Corrosion resistance and antibacterial properties of copper coating deposited by cold gas spray

This work describes the morphology, corrosion resistance, and antibacterial performance of copper coating deposited onto carbon steel by cold gas spray (CGS). Cross-sectional images of the coating showed a dense microstructure, with porosity lower than 1%. XRD analysis revealed no oxides or phases different to pure copper. The results of electrochemical tests demonstrated the efficient barrier properties and the compact microstructure of the coating, which protected the substrate against corrosion in chloride solution for > 1000 h. The copper coating was effective as an antimicrobial agent for inhibiting the growth of Staphylococcus aureus, with bacterial growth being completely inhibited after 10 min of direct contact between the bacteria and the coating surface

Quenching of chlorophyll fluorescence induced by silver nanoparticles

The interaction between chlorophyll (Chl) and silver nanoparticles (AgNPs) was evaluated by analyzing the optical behavior of Chl molecules surrounded by different concentrations of AgNPs (10, 60, and 100 nm of diameter). UV–Vis absorption, steady state and time-resolved fluorescence measurements were performed for Chl in the presence and absence of these nanoparticles. AgNPs strongly suppressed the Chl fluorescence intensity at 678 nm. The Stern-Volmer constant (KSV) showed that fluorescence suppression is driven by the dynamic quenching process. In particular, KSV was nanoparticle size-dependent with an exponential decrease as a function of the nanoparticle diameter. Finally, changes in the Chl fluorescence lifetime in the presence of nanoparticles demonstrated that the fluorescence quenching may be induced by the excited electron transfer from the Chl molecules to the metal nanoparticles

Development of a TiO 2 nanotube photoanode decorated with MIL-53(Fe) for the photoelectrochemical degradation of 2,4-dimethylaniline

Metal-organic frameworks (MOFs) based on Fe exhibit great potential as highly effective photocatalysts for water treatment applications. TiO2 nanotube photoanodes decorated with 170–370 μg cm−2 of MIL-53(Fe) and Fe-MOF (i.e., melamine-modified MIL-53(Fe)) were synthesized and evaluated in the photoassisted electrochemical degradation of 2,4-dimethylaniline (2,4-DMA) under visible light irradiation. The morphological, optical, and electrochemical properties of the photoanodes were evaluated by SEM, TEM, FTIR, XPS, BET, PL, XRD, DRS, zeta potential, linear voltammetry, EIS, and Mott-Schottky technique, respectively. The absorption band of the carboxyl groups coordinated to the iron centers is observed by FTIR at 1550 cm−1, whereas a peak at 538 cm−1 is related the formation of metal-oxo bonds between the carboxylic group of terephthalic acid and Fe3+. The modification of MIL-53(Fe) through the insertion of melamine led to a reduction in the formed nanoparticles. The photoelectrochemical activity of MIL-53(Fe) at pH 3.0 was optimized using a central composite design (CCD) experimental plan, with H2O2 concentration, applied anode potential (Ean) and reaction time as variables under study. Upon addition of 10 mg L−1 H2O2, a degradation of 74.4% of 2,4-DMA was achieved at Ean = 1.0 V after 110 min, outperforming the 57% reached using an unmodified TiO2 nanotube photoanode. Further modification of the MIL-53(Fe) with melamine allowed obtaining an almost total degradation. A plausible degradation pathway for 2,4-DMA is discussed from NMR and HPLC-MS/MS results. This work demonstrates the promising photoelectrocatalytic activity of TiO2 photoanodes decorated with Fe-based MOFs