A high-performance fluorescent and ratiometric colorimetric detection of Cu2+ in practice

To monitor Cu2+ efficiently, a kind of D-pi-A-pi-D conjugated 3,5-di-(2-hydroxyl naphthaldehyde)-iminyl triazole (HNIT) was developed, using triazole as the electron acceptor, 2-hydroxyl naphthaline as the electron donor, and -C=N- as the bridging group. The proposed HNIT possessed superior UV-vis and fluorescent spectral property with high molar absorption coefficient of 2.313 x 10(4) L mol(-1) cm(-1) and fluorescence quantum yield of 36.2%. Trace Cu2+ could exclusively alter its UV-vis and fluorescent property with clear color change. Under the optimized conditions, a high-performance fluorescent and ratiometric colorimetric detection of Cu2+ based on HNIT was efficient, with low detection limits of 3.3 x 10(-8) mol L-1 (S/N = 3) and 9.6 x 10(-8) mol L-1 (S/N = 3), respectively. It well satisfied with the safe value of 31.5 mu M Cu2+ in drinking water recommended by World Health Organization (WHO). When applied for detection of Cu2+ in real environmental samples, the recovery was in the range of 97.5-105.2%. The recognition mechanism for HNIT to Cu2+ realized quite stable 6-membered rings between electron-deficient Cu2+ and electron-rich N and O atoms in HNIT with 1 : 2 chemical stoichiometry of HNIT to Cu2+.

Automated summary

A D-pi-A-pi-D conjugated 3,5-di-(2-hydroxyl naphthaldehyde)-iminyl triazole (HNIT) was developed for efficient monitoring of Cu2+. HNIT showed superior UV-vis and fluorescent spectral properties, and exhibited high selectivity towards Cu2+. Under optimized conditions, a fluorescent and colorimetric detection method based on HNIT achieved low detection limits and can be applied to real environmental samples.