Interdigitated electrodes (IDEs) are made of two individually addressable interdigitated comb-like electrode structures. IDEs are one of the most favored transducers, widely utilized in technological applications especially in the field of biological and chemical sensors due to their inexpensive, ease of fabrication process and high sensitivity. In order to detect and analyze a biochemical molecule or analyte, the impedance and capacitance signal need to be obtained. This paper investigates the working principle and influencer of the impedance and capacitance biosensors. The impedance biosensor depends on the resistance and capacitance while the capacitance biosensor influenced by the dielectric permittivity. However, the geometry and structures of the interdigitated electrodes affect both impedance and capacitance biosensor. The details have been discussed in this paper.

Cuprous oxide (Cu₂O) thin films were deposited onto indium tin oxide (ITO) coated glass substrate by sol-gel spin coating technique using different additives, namely, polyethylene glycol and ethylene glycol. It was found that the organic additives added had a significant influence on the formation of Cu₂O films and lead to different microstructures and optical properties. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and ultraviolet-visible spectroscopy (UV-Vis). Based on the FESEM micrographs, the grain size of film prepared using polyethylene glycol additive has smaller grains of about 83 nm with irregular shapes. The highest optical absorbance film was obtained by the addition of polyethylene glycol. The Cu₂O thin films were used as a working electrode in the application of photoelectrochemical solar cell (PESC).

Nowadays, concepts of self-cleaning have received great attention in construction building materials. Self-cleaning with the presence of photocatalyst has been applied in building materials to overcome the problem of building surfaces becoming dirty after exposure for a long time in highly polluted areas. To date, the concept of green blending materials has led to the development of a new binding material for green materials, which is geopolymer with an addition of photocatalyst. This review focused on the development of conventional self-cleaning paste, including the method of preparation and the impact of adding photocatalyst on physical and mechanical properties. However, although self-cleaning has been widely applied in conventional cement paste, its applications in geopolymers are still in the early stages of development and require more research. Therefore, this paper also intended to review the current knowledge on properties of geopolymer cement-based composite and its potential to be applied as a self-cleaning coating.

High entropy alloy (HEA) involves the addition of five or more elements into the materials system. This provides a multidimensional configuration space that is limitless in terms of its properties and functions. Some high-entropy alloys have already been shown to have superior properties over conventional alloys, especially the CoCr-based HEA materials. Better high-entropy alloy applications may be discovered, especially in micro- and nano-level structures, hence the development of thin film/coating -based HEA materials. Therefore, in this review paper, we are aiming to provide recent studies on the thin film/coating-based high-entropy alloy on fundamental issues related to methods of preparation, phase formation and mechanical properties. We found that sputtering has been extensively used to grow thin-film-based HEAs as it allowed parameters to be controlled with homogeneous growth. The evolution from bulk to thin samples can also be observed with the mechanical properties has exceeded the bulk-based HEA expectations, which are high hardness, better interfacial bonding and tribological behaviour and higher corrosion resistant.

Two different phases of alumina (Al2O3) nanoparticles (γ-alumina and α-alumina) have successfully been synthesized by using a sol-gel method. During the process a mixture of aluminum nitrate and citric acid (C/N=0.5) was heated at 60°C followed by 80°C until a gel was formed. The amorphous gel structure then was dried and sintered from 600°C to 1200°C. From the X-ray diffraction (XRD) analysis, crystalline structure of γ-alumina started to form at 800°C with average crystallite size of 11.5 nm, followed by the formation of the mixture phase of γ-alumina and α-alumina at 1000°C. The transformation from γ- to α-alumina occured at 1100°C of sintering temperature and above with the average crystallite size of 49 nm. The efficiency of the synthesized alumina nanoparticles as an adsorbents was tested by immersing the powder into the copper ions solution. The percentage of the copper removal was measured by using atomic absorption spectroscopy (AAS). It was found that, the efficiency of the alumina nanoparticles as an adsorbent was not depending on their phases, but might due to the increased of the particle size at higher sintering temperature. The highest percentage of removal 82.1% was obtained when using the alumina sintered at 1200°C.

The electron transfer layer (ETL) plays a vital role in achieving high-performance perovskite solar cells (PSCs). Titanium dioxide (TiO₂) is primarily utilised as the ETL since it is low-cost, chemically stable, and has the simplest thin-film preparation methods. However, TiO₂ is not an ideal ETL because it leads to low conductivity, conduction band mismatch, and unfavourable electron mobility. In addition, the exposure of TiO₂ to ultraviolet light induces the formation of oxygen vacancies at the surface. To overcome these issues, doping TiO₂ with various metal ions is favourable to improve the surface structure properties and electronic properties. This review focuses on the bulk modification of TiO₂ via doping with various metal ions concentrations to improve electrical and optical properties, charge carrier density, and interfacial electron–hole recombination, thus contributing to enhancing the power conversion efficiency (PCE) of the PSCs.