RESUMO
AIM: We evaluated the effects of the incorporation of zinc oxide (ZnO) nanoparticles in a mesoporous matrix, aiming to improve the textural, structural and morphological properties and verify their safety so that they can be applied in sunscreen cosmetics. MATERIALS AND METHODS: ZnO nano-particles were incorporated into an ordered mesoporous silica matrix known as Santa Barbara Amorphous-15 (SBA-15), using post-synthesis methodology. The resulting nanocomposites were characterized using X-ray diffraction, small angle X-ray scattering, N2 adsorption-desorption isotherms, Fourier transform infrared spectroscopy, scanning electron microscopy and predicted in vitro sun protector factor (SPF) estimation. Effectiveness and safety were evaluated by antimicrobial activity, in vitro cell toxicity and non-invasive multi-photon tomography with fluorescence lifetime imaging. RESULTS: The structure of the nanocomposites was similar to that of SBA-15, with little perturbation caused by ZnO incorporation. Nanocomposites had an increased in vitro SPF, reduced cytotoxic activity and favourable antimicrobial properties compared to ZnO. ZnO:SBA-15 nanocomposites exhibited no measurable toxicity when applied to human skin in vivo. CONCLUSION: Due to their suitable physicochemical properties and improved safety compared to bare ZnO nanoparticles, the ZnO:SBA-15 nanocomposites show promise for use in cosmetic applications.
Assuntos
Composição de Medicamentos/métodos , Nanocompostos/administração & dosagem , Dióxido de Silício/administração & dosagem , Absorção Cutânea/efeitos dos fármacos , Protetores Solares/administração & dosagem , Óxido de Zinco/administração & dosagem , Adulto , Animais , Células 3T3 BALB , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/fisiologia , Relação Dose-Resposta a Droga , Portadores de Fármacos/administração & dosagem , Portadores de Fármacos/síntese química , Portadores de Fármacos/metabolismo , Combinação de Medicamentos , Humanos , Camundongos , Nanocompostos/química , Dióxido de Silício/síntese química , Dióxido de Silício/metabolismo , Absorção Cutânea/fisiologia , Protetores Solares/síntese química , Protetores Solares/metabolismo , Testes de Toxicidade Aguda/métodos , Difração de Raios X/métodos , Adulto Jovem , Óxido de Zinco/síntese química , Óxido de Zinco/metabolismoRESUMO
ZnO samples were prepared by sol-gel method applying a factorial design in order to improve the photocatalytic properties of the semiconductor oxide in the NO photooxidation reaction. The concentrations of zinc acetate and ammonium hydroxide were selected as critical variables in the synthesis of ZnO. Nine samples of ZnO were obtained as product of the factorial design and were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy, and N2 adsorption-desorption isotherms. The photocatalytic activity of ZnO samples was associated with the physical properties developed by each sample according to its respective conditions of synthesis. Some photocatalytic reaction parameters, such as mass of photocatalyst, irradiance, and relative humidity, were modified in order to evaluate its effect in the photocatalytic conversion of NO. As a relevant point, the relative humidity played an important role in the increase of the selectivity of the NO photooxidation reaction to innocuous nitrate ions when ZnO was used as photocatalyst.
Assuntos
Poluentes Ambientais/química , Óxido Nítrico/química , Processos Fotoquímicos , Óxido de Zinco/química , Óxido de Zinco/síntese química , Adsorção , Hidróxido de Amônia/química , Catálise , Poluentes Ambientais/isolamento & purificação , Óxido Nítrico/isolamento & purificação , Oxirredução , Acetato de Zinco/químicaRESUMO
ABSTRACT ZnO nanoparticles (NPs) were synthesized via a green biochemical method using Corymbia citriodora leaf extract as a reducing and stabilizing agent. The biosynthesized ZnO NPs were characterized by SEM and XRD. An electrochemical H2O2 biosensor was fabricated by modification of a glassy carbon electrode using our proposed ZnO NPs. The electrochemical sensor showed excellent detection performance towards trace amounts of H2O2, demonstrating that it could potentially be used in clinical applications.
Assuntos
Óxido de Zinco/síntese química , Peróxido de Hidrogênio/classificação , Extratos Vegetais/efeitos adversos , Folhas de Planta , MyrtaceaeRESUMO
In this work, nitrogen-doped ZnO material was synthesized by the sol-gel method using zinc acetate as the precursor and urea as the nitrogen source (15, 20, 25 and 30% wt.). For comparative purposes, bare ZnO was also prepared. The influence of N doping on structural, morphological, optical and photocatalytic properties was investigated. The synthesized catalysts were characterized by XRD, SEM-EDS, diffuse reflectance UV-Vis spectroscopy, BET and XPS analysis. The photocatalytic activity of N-doped ZnO catalysts was evaluated during the degradation of a mixture of herbicides (2,4-D and picloram) under visible radiation ≥400 nm. The photo-absorption wavelength range of the N-doped ZnO samples was shifted to longer wavelength compared to those of the unmodified ZnO. Among different amounts of dopant agent, the 30% N-doped ZnO material showed higher visible-light activity compared with pure ZnO. Several degradation by-products were identified by using HPLC and ESI-MS/MS. The enhancement of visible photocatalytic activity of the N-doped ZnO semiconductor could be mainly due to their capability in reducing the electron-hole pair recombination.
Assuntos
Ácido 2,4-Diclorofenoxiacético/química , Herbicidas/química , Nitrogênio/química , Processos Fotoquímicos , Picloram/química , Óxido de Zinco/química , Óxido de Zinco/síntese química , Catálise , Técnicas de Química SintéticaRESUMO
A family of anionic iron(III) porphyrins (FePor) was immobilized onto zinc oxide (ZnO) obtained by the in situ hydrothermal decomposition of zinc hydroxide nitrate, a layered hydroxide salt. The immobilization probably occurred via the interaction between the anionic charges on the porphyrins and the positively charged surface of the ZnO, in slightly acidic to neutral pH. The resulting solids were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRDP), Fourier transform infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR), and ultraviolet-visible spectroscopy (UV-Vis) (solid samples), which confirmed the formation of ZnO and the immobilization of the FePor. The prepared materials were employed as catalysts for the heterogeneous catalytic oxidation of cyclooctene, cyclohexane, and n-heptane, using iodosylbenzene as the oxygen donor. Good catalytic results were achieved for all the substrates, and selectivity for the alcohol was verified during the oxidation of alkanes. The reuse capacity of the solid catalyst was also investigated.