Reduced graphene quantum dot based versatile platform for l-dopa sensing: Fluorescence turn-on, filter paper, and air-stable flexible electronic devices

Abstract

L-dopa is a chiral drug that has been extensively used for the treatment of Parkinson’s disease. The concentration of L-dopa plays a vital role in the treatment, and this work emphasizes on designing a versatile platform for the quantitative and selective detection of L-dopa using reduced graphene quantum dot (rGQD). The platform is efficient in three different sensing methods, viz. fluorescence turn-on, filter paper-based sensing, and electronic measurements. The rGQD undergoes a dramatic fluorescence turn-on in the presence of L-dopa in aqueous media and artificial urine with a detection limit as low as 1.307 µM and 1.217 µM respectively. Experimental evidence revealed that the fluorescence enhancement is attributed to aggregation-induced emission mechanism. The system is also applicable for visual detection of L-dopa using filter paper strips treated with rGQD and develops bright fluorescence under ultra-violet irradiation. Apart from this, electrical sensors for L-dopa were also developed by preparing rGQD treated poly-vinyl alcohol films, and the increase in the current conduction with varying concentrations of L-dopa was observed. The films produce 2.5 order higher current conduction at 300 μM of L-dopa with a detection limit of about 13.136 µM. At the final stage, we have designed flexible electronic devices using these materials that develop 1.3 order higher current for L-dopa. The devices exhibit excellent air stability under varied relative humidity conditions as well as high bending stability for potential practical applications.