The toxicity issue of lead hinders large-scale commercial production and photovoltaic field application of lead halide perovskites. Some novel non- or low-toxic perovskite materials have been explored for development of environmentally friendly lead-free perovskite solar cells (PSCs). This review studies the substitution of equivalent/heterovalent metals for Pb based on first-principles calculation, summarizes the theoretical basis of lead-free perovskites, and screens out some promising lead-free candidates with suitable bandgap, optical, and electrical properties. Then, it reports notable achievements for the experimental studies of lead-free perovskites to date, including the crystal structure and material bandgap for all of lead-free materials and photovoltaic performance and stability for corresponding devices. The review finally discusses challenges facing the successful development and commercialization of lead-free PSCs and predicts the prospect of lead-free PSCs in the future.

Effective disinfection technology to combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can help reduce viral transmissions during the on-going COVID-19 global pandemic and in the future. Ultraviolet (UV) devices emitting UVC irradiation (200-280 nm) have proven to be effective for virus disinfection, but limited information is available for SARS-CoV-2 due to the safety requirements of testing, which is limited to biosafety level (BSL) 3 laboratories. In this study, inactivation of SARS-CoV-2 in thin-film buffered aqueous solution (pH 7.4) was determined across UVC irradiation wavelengths (222 nm to 282 nm) from krypton chloride (KrCl*) excimers, a low-pressure mercury-vapor lamp, and two UVC light emitting diodes. Our results show that all tested UVC devices can effectively inactivate SARS-CoV-2, among which the KrCl* excimer had the best disinfection performance (i.e., highest inactivation rate). The inactivation rate constants of SARS-CoV-2 across wavelengths are similar to those for murine hepatitis virus (MHV) from our previous investigation, suggesting that MHV can serve as a reliable surrogate of SARS-CoV-2 with a lower BSL requirement (BSL-2) during UV disinfection tests. This study provides fundamental information for UVC action on SARS-CoV-2 and guidance for achieving reliable disinfection performance of UVC devices. IMPORTANCE UV light is an effective tool to help stem the spread of respiratory viruses and protect public health in commercial, transportation and healthcare settings. For effective use of UV, there is a need to determine the efficiency of different UV wavelengths in killing pathogens, specifically SARS-CoV-2, to support efforts to control the on-going COVID-19 global pandemic and future coronavirus-caused respiratory virus pandemics. We found that SARS-CoV-2 can be inactivated effectively using a broad range of UVC wavelengths, and 222nm provided the best disinfection performance. Interestingly, 222 nm irradiation has been found to be safe for human exposure up to thresholds that are beyond effective for inactivating viruses. Therefore, applying UV light from KrCl* excimers in public spaces can effectively help reduce viral aerosol or surface transmissions.

Ultraviolet (UV) devices emitting UVC irradiation (200− 280 nm) have proven to be effective for virus disinfection, especially on surfaces and in air, due to their rapid effectiveness and limited to no material corrosion. Numerous studies of UV-induced inactivation focused on nonenveloped viruses. Little is known about UVC action on enveloped viruses across UVC wavelengths. In this study, we determined inactivation efficiencies of two coronaviruses (ssRNA) and an enveloped dsRNA bacteriophage surrogate in buffered aqueous solution (pH 7.4) using five commonly available UVC devices that uniquely emit light at different wavelengths spanning 222 nm emitting krypton chloride (KrCl*) excimers to 282 nm emitting UVC LEDs. Our results show that enveloped viruses can be effectively inactivated using UVC devices, among which the KrCl* excimer had the best disinfection performance (i.e., highest inactivation rate) for all three enveloped viruses. The coronaviruses exhibited similar sensitivities to UV irradiation across the UVC range, whereas the bacteriophage surrogate was much more resistant and exhibited significantly higher sensitivity to the Far UVC (<230 nm) irradiation. This study provides necessary information and guidance for using UVC devices for enveloped virus disinfection, which may help control virus transmission in public spaces during the ongoing COVID-19 pandemic and beyond.

Developing a sophisticated nanomedicine platform to deliver therapeutics effectively and safely into tumor/cancer cells remains challenging in the field of nanomedicine. In particular, reliable peptide drug delivery systems capable of overcoming biological barriers are still lacking. Here, we developed a simple, rapid, and robust strategy to manufacture nanoclusters of ∼90 nm in diameter that are self-assembled from lanthanide-doped nanoparticles (5 nm), two anticancer peptides with different targets (BIM and PMI), and one cyclic peptide iNGR targeted to cancer cells. The peptide-lanthanide nanoclusters (LDC-PMI-BIM-iNGR) enhanced the resistance of peptide drugs to proteolysis, disassembled in response to reductive conditions that are present in the tumor microenvironment and inhibited cancer cell growth in vitro and in vivo. Notably, LDC-PMI-BIM-iNGR exhibited extremely low systemic toxicity and side effects in vivo. Thus, the peptide-lanthanide nanocluster may serve as an ideal multifunctional platform for safe, targeted, and efficient peptide drug delivery in cancer therapy.