Smart Luminescent Materials: From Basic Luminophores to Stimuli-Responsive Luminescent Systems

Smart luminescent materials (SLMs) represent an emerging class of intelligent optical systems that can convert external stimuli into adaptive and programmable photonic outputs. By integrating molecular photophysics with dynamic structural regulation, SLMs enable precise modulation of emission intensity, wavelength, polarization, lifetime, and energy conversion pathways with high spatiotemporal controllability. Recent advances in molecular engineering, supramolecular assembly, and hierarchical material design have driven a transition from conventional luminescence switching toward multifunctional systems featuring multilevel, multistimulus, and information-enriched optical responses. This review provides a comprehensive and mechanism-oriented overview of recent progress in SLMs across diverse material platforms, including solution-phase systems, solid-state materials, dynamic hydrogels, chiral circularly polarized luminescence (CPL) systems, and lanthanide-doped upconversion nanoparticles. Particular emphasis is placed on how external stimuli regulate excited-state electronic structures, molecular conformations, supramolecular organizations, and hierarchical architectures to achieve adaptive luminescent behaviors. In addition, emerging strategies for stimuli-responsive CPL regulation and intelligent photon conversion based on upconversion nanomaterials are highlighted, demonstrating how molecular-level control can be translated into dynamic optical functionalities. Finally, current challenges and future opportunities are discussed toward the rational design of next-generation smart luminescent materials for applications in information security, wearable electronics, soft robotics, biophotonics, and intelligent photonic devices.