INTRODUCTION:

Nanotechnology has gained huge attention over time. The fundamental component of nanotechnology is the nanoparticles. Nanoparticles are particles between 1 and 100 nanometres in size and are made up of carbon, metal, metal oxides or organic matter¹. The nanoparticles exhibit a unique physical, chemical and biological properties at nanoscale compared to their respective particles at higher scales. This phenomena is due to a relatively larger surface area to the volume, increased reactivity or stability in a chemical process, enhanced mechanical strength, etc.². These properties of nanoparticles has led to its use various applications.

The nanoparticles differs from various dimensions, to shapes and sizes apart from their material ³.

A nanoparticle can be either a zero dimensional where the length, breadth and height is fixed at a single point for example nano dots, one dimensional where it can possess only one parameter for example graphene, two dimensional where it has length and breadth for example carbon nanotubes or three dimensional where it has all the parameters such as length, breadth and height for example gold nanoparticles.

The nanoparticles are of different shape, size and structure. It be spherical, cylindrical, tubular, conical, hollow core, spiral, flat, etc. or irregular and differ from 1 nm to 100 nm in size. The surface can be a uniform or irregular with surface variations. Some nanoparticles are crystalline or amorphous with single or multi crystal solids either loose or agglomerated⁴.

Numerous synthesis methods are either being developed or improved to enhance the properties and reduce the production costs. Some methods are modified to achieve process specific nanoparticles to increase their optical, mechanical, physical and chemical properties³. A vast development in the instrumentation has led to an improved nanoparticle characterisation and subsequent application. The nanoparticles are now used in every objects like from cooking vessel, electronics to renewable energy and aerospace industry. Nanotechnology is the key for a clean and sustainable future.

Classification of Nanoparticles:

The nanoparticles are generally classified into the organic, inorganic and carbon based.

Organic nanoparticles:

Dendrimers, micelles, liposomes and ferritin, etc. are commonly knows the organic nanoparticles or polymers. These nanoparticles are biodegradable, non-toxic, and some particles such as micelles and liposomes has a hollow core (Figure1), also known as nanocapsules and are sensitive to thermal and electromagnetic radiation such as heat and light⁵. These unique characteristics makes them an ideal choice for drug delivery. The drug carrying capacity, its stability and delivery systems, either entrapped drug or adsorbed drug system determines their field of applications and their efficiency apart from their normal characteristics such as the size, composition, surface morphology, etc. The organic nanoparticles are most widely used in the biomedical field for example drug delivery system as they are efficient and also can be injected on specific parts of the body that is also known as targeted drug delivery.

Figure 1: Organic nanoparticles: a – Dendrimers, b – Liposomes and c – micelles.

Inorganic nanoparticles:

Inorganic nanoparticles are particles that are not made up of carbon. Metal and metal oxide based nanoparticles are generally categorised as inorganic nanoparticles

Metal based:

Nanoparticles that are synthesised from metals to nanometric sizes either by destructive or constructive methods are metal based nanoparticles. Almost all the metals can be synthesised into their nanoparticles [6]. The commonly used metals for nanoparticle synthesis are aluminium (Al), cadmium (Cd), cobalt (Co), copper (Cu), gold (Au), iron (Fe), lead (Pb), silver (Ag) and zinc (Zn). The nanoparticles have distinctive properties such sizes as low as 10 to 100nm, surface characteristics like high surface area to volume ratio, pore size, surface charge and surface charge density, crystalline and amorphous structures, shapes like spherical and cylindrical and colour, reactivity and sensitivity to environmental factors such as air, moisture, heat and sunlight etc.

Metal oxides based. The metal oxide based nanoparticles are synthesised to modify the properties of their respective metal based nanoparticles, for example nanoparticles of iron (Fe) instantly oxidises to iron oxide (Fe₂O₃) in the presence of oxygen at room temperature that increases its reactivity compared to iron nanoparticles. Metal oxide nanoparticles are synthesised mainly due to their increased reactivity and efficiency⁷. The commonly synthesised are Aluminium oxide (Al₂O₃),

Cerium oxide (CeO₂), Iron oxide (Fe₂O₃), Magnetite (Fe₃O₄), Silicon dioxide (SiO₂), Titanium oxide (TiO₂), Zinc oxide (ZnO). These nanoparticles have possess an exceptional properties when compared to their metal counterparts.

Carbon based:

The nanoparticles made completely of carbon are knows as carbon based⁸. They can be classified into fullerenes, graphene, carbon nano tubes (CNT), carbon nanofibers and carbon black and sometimes activated carbon in nano size and are presented in Figure2.

Figure 2: Carbon based nanoparticles: a – fullerenes, b – graphene, c – carbon nanotubes, d – carbon nanofibers and e – carbon black

Fullerenes. Fullerenes (C₆₀) is a carbon molecule that is spherical in shape and made up of carbon atoms held together by sp² hybridization. About 28 to 1500 carbon atoms forms the spherical structure with diameters up to 8.2nm for a single layer and 4 to 36 nm for multi-layered fullerenes.

Graphene.

Graphene is an allotrope of carbon. Graphene is a hexagonal network of honeycomb lattice made up of carbon atoms in a two dimensional planar surface. Generally the thickness of the graphene sheet is around 1 nm.

Carbon Nano Tubes (CNT). Carbon Nano Tubes (CNT), a graphene nanofoil with a honeycomb lattice of carbon atoms is wound into hollow cylinders to form nanotubes of diameters as low as 0.7 nm for a single layered and 100nm for multi-layered CNT and length varying from a few micrometres to several millimetres. The ends can either be hollow or closed by a half fullerene molecule.

Carbon Nanofiber. The same graphene nanofoils are used to produce carbon nanofiber as CNT but wound into a cone or cup shape instead of a regular cylindrical tubes.

Carbon black. An amorphous material made up of carbon, generally spherical in shape with diameters from 20 to 70nm. The interaction between the particles are so high that they bound in aggregates and around 500 nm agglomerates are formed.

Synthesis of Nanoparticles:

The nanoparticles are synthesised by various methods that are categorised into bottom-up or top-down method. A simplified representation of the process is presented in Figure3.

Figure 3. Synthesis process.

Bottom-up method

Bottom-up or constructive method is the build-up of material from atom to clusters to nanoparticles. Sol-gel, spinning, chemical vapour deposition (CVD), pyrolysis and biosynthesis are the most commonly used bottom-up methods for nanoparticle production.

Sol-gel. The sol – a colloidal solution of solids suspended in a liquid phase. The gel – a solid macromolecule submerged in a solvent. Sol-gel is the most preferred bottom-up method due to its simplicity and as most of the nanoparticles can be synthesised from this method. It is a wet-chemical process containing a chemical solution acting as a precursor for an integrated system of discrete particles. Metal oxides and chlorides are the typically used precursors in sol-gel process ⁹. The precursor is then dispersed in a host liquid either by shaking, stirring or sonication and the resultant system contains a liquid and a solid phase. A phase separation is carried out to recover the nanoparticles by various methods such as sedimentation, filtration and centrifugation and the moisture is further removed by drying¹⁰.

Spinning. The synthesis of nanoparticles by spinning is carried out by a spinning disc reactor (SDR). It contains a rotating disc inside a chamber/reactor where the physical parameters such as temperature can be controlled. The reactor is generally filled with nitrogen or other inert gases to remove oxygen inside and avoid chemical reactions⁷. The disc is rotated at different speed where the liquid i.e. precursor and water is pumped in. The spinning causes the atoms or molecules to fuse together and is precipitated, collected and dried¹¹. The various operating parameters such as the liquid flow rate, disc rotation speed, liquid/precursor ratio, location of feed, disc surface, etc. determines the characteristics nanoparticles synthesised from SDR.

Chemical Vapour Deposition (CVD). Chemical vapour deposition is the deposition of a thin film of gaseous reactants onto a substrate. The deposition is carried out in a reaction chamber at ambient temperature by combining gas molecules. A chemical reaction occurs when a heated substrate comes in contact with the combined gas⁸. This reaction produces a thin film of product on the substrate surface that is recovered and used. Substrate temperature is the influencing factor in CVD. The advantages of CVD are highly pure, uniform, hard and strong nanoparticles. The disadvantages of CVD are the requirement of special equipment and the gaseous by-products are highly toxic¹².

Pyrolysis. Pyrolysis is the most commonly used process in industries for largescale production of nanoparticle. It involves burning a precursor with flame. The precursor is either liquid or vapour that is fed into the furnace at high pressure through a small hole where it burn¹³. The combustion or by-product gases is then air classified to recover the nanoparticles. Some of the furnaces use laser and plasma instead of flame to produce high temperature for easy evaporation ¹⁴. The advantages of pyrolysis are simple, efficient, cost effective and continuous process with high yield.

Biosynthesis. Biosynthesis is a green and environmental friendly approach for the synthesis of nanoparticles that are nontoxic and biodegradable ¹⁵. Biosynthesis uses bacteria, plant extracts, fungi, etc. along with the precursors to produce nanoparticle instead of convention chemicals for bioreduction and capping purposes. The biosynthesised nanoparticles has unique and enhanced properties that finds its way in biomedical applications¹.

Top-down method

Top-down or destructive method is the reduction of a bulk material to nanometric scale particles. Mechanical milling, nanolithography, laser ablation, sputtering and thermal decomposition are some of the most widely used nanoparticle synthesis methods.

Mechanical milling. Among the various top-down methods, mechanical milling is the most extensively used to produce various nanoparticles. The mechanical milling is used for milling and post annealing of nanoparticles during synthesis where different elements are milled in an inert atmosphere ¹⁶. The influencing factors in mechanical milling is plastic deformation that leads to particle shape, fracture leads to decrease in particle size and cold-welding leads to increase in particle size.

Nanolithography. Nanolithography is the study of fabricating nanometric scale structures with a minimum of one dimension in the size range of 1 to 100 nm. There are various nanolithographic processes for instance optical, electron-beam, multiphoton, nanoimprint and scanning probe lithography ¹⁷. Generally lithography is the process of printing a required shape or structure on a light sensitive material that selectively removes a portion of material to create the desired shape and structure. The main advantages of nanolithography is to produce from a single nanoparticle to a cluster with desired shape and size. The disadvantages are the requirement of complex equipment and the cost associated ¹⁸.

Laser ablation. Laser Ablation Synthesis in Solution (LASiS) is a common method for nanoparticle production from various solvents. The irradiation of a metal submerged in a liquid solution by a laser beam condenses a plasma plume that produces nanoparticles ¹⁹. It is a reliable top-down method that provides an alternative solution to conventional chemical reduction of metals to synthesis metal based nanoparticles. As LASiS provides a stable synthesis of nanoparticles in organic solvents and water that does not require any stabilising agent or chemicals it is a ‘green’ process.

Sputtering. Sputtering is the deposition of nanoparticles on a surface by ejecting particles from it by colliding with ions ²⁰. Sputtering is usually a deposition of thin layer of nanoparticles followed by annealing. The thickness of the layer, temperature and duration of annealing, substrate type, etc. determines the shape and size of the nanoparticles ²¹.

Thermal decomposition. Thermal decomposition is an endothermic chemical decomposition produced by heat that breaks the chemical bonds in the compound ⁶. The specific temperature at which an element chemically decomposes is the decomposition temperature. The nanoparticles are produced by decomposing the metal at specific temperatures undergoing a chemical reaction producing secondary products. Table 1 lists some of the nanoparticles synthesised from these methods.

Table 1. Categories of the nanoparticles synthesised from the various methods

Category	Method	Nanoparticles
Bottom-up	Sol-gel	Carbon, metal and metal oxide based
	Spinning	Organic polymers
	Chemical Vapour Deposition (CVD)	Carbon and metal based
	Pyrolysis	Carbon and metal oxide based
	Biosynthesis	Organic polymers and metal based
Top-down	Mechanical milling	Metal, oxide and polymer based
	Nanolithography	Metal based
	Laser ablation	Carbon based and metal oxide based
	Sputtering	Metal based
	Thermal decomposition	Carbon and metal oxide based

Properties of Nanoparticles:

The properties of nanoparticles are generally categorised into physical and chemical. The properties of few common nanoparticles are given in Table 2.

As discussed earlier, various physicochemical properties such as large surface area, mechanically strong, optically active and chemically reactive make NPs unique and suitable applicants for various applications. Some of their important properties are discuss in the following section.

5.1. Electronic and optical properties:

The optical and electronic properties of NPs are inter-dependent to greater extent. For instance, noble metals NPs have size dependent optical properties and exhibit a strong UV–visible extinction band that is not present in the spectrum of the bulk metal. This excitation band results when the incident photon frequency is constant with the collective excitation of the conduction electrons and is known as the localized surface plasma resonance (LSPR). LSPR excitation results in the wavelength selection absorption with extremely large molar excitation coefficient resonance Ray light scattering with efficiency equivalent to that of ten fluorophores and enhanced local electromagnetic fields near the surface of NPs that enhanced spectroscopies. It is well established that the peak wavelength of the LSPR spectrum is dependent upon the size, shape and interparticle spacing of the NPs as well as its own dielectric properties and those of its local environment including the substrate, solvents and adsorbates (Eustis and El-Sayed, 2006). Gold colloidal NPs are accountable for the rusty colors seen in blemished glass door/windows, while Ag NPs are typically yellow. Actually, the free electrons on the surface in these NPs (d electrons in Ag and gold) are freely transportable through the nanomaterial. The mean free path for Ag and gold is ∼50 nm, which is more than the NPs size of these materials. Thus, no scattering is expected from the bulk, upon light interaction, instead they set into a standing resonance conditions, which is responsible for LSPR in these NPs (Khlebtsov and Dykman, 2010a, Khlebtsov and Dykman, 2010b).

Graphical illustration exemplifying the localized surface plasmon (LSPR) on nanoparticle outer surface (Khlebtsov and Dykman, 2010a, Khlebtsov and Dykman, 2010b).

5.2. Magnetic properties:

Magnetic NPs are of great curiosity for investigators from an eclectic range of disciplines, which include heterogenous and homogenous catalysis, biomedicine, magnetic fluids, data storage magnetic resonance imaging (MRI), and environmental remediation such as water decontamination. The literature revealed that NPs perform best when the size is <critical value i.e. 10–20 nm (Reiss and Hütten, 2005). At such low scale the magnetic properties of NPs dominated effectively, which make these particle priceless and can be used in different applications (Faivre and Bennet, 2016, Priyadarshana et al., 2015, Reiss and Hütten, 2005, Zhu et al., 1994). The uneven electronic distribution in NPs leads to magnetic property. These properties are also dependent on the synthetic protocol and various synthetic methods such as solvothermal (Qi et al., 2016), co-precipitation, micro-emulsion, thermal decomposition, and flame spray synthesis can be used for their preparation (Wu et al., 2008).

5.3. Mechanical properties:

The distinct mechanical properties of NPs allow researchers to look for novel applications in many important fields such as tribology, surface engineering, nanofabrication and nanomanufacturing. Different mechanical parameters such as elastic modulus, hardness, stress and strain, adhesion and friction can be surveyed to know the exact mechanical nature of NPs. Beside these parameters surface coating, coagulation, and lubrication also aid to mechanical properties of NPs. NPs show dissimilar mechanical properties as compared to microparticles and their bulk materials. Moreover, in a lubricated or greased contact, the contrast in the stiffness between NPs and the contacting external surface controls whether the NPs are indented into the plan surface or deformed when the pressure at contact is significantly large. This important information could divulge how the NPs perform in the contact situation. Decent controls over mechanical features of NPs and their interactions with any kind of surface are vital for enlightening the surface quality and elevating material removal. Fruitful outcomes in these fields generally need a deep insight into the basics of the mechanical properties of NPs, such as elastic modulus and hardness, movement law, friction and interfacial adhesion and their size dependent characteristics.

5.4. Thermal properties:

It is well-known fact that metals NPs have thermal conductivities higher than those of fluids in solid form. For example, the thermal conductivity of copper at room temperature is about 700 times greater than that of water and about 3000 times greater than that of engine oil. Even oxides such as alumina (Al₂O₃) have thermal conductivity higher than that of water. Therefore, the fluids containing suspended solid particles are expected to display significantly enhanced thermal conductivities relative to those of conventional heat transfer fluids. Nanofluids are produced by dispersing the nanometric scales solid particles into liquid such as water, ethylene glycol or oils. Nanofluids are expected to exhibit superior properties relative to those of conventional heat transfer fluids and fluids containing microscopic sized particles. Because the heat transfer takes place at the surface of the particles, it is desirable to use the particles with large total surface area. The large total surface area also increases the stability suspension (Lee et al., 1999). Recently it has been demonstrated that the nanofluids consisting of CuO or Al₂O₃ NPs in water or ethylene exhibit advance thermal conductivity (Cao, 2002).

Physical:

The physical properties include optical such as the colour of the nanoparticle, its light penetration, absorption and reflection capabilities, and UV absorption and reflection abilities in a solution or when coated onto a surface. It also includes the mechanical properties such as elastic, ductile, tensile strengths and flexibility that play a significant factor in their application. Other properties like hydrophilicity, hydrophobicity, suspension, diffusion and settling characteristics has found its way in many modern everyday things. Magnetic and electrical properties such as conductivity, semi conductivity and resistivity has led a path for the nanoparticles to be used in modern electronics thermal conductivity in renewable energy applications.

Chemical:

The chemical properties such as the reactivity of the nanoparticles with the target and stability and sensitivity to factors such as moisture, atmosphere, heat and light determine its applications. The anti- bacterial, anti-fungal, disinfection, and toxicity, properties of the nanoparticles are ideal for biomedical and environmental applications. Corrosive, anti-corrosive, oxidation, reduction and flammability characteristics of the nanoparticles determine their respective usage.

Applications:

Below are some of the significant applications of nanoparticles.

Cosmetics and Sunscreens:

The conventional ultraviolet (UV) protection sunscreen lacks long-term stability during usage. The sunscreen including nanoparticles such as titanium dioxide provides numerous advantages. The UV protection property of titanium oxide and zinc oxide nanoparticles as they are transparent to visible light as well as absorb and reflect UV rays found their way to be used in some sunscreens. Some lipsticks use iron oxide nanoparticles as a pigment²².

Electronics:

The higher necessity for large size and high brightness displays in recent days that are used in the computer monitors and television is encouraging the use of nanoparticles in the display technology. For example nanocrystalline lead telluride, cadmium sulphide, zinc selenide and sulphide, are used in the light emitting diodes (LED) of modern displays²³.

The development in portable consumer electronics such as mobile phones and laptop computers led to the enormous demand for a compact, lightweight and high capacity batteries. Nanoparticles are the ideal choice for separator plates in batteries. A considerable more energy can be stored compared to traditional batteries due to their foam like (aerogel) structure. Batteries made from nanocrystalline nickel and metal hydrides, due to their large surface area require less recharging and last longer²⁴.

The increase in electrical conductivity of nanoparticles are used to detect gases like NO₂ and NH₃³⁰. This is due to increase in the pores of nanoparticles due to charge transfer from nanoparticles to NO₂ as the gas molecules bind them together making them a better gas sensors.

Catalysis:

Nanoparticles contain high surface area that offers higher catalytic activity. Due to their extremely large surface to volume ratio the nanoparticles function as efficient catalyst in the production of chemicals ²⁵. One of the important application is the use of platinum nanoparticles in the automotive catalytic converters as they reduce the amount of platinum required due to very high surface area of the nanoparticles thus reducing the cost significantly and improving performance. Some chemical reactions for example, reduction of nickel oxide to metal nickel (Ni) is performed using nanoparticles.

Medicine:

Nanotechnology has improved the medical field by use of nanoparticles in drug delivery. The drug can be delivered to specific cells using nanoparticles²⁶. The total drug consumption and side effects are significantly lowered by placing the drug in the required area in required dosage. This method reduces the cost and side effects. The reproduction and repair of damaged tissue (Tissue engineering) can be carried out with the help nanotechnology. The traditional treatments such as artificial implants and organ transplants can be replaced by tissue engineering. One such example is the growth of bones carbon nanotube scaffolds²⁷. The use of gold in medicine is not new. In Ayurveda an Indian medical system, gold is used in several practices. One common prescription is the use of gold for memory enhancement. To enhance the mental fitness of a baby gold is included in certain medical preparations²⁸.

Food:

The improvement in production, processing, protection and packaging of food is achieved by incorporating nanotechnology. For example a nanocomposite coating in a food packaging process can directly introduce the anti-microbial substances on the coated film surface²⁹. One of the example is the canola oil production industry includes nanodrops, an additive designed to transfer the vitamins and minerals in the food.

Construction:

Nanotechnology has improved the construction processes by making them quicker, inexpensive and safer. For example when nanosilica (SiO₂) is mixed with the normal concrete, the nanoparticles can improve its mechanical properties, and also improvements in durability³⁰. The addition of haematite (Fe₂O₃) nanoparticles increases the strength of the concrete. Steel is the most widely available and used material in the construction industry. The properties of steel can be improved by using nanotechnology in steel for example in bridge construction the use of nano size steel offers stronger steel cables³⁰. The other important construction material is glass. Extensive research is being performed on the application of nanotechnology in construction glass. Since titanium dioxide (TiO₂) nanoparticles has sterilizing and anti-fouling properties and catalyse powerful chemical reaction that breakdown volatile organic compound (VOV) and organic pollutants it is used to coat glazing³¹. The use of nanotechnology provides a better blocking of light and heat penetrating through the windows. The paints with self-healing abilities and corrosion resistance and insulation are obtained by adding nanoparticles to the paints. The hydrophobic property of these paints repels water and hence can be used to coat metal pipes to offer protection from salt water attack. The addition of nanoparticles in paints also improves its performance by making them lighter with enhanced properties³² so when used for example on aircraft, it might reduce their overall weight and the amount of paint required, which is favourable to the environment as well the company to improve cost savings.

Renewable energy and environmental remediation:

The unique physical and chemical properties of nanoparticles has made them an ideal choice to be used nowadays in environmental remediation to enhancing the performance in renewable energy sector³³. Nanoparticles occur in nature themselves and some of them are found to cure the environment.

Environmental remediation using nanoparticles or nanoremediation is successfully being used to treat or decontaminate the air, water and soil for over a decade². Nanoremediation is one of the effective solutions as it offers in situ treatment eliminating the necessity of pumping the ground water out for treatment and the need for excavation to reach the target destination. The nanoparticles are injected into the desired location and gets carried along the groundwater flow and decontaminates the water by immobilising the contaminants. The general mechanism involving in decontamination is the redox reactions.

The nanoparticles are used to treat the surface water by disinfection, purification and desalination. Some of the contaminants are most likely to be heavy metals, pathogens and organic contaminants. It has proven to be efficient and eliminating the need for chemicals that may sometime produce secondary reaction products.

Oil spill is one of the major problem worldwide as it may spread over very long distances. Cleaning them by conventional methods is difficult and time consuming that makes the situation worse as it may spread more. The nanoparticles are also used to clean-up oil spills and has also established to be effective method.

The major use of nanoparticles are to treat municipal and industrial wastewater as well as the sludge produced. The replacement of nanoparticles for conventional chemicals is due to less cost, higher efficiency and lower quantity required for treatment. Nanofiltration is a recent membrane filtration system for water purification widely used in food and dairy industries.

Soil contamination is also an increasing concern. Contaminated soil is cleaned or treated using nanoparticles by injecting the nanoparticles into specific target locations for heavy metal contamination, toxic industrial waste, etc. The higher surface area of certain nanoparticles has been used as a nanocatalyst in gaseous reactions. The most widely used area is in industrial stacks to reduce the contaminant level to prescribed limits or to remove completely that reduces the air pollution.

Extensive research is being carried out in the use of nanoparticles for renewable energy. Higher light and UV absorption with a very low reflection coatings in solar cells has improved their efficiency by considerable extent. The hydrophobic property of some nanoparticles has led to self-cleaning solar cells. High thermal conductivity and heat absorption capacity of certain nanoparticles are used to coat boilers and solar concentrators to improve their thermal efficiency.

CONCLUSION:

Nanotechnology is improving our everyday lives by enhancing the performance and efficiency of everyday objects. It provides a clean environment by providing safer air and water, and clean renewable energy for a sustainable future. Nanotechnology has gained a wide attention where more investment is made for the research and development by top institutions, industries and organisations. Nanotechnology has established to be an advanced field of science where extensive research is carried out to implement the technology. It is being tested for various new applications to increase the efficiency and performance of the object or process and subsequently reduce the cost so that it is accessible for everyone. The nanotechnology has a great future due to its efficiency and environmental friendly property.

REFERENCES:

1. Hasan S 2015 A Review on Nanoparticles: Their Synthesis and Types Biosynthesis: Mechanism 4 9–11

2. Assessment R 2007 Nanoparticles in the Environment

3. Cho E J, Holback H, Liu K C, Abouelmagd S A, Park J and Yeo Y 2013 Nanoparticle characterization: State of the art, challenges, and emerging technologies

4. Machado S, Pacheco J G, Nouws H P A, Albergaria J T and Delerue-Matos C 2015 Characterization of green zero-valent iron nanoparticles produced with tree leaf extracts Sci. Total Environ. 533 76–81

5. Tiwari D K, Behari J and Sen P 2008 Application of Nanoparticles in Waste Water Treatment 3 417–33

6. Salavati-niasari M, Davar F and Mir N 2008 Synthesis and characterization of metallic copper nanoparticles via thermal decomposition Polyhedron 27 3514–8

7. Tai C Y, Tai C, Chang M and Liu H 2007 Synthesis of Magnesium Hydroxide and Oxide Nanoparticles Using a Spinning Disk Reactor 5536–41

8. Bhaviripudi S, Mile E, Iii S A S, Zare A T, Dresselhaus M S, Belcher A M and Kong J 2007 CVD Synthesis of Single-Walled Carbon Nanotubes from Gold Nanoparticle Catalysts 1516–7

9. Ramesh S 2013 Sol-Gel Synthesis and Characterization of 2013

10. Mann S, Burkett S L, Davis S A, Fowler C E, Mendelson N H, Sims S D, Walsh D and Whilton N T 1997 Sol - Gel Synthesis of Organized Matter 4756 2300–10

11. Mohammadi S, Harvey A and Boodhoo K V K 2014 Synthesis of TiO 2 nanoparticles in a spinning disc reactor Chem. Eng. J. 258 171–84

12. Search H, Journals C, Contact A, Iopscience M and Address I P Nanoparticle Synthesis by Ionizing Source Gas in Chemical Vapor Deposition Nanoparticle Synthesis by Ionizing Source Gas in Chemical Vapor Deposition 77 4–7

13. Kammler B H K, Mädler L and Pratsinis S E 2001 Flame Synthesis of Nanoparticles 24 583–96 13 1234567890 14th ICSET-2017 IOP Publishing IOP Conf. Series: Materials Science and Engineering 263 (2017) 032019 doi:10.1088/1757-899X/263/3/032019

14. Amato R D, Falconieri M, Gagliardi S, Popovici E, Serra E, Terranova G and Borsella E 2013 Journal of Analytical and Applied Pyrolysis Synthesis of ceramic nanoparticles by laser pyrolysis: From research to applications J. Anal. Appl. Pyrolysis 104 461–9

15. Kuppusamy P, Yusoff M M and Govindan N 2014 Biosynthesis of metallic nanoparticles using plant derivatives and their new avenues in pharmacological applications - An updated report SAUDI Pharm. J.

16. Yadav T P, Yadav R M and Singh D P 2012 Mechanical Milling: a Top Down Approach for the Synthesis of Nanomaterials and Nanocomposites. 2 22–48

17. Pimpin A and Srituravanich W Review on Micro- and Nanolithography Techniques and their Applications 16 37–55

18. Hulteen J C, Treichel D A, Smith M T, Duval M L, Jensen T R and Duyne R P Van 1999 Nanosphere Lithography: Size-Tunable Silver Nanoparticle and Surface Cluster Arrays 3854–63

19. Amendola V and Meneghetti M 2009 Laser ablation synthesis in solution and size manipulation of noble metal nanoparticles 3805–21

20. Shah P and Gavrin A Ã 2006 Synthesis of nanoparticles using high-pressure sputtering for magnetic domain imaging 301 118–23

21. Lugscheider E, Bärwulf S, Barimani C, Riester M and Hilgers H 1998 Magnetron-sputtered hard material coatings on thermoplastic polymers for clean room applications Surf. Coatings Technol. 108-109 398–402

22. Wiechers J W and Musee N 2010 Engineered Inorganic Nanoparticles and Cosmetics: Facts, Issues, Knowledge Gaps and Challenges 6

23. Teng W, Jeng S, Kuo C, Lin Y, Liao C and Chin W 2008 liquid crystal displays 33 1663–5

24. Published A, Link C and Terms D 2016 Platinum-Gold Nanoparticles: A Highly Active Bifunctional Electrocatalyst for Rechargeable Lithium-Air Batteries The MIT Faculty has made this article openly available. Please share Citation and may be subject to US copyright law. Please refer to the P

25. Liu X, Zhang J, Wang L, Yang T, Guo X, Wu S and Wang S 2011 3D hierarchically porous ZnO structures and their functionalization by Au nanoparticles for gas sensors 349–56

26. Crooks R M, Zhao M, Sun L I, Chechik V and Yeung L E E K 2001 Dendrimer-Encapsulated Metal Nanoparticles: Synthesis, Characterization, and Applications to Catalysis 34 181–90

27. Ganesh K and Archana D 2013 Review Article on Targeted Polymeric Nanoparticles: An Overview [33] Mudshinge S R, Deore A B, Patil S and Bhalgat C M 2011 Nanoparticles: Emerging carriers for drug delivery Saudi Pharm. J. 19 129–41

28. Shinde N C, Keskar N J and Argade P D Research Journal of Pharmaceutical, Biological and Chemical Sciences REVIEW Article Nanoparticles: Advances in Drug Delivery Systems 3 922–9

29. Laad M and Jatti V K S 2016 Titanium oxide nanoparticles as additives in engine oil J. KING SAUD Univ. - Eng. Sci. 0–6 14 1234567890 14th ICSET-2017 IOP Publishing IOP Conf. Series: Materials Science and Engineering 263 (2017) 032019 doi:10.1088/1757-899X/263/3/032019

30. Nazari A and Riahi S 2011 Composites: Part B The effects of SiO 2 nanoparticles on physical and mechanical properties of high strength compacting concrete Compos. Part B 42 570–8

31. Xu X, Stevens M and Cortie M B 2007 In situ precipitation of gold nanoparticles onto glass for potential architectural applications

32. Machado S, Pacheco J G, Nouws H P A and Albergaria J T 2015 Science of the Total Environment Characterization of green zero-valent iron nanoparticles produced with tree leaf extracts Sci. Total Environ. 533 76–81

Received on 21.01.2022 Modified on 10.02.2022

Res. J. Pharmacology and Pharmacodynamics.2022;14(2):117-124.

DOI: 10.52711/2321-5836.2022.00020