A single excitation dual emission semi-salamo type multi-functional probe for sensitive pH and Cu²⁺ detection

pH and Cu²⁺ ion concentration changes are linked to disorders like Alzheimer's and cancer. Rapid detection of pH and Cu²⁺ ions is critical for public health and environmental concerns. The semi-salamo-type probe (E)-2-hydroxy-1-naphthaldehyde O-(2-(aminooxy)ethyl) oxime (NSS) demonstrated substantial dual-functional performance, sensing pH change and Cu²⁺ ions. A single excitation and double emission characteristic on the probe NSS made it distinctive. Probe NSS exhibits pH-dependent excited state intramolecular proton transfer (ESIPT), and its optical properties vary based on the pH environment. Probe NSS detects pH changes from 2 to 11 by changing the "off-on-off" of the excited state intra-molecular proton transfer (ESIPT) mechanism, exhibiting rapid, reversible, and selective responses. In addition, the luminescent salamo-like naphthalene-based probe NSS can coordinate with Cu²⁺ ions, achieving great selectivity and sensitivity to identify Cu²⁺ ions with a detection limit of 0.84 ppb (13.2 nM) Probe NSS can detect Cu²⁺ ions in actual water samples such as tap water and yellow river water. The test strip loaded with probe NSS enabled quick and accurate detection of Cu²⁺ ions in water samples. Consequently, the versatile salamo-type probe NSS lays the foundation for developing high sensitivity and fast-response dual-mode pH meters as well as Cu²⁺ sensing.