Xiu Wang

3D origami electrochemical device for sensitive Pb2+ testing based on DNA functionalized iron-porphyrinic metal-organic framework

A highly sensitive electrochemical (EC) biosensor combined with a 3D origami device for detection of Pb2+was developed based on novel Au nanoparticles modified paper working electrode (Au-PWE) as sensor platform and DNA functionalized iron-porphyrinic metal-organic framework ((Fe-P)n-MOF-Au-GR) hybrids as signal probes. In the presence of Pb2+, GR could be specifically cleaved at the ribonucleotide (rA) site, which produced the short (Fe-P)n-MOF-linked oligonucleotide fragment to hybridize with hairpin DNA immobilized on the surface of Au-PWE. Because of the mimic peroxidase property of (Fe-P)n-MOF, enzymatically amplified electrochemical signal was obtained to offer the sensitive detection of Pb2+. In addition, benefiting from the Pb2+ dependent GR, the proposed assay could selectively detect Pb2+ in the presence of other metal ions. This method showed a good linear relationship between the current response and the Pb2+ concentration ranging from 0.03 to 1000nmolL-1 with a detection limit of 0.02nmolL-1. The Au-PWE based electrochemical sensor along with the (Fe-P)n-MOF-Au-GR probe exhibited the advantages of low-cost, simple fabrication, high sensitivity and selectivity, providing potential application of real-time Pb2+ detection both in environmental and biological samples.

A 3D electrochemical immunodevice based on an Au paper electrode and using Au nanoflowers for amplification

A highly sensitive electrochemical (EC) immunosensor combined with a 3D origami device for the detection of cancer antigen 125 (CA 125) was developed based on a novel Au nanoparticle-modified paper working electrode (Au-PWE) as sensor platform and Au nanoflowers (AuNFs) as signal amplification label. The microfluidic origami electrochemical device was fabricated by directly screen-printing electrodes on wax-patterned cellulose paper in bulk. The Au-PWE was fabricated using a seed-mediated growth approach and served as an effective matrix for antibody attachment with good bioactivity and stability. Molybdenum disulfide catalyzed the hydrogen peroxide so that the current peak was presented with differential pulse voltammetry (DPV). On the basis of the considerably amplified DPV signal and sandwich-type format, the proposed method successfully fulfilled the highly sensitive detection of CA 125 with a linear range of 0.001 to 50 ng mL−1 and a detection limit of 0.36 pg mL−1. This facile origami EC immunodevice exhibited high sensitivity, specificity and excellent performance in real human serum assay, and it could be applied in point-of-care testing of other tumor markers in remote regions and developing countries.

A sensitive quenched electrochemiluminescent DNA sensor based on the catalytic activity of gold nanoparticle functionalized MoS2

In this paper, molybdenum disulfide (MoS2) was synthesized through the hydrothermal method, which was further fabricated into gold nanoparticle (AuNP) functionalized MoS2 (MoS2–Au). The prepared MoS2–Au showed an excellent catalytic performance of hydrogen peroxide (H2O2) in the reduction reaction. In addition, the CdS/ZnS quantum dots coated with polyethyleneimine (PEI-CdS/ZnS QDs) with good electrochemiluminescence (ECL) properties were prepared. Finally, the prepared MoS2–Au and PEI-CdS/ZnS QDs were applied in a simple sandwich-type ECL sensor for DNA detection. In the DNA sensor, PEI-CdS/ZnS QDs acted as solid supports for capturing DNA and MoS2–Au was employed as the supporter of reporter DNA. MoS2–Au could quench the ECL signal of the PEI-CdS/ZnS QDs in which Au could facilitate the ECL measure and the quenching ECL intensity could be obtained. The proposed DNA sensor enabled target DNA concentrations to be determined in the 0.05–1000 fM concentration range, with a detection limit of 0.023 fM. The DNA sensor showed a low detection limit, good specificity, high sensitivity and reproducibility. Hence, the use of proposed electrochemiluminescent biosensors could become a promising method for DNA detection.

On–off–on fluorescence sensing of glutathione in food samples based on a graphitic carbon nitride (g-C3N4)–Cu2+ strategy

A novel fluorescence sensor based on a g-C3N4 nanosheet–Cu2+ system has been developed for rapid, sensitive and selective sensing of glutathione (GSH) in food samples. The g-C3N4 nanosheets were used here as a new type of carbon-based nanomaterial with high fluorescence quantum yield and specific surface area. The fluorescence of the g-C3N4 nanosheets was quenched by Cu2+via a photoinduced electron transfer (PET) process. In the presence of GSH, the fluorescence sensor was switched on, which was attributed to coordination of Cu2+ to GSH and the functional groups on the surface of the g-C3N4 nanosheets. Under optimal conditions, a limit of detection (LOD) of 20 nM for GSH was reached over a wide GSH concentration range of 0.05 to 900 μM. Moreover, the proposed sensor shows excellent performance, and has advantages such as low cost, easy preparation, rapid detection and switch-on fluorescence response. The fluorescence sensor was successfully applied for GSH detection in different food samples.

A sensitive electrochemiluminescent immunosensor based on 3D-flower-like MoS2 microspheres and using AuPt nanoparticles for signal amplification

We herein report the synthesis of MoS2, consisting of three-dimensional flower-like microspheres assembled by bent flakes with a thickness of several nanometers. The diameter of theses spheres was approximately 1.5 μm, and they showed good catalysis of H2O2 and could increase the electrochemiluminescence (ECL) intensity of luminol. The ECL properties of luminol were investigated and a type of luminol composite (MoS2–luminol) was prepared. Glucose oxidase–AuPt nanoparticles (GOx–AuPt) showed excellent catalytic performance for the reduction reaction of glucose. The prepared GOx–AuPt and MoS2–luminol were applied in a sandwich-type ECL immunosensor for prostate-specific antigen (PSA). In the immunosensor, MoS2–luminol acted as a solid support for PSA primary antibody, and GOx–AuPt was employed as a support for PSA secondary antibody. With the addition of glucose, hydrogen peroxide was prepared and the ECL properties of the MoS2–luminol were enhanced. The proposed immunosensor enabled PSA concentrations to be determined in the range of 0.001 ng mL−1 to 100 ng mL−1, with a detection limit of 0.28 pg mL−1. The experimental results indicated that the immunosensor exhibited simple instrumentation, high sensitivity, wide linear range and excellent analytical performance, and could be a promising technique for tumor marker detection.

Using carbon nanotubes-gold nanocomposites to quench energy from pinnate titanium dioxide nanorods array for signal-on photoelectrochemical aptasensing

On the basis of the absorption and emission spectra overlap, an enhanced resonance energy transfer caused by excition-plasmon resonance between carbon nanotubes-gold nanoparticles (CNTs-Au) and pinnate titanium dioxide nanorods array (P-TiO2 NA) was obtained. Three-dimensional single crystalline P-TiO2 were prepared successfully on fluorine-doped tin oxide conducting glass (FTO glass), and its optical absorption properties and photoelectrochemical (PEC) properties were investigated. With the synergy of CNTs-Au as energy acceptor, it resulted in the enhancement of energy transfer between excited P-TiO2 NA and CNTs-Au. Upon the novel sandwichlike structure formed via DNA hybridization, the exciton produced in P-TiO2 NA was annihilated and a damped photocurrent was obtained. With the use of carcinoembryonic antigen (CEA) as a model which bonded to its specific aptamer and destroyed the sandwichlike structure, the energy transfer efficiency was lowered, leading to PEC response augment. Thus a signal-on PEC aptasensor was constructed. Under the optimal conditions, the PEC aptasensor for CEA determination exhibited a linear range from 0.001 to 2.5ngmL(-1) with a detection limit of 0.39pgmL(-1) and was satisfactory for clinical sample detection. Furthermore, the proposed aptasensor shows satisfying performance, such as easy preparation, rapid detection and so on. Moreover, since different aptamer can specifically bind to different target molecules, the designed strategy has an expansive application for the construction of versatile PEC platforms.

A sensitive Pb2+ testing method based on aptamer-functionalized peroxidase-like 3D-flower MoS2 microspheres

Herein, we proposed an electrochemical Pb2+ sensor using peroxidase-like GR aptamer-functionalized 3D-flower MoS2 microsphere (MoS2–GR) hybrids as signal probes. AuPt nanoparticles and multiwalled carbon nanotube composites (AuPt–MCNTs) were successively modified on a glassy carbon electrode (GCE), which improved the electronic transfer rate as well as increased the amount of immobilized capture hairpin DNA (HP). In the presence of Pb2+, GR could be specifically cleaved at the ribonucleotide (rA) site, which produced the short MoS2–GR to hybridize with HP immobilized on the surface of the GCE. Because of the mimic peroxidase property of MoS2, an enzymatically amplified electrochemical signal was obtained to achieve the sensitive detection of Pb2+. In addition, benefiting from the Pb2+-dependent GR, the proposed assay could selectively detect Pb2+ in the presence of other metal ions. This method showed a good linear relationship between the current response and the Pb2+ concentration ranging from 0.03 to 500 nmol L−1 with a detection limit of 0.015 nmol L−1. The new, robust, and convenient assay systems can be widely utilized for the identification of other target molecules.

A novel fluorescence probe based on p-acid-Br and its application in thiourea detection

In this paper, a novel phenyleneethynylene derivative 4,4′-(2,5-dimethoxy-1,4-phenylene)bis(ethyne-2,1-diyl) dibenzoic acid (p-acid) and its derivative p-acid-Br were synthesized. Infrared spectroscopy (IR), fluorescence (FL) spectroscopy and ultraviolet visible (UV-vis) spectroscopy were applied to characterize p-acid and p-acid-Br. To research the practical applicability, a sample thiourea sensor was constructed using the p-acid-Br label, in which the FL intensity response was proportional to the thiourea concentration in the range of 0.5–1000 nM, with a detection limit of 0.26 nM. Furthermore, the sensor showed high specificity, excellent stability, and good reproducibility. The p-acid-Br-based thiourea sensor can also provide potential application for detection of other organics. The method showed low detection limit, good specificity, high sensitivity and reproducibility. Satisfactory results were obtained for the determination of thiourea in various water samples and fruit juice samples. This work is to open new avenues in the application of the phenyleneethynylene derivative for a sensitive thiourea assay. Hence, the proposed fluorescence sensor could become a promising method for local market.

Research on Dynamic Behavior of Disc Indexing Cam Mechanism Based on Virtual Prototype Technology

Dynamic modelling method for disc indexing cam mechanism was presented based on virtual prototype technology according to the analysis of mechanism feature. Rigid-flexible coupled dynamic model was established by means of Adams, Pro/E and Ansys softwares. Dynamic simulation has been done. It follows the analysis of simulation that effects of input speed, and stroke angle to torsional vibration were illustrated corresponding to dynamics simulation. Dynamic characteristics of different transmission functions commonly used in practical engineering were analyzed in detail. The application principle of transmission functions was presented based on dynamic simulation and analysis results. Construction method of transmission function was presented finally.

Synthesis, characterization of a novel phenyleneethynylene derivative and application in a fluorescence DNA sensor

In this paper, a novel phenyleneethynylene derivative 4,4′-(2,5-dimethoxy-1,4-phenylene)bis(ethyne-2,1-diyl) dibenzoic acid (p-acid) was synthesized. Infrared spectroscopy (IR), nuclear magnetic resonance (NMR), photoluminescence (PL) spectroscopy and ultraviolet visible (UV-vis) spectroscopy were applied to characterize p-acid. The p-acid doped silica nanoparticle (p-acid@SiO2) was assembled in layer-by-layer (LBL) self-assembling processes using tetraethoxysilane (TEOS). Scanning electron microscope (SEM) and transmission electron microscope (TEM) were applied to characterize p-acid@SiO2. To research the practical applicability, a sample DNA sensor was constructed using p-acid@SiO2 label, in which the PL intensity response was proportion to the target-DNA (S2) concentration in the range of 0.05–1000 fM, with a detection limit of 20 pM. Furthermore, the DNA sensor showed high specificity, excellent stability, and good reproducibility. The p-acid@SiO2-based DNA sensor can also provide potential application for detection of other pathogen DNA.