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Shape and size control of metal nanocrystals has become a powerful tool in tuning their physicochemical properties for applications, however, the growth mechanisms controlling shape and size are not fully elucidated. Gold nanocuboids provide a simple nanoparticle system for investigating nanocrystal growth mechanisms. Here, we study the control over size and shape anisotropy of gold nanocuboids by copper additives. We first optimize the synthesis and yield. We find that, in the presence of copper additives, symmetry is broken and anisotropic growth can occur, leading to nanobars, rather than nanocubes, accompanied by a significant reduction in particle size. We show that symmetry breaking is caused by a combination of rapid deposition on {111} facets coupled with the slow surface diffusion rate introduced by surface copper. This reveals a mechanism by which metal additives can cause symmetry breaking and control shape in nanoparticle growth. [ABSTRACT FROM AUTHOR]

CsPbI3 perovskite nanocrystals are a promising optoelectronic material when stabilized in their cubic phase. While ongoing efforts have addressed this structural challenge through a variety of meta-stabilization approaches, the postsynthesis purification of these nanocrystal dispersions has remained a challenge. In this article, we undertake a detailed investigation into the chemical, optical, and structural changes that arise during purification of CsPbI3 nanocrystals. It is found that nanocrystal degradation can only be avoided through the judicious control of additives within each purification cycle. Under optimized additive-to-nanocrystal ratios, multiple purification cycles can be readily achieved, while retaining the quality and phase stability of the CsPbI3. This facile purification protocol ensures the preparation of high purity and high quality CsPbI3 nanocrystal inks that are suitable for better characterization or integration in optoelectronic devices. The approach has been generalized for CsPbX3 (X = Cl−, Br−, and I−). [ABSTRACT FROM AUTHOR]

Polymer blends are important for both commercial utility and scientific understanding. The degree of interfacial mixing in polymer blends is important since it influences the blends' mechanical properties. Understanding bulk properties in multiphase polymeric materials requires knowledge of the interfacial properties of the materials. The characterization of the interface, in terms of its width and composition profile, provides insight about the bulk behaviour of the material. Chemical microscopy through electron energy‐loss spectroscopy (EELS) in a transmission electron microscope is gaining popularity to characterize narrow polymer–polymer interfaces. In this work, we show how scanning transmission electron microscopy spectrum imaging, a spatially resolved energy‐loss spectroscopy, can be employed to calculate the interfacial width in a pair of immiscible polymers, taking a polycarbonate–polystyrene (PC‐PS) bilayer as an example. By mapping peaks unique to each of the blend constituents at several points across the interface, we show how the interfacial profile concentrations can be determined. With this method we calculated the interfacial width in the PC‐PS bilayer sample to be approximately 32 nm, even utilizing low resolution spectrometers, which are more widely available. Using the technique described with higher resolution EELS instruments having a better signal‐to‐noise ratio, a higher spatial resolution can be achieved. Using EELS chemical fingerprints of polymers that have been developed earlier, the technique presented here has the potential for effective visualization and morphological measurements of phase‐differentiated polymer blends. This paper is an attempt to enable a new user to characterize polymer–polymer interfaces using chemical microscopy. © 2022 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

The solvatochromic fluorescence probe coumarin 153 (C153) is used to study the temperature dependence of the solvation dynamics and fluorescence depolarization dynamics in the ionic liquids. The C153 fluorescence anisotropy has shown very long time scale orientational relaxation time constants dynamics in the order of 100 ns.

The results of an investigation of a series of poly(arylene ethynylene)s (PAE)s and poly(phenylene ethynylene)s (PPE)s that are end-capped with alpha-terthiophene( T3) groups are reported and are characterized by proton NMR, GPC, and optical spectroscopy. These polymers were designed to allow investigation of the spectroscopy and dynamics of cation radicals created on the single polymer chains by pulse radiolysis.

Semiconductor quantum dots (QDs) are used to dope wide-bandgap chalogenide glasses via sol-gel processing. Such chalcogenides enhance surface passivation of the quantum dots, as evidenced by the increased PL emissions of both core and core shell species used, while a ZnO glass leads to irreversible oxidation of the embedded quantum dots. The embedded QDs are photostable. [ABSTRACT FROM AUTHOR]

We have investigated the ultrafast molecular dynamics of five pyrrolidinium cation room temperature ionic liquids using femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy. The ionic liquids studied are N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide P14+/NTf2-), N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide P1EOE+/NTf2-), N-ethoxyethyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide P1EOE+/NTf2-), N-ethoxyethyl-N-methylpyrrolidinium bromideP1EOE+, and N-ethoxyethyl-N-methylpyrrolidinium dicyanoamide P1EOE+/DCA-). For comparing dynamics among the five ionic liquids, we categorize the ionic liquids into two groups. One group of liquids comprises the three pyrrolidinium cations P14+, P1EOM+, and P1EOE+ paired with the NTf2- anion. The other group of liquids consists of the P1EOE+ cation paired with each of the three anions NTf2-, Br-, and DCA-. The overdamped relaxation for time scales longer than 2 ps has been fit by a triexponential function for each of the five pyrrolidinium ionic liquids. The fast (∼2 ps) and intermediate (∼20 ps) relaxation time constants vary little among these five ionic liquids. However, the slow relaxation time constant correlates with the viscosity. Thus, the Kerr spectra in the range from 0 to 750 cm-1 are quite similar for the group of three pyrrolidinium ionic liquids paired with the NTf2- anion. The intermolecular vibrational line shapes between 0 and 150 cm-1 are fit to a multimode Brownian oscillator model; adequate fits required at least three modes to be included in the line shape. [ABSTRACT FROM AUTHOR]

The rapid and reversible tuning of surface plasmon resonance of a single gold nanocrystal by tens of nanometers electrochemically is reported. The spectral shifts observed for the single metal nanocrystals are found to be more sensitive for elongated morphologies such as rods and lead to color changes perceptible by eye.

The study about the ion radicals of two series of platinum acetylide oligomers conducted by employing electrochemical and pulse radiolysis/transient absorption methods is presented. Results suggest that the polarons are delocalized to some extent on the platinum acetylide chains.

Transfer of protons from the solvent result in decay in the aryl radical anions synthesized from liquid alcohols on microsecond time scale. A 4.5 decade range of rate constants for proton transfer from a single, weak acid, ethanol, to a series of unsubstituted aryl radical anions is described.

The charge and energy transport properties of conjugated polymers were investigated by making use of triplet states of terthiophene ([T.sub.3]) end-capped poly(phenylene ethylene) (PPE). The 1.8-nm delocalization length of triplet excited states in PPE is significantly larger than found in metal-containing PPE polymers, suggesting that the incorporation of the metal into the polymer backbone leads to the confinement of the triplet exciton.