RESUMO Nanomateriais exibem propriedades que se aplicam nas mais variadas áreas, entre estas, na área da saúde e agrícola, nas quais as pesquisas vêm aumentando progressivamente. Neste trabalho sintetizamos nanopartículas de sílica não porosas dopadas com óxido de cobre (CuO) usando método de Stöber com pequenas modificações. Em adição, a atividade antimicrobiana destes compostos contra Staphylococcus aureus, Escherichia coli e Candida albicans foi avaliada. Primeiramente, o nanomaterial foi caracterizado por difração de raios-X para identificação da fase CuO na matriz de sílica, e espectroscopia no infravermelho por transformada de Fourier identificando as principais bandas do SiO2 e a funcionalização do CuO. Por fim, a morfologia das partículas foi observada por microscopia eletrônica de varredura a qual mostrou formação de nanopartículas esféricas com tamanho aproximado de 70 nm. As nanopartículas de sílica dopadas com CuO mostraram eficiência na inibição dos três tipos de microrganismos testados neste trabalho, formando halos de inibição entre 19,0 e 25,0 mm. Nos ensaios de adsorção usando azul de metileno, foi possível observar que a presença de CuO na superfície das nanopartículas de sílica modificou as características de adsorção, aumentando a capacidade e a cinética de adsorção e desta forma mostrando ser um nanomaterial com características interessantes para aplicações na agricultura e em diferentes áreas da saúde.

ABSTRACT Nanomaterials exhibit properties that apply in a wide range of area, including health and agriculture, where research is progressively increasing. In this work we synthesize non-porous silica nanoparticles doped with copper oxide (CuO) using Stöber's method with small modifications. In addition, the antimicrobial activity of these compounds against Staphylococcus aureus. Escherichia coli and Candida albicans was evaluated. First, the nanomaterial was characterized by X-ray diffraction to identify the CuO phase in the silica matrix, and Fourier transform infrared spectroscopy identifying the main SiO2 vibration bands and the CuO functionalization. Finally, the particle morphology was observed by scanning electron microscopy which showed formation of spherical nanoparticles size ~70 nm. CuO-doped silica nanoparticles showed efficiency in the inhibition of the three types of microorganisms tested in this work, forming inhibition halos between 19.0 and 25.0 mm. In the adsorption tests using methylene blue, it was possible to observe that the presence of CuO on the surface of the silica nanoparticles modified the adsorption characteristics, increasing the adsorption capacity and kinetics and thus showing to be a nanomaterial with interesting characteristics for applications in the agriculture and in different areas of health.

Resumo Os materiais antimicrobianos têm sido amplamente empregados como um meio eficaz de reduzir os riscos proporcionados aos seres humanos por fungos, bactérias e outros microrganismos. Estes materiais são essenciais em ambientes onde predominam a limpeza, o conforto e a higiene. Este estudo apresenta resultados preliminares do desenvolvimento de um material vítreo com propriedade bactericida, obtido pela incorporação de espécies iônicas de prata, através de reações de troca iônica. O vidro em pó foi submetido à troca iônica em um meio iônico contendo AgNO3 como fonte de íons de prata. Diferentes concentrações de AgNO3 no meio iônico e diferentes tamanhos de partícula do vidro foram utilizados no desenvolvimento das amostras. A análise microbiológica das amostras foi realizada empregando o método de disco-difusão para as espécies de bactéria Escherichia coli e Staphylococcus aureus. As amostras também foram submetidas à caracterização pelas técnicas microscopia eletrônica de varredura, espectroscopia de energia dispersiva de raios X, espectroscopia de absorção atômica e por difração de raios X. Os resultados mostraram que o efeito bactericida foi dependente da concentração de AgNO3 no meio iônico, mas não foi dependente do tamanho de partícula do vidro.

Abstract Antimicrobial materials have long been used as an effective means of reducing the risks posed to humans by fungi, bacteria and other microorganisms. These materials are essential in environments where cleanliness, comfort and hygiene are the predominant concerns. This work presents preliminary results for a bactericidal vitreous material that is produced by the incorporation of a silver ionic specimen through ionic exchange reactions. Powdered glass was submitted to ionic exchange in an ionic medium containing AgNO3 as silver ions source. Different AgNO3 concentrations in ionic medium and different particle sizes of the glass were used in the samples development. Microbiological analysis of the samples was made by disk diffusion method in the Escherichia coli and Staphylococcus aureus bacterium species. Samples were still submitted to SEM-EDS, atomic absorption and X-ray diffraction techniques. Results showed that the bactericidal effect was dependent on AgNO3 concentration in the ionic exchange medium, but was not dependent on the particle size of the glass.

This work evaluated the water absorption of glazed porcelain stoneware ceramic tiles using three different methods. Two methods were based on a procedure of boiling in water, specified by standards ISO 10545 and ASTM C373, and the third was the vacuum method proposed by the standard ISO 10545. The three products produced under the three different firing conditions were tested according to a 22 factorial design, with intervening factors of the boiling time and immersion time for the methods involving boiling, and of pressure and immersion time for the vacuum method. The maximum saturation of the plates was evaluated by helium gas pycnometry testing. The results showed that no sample saturation occurs in the boiling water absorption test performed according to the conditions established by standards ISO 10545 and ASTM C373. The values of open porosity, using the method of helium gas picnometry, showed absolute values of saturation higher than those presented by the water absorption measured according to the current standards. Thus, the results showed that the current methods for determining the water absorption of glazed porcelain stoneware ceramic tiles do not guarantee the complete saturation of the plates and, therefore, they are not able to correctly measure this property.