First-in-class hydrazone–pyrazoline sensors for selective detection of Zn2+, Cd2+, and Hg2+ in aqueous environments†

Six first-in-class hydrazone–pyrazoline fluorescent sensors that selectively detect Zn²⁺, Cd²⁺, and Hg²⁺ at three distinct wavelengths in aqueous environments are reported. These novel hybrid sensors are synthesized in just two steps from inexpensive, commercially available materials, enabling rapid generation and screening for desirable photophysical properties. Lead sensor P1 was validated for in situ detection of group 12 metals in river and pond water using a portable, low-cost device. Crucially, this system enabled rapid, naked-eye detection of toxic metals directly in the environment without the need for expensive instrumentation or mains electricity. These findings establish a new direction in pyrazoline sensor research and set a high benchmark for future sensor development.