ZnO nanorods with various lengths were synthesized by a two-stage route (by changing the time of growth between 0-240 min) and were characterized using XRD, SEM, UV–Vis and PL techniques. The SEM and XRD results confirmed a fast growth of (0 0 2) plane in the preferential longitudinal orientation, in contrast to lateral growth and therefore, by increasing the time of hydrothermal growth, nanorods with higher aspect ratios are obtained. Naturally, by increasing the length of nanorods, not only the average transmittance in both near ultraviolet and visible ranges is decreased, but also the PL peaks are red-shifted and extinct. Finally, ultra-violet photodetection of the samples shows that higher active surface area (with respect to the time of growth) is appropriate for photo-induced interactions leading to higher UV-sensitivity. پرونده مقاله

Various nanocomposites of TiO2, ZnO and ZrO2 decorated single wall Carbon nanotubes (SWNTs) were fabricated by facile and template free continuous ultrasonication/stirring of virgin metal oxide nanopowders and SWNTs in ethanol under UV-light illumination. The TEM micrographs showed that nanoparticles (NPs) were uniformly dispersed and bonded on the surface of SWNTs. The results of XRD as well as FTIR spectroscopy revealed coexistence of the precursors in each nanocomposite. The Hydrogen storage capacity of the nanocomposites was evaluated by a purpose-built sievert-type apparatus in kinetic mode measurement. The reversible values of hydrogen storage of the virgin single walled carbon nanotube (SWNT) and also the nanocomposites TiO2, ZrO2 and ZnO decorated SWNTs at room temperature was acquired 0.08, 0.4, 0.31 and 0.25 wt.%, respectively. The elevated absorption ability in nanocomposites is explained by catalytically effect of metal oxides in dissociation and compression of hydrogen into the absorbent sites of carbon nanotube (CNT). پرونده مقاله

One-dimensional (1D) undoped and Cr doped ZnO nanorods with average length of 1 µm and diameter of 80 nm were synthesized using hydrothermal method where a fast growth of ZnO nanorods on the seed layer was observed. Afterwards, the effects of Cr dopant on structural, surface morphology and optical properties of nanorods were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultra-violet visible (UV-Vis) spectroscopy. The results showed that ZnO has a wurtzite hexagonal structure and that the Cr atoms were well incorporated into the ZnO crystal structure. Moreover, it was found that the Cr atoms could facilitate the preferential growth of nanorods in C-axis. Also, it was concluded from optical properties that doped ZnO nanorods was so appropriate for photocatalytic applications because the optical band gap. For example, the calculated band gap of ZnO nanorod decreased from 3.12 eV for pure ZnO nanorods to about 2.41eV for 3 at. % Cr doped ZnO nanorods which is quite enough to be activated even at visible (550nm) light for photocatalyst aims. پرونده مقاله

ZnO nanorods with various aspect ratios (by changing the time of growth between 0-240 min) were synthesized using hydrothermal method and were investigated using XRD, SEM, UV–Vis and PL. It was found that growth time is directly coupled with the length, orientation and aspect ratio of the nanorod arrays. The optical transmittance of the NR arrays indicated a regular decrement of average transmittance with increasing the aspect ratio of NRs in the visible range. The optical constants (absorption coefficient, extinction coefficient and refractive index) can be account as a function of refractive index were determined. The porous ZnO nanorod with the thickness of ∼ 1560 nm and texture coefficient of 0.96 for (002) plane exhibits the average visible transmittance <60%, refractive index 1.34, packing density 0.26 and lowest optical band gap, was fabricated in the longest time of hydrothermal growth (240 min). As the growth time was increased, the photoluminescence properties was sustained a general weakening tendency and a red-shift of UV-emission peak position. The UV-assisted photocatalytic degradation of 4-Nitrophenol (4-NP) of ZnO NRs were investigated. The considerable photocatalytic performance of ZnO NRs with highest aspect ratio was explained by its porosity and optical characteristics. پرونده مقاله