Influence of solvents and irradiation time on structural and optical properties of cubic PbS nanoparticles

In the present paper, different particle sizes of lead sulfide (PbS) nanoparticles with a cubic structure were successfully prepared using a microwave irradiation method from lead acetate [(CH₃COO)₂Pb.3H₂O] and thioacetamide (CH₃CSNH₂) as the starting materials. Ethylene glycol (C₂H₆O₂), distilled water (H₂O), ethylene alcohol (C₂H₅OH) and isopropanol (C₃H₈O) were used as solvents and a 650W oven operating at 20% of the nominal power in the period of 10 min was employed. The effect of the microwave irradiation time was investigated by varying the irradiation time from 10 to 50 minutes respectively. The resulting nanoparticles in different sizes were characterized using X–ray diffraction, Transmission electron microscopy (TEM) and UV–Vis absorption spectroscopy. The crystallite sizes were calculated from the broadening of the XRD peak using Scherrer’s equation. The results showed that the increased intensity of the XRD peak and the dipole moment of the solvents being decreased corresponded with the reduction in particle sizes. The TEM results indicated that the samples consisted of separated, well–defined spherical particles and showed a small distribution size. As can be seen from the UV–vis spectrum, the band gap energy of each sample had increased and showed a characteristic blue shift due to the quantum confinement in their optical absorption. The mechanism that influenced the solvents and irradiation time for the formation of the PbS nanoparticles were discussed

A facile synthesis of amorphous silica nanoparticles by simple thermal treatment route

A facile thermal treatment route was for the first time used to successfully synthesize amorphous silica nanoparticles. Various techniques were employed to study the structural, phase and elemental composition of the material at different calcination temperature between 500-750oC. The XRD analysis confirms the formation silica to be in an amorphous state and further revealed that the material remained in amorphous state even when calcined at 750oC. The FT-IR spectra shows that the calcination process has enable the removal of organic source from PVP and formation of amorphous silica nanoparticles. The average particle size of the material estimated from the TEM images shows that the particle were <10nm. The optical absorbance exhibited in the UV region reveals amorphous silica nanoparticles possess a wide band gap ranging from 3.803-4.126eV calcined between 500 to 750oC. The EDX analysis has confirmed the presence of Si and O as the only elements in the material formed, which implies thermal treatment method is effective for the synthesis of amorphous silica nanoparticles

Effect of reaction time on structural and optical properties of porous SiO2 nanoparticles

The effect of different reaction time on the structural and optical properties of porous SiO2 nanoparticles by simple precipitation method was comprehensively studied in this work. In this study, an aqueous sodium silicate was reacted with ethanol in deionized water and stirred between 30 to 180 min as for mixture to react. The filtered product was subjected to drying and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared reflection (FTIR), surface area analyzer, Raman and UV-Vis spectroscopy. The produced SiO2 nanoparticles powder was in amorphous form with the average particle size less than 100 nm. The sample with reaction time 90 min shows fine porous characteristic with the highest specific surface area and average pore volume. This different characteristic also gives a significant change in optical properties of the final product

The Influence of Calcination Temperature on Structural and Optical properties of ZnO-SiO2 Nanocomposite by Simple Thermal Treatment Route

This study offers a new method to synthesize facilely willemite (Zn2 SiO4 ) based phosphor at the temperature of 800°C. The ZnO-SiO2 nanocomposite was calcined at different temperatures between 500 and 1000°C. The structural, morphological and optical properties of the nanocomposite obtained at various calcination temperatures were studied using different techniques. The FT-IR, XRD and the UV-vis result confirmed the formation of willemite phase. The precursor was confirmed to be amorphous by XRD at room temperature, but upon calcination temperature at 500°C, it was transformed into a crystalline structure. The crystallinity and the particle size of the nanocomposite increase as the calcination temperature were increased as revealed by XRD and TEM measurement. The sample exhibits a spherical morphology from 500 to 800°C and dumbbell-like morphology above 800°C as shown by the FESEM images. The absorption spectrum suffers intense in lower temperature and tends to shift to lower wavelength in the UV region as the calcination temperature increases. The band gap values were found to be increasing from 3.228-5.550 eV obtained between 500 to 1000°C, and all the results confirm the formation of willemite phase at 800°C