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A new curcuminoid molecule (3) has been designed and synthesized, containing a central -(CH2)2-COOH chain at the α carbon of the keto-enol moiety in the structure. The carboxylic acid group is added to react with exposed amino groups on silica oxide nanoparticles (nSiO2), forming an amide bond to attach the curcuminoid moiety to the nSiO2 covalently. The Kaiser test quantifies the functionalization degree, yielding 222 µmol of curcuminoid per gram of nanoparticles. The synthesized hybrid nanosystem, nSiO2-NHCO-CCM, displays significant emission properties, with a maximum emission at 538 nm in dichloromethane, similar to curcuminoid 1 (without the central chain), which emits at 565 nm in the same solvent. Solvent-induced spectral effects on the absorption and emission bands of the new hybrid nanosystem are confirmed, similar to those observed for the free curcuminoid (1). The new nanosystem is evaluated in the presence of kerosene in water, showing an emission band at 525 nm as a detection response. The ability of nSiO2-NHCO-CCM to change its fluorescence when interacting with kerosene in water is notable, as it overcomes the limitation caused by the insolubility of free curcuminoid 1 in water, allowing for the exploitation of its properties when connected to the water-stable nanosystem for future detection studies.

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The catalytic properties of three copper complexes, [Cu(en)2](ClO4)2 (1), [Cu(amp)2](ClO4)2, (2) and [Cu(bpy)2](ClO4)2 (3) (where en = ethylenediamine, amp = 2-aminomethylpyridine and bpy = 2,2'-bipyridine), were explored upon the oxidation of benzyl alcohol (BnOH). Maximized conversions of the substrates to their respective products were obtained using a multivariate analysis approach, a powerful tool that allowed multiple variables to be optimized simultaneously, thus creating a more economical, fast and effective technique. Considering the studies in a fluid solution (homogeneous), all complexes strongly depended on the amount of the oxidizing agent (H2O2), followed by the catalyst load. In contrast, time seemed to be statistically less relevant for complexes 1 and 3 and not relevant for 2. All complexes showed high selectivity in their optimized conditions, and only benzaldehyde (BA) was obtained as a viable product. Quantitatively, the catalytic activity observed was 3 > 2 > 1, which is related to the π-acceptor character of the ligands employed in the study. Density functional theory (DFT) studies could corroborate this feature by correlating the geometric index for square pyramid Cu(II)-OOH species, which should be generated in the solution during the catalytic process. Complex 3 was successfully immobilized in silica-coated magnetic nanoparticles (Fe3O4@SiO2), and its oxidative activity was evaluated through heterogenous catalysis assays. Substrate conversion promoted by 3-Fe3O4@SiO2 generated only BA as a viable product, and the supported catalyst's recyclability was proven. Reduced catalytic conversions in the presence of the radical scavenger (2,2,6,6-tetrametil-piperidi-1-nil)oxil (TEMPO) indicate that radical and non-radical mechanisms are involved.

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Luminescent solar concentrators (LSCs) have become an attractive way to produce green energy via their integration into buildings as photovoltaic windows. Recently, carbon quantum dots (C-QDs) have become the most studied luminescent material for the manufacture of luminescent solar concentrators due to their advantages, such as low toxicity, sustainability, and low cost. Despite the advantages of carbon quantum dots, they remain a low-efficiency material, and it is difficult to fabricate LSCs with a good performance. To address this problem, some of the research has used SiO2 nanoparticles (Nps) to produce a light-scattering effect that helps to improve the system performance. However, these studies are limited and have not been discussed in detail. In this regard, this research work was designed to evaluate the contribution of the scattering effect in different systems of carbon quantum dots used in a possible luminescent solar concentrator. To carry out this study, C-QDs and SiO2 Nps were synthesized by hydrothermal methods and the Stober method, respectively. We used different concentrations of both materials to fabricate film LSCs (10 × 10 cm2). The results show that the light scattered by the SiO2 Nps has a double contribution, in terms of light redirected towards the edges of the window and as a secondary source of excitation for the C-QDs; thus, an improvement in the performance of the LSC is achieved. The best improvement in photoluminescence is achieved when the films are composed of 20% wt carbon quantum dots and 10% wt SiO2 Nps, reaching a gain of 16% of the intensity of the light incident on the edges of the window with respect to the LSCs where only C-QDs were used.

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A nanosensor based on magnetic core-shell nanoparticles functionalized with rhodamine derivative, N-(3-carboxy)acryloyl rhodamine B hydrazide (RhBCARB), using (3-aminopropyl)triethoxysilane (APTES) as a linker, has been synthesized for detection of Cu(II) ions in water. The magnetic nanoparticle and the modified rhodamine were fully characterized, showing a strong orange emission sensitive to Cu(II) ions. The sensor shows a linear response from 10 to 90 µg L-1, detection limit of 3 µg L-1 and no interference of Ni(II), Co(II), Cd(II), Zn(II), Pb(II), Hg(II) and Fe(II) ions. The nanosensor performance is similar to those described in the literature, being a viable option for the determination of Cu(II) ions in natural waters. In addition, the magnetic sensor can be easily removed from the reaction medium with the aid of a magnet and its signal recovered in acidic solution, allowing its reuse in subsequent analysis.

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Objetivo: Este estudo teve como objetivo avaliar a resistência ao desgaste de dentes em acrílico para próteses contendo nanopartículas de dióxido de silício (nano-SiO2 ) e dióxido de alumínio (nanoAl2 O3 ). Material e Métodos: O material em polimetilmetacrilato (PMMA) foi utilizado para fabricar 84 amostras (n=10) contendo nano-SiO2 e nano-Al2 O3 nas concentrações 0,1% em peso, 0,3% em peso e 0,5% em peso de pó acrílico. Uma máquina de teste de desgaste de dois corpos e um microscópio digital foram usados para medir as mudanças na perda de peso e rugosidade da superfície, respectivamente. Testes de ANOVA a um fator e testes de comparações múltiplas de Tukey foram utilizados para análise dos dados (α = 0,05). Resultados: O material modificado com nano-SiO2 demonstrou um aumento significativo na perda de peso em comparação com o material acrílico artificial convencional (p ˂ 0,05) enquanto o material modificado com nano-Al2 O3 demonstrou aumento não significativo na perda de peso, exceto no subgrupo 0,5% (p < 0,05). Não há diferenças significativas em relação à alteração da rugosidade após a simulação de desgaste entre todos os grupos testados (p > 0,05). Conclusão: As nanopartículas de nano-Al2 O3 exibem menos efeito negativo que o nanoSiO2 , podendo ser usado com cautela, se necessário. (AU)

Objective: This study aimed to evaluate the wear resistance of acrylic denture teeth containing silicon dioxide (nano-SiO2 ) and aluminum dioxide (nano-Al2 O3 ) nanoparticles. Material and Methods: Poly methyl methacrylate (PMMA) denture tooth material was used to denture tooth material was used to fabricate 84 specimens (n=10) containing nano-SiO2 and nano-Al2 O3 in concentrations 0.1wt%, 0.3wt%, and 0.5wt% of acrylic powder. A two-body wear testing machine and digital microscope were used to measure the changes in weight loss and surface roughness respectively. One-way ANOVA and pair-wise Tukey's post-hoc tests were used for data analysis (α = 0.05). Results: Nano-SiO2 modified teeth material demonstrated a significant increase in weight loss in comparison conventional artificial acrylic teeth material (p ˂ 0.05) while nanoAl2 O3 modified teeth material demonstrated non-significant increase in weight loss except for 0.5% subgroup (p ˂ 0.05). There is no significant differences regarding roughness change after wear simulation among all tested groups (p > 0.05). Conclusion: Nano-Al2 O3 nanoparticles exhibit less negative effect than nano-SiO2 so; it could be used with caution if necessary. (AU)

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The demand for hydrophobic polymer-based protective coatings to impart high corrosion resistance has increased recently. The increase of the hydrophobicity in a hybrid coating is a new challenge, for that reason and in order to protect a metallic surface of oxidant agents, a poly (methyl methacrylate) (PMMA) coating with the addition of a different amount of silicon dioxide (SiO2) was developed. The hybrid coating was applied on a sample of stainless steel AISI 304 by the dip-coating method. The characterization of the coatings was determined by electrochemical impedance spectroscopy and with a scanning electrochemical microscopy. The best coatings were PMMA and PMMA + SiO2 0.01% that exhibits a real impedance in the Nyquist diagram of 760 and 427,800 MΩ⋅cm2, respectively, and the modulus of the real impedance in the Bode diagram present values of 2.2 × 108 and 3.3 × 108 Ω⋅cm2. Moreover, the phase angle presents constant values around 75° to 85° and 85° for the PMMA and PMMA + SiO2 0.01%, respectively. Moreover, the values of the real resistance for the PMMA + SiO2 0.01% coating present values in the order of Mega-ohms despite the coating exhibits an artificial defect in their surface. The contact angle test showed that the hydrophobicity of the hybrid PMMA + SiO2 0.01% coating is higher than that of the pure PMMA coatings. The hybrid PMMA + SiO2 coatings developed in this work are a very interesting and promising area of study in order to develop efficient products to protect metallic surfaces from corrosion phenomenon.

RESUMO

SiO2NPs as an inhibitor of pepsin enzyme for treatment of gastro-esophageal reflux disease (GERD) were investigated. Silicon dioxide nanoparticles (pepsin coated SiO2NPs) are among the safest nanoparticles that can be used inside the human body. The activity of pepsin before and after the addition of certain amounts of the NPs to the reaction mixture was measured spectrophotometrically. Furthermore, these experiments were repeated at different temperatures, different weights of NPs, and different ionic strengths. The kinetic parameters (Km & Vmax) of the pepsin-catalyzed reactions were calculated from the Lineweaver-Burk plots. The results showed that there is a significant reduction of pepsin activity by SiO2NPs (Vmax of free pepsin = 4.82 U and Vmax of the immobilized pepsin = 2.90 U). The results also indicated that the presence of ionic strength causes remarkable reduction of pepsin activity. It can be concluded the best condition for inhibition of pepsin activity is by using a combinationof SiO2NPs and high concentration NaCl at 37 °C.

Se usaron nanopartículas de dióxido de silicio como inhibidores de la pepsina para el tratamiento del reflujo gastroesofágico (GERD). Estas nanopartículas (SiO2NPs recubiertas de pepsina) son unas de las más seguras y pueden usarse en el cuerpo humano. Se midió a través de espectrofotometría la actividad de la pepsina antes y después de añadir cierta cantidad de NPs a la mezcla reactante. Adicionalmente, se repitieron estas pruebas a diferentes temperaturas, variando el peso de las NPs y la fuerza iónica. Se calcularon los parámetros cinéticos (Km y Vmax) de las reacciones catalizadas con pepsina a través de las gráficas de Lineweaver-Burk. Los resultados mostraron que, usando SiO2NPs (Vmax de pepsina libre = 4.82 U y Vmax de pepsina inmovilizada = 2.90 U) y a través de la presencia de fuerza iónica, la actividad enzimática se reduce significativamente. Se concluye que la mejor condición para inhibir la actividad enzimática es usando una combinación de SiO2NPs y una alta concentración de NaCl a 37 °C.

Foram usadas nanopartículas de dióxido de silício como inibidores da pepsina para o tratamento do refluxo gastroesofágico (GERD). Estas nanopartículas (SiO2NPs cobertas de pepsina) são uma das mais seguras e podem usar-se no corpo humano. Foi medida a atividade da pepsina mediante espectrofotometria antes e depois de agregar certa quantidade de NPs à mistura de reação. Adicionalmente, repetiram-se estas provas a diferentes temperaturas, variando o peso das NPs e a força iónica. Foram calculados os parâmetros cinéticos (Km e Vmax) das reações catalisadas com pepsina a través das gráficas de Lineweaver-Burk. Os resultados mostraram que, usando SiO2NPs (Vmax de pepsina livre = 4.82 U e Vmax de pepsina imobilizada = 2.90 U) e a través da presença de força iónica, a atividade enzimática se reduze significativamente. Foi concluído que a melhor condição para inibir a atividade enzimática é usando uma combinação de SiO2NPs e uma alta concentração de NaCl a 37 °C.

RESUMO

In the present study, SiO2 nanoparticles functionalized with 3-(2-aminoethylamino)propyl group (SiNP-AAP) were used, for the first time, to covalently bond rose bengal (SiNP-AAP-RB) or 9,10-anthraquinone-2-carboxylic acid (SiNP-AAP-OCAq). The functionalized SiNP were characterized by: Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM); elemental analysis (CHN) for determination of the dye concentration; FTIR and UV-vis diffuse reflectance (DR-UV-vis) and a surface area study (BET). The functionalized SiNPs were applied in photodynamic therapy (PDT) against lung cancer cell lines. The evaluated cytotoxicity revealed 20-30% cell survival after 15min of PDT for both materials but the OCAq concentration was half of the RB nanomaterial. The phototoxicity was mainly related to oxidative stress generated in the cellular environment by singlet oxygen and by hydrogen abstraction as confirmed by the laser flash photolysis technique. The unprecedented results indicate that SiNP-AAP-OCAq is a possible system for promoting cell apoptosis by both type I and type II mechanisms.

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