In this study, porous silicon (PSi) was prepared and tested as an extended gate field-effect transistor (EGFET) for pH sensing. The prepared PSi has pore sizes in the range of 500 to 750 nm with a depth of approximately 42 µm. The results of testing PSi for hydrogen ion sensing in different pH buffer solutions reveal that the PSi has a sensitivity value of 66 mV/pH that is considered a super Nernstian value. The sensor considers stability to be in the pH range of 2 to 12. The hysteresis values of the prepared PSi sensor were approximately 8.2 and 10.5 mV in the low and high pH loop, respectively. The result of this study reveals a promising application of PSi in the field for detecting hydrogen ions in different solutions.

In this paper, we address the synthesis of nano-coalesced microstructured zinc oxide thin films via a simple thermal evaporation process. The role of synthesis temperature on the structural, morphological, and optical properties of the prepared zinc oxide samples was deeply investigated. The obtained photoluminescence and X-ray photoelectron spectroscopy outcomes will be used to discuss the surface structure defects of the prepared samples. The results indicated that the prepared samples are polycrystalline in nature, and the sample prepared at 700 °C revealed a tremendously c-axis oriented zinc oxide. The temperature-driven morphological evolution of the zinc oxide nano-coalesced microstructures was perceived, resulting in transformation of quasi-mountain chain-like to pyramidal textured zinc oxide with increasing the synthesis temperature. The results also impart that the sample prepared at 500 °C shows a higher percentage of the zinc interstitial and oxygen vacancies. Furthermore, the intensity of the photoluminescence emission in the ultraviolet region was enhanced as the heating temperature increased from 500 °C to 700 °C. Lastly, the growth mechanism of the zinc oxide nano-coalesced microstructures is discussed according to the reaction conditions.

The aim of this study was to prepare β-wollastonite using a green synthesis method (autoclaving technique) without organic solvents and to study its bioactivity. To prepare β-wollastonite, the precursor ratio of CaO:SiO₂ was set at 55:45. This mixture was autoclaved for 8 h and later sintered at 950 °C for 2 h. The chemical composition of the precursors was studied using X-ray fluorescence (XRF), in which rice husk ash consists of 89.5 wt % of SiO₂ in a cristobalite phase and calcined limestone contains 97.2 wt % of CaO. The X-ray diffraction (XRD) patterns after sintering showed that only β-wollastonite was detected as the single phase. To study its bioactivity and degradation properties, β-wollastonite samples were immersed in simulated body fluid (SBF) for various periods of time. Throughout the soaking period, the molar ratio of Ca/P obtained was in the range of 1.19 to 2.24, and the phase detected was amorphous calcium phosphate, which was confirmed by scanning electron microscope with energy dispersive X-ray analysis (SEM/EDX) and XRD. Fourier-transform infrared spectroscopy (FTIR) analysis indicated that the peaks of the calcium and phosphate ions increased when an amorphous calcium phosphate layer was formed on the surface of the β-wollastonite sample. A cell viability and proliferation assay test was performed on the rice husk ash, calcined limestone, and β-wollastonite samples by scanning electron microscope. For heavy metal element evaluation, a metal panel that included As, Cd, Pb, and Hg was selected, and both precursor and β-wollastonite fulfilled the requirement of an American Society for Testing and Materials (ASTM F1538-03) standard specification. Apart from that, a degradation test showed that the loss of mass increased incrementally as a function of soaking period. These results showed that the β-wollastonite materials produced from rice husk ash and limestone possessed good bioactivity, offering potential for biomedical applications.

Nanofluid has attracted great attention due to its superior thermal properties. In this study, chemical oxidative polymerization of aniline was carried out in the presence of dodecylbenzenesulfonic acid (DBSA) as a dopant. Particles of DBSA-doped polyaniline (DBSA-doped PANI) with the size range of 15 to 50 nm were obtained, as indicated by transmission electron microscope (TEM). Results of ultra violet-visible (UV-Vis) absorption and Fourier transform infrared (FTIR) spectroscopies as well as thermogravimetric analysis showed that PANI nanoparticles were doped with DBSA molecules. The doping level found was 36.8%, as calculated from elemental analysis data. Thermal conductivity of water was enhanced by 5.4% when dispersed with 1.0 wt% of DBSA-PANI nanoparticles. Specific heat capacity of water-based nanofluids decreased with increasing amount of DBSA-PANI nanoparticles.

Zinc oxide (ZnO) nanorods (NRs) have been synthesized via the hydrothermal process. The NRs were grown over a conductive glass substrate. A non-enzymatic electrochemical sensor for hydrogen peroxide (H₂O₂), based on the prepared ZnO NRs, was examined through the use of current-voltage measurements. The measured currents, as a function of H₂O₂ concentrations ranging from 10 μM to 700 μM, revealed two distinct behaviours and good performance, with a lower detection limit (LOD) of 42 μM for the low range of H₂O₂ concentrations (first region), and a LOD of 143.5 μM for the higher range of H₂O₂ concentrations (second region). The prepared ZnO NRs show excellent electrocatalytic activity. This enables a measurable and stable output current. The results were correlated with the oxidation process of the H₂O₂ and revealed a good performance for the ZnO NR non-enzymatic H₂O₂ sensor.