Construction And Properties Of Novel Ratiometric Electrochemical Sensor Based On Carbon-based Nanomaterials

Ratiometric electrochemical sensor(RES)can reduce the interference caused by internal or external factors since a ratio of two current signals(target signal and reference signal)at different potentials is used as the output signal,which enable itself to detect the target with enhanced accuracy and reliability.Although varied targets have been determined by the RES,few kinds of reference signal probes have been reported,limiting the construction and application of the sensor.Meanwhile,RES still faces with the problem of insufficient selectivity.With the goal of developing novel internal reference signal probes and improving the selectivity of the sensor,three novel RES were constructed in this paper to achieve specific,sensitive and reliable detection of small biological molecules and metal ions by using metal-organic framework material,nanozyme catalyzed products as internal reference signal probes,and phenylboronic acid pinacol ester dissociation products as signaling probes indicating targets.Carbon-based nanomaterials,with the advantages of large specific surface area and good electrical conductivity,also were employed for the preparation of RES to improve the sensitivity.The main research work of this paper is as follows:1.A kind of redox-active metal-organic frameworks material(Cu-THQ MOFs)was synthesized at room temperature and characterized by scanning electron microscope,transmission electron microscope,X-ray powder diffractometer,and X-ray photoelectron spectroscopy techniques.Cu-THQ MOFs were composited with carboxylic group functionalized multi-walled carbon nantubes(MWCNTs-COOH)to construct a novel ratiometric electrochemical sensor for sensitive detection of dopamine(DA).The oxidation peak potential difference between DA and Cu-THQ MOFs was about 270 mV,and the peak current of Cu-THQ MOFs did not change with the increase of DA concentration.Accordingly,a current ratio(iDA/iMOFs)was employed as a readout signal for DA detection with a linear range and limit of detection(LOD)of 3.0 × 10-7-4.0×10-5 mol/L and 2.6 ×10-8 mol/L,respectively.Compared with single signal of iDA,ratiometric strategy exhibited high accuracy and reliability for DA determination.2.Gold-platinum nanoclusters(AuPt NCs)can catalyze the oxidation of ophenylenediamine(OPD)to 2,3-diaminophenazine(DAP)in the presence of hydrogen peroxide(H2O2).DAP can undergo electroreduction on the electrode surface to generate an electrochemical signal.A novel ratiometric sensor based on AuPt NCs-loaded reduced graphene oxide(rGO)using the reduction peak of DAP as a new internal reference signal was constructed for the detection of cadmium ions(Cd2+).The reduction peaks of Cd2+and DAP were not only clearly separated,but also the peak current of DAP remained stable with the increase of Cd2+ concentration.Based on the ratio of the peak current value of Cd2+ to DAP(icd2+/iDAP),the obtained linear range and LOD were 5.0 ×10-8-1.0×10-4 mol/L and 3.1×10-8 mol/L,respectively.The ratiometric strategy based sensor possessed good accuracy,reliability,and stability,and successfully determined Cdr2+ content in three different water samples with satisfactory results.3.Ketjen black(KB),gold nanoparticles(AuNPs),and poly(thionine)(TH)as an internal reference probe were modified on the glassy carbon electrode surface by drop coating and electrochemical polymerization.The non-electroactive 4-aminophenylboronic acid pinacol ester(ABAPE)dissociation was specifically triggered by H2O2 to generate electro-active 4-aminophenol(4-AP)in solution.4-AP not only can be oxidized to indirectly indicate the concentration of H2O2,but also endowed the sensor with high selectivity due to the specific reaction of ABAPE with H2O2.Meanwhile,KB and AuNPs displayed high electrocatalytic activity to 4-AP.An oxidation peak current ratio between 4-AP and TH(i/iTH)showed a good linear relationship with the logarithm of H2O2 concentration in a range of 3.0 × 10-7-1.0 × 104 mol/L with LOD of 2.6 × 10-7 mol/L.The design based on the specific trigger dissociation between ABAPE and H2O2 can not only improve the high selectivity of the sensor through simple experimental operations,but also provide new detection ideas for non-electroactive molecules or target substances that are difficult to detect by electrochemical methods.