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

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. Here, aggregation of particles is shown after the interaction in between rGQD and L -dopa that lead to aggregation induced emission. Flexible electronic devices were fabricated for the electrical sensing of L -dopa. • rGQD is used for the sensing of L -dopa in aqueous media. PVA/rGQD based flexible devices are also designed for the electrical measurement based sensing of L -dopa. • rGQD treated filter paper strips develops bright fluorescence under the influence of L -dopa. • The flexible device works at different bending angles and show similar current-voltage characteristics ensuring its applicability as wearable biosensor. Also, the effect of varying humidity is negligible.