MXene-Integrated Metal Oxide Transparent Photovoltaics and Self-Powered Photodetectors

MXene-integrated photovoltaic devices can be used to create optically transparent systems to produce electrical energy. MXenes, an emerging family of two-dimensional materials, have attracted a tremendous amount of interest for their use in various applications. In particular, their optical transparency, metallic conductivity, and large-scale processing make MXenes highly applicable in transparent photovoltaic devices (TPVDs). Here we propose a Ti3C2Tx MXene-based inorganic TPVD. Reducing the sheet resistance of MXene and improving its contact with the metal oxide (NiO/TiO2) heterojunction enables the generation of electric power (30 μW cm–2) from ultraviolet light while selectively passing visible light for high-transparency (39.73%). Moreover, the photovoltaic effect induces a high photovoltage of 0.45 V to enable the TPVD to work in self-powered mode. The MXene-embedded transparent photodetector works in photovoltaic mode and has a fast response speed of 80 μs and high detectivity of 1.6 × 1010 Jones. The spacing of the MXene-transparent devices at color-neutral coordinates in color maps indicates the invisibility of the device. This work demonstrates the large-scale application of MXene as a seamless platform for transparent electronics of photovoltaics and photodetectors. Transparent photoelectric interfaces can be used for energy generation; in bioelectronics; and in windows of building, vehicles, and displays

Hematoporphyrin Photosensitizer-Linked Carbon Quantum Dots for Photodynamic Therapy of Cancer Cells

The direct use of conventional photosensitizers in photodynamic therapy (PDT) of cancer cells has been thwarted by their low solubility, poor photostability, and aggregation tendency. Hence, complex and hectic synthetic procedures, such as developing nanomaterials and subsequently loading them with photosensitizers, have become mandatory for the effective use of photosensitizers in PDT. In this study, we have avoided complex procedures and produce hematoporphyrin (HP) photosensitizer-encapsulated carbon quantum dots (CQDs) (HP-CQDs) facilely through a well-controlled one-step microwave reaction by using the HP monomer as one of the precursors. The as-synthesized HP-CQDs retained all intrinsic optical and chemical properties of HP, while displaying excellent solubility in water. Importantly, the excellent reactive oxygen species generation ability of HP-CQDs under the illumination of deep red light favored their applicability in PDT-assisted efficient eradication of human breast cancer cells (MCF-7). Compared to HP, HP-CQDs exhibited very high phototoxicity and low dark toxicity toward MCF-7 cells. Overall, this study offers a proof of concept that photosensitizer-implanted CQDs, having excellence in PDT-assisted cancer treatment, can be easily designed by strategically exploiting the diversity available in the selection of precursors and synthesis conditions to produce CQDs

Ultraviolet–Ozone-Activation-Driven Ag Nanoparticles Grown on Plastic Substrates for Antibacterial Applications

A simple, cheap, and environment-friendly method is developed to fabricate antibacterial plastic films or fibers. We report a robust method to decorate silver nanoparticles (AgNPs) on plastics or fibers, which is achieved easily by dipping ultraviolet–ozone (UVO)-treated plastic films or fibers into a silver nitrate solution under mild conditions. Apart from silver nitrate, neither a stabilizer nor a reducing agent is required, and no post-treatment is required to reduce the Ag+ ions into AgNPs. The only process required is the pre-treatment of the plastic substrates using UVO under an ambient condition for their surface activation. Most importantly, the AgNP-coated plastics show a robust adhesion ability and high bactericidal activity, more than 99% toward both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Because the AgNP-decoration on plastic substrates by UVO-treatment is environmentally benign, highly reproducible, economically beneficial, and universally acceptable for many kinds of plastic substrates, it could be widely utilized for producing AgNP-coated plastics suitable for biological and environmental applications in both academics and industries