Mechanism of visible light enhanced catalysis over curcumin functionalized Ag nanocatalysts

Thermosensitive curcumin/silver/montmorillonite-F127 hydrogels with synergistic photodynamic/photothermal/silver ions antibacterial activity

Bacterial infections and the emergence of super-resistant bacteria pose a significant risk to human health. Effective sterilization to prevent the development of bacterial drug resistance remains a challenge. Herein, curcumin/silver/montmorillonite (Cur/Ag/Mt) was prepared through a green chemical reduction method with montmorillonite as the carrier, curcumin as the reducing agent and the capping agent, and citric acid as the structure guide agent. Then, a novel dual light-responsive and thermosensitive Pluronic F127-based hydrogel (CAM-F) was prepared by encapsulating Cur/Ag/Mt within the F127 hydrogel. The Cur/Ag/Mt showed strong absorption in the near-infrared region that efficiently converts light into heat for photothermal therapy when the molar ratio of curcumin to silver nitrate was 2 : 1. Specifically, triangular silver nanoparticles reduced by curcumin were immobilized on the Mt layers, which could enhance photodynamic therapy by the metal-enhanced singlet oxygen and metal-enhanced fluorescence mechanisms. Upon combining 405 nm and 808 nm laser irradiation, the CAM-F hydrogel could simultaneously generate reactive oxygen species, increase the local temperature, and sustain the release of Ag+, thus displaying excellent bactericidal performance against Gram-negative and Gram-positive bacteria. The antibacterial rates of CAM-F hydrogels were 99.26 ± 0.95% and 99.95 ± 0.98% for Escherichia coli and Staphylococcus aureus, respectively. The findings suggest the potential of the CAM-F hydrogel as a stable, biologically safe, and broad-spectrum antimicrobial material. The thermosensitive CAM-F hydrogels for synergetic phototherapy may provide a promising strategy for solving clinical problems caused by pathogenic infections.

Fabrication of close-contact S-scheme Cr2Bi3O11-Bi2O3/Fe3O4@porous carbon microspheres based on in-situ reaction: Enhanced photo-Fenton wastewater treatment

Low photo-induced carrier recombination rate, exceptional light absorption, and advantageous recycling performance are crucial attributes of semiconductor photocatalyst for wastewater purification. Herein, based on in-situ reaction, close-contact S-scheme bismuth chromate/bismuth oxide/ferroferric oxide@porous carbon microspheres (Cr2Bi3O11-Bi2O3/Fe3O4@PCs) (F-CBFP) was fabricated using alginates as precursor. Due to the abundance of functional groups on the porous carbon (PCs), Bi2O3 and Cr2Bi3O11 nanoparticles (NPs) are in situ deposited onto the highly conductive 3D magnetic porous Fe3O4@PCs microsphere surface, which not only form tight interfacial contacts and reduces interfacial potential barriers but also prevent agglomeration or shedding of the NPs during photocatalytic reactions. Moreover, density functional theory (DFT) calculations further confirm that the formation of a robust built-in electric field (BIEF) within F-CBFP prompts photo-induced electrons in the conduction band (CB) of Bi2O3 to combine with holes in the valence band (VB) of Cr2Bi3O11, effectively constructing a S-scheme heterojunction system. Also, Fe3O4 can act as a Fenton catalyst, activating the H2O2 generated by Cr2Bi3O11 under illumination. In wastewater treatment, the obtained F-CBFP shows remarkable photo-Fenton degradation (towards methyl orange (97.8 %, 60 min) and tetracycline hydrochloride (95.3 %, 100 min)) and disinfection performance (100 % E. coli inactivation), and exceptional cyclic stability.

Computational Modeling of the Interaction of Silver Clusters with Carbohydrates

Silver nanoparticles are recognized for their numerous physical, biological, and pharmaceutical applications. In the present study, the interaction of silver clusters with monosaccharide molecules is examined to identify which molecule works better as a reducing agent in the application of a green synthesis approach. Geometry optimization of clusters containing one, three, and five silver atoms is performed along with the optimization of α-d-glucose, α-d-ribose, d-erythrose, and glyceraldehyde using density functional theory. Optimized geometries allow identifying the interaction formed in the silver cluster and monosaccharide complexes. An electron localization function analysis is performed to further analyze the interaction found and explain the reduction process in the formation of silver nanoparticles. The overall results indicate that glyceraldehyde presents the best characteristics to serve as the most efficient reducing agent.

Experimental and DFT calculation study of interaction between silver nanoparticle and 1-butyl-3-methyl imidazolium tetrafluoroborate ionic liquid

The mechanism of stabilization of silver nanoparticles (Ag NPs) by 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid (IL) is elucidated from experimental spectroscopic investigations and density functional theory (DFT) calculations. FTIR spectrum of the synthesized IL stabilized silver nanoparticles reveals small red shift in B–F stretching frequency while C–H stretching remains unshifted. There is no shift in NMR peaks of IL before and after the synthesis of IL stabilized Ag NPs. This suggests that Ag NPs are surrounded by anions of ILs. The optimized structure obtained from density functional theory (DFT) calculations also shows the anionic part of the IL surrounding the Ag nanocluster. This is supported by the IR frequency data calculated using DFT. The calculated binding energy and interaction energy obtained between cluster and IL is considerably attractive. Density of State (DOS) calculation shows that the HOMO-LUMO gap of the Ag cluster-IL composite is significantly lesser than that of the IL alone.