Enhanced Solid-State Electrochemiluminescence Platform Via Finely-Tuned Thickness Dependent Graphitic Carbon Nitride Nanosheets for Towards Selective Sensing of Glutathione

Compared with conventional luminophores, the metal-free two-dimensional semiconductor like graphitic carbon nitride (g-C3N4) has emerged as a greener alternative luminophore in electrochemiluminescence (ECL) based biosensing application. Herein, we investigate for the first time the thickness-dependent solid-state ECL studies on graphitic carbon nitride nanosheets (g-C3N4 N.S) modified on glassy carbon electrode by synthesising an environmentally friendly, solvent-free thermal polycondensation method. Systematic spectral and morphological studies confirm that the optimized ratio of melamine to ammonium sulfate produces a precisely tuned thickness of g-C3N4 N.S. Ultrathin g-C3N4 N.S with a thickness of 23 nm exhibits significantly enhanced both anodic and cathodic solid-state ECL intensity without involving any additional co-reactant during electrochemical cycling at ambient conditions of physiological pH -7.4. More precisely, the intensity of cathodic and anodic solid-state ECL of g-C3N4 N.S (thickness 23 nm) is 12 times and 2 times greater than that of bulk g-C3N4, which is due to the g-C3N4 N.S electrocatalytically producing more reactive oxygen species (ROS) via the dissolved oxygen reduction reaction. Interestingly, when K2S2O8 is introduced as an external co-reactant, the same 23 nm thickness g-C3N4 N.S shows an impressive 205-fold increase specifically in cathodic ECL intensity under even nitrogen gas saturated conditions. This effect becomes even more remarkable, reaching a 350-fold increase under oxygen-saturated conditions where both in-situ and ex-situ co-reactants are present in the electrolyte solution and show stable solid-state ECL up to 180 seconds with a color purity of 33.95%. This kind of unique thickness-dependent surface-enhanced g-C3N4 N.S was used as a solid-state ECL platform for the selective detection of reduced glutathione (GSH), as a proof-of-concept experiment. This exceptional ECL probe stands as a testament to unparalleled sensitivity, rapid response times, and unmatched accuracy for GSH concentrations ranging from 1.0×10-6 to 5.0×10-3 M, culminating in a LOD of 43×10-9 M in a human urine sample with good recovery results. This study ignites inspiring insights into revolutionary approaches for quantifying GSH levels in urine, paving the way for significant advancements in non-invasive, stable, accessible alternative medical diagnostics.