RESUMO
The current study aims to characterize and evaluate the photocatalytic treatability of the "red water" effluent from a Brazilian TNT production industry. Analyses were performed using physical, chemical, spectroscopic and chromatographic assays, which demonstrated that the effluent presented a significant pollution potential, mainly due to COD, BOD, solids and to the high concentration of nitroaromatic compounds such as 1,3,5-trinitrobenzene, 1-methyl-2,4-dinitrobenzene, 2-methyl-1,3-dinitrobenzene, 2,4,6-trinitrotoluene-3,5-dinitro-p-toluidine and 2-methyl-3,5-dinitro-benzoamine. By a modified sol-gel and a dip-coating technique, it was possible to obtain a TiO2 film on borosilicate glass substrate which functional composition and microstructure were characterized by infrared spectroscopy and scanning electron microscopy. The evaluation of the photocatalytic treatability using borosilicate-glass-TiO2 demonstrated high degradation efficiency. In this context, a reduction of 32 and 100% for COD and nitroaromatic compounds, respectively, was observed. Although the proposed photocatalytic process has found difficulties in reducing the content of organic matter and effluent color in the red water, its potential for degrading refractory chemical compounds such as the nitroaromatic ones enables it to be used as tertiary treatment.
Assuntos
Derivados de Benzeno , Nanoestruturas , Silicatos , Titânio , Trinitrotolueno , Poluentes Químicos da Água , Animais , Derivados de Benzeno/química , Derivados de Benzeno/toxicidade , Análise da Demanda Biológica de Oxigênio , Brasil , Catálise , Cor , Daphnia/efeitos dos fármacos , Vidro , Resíduos Industriais , Nanoestruturas/química , Nanoestruturas/efeitos da radiação , Silicatos/química , Silicatos/efeitos da radiação , Titânio/química , Titânio/efeitos da radiação , Testes de Toxicidade Aguda , Raios Ultravioleta , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Poluentes Químicos da Água/toxicidadeRESUMO
Anatase TiO2 is a promising photocatalyst due to its chemical stability, non-toxic characteristics, notable UV light absorption as well as photo-corrosion resistance and oxidative properties. Surface area and TiO2 dispersion quality are important factors that affect photoactivity of TiO2:SiO2 nanocomposites. In order to improve these factors, TiO2 nanoparticles were immobilized on mesoporous silica substrate through the polymeric precursors method, obtaining the nanocomposites in a simple routine. The TiO2 resin was synthesized by the polymeric precursors method and different resin thickness (0.5; 1.0; 2.0; 3.5; 5.0 nm) on silica were synthesized by calcination during 4 hours at 450 degrees C in pH 1.5. The selected pH for immobilization ensured adhesion of TiO2 nanoparticles onto the silica substrate surface. X-Ray Diffraction patterns indicate that all samples were predominantly anatase phase and immobilization improved surface area. Ametryn kinetic evaluation presents better results for SAM 3.5 and SAM 0.5. The results show that difference in TiO2 loading, surface area and crystallinity of samples are factors that influence photocatalytic efficiency.
Assuntos
Nanoestruturas/química , Nanoestruturas/ultraestrutura , Fotoquímica/métodos , Dióxido de Silício/química , Titânio/química , Triazinas/química , Catálise , Luz , Teste de Materiais , Nanoestruturas/efeitos da radiação , Tamanho da Partícula , Polímeros/química , Dióxido de Silício/efeitos da radiação , Titânio/efeitos da radiação , Triazinas/isolamento & purificação , Triazinas/efeitos da radiaçãoRESUMO
We have systematically studied the single-particle states in quantum rings produced by a set of concentric circular gates over a graphene sheet placed on a substrate. The resulting potential profiles and the interaction between the graphene layer and the substrate are considered within the Dirac Hamiltonian in the framework of the envelope function approximation. Our simulations allow microscopic mapping of the character of the electron and hole quasi-particle solutions according to the applied voltage. General conditions to control and operate the bound state solutions are described as functions of external and controllable parameters that will determine the optical properties ranging from metallic to semiconductor phases. Contrasting behaviors are obtained when comparing the results for repulsive and attractive voltages as well as for variation of the relative strength of the graphene-substrate coupling parameter.
Assuntos
Grafite/química , Grafite/efeitos da radiação , Modelos Químicos , Modelos Moleculares , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Simulação por Computador , Campos Eletromagnéticos , Substâncias Macromoleculares/química , Substâncias Macromoleculares/efeitos da radiação , Teste de Materiais , Conformação Molecular/efeitos da radiação , Nanoestruturas/efeitos da radiação , Tamanho da Partícula , Propriedades de Superfície/efeitos da radiaçãoRESUMO
This paper describes the development of ZnO nanoparticles by a chemical method, to test them in the photocatalysis of the degradation of textile dyes, using Rhodamine B (RhB) as a probe reaction. The samples were submitted to different heat treatments in order to observe the annealing effects on the photocatalytical properties, surface decontamination and the consequent particle change, in terms of crystallinity. The as-prepared samples (ZOA) correspond to a metastable phase (oxy or hydroxy zinc acetate) and post annealing leads to ZnO crystallization. In spite of the XRD patterns showing only the ZnO phase for heat treatment at 100 degrees C, FTIR data show that carboxylate groups remains attached to the ZnO surface up to 300 degrees C. Up to 300 degrees C the presence of these carboxylate groups, provided by the synthesis method, showed to be more relevant to photoactivity than the specific surface area. At higher temperatures, crystallinity becomes the dominant factor and an increasing of crystallinity favors the photoactivity.
Assuntos
Cristalização/métodos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Óxido de Zinco/química , Óxido de Zinco/efeitos da radiação , Catálise , Dureza , Temperatura Alta , Luz , Teste de Materiais , Conformação Molecular/efeitos da radiação , Nanoestruturas/efeitos da radiação , Tamanho da Partícula , Propriedades de Superfície/efeitos da radiaçãoRESUMO
Nanodiamond thin films were deposited onto Si (100) substrates using Tequila as precursor by pulsed-liquid injection chemical vapour deposition at 850 degrees C. Some samples were exposed to beta particle irradiation in the dose range from 100 to 1600 Gy, and it was found that the thermoluminescence (TL) response is a linear function of dose. The glow curve displays two maxima centred at 170 and 350 degrees C, which does not shift when dose changes, indicating that first-order kinetics processes are involved. From the results, it is concluded that the new nanodiamond films are promising high-dose TL dosimeters.
Assuntos
Diamante/química , Diamante/efeitos da radiação , Nanoestruturas/química , Nanoestruturas/efeitos da radiação , Dosimetria Termoluminescente/métodos , Relação Dose-Resposta à Radiação , México , Doses de RadiaçãoRESUMO
Raman scattering is used to study the effect of low energy (90 eV) Ar(+) ion bombardment in graphene samples as a function of the number of layers N. The evolution of the intensity ratio between the G band (1585 cm(-1)) and the disorder-induced D band (1345 cm(-1)) with ion fluence is determined for mono-, bi-, tri- and â¼50-layer graphene samples, providing a spectroscopy-based method to study the penetration of these low energy Ar(+) ions in AB Bernal stacked graphite, and how they affect the graphene sheets. The results clearly depend on the number of layers. We also analyze the evolution of the overall integrated Raman intensity and the integrated intensity for disorder-induced versus Raman-allowed peaks.
Assuntos
Grafite/química , Grafite/efeitos da radiação , Modelos Químicos , Nanoestruturas/química , Nanoestruturas/efeitos da radiação , Análise Espectral Raman/métodos , Simulação por Computador , Íons Pesados , Substâncias Macromoleculares/química , Substâncias Macromoleculares/efeitos da radiação , Teste de Materiais , Conformação Molecular/efeitos da radiação , Nanoestruturas/ultraestrutura , Tamanho da Partícula , Doses de Radiação , Propriedades de Superfície/efeitos da radiaçãoRESUMO
The objective of this work was to verify if hydrophilic gels containing benzophenone-3 loaded nanocapsules (HG-NCBZ3) could improve the sunscreen in vitro effectiveness against UVA radiation and its photostability compared to a conventional hydrogel containing the free sunscreen (HG-BZ3). In parallel, the immune response of the nanostructured system was evaluated by mouse ear swelling test and the local lymph node assay. The nanocapsules were prepared by interfacial deposition of poly(epsilon-caprolactone) and characterized in terms of particle size, polydispersity index, zeta potential, drug content and encapsulation efficiency. HG-NCBZ3 UV scans showed higher absorption intensity values than HG-NCplacebo, prepared using unloaded nanocapsules. Films of the gels were irradiated with UVA light and the BZ3 recovery was evaluated by HPLC. BZ3 recovery decreased from 100% to 29% for HG-BZ3 and to 56% for HG-NCBZ3 after 13 h. After wavelength scans within 13 h, the relative areas under the curves (AUC) decreased from 1.00 to 0.62 for HG-BZ3 and remained constant for HG-NCBZ3. Sensitization assay showed that stimulation indexes lower than 3 for all the hydrogel samples. Formulations did not induce increases higher than 10% in ear swelling, indicating that the hydrogels did not cause cutaneous sensitization in mice. The nanoencapsulation improved both the photostability and the effectiveness of BZ3 compared to the non-encapsulated sunscreen and the topical application of free and nanoencapsulated BZ3 did not produce significant allergy response in mice.
Assuntos
Portadores de Fármacos/química , Toxidermias/imunologia , Nanoestruturas/química , Protetores Solares/administração & dosagem , Animais , Portadores de Fármacos/efeitos adversos , Portadores de Fármacos/efeitos da radiação , Toxidermias/diagnóstico , Luz , Teste de Materiais , Camundongos , Nanoestruturas/efeitos adversos , Nanoestruturas/efeitos da radiação , Pós , Protetores Solares/efeitos adversosRESUMO
The aim of this study was to prepare and to evaluate the physicochemical and in vitro drug release characteristics of different nanostructured systems containing clobetasol propionate (CP): CP-loaded polymeric nanoparticles (nanocapsules and nanospheres) and CP-loaded nanoemulsion. Physicochemical characteristics of the formulations were monitored up to 9 months after preparation by means of drug content, encapsulation efficiency, mean size, polydispersity index, pH, and zeta potential. In vitro drug release studies were carried out using the dialysis bag method. Photostability of CP-loaded nanoparticles was evaluated by their exposition to UVA radiation. All formulations presented nanometric mean size (140-220 nm), polydispersity index below 0.25, neutral pH values, negative zeta potential and encapsulation efficiency close to 100%. All these parameters, except pH, remained unchangeable up to 9 months of storage at room temperature for CP-loaded nanocapsules. On the other hand, CP-loaded nanospheres and nanoemulsion showed an increase in their mean size, as well as in polydispersity index under storage (after 3 and 6 months, respectively). In vitro drug release studies showed a controlled release of CP from nanoparticles (nanocapsules > nanospheres > nanoemulsion) with a low burst release. Photostability of CP under UVA radiation was improved by its incorporation into nanoparticles (nanocapsules > nanoemulsions > nanospheres).
Assuntos
Clobetasol/química , Preparações de Ação Retardada/química , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Água/química , Clobetasol/efeitos da radiação , Preparações de Ação Retardada/efeitos da radiação , Difusão , Estabilidade de Medicamentos , Luz , Teste de Materiais , Nanoestruturas/efeitos da radiação , Tamanho da PartículaRESUMO
Poly(acryloxyethyl-trimethylammonium chloride-co-2-hydroxyethyl methacrylate) [poly(Q-co-H)]/ sodium alginate gel (Ca2+) [AlgNa]/poly-l-lysine [PLL] films have been prepared on a mica surface. The structural arrangement and elasticity of the polyelectrolyte complexes have been studied with nanoscale resolution using Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM). The elastic contrast on the AlgNa surface is indicative of the formation of a biopolymer network. On the AlgNa film, the surface morphology is mostly characterized by areas with rounded beads (approximately =150 nm in diameter) and polymer strands. Flatter, more homogenous surface regions are also present, presumably related to outdiffused PLL. Incorporation of the poly(Q-co-H) layer results in an increased compactness of the film, and an enhancement of the previous AlgNa topographic features. The unique subsurface sensitivity provided by UFM allows us to resolve the elastic bonding distribution in the buried biopolymer network by imaging from the poly(Q-co-H) overlayer. Provided the biocompatibility of the resulting polyelectrolyte complex film, we propose this system as a novel scaffold for bioengineering applications. The results we present demonstrate the potential of UFM to get insight in the elastic behavior of encapsulated bionetworks.
Assuntos
Eletrólitos/química , Eletrólitos/efeitos da radiação , Membranas Artificiais , Microscopia de Força Atômica/métodos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Sonicação/métodos , Teste de Materiais , Nanoestruturas/efeitos da radiação , Propriedades de SuperfícieRESUMO
Aspects of the growth mechanism of silver triangular nanoplates by photochemical synthesis were addressed by detailed characterization using ultraviolet-visible spectroscopy, electron microscopies, and atomic force microscopy. The quantitative characterization of their size and thickness during the reaction showed that both increase with time as well as the aspect ratio. Samples irradiated by different wavelengths showed that the size of the nanoplates can be controlled by the incident wavelength and it is responsible for the increase of the aspect ratio, but the thickness seems to be determined by the conditions of the initial seeds. It was also found that irradiation with wavelength out of resonance with the surface plasmon of the initial seeds leads to a slower kinetics. The results suggested that rational exploration of the synthesis parameter such as the type of the initial seeds in combination with the wavelength irradiation may lead to a broader type of particles already obtained by this method.