Wet-chemical Synthesis Process Research Articles

Confirmation of the presence of edge dislocations in the prepared FCC ZnTe nanocrystals from the study of structural analysis through the MWH method with added Fourier analysis (W-A method) of diffraction peaks

Nanocrystalline ZnTe with cubic mono-phase has been synthesized by a wet-chemical synthesis process for the study of the presence of dislocations through X-ray diffraction peak profile analysis. The average size of the ZnTe nanocrystals has been determined from the High-Resolution Transmission Electron Microscopic (HRTEM) analysis as 21.9 nm. In the XRD pattern, (111), (200), (220), (311), and (400) diffraction planes have been observed, which confirms the formation of cubic mono-phase of ZnTe. For the extraction of microstructural details, the Rietveld refinement has been performed using Fullprof software and from this refinement, the lattice constant has been obtained as 6.17 Å under the space group of f-43. Here, X-ray diffraction peak has been analyzed through the Williamson-Hall (W–H) analysis method and the Warren-Averbach (W-A) analysis method. Williamson-Hall approach is based on the full-width at half-maxima analysis, whereas the Warren-Averbach method is related to the analysis of the Fourier transform of the broadened X-ray diffraction peaks. For considering and analyzing the anisotropic broadening of the peak, modified Williamson-Hall and modified Warren-Averbach methods have been used for the calculation of size, strain, and dislocation density. The presence of prominent edge dislocation of about 71 % has been confirmed from the anisotropic peak broadening study. In addition, the HRTEM image directly verifies the presence of edge dislocations in both the lattice planes of (111) and (220).

An environmentally friendly green synthesis of Co2+ and Mn2+ ion doped ZnO nanoparticles to improve solar cell efficiency

Global warming is a threat to human health in the context of increasing organic or inorganic pollutants, which are produced by various products. The “Green synthesis” method effectively eliminates toxic and/or harmful effects that arise due to the wet-chemical synthesis process. Different concentrations of Co2+ and Mn2+ ion doped ZnO-nanoparticles (NPs) were designed at a low temperature, about 70 °C by utilizing an eco-friendly sustainable method with dandelion leaf (DL) extract as a solvent and these biosynthesized NPs were annealed to grow the crystallinity enhancement. The confirmation of NPs crystal phase, phase purity, and grain size was performed by XRD, showing the hexagonal-Wurtzite phase structure. SEM and TEM images of the NPs demonstrated sub-100 nm spherical-shaped particles. Fourier transform infrared displays characteristics band about ∼523 cm–1 which corresponds to Zn–O tetrahedron asymmetric stretching vibrations. Both UV-Visible and luminescence studies confirmed the adjacent band edge emission of ZnO and successive incorporation of Co2+ and Mn2+ ion-doped ZnO host. For improving power conversion efficiency, the polycrystalline silicon solar cells (PSSCs), different layers of Co2+ and Mn2+ ion-doped ZnO-NPs coated on bare PSSCs are promising strategies. Additionally, solar cell efficiency decreases with further coating of NPs layers and/or thickness. Optimum solar cell efficiency was observed for 5 at% Mn2+ ion-doped ZnO-NPs with three layers. Finally, Radish and Cress plants are grown, using the biosynthesized ZnO-NPs supernatant from DL extract, which showed high environmental biocompatibility.

Self-Activation of Inorganic-Organic Hybrids Derived through Continuous Synthesis of Polyoxomolybdate and para-Phenylenediamine Enables Very High Lithium-Ion Storage Capacity.

Inorganic-organic hybrid materials with redox-active components were prepared by an aqueous precipitation reaction of ammonium heptamolybdate (AHM) with para-phenylenediamine (PPD). A scalable and low-energy continuous wet chemical synthesis process, known as the microjet process, was used to prepare particles with large surface area in the submicrometer range with high purity and reproducibility on a large scale. Two different crystalline hybrid products were formed depending on the ratio of molybdate to organic ligand and pH. A ratio of para-phenylenediamine to ammonium heptamolybdate from 1 : 1 to 5 : 1 resulted in the compound [C6 H10 N2 ]2 [Mo8 O26 ] ⋅ 6 H2 O, while higher PPD ratios from 9 : 1 to 30 : 1 yielded a composition of [C6 H9 N2 ]4 [NH4 ]2 [Mo7 O24 ] ⋅ 3 H2 O. The electrochemical behavior of the two products was tested in a battery cell environment. Only the second of the two hybrid materials showed an exceptionally high capacity of 1084 mAh g-1 at 100 mA g-1 after 150 cycles. The maximum capacity was reached after an induction phase, which can be explained by a combination of a conversion reaction with lithium to Li2 MoO4 and an additional in situ polymerization of PPD. The final hybrid material is a promising material for lithium-ion battery (LIB) applications.

Operating interfaces to synthesize L10-FePt@Bi-rich nanoparticles by modifying the heating process.

A facile strategy to operate interfaces when synthesizing L10-FePt@Bi-rich nanoparticles (NPs) has been proposed. Two interfaces are indispensable to obtain the high ordering L10-FePt structure. One is the mismatched interfaces between the initial γ-PtBi2 nuclei and the disordered fcc-FePt phase. The other is the in situ grown coherent interfaces between the L10-FePt and Bi-rich phases. Increasing the heating rates when the temperature rises from 120 °C to 310 °C benefits the formation of mismatched interfaces and improves the uniformity of phases and composition in NPs. Reducing the heating rate at higher temperature ensures sufficient time for Bi to diffuse across the coherent interface, which facilitates the disorder-order transition of L10-FePt NPs. This study provides a new perspective on operating interfaces during the wet-chemical synthesis process.

Effect of Zr/Gnp hybrid filler on thermal and ablation properties of carbon‐epoxy composites

AbstractIn this work, the Zirconia (Zr) particles were coated with graphene nanoplatelets (Gnps) using the wet chemical synthesis process and sintered at 500°C and 900°C. At sintering temperature of 900°C, the Zr coated with 0.25 wt% Gnp fillers exhibited better oxidation resistance. Thus, the carbon epoxy (C‐Ex) composites containing Zr/Gnp, 0.25 wt%, were fabricated by the hand‐layup technique. The prepared composites were characterized by scanning electron microscopy, thermogravimetry analysis (TGA), flexural, and ablation tests. The C‐Ex composites modified with Zr/Gnps fillers showed significant improvement in thermal stability and flexural strength compared with the pristine sample. The composite containing 0.25 wt% Zr/Gnp filler reduced the mass ablation rate to 23%, whereas back‐surface temperature was decreased to 170°C compared with pure C‐Ex composite. The surface morphology of ablated composite samples revealed that the Zr/Gnp produced char droplet spheres on the carbon fibres, which prevented the further oxidation of the matrix and thus improved the ablative performance.

Effect of Nickel Doping on the Properties of Hydroxyapatite Nanoparticles.

Herein, we studied the effect of nickel (Ni) doping on the properties of hydroxyapatite (HAp) nanoparticles synthesized by facile ultrasonication assisted wet chemical synthesis process. Various doping concentrations of nickel, i.e., 0.01 M, 0.05 M and 0.10 M, were used to dope into hydroxyapatite nanoparticles. The synthesized nanoparticles were characterized by X-ray diffraction (XRD) pattern, scanning electron spectroscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, UV-Visible spectroscopy and Raman-scattering spectroscopy. The detailed structural characterizations confirmed that the crystallite sizes of the Ni-doped hydroxyapatite nanoparticles were reduced up to 53% compared to pure hydroxyapatite upon the doping of different concentrations of Ni ions. The agglomeration in the nanoparticles was also reduced by increasing the doping concentration of Ni ions. The XRD studies revealed that the average crystallite size of the synthesized Ni-doped HAp was decreased with increasing the concentration of Ni2+ ion doping and this observation was well-consistent with the SEM results. The FTIR and Raman studies well-confirmed the formation of pure HAp and Ni-doped HAp. Further, doping with Ni creates a new level of energy between the conductive band and the valence band and hence with increasing the concentration of Ni2+, the intensity in the UV-vis spectra was enhanced.

Activity and stability optimization of RuxIr1-xO2 nanocatalyst for the oxygen evolution reaction by tuning the synthetic process

IrO2 and RuO2 are known as two of the best catalysts for the oxygen evolution reaction (OER) in acidic electrolyte. It is reported that RuO2 has higher OER catalytic activity, while IrO2 possesses better electrochemical stability during the OER process in acid. Therefore, many combined strategies have been proposed to utilize the advantages of both IrO2 and RuO2 catalysts in water electrolysis applications. In this article we describe how, by tuning the wet-chemical synthesis process in which the Ir precursor is added after the synthesis of RuO2 nanoparticles (NPs) (two-step), the Ru0.5Ir0.5O2 NPs have been synthesized to improve the OER catalytic activity in both acidic and alkaline media. In detail, the specific OER activity of the Ru0.5Ir0.5O2 NPs (with a particle size of ca. 10 nm) is 48.9 μA cm−2 at an overpotential ŋ = 0.22 V (vs. RHE) and 21.7 μA cm−2 at ŋ = 0.27 V (vs. RHE) in 0.1 M HClO4 and 0.1 M KOH, respectively. These values are higher than those for the one-step (Ir0.5+Ru0.5)O2 NPs (obtained by contemporaneously adding both Ru and Ir precursors), which are 19.5 and 15.5 μA cm−2 at the same measuring conditions, respectively. Additionally, with more IrO2 component distributed on the particle surface, the two-step Ru0.5Ir0.5O2 NPs show better OER catalytic stability than RuO2 NPs.

Crystal Growth Mechanisms of BiFeO3 Nanoparticles.

A wet-chemical synthesis process was designed to obtain reproducible single-phase multiferroic BiFeO3 nanoparticles. The phase purity, single crystallinity, and size of the nanoparticles are confirmed through the analysis of X-ray diffraction patterns, Raman spectroscopy, and high resolution transmission electron microscopy experiments. Crystal nucleation happens within the amorphous-rich area in multiple seeds, leading to the formation of single crystalline nanoparticles with no preferential faceting. Crystallization mechanisms of BiFeO3 nanoparticles were investigated following the Kissinger-Akahira-Sunose approach, indicating that two crystallization steps are responsible of the complete BiFeO3 nanoparticle formation. The first crystallization step involves a maximum of 70% of the final crystal volume, arising from nanocrystal nucleation and growth. The second step occurs above this threshold crystal volume fraction, and it is related to the nanocrystallite coalescence process. Analysis of the thermodynamic process of the crystallization of BiFeO3 nanoparticles following Ostwald rules suggests a relatively low energy barrier for crystal nucleation, highlighting that phase pure, single crystalline BiFeO3 nanoparticles are obtained using the present optimized wet-chemical synthesis process, with temperatures as low as 450 °C.

Wet Synthesis of Energetic Aluminum Hydride

AbstractAluminum hydride (alane, AlH3) is a promising candidate material for solid propulsion, explosives and beyond, particularly in the aerospace field due to its high energetic capacity. This study attempted to produce a stable alane structure through a wet chemical synthesis process. Preliminary dissolution of starting reactants in ether produced a consistent crystal structure (cubic shape) and elemental constituents analogous to the theoretical composition. The chemical structure, when examined by XRD, matched well with the standard reference α‐type alane, and the resulting particle size of the precipitated α‐type alane ranged from 7 to 13 μm. A pivotal step in the alane synthesis was selective crystallization from the liquid phase alane−etherate (AlH3 ⋅ (Et2O)n), followed by acid treatment of the precipitated particulate alanes using an appropriately mixed solution.

Band gap engineered zinc oxide nanostructures via a sol-gel synthesis of solvent driven shape-controlled crystal growth.

A reliable sol–gel approach, which combines the formation of ZnO nanocrystals and a solvent driven, shape-controlled, crystal-growth process to form well-organized ZnO nanostructures at low temperature is presented. The sol of ZnO nanocrystals showed shape-controlled crystal growth with respect to the solvent type, resulting in either nanorods, nanoparticles, or nanoslates. The solvothermal process, along with the solvent polarity facilitate the shape-controlled crystal growth process, augmenting the concept of a selective adhesion of solvents onto crystal facets and controlling the final shape of the nanostructures. The XRD traces and XPS spectra support the concept of selective adhesion of solvents onto crystal facets that leads to yield different ZnO morphologies. The shift in optical absorption maxima from 332 nm in initial precursor solution, to 347 nm for ZnO nanocrystals sol, and finally to 375 nm for ZnO nanorods, evidenced the gradual growth and ripening of nanocrystals to dimensional nanostructures. The engineered optical band gaps of ZnO nanostructures are found to be ranged from 3.10 eV to 3.37 eV with respect to the ZnO nanostructures formed in different solvent systems. The theoretical band gaps computed from the experimental XRD spectral traces lie within the range of the optical band gaps obtained from UV-visible spectra of ZnO nanostructures. The spin-casted thin film of ZnO nanorods prepared in DMF exhibits the electrical conductivity of 1.14 × 10−3 S cm−1, which is nearly one order of magnitude higher than the electrical conductivity of ZnO nanoparticles formed in hydroquinone and ZnO sols. The possibility of engineering the band gap and electrical properties of ZnO at nanoscale utilizing an aqueous-based wet chemical synthesis process presented here is simple, versatile, and environmentally friendly, and thus may applicable for making other types of band-gap engineered metal oxide nanostructures with shape-controlled morphologies and optoelectrical properties.

One-pot wet chemical synthesis of fluorine-containing TiO2 nanoparticles with enhanced photocatalytic activity

Two types of TiO2 nanoparticles: i) fluorine-containing TiO2 (F-TiO2) and ii) fluorine-free TiO2 (H-TiO2) nanoparticles, were prepared through a simple, scalable wet-chemical synthesis process, and a comparative study of their photocatalytic properties was conducted. This facile process begins with a one-pot precipitation process at 90 °C, followed by heat treatment at 600 °C for 1 h in air, resulting in hierarchical, sphere-like, mesoporous structures composed of primary nanoparticles. The microstructural features and crystallographic structures of both types of nanoparticles were systematically investigated by X-ray diffraction, thermogravimetric/differential thermal analysis, X-ray photoelectron spectroscopy, N2 physical adsorption-desorption, field emission scanning electron microscopy, and transmission electron microscopy analyses. The photocatalytic activities were also evaluated by measuring the degradation of MB. The F-TiO2 nanoparticles showed enhanced photocatalytic activity compared to H-TiO2, which can be attributed to adsorbed fluorine on the surface which leads to various positive effects on the photocatalytic degradation reactions.

Reconstruction of the Wet Chemical Synthesis Process: The Case of Fe5C2 Nanoparticles

Wet chemical synthesis (WCS), especially under high temperatures, is one of the most frequently used strategies for nanostructured material construction, which has been used extensively in medical-, energy-, and environment-related applications. Although knowledge about the WCS process has been accumulated in the past two decades, the high temperature used in the process and multiphase nature of intermediates and products are key factors preventing the processes from rationalization. In this paper, by using multilevel in situ cells, we developed a strategy to monitor the reaction details of WCS processed in the solid, liquid, and gas phase simultaneously. This protocol has proven successful to reconstruct the WCS process of Fe5C2 nanoparticles (NPs) and unravel the complicated chemistry in the synthesis process.

Synthesis and characterization of mesoporous and superparamagnetic bilayered-shell around silica core particles

Multifunctional bilayered shell around monodispersed silica core particles was prepared by wet-chemical synthesis process. The first outer layer was composed of mesoporous silica and the second internal layer was composed of superparamagnetic Fe3O4 nanoparticles. Ferrite nanoshell was synthesized by assembling of oppositely charged ferrite (Fe3O4) nanoparticles on the surface of the monodispersed silica core particles (having average size of ~0.5µm and prepared by hydrolysis and condensation of tetraethylortosilicate). The obtained Fe3O4 layer was superparamagnetic and had very weakly developed pore structure. The second layer on the previously obtained particles with silica core and Fe3O4 shell was formed by deposition of silica nanoparticles from a silicate solution. To allow electrostatic assembling of the silica nanoparticles and formation of external silica layer around the silica/Fe3O4 particles, the latter were functionalized with poly(diallyldimethylammonium chloride) (PDDA). Obtained silica layer had well developed pore structure with average pore size of 10nm. The obtained composite particles with two functional layers can be used in bioengineering for immobilization of enzymes inside external mesoporous silica layer while internal superparamagnetic ferrite layer would allow magnetic separation from reaction mixture.

Complex additive systems for Mn-Zn ferrites with low power loss

Mn-Zn ferrites were prepared via an oxalate-based wet-chemical synthesis process. Nanocrystalline ferrite powders with particle size of 50 nm were sintered at 1150 °C with 500 ppm CaO and 100 ppm SiO2 as standard additives. A fine-grained, dense microstructure with grain size of 4–5 μm was obtained. Simultaneous addition of Nb2O5, ZrO2, V2O5, and SnO2 results low power losses, e.g., 65 mW/cm3 (500 kHz, 50 mT, 80 °C) and 55 mW/cm3 (1 MHz, 25 mT, 80 °C). Loss analysis shows that eddy current and residual losses were minimized through formation of insulating grain boundary phases, which is confirmed by transmission electron microscopy. Addition of SnO2 increases the ferrous ion concentration and affects anisotropy as reflected in permeability measurements μ(T).

Controlled Fabrication of Highly Monodispersed, Gold Nanoparticles Grafted Polyaniline (Au@PANI) Nanospheres and their Efficient Ammonia Gas Sensing Properties

In the present study, highly monodispersed polyaniline (PANI) and gold nanoparticles grafted PANI nanospheres (Au@PANI) have been fabricated through a facile wet-chemical synthesis process by in-situ polymerization of aniline. The structural characterization of the PANI and Au@PANI nanospheres were carried out by UV-Vis spectroscopy, FT-IR spectroscopy, and High Resolution Transmission Electron Microscopy (HR-TEM). Stable uniform sized nanospheres of PANI and Au@PANI obtained were found to exhibit superior gas sensor performance towards trace-level concentration of ammonia (NH3) gas in the range of 1-5 ppm. A comparative analysis of the sensor properties of PANI and Au@PANI nanospheres were performed under ambient conditions. Au@PANI nanospheres exhibited enhanced gas sensing performance with high sensitivity (58.2%), rapid response (48 s) and recovery (58 s) characteristics (1 ppm of NH3). The results indicate the potential use of Au@PANI nanospheres for fabrication of efficient NH3 sensors for varied applications.

Vapor-phase preparation of gold nanocrystals by chloroauric acid pyrolysis

We report that gold nanocrystals can be prepared from vapor phase using chloroauric acid (HAuCl4) as the precursor. By tuning the vapor-phase deposition parameters, the size and space distribution of the gold nanocrystals can be well controlled on substrates. Systematic control experiments demonstrate that intermediate AuCl and AuCl3 products pyrolyzed from HAuCl4 play an essential role in this vapor-phase deposition process. Compared to conventional wet-chemical synthesis process, vapor-phase process enables direct deposition of gold nanoparticles on solid substrates with better coverage and uniformity, which may find applications in surface-enhanced Raman scattering and plasmon-enhanced photocatalysis.

CdS quantum dot-sensitized solar cells based on nano-branched TiO2 arrays

Nano-branched rutile TiO2 nanorod arrays were grown on F:SnO2 conductive glass (FTO) by a facile, two-step wet chemical synthesis process at low temperature. The length of the nanobranches was tailored by controlling the growth time, after which CdS quantum dots were deposited on the nano-branched TiO2 arrays using the successive ionic layer adsorption and reaction method to make a photoanode for quantum dot-sensitized solar cells (QDSCs). The photovoltaic properties of the CdS-sensitized nano-branched TiO2 solar cells were studied systematically. A short-circuit current intensity of approximately 7 mA/cm2 and a light-to-electricity conversion efficiency of 0.95% were recorded for cells based on optimized nano-branched TiO2 arrays, indicating an increase of 138% compared to those based on unbranched TiO2 nanorod arrays. The improved performance is attributed to a markedly enlarged surface area provided by the nanobranches and better electron conductivity in the one-dimensional, well-aligned TiO2 nanorod trunks.

Magnetic and structural characterization of transition metal co-doped CdS nanoparticles

We report the structural and magnetic properties of the CdS nanoparticles co-doped with Ni and Cu; 3% Ni, Cu co-doped CdS nanoparticles were synthesized by using wet chemical synthesis process. From high-resolution transmission electron microscopy (HR-TEM), it is found that the average diameter of the Ni, Cu co-doped CdS nanoparticles is about 5 nm. X-ray diffraction (XRD) studies show the zinc blende (cubic) structure of Ni, Cu co-doped CdS nanoparticles. Energy dispersive spectroscopy (EDS) confirms the elemental composition of the doped sample. Room temperature magnetic studies are made by the analysis of M-H curves, obtained using superconducting quantum interference device (SQUID). The magnetic behavior has been shown by CdS nanoparticles doped with 3% nickel as well as CdS nanoparticles co-doped with 3% Ni and Cu.

Influence of point defects on the performance of InVO<sub>4</sub> photoanodes

The properties of thin film InVO4 photoanodes for water splitting have been studied. Compact films of InVO4 were prepared by spray pyrolysis and are found to be stable between pH 3 and 11. Although the indirect bandgap is 3.2 eV, a modest amount of visible light absorption is observed. The origin of this absorption is attributed to the presence of deep donor states at ?0.7 eV below the conduction band. These donor states presumably correspond to oxygen vacancies, which form as a result of small but unavoidable deviations of In:V from the ideal 1:1 stoichiometry during the wet-chemical synthesis process. Shallow donors are absent in this material, in contrast to what is normally observed for metal oxides. The deep donor model explains the much stronger visible light absorption of powders compared to thin films. The defect chemical reactions that lead to the formation of the deep donors are shown, and are supported by photoluminescence data

Rutile TiO2 nano-branched arrays on FTO for dye-sensitized solar cells

Hierarchical TiO(2) nanostructures would be desirable for preparing dye-sensitized solar cells because of their large amount of dye adsorption and superior light harvesting efficiency, as well as efficient charge separation and transport properties. In this study, rutile TiO(2) nano-branched arrays grown directly on transparent conductive glass (FTO) were prepared by a facile two-step wet chemical synthesis process, using a simple aqueous chemical growth method involving immersing the TiO(2) nanorod arrays in an aqueous TiCl(4) solution as seeds, which were prepared by a hydrothermal method. The dye-sensitized solar cells based on the TiO(2) nano-branched arrays which were only about 3 μm in length show a short-circuit current intensity of 10.05 mA cm(-2) and a light-to-electricity conversion efficiency of 3.75%, which is nearly three times as high as that of bare nanorod arrays, due to the preferable nanostructure, which not only retains the efficient charge separation and transport properties of the nanorod arrays, but also can improve the amount of dye adsorption due to the increased specific surface area from the nanobranches.