BioNanoScience https://doi.org/10.1007/s12668-018-0516-5

Review of Green Methods of Iron Synthesis and Applications

Heba Mohamed Fahmy1 & Fatma Mahmoud Mohamed1 & Mariam Hisham Marzouq1 & Amira Bahaa El-Din Mustafa1 & Asmaa M. Alsoudi1 & Omnia Ashoor Ali1 & Maha A. Mohamed1 & Faten Ahmed Mahmoud1

# Springer Science+Business Media, LLC, part of Springer Nature 2018

Abstract Green chemistry becomes an eye-catching topic of interest in the past few years because it is a comfortable, secure, inexpensive, and eco-friendly way of synthesis. Iron oxide nanoparticles with different morphologies and sizes have been extensively studied due to their broad applications. Iron nanoparticles (Fe NPs) have drawn interest in site remediation and also in the treatment of organic or inorganic pollutants of water. The present review shows different synthesis methods of zero-valent and iron oxide nanoparticles from different plant extracts including tea extracts (Oolong tea, tea powder, tea waste,andtea polyphenols), from other plant extracts (Amaranthus dubius, Murraya koenigii, Eucalyptus, Syzygium aromaticum, curcuma, Ocimum sanctum, Emblica officinalis, Tridax procumbens, Dodonaea viscosa, Spinacia oleracea, Lawsonia inermis (henna), Gardenia jasminoides, Punica granatum, and Colocasia esculenta), from bio-microorganisms (Acinetobacter spp. bacterium, Aspergillus oryzae, Sargassum muticum), and from magnetite sand. The different potential applications of iron nanoparticles in remediation, in dye removal, and as an antibacterial agent point to the importance of iron nanoparticles in the environmental removal of contamination.

Keywords Antibacterial effect . Dye removal . Iron nanoparticles . Plant extracts . Remediation

1 Introduction fresh, nontoxic, and also environment-friendly procedures is intended for functionality. Nanotechnology is defined as the manipulation of matter via a Green chemistry synthesis methods for nanoparticles have number of ingredients and/or material processes to produce positive aspects over chemical methods, for example being components along with specific attributes, which can be ap- safe, eco-friendly, harmful compounds are not employed, plied in a variety of applications [1]. A nanoparticle could be and also cheap [5]. Examples of green synthesis methods are defined as a tiny particle which includes a minimum of one as follows: firstly, the active biological component such as sizing below 100 nm in dimensions [2]. Unlike bulk compo- enzymes works as reducing and also as capping agents, and nents, they had exclusive optical, thermal, and electrochemi- this is the reason why these small nanoparticles could be gen- cal properties [3], that is why many people uncover a number erated in the course of large-scale production [6]. Secondly, of applications in the actual areas of environment, medicine, the plant extracts also reduce the metal ions in a short time, energy, agriculture, chemistry, information, communication, and it is widely used because of the presence of reducing and heavy industry, and consumer goods [4]. Chemical synthesis stabilizing agents in their extracts [7]. Finally, an incredibly strategies for nanoparticles (e.g., element lowering, sol serum wide range of natural resources such as germs (bacteria, approach, and so on) include the use of harmful compounds, thrush, fungi, algae, and also viruses) and crops could be uti- creation of hazardous by-products, and also, contamination lized intended for nanoparticle functionality [8]. through precursor compounds [2]. So, the benefit of acquiring They are nontoxic in nature, and iron nanoparticles readily form oxides. Fe nanoparticles possess a high magnetic nature, high surface area, and electrical and thermal conductivity. * Heba Mohamed Fahmy [email protected] They also have excellent dimensional stability. Due to the properties of iron nanoparticles, they are known as magnetic

1 nanoparticles. Magnetic nanoparticles have been explored Department of Biophysics, Faculty of Science, Cairo University, widely in the last decades due to their large number of Nahdet Misr Street, Giza 12613, Egypt BioNanoSci. applications in the areas of spintronics, biology, and medical on magnetic particles for targeting folate receptors [33, 34]. science. Nanoparticles that are made of ferro- or ferromagnetic Magnetic nanoparticles are converted into sensing materials, below a certain size (generally 10–20 nm), can ex- superparamagnetic agents [35]. These nanosensors are de- hibit a unique form of magnetism called superparamagnetism. signed to detect molecular interactions in biological media This is an important phenomenon that is found only in iron after grafting of biomolecules to their surfaces [36, 37]. nanoparticles. Another application of iron oxide nanoparticles is the There are a number of applications of iron nanoparticles functionalization for in vitro protein or cell separation [38]. such as magnetic and electrical applications and biomedical Magnetic separation techniques have several advantages in applications, which include the labeling and magnetic separa- comparison to traditional separation procedures. This process tion of biological materials, directed drug delivery, MRI con- is very simple, and all steps of the purification can take place trast enhancement, and hyperthermia treatment [9]. in one test tube without expensive liquid chromatography sys- Hyperthermia as a medical treatment relies upon locally tems [39]. Magnetic iron oxide nanoparticles coated with heating tissues to temperatures higher than 42 °C for approx- phospholipids are also useful for the separation of proteins imately 30 min to destroy the tissue, particularly tumors [10]. from the mixture [40]. Magnetic drug targeting employing The difficulty in applying this therapeutically refers to the nanoparticles as carriers is used for cancer treatment, avoiding difficulty of selectively heating diseased tissue. The heating the side effects of conventional chemotherapy. Iron oxide of magnetic particles has been investigated for decades as a nanoparticles covered by starch derivatives with phosphate possible approach to selectively heat cancerous tumors. groups, which bound mitoxantrone, have been used as che- Iron oxide nanoparticles (Fe NPs) with different poly- motherapy. Alexiou et al. have shown that a strong magnetic morph structures were actually extensively studied due to their field gradient at the tumor location induces accumulation of extensive applications throughout contemporary science and the nanoparticles [41]. technological innovation [11]. The most common iron oxide There are several chemical ways for iron oxide nanoparti- polymorphs are α-Fe2O3, γ-Fe2O3,Fe3O4, and FeO. The α- cle preparation, and one of them is the hydrothermal precipi- Fe2O3 type has provided purposes throughout catalysts, high- tation method. The hydrothermal precipitation method has density permanent magnetic storage media, solar energy con- received great attention due to the advantages of this technol- version, water splitting, pigments, water purification, gas sen- ogy, such as fast reaction time, great control of particle shape, sors, and anticorrosive agents [12–15]. γ-Fe2O3 and Fe3O4 and low impurities into the particles [42]. Another common nanoparticles are widely used throughout permanent magnetic route of synthesis of magnetic nanoparticles which is widely resonance image resolution (MRI) as contrast agents, for hy- used is the chemical co-precipitation method [43]. perthermia cell labeling, as ferrofluids, for anticancer thera- pies, for targeting drug delivery, and for separation due to their nontoxicity and biocompatibility [16–19]. 2 Various Methods of Green Synthesis An iron nanoparticle conjugate serves both as a contrast of Nanoparticles agent in MRI and as a drug carrier in controlled drug delivery, targeted at cancer diagnostics and therapeutics. Molecular im- 2.1 From Plant Extracts aging is one of the important applications of targeted iron oxide nanoparticles. Most applications that use targeted iron Many researchers discovered constituents of various herbs, oxide nanoparticles are performed in vitro and in animal ex- spices, and plants that act like powerful antioxidant com- periments [20]. Specific cell tracking is another application of pounds such as amino acids, polyphenols, nitrogenous bases, iron oxide nanoparticles in MRI. The power to load enough and reducing sugars [44]. These compounds act as capping magnetic particles (micromolar Fe concentration) in cell cul- [45, 46] and reducing agents [47] for the synthesis of nano- ture via cell-permeable peptide or transfection agents in com- particles. Because of plant diversity, we can control the mor- bination with the negatively charged surface of magnetic par- phology and the size of the wanted nanoparticles by changing ticles provided a helpful technique to label and track cells the source of the extract [48]. A plant leaf extract used for NP in vivo by MRI [21, 22]. synthesis can be scaled up and applied for larger-scale produc- The first cellular imaging studies were performed with tion in addition of its economic advantages [49]. The metal unfunctionalized iron oxide nanoparticles for labeling leuko- and metal oxide NPs produced from a plant extract are usually cytes, lymphocytes, etc. [23–26]. If a cell is loaded with mag- stable even after a month and do not show any visible changes netic particles, MRI permits cell tracking with a resolution [50]. In previous studies, the aqueous extracts of leaves, stem, approaching the size of the cell [27]. To increase the cellular and flower of Datura inoxia, Calotropis procera, Euphorbia uptake of magnetic iron oxide particles, particles vectorized milii, Tinospora cordifolia, Cymbopogon citratus,andTridax with various peptides and fragments of proteins [28–31]or procumbens were used to evaluate their potential in the syn- coated with dendrimers [32] are used. Folic acid is grafted thesis of Fe NPs. BioNanoSci.

2.1.1 Synthesis of Fe NPs from Tea Extracts in it by stirring for 4 h and then left overnight. By filtration,

FeCl3⋅6H2O-treated tea residue was obtained and was dried in A concentration of 60 g of Oolong tea extract [51]per1Lof an oven. Then, in a muffle furnace, it was heated for 6 h at water was heated at 80 °C for 1 h and was vacuum-filtered, 450 °C, washed, and dried. The resultant product was a cu- then 0.1 mol/L of FeSO4 was added to the extract at a ratio of boid-/pyramid-shaped crystal structure of Fe3O4 (magnetite) 1:2 in volume. Scanning electron microscopy (SEM) analysis with size ranging from 5 to 25 nm that tends to cluster because showed that the synthesized Fe NPs had a spherical shape with of their magnetic nature. Nanoparticles synthesized in this diameters that ranged from 40 to 50 nm. X-ray diffraction way performed an excellent removal behavior for As (III) (XRD) showed that the prepared Fe NPs were crystalline in and As (V) arsenic ions in water. By comparison with other nature. Fe NPs prepared by this method were used in the reported adsorbents, magnetic iron nano oxide novel from tea degradation of Malachite Green (MG), in aqueous solution, (MINON-tea) had proved to possess the highest adsorption where 12.3% of MG was observed to be removed by the effect capacity for arsenic removal, as it uses tea waste, so it is of capping agents found in the tea extract represented as poly- considered the most economical method [56]. phenols and caffeine. They acted also as reducing agents, In a previous study for testing the biocompatibility of tea where its removal efficiency using Fe NPs was observed to polyphenol-based nanoparticles, the synthesis of nanoscale be 61.9% at 10 min and reached equilibrium at 75.5% within zero-valent iron particles (NZVI) using tea polyphenols was 60 min with a rate of 0.045/min. Degradation of MG was performed [57], where caffeine/polyphenols were acting as mainly due to cleavage of ─C═C─ and ═C═N─ bonds. The reducing and capping agents as previously mentioned. Two same method of extraction and synthesis was used with green grams of tea powder were extracted in 100 mL hot water and tea [52, 53]. The degradation and characterization results then used to carry out the reaction with 0.1 N Fe(NO ) . agreed with the green tea iron nanoparticles (GT-Fe NPs) Different proportions of Fe(NO ) and tea extracts were pre- mentioned in a previous study on the effect of various param- pared at room temperature. The reaction was accompanied by eters affecting this degradation such as the solution tempera- a change in color from yellow to dark brown indicating the ture, Fe NP dosage, initial pH, and effect of H2O2 dosage [54]. synthesis of nanoparticles as depicted in Fig. 1. TEM images Iron nanoparticles were synthesized from extracts of green tea showed different structures of nanoparticles: spherical, plate- leaves (GT-Fe NPs) as follows: the extract was prepared by lets, and nanorods. These differences in the synthesized nano- boiling 60.0 g/L green tea (Alwald brand) and settling it for particle structures were due to the role of the concentration of 1 h, then it was filtered by vacuum filtration method. tea extract as a key factor for determining the size and the final

Independently, the addition of 19.9 g of solid FeCl2·4H2Oto structure of iron nanoparticles. The increase in concentration 1.0 L of deionized water formed a 0.10-M FeCl2·4H2Osolu- of caffeine/polyphenol in the reaction mixture decreased the tion. After that, a 2:3 volume ratio solution was formed by particle size. Biocompatibility of NZVI was examined using adding 0.10 M FeCl2·4H2O solution to 60.0 g/L green tea. the human keratinocyte cell (HaCaT) line as a representative Subsequently, the pH reached 6.0 by adding 1.0 M NaOH solution. The formation of intense black precipitate indicated the presence of ready GT-Fe NPs. The prepared nanoparticles by this method were separated by water evaporation from iron solution on a hot plate, then letting them dry in a fume hood overnight. The characterization of the prepared nanoparticles using transmission electron microscopy (TEM), SEM, XRD, and Fourier transform infrared spectroscopy (FTIR) tech- niques showed that it contained mainly iron oxohydroxide and iron oxide. Then, the prepared nanoparticles were used for the decolorization of an aqueous solution of methyl orange (MO) dyes and methylene blue (MB) as a Fenton-like catalyst. GT-Fe NPs improved the capabilities of the removal for both MB and MO, in terms of the kinetics and the extent of remov- al. GT-Fe NPs showed faster kinetics and higher dye removal percentages when used as a Fenton-like catalyst compared with sodium borohydride Fe NPs [55]. As an application for arsenic removal, tea waste was used and tea residue was sun dried after being washed with water. Fig. 1 UV spectra of (a) Fe(NO3)3 control, (b) control tea extract, and (c) the reaction product (Fe nanoparticles) obtained from Fe(NO3)3 and tea Then,30gofdrytearesiduewasaddedtoasolutionof extract. The inset shows the photographic image of the tea extract, control 150 mL distilled water, and 15 g of FeCl3⋅6H2O was dissolved Fe(NO3)3 solution, and after mixing them (from left to right vials) [54] BioNanoSci. skin exposure model for time periods of 24 and 48 h [58]. The solution with continuous stirring for 90 min. Precipitates were appraisal of mitochondrial function (MTS) and membrane in- washed with absolute ethanol, then dried in an oven at 60 °C tegrity (LDH) in human keratinocytes showed that these for 180 min and stored in sealed bottles under dry condition. NZVI were nontoxic in the human keratinocytes exposed The antioxidant activity increased from 34.2 to 94.9 by the and induced a prolific response in the cellular function com- increase in the mass of leaves from 5 to 20 g per 100 mL of pared with samples synthesized using sodium borohydride as water and also increased with the increase in temperature from reducing agent. As a conclusion, tea extraction is the most 40 to 50 °C, and temperature above 50 °C showed a decrease common successful green method used for the synthesis of in the antioxidant activity from 94.9 to 52. When heating time Fe NPs. was more than 45 min, it led to the degradation of the antiox- idant compound, and when it was less than 45 min, it was not 2.1.2 Synthesis of Fe NPs from Other Plant Species enough for extraction. The zeta-potential value increased from − 44 to − 66 mV indicating the increase of the stability of the The synthesis of Fe NPs from different plant species was particles. SEM image showed that Fe NPs were roughly extensively studied and the results revealed different sizes spherical in shape having sizes ranging from 60 to 300 nm. and morphologies of the synthesized Fe NPs, which could The particle-size distribution results revealed that the leaf ex- be used in different applications as will be discussed after- tract Fe NP size ranges from 58 to 530 nm with less agglom- wards. Successfully synthesized hematite (-Fe2O3) nanoparti- eration even after 1 month. Catalytic activity was also studied cles were synthesized from curcuma and tea leaves [59]. For and showed that increasing the nanoparticle concentration re- the synthesis from tea leaves,10 mL of the tea extract was sulted in an increase of the color removal efficiency of MO to added to the iron nitrate solution prepared by dissolving 81% under UV irradiation. Decolorization occurred due to the

1 mM of Fe(NO3)3·9H2O in 100 mL of distilled water using generation of hydroxyl radical by excited surface electrons magnetic stirring about 6 h, then two solution mixtures were from the nanoparticles that are captured through dissolved stirred using magnetic stirring at 50 °C for 24 h. In the method oxygen molecules on its surface. The synthesized nanoparti- of synthesis using curcuma, 0.1 g of curcuma was added to cles exhibited higher antioxidant activity due to the site of 20 mL of distilled water with stirring for 6 h, then 40 mL of attachment of the metals and its consequence on the activity

1mMFe(NO3)3⋅9H2O was added with stirring at 50 °C for of the antioxidant agent [64]. 24 h. The two products were centrifuged at 15,000 rpm for Another method of synthesis of Fe NPs was from Murraya 20 min, washed, and then dried in a vacuum at 70 °C. The α- koenigii (curry leaves) [65], because the leaf extract has a high

Fe2O3 nanoparticles were well crystallized with crystallite size concentration of water-soluble ingredients such as alkaloids, 4and5nmforα-Fe2O3 from curcuma and tea extract, respec- flavonoids, carbazole, and polyphenols [66]. Briefly, a solu- tively, with uniform size distribution of spherical-like shape. tion of 3 mL of the curry leaf extract was added to 7 mL of

The prepared nanoparticles revealed high-purity iron oxide 1 mM FeSO4 solution and was stirred using a magnetic stirrer nanoparticles, which consisted only from iron and oxygen. for 5 min. Then, the product was centrifuged at (15,000 rpm,

The photocatalytic activity of α-Fe2O3 nanoparticles was used 20 °C) for 20 min, then washed several times with distilled to measure the photocatalytic degradation of MO dye in dis- water, and dried in a hot air oven. The color changed from a tilled water under visible illumination. The results showed that transparent yellow to black color within 5 min, indicating the the color of the MO solution turned into colorless within synthesis of Fe NPs. UV-visible spectra showed two absorp- 120 min of illumination time and the concentration of the tion peaks at 284 and 315 nm originated from a single surface MO solution changed as a function of illumination time. On plasmon resonance (SPR). FTIR analysis identified that the the other hand, the other synthesis methods that showed synthesized iron oxide nanoparticles surrounded by polyphe- higher stability and efficiency to degradation of MO dye under nols, proteins, and amines acted as capping agent. SEM im- UV illumination were from Amaranthus dubius leaf extract ages revealed that the morphology of the nanoparticles was [60] that was utilized for the synthesis of Fe NPs because it porous and has a sponge-like form with various particle sizes contains various photochemicals such as isoamaranthine, am- due to the agglomeration of nanoparticles during the sample aranthine, flavonoids, phenols, and lysine that were used as preparation [67]. TEM images showed that iron oxide nano- reducing agents [61, 62] and had many healing properties that particles were spherical along with some irregular shape. are inexpensive and easily usable [63]. For the synthesis pro- Dynamic light scattering (DLS) analysis showed that the size cedures, 20 g of leaves were heated with 100 mL distilled of nanoparticles was 61 nm. Ferredoxin acted as an electron water at 50 °C for 45 min, then filtered through a Whatman carrier in hydrogenase to produce molecular hydrogen, and filter paper and stored at 4 °C for further use. Forty milliliters iron is a component of ferredoxin, so, iron can improve the of the solution of leaf extract was added to 50 mL of 0.5 M hydrogenase activity and led to the enhancement of the fer-

FeCl3 solution. The leaf extract was adjusted to pH 6 by using mentative hydrogen production [68]. The effect of iron oxide 0.1 N HCl and 0.1 N NaOH by adding it dropwise to the FeCl3 nanoparticles on fermentative hydrogen production using BioNanoSci.

Clostridium acetobutylicum NCIM 2337 for 24 h was studied; nanoparticles was spherical with a size range from 50 to the hydrogen production was improved by the supplementa- 60 nm as shown by high-resolution transmission electron tion of 175 mg/L Fe NPs when compared to control by 254 ± microscopy (HRTEM) (Fig. 2). The Dodonaea viscosa leaf 12 and 314 ± 4 mL, respectively. On the other hand, the hy- extract was used to synthesize ZVI nanoparticles because of drogen production rate was found to be decreased at the con- its rich content of flavonoids such as tannins, santin, centration of 250 mg/L of Fe NPs because the excess concen- Pendleton, saponins, and pinocembrin [72], which act as re- tration of Fe NPs was harmful to microorganisms [69]. Fe3O4 ducing and capping agents. The antibacterial effects of ZVI magnetic nanoparticles (Fe3O4 MNPs) were also synthesized nanoparticles on Escherichia coli, Klebsiella pneumoniae, from watermelon. In this method, 2.26 g of FeCl3⋅6H2Oand Bacillus subtilis, Staphylococcus aureus,andPseudomonas 6.46 g of sodium acetate dissolved in 30 mL of freshly pre- fluorescens were studied, and the result showed that ZVI pared watermelon rind powder extract (WRPE) were mixed nanoparticles (12 μg) decreased the growth of bacteria by a and stirred vigorously for 3 h at 80 °C. After 3 h, the solution zone of inhibition (ZOI) 8, 10, 12, 14, and 24 mm, respective- became homogeneous black in color indicating the formation ly [73]. This method has the advantage of simplicity and rapid of Fe3O4 MNPs. FTIR spectra showed the existence of surface extraction within 5–10 min from Spinacia oleracea extract as functional groups, and this was because the watermelon rinds a reducing and stabilizing agent used for the synthesis of Fe were rich in polyphenols, acid derivatives, and proteins. The NPs [74]. A solution of 5 mL of Spinacia extract was added to

SEM images of watermelon-prepared Fe3O4 MNPs showed a 5 mL of 1 mM ferric chloride aqueous solution. The color highly crystalline structure with size ~ 16 nm, which is very turned from colorless to yellowish brown color indicating close to the TEM results that showed spherical morphology the synthesis of Fe NPs. The UV-visible spectrum showed that with an average size of 20 nm. The results of energy- Fe NPs gave rise to the plasma resonance absorption band due dispersive spectroscopy (EDX) showed the deep-rooted sig- to combined vibration of metal nanoparticles in resonance nificant presence of elemental iron. The watermelon- with the light wave at 422 and 261 nm. The zeta potential synthesized Fe3O4 MNPs exhibited catalytic activity, so it was found to be − 114 mV indicating high stability of Fe has been used for the synthesis of 2-oxo-1,2,3,4- NPs. The antimicrobial activity of Fe NPs (20 μL) was eval- tetrahydropyrimidine compounds. The study showed that uated by the disc method against Bacillus megaterium,

Fe3O4 MNPs had several advantages like high yields (94%) Staphylococcus aureus, Pseudomonas aeruginosa, and low catalyst loading (5 mmol) [70]. Escherichia coli (D), E. coli (M), and Klebsiella pneumoniae. In an another study that aimed to test the antibacterial effect The cultures showed zones of inhibition of about 1.7, 1.2, 1.6, of iron nanoparticles, the Tridox procumbens leaf extract was 2.3, 1.8, and 1.4 cm in diameter, respectively. used for the synthesis of iron oxide nanoparticles (Fe3O4) A simple conventional heating method has been employed [71]. Tridox procumbens was chosen due to its content of in the synthesis of (Fe NPs) from Lawsonia inermis (henna) carbohydrates that can act as reducing agent. By adding and Gardenia jasminoides leaf extract [75] which acted as re- 10 mL of Tridax procumbens leaf extract to 10 mL ferric ducing, capping, and stabilizing agents [76]. A solution of 2 mL chloride solution, the color changed after 10 min from brown of plant extract was added every 5 min to 10 mL of 0.01 M to black due to the presence of iron oxide nanoparticles. The FeSO4 until reaching 50 mL of a mixture. After every 5 min, XRD spectrum indicated crystalline Fe3O4 with crystalline size in the range of 80–100 nm, where SEM showed irregular sphere shapes of Fe3O4 with rough surfaces. By using the agar well diffusion method, the antibacterial activity of the synthe- sized Fe3O4 nanoparticles was performed against Pseudomonas aeruginosa. The results showed that by using nutrient agar and potato dextrose agar (PDA) at which bacteria were cultured, wells of 10 mm diameter were made and dif- ferent concentrations of nanoparticles (10, 20, 30, and 40 μL) were added to bacterial cultures which result in increasing the inhibition zone around wells by 1.0, 1.6, 1.8, and 2.0 mm, respectively. The iron nanoparticles synthesized by this method were found to be well separated and not agglom- erated. Another synthesis method that showed immediate synthesisofFeNPswasachievedbyadding5mLofleaf extracted from Dodonaea viscosa to 10 mL of FeCl solu- 3 Fig. 2 HRTEM image of biosynthesized ZVI nanoparticles in 100-nm tion (10 mM), and the immediate color change indicated scale with inset showing SAED pattern of corresponding nanoparticles the formation of ZVI nanoparticles. The morphology of [68] BioNanoSci.

difference of temperature was noted to cool down. The main Another green synthesis method of Fe3O4 magnetic nano- component of henna extract is lawsone (2-hydroxy-1,4- rods (Fe3O4 MNRs) was from Punica granatum [85]. Rind naphthoquinone), and it contains p-benzoquinone unit, benzene extract was applied for the removal of Pb (II) which is consid- unit, and phenolic group. The size of Fe NPs synthesized using ered as a heavy metal that is not biodegradable and accumulate henna and Gardenia leaf extracts was found to be 21 and in living organisms causing a lot of problems for humans [86] 32 nm, respectively, as detected from TEM images. SEM image specially Pb (II), the most toxic heavy metal responsible for a of Fe NPs from henna extract indicated that the formed nano- lot of disorders [87–89] and many other methods were used particles were agglomerated because of the adhesive nature, for its removal [90–94]. In this method, 2.16 g of FeCl⋅6H2O having the morphology of distorted hexagonal-like appearance. and 6.56 g of sodium acetate were dissolved in 40 mL of In the case of Fe NPs synthesized using an extract of Gardenia, P. granatum rind extract solution, then 0.926 g of dried it was agglomerated because of the adhesive nature, having the Fe3O4 MNRs and 0.7288 g dimercaptosuccinic acid morphology of shattered rock-like appearance. Henna leaf ex- (DMSA) were mixed together by ultrasonication for 10 h at tract was determined by using EDX analysis, and the percent- room temperature to form DMSA@Fe3O4 MNRs. XRD re- ageofironwasfoundtobe6.86%,carbon54.59%,oxygen sults showed that the cubic inverse spinel structure of both

36.57%, magnesium and phosphorus 0.68%, and potassium Fe3O4 MNRs and DMSA@Fe3O4 MNRs and the diffraction 0.63%. In the case of Fe NPs synthesized using Gardenia peak width of Fe3O4 MNRs slightly differed from that of leaves, the elemental composition that was found was as fol- DMSA@Fe3O4 MNRs with no phase change of Fe3O4 lows: iron 4.68%, carbon 50.79%, oxygen 41.37%, aluminum MNRs, whereas TEM images showed that Fe3O4 and 0.76%, silicon 1.57%, and potassium 0.83%. The particular DMSA@Fe3O4 MNRs had an average diameter of 40 nm antibacterial effect associated with (30 L/mL) Lawsonia and length above 200 nm. The nanorods slightly changed be- inermis-synthesized Fe NPs and Gardenia jasminoides leaves cause of DMSA ligands that became connected with the sur- ended up being stronger toward Staphylococcus aureus with a face of Fe3O4 MNRs through COO- groups, and this favored ZOI 16 mm, whereas for Lawsonia inermis, it was 15 mm. the stability of the colloidal dispersion. Also, the nanorods Next to Escherichia coli, Salmonella enterica and Proteus resulted from selected area diffraction (SEAD) pattern that mirabilis ZOI associated with Fe NPs synthesized by have a polycrystalline nature. The P. granatum rind contained Lawsonia inermis and Gardenia jasminoides endedupbeing rich polyphenols, carbohydrates, acid derivatives, proteins, 14 and 15 mm, 9 and 12 mm, and 11 and 13 mm, respectively. lipids, and fibers which were used as reducing and stabilizing The significant applications of iron nanoparticles in biore- agents [95]. The effect of pH value on the removal of Pb (II) mediation were investigated. Emblica officinalis leaf extract ion by Fe3O4 and DMSA@Fe3O4 MNRs was studied at pH 2– was used to synthesize zero-valent iron nanoparticles 7 and different concentrations of Pb (II) at 20, 40 and 60 mg/L. (ZVINPs) [77]. An aqueous solution of FeCl was mixed with The results showed that by increasing the pH from 2 to 5, the filtered leaf extract in different ratios at room temperature. The percentage removal of Pb (II) increased, but decreased with an color changed from yellow to black indicating the synthesis of increased pH 6–7 and maximum removal of 96.68% at pH 5.0, ZVINPs. Polyphenol content and ascorbic acid acted as with an initial concentration of 20 mg/L. reducing and stabilizing agents for the synthesis of In a different study, a very simple, efficient, and applicable ZVINPs [78–80]. SEM images showed uniform and spher- synthesis method at room temperature from Eucalyptus leaves ical morphology of the ZVINPs, where the TEM image was performed [96]. Eucalyptus leaf extract iron nanoparticles demonstrated that iron nanoparticles were spherical in (EL-Fe NPs) were synthesized at room temperature by mixing shape, having an average size of 22.6 mm. Zeta potential the extract with 0.10 M FeSO4 at a volume ratio of 2:1. The was found to be equal to − 26.7 mV which indicated that presence of black color immediately showed the reduction of ZVINPs were moderately stabilized. Batch tests were per- Fe2+ ions. SEM proved the synthesis of spheroidal iron nano- formed to evaluate the lead remediation potential of particles; in addition, FTIR and XRD techniques showed that ZVINPs, and the results showed that when the concentra- some polyphenols were presented on the surfaces of EL-Fe tion of lead was low, a lower concentration of ZVINPs and NPs as capping/stabilizing agents. In the extract, polyphenols lesser time were required for its remediation. More time reduced the aggregation of Fe NPs and improve their reactiv- duration was required to remove a higher concentration ity. The application of EL-Fe NPs on a swine wastewater of lead. The authors concluded that the efficiency of showed the removal of 71.7% of total nitrogen, 30.4% of total ZVINPs was dependent on the concentration of lead and phosphorus, and 84.5% of chemical oxygen, respectively. ZVINPs and the time duration needed for the remediation This demonstrated the enormous potential of EL-Fe NPs for of lead [81, 82]. The potential of ZVINPs in remediation in situ remediation of wastewater and prevention of eutrophi- was due to the combination of reduction, oxidation/reoxi- cation [97]. The nontoxic and biodegradable Eucalyptus dation, adsorption, and precipitation processes of the leaves, which were easily obtainable and environmentally ZVINPs at the time of remediation of lead [83, 84]. friendly, were normally considered as waste. Whereas a high BioNanoSci. temperature is required for Fe NP synthesis, the extract of 10,000 rpm for 15 min. The supernatant was then washed with Eucalyptus was prepared by boiling a mixture of 250 mL Milli-Q water and dried in a hot-air oven. The various vol- deionized water and 15 g dry leaves of the plant at 80 °C for umes of leaf extract were added to the constant volume of

1 h in addition of its vacuum filtration, following the same FeSO4 solution at different pH conditions to study the effect steps on a green tea extract. The Fe NPs were obtained by of volumes of leaf extract and pH on the synthesis of nano- adding every extract separately to 0.10 FeSO4 with a ratio of particles. The color changed from colorless to black indicating 2:1 of volume at room temperature and for 30 min constantly the formation of Fe2O3. UV-visible spectroscopy showed that stirred. To confirm the reduction of Fe2+ ions, a black color the maximum absorbance was observed at 285 and 324 nm appeared. Both types of nanoparticles were quasi-spherical due to surface plasmon vibration excitation. SEM images re- shaped with a range of diameters from 20 to 80 nm. The vealed that the synthesized iron oxide nanoparticles were ag- reactivity of these NPs for nitrogen removal was investigated gregated as irregular sphere shapes that have rough surfaces. and compared with the ordinary zero-valent and Fe3O4 nano- The morphology of the nanoparticles appeared mostly to be particles chemically prepared. Although the prepared Fe NPs porous and spongy. The results depicted that the optimum showed less activity in the removal of nitrogen, they perform volume of the leaf extract was 5.0 mL and the optimum pH very high stability in the air after aging, although their activity was found to be 5.0 for the synthesis of iron nanoparticles. remained the same, while those of ZVI and Fe3O4 nanoparti- cles dropped around 50% [98]. 2.2 Microorganism-Based Methods for NP Synthesis Another way of Fe NP synthesis that showed benefit in remediation applications was preparing magnetic iron oxide/ These methods are based on bio-microorganisms like bacteria reduced graphene oxide nanohybrid (IO\RGO) following [102, 103], algae [104, 105], and fungi [106, 107]toproduce Hummer’smethod[99]. The IO\RGO was prepared by soni- nanoparticles. Metallic nanoparticles are made by adding me- cation for 30 min to disperse 50 mg of GO in 50 mL water. By tallic ions to the medium of culture of these microorganisms in constantly stirring for 1 h, 64.8 mg of FeCl3 and 39.6 mg of controlled conditions. Prokaryotic bacteria have had an easy FeCl2 were added to the suspension under N2 atmosphere. way of manipulation, that is why it was the most investigated After that, 10 mL of Colocasia esculenta leaf aqueous extract microorganisms among all of the mentioned ones for the syn- and 20 mL of banana peel ash extract were added to the pre- thesis of metallic nanoparticles [2]. viously prepared suspension. To reduce GO and form IO nanoparticle, the above suspension was stirred for 30 min. 2.2.1 Synthesis of Fe NPs from Various Bio-microorganisms Colocasia esculenta leaf aqueous extract was used as the re- ducing agent and banana peel ash aqueous extract was used as Bio-microorganisms had been used in the synthesis of iron the base source. This method was implemented at room tem- nanoparticles. The first method to be discussed here is from perature. The efficiency of this nanohybrid in removing pol- the algae brown seaweed (Sargassum muticum)[108]. It is a lutants proved itself by removing both organic and inorganic kind of food found in coastal communities that can be used in pollutants in a short time from contaminated water, and for synthesis in a rapid single step. Extract pollutants, the adsorption processes were endothermic and from Sargassum muticum contained sulfated polysaccharides, spontaneous, and also, they were easily recycled. which acted as reducing agent and stabilizer that provide cap- Other methods of synthesis from Syzygium aromaticum ping for nanoparticles formed. One gram of frozen sample at (clove) were used for the synthesis of zero-valent iron nano- − 20 °C and a dried sample of brown seaweed were boiled particles (ZVINPs) [100]. A solution of 1:1 proportion of with 100 g of distilled deionized water in an Erlenmeyer flask, freshly prepared 0.001 M aqueous of FeCl3 solution and ex- then a solution of FeCl3 was added to the extract at a volume tract were mixed with constant stirring at 50–60 °C and with ratio of 1:1. The solution’s color is immediately changed from the addition of 1% of chitosan and 1% of PVA to stabilize Fe yellow to dark brown indicating the formation of Fe3O4 nano- NPs. The formation of Fe NPs was accompanied by a reduc- particles as seen in Fig. 3. The colloidal suspension obtained tion of pH from high acidic to low acidic (from 4.22 to 1.88). was centrifuged and washed many times using ethanol, then

SEM studies confirmed that the prepared Fe NPs from dried at 40 °C under vacuum to obtain Fe3O4-NPs. XRD Syzygium aromaticum have dispersed spheres having diame- analysis indicated the spinel phase and crystalline structure ters around 100 nm. The UV-visible spectroscopy of the syn- of magnetite nanoparticles formed with average sizes in the thesized Fe NPs by this method showed two peaks at 216– range of 17–25 nm. TEM confirmed the crystalline structure

265 nm because of SPR phenomenon of nanoparticles. In a of Fe3O4-NP with a mean diameter of 18 ± 4 nm, where field different study, Ocimum sanctum (Krishna Tulsi) leaf extract emission scanning electron microscopy image showed Fe3O4- was used for the synthesis of Fe2O3 nanoparticles [101]. The NPs in a cubic shape. Energy-dispersive X-ray fluorescence leaf extract and the precursor salt FeSO4 were mixed in 1:5 spectrum showed the presence of Fe3O4-NP without any im- proportions. The reaction mixture was centrifuged at purities, and the UV-vis spectra also admitted the presence of BioNanoSci.

Fig. 3 Photograph of synthesized Fe3O4 in BS extract [106]

Fe3O4-NPs at wavelengths of 402 and 415 nm. Another meth- because of bio-microorganic molecules secreted by the bacte- od used to identify the magnetic properties of Fe3O4-NP as it rium. The advantage of this method of synthesis (from confirmed the superparamagnetic nature of iron nanoparticles Acinetobacter spp.) is the short time of reaction and the ap- formed showed that green synthesis produced nanoparticles pearance of its results by contrast with many other bacteria. In having low magnetic properties compared with that synthe- contrast, in an anaerobic medium, the mineralization of iron sized by the co-precipitation chemical method. oxide occurred using Tobacco Mosaic virus-stirred suspen- A second method for the preparation of Fe NPs from bio- sion (0.5 mg/mL) in MES buffer (0.1 M, pH 6.4) added to microorganisms is by using Aspergillus oryzae TFR9 (fun- an aliquot of (NH4)2Fe(SO4)2⋅6HO2 (15 μL, 12 mM) and gus). This fungus is left in a 50-mL potato dextrose broth allowed to oxidize for 1 h in the air [111]. medium to grow at pH 5.8, 28 °C for 72 h at 150 rpm on shaker medium, by using Whatman filter paper no. 1. 2.3 Synthesis of Iron Oxide Nanoparticles (F-IONPs) Mycelia were filtered from the culture, 150 rpm shaker, at from Magnetite Sand 28 °C for 12 h, and were kept after resuspension in 50 mL

Milli-Q water by a 0.45 micro size membrane filter. The fun- The synthesis of IONPs (magnetite-Fe3O4) from magnetite gal biomass was separated to obtain a cell-free filtrate, then, sand from the River Palar by acid leaching fibrin-coated the filtrate was used to prepare 0.001 M salt solution of FeCl3, IONPs (F-IONPs) synthesis had been reported. XRD showed and the whole mixture was left on a 150-rpm shaker at 28 °C that the IONPs and the F-IONPs were of crystalline cubic for 12 h. Then, the product was collected for characterization. shape. The hydrodynamic diameters of IONPs and F-IONPs The polydispersity index was 0.258. The size of the particle were 15 and 35 nm, respectively, and the zeta potentials of the was in the range of 10 and 24.6 nm, and the shape of Fe NPs prepared IONPs and F-IONPs were − 8.6 and − 37.4 mV, re- was spherical. The authors suggested this method to be useful spectively, which indicate that F-IONPs were more stable than in engineering, biomedical, and agriculture sectors [109]. IONPs. TEM showed that IONPs and F-IONPs were spherical In a different synthesis method, the bacteria Acinetobacter in shape with particle sizes ranging 10–15 and 22–28 nm. The spp. [110] were isolated carefully from an aqueous mixture of authorshavedeclaredthattheF-IONPswerenovelandcheap potassium ferricyanide/ferrocyanide that had been in the air and could be used as contrast agent for enhanced MRI sensi- for 2 weeks, and the formation of magnetite occurred after the tivity, showing a low percentage of hemolysis and exhibiting reaction of the bacterium with the mentioned solution in fully higher viability and effective cellular internalization than aerobic conditions. After 24 h, an image of iron oxide nano- IONPs when incubated with cells [112]. particles was taken in this reaction medium which showed a In another work performed in a coastal region, natural high percentage of quasi-spherical shape with size in the range iron sand was taken and was washed using water and then of 10–40 nm. But after 48 h of the reaction, nanoparticles of was allowed to dry. At that point, it was sieved to get sand cubic shape with sizes from 50 to 150 nm were shown, and the particles with size ranging from 75 to 125 mm and became number of spherical particles was reduced. The formed nano- free of dust. Finally, the particles were pulverized manually particles assembled in cubic shape have been stable for weeks utilizing a mortar and pestle. To get particles in nanoscale, BioNanoSci.

Table 1 A summary of green methods of iron nanoparticle synthesis and applications

Type of plant Size Morphology Application No. Reference

1. Oolong tea 40–50 nm Spherical in shape, crystalline Degradation of malachite green [52] in nature 2. Green tea extracts –– Decolorization of aqueous solutions [56] having methyl orange dye (MO) and methylene blue (MB) as Fenton-like catalyst 3. Tea waste 5–25 nm Cuboidal/pyramid-shaped Removal for As (III) and As (V) arsenic [57] crystalline in nature ions in water 4. Tea powder (tea polyphenol) – Spherical, platelet and – [58] nanorod shape 5. Tea leaves and curcuma 4–5 nm Spherical in shape, crystalline Photocatalytic degradation of methyl [59] in nature orange dye (MO) under VL illumination 6. Amaranthus dubius 60–300 nm Spherical in shape Degradation of methyl orange dye (MO) [60] under UV illumination 7. Murraya Koenigii (curry leaves) 61 nm Spherical with irregular shape Increases hydrogen production for [65] C. acetobutylicum 8. Watermelon 16–20 nm Spherical—highly crystalline Its catalytic activity used for the synthesis [70] in nature of 2-oxo-1,2,3,4-tetrahydropyrimidine compound 9. Tridox procumbens 80–100 nm Irregular sphere shapes with Killer of Pseudomonas aeroginosa [71] rough surfaces bacteria 10. Shrub Dodonaea viscosa 50–60 nm Spherical in shape Has antimicrobial activity against [72] human pathogens 11. Spinacia oleracea –– Has antimicrobial activity [74] 12. Lawsonia inermis (henna) 21 nm Has distorted hexagonal-like Antibacterial effect on Staphylococcus [81] appearance 13. Gardenia jasminoides 32 nm Shattered rock-like Has antibacterial effect on [81] appearance Staphylococcus 14. Emblica officinalis 22.6 nm Uniform spherical shape Used in lead remediation [83] 15. Punica granatum 40 nm in diameter Cubic inverse spinel structure Used for removal of lead, Pb (II) [91] and 200 in length of magnetic nanorods 16. Eucalyptus at room temperature 20–80 nm Spheroidal in shape Used in removing water pollutants [104] 17. Eucalyptus at boiling temperature 20–80 nm Quasi-spherical shape Used in removing water pollutants [106] 18. Colocasia esculenta –– Used in removing water pollutants [107] 19. Syzygium aromaticum (clove) 100 nm Sphere in shape – [108] 20. Ocimum sanctum – Irregular sphere shape with – [109] (Krishna Tulsi) rough surface appeared to be porous and spongy 21. Algae brown seaweed 17–25 nm Cubic shape, crystalline Has superparamagnetic nature [108] (Sargassum muticum) in nature 22. Aspergillus oryzae TFR9 10–24.6 nm Spherical in shape Useful in engineering, biomedical, [109] or agricultural sectors 23. Acinetobacter spp. 10–40 nm change Quasi-spherical shape and – [110] aerobic bacterium into 50–150 nm change into cubic shape in 48 h within 48 h 24. Magnetite sand 15–35 nm Cubic-spherical Used as a contrast agent in [112] MRI imaging

10 g of the particles were placed in a stainless steel con- 3 Conclusion tainer of a planetary ball mill (Retsch) with eight stainless steel balls of 10 mm diameter. The dry milling process is In this review, different green synthesis methods of iron nano- carried out in rotation at 450 rpm for 30 min with an inter- particles from different plants and microorganisms were val of 15 min [113]. discussed. By comparing these two ways of synthesis, the A summary of green methods of iron nanoparticle synthe- plant extract method is the recommended one. This may refer sis and applications discussed in the present review is demon- to its easiness, small time of reaction, and its safety in contrast strated in Table 1. to the microorganism-based synthesis methods which may BioNanoSci. lead to infection or to products of high toxicity. Green synthe- 11. Zboril, R., Mashlan, M., & Petridis, D. (2002). Iron(III) oxides — sis methods led to different shapes and morphologies of nano- from thermal processes synthesis, structural and magnetic prop- erties, Mössbauer spectroscopy characterization, and applications. particles that had been used in a variety of applications. The Chemistry of Materials, 14,969–982. green methods reported in this review showed more stability 12. Shin, E. J., Miser, D. E., Chan, W. G., & Hajaligol, M. R. (2005). than many chemical methods. Lately, green synthesis methods Catalytic cracking of catechols and hydroquinones in the presence – were widely used since they are easy, safe, cheap, and also of nano-particle iron oxide. Applied Catalysis, 61,79 89. 13. Prucek, R., Hermanek, M., & Zbořil, R. (2009). An effect of iron eco-friendly. The synthesized iron nanoparticles were used in (III) oxides crystallinity on their catalytic efficiency and applicabil- different applications: some of them are used in bioremedia- ity in phenol degradation—a competition between homogeneous tion, others are used for their antibacterial effect, and finally, and heterogeneous catalysis. Applied Catalysis, 366, 325–232. α others are used as dye removal. These applications will greatly 14. Rettig, F., & Moos, R. (2010). -Iron oxide: an intrinsically semi- conducting oxide material for direct thermoelectric oxygen sen- help to save our environment from contamination. sors. Sensors and Actuators B: Chemical, 145,685–690. 15. Cesar, I., Kay, A., Martinez, J. A. G., & Grätzel, M. (2006). Authors’ Contributions All the authors researched the existing literatures, Translucent thin film Fe2O3 photoanodes for efficient water split- wrote the manuscript, designed the manuscript, developed the concept, ting by sunlight: -directing effect of Si-doping. and read and approved the final manuscript. Journal of the American Chemical Society, 128,4582–4583. 16. Amara, D., Grinblat, J., & Margel, S. (2012). Solventless thermal Funding Information This work was supported by the Biophysical decomposition of ferrocene as a new approach for one-step syn- Scientific Society under the supervision of Biophysics Department, thesis of magnetite nanocubes and nanospheres. Journal of – Faculty of Science, Cairo University. Materials Chemistry, 22,2188 2195. 17. Breen, M. L., Dinsmore, A. D., Pink, R. H., Qadri, S. B., & Ratna, B. R. (2001). Sonochemically produced ZnS-coated polystyrene Compliance with Ethical Standards core−shell particles for use in photonic crystals. Langmuir, 17, 903–907. Competing Interests The authors declare that they have no competing 18. Deng, Y., Qi, D., Deng, C., Zhang, X., & Zhao, D. (2008). interests. Superparamagnetic high-magnetization microspheres with an Fe3O4@SiO2 core and perpendicularly aligned mesoporous SiO2 shell for removal of microcystins. Journal of the American Chemical Society, 130,28–29. References 19. Caruso, F., Susha, A. S., Giersig, M., & Möhwald, H. (1999). Magnetic core–shell particles: preparation of magnetite multilayers – 1. Usepa U. (2007). Nanotechnology White Paper. Prepared for the on polymer latex microspheres. Advanced Materials, 11,950 953. US Environmental Protection Agency by Members of the 20. Laurent, S., Forge, D., Port, M., Roch, A., Robic, C., Elst, L. V.,& Nanotechnology Workgroup, a Group of Epa's Science Policy Muller, R. N. (2008). Magnetic iron oxide nanoparticles: synthe- Council Science Policy Council (pp. 20460). Washington, DC: sis, stabilization, vectorization, physicochemical characterizations, – US Environmental Protection Agency. and biological applications. Chemical Reviews, 108,2064 2110. 2. Thakkar, K. N., Mhatre, S. S., & Parikh, R. Y. (2010). Biological 21. Bulte, J. W., Douglas, T., Witwer, B., Zhang, S. C., Strable, E., synthesis of metallic nanoparticles. Nanomedicine, 6,257–262. Lewis, B. K., Zywicke, H., Miller, B., van Gelderen, P., Moskowitz, B. M., & Duncan, I. D. (2001). Magnetodendrimers 3. Panigrahi, S., Kundu, S., Ghosh, S. K., Nath, S., & Pal, T. (2004). allow endosomal magnetic labeling and in vivo tracking of stem General method of synthesis for metal nanoparticles. Journal of cells. Nature Biotechnology, 19(12), 1141. Nanoparticle Research, 6,411–414. 22. Arbab, A. S., Yocum, G. T., Kalish, H., Jordan, E. K., Anderson, 4. T E R I. (2010). Nanotechnology development in India: building S. A., Khakoo, A. Y., Read, E. J., & Frank, J. A. (2004). Efficient capability and governing the technology [TERI Briefing Paper], magnetic cell labeling with protamine sulfate complexed to supported by IDRC, Canada. ferumoxides for cellular MRI. Blood, 104(4), 1217–1223. 5. Senapati, S., Ahmad, A., Khan, M. I., Sastry, M., & Kumar, R. 23. Kalish, H., Arbab, A. S., Miller, B. R., Lewis, B. K., Zywicke, H. (2005). Extracellular biosynthesis of bimetallic Au–Ag alloy – A., Bulte, J. W., Bryant, L. H., & Frank, J. A. (2003). Combination nanoparticles. Small, 1,517 520. of transfection agents and magnetic resonance contrast agents for 6. Klaus, T., Joerger, R., Olsson, E., & Granqvist, C. G. (1999). cellular imaging: relationship between relaxivities, electrostatic Silver-based crystalline nanoparticles, microbially fabricated. forces, and chemical composition. Magnetic Resonance in Proceedings of the National Academy of Sciences of the United Medicine, 50(2), 275–282. – States of America, 96,13611 13614. 24. Schulze, E., Ferrucci, J. J., Poss, K., Lapointe, L., Bogdanova, A., 7. Rai, M., Yadav, A., & Gade, A. (2008). Current trends in & Weissleder, R. (1995). Cellular uptake and trafficking of a pro- phytosynthesis of metal nanoparticles. Critical Reviews in totypical magnetic iron oxide label in vitro. Investigative – Biotechnology, 28,277 284. Radiology, 30(10), 604–610. 8. Mohanpuria, P., Rana, N. K., & Yadav, S. K. (2008). Biosynthesis 25. Moore, A., Marecos, E., Bogdanov Jr., A., & Weissleder, R. of nanoparticles: technological concepts and future applications. (2000). Tumoral distribution of long-circulating dextran-coated Journal of Nanoparticle Research, 10,507–517. iron oxide nanoparticles in a rodent model. Radiology, 214(2), 9. Pankhurst, Q. A., Connolly, J., Jones, S. K., & Dobson, J. (2003). 568–574. Applications of magnetic nanoparticles in biomedicine. Journal of 26. Sipe, J. C., Filippi, M., Martino, G., Furlan, R., Rocca, M. A., Physics D, 36,167–181. Rovaris, M., Bergami, A., Zyroff, J., Scotti, G., & Comi, G. 10. Gilchrist, R. K., Medal, R., Shorey, W. D., Hanselman, R. C., (1999). Method for intracellular magnetic labeling of human Parrot, J. C., & Taylor, C. B. (1957). Selective inductive heating mononuclear cells using approved iron contrast agents. Magnetic of lymph nodes. Annals of Surgery, 146,596–606. Resonance Imaging, 17(10), 1521–1523. BioNanoSci.

27. Modo, M., Hoehn, M., & Bulte, J. W. (2005). Cellular MR imag- 47. Malik, P. M., Shankar, R., Malik, V.,Sharma, N., & Mukherjee, T. ing. Molecular Imaging, 4(3), 15353500200505145. K. (2014). Green chemistry based benign routes for nanoparticle 28. Zhao, M., Beauregard, D. A., Loizou, L., Davletov, B., & Brindle, synthesis. Journal of Nanoparticles. https://doi.org/10.1155/2014/ K. M. (2001). Non-invasive detection of apoptosis using magnetic 302429. resonance imaging and a targeted contrast agent. Nature Medicine, 48. Praveen, K. T., Ritesh, C. S., & Santosh, B. (2013). Removal of 7(11), 1241. arsenic(III) from water with clay-supported zerovalent iron nano- 29. Frankel, A. D., & Pabo, C. O. (1988). Cellular uptake of the tat particles synthesized with the help of tea liquor. Industrial and protein from human immunodeficiency virus. Cell, 55(6), 1189– Engineering Chemistry Research, 52,10052–10058. 1193. 49. Ayman, A. A., Medhat, A. A. G., Mana, F., Mona, B. M., & 30. Koch, A. M., Reynolds, F., Kircher, M. F., Merkle, H. P., Abdel-Mohamed, M. S. A. (2013). Phytosynthesis of Au, Ag, Weissleder, R., & Josephson, L. (2003). Bioconjugate and Au–Ag bimetallic nanoparticles using aqueous extract of sago Chemistry, 14,1115. pondweed (Potamogetonpectinatus L). ACS Sustainable 31. Zhao, M., Kircher, M. F., Josephson, L., & Weissleder, R. (2002). Chemistry & Engineering, 1,1520–1529. Differential conjugation of tat peptide to superparamagnetic nano- 50. Haung, L., Weng, X., Chen, Z., Megharaj, M., & Naidu, R. (2014). particles and its effect on cellular uptake. Bioconjugate Chemistry, Synthesis of iron-based nanoparticles using oolong tea extract for 13(4), 840–844. the degradation of malachite green. Spectrochimica Acta Part A: 32. Strable, E., Bulte, J. W., Moskowitz, B., Vivekanandan, K., Allen, Molecular and Biomolecular Spectroscopy, 117,801–804. M., & Douglas, T. (2001). Synthesis and characterization of solu- 51. Njagi, E. C., Huang, H., Stafford, L., Homer, G., Hugo, M. G., ble iron oxide−dendrimer composites. Chemistry of Materials, Collins, B. C., et al. (2010). Biosynthesis of iron and silver nano- 13(6), 2201–2209. particles at room temperature using aqueous sorghum bran ex- 33. Stella, B., Arpicco, S., Peracchia, M. T., Desmaële, D., Hoebeke, tracts. Langmuir, 27,264–271. J., Renoir, M., D’Angelo, J., Cattel, L., & Couvreur, P. (2000). 52. Smuleac, V., Varma, R., Sikdar, S., & Bhattacharyya, D. (2011). Design of folic acid-conjugated nanoparticles for drug targeting. Green synthesis of Fe and Fe/Pd bimetallic nanoparticles in mem- Journal of Pharmaceutical Sciences, 89(11), 1452–1464. branes for reductive degradation of chlorinated organics. Journal 34. Zhang, Y., Kohler, N., & Zhang, M. (2002). Surface modification of Membrane Science, 379,131–137. of superparamagnetic magnetite nanoparticles and their intracellu- 53. Wu, Y., Zeng, S., Wang, F., Megharaj, M., Naidu, R., & Chen, Z. lar uptake. Biomaterials, 23(7), 1553–1561. (2015). Heterogeneous Fenton-like oxidation of malachite green 35. Perez, J. M., Josephson, L., & Weissleder, R. (2004). Use of mag- by iron-based nanoparticles synthesized by tea extract as a cata- netic nanoparticles as nanosensors to probe for molecular interac- lyst. Separation and Purification Technology, 154,161–167. tions. Chembiochem, 5(3), 261–264. 54. Shahwan, T., Abu Sirriah, S., Nairat, M., Boyaci, E., Eroglu, A. E., 36. Perez, J. M., O’Loughin, T., Simeone, F. J., Weissleder, R., & Scott, T. B., & Hallam, K. R. (2011). Green synthesis of iron Josephson, L. (2002). DNA-based magnetic nanoparticle assem- nanoparticles and their application as a Fenton-like catalyst for bly acts as a magnetic relaxation nanoswitch allowing screening of the degradation of aqueous cationic and anionic dyes. Chemical DNA-cleaving agents. Journal of the American Chemical Society, Engineering Journal, 172,258–266. 124(12), 2856–2857. 55. Lunge, S., Singh, S., & Sinha, A. (2014). Magnetic iron oxide 37. Perez, J. M., Josephson, L., O’Loughlin, T., Högemann, D., & (Fe3O4) nanoparticles from tea waste for arsenic removal. Weissleder, R. (2002). Magnetic relaxation switches capable of Journal of Magnetism and Magnetic Materials, 356,21–31. sensing molecular interactions. Nature Biotechnology, 20(8), 816. 56. Nadagouda, M. N., Castle, A. B., Murdock, R. C., Hussain, S. M., 38. Gao, Y. (2005). Biofunctionalization of magnetic nanoparticles. & Varma, R. S. (2010). In vitro biocompatibility of Nanotechnologies for the Life Sciences. Weinheim: Wiley-VCH. nanoscalezerovalent iron particles (NZVI) synthesized using tea 39. Safarik, I., & Safarikova, M. (2004). Magnetic techniques for the polyphenols. Green Chemistry, 12,114–122. isolation and purification of proteins and peptides. BioMagnetic 57. Alagiri, M., & Abdul Hamid, S. B. (2014). Green synthesis of α- Research and Technology, 2(1), 7. Fe2O3 nanoparticles for photocatalytic application. Journal of 40. Bucak, S., Jones, D. A., Laibinis, P. E., & Hatton, T. A. (2003). Materials Science: Materials in Electronics, 25,3572–3577. Protein separations using colloidal magnetic nanoparticles. 58. Harshiny,M.,Iswarya,C.N.,&Matheswaran,M.(2015). Biotechnology Progress, 19(2), 477–484. Biogenic synthesis of iron nanoparticles using Amaranthus dubius 41. Alexiou, C., Schmid, R. J., Jurgons, R., Kremer, M., Wanner, G., leaf extract as a reducing agent. Powder Technology, 286,744– Bergemann, C., Huenges, E., Nawroth, T., Arnold, W., & Parak, F. 749. G. (2006). Targeting cancer cells: magnetic nanoparticles as drug 59. Yizhong, C., Mei, S., & Harold, C. (2003). Antioxidant activity of carriers. European Biophysics Journal, 35(5), 446–450. betalains from plants of the Amaranthaceae. Journal of 42. Kandori, K., & Ishikawa, T. (2004). Preparation and microstruc- Agricultural and Food Chemistry, 51,2288–2294. tural studies on hydrothermally prepared hematite. Journal of 60. Jannathul, M., & Lalitha, P. (2014). Competence of different Colloid and Interface Science, 272(1), 246– 248. methods in the biosynthesis of silver nanoparticles. Journal of 43. Petcharoen, K., & Sirivat. (2012). Synthesis and characterization Chemical and Pharmaceutical Research, 6,1089–1093. of magnetite nanoparticles via the chemical co-precipitation meth- 61. Ratul, K. D., Nayanmoni, G., Punuri, J. B., Pragya, S., Chandan, od. Materials Science and Engineering B, 177,421–427. M., & Utpal, B. (2012). The synthesis of gold nanoparticles using 44. Valentin, V. M., Svetlana, S. M., Andrew, J. L., Olga, V. S., & Amaranthus spinosus leaf extract and study of their optical prop- Anna, O. D. (2014). Biosynthesis of stable iron oxide nanoparti- erties. Advances in Materials Physics and Chemistry, 2,275–281. cles in aqueous extracts of Hordeumvulgare and Rumexacetosa 62. Kumar, B., Kumari, S., Cumbal, L., Debut, A., & Angulo, Y. plants. Langmuir, 30,5982–5988. (2017). Biofabrication of copper oxide nanoparticles using 45. Raveendran, P., Fu, J., & Wallen, S. L. (2003). Completely Andean blackberry (RubusglaucusBenth.) fruit and leaf. Journal Bgreen^ synthesis and stabilization of metal nanoparticles. of Saudi Chemical Society, 21, S475–S480. Journal of the American Chemical Society, 125, 13940–13941. 63. Mohanraj, S., Kodhaiyolii, S., Rengasamy, M., & Pugalenthi, V. 46. Mervat, F. Z., EWael, H. E., & Shabaka, A. A. (2012). (2014). Green synthesized iron oxide nanoparticles effect on fer- Malvaparviflora extract assisted green synthesis of silver nanopar- mentative hydrogen production by Clostridium acetobutylicum. ticles. Spectrochimica Acta, Part A, 98,423–428. Applied Biochemistry and Biotechnology, 173,318–331. BioNanoSci.

64. Christensen, L., Vivekanandhan, S., Misra, M., & Mohanty, A. K. 81. Li, X., Elliott, D. W., & Zhang, W. (2006). Zero-valent iron nano- (2011). Biosynthesis of silver nanoparticles using Murraya particles for abatement of environmental pollutants: materials and koenigii (curry leaf): an investigation on the effect of broth con- engineering aspects. Critical Reviews in Solid State and Materials centration in reduction mechanism and particle size. Advances Sciences, 31,111–122. Material Letters, 2,429–434. 82. O’Carroll, D., Sleep, B., Krol, M., Boparai, H., & Kocur, C. 65. Babu, S. A., & Prabu, H. G. (2011). Synthesis of AgNPs using the (2013). Nanoscale zero valent iron and bimetallic particles for extract of Calotropisprocera flower at room temperature. contaminated site remediation. Advances in Water Resources, Materials Letters, 65,1675–1677. 51,104–122. 66. Wang, J., & Wan, W. (2008). Effect of Fe2+ concentration on 83. Venkateswarlu, S., Natesh Kumar, B., Prathima, B., SubbaRao, Y., fermentative hydrogen production by mixed cultures. & Vijaya Jyothi, N. V. (2014) A novel green synthesis of Fe3O4 International Journal of Hydrogen Energy, 33,1215–1220. magnetic nanorodsusing Punica granatum rind extract and its ap- 67. Han,H.,Cui,M.,Wei,L.,Yang,H.,&Shen,J.(2011). plication for removal of Pb(II) from aqueous environment. Enhancement effect of hematite nanoparticles on fermentative Arabian Journal of Chemistry. https://doi.org/10.1016/j.arabjc. hydrogen production. Bioresource Technology, 102,7903–7909. 2014.09.006. 68. Prasad, C., Gangadhara, S., & Venkateswarlu, P. (2015). Bio- 84. Jang, S. H., Min, B. G., Jeong, Y. G., Lyoo, W. S., & Lee, S. C. inspired green synthesis of Fe3O4 magnetic nanoparticles using (2008). Removal of lead ions in aqueous solution by hydroxyap- watermelon rinds and their catalytic activity. Applied atite polyurethane composite foams. Journal of Hazardous Nanoscience, 5,847–855. Materials, 152,1285–1292. 69. Senthil, M., & Ramesh, C. (2012). Biogenic synthesis of Fe3O4 85. Wu, S. C., Peng, X. L., Cheng, K. C., Liu, S. L., & Wong, M. H. nanoparticles using Tridax procumbens leaf extract and its anti- (2009). Adsorption kinetics of Pb and Cd by two plant growth bacterial activity on Pseudomonas aeruginosa. Digest Journal of promoting rhizobacteria. Bioresource Technology, 100, 4559–4563. and Biostructures, 7,1655–1660. 86. Ni, J., Xiong, L., Chen, C., & Chen, Q. (2011). Adsorption of Pb 70. Venkatesh, S., Reddy, Y. S. R., Ramesh, M., Swamy, M. M., (II) and Cd(II) from aqueous solutions using titanate nanotubes Mahadevan, N., & Suresh, B. (2008). Pharmacognostical studies prepared via hydrothermal method. Journal of Hazardous on Dodonaea viscosa. African Journal of Pharmacy and Materials, 189,741–748. Pharmacology, 2,083–088. 87. Shah, F., Kazi, T. G., Afridi, H. I., Khan, S., Kolachi, N. F., Arain, 71. Kiruba Daniel, S. C. G., Vinothini, G., Subramanian, N., Nehru, M. B., & Baig, J. A. (2011). The influence of environmental ex- K., & Sivakumar, M. M. (2013). Biosynthesis of Cu, ZVI, and Ag posure on lead concentrations in scalp hair of children in Pakistan. nanoparticles using Dodonaea viscosa extract for antibacterial ac- Ecotoxicology and Environmental Safety, 74,727–732. tivity against human pathogens. Journal of Nanoparticle 88. Madadrang, C. J., Kim, H. Y., Gao, G., Wang, N., Zhu, J., Feng, Research, 15,1–10. H., et al. (2012). Adsorption behavior of EDTA-graphene oxide 72. Eftekhari, K., Pasha, K. M., Tarigopula, S. P., Sura, M., & for Pb (II) removal. ACS Applied Materials & Interfaces, 4,1186– Daddam, J. R. (2014). Biosynthesis and characterization of silver 1193. and iron nanoparticles from Spinacia oleracea and their antimicro- 89. Stafej, A., & Pyrzynska, K. (2007). Adsorption of heavy metal bial studies. International Journal of Plant Animal and ions with carbon nanotubes. Separation and Purification Environmental Sciences, 5,166. Technology, 58,49–52. 73. Naseem, T, & Farrukh, M. A. (2015). Antibacterial activity of 90. Hua, M., Zhang, S., Pan, B., Zhang, W., Lv, L., & Zhang, Q. green synthesis of iron nanoparticles using Lawsonia inermis (2012). Heavy metal removal from water/wastewater by and Gardenia jasminoides leaves extract. Journal of Chemistry, nanosized metal oxides. Journal of Hazardous Materials, 211– 1–7. https://doi.org/10.1155/2015/912342. 212,317–331. 74. Makarov, V. V., Love, A. J., Sinitsyna, O. V., Makarova, S. S., 91. Hajdu, I., Bodnar, M., Csikos, Z., Wei, S., Daroczi, L., Kovacs, B., Yaminsky, I. V.,Taliansky, M. E., et al. (2014). BGreen^ nanotech- et al. (2012). Combined nano-membrane technology for removal nologies: synthesis of metal nanoparticles using plants. Acta of lead ions. Journal of Membrane Science, 409,44–53. Naturae, 6,35–44. 92. Suc, N. V., Ho, T. Y., & Ly. (2013). Lead (II) removal from aque- 75. Kumar, R., Singh, N., & Pandey, N. (2015). Potential of green ous solution by chitosan flake modified with citric acid via synthesized zero-valent iron nanoparticles for remediation of crosslinking with glutaraldehyde. JournalofChemical lead-contaminated water. Science and Technology, 12,3943– Technology and Biotechnology, 88,1641–1649. 3950. 93. Barakat, M. A., & Schmidt, E. (2010). Polymer-enhanced ultrafil- 76. Nadagouda, M. N., & Varma, R. S. C. (2007). A greener synthesis tration process for heavy metals removal from industrial wastewa- of core (Fe, Cu)-shell (Au, Pt, Pd, and Ag) nanocrystals using ter. Desalination, 256,90–93. aqueous vitamin C. Crystal Growth & Design, 7,2582–2587. 94. Uluozlu, O. D., Sari, A., Tuzen, M., & Soylak, M. (2008). 77. Sun, K., Qiu, J., Liu, J., & Miao, Y. (2009). Preparation and char- Biosorption of Pb(II) and Cr(III) from aqueous solution by lichen acterization of gold nanoparticles using ascorbic acid as reducing (Parmelinatiliaceae) biomass. Bioresource Technology, 99, 2972– agent in reverse micelles. Journal of Materials Science, 44,754– 2980. 758. 95. Çam, M., & Hışıl, Y. (2010). Pressurised water extraction of poly- 78. Hoag, G. E., Collins, J. B., Holcomb, J. L., Hoag, J. R., phenols from pomegranate peels. Food Chemistry, 123,878–885. Nadagouda, M. N., & Varma, R. S. (2009). Degradation of 96. Wang, T., Jin, X., Chen, Z., Megharaj, M., & Naidu, R. (2014). bromothymol blue by ‘greener’ nano-scale zero-valent iron syn- Green synthesis of Fe nanoparticles using eucalyptus leaf extracts thesized using tea polyphenols. Journal of Materials Chemistry, for treatment of eutrophic wastewater. Science of the Total 19,8671–8677. Environment, 466-467,210–213. 79. Liu, Q., Bei, Y., & Zhou, F. (2009). Removal of lead(II) from 97. Eneji, A. E., Islam, R., An, P., & Amalu, U. C. (2013). Nitrate aqueous solution with amino-functionalized nanoscale zero- retention and physiological adjustment of maize to soil amend- valent iron. Central European Journal of Chemistry, 7,79–82. ment with superabsorbent polymers. Journal of Cleaner 80. Zhang, X., Lin, S., Lu, X. Q., & Chen, Z. (2010). Removal of Pb Production, 52,474–480. (II) from water using synthesized kaolin supported nanoscale zero- 98. Wang, T., Lin, J., Chen, Z., Megharaj, M., & Naidu, R. (2014). valent iron. Chemical Engineering Journal, 163,243–248. Green synthesized iron nanoparticles by green tea and eucalyptus BioNanoSci.

leaves extracts used for removal of nitrate in aqueous solution. 107. Mukherjee, P., Roy, M., Mandal, B., Day, G., Ghatak, J., Tyagi, Journal of Cleaner Production, 83,413–419. A., et al. (2008). Green synthesis of highly stabilized nanocrystal- 99. Thakur, S., & Karak, N. (2012). Green reduction of graphene line silver particles by a non-pathogenic and agriculturally impor- oxide by aqueous phytoextracts. Carbon, 50,5331–5339. tant fungus T. asperellum. Nanotechnology, 19,75103–75110. 100. Pattanayak, M., Mohapatra, D., & Nayak, P. L. (2013). Green 108. Mahdavi, M., Namvar, F., Bin Ahmed, M., & Mohamad, R. synthesis and characterization of zero valent iron nanoparticles (2013). Green biosynthesis and characterization of magnetic iron from the leaf extract of Syzygium aromaticum (clove). Middle- oxide (Fe3O4) nanoparticles using seaweed (Sargassum muticum) East Journal of Scientific Research, 18,623–626. aqueous extract. Molecules, 18,5954–5964. 101. Balamurughan, M. G., Mohanraj, S., Kodhaiyolii, S., & 109. Tarafdar, J. C., & Raliya, R. (2013). Rapid, low-cost, and Pugalenthi, V. (2014). National Conference on Green ecofriendly approach for iron nanoparticle synthesis using Engineering and Technologies for Sustainable Future-2014 Aspergillus oryzae TFR9. Journal of Nanoparticles. https://doi. Ocimum sanctum leaf extract mediated green synthesis of iron org/10.1155/2013/141274. oxide nanoparticles: spectroscopic and microscopic studies. 110. Bharde, A., Wani, A., Shouche, Y., Pa, J., Prasad, B. L. V., & – National Conference on Green Engineering and Tec 4:201 204. Sastry, M. (2005). Bacterial aerobic synthesis of nanocrystalline 102. Lengke, M. F., Fleet, M. E., & Southam, G. (2007). Biosynthesis magnetite. Journal of the American Chemical Society, 127,9326– of silver nanoparticles by filamentous cyanobacteria from a silver 9327. – (I) nitrate complex. Langmuir, 23,2694 2699. 111. Shenton, W., Douglas, T., Young, M., Stubbs, G., & Mann, S. 103. Husseiny, M., El-Aziz, M. A., Badr, Y., & Mahmoud, M. (2007). (1999). Inorganic organic nanotube composites from template Biosynthesis of gold nanoparticles using Pseudomonas mineralization of tobacco mosaic virus. Advanced Materials, 11, aeruginosa. Spectrochimica Acta Part A, Molecular and 253–256. Biomolecular Spectroscopy, 67,1003–1006. 112. Periyathambi, P., Vedakumari, W. S., Bojja, S., Kumar, S. B., & 104. Xie, J., Lee, J. Y., Wang, D. I., & Ting, Y. P. (2007). Identification Sastry, T. P. (2014). Green biosynthesis and characterization of of active biomolecules in the high-yield synthesis of single- fibrin functionalized iron oxide nanoparticles with MRI sensitivity crystalline gold nanoplates in algal solutions. Small, 3,672–682. and increased cellular internalization. Materials Chemistry and 105. Chen, J., Lin, Z., & Ma, X. (2003). Evidence of the production of Physics, 148,1212–1220. silver nanoparticles via pretreatment of Phoma sp.3.2883 with silver nitrate. Letters in Applied Microbiology, 37,105–108. 113. Widanarto, W., Sahar, M. R., Ghoshal, S. K., Arifin, R., Rohani, 106. Bhainsa, K. C., & Souza, S. D. (2006). Extracellular biosynthesis M. S., & Hamzah, K. (2013). Effect of natural Fe3O4 nanoparticles on structural and optical properties of Er 3+ doped tellurite glass. of silver nanoparticles using the fungus Aspergillus fumigates. – Colloids and Surfaces, B: Biointerfaces, 47,160–164. Journal of Magnetism and Magnetic Materials, 326,123 128.