An electrochemical fabrication method of Ru[bpy] 3 2+ @Cu-MOF(-SH)/Au (MOF = metal–organic framework) was developed with a photo/electrochemical information characterization and a DNA-based biosensing validation for the proposed interface. Applying an anodic synthesis method, a modification layer of Ru[bpy] 3 2+ encapsulated with MOF was formed on the Au electrode surface to fabricate an interface with photo/electrochemical dual-signal response. Combining the scanning electrochemical microscopy (SECM) imaging technology with electrochemical and electrochemiluminescence (ECL) detection, the information about the interfacial photo/electrochemical bi-functional properties was explored from three aspects of the parameter variable, intensity variable, and morphology variable. The results show that the effect of parameter variables on the interfacial response follows an “interference effect” mechanism. Under the optimized conditions, the background and the saturation ECL intensities are 610.0 and 24.0 with a quenching efficiency of 96.1% and a detection limit of 30 fM. The saturation current is 48.8 µA with a detection limit of 330.0 nM. Both ECL and electrochemical imaging methods can corroborate each other, validating the logical correlation between the interface fabrication and the response performance in the regional interfacial distribution and laying a methodological foundation for evaluating the interface fabrication quality based on imaging morphology qualitatively. The proposed interface can construct photo/electrochemical dual-signal DNA-based biosensors.
Methylated mercury compounds are neurotoxins; they are ubiquitous in muddy sediments of water bodies under anaerobic conditions . A variety of coupled techniques such as capillary gas chromatography with inductively coupled plasma mass spectroscopy , or atomic fluorescence spectroscopy is used for detection of methylated mercury compounds. However, a sensitive analytical method for rapid screening of methylated mercury compounds is required. This work it was developed an electrochemical method for the detection of methylmercury in environmental samples using chemically modified Au electrodes via the bandgap modulation strategy. For the chemical modification, the sulfur-doped g-C 3 N 4 was used as a starting material. The forbidden bandgap of the sulfur-doped g-C 3 N 4 was regulated with urea and thiourea admixture fabricated by thermal polymerization at an optimal ratio (urea: thiourea = 3:1; hereafter UT-gCN (3:1). The UT-gCN (3:1) modified Au electrode was used for rapid detection of CH 3 Hg + by differential pulse voltammetry (DPV) method operated at −0.80 V deposition potential, 800 s accumulation time in NaAc/HAc buffers (pH=5.0). The calibration curve of CH 3 Hg + showed linearity within concentration range 0–25 ppb CH 3 Hg + with 0.52 μA/ppb sensitivity and 0.175 ppb detection limit. The new electrochemical sensor is robust and interference-free to Cu 2+ , Cd 2+ , Pb 2+ , Bi 3+ , As 3+ . The efficiency of the UT-gCN(3:1) sensor can be replenished by protonation with HCl. Present results indicate the potential applications of UT-gCN (3:1) modified Au electrodes in the rapid detection of methylmercury in environmental samples.
In the present work, a convenient signal-on electrochemical label-free aptasensor for 17β-estradiol (E2), a typical steroidal hormones endocrine disrupting chemicals , was proposed. 6-mercapto-1-hexanol (MCH) self-assembled monolayer (SAM) modified Au (MCH/Au) electrode was used as the substrate electrode. Graphene is used with bi-functions, not only to adsorb E2 binding aptamer, serving as the recognition element to E2, but also to be assembled onto MCH/Au electrode when sensing E2, to controllably turn on the electron transfer (eT), and further indicate the signal to E2 concentration. With the synergistic effect of DNase I enzyme, highly sensitive detection of E2 was achieved at this aptasensing system, with a linear range from 0.07 to 10 pM and a detection limit of 50 fM. An outstanding selectivity towards E2 was proven for the sensing system by simultaneously detecting 100-fold potential co-existing interferences. The stability and reproducibility were also evaluated to be satisfactory. Spiked real water analysis further indicated its reliability and potential in practical environmental monitoring.
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