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We report on remarkable improvement of photoelectrochemical (PEC) properties of TiO2 nanotubes by loading of Ag nanoparticles into them. The silver nanoparticles were loaded on the nanotubes by sequential chemical bath deposition (S-CBD) with different number of deposition cycles. Various characterizations including field emission scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray analysis (EDX), all confirm that the silver nanoparticles were deposited inside and outside of TiO2 nanotubes. In addition, the PEC properties of the samples were investigated using linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The PEC analyses clearly show that the photo-electrochemical activity of the Ag-loaded samples are considerably higher than the bare TiO2 nanotubes (about 3 times). This mostly originates from the improvement of light absorption due to the plasmonic effects in addition to better separation and transport of electron-hole pairs in the Ag-loaded samples relative to the bare TiO2 nanotubes. All results indicate that the maximum efficiency were obtained for the 8-cycle of S-CBD Ag-loading on the bare TiO2 nanotubes. [ABSTRACT FROM AUTHOR]

Chemical adsorption and sensing reactions of liquid petroleum gas over the surface and between grain boundaries of nanostructured zinc oxide thin films were investigated and monitored under the influence of various post-synthesis thermal annealing and target gas concentration conditions. Prior to sensing tests, zinc oxide thin films were synthesized in three steps: at first, zinc oxide nanoparticles were synthesized by a sol-gel method using zinc acetate dihydrate, ethanol and monoethanolamine as precursor, solvent and stabilizing agent, respectively. Then, untreated zinc oxide thin films were prepared from zinc oxide sol through spin coating procedure and finally, thermal post-annealing treatment with different temperatures was performed to yield heated thin films. The formation of the synthesized nanoparticles, morphology, crystalline size, porosity and transparency of final thin films were characterized by field emission-scanning electron microscopy, X-ray diffraction and ultraviolet-visible spectroscopy techniques. Sensing tests showed the dependence of the liquid petroleum gas detection on the thermal annealing process and gas concentration and indicated a maximum response of 75 % at the operation temperature of 300 °C for the zinc oxide film pre-annealed at 600 °C and 1,000 ppm gas. Moreover, the results exhibit excellent sensitivity for the sensor via short response and recovery times of 34 and 220 s, respectively. [ABSTRACT FROM AUTHOR]

Pulse instability in Q-switched solid-state lasers at enough high repetition rates is a significant problem for getting high powers. This issue is more critical for Thin-Disk-Lasers (TDLs) due to the smallness of round-trip gain in the thin active media. The main idea of this work is that increasing the round-trip gain of a TDL makes it possible to diminish its pulse instability at high repetition rates. Accordingly, a novel 2V-resonator is introduced to overcome the low gain of TDLs, in which the passage of the laser beam from the active media is twice that of the standard V-resonator. The experiment and simulation results indicate that the threshold of laser instability considerably improves for the 2V-resonator relative to the traditional V-resonator. This improvement is well seen for various time windows of the Q-switching gate and different pump powers. By choosing appropriate Q-switching time and pump power, the laser was stably run at 18 kHz, a recorded repetition rate for Q-switched TDLs.

We have investigated the effect of deposition of a α-Fe 2 O 3 thin layer on a substrate of TiO 2 nanoparticles for photoelectrochemical (PEC) water splitting. The TiO 2 layer was coated on an FTO substrate using the paste of TiO 2 nanoparticles. The α-Fe 2 O 3 layer was deposited on the TiO 2 thin film, using the method of Successive Ionic Layer Adsorption and Reaction (SILAR) with different cycles. Various characterizations including XRD, EDX and FE-SEM confirm the formation of α-Fe 2 O 3 and TiO 2 nanoparticles on the electrode. The UV-visible absorption spectrum confirms a remarkable enhancement of the absorption of the α-Fe 2 O 3 /TiO 2 /FTO composite relative to the bare TiO 2 /FTO. In addition, the photocurrents of the composite samples are remarkably higher than the bare TiO 2 /FTO. This is mainly due to the low band gap of α-Fe 2 O 3 , which extends the absorption spectrum of the α-Fe 2 O 3 /TiO 2 composite toward the visible region. In addition, the impedance spectroscopy analysis shows that the recombination rate of the charge carriers in the α-Fe 2 O 3 /TiO 2 is lower than that for the bare TiO 2 . The best PEC performance of the α-Fe 2 O 3 /TiO 2 sample was achieved by the sample of 70 cycles of α-Fe 2 O 3 deposition with about 7.5 times higher photocurrent relative to the bare TiO 2 ., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)