In this study, the structure and photoelectrochemical properties of CuWO 4 porous films synthesized by a co-precipitation method followed by a hydrothermal treatment were investigated. The film was deposited on fluorine-doped tin oxide (FTO)-conducting glass, from a suspension containing polyethylene glycol, and heat-treated at 500 C for 30 min. X-ray diffraction patterns, the Rietveld refinement data, and the micro-Raman spectrum showed that the CuWO 4 film has a triclinic structure. The optical band gap energy of the film was estimated to be 2.45 eV by the Tauc plot. Field emission scanning electron microcopy images of the films indicated that they are about 4.0 AE 0.5 mm thick. The photoelectrochemical properties of the film were investigated in a Na 2 SO 4 aqueous solution, in the absence of light and under polychromatic irradiation. The CuWO 4 film exhibited photoelectrochemical behavior of a n-type semiconductor, with a negative photopotential and an anodic photocurrent density of 68 mA cm À2 at 0.73 V vs. Ag/AgCl (1.23 V vs. RHE). The n-type photoelectrochemical behavior was confirmed by a chronoamperometry measurement biased condition at + 0.7 V, at different pH values. From these studies, it was noted that when the pH values increased from 3 to 11, the photocurrent density increased about 9 times. Also, the flat band potential (E fb) of the semiconductor was estimated by the Butler-Gärtner model at + 0.34 V, which was utilized to calculate the conduction band edge. The studies presented here reveal that the CuWO 4 porous film is a promising candidate to be applied as a photoanode in photocatalytic processes under irradiation by visible light.

In this paper, gold microelectrode array (Au‐MEA) were employed to determination of ethambutol in aqueous medium. Au‐MEA was constructed with an electronic microchip integrated circuit. The standard curve (analytical curve) was constructed for a single microelectrode (ME) in a concentration range of 5.0×10−5 to 2.0×10−3 mol L−1, allowing estimation of both the limit of detection (LOD) (4.73×10−5 mol L−1) and the limit of quantification (LOQ) (1.57×10−4 mol L−1) for ethambutol. When the MEA was utilized, the LOD and LOQ were 1.55×10−7 and 5.18×10−7 mol L−1, respectively. Our results indicated that Au‐MEA can be utilized as amperometric sensors for ethambutol determination in aqueous media.

No abstract

In this communication, we report the growth of pure gamma-phase tungsten oxide (γ-WO 3 ) films on a conducting substrate (fluorinedoped tin oxide), followed by heat treatment at 500°C for 2 h, and finally modification with either silver (Ag 0 ) or platinum (Pt 0 ) metallic nanoparticles. These γ-WO 3 thin films can be obtained from a tungsten citrate solution by a drop-coating method, and their surfaces are modified with Ag 0 and Pt 0 nanoparticles by photoreduction. X-ray diffraction analysis indicates that all the thin films have a monoclinic structure. Field emission-scanning electron microscopy analysis reveals large and fine grains for pure γ-WO 3 film and modified WO 3 films, respectively, with an average grain size of~48 nm and thickness of~986 nm. Finally, an enhancement in photoelectrochemical performance by a factor of~2.5 is noted to modified γ-WO 3 films, which is attributed to superior electron-hole charge recombination lifetime under polychromatic irradiation. It is observed that, even under bias, an exponential reduction in photocurrent intensity is associated with charge recombination instead of mass transport conditions like diffusion. Keywords γ-WO 3 films . Ag 0 /Pt 0 nanoparticles . Recombination lifetime . Transient photocurrent

No abstract

No abstract

Direitos para esta edição cedidos à Atena Editora pelos autores. Todo o conteúdo deste livro está licenciado sob uma Licença de Atribuição Creative Commons. Atribuição-Não-Comercial-NãoDerivativos 4.0 Internacional (CC BY-NC-ND 4.0).O conteúdo dos artigos e seus dados em sua forma, correção e confiabilidade são de responsabilidade exclusiva dos autores, inclusive não representam necessariamente a posição oficial da Atena Editora. Permitido o download da obra e o compartilhamento desde que sejam atribuídos créditos aos autores, mas sem a possibilidade de alterá-la de nenhuma forma ou utilizá-la para fins comerciais. Todos os manuscritos foram previamente submetidos à avaliação cega pelos pares, membros do Conselho Editorial desta Editora, tendo sido aprovados para a publicação com base em critérios de neutralidade e imparcialidade acadêmica.A Atena Editora é comprometida em garantir a integridade editorial em todas as etapas do processo de publicação, evitando plágio, dados ou resultados fraudulentos e impedindo que interesses financeiros comprometam os padrões éticos da publicação. Situações suspeitas de má conduta científica serão investigadas sob o mais alto padrão de rigor acadêmico e ético.

No abstract