Green Synthesis and Applications of ZnO and TiO2 Nanostructures.

Over the last two decades, oxide nanostructures have been continuously evaluated and used in many technological applications. The advancement of the controlled synthesis approach to design desired morphology is a fundamental key to the discipline of material science and nanotechnology. These nanostructures can be prepared via different physical and chemical methods; however, a green and ecofriendly synthesis approach is a promising way to produce these nanostructures with desired properties with less risk of hazardous chemicals. In this regard, ZnO and TiO2 nanostructures are prominent candidates for various applications. Moreover, they are more efficient, non-toxic, and cost-effective. This review mainly focuses on the recent state-of-the-art advancements in the green synthesis approach for ZnO and TiO2 nanostructures and their applications. The first section summarizes the green synthesis approach to synthesize ZnO and TiO2 nanostructures via different routes such as solvothermal, hydrothermal, co-precipitation, and sol-gel using biological systems that are based on the principles of green chemistry. The second section demonstrates the application of ZnO and TiO2 nanostructures. The review also discusses the problems and future perspectives of green synthesis methods and the related issues posed and overlooked by the scientific community on the green approach to nanostructure oxides.

Cotton-Like Three-Dimensional Sb4O5Cl2 Structures: Synthesis and Ammonium Hydroxide Sensing.

Nanostructured materials have emerged as valuable tools for the advancement of novel electrocatalysts. Among them, three-dimensional metal oxides have gained significant attention due to their excellent conductivity, cost-effectiveness, and unique design. This study focuses on the synthesis of cotton-like three-dimensional antimony oxychloride (Sb4O5Cl2) structures through a straightforward precipitation method. The nanostructures exhibit immense potential for sensing applications. Electrochemical characterization reveals that the Sb4O5Cl2 heterostructure demonstrates a remarkable double-layer capacitance of 662 F/cm2, accompanied by excellent cyclic stability. The sensor's performance was tested for the detection of ammonium hydroxide (HA) in NaCl solution, yielding sensitivities ranging from 0.95 to 0.140 mA mM-1 cm-2 and a detection limit of 4.54 µM within a wide detection range of 0.3-250 mM. The sensor device possesses a distinctive cotton-like structure and is synthesized through a simple and cost-effective route.

Electron-phonon scattering in Sn-doped In2O3 FET nanowires probed by temperature-dependent measurements.

We report on the structural and electrical characterization of individual Sn-doped In(2)O(3) nanowires. Key information on the nanowire's electron transport such as the carrier's mobility and density are presented. The mobility data was found to decrease as the temperature increases, providing direct evidence of the electron-phonon interaction as the dominant scattering mechanism in this oxide system. The results were confirmed by resistivity measurements and additionally the electron density could be directly calculated providing n = 5 x 10(24) cm(-3), confirming the samples' metallic character.

Back-to-back Schottky diodes: the generalization of the diode theory in analysis and extraction of electrical parameters of nanodevices.

We report on the analysis of nonlinear current-voltage characteristics exhibited by a set of blocking metal/SnO(2)/metal. Schottky barrier heights in both interfaces were independently extracted and their dependence on the metal work function was analyzed. The disorder-induced interface states effectively pinned the Fermi level at the SnO(2) surface, leading to the observed Schottky barriers. The model is useful for any two-terminal device which cannot be described by a conventional diode configuration.

Measuring the mobility of single crystalline wires and its dependence on temperature and carrier density.

Kinetic transport parameters are fundamental for the development of electronic nanodevices. We present new results for the temperature dependence of mobility and carrier density in single crystalline In(2)O(3) samples and the method of extraction of these parameters which can be extended to similar systems. The data were obtained using a conventional Hall geometry and were quantitatively described by the semiconductor transport theory characterizing the electron transport as being controlled by the variable range hopping mechanism. A comprehensive analysis is provided showing the contribution of ionized impurities (low temperatures) and acoustic phonon (high temperatures) scattering mechanisms to the electron mobility. The approach presented here avoids common errors in kinetic parameter extraction from field effect data, serving as a versatile platform for direct investigation of any nanoscale electronic materials.

Magnetoresistance in Sn-Doped In2O3Nanowires.

In this work, we present transport measurements of individual Sn-doped In2O3nanowires as a function of temperature and magnetic field. The results showed a localized character of the resistivity at low temperatures as evidenced by the presence of a negative temperature coefficient resistance in temperatures lower than 77 K. The weak localization was pointed as the mechanism responsible by the negative temperature coefficient of the resistance at low temperatures.