Publicações em destaque
Bacterial Photoinactivation Using PLGA Electrospun Scaffolds
The use of ultraviolet (UV) and blue irradiation to sterilize surfaces is well established, but commercial applications would be enhanced if the light source is replaced with ambient light. In this paper, it is shown that nanofibers can be explored as an alternative methodology to UV and blue irradiation for bacterial inactivation. It is demonstrated that this is indeed possible using spun nanofibers of poly[lactic-co-(glycolic acid)] (PLGA). This work shows that PLGA spun scaffolds can promote photoinactivation of Staphylococcus aureus and Escherichia coli bacteria with ambient light or with laser irradiation at 630 nm. With the optimized scaffold composition of PLGA85:15 nanofibers, the minimum intensity required to kill the bacteria is much lower than in antimicrobial blue light applications. The enhanced effect introduced by PLGA scaffolds is due to their nanofiber structures since PLGA spun nanofibers were able to inactivate both S. aureus and E. coli bacteria, but cast films had no effect. These findings pave the way for an entirely different method to sterilize surfaces, which is less costly and environmentally friendly than current procedures. In addition, the scaffolds could also be used in cancer treatment with fewer side effects since photosensitizers are not required.
Aline O. Pereira, Isabella M. I. Lopes, Thiago R. Silva, Thaila Q. Corrêa, Rafaella T. Paschoalin, Natalia M. Inada, Ievgeniia Iermak, Francisco van Riel Neto, Juliana C. Araujo-Chaves, Alexandre Marletta, José R. Tozoni, Luiz Henrique C. Mattoso, Vanderlei S. Bagnato, Iseli L. Nantes-Cardoso, Osvaldo N. Oliveira, and Patricia T. Campana , Article ASAP
Disassembly of TEMPO-Oxidized Cellulose Fibers: Intersheet and Interchain Interactions in the Isolation of Nanofibers and Unitary Chains
Cellulose disassembly is an important issue in designing nanostructures using cellulose-based materials. In this work, we present a combination of experimental and theoretical study addressing the disassembly of cellulose nanofibrils. Through 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidation processes, combined with atomic force microscopy results, we show the formation of nanofibers with diameters corresponding to that of a single-cellulose polymer chain. The formation of these polymer chains is controlled by repulsive electrostatic interactions between the oxidized chains. Further, first-principles calculations have been performed in order to provide an atomistic understanding of the cellulose disassembling processes, focusing on the balance between the interchain (IC) and intersheet (IS) interactions upon oxidation. First, we analyze these interactions in pristine systems, where we found the IS interaction to be stronger than the IC interaction. In the oxidized systems, we have considered the formation of (charged) carboxylate groups along the inner sites of elementary fibrils. We show a net charge concentration on the carboxylate groups, supporting the emergence of repulsive electrostatic interactions between the cellulose nanofibers. Indeed, our total energy results show that the weakening of the binding strength between the fibrils is proportional to the concentration and net charge density of the carboxylate group. Moreover, by comparing the IC and IS binding energies, we found that most of the disassembly processes should take place by breaking the IC O−H···O hydrogen bond interactions and thus supporting the experimental observation of single- and double-cellulose polymer chains.
Gustavo H. Silvestre, Lidiane O. Pinto, Juliana S. Bernardes, Roberto H. Miwa, and Adalberto Fazzio, J. Phys. Chem. B 125, 14, 3717–3724 (2021).
Flexible and Transparent Electrodes of Cu2−XSe with Charge Transport via Direct Tunneling Effect
In this paper, it is demonstrated that copper selenide (Cu2−XSe) films onto polyester sheets may serve as transparent electrodes in inorganic–organic hybrid light emission devices (IOHLED), as possible replacement to indium tin oxide or fluorine-doped tin oxide. The Cu2−XSe film synthesized via
bath chemical deposition is electrically stable with a sheet resistance of 148 Ω sq−1 and optical bandgap of 2.3 eV. IOHLED are made with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as an organic layer for hole transport and poly[2-metoxy-5-(2-ethylhexyloxy)-1,4-henylenevinylene] (MEH-PPV) as electroluminescent semiconductor. The IOHLED emits in the visible range owing to the simultaneous emission from Cu2−XSe and MEH-PPV layers. The enhanced performance is explained by analyzing the charge transport mechanisms at the inorganic–organic interface, which for Cu2−XSe/PEDOT:PSS changes from Fowler-Nordheim to direct tunneling regardless of the device temperature (90–370 K). The onset voltage is 75% smaller than in the absence of the PEDOT:PSS layer due to a 27 meV decrease in the potential barrier, and the direct tunneling becomes more relevant to device performance than the sheet resistance of the Cu2−XSe layer. Upon adding transparency, mechanical flexibility, and covering large areas, the ultrathin Cu2−XSe films on polyester substrates permit new designs for electro-optical devices with inorganic–organic heterojunctions.
Silésia F. C. Silva, Bruno S. Zanatta, Adriano C. Rabelo, Otávio L. Bottecchia, José R. Tozoni, Osvaldo N. Oliveira Jr, and Alexandre Marletta, Adv. Electron. Mater. 2001189 (2021).