We developed a luminescent probe for the selective and sensitive detection of an explosive, i.e., picric acid (PA), based on the luminescence quenching of CeIII and TbIII co-doped Sr2GdF7 nanocrystals. A new colloidal synthesis route at low temperature (80 °C) was developed to synthesize the luminescent nanocrystals host matrix Sr2GdF7. The nanocrystals showed strong green emission under UV excitation (290 nm) by efficient energy transfer from CeIII to TbIII ions. The functionalization of the nanocrystals with l-cysteine (Cys) rendered the luminescent probe water dispersible. The presence of the −NH2 groups of Cys allowed the selective interaction of the probe with PA among other nitro explosives. This caused a 92 % reduction of the photoluminescence intensity of TbIII in the Sr2GdF7 nanocrystals, and led to the selective detection of PA with an unprecedented limit of detection (LOD) of approx. 4 nm.
- Picric acid