Antimicrobial substances may be used to reduce hospital infections and inhibit food contamination, thus ensuring the safety and well being of humans. The objective of this study was to evaluate the antimicrobial activity of the polymeric nanocomposites polydimethylsiloxane (PDMS) embedded with two types of fillers based on titanium dioxide (commercial TiO 2 P25 versus TiO 2 via facile Microwave-assisted hydrothermal-MAH synthesis) and graphene oxide (GO). The nanocomposites were prepared using different compositions, concentrations, and functionalizations (PDMS/TiO 2 /GO; PDMS/TiO 2 and PDMS/GO). The antimicrobial activity of the samples was evaluated for different treatments on Candida albicans, Staphylococcus aureus, and Enterococcus faecalis, by a modified direct contact test (mDCT). The samples were also evaluated on surface morphology and the roughness as a function of active particles insertion by atomic force microscopy (AFM). Most of the PDMS films whose polymer was embedded with GO and hydrothermal TiO 2 showed the highest inhibition growth of bacteria and Candida over 24 h. After 24 h, F, J, and H samples showed the best antibacterial activity, whereas E showed the best antifungal activity. The results indicated that the nanocomposites PDMS/GO/TiO 2 MAH and PDMS/GO sample enhanced antimicrobial activity in the treatments tested, therefore they were functional for contaminant reduction.
In this work, a feasible,
fast, clean and efficient microwave-induced
combustion method for direct synthesis of LiNbO3 in solid
phase was developed. X-ray powder diffraction studies showed that
quasi-pure Li–Nb–O phases, such as LiNbO3 and Li3NbO4, or mixtures of LiNbO3, Li3NbO4 and LiNb3O8, could be successfully synthesized. The resulting powders were efficiently
applied as catalysts under ambient conditions in the oxidation process
of aniline using hydrogen peroxide as oxidant. The proposed method
was performed in a commercial system using high-pressure quartz vessels,
which allowed safe control of the reactions–that usually occurs
in less than 1 min. The results showed that the reaction conditions
as well as the structural and morphological characteristics of the
catalyst influenced the aniline oxidation process. Therefore, the
present method for the preparation of LiNbO3 described
herein, displayed many advantages when compared to conventional combustion
methods, such as the physical characteristics of the obtained compound.
Moreover, this new approach is considerably faster, safer and cleaner
than other traditional procedures described in literature for LiNbO3 synthesis. This new microwave-induced combustion method is
less time-consuming, saves energy, as well as affording the stoichiometric
formation of inorganic particles.
Composite of PZT (lead zirconate titanate) and PLZT (lead lanthanum zirconate titanate) along an organic, renewable, conductive, and flexible matrix have been developed. The conductive paper was obtained through the reaction between the cellulose extracted from banana stem and functionalized MWCNT. This reaction was made in the presence of hydrogen (from H2SO4), which reduced the size of the cellulose by acid hydrolysis and promotes the interaction between its hydroxyls and the carboxyl groups of nanotubes. Afterward, the PZT particles were synthesized and grown up on the conductive paper by microwaves-assisted hydrothermal synthesis (MHS). The composite material was characterized by structure and morphology. Moreover, gas-sensing in the presence of methanol and electrical resistance as a function of temperature were also investigated. In this way, a simple, low-cost and successful synthesis was reported. Also, a promising flexible was obtained using a chemical transformation process from banana residue as source of cellulose.
This study aimed to develop a flexible carbon fiber/oxide layer coating composite with improved electrical properties for use in electronic devices. For this, lead titanate zirconate, cerium-doped lead titanate zirconate, and yttrium-doped lead titanate zirconate were grown on carbon fibers via microwaves-assisted hydrothermal synthesis. The performed synthesis presented advantages when compared to conventional routes used in nanoparticles obtention since it allows the morphological control even at low temperatures. Carbon fiber was selected as substrates due to their thermal stability, excellent mechanical properties, chemical characteristics that allow the creation of functional groups on their surface, and good microwave radiation absorption. The composites were investigated by X-ray diffraction, spectroscopy Raman, and field emission scanning electron microscopy. The electrochemical evaluations were made by four-point probe method, cyclic voltammetry, and electrochemical impedance spectroscopy. The syntheses were successful and the carbon fiber coated with lead zirconate titanate had promissory results, with a boost in the electrical conductivity and better capacitance behavior when compared to the undoped carbon fiber, showing to be a good alternative for applications in electrical devices.
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