Xinyu Gou, Junxia Peng*, Yu Fang*. Responsive Mater., 2026, e70041, DOI: https://doi.org/10.1002/rpm2.70041

Film-based fluorescent sensors (FFSs), an “IUPAC Top Ten Emerging Technology in Chemistry 2022”, are attracting growing interest for applications in public safety, environmental monitoring, and disease diagnosis, driven by their high sensitivity, rapid response, and facile integration. The core of FFSs lies in their engineered sensing films, where efficient molecular channels within the film's architecture dictate key performance metrics like response/recovery speed and signal-to-noise ratio. To break through the bottlenecks in traditional fluorescent sensitive films such as slow molecular diffusion and low signal-to-noise ratio, rational design and precise fabrication of sensing films with integrated molecular channels are proposed.

Figure 1 Schematic illustration for the innovative development of FFSs

This review presents a critical overview of recent advances in constructing fluorescent sensing films with abundant molecular channels, and focuses on exploring strategies to enhance molecular transport and sensing efficiency: (1) Introducing nonplanar geometries into fluorophores and depositing them onto a proper substrate by spin-coating, drop-casting, Langmuir-Blodgett/Schaeffer (LB/LS) technique. These nonplanar molecular structures hinder dense molecular packing during film formation, promoting the formation of molecular-level porous structures; (2) Fabricating fluorescent LMWGs and forming molecular-gel-based films with continuous 3D networks through the supramolecular assembly of gelators. Subsequent solvent removal produces abundant porous structures, which is beneficial to enhance the response speed and reversibility of the sensing film while offering excellent photostability and processability; (3) Integrating framework materials with ordered topological structures—such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and conjugated microporous polymers (CMPs) into fluorescent film fabrication. These materials provide permanent porosity, well-defined pore sizes, and uniform distribution of sensing sites, all of which facilitate analyte diffusion and binding; (4) Employing interfacial confined polymerization to incubate self-standing nanofilms in situ with high specific surface areas. These films provide both physical isolation of fluorophores and optimized mass transport pathways, contributing to improving photostability and signal reproducibility under practical applications.

The emerging applications of FFSs in detecting various targets, including illicit drugs, chemical warfare agents, volatile organic compounds (VOCs), foodborne chemical residues, humidity, temperature, ultraviolet (UV) light, and pressure are also summarized. By synergizing rational molecular design with thin-film engineering, multiple systems have achieved ppb or even lower detection limits, while featuring second-level response and good cycling stability. Finally, it is proposed that integrating molecular engineering, device integration, and data-driven methods will be the core path for promoting the practical application and intelligent development of FFSs.

Figure 2 The preparation strategy and functional application of fluorescent sensing films with “molecular channels”

First Author: Gou Xinyu, doctoral candidate, Shaanxi Normal University

Correspondence Authors: Prof. Peng Junxia, Prof. Fang Yu, Shaanxi Normal University

Full Text Link: https://doi.org/10.1002/rpm2.70041