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The high pressure response of the optical properties of nanomaterials aords unique insight into their mechanical properties and their interplay with the reduced dimensionality of the material. We probe the eects of high hydrostatic pressure on the optical band gap in zincblende CdSe/CdZnS core−shell nanoplatelets with 4 and 6 monolayer thick cores by following the evolution of their photoluminescence spectra from ambient pressure up to ∼6 GPa. We observe that the band gap increases nearly linearly by ∼33 meV/GPa, significantly slower than for bulk CdSe or for colloidal CdSe quantum dots in the same size regime. Using density functional theory and theoretical modeling, we trace this behavior to hardening of the CdSe core due to strain induced by lattice mismatch between core and shell, impacting the electronic structure of the core. 

We report cryogenic ion vibrational spectroscopy of chloride, bromide, and iodide complexes with octa-methyl calix[4]pyrrole (omC4P) and with the tetra-α “four wall” 4-nitroaryl-extended calix[4]pyrrole (AEC4P). 

Ion receptors are molecular hosts that bind ionic guests, often with great selectivity. The interplay of solvation and ion binding in anion host-guest complexes in solution governs the binding efficiency and selectivity of such ion receptors. To gain molecular-level insight into the intrinsic binding properties of octamethyl calix[4]pyrrole (omC4P) host molecules with halide guest ions, we performed cryogenic ion vibrational spectroscopy (CIVS) of omC4P in complexes with fluoride, chloride, and bromide ions. We interpret the spectra using density functional theory, describing the infrared spectra of these complexes with both harmonic and anharmonic second-order vibrational perturbation theory (VPT2) calculations. The NH stretching modes of the pyrrole moieties serve as sensitive probes of the ion binding properties, as their frequencies encode the ion-receptor interactions. While scaled harmonic spectra reproduce the experimental NH stretching modes of the chloride and bromide complexes in broad strokes, the high proton affinity of fluoride introduces strong anharmonic effects. As a result, the spectrum of F−·omC4P is not even qualitatively captured by harmonic calculations, but it is recovered very well by VPT2 calculations. In addition, the VPT2 calculations recover the intricate coupling of the NH stretching modes with overtones and combination bands of CH stretching and NH bending modes and with low-frequency vibrations of the omC4P macrocycle, which are apparent for all halide ion complexes investigated here. A comparison of the CIVS spectra with infrared spectra of solutions of the same ion-receptor complexes in d3-acetonitrile and d6-acetone shows how ion solvation changes the ion-receptor interactions for the different halide ions.