Shupei Zhang

Enhanced Photoelectrochemical Activity of a Hierarchical-Ordered TiO2 Mesocrystal and Its Sensing Application on a Carbon Nanohorn Support Scaffold

A ternary hybrid was developed through interaction between a hierarchical-ordered TiO2 and a thiol group that was obtained by in situ chemical polymerization of L-cysteine on the carbon nanohorn (CNH) superstructure modified electrode. Herein, unique-ordered TiO2 superstructures with quasi-octahedral shape that possess high crystallinity, high porosity, oriented subunit alignment, very large specific surface area, and superior photocatalytic activity were first introduced as a photosensitizer element in the photoelectrochemical determination. Additionally, the assembly of hierarchical-structured CNHs was used to provide an excellent electron-transport matrix to capture and transport an electron from excited anatase to the electrode rapidly, hampering the electron-hole recombination effectively, resulting in improved photoelectrochemical response and higher photocatalytic activity in the visible light region. Owing to the dependence of the photocurrent signal on the concentration of electron donor, 4-methylimidozal, which can act as a photogenerated hole scavenger, an exquisite photoelectrochemical sensor was successfully fabricated with a wide linear range from 1 × 10(-4) to 1 × 10(-10) M, and the detection limit was down to 30 pM. The low applied potential of 0.2 V was beneficial to the elimination of interference from other reductive species that coexisted in the real samples. More importantly, the mesocrystal was first introduced in the fabricating of a biosensor, which not only opens up a new avenue for biosensors manufactured based on mesocrystal materials but also provides beneficial lessons in the research fields ranging from solar cells to photocatalysis.

Carbon nanotubes functionalized electrospun nanofibers formed 3D electrode enables highly strong ECL of peroxydisulfate and its application in immunoassay

A new biosensing platform based on electrospun carbon nanotubes nanofibers (CNTs@PNFs) composite, which enabled strong electrochemiluminescent emission of peroxydisulfate, was firstly developed for immunoassay with favorable analytical performances, and then was utilized to evaluate the interaction between antibody and antigen in vitro. Moreover, the obvious ECL image of peroxydisulfate on the prepared sensing platform was firstly recorded in this report. In order to expand the application of peroxydisulfate ECL, the specific recognization biomolecules, α-fetoprotein (AFP) antibody was bound to the functionalized film via electrostatic interaction for fabricating label-free ECL immunosensor to detect α-AFP. Based on the ECL change resulting from the specific immunoreaction between antigen and antibody, the quantitative analysis for AFP with wide dynamic response in the range from 0.1 pg mL(-1) to 160 ng mL(-1) was realized. And the limit of detection was estimated to be 0.09 pg mL(-1). Therefore, the flexible sensing platform not only acted as the sensitized sensing element, but also offered a suitable carrier for immobilization of biological recognition elements with low-toxicity and eco-friendliness, which opened a promising approach to developing further electrospun nanofiber based amplified ECL biosensor with favorable analytical performances.

The photoelectrochemical exploration of multifunctional TiO2 mesocrystals and its enzyme-assisted biosensing application

Mesocrystals, as the assemblies of crystallographically oriented nanocrystals, have single-crystal-like atom structures and scattering features but with much higher porosity than single-crystalline materials, making them promising substitutes for conventional single crystals in photoelectrochemical application. As a proof-of-concept, a series of photoelectrochemical tests were investigated to understand the influence of the differences between them on photoelectrochemical activity. Expectedly, comparing with TiO2 single crystals, TiO2 mesocrystals demonstrated higher photoelectrochemical capability, which provides unique new opportunities for materials design in the fields of solar-energy conversion and catalysis. Therefore, an elegant photoelectrochemical biosensing platform was firstly developed by virtue of carbon nanohorns with outstanding electrical conductivity support multifunctional TiO2 mesocrystals to accelerate the transfer of photogenerated electrons, and then horseradish peroxidase was introduced through the immune recognition reaction for enzyme-assisted in situ generating CdS QDs. The multiplex amplification strategy successfully achieved the ultrasensitive detection of α-fetoprotein antigen. Promisingly, the successful application of multiplex amplification strategy affords a rational and practical consideration for the fabrication of new and high-performance photoelectrochemical sensing devices.

Electrochemical bisphenol A sensor based on carbon nanohorns

Herein, a new carbon material, carbon nanohorns (CNHs), was firstly employed as the sensing element to fabricate a simple electroanalytical platform for detecting food born contaminants. Bisphenol A (BPA) was chosen as the model to be tested in this sensing platform. The detailed electrochemical behavior of BPA was investigated on the modified electrode and its kinetic parameters were further calculated. The relative results pointed out that CNHs, which have a similar electrocatalysis effect as previously reported carbon materials, like graphene and carbon nanotubes, could obviously amplify the electrochemical oxidation response of BPA because of its unique and charming properties. The experimental conditions affecting the BPA determination were optimized. The relative results indicate the potential application of CNHs in designing sensitive and convenient sensors for the rapid and on-site monitoring of food born contamination.

Silver Iodide-Chitosan Nanotag Induced Biocatalytic Precipitation for Self-Enhanced Ultrasensitive Photocathodic Immunosensor

In this work, we first exposed that the application of p-type semiconductor, silver iodide-chitosan nanoparticle (SICNP), acted as peroxidase mimetic to catalyze the bioprecipitation reaction for signal-amplification photocathodic immunosensing of human interleukin-6 (IL-6). After immobilization of captured antibody onto a polyethylenimine-functionalized carbon nitride (CN) matrix, SICNPs as photoactive tags and peroxidase mimetics were labeled on secondary antibodies, which were subsequently introduced onto the sensing interface to construct sandwich immunoassay platform through antigen-antibody specific recognition. Due to the matched energy levels between CN and AgI, the photocurrent intensity and photostability of SICNP were dramatically improved with rapid separation and transportation of photogenerated carriers. Moreover, the insoluble product in effective biocatalytic precipitation reaction served as electron acceptor to scavenge the photoexcited electron, leading to great amplification of the photocurrent signal of SICNP again. With the help of multiamplification processes, this photocathodic immunosensor presented a turn-on photoelectrochemical performance for IL-6, which showed wide linear dynamic range from 10(-6) to 10 pg/mL with the ultralow detection limit of 0.737 ag/mL. This work also performed the promising application of SICNP in developing an ultrasensitive, cost-effective, and enzyme-free photocathodic immunosensor for biomarkers.

Highly photoactive heterojunction based on g-C3N4 nanosheets decorated with dendritic zinc(II) phthalocyanine through axial coordination and its ultrasensitive enzyme-free sensing of choline

A heterojunction with excellent photocatalytic performance based on graphene-like carbon nitride (g-C3N4) nanosheets and dendritic zinc(II) phthalocyanine was proposed. Herein, the g-C3N4 with excellent photo-activity and high nitrogen content was readily available as a functional material. The g-C3N4 acted as an electron pair donor for dendritic zinc(II) phthalocyanine through axial coordination, forming the p–n heterojunction. Then by taking advantage of the distortion of dendritic zinc(II) phthalocyanine, the spatial charge separation of photo-generated charge carriers in this metal macrocycle achieved high efficiency, resulting in the enhanced photo-to-electric conversion efficiency. Therefore, the optoelectronic sensing device based on the heterojunction led to an enhanced photocurrent, and made it a promising candidate for establishing photoelectrochemical biosensors. Moreover, the p–n heterojunction was successfully applied to the detection of choline with a wide linear range from 10 nM to 5 μM, which could be oxidized by the photo-generated holes. Along with these attractive features, the as-proposed biosensor also displayed a remarkable specificity against other interferents and could be successfully used for detecting choline in real samples. The heterojunction with enhanced photoelectronic properties provides a promising format for the future development of photoelectrochemical biosensors.

A sensitive arecoline photoelectrochemical sensor based on graphitic carbon nitride nanosheets activated by carbon nanohorns

For the first time, a sensitive and high efficient photoelectrochemical biosensor has been developed for the quantitative detection of arecoline based on graphitic carbon nitride nanosheets with the assistance of carbon nanohorns

All-in-one bioprobe devised with hierarchical-ordered magnetic NiCo2O4 superstructure for ultrasensitive dual-readout immunosensor for logic diagnosis of tumor marker

A new enzyme-free all-in-one bioprobe, consisted of hematin decorated magnetic NiCo2O4 superstructure (ATS-MNS-Hb), was designed for ultrasensitive photoelectrochemical and electrochemical dual-readout immunosensing of carcinoembryonic antigen (CEA) on carbon nanohorns (CNH) support. Herein, the MNS, possessed hierarchical-ordered structure, good porosity and magnetism, acted as nanocarrier to absorb abundant Hb molecular after functionalization, providing a convenient collection means by magnetic control as well as enhanced dual-readout sensing performances. CNH superstructures were employed as support to immobilize abounding captured antibodies, and then as-designed dual mode bioprobe, covalent binding with secondary antibody of CEA, was introduced for ultrasensitive detection of CEA by sandwich immunosensing. Photoelectrochemical response originated from plentiful hematin molecular, a excellent photosensitizer with good visible light harvesting efficiency, absorbed by functionalized porous MNS. The resultant concentration dependant linear calibration range was from 10 fg/mL to 1 ng/mL with ultralow detection limit of 10 fg/mL. For electrochemical process, catalase-like property of MNS was validated, moreover, MNS-Hb hybrid exhibited much higher mimic enzyme catalytic activity and evidently amplified electrocatalytic signal, performing a wide dynamic linear range from 1 ng/mL to 40 ng/mL with low detection limit of 1 ng/mL. Additionally, due to the improved accuracy of dual signals detection, the exact diagnoses of serum samples were gotten by operating resulting dual signals with AND logic system. This work demonstrated the promising application of MNS in developing ultrasensitive, cost-effective and environment friendly dual-readout immunosensor and accurate diagnoses strategy for tumor markers.

Amplified electrochemiluminescence of lucigenin triggered by electrochemically reduced graphene oxide and its sensitive detection of bisphenol A

An amplified and stable electrochemiluminescent signal of lucigenin was observed on an electrochemically reduced graphene oxide-containing sensing platform. Herein, chitosan was used as an excellent dispersant, which favors the better dispersion of graphene oxide in solution and improved electrochemical reduction of graphene oxide. The electrochemically reduced graphene oxide showed outstanding conductivity which was propitious to the transfer of electrons, leading to the enhancement of the electrochemiluminescent signals of lucigenin. In addition, bisphenol A, as a classical food borne pollutant, was first detected due to its strong inhibiting action of the electrochemiluminescent response of lucigenin. Then, we studied the quenched electrochemiluminescent system and the possible mechanism of the platform in detail. Under optimum conditions, the proposed electrochemiluminescent sensor exhibited a linear response range from 1.0 × 10−9 mol L−1 to 1.0 × 10−4 mol L−1 with a low detection limit of 3.0 × 10−10 mol L−1 for bisphenol A, which might find promising applications in developing a new type of biosensor.

TiO2-B nanorod based competitive-like non-enzymatic photoelectrochemical sensing platform for noninvasive glucose detection

TiO2-B nanorods, with excellent properties including large specific surface area, open structures with significant voids, and continuous channels, were explored for the first time in the photoelectrochemical biosensing field. To reduce the destructive effect of UV light on biomolecules, dopamine was introduced onto the TiO2-B nanorod surface through the coordination of dopamine to the undercoordinated titanium atoms of the TiO2-B nanorods, which makes the complex a promising matrix for subsequent biosensing. Furthermore, concanavalin A as a recognition element was attached onto the TiO2-B nanorod/dopamine modified electrode surface by virtue of covalent interaction between concanavalin A and dopamine. Accordingly, a new competitive-like non-enzymatic photoelectrochemical biosensor was established by using glucose labeled SiO2 nanospheres of fixed concentration as photoelectrochemical signal inhibitors competing with target glucose of various concentrations for reaction with concanavalin A. Moreover, this ultrasensitive biosensor with excellent analytical performance was successful applied to noninvasive glucose determination in human saliva. Promisingly, the successful application of TiO2-B nanorods in this research provides a new consideration in the selection of excellent photoactive materials for photoelectrochemical sensing.