Inorganic Salt Precursors Research Articles

Synthesis of single-atom dispersed Co-NC catalytic materials in supercritical CO2 environment with inorganic salt precursor

Supported single-atom catalytic materials (SACMs) have aroused extensive interest due to their remarkable properties. Herein, a novel method was proffered to prepare Co-NC SACMs using custom-designed N-doped carbon (NC) as support, CoCl2 as the precursor in supercritical CO2 with appropriate co-solvent. It was found that when ethanol was used as co-solvent, nanoparticles were obtained while only Co single-atom was obtained when N, N-Dimethylformamide (DMF) was used as co-solvent. Both the theoretical loading and the deposition time influenced the Co loading a lot, and the maximum Co loading was as high as 1.71 wt%. Strong acid, strong alkali, corrosive solvent, and high-temperature treatment were avoided in the whole process. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM), X-ray photoelectron spectroscopy (XPS), Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), and Energy Dispersive X-ray spectroscopy (EDX) were conducted to confirm the existence and uniform distribution of Co atoms over the N-doped carbon materials. The conversion rate of 90.0% and selectivity of 86.0% were obtained for the solvent-free selective oxidation of benzyl alcohol to benzaldehyde at 70 °C and 1 h using the Co-NC SACMs.

Inkjet-Printed Hydrogen Peroxide Sensor With Sensitivity Enhanced by Plasma Activated Inorganic Metal Salt Inks

Printed sensors that rely on low-cost substrate materials and additive fabrication processes are needed for wearable and disposable device applications. A critical challenge associated with currently available printed sensors is their inferior performance compared with sensors fabricated by thin-film deposition or nanoscale assembly. In this paper, we report on an inkjet-printed hydrogen peroxide (H2O2) sensor possessing a sensitivity >30X higher than those made by conventional sputtering. The key enabling step in our printing approach is low-temperature plasma conversion of an inorganic salt precursor to produce silver (Ag). The resistivity of the printed Ag measured by four-point probe is found to be only 6X higher than that of bulk Ag and 5X higher than that of sputtered Ag. Additionally, the surface roughness of the printed Ag characterized by optical profilometry and atomic force microscopy is much higher than that of the sputter-deposited Ag. The resulting large surface area of the printed Ag leads to a significantly improved reaction rate with H2O2, and is responsible for the increased sensitivity of the sensor.

Inorganic-salt coprecipitation synthesis, fluoride-doping, bioactivity and physiological pH buffering evaluations of bredigite

Bredigite (Ca7MgSi4O16), with suitable bioactivity, biodegradation, biocompatibility and mechanical properties, is a promising candidate for the repair and regeneration of damaged bone tissues. In this research, for the first time, bredigite was synthesized by a facile and inexpensive coprecipitation method using inorganic salt precursors, followed by calcination at 1200 °C. Additionally, 0.5 mol% fluoride was successfully doped into the structure without the formation of any second phases. X-ray diffraction and Fourier-transform infrared spectroscopy confirmed the formation of single-phase orthorhombic bredigite in the samples and the incorporation of fluoride in the doped sample, respectively. Both the undoped and doped samples exhibited apatite-formation ability in terms of the precipitation of hydroxycarbonate apatite when exposed to a simulated physiochemical medium, with an increase in this characteristic as a result of fluoride doping. The addition of fluoride also lowered and buffered the pH value of the medium, where the enhancement of this parameter is due to the fast bioresorption of bredigite affecting disadvantageously biocompatibility.

Colloidally Confined Crystallization of Highly Efficient Ammonium Phosphomolybdate Catalysts.

Nanodroplets in inverse miniemulsions provide a colloidal confinement for the crystallization of ammonium phosphomolybdate (APM), influencing the resulting particle size. The effects of the space confinement are investigated by comparing the crystallization of analogous materials both in miniemulsion and in bulk solution. Both routes result in particles with a rhombododecahedral morphology, but the ones produced in miniemulsion have sizes between 40 and 90 nm, 3 orders of magnitude smaller than the ones obtained in bulk solution. The catalytic activity of the materials is studied by taking the epoxidation of cis-cyclooctene as a model reaction. The miniemulsion route yields APM particles catalytically much more active than analogous samples produced in bulk solution, which can be explained by their higher dispersibility in organic solvents, their higher surface area, and their higher porosity. Inorganic phosphate salt precursors are compared with organic phosphate sources. APM nanoparticles prepared in miniemulsion from d-glucose-6-phosphate and O-phospho-dl-serine yield a conversion in the epoxidation reaction of more than 90% after only 1 h, compared to 30% for materials prepared in bulk solution. In addition, the catalysts prepared in miniemulsion display a promising recyclability.

Synthesis and Characterization of Nanocrystalline M-Mg-O and Carbon-Coated MgO Systems

Two different approaches to modify the structure and reaction ability of nanocrystalline MgO have been discussed. In the first case, a series of two-component x%MOx–MgO systems (M = Fe, Co and Ni, x = 1–45 wt.%) was synthesized via sol–gel technique. Aqueous solution of inorganic salt precursor was used as a hydrolyzing agent. Samples obtained were characterized by number of physicochemical methods (differential thermal analysis, X-ray diffraction analysis, low-temperature adsorption, etc.). It was shown that presence of inorganic salt in magnesium hydroxide matrix shifts the temperature of decomposition of latter towards lower values. Structural and textural characteristics of MgO-based oxide systems were found to be strongly affected by the presence of additive and their concentration. Formation of joint phase was observed in the case of cobalt oxide only. Second way of MgO modification was represented by creating a controlled carbon coating over its surface via decomposition of C4H10 at 400 °C. The obtained x%C/MgO (x = 1–10 wt.%) samples were shown to possess the improved reaction ability in destruction sorption of CF2Cl2 as well as in catalytic dehydrochlorination of 1-chlorobutane in presence of water vapors.

Synthesis of vaterite CaCO3 as submicron and nanosized particles using inorganic precursors and sucrose in aqueous medium

It is reported the synthesis of CaCO3 vaterite as stable nanoparticles and submicron-sized by a simple and relatively rapid procedure. XRD, SEM and FTIR techniques have been used to characterize the precipitated products. The synthesis is based on chemical precipitation of inorganic salt precursors, calcium nitrate tetrahydrate and sodium bicarbonate, and using the disaccharide sucrose as an additive in aqueous medium. The role of the disaccharide sucrose is to control the vaterite precipitation after nucleation and growth. It has been found that an increase in sugar concentration promotes the crystal precipitation of vaterite with spherulitic morphology, as revealed by SEM, and changed the surface of the precipitated particles. There is a significant difference between CaCO3 precipitation in the absence and presence of sucrose. Addition of 0% of sucrose leads to 83% of calcite as identified by XRD methods. In contrast, addition of 67% of sucrose in aqueous medium produces 100% vaterite. The present results may be useful to provide a quick, simple, inexpensive and novel method for the controlled synthesis of new advanced biomaterials based on vaterite particles without hazardous chemicals and inert atmosphere, with great possibilities for industrial scale production.

Chemical solution deposition of ferroelectric Sr:HfO2 film from inorganic salt precursors

Strontium doped hafnium oxide (Sr:HfO2) ferroelectric thin films with strontium concentrations ranging from 0 to 20mol% were processed with inorganic hafnium source and strontium source using a chemical solution deposition technique. The co-existence of monoclinic phase and ferroelectric orthorhombic phase in the Sr doped HfO2 thin film was confirmed by x-ray diffraction and high-resolution transmission electron microscopy results. The atomic force microscope measurements were adopted and the thin films showed crack-free surface. The intrinsic ferroelectricity of the doped HfO2 thin films could be demonstrated by polarization–voltage hysteresis loops together with piezoelectric force microscope. The maximum twofold remnant polarization value of 3.02 μC/cm2 with a coercive field of 2.0 MV/cm was achieved when the Sr content was 7.5 mol%. Meanwhile, the polarization didn't show obvious degradation until 107 electric cycles, indicating the good fatigue performance of the Sr:HfO2 film. These findings indicate that it is a feasible way to prepare Sr:HfO2 ferroelectric thin films via chemical solution deposition with inorganic salt precursors.

Sol–gel synthesis and characterization of two-component systems based on MgO

A series of two-component MO x –MgO systems, where M is Cu, Ni, Co, Fe, Mo or W, was synthesized by sol–gel technique. Aqueous solution of inorganic salt-precursor was used as a hydrolyzing agent. Initial xerogels and final oxides were characterized using X-ray diffraction analysis, scanning electron microscopy and low-temperature nitrogen adsorption. Decomposition of xerogels was studied by differential thermal analysis. According to X-ray diffraction analysis, all xerogel samples are characterized with turbostratic structures regardless of nature of the second component. At the same time, presence of inorganic salt in magnesium hydroxide matrix shifts the temperature of decomposition of latter towards lower values. Structural and textural characteristics of MgO-based oxide systems were found to be strongly affected by the additive. Formation of joint phase was observed in the case of cobalt oxide. In most cases, additives turned out to be even distributed in the bulk of MgO, except for WO3. This oxide formed large agglomerates because of low solubility of precursor.

Sustainable innovative method to synthesize different shades of iron oxide pigments

The iron oxide pigments (IOPs) were synthesized using citrus pectin as a colloidal template that allows the generation of different shades of pigment. The innovation is that the same batch generates different colors for the hematite phase function of calcination temperature (300, 600 and 1000 °C) determined by thermal analysis. This sustainable innovative method (SIM) does not produce waste, requires a quantity of water proportional to the volume of the prepared colloid, and does not involve filtration, purification or grinding. The use of the inorganic salt precursor, iron sulfate, was evaluated as an important iron source and their influence on the pigment color. Six IOPs were prepared; iron (II) sulfate generated the IOP-II300 (yellow), IOP-II600 (red) and IOP-II1000 (purple); while iron (III) sulfate produced IOP-III300 (yellow), IOP-III600 (red) and IOP-III1000 (violet). The IOPs were characterized by their thermal behavior, structural and morphological properties, electronic and vibrational spectroscopy. The colloidal stability was determined by electrophoretic mobility and the dispersions optimized to the ideal pH. Dispersion tests were conducted on commercial white paint (water-based), and colorimetric profile (CIEL*a*b*) evaluated microscope slides coated with pigmented paint.

Large Magnetoresistance and Electrostatic Control of Magnetism in Ordered Mesoporous La1–xCaxMnO3 Thin Films

Ferroic nanomaterials have received much attention in recent times because of their potential for novel applications. Here, we report a facile bottom–up synthetic approach to the first ordered mesoporous mixed-valence manganese oxide. Continuous thin films of perovskite-type La0.68Ca0.30Mn1.02O3−δ have been prepared from common inorganic salt precursors by taking advantage of the superior templating properties of a polyisobutylene-block-poly(ethylene oxide) diblock copolymer. This novel solution-processed mesostructured material is well-defined at the nanometer and micrometer levels and behaves superparamagnetically above 230 K. Furthermore, it exhibits large magnetoresistance over a wide range of temperatures due to complex percolation pathways for electron transport imparted by the unique pore–solid architecture, and it is ferromagnetic metallic below 180 K. We also demonstrate reversible magnetization modulation of up to 8.5% by electrostatic charge carrier doping in the polymer-templated thin films. T...

Synthesis of nanostructured La2Zr2O7 by a non-alkoxide sol–gel method: From gel to crystalline powders

Nanocrystalline La 2 Zr 2 O 7 powders of single prochlore phase were synthesized by a non-alkoxide sol–gel process. Homogeneous sol, free of precipitation, was prepared by addition of citric acid, polyethylene glycol and formamide to aqueous solutions of Zr 4+ and La 3+ inorganic salt precursors. We found that fluorite structure La 2 Zr 2 O 7 was crystallized at 1000 °C, and then transformed to pyrochlore structure at 1200 °C. With further increase in temperature, the crystalline degree of pyrochlore La 2 Zr 2 O 7 powders increased. The particle size of the as-prepared La 2 Zr 2 O 7 powders at 1200 °C was about 80–200 nm. With temperature increase, sintering of La 2 Zr 2 O 7 particles resulted in grain size growth. Mechanism of La 2 Zr 2 O 7 nano-particles as function of temperature during heat treatment was analyzed. The density of the powders sintered at 1600 °C was 96.0% of the theoretical value, and thermal conductivity ranged from 0.65 to 0.85 W·m −1 ·K −1 , which was much lower than that of 7YSZ.

Fluoride removal by ordered and disordered mesoporous aluminas

Highly ordered and disordered (MA-n) mesoporous aluminas with excellent fluoride adsorption performance have been successfully developed. The physicochemical and adsorption properties were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption isotherms and fluoride removal experiments. Highly ordered mesoporous structure (OMA) was produced by using aluminum metal organic as precursor and wormlike disordered mesoporous structure (MA-n, MA-cl) was synthesized from inorganic aluminum salt precursors. The synthesized mesoporous alumina with a large pore size distribution of 7–14nm and large surface areas in the range of 163–338m2/g are beneficial for transport of solution in interconnected mesoporous channels and the fluoride ion was anchored on plenty of surface hydroxyl groups which provide high fluoride adsorption capacity and efficiency. Adsorption kinetics was described by pseudo-second-order, pseudo-first-order and intra-particle pore diffusion models, while, their adsorption equilibrium isotherms were described reasonably well by Langmuir model. Maximum fluoride adsorption capacities of OMA-400, OMA-850 and MA-n were 135, 91 and 95mg/g, respectively, which are higher than many reported alumina based adsorbents. Due to the ordered mesoporous structure which decreases the liquid transfer resistance, the OMA-400 showed extremely faster adsorption kinetics with a removal of 90% of F− within 20min at an optimal pH of 6. Presence of other anions like SO42−, NO3−, Cl− and HCO3− effect on fluoride removal efficiency and desorption study of OMA-400 and OMA-850 were also determined and compared.

Silica-g-poly[2-(N,N-dimethyl amino) ethyl methacrylate] hybrid nanospheres with polymer brushes as stabilizer for metallic nanocolloids

The silica-g-poly[2-(N,N-dimethyl amino)ethyl methacrylate] (SiO2-g-PDMAEMA) hybrid microspheres with polymer brushes were synthesized by the surface-grafted atom transfer radical polymerization (ATRP) from the surface alkyl bromide functionalized silica nanospheres. The inorganic nanosphere as surface-initiating polymerization site was prepared by the amide reaction of 2-bromoisobutyryl bromide with the surface amino group of silica via modification with (3-aminopropyl) trimethoxysilane (APS). The grafted PDMEMA brushes stabilized metallic nanocolloids (silver and palladium) were prepared by the in situ reduction of the inorganic salt precursors (AgNO3 and PdCl2) through the coordination effect of the amino groups to the metallic atom (Au, Ag). The catalytic properties of PDMAEMA brush-stabilized silver and palladium metallic nanocolloids were investigated via the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AnP) by sodium borohydride (NaBH4) as a model reaction with a facilely recoverable and stable catalytic property. The resultant hybrid microspheres were characterized by transmission electron microscopy (TEM), thermal gravimetric analyzer (TGA), Fourier infrared (FT-IR) spectra, and inductive coupled plasma emission spectrum (ICP).

Ordered Mesoporous β‐MgMoO4 Thin Films for Lithium‐Ion Battery Applications

Ordered mesoporous β-MgMoO4 thin film electrodes with uniform pores averaging 19 nm in diameter are prepared through polymer templating of inorganic salt precursors. The unique combination of open mesopore cavities with nanocrystalline walls provides a beneficial microstructure for lithium-ion battery applications.

Formation of bimodal porous silica-titania monoliths by sol-gel route

Silica-titania monoliths with micrometer-scale macroporous and nanometer-scale mesoporous structure and high titania contents are prepared by sol-gel process and phase separation. Titanium alkoxide precursor was not effective in the preparation of high titania content composites because of strong decrease in phase separation tendency. Bimodal porous gels with high titania content were obtained by using inorganic salt precursors such as titanium sulfate and titanium chloride. Various characterization techniques, including SEM, XRD, Hg porosimetry and N2 adsorption have been carried out to investigate the formation process and physical-chemical properties of silica-titania monoliths. The characterization results show that the silica-titania monoliths possess a bimodal porous structure with well-dispersed titania inside silica network. The addition of titania in silica improves the thermal stability of both macroporous and mesoporous structures.

Synthesis of a Low-Density Copper Oxide Monolithic Aerogel Using Inorganic Salt Precursor

Copper oxide monolithic aerogel was prepared by sol–gel method using inorganic salt as precursor, ethanol as the solvent, and propylene oxide as the gelation agent. Calcination of the as-prepared aerogels at different temperatures induced a phase change which resulted in the formation of a mesoporous copper oxide aerogels. Field emission scanning electron microscopy (FESEM), Highresolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller(BET) methods were used to characterize the as-prepared aerogels. The combined results indicated that the as-prepared CuO aerogel has high porosity, high surface area, and low density. The X-ray diffraction (XRD) patterns show that the as-prepared CuO aerogel is highly crystalline and is identified to be predominantly copper chloride hydroxide, Cu2Cl(OH)3。

Template-assisted preparation of films of transparent conductive indium tin oxide

Thin films of ITO distinguished by an accessible uniform mesoporosity providing an unhindered access to well-defined inner surface, high transparency and good electrical conductivity were prepared by a template-assisted synthesis procedure. Indium acetylacetonate serving as the source of indium oxide made it possible to slow down the crystallization of indium oxide as compared to inorganic salt precursors. The preparation procedure included the following steps: (1) slow condensation step at 100–300 ∘C in air, providing the amorphous ITO precursor with a high level of 3D-organization around the template micelles; (2) treatment in air at 450–550 ∘C necessary for the removal of the template and opening the mesoporosity; (3) treatment in nitrogen at 450 ∘C required for the improvement of the film’s conductivity.

Comparative examination of titania nanocrystals synthesized by peroxo titanic acid approach from different precursors

Titanium dioxide nanocrystalline particles were synthesized by peroxo titanium acid (PTA) approach from titanium alkoxide and inorganic salt precursors, and their structural and surface properties, porosities, and photocatalytic activities were comparatively examined by XRD, TG/DTA, DRIFT, UV–vis, low temperature N 2 adsorption, and methyl orange (MO) degradation. It was found that nanoparticles with single anatase phase can be obtained from alkoxide precursor even near room temperature if synthesis conditions are appropriately controlled. PTA-derived anatase nanoparticles from titanium alkoxide precursor have smaller crystalline sizes and better porosities, and contain less amount of peroxo group and no organic impurities as compared to those from TiCl 4 precursor. The advantages in structural property, porosity, and surface properties (few deficiencies) lead to a much better photocatalytic activity for TiO 2 nanoparticles from titanium alkoxide precursor in comparison with those from TiCl 4 precursor.

A novel route to the synthesis of bulk and well dispersed alumina-supported Ni2Mo3N catalysts via single-step hydrogen thermal treatment

In this study, a facile method for the synthesis of bulk and alumina-supported Ni2Mo3N is described. The synthesis is based on the heat treatment of a mixed-salt precursor in a H2 flow at 873 K. The mixed-salt precursor is obtained by evaporating ammonia solution of Ni(CH3COO)2 and (NH4)6Mo7O24 with a fixed Ni/Mo molar ratio of 2 : 3. The formation process of the bimetallic molybdenum nitride has been investigated, which indicates that the labile NH4+ contained in the inorganic salt precursor is utilized as N source to form Ni2Mo3N in the H2 flow when elemental nickel is present. The high NH3 flow rate required in the conventional temperature-programmed nitridation method is not necessary in this hydrogen thermal treatment method. Alumina-supported Ni2Mo3N has also been successfully prepared by this method. The resultant catalyst has better dispersion of Ni2Mo3N and exhibits higher catalytic activity compared to the catalyst prepared by the conventional method.

Simplified synthesis of isomorphously nickel substituted ZSM-5

Isomorphously nickel-substituted nano-crystalline ZSM-5 is synthesized in the absence of acidic aqueous fluoride medium incorporating simple and low-cost metal inorganic salt precursor NiCl2.6H2O instead of large organic cationic salt like bis (tetraethyl ammonium) tetrachloronickelate (II) with less water quantity to minimize the synthesis waste. PXRD, FT-IR, TG/DTG, XPS, UV–Vis DRS, SEM, TEM, ICP and N2 adsorption-desorption techniques were used to confirm the presence of nano-crystalline material having a MFI structure and heteroatom substitution. The unit cell dimensions increase with increasing levels of nickel substitution. The crystallite size of as synthesized samples was in the range of 60–75 nm, which increased to 60–160 nm after calcination at 550°C. Percentage crystallinity and crystallite size increases with increasing nickel substitution level up to 0.17 mol and beyond that the material becomes amorphous.