N-S dual-doped 3D porous laser-induced graphene electrode for curcumin determination in turmeric

The determination of curcumin (CM), the active ingredient of turmeric, can be used to control the quality of turmeric rhizomes and products. A CM sensor was developed based on a nitrogen and sulfur dual-doped laser-induced graphene (N-S@LIG) material fabricated in the form of a three-electrode system on a polyethylene terephthalate (PET) substrate. N-S@LIG was synthesized by the one-step laser ablation of a polyimide (PI) carbon source coated with a methylene blue (MB) N and S source. The surface morphology of the fabricated electrode was studied by scanning electron microscopy, energy dispersive x-ray analysis, Raman spectroscopy, contact angle analysis, and X-ray photoelectron spectroscopy. The electrode showed an excellent electron transfer ability and good electrocatalytic performances for the detection of CM. The N and S dual-doped laser-induced graphene electrode (N-S@LIGE) was employed to determine CM by differential pulse adsorptive stripping voltammetry (DPAdSV). To enable on-site analysis of CM in turmeric samples, the N-S@LIGE was incorporated with a small potentiostat plugged into a smartphone to manage the measurements and to display results. The developed CM sensor displayed a linear determination range from 0.10 to 30 μmol L^-1, a detection limit of 0.036 μmol L^-1, good repeatability, reproducibility and anti-interference properties. The developed CM sensor was used to measure CM in cultivated rhizomes and commercial turmeric powder. The analysis results correlated well with the results from the standard spectrophotometric analysis and high-performance liquid chromatography.