Synchronized Fluorescence Emission and UV–Vis Absorption Wavelength Shift Sensing for Trace Moisture in Highly Polar Aprotic Solvents

ABSTRACT Accurate trace‐moisture detection in organic solvents is crucial for numerous industrial and scientific applications, yet conventional fluorescence sensors often suffer from poor accuracy due to their dependence on environmentally sensitive intensity signals. Herein, we report a wavelength‐shifted fluorescence and colorimetric dual‐mode sensing strategy, in which moisture variations are reflected by synchronized wavelength shifts of emission and absorption maxima. This strategy employs a novel fluorescent probe, termed λ‐probe , whose excited‐state behavior is regulated by water‐mediated hydrogen bonding. Specifically, as the moisture content increases, both the emission and absorption spectra of the λ‐probe exhibit a progressive blue shift, with a shift magnitude of approximately 80 nm. Both emission and absorption peak wavelengths exhibit piecewise‐linear relationships with moisture content, enabling dual peak‐position quantification over a broad range of 0%–90%. Furthermore, a smartphone‐based fluorescence‐colorimetric dual‐mode sensing platform was developed to achieve rapid on‐site quantitative detection. The a* value extracted from fluorescence and colorimetric images using a custom MATLAB program both show linear correlations with moisture content, achieving limit of detections (LODs) of 0.97% and 0.20%, respectively. This work establishes a dual peak‐position sensing strategy and provides a smartphone‐assisted platform for rapid on‐site moisture quantification in highly polar aprotic solvents.