A General Synthesis Method for Covalent Organic Framework and Inorganic 2D Materials Hybrids.

Two-dimensional (2D) inorganic/organic hybrids provide a versatile platform for diverse applications, including electronic, catalysis, and energy storage devices. The recent surge in 2D covalent organic frameworks (COFs) has introduced an organic counterpart for the development of advanced 2D organic/inorganic hybrids with improved electronic coupling, charge separation, and carrier mobility. However, existing synthesis methods have primarily focused on few-layered film structures, which limits scalability for practical applications. Herein, we present a general synthesis approach for a range of COF/inorganic 2D material hybrids, utilizing 2D inorganic materials as both catalysts and inorganic building blocks. By leveraging the intrinsic Lewis acid sites on the inorganic 2D materials such as hexagonal boron nitride (hBN) and transition metal dichalcogenides, COFs with diverse functional groups and topologies can grow on the surface of inorganic 2D materials. The controlled 2D morphology and excellent solution dispersibility of the resulting hybrids allow for easy processing into films through vacuum filtration. As proof of concept, hBN/COF films were employed as filters for Rhodamine 6G removal under flow-through conditions, achieving a removal rate exceeding 93%. The present work provides a simple and versatile synthesis method for the scalable fabrication of COF/inorganic 2D hybrids, offering exciting opportunities for practical applications such as water treatment and energy storage.

Gender differences in the association between dietary protein intake and constipation: findings from NHANES.

Purpose: Dietary factors play a crucial role in the development and management of chronic constipation, yet the relationship between dietary protein intake and constipation remains underexplored. This study aims to investigate the association between dietary protein intake and the prevalence of constipation among American adults, with a focus on potential gender differences, using large-scale national data. Materials and methods: Data from 14,048 participants aged 20 and above (7,072 men and 6,976 women) from the National Health and Nutrition Examination Survey (NHANES) 2005-2010 were analyzed. The Bristol Stool Form Scale's types 1 (separate hard lumps, resembling nuts) and 2 (sausage-shaped, but lumpy) were used to define constipation. A 24-h dietary recall technique was used to measure dietary protein intake. After controlling for covariates, the association between protein consumption and constipation risk was examined using multivariable logistic regression, smooth curve fitting, and testing for gender interaction effects. We then further determined the threshold effect between dietary protein intake and constipation risk. Results: Constipation was present in 7.49% of people overall, with a higher proportion among women (10.19%) than among males (4.82%). In men, higher protein intake was significantly associated with a lower rate of constipation. However, in women, higher protein intake correlated with an increased risk of constipation, and the interaction between gender was significant (P for interaction = 0.0298). These results were corroborated by smooth curve fits, which also demonstrated a dose-response effect. Further threshold effect analysis showed that the turning points of dietary protein intake differed between male and female participants (119.42 gm/day for men; 40.79 gm/day for women). Conclusion: The association between dietary protein intake and constipation was different in different genders with threshold effect. For men, moderately increasing protein intake could be beneficial, while for women, exceeding a certain level may increase the risk of constipation. These insights are crucial for guiding dietary protein recommendations for different genders and have significant clinical implications.

Electrochemical oxidation of surfactants as an essential step to enable greywater reuse.

The practical application of electrochemical oxidation technology for the removal of surfactants from greywater was evaluated using sodium dodecyl sulfate (SDS) as a model surfactant. Careful selection of electrocatalysts and optimization of operational parameters demonstrated effective SDS removal in treating a complex greywater matrix with energy consumption below 1 kWh g-1 COD (Chemical Oxygen Demand), paving the way for a more sustainable approach to achieving surfactant removal in greywater treatment when aiming for decentralized water reuse. Chromatographic techniques identified carboxylic acids as key byproducts prior to complete mineralization. These innovative approaches represent a novel pathway for harnessing electrochemical technologies within decentralized compact devices, offering a promising avenue for further advancements in this field.

Electrospun Nanofibrous Membranes for Controlling Airborne Viruses: Present Status, Standardization of Aerosol Filtration Tests, and Future Development.

The global COVID-19 pandemic has raised great public concern about the airborne transmission of viral pathogens. Virus-laden aerosols with small size could be suspended in the air for a long duration and remain infectious. Among a series of measures implemented to mitigate the airborne spread of infectious diseases, filtration by face masks, respirators, and air filters is a potent nonpharmacologic intervention. Compared with conventional air filtration media, nanofibrous membranes fabricated via electrospinning are promising candidates for controlling airborne viruses due to their desired characteristics, i.e., a reduced pore size (submicrometers to several micrometers), a larger specific surface area and porosity, and retained surface and volume charges. So far, a wide variety of electrospun nanofibrous membranes have been developed for aerosol filtration, and they have shown excellent filtration performance. However, current studies using electrospinning for controlling airborne viruses vary significantly in the practice of aerosol filtration tests, including setup configurations and operations. The discrepancy among various studies makes it difficult, if not impossible, to compare filtration performance. Therefore, there is a pressing need to establish a standardized protocol for evaluating the electrospun nanofibrous membranes' performance for removing viral aerosols. In this perspective, we first reviewed the properties and performance of diverse filter media, including electrospun nanofibrous membranes, for removing viral aerosols. Next, aerosol filtration protocols for electrospun nanofibrous membranes were discussed with respect to the aerosol generation, filtration, collection, and detection. Thereafter, standardizing the aerosol filtration test system for electrospun nanofibrous membranes was proposed. In the end, the future advancement of electrospun nanofibrous membranes for enhanced air filtration was discussed. This perspective provides a comprehensive understanding of status and challenges of electrospinning for air filtration, and it sheds light on future nanomaterial and protocol development for controlling airborne viruses, preventing the spread of infectious diseases, and beyond.

Photosensitized Electrospun Nanofibrous Filters for Capturing and Killing Airborne Coronaviruses under Visible Light Irradiation.

To address the challenge of the airborne transmission of SARS-CoV-2, photosensitized electrospun nanofibrous membranes were fabricated to effectively capture and inactivate coronavirus aerosols. With an ultrafine fiber diameter (∼200 nm) and a small pore size (∼1.5 µm), optimized membranes caught 99.2% of the aerosols of the murine hepatitis virus A59 (MHV-A59), a coronavirus surrogate for SARS-CoV-2. In addition, rose bengal was used as the photosensitizer for membranes because of its excellent reactivity in generating virucidal singlet oxygen, and the membranes rapidly inactivated 97.1% of MHV-A59 in virus-laden droplets only after 15 min irradiation of simulated reading light. Singlet oxygen damaged the virus genome and impaired virus binding to host cells, which elucidated the mechanism of disinfection at a molecular level. Membrane robustness was also evaluated, and in general, the performance of virus filtration and disinfection was maintained in artificial saliva and for long-term use. Only sunlight exposure photobleached membranes, reduced singlet oxygen production, and compromised the performance of virus disinfection. In summary, photosensitized electrospun nanofibrous membranes have been developed to capture and kill airborne environmental pathogens under ambient conditions, and they hold promise for broad applications as personal protective equipment and indoor air filters.

Radical-Driven Decomposition of Graphitic Carbon Nitride Nanosheets: Light Exposure Matters.

Understanding the transformation of graphitic carbon nitride (g-C3N4) is essential to assess nanomaterial robustness and environmental risks. Using an integrated experimental and simulation approach, our work has demonstrated that the photoinduced hole (h+) on g-C3N4 nanosheets significantly enhances nanomaterial decomposition under •OH attack. Two g-C3N4 nanosheet samples D and M2 were synthesized, among which M2 had more pores, defects, and edges, and they were subjected to treatments with •OH alone and both •OH and h+. Both D and M2 were oxidized and released nitrate and soluble organic fragments, and M2 was more susceptible to oxidation. Particularly, h+ increased the nitrate release rate by 3.37-6.33 times even though the steady-state concentration of •OH was similar. Molecular simulations highlighted that •OH only attacked a limited number of edge-site heptazines on g-C3N4 nanosheets and resulted in peripheral etching and slow degradation, whereas h+ decreased the activation energy barrier of C-N bond breaking between heptazines, shifted the degradation pathway to bulk fragmentation, and thus led to much faster degradation. This discovery not only sheds light on the unique environmental transformation of emerging photoreactive nanomaterials but also provides guidelines for designing robust nanomaterials for engineering applications.

Development of Electrospun Nanofibrous Filters for Controlling Coronavirus Aerosols.

Airborne transmission of SARS-CoV-2 plays a critical role in spreading COVID-19. To protect public health, we designed and fabricated electrospun nanofibrous air filters that hold promise for applications in personal protective equipment (PPE) and the indoor environment. Due to ultrafine nanofibers (∼300 nm), the electrospun air filters had a much smaller pore size in comparison to the surgical mask and cloth masks (a couple of micrometers versus tens to hundreds of micrometers). A coronavirus strain served as a SARS-CoV-2 surrogate and was used to generate aerosols for filtration efficiency tests, which can better represent SARS-CoV-2 in comparison to other agents used for aerosol generation in previous studies. The electrospun air filters showed excellent performance by capturing up to 99.9% of coronavirus aerosols, which outperformed many commercial face masks. In addition, we observed that the same electrospun air filter or face mask removed NaCl aerosols equivalently or less effectively in comparison to the coronavirus aerosols when both aerosols were generated from the same system. Our work paves a new avenue for advancing air filtration by developing electrospun nanofibrous air filters for controlling SARS-CoV-2 airborne transmission.

Photocatalytic graphitic carbon nitride-chitosan composites for pathogenic biofilm control under visible light irradiation.

Photocatalysis holds promise for inactivating environmental pathogens. Visible-light-responsive composites of carbon-doped graphitic carbon nitride and chitosan with high reactivity and processability were fabricated, and they can control pathogenic biofilms for environmental, food, biomedical, and building applications. The broad-spectrum biofilm inhibition and eradication of the photocatalytic composites against Staphylococcus epidermidis, Pseudomonas aeruginosa PAO1, and Escherichia coli O157: H7 under visible light irradiation were demonstrated. Extracellular polymeric substances in Escherichia coli O157: H7 biofilms were most resistant to photocatalytic oxidation, which led to reduced performance for biofilm removal. 1O2 produced by the composites was believed to dominate biofilm inactivation. Moreover, the composites exhibited excellent performance for inhibiting biofilm development in urine, highlighting the promise for inactivating environmental biofilms developed from multiple bacterial species. Our study provides fundamental insights into the development of new photocatalytic composites, and elucidates the mechanism of how the photocatalyst reacts with a microbiological system.

3D printed photoreactor with immobilized graphitic carbon nitride: A sustainable platform for solar water purification.

Solar-energy-enabled photocatalysis is promising for sustainable water purification. However, photoreactor design, especially immobilizing nano-sized photocatalysts, remains a major barrier preventing industrial-scale application of photocatalysis. In this study, we immobilized photocatalytic graphitic carbon nitride on chitosan to produce g-C3N4/chitosan hydrogel beads (GCHBs), and evaluated GCHB photoreactivity for degrading phenol and emerging persistent micropollutants in a 3D printed compound parabolic collector (CPC) reactor. The CPC photocatalytic system showed comparable performance with slurry reactors for sulfamethoxazole and carbamazepine degradation under simulated sunlight, and it maintained the performance for contaminant removal in real water samples collected from water/wastewater treatment plants or under outdoor sunlight irradiation. Global drinking water production was estimated for the CPC system, and it holds promise for small-scale sustainable water treatment, including, but not limited to, the production of high-quality potable water for single houses, small communities, rural areas, and areas impacted by natural disasters in both developed and developing countries.

Acquisition of time-frequency localized mechanical properties of biofilms and single cells with high spatial resolution.

Biofilms are a cluster of bacteria embedded in extracellular polymeric substances (EPS) that contain a complex composition of polysaccharides, proteins, and extracellular DNA (eDNA). Desirable mechanical properties of the biofilms are critical for their survival, propagation, and dispersal, and the response of mechanical properties to different treatment conditions also sheds light on biofilm control and eradication in vivo and on engineering surfaces. However, it is challenging yet important to investigate mechanical behaviors of biofilms with a high spatial resolution because biofilms are very heterogeneous. Moreover, biofilms are viscoelastic, and their time-dependent mechanical behavior is difficult to capture. Herein, we develop a powerful technique that combines the high spatial resolution of an atomic force microscope (AFM) with a rigorous history-dependent viscoelastic analysis to deliver highly spatial-localized biofilm properties within a wide time-frequency window. By exploiting the use of static force spectroscopy in combination with an appropriate viscoelastic framework, we highlight the intensive amount of time-dependent information experimentally available that has been largely overlooked. It is shown that this technique provides a detailed nanorheological signature of the biofilms even at the single-cell level. We share the computational routines that would allow any user to perform the analysis from experimental raw data. The detailed localization of mechanical properties in space and in time-frequency domain provides insights into the understanding of biofilm stability, cohesiveness, dispersal, and control.

Visible-Light-Responsive Photocatalyst of Graphitic Carbon Nitride for Pathogenic Biofilm Control.

Pathogenic biofilms raise significant health and economic concerns, because these bacteria are persistent and can lead to long-term infections in vivo and surface contamination in healthcare and industrial facilities or devices. Compared with conventional antimicrobial strategies, photocatalysis holds promise for biofilm control because of its broad-spectrum effectiveness under ambient conditions, low cost, easy operation, and reduced maintenance. In this study, we investigated the performance and mechanism of Staphylococcus epidermidis biofilm control and eradication on the surface of an innovative photocatalyst, graphitic carbon nitride (g-C3N4), under visible-light irradiation, which overcame the need for ultraviolet light for many current photocatalysts (e.g., titanium dioxide (TiO2)). Optical coherence tomography and confocal laser scanning microscopy (CLSM) suggested that g-C3N4 coupons inhibited biofilm development and eradicated mature biofilms under the irradiation of white light-emitting diodes. Biofilm inactivation was observed occurring from the surface toward the center of the biofilms, suggesting that the diffusion of reactive species into the biofilms played a key role. By taking advantage of scanning electron microscopy, CLSM, and atomic force microscopy for biofilm morphology, composition, and mechanical property characterization, we demonstrated that photocatalysis destroyed the integrated and cohesive structure of biofilms and facilitated biofilm eradication by removing the extracellular polymeric substances. Moreover, reactive oxygen species generated during g-C3N4 photocatalysis were quantified via reactions with radical probes and 1O2 was believed to be responsible for biofilm control and removal. Our work highlights the promise of using g-C3N4 for a broad range of antimicrobial applications, especially for the eradication of persistent biofilms under visible-light irradiation, including photodynamic therapy, environmental remediation, food-industry applications, and self-cleaning surface development.