Rectangular shaped, high crystalline quality, defect free and colorless 3D perovskite single crystals of CH₃NH₃PbCl₃ were grown using the solvent evaporation method at room temperature for the first time.

Guest capture and release are important properties of self-assembling nanostructures. Over time, a significant fraction of guests might engage in short-lived states with different symmetry and stereoselectivity and transit frequently between multiple environments, thereby escaping common spectroscopy techniques. Here, we investigate the cavity of an iron-based metal organic polyhedron (Fe-MOP) using spin-hyperpolarized ¹²⁹Xe Chemical Exchange Saturation Transfer (hyper-CEST) NMR. We report strong signals unknown from previous studies that persist under different perturbations. On-the-fly delivery of hyperpolarized gas yields CEST signatures that reflect different Xe exchange kinetics from multiple environments. Dilute pools with ~ 10⁴-fold lower spin numbers than reported for directly detected hyperpolarized nuclei are readily detected due to efficient guest turnover. The system is further probed by instantaneous and medium timescale perturbations. Computational modeling indicates that these signals originate likely from Xe bound to three Fe-MOP diastereomers (T, C₃, S₄). The symmetry thus induces steric effects with aperture size changes that tunes selective spin manipulation as it is employed in CEST MRI agents and, potentially, impacts other processes occurring on the millisecond time scale.

A water-soluble PET-based chemosensor is developed which can detect Al(iii) and F⁻ ions up to nano- and picomolar (lowest detection so far) detection limit, respectively, also utilized to establish aluminum-toxicity effect in biological systems.

Broad-band emissions related to self-trapped excitons (STEs) in the sub-bandgap region in organic–inorganic hybrid perovskites and double perovskite crystals have drawn attention in recent times due to their potential in optoelectronic device applications. In this study, we have shown that the formation of STEs in CH₃NH₃PbBr₃ single crystals can be controlled using a suitable sample synthesis procedure. We have observed a broad-band emission (FWHM ∼ 80 nm) for crystals whose crystallization is fast, whereas it was absent if we follow slow crystallization procedures. Using UV-Visible absorption spectroscopy, temperature-dependent photoluminescence (PL), time-resolved PL (TRPL), and dc magnetization studies, we concluded that defect-assisted extrinsic self-trapping is dominant here over the intrinsic self-trapping process and excess Pb atoms in interstitial positions are predominantly responsible for the extrinsic self-trapping process.

N-Sulfonyl-activated aziridines are known to undergo anionic-ring-opening polymerizations (AROP) to form polysulfonyllaziridines. However, the post-polymerization deprotection of the sulfonyl groups from polysulfonyllaziridines remains challenging. In this report, the polymerization of tert-butyl aziridine-1-carboxylate (BocAz) is reported. BocAz has an electron-withdrawing tert-butyloxycarbonyl (BOC) group on the aziridine nitrogen. The BOC group activates the aziridine for AROP and allows the synthesis of low-molecular-weight poly(BocAz) chains. A ¹³C NMR spectroscopic analysis of poly(BocAz) suggested that the polymer is linear. The attainable molecular weight of poly(BocAz) is limited by the poor solubility of poly(BocAz) in AROP-compatible solvents. The deprotection of poly(BocAz) using trifluoroacetic acid (TFA) cleanly produces linear polyethyleneimine. Overall, these results suggest that carbonyl groups, such as BOC, can play a larger role in the in the activation of aziridines in anionic polymerization and in the synthesis of polyimines.