The ever-growing demand for faster and smaller devices has been successfully fulfilled by the semiconductor industry through formidable scientific and technological advances in the manufacturing of ever-smaller silicon-based devices. However, this astonishing progress is almost reaching its physical limits [1] as the size of the components goes further into the nanoscale world, requiring the urgent development of devices with innovative architectures. Efforts are underway to identify and develop alternative systems to the current complementary metal oxide semiconductor (CMOS) technology, such as quantum cellular automata, [2] single-electron transistors (SETs), [3] and quantum computing [4] and molecular systems. [5] Molecular systems are interesting candidates for the storage, processing, and communication of information/data. Recently, several examples have been reported that emulate the functions of memories, transistors, rectifiers, switches, and wires. [6][7][8][9] Great attention is also being given to the construction of molecular logic gates that mimic the functions of present silicon devices. Accordingly, several systems using electrical, chemical, optical, or mechanical signals as inputs and outputs [5,[10][11][12][13] have been described that generally involve complicated arrangements, equipment, or processes.One of the biggest challenges to the development of a viable technology based on molecular systems is the external addressability and compatibility with present-day electronic/ nanoelectronic devices and circuits. Generally, conceptual models that explore molecular junction properties involve one or more steps in which a solution is injected into the system. Consequently, function of the device is compromised by long washout times. Herein, we report the first molecular optoelectronic XOR logic gate that operates exclusively with

Recebido em 4/5/01; aceito em 24/8/01 PREPARATION OF ALUMINUM COMPOUNDS FROM BAUXITE: CONSIDERATIONS ABOUT SOME ASPECTS INVOLVED IN A DIDACTIC EXPERIMENT. Aluminum metal and aluminum compounds have many applications in several branches of the industry and in our daily lives. The most important raw material for aluminum and its manufactured compounds is bauxite, a rock constituted mainly by aluminum hydroxides minerals. In this work, a didactic experiment aiming the preparation of alumina and potassium alum starting from bauxite is proposed for undergraduate students. Both compounds are of great commercial, scientific and historical interest. The experiment involves applications of important chemical principles such as acidbase and precipitation. Some chemical properties and uses of aluminum compounds are also illustrated.Keywords: bauxite; aluminum oxide; potassium alum. INTRODUÇÃOO alumínio pode ser considerado um elemento bastante "popular" pois está presente em quase todas as esferas da atividade humana. As inúmeras aplicações em diversos setores da indústria (transportes: automóveis, aeronaves, trens, navios; construção civil: portas, janelas, fachadas; eletro-eletrônico: equipamentos elétricos, componentes eletrônicos e de transmissão de energia; petroquímica, metalurgia e outros) e a freqüente presença no nosso dia-a-dia (mó-veis, eletrodomésticos, brinquedos, utensílios de cozinha, embalagens de alimentos, latas de refrigerantes, produtos de higiene, cosméticos e produtos farmacêuticos) ilustram bem a sua importância econômica no mundo contemporâneo. A própria reciclagem de embalagens de alumínio, setor no qual o Brasil se destaca, tem papel relevante do ponto de vista econômico, social e ambiental.Embora hoje a forma mais conhecida do alumínio seja a metáli-ca, o metal já foi considerado tão raro e precioso antes das descobertas de Charles Martin Hall e Paul-Louis-Toussaint Héroult (1888), que chegou a ser exibido ao lado de jóias da coroa e utilizado em lugar do ouro em jantares da nobreza no século XIX. Os compostos de alumínio, por outro lado, servem a humanidade há mais de 4000 anos. Os egípcios já empregavam o alúmen como mordente e os gregos e os romanos também o usavam para fins medicinais, como adstringente, na Antigüidade 1,2 . Diversos compostos de íons Al 3+ apresentam relevância industrial no mundo atual, como, por exemplo: Al(OH) 3 , Al 2 O 3 , Na[Al(OH) 4 ], Al 2 (SO 4 ) 3 e haletos de alumínio, dos quais os dois primeiros, usados para a produção do metal, são os de maior importância econômica. Dentre as principais aplicações dos compostos de alumínio, destacam-se o tratamento para obtenção de água potável, o tingimento de tecidos, a manufatura de produtos de higiene, medicamentos, refratários e catalisadores 1,2 .O alumínio não ocorre na forma elementar na natureza. Devido à alta afinidade pelo oxigênio, ele é encontrado como íon Al 3+ , na forma combinada, em rochas e minerais. Embora constitua apenas cerca de 1% da massa da Terra, é o primeiro metal e o terceiro elemento químico (O = 45,...

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Background: The risk of contamination and dissemination by SARS-CoV-2 has a strong link with nasal, oral and pharyngeal cavities. Recently, our research group observed the promising performance of an anionic phthalocyanine derivative (APD) used in a mouthwash protocol without photoexcitation; this protocol improved the general clinical condition of patients infected with SARS-CoV-2. Methods: The present two-arm study evaluated in vitro the antiviral activity and cytotoxicity of APD. Additionally, a triple-blind randomized controlled trial was conducted with 41 hospitalized patients who tested positive for COVID-19. All the included patients received World Health Organization standard care hospital treatment (non-intensive care) plus active mouthwash (experimental group AM/n=20) or nonactive mouthwash (control group NAM/n=21). The adjunct mouthwash intervention protocol used in both groups consisted one-minute gargling/rinsing / 5 times/day until hospital discharge. Groups were compared considering age, number of comorbidities, duration of symptoms prior admission and length of hospital stay (LOS). The associations between group and sex, age range, presence of comorbidities, admission to Intensive care unit (ICU) and death were also evaluated. Results: The in vitro evaluation demonstrated that APD compound was highly effective for reduction of SARS-CoV-2 viral load in the 1.0 mg/mL (99.96%) to 0.125 mg/mL (92.65%) range without causing cytotoxicity. Regarding the clinical trial, the median LOS of the AM group was significantly shortened (4 days) compared with that of the NAM group (7 days) (p=0.0314). Additionally, gargling/rinsing with APD was very helpful in reducing the severity of symptoms (no ICU care was needed) compared to not gargling/rinsing with APD (28.6% of the patients in the NAM group needed ICU care, and 50% of this ICU subgroup passed way, p=0.0207). Conclusions: This study indicated that the mechanical action of the protocol involving mouthwash containing a compound with antiviral effects against SARS-CoV-2 may reduce the symptoms of the patients and the spread of infection. The use of APD in a mouthwash as an adjuvant the hospital COVID-19 treatment presented no contraindication and reduced the hospital stay period. Trial Registration: The clinical study was registered at REBEC - Brazilian Clinical Trial Register (RBR-58ftdj).

Recebido em 12/7/01; aceito em 5/3/02 CHEMISTRY OF SUPRAMOLECULAR SYSTEMS CONTAINING PORPHYRINS AND METAL COMPLEXES. Supramolecular chemistry is expected to keep a high developing pace in the next years, giving support to the advancement of molecular devices and nanotechnology. In this sense, porphyrins and their analogues should play a significant role as a consequence of their catalytic, electrocatalytic, photochemical and photoelectrochemical properties. In this review we focused on our own strategy based on coordination chemistry for the design and build-up of supermolecules and supramolecular structures constituted by polynuclear porphyrins and metalloporphyrins. Included are also their properties and potential applications.