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An ultrasensitive photoelectrochemical (PEC) immunosensor for the detection of carcinoembryonic antigen (CEA) was constructed using CdS@Cu 2 O co-sensitized porous ZnO nanosheets as photoactive materials and multiwalled carbon nanotubes (MWCNTs) as electrons sink. Porous ZnO was assembled on the MWCNTs modified indium tin oxides electrode to immobilize capture antibodies. With a sandwich immunoassay format, CEA and signal antibodies labeled CdS@Cu 2 O were introduced in sequence via specific immunoreaction, and the ultrahigh sensitivity of this immunoassay results from the following three aspects. First, the co-sensitization of Cu 2 O and CdS extends the absorption range of ZnO from ultraviolet region to visible light region, which can adequately utilize the light energy. Second, the effective matching of energy levels between the ZnO, CdS and Cu 2 O accelerates the separation and transfer of photogenerated electron-hole pairs and improves the PEC performance, significantly. Finally, the introduced MWCNTs evidently expedite the interfacial electron transfer from ZnO to electrode, further resulting in noticeably increased photocurrent. On the basis of multiple signal amplification strategy, a largely increased linear detection range from 1.0 pg mL −1 to 80 ng mL −1 with a low detection limit (0.4 pg mL −1 ) are obtained. Meanwhile, the prepared materials with attractive properties provide a promising platform for PEC detection. [ABSTRACT FROM AUTHOR]

Herein, a photoelectrochemical (PEC) immunoassay is constructed for squamous cell carcinoma antigen (SCCA) detection using zinc oxide nanoflower-bismuth sulfide (Bi 2 S 3 ) composites as photoactive materials and reduced graphene oxide (rGO) as signal labels. Horseradish peroxidase is used to block sites against nonspecific binding, and then participated in luminol-based chemiluminescence (CL) system. The induced CL emission is acted as an inner light source to excite photoactive materials, simplifying the instrument. A novel signal amplification strategy is stem from rGO because of the rGO acts as an energy acceptor, while luminol serves as a donor to rGO, triggering the CL resonance energy transfer phenomenon between luminol and rGO. Thus, the efficient CL emission to photoactive materials decreases. Furthermore, the signal amplification caused by rGO labeled signal antibodies is related to photogenerated electron–hole pairs: perfect matching of energy levels between rGO and Bi 2 S 3 makes rGO a sink to capture photogenerated electrons from Bi 2 S 3 ; the increased steric hindrance hinders the electron donor to the surface of Bi 2 S 3 for reaction with the photogenerated holes. On the basis of the novel signal amplification strategy, the proposed immunosensor exhibits excellent analytical performance for PEC detection of SCCA, ranging from 0.8 pg mL −1 to 80 ng mL −1 with a low detection limit of 0.21 pg mL −1 . Meanwhile, the designed signal amplification strategy provides a general format for future development of PEC assays. [ABSTRACT FROM AUTHOR]

Combining multibranched hybridization chain reaction (mHCR), the photoelectrochemical (PEC) immunosensor was fabricated with a microfluidic paper-based analytical devices using different sizes of CdTe quantum dots (QDs) sensitized flower-like 3D ZnO superstructures as photoactive materials. Firstly, 4-aminothiophenol (PATP) functioned ZnO was anchored on gold-paper working electrode. With the aid of PATP, large-sized CdTe-COOH QDs (QDs1) were conjugated onto the ZnO surface because of the formation of a strong bond (Zn-S) between the thiol of PATP molecule and the ZnO, and the remaining amino group formed an amide bond with carboxylic acid group capping CdTe. Then the small-sized CdTe-NH 2 QDs (QDs2) were modified on the QDs1 by forming amide bond, which leaded to a very strong photocurrent response because of the formation of cosensitized structure. The designed mHCR produced long products with multiple branched arms, which could attached multiple PdAu nanoparticles and catalyze the oxidation of hydroquinone (HQ) using H 2 O 2 as anoxidant. Double strands DNA with multiple branched arms (mdsDNA) was formed by mHCR. In the presence of carcinoembryonic antigen (CEA), PdAu-mdsDNA conjugates-labeled CEA antibody was captured. The concentrations of CEA were measured through the decrease in photocurrent intensity resulting from the increase in steric hindrance of the immunocomplex and the polymeric oxidation product of HQ. In addition, the oxidation product of HQ deposited on the as-obtained electrode, which could efficiently inhibit the photoinduced electron transfer. Under optimal conditions, the PEC immunosensor exhibited excellent analytical performance: the detection range of CEA was from 0.001 to 90 ng mL −1 with low detection limit of 0.33 pg mL −1 . The as-obtained immunosensor exhibited excellent precision, prominent specificity, acceptable stability and reproducibility, and could be used for the detection of CEA in real samples. The proposed assay opens a promising platform of clinical immunoassay for other biomolecules. [ABSTRACT FROM AUTHOR]

In this work, multiplexed photoelectrochemical (PEC) immunoassays are introduced into an indium tin oxide (ITO) device. Firstly, the ITO device is fabricated using a simple acid etch treatment method. Secondly, AuPd alloy nanoparticles are electro-deposited on ITO working electrodes as electron sink to construct the immunosensor platform. After that, ZnO nanotubes (ZNTs) arrays are synthesized via chemical etching of ZnO nanorods that are grown on AuPd surface by electrochemical deposition method. Subsequently, CdS is electro-deposited on ZNTs arrays and used as photoactive material. Then, CuO nanoseeds are labeled with signal antibodies and firstly used as PEC signal amplification label. The introduction of CuO brings signal amplification because of the conduction band (CB) of both CuO and ZnO are lower than that of CdS, CuO will compete the photo-induced electrons in CB of CdS with ZnO, leading to the decrease of the photocurrent intensity. Using cancer antigen 125, prostate specific antigen and α-fetoprotein as model analytes, the proposed immunoassay exhibits excellent precision and sensitivity. Meanwhile, this work provides a promising, addressable and simple strategy for the multi-detection of tumor markers. [ABSTRACT FROM AUTHOR]

Abstract: Combining microfluidic paper-based analytical device (μ-PAD) and the molecular imprinting technique, a visible light photoelectrochemical (PEC) sensing platform for the detection of pentachlorophenol (PCP) was established on gold nanoparticles (AuNPs) decorated paper working electrode using polypyrrole-functionalized ZnO nanoparticles. Ascorbic acid (AA) was exploited as an efficient and nontoxic electron donor for scavenging photogenerated holes under mild solution medium and facilitating the generation of stable photocurrent. The microfluidic molecular imprinted polymer-based PEC analytical origami device is developed for the detection of PCP in the linear range from 0.01ngmL−1 to 100ngmL−1 with a low detection limit of 4pgmL−1. This disposable microfluidic PEC origami device would provide a new platform for sensitive, specific, and multiplex assay in public health, environmental monitoring, and the developing world. [Copyright &y& Elsevier]

An ultrasensitive photoelectrochemical (PEC) immunoassay was introduced into microfluidic paper-based analytical devices (μ-PADs) based on a multiple electron transfer system for the first time, which was constructed using narrow-band-gap semiconductor nanoparticles (NPs), wide-band-gap semiconductor NPs, and an electron-accepting medium. [ABSTRACT FROM AUTHOR]

A novel self-assemble approach was developed for constructing a linear bicontinuous donor–acceptor, (H 2 BCPP) n –C 60 , arrays on indium-tin oxide electrode. Electronic absorption spectra, fluorescence spectra and atomic force microscopy were used as powerful tools to characterize H 2 BCPP, (H 2 BCPP) n arrays and (H 2 BCPP) n –C 60 arrays. The (H 2 BCPP) n –C 60 arrays enhanced the photocurrent generation capability, and presented an efficient photoelectrochemical immunosensing platform for the ultrasensitive detection of carcinoembryonic antigen (CEA). The quantitative measurement of CEA was based on the decrease in the photocurrent intensity of the (H 2 BCPP) n –C 60 arrays, which was resulted from the competition between CEA and CEA-CdTe. A linear relationship between the photocurrent decrease and the CEA concentration was obtained in the wide range from 0.01 to 60 ng mL −1 with a detection limit of 3.4 pg mL −1 . The proposed sensor showed high sensitivity, stability and reproducibility, and provided a promising platform for other biomolecular detection. [ABSTRACT FROM AUTHOR]