Aqueous Precursor Solution Research Articles

Ultrasonication assisted and surfactant mediated synergistic approach for synthesis of calcium sulfate nano-dendrites

Calcium sulfate (CaSO4) nano-dendrimers were fabricated successfully via ultrasonic irradiation method using calcium chloride [CaCl2] and ammonium per sulfate [(NH4)2SO4] as precursors in aqueous solution by using cetyl trimethyl ammonium bromide (CTAB) as chemical surfactants. Diffusion-induced branching growth mechanism (DIBGM), influenced with the action of head-group and hydrocarbon chain effect of cationic surfactants, was the backbone in the formation of CaSO4 nano-dendrites. Fourier Transform Infra-red Spectroscopy (FTIR), X-Ray powder Diffraction (XRD), Atomic Emission Spectroscopy (AES), Selected Area Electron Diffraction (SAED), Field-Emission Scanning Electron Microscopy (FE-SEM), Energy-Dispersive Spectroscopy (EDS), Dynamic Light Spectroscopy (DLS) and BET surface area analyzer were used to characterize the products. Results obtained were compared with conventional stirring method that proved the superiority of sonication method to obtain well-crystalline nanostructures. Also, surfactant concentration, sonication frequency and time were noticed as the critical factors to generate such absolute morphologies at nano-crystalline size.

Effect of micro-nano-hybrid structured hydroxyapatite bioceramics on osteogenic and cementogenic differentiation of human periodontal ligament stem cell via Wnt signaling pathway.

The surface structure of bioceramic scaffolds is crucial for its bioactivity and osteoinductive ability, and in recent years, human periodontal ligament stem cells have been certified to possess high osteogenic and cementogenic differential ability. In the present study, hydroxyapatite (HA) bioceramics with micro-nano-hybrid surface (mnHA [the hybrid of nanorods and microrods]) were fabricated via hydrothermal reaction of the α-tricalcium phosphate granules as precursors in aqueous solution, and the effects of mnHA on the attachment, proliferation, osteogenic and cementogenic differentiations of human periodontal ligament stem cells as well as the related mechanisms were systematically investigated. The results showed that mnHA bioceramics could promote cell adhesion, proliferation, alkaline phosphatase (ALP) activity, and expression of osteogenic/cementogenic-related markers including runt-related transcription factor 2 (Runx2), ALP, osteocalcin (OCN), cementum attachment protein (CAP), and cementum protein (CEMP) as compared to the HA bioceramics with flat and dense surface. Moreover, mnHA bioceramics stimulated gene expression of low-density lipoprotein receptor-related protein 5 (LRP5) and β-catenin, which are the key genes of canonical Wnt signaling. Moreover, the stimulatory effect on ALP activity and osteogenic and cementogenic gene expression, including that of ALP, OCN, CAP, CEMP, and Runx2 of mnHA bioceramics could be repressed by canonical Wnt signaling inhibitor dickkopf1 (Dkk1). The results suggested that the HA bioceramics with mnHA could act as promising grafts for periodontal tissue regeneration.

Thickness-dependent phase evolution and dielectric property of Hf0.5Zr0.5O2 thin films prepared with aqueous precursor

Hf0.5Zr0.5O2 thin films were prepared on silicon substrates by sol–gel method. The crystallization temperature, thickness, density, surface morphology, crystalline structure, and chemical bonding features of the films were investigated using TGA, DSC, XRR, AFM, GIXRD, and XPS techniques. The results showed that the crystallization temperature was 496 °C, the film surfaces were smooth and flat, and no pores and micro-cracks were discernable. The density increased significantly from 5.1 to 8.0 g/cm3 after annealing at 700 °C. The crystalline structure depends strongly on the film thickness. The tetragonal phase could be stabilized in Hf0.5Zr0.5O2 films thinner than 12.9 nm. An increase in the thickness led to a gradual appearance of the monoclinic phase, which ultimately became the dominant phase for films thicker than 46.1 nm. The results could be explained by the surface energy effect. Measured at 1 MV/cm, the leakage current density was about 3.5 × 10−6 A/cm2, further indicating high quality of the thin films derived from aqueous solution precursor.

Direct formation and phase stability of luminescent γ-Ga2O3 spinel nanocrystals via hydrothermal method

Nanocrystals of γ-gallium oxide (γ-Ga2O3) were directly synthesized as a single phase of spinel-type structure from the aqueous precursor solution of Ga(NO3)3 or Ga2(SO4)3 under weakly basic conditions in the presence of citric acid by mild hydrothermal method. The crystallite size of γ-Ga2O3 spinel that was hydrothermally formed at 180–240 °C for 5 h was in the dimension range from 5 to 9 nm. The optical band gap of the as-prepared γ-Ga2O3 was 4.88 eV. The γ-Ga2O3 nanocrystals synthesized at 180 °C showed a broad-band visible violet–blue light emission with a peak wavelength at 410 nm, centered at around 425 nm under excitation at 325 nm. The emission intensity of γ-Ga2O3 synthesized at 210 and 240 °C was lower than that of 180 °C. The spinel-type structure of γ-Ga2O3 was maintained up to 600 °C. The γ-Ga2O3 phase fully transformed into β-Ga2O3 after heating at 800 °C. The luminescence intensity of gallium oxide decreased, and the peak wavelength of emission spectrum shifted into lower wavelengths via heat treatment at 600 and 800 °C for 1 h in air.

Fabrication of Cu(In,Ga)(S,Se)2 thin film solar cells via spray pyrolysis of thiourea and 1-methylthiourea-based aqueous precursor solution

A detailed process of fabricating Cu(In,Ga)(S,Se)2 via the spray pyrolysis of a thiourea-based precursor solution followed by selenization is reported. The optimization of the selenization condition for the fabrication of the Cu(In,Ga)(S,Se)2 film led to a conversion efficiency of 7.8% for the Cu(In,Ga)(S,Se)2-based device. We also showed that 1-methylthiourea was a more suitable sulfur source for the spray pyrolysis technique, resulting in a conversion efficiency of 8.7% (VOC = 0.52 V, JSC = 31 mA cm−2, and FF = 0.54) without any antireflection coating.

Effect of Heat-Treatment and Composition on Structure and Luminescence Properties of Spinel-Type Solid Solution Nanocrystals.

The compositional dependence of the structure and properties of spinel-type solid solutions, Zn(A,Ga)2O4 was investigated by comparison with samples hydrothermally prepared and those after heat treatment at 1000 °C in air. Nanocrystalline spinel-type solid solutions in the whole composition range in the ZnAl2O4-ZnGa2O4 system were directly formed from the aqueous precursor solutions of ZnSO4, Al(NO3)3 and Ga(NO3)3 under hydrothermal conditions at 180 °C for 5 h in the presence of tetramethylammonium hydroxide. The incorporation of aluminum into the lattice, Zn(AlxGa1-x)2O4, resulted in lower crystallinity of the spinel. The relationship between the lattice parameter of as-prepared samples and the Al atomic ratio in the spinel composition was slightly apart from the ideal linear relationship that was obtained in the samples after heat treatment at 1000 °C. The optical band gap of both as-prepared solid solutions and those heat treated linearly increased from 4.1~4.2 to 5.25 eV by the incorporation of aluminum ion into the lattice, Zn(AlxGa1-x)2O4. Two main broad-band emission spectra centered at around 360 and 430 nm in the range of 300-600 nm were observed in the spinel solid solutions under excitation at 270 nm, thought their broad-band emission spectra and their peak wavelengths subtly changed depending on the composition and heat treatment.

Modulation of aqueous precursor solution temperature for the fabrication of high-performance metal oxide thin-film transistors

In this study, we present a simple process for the fabrication of aqueous-solution-processed metal oxide thin-film transistors (TFTs) via the manipulation of precursor solution temperature. Indium oxide TFTs fabricated from a solution of indium nitrate at 4 °C exhibited the highest mobility of 2.73 cm2/(V·s) at an annealing temperature of 200 °C. When the temperature of the metal oxide precursor solution is 4 °C, metal cations within the solution can be fully surrounded by H2O molecules owing to the high dielectric constant of H2O at low temperatures. These metal complexes are advantageous for the conversion of metal oxides via thermally driven hydrolysis and condensation processes due to their high potential energies. The same techniques have been applied successfully with high-order metal oxides including indium zinc oxide, indium gallium oxide, and indium gallium zinc oxide.

Direct formation of spinel-structured γ-Ga2O3-Al2O3 nanoparticles by a mild hydrothermal method

Spinel-structured γ-Ga2O3-based nanoparticles doped with Al2O3 component, i.e., (AlxGa1.00−x)2O3, x=0–0.85, with crystallite size of spinel phase in the range of 4–5nm were directly synthesized from the aqueous precursor solutions of Ga(NO3)3 and Al2(SO4)3 under weakly basic conditions using aqueous ammonia in the presence of citric acid by the mild hydrothermal method at 180°C for 5h. A broad-band visible violet–blue light emission with a peak wavelength at 410–415nm was observed in each of the as-prepared (AlxGa1.00−x)2O3 samples under excitation at 325nm Xe lamp. The as-prepared spinel-structured nanoparticles with composition (Al0.50Ga0.50)2O3 showed the most intense emission. The spinel-type structure of nanoparticles in all composition ranges was maintained after heating at 600°C. The β-Ga2O3 structure that was transformed from the spinel structure was observed in the nanoparticles with compositions from Ga2O3 to (Al0.50Ga0.50)2O3 after heat treatment at 1000°C. The spinel-type structure was still maintained in the (Al0.75Ga0.25)2O3 nanoparticles after heat treatment at 1000°C in contrast with a single phase of θ-Al2O3 in the case of pure Al2O3 composition.

Nb2O5 and Ta2O5 Thin Films from Polyoxometalate Precursors: A Single Proton Makes a Difference

Thin film materials from water-based precursors follow the principals of green chemistry, leading to a more sustainable future in the energy intensive era in which we currently reside. While simple in practice, aqueous metal-oxide chemistry is complex at the molecular level. Here we develop the first water-based formation of Nb2O5 and Ta2O5 thin films; utilizing tetramethylammonium salts of [H2Ta6O19]6– and [H3Nb6O19]5– polyoxometalates. Although the clusters are structurally identical group V analogues and differ only by a single proton, this difference has a considerable influence on the quality of the films that are obtained. Through characterization of the solid-state precursor (single-crystal X-ray diffraction), the aqueous precursor solution (X-ray scattering), and the thin films (atomic force and scanning electron microscopies, X-ray diffraction, and reflectivity), we rationalize the important roles of cluster protonation that carry through all chemical processes from the precursor to the metal oxide coating.

Effect of reduction enhancer on a radiolytic synthesis of carbon-supported Pt–Cu nanoparticles and their structural and electrochemical properties

In order to clarify the effect of reduction enhancer on the nanoparticle formation process and their structural and catalytic properties, carbon-supported Pt–Cu nanoparticles were synthesized by electron beam irradiation on an aqueous precursor solution in the presence/absence of reduction enhancer. In the absence of reduction enhancer, tetravalent platinum oxide particles of approximately 1 nm in diameter were formed on carbon support with copper barely precipitated, while in the presence of 2-propanol or ethylene glycol or glucose both platinum and copper precipitated as few-nanometer-sized alloy particles together with copper oxides. It was suggested that the metal nuclei produced upon electron beam irradiation do not have enough lifetime without reduction enhancer due to fast oxidation of the nuclei by oxidizing radicals, while the reduction enhancer scavenges these oxidizing radicals preventing oxidation of metallic clusters and prolonging their lifetime. Ethylene glycol gave smaller and better alloyed particles with less copper oxides compared to 2-propanol since the carbonyl compounds derived from oxidation of ethylene glycol protect metallic clusters from oxidation further prolonging their lifetime. In the electrochemical measurements, the methanol oxidation activities of Pt–Cu/C catalysts were well explained by their structural characteristics.

ChemInform Abstract: Enhanced Catalytic Activity for NO Oxidation over Ba Doped LaCoO3 Catalyst.

AbstractA series of A‐side modified La1‐xBaxCoO3 (x = 0, 0.1, 0.2, 0.3) perovskites is prepared by a modified sol‐gel method using citric acid and EDTA as complexons with aqueous solutions of the metal nitrate precursors followed by drying and calcining in air (700 °C, 5 h).

Investigations of superparamagnetism in magnesium ferrite nano-sphere synthesized by ultrasonic spray pyrolysis technique for hyperthermia application

In this paper, we present the synthesized of magnesium ferrite (MgFe2O4) nano-spheres by a single-step ultrasonic spray pyrolysis (USP) technique from the aqueous metal nitrate precursor solution without any organic additives or post-annealing processes. The effects of different pyrolysis temperatures on the particles size, morphology and their superparamagnetic behavior have been investigated to evaluate the heat generation efficiency in an AC magnetic field. The X-ray powder diffraction spectra of MgFe2O4 nano-spheres synthesized at the pyrolysis temperatures of 600, 700, 800 and 900°C exhibited single phase cubic structure and obtained mean crystallite size (primary particles) of 4.05, 9.6, 15.97 and 31.48nm, respectively. Transmission electron microscopy (TEM) confirms that the particles consisted of aggregates of the primary crystallite had densely congested spherical morphology with extremely smooth surface appearance. Field emission electron microscopy (FESEM) reveals that the shape and size of the nano-spheres (secondary particles) does not change significantly but the degree of agglomeration between the secondary particles was reduced with increasing the pyrolysis temperature. The average size and size distribution of nano-spheres measured using electrophoretic scattering photometer have found very low polydispersity index (PDI) for all samples. The field dependent magnetization studies indicated superparamagnetic nature for the particles having crystallite size i.e. 4.05 and 9.6nm and exhibited ferromagnetic nature for 15.97 and 31.48nm. It is also demonstrated that, as the pyrolysis temperature increases, the saturation magnetization of the MgFe2O4 nanopowders increases due to enhancement of crystallites. The shift in Curie temperature is well described by the finite-size scaling formula. The magnetically loss heating values of selected samples in crystallite size of 9.6 and 15.97nm were investigated by measuring the time dependent temperature curves in an external alternating magnetic field (370kHz, 1.77kA/m). The more heat generation ability was obtained for 9.6nm in crystal size because of minimum squareness ratio with coercivity in superparamagnetic range. The results reported in this study are useful to find out of superparamagnetic limit for the preparation of MgFe2O4 nanopowders.

Preparation of fluorescent conjugated polymer fibrous membranes for rapid recognition of aromatic solvents.

Fluorescent poly(phenylenevinylene) (PPV)/poly(vinyl alcohol) (PVA) fibrous membrane was prepared via electrospinning of PPV precursor and PVA aqueous solution followed by thermal elimination. Further cross-linking produced the cross-linked membrane PPV/CPVA. Both PPV/PVA and PPV/CPVA membranes were found to have similar morphology and photophysics. These membranes showed a great fluorescence quenching response to aromatic solvents and a much smaller response to other organic solvents. Water also effectively quenched the fluorescence of PPV/PVA but not that of PPV/CPVA. This was attributed to un-cross-linked PVA being able to dissolve in water and the cross-linking improving the resistance of the membrane toward water. The sensing behavior was found to have good reversibility. The contact angle study showed that addition of only about 1% of PPV into the matrix reduced the hydrophilicity of the membrane significantly, suggesting that the PPV chains would be located at the surface of the fibers. X-ray photoelectron spectroscopy (XPS) investigation further confirmed such surface enrichment of PPV in the binary polymer blends. The PPV chain on the surface facilitated the π-π interaction between the polymer backbones and the aromatic molecules, thus leading to good selectivity and fast response of the two fibrous membranes toward aromatic solvents.

Cu(In,Ga)(S,Se)₂ thin film solar cell with 10.7% conversion efficiency obtained by selenization of the Na-doped spray-pyrolyzed sulfide precursor film.

Selenium-rich Cu(In,Ga)(S,Se)2 (CIGSSe) thin films on an Mo-coated soda-lime glass substrate were fabricated by spray pyrolysis of an aqueous precursor solution containing Cu(NO3)2, In(NO3)3, Ga(NO3)3, and thiourea followed by selenization at 560 °C for 10 min. We studied the effects of intentional sodium addition on the structural and morphological properties of the fabricated CIGSSe films by dissolving NaNO3 in the aqueous precursor solution. The addition of sodium was found to affect the morphology of the final CIGSSe film: the film had denser morphology than that of the CIGSSe film obtained without addition of NaNO3. Photoelectrochemical measurements also revealed that the acceptor density of the nondoped CIGSSe film was relatively high (N(a) = 7.2 × 10(17) cm(-3)) and the addition of sodium led to a more favorable value for solar cell application (N(a) = 1.8 × 10(17) cm(-3)). As a result, a solar cell based on the sodium-modified CIGSSe film exhibited maximum conversion efficiency of 8.8%, which was significantly higher than that of the cell based on nondoped CIGSSe (4.4%). In addition, by applying MgF2 antireflection coating to the device, the maximum efficiency was further improved to 10.7%.

Preparation of Li4Ti5O12 electrode thin films by a mist CVD process with aqueous precursor solution

Spinel Li4Ti5O12 thin films were prepared by a mist CVD process, using an aqueous solution of lithium nitrate and a water-soluble titanium lactate complex as the source of Li and Ti, respectively. In this process, mist particles ultrasonically atomized from a source aqueous solution were transferred by nitrogen gas to a heating substrate to prepare thin films. Scanning electron microscopy observation showed that thin films obtained by this process were dense and smooth, and thin films with a thickness of about 500 nm were obtained. In the X-ray diffraction analysis, formation of Li4Ti5O12 spinel phase was confirmed in the obtained thin film sintered at 700 °C for 4 h. The cell with the thin films as an electrode exhibited a capacity of about 110 mAh g−1, and the cell showed good cycling performance during 10 cycles.

Localized Laser‐Based Photohydrothermal Synthesis of Functionalized Metal‐Oxides

We discuss the rapid in situ hydrothermal synthesis of metal oxide materials based on the photothermal superheating of light‐absorbing metal layers for simple and facile on‐demand placement of semiconductor materials with micrometer‐scale lateral resolution. Localized heating from pulsed and focused laser illumination enables ultrafast growth of metal oxide materials with high spatiotemporal precision in aqueous precursor solution. Among many possible electronic and optoelectronic applications, the proposed method can be used for laser‐based in situ real‐time soldering of separated metal structures and electrodes with functionalized semiconductor materials. Resistive electrical interconnections of metal strip lines as well as sensitive UV detection using photohydrothermally grown metal oxide bumps are experimentally demonstrated.

Photochemically Activated Flexible Metal-Oxide Transistors and Circuits Using Low Impurity Aqueous System

High mobility flexible metal-oxide thin-film transistors and circuits have been fabricated on an ultrathin plastic substrate using environmentally benign aqueous solution system and low-temperature photochemical activation process ( $\sim 150$ °C). Results show that the indium-gallium–zinc oxide (IGZO) thin-film transistors (TFTs) fabricated from nitrate-based precursors in aqueous solution outperform the devices from acetate-based precursors in alcohol solution. Here, IGZO TFTs and seven-stage ring oscillators are demonstrated on a $3\sim 5~\mu $ m-thick polyimide substrates with an average mobility of $>6.9~\mathrm{cm}^{2}$ /V-s, subthreshold slope of $\sim 0.14$ V/decade, and oscillation frequency of $\sim 340$ kHz corresponding to 210 ns of propagation delay per stage at a supply bias of 20 V.

Biodegradation-tunable mesoporous silica nanorods for controlled drug delivery.

Mesoporous silica in the forms of micro- or nanoparticles showed great potentials in the field of controlled drug delivery. However, for precision control of drug release from mesoporous silica-based delivery systems, it is critical to control the rate of biodegradation. Thus, in this study, we demonstrate a simple and robust method to fabricate "biodegradation-tunable" mesoporous silica nanorods based on capillary wetting of anodic aluminum oxide (AAO) template with an aqueous alkoxide precursor solution. The porosity and nanostructure of silica nanorods were conveniently controlled by adjusting the water/alkoxide molar ratio of precursor solutions, heat-treatment temperature, and Na addition. The porosity and biodegradation kinetics of the fabricated mesoporous nanorods were analyzed using N2 adsorption/desorption isotherm, TGA, DTA, and XRD. Finally, the performance of the mesoporous silica nanorods as drug delivery carrier was demonstrated with initial burst and subsequent "zero-order" release of anti-cancer drug, doxorubicin.

Simple and Efficient Synthesis of Strongly Green Fluorescent Carbon Dots with Upconversion Property for Direct Cell Imaging

The strong green fluorescent carbon dots (CDs) with the upconversion property have been directly synthesized using ammonium citrate, NH3·H2O, and H2O2 as the precursors in aqueous solution through a simple hydrothermal process. The synthesized green fluorescent CDs also show excellent upconversion property and can be directly used for live HeLa cell imaging without any further modifications.

Highly porous carbon materials filled with gold and manganese oxide nanoparticles for electrochemical use

The reduction of aqueous solutions of precursors (HAuCl4 and KMnO4) by the carbon matrix was used to synthesize nanostructured composites based on highly porous carbon materials that are filled with Au or MnxOy nanoparticles. The resulting composites were characterized using a complex of complementary physicochemical methods (XRD, SAXS, low-temperature nitrogen sorptometry, and CV). It was shown that at low concentrations of Au or MnxOy the surface of matrix pores is decorated with the filler nanoparticles, which block mesopores; the role of such blocking increases with the filler content. The optimal concentration of fillers in the composites was found. A maximum capacitance of composite electrodes, which exceeds the capacitance of electrodes based on the initial matrices by a factor of 2–2.5, was observed at a gold content of 1wt.%. Nanocomposite Au/C electrodes based on highly porous carbon material Kemerit2, which were obtained in the study, showed the highest capacitance (up to 1000F/g). For the composite systems filled with manganese oxides, a 700F/g capacitance of composite electrodes (at a 10mV/s scanning rate of potential) was reached at a 2wt.% content of manganese in the composites.