Portable and non-invasive fluorescent thin films from photocatalytically active carbon dots for selective and trace-level detection of picric acid

Portable fluorescent (FL) sensors for on-site detection of pollutants have strong implications in the practical world. Herein, we report a simple one-pot synthesis of N, S and P-doped carbon dots (CDs) derived from C. thevetia flowers (TF-CDs), which exhibit selectivity for the sensitive detection of picric acid (PA). Further integration of this FL probe onto polyvinylidene fluoride (PVDF) enables the fabrication of a highly porous, thin, and flexible TF-CD@PVDF film strip via a simple phase inversion method, enabling the selective and trace-level detection of a potent explosive, picric acid (PA). The TF-CD@PVDF strip shows a limit of detection (LOD) of 244 nM for PA, whereas TF-CD itself in suspended form shows sensitivity as low as 104 nM. The findings reveal a static quenching mechanism for TF-CDs in the presence of PA. As the application of TF-CD is not restricted to sensing, its potency towards sunlight photodegradation of methyl orange (MO), an azo dye, is also investigated. TF-CDs showed fast degradation kinetics for MO under sunlight with a removal efficiency of 96.8% in about 60 min. The real sample analysis was further performed by externally spiking real water samples, validating the real-world applicability of the as-prepared TF-CDs for the sensing and decontamination of polluted water. The present study paves the way for designing portable, flexible florescent platforms for extended applications. Multifunctional N, S and P-doped CDs derived from C. thevetia flowers are used in a PVDF-based portable recyclable thin film fluorescent probe for selective trace level detection of picric acid and for the environmental remediation of azo dyes, acting as a potential solar photocatalytic material.

Automated summary

A simple one-pot synthesis of N, S and P-doped carbon dots (CDs) derived from C. thevetia flowers (TF-CDs) is reported, which can be used for the sensitive detection of picric acid. A highly porous, thin, and flexible TF-CD@PVDF film strip is fabricated, enabling the selective and trace-level detection of picric acid. The TF-CDs also show potential for sunlight photodegradation of azo dyes.