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Key Points Question How has the 2017 Philadelphia beverage tax factored into longer-term changes in beverage prices and purchases in independent food retail stores based on observational data? Findings This cross-sectional study found that, 2 years after tax implementation, price audits of stores showed 137% of the tax was passed through to prices and bag checks indicated a 42% decline in volume of taxed beverages purchased in Philadelphia compared with Baltimore. Total calories purchased from beverages and high-sugar foods declined, suggesting food substitution did not offset beverage declines. Meaning These findings suggest a city-level beverage excise tax was associated with persistent declines in purchases of sweetened drinks and calories from sugar in independent stores.

Reducing the size of metal halide perovskite crystals to the nanoscale has been demonstrated to stabilize high-performance metastable polymorphs at room temperature. Cesium lead iodide (CsPbI3), for example, typically exists as the insulating δ-phase at room temperature but can adopt the narrow-bandgap γ-phase when the crystal size is reduced to the nanometer length scale. Here we advance a fundamental understanding of the role of nanoconfinement in CsPbI3 polymorph stabilization through a combination of X-ray diffraction and temperature-dependent photoluminescence. Using a wet annealing method to directly form γ-CsPbI3 from solution in the cylindrical nanopores of anodized aluminum oxide, we discovered that nanoconfinement lowers the δ−γ solid-state phase transition temperature from 448 K in the bulk to 370 K. Once formed, nanoconfined γ-CsPbI3 crystals were found to be stable across the temperature range of 4–610 K and upon an unprecedented one year of air exposure at room temperature. Taking advantage of the nanoconfinement-induced suppression of phase transitions, we report for the first time a detailed analysis of electron–phonon interactions in γ-CsPbI3 via temperature-dependent photoluminescent measurements. In-depth analysis of the temperature-dependent peak broadening revealed electron–phonon interactions to be dominated by Fröhlich scattering, similar to that observed in inorganic–organic hybrid perovskite systems. Photoluminescence mapping further confirmed that nanoconfined γ-CsPbI3 crystals exhibit spatial uniformity on the tens of micrometers length scale, suggesting nanoconfinement as a promising strategy to form stable, high-performance perovskite films from solution for light-emitting and light-harvesting applications.

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