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An integrated dual-signal bioassay was devised to fulfil thrombin (TB) ultrasensitive detection by integrating visualization with the photoelectrochemical technique based on G-quadruplex/hemin. During the process, branched sheet embedded copper-based oxides prepared with illumination and alkaline condition play a vital role in obtaining the desirable photocurrent. The switchover of photoelectrochemical signal was realized by the adjustable distance between electron acceptor G-quadruplex/hemin and interface materials due to dissociation of the Cu/Mn double-doped cerium dioxide (CuMn@CeO2)/DNA caused by the addition of TB. Then, CuMn@CeO2 transferred onto visual zones triggered catalytic reactions under the existence of 3,3′,5,5′-tetramethylbenzidine and hydrogen peroxide, making a variation in color recognized by the naked eye and providing visual prediction. Under optimized conditions, this bioassay protocol demonstrated wide linear ranges (0.0001–50 nM), high selectivity, stability, and reproducibility. More importantly, the proposed visual/photoelectrochemical transduction mechanism platform exhibits a lower background signal and more reliable detection results, which also offers an effective way for detecting other proteins and nucleic acids. [ABSTRACT FROM AUTHOR]

Graphical abstract A quasi-solid-state tandem photoelectrochemical fuel cell that yields an open circuit voltage of 0.78 V and a maximum power density of 130 μW·cm−2 was assembled by utilizing hydrogel electrolyte, Au-TiO 2 NRAs photoanode and pTTh-Cu 2 O pohotocathode. The pTTh-layer protected Cu 2 O exhibited remarkably improved photostability as well as achieved significantly accelerated oxygen reduction reaction performance. Highlights • A quasi-solid-state tandem photoelectrochemical fuel cell was fabricated. • Polyterthiophene coated p-type cuprous oxide was prepared as photocathode. • Photocathode exhibited improved anti-photocorrosion and photocatalytic activity. • Gold nanoparticles decorated TiO 2 nanorod arrays was presented as photoanode. Abstract Photoelectrochemical fuel cells (PFCs) serve as a model system for harvesting electric energy from solar and biomass based on anodic fuel oxidation and cathodic oxygen reduction reaction (ORR). However, the sluggish ORR thereby limits the performance of PFC. Herein, we present a novel photocathode with polyterthiophene (pTTh) coated p-type cuprous oxide (Cu 2 O) (pTTh-Cu 2 O) that achieves boosted ORR kinetics, as well as exhibits remarkably improved photostability. By utilizing a hydrogel electrolyte which can avoid the leakage and volatilization of liquid electrolyte, a quasi-solid-state PFC device with eminent stability that consists of gold nanoparticles (Au NPs) decorated TiO 2 nanorod arrays (Au-TiO 2 NRAs) photoanode and pTTh-Cu 2 O photocathode can be assembled. And the fabricated PFC exhibits outstanding performance that yields an open circuit voltage of 0.78 V and a maximum power density of 130 μW·cm−2 utilizing glucose as feeding under illumination. Furthermore, the as-prepared quasi-solid-state PFC demonstrates its potential for practical application by lighting a commercial light-emitting diode (LED). It is our believe that such rational design not only can be expanded for organic wastes degradation and water splitting, but also shed a light on the development of portable electronics driven by solar. [ABSTRACT FROM AUTHOR]

A microfluidic paper-based analytical device (μPAD) was simply constructed for highly sensitive detection of L -glutamic acid and L -cysteine. The μPAD featured with two functional zones on one strip of paper achieved by preferable multi-plate ZnO nanoflowers (ZnO NFs) and molecularly imprinting polymer (MIP) membranes. The as-designed μPAD was established based on the inherent relation between the photo-oxidation products and photoelectrochemical (PEC) performance with the highly sensitive detection of biomolecules. The ZnO NFs were utilized to produce photo-oxidation products by driving the reaction between ferrocenemethanol and photogenerated holes under ultraviolet light. The photo-oxidation products easily flowed to MIP membranes along the hydrophilic channel via capillary action. MIP membranes as the receptors specifically recognized the analytes as well as decreased the electron loss by blocking the reduction reaction between electrons and photo-oxidation products. The PEC response was obtained in the processes of electrons transfer and exhibited the direct relationships corresponding to the concentrations of target analytes. The μPAD showed the detection limits toward L -glutamic acid and L -cysteine as low as 9.6 pM and 24 pM, respectively. Moreover, it is interesting to point out that ZnO NFs nanostructure shows superior PEC signal compared with those of ZnO nanospheres, nanosheets, and nanorod arrays. In current work, photo-oxidation products are utilized to achieve highly sensitive PEC detection for biomolecules under ultraviolet light as well as avoid the effects of multiple modifications in the same region on the reproducibility, which is beneficial for opening up rich possibility for designing more efficient analytical strategy. [ABSTRACT FROM AUTHOR]

This work described that one–step synthesis three dimensional anatase hierarchically cactus–like TiO 2 arrays (AHCT) and their application in constructing a novel photoelectrochemical (PEC) and visualized sensing platform based on molecular imprinting technique, which reports its result with the prussian blue (PB) electrode served as the electrochromic indicator for the detection of glycoprotein (RNase B). The AHCT arrays were perpendicularly grown on FTO substrate with tunable sizes, offering many advantages, such as large contact area, rapid charge electron separation and transport. A possible formation process of the interesting AHCT arrays has been investigated based on time–dependent experiment. In addition, the PEC and visualized sensing platform was constructed based on the molecularly imprinted polymer modified AHCT arrays. Specifically, in the proposed system, the more RNase B being, the more insulating layer was formed on the surface of AHCT arrays that impeded the harvesting of light and electron transfer, resulting in the reduction of photocurrent. When upon light illumination, the photogenerated electrons flow through an external circuit to PB, leading to the reduction of PB to prussian white (PW), which is transparent. The rate of decolourization of PB is proportional to the concentration of RNase B. In this way, a visualized PEC sensing platform that gives its quantitative information could be performed by monitoring the change of color intensity. Under optimal conditions, the protocol possessed a detection range of 0.5 pM to 2 μM (r=0.997) and the limit of detection was 0.12 pM toward RNase B. Our method eliminates the need for sophisticated instruments and high detection expenses, making it possible to be a reliable alternative in resource–constrained regions. [ABSTRACT FROM AUTHOR]

By incorporating the Prussian Blue (PB) electrochromic display as cathode, a solar-driven photoelectrochemical (PEC) cell was constructed through combining sandwich-structured graphite-like carbon nitride (g-C 3 N 4 )-Au-branched-titanium dioxide (B-TiO 2 ) nanorods as photoanode for self-powered hydrogen peroxide (H 2 O 2 ) sensing, which exhibits both direct photoelectrochemical and electrochromic response. The gold nanoparticles (Au NPs) sandwiched between the B-TiO 2 nanorods and the g-C 3 N 4 layer served as electron relay as well as plasmonic photosensitizer to enhance the solar-to-chemical energy conversion efficiency. Owing to the effective disproportionation of H 2 O 2 and specific recognition of mannose on cell surface, concanavalin-A conjugated porous AuPd alloy nanoparticles were introduced as the catalytically active nanolabels promoting generation of hydroxyl radicals (·OH). Based on the cleavage of DNA with the participation of ·OH radicals generated by the decomposition of H 2 O 2 under the catalysis of AuPd alloy result in the disassembly of cancer cells to achieve further signal enhancement. The multiple-signal-output sensing response not only provides a promising strategy for different analytical purposes based on novel stimuli-responsive materials, but also enhances the reliability in the analyte detection. [ABSTRACT FROM AUTHOR]

The sequence-specific detection of DNA hybridization has attracted considerable interest in numerous fields. Although traditional DNA biosensors have been widely explored due to their high sensitivity, it is still challenging to develop a low-cost, portable, disposable, fast, and easy-to-use DNA detection method for public use at home or in the field. To address these challenges, herein, we report a novel microfluidic photoelectrochemical (PEC) paper-based analytical platform, integrated with an internal chemiluminescent light source, a novel paper supercapacitor (PS) amplifier, and a terminal digital multi-meter (DMM) detector, for sensitive DNA detection using a graphene-modified porous Au-paper electrode as the working electrode to obtain enhanced PEC responses. The quantification mechanism of this strategy is based on the charging of this PS, which was constructed on a paper-based analytical platform through a simple “drawing and soaking” method, by the generated photocurrent. After a fixed period, the PS was automatically shorted under the control of a novel built-in fluidic delay-switch to output an instantaneously amplified current, which could be sensitively detected by the DMM. At optimal conditions, this paper-based analytical platform can detect DNA at concentrations at femtomolar level. This approach also shows excellent specificity toward single nucleotide mismatches. [ABSTRACT FROM AUTHOR]

A molecular imprinted polymer (MIP) thin film for photoelectrochemical (PEC) sensing of lindane molecules was constructed by electropolymerizing o-phenylenediamine ( o-PD) monomer and lindane template molecule on titanium dioxide nanotubes. The resulting PEC sensors were characterized by scanning electron microscopy, ultraviolet (UV)-vis spectra and electrochemical impedance spectra. Clearly, the imprinted film showed high selectivity to lindane in our case. Under visible light irradiation, MIP film can generate the photoelectric transition from the highest occupied molecular orbital to the lowest unoccupied molecular orbital, delivering the excited electrons to the conduction band of titanium dioxide nanotubes. Simultaneously, it is believed that a positive charged hole (h) of MIP that took part in oxidation process was consumed to promote the amplifying photocurrent response. The MIP-based PEC sensor had an excellent specificity and could be successfully applied to the recognition and detection of lindane, indicating a promising application in handling with organochlorine pesticide. [ABSTRACT FROM AUTHOR]

• A tandem photoelectrochemical cell was designed for bias-free overall solar water splitting. • ZIF-67 decorated WO 3 photoanode exhibited superior photoelectrochemical performance. • Z-scheme black phosphorus/BiVO 4 photocathode was presented. • The pseudo-capacitive WO 3 photoanode makes it possible to realize round-the-clock hydrogen production. Photoelectrochemical (PEC) cell, representing as one of the most promising candidates to implement solar-driven unassisted overall water splitting, still remains a bottleneck in the construction of technology strategies for efficient solar energy utilization due to the intermittent nature of sunlight. Herein, we demonstrate an approach to realize round-the-clock hydrogen production by a solar rechargeable tandem PEC cell with two photoactive electrodes, where the photoanode is composed of a pseudocapacitive WO 3 nanoflakes film sensitized with visible-light responsive zeolitic-imidazolate-framework-67 (ZIF-67), and the photocathode is constituted with a Z-scheme BiVO 4 -black phosphorus (BP) heterojunctions that can broaden the light absorption to near-infrared (NIR) region as well as maintain the strong redox ability to fasten hydrogen evolution reactions by the effective charge separation. Deliberately, the alignment of Fermi level between the as-prepared WO 3 -ZIF-67 photoanode and BiVO 4 -BP photocathode permits us to realize a tandem PEC cell with reversible electron storage property, enabling light-induced charge storing and on-demand release in the dark, for the application of unassisted overall water splitting. The formed tandem PEC cell shows a promising strategy for the conversion of solar power into hydrogen fuel by integrating pseudocapacitive materials into man-made photovoltaic cells, and provides a new guidance for the design of multi-functional PEC device. [ABSTRACT FROM AUTHOR]