Colorimetric/photothermal dual-mode sensing detection of ascorbic acid based on a Ag[<scp>i</scp>] ion/3,3′,5,5′-tetramethylbenzidine (TMB) system

Abstract

In this work, a novel strategy of colorimetric and photothermal dual-mode sensing determination of ascorbic acid (AA) based on a Ag⁺/3,3',5,5'-tetramethylbenzidine (TMB) system was developed. In this sensing system, Ag⁺ could oxidize TMB with a distinct color change from colorless to blue color, strong absorbance at 652 nm and a photothermal effect under 808 nm laser irradiation due to the formation of oxidized TMB (oxTMB). When AA was present, oxTMB was reduced accompanied by a change from blue to colorless, and a decrease in absorption peak intensity and the photothermal effect. AA concentration showed a negative linear correlation with the value of both the absorbance intensity at 652 nm and temperature in the range of 0.2-10 μM (<i>A</i> = -0.03<i>C</i> + 0.343 (<i>R</i> ², 0.9887; LOD, 50 nM); Δ<i>T</i> = -0.57<i>C</i> + 8.453 (<i>R</i> ², 0.997; LOD, 7.8 nM)). Based on this, a sensing approach for detection of AA was proposed with dual-mode and without the complicated synthesis of nanomaterials. The photothermal effect and colorimetric signal provided a dual-mode detection strategy for AA, overcoming the limitations of any single mode. This colorimetric and photothermal dual-mode detection has great potential in the detection of AA in clinical pharmaceuticals and the construction of portable and highly sensitive sensors.