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A photoanode using dye-sensitized ZnO nanowire (NW) is a good candidate for low-cost, colorful, light-weight and flexible solar cell material. We have synthesized a ZnO NW anode and a ZnO nanowire–nanoparticle (NWNP) anode, in which ZnO nanoparticles (NPs) are decollated on the surface of NWs. Photo-induced electron transfer dynamics from the excited state of sensitizer dye (D149) to the conduction band of ZnO NW and ZnO NWNP was clarified using femtosecond transient absorption spectroscopy. The decay of the single excited state ($S_1$) of D149 was faster in ZnO NW than that of ZnO NWNP, indicating that NW is more suitable as an efficient electron acceptor.

Polycrystalline ZnO nanowires composed of nanosized grains were produced by pyrolizing one-dimensional (1D) zinc oxalate-based nanowires at 450°C. The oxalate-based nanowires were synthesized at 25°C–100°C in an aqueous solution with the aid of a hexamethyleneamide (HMA) template and catalytic ammonia. Due to its low solubility in aqueous solution, zinc oxalate was not the popular reactant for the synthesis of ZnO. With a fixed ammonia concentration and a HMA/[ZnC₂O₄ ⋅ H₂O] molar ratio of 1, the growth of zinc oxalate-based wires was investigated by changing growth temperature and growth duration. Different growth behaviors were observed and explained based upon the decomposition rate of complex and the interaction between zinc oxalate molecules and surfactants. The best growth condition was at 80°C for less than 1 h. After low-temperature calcination at 450°C, zinc oxalate-based nanowires were pyrolized into polycrystalline ZnO nanowires. This synthesis provides a simple route to prepare nanoparticle-covered ZnO nanowires.

Single-crystal ZnO nanowires are synthesized by direct oxidation of zinc particles in air at a temperature much lower than the melting temperature of zinc solids. This simple and low-cost technique produces dense and high-quality ZnO nanowires. SEM and TEM studies revealed that as-grown ZnO nanowires have a uniform diameter and defect-free single-crystal structure. The growth direction of ZnO nanowires is the a axis, which is different from the common growth direction of one-dimensional ZnO structure. Room temperature PL spectra of ZnO nanowires grown with different oxygen pressures indicated that the quality of ZnO nanowires grown in air is much better than that of wires grown at reduced oxygen pressure. The excellent property of ZnO nanowires grown in air was confirmed by electrical transport measurements of individual ZnO nanowire field effect transistors.

We report on the growth of Co-doped ZnO nanowires (NWs) on Si substrate using a self-catalytic vapor deposition method from a Co-doped ZnO nanopowder source and study its structural, optical and magnetic properties for the as-grown and rapid thermal annealed samples. Co (5%)-doped ZnO (ZnCoO) nanoparticles (NPs) are used as source material for the growth process. Electron microscopy imaging clearly reveals the formation of long ZnO NWs with uniform diameter. X-ray diffraction analysis confirms the single crystalline hexagonal structure of Co-doped ZnO NWs without impurities of metallic cobalt or other phases. Micro-Raman studies of doped samples show doping/disorder induced additional modes as compared to the undoped ZnO. Room temperature photoluminescence spectra of the doped ZnO NWs show strong emission band at ~380 nm and no significant emission was observed in the visible region indicating low defect content in the NWs. The field dependent magnetization (M–H curve) measured at room temperature exhibits paramagnetic nature for the NWs with the magnetic moment in the range 2–3.7 milli-emu/cm² for the applied field of 2 Tesla, while the source ZnCoO NPs exhibit room temperature ferromagnetism with saturation magnetization ~6 emu/g. Possible mechanism of alteration in magnetic behavior in doped NWs are discussed based on the growth conditions and role of defects.

Zinc oxide (ZnO) nanowire (NW) films were synthesized at low temperature (95°C) through amine-assisted solution process and used as photoanode for the fabrication of dye-sensitized solar cells (DSSCs). It was found that with the addition of polyethyleneimine (PEI) and ammonium hydroxide (NH₄OH) in growth solution, the NWs were smaller in diameter and longer in length by prolonging the growth time without refreshing the growth solution. A reasonable overall conversion efficiency of 1.25% was achieved with photoanode based on ZnO NWs containing PEI and NH₄OH. However, DSSC fabricated with ZnO NWs not containing PEI and NH₄OH showed low conversion efficiency of 0.58%. All the DSSCs exhibited almost similar values of open circuit voltage (V_OC) and fill factor (FF). Interestingly, DSSC based on ZnO NWs with PEI and NH₄OH obtained two times higher short circuit current density (J_SC) compared to ZnO NWs photoanode without PEI and NH₄OH. The increase in efficiency and J_SC with the length of NWs is attributed to the increase in internal surface area for sufficient dye loading and light harvesting.

In this paper, we have reported the high sensitive UV detector using ZnO nanowires prepared on porous silicon (PS). The aligned naturally doped n-type zinc oxide (ZnO) nanowires were grown on both PS and n-Si(100) substrates to produce isotype heterojunctions using hydrothermal method. The length of the nanowires ranges 3–4$\mu$m and the diameter 150–200nm. Grown ZnO nanowires on PS substrate has lower reflectivity value compared with Si substrate. The electrical behavior of such devices has been examined at different intensities of UV radiation. The current–voltage curve of the isotype heterojunction shows rectifying behavior in a dark environment. Under UV light, the current was increased by using PS instead of n-Si under reverse bias. The I–V characteristics of the device show a significant rise in the current for low intensity of UV radiation evidencing the high sensitivity of the reported structure. The sensitivity for such devices is obtained, $2.2\times 10^3,0.47\times 10^3$ and $0.21\times 10^3$ at UV radiation of 1.5mW/cm² intensity at bias voltage of −0.75 V for three proposed structures. The samples have been analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to investigate their structures and geometries.

In this work, zinc oxide (ZnO) nanowire is proposed for elastocaloric application which has been overlooked until now. The elastocaloric effect ($e$CE) is calculated by Maxwell relation. The large elastocaloric temperature and entropy change evaluated as 17 K and 28 J/kgK, respectively, at 300 K correspond to the stress of 12 GPa or strain of 5.5% by the simulation data. The elastocaloric temperature can be increased to 22 K under the operating tempering of 600 K. However, $e$CE estimated from the experimental data is found as 2.6 K at 300 K, which corresponds to stress of 6 GPa. These results are expected to significantly expand the knowledge of ZnO nanomaterials as a potential candidate for $e$CE. The results are based on the indirect approximation; hence, a direct measurement is needed to verify the obtained results.