Essay: Green synthesis of nanoparticles

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1. Introduction

Nanotechnology was defined as the manipulation of matter via a number of elements and/or real processes to produce components along with specific properties, which can be used in certain application [1]. A new nanoparticle could be defined as a new tiny particle which includes a minimum of one sizing below 100 nanometers in proportions [2]. Unlike bulk components, they have had exclusive optical, thermal, electro-mechanical, element, as well as real properties [3] , that’s why, many people uncover a number of applications in the actual areas of medicine, chemistry, environment, energy, agriculture, information, and communication, heavy industry, and consumer goods [4].Chemical synthesis strategies for nanoparticle synthesis (e. g., element lowering, sol serum approach, and so on.) include things like the use of harmful compounds, creation of hazardous byproducts, and also contamination through precursor compounds [2]. And so, the benefit of acquiring fresh, nontoxic, and also environment-friendly procedures intended for nanoparticle functionality. Green chemistry synthesis methods for nanoparticles have possessed positive aspects over chemical methods, for example safe, eco-friendly, harmful compounds will not be employed, and also cheap [5]. Examples of green synthesis were as follows, the active biological component such as enzyme itself have worked as a reducing and also capping agent, small nanoparticles could be generated even in the course of large-scale production [6], The Plant extracts also have reduced the metal ions in a shorter time, it was widely used due to the presence of reducing and stabilizing agent at its extract (10). An incredibly wide range of natural resources such as germs (bacteria, thrush, fungi, algae, and also viruses) and crops could be utilized intended for nanoparticle functionality [8]. Iron oxide nanoparticles (FeNPs) with different polymorph structures were actually extensively studied due to their extensive app throughout contemporary science and technological innovation (R. Zboril et al. 2002). The most common iron oxide polymorphs were usually α-Fe2O3, γ-Fe2O3, Fe3O4 and FeO. The α-Fe2O3 type has provided purposes throughout catalysts, high-density permanent magnetic storage media, pigments, anticorrosive agents, water splitting, water purification, solar energy conversion and gas sensors (E.J. Shin et al. 2005; R. Prucek et al. 2009; F. Rettig and R. Moos, 2010; I. Cesar et al. 2006. ) The γ-Fe2O3 and Fe3O4 nanoparticles were widely-used throughout permanent magnetic resonance image resolution (MRI) form a contrast agencies, ferrofluids, targeting drug delivery, anticancer therapies, hyperthermia cell labelling and separation. Because of the biocompatibility and non-toxicity. (D. Amara et al. 2012; L. L. Breen et al. 2001; Ymca. Deng et al. 08; Farreneheit. Caruso et al. 1999).

2. Various types of green synthesis of nanoparticles

2.1. From plant extract

Many researchers discovered constituents of various herbs, spices and plants that act as a powerful antioxidant compounds such as amino acids, polyphenols, nitrogenous bases and reducing sugars [16].These compounds act as capping [16,18] and reducing agents for the synthesis of nanoparticles[17]. Because of plant diversity, we can control the morphology and the size of the wanted nanoparticle by changing the source of the extract. (Malik et al. 2014). The plant leaf extract used for NPs synthesis can be scaled up and applied for larger scale production in addition of its economic advantages [21]. The metal and metal oxide NPs produced from a plant extract are usually stable even after a month no visible changes were remarked. [19] .A research studied, the aqueous extracts of leaves, stem and flower of Euphorbia milli, Datura innoxia, Calotropis procera , Tinospora cordifolia , Tridax procumbens and leaves of Cymbopogon citratus to evaluate their potential in the synthesis FeNPs . And their methods of extraction were as follows , 20gm of leaves, 10 g of stem and 2 g flower were washed with running and then with distilled water to remove the dust particles . They were dried by the use of blotting paper, cut into fine pieces by the use of a sterilized blade and with pestle they were crushed in a mortar. After 5-10 min of boiling them with 100 ml distilled water at 800C then cooled and filtered by Whatman filter paper no.1, then the extract was ready. At a temperature of about 50-60 C a mixture of 5 ml 0,001 M ferric chloride and 5ml of the plant extract Pattanayak M and Nayak PL. a change in color occurs by a final appearance of dark blue indicates the formation of Fe NPs. Shah S.

2.2. Microorganism-based methods for NPs synthesis

These methods are based on microorganisms like bacteria [10–22], algae [26–28] and fungi [23–25], to produce nanoparticles. Metallic nanoparticles are produced by adding metallic ions to the medium of culture of these microorganisms in controlled conditions. Prokaryotic bacteria have had an easy way of manipulation that’s why it was the most investigated microorganisms among all of the mentioned ones for the synthesis of metallic nanoparticles [1].

3. Synthesis of FeNps from plant extract

3.1. Commonly Used Plant Species (Tea extract)

First, in this method (Haung L et al. 2014.). A concentration of 60 g of Oolong tea extract per 1L of water was heated at 80 degrees Celsius for 1hour and a vacuum-filtered, then 0.1 mol/L of FeSO4 added to the extract at a ratio of 1:2 in volume. SEM (Scanning Electron Microscopy) image shows that the synthesized FeNPs has a spherical shape with a range of diameters from 40 to 50 nm. XRD (X-ray Diffraction) is another method showed that FeNPs was crystalline in nature. FeNPs could be used in the degradation of Malachite Green (MG), in aqueous solution where 12.3% of MG observed to be removed by effect of capping agents found in tea extract which are polyphenols and caffeine, which act also as reducing agents, where its removal efficiency using FeNPs observed to be 61.9% at 10 min and reached equilibrium at 75.5% within 60 min with a rate of0.045/ min. Degradation of MG caused due to cleavage of ─C═C─ and ═C═N─ bonds. The same method of extraction and synthesis was used with green tea[14,15]. And the same degradation and characterization results agreed with the green tea iron nanoparticles GT-FeNPs with a study of the effect of various parameters affecting this degradation as the solution temperature, FeNPs dosage, initial PH and the effect of H2O2 dosage [1]. By the mention of dyes a study on the degradation of cationic and anionic dyes were established based on GT-FeNPs also. Iron nanoparticles were synthesized by extracts of green tea leaves (GT-Fe NPs). The extract was prepared by boiling 60.0 g/L green tea (Alwald Brand) and settling for 1h, then filtering by vacuum filtration method. Independently, an addition of 19.9 g of solid FeCl2•4H2O (Aldrich 22029-9) in 1.0 L of deionized water occur to form a 0.10 M FeCl2•4H2O solution. Following this a 2:3 volume ratio solution was formed by adding 0.10 M FeCl2•4H2O solution to 60.0 g/L green tea. Subsequently, the pH reached 6.0 by adding 1.0 M NaOH solution and the formation of intense black precipitate indicates the presence of ready GT-Fe NPs. The nanoparticles were separated by water evaporation from iron solution on a hot plate, then by letting it dry in a fume hood overnight. The characterization of the material using TEM (Transmission Electron Microscopy), SEM, XRD, and FTIR (Fourier Transform Infrared Spectroscopy) techniques showed that it contains mainly iron oxohydroxide and iron oxide. Then nanoparticles were used for decolorization of aqueous solutions having methyl orange (MO) dyes and methylene blue (MB) as a Fenton-like catalyst. The applicable experiments searched the effect of concentration for both MB and MO and the removal kinetics. GT-Fe NPs improved high capabilities of removal for both of MB and MO, in terms of the kinetics and the extent of removal. GT- Fe NPs showed faster kinetics and higher dye removal percentages when used as a Fenton-like catalyst comparing with sodium borohydride Fe NPs [3]. As an application for arsenic removal tea waste was used, tea residue was sun dried after washing with water. 30g of dry tea residue was added to a solution of 150 ml distilled water and 15g of FeCl3.6H2O dissolved in it stirred for 4 h and left overnight. By filtration, FeCl3.6H2O treated tea residue was obtained and dried in an oven. Then in a muffle furnace, it was heated for 6 h at 450 degree Celsius and washed and dried. The resultant product was cuboid/pyramid shaped crystal structure of Fe3O4 (magnetite) with a size range from 5 to 25 nm that tend to cluster because they are magnetic in nature. This nanoparticles performed an excellent removal behavior for As(III) and As (V) arsenic ions in water. Magnetic iron nano oxide novel from tea (MINON-tea) has proved an efficient, high absorbent by making a comparison of adsorption capacity for arsenic removal. As it uses tea waste this is the most economical method [4]. Finally, there was a study of biocompatibility of tea polyphenols based nanoparticles (Mallikarjuna et al., 2009). The Synthesis of Nanoscale Zero Valent Iron particles (NZVI) using tea polyphenols. Where the Caffeine/polyphenols were acting as reducing and capping agents as previously mentioned. Tow grams of tea powder (Red label from Tata, India Ltd. 99%) were extracted in 100 ml hot water and then used to carry out the reaction with 0.1 N Fe (NOɜ)ɜ. The different proportion of Fe (NOɜ)ɜ and tea extract were prepared at room temperature. The reaction is accompanied by a change in color from yellow to dark brown this indicates the synthesis of nanoparticles. TEM images show different structures of nanoparticles spherical, platelets and nanorods. This is due to the role of the concentration of tea extract as a key of size and the final structure of the iron nanoparticles. The increase in concentration of caffeine/polyphenol in the reaction mixture decreases the particle size. Biocompatibility of NZVIis examined using the human keratinocyte cell (HaCaT) line as a representative skin exposure model for time periods of 24 and 48 h. The appraisal of mitochondrial function (MTS) and membrane integrity (LDH) in human keratinocytes showed that these NZVI were nontoxic in the human keratinocytes exposed and induced a prolific response in the cellular function compared with samples synthesized using a sodium borohydride as reducing agent.

Tea extract is the most common method in the synthesis of FeNPs, there are other application of tea extract mentioned with other plant extracts mentioned below such as curcuma”مرجع الكركم “and eucalyptus”مرجع الايوكاليبتاس مع الشاي”.

3.2. Synthesis FeNPs from Other Plant Species

The synthesis of FeNPs from different plant species is studied and the results showed different size and morphology of FeNps which could be used in different application as follows.

First, iron nanoparticle as a dye removal. A successfully synthesized hematite (-Fe2O3) Nanoparticles was synthesized from curcuma and tea leaves (Alagiri et al., 2014). For synthesis from tea leaves,10 ml of the tea extract was added to the iron nitrate solution prepared by dissolving 1 mM of Fe(NO3)3•9H2O in 100 ml of distilled water with magnetic stirring around 6 h then two solution mixture was stirred by magnetic stirring at 50°C for 24 h. In case of synthesis by curcuma, 0.1 g of curcuma was added to 20 ml of distilled water with continued stirring for 6 h then 40 ml of Fe(NO3)3 • 9H2O (1 mM) was added with vigorous stirring at 50° C for 24 h. The two products were centrifuged at 15,000 rpm for 20 min and washed, then dried in a vacuum at 70°C. XRD results showed that α-Fe2O3 nanoparticles are well crystallinity with crystallite size 4 and 5 nm for α-Fe2O3 from curcuma and tea extract, respectively. SEM result showed that samples possess spherical-like shape. The photocatalytic activity of α-Fe2O3 nanoparticles was used to measure the photocatalytic degradation of methyl orange (MO) dye in distilled water under the illumination of visible light which is measured every 30 min irradiation time. The color of the MO solution turns into a colorless within 120 min of illumination time and the concentrations of MO solution changes as a function of illumination time.

The other synthesis that show more stability and higher efficiency to degradation of MO dye under UV illumination was from Amaranthus dubius leaf extract ( Muthukumar et al.,2015), used for the synthesis of iron nanoparticles(FeNPs) because its content of various photochemicals like amaranthine, isoamaranthine, phenols, flavonoids, and lysine that were used as reducing agents(Yizhong et al., 2003; Jannathul et al., 2014). For the synthesis 20 g of leaves was heated with 100 mL distilled water at 50 °C for 45 min, then filtered through a Whatmann filter paper and stored at 4 °C for further use. Solution of leaf extract 40 ml was added to 50 ml of 0.5 M FeCl3 solution. The leaf extract pH 6 adjusted using 0.1 N HCl and 0.1 N NaOH by adding drop wise to the FeCl3 solution with continuous stirring for 90 minutes. Precipitates were washed with absolute ethanol, then dried in an oven at 60 °C for 180 min and stored in sealed bottles under dry condition. The study showed that the antioxidant activity increased from 34.2 to 94.9 by the increase in mass of leaves from 5 to 20 g per 100 ml of water. The antioxidant activity also increased with the increase of temperature from 40 to 50 °C, temperature above 50 °C showed decrease in antioxidant activity from 94.9 to 52%. When heating time was more than 45 min it leaded to degrade the antioxidant compound and when it was less than 45 min it was not enough for extraction. The zeta-potential value increased from −44 to −66 mV indicates the stability of the particles. SEM studies confirmed that FeNps were roughly spherical in shape and size range from 60 to 300 nm. The PSD (Particle-Size Distribution) results showed that leaf extract FeNps size ranges varying from 58 to 530 nm with less agglomeration even after 1 month. Catalytic activity was investigated by monitoring the decolourization of MO dye using UV irradiation showed that increasing the nanoparticles concentration resulted in an increase of color removal efficiency of MO. Decolourization occurred due to excited surface electrons from the nanoparticles that are captured through dissolved oxygen molecules on its surface and generate hydroxyl radical.

Another synthesis of iron nanoparticles used as catalyst. First, from Murraya koenigii (curry leaves) (Sundaresan et al., 2014). A solution of 3 mL of extract was added to 7 mL of 1 mM FeSO4 solution and stirred on a magnetic stirrer for 5 min. Centrifugating the result at (15,000 rpm, 20 °C) for 20 min, then washed several times with distilled water and dried in a hot air oven. The color change from transparent yellow to black color indicated the synthesis of FeNPs. UV–visible spectra showed two absorption peaks at 284 and 315 nm because of a single surface plasmon resonance (SPR). FTIR analysis identified that the synthesized iron oxide nanoparticles surrounded by polyphenols, proteins and amines acted as capping agent .SEM images revealed that the morphology of the nanoparticles was appeared to be a porous, sponge like form, where TEM image showed that iron oxide nanoparticles was spherical along with some irregular shape. Dynamic light scattering analysis (DLS) found that the size of nanoparticles was 61nm. The iron oxide nanoparticles and FeSO4 used to study their effects on fermentative hydrogen production using C. acetobutylicum NCIM 2337.This supplementation involving FeNPs enhanced the hydrogen production in comparison with its of FeSO4. This supplementation involving FeNPs resulted could modify the metabolic pathway in the direction of increasing hydrogen production as a result of the development involving ferredoxinactivity.

Second, the synthesis of Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) using watermelon rinds is applied (P), A 2.26 g of FeCl3_6H2O and 6.46 g of sodium acetate dissolved in 30 ml of freshly prepared watermelon rind powder extract (WRPE) and stirred vigorously for 3 h at 80 °C. After 3 h the solution becomes homogenous black in color indicates the formation of Fe3O4 MNPs. FTIR spectra show that the existence of surface functional groups because the watermelon rinds are rich in polyphenols, acid derivatives and proteins. The synthesized Fe3O4 MNPs were highly crystalline with size ~16 nm, which is very close to the TEM result that show spherical morphology with an average size 20 nm. The result of energy dispersive spectroscopy (EDX) showed the deep-rooted significant presence of elemental iron. The synthesized Fe3O4 MNPs exhibit catalytic activity, so they are used it for the synthesis of 2-oxo-1,2,3, 4 tetrahydropyrimidine compounds. The studied show that Fe3O4 MNPs had several advantages of low catalyst loading (5 mmol) and high yields (94 %).

Another level of application was iron nanoparticles and their antibacterial effect, First, The Tridox Procumbens leaf extract in synthesis of iron oxide nanoparticles (Fe3O4), (M. Senthil and C. Ramesh., 2012) due to its content of carbohydrates, proteins and lipids that acted as reducing agents. By adding the extract to Ferric chloride solution, its color was changed from brown to black due to the presence of iron oxide nanoparticles. XRD spectrum indicated crystalline Fe3O4 in the range of 80-100 nm in size, where SEM showed irregular sphere shapes of Fe3O4 with rough surfaces. The antibacterial activity of Tridax procumbens mediated Fe3O4 nanoparticles was performed against Pseudomonas aeruginusa using the agar well diffusion method. Among various nanoparticles Fe3O4 was the best killer of Pseudomonas erogenous bacteria because of its Reactive Oxygen Species (ROS) content that kills bacteria preventing nonbacterial cells from any damage. By using agar and Potato Dextose Agar (PDA) wells of 10 mm diameter were made and different concentrations of nanoparticle samples were added to bacterial cultures, that results in decreasing growth rates of bacteria by increasing concentration of nanoparticles.

Second, the evergreen shrub Dodonaea viscosa (29) leaf extract used to synthesize iron nanoparticles. The plant extract contains flavonoids, Tannin and saponins that play a key role as reducing and capping agent. The effect of leaf extract concentration on nanoparticle synthesis was studied. The antimicrobial activity of synthesized nanoparticles was evaluated against human pathogens, namely, E. coli, K. pneumonia, P. fluorescens, S. aureus, and B. subtilis. A very low concentration of synthesized nanoparticles was sufficient to display effective antimicrobial action as compared to earlier stories.

Third, Spinacia oleracea extract act as reducing and stabilizing agent for synthesis FeNPs (S). A solution of 5 ml of spinancia extract was added into 5ml of 1 mM ferric chloride aqueous solution. The color return from colorless to yellowish brown color indicate synthesis of FeNps. UV-Visible spectrum show that FeNps gives rise to plasma resonance absorption band due to combined vibration of metal nanoparticles in resonance with the light wave at 422nm and 261nm.The zeta potential is found to be -114mV which indicate stability of FeNps. The antimicrobial activity of FeNps was evaluated against Gram positive: Bacillus megaterium, Staphylococcus aureus, Gram negative: Escherichia coli (M&D), Pseudomonas aeruginosa, klebsiella pneumonia by disc method. Gram positive Bacillus megaterium, staphylococcus aures, Gram negative Escherichia coli (M), Escherichia coli (D), pseudomonas aeruginosa, klebsila pneumonia. The cultures shown zone of inhibition was about 1.7,1.2,1.8,2.3,1.6,1.4 in diameter respectively. The culture of Escherichia (D) shows maximum zone of inhibition. This method of synthesis is simple and rapid extraction within 5- 10 min.

Finally, A simple conventional heating method being employed in the synthesis of (FeNPs) from Lawsonia inermis (Henna) and Gardenia jasminoides leaves extract (H)which act as reducing, capping, and stabilizing [33]. A solution of plant extracts was added 2ml every 5 mi until 50 ml on a solution of 10ml of 0.01M FeSO4, after every 5 min the difference of temperature was noted to cool down. Henna extract main component is Lawson (2-hydroxy-1,4-naphthoquinone), it contains benzene unit, p-benzoquinone unit, and phenolic group. FTIR analysis for FeNPs from Henna extract show that Lawson has coordinated with Fe through the phenolic oxygen, aromatic ring, and C=O group of the p-benzoquinone resulting in the formation of Fe. The size of FeNPs synthesized using Henna and Gardenia leaves extract observed to be 21 and 32nm respectively from TEM images. SEM image of FeNPs from Henna extract indicates that nanoparticles formed are agglomerated because of the adhesive nature having morphology of distorted hexagonallike appearance. In case of FeNPs synthesized using extract of Gardenia, It was agglomerated because of the adhesive nature having morphology of shattered rock-like appearance. Henna leaves extract was determined by using EDX (Energy Dispersive X-ray) analysis. It was observed that the percentage of iron is 6.86%, carbon is 54.59%, oxygen is 36.57%, magnesiumand phosphorus are 0.68%, and potassium is 0.63%. And in case of FeNPs synthesized using Gardenia leaves Elemental composition was found as percentage of iron is 4.68%, carbon is 50.79%, oxygen is 41.37%, aluminium is 0.76%, silicon is 1.57%, and potassium is 0.83%. The particular antibacterial effect associated with synthesized FeNPs coming from Lawsonia inermis along with Gardenia jasminoides actually leaves draw out is usually examined along with benefits present that FeNPs associated with Gardenia jasminoides ended up stronger towards Staphylococcus aureus using with zone of inhibition (ZOI) 16mm, whereas for Lawsonia inermis it was 15mm. Next to Escherichia coli, Salmonella enterica, along with Proteus mirabilis your ZOI associated with FeNPs ended up being 14mm and 15 mm, 9mm and 12 mm, 11mm along with 13 mm, respectively.

The significant issue of iron nanoparticles in bioremediation was researched. First, by Emblica officinalis leaf extract usage to synthesize ZVINPs (Kumar et al., 2015). Aqueous solution of FeClɜ and filtered leaf extract were mixed in different ratios at room temperature. The color change from yellow to black indicated the synthesis of ZVINPs. Polyphenol content and ascorbic acid acted as reducing and stabilizing agent for synthesis ZVINPs (Nadagouda and Varm, 2007; Sun et al., 2009; Hoag et al., 2009).SEM image showed that uniform and spherical morphology of the ZVINPs, where TEM image found that iron nanoparticles were spherical in shape, having an average size of 22.6 mm. Zeta potential was found equal to -26.7 mV which indicates that ZVINPs are moderately stabilized. Batch tests were performed to evaluate the lead remediation potential of ZVINPs. The results show that when concentration of lead was low, a lower concentration of ZVINPs and lesser time was required for its remediation. More time duration was required to remove a higher concentration of lead. The efficiency of ZVINPs is not only dependent on the concentration of lead and ZVINPs but also on the time duration of its application as in results for the remediation of lead (Liu et al., 2009; Zhang et al., 2010, 2011). Also, a green synthesis of Fe3O4 magnetic nanorods (Fe3O4 MNRs) using Punica Granatum (R ) rind extract is applied for remove Pb(II), A 2.16 g of FeCl.6 H2O and 6.56 g of sodium acetate were dissolved in 40 ml of P. Granatum rind extract solution then a 0.926 g of dried Fe3O4 MNRs and 0.7288 g dimercaptosuccinic acid (DMSA) were mixed together by ultrasonication for 10 h at room temperature to form [email protected] MNRs. XRD show that the cubic inverse spinel structure of both Fe3O4 MNRs and [email protected] MNRs and the diffraction peak width of Fe3O4 MNRs slightly differs from that of [email protected] MNRs with no phase change of Fe3O4 MNRs. Where TEM images show that Fe3O4 and [email protected] MNRs has an average diameter of 40 nm and length above 200 nm. The nanorods slightly change because of DMSA ligands which became interlinked on the surface of Fe3O4 MNRs through COO- groups this favors the stability of colloidal dispersion. In addition, the poly crystalline nature of nanorods result from selected area diffraction (SEAD) pattern. The P. Granatum rind contained rich polyphenols, carbohydrates, acid derivatives, proteins, lipids, and fibers which used as reducing and stabilizing agent (Cama and Hısıl, 2010). The effect of the pH value on the removal of Pb(II) ion by Fe3O4 and [email protected] MNRs was studied at pH 2–7 and different concentration of Pb(II) 20, 40 and 60 mg/L. The results show that with an increase in pH from 2 to 5 the percentage removal of Pb(II) increased but decreased with an increased pH 6–7 and the maximum removal of 96.68% at pH 5.0, initial concentration of 20 mg/L.

Second, Eucalyptus leaves for the synthesis of iron nanoparticles (Wang et al, 2014). Eucalyptus leaf extract iron nanoparticles (EL-FeNPs) were synthesized at room temperature by mixing the extract with 0.10 M FeSo4at a volume ratio of 2:1. The presence of black color immediately represented the reduction of Fe2+ ions. SEM proved the synthesis of the spheroidal iron nanoparticles. In addition, FTIR and XRD showed that some polyphenols are present on the surfaces of EL-FeNPs as a capping/stabilizing agent. In the extract polyphenols reduced the aggregation of FeNPs and improve their reactivity. The application of EL-FeNPs showed 71.7% of total Nitrogen, 30.4% of total phosphorus and 84.5% of Chemical Oxygen Demand were removed from a swine wastewater, respectively. This demonstrated the enormous potential in situ remediation of wastewater. The non-toxic and biodegradable eucalyptus leaves, which were easily obtainable and environmentally friendly, are normally considered as waste. This way of synthesis was very simple, efficient and applicable at room temperature. Another work needed a high temperature (Wang, 2014), The extract of eucalyptus was prepared by boiling a mixture of 250 ml deionized water and 15 g dry leaves of the plant at 80 degrees Celsius for 1 h in addition of its vacuum filtration, following the same steps a green tea extract was prepared. The FeNps were obtained by adding every extract separately to 0.10 FeSo4 with a ratio 2:1 of volume at room temperature and for 30 min constantly stirred. To confirm the reduction of Fe2+ ions a black color will appear. Both types of nanoparticles were quasi-spherical shaped by a range of diameters from 20 to 80 nm. The reactivity of these NPs for nitrogen removal was investigated and compared with the ordinary Zero valent and Fe3O4 nanoparticles chemically prepared. Although they showed a less activity for removal of nitrogen, they perform a high stability in the air after aging, their activity remains the same while the one of ZVI and Fe3O4 nanoparticles dropped around 50%. another way for the same application was preparing magnetic iron oxide/reduced graphene oxide nanohybrid (IO\\RGO) as follows, Graphene Oxide (GO) was prepared following Hummer’s method [18]. The IO\\RGO was prepared by sonification for 30 min to disperse a 50 mg of GO in 50 mL water. Then by constantly stirring for 1h a 64.8 mg of FeCl3 and 39.6 mg of FeCl2 was added to the suspension under the N2 atmosphere. After that 10 mL of Colocasia esculenta leaves aqueous extract and 20 mL of the banana peel ash extract were added in the previous suspension. To reduce GO and form IO nanoparticle stirring for the above suspension occur for 30 min.Colocasia esculenta leaves aqueous extract was used as the reducing agent and banana peel ash aqueous extract was used as the base source. This method occurs at room temperature. The efficiency of these nanohybrid in removing pollutants proved itself by removing both organic and inorganic pollutants in a short time from contaminated water and for pollutants the adsorption processes were endothermic and spontaneous. Also, they are easily recycled. Other ways for the synthesis of FeNPs was investigated. First, Syzygium aromaticum (clove) for the synthesis of Zero Valent Iron Nanoparticles (ZVINPs) (Monalisa et al., 2013). A solution of 1:1 proportion of freshly prepared 0.001 M aqueous of FeCl3 solution and extract were mixed with constant stirring at 50-60°C and an addition of 1% of Chitosan and 1% of PVA to stabilize Iron Nanoparticles (FeNps). Formation of (FeNps) accompanied by reduced of pH from high acidic to low acidic 4.22 to 1.88. SEM studies confirmed that (FeNps) were dispersed spheres having diameters around 100 nm. The UV visible spectroscopy of the synthesized (FeNps) show tow peaks at 216-265 nm because of surface Plasmon resonance (SPR) of nanoparticles. Second, Ocimum sanctum (Krishna Tulsi) leaf extract for synthesis of Fe2O3 Nanoparticles (Balamurughan et al., 2014). The leaf extract and the precursor salt FeSO4 were mixed in 1׃5 proportions. The reaction mixture was centrifuged at 10,000 rpm for 15 min. The supernatant was washed with MilliQ water and dried in hot air oven. The various volumes of leaf extract were added to the constant volume of FeSO4 solution at different pH conditions to study the effect of volumes of leaf extract and pH on the synthesis of nanoparticles. The color change from colorless to black indicated the formation of Fe2O3. UV-visible spectroscopy showed that the maximum absorbance was observed at 285 and 324 nm due to the excitation of surface plasmon vibrations. SEM images revealed that the synthesized iron oxide nanoparticles were aggregated as irregular sphere shapes with rough surfaces. The morphology of the nanoparticles mostly appeared to be porous and spongy. The results depicted that the optimum volume of leaf extract 5.0 mL and the optimum pH was found to be 5.0 for synthesis iron nanoparticles.

3.3. Various Bio-microorganisms.

Methods using various bio-microorganisms in synthesis of iron nanoparticles. First, from the algae Brown seaweed (Sargassum muticum). It is a kind of food found in coasted communities ( Mahdavi M et a, 2013) that can be used in iron oxide nanoparticle synthesis in rapid single step, extract from Sargassum muticum contained sulphated polysaccharides which acts as reducing agents and stabilizers that provide capping for nanoparticles formed. Where 1g of frozen at -20C and dried sample of brown seaweed boiled with 100g of distilled deionized water in Erlenmeyer flask, then a solution of FeCl3 was added to the extract at a volume ratio of 1:1; solution’s color is immediately changed from yellow to dark brown indicating formation of Fe3O4 nanoparticles. The colloidal suspension obtained needed to be centrifuged and washed many times using ethanol, then dried at 40C under vacuum to obtain Fe3O4 nanoparticles (Fe3O4-NP). XRD indicated the spinel phase and crystalline structure of magnetite nanoparticles formed with average sizes in the range of 17-25 nm. TEM confirmed the crystalline structure of Fe3O4-NP with a mean diameter of 18±4 nm, where FESEM(Field Emission Scanning Electron Microscopy) image showed Fe3O4-NP in a cubic shape. EDXRF (Energy Dispersive X-ray Fluorescence) spectrum showed the presence of Fe3O4-Np without any impurities, and UV-Vis spectra also admitted presence of FE3O4-NP at wavelengths of 402nm and 415nm. Another method used to identify the magnetic property of Fe3O4-NP as it confirmed the superparamagnetic nature of iron nanoparticles formed showing that green synthesis produced nanoparticles having low magnetic property compared with that synthesized by co-precipitation chemical method.Mahdavi M. Second, Using Aspergillus oryzae TFR9 (fungus) as it was left in a 50mL potato dextrose broth medium to grow up in pH 5.8, 28∘C for 72 h at150 RPM on shaker medium, by using Whatman filter paper no.1 mycelia was filtered from the culture, 150 RPM shaker, at 28∘C for 12 h the mycelia was kept after resuspention in 50mL Milli-Q water, by a 0.45 micro size membrane filter the fungal biomass was separated to obtain cell-free filtrate, then we use the filtrate to prepare 0.001 M salt solution of FeCl3, the whole mixture was left on 150 RPM shaker at 28∘C for 12 h. Then the product was collected for characterization. The polydispersity index was 0.258. The size of the particle was in range of 10 nm and 24.6 nm, and it appears that the shape of iron nanoparticles is spherical. This method may be useful in engineering, biomedical and agriculture sector[.Tarafdar J]. Another study by Using Actinobacter spp. aerobic bacterium, by its isolation from an aqueous mixture of potassium ferricyanide/ferrocyanide that had been in the air for 2 weeks, the formation of magnetite occurs after the reaction of the bacterium with the mentioned solution in fully aerobic conditions. After 24 h, an image of iron oxide nanoparticles was taken in this reaction medium showed a high percentage of quasi-spherical shape with a size in the range of 10-40 nm. But after 48 h of the reaction, the results showed nanoparticles of cubic shape, sizing from 50-150 nm and the number of spherical particles was reduced. The nanoparticle assemblies in cubic shape were stable for weeks because of bio-microorganic molecules secreted by the bacterium. The advantage from using Actinobacter spp. Is the short time of reaction and the appearance of its results by contrast with other bacteria [Bharde A]. By contrast, in an anaerobic medium the mineralization of iron oxide occurs using Tobacco Mosaic virus stirred suspension (0.5 mg/mL) in MES buffer (0.1 M, pH 6.4) added to an aliquot of (NH4)2Fe(SO4)2.6HO2 (15 micro L , 12 mM) and allowed to oxidize for 1h in the air between additions. After washing the resulting suspension with buffer and concentrating it with a microcon 100, a drop of it was placed on carbon-coated Cu grids for examination of TEM.[Shenton]

3.4. Synthesis of iron oxide NPs from magnetite sand

Synthesis of IONPs (magnetite-Fe3O4) from Magnetite sand from River Palar by acid leaching (Periyathambi P et al., 2014). Fibrin coated IONPs (F-IONPs) synthesis because fibrin has high magnetic property can serve as a novel platform for enhanced MRI sensitivity. XRD show that IONPs and F-IONPs are crystalline cubic structure. The hydrodynamic diameters of IONPs and FIONPs were 15 nm and 35 nm, respectively The zeta potentials of IONPs and F-IONPs were -8.6 mV and -37.4 mV respectively which indicate that F-IONPs more stable than IONPs. Another technique TEM show that nanoparticles spherical shaped with a particle size of ranges 10-15 nm and 22- 28 nm were obtained for IONPs and F-IONPs respectively. The F-IONPs is novel and cheap to use as contrast agent for enhanced MRI sensitivity, show low percentage of haemolysis also exhibit higher viability and effective cellular internalization than IONPs when incubated in cells.Periyathambi P

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