High‐Yielding Green Emissive Carbon Dots as Band‐Shifted Fluorescence‐Enhancing Sensor for Cd(II)

Cadmium ion is a notorious toxic heavy metal ion found in the environment due to its industrial applications. Its contamination induces a variety of diseases in human health. Therefore, development of a selective and sensitive probe for Cd(II) detection is highly demandable. Herein, green emissive carbon dots (G‐CDs) with high production yield (60%) and decent quantum yield (14.9%) by the hydrothermal route using sodium alginate and 1,4‐diaminobenzene as precursors have been synthesized. Notably, the G‐CDs show green emission and fluoresced at 542 nm. The synthesized G‐CDs have large Stoke shift of 172 nm, which can prevent possible reabsorption. In the presence of Cd(II), G‐CDs show fluorescence enhancement and blue shifting of the emission band. This might be attributed to the complex formation between surface functional groups of G‐CDs with Cd(II). Further, the photoluminescence response of G‐CDs is visually demonstrated under 365 nm UV light. The G‐CDs sensor exhibits high selectivity for Cd(II) and shows a good linear relationship in the range 0.1–6 µM with a detection limit of 0.22 µM. The sensitivity of the probe is verified by interference studies in the presence of different ions. Interestingly, a good reversible on–off fluorescent intensity is observed using ethylenediaminetetraacetic acid for three consecutive cycles. The fabricated G‐CDs sensor is also applied for real‐time detection of Cd(II) in tap water, pond water, and urine.