PHOTOELECTROCATALYSIS ON SEMICONDUCTORS: FROM THE FUNDAMENTALS TO ITS CONFORMATION AT THE NANOSCALE LEVEL. The science of semiconductors, essential in electronics, is pivotal also for the most active research fields of environmental science and engineering today -the development of solar energy conversions and advanced oxidation processes, exemplified by the harvesting of sun daylight to produce electric energy, environmentally friendly fuels and to clean up water from harmful pollutants. The advancement of such fields relies on the fundamentals of the photocatalysis at semiconductors, summarized in this review in language familiar to chemists. The theory and experimental onrush emerged mainly during the first half of the 20 th century but the rising interest in the science of nanostructured materials in recent decades, besides many insights about the potential of this scale-down of sizes, also forced a revision of the theoretical models. Essentially, the interfacial model of the space-charge layer cannot explain the behavior of nanoparticulate films, even at doped conditions comparable to monocrystalline materials. The present work encompasses the conformation of classical photocatalytic models to the nanoscale size, critically reviewing their features and role for modern electrochemical applications.Keywords: photoelectrocatalysis; monocrystalline semiconductors; nanoparticulate semiconductors; space-charge layer; band bending. INTRODUÇÃOO tema fotocatálise já foi alvo de diversas revisões na literatura, inclusive em alguns manuscritos de cunho exaustivo com centenas de referências. Nesse sentido, destacam-se entre os trabalhos clássicos o do professor Michael R. Hoffmann e col.1 que acumula mais de 17 mil citações desde 1995 e os do professor Akira Fujishima e col. 4,5 visando a discussão da aplicação do TiO 2 para remediação ambiental e a discussão de mecanismos de fotodegradação de compostos orgânicos catalisados por ele. A fotoeletrocatálise, entretanto, nunca foi focalizada em trabalhos de revisão em vernáculo. Por algumas vezes, ela foi abordada em trabalhos de inovação técnica contemplando novas aplicações, 6-9 mas não uma visão fundamentada e sistematizada do tema balizada em literatura selecionada e acompanhada de discussão crítica do estado da arte e possíveis tendências. A fundamentação teórica da fotoeletrocatálise remonta ao final da Segunda Guerra Mundial, com os estudos da semicondução no silício e germânio orientados por Lark-Horovitz 10 e que desencadearam o enorme avanço tecnológico representado por componentes eletrônicos como diodos e transistores, formados por junções entre semicondutores com dopagem diferente, presentes hoje em praticamente todos os dispositivos eletrônicos. Os componentes semicondutores também se impuseram na detecção e emissão de radiação eletromagnética, servindo de exemplos os fotodiodos e os diodos emissores de luz (LEDs). Assim, segue a fundamentação teórica da matéria. A TEORIA DE BANDAPor definição simples, um semicondutor é um material com condutividade elétrica ...

Melanoma is the most aggressive type of skin cancer. Despite the available therapies, the minimum residual disease is still refractory. Reactive oxygen and nitrogen species (ROS and RNS) play a dual role in melanoma, where redox imbalance is involved from initiation to metastasis and resistance. Redox proteins modulate the disease by controlling ROS/RNS levels in immune response, proliferation, invasion, and relapse. Chemotherapeutics such as BRAF and MEK inhibitors promote oxidative stress, but high ROS/RNS amounts with a robust antioxidant system allow cells to be adaptive and cooperate to non-toxic levels. These proteins could act as biomarkers and possible targets. By understanding the complex mechanisms involved in adaptation and searching for new targets to make cells more susceptible to treatment, the disease might be overcome. Therefore, exploring the role of redox-sensitive proteins and the modulation of redox homeostasis may provide clues to new therapies. This study analyzes information obtained from a public cohort of melanoma patients about the expression of redox-generating and detoxifying proteins in melanoma during the disease stages, genetic alterations, and overall patient survival status. According to our analysis, 66% of the isoforms presented differential expression on melanoma progression: NOS2, SOD1, NOX4, PRX3, PXDN and GPX1 are increased during melanoma progression, while CAT, GPX3, TXNIP, and PRX2 are decreased. Besides, the stage of the disease could influence the result as well. The levels of PRX1, PRX5 and PRX6 can be increased or decreased depending on the stage. We showed that all analyzed isoforms presented some genetic alteration on the gene, most of them (78%) for increased mRNA expression. Interestingly, 34% of all melanoma patients showed genetic alterations on TRX1, most for decreased mRNA expression. Additionally, 15% of the isoforms showed a significant reduction in overall patient survival status for an altered group (PRX3, PRX5, TR2, and GR) and the unaltered group (NOX4). Although no such specific antioxidant therapy is approved for melanoma yet, inhibitors or mimetics of these redox-sensitive proteins have achieved very promising results. We foresee that forthcoming investigations on the modulation of these proteins will bring significant advances for cancer therapy.

TiO 2-MEDIATED PHOTOCATALYSIS AT THE NANOPARTICULATE STATE: REVIEW OF THE REACTIVITY BY THE TRAPPING CONCEPT AND SOME APPLICATIONS IN ANALYTICAL CHEMISTRY. TiO 2 has been used as a white pigment and studied since the first decades of the XX century for the undesirable chalking of outdoor paintings exposed to sunlight. Since the first report of Honda and Fujishima (1972) of the water splitting by the harvesting of sunlight on a n-type single crystal TiO 2 electrode, the engagement of researchers with the field has grown steadily. TiO 2-photocatalysis has joined the group of advanced oxidation processes for potential new water and wastewater treatments but, despite of its high chemical and photochemical stability and the great oxidizing power of its photogenerated holes, photons in UVA spectral region are needed to accomplish the high band gap, limiting the yield of sun-driven environmental applications. Nevertheless, this shortcoming has not restricted benchtop research and small and medium scale applications also relying on artificial UV sources, especially nowadays that highly-efficient UVA-LEDs are available. Herein, we review the fundamental aspects and the practical attributions of the trapping model in the charge transfer kinetics of photogenerated holes in nanoparticulate TiO 2. Regarding to new practical uses, we focus our attention on some ingenious applications of this photocatalyst in the field of analytical chemistry, covering also subjects never reviewed before.