Synthesis of novel Type-II MnNb2O6/g-C3N4 Mott-Schottky heterojunction photocatalyst: Excellent photocatalytic performance and degradation mechanism of fluoroquinolone-based antibiotics

Fluoroquinolone antibiotics have been encountered in aquatic environments in quantities giving rise to significant concern recently. To cope with this problem, it is necessary to design a semiconductor photocatalyst having excellent photocatalytic efficiency to eliminate the antibiotics. The heterojunction is a likely situate where the efficiency of relevant photocatalyst can be strengthened. In this study, the performance of MnNb₂O₆/g-C₃N₄ (MNO/g-CN) composites in the photocatalytic degradation of ciprofloxacin (CIP) and tetracycline-HCl (TCH) antibiotics was explored. Enhanced photocatalytic activity of MNO/g-CN was found to be owing to electron's shifting between the MNO, and g-CN sheets, which promotes the formation of photo-generated e⁻/h⁺ pairs. This shows a low-waste, high-performance material exists to eradicate CIP and TCH from wastewater. Further, the structural, photochemical and light interacted properties of the MNO/g-CN photocatalyst, prepared by solvothermal method and sonication, were described using photochemical, physiochemical and electrochemical approaches. The synthesized photocatalyst owes its particular efficiency to its methodical photo-degradation of CIP and TC using visible light. The optimum composite 15% MNO/g-CN evinced the greatest photocatalytic efficiency with CIP and TCH photo-degradation of 94.10%, and 98.50%, respectively, and degradation mechanism were investigated using LC-MS spectroscopy. The suitable photocatalytic activity is ascribed to lower the recombination's rate of e⁻/h⁺ pairs. The scavenging evaluations proved that the h⁺ and ^•O₂^- were two major photoactive species accomplishing the CIP and TCH photodegradation over MNO/g-CN under visible region. Our findings pave the way for the construction of efficient binary photocatalysts for antibiotic restitution.

Recent progress in nanomaterial-functionalized membranes for removal of pollutants

Membrane technology has gained tremendous attention for removing pollutants from wastewater, mainly due to their affordable capital cost, miniature equipment size, low energy consumption, and high efficiency even for the pollutants present in lower concentrations. In this paper, we review the literature to summarize the progress of nanomaterial-modified membranes for wastewater treatment applications. Introduction of nanomaterial in the polymeric matrix influences membrane properties such as surface roughness, hydrophobicity, porosity, and fouling resistance. This review also covers the importance of functionalization strategies to prepare thin-film nanocomposite hybrid membranes and their effect on eliminating pollutants. Systematic discussion regarding the impact of the nanomaterials incorporated within membrane, toward the recovery of various pollutants such as metal ions, organic compounds, dyes, and microbes. Successful examples are provided to show the potential of nanomaterial-functionalized membranes for regeneration of wastewater. In the end, future prospects are discussed to develop nanomaterial-based membrane technology.

Self-redox reaction driven in situ formation of Cu2O/Ti3C2Tx nanosheets boost the photocatalytic eradication of multi-drug resistant bacteria from infected wound

BACKGROUND

MXenes with interesting optical and electrical properties have been attractive in biomedical applications such as antibacterial and anticancer agents, but their low photogeneration efficiency of reactive oxygen species (ROS) and poor stability are major concerns against microbial resistance.

METHODS

Water-dispersible single layer Ti₃C₂T_x-based MXene through etching tightly stacked MAX phase precursor using a minimally intensive layer delamination method. After addition of Cu(II) ions, the adsorbed Cu(II) ions underwent self-redox reactions with the surface oxygenated moieties of MXene, leading to in situ formation of Cu₂O species to yield Cu₂O/Ti₃C₂T_x nanosheets (heterostructures).

RESULTS

Under NIR irradiation, the Cu₂O enhanced generation of electron-hole pairs, which boosted the photocatalytic production of superoxide and subsequent transformation into hydrogen peroxide. Broad-spectrum antimicrobial performance of Cu₂O/Ti₃C₂T_x nanosheets with sharp edges is attributed to the direct contact-induced membrane disruption, localized photothermal therapy, and in situ generated cytotoxic free radicals. The minimum inhibitory concentration of Cu₂O/Ti₃C₂T_x nanosheets reduced at least tenfold upon NIR laser irradiation compared to pristine Cu₂O/Ti₃C₂T_x nanosheets. The Cu₂O/Ti₃C₂T_x nanosheets were topically administrated on the methicillin-resistant Staphylococcus aureus (MRSA) infected wounds on diabetic mice.

CONCLUSION

Upon NIR illumination, Cu₂O/Ti₃C₂T_x nanosheets eradicated MRSA and their associated biofilm to promote wound healing. The Cu₂O/Ti₃C₂T_x nanosheets with superior catalytic and photothermal properties have a great scope as an effective antimicrobial modality for the treatment of infected wounds.

Catalytic and photoresponsive BiZ/CuxS heterojunctions with surface vacancies for the treatment of multidrug-resistant clinical biofilm-associated infections

We report a one-pot facile synthesis of highly photoresponsive bovine serum albumin (BSA) templated bismuth-copper sulfide nanocomposites (BSA-BiZ/Cu_xS NCs, where BiZ represents in situ formed Bi₂S₃ and bismuth oxysulfides (BOS)). As-formed surface vacancies and BiZ/Cu_xS heterojunctions impart superior catalytic, photodynamic and photothermal properties. Upon near-infrared (NIR) irradiation, the BSA-BiZ/Cu_xS NCs exhibit broad-spectrum antibacterial activity, not only against standard multidrug-resistant (MDR) bacterial strains but also against clinically isolated MDR bacteria and their associated biofilms. The minimum inhibitory concentration of BSA-BiZ/Cu_xS NCs is 14-fold lower than that of BSA-Cu_xS NCs because their multiple heterojunctions and vacancies facilitated an amplified phototherapeutic response. As-prepared BSA-BiZ/Cu_xS NCs exhibited substantial biofilm inhibition (90%) and eradication (>75%) efficiency under NIR irradiation. Furthermore, MRSA-infected diabetic mice were immensely treated with BSA-BiZ/Cu_xS NCs coupled with NIR irradiation by destroying the mature biofilm on the wound site, which accelerated the wound healing process via collagen synthesis and epithelialization. We demonstrate that BSA-BiZ/Cu_xS NCs with superior antimicrobial activity and high biocompatibility hold great potential as an effective photosensitive agent for the treatment of biofilm-associated infections.

Bio-nanocomposite based highly sensitive and label-free electrochemical immunosensor for endometriosis diagnostics application

In this research, for the first time, a bio-nanocomposites based highly sensitive and label-free electrochemical immunosensor is reported with the aim of endometriosis diagnostics application. Multiwalled carbon nanotube and magnetite nanoparticle (MWCNT-Fe₃O₄) was dispersed in chitosan (CS) to fabricate a bio-nanocomposite to immobilize very monoclonal specific antibody (via cross-linking using glutaraldehyde) for selective electrochemical immuno-sensing of carbohydrate antigen 19-9 (CA19-9), a potential biomarker for endometriosis diagnostics. Well-characterized Anti-Abs_CA19-9/CS-MWCNT-Fe₃O₄ immune-electrode fabricated on glassy carbon electrode (GCE) successfully detect CA 19-9 and exhibited a high sensitivity as (2.55 µA pg^-1 cm^-1), a detection limit of 0.163 pg mL^-1, detection range from 1.0 pg mL^-1 to 100 ng mL^-1. Our fabricated electrochemical Abs_CA19-9/CS-MWCNT-Fe₃O₄ immunosensor performed CA19-9 sensing in physiological range and at a very level which suggest it application for early-stage diagnostics, diseases monitoring, and optimization of therapy. To claim the clinical application, our sensor was tested using real samples and sensing performance was validated using enzyme-linked immune-sorbent assay (ELISA). The results of the studies projected Abs_CA19-9/CS-MWCNT-Fe₃O₄ electrochemical CA19-9 immunosensor as a potential and affordable alternate of conventional techniques like ELISA. We believe that our fabricated sensor can be the plane of a disease's management program due to affordable, rapid, label-free, and sensitive detection of a targeted biomarker.

Gold Nanoparticle Embedded on a Reduced Graphene Oxide/polypyrrole Nanocomposite: Voltammetric Sensing of Furazolidone and Flutamide

A new electrochemical sensor has been constructed based on the in situ preparation of gold nanoparticle embedded on reduced graphene oxide and polypyrrole nanotube (AuNP@rGO/PPyNT) composite through a nanosecond laser-induced heating technique. The as-prepared composite is used for individual as well as the simultaneous electrochemical determination of chemotherapy drug (furazolidone, FU) and anticancer drug (flutamide, FLT). The composite was analyzed by X-ray Diffraction, scanning electron microscopy/energy-dispersive X-ray analysis, transmission electron microscopy, Raman spectrometry, and X-ray photoelectron spectroscopy analysis, thus confirming the successful synthesis of this composite and its physical features. The modified AuNP@rGO/PPyNT electrode was examined through cyclic voltammetry and differential pulse voltammetry (DPV) methods in pH 7.0 for the determination of FU and FLT in individual, simultaneous, and mixed systems. The fabricated sensor showed wide linear responses (0.01-1080.11 μM and 0.01-1214.11 μM) of analytes, with the lower limits of detection of 2.3 and 2.45 nM and higher sensitivity of 53.75 and 50.06 μA μM^-1 cm^-2, respectively. Furthermore, the constructed sensor demonstrates higher stability, reproducibility, and repeatability, and is effectively applied for the analysis of FU and FLT content in the human serum sample analysis with satisfactory recovery.

Highly sensitive electrode materials for the voltammetric determination of nitrofurantoin based on zinc cobaltate nanosheets

Schematic illustration of the electrocatalytic activity of nitrofurantoin (NFT) on ZnCo₂O₄ nanosheets.

Sr-Doped NiO3 nanorods synthesized by a simple sonochemical method as excellent materials for voltammetric determination of quercetin

A fabricated Sr-doped NiO₃ nanorod-modified GCE was developed for electrochemical sensing of quercetin.