Huanhuan Dong^#, Xinyu Gou^#, Nianhua Zhao, Weina Wang, Yu Fang*, Junxia Peng*, J. Phys. Chem. B, 2026.  https://doi.org/10.1021/acs.jpcb.6c04332

Fluorescent eutectogels, as emerging smart materials that integrate the unique microenvironment, excellent temperature resistance, and eco-friendliness of deep eutectic solvents (DESs), have driven remarkable advancement in flexible optical materials and information encryption.

Here we report a transparent fluorescent eutectogel prepared by incorporating the environmentally sensitive cationic luminophore 2,5-bis(2-pyridiniumyl)-1H-pyrrole bis(hexafluorophosphate) ([H₃DPP]²⁺) into a glycerol/Zn(NO₃)₂·6H₂O DES followed by in situ photopolymerization of acrylamide. The nitrate-containing DES strongly reshapes the photophysical behavior of [H₃DPP]²⁺, producing a pronounced red shift and enhanced emission relative to glycerol or aqueous Zn(NO₃)₂ solution. The addition of monomer has little influence on the DES-regulated emission, whereas gel-network formation causes only moderate fluorescence attenuation while largely preserving the DES-defined emissive state. Spectroscopic analysis and DFT/TD-DFT calculations indicate that directional hydrogen-bonding interactions between NO₃^- and the protonated/pyrrolic N-H sites of [H₃DPP]²⁺ modulate its electronic structure and optical transitions. The resulting eutectogel exhibits high visible transparency, tensile strength of 230 kPa, stretchability of 820%, adhesion to diverse substrates (0.25 MPa on PTFE), and excellent solvent retention, maintaining 95% of its solvent after storage at 70 °C for 9 days. The fluorescence also remains visible after prolonged storage at 25, 70, and -25 °C. Moreover, relying on the high transparency, good mechanical properties and stimulus-responsive fluorescence characteristics of this eutectogel, localized chemical writing, UV-triggered visualization and barcode digital reading can be realized.

This work demonstrates that DES-regulated microenvironments offer a robust platform for tuning molecular emission and developing stable, stimuli-responsive fluorescent soft materials for visual anti-counterfeiting and information encryption.

Figure 1. Microenvironment-dependent photophysical behavior and interaction analysis of [H₃DPP]²⁺.

Figure 2. Theoretical calculations for the interaction between [H₃DPP]²⁺ and NO₃^-.

Figure 3. Mechanical properties, thermal stability, and environmental stability of the [H₃DPP]²⁺-doped eutectogel.

Figure 4. Information writing, visualization, and digital readout based on Fe³⁺-induced fluorescence quenching of the [H₃DPP]²⁺-doped eutectogel.

First Authors: Dong Huanhuan and Gou Xinyu, doctoral candidate, Shaanxi Normal University

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

Full Text Link: https://doi.org/10.1021/acs.jpcb.6c04332