Change In Photocurrent Research Articles

A split-type near-infrared photoelectrochemical and colorimetric dual-mode biosensor for the high-performance determination of HepG2 cells.

Hepatocellular carcinoma (HCC) stands as a grave illness characterized by elevated death rates. Early identification plays a vital role in improving patient survival. Herein, a novel split-type dual-mode biosensor featuring with near-infrared photoelectronchemical (PEC) and colorimetric sensing characteristics was developed for the high-performance detection of HepG2 cells. Biotin labeled aptamer (Bio-Apt1) was immobilized onto 96-well plates functionalized with streptavidin to capture HepG2 cells through specific binding. HepG2 cells were then labeled with another aptamer (Apt-2) by recognizing GPC3 on the surface of HepG2 cells. Apt 2 could form DNA double strand (dsDNA-ALP) with ALP-labeled complementary DNA (cDNA-ALP). Subsequently, ALP was released to catalyze AAP to form ascorbic acid (AA), and AA reduced HAuCl4 to form gold nanoparticles (AuNPs). Then the mixture containing AuNPs was introduced onto the surface of Y-MOFs/GCE to enhance the photocurrent response. The change of photocurrent corresponding to the concentration of HepG2 cells can be used for the PEC determination. ALP can catalyze the hydrolysis of disodium phenyl phosphate to produce phenol, followed by a reaction with 4-aminoantipyrine and potassium ferricyanide, resulting in a quinone derivative for the colorimetric determination. The photoelectrochemical and colorimetric detection models show excellent selectivity and sensitivity in identifying HepG2 cells, exhibiting a linear reaction range from 1.0×102 to 1.0×106cells mL-1 and a detection limit of 13cells mL-1 and 51cells mL-1, respectively. The dual-mode split type biosensor avoided direct damage to biomolecules from high-energy light, and the independent signal transduction enabled the acquisition of reliable results.

Photocurrent Polarity-Switchable Imaging of Single Living Cells by Light-Addressable Electrochemical Sensor.

The light-addressable electrochemical sensor (LAES) is a powerful tool for single-cell imaging due to its label-free and probe-free advantages. In this work, we report a photocurrent polarity-switchable LAES using a single-phase photoelectrode of a BiFeO3 thin film for living cell imaging. The proposed BiFeO3 could show both p- and n-type photocurrent behavior by simply altering the external bias voltage. LAES imaging of the same individual MCF-7 cells was performed in anodic and cathodic modes. Decreases in both photocurrents were observed due to the hindering effect of the adherent cells on local photoinduced Faraday currents. Furthermore, the dynamic photocurrent changes on cells after trypsin treatment were imaged and studied at anode and cathode polarities. Both polarities showed an increase in local photocurrents on cells as the cell-substrate junction weakened, and this change displayed heterogeneous characteristics. This is the first time that LAES cell imaging was achieved in a p-type mode. Meanwhile, our photocurrent polarity-switchable imaging approach overcomes the limitations of conventional photoelectrodes, which have been confined to single-polarity operation. We believe this work has the potential to significantly broaden the application scope of LAES in single-cell visualization and analysis, offering great insights into cellular behavior and function.

Organic photoelectrochemical transistor biosensor based on BiVO4-ZnIn2S4 material for efficient and sensitive detection of MCF-7 cells

Recently, organic photoelectrochemical transistor (OPECT) has become a very interesting biological measurement method in photoelectrochemical (PEC) bioanalysis and future bio-related applications. OPECT is expected to be a powerful tool for disease detection and early warning. Circulating tumor cells (CTCs) are generally deemed to be the dominant factor of tumor metastasis, and 90 % of cancer patients die from this metastatic disease. Therefore, there is an imminent need to develop a highly sensitive CTCs detection sensing system to improve the survival rate of cancer patients. Here, we use a DNA tetrahedrons (DNA NTH) with an aptamer at the top to immobilize on the surface of the photoelectric material to capture cells (MCF-7). Specifically, the BiVO4-ZnIn2S4 hybrid was synthesized by a simple hydrothermal method, which can effectively modulated devices with high current gain. Au NPs were directly integrated on the electrode surface to construct an OPECT photoelectric sensing platform. Subsequently, the aptamer which is thiol-functionalized (SH-Apt) was immobilized on the electrode surface. Because of the overexpression of MUC1 protein on the cell membrane, it can specifically capture MCF-7 cells. The introduction of MCF-7 cells resulted in a significant decrease in the current signal. There is a relationship between the change of photocurrent and the logarithm of MCF-7 cell concentration, which is a good linear relationship ranging from 50 to 5 × 105 cell mL−1. The obtained detection limit is 43 cell mL−1. The biosensor has high selectivity and sensitivity, and achieves sensitive detection of MCF-7.

Photoelectrochemical immunosensor for chloramphenicol detection based on cation exchange reaction-mediacted photocurrent enhancement of ZnIn2S4/TiO2/Ti3C2 MXene coupled with controlled-release strategy.

Aphotocurrent enhancing photoelectrochemical (PEC) immunosensor was developedfor chloramphenicol (CAP) detection based on cation exchange reaction. The efficient split-type PEC immunosensor combined with controlled-release strategy was established using the ZnIn2S4/TiO2/Ti3C2 MXene (ZIS/T/M) composite as the photoactive material and CuO as the signal response probe. In the presence of target CAP, CuO-labeled CAP antibody (CuO-mAb) was introduced onto the microplate via a competitive-type immunoassay. Under acidic conditions, a large amount of Cu2+ released from CuO-mAb, which triggered a cation exchange reaction with the Zn2+ in ZIS/T/M-modified photoelectrode to generate CuxS, resulting in enhancingthe photocurrent. As a result, the quantitative detection of CAP was achieved by detecting the photocurrent change. Under optimized conditions, the linear range of the sensor was 1pg/mL to 50ng/mL, and the detection limit was 0.24pg/mL. The excellent PEC behavior of ZIS/T/M composite could be attributed to the fact that heterojunction formation improved the migration and separation of thephotocarrier. Additionally, by virtue of the photocurrent-enhancing strategy via cation exchange reaction and the controlled releasing signal amplification method of ion, the PEC immunosensor has high sensitivity and satisfactory accuracy, offering great potential applications in the determinationof CAP.

A split organic photophotochemical transistor/vision sensing platform based on MNZ composite and ZIF-67/CuCoO nanospheres for ultra-sensitive detection of CEA

In this study, a novel organic photophotochemical transistor (OPECT) biosensing platform was proposed for dual-mode detection of CEA. The dual-mode detecting system is achieved benefit from the exceptional photoelectric performance of MIL-53(Fe) -NH2@ZnIn2S4 (MNZ) and the peroxidase enzyme (POD) activity of ZIF-67/Cu0.76Co2.24O4 (ZIF-67/CuCoO). Ab2- ZIF-67/CuCoO probe was immobilized on a 96-well plate by enzyme-linked immunosorbent assay, which accelerated the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide and thus successfully realized visual detection of CEA. Additionally, in OPECT biosensing mode, the oxidized form of TMB (oxTMB·) serves as a consumptive agents of the electron donor AA, which cause the photocurrent change of MNZ heterojunction, leading to a decrease in the channel current of poly (ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) organic transistor. The integration of nanobiocatalysts and the OPECT system demonstrates excellent detection performance for CEA, with a detection limit as low as 3.24 fg mL−1 and expanded their prospective applications for clinical detection of nucleic acids, proteins, and other tumor markers.

Revealing Bipolar Photoresponse in Multiheterostructured WTe2-GaTe/ReSe2-WTe2 P-N Diode by Hybrid 2D Contact Engineering.

The van der Waals (vdW) heterostructures based on two-dimensional (2D) semiconducting materials have been thoroughly investigated with regard to practical applications. Recent studies on 2D materials have reignited attraction in the p-n junction, with promising potential for applications in both electronics and optoelectronics. 2D materials provide exceptional band structural diversity in p-n junction devices, which is rare in regular bulk semiconductors. In this article, we demonstrate a p-n diode based on multiheterostructure configuration, WTe2-GaTe-ReSe2-WTe2, where WTe2 acts as heterocontact with GaTe/ReSe2 junction. Our devices with heterocontacts of WTe2 showed excellent performance in electronic and optoelectronic characteristics as compared to contacts with basic metal electrodes. However, the highest rectification ratio was achieved up to ∼2.09 × 106 with the lowest ideality factor of ∼1.23. Moreover, the maximum change in photocurrent (Iph) is measured around 312 nA at Vds = 0.5 V. The device showed a high responsivity (R) of 4.7 × 104 m·AW-1, maximum external quantum efficiency (EQE) of 2.49 × 104 (%), and detectivity (D*) of 2.1 × 1011 Jones at wavelength λ = 220 nm. Further, we revealed the bipolar photoresponse mechanisms in WTe2-GaTe-ReSe2-WTe2 devices due to band alignment at the interface, which can be modified by applying different gate voltages. Hence, our promising results render heterocontact engineering of the GaTe-ReSe2 heterostructured diode as an excellent candidate for next-generation optoelectronic logic and neuromorphic computing.

Self-validating photoelectrochemical/photoelectrochromic visual sensing platform for ciprofloxacin precise detection in milk

BackgroundIn the process of food production, ciprofloxacin (CIP), a highly prescribed fluoroquinolone antibiotic, is often excessively used to reduce the risk of bacterial infection. However, this overuse can cause severe harm to human health, including allergic responses, gastrointestinal complications, and potential renal dysfunction. The development of a robust and precise detection method for CIP is crucial, given the interconnection between food security and human health. Compared to the single-mode detection methods currently in use, dual-mode detection provides enhanced accuracy in detecting results due to its inherent self-validation and self-correction capabilities. ResultsHerein, a photoelectrochemical and photoelectrochromic self-validated dual-mode sensing platform was developed to detect CIP in milk by laser etching method, signal generation (SG) region, signal output (SO) region and conductive channel was integrated on the same fluoide-doped tin oxide electrode and Ti3C2/ZnO composite was modified in the electron SG region, and Prussian blue (PB) was electrodeposited in the SO region. By irradiating the SG region, photogenerated electrons are generated and injected into the SO region through the conductive pathway, resulting in the reduction of the PB to Prussian white (PW). Because the binding of CIP to its specifically recognized aptamers hinders electron transfer, a “Signal-Off” response mechanism can be used for simultaneous quantitative detection of CIP using photocurrent or color changes, which presents a great advantage in the detection process. SignificanceBy integrating different detection mechanisms within a single linear range, the constructed dual-mode sensor has a wide detection range and low detection limit in milk samples. Additionally, it shows good selectivity in anti-interference experiments, providing a new idea for the development of visual analysis and detection platforms for food safety.

Photocurrent-polarity-switching photoelectrochemical and electrochemical dual-mode sensing platform for the highly selective detection of trenbolone

As an emerging contaminant in the environment, trenbolone (TBE) has aroused a global health crisis and caused the huge impact on ecosystem. Its sensitive detection is critical to safeguard human health and ecosystem. Herein, a photocurrent polarity switching photoelectrochemical (PEC)-electrochemical (EC) dual-mode sensing platform was presented for highly selective and sensitive detection of TBE by ingeniously tailor signal probe. The tailored Cu2O@CuO-hemin acting as both photocurrent polarity reversal and electroactivity factor were cross-linked with TBE-BSA to obtain competitive conjugates for TBE. When the competitive response was initiated, numerous of Cu2O@CuO-hemin nanocomposites are introduced on the CdS-modified indium tin oxide electrode, serving as the reporting agent of EC/PEC dual-mode assay. The photocurrent polarity of the CdS-modified ITO can be effectively switched, enabling PEC analysis of TBE with distinguishing photocurrent changes. The linear response range is 1 pg/mL to 500 ng/mL, and the detection limit is 15.0 fg/mL. Meanwhile, the Cu2O@CuO could triggered the amplified current variations via effectually catalyzing the H2O2 decomposition compared to the CdS NPs, leading to the sensitive electrochemical detection of TBE with a detection limit 200 fg/mL and a linear response range from1 pg/mL to 500 ng/mL. Additionally, the developed sensing platform enabled mutual authentication of PEC/EC detection results, being conducive to increasing the assay reliability and accuracy. Such the dual-mode sensor has great potential for detecting environmental pollutants due to its improved selectivity and mutual authentication of results.

Enhanced detection of cardiac troponin-I using CdSe/CdS/ZnS core-shell quantum dot/TiO2 heterostructure photoelectrochemical sensor

This paper introduces a photoelectrochemical sensor employing red-emitting CdSe/CdS/ZnS core-shell quantum dot/TiO2 heterostructure for detecting cardiac troponin-I (cTnI) biomarkers. The sensor utilizes a photoactive layer-by-layer self-assembly of CdSe/CdS/ZnS nanocrystals within a TiO2 nanoparticle photon-sensitive layer to enhance charge separation, thereby boosting sensor photocurrent. Additionally, the CdSe/CdS/ZnS quantum dot layer enhances photocurrent stability by facilitating the separation of photo-excited electrons and holes. Functionalization of the CdSe/CdS/ZnS core-shell quantum dot/TiO2 heterostructure-based photoelectrochemical sensor with anti-troponin involves first activating -COOH functionalized CdSe/CdS/ZnS with carbodiimide cross-linkers, followed by cTnI protein capture. Photocurrent changes are measured using amperometry. The sensor format exhibits an enhanced photocurrent signal proportional to concentration, with a detection range of 10 pg/mL to 0.2 ng/mL of cTnI protein. The use of a red-emitting CdSe/CdS/ZnS quantum dot layer ensures chemical stability during and after chemical coupling on the sensor. This study showcases the successful application of CdSe/CdS/ZnS core-shell quantum dot/TiO2 heterostructure-based photoelectrochemical sensors for early detection of troponin-I protein in cardiac disease diagnostics.

(Invited) Electrochemistry of CdSe Quantum Dots in Organic Solvents. from Stochastic Electrochemistry to Film Behavior

We present our electrochemistry results of CdSe quantum dots in two organic solvents: neat methanol and acetonitrile. In MeOH, the quantum dots (QDs) can be detected through stochastic collisions; that is, as agglomerates of QDs collide with an electrode surface, the photocurrent changes as a result of the CdSe entities that collide with the electrode surface.1 The experiment presented here uses Pt ultramicroelectrodes (UME), that is, electrodes with a diameter of 25 μm or less. Our results show that the CdSe can accumulate on the surface of the electrode, and the technique provides a high degree of control. By controlling the time the electrode collects QDs, one can control the amount of CdSe that accumulates at the electrode surface. After collecting CdSe on the surface, we perform cyclic voltammetry experiments to confirm that the electrode surface has changed. In acetonitrile (MeCN), we can perform CVs over large potential windows to study the electrochemistry of the deposited CdSe. The electrochemical response of the deposited CdSe resembles that of a film, although the surface has sub-monolayer coverages, as will be discussed from the images of scanning electron microscopy (SEM).Figure 1 shows an example of a LSV in a region of interest where the current due to the CdSe significantly deviates from the background current. The LSV was run in the dark, so the current in the figure is a function of the density of states in the CdSe structures. It is also a function of the reversibility of the CV, i.e., mainly of the scan rate of the experiment. After the CV experiments, the Pt UME can be imaged in the SEM to correlate the electrochemical results with the CdSe deposited on the electrode surface. We will discuss our findings in terms of the results in the literature on CdSe electrochemistry (e.g., refs 2-5). References. (1) Subedi, P.; Parajuli, S.; Alpuche-Aviles, M. A., "Single Entity Behavior of CdSe Quantum Dot Aggregates During Photoelectrochemical Detection", Frontiers in Chemistry 9 (2021) DOI: 10.3389/fchem.2021.733642(2) Kohl, P. A.; Bard, A. J., "Semiconductor electrodes. 13. Characterization and behavior of n-type zinc oxide, cadmium sulfide, and gallium phosphide electrodes in acetonitrile solutions", Journal of the American Chemical Society 99, 7531-7539 (1977) DOI: 10.1021/ja00465a023(3) Hines, M. A.; Guyot-Sionnest, P., "Synthesis and characterization of strongly luminescing ZnS-capped CdSe nanocrystals", The Journal of Physical Chemistry 100, 468-471 (1996) DOI: 10.1021/jp9530562(4) Zhang, J. Z., "Interfacial Charge Carrier Dynamics of Colloidal Semiconductor Nanoparticles", The Journal of Physical Chemistry B 104, 7239-7253 (2000) DOI: 10.1021/jp000594s(5) Myung, N.; Ding, Z.; Bard, A. J., "Electrogenerated chemiluminescence of CdSe nanocrystals", Nano Letters 2, 1315-1319 (2002) Figure 1

Self-powered, multi-angle gas flow sensing based on photovoltaics with porous graphite electrodes

A self-powered, multi-attack angle gas/air flow sensor without azimuth directional constraints has been designed and developed in this study. Two essential components, the porous graphite cathode and the perovskite photovoltaics, work synergistically in the device. The gas flow penetrates the bulky porous cathode, causing the pressure differences between the upper and lower sides of the nano/micro sheets, leading to the micro lift-force (Bernoulli theory) or dynamic pressure, consequently breaking or forming the electrically conductive paths among the nano/micro sheets. Therefore, the altered electrical conductivity of the cathode prompts a change in the output photocurrent of the perovskite photovoltaic unit. The thin film photovoltaic device design eliminates the requirement for external power sources, enabling multi-attack angle sensing without any azimuth directional limitations.It's important to highlight the scarcity of micro airfoil structures in the gas flow sensing domain by utilizing the nano/micro graphite sheets as the electrode and the thin film photoelectrical device as the power source, which challenges the conventional design typically based on macro-mechanical theory. It is expected that this study could provide researchers with a fresh and distinct perspective for designing and advancing the next generation of multi-angle gas-flow sensors.

Low temperature self-growth of organic-inorganic perovskite nanowires for high performance flexible photodetectors

There has been a huge drive to explore flexible photodetectors for the large area growth of wearable, bendable, repeatable and lightweight electronics. This work describes the large-area ordered growth of MAPbI3 nanowires on PET (polyethylene terephthalate) by self-growth method at low temperature. The devices made of MAPbI3 nanowire exhibit high detectivity and responsivity of 2.403 × 1011 Jones and 7.62 A/W, respectively. Subsequently, the devices are bent at different angles (10°, 20°, 30°, 40° and 50°) and the on/off ratio of the photodetectors decreased by only 18.8 %. The device also maintained an extremely high photocurrent (a retention rate of 84.8 %) after 1000 bending cycles at 50°. Furthermore, the fluctuations of photocurrents and dark currents are small (fluctuating ∼4 %) after repeatedly bending in the range of 0° and 50° for 150 times, revealing that the MAPbI3 nanowire flexible photoelectronic device possesses good mechanical stability and excellent repeatability. Compared with that of the non-encapsulation device, the long-term stability of the encapsulated device is improved by 52.15 %. The simulation results also show that the photocurrent changes slightly with the change of bending angle, which further verifies that the MAPbI3 nanowires possesses advanced flexibility and stability at low bending angle. This method offers a straightforward and efficient way to prepare flexible photodetectors with high performance.

Light-induced, room-temperature hydrogen gas detection based on SnO2 quantum Dots/p-Si

The continuous monitoring of the hydrogen gas level under low-temperature conditions is vital to prevent explosive accidents. Metal oxide-based chemoresistors have attracted significant attention owing to their excellent gas sensitivity. However, high operating temperature required to remove adsorbed oxygen species is still considered as an obstacle, limiting the application of the system. In addressing the temperature issue, this study introduced an approach in which a gas interaction layer was separated from the signal-sensing region. The proposed two-terminal device comprises a gas interaction layer of SnO2 quantum dots (QDs) and a p-doped silicon (p-Si) region characterized by high electronic conductivity and light sensitivity. Through visible light illumination, the recombination between gas interaction-induced electrons and photo-generated holes induces a change in output photocurrent, enabling room-temperature gas sensing without additional temperature control. Using this gas sensing scheme, the proposed sensor showed impressive gas detection performance in the low-temperature range, achieving a detection range of a few parts per million (ppm) in concentration (limit of detection range: 9.46–50 ppm).

Ultrasensitive monitoring of PCB77 in environmental samples using a visible-driven photoelectrochemical sensing platform coupling with exonuclease I assisted in target recycling

Due to the urgent need for detecting trace amounts of 3,3′,4,4′-tetrachlorobiphenyl (PCB77) in the environment, we have developed an efficient and visible-driven photoelectrochemical (PEC) sensing platform based on carbon quantum dots (CQDs) modified titanium dioxide nanorods (TiO2 NRs), coupling with exonuclease I (Exo I) assisted in target recycling for significant signal amplification. CQDs/TiO2 NRs with high visible-light absorption ability and electron-hole separation efficiency is used as photoactive substrate for anchoring anti-PCB77 aptamer and its complementary DNA (cDNA). With the addition of PCB77, the specific interaction between PCB77 and its aptamer forces aptamer to separate from the electrode surface, resulting in an increase in photocurrent density. Adding Exo I in the test system, a self-catalytic target cycle was motivated, which significantly increased the PEC signal by more than twice, achieving signal amplification. The relationship between the photocurrent density changes and the concentrations of PCB77 are utilized to achieve quantitative detection of PCB77. The designed PEC sensing platform has good analytical performance with a detection limit as low as 0.33 pg L−1, high selectivity and stability. Moreover, the PEC sensor is successfully used to evaluate the content of PBC77 in the environment samples. The established sensing platform provides a simple and efficient method for detecting trace amounts of PCB77 in the environment.

Upconversion-Powered Photoelectrochemical Bioanalysis for DNA Sensing.

In this work, we report a new concept of upconversion-powered photoelectrochemical (PEC) bioanalysis. The proof-of-concept involves a PEC bionanosystem comprising a NaYF4:Yb,Tm@NaYF4 upconversion nanoparticles (UCNPs) reporter, which is confined by DNA hybridization on a CdS quantum dots (QDs)/indium tin oxide (ITO) photoelectrode. The CdS QD-modified ITO electrode was powered by upconversion absorption together with energy transfer effect through UCNPs for a stable photocurrent generation. By measuring the photocurrent change, the target DNA could be detected in a specific and sensitive way with a wide linear range from 10 pM to 1 μM and a low detection limit of 0.1 pM. This work exploited the use of UCNPs as signal reporters and realized upconversion-powered PEC bioanalysis. Given the diversity of UCNPs, we believe it will offer a new perspective for the development of advanced upconversion-powered PEC bioanalysis.

Geometric Shape Recognition with an Ultra-High Density Perovskite Nanowire Array-Based Artificial Vision System.

Artificial vision systems (AVS) have potential applications in visual prosthetics and artificially intelligent robotics, and they require a preprocessor and a processor to mimic human vision. Halide perovskite (HP) is a promising preprocessor and processor due to its excellent photoresponse, ubiquitous charge migration pathways, and innate hysteresis. However, the material instability associated with HP thin films hinders their utilization in physical AVSs. Herein, we have developed ultrahigh-density arrays of robust HP nanowires (NWs) rooted in a porous alumina membrane (PAM) as the active layer for an AVS. The NW devices exhibit gradual photocurrent change, responding to changes in light pulse duration, intensity, and number, and allow contrast enhancement of visual inputs with a device lifetime of over 5 months. The NW-based processor possesses temporally stable conductance states with retention >105 s and jitter <10%. The physical AVS demonstrated 100% accuracy in recognizing different shapes, establishing HP as a reliable material for neuromorphic vision systems.

Self-Powered Programmable van der Waals Photodetectors with Nonvolatile Semifloating Gate.

Tunable photovoltaic photodetectors are of significant relevance in the fields of programmable and neuromorphic optoelectronics. However, their widespread adoption is hindered by intricate architectural design and energy consumption challenges. This study employs a nonvolatile MoTe2/hexagonal boron nitride/graphene semifloating photodetector to address these issues. Programed with pulsed gate voltage, the MoTe2 channel can be reconfigured from an n+-n to a p-n homojunction and the photocurrent transition changes from negative to positive values. Scanning photocurrent mapping reveals that the negative and positive photocurrents are attributed to Schottky junction and p-n homojunction, respectively. In the p-n configuration, the device demonstrates self-driven, linear, rapid response (∼3 ms), and broadband sensitivity (from 405 to 1500 nm) for photodetection, with typical performances of responsivity at ∼0.5 A/W and detectivity ∼1.6 × 1012 Jones under 635 nm illumination. These outstanding photodetection capabilities emphasize the potential of the semifloating photodetector as a pioneering approach for advancing logical and nonvolatile optoelectronics.

Dual-mode sensing chip for photoelectrochemical and electrochromic visual determination of deoxynivalenol mycotoxin.

Thesuccessful development of a dual-mode sensing chip for deoxynivalenol (DON) detection using photoelectrochemical (PEC) and electrochromic visualization techniquesis reported. By laser etching technology, different functional areas, including the photoanode, the cathode, and the electrochromic area, are fabricated on indium tin oxide (ITO) glass. Then, these three areas are further respectively modified with PEC active materials, platinum nanoparticles, and Prussian blue. Under light illumination, photocurrents generate between the photoanode and the cathode due to the separation of photo-induced electrons and holes in the TiO2/3DNGH material. Meanwhile, the photo-induced electrons are transferred to Prussian blue on the visualization area, which will be reduced to colorless Prussian white. The binding of DON molecules and aptamers can promote electron transfer and reduce the recombination of electrons and holes, allowing for simultaneous quantitative detection of DON using either the photocurrent or color change. The sensor chip has a broad detection range of DON concentrationsof 1 fg⋅mL-1 to 100 pg⋅mL-1 in the PEC mode with the limit of detection of 0.37 fg⋅mL-1, and 1 to 250 ng⋅mL-1 in the visualization mode with the limit of detection of 0.51 ng⋅mL-1. This portable dual-mode sensor chip can be used in both laboratory and field settings without the need for specialized instruments, making it a powerful tool for ensuring food safety. At the same time, the analysis of the standard addition method of the actual sample by using the sensor chip shows that, in the PEC mode, the recoveries of the dual-mode aptasensor chip were 91.3 to 99.0% with RSD values of 1.73~2.55%, and in visualization mode, the recoveries of the dual-mode aptasensor chip were 99.2 to 102.0% with RSD values of 1.00~6.21%, which indicate good accuracy and reproducibility.

Contactless photoelectrochemical biosensors based on hierarchical MXene/Bi2S3 nanosheets with the branched hybridization chain reaction

Ethyl carbamate, a substance frequently occurring in fermented foods, seriously affects people's health; however, poor sensitivity constrains the development of ethyl carbamate sensors. In this work, hierarchical Bi2S3/MXene nanosheets were synthesized using a hydrothermal method, and experimentally their coupled UV light is an efficient NH3 sensing material. Meanwhile, the density functional theory (DFT) confirms that the MXene/Bi2S3 nanosheet interface has an excellent ability to adsorb NH3, resulting in a change of photocurrent. As a proof-of-concept, a highly sensitive ethyl carbamate photoelectrochemical (PEC) biosensor was constructed based on the ammonia generation strategy of glutamate dehydrogenase coupled to the branched hybridization chain reaction (bHCR). Specifically, the target-triggered bHCR enriches a large number of enzyme-encapsulated liposomes, while the enzymatic NH3-generation reaction will cause a change in the Bi2S3/MXene photocurrent, which completes the target detection process. Under optimal conditions, the constructed PEC biosensors exhibited superior analytical performance toward ethyl carbamate in the range of 0.01 μg/mL to 1 μg/mL and limit of detection (LOD) down to 0.001 μg/mL. In addition, it offers an effective method for food safety monitoring due to its excellent stability, fast response, and maneuverability on real samples (red wine, yellow wine, and brandy).

Scalable and cost-effective synthesis of flexible paper-based Indium doped SnS photodetector in the VIS-NIR range

Broadband light detection is one of the growing needs for technological advancement. Very few materials are available that can entertain the whole Ultraviolet to infrared light range. Devices based on these materials are in high demand. 2D layered materials are promising materials as their bandgap can be easily modified by effective cation/anion doping or forming hetero-structure with base materials which effectively increases the overall photodetection properties. SnS is one of the members of the 2D layered material family. Here in the present work, we carried doping of In element in pristine SnS and investigated improvement in photodetection properties. We studied different doping concentrations of In such as 2, 5, 6, 7, 8, 10 and 12 %. All these pristine and In doped SnS materials were synthesized using a simple hydrothermal approach. Paper-based flexible, large-area Photodetector devices were fabricated from as-synthesized materials. As-fabricated photodetectors show excellent photo response in NIR to the visible region with a maximum responsivity value of 18.2 mA/W and a specific detectivity of 1.07x1010 Jones. We also investigated the flexibility and durability of as-prepared devices which suggest no change in photocurrent after several bending cycles.