Shouzhuo Yao

A double signal amplification platform for ultrasensitive and simultaneous detection of ascorbic acid, dopamine, uric acid and acetaminophen based on a nanocomposite of ferrocene thiolate stabilized Fe3O4@Au nanoparticles with graphene sheet

A double signal amplification platform for ultrasensitive and simultaneous detection of ascorbic acid (AA), dopamine (DA), uric acid (UA) and acetaminophen (AC) was fabricated by a nanocomposite of ferrocene thiolate stabilized Fe₃O₄@Au nanoparticles with graphene sheet. The platform was constructed by coating a newly synthesized phenylethynyl ferrocene thiolate (Fc-SAc) modified Fe₃O₄@Au NPs coupling with graphene sheet/chitosan (GS-chitosan) on a glassy carbon electrode (GCE) surface. The Fe₃O₄@Au-S-Fc/GS-chitosan modified GCE exhibits a synergistic catalytic and amplification effect toward AA, DA, UA and AC oxidation. The oxidation peak currents of the four compounds on the electrode were linearly dependent on AA, DA, UA and AC concentrations in the ranges of 4-400 μM, 0.5-50 μM, 1-300 μM and 0.3-250 μM in the individual detection of each component, respectively. By simultaneously changing the concentrations of AA, DA, UA and AC, their electrochemical oxidation peaks appeared at -0.03, 0.15, 0.24 and 0.35 V, and good linear current responses were obtained in the concentration ranges of 6-350, 0.5-50, 1-90 and 0.4-32 μM with the detection limits of 1, 0.1, 0.2 and 0.05 μM (S/N=3), respectively.

Sensitive detection of rutin with novel ferrocene benzyne derivative modified electrodes

A new ferrocene benzyne derivative (Fc-SAc) that contained oligo-(phenylene-ethynylene) skeleton, ferrocene and thiolate terminal groups was firstly synthesized. The hydrolysis product of Fc-SAc (Fc-SH) was immobilized onto gold nanoparticles (AuNPs) modified glass carbon electrode (GCE) as sensing element for rutin detection with high sensitivity. The new sensing strategy was proposed by using two Fc-SH modified electrodes: Fc-S/AuNPs/GCE (Electrode1) and Fc-S/AuNPs/graphene-chitosan/GCE (Electrode2). The electrochemical oxidation of rutin on Electrode2 was a diffusion-controlled process, which was different from a mass-controlled process on Electrode1. Under the optimal conditions, the peak currents of the sensors were linearly related to the concentrations of rutin. The linear responses ranges were 0.05-30 μM and 0.04-100 μM with the regression coefficients of 0.998 and 0.997 on Electrode1 and Electrode2, respectively. Electrode2 presented wider linear range, superior high sensitivity, lower detection limit and better stability on determination of rutin.

A double signal electrochemical human immunoglobulin G immunosensor based on gold nanoparticles-polydopamine functionalized reduced graphene oxide as a sensor platform and AgNPs/carbon nanocomposite as signal probe and catalytic substrate

In this paper, a double signal electrochemical Human immunoglobulin G (HIgG) immunosensor based on AgNPs/carbon nanocomposite (Ag/C NC) as the signal probe and catalytic substrate was developed for fast and sensitive detection of HIgG. The as-prepared AuNPs-PDA-rGO nanocomposite and Ag/C NC were confirmed by UV-vis, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. Electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical properties of the proposed immunosensor. The AuNPs-PDA-rGO nanocomposite can improve the electron transfer rate and capture more Ab1. In the sandwich-type immunoassay process, the Ag/C NC functionalized bioconjugates were captured on HIgG/Ab1/AuNPs-PDA-rGO surface and the electrochemical double-signal strategy was employed. These double electrochemical detection signals were directly monitored the oxidation current originated from Ag/C NC and indirectly detected the reduction current of benzoquinone which was produced from the reaction of H2O2 and HQ by catalysis of Ag/C NC in electrochemical detection of HIgG. Under the optimized conditions, the current responses were changed with the concentrations of HIgG for the proposed immunosensor with wide linear ranges of 0.1 to 100 ngmL(-1) and 0.01-100 ngmL(-1) with the lowest detection concentration of 0.001 ng mL(-1) in the absence and presence of H2O2 and HQ. The double-signal strategy is used for detection of HIgG, and the results came from the two signals were well consistent with each other. The proposed immunosensor was successfully applied in analysis of human IgG in real samples and this strategy may provide a relative simple and effective method for construction of other immunsensors in detection of other biomarkers in clinical medicine.

A novel multiple signal amplifying immunosensor based on the strategy of in situ-produced electroactive substance by ALP and carbon-based Ag-Au bimetallic as the catalyst and signal enhancer

In this work, a novel immunosensor was constructed based on the alkaline phosphatase (ALP) in situ generating an electroactive substance by enzymatic hydrolysis the inactive substrates. The new signal-amplified strategy for sensitive detection of HIgG was based on the catalytic oxidation of ALP-generated products, ascorbic acid (AA), using carbon-based Ag-Au bimetallic as the catalyst and signal enhancer. Through a sandwich reaction, ALP-Ab2 bioconjugates were captured on the electrode surface and the amplified signal can be obtained as follows: the ALP catalyzed the inactive substrate L-ascorbic acid 2-phosphate (AAP) to in situ produce AA; AA as an electroactive product then can be directly electro-oxidized to generate electrochemical signal; At the same time, AA could be catalytic oxidized by Ag-Au bimetallic and resulted in the amplification of electrochemical signal; Finally, the oxidation of Ag on the Ag-Au bimetallic maybe further enhance the detection signal. The proposed immunosensor achieved good linear in the range of 0.005-100ngmL-1 with the detection limit of 0.0009ngmL-1 (S/N =3). The proposed immunosensor was successfully applied in the analysis of human IgG in real samples and got satisfied results. The present work demonstrates a general strategy for the design of multifunctional nanomaterials based on carbon-based bimetallic nanoparticles for different applications, such as biosensors, immunosensors and nanocatalysts.

An electrochemical sensor for highly sensitive detection of copper ions based on a new molecular probe Pi-A decorated on graphene

In this paper, a new electrochemical sensor based on a new fluorescent probe N-(2-(1-(p-tolyl)-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)picolinamide (Pi-A) decorated reduced graphene oxide (RGO) nanocomposite modified glassy carbon electrode (GCE) was developed for highly selective detection of copper ions using the electrochemical method. The fluorescent probe Pi-A was immobilized on the reduced graphene oxide surface (Pi-A/RGO) via π–π stacking interactions and the Pi-A/RGO was able to selectively capture copper ions with high sensitivity. Under the optimal conditions, the stripping peak current increased with the concentration of copper ions, and the linear range was 5–300 μg L−1 with a detection limit (S/N = 3) of 0.67 μg L−1. Most importantly, the sensor based on the Pi-A/RGO modified electrode shows good selectivity owing to the presence of Pi-A and it has been successfully applied in the detection of copper ions in tap water, river water, and mountain spring samples. The present work provides a methodology for the construction of electrochemical sensors for the specific detection of Cu2+ combining the specific recognition properties of molecular probes and the good conductivity and large surface area of RGO. Moreover, the combination of molecular probes with RGO will expand the application of fluorescent probes in biological and electrochemical sensing areas.

In Situ Piezoelectric Infrared Spectroelectrochemistry for Study of Electrochemical Oxidation of o-Tolidine

Abstract In situ piezoelectric infrared spectroelectrochemistry was used to study the electrochemical behavior of o -tolidine (OTD) on gold electrode. The piezoelectric and electrochemistry results showed that the oxidation of OTD in BR buffer solution was greatly affected by the potential. In the range of 0–0.4 V, the intermediate compound was formed and dissolved during the potential scanning, while the potential scanned up to 0.6 V, the intermediate compound was formed and dissolved, and some of it was deposited on the electrode surface at the same time. If the potential expanded to 0–0.75 V, the intermediate compound formed, dissolved, and deposited and the polymerization of OTD was found. In situ piezoelectric infrared spectroelectrochemistry showed that the intermediate compound was formed between the first oxidation products of OTD. The effect of large-sized anion such as heparin was also investigated.

Silver ions enhanced AuNCs fluorescence as a turn-off nanoprobe for ultrasensitive detection of iodide

Fluorescence nanoprobes are frequently employed to construct sensitive biosensors via turn-on and turn-off strategy. In this paper, a novel strategy for ultrasensitive detection of iodide was firstly constructed based on Ag+ regulated photoluminescence enhancement of gold nanoclusters (AuNCs) as a turn-off nanoplatform. In the presence of Ag+, the fluorescence (FL) intensity of AuNCs can be enhanced obviously. When adding iodide ions (I-) in the Ag+-AuNCs, Ag+ can be pulled down from AuNCs and results in quenching of the fluorescent effectively owing to the combination between Ag+ and I-. Compared with that of I- directly reaction with AuNCs, the introducing of Ag+ shows improved quenching efficiency from 32% to 66% since I- can react with Ag+ as well as AuNCs. Therefore, the platform could be applied to assay Ag+ and I-, on the basis of the FL enhancement and the further FL quenching. The detection ranges and detection limits were 0.2-12μM and 0.06μM for Ag+, 0.001-6μM and 0.3nM for I-, respectively. The new sensing method based on ion regulation to enhance the detection sensitivity can extend to the appliance of other fluorescent materials in biosensing and biomedical field.

Synthesis, characterization of conjugated oligo-phenylene-ethynylenes and their supramolecular interaction with β-cyclodextrin for salicylaldehyde detection

Four new conjugated oligo-phenylene-ethynylenes derivatives, N-methyl-4-(4-acetylthiophenylethynyl)-1,8-naphthalimide (1), thioacetic acid S-[4-(4-aminophenyl-ethynyl)phenyl]ester (2), 4-methylthiophenylethynylbenzenamine (3), N-methyl-4-(4-methyl-thiophenyl-ethynyl)-1,8-naphthalimide (4), were synthesized by Sonogashira and Eglinton cross-coupling reactions. The structures of the four compounds were confirmed by (1)HNMR, (13)CNMR, MS and IR and their spectral characteristics were studied by ultraviolet and visible (UV) spectroscopy as well as fluorescence spectroscopy in different medium. It was found that the fluorescence properties of compounds 2 and 3 were notably improved in aqueous solutions in the presence of β-cyclodextrin (β-CD). Spectral analysis supported the suppositions that the fluorescence intensity enhancement was due to the formation of inclusion complex with β-CD. The supramolecular interaction was investigated in detail and the reaction mechanism was provided. A salicylaldehyde determination method in aqueous medium was established based on the supramolecular complex of compound 3. Under the optimum conditions, the supramolecular complex exhibited a dynamic fluorescence response range for salicylaldehyde from 0.6 to 240×10(-6) molL(-1), with a detection limit of 1×10(-8) molL(-1).

Etching and anti-etching strategy for sensitive colorimetric sensing of H2O2 and biothiols based on silver/carbon nanomaterial

In this paper, the colorimetric sensing of H2O2 related molecules and biothiols based on etching and anti-etching strategy was firstly proposed. Ag/carbon nanocomposite (Ag/C NC) was served as the sensing nanoprobe, which was synthesized via carbon dots (C-dots) as the reductant and stabilizer. The characteristic surface plasmon resonance (SPR) absorbance of Ag nanoparticles (AgNPs) was sensitive to the amount of hydrogen peroxide (H2O2). It exhibited strong optical responses to H2O2 with the solution colour changing from yellow to nearly colourless, which is resulted from the etching of Ag by H2O2. The sensing platform was further extended to detect H2O2 related molecules such as lactate in coupling with the specific catalysis oxidation of L-lactate by lactate oxidase (LOx) and formation of H2O2. It provides wide linear range for detecting H2O2 in 0.1-80μM and 80-220μM with the detection limit as low as 0.03μM (S/N=3). In the presence of biothiols, the etching from the H2O2 can be hampered. Other biothiols exhibit anti-etching effects well. The strategy works well in detecting of typical biothiols including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH). Thus, a simple colorimetric strategy for sensitive detection of H2O2 and biothiols is proposed. It is believed that the colorimetric sensor based on etching and anti-etching strategy can be applied in other systems in chemical and biosensing areas.