Nanoparticles (NPs) of α-MnO₂ have high applicability in photoelectrochemical, heterogeneous photocatalysis, optical switching, and disinfection processes. To widen this panorama about MnO₂ NPs, the formation of this material by laser ablation and deposition by dip-coating on fluorine-doped tin oxide (FTO), were considered in this study. The optical, spectroscopic, electrochemical characterization, and the evaluation of the antimicrobial activity, plus the photocatalytic response, were measured herein in colloidal media and deposited. For the deposition of NPs on FTO sheet, an anode is produced with a pseudocapacitive behavior, and 2.82 eV of band gap (GAP) in comparison with colloidal NPs for a value of 3.84 eV. Both colloidal suspension and deposited NPs have intrinsic antibacterial activity against two representative microorganisms (E. coli and S. aureus), and this biological activity was significantly enhanced in the presence of UVA light, indicating photocatalytic activity of the material. Thus, both the colloidal suspension and deposited NPs can act as disinfecting agents themselves or via light activation. However, an antibacterial behavior different for E. coli and S. aureus was observed, in function of the aggregation state, obtaining total E. coli disinfection at 30 min for deposited samples on FTO.

The search for coatings that extend the useful life of biomedical devices has been of great interest, and titanium has been of great relevance due to its innocuousness and low reactivity. This study contributes to the investigation of Ti/Ag films in different configurations (monolayer and multilayer) deposited by magnetron sputtering. The sessile droplet technique was applied to study wettability; greater film penetrability was obtained when Ag is the external layer, conferring high efficiency in cell adhesion. The morphological properties were characterized by SEM, which showed porous nuclei on the surface in the Ag coating and crystals embedded in the Ti film. The structural properties were studied by XRD, revealing the presence of TiO₂ in the anatase crystalline phase in a proportion of 49.9% and the formation of a silver cubic network centered on the faces. Tafel polarization curves demonstrated improvements in the corrosion current densities of Ag/Ti/Ag/Ti/Ag/Ti/Ag/Ti and Ti/Ag compared to the Ag coating, with values of 0.1749, 0.4802, and 2.044 nA.m⁻², respectively. Antimicrobial activity was evaluated against the bacteria Pseudomonas aeruginosa and Bacillus subtilis and the yeasts Candida krusei and Candida albicans, revealing that the Ti/Ag and Ag/Ti/Ag/Ti/Ag/Ti/Ag/Ti coatings exhibit promise in biomedical material applications.

Advanced Oxidation Processes (AOPs) offer promising methods for disinfection by generating radical species like hydroxyl radicals, superoxide anion radicals, and hydroxy peroxyl, which can induce oxidative stress and deactivate bacterial cells. Photocatalysis, a subset of AOPs, activates a semiconductor using specific electromagnetic wavelengths. A novel material, Cu/Cu₂O/CuO nanoparticles (NPs), was synthesized via a laser ablation protocol (using a 1064 nm wavelength laser with water as a solvent, with energy ranges of 25, 50, and 80 mJ for 10 min). The target was sintered from 100 °C to 800 °C at rates of 1.6, 1.1, and 1 °C/min. The composite phases of Cu, CuO, and Cu₂O showed enhanced photocatalytic activity under visible-light excitation at 368 nm. The size of Cu/Cu₂O/CuO NPs facilitates penetration into microorganisms, thereby improving the disinfection effect. This study contributes to synthesizing mixed copper oxides and exploring their activation as photocatalysts for cleaner surfaces. The electronic and electrochemical properties have potential applications in other fields, such as capacitor materials. The laser ablation method allowed for modification of the band gap absorption and enhancement of the catalytic properties in Cu/Cu₂O/CuO NPs compared to precursors. The disinfection of E. coli with Cu/Cu₂O/CuO systems serves as a case study demonstrating the methodology’s versatility for various applications, including disinfection against different microorganisms, both Gram-positive and Gram-negative.

The introduction of the first list of priority pathogenic fungi by the World Health Organization stresses the need to research and develop public health actions to mitigate infections caused by fungi. One of those actions involves the water disinfection systems, which comprise classical and alternative methods that have been developed in the last decades. Thereby, this work reviews the disinfection of fungi by classical methods such as chlorination, ozonation, and ultraviolet (UV) treatments and alternative advanced oxidation processes (AOPs) such as photo-Fenton, photocatalysis, or couplings of UV with peroxides. The matrices of aquatic systems (sewage, groundwater, drinking water, among others) were considered. A bibliometric analysis is performed initially, and then some aspects of the resistance to antifungals are presented, and the efficiency of the diverse processes in the reduction in fungal loading is also revised. Herein, it is shown the role of the disinfecting agents (e.g., chlorine, hydroxyl radical, or light) and their effects on fungi structures (e.g., direct DNA damage, or indirect damage due to the action of radicals). Moreover, gaps, such as the treatment of antifungal-resistant fungi and limited information about combinations among AOPs, related to the disinfection of water polluted by fungi, were identified.

The correlation of two instrumental techniques for chlorides determination in Colombian cheese, Queso Molido Nariñense (a type of white cheese), was analyzed. Potentiometry of chloride precipitation is the standard technique to determined salt in cheese. Conductimetry is an alternative technique. Samples of Queso Molido Nariñense were made. In the processed cheeses the salt concentration (NaCl: 0.5 %, 0.8 %, 1.0 %, 2.0 %, 3.0% and 6.0 %) was varied. Chlorides were determined by titration with silver nitrate in the potentiometric technique. In the conductimetric technique, each sample was analyzed by direct measuring its conductivity at room temperature. It was found that there is an adequate correlation between potentiometry and conductimetry. A maximum concentration of 2% NaCl in cheese is equivalent to 2.9 S/cm for conductivity readings. Additionally, it was verified that the conductimetry constitutes an analytically reliable technique for the determination of chlorides in cheese, it is friendlier to the environment, cheaper and faster.

Wastewater samples from flexographic printing machines, characterized by high coloration, low pH, high chemical oxygen demand, and low biodegradability, were subjected to primary physicochemical treatments and a subsequent Fenton process to decrease the chemical oxygen demand (COD). The primary treatment consisted of coagulation with aluminium polychloride or ferric chloride followed by filtration over activated carbon. The Fenton process was optimized by varying pH, and the iron and hydrogen peroxide concentrations. Upon primary treatment, aluminium polychloride was the better coagulation agent. After one hour of treatment with the Fenton process at pH: 4.0; 40 mgL^-1 ferric chloride, 200 mgL^-1 hydrogen peroxide, COD removal of up to 92% was achieved. Thus, coupling of physicochemical treatments with the Fenton process yields wastewater of low environmental impact