RESUMO
Bacterial contamination and biofilm formation generate severe problems in many fields. Among these biofilm-forming bacteria, Staphylococcus epidermidis (S. epidermidis) has emerged as a major cause of nosocomial infection (NI). However, with the dramatic rise in resistance toward conventional antibiotics, there is a pressing need for developing effective anti-biofilms. So, fabrication of copper oxide nanoparticles (NPs) is one of the new strategies to combat biofilms. Notably, doped CuO NPs in anti-biofilm therapy have become a hot spot of attention in recent years due to their physicochemical properties. In this context, the present work deals with the investigation of undoped and transition metal (TM)-doped CuO NPs (TM = Zn, Ni, Mn, Fe and Co), synthesized via the co-precipitation method. The synthesized CuO NPs are characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Results consistently revealed the successful formation of CuO NPs using the co-precipitation method and confirmed that TM ions are successfully inserted into CuO crystal lattice. We found that doping changes the morphology of the CuO NPs and increases their crystallite size. The XPS results show a non-uniform distribution of the doping concentration, with a depletion or an enrichment of the NP surface depending on the element considered. Furthermore, the anti-adhesive potential of CuO NPs against S. epidermidis S61 biofilm formation is evaluated in this study by crystal violet and fluorescence microscopy assays. All synthesized NPs exhibit considerable anti-adhesive activity against S. epidermidis S61 biofilm. Interestingly, compared to undoped CuO, Fe and Ni-doped oxides show an improved activity when used at high concentrations, whereas Mn-doped CuO is the most efficient at low concentrations. This makes TM-doped CuO a promising candidate to be used in biomedical applications.
RESUMO
Aiming the degradation of harmful molecules under visible light, new photocatalytic systems were created. For this purpose, the surface of chitosan thin films was modified in heterogeneous phase via a simple and straightforward mild chemical process: chemisorption of silver ions followed by the synthesis in situ of TiO2 at low temperature (100⯰C). A high photocatalytic activity under visible light was observed, leading to the degradation and/or mineralization of different organic products such as o-toluidine, salicylic acid and 4-aminomethyl benzoic acid. This efficiency is partly attributed to the formation of Ag NPs and also to the unexpected appearance of AgCl NPs, likely formed from the residual chlorine contained in the chitosan. The resulting TiO2/Ag/AgCl/Chitosan system is easy to prepare under mild conditions, avoiding calcination treatments and opens new perspectives for the production of visible light-driven photocatalysts. Samples were analysed by different techniques: XRD, Raman, FE-SEM, XPS, TGA, GSDR, LIF and LIP.
RESUMO
Electrochemical reduction of aryldiazonium salts (in acetonitrile or acidic aqueous medium) on an iron or mild steel surface permits the strong bonding (which resists an ultrasonic cleaning) of aryl groups on these surfaces. Attachment of aryl groups was demonstrated by the combined used of electrochemistry, infrared spectroscopy and polarization modulation infrared reflection spectroscopy (PMIRRAS), Rutherford backscattering, X-ray photoelectron spectroscopy, and capacity measurements. The substituents of aryl groups, which can be widely varied, include NO2, I, COOH, and long alkyl chains. It is shown that the attachment of the aryl groups is to an iron and not to an oxygen atom and that the bond is covalent.
