Chapter 8 - Synthesis of metal oxide nanoparticles

ABSTRACT: Metal oxide nanoparticles are metal oxide which have the particle size between 1-100nm. Metal oxide nanoparticles include the oxides of various metal such iron oxide, zinc oxide, cupric oxide, magnesium oxide, silver oxide, titanium oxide etc. The synthesis of metal oxide nanoparticles has been widely explored in recent times due to its wide applications. Metal oxide nanoparticles have been greatly exploited due its unique ability to remove various organic and inorganic pollutants from contaminated water. They also show anti-microbial activities against various disease -causing micro-organisms. Apart from this, they also find their applications in drug delivery, biosensing, electronic devices. Synthesis of metal oxide nanoparticles includes physical, chemical and biological method. Water pollution is a serious cause of concern of this century. Various methods have been developed for the purification of wastewater treatment. One of the most important application of metal oxide nanoparticles is their ability to remove various organic and inorganic pollutants from contaminated water. Metal oxide nanoparticles due to its high surface area acts as efficient catalyst and adsorbent. This properties of them make them an efficient source for the photocatalytic degradation and also adsorption of contaminants from contaminated water.

41 - Surface modification of inorganic nanoparticles by organic functional groups

Nonaqueous synthesis of metal oxide nanoparticles: Short review and doped titanium dioxide as case study for the preparation of transition metal-doped oxide nanoparticles

Many attempts have been made for green synthesis of metal oxide nanoparticles; revealing the importance of plant extracts in reducing metal/ metal oxide precursor to nanoparticles and their applications in various scientific domains. Cajanus cajan (L.) Mill sp. (Pigeon pea), one of the pulses in human diet is legume plant, belonging to family Fabaceae or Papilionaceae. This plant has been reported to contain several phytochemicals like flavonoids glycosides, stilbenes. This article focus on applications of Cajanus cajan extract in fabrication of nanoparticles of various metals and metal oxides like silver, gold, titanium dioxide, zinc oxide. In respective research attempts, these nanoparticles were evaluated for one or more applications like anti-microbial activity and/or photocatalytic activity. Use of polar extract of Cajanus cajan indicated involvement of its polar phyto-compounds in reducing the metal source and stabilizing the nanoparticles.

This study identifies bulk metal carbonates and nitrates as cost-effective starting materials for a large-scale, one-pot synthesis of monodisperse metal oxide nanoparticles of MnO, Fe3O4, and CoO phases. The thermal decomposition of bulk metal carbonates or nitrates in hot fatty acid forms monodisperse metal oxide nanoparticles on a large scale. The release of carbon monoxide and nitrogen dioxide gas molecules from these precursors would in situ form molecular metal-oxo species, lightly stabilized by complexation with fatty acid, which would in turn undergo subsequent agglomeration to form metal oxide nanoparticles. The particle size and shape could be controlled simply by varying the reaction conditions, namely the amount and nature of added alkylamine. This general and convenient synthetic methodology would be greatly beneficial to the practical application of thermally synthesized metal oxide nanoparticles.

4 - Aqueous methods for the synthesis of colloidal metal oxide nanoparticles at ambient pressure

This paper deals with the facile approach to the synthesis of different metal oxide nanoparticles and their comparative study for humidity sensing application at room temperature. The synthesis of these metal oxide nanoparticles is through co-precipitation method for nickel oxide and tin ferrite and hydrothermal route for cuprous oxide. The SEM and EDX reveal the porous morphology and confirmed composition of the synthesized metal oxides. FTIR detects the presence of functional groups like –OH and confirms the inverse spinal structure in tin ferrite. The optical band gap was determined by UV spectroscopy: 3.86[Formula: see text]eV for NiO, 4.13[Formula: see text]eV for Cu2O, and 4.07[Formula: see text]eV for SnFe2O4. XRD gives the information about the average crystallite size for tin ferrite 2.42[Formula: see text]nm, cuprous oxide 12.88[Formula: see text]nm and nickel oxide 22.51[Formula: see text]nm as the size comes to nano range the surface area increases, which is a good indication for humidity sensing. The humidity sensing of materials was detected by electrical modes. The deposited thin films were prepared by spin coater and observed sensitivity of these films was 0.72[Formula: see text]M[Formula: see text]/%RH for NiO, 1.59[Formula: see text]M[Formula: see text]/%RH for Cu2O, and 2.07[Formula: see text]M[Formula: see text]/%RH for SnFe2O4. The experiments were repeated after few weeks and the aging effects of samples were found negligible which makes the sensor stable.

The present study deals with the green synthesis, physical characterization, and antibacterial activity testing of various metal oxide nanoparticles (NPs) formed by making use of the star fruit extract. Followed by the synthesis of metal oxide NPs such as ZnO, MgO, and CuO, these have been characterized thoroughly for the optical properties, surface functionality, crystallinity, morphology, and elemental composition. From the UV–vis studies, the observation of absorption bands at 336, 292, and 421 nm confirms the presence of ZnO, MgO, and CuO NPs, respectively. Also, the powder XRD pattern confirm that the prepared NPs are crystalline in nature and fall in the nanoscale size range of 11–22 nm. The field emission scanning electron microscopy (FESEM) provided surface morphological studies of ZnO, MgO, and CuO NPs suggested that the particles are formed in many different shapes of spherical, rod, and hexagonal shape, respectively. The X-ray spectroscopy studies performed in parallel to the FESEM analysis provided a proof for the persistence of Zn, Mg, Cu, and O elements in the respective samples, and thereby confirming for the successful formation of ZnO, MgO, and CuO. Further testing of the antibacterial activity against the clinically important pathogens, such as Staphylococcus aureus, Bacillus, and Pseudomonas, the as-synthesized ZnO, CuO, and MgO NPs are proved to be highly effective. From the overall analysis, this green synthesis route is facile and can be beneficial for the large-scale production of metal oxide NPs that have potential biotechnological significance.

Green synthesis of various metal oxide nanoparticles for the environmental remediation-An overview

Rapid cooling of reactants quenches the intermediate state of chemical reactions and enables the synthesis of novel materials that cannot be realized by thermodynamic equilibrium processes. In this study, we estimated the cooling rate of reactant solutions during the supercritical hydrothermal synthesis of metal oxide nanoparticles. Neutron radiography measurements were performed to visualize the profile of the average water density at a junction where a stream of heated water was mixed with another stream of cooling water. The cooling rate of the heated water that mimicked the reactant solution was estimated using the relationship between the density and temperature of water under constant pressure conditions. This result should provide vital information about the flow-type synthesis of novel metal oxide nanoparticles.

Hydrothermal synthesis of metal oxide (AlOOH/Al2O3, CuO, Fe2O3, NiO, ZrO2) nanoparticles from metal nitrate aqueous solution was carried out at 673 K and pressures ranging from 25 MPa to 37.5 MPa with a flow-through supercritical water method. Size, phase and crystallinity of the obtained particles were characterized by TEM, XRD and TG, respectively. Effect of the difference of the metals in starting materials, pressures and concentrations on particle size and crystallinity was analyzed on the basis of supersaturation, which was evaluated by estimated metal oxide solubility. The result suggests that supersaturation should be set to higher than around 104 in this method to obtain particles under 10 nm in diameter. Further, crystallinity of the obtained particles was evaluated as weight loss through TG analysis. It was found that higher supersaturation decreased the crystallinity. This result can be explained that high supersaturation led to the inclusion of water molecules during the formation of particles.

In the present times, low cost and greener biogenic synthesis of nanomaterials is considered as an alternative to the chemical synthesis, but in depth mechanism and the incorporated phytochemicals in the synthesized material still need to be investigated. In this regard, here we have investigated the phyto-compounds of Ficus palmata Forssk (Moraceae) leaves to develop an organic framework for the synthesis and functionalization of metal oxide nanoparticles. A simple procedure was followed to identify F. palmata leaf’s organic compounds by reversed-phase high performance liquid chromatography (HPLC), gas chromatography–mass spectroscopy (GC–MS), and Fourier transform infrared spectroscopy (FTIR). The chromatographic analysis revealed the presences of dl-3-aminobutyric acid, octodrine, alanine, azabicyclo, aminonadecane, 2-pentadecen-4-yne and cyclobutanol in the F. palmata. Subsequently, the identified phytochemicals were employed as source of organic species for synthesis of metal oxide nanoparticles (MoO3 NPs) by hydrothermal route. The investigated aqueous extract was made to react with ammonium heptamolybdate tetrahydrate-H4MO7N6O24.4H2O (AHM) aqueous complex to procure phyto-functionalized MoO3 NPs. The phase purity and nanostructures of synthesized MoO3 were analyzed by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and field emission-scanning electron microscopy (FE-SEM). GC–MS demonstrated the presence of four organic compounds (dimethylamine, d-alanine, octodrine and benzenemethanol) in the synthesized MoO3 NPs. Therefore, the findings of the present research have successfully revealed the organic species of F. palmata and their incorporation into MoO3 NPs by simple, and cost effective inorganic–organic framework leading to the greener sample preparation and analytical methods.

Green synthesis of metal oxide nanoparticles has been emerging highlight of the research owing to its unique properties that make them applicable in various fields of science and technology. The method of synthesis is simple, cost effective and environmental friendly. After review, we reported the phyto-synthesis of metal oxide nanoparticles using plant extract with an emphasis on recent developments. Biomolecules such as alkaloids, flavonoids, polyphenols etc. present in the plant extract can be used for the reduction of metal ions to nanoparticles in a single step process. These extract also act as a stabilizing agent. Although, a good number of work has been reported for the synthesis of gold and silver nanoparticles. However, limited no of work has been reported for the synthesis of copper, zinc and iron oxide nanoparticles. We have discussed the green synthesis of copper, zinc and iron oxide nanoparticles and potential of their antibacterial efficacy

Here, we report the size- and shape-controlled synthesis of metal oxide nanoparticles through the introduction of rare-earth metals. The addition of gadolinium oleate in the synthesis of iron oxide nanoparticles induced sphere-to-cube shape changes of nanoparticles and generated iron oxide nanocubes coated with gadolinium. Based on experimental investigations and density functional theory (DFT) calculations, we attribute the shape change to the facet-selective binding of undecomposed gadolinium oleates. While many previous studies on the shape-controlled syntheses of nanoparticles rely on the stabilization of specific crystal facets by anionic surfactants or their decomposition products, this study shows that the interaction between growing transition metal oxide nanoparticles and rare-earth metal complexes can be used as a robust new mechanism for shape-controlled syntheses. Indeed, we demonstrated that this approach was applicable to other transition metal oxide nanoparticles (i.e., manganese oxide and manganese ferrite) and rare earth metals (i.e., gadolinium, europium, and cerium). This study also demonstrates that the nature of metal-ligand bonding can play an important role in the shape control of nanoparticles.

Azadirachta indica leaves mediated green synthesis of metal oxide nanoparticles: A review