Comparative performance and mechanism of bacterial inactivation induced by metal-free modified g-C3N4 under visible light: Escherichia coli versus Staphylococcus aureus

Eco-Friendly Multifunctional Hydrogel Sensors Enabled Sustainable and Accurate Human-Machine Interaction System

Wearable epidermic electronics assembled by conductive hydrogels exhibit great application potential for their seamless integration with the human body for human-machine interactions (HMI). However, most multifunctional hydrogel sensors are prone to water loss and become useless e-waste, resulting in a growing threat to the global environment and human health. Inspired by the resurrection plants, this paper introduces the reversible intermolecular forces and physical crosslinking method into the hydrogel system to obtain a fully recyclable multifunctional smart hydrogel sensor (RMSHS), which can be completely recycled in a simple step. Meanwhile, RMSHS possesses admirable biocompatibility, excellent antibacterial ability (S. aureus and E. coli bacterial inhibition rate of 99.8%), rapid self-healing ability, and outstanding sensing performances such as low detection limit, fast response/recovery time (160/200 ms). Intelligent medical rehabilitation and smart HMI systems are developed for medical diagnostics and real-time remote controlling. Moreover, the recyclable triboelectric nanogenerator (R-TENG) intelligent array, designed based on RMSHS, replaces the electrode consumables in traditional TENGs, realizing the generation of green energy and 100% recyclability of electrode materials. RMSHS can be generalized and applied to other remote-controlling platforms, paving the way for large-scale, multi-scenario applications.

Blue TiO2-Based Photocatalysis under Ambient Indoor Light for Prolonged Food Storage

Conventional food preservation techniques often require external devices, increasing costs and posing challenges in maintaining food quality. In this study, we developed blue titanium dioxide-tungsten trioxide-carboxymethyl cellulose (BTO-WO3-CMC) photocatalyst surfaces integrated onto inert substrates for food preservation. The inclusion of CMC enhanced Z-scheme heterojunction formation, improving visible light absorption, as confirmed by ultraviolet-visible spectra. Sodium silicate (SS) improved adhesion between BTO-WO3-CMC and the target substrate via hydrogen bonding. Analysis with X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy-dispersive X-ray spectroscopy (EDS) confirmed the crystalline integrity of BTO and WO3 and a consistent coating smoothness. BTO-WO3-CMC coatings extended the shelf life of strawberries to 14 days under ambient indoor lighting at 600 lx. Optimal preservation was achieved with a 0.01 g, 4 μm thick catalyst coating. Comparative experiments showed BTO-WO3-CMC's superior efficacy over P25-WO3-CMC and BTO-CMC. The coating was nontoxic in darkness and minimally reduced cell viability under room light. Antibacterial effects, attributed to reactive oxygen species (ROS) generation, were confirmed against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). This study presents a noninvasive, device-free method to extend food longevity, presenting a promising solution to the food waste challenge.

Photodegradation behavior and mechanism of dibutyl phthalate in water under flood discharge atomization

Flood discharge atomization is a prevalent hydraulics phenomenon in reservoir scheduling operations, however, its effect on the migration and transformation behavior of pollutants has not been examined. In this study, the behaviors and mechanisms of the direct photodegradation of dibutyl phthalate (DBP) in atomized water and the indirect photodegradation of DBP in the presence of ferric ions and nitrate were investigated. The results showed that the photodegradation rate of DBP was accelerated under atomization conditions by sunlight irradiation. The photodegradation efficiency of DBP in the presence of ferric ions and nitrate under atomization conditions was increased by 2.20 times and 1.82 times compared with no-atomization conditions, respectively. The quencher experiments indicated that the main active species for DBP photodegradation in the presence of ferric ions were hydroxyl radicals (·OH) and superoxide radicals (·O₂^-) with atomization, while the main active species in the presence of nitrate were ·OH, ·O₂^- and electrons (e^-). In addition, the differences were found in the photodegradation products and pathways of DBP between with and without atomization treatment. In the presence of ferric ions, the benzene ring of DBP was opened to produce fumaric acid, while phthalic acid bis(4-hydroxybutyl) ester was produced in the presence of nitrate under atomization conditions. The results of this study provide a scientific basis for assessing the effect of water conservancy projects on the migration and transformation behaviors of pollutants, which is of great theoretical significance and scientific value.

Advanced photocatalytic sterilization for recalcitrant Enterococcus sp. contaminated water by newly developed Z-scheme Bi2WO6 based composites under solar light

Pathogenic contamination is one of the major causes of clean water shortage, which poses great risk to human health. Herein, g-C₃N₄ (CN) was firstly introduced to Ag/Ag₂O/BiPO₄/Bi₂WO₆ (Ag/P/BWO) to construct a novel Z-scheme composite CN-Ag/P/BWO for disinfecting Enterococcus sp. contaminated water. CN-Ag/P/BWO showed excellent disinfection performance toward recalcitrant Enterococcus sp. under simulated solar light irradiation, achieving complete inactivation of 1.5 × 10⁷ cfu mL^-1 of bacterial cells only within 60 min, which was mainly attributed to the improved light absorption ability, charge carries separation/transfer efficiency and surface wettability. Additionally, the disinfection mechanism of CN-Ag/P/BWO toward Enterococcus sp. was systematically investigated. Photogenerated active species h⁺, ·OH and ·O₂^- worked together and played crucial roles in photocatalytic inactivation. The antioxidant system enabled Enterococcus sp. self-protection ability at the beginning of disinfection through secreting more antioxidant enzymes. However, with accumulation of active species, bacterial cell membrane and energy system were damaged, which further led to leakage of intracellular components and decomposition of bacteria. Besides, CN-Ag/P/BWO exhibited high practicability for different environmental factors and also performed well for real lake water disinfection. The high stability further confirmed its practicability for water disinfection. This work not only systematically revealed the disinfection mechanism toward Enterococcus sp., but also provided an efficient method for water disinfection.

Visible-light-responsive photocatalytic inactivation of ofloxacin-resistant bacteria by rGO modified g-C3N4

The visible light responsive graphitic nitride (g-C₃N₄) mediated photocatalysis has drawn extensive attention in water treatment field. Carbon doping could improve the photocatalytic activity of g-C₃N₄ in promoting charge separation efficiency, visible-light utilization, etc. In this paper, the g-C₃N₄ (as MC) was modified by barbituric acid (as MCB_0.07) and further treated by reduced graphene oxide (rGO) (as n%GCN) and then applied to inactivate ofloxacin-resistant bacteria (OFLA) under light irradiation at UVA-visible wavelength. The results showed that the n%GCN presented strong photocatalytic activity when the GO mass ratio was 7.5% (as 7.5%GCN). The inactivation efficiencies of OFLA by MC, MCB_0.07, and 7.5%GCN were 5.77 log, 8.48 log, and 8.25 log, respectively, under UVA-visible wavelength (λ > 305 nm), compared to 4.83 log, 5.56 log, and 6.08 log, respectively, within 16 h under visible wavelength (λ > 400 nm). The rGO-doping obviously improved the inactivation efficiency of MCB_0.07 on OFLA under visible wavelength. Furthermore, the photoreactivation and dark repair phenomena of OFLA were examined after MC, MCB_0.07, and 7.5%GCN treatment, respectively, and it was found that all approaches led to permanent damage to OFLA of which the regrowth was not observed after 24-48 h. Based on the quenching test, reactive oxygen species of O₂^-• and hole (h⁺) exhibited dominant roles in the photocatalytic inactivation of OFLA, which may result in oxidative stress and damage to the cell membrane. This study could shed light on the inactivation of OFLA under visible light radiation by rGO modified g-C₃N₄.

Photocatalytic degradation of pharmaceuticals by pore-structured graphitic carbon nitride with carbon vacancy in water: Identification of intermediate degradants and effects of active species

Pharmaceuticals are increasingly used in daily life and have been massively discharged to the aquatic environment. The removal of pharmaceuticals from water by various nanomaterials including graphitic carbon nitride (g-C₃N₄) has received extensive attention. Herein, we synthesized a carbon-defective carbon nitride with pore structure through a simple thermal polymerization method for photodegradation of lidocaine, mepivacaine and ropivacaine (typical amide local anesthetics). The results showed that the degradation process conformed to the pseudo-first-order reaction kinetics, and the degradation rate constant of organic pollutants using CCN-600 (i.e., g-C₃N₄ synthesized at 600 °C) reached 5.05 × 10^-2 min^-1, about 2.5 times higher than that of the prototype g-C₃N₄ (2.09 × 10^-2 min^-1). The capture experiment of active species and the electron paramagnetic resonance (EPR) test demonstrated that superoxide radical (O₂^-) played a major role in the degradation process. Based on the possible photodegraded intermediate products identified, the degradation pathways were deduced. This study provides not only a new strategy for fabrication of pore-structured g-C₃N₄ with carbon vacancy, but also a reference method for the treatment of pharmaceuticals in water bodies.

Photoelectrocatalytic inactivation mechanism of E. coli DH5α (TET) and synergistic degradation of corresponding antibiotics in water

The occurrence and proliferation of antibiotic-resistance genes (ARGs) / antibiotic-resistant bacteria (ARB) have been currently aggravating due to the increase of antibiotic residues in the aquatic environment. The interaction of ARB/ARGs with antibiotics inevitably occurred during water purification, yet their synergistic purification mechanism remains unclear. Herein, a systematic approach was developed to understand, in-depth, the synergistic mechanism in the coexisted E. coli DH5α (TET) inactivation and tetracycline hydrochloride (TET) degradation using photoelectrocatalysis (PEC) as a model technology. Results showed that low dosage (0 - 40 ppm) of TET exerted a negative influence on ARB inactivation with prolonged bactericidal time from 60 to 160 min. Addition of TET in environmental concentration (5 - 60 ppm) resulted in sub-lethal damage and prolonged PEC treatment time (100 - 160 min), accounting for inhibition effects on ARB inactivation. The major reactive species (RSs) involved in ARB inactivation and TET degradation were evidenced as photogenerated hole, ^•OH and O₂^•-, whereas hole and O₂^•- were demonstrated to be the major disinfectants for ARB/ARG inactivation. The bacterial defense system displayed increased antioxidative activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to protect ARB cells against oxidative stress. Exposure to 60 ppm TET was a threshold where certain ARB cells were induced into viable but nonculturable bacterial cell (VBNC) state, as evidenced by plate counting and ATP activity analysis, together with the integral cell membranes observed by flow cytometry (FCM) and scanning electron microscope (SEM). These findings appeal for appropriate technical adjustments for water and wastewater treatment to ensure safety of water.

Photocatalytic membrane reactors for produced water treatment and reuse: Fundamentals, affecting factors, rational design, and evaluation metrics

Treatment and reuse of produced water (PW), the largest wastewater stream generated during oil and gas production, provides a promising option to address the increasing clean water demands. High-performance treatment technologies are needed to efficiently remove the organic and inorganic contaminants in PW for fit-for-purpose applications. Photocatalytic membrane reactor (PMR) is an emerging green technology for removal of organic pollutants, photoreduction of heavy metals, photo-inactivation of bacteria, and resource recovery. This study critically reviewed the mechanisms of photocatalysis and membrane processes in PMR, factors affecting PMR performance, rational design, and evaluation metrics for PW treatment. Specifically, PW characteristics, photocatalysts properties, membranes applied, and operating conditions are of utmost importance for rational design and reliable operation of PMR. PW pretreatment to remove oil and grease, colloidal and suspended solids is necessary to reduce membrane fouling and ensure optimal PMR performance. The metrics to evaluate PMR performance were developed including light utilization, exergetic efficiency, water recovery, product water improvement, lifetime of the photocatalyst, and costs. This review also presented the research gaps and outlook for future research.

One-step synthesis of melamine-sponge functionalized carbon nitride for excellent water sterilization via photogenerated holes and photothermal conversion

In recent years, graphitic carbon nitride (g-C₃N₄) has been developed greatly in the domain of water treatment. We adopted one-step calcination to enhance the light absorption of g-C₃N₄ with melamine-sponge (MS). A novel form of photocatalysts (gCNMx, x  = 0.1, 0.2 and 0.3) were successfully prepared. The color of gCNMx changed with addition of MS. Experimental analysis demonstrated that C-doping and N vacancies increased the capacity of light absorption of gCNM0.2, and further increased efficiency of photothermal conversion and photogenerated holes. The sterilization efficiency of gCNM0.2 could rival a variety of metal photocatalysts. Moreover, the preparation of gCNM0.2 was cost-effective and environmental-friendly. Interestingly, the inactivation efficacy of gCNM0.2 for S. aureus depended heavily on the photogenerated holes, however, the decisive force toward S. typhimurium was photothermal conversion.