Colloidal lead halide perovskite (LHP) nanocrystals are of interest as photoluminescent quantum dots (QDs) whose properties depend on the size and shape. They are normally synthesized on subsecond time scales through hard-to-control ionic metathesis reactions. We report a room-temperature synthesis of monodisperse, isolable spheroidal APbBr 3 QDs (A=Cs, formamidinium, methylammonium) that are size-tunable from 3 to over 13 nanometers. The kinetics of both nucleation and growth are temporally separated and drastically slowed down by the intricate equilibrium between the precursor (PbBr 2 ) and the A[PbBr 3 ] solute, with the latter serving as a monomer. QDs of all these compositions exhibit up to four excitonic transitions in their linear absorption spectra, and we demonstrate that the size-dependent confinement energy for all transitions is independent of the A-site cation.

Tin fluoride (SnF 2 ) is an indispensable additive for high-efficiency Pb-Sn perovskite solar cells (PSCs). However, the spatial distribution of SnF 2 in the perovskite absorber is seldom investigated while essential for a comprehensive understanding of the exact role of the SnF 2 additive. Herein, we revealed the spatial distribution of the SnF 2 additive and made structure-optoelectronic properties-flexible photovoltaic performance correlation. We observed the chemical transformation of SnF 2 to a fluorinated oxyphase on the Pb-Sn perovskite film surface due to its rapid oxidation. In addition, at the buried perovskite interface, we detected and visualized the accumulation of F − ions. We found that the photoluminescence quantum yield of Pb-Sn perovskite reached the highest value with 10 mol % SnF 2 in the precursor solution. When integrating the optimized absorber in flexible devices, we obtained the flexible Pb-Sn perovskite narrow bandgap (1.24 eV) solar cells with an efficiency of 18.5% and demonstrated 23.1% efficient flexible four-terminal all-perovskite tandem cells.

In this work the possibility was investigated to synthesize in-situ silver nanoparticles (AgNP) on graphene oxide (GO) surface without commonly used additional reducing or alkalizing agents or increased temperature. Using diverse microscopic (AFM, TEM) and spectroscopic methods, it was proved that very small AgNPs were formed on GO by simple incubation for 2 hours a mixture of GO dispersion and AgNO3. The prepared nanomaterial (GO_Ag) was also assessed using electrochemical methods and it exhibited electrochemical behavior similar to GO_Ag nanomaterial prepared with a help of citric acid as a reducing agent. Furthermore, it was found that i) electrochemical reduction of the GO_Ag on electrode surface decreased the voltammetric response even though this step has increased the surface conductivity and ii) GO_Ag can be employed for sensing of chlorides with detection limit of 79 M and a linear range up to 10 mM. It could also provide electrochemical response toward chloroacetanilide herbicide metazachlor. Hence, the reducing capabilities of GO were proved to be applicable for insitu synthesis of metal nanoparticles with the highest possible simplification and the as-prepared nanomaterials could be employed for fabrication of different electrochemical sensors.

N-heterocyclic moieties are abundant among pharmaceuticals and agrochemicals, but a challenge for metalorganic and organocatalytic transformations. We present tripeptides of the type H-Pro-Pro-Xaa as catalysts for stereoselective conjugate addition reactions between N-heterocyclic substituted aldehydes and electrophiles. Alkyl substituents at the N-terminal proline, the reactive site, were crucial for high chemo-and stereoselectivity. Different N-heterocyclic moieties, even at both reaction partners, were readily tolerated and products were obtained in yields of 61-95% and enantioselectivities of up to 98% ee.

Colloidal lead halide perovskite (LHP) nanocrystals (NCs, with bright and spectrally narrow photoluminescence (PL) tunable over the entire visible spectral range, are the latest generation of semiconductor quantum dots (QDs) of immense interest as classical and quantum light sources. LHP NCs form by sub-second fast and hence hard-to-control ionic metathesis reactions, which severely limits the access to size-uniform and shape-regular NCs in the sub-10 nm range. We posit that a synthesis path comprising an intricate equilibrium between the precursor (PbBr2) and the Cs[PbBr3] solute for the QD nucleation may circumvent this challenge. Here, we report a room-temperature synthesis of monodisperse, isolable spheroidal CsPbBr3 QDs, size-tunable in the 3-13 nm range. The kinetics of both nucleation and therefrom temporally separated growth are drastically slowed down by the formation of transient Cs[PbBr3], resulting in total reaction times of up to 30 minutes. The methodology is then extended to FAPbBr3 (FA = formamidinium) and MAPbBr3 (MA = methylammonium), allowing for thorough experimental comparison and modeling of their physical properties under intermediate quantum confinement. In particular, QDs of all these compositions exhibit up to four excitonic transitions in their linear absorption spectra and we demonstrate that the size-dependent confinement energy for all transitions is independent of the A-site cation.