Monocycloplatinated Solvento Complex Displays Turn-on Ratiometric Phosphorescence Responses to Histamine.

The study of biological histamine (HA) requires probes capable of ratiometric photoluminescence detection of HA. We discovered that a monocycloplatinated complex having two solvento ligands ([Pt(2-(2-naphthyl)quinolinate)(NCCH3)2]ClO4) could produce ratiometric phosphorescence responses to HA in aerated aqueous solutions buffered to pH 7.4. The HA response was characterized with a hypsochromic shift of an emission peak wavelength from 635 to 567 nm. The corresponding phosphorescence intensity ratio (i.e., I567 nm/ I635 nm) increased from 0.26 to 1.90. Spectroscopic and spectrometric investigations indicated an occurrence of spontaneous displacement of the labile CH3CN ligands with HA. An independently prepared HA adduct supported this notion. The ratiometric phosphorescence responses to HA were highly tolerant to other biological stimuli, including changes in pH and the presence of biometals and biological Lewis bases such as amino acids, nucleosides, biothiols, neurotransmitters, and small molecular metabolites. Of note was the high selectivity toward HA over common biological ligands, including histidine, cysteine, and homocysteine, which was ascribed to tighter HA binding. Our phosphorescence measurements employing Boc-protected derivatives of HA suggested that the bis-chelate motif involving imidazolyl and terminal amino groups was crucial for eliciting the ratiometric phosphorescence signaling. Finally, the bioimaging utility of the HA probe was validated using RAW 264.7 macrophages that were exogenously supplemented with HA or stimulated with thapsigargin to enrich intracellular HA. Ratiometric phosphorescence imaging microscopy experiments demonstrated the ability of the probe for monitoring intracellular HA uptake. In addition, photoluminescence lifetime imaging microscopy techniques could be applied for visualization of HA within the RAW 264.7 cells, because the HA binding elongated the photoluminescence lifetime. Our study demonstrated the promising utility of inner-sphere interactions of phosphorescent Pt(II) complexes for detection of biological HA.

Narrowing the Phase Distribution of Quasi-2D Perovskites for Stable Deep-Blue Electroluminescence.

Solution-processed quasi-2D perovskites contain multiple quantum wells with a broad width distribution. Inhomogeneity results in the charge funneling into the smallest bandgap components, which hinders deep-blue emission and accelerates Auger recombination. Here, a synthetic strategy applied to a range of quasi-2D perovskite systems is reported, that significantly narrows the quantum well dispersity. It is shown that the phase distribution in the perovskite film is significantly narrowed with controlled, simultaneous evaporation of solvent and antisolvent. Modulation of film formation kinetics of quasi-2D perovskite enables stable deep-blue electroluminescence with a peak emission wavelength of 466 nm and a narrow linewidth of 14 nm. Light emitting diodes using the perovskite film show a maximum luminance of 280 cd m-2 at an external quantum efficiency of 0.1%. This synthetic approach will serve in producing new materials widening the color gamut of next-generation displays.

Block copolymer micelles enable facile synthesis of organic-inorganic perovskite nanostructures with tailored architecture.

We report a distinct method for the production of organic-inorganic hybrid perovskite (OIHP) nanostructures using block copolymer micelles as scaffolds. We reveal that various nanostructures can be obtained by controlling the parameters related to micelle disassembly. The strategy reported herein can be generalized for the fabrication of diverse nanostructures toward target-oriented potential applications.

Spectral Instability of Layered Mixed Halide Perovskites Results from Anion Phase Redistribution and Selective Hole Injection.

Despite the ability to precisely tune their bandgap energies, mixed halide perovskites (MHPs) suffer from significant spectral instability, which obstructs their utilization for the rational design of light-emitting diodes. Here, we investigate the origin of the electroluminescence peak shifts in layered MHPs containing bromide and iodide. X-ray diffraction and steady-state absorption measurements prove effective integration of iodide into the cubic lattice and the spatially uniform distribution of halides in the ambient environment. However, the applied electric field during the device operation is found to drive the systematic halide migration. Quantum mechanical density functional theory calculations reveal that the different activation energies required for directional ion hopping lead to the redistribution of anions. In-depth analyses of the electroluminescence spectra indicate that the spectral shifting rate is dependent on the drift velocity of halides. Finally, it is suggested from our study that the dominant red emission is ascribed to the thermodynamically favorable selective hole injection. Our mechanistic study provides insights into the fundamental reason for the spectral instability of devices based on MHPs.

Universal perpendicular orientation of block copolymer microdomains using a filtered plasma.

Sub-10 nm patterns prepared by directed self-assembly (DSA) of block copolymer (BCP) thin films offer a breakthrough method to overcome the limitations of photolithography. Perpendicular orientation of the BCP nanostructures is essential for lithographic applications, but dissimilar surface/interfacial energies of two blocks generally favour parallel orientations, so that the perpendicular orientation could only be obtained under very limited conditions. Here, we introduce a generalized method for creating perpendicular orientations by filtered plasma treatment of the BCP films. By cross-linking the surface of disordered BCP films using only physical collisions of neutral species without ion bombardment or UV irradiation, neutral layers consistent with the BCP volume fraction are produced that promote the perpendicular orientations. This method works with BCPs of various types, volume fractions, and molecular weights individually at the top and bottom interfaces, so it was applied to orientation-controlled 3D multilayer structures and DSA processes for sub-10 nm line-spacing patterns.