BioNanoScience https://doi.org/10.1007/s12668-018-0516-5 Review of Green Methods of Iron Nanoparticles 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 nanoparticle 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