cryochemical synthesis, and spray/laser paralysis are an example of wet chemistry methods. The last three processes exhibit variation from the surrounding temperature. Cryochemical synthesis takes place below room temperature, and solvothermal synthesis and spray pyrolysis take place above it. Nonwet chemical synthesis includes inert gas condensation, laser ablation, laser-assisted synthesis, and plasma-assisted synthesis [5].

4. Mechanism of nanoparticles synthesis

At present, there is no consensus on the mechanism underlying the synthesis of metallic nanoparticles mediated by plant extracts. However, it is widely recognized that secondary metabolites found in various plant components play a critical role in the process. These secondary metabolites include polyphenols, flavonoids, tannic acids, terpenoids, ascorbic acids, carboxylic acids, aldehydes, and amides. Many investigations have employed the IR spectroscopic technique to confirm the existence of numerous reducing sugars, which are often present in plants. Plant extracts containing phytochemicals with appropriate redox characteristics can effectively reduce metal precursors and convert them into matching metallic nanoparticles. According to one hypothesis, radical tannins “R” reduce metal under the influence of pH.

4.1 Method

The following methods can be used to initiate the bio-reduction process:

$${\mathrm{\text{FeCl}}}_{\mathrm{3}}+{\mathrm{H}}_{\mathrm{2}}\mathrm{O}\to {\left[\mathrm{Fe}{\left({\mathrm{H}}_{\mathrm{2}}\mathrm{O}\right)}_{\mathrm{n}}\right]}^{+\mathrm{3}}+{\mathrm{H}}_{\mathrm{2}}\mathrm{O}$$E1

$$\mathrm{R}+{\left[\mathrm{Fe}{\left({\mathrm{H}}_{\mathrm{2}}\mathrm{O}\right)}_{\mathrm{n}}\right]}^{+\mathrm{3}}+{\mathrm{H}}_{\mathrm{2}}\mathrm{O}\to {\left[\mathrm{Fe}{\left({\mathrm{H}}_{\mathrm{2}}\mathrm{O}\right)}_{\mathrm{n}}\right]}^{+\mathrm{2}}+{\mathrm{H}}^{+}+\mathrm{R}-\mathrm{OH}$$E2

$${\left[\mathrm{Fe}{\left({\mathrm{H}}_{\mathrm{2}}\mathrm{O}\right)}_{\mathrm{n}}\right]}^{+\mathrm{2}}{\mathrm{\text{2R}}}^{-}+{\mathrm{H}}^{+}+{\mathrm{OH}}^{-}\to {\mathrm{Fe}}^{+\mathrm{2}}{\mathrm{O}}^{-\mathrm{2}}+{\mathrm{O}}^{-\mathrm{2}}+\mathrm{R}-\mathrm{H}+\mathrm{R}-\mathrm{OH}$$E3

The iron-polyphenol complex nanoparticles (Fe-P NPs) structure was produced by eucalyptus leaves, in a different research. The polyphenols found in eucalyptus extract possess the ability to convert Fe³⁺ into Fe²⁺ and at its reduction potential. However, the extract does not entirely convert the Fe²⁺ to zero-valent iron [6]. Due to the presence of polyphenol ligands, Fe²⁺ is firmly stabilized; yet, Fe³⁺polyphenol complexes are quickly formed when Fe²⁺oxidizes in the presence of oxygen, which is known as autoxidation. As a result, a black nano-iron colloid is produced when an iron metal solution reacts with a plant extract. An experiment using the X-ray absorption (XAS) spectroscopy technique indicated that plant polyphenols were located in a globular position and chelated with ferric ion (Fe³⁺). A similar response mechanism was hypothesized for Sage (Salvia). Plant polyphenols can be cross-linked via polyphenol condensation following a reaction with iron chloride (FeCl₃) (Eq. (1)) [4, 5, 7].

5. Green synthesis of nanoparticles

Compared to microorganisms, plants generate more stable metal nanoparticles and are considered the best candidates for large-scale and quick synthesis. Plants naturally contain a wide range of organic reducing chemicals that are well-suited to the synthesis of nanoparticles. Higher levels of antioxidants found in seeds, fruits, leaves, and stems are masked by the diversity of herbs and plant sources. Therefore, the use of plant-based phytochemicals in the entire synthesis and construction of nanoparticles creates an essential synergy between natural/plant sciences and nanotechnology. This affiliation offers nanotechnology a distinctly “green” perspective, known as green nanotechnology, which can be used without causing significant environmental contamination, setting new benchmarks for highly viable clean and green technology [4, 7]. In contrast to microbe-based synthesis, the creation of nanomaterials from plants is more uniform and faster. Various plant components, including the leaf, stem, seed, and root, are commonly used in the easiest, most affordable, and reproducible method of creating metallic nanoparticles (Table 1 and Figure 4) [27].

Plant	Material	Parameters Temp (°C) /stirring (rpm) /time (min^−1) /pH	Size of iron and iron oxide NPs (nm)
Camellia sinensis (Leaf)	Fe (NO3)3.9H2O	75/5000/04	nZVI (10–20) [8, 9]
Azadirarachta indica (Leaf)	FeCl3.6H2O triple distilled water	70/5000/4–5	9–12 [10]
Punica granatum (Leaf)	NH4Fe(SO4)2.6H2O; NH4Fe(SO4)2.12H 2O; NaOH	30/6000/15	46.1 [11]
Punica granatum (Seed)	FeCl3.6H2O (99.9%) Distilled water	70/15000 /10	40–50 [11]
Platanus orientalis (Leaf)	Fe(NO3)3.9H2O (98%); Dabouraud dextrose agar and potatoes agar; Hexahit; Double distilled H2O	25/ 6000/20	38 [12, 13]
Daphne mezereum (Leaf)	FeCl3.6H2OConc.HCl Deionized water(DI)	50/6000/25	9–10 [14]
Lagenaria Siceraria (Leaf)	FeCl3.6H2O (98%) Distilled water	40/4000/60	30–100 [15]
Spinancia oleracea (Leaf)	FeCl3.6H2O Deionized water(DI)	60/5000/30	10–100 [6, 16, 17]
Avicennia marina (Flower)	Ferric chloride (FeCl3); Triple distilled de-ionized H2O	125/10,000/30	30–100 [18]
Cupressus sempervirens (Leaf)	FeCl3.6H2O; The HCl solution, Ultrapure water, Al-foil	50/5000/10	9–31 [19]
Vaccinium sect. Syanococcus (Leaf)	FeCl3.6H2O; Distilled water; CH3COCH3	−18/9000 / 30	52.4 [20]
Glycosmis mauritiana (Leaf)	FeCl2.4H2O FeCl3.6H2O; DI water NaOH; Whatman’s filter paper	80/2000/120	100 [21]
Syzygium aromaticum (Bud)	Distilled water, Whatman’s filter paper NaOH; Fe(NO3)3	25/13,000/20 /pH 6	216–268 [22]
Camellia sinensis assamica (Leaf)	FeCl3.6H2O; Distilled water; Filter paper; Mortar and pestle Ethanol	65/10000/20 /pH 7	40–50 [23]
Rosa indica (Leaf)	FeCl3.6H2O; Deionized water; Filter paper	50–60 /5000/5	51 [24]
Terminalia Chebula (Fruit)	FeSO4.7H2O; Distilled water; Ethanol	—	Less than 80 [25]
Rumex acetosa (Leaf)	FeCl3.6H2O (99.9%) Distilled water FeSO4.7H2O NaOH	500/4000/15	10–40 [23]
Bellissima (Fruit)	Ethanol; Distilled water, FeCl3	—	22.3 [26]

Table 1.

Different plant extracts for the green synthesis of iron and iron oxides.

Figure 4.

Flow sheet of green synthesis.

6. Characterization of iron and iron oxides nanoparticles

6.1 UV: Visible spectroscopy

The UV-Visible spectroscopy of iron nano.

Particles is in the absorption peak of 216–265 nm (Figure 5).

Figure 5.

The UV–visible spectrum of FeNPs [28].

6.2 Fourier transform infrared (FTIR) spectroscopy

Peaks at 991,1070, 1631, 2800, and 3467 cm⁻¹ in the Fourier transform infrared (FTIR) spectrum of green-synthesized iron nanoparticles (INPs) were caused by the bonds C▬O, C〓O, C▬H, and OH, respectively (Figure 6).

Figure 6.

FTIR spectrum of FeNPs [29].

6.3 X-ray diffraction spectroscopy

The characteristics peak of iron nanoparticles were observed in the XRD pattern at 2θ-values 18.97, 29.81, 35.24, 39.53, and 48.30°. The iron nanoparticles were crystalline in nature. The reduction of metal ions by the extract is clearly showing the iron nanoparticles by X-ray diffraction. By using the Scherer formula we can find out the average particle size of iron oxide nanoparticles [30]. The average size of iron oxide nanoparticles is 45.09 nm (Figure 7).

Figure 7.

XRD analysis of FeNPs [31].

6.4 Scanning electron microscopes

This scanning electron microscope (SEM) is mostly used to identify the structure of the nanomaterial; it can tell us the morphology of the nanoparticles, and the image of iron nanoparticles obtained by the scanning electron microscope looks like a honeycomb. The image of iron nanoparticles in a scanning electron microscope is seen as nonuniform, and its size ranges from 10 to 40 nm with a smooth surface, but they are not uniform (Figure 8).

Figure 8.

SEM spectrum of FeNPs [32].

6.5 Field emission-scanning electron microscopy and zeta potential

Although there is much disagreement on the size threshold to separate NPs from bulk materials, size is a crucial factor in defining NPs [33, 34, 35]. The particles were suspended in water that had a viscosity of 0.887, a refractive index of 1.33, and a dielectric constant of 78.5. The zeta potential reflects the potential difference between the electrophoretically mobile particles EDL (electric double layer) and the layer of dispersant surrounding them at the sliding plane. The potential at the slipping/shear plane of a colloid particle moving through an electric field is also known as electrokinetic potential. The particle size distribution is a result (Tables 2–4 and Figure 9).

Plants	FTIR (cm^−1)
Azadirachta indica (leaf extract)	O▬H at 3268.9 (stretching) and COOH at 1636.3 (stretching) [10]
P.granatum (seed extract)	C〓C at 1500 C〓N at 1640 C〓O at 1720 N▬H(amine salt) at 3000 N▬H at 3400 [11]
P.orientalis	C▬H at 3196(stretching) H▬C▬H at 1315(bending) C▬O at 1410 C▬C at 1000–1450 Fe▬O▬Fe at 663,462,426 [12, 13]
D.mezereum	Fe▬O at 516; O▬H of carboxylic acid at 3448; C〓C at 1635 (ring stretching) [14]
L.siceraria	O▬H bond at 3354; C〓O at 1701; Inorganic compound at 624 [15]
Spinancia oleracea (leaf extract)	OH at 3500–3200; C▬H at 2800; C〓O at 1658; C〓C at 1540,1402; Fe NPs at 670, 612.63 [6, 16, 17]
A. marina	M▬O bond at 400–450; Fe▬O at 618 and 467; Aromatic comp. at 2923,2853; C▬H bonds at 3422; O▬H group at 1630 [18]
G. mauritiana	OH at 3334.7 (stretching) C☰N at 2115.9 (stretching); (▬C〓O) at 1632 [21]
Camellia sinensis assamica	C▬O▬C at 1064; C〓C at 1616 (stretching); O▬H at 3355; C〓C at 1608 (ring stretching) [23]
Murraya koenigii	OH at 3454 (stretching); C▬H at 2427 (stretching); C〓O at 1767 ester group (stretching); The amino acid at 1637; Germinal CH3 group at 1384; Fe▬O at 831, 537, and 459 (stretching) [36, 37]
Urtica dioica	C▬O at 1070; C〓O at 1636; C▬H at 2800; OH at 3467 [23, 37]
Pinus eldarica	O▬H at 3420.97; C〓O at 1616.05; C▬O at 1069.05; C–H at 2918; Fe▬O at 640 and 450 [7, 36]

Table 2.

FTIR analysis of different plant extract.

Plants Extracts	SEM (nm)	TEM (nm)
Camellia sinensis	16	14 [8, 9]
Punica granatum seed	10–40	38 [11]
P.orientalis	—	9.2 [12, 13]
D.mezerium	—	20–50 [14]
S. oleracea	30–100	Below 100 [6, 16, 17]
A. marina	Average 80.2	Average ~ 52.4 [18]
Vaccinium sect. Syanococcus	58–79	20 [20]
G. mauritiana	50–80	10–20 [21]
C.sinensisassamica	15–45	Size depends on the Polyphone concentration ranges from 40 to 200 [23]
Rosa indica	61	51 [24]
Murrayakoenigii	500	7–15 [37]
M. indica	0.075–6.5 μm	11.5 [15]
Laurus nobilis	200	60 [8]

Table 3.

TEM and SEM value of Fe and Fe▬O nanoparticles of different plants.

Plants	XRD Pattern result
Punica granatum (Pomegranate seed extract) [8]; Kingdom: Plantae; Family: Punica	The sharp peaks at 18.38°, 30.18°, 35.55°, 43.25°, 53.60°, 57.11°, 62.76°, 71.30°, and 74.50° 141 corresponded to the crystal planes of 142 (111), (220), (311), (400), (422), (511), (440), (620), and (533). This demonstrated that the majority of the 143 IONPs synthesized were Fe3O4.
P.orientalis [JCPDS 00–003-0863]; Family: Platanaceae; kingdom: Plantae; Order: Proteales; Rank: Species	The XRD pattern of Fe▬O revealed the presence of three peak of αFe2O3,γFe2O3 whoes hkI value is (012),(410) and (221) respectively.
A. marina [PDF No.: 46–1312 JCPDS]; Kingdom: Plantae; Family: Acanthaceae; Genus: Avicennia; Species: A. marina Order: Lamiales	The XRD pattern of FeO-NPs revealed the presence of FeO at five peaks: 36.42°,42.24°,61.29°,73.24°, and 77.07°, which correspond to the (111), (200), (220), (311), and (222) planes of FeO, respectively.
L.siceraria [JCPDS card No. 39–1346]; Kingdom: Plantae; Order: Cucurbitales; Family: Cucurbitaceae; Genus: Lagenaria; Species: Lagenaria siceraria	It is discovered that the exits strong diffraction peaks with 2 values of 28.26° and 32.28°, which correlate to the hkl value of (220),(222), denoting the crystalline phase of Fe3O4-NPs.
A.indica; [JCPDS file No.19–0629]; Kingdom: Plantae; Order: Sapindales; Family: Meliaceae	The Fe3O4 XRD pattern revealed six typical diffraction peaks at planes 2θ = (220) at 30.3° (311) at 35.6°, (400) at 43.3°, (422) at 53.2°, (511) at 57.1°, and (440) at 62.8°.
G. mauritiana [JCPDS NO. 89–8104]; Kingdom: Plantae; Class: Rosidaceae; Order: Sapindales; Family: Rutaceae; Genus: Glycosmis; Species: mauritiana	The significant strong characteristic peaks of iron oxide particles are found at 2θ = 24.14°, 33.14°, 35.61°, 40.84°, 49.45°, 54.06°, 62.42°, and 64.00°, which correspond to iron oxide amorphous structures (220), (311), (400), (442), (511), and (440).
M.indica [(α-Fe2O3) JCPDS 87–1164]; [(γ-Fe2O3) JCPDS 39–1346]; Common name: mango; Family name: Anacardiaceae	Hematite (-Fe2O3) JCPDS 87–1164, and maghemite (-Fe2O3) JCPDS 39–1346 in gamma phase. –Fe2O3 appears (in black) in diffracted planes (311) and (220), where -Fe2O3 appears (in blue) at (012), (104), (110), (113), (024), and (116).
S.aromaticum; [JCPDF card #39–1346]; Common name: clove; Plant part is taken: buds; Family name: Myrtaceae	The Fe2O3 characteristic XRD peaks suggest a hematite structure and are indexed as (012), (110), (222), (421), (422), and Fe3O4 is characterized as (111), (311), (222), (400), (422) and (440), indicating the co-existence of iron oxide phases.

Table 4.

XRD pattern result of the iron and iron oxides from different plants.

Figure 9.

Zeta potential spectrum of FeNPs [38].

6.6 Application of nanoparticles

Magnetic nanoparticles have a variety of uses, including in biomedicine, healthcare, agriculture, food production, environmental management systems, energy, textiles, electronics, building materials, machines, etc. (Figure 10).

Figure 10.

Application of iron and iron oxides nanoparticles.

7. Conclusion

This study focuses on the engineering of iron nanoparticles using several environmentally friendly techniques and their potential to remove contaminants from the environment (Table 5). To some extent, efforts are made to emphasize the many environmentally friendly agents for the production of iron nanoparticles, including polymers, amino acids, bacteria, fungi, plant extracts, etc. This review also covers the relationship between particle size, morphology, and other aspects and the characteristics of materials, processes, and protocols. According to the literature, several plants and components linked to plants have been used to easily synthesize iron nanoparticles, which have proven to be effective catalysts for a variety of environmental applications. As a result, plant materials appear increasingly viable as producers of iron nanoparticles because of their environmental benefits and high economic worth. To better understand the phytochemistry involved in the creation of iron nanoparticles, which has not yet been thoroughly defined. Additional study is required to examine more nearby and easily accessible resources for the production of iron nanoparticles in order to accomplish the sustainability of nanomaterial synthesis. Any novel methodology must first comprehend the biochemical processes involved in nanoparticle creation, and any solution must be cost-effective relative to traditional approaches. Utilizing local resources can help keep costs down in the long run as their development. A clearer explanation of biomolecules and their function in modulating the creation of nanoparticles will be provided in future studies with a more in-depth investigation. The objective is to alter the rate of synthesis and boost the stability of nanoparticles. Additionally, research should be done to boost the reactivity of iron nanoparticles during manufacture in order to accelerate the breakdown of environmental pollutants with the fewest possible eco-toxicological effects. Few investigations have confirmed that biosynthesized nanoparticles are less hazardous than manufactured nanoparticles. Additionally, a thorough risk evaluation of green-fabricated Fe NPs should be carried out, taking into account the nanoparticles kinetics, fate, transport, aggregation, and dissolution during processing. A variety of biochemical or functionalized nanoparticles can be produced using the green nanotechnology processes described in this paper as a solid foundation. These new products could be used in the environmental restoration sectors.

Field	Application of iron Nanoparticles
Biomedical	Cellular therapies (cell labeling/tissue repair/cell separation and handling/purifying cell populations/magneto-reception, diseases of the musculoskeletal system/severe inflammation, disability, and pain are all possible uses for magnetic nanoparticles (especially those coated with liposomes) for drug delivery [39].
Health care	Nanophotothermolysis with pulsed lasers for the treatment of cancer, hepatitis B virus, respiratory syncytial virus, influenza virus, antiviral agents against HIV-1, Monkeypox virus, herpes simplex virus type 1, and Tacaribe virus; delivering antigens for a vaccine; nanoscale biosensors and imaging; nanocoatings on surfaces; implants; nanocarrier for vaccination; antimicrobial activities; SLN in drug delivery and research; delivering antigens for a particular disease into the bloodstream; preventing aging of the skin [39]
Agriculture and food	Crop yields are increased by nano-based products (nano-fertilizers, nano-fungicides, and nano-pesticides), designed NPs, and CNTs; pyrite NPs are employed as a seed treatment for different plants before the seeds are sown, and more leaf quantity, greater leaf size, and higher biomass. Improved starch breakdown after storage. This suggests that iron pyrite nanoparticles might be created as a commercial seed treatment product (pro-fertilizer). As no NPs are introduced into the soil throughout the procedure, the method is secure. Fewer doses are needed than with chemical fertilizers. There are no negative impacts on plant development. Nanoporous membranes, gene transfer (crop enhancement), nano-composites, nanosensors, nanofood, encapsulation, food packaging, nanocoatings, and precision farming [39].
Environmental Remediation	Detection, monitoring, and treatment of pollution. Treatment of wastewater (adsorption, membrane filtration, and permeable reactive barriers). Palladium (Pd), climate change (carbon capture), synthetic leaves for CO2 sequestration, mineral carbonation, biomimetic carbonation, N2O breakdown, and methane combustion are some examples of catalyst coatings. Enhances manufacturing processes (efficiency, waste reduction), dematerialization (reduction in material quantity), sensing (pollutant sensors, nanoporous membranes, chemical and bionanosensors, nanowire sensor for explosives), and energy (heat distribution, for example, ceramic-like materials that sufficiently provide the structure’s dependability and durability) [39].
Energy	The conversion of waste heat from computers, cars, homes, power plants, etc. into usable electrical power using photovoltaic film coatings, more efficient fuel production and consumption, fuel cells, prototype batteries, aerogels, and thermoelectric materials [39].
Military and aerospace	Smart materials, nano-composites, nanocoatings, sensors, electronics, fuel additives, and energy devices [39].
Construction	Smart materials, concrete additives, nanoscale sensors, nano-composites, and nanocoatings. In order to color concrete, brick, tile, and other building materials, iron oxide pigments are utilized [39].
Electronics	Printed electronics, carbon nanotubes, nanowires, NEMS, spintronics, and quantum dots [39] are examples of emerging technologies.

Table 5.

Application of nanoparticles in different fields.

Conflict of interest

The authors declare no conflict of interest.