Molar Ratio In Precursor Solution Research Articles

Polyoxymethylene dimethyl ethers synthesis from methanol and formaldehyde solution over one-pot synthesized spherical mesoporous sulfated zirconia

The synthesis of polyoxymethylene dimethyl ethers as an ideal diesel fuel additive is the current hot topic of modern petrochemical industry for their expedient properties in mitigating air pollutants emission during combustion. In this work, a series of spherical sulfated zirconia catalysts were prepared by a one-pot hydrothermal method assisted with surfactant cetyltrimethylammonium bromide (CTAB). The prepared sulfated zirconia catalysts were used to catalyze PODEn synthesis from methanol and formaldehyde solution. Various characterization (XRD, BET, SEM, TGA, NH3-TPD, FTIR, and Py-IR) were employed to elaborate the structure–activity relationship of the studied catalytic system. The results demonstrated that S/Zr molar ratio in precursor solution played an effective role on catalyst morphology and acidic properties, where the weak Brønsted acid sites and strong Lewis acid sites were favorable to the conversion of methanol and formation of long-chain PODEn, respectively. The reaction parameters such as catalyst amount, molar ratio of FA/MeOH, reaction time, temperature and pressure were optimized. The speculated reaction pathway for PODEn synthesis was proposed based on the synergy of Brønsted and Lewis acid sites, which suggested that Brønsted and Lewis acid sites might be advantageous to the activation of polyoxymethylene hemiformals [CH3(OCH2)nOH] and methylene glycol (HOCH2OH), respectively.

Effect of Pb:S molar ratio in precursor solution on the properties of lead sulphide thin films by ultrasonic spray pyrolysis

In this work, PbS thin films were deposited onto glass substrate at 225°C by spraying precursor solution prepared with different molar ratio of lead acetate and thiourea as a source of Pb2+ and S2- respectively in order to investigate the effect of Pb:S molar ratio in the precursor solution on the physical properties of PbS thin films. Structural investigations carried out by X-ray diffractometer have shown that all films have fcc cubic structure and the average crystal size increased from 11nm to 25nm with the increasing the thiourea ratio in the precursor solution. In order to analyze the surface morphology of PbS thin films, AFM and SEM images were taken and elemental analysis of the films was performed by EDS. Optical transmittance and absorption spectra show that all deposited films have fairly low transmittance and high absorbance in the visible region. Additionally, it was determined that optical band gap of the deposited films were varied between 1.18eV and 1.37eV. As a consequence of electrical investigations, it was seen that all films have p-type conductivity and electrical resistivity decreased by increasing thiourea molar ratio in the precursor solution. All examinations have revealed that the molar ratio of lead acetate and thiourea has a significant effect on the physical properties of PbS thin films.

Growth and characterization of CuInS2 nanoparticles prepared using sonochemical synthesis

In this study, copper indium disulfide (CuInS2) nanoparticles were synthesized using the sonochemical method. The structural, optical, and electrical properties of the CuInS2 nanoparticles were investigated as a function of the [Cu]/[Cu+In] molar ratio in the precursor solution. X-ray diffraction patterns show that all samples consisted of the tetragonal CuInS2 phase with a preferential orientation along the (112) crystal plane. With a decrease in the [Cu]/[Cu+In] molar ratio in precursor solution, the diffraction peaks slightly shifted to lower angles. Transmission electron microscopy images confirm that the samples consisted of the tetragonal CuInS2 phase with an average diameter in the range of 9.2–14.8nm. Samples with [Cu]/[Cu+In] molar ratio greater than 0.50 were p-type semiconductors whereas those with [Cu]/[Cu+In] molar ratio of less than 0.47 were n-type semiconductors. The carrier concentrations and mobilities of the samples are in the ranges of 3.31×1018–8.16×1015cm−3 and 2.13–59.0cm2V−1s−1, respectively. The conversion efficiency of a thin-film solar cell with the structure glass/Mo/CuInS2/CdS/i-ZnO/ZnO:Al was around 1% under illumination at 100mW/cm2.