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In this study, based on in situ generation of CdS quantum dots (QDs) on the surface of branched TiO 2 (B-TiO 2 ) nanorods, an solar innovative photoelectrochemical (PEC) sensing platform was constructed for real-time, and sensitive detection of cellular H 2 S. Specifically, B-TiO 2 nanorods arrays consisting of TiO 2 nanorods directly grown on fluorine-doped tin oxide (FTO) further using TiCl 3 mediated surface treatment of TiO 2 nanorods are designed and fabricated as a new type of photoelectrode. CdS quantum dots (QDs) was formed on the surface of B-TiO 2 nanorods arrays through the reaction between Cd 2+ and S 2- . And a significant enhancement in the photocurrent was obtained that ascribed to the formation of CdS-B-TiO 2 heterostructures, thus leading to sensitive PEC recording of the H 2 S level in buffer and cellular environments. By using Prussian blue (PB) a electrochromic material to capture the photoelectron generated from the photoelectrode, a new visual system was proposed due to the formation of Prussian white (PW), which could be used to visualize the quantum photoelectric effect. This novel PEC sensing platform not only achieved satisfied analysis results toward S 2- , but also showed excellent sensitivity, selectivity, low cost, and portable features. The strategy through the in situ generation of semiconductor nanoparticles on the surface of wide band-gap semiconductor paves the way for the improvements of PEC analytical performance. Meanwhile, the quantitative read-out electrochromic display paves a facile avenue and initiates new opportunities for creation of cheap, miniaturization sensors for other relevant analytes. [ABSTRACT FROM AUTHOR]

A platelike tungsten trioxide (WO 3 ) sensitized with CdS quantum dots (QDs) heterojunction is developed for solar-driven, real-time, and selective photoelectrochemical (PEC) sensing of H 2 O 2 in the living cells. The structure is synthesized by hydrothermally growing platelike WO 3 on fluorine doped tin oxide (FTO) and subsequently sensitized with CdS QDs. The as-prepared WO 3 -CdS QDs heterojunction achieve significant photocurrent enhancement, which is remarkably beneficial for light absorption and charge carrier separation. Based on the enzymatic etching of CdS QDs enables the activation of quenching the charge transfer efficiency, thus leading to sensitive PEC recording of H 2 O 2 level in buffer and cellular environments. The results indicated that the proposed method will pave the way for the development of excellent PEC sensing platform with the quantum dot sensitization. This study could also provide a new train of thought on designing of self-operating photoanode in PEC sensing, promoting the application of semiconductor nanomaterials in photoelectrochemistry. [ABSTRACT FROM AUTHOR]

In this work, a “signal-off” photoelectrochemical DNA sensing strategy was proposed on the basis of the DNA hybridization induced conformational conversion using CdS quantum dots (QDs) sensitized titanium oxide (TiO 2 ) nanorod array as photoactive material. Highly oriented, single-crystalline TiO 2 nanorod arrays were grown directly on fluorine doped tin oxide (FTO) substrate by the hydrothermal method and employed as matrix for immobilization of capturing hairpin DNA probe, whereas CdS QDs as visible light antennae were successively labeled on the terminal of capturing hairpin DNA probe. Compared with pure TiO 2 nanorods array, CdS QDs sensitized TiO 2 nanorods array evidently extended the absorption edge and exhibited enhanced photoelectrochemical response in the visible region. In the absence of the target DNA, the direct attachment of CdS QDs to TiO 2 nanorod array could reduce charge recombination and hence amplify photocurrent intensity. While in the presence of target DNA, the specific recognition of the target DNA with the capturing hairpin DNA–CdS probe would trigger the conformational conversion of capturing hairpin DNA–CdS probe leading to the quenching of photocurrent. Under optimized conditions, this “signal-off” photoelectrochemical sensing strategy shows a linear relationship between photocurrent variation and the logarithm of target DNA concentration in the range from 10 aM to 100 pM with a detection limit of 5.2 aM. Moreover, it exhibits good performance of excellent specificity, high stability, and acceptable fabrication reproducibility. This present strategy opens an alternative avenue for photoelectrochemical signal transduction and expands the applications of photoelectrochemical biosensing and clinical diagnosis. [ABSTRACT FROM AUTHOR]

A chemiluminescent (CL) excited photoelectrochemical (PEC) immunosensor for detection of carcinoembryonic antigen (CEA) was introduced into microfluidic paper-based analytical devices (μ-PADs) integrated with a paper supercapacitor (PS) amplifier, and a terminal digital multi-meter (DMM) detector, based on CdS/TiO 2 hybrid modified porous Au-paper electrode. The effective matching of energy levels between the conduction bands of CdS and TiO 2 allowed for fast electron injection from excited CdS to TiO 2 upon irradiation, which inhibited the recombination process of electron–hole pairs and prompted PEC performance. Using CEA/ABEI-AuNPs-GOx bioconjugates as signal labels which featured CEA, N-(aminobutyl)-N-(ethylisoluminol) (ABEI) and glucose oxidase (GOx) linked to Au nanoparticles for signal amplification could greatly enhance the sensitivity. GOx could catalyze glucose to produce H 2 O 2 , which acted as a co-reactant in the ABEI-AuNPs-H 2 O 2 - p -iodophenol (PIP) CL system as well as sacrificial electron donor to scavenge the photogenerated holes in the valence band of CdS QDs, further causing an enhanced photocurrent. The quantification mechanism of this strategy is based on the charging of this PS by the photocurrent. The generated photocurrent could be stored by the PS and released instantaneously through a low cost, portable, and simple DMM to obtain an amplified current for the quantification of CEA. Under the optimal conditions, this analytical platform could detect CEA at concentrations at picomole level. This work offers a new route to highly selective and sensitive detection of biologically important small molecules. [ABSTRACT FROM AUTHOR]

Highlights: [•] A sandwich-type photoelectrochemical immunosensor was fabricated. [•] Highly crystalline rhombic TiO2 NCs was prepared through solvothermal method. [•] Ru complex was used as the photoelectrochemical signal-generating molecule. [•] Ru complex hybridized RGO was prepared and used as signal amplification label. [ABSTRACT FROM AUTHOR]

In this paper, a simple and sensitive sandwich-type photoelectrochemical (PEC) immunosensor for measurement of biomarkers on a gold nanoparticle-modified indium tin oxide (ITO) electrode through electrodeposition for point-of-care testing was developed by using a tin dioxide quantum dot–graphene nanocomposite (G–SnO2) as an excellent label with amplification techniques. The capture antibody (Ab1) was firstly immobilized on the gold nanoparticle-modified ITO electrode due to the covalent conjugation, then the antigen and the AuNP/PDDA–G–SnO2 nanocomposite nanoparticle labeled signal antibody (Ab2) were conjugated successively to form a sandwich-type immunocomplex through a specific interaction. Under irradiation with a common ultraviolet lamp (∼365 nm, price $50), the SnO2 NPs were excited and underwent charge-separation to yield electrons (e−) and holes (h+). As the holes were scavenged by ascorbic acid (AA), the electrons were transferred to the ITO electrode through RGO to generate a photocurrent. The photocurrents were proportional to the CEA concentrations, and the linear range of the developed immunosensor was from 0.005 to 10 ng mL−1 with a detection limit of 0.036 pg mL−1. The proposed sensor shows high sensitivity, stability, reproducibility, and can become a promising platform for other biomolecular detection. [ABSTRACT FROM AUTHOR]

Abstract: Driven by the urgent demand of high-selectively point-of-care testing device for pesticide, molecular imprinting-photoelectrochemistry (MI-PEC) was introduced into microfluidic paper-based analytical strategy to design a novel paper-based photoelectrochemical (paper-based PEC) protocol. The MI-PEC strategy was constructed based on CdTe quantum dots dotted molecular imprinted polymers (CdTe QDs@MIPs), and triggered by a common ultraviolet lamp (∼365nm, 50$). The paper-based PEC sensor was fabricated by immobilizing CdTe QDs@MIPs on paper-based screen-printed working electrodes (WEs) via gold nanoparticles (Au NPs), which was electrodeposited on the surface of WE to improve the electron transfer efficiency for high sensitivity. Using S-fenvalerate as model analyte, the produced photocurrent from the proposed paper-based MI-PEC sensor upon ultraviolet radiation decreased with the increasing concentrations of S-fenvalerate solution, and the quenched paper-based MI-PEC showed a low detection limit of 3.2×10−9 molL−1. This study has made a successful attempt in the development of highly selective and sensitive photoelectrochemical sensor for S-fenvalerate monitoring. [Copyright &y& Elsevier]

The hybrids, N -aminobutyl- N -ethylisoluminol (ABEI), horseradish peroxidase (HRP) and cancer antigen 125 s antibody (Ab2) immobilized graphene oxide (GO), were prepared, which exhibited excellent chemiluminescence (CL) activity. The zinc oxide nanorods (ZNRs) grew on reduced graphene oxide (RGO) modified paper working electrode (ZNRs-RGO/PWE) via an in situ growth method. The deposition of CdS quantum dots (QDs) on ZNRs/RGO-PWE resulted in an enhanced excitation and photo-to-electric conversion efficiency. The ABEI-GO@HRP/Ab2CL system was employed as an internal excited light source. A photoelectrochemical (PEC) immunosensor based on CdS-sensitized ZNRs anchored RGO as the photoactive matrix and ABEI-GO@HRP/Ab2 as the CL labels was established for sensitive detection of cancer antigen 125 (CA 125). As a model, sandwich CA 125-antibody was taken as molecular reorganization elements on this sensor for the sensitive determination of CA 125 in the linear range from 5.0 × 10 −4 U/mL to 500 U/mL with a detection limit of 2.0 × 10 −4 U/mL. The specificity, reproducibility, and stability of this sensor were also investigated. This proposed method might be attractive for clinical and biomedical applications. [ABSTRACT FROM AUTHOR]