Metabolomics reveals synergy between Ag and g-C3N4 in Ag/g-C3N4 composite photocatalysts: a unique feature among Ag-doped biocidal materials

Abstract

IntroductionThe silver/graphitic carbon nitride (Ag/g-C 3 N 4 ) composite system exerts biocidal activity against the pathogenic bacterium Escherichia coli 1337-H that is stronger than that of well-known silver and titanium oxide (TiO 2 )-based composites. However, whether the Ag/g-C 3 N 4 composite system has biocidal properties that the parent components do or do not have as separate chemical entities and whether they differ from those in Ag/TiO 2 composite photocatalysts have not been clarified. Objective We investigated the chemical (cooperative charge handling and electronic properties) and biological (metabolic) effects exerted by the addition of Ag to g-C 3 N 4 and to TiO 2 . Methods In this work, we undertook metabolome-wide analysis by liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry to compare the metabolite profiles of untreated E. coli 1337-H cells or those subjected to disinfection with Ag, g-C 3 N 4 , 2Ag/g-C 3 N 4 , TiO 2 and 2Ag/TiO 2 . Results While Ag or g-C 3 N 4 moderately affected microbial metabolism according to the mean of the altered metabolites, multiple cell systems contributing to rapid cell death were immediately affected by the light-triggered radical species produced when Ag and g-C 3 N 4 were as xAg/g-C 3 N 4. The effects include drastically reduced production of small metabolites essential for detoxifying reactive oxygen species and those that regulate DNA replication fidelity, cell morphology and energy status. These biological consequences were different from those caused by Ag/TiO 2 -based biocides, demonstrating the uniqueness of the Ag/g-C 3 N 4 system. Conclusions Our results support the idea that the unique Ag/g-C 3 N 4 biocidal properties are based on synergistic action and reveal new directions for designing future photocatalysts for use in disinfection and microbial control.

Adsorption-enhanced photocatalytic property of Ag-doped biochar/g-C3N4/TiO2 composite by incorporating cotton-based biochar

“…More recently, a few biochar-based photocatalysts, such as biochar/ZnO [41], TiO 2 /biochar [42], Fe 2 O 3 / TiO 2 -biochar [43,44], Fe 3 O 4 /TiO 2 /biochar [45,46], and α-Fe 2 O 3 /O-doped-g-C 3 N 4 /biochar [47], have been fabricated for the photocatalytic degradation of organic dyes like congo red, rhodamine-B, methylene blue, and methyl orange, and various antibiotics like oxolinic acid, sulfadiazine, metronidazole, and tetracycline. It is reported that the Agdoped g-C 3 N 4 /TiO 2 possesses higher photocatalytic activity than (Ag-doped) g-C 3 N 4 or TiO 2 and g-C 3 N 4 /TiO 2 under visible light [48]. Conversely, its adsorptive ability to pollutants is not satisfactory.…”