Phase‐Selective Growth and 2D Fixation of Na(Gd 1‐x Er x )S ₂ for Ultrasensitive Thermometry and Anti‐Stokes Photon Imaging

The precise mapping of temperature distributions with laser‐induced imaging is critical across diverse fields, from microelectronics to energy storage and biomedical engineering. Herein, phase‐selective growth is conducted in a non‐vacuum sulfur‐rich environment, where NaGd 1‐x Er x S 2 (NaGdS 2 ‐E x ) phosphors with high‐efficiency up‐conversion luminescence are successfully prepared. The ordered segregation of Er 3+ within the GdS 6 layers effectively suppresses non‐radiative relaxation, producing a nonlinear quantum yield enhancement driven by an explosive surge in photon output upon increasing excitation power, which enables anti‐stokes photon imaging. Furthermore, the microcrystals are successfully incorporated into NaGdS 2 ‐E x @polyacrylonitrile‐polyurethane (NaGdS 2 ‐E x @PAN‐TPU) membranes via electrospinning, achieving 2D fixation while preserving high luminescence efficiency, thereby expanding the application adaptability. Remarkably, the design of a thermally and non‐thermal coupled upconverting based on the NaGdS 2 ‐E x @PAN‐TPU system results in highly sensitive temperature sensing, achieving maximum relative sensitivities of 1.069 and 0.475% K −1 at 313 K. These findings provide a flexible platform, particularly for its potential in real‐time visual thermometry within micro‐nano electronic devices, while also paving the way for laser identification in maritime search and rescue operations.