Picheng Gao

Label-free photoelectrochemical immunosensor for sensitive detection of Ochratoxin A

A general label-free photoelectrochemical (PEC) platform was manufactured by assembly of CdSe nanoparticles (NPs) sensitized anatase TiO2-functionalized electrode via layer-by-layer (LBL) strategy. CdSe NPs were assembled on anatase TiO2-functionalized electrode through dentate binding of TiO2 NPs to -COOH groups. Ascorbic acid (AA) was used as an efficient electron donor for scavenging photogenerated holes under visible-light irradiation. The photocurrent response of the CdSe NPs modified electrode was significantly enhanced as a result of the band alignment of CdSe and TiO2 in electrolyte. Ochratoxin A (OTA), as model analyte, was employed to investigate the performance of the PEC platform. Antibodies of OTA were immobilized on CdSe sensitized electrode by using the classic 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride coupling reactions between -COOH groups on the surfaces of CdSe NPs and -NH2 groups of the antibody. Under the optimized conditions, the photocurrent was proportional to OTA concentration range from 10pg/mL to 50ng/mL with detection limit of 2.0pg/mL. The employed PEC platform established a simple, fast and inexpensive strategy for fabrication of label-free biosensor, which might be widely applied in bioanalysis and biosensing in the future.

Anatase TiO2 based photoelectrochemical sensor for the sensitive determination of dopamine under visible light irradiation

Dopamine (DA), an important neurotransmitter in the central nervous system, is thought to control emotions and the balance of hormones in the human body. A photoelectrochemical sensor based on anatase TiO2 nanoparticles was developed to detect DA under visible light irradiation. The TiO2 nanoparticles were prepared by a previously reported hydrothermal method and the anatase phase was confirmed by X-ray diffraction. Under visible light irradiation, the electrode modified with TiO2 nanoparticles showed a weak photocurrent response in the absence of DA; however, the photocurrent was significantly improved after DA was added to the electrolyte. The proposed photoelectrochemical sensor had a sensitive response to DA with excellent reproducibility, stability and a wide linear range. This sensor may have potential applications in the determination of DA in real samples.

A signal-off sandwich photoelectrochemical immunosensor using TiO2 coupled with CdS as the photoactive matrix and copper (II) ion as inhibitor

In this work, a novel sandwich photoelectrochemical (PEC) biosensor was developed based on a signal-off strategy using TiO2 coupled with CdS quantum dots (QDs) as the photoactive matrix and copper (II) ion (Cu(2+)) as inhibitor. TiO2/CdS modified indium tin oxide (ITO) electrode was employed for primary antibody (Ab1) immobilization and the subsequent sandwich-type antibody-antigen (Ab-Ag) affinity interactions. Flower-like copper oxide (CuO) was used as labels of secondary antibody (Ab2) and immobilized on the modified electrode via specific affinity interactions between Ab2 and Ag. Cu(2+) was released by dissolving CuO with HCl, and then reacted with CdS to form CuxS (x=1, 2), which would create new energy levels for electron-hole recombination and resulted in a decrease of the photocurrent. CuO, as the labels of Ab2, was first applied in PEC biosensor based on the signal-off strategy of the Cu(2+) for CdS. Greatly enhanced sensitivity was achieved through the coupling of CdS QDs with TiO2. Besides, the introduction of polythiophene (PT-Cl) on the surface of TiO2 made the PEC signal more stable. Under 405nm irradiation at 0.1V, the PEC biosensor for H-IgG determination exhibited a linear range from 0.1pgmL(-1) to 100ngmL(-1) with a low detection limit of 0.03pgmL(-1). The proposed biosensor showed high sensitivity, stability and selectivity, which opens up a new promising signal-off PEC platform for future bioassay.

Facile synthesized highly active BiOI/Zn2GeO4 composites for the elimination of endocrine disrupter BPA under visible light irradiation

A simple chemical bath approach for the facile synthesis of a BiOI/Zn2GeO4 composite has been demonstrated. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The XRD results indicate that the BiOI and Zn2GeO4 co-exist in the composite. The HRTEM image, showing clear lattice fringes, proves the formation of a heterojunction between BiOI and Zn2GeO4. The photo-degradation of bisphenol A indicates that the BiOI/Zn2GeO4 composites are more photoactive than BiOI and Zn2GeO4. The photocatalytic activity enhancement, which is mainly ascribed to the strong sensitization of BiOI to Zn2GeO4, broadened the photoabsorption of Zn2GeO4, and the heterojunction of BiOI/Zn2GeO4 facilitated the transfer and separation of photo-generated charge carriers. In addition, the active species trapping experiments showed that h+ and ˙O2− were the dominant reactive species, while molecular oxygen plays a fatal role for photocatalytic interactions. Subsequently, a possible degradation mechanism is proposed. Furthermore, the BiOI/Zn2GeO4 photocatalysts exhibit a higher mineralization capacity for bisphenol A, suggesting hopeful prospects for its use in practical applications for the decomposition of organic pollutants.

Engineering microstructured porous films for multiple applications via mussel-inspired surface coating

Surface functionalization of porous materials provides an elegant approach for the development of advanced functional materials. In this work, microstructured porous films, both hydrophobic honeycomb films prepared by the breath figure method and commercially available microfiltration membranes, were modified by the mussel-inspired surface coating. Scanning electron microscopy (SEM) and contact angle measurements confirmed the successful deposition of thin polydopamine layers. Biomolecules could be easily immobilized onto the modified surface. A simple method was proposed to fabricate arrays of honeycomb structures and hierarchical micropatterns of biomolecules could be obtained. Noble metal nanoparticles were decorated on the modified microfiltration membranes, which could be confirmed by EDS analysis and XRD measurements. Furthermore, the fabricated porous membranes showed surface-enhanced Raman scattering (SERS) activity. Mussel-inspired surface coating will undoubtedly expand the application of the porous materials.

Mulberry-like gold nanospheres supported on graphene nanosheets: one-pot synthesis, characterization and photoelectrochemical property

A facile route was proposed to synthesize mulberry-like gold nanospheres (MGNS) uniformly deposited on graphene nanosheets (GNs). Aniline was used as the reducing agent of both tetrachloroaurate and graphene oxide (GO). GO was partially reduced to GNs and acted as a support of the MGNS. The influence of the reaction time, reaction temperature and aniline concentration on the morphology of the MGNS were investigated. The resulting MGNS–GNs composites were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction spectroscopy, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy and electrochemical techniques. The formation mechanism of the MGNS–GNs was proposed based on the contrast experiments. The results illustrated that GO plays a key role in the uniform distribution of the MGNS and polyaniline is responsible for the formation of the MGNS. Compared with GO, the MGNS–GNs showed an enhanced photoelectrochemical property, which has potential application in the fields of sensors and energy.

Visible-light driven Photoelectrochemical Immunosensor Based on SnS 2 @mpg-C 3 N 4 for Detection of Prostate Specific Antigen

Herein, a novel label-free photoelectrochemical (PEC) immunosensor based on SnS2@mpg-C3N4 nanocomposite is fabricated for the detection of prostate specific antigen (PSA) in human serum. Firstly, mesoporous graphite-like carbon nitride (mpg-C3N4) with carboxyl groups is synthesized successfully which possesses high specific surface area and large pore volume. Then, SnS2 as a typical n-type semiconductor with weak photoelectric conversion capability is successfully loaded on carboxylated mpg-C3N4 to form a well-matched overlapping band-structure. The as-synthesized SnS2@mpg-C3N4 nanocomposite performs outstanding photocurrent response under visible-light irradiation due to low recombination rate of photoexcited electron-hole pairs, which is transcend than pure SnS2 or pure mpg-C3N4. It is worth noting that SnS2@mpg-C3N4 nanocomposite is firstly employed as the photoactive material in PEC immunosensor area. The concentration of PSA can be analyzed by the decrease in photocurrent resulted from increased steric hindrance of the immunocomplex. Under the optimal conditions, the developed PEC immunosensor displays a liner photocurrent response in the range of 50 fg·mL−1 ~ 10 ng·mL−1 with a low detection limit of 21 fg·mL−1. Furthermore, the fabricated immunosensor with satisfactory stability, reproducibility and selectivity provides a novel method for PSA determination in real sample analysis.

A sensitive photoelectrochemical immunoassay based on mesoporous carbon/core–shell quantum dots as donor–acceptor light-harvesting architectures

Herein, we demonstrate the protocol of a label-free photoelectrochemical (PEC) immunoassay on the basis of ordered mesoporous carbon (CMK-3) and water-soluble CdSe@ZnS core–shell quantum dots (QDs) coupled with a biospecific interaction for the ultrasensitive detection of human immunoglobulin (antigen, H-IgG) as a model protein. The CMK-3 was dispersed with chitosan (CS-CMK-3), which contains a large amount of amino groups (–NH2), and the CdSe@ZnS QDs were treated with thioglycolic acid, which contains carboxylic acid groups (–COOH). The layer-by-layer assembling of CdSe@ZnS QDs and CS-CMK-3 achieved through the covalent bonding of –COOH and –NH2 was employed as a photoactive antibody (Ab) immobilization matrix. Improved sensitivity was achieved through the synergistic effect of the excellent electrical conductivity and high specific surface area of CMK-3, as well as the high photon-to-electron conversion efficiency of CdSe@ZnS QDs. The photoexcitation of a CMK-3/CdSe@ZnS QDs-modified ITO electrode potentiostated at 0 V (vs. Ag/AgCl) under white light led to a stable anodic photocurrent. To perform the immunoassay, anti-human immunoglobulin (antibody, anti-H-IgG) was conjugated onto the CdSe@ZnS QDs-modified electrode by using EDC–NHS coupling reactions between –COOH of CdSe@ZnS QDs and –NH2 of the antibody. The concentrations of H-IgG were measured through the decrease in photocurrent intensity resulting from the increase in steric hindrance due to the formation of the immunocomplex. Under the optimal conditions, a linear relationship between photocurrent decrease and H-IgG concentration was obtained in the range 10 pg mL−1–100 ng mL−1 with a detection limit of 5 pg mL−1. This strategy opens a simple perspective for the application of mesoporous conductive material and core–shell QDs as light-harvesting architecture, which might be of great significance in PEC bioanalysis in the future.

Ultrasensitive electrochemical immunosensor for squamous cell carcinoma antigen detection using lamellar montmorillonite-gold nanostructures as signal amplification.

Sodium montmorillonites (Na-Mont), which could be transformed from nano-montmorillonites, have large surface area, chemical stability, nontoxicity, high cation exchange property and superior adsorption ability. In this paper, Na-Mont were used as a support of polyaniline (PANI) and gold nanoparticles (AuNPs) via the interaction of aniline and HAuCl4 solution. A sandwich-type electrochemical immunosensor was developed to detect squamous cell carcinoma antigen (SCC-Ag). It used nitrogen-doped graphene sheets (N-GS) for the immobilization of primary anti-SCC antibodies (Ab1) and the combined Na-Mont-PANI-AuNPs nanocomposites as labels. Na-Mont-PANI-AuNPs have excellent catalytic ability towards the reduction of H2O2, thus enhance the sensitivity of the immunosensor. The immunosensor exhibits a wide linear range (1 pg/mL-5 ng/mL), a low detection limit (0.3 pg/mL), good reproducibility, selectivity and stability. This new type of immunosensor with Na-Mont-PANI-AuNPs as labels may provide potential application for the detection of SCC-Ag.

Radially aligned microchannels prepared from ordered arrays of cracks on colloidal films

Arrayed microchannels with dimensions of tens to hundreds of micrometres show great potential for application in microfluidics, microreactor devices and other areas. In this work, we report the formation of ordered arrays of cracks on solution-cast colloidal films, and the preparation of radially aligned microchannels. The polymer film coating enables the colloidal film to be detached from the substrate, retaining the crack patterns on the bottom side. The subsequent chemical corrosion converts the cracks into microchannels. Crack-patterned colloidal films are also used as structured substrates for the preparation of honeycomb films by the breath figure method. Hierarchical honeycomb structures are obtained, giving rise to improved support for colloidal films.