Electrochemical performance of three shaped ZnO nanoparticles prepared in LiOH, NaOH and KOH alkaline solutions as anodic materials for Ni/Zn redox batteries

Controlled dispersion of ZnO nanoparticles produced by basic precipitation in solvothermal processes

Zinc oxide nanoparticles were successfully synthesized under precipitation processes, using ZnSO4·7H2O as a Zn2+ precursor and K2CO3 used as a basic source, and hydrozincite was obtained as an intermediary, which was treated under two procedures; first procedure involved multiple stages to get final precipitated with NaOH, and in the second procedure the hydrozincite was straightforwardly dried at 220 °C. By both processes ZnO structures were obtained, which were turned into nanoparticles by a solvothermal treatment, for four hours in ethylene glycol at 200 °C. The final products for the first procedure was conglomerate of spherical nanoparticles with sizes ranged between 5-10 nm and dispersed ellipsoidal nanoparticles for the second procedure. Apart off the two procedures mentioned above, another synthesis was carried out with the same Zn2+ precursor but now using NaOH, and the solvothermal treatment produced ZnO mixed micro-structures which under ultrasonic cavitation disaggregated on mesoporous ZnO nanoplates of hexagonal shapes with nanopore sizes of approximately 0.35 nm. All ZnOs synthesized were structurally characterized with XRD, TEM and FT-IR techniques, and electronically with UV-Vis absorption and diffuse reflectance spectroscopies.

Preparation of a Highly Conductive Seed Layer for Calcium Sensor Fabrication with Enhanced Sensing Performance

The seed layer plays a crucial role in achieving high electrical conductivity and ensuring higher performance of devices. In this study, we report fabrication of a solution-gated field-effect transistor (FET) sensor based on zinc oxide nanorods (ZnO NRs) modified iron oxide nanoparticles (α-Fe₂O₃ NPs) grown on a highly conductive sandwich-like seed layer (ZnO seed layer/Ag nanowires/ZnO seed layer). The sandwich-like seed layer and ZnO NRs modification with α-Fe₂O₃ NPs provide excellent conductivity and prevent possible ZnO NRs surface damage from low pH enzyme immobilization, respectively. The highly conductive solution-gated FET sensor employed the calmodulin (CaM) immobilization on the surface of α-Fe₂O₃-ZnO NRs for selective detection of calcium ions (Ca²⁺). The solution-gated FET sensor exhibited a substantial change in conductance upon introduction of different concentrations of Ca²⁺ and showed high sensitivity (416.8 μA cm^-2 mM^-1) and wide linear range (0.01-3.0 mM). In addition, the total Ca²⁺ concentration in water and serum samples was also measured. Compared to the analytically obtained data, our sensor was found to measure Ca²⁺ in the water and serum samples accurately, suggesting a potential alternative for Ca²⁺ determination in water and serum samples, specifically used for drinking/irrigation and clinical analysis.

In-situ Cutting of Graphene into Short Nanoribbons with Applications to Ni-Zn Batteries

Rechargeable Ni–Zn batteries, with high safety, low cost and nontoxicity, can be expected to compete with lithium-ion batteries for market share. However, the issue of dissolution of zinc electrode largely limit the battery cycle life and remains unsolved. We designed a kind of graphene-ZnO hybrid electrode in which in-situ cutting of graphene into short nanoribbons can effectively anchor plenty of zinc atoms onto the surface of graphene. This not only thoroughly fixes the issue of dissolution of zinc electrode but also increases the specific surface areas of zinc and promotes chemical reaction rate of the charge-discharge processes. By performing experimental measurements, we found that the discharge capacity of the new designed Ni-Zn batteries can be as high as 2603 mAh/g_Zno, and the superior electrochemical performance can be kept in 10,000 test cycles, suggesting that the new developed in-situ cutting technique is very useful in electrochemical fields.

Enhanced moisture sensing properties of a nanostructured ZnO coated capacitive sensor

This work reports the enhancement in sensitivity of a simple and low-cost capacitive moisture sensor using a thin film of zinc oxide (ZnO) nanoparticles on electrodes.