A Switchable Sensor for Cu2+ and Zn2+ Based on Xanthene Moietymaking a Path for a Complex Molecular Encryption System Based on Color and Fluorescent Change

Colorimetric and fluorescent detection methods for metal analytes has become a powerful tool for qualitative and quantitative analysis in the last decade due to their immediate output, cost-effectiveness, specificity/selectivity, zero interference, high detection limit, and application in practical samples. Sensing Cu²⁺, Ni^2+, or Zn²⁺ like analytes gained a lot of attention due to their significance in biological, medical, and environmental purposes. To account for this purpose, we synthesized and designed a colorimetric, fluorescent off-on, and reversible chemosensor EYM having xanthene as a signaling moiety and 4-carbamoyl-3-Butenoic acid as a receptor moiety. The EYM probe is then screened with Al³⁺, V³⁺, Na⁺, K⁺, Fe³⁺, Mg²⁺, Ca²⁺, Fe²⁺, Co²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Mn²⁺, Co³⁺, Pb²⁺, Cu²⁺, Pd²⁺, and V⁴⁺ in DMSO: H₂O (4:1) solvent system where EYM shows absorbance change specifically for Cu²⁺ at 541nm changing from colorless to dark pink. The detection limit and association constant of the EYM probe for Cu²⁺ is 78.5nM and (6.013-5.947)´10⁹ M^-1, respectively. The coordination of Cu²⁺ with EYM is in (1:2: Ligand: Metal) stoichiometric ratio. The immediate saturation time (~2 sec) and low detection limit (78.5nM) of the EYH probe give competitiveness over other sensors in practical applicability in real-life samples detection of Cu²⁺. Not only this, the EYM sensor can switch from mono to bi to tri-functional sensor for Cu²⁺, Ni^2+, and Zn²⁺ with the stimuli of water in the DMSO solvent. The EYM shows specific abnormal fluorescent enhancement in contact with Zn²⁺ in DMSO solvent. The detection limit for Zn²⁺ is 79nM same as Cu²⁺ in a colorimetric assay. Switchable sensing is utilized to make complex molecular LOGIC GATE operations, including password-protected molecular encryption systems.