Co-MOFs derivative for dual-mode detection of L-Cys based on colorimetric analysis and smartphone
A metal-cobalt organic framework-derived fibrous rod-like carbon material(Co-DM)with peroxidase-like properties was synthesized via room-temperature synthesis-pyrolysis method.The Co-DM obtained was characterized by SEM,TEM,XRD and XPS then for analyses on morphology,structure and elemental composition,and active oxygen capture experiment was further conducted for investigation of its catalytic mechanism.It was found that H2O2 under the catalysis of Co-DM released superoxide anion radicals(·O2-)and hydroxyl radicals(·OH),thus oxidizing the colorless chromogenic substrate 3,3',5,5'-tetramethylbenzidine(TMB)to blue oxidation state product(oxTMB)with the largest adsorption peak at 652 nm.Since L-cysteine(L-Cys),with antioxidant properties,could reduce oxTMB thus leading the blue color product back to colorless,a colorimetric method for L-Cys detection was accordingly established.Under the optimal conditions of pH=4.0,temperature of 40℃,the concentration of L-Cys in the range of 0.1～15.0 μmol/L showed a linear relationship with absorbance at 652 nm,and the limit of detection(LOD)was 0.35 μmol/L.In addition,the quantitative relationship between the relative activity of Co-DM and the color characteristic values was established by recording the characteristic values R(red),G(green),and B(blue)values of color change in the range of white(0,0,0)to black(255,255,255)for solutions at different concentrations of L-Cys with the aid of a homemade smartphone optical device and Color Garb software.The detection range was 0.1～70.0 μmol/L and the LOD was 0.27 μmol/L.This method was also successfully applied in the detection of L-Cys in clinical human serum,with recovery rate between 94.0%～101.5%.
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