Unraveling the Role of 2D Ti3C2Tx MXene Nanosheets in Cu-Based Double Perovskite Active Layer for Enhanced Photovoltaic Performance.

Although the atmospheric stability of lead-free inorganic double perovskite (DP) solar cells (PSCs) looks promising, their further development is hampered by inadequate film quality and non-radiative carrier recombination at the interfaces. Herein, the incorporation of a newly developed intriguing class of 2D material Ti3C2Tx MXene nanosheets with the photo-absorbing Cu2AgBiI6 (CABI) active layer of a fully inorganic solar cell is reported. The highly conductive Ti3C2Tx nanosheets work as a multi-functional additive by tuning the band gap, reducing the non-radiative carrier recombination, and inhibiting carrier accumulation. In addition, the presence of Ti3C2Tx MXene increases the surface free energy of the perovskite film, which elevates the energy barrier for nucleation and realizes a highly crystalline CABI perovskite film. Primarily, the MXene modification accelerates the charge extraction and transport at the interfaces of the active layer, utilizing energy level alignment with the charge transport layers. Consequently, the photo-conversion efficiency (PCE) of the device with MXene is substantially enhanced to 1.50%. Moreover, the 2D Ti3C2Tx nanosheets increased the long-term stability of the devices by retaining 70% of the initial PCE after 1680 h. With regard to relieving the severe carrier recombination at the interfaces, this work sets a new paradigm toward imminent solar energy conversion.

Oxidative Addition to the N-C Bond Vs Formation of the Zwitterionic Intermediate in Platinum(II)-Catalyzed Intramolecular Annulation of Alkynes to Form Indoles: Mechanistic Studies and Reaction Scope.

In this study, Pt(II)-catalyzed intramolecular translocation annulation of ortho-alkynylamides to the formation of indoles is presented, where a proposed intermediacy of zwitterionic intermediate has been substantiated over the oxidative addition. We focused our attention on Pt(II)-catalyzed aminoacylation of alkynes both theoretically and experimentally using low boiling solvent where the formation of deacylation product was suppressed simultaneously. One-step intramolecular [1,3]-acyl migration from the zwitterionic intermediate is highly unlikely, which imparts a high energy barrier of +99.0 kcal mol-1. Another possible approach involving oxidative addition to the N-C bond, migratory insertion to alkyne, and subsequent reductive elimination is also explored through DFT studies to justify the reaction consequence. However, based on the computational studies, it is suggested that initial zwitterion formation is highly favored over oxidative addition. We suggest the formation of an acylium intermediate, which can further react with indol-3-ylplatinum species in an intramolecular manner, albeit within the same solvent cage to form 3-acyl indoles.

Water extract of red mud: an efficient and renewable medium for environmentally benign synthesis of 2-amino-4H-chromenes.

In this study, an efficient and convenient domino Michael addition/intramolecular cyclization protocol is presented for the synthesis of biologically relevant 2-amino-4H-chromenes in short reaction times using water extract of red mud (WERM) at room temperature. Red mud is generated abundantly as wastes in aluminum industries and this is the first report to utilize WERM as an effective and renewable medium in organic synthesis. As the precursor material is a waste, the present method is environmentally benign and economical. The final 2-amino-4H-chromenes were obtained in high yields by simple precipitation and subsequent washing by aqueous ethanol which eliminates the chromatographic separation. The present method is tolerated by electronically diverse functional groups and also applicable for large-scale synthesis. Moreover, WERM was recovered from the reaction medium and reused for several cycles without significant loss of reactivity.