A Stimuli-Responsive Nanogel-Based Sensitive and Selective Fluorescent Sensor for Cr3+ with Thermo-Induced Tunable Detection Sensitivity

Stimuli-responsive poly( N -isopropylacrylamide) nanogel with covalently labeled rhodamine B urea derivatives (P(NIPAM- co -RhBUA)) is utilized as a sensitive fluorescent probe for Cr 3+ in aqueous solution, and its thermo-induced tunable detection capacity is investigated. At 20 °C, non-fluorescent nanogel can selectively bind with Cr 3+ over some other metal ions, leading to prominent fluorescence OFF–ON switching due to the recognition of RhBUA with Cr 3+ . Upon heating above the phase transition temperature, enhanced fluorescence intensity is observed (≈61-fold increase at 45 °C) for the nanogel in the presence of Cr 3+ , accompanied with an improved detection sensitivity, which suggest that hydrophobic microenvironment generated in the collapsed nanogel plays an active role for their detection performance.