Colorimetric Monitoring of a Chemical Reaction Using Cesium Lead Halide Assays

Cesium lead halide (CsPbX3, X = F, Cl, Br, I ) nanomaterials have a number of novel optoelectronic and physical properties, both of which are tailorable based on halide type and concentration, such as halide composition-dependent photoluminescence and rapid halide exchange while maintaining crystal structure. In this work we take advantage of these properties and use colloidal CsPbI3 nanoparticles as a proxy and colorimetric sensor of a chemical reaction in real-time. A solvolysis reaction between 2-bromo-2-methylbutane and butanol was used as a model system. A product of reaction, a bromide ion, could be detected via halide exchange with CsPbI3, by way of a quantitative blue shift (Δλ) in photoluminescence. The kinetics of this shift was calibrated against a known Br - source, which allowed for conversion to apparent values solvation kinetics. The observed rate constants (k) and corresponding activation energies (Ea) measured via the CsPbI3 probe were consistent with literature values for the reaction, confirming the validity of the approach.