Boron fused pyrazolyl zinc salen as a self-powered ultra-sensitive sensor for pico-molar nicotine detection in realistic smoke environments

Abstract

Sensitive detection of nicotine is essential owing to its adverse effects on human health; in particular, nicotine is associated with increased risk of cardiovascular and respiratory disorders and multiple types of cancers. Although a large number of sensors for the detection of nicotine are known, development of quick, easy and sensitive methods is in great demand. Herein, we report a tetra-coordinated boron-embedded zinc salen complex (TPZBSA-Zn) as a dual-mode sensor for the detection of nicotine. The complex exhibited a hypsochromic shift in fluorescence from green to blue upon the addition of nicotine. The observed luminescence shift is rationalized owing to the interaction between nicotine's pyridine nitrogen and the zinc center, as confirmed by NMR. Single crystal X-ray analysis revealed the binding mode of nicotine to the zinc-salen which is responsible for the color change realized in fluorescence studies. We further developed a highly sensitive nicotine detection device based on conductivity modulation arising from Zn-N coordination, capable of detecting nicotine in both vapour and liquid phases at concentrations as low as 1 pM (10⁻¹² M). The device exhibited exceptional responsiveness and reliability, demonstrating superior performance even under real cigarette and bidi smoke exposure in indoor settings.