Among the different chemical compounds used to prevent the aggregation and to control the size of silver nanoparticles, the aminosilanes are interesting because they can simultaneously act as stabilizing and coupling agents. The aim of this study was to investigate the effects of different concentrations of an aminosilane on the synthesis of silver nanoparticles. The functionalized nanoparticles were characterized using UV–vis spectrophotometry, transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), and zeta (ζ) potential. Antibacterial assays were also performed. According to the results, increasing the concentration of the aminosilane produced smaller, less dispersed, and more stable silver nanoparticles. Besides the effective antibacterial activity verified in all the concentrations tested, a significant influence on the kinetics of bacteria annihilation was also observed when aminosilane was used in a concentration dependent fashion. These findings indicated the important effects of aminosilane concentrations in controlling the size and stability of the colloids, as well as the rate of silver ions releasing from nanoparticles.

The correct manipulation of particle size distribution in suspension polymerization is important because particle size determines the product applicability and processability. Methyl methacrylate suspension polymerization was studied in order to determine the effect of operational parameters in manipulating the particle size distribution (PSD) while keeping suspension stability. The effects of stirring rate, stabilizer concentration, and stabilizer addition time were evaluated on particle size distribution, Sauter mean diameter, and suspension stability. Stabilizer concentration affected particle sizes but at the expense of system stability as low amounts of stabilizer led to uncontrolled coagulation of the particles. Changing the stirring rate was efficient in manipulating particle sizes although its increase led to the broadening of the PSDs while reducing the Sauter mean diameter. The moment stabilizer was fed has shown to be a very efficient way to manipulate the PSD as delaying the stabilizer addition increased the Sauter mean diameter and narrowed the distributions. However, there was a limit in increasing the addition time as adding the stabilizer at higher conversions compromised the suspension stability.

RESUMOQueimaduras causam lesões do revestimento epitelial, a partir de um agente externo, podendo variar desde uma pequena bolha flictena até formas mais graves, capazes de desencadear respostas sistêmicas. O uso de curativos contendo substâncias cicatrizantes e antimicrobianas é uma opção para terapia local. Os curativos de nanocelulose bacteriana (BNC) já demonstraram seu grande potencial de aplicação devido às suas propriedades como alto teor de pureza, alto poder de absorção de água e ótima adaptabilidade biológica. A incorporação de metais na membrana de nanocelulose é bastante promissora. Nanopartículas de prata (NPAgs) têm sido objeto de vários estudos devido às suas propriedades antibacterianas; nitrato de cério, Ce(NO 3 ) 3 , por sua vez, aumenta a eficácia no tratamento por apresentar propriedades imunomoduladoras. O objetivo deste trabalho foi sintetizar e caracterizar membranas de nanocelulose bacteriana funcionalizadas com nitrato de cério e nanopartículas de prata visando aplicação no tratamento de pele humana lesionada por queimadura. O comportamento térmico, interações entre a BNC, Ce(NO 3 ) 3 e NPAg, bem como a morfologia, capacidade de retenção de água, reidratação e potencial antimicrobiano foram analisadas por termogravimentria (TGA), microscopia eletrônica de varredura (MEV), análise de conteúdo de capacidade de água, capacidade de reidratação e atividade antimicrobiana. A membrana formada pela incorporação de Ce(NO 3 ) 3 e NPAgs simultaneamente, e submetida ao tratamento térmico, conservou as propriedades térmicas de ambos os materiais, assim como também boa capacidade de reidratação e um potencial de redução microbiana de 98% para Staphylococcus aureus. A análise de MEV apresentou alteração na morfologia, redução de poros e a presença de partículas, o que sugere adequada incorporação dos compostos. Palavras-chave:Antimicrobianos, Nanocelulose bacteriana, Gluconacetobacter hansenii, nanotecnologia. ABSTRACTBurns cause lesions of the epithelial lining, from an external agent, and can range from a small injury to more severe forms, capable of triggering systemic responses. The use of dressings containing healing and antimicrobial substances are options for local therapy. Bacterial nanocellulose (BNC) dressings have already demonstrated their great potential due to their properties such as high purity, high water absorption capacity and optimum biological adaptability. The incorporation of metals in the nanocellulose membrane is quite promising. Silver nanoparticles (AgNPs) have been studied because of their antibacterial properties; cerium nitrate, Ce(NO 3 ) 3 , on the other hand, increases the efficacy of the treatment because of its immunomodulatory properties. The objective of this work was to synthesize and characterize bacterial nanocellulose membranes functionalized with cerium nitrate and silver nanoparticles aiming the treatment of human skin that has been subject to burning injuries. Thermal behavior, interactions between BNC, Ce(NO 3 ) 3 and AgNP, as well as morphology, water retent...

The present work investigated in detail the effects of stirring rate, temperature, and the feed flow rate of the reducing agent on the properties of functionalized silver nanoparticles produced in a semi‐batch reactor. In addition, a specific formulation was tested in chemical reactors with different volumes to demonstrate the scalability of the process. The colloids were characterized using UV‐Vis spectrophotometry, transmission electron microscopy, X‐ray diffraction, and zeta potential. The scale up of the process was successfully performed, producing similar results at larger scales to those obtained in the small scale. Standardized antibacterial assays showed that fabric and polymer samples functionalized with the produced silver colloids presented outstanding antibacterial activity. These findings demonstrated that silver nanoparticles with specific properties and promising antibacterial applications can be rapidly produced through suitable tuning of the process parameters regardless the scale of production.

The importance of the preservation of water resources has resulted in the application of technologies such as nanostructured materials, which are able to minimize the impact associated with water contamination. This work evaluated the application of polyamide-66 (PA) pellets functionalized with silver nanoparticles (AgNPs) at polymer mass percentages of 0.05, 0.10 and 0.50% to disinfect of drinking water. Studies were carried out in three stages. The first stage was the synthesis of the silver nanoparticles by using silver nitrate as a metal precursor and sodium borohydrate as a reduction agent. The colloidal dispersion was characterized by UV-Vis spectrophotometry and transmission electron microscopy (MET). Afterwards, the nanostructures were incorporated into a polyamide-66 polymeric matrix. In the second stage, the silver ions leached from the polymer matrix in the water after a three-hour period were quantified in order to evaluate the limit established by Conama Resolution 357/2005, which imposes a concentration limit of 0.010 mg L-1. The best results were obtained with the application of 0.05% AgNPs in the polymeric matrix, yielding an average concentration of silver ions lixiviated of 0.008 mg L-1. The last step comprised the quantification of the antibacterial activity of the polymer matrix containing 0.05% of AgNPs against the microorganism E. coli using the Standard Test Method for Determining the Antimicrobial Agents Under Dynamic Contact Conditions. The samples containing 0.05% of AgNPs exhibited an antibacterial reduction of 97.89% after 24 h of incubation under stirring at room temperature (25°C).

The present work developed an experimental and simulation study to evaluate the influence of some operational conditions and mold design on the efficiency of an injection process used to produce polystyrene parts. The software SolidWorks Plastic was used to simulate the injection process and assess the performance of the mold considering the absence and the presence of venting. Experimental results obtained by varying the injection pressure, injection temperature as well as the mold temperature were used to validate the simulation data generated considering both mold designs. The findings revealed air entrapment at the end of the mold cavity and low process efficiency when the mold was operated with no venting, regardless the processing conditions. Simulation results indicated a remarkable increase of the process efficiency when vents were included on the parting line of the mold. In addition, the range of processing conditions which led to the highest process efficiency was virtually identified and tested in the real modified mold (with venting system). The findings revealed that the injection cycle time reduced in approximately 35% and the waste generation diminished from 65% to less than 1% when venting was included in the mold design and the optimal operational conditions were used.

Continuous polymerization processes have advantages when large amounts of product are required; moreover, higher quality can be obtained because of the elimination of variability between batches. Tubular reactors are economically attractive because of their simple geometry and high heat exchange area; however, they are not commonly used for commercial purposes, mainly because of the large radial profiles. This study elucidates the operation of this kind of reactors in three different ways: first a detailed two-dimensional mathematical model was developed, in which a complete visualization of all axial and radial profiles is possible, allowing a safe analysis at different operating conditions. In a second step a system composed of a continuously stirred tank reactor in series with a tubular reactor was used. A reduction in radial profiles can be clearly observed when prepolymerization is taken into account, improving both the homogeneity and the end properties of the polymer. In a third approach neural networks (NNs) were used in parallel with a one-dimensional model. The objective of this study was to illustrate how NNs can improve the prediction capability when it is not possible to build a reliable model because of uncertainties in parameters and incomplete knowledge of the system. The NNs generated good results, showing that the hybrid model was able to accurately simulate the reactor, even when uncertainty in kinetic and diffusional parameters was imposed to the model.

In this work, silver nanoparticles were incorporated in four different concentrations into rice husk ash (RHA) to promote an antimicrobial effect. The suspension was magnetic stirred and dried at 80°C for 24 h. The samples were characterized by scanning electron microscopy (SEM), specific surface area and zeta potential measurements. Microbiological analyses were conducted test the efficiency of the material in the elimination of the bacteria Escherichia coli. SEM results revealed a homogeneous dispersion of silver nanoparticles on the substrate, surface area values similar to those found in the literature and effective antimicrobial activity at low silver concentration.