Real time monitoring of heavy metal adulteration in biodiesel using Arduino UNO platform@A promising multi-purpose stimuli-responsive azomethine based chemoreceptor for hierarchical tri-ionic sensing

The presence of metallic adulteration even in very trace level may lead to deleterious impact on the biodiesel quality and ultimately may be responsible for the dropping down of system efficiency, which necessitates the trace level recognition of heavy metal adulteration from biodiesel. In this context, herein using an azomethine functionalized chromogenic chemoreceptor, 1-((E)-(4-hydroxyphenylimino) methyl) napthalen-2-ol (HMN) has been reported for the selective chemodosimetric recognition of Cu²⁺ with a lower detection threshold of 7.8 ppb via distinct chromogenic variation of HMN. In addition to this, it has also exhibited selective and reversible naked eye chromogenic sensing behaviour towards F⁻ (LOD=160 ppb) and Al³⁺ (LOD=48 ppb) at very trace level, which is quite lower than the WHO permissible limit. Distinct chromogenic recognition of F⁻ by HMN proceeds via strong intermolecular hydrogen bonding mediated improved intramolecular charge transfer. The spectroscopic response of HMN in alternate presence and absence of the targeted analytes made it suitable to formulate AND-NOT-XNOR-NAND-OR gate based ‘Castle-like’ complicated logic circuitry. In-vitro cell imaging study using A549, human lung carcinoma cell line attests intracellular recognition capability of HMN, demonstrating its effectual bio-medicinal applications. Interestingly, inspired by the capability of HMN towards recognition of copper from biodiesel specimen, an RGB-assisted device comprised of TCS color sensor and an Arduino UNO 8-bit microcontroller has been developed for real-time quantitative analysis of the biodiesel adulteration. Going one step further, utilization of lab-on-a-box based prototype to monitor the concentration-dependent chromogenic fluctuation via RGB analysis is undoubtedly beneficial for the determination of copper adulteration in biodiesel sample. The presently developed chemoreceptor can thus be regarded as a valuable addition in the field of supramolecular chemistry as well as a significant initiative towards regular monitoring of the biodiesel quality control parameters as a part of sustainable environment.