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Monodispersed silica (SiO2) nano- and microparticles can be fabricated by the sol-gel process. For device fabrication, precise formation of composite particles with a homogeneous and facile arrangement that form well-ordered, close-packed arrays is important. In this study, formation of electrostatically assembled SiO2–SiO2 composite particles with excellent homogeneity in arrangement was first demonstrated using sol-gel-derived monodispersed SiO2 particles with average particles sizes of 200 nm and 16 µm. Formation of two- and three-dimensionally, close-packed arrays by electrophoresis-induced stimulation with direct-current and alternating-current electric fields was achieved for the first time using these electrostatically assembled SiO2–SiO2 composite particles. Detailed morphological observation by scanning electron microscopy revealed that the structure of the SiO2–SiO2 composite particles remained intact even after electrophoretic stimulation. The feasibility of obtaining well-ordered arrays of electrostatically assembled sol–gel-derived SiO2–SiO2 composite particles is important for further development of sol-gel-related technology in various applications, such as advanced composites and optical devices. Highlights: Electrostatically assembled SiO2–SiO2 composite particles were prepared using monodispersed sol–gel-derived SiO2 particles with two sizes. Ordered two- and three-dimensional SiO2–SiO2 composite-particle arrangements were obtained. Superimposition of AC and DC electric fields through electrophoresis-induced stimulation generated a two-dimensional close-packed structure. Simultaneous gravitational sedimentation and AC field application led to formation of three-dimensionally ordered arrays. [ABSTRACT FROM AUTHOR]

Hexavalent chromium is very carcinogenic, and it is, therefore, important to remove it from wastewater prior to disposal. This study reports the photoreduction of Cr(VI) under simulated sunlight using graphene-derived TiO2 nanowire (TNW) composites. Electrophoretic deposition (EPD) of graphene oxide (GO) and reduced graphene oxide (rGO) was carried out on rutile phase TNWs. The TNWs were fabricated by thermal oxidation of titanium foil in the presence of 1M potassium hydroxide mist at 750 °C. The TNWs uniformly covered the surface of the titanium foil. EPD of GO or rGO was done as a function of time to produce deposits of different thicknesses. The photocatalytic performances of the GO/TNWs or rGO/TNWs were tested to reduce Cr(VI) under visible light. The performance of rGO/TNWs in reducing Cr(VI) was better than GO/TNWs. A 10-second-deposited rGO on TNW samples can reduce 10 mg/L Cr(VI) within 30 min under visible light, likely as a result of the high electron transfer from rGO to TNWs accelerating the Cr(VI) reduction. [ABSTRACT FROM AUTHOR]

In this study, nanoporous anodic film was produced by anodization of niobium, Nb in a fluoride ethylene glycol electrolyte. The effect of anodization voltage and electrolyte temperature was studied to find an optimum condition for circular, ordered, and uniform pore formation. The diameter of the pores was found to be larger when the applied voltage was increased from 20 to 80 V. The as-anodized porous film was also observed to comprise of nanocrystallites which formed due to high field-induced crystallization. The nanocrystallites grew into orthorhombic Nb2O5 after post-annealing treatment. The Cr(VI) photoreduction property of both the as-anodized and annealed Nb2O5 samples obtained using an optimized condition (anodization voltage: 60 V, electrolyte temperature: 70 °C) was compared. Interestingly, the as-anodized Nb2O5 film was found to display better photoreduction of Cr(VI) than annealed Nb2O5. However, in terms of stability, the annealed Nb2O5 presented high photocatalytic efficiency for each cycle whereas the as-anodized Nb2O5 showed degradation in photocatalytic performance when used continually. [ABSTRACT FROM AUTHOR]

In recent years, heteroatoms-doped graphene, with its exceptional properties, has generated significant advances in many fields of modern nanoscience and nanotechnology. With the rapid progress in doped graphene research, advanced graphene materials have been developed and frequently used in electromagnetic shielding applications. In this context, heteroatom-doping of graphene materials has been considered as an efficient strategy for the development of novel electromagnetic interference (EMI) shielding materials. This article aims to provide a timely update on the synthesis and EMI shielding applications of doped graphene materials. Heteroatom-doped and co-doped graphene-based materials (n-type and p-type doping) have been synthesized using various chemical and physical routes. Extensive approaches and strategies have been applied for achieving the intended doping/co-doping levels in graphene-based materials. Doping in graphene and its derivatives induces the formation of defects, changing the electrical conductivity as well as the mechanical properties. This results in an increase of reflection, and an improvement of absorption, enhancing shielding effectiveness. This review article provides a comprehensive overview of doping strategies for graphene and related composites, their EMI shielding performance, as well as comments on the future perspectives and possible challenges for doped graphene-based materials. We hope this review article offers a valuable starting point for researchers entering the field, providing an overview of synthesis approaches and EMI shielding applications. [ABSTRACT FROM AUTHOR]

TiO2 nanotubes (TNTs) with self-aligned 7.25 ± 0.51-µm length, 66.78 ± 4.18-nm diameter, and 41.48 ± 4.31-nm wall thickness were fabricated using Ti wire in an anodic process using an ethylene glycol (EG)/NH4F–air bubbles electrolyte. The possible growth of TNTs in the electrolyte with different water content was explored. It was found that the growth rate of TNTs in an electrolyte with air bubbles and no water content was significantly faster than that in an electrolyte with 1–5-vol% water content. The degradation of methylene blue (MB) dye with sodium borohydride (NaBH4) as the sacrificial reagent (hole scavenger) under ultraviolet (UV) irradiation was investigated in a photocatalytic study of 400 °C annealed optimized TNTs. The results showed that TNTs can reduce MB at approximately 99%, 74%, and 40% removal efficiency using the first, second, and third cycles, respectively, for 70-min reaction time each. A kinetic study revealed that the photoreduction process followed the pseudo-first-order kinetic with reaction rates of 0.0280, 0.0213, and 0.0052 min−1 for the first, second, and third cycles, respectively. This study's findings will provide new insights into the design of UV light induced on anodized TNTs using Ti wire in EG/NH4F electrolytes with air bubbles aided by NaBH4 for the degradation of MB dye. [ABSTRACT FROM AUTHOR]