Janus monolayers and their van der Waals heterostuctures are investigated by hybrid density functional theory calculations.

Organic–inorganic halide perovskites are quite promising in applications of large scale photovoltaic technology. However, toxicity is one of the crucial issues in these materials, and searching for environmentally friendly perovskite materials for green energy applications is in high demand. Here we present a systematic ab initio study on the replacement of toxic Pb in the perovskite CH3NH3PbI3 (MAPbI3) with possible mono- and a few binary replacements. In the mono-replacements study, Ge and Sn are the best alternatives to Pb. In the binary replacements, we replace Pb by mixing Ca/Si and Zn/Si. In case of Ca/Si, a monotonic decrease in band gaps with a monotonic increase in the optical absorption was observed with increasing the Ca concentration. It is observed for the first time that the substitution of Ca/Si (or Zn/Si) at the B-site with various ratios would lead to remarkably high device absorption efficiencies. The band gaps of the studied mixed replacements are in the ideal ranges for single-junction solar cell and one cell in tandem architecture. As a result of the smaller effective masses, the mixed replacements could have better carrier mobility. An ab initio molecular dynamic simulation demonstrates the stability of the mixed replacements. More importantly, the mixed substituting elements are highly abundant in the earth. This work is helpful to gain further insights into developing green solar cells with low cost and high performance and would lead to wide applications in the future.

Novel stable perovskites: Pb in CH3NH3PbI3 is replaced by Ca/(Ge, Sn) or Sr/(Ge, Sn) and exhibits high optical absorption.

Gelatin is a protein obtained from the hydrolysis of collagen. Gelatin is an attractive biodegradable material for use in nano-biotechnology and nano-pharmaceutics. Gelatin nanoparticles (NPs) have been widely used as drug and gene carrier to targeted sick tissues including cancer, tuberculosis, HIV infection along with the treatment of vasospasm and restenosis, due to its biocompatibility and biodegradability. For instance, coating with gelatin lowers the cytotoxicity of quantum dots. Moreover, gelatin NPs have the ability to cross the blood-brain barrier, hence proven as a promising candidate to target brain disorders. Macrophage targeting with gelatin NPs for remedy of different diseases is repeatedly reported in previous years. In tissue engineering gelatin is actively utilized for construction of biological and life-long 3D scaffolds for bio-artificial tissues and organ production. Gelatins have a wide range of potential applications which needs to be unraveled in more detail. This review is mainly focused on the applications of gelatin NPs in biomedical sciences.