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The increased growth of electronics and wireless communication systems causes the urge to find microwave absorbing materials that are lightweight, inexpensive, and environmentally friendly. In this study, we successfully synthesize activated carbon materials from the oil palm empty fruit bunch (OPEFB) as future microwave absorbing material candidates with a porous structure using different kalium hydroxide (KOH) concentrations during the activation process followed by physical carbonization at 800 °C under an inert atmosphere. The prepared porous activated carbon (PAC)-based OPEFB was characterized by several techniques, including x-ray diffraction, scanning electronic microscopy-energy dispersive x-ray analysis, and Brunauer–Emmett–Teller analysis. The microwave absorption properties of the PAC-based OPEFB were measured using one port rectangular waveguides at the X-band frequency range (from 8 to 12 GHz). A minimum reflection loss value of −32.21 dB (more than 99.9% absorption) at 10.64 GHz is obtained for the PAC-based OPEFB with 20% of KOH concentration. The SEM observations confirm the porous structure of activated carbon, and the BET analysis measures the surface area of the PAC-based OPEFB with 20% of KOH concentration of about 693.06 m2/g. The improvement of reflection loss of the PAC-based OPEFB compared to its raw materials is attributed to the better impedance matching, and multiple reflections occur in the porous structure of activated carbon. This study suggests that the PAC-based OPEFB can become a future potential material for microwave absorbers used in electronics and wireless communications devices. [ABSTRACT FROM AUTHOR]

The main reason ZnO is attractive for optoelectronic applications is its polarization behavior, which can modify its optical and electronic properties. Here, the polarization of ZnO is highly dependent on its structure and morphology. We study the polarization behavior of ZnO with different structures and morphology. A seedless ZnO nanocolumnars (ZnO NCs) array is fabricated using DC-unbalanced magnetron sputtering (DC-UBMS) with further thermal annealing treatment. Thermal annealing transforms the cone-like ZnO NCs to become rod-like ZnO NCs and significantly reduces the intensity of the crystal plane (002). Thermal annealing changes the polarization, where the annealed-ZnO 600°C exhibits the highest polarization that promotes the increase in lattice constant c and crystallite size. We found a football-like polarization response without saturation polarization, which indicates a presence of leakage current and defect on the samples. Interestingly, a ferroelectric characteristic is observed in annealed-ZnO 800°C with lower polarization than the annealed-ZnO 600°C. The origin of ferroelectricity is further investigated using a comprehensive study. This study provides a new understanding of polarization behavior on ZnO NCs, which is the essential key in designing switchable and non-volatile-based devices. [ABSTRACT FROM AUTHOR]

Polylactic-acid–starch-based polymer composite (PLA/TPS) has good thermal stability for biocomposites. However, the physical and mechanical properties of PLA/TPS do not meet the standards. It needed additives to enhance its physical and mechanical properties. The aim was to improve the physical and mechanical properties of PLA/thermoplastic starch using sucrose. In addition, this study evaluated the enhancement of thermal properties of PLA/thermoplastic starch using sucrose. This study used sucrose as an additive to enhance the PLA/TPS composite. The addition of sucrose inhibits the degradation of biocomposites. This means that thermal stability increases. The thermal stability increased because the degree of crystallinity increased with the addition of sucrose, which was also proven in the XRD result. The addition of sucrose caused the morphology of the biocomposite to have pores. The FESEM results showed that biocomposites with the addition of sucrose had pores and gaps. These gaps result from low adhesion between polymers, causing a decrease in the mechanical and physical properties of the sample. Based on the FTIR spectra, biocomposite PLA/TPS blends with the addition of sucrose still have many hydroxyl groups that will lead to attracting other molecules or ions, such as oxygen or water. This phenomenon affects the physical and mechanical properties of materials. The physical and mechanical properties increased with sucrose addition. The best composite was prepared using 3% sucrose. This is because sucrose has a crystalline structure that affects the properties of biocomposites. However, the addition of 3% sucrose was not as effective as that of neat PLA. [ABSTRACT FROM AUTHOR]

We study room temperature optics and electronic structures of ZnO:Cu films as a function of Cu concentration using a combination of spectroscopic ellipsometry, photoluminescence, and ultraviolet-visible absorption spectroscopy. Mid-gap optical states, interband transitions, and excitons are observed and distinguishable. We argue that the mid-gap states are originated from interactions of Cu and oxygen vacancy (Vo). They are located below conduction band (Zn4s) and above valence band (O2p) promoting strong green emission and narrowing optical band gap. Excitonic states are screened and its intensities decrease upon Cu doping. Our results show the importance of Cu and Vo driving the electronic structures and optical transitions in ZnO:Cu films. [ABSTRACT FROM AUTHOR]

Water pollution from dye waste presents a pressing environmental challenge that urgently requires innovative and sustainable solutions. In this regard, reusable visible-light-driven photocatalysts prepared using renewable resources are essential to overcome the problem. This research aims to develop Pangium edule (PE) kernel biomass-derived NCQDs/TiO 2 /PVA nanocomposite films for reusable visible light-assisted photodegradation. The effect of incorporating NCQDs and TiO 2 into the PVA matrix was investigated for its photodegradation performance using methylene blue (MB) as a model pollutant dye. The characterization results indicated cooperative interaction between NCQDs and TiO 2 in terms of Ti–O–C bonds. Moreover, NCQDs/TiO 2 /PVA promotes an increase in the photodegradation performance of MB, which depends on the NCQDs' content. Interestingly, beyond a certain threshold, augmenting the number of NCQDs exhibited a diminishing effect on photodegradation performance. The NCQDs/TiO 2 /PVA-2 nanocomposite film demonstrated optimal catalytic efficiency of 98.2 % and exhibited stability as a photocatalyst for MB degradation over five cycles. Overall, utilizing an easy synthetic route for NCQDs/TiO 2 /PVA nanocomposite film demonstrate outstanding photodegradation performance, offering an eco-friendly and sustainable water remediation technology. • A facile preparation of Pangium edule kernel biomass-derived NCQDs/TiO 2 /PVA. • NCQDs content showed important factor in photodegradation performance. • NCQDs/TiO 2 /PVA exhibit outstanding photodegradation performance over MB. • NCQDs/TiO2/PVA showed excellent reusability of photocatalyst. [ABSTRACT FROM AUTHOR]

The use of zinc oxide-based photocatalysts has been extensively conducted to breakdown harmful pollutants in wastewater treatment. Recently, ZnO doped non-metal can improve photocatalytic activity by reducing charge carrier recombination. Here, S-doped ZnO thin films, with a sulfur dopant of 1 and 5% molar, were synthesized by a seed-mediated hydrothermal process. The enhancement in crystal structure and morphology were noted with the presence of sulfur in the ZnO system. The photocatalytic test shows that the presence of sulfur enhances Rhodamine B (RhB) degradation efficiency up to 92% with reaction rates of 1.67 × 10−2 min−1 under visible light. The S-doped ZnO thin film is potentially applied as a stable photocatalyst for wastewater purification, with a noted photocatalytic efficiency of 75% after repeated use. • The sulfur-doped ZnO thin films have a good performance as a photocatalyst. • The photocatalyst process for rhodamine B can take place under visible light. • The sulfur dopant promotes an increase in surface density and crystallinity. • The recyclability test shows the sulfur-doped ZnO can be used repeatedly. [ABSTRACT FROM AUTHOR]