A down converting serine-functionalised NaYF4:Ce3+/Gd3+/Eu3+@NaGdF4:Tb3+ photoluminescent probe for chemical sensing of explosive nitroaromatic compounds

In this study we demonstrate a Ser-CS (serine-functionalized NaYF4:Ce3+/Gd3+/Eu3+@NaGdF4:Tb3+ core shell) nanophosphor for the effective detection of nitroaromatic derivatives. The Ser-CS nanophosphors have a remarkable sensitivity towards electron deficient nitroaromatics. viz., ortho-nitrophenol (2-NP), para-nitrophenol (4-NP), 2,4-dinitrophenol (2,4-DNP), picric acid (PA), 1,3-dinitrobenzene (1,3-DNB) and para-nitrotoulene (4-NT). The presence of serine amino acid residues on the core–shell surface inhibits aggregation and increases the stability and solubility of the probe in aqueous medium. The Ser-CS exhibits strong and sharp emission peaks around 493, 548, 594, 610 and 700 nm. Importantly, the peak centred at 610 nm exhibits a noticeable quenching effect on addition of nitro-compounds to the aqueous solution of the nanophosphor. The high quenching constant (KSV) (4.364 × 104 M−1) and low detection limit (1.67 ppm) for PA imply the high selectivity and sensitivity towards PA relative to other explosive nitroaromatics compounds.