Synthesis, microstructural and optical characterizations of sol-gel grown gadolinium doped cerium oxide ceramics.

In this study, through the utilization of the sol-gel combustion tactic, gadolinium (Gd)-doped cerium oxide (CeO2), Ce1-xGdxO2 (x = 0.00, 0.10, 0.20 and 0.30 (GDC)) ceramics were attained. The synthesized GDC ceramics were investigated using X-ray diffraction (XRD) to scrutinize their crystal structures and phase clarities. The obtained GDC ceramics have a single-phase cubic structure and belong to the crystallographic space group fm3̄m (225). The measurement of the diffraction angle of each reflection and the subsequent smearing of the renowned Bragg's relation provided coarse d-interplanar spacings. The stacking fault (SF) values of pure and Gd-doped CeO2 ceramics were assessed. To muse the degree of preferred orientation (σ) of crystallites along a crystal plane (h k l), the texture coefficient (Ci) of each XRD peak of GDC ceramics is gauged. By determining the interplanar distance (dh k l), the Bravais theory sheds light on the material's development. By exploiting Miller indices for the prime (1 1 1) plane, the lattice constants of GDC ceramics and cell volumes were obtained. Multiple techniques were employed to ascertain the microstructural parameters of GDC ceramics. A pyrometer substantiated the density of GDC ceramics. The room temperature (RT) Fourier transform infrared (FTIR) spectra of both un-doped and Gd-doped CeO2 were obtained. The UV-vis-NIR spectrometer recorded the GDC ceramics' reflectance (R) spectra at RT. For both undoped and Gd-doped CeO2, the absorption coefficient (α) spectra showed two distinct peaks. The R-dependent refractive index (η) and the α-dependent extinction coefficient (k) were determined for all GDC samples. The optical band gap (Eg) was obtained by integrating the Tauc and Kubelka-Munk approaches for GDC ceramics. For each GDC sample, the imaginary (εi) and real (εr) dielectric constants, as well as the dissipation factor (tan δ), were determined local to the characteristic wavelength (λc). Calculations were made for the Urbach energy (EU) and Urbach absorption coefficient (α0) for GDC ceramics. The minimum and maximum values of optical (σo) and electrical (σe) conductivity for GDC ceramics were determined. The volume (VELF) and surface (SELF) energy loss functions, which depend on the constants εi and εr, were used to measure electrons' energy loss rates as they travel across the surface. Raman spectroscopy revealed various vibrational modes in GDC ceramics. Finally, the implications are discussed herein.

Note: Simultaneous water quality monitoring and degradation of hazardous organic pollutants.

Here, we report a simple technique that uses mesoporous SnO2 to monitor the water quality and degrade the hazardous organic pollutants simultaneously. The technique generates hydroxyl radicals and a voltage that is hindered by the presence of hazardous organic pollutants. Pollutant as low as 1 ppb concentration level can easily be detected. The developed system not only monitors the water quality but also is capable of degrading hazardous dyes (organic pollutants) through its self-power, not relying on any external stimuli such as light, heat, radiation, and current. A simple digital laboratory multimeter is shown to be useful for the overall study. Overall, the study indicates that spectrophotometer generally used to monitor the dye concentration can be avoided.

Sequential Elemental Dealloying Approach for the Fabrication of Porous Metal Oxides and Chemiresistive Sensors Thereof for Electronic Listening.

Highly porous materials, with large surface area and accessible space, variable chemical compositions, and porosity at different length scales, have captivated the attention of researchers in recent years as an important family of functional materials. Here, we report a novel approach to grow porous metal oxides (PMOs) by sequential elemental dealloying in which a highly mobile element gets dealloyed first under the thermal treatment (annealing) and facilitates the formation of PMOs. Subsequently, a chemiresistive sensor based on porous SnO2 was fabricated for humidity sensing at room temperature which shows a high sensitivity of 348 in a fully humid [>99% relative humidity (RH)] atmosphere with an accuracy of 1% RH change. In addition, the sensor is highly durable and reproducible. Eventually, the chemiresistive sensor has been exploited for electronic listening toward speaking, whistling, and breath monitoring. Overall, the results advocate the fabrication of PMOs and the development of resistive humidity sensors for electronic listening as well as for biomedical applications.