RESUMO
Graphene oxide (GO) microfibers with controlled and homogeneous shapes and tunable diameters were fabricated using the 3 dimensional (3D) hydrodynamic focusing concept on a microfluidic device. Thermal and microwave treatments are used to obtain reduced graphene oxide (rGO) microfibers with outstanding electrical properties, thus enabling the development of ionic liquid-gate field-effect transistors (FET) based on graphene derivative microfibers.
RESUMO
The purification process of graphene oxide (GO) is a key stage in the production of this two-dimensional material by the Hummers method. This step demands a large amount of water, energy and time. The inefficient removal of the contaminants present in GO may affect its properties and make it unfeasible for some applications, such as in the field of biology. Here, we develop a simple and efficient method for the purification of an aqueous GO dispersion based on a fluidic diffusion cell system with a porous nitrocellulose membrane. The effectiveness of the fluidic diffusion cell system was compared with that of traditional purification methods, such as dialysis and centrifugation. The proposed strategy achieves the best performance in the removal of the major contaminants (K(aq.)+, Na(aq.)+, Cl(aq.)-, SO4(aq.)2-, Mn(aq.)2+ and MnO2(s)), demanding â¼95% less water than dialysis and in a shorter time (â¼23 h). The system operates under flow conditions, with minimum handling by the operator and is able to select the GO flakes with bigger lateral dimensions. This work represents a simple and fast alternative for purification of GO dispersions that can be easily scaled-up.
RESUMO
Graphene oxide (GO) with their interesting properties including thermal and electrical conductivity and antibacterial characteristics have many promising applications in medicine. The prevalence of resistant bacteria is considered a public health problem worldwide, herein, GO has been used as a broad spectrum selective antibacterial agent based on the photothermal therapy (PTT)/photodynamic therapy (PDT) effect. The preparation, characterization, determination of photophysical properties of two different sizes of GO is described. In vitro light dose and concentration-dependent studies were performed using Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria based on the PTT/PDT effect used ultra-low doses (65 mW cm-2) of 630 nm light, to achieve efficient bacterial decontamination. The results show that GO and nanographene oxide (nGO) can sensitize the formation of 1O2 and allow a temperature rise of 55°C to 60°C together nGO and GO to exert combined PTT/PDT effect in the disinfection of gram-positive S. aureus and gram-negative E. coli bacteria. A complete elimination of S. aureus and E. coli bacteria based on GO and nGO is obtained by using a dose of 43-47 J cm-2 for high concentration used in this study, and a dose of around 70 J cm-2 for low dose of GO and nGO. The presence of high concentrations of GO allows the bacterial population of S. aureus and E. coli to be more sensitive to the use of PDT/PTT and the efficiency of S. aureus and E. coli bacteria disinfection in the presence of GO is similar to that of nGO. In human neonatal dermal fibroblast, HDFs, no significant alteration to cell viability was promoted by GO, but in nGO is observed a mild damage in the HDFs cells independent of nGO concentration and light exposure. The unique properties of GO and nGO may be useful for the clinical treatment of disinfection of broad-spectrum antimicrobials. The antibacterial results of PTT and PDT using GO in gram-positive and gram-negative bacteria, using low dose light, allow us to conclude that GO and nGO can be used in dermatologic infections, since the effect on human dermal fibroblasts of this treatment is low compared to the antibacterial effect.