A self-powered photoelectrochemical cathodic molecular imprinting sensor based on Au@TiO2 nanorods photoanode and Cu2O photocathode for sensitive detection of sarcosine

Self-powered PEC platform with large and stable photocurrent for blocker-free sensitive assay of Caspase-3 activity based on CdIn2S4/CdS QDs anode and NH2-MIL-125(Ti)@MAPbI3/Au NPs cathode

The diagnosis of apoptosis is of particular importance for assessing apoptosis-related disease progression and improving the therapy efficiency. Caspase-3 is the most frequently activated cysteine protease and a key mediator of cell apoptosis, therefore, its activity assay is vital. Here, by encapsulating of MAPbI3 in NH2-MIL-125(Ti) and constructing "Z-scheme" structure between CdIn2S4 microspheres and CdS quantum dots (QDs) to obtain high-photoelectrochemical (PEC)-stability and large-photocurrent NH2-MIL-125(Ti)@MAPbI3/Au NPs photocathode and CdIn2S4/CdS QDs photoanode, respectively, a new dual-photoelectrode self-powered PEC platform was constructed for highly sensitive and blocker-free assay of caspase-3 activity. The designed negatively-charged CC-DEVD-peptide chains were immobilized on the positive-charged NH2-MIL-125(Ti)@MAPbI3/Au NPs hybrids in flat-lying state due to the electrostatic interaction and double Au-S bonds to maximally suppress the photocurrent signal and to make blockers be not needed. When caspase-3 was present, the CC-DEVD-peptide chains were specifically recognized and cleaved, and only a short Cys-Cys dipeptide remained on the NH2-MIL-125(Ti)@MAPbI3/Au NPs/ITO photocathode, leading to an obviously enhanced photocurrent. Due to the good PEC properties and the matched energy levels of CdIn2S4/CdS QDs and NH2-MIL-125(Ti)@MAPbI3/Au NPs, the developed dual-photoelectrode self-powered PEC platform had large open circuit voltage and photocurrent, and the caspase-3 activity was sensitively assayed (linear range, 0.1 pg mL-1 - 1.0 μg mL-1; detection limit, 5.7 fg mL-1), implying its promising applications in assessment of disease progression and therapy efficiency associated with apoptosis, and rapid screening of caspase-3-related drugs.

Interface self-shelling effect-mediated photoinduced carrier transport and multiplexed signal amplification mechanism in self-powered photoelectrochemical biosensing

In the realm of biomedical diagnostics, the development of sensitive and specific detection methods for cancer biomarkers is of paramount importance. Herein, we report on the design and implementation of a self-powered photoelectrochemical (PEC) sensor that harnesses amplified photocathode signals for the deterioration of carbohydrate antigen 125 (CA125) associated with ovarian cancer. This self-powered sensing platform integrates Cu2O/Cu3SnS4 heterojunction and ZnIn2S4 sensitized TiO2 with flower-like structure as photocathode and photoanode. Moreover, the PEC biosensor introduces the interface shedding effect to overcome the limitations of weak or unstable photocathode PEC signals. When MnO2 nanoparticles are used as the quenching source, the cathode photocurrent experiences a reduction to a certain extent owing to the phenomenon of competitive light absorption. To enhance the application for efficient CA125 detection, the interface self-shelling effect is introduced. The effect is implemented through the hydrolysis reaction of Acetylcholinesterase (AChE), producing thiocholine (TCh) as the interface detachment initiator. Which resulting in the detachment of layer modifiers, including MnO2, from the electrode surface and achieving the effect of significant enhancement of the photoelectric signal. Therefore, multiple signal amplification effects synergistically enhanced the photoelectric response. The self-powered PEC biosensing with a wide linear range of 0.001 U/mL-200 U/mL and a low detection limit of 0.32 mU/mL, which shows excellent performance in terms of sensitivity, specificity, and stability, making it a promising candidate for point-of-care diagnostics.

Self-powered photoelectrochemical sensor based on molecularly imprinted polymer-coupled CBFO photocathode and Ag2S/SnS2 photoanode for ultrasensitive dimethoate sensing

Dimethoate (DIM) is one of the most extensively applied organophosphorus pesticides (OPs), which is used to boost farm productivity due to its high insecticidal efficacy. However, the excessive use of DIM can result in the extensive contamination of soil, groundwater and food. Monitoring of DIM in environmental and food samples is crucial in view of its potential health risks and environmental hazards from excessive residues. The expensive equipment and complex operations for current detection methods greatly limit their practical applications. Herein, a self-powered photoelectrochemical (PEC) sensing platform based on Ag2S/SnS2 photoanode, iron-doped cobalt borate (CBFO) photocathode, and molecularly imprinted polymers (MIPs) was proposed for the detection of DIM. The molecularly imprinted polymers at CBFO photocathode endow the self-powered PEC sensor with high selectivity. The Ag2S/SnS2 photoanode enhances the efficient of electron transfer between the photoanode and photocathode, contributing to the high sensitivity of PEC sensor. The self-powered molecularly imprinted PEC sensor exhibits outstanding sensitivity and selectivity for DIM at concentrations from 1 × 10-2 to 1 × 105 nM with a detection limit of 5.9 pM. Excellent recoveries (95.4 ± 2.6 %, 98.4 ± 2.3 %, 106.3 ± 3.3 %) were achieved in spiked crown pear samples, indicating that the molecularly imprinted PEC sensor is capable of detecting DIM in real samples. This research provides a novel simple, fast, highly selective and sensitive self-powered molecularly imprinted photoelectrochemical sensing platform for detection of DIM. The fabricated PEC sensor offers a promising candidate for the detection method of organophosphorus pesticides residues, which is of great significance for the fields of food safety and environmental protection.

Integrating detection and degradation of bisphenol A by photocatalytic fuel cell-driven photoelectrochemical sensor

To ensure food safety and environmental protection, it is crucial to rapidly identify and remove bisphenol A (BPA), a plasticizer commonly used in the inner lining of food containers and beverage packaging. Here, a photocatalytic fuel cell (PFC)-integrated self-powered photoelectrochemical (PEC) sensor is constructed. Unlike conventional single PEC or PFC sensors, this PFC-integrated PEC sensor relies on not only the difference in Fermi energy levels between photoanode and photocathode but also charge accumulation resulted from the oxidation of BPA by photogenerated holes. Consequently, this sensor achieved a remarkable maximum output power (Pmax) of 8.58 μW cm-2, as well as a high sensitivity, wide linear detection range (0.1-200 μM), low detection limit (0.05 μM), great stability, reproducibility, and real sample detection capability. This work integrates PFC and PEC technologies successfully for the rapid identification and efficient removal of BPA.

Self-powered photoelectrochemical aptasensor for fumonisin B1 detection based on a Z-scheme ZnIn2S4/WO3 photoanode

The incidence of esophageal cancer is positively associated with fumonisin contamination. It is necessary to develop methods for the rapid detection of fumonisins. In this work, a self-powered photoelectrochemical aptamer sensor based on ZnIn2S4/WO3 photoanode and Au@W-Co3O4 photocathode is proposed for the sensitive detection of fumonisin B1 (FB1). Among them, under visible light irradiation, the Z-type heterostructure of ZnIn2S4/WO3 acts as a photoanode to improve the electron transfer rate, which contributes to the enhancement of the photocathode signal and lays the foundation for a wider detection range. The Au@W-Co3O4 photocathode as a sensing interface reduces the probability of false positives (comparison of anode sensing platforms). The PEC sensor has a good working performance in the detection range (10 pg/mL-1000 ng/mL) with a detection limit of 2.7 pg/mL (S/N = 3). In addition, the sensor offers good selectivity, stability and excellent recoveries in real sample analysis. This work is expected to play a role in the field of analyzing environmental toxins.

A Lanthanide-Incorporated Phospho(III)tungstate Aggregate Constructed from [HPIIIW8O31]10- and [W11O39]12- Building Blocks and Its Nanocomposite with CdS for Ultrasensitive Photoelectrochemical Detection of Oxytetracycline

A novel tartronic acid decorated hexa-CeIII-incorporated phospho(III)tungstate aggregate (C4H12NO)6Na18H2[(HPW8O31)2[W11O39]2(H2TAD)4(H2O)4W4Ce6H2P2O14]·84H2O (1, H3TAD = tartronic acid) was synthesized by a one-step assembly strategy. Its main skeleton is constructed from two [W11O39]12- fragments, two [HPIIIW8O31]10- segments and one H2TAD--ornamented dodecanuclear heterometallic [W4Ce6H2PIII2O14(H2TAD)4(H2O)4]18+ cluster. In the structure, the [HPIIIO3]2- groups not only work as the heteroatom template to induce the formation of lacunary [HPIIIW8O31]10- segments but also function as the connector to bridge Ce3+ cations. With the help of a reaction strategy of combining ultrasonication treatment with the continuous ion layer adsorption method, the 1/CdS composite was constructed and exhibits prominent photoelectrochemical activity. The 1/CdS composite was used as a photoelectrochemical sensor for oxytetracycline detection at 0 V (vs Ag/AgCl), which displays excellent properties with quick response and low limit of detection (0.042 nM). This work can provide some helpful references in the construction of novel PIII-induced polyoxometalates consisting of different building blocks and can extend the applications of polyoxometalate-based nanocomposites into photoelectrochemical detection for antibiotics as well as biomolecules.

A molecularly imprinting photoelectrochemical sensor based on Bi2O2S-sensitized perovskite Cs2AgBiBr6 for sarcosine determination

An original molecular imprinting photoelectrochemical (PEC) sensor for sarcosine detection based on stable lead-free inorganic halide double perovskite Cs2AgBiBr6 is proposed. Cs2AgBiBr6 as a lead-free halide perovskite material possesses several positive optoelectronic properties for PEC analysis, such as long-lived component to the charge-carrier lifetime, and strong absorption of visible light. At the same time, two-dimensional materials also offer excellent electronic and mechanical properties; thus, Bi2O2S was used and combined with Cs2AgBiBr6 to provide a stable and large photocurrent, which also benefits from the  stability of perovskite Cs2AgBiBr6. Based on this novel PEC assay, the detection range for sarcosine was between 0.005 and 5000 ng/mL with a low detection limit of 0.002 ng/mL. This work also improved the adhibition of metal halide perovskite in analytical chemistry field, providing a novel way for other small molecule detection.

Self-powered photoelectrochemical immunosensing platform for sensitive CEA detection using dual-photoelectrode synergistic signal amplification

Self-powered photoelectrochemical (PEC) sensing, as an emerging sensing mode, can effectively solve the problems such as weak anti-interference ability and poor signal response of individual photoanode or photocathode sensing. In this work, an ITO/Co-CuInS2 photocathode and ITO/WO3@CdS photoanode based self-powered cathodic PEC immunosensor was developed, which integrated dual-photoelectrode to synergistic amplify the signal for highly sensitive and specific detection of carcinoembryonic antigen (CEA). The self-powered PEC sensor could drive electrons transfer through the difference in Fermi levels between the two photoelectrodes without an external bias voltage. The photoanode was introduced to amplify the photoelectric signal, and the photocathode was only designed for the construction of sensing interfaces. The proposed sensor quantitatively determined the target CEA with the detection limit of 0.23 pg/mL and a linear correlation confine of 0.1 pg/mL ∼100 ng/mL. The constructed immunosensing platform exhibited high sensitivity, satisfactory stability and great biological detection selectivity, providing a feasible and effective strategy for the manufacture of new self-powered sensors in high-performance PEC bioanalytical applications.

Metal-organic-framework-confined quantum dots enhance photocurrent signals: A molecularly imprinted photoelectrochemical cathodic sensor for rapid and sensitive tetracycline detection

BACKGROUND

Tetracycline (TC), a cost-effective broad-spectrum antibacterial drug, has been excessively utilized in the livestock and poultry industry, leading to a serious overabundance of TC in livestock wastewater. However, conventional analytical methods such as liquid chromatography and gas chromatography face challenges in achieving sensitive detection of trace amounts of TC in complex substrates. Therefore, it is imperative to develop a highly sensitive and anti-interference analytical method for the detection of tetracycline in livestock wastewater.

RESULTS

A porphyrin-based MOF (PCN-224)-confined carbon dots (CDs) material (CDs@PCN-224) was synthesized by a "bottle-around-ship" strategy. The reduced carrier migration distance is conducive to the separation of electron-hole pairs and enhanced the photocurrent signal due to the tight coupling of CDs and PCN-224. Further, molecularly imprinted polymer (MIP) was synthesized by rapid in-situ UV-polymerization and employed as a recognition element. The specific recognition of the target by imprinted cavities blocks electron transfer, resulting in a "turn off" response signal, thus realizing the selective detection of TC. Under optimal conditions, the constructed MIP-PEC cathodic sensor detected 1.00 × 10-12 M to 1.00 × 10-7 M of TC sensitively, with a limit of detection of 3.72 × 10-13 M. In addition, the proposed MIP-PEC sensor demonstrated good TC detection performance in actual livestock wastewater.

SIGNIFICANCE

The strategy based on MOF pore-confined quantum dots can effectively enhance the photocurrent response of the photosensitive substrate. Simultaneously, the MIP constructed by in-situ rapid UV-polymerization showed excellent anti-interference and reusable properties. This work provides a promising MIP-PEC cathodic sensing method for the rapid and sensitive detection of antibiotics in complex-matrix environmental samples.

N-doped TiO2/Ti3C2-driven self-photocatalytic molecularly imprinted ECL sensor for sensitive and steady detection of dexamethasone

The conventional luminol-based electrochemiluminescence (ECL) biosensor suffers from hampered signal stability due to the self-decomposition of the H2O2 co-reactant. Here, we propose an N-doped TiO2/Ti3C2 heterojunction driven self-photocatalytic platform for ECL signal amplification and then combine it with molecular imprinting technology for sensitive and steady detection of dexamethasone (DXM). Unlike traditional cases involving specific catalysts or external electron injection, the initial luminescence of luminol in this new system is utilized as the excitation light of N-doped TiO2/Ti3C2 photocatalyst to promote the conversation of dissolved oxygen to H2O2, supplying more co-reactants to improve ECL of luminol in turn. Thanks to the heterojunction and self-photocatalytic cyclic amplification, this molecularly imprinted ECL sensor exhibits a wide linear range (1.0 × 10-6-1.0 × 101 μg mL-1) and a low detection limit, as well as excellent anti-interference capability, sensitivity, and stability. This work contributes to more reliable and steady detection of DXM and brings new insights into developing exogenous co-reactant-free self-enhancement ECL models for biosensor applications.

Portable and Rapid Dual-Biomarker Detection Using Solution-Gated Graphene Field Transistors in the Accurate Diagnosis of Prostate Cancer

Prostate-specific antigen (PSA) is the common serum-relevant biomarker for early prostate cancer (PCa) detection in clinical diagnosis. However, it is difficult to accurately diagnose PCa in the early stage due to the low specificity of PSA. Herein, a new solution-gated graphene field transistor (SGGT) biosensor with dual-gate for dual-biomarker detection is designed. The sensing mechanism is that the designed aptamers immobilized on the surface of the gate electrodes can capture PSA and sarcosine (SAR) biomolecules and induce the capacitance changes of the electric double layers of SGGT. The limit of detections of PSA and SAR biomarkers can reach 0.01 fg mL-1 , which is three-to-four orders of magnitude lower than previously reported assays. The detection time of PSA and SAR is ≈4.5 and ≈13 min, which is significantly faster than the detection time (1-2 h) of conventional methods. The clinical serum samples testing demonstrates that the biosensor can distinguish the PCa patients from the control group and the diagnosis accuracy can reach 100%. The SGGT biosensor can be integrated into the portable platform and the diagnostic results can directly display on the smartphone/Pad. Therefore, the integrated portable platform of the biosensor can distinguish cancer types through the dual-biomarker detection.

Triple-Mode Sensor Coupled by Photoelectrochemical, Electrochromic, and Spectral Signals for Sensitive Visualized Detection of Nonylphenol

Conventional photoelectrochemical (PEC) biosensors suffer from the difficulty of visualizing rapid detection and limited accuracy due to a single-signal output. Here, we develop a PEC, electrochromic (EC), and spectral (ST) triple-mode platform for the sensitive visualized detection of nonylphenol (NP). First, the reasonably stepped Fermi energy level arrangement between the defective TiO2 anode and MoO3 cathode enables a remarkable photocurrent response (Mode 1). Then, MoO3 itself is a widely used EC candidate, which can react with free Li-ions to form a LixMoO3 intermediate, and its color will change from white to blue accordingly (Mode 2). More importantly, MoO3 is also a Li-ion host and the potential of LixMoO3 depends on the inserted Li-ion quantity deduced by spectral analysis on residual Li-ions in the electrolyte (Mode 3). The EC signal endows fast visual detection, and triple-mode cross-validation improves reliability and accuracy. As a result, this PEC-EC-ST triple-mode molecularly imprinted sensor has a wide linear range (1-5000 μg L-1), a low detection limit (0.18 μg L-1), selectivity, stability, reproducibility, and actual sample detection capability. This innovative multimode platform not only improves detection reliability but also broadens applications of electrochromic/energy storage materials in biosensors.

Long-Wavelength Illumination-Induced Photocurrent Enhancement of a ZnPc Photocathodic Material for Bioanalytical Applications

Herein, a novel photocathodic nanocomposite poly{4,8-bis[5-(2-ethylhexyl)-thiophen-2-yl] benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)-carbonyl]thieno[3,4-b]thiophene-4,6-diyl}/phthalocyanine zinc (PTB7-Th/ZnPc) with high photoelectric conversion efficiency under long-wavelength illumination was prepared to construct an ultrasensitive biosensor for the detection of microRNA-21 (miRNA-21), accompanied by a prominent anti-interference capability toward reductive substances. Impressively, the new heterojunction PTB7-Th/ZnPc nanocomposite could not only generate a strong cathodic photocurrent to improve the detection sensitivity under long-wavelength illumination (660 nm) but also effectively avoid the high damage of biological activity caused by short-wavelength light stimulation. Accordingly, by coupling with rolling circle amplification (RCA)-triggered DNA amplification to form functional biquencher nanospheres, a PEC biosensor was fabricated to realize the ultrasensitive analysis of miRNA-21 in the concentration range of 0.1 fM to 10 nM with a detection limit as low as 32 aM. This strategy provided a novel long-wavelength illumination-induced photocurrent enhancement photoactive material for a sensitive and low-damage anti-interference bioassay and early clinical disease diagnosis.

A closed-loop catalytic nanoreactor system on a transistor

Precision chemistry demands miniaturized catalytic systems for sophisticated reactions with well-defined pathways. An ideal solution is to construct a nanoreactor system functioning as a chemistry laboratory to execute a full chemical process with molecular precision. However, existing nanoscale catalytic systems fail to in situ control reaction kinetics in a closed-loop manner, lacking the precision toward ultimate reaction efficiency. We find an inter-electrochemical gating effect when operating DNA framework-constructed enzyme cascade nanoreactors on a transistor, enabling in situ closed-loop reaction monitoring and modulation electrically. Therefore, a comprehensive system is developed, encapsulating nanoreactors, analyzers, and modulators, where the gate potential modulates enzyme activity and switches cascade reaction "ON" or "OFF." Such electric field-effect property enhances catalytic efficiency of enzyme by 343.4-fold and enables sensitive sarcosine assay for prostate cancer diagnoses, with a limit of detection five orders of magnitude lower than methodologies in clinical laboratory. By coupling with solid-state electronics, this work provides a perspective to construct intelligent nano-systems for precision chemistry.

Biological redox cycling amplification in a self-powered photoelectrochemical sensor based on TiO2/CdIn2S4/ g-C3N4-WO3 photoanode for sensitive detection of Hg2

A photoelectrochemical (PEC) sensor is proposed with a TiO₂/CdIn₂S₄ co-sensitive structure and a g-C₃N₄-WO₃ heterojunction as the photoanode to form a self-powered system. The photogenerated hole-induced biological redox cycle of TiO₂/CdIn₂S₄/g-C₃N₄-WO₃ composites is used as a signal amplification strategy for Hg²⁺ detection. In the test solution, ascorbic acid is first oxidized by the photogenerated hole of the TiO₂/CdIn₂S₄/g-C₃N₄-WO₃ photoanode, which triggers the ascorbic acid－glutathione cycle to achieve signal amplification and increase the photocurrent. However, in the presence of Hg²⁺, glutathione forms a complex with Hg²⁺, which destroys the biological cycle and leads to a decreased of photocurrent, thus achieving detection of Hg²⁺. Under optimal conditions, the proposed PEC sensor has a wider range (from 0.1 pM to 100 nM), and lower limit of Hg²⁺ detection (0.44 fM) than most other Hg²⁺ detection methods. In addition, the developed PEC sensor can be used to detect of real samples.

Design of a Double-Photoelectrode Sensing System with a Metal-Organic Framework-Based Antenna-like Strategy for Highly Sensitive Detection of PD-L1

Currently, the construction of heterojunctions as a method to enhance photoelectrochemical (PEC) activity has shown prospective applications in the analytical field. Restricted by carrier separation at the interface, developing a heterojunction sensing platform with high sensitivity remains challenging. Here, a double-photoelectrode PEC sensing platform was fabricated based on an antenna-like strategy by integrating MIL-68(In)-NH2, a p-type metal-organic framework (MOF) photocatalyst, as a photocathode with the type-II heterojunction of CdSe/MgIn2S4 as a photoanode synchronously. According to the ligand-to-metal charge transition (LMCT), the photo-generated carriers of MIL-68(In)-NH2 transferred from the organic ligand to the metal cluster, which provides an efficient antenna-like transfer path for the charge at the heterojunction interface. In addition, the sufficient Fermi energy difference between the double photoelectrode provides the continuous internal driving force required for rapid carrier separation at the anode detection interface, significantly improving the photoelectric conversion efficiency. Hence, compared with the traditional heterojunction single electrode, the photocurrent response of the double-photoelectrode PEC sensing platform developed using the antenna-like strategy is 2.5 times stronger. Based on this strategy, we constructed a PEC biosensor for the detection of programed death-ligand 1 (PD-L1). The elaborated PD-L1 biosensor exhibited sensitive and precise detection capability with a detection range of 1 × 10-5 to 1 × 103 ng/mL and a lower detection limit of 3.26 × 10-6 ng/mL and demonstrated the feasibility of serum sample detection, providing a novel and viable approach for the unmet clinical need of PD-L1 quantification. More importantly, the charge separation mechanism at the heterojunction interface proposed in this study provides new creative inspiration for designing sensors with high-sensitivity PEC performance.

Boosting ultralong chemiluminescence for the self-powered time-resolved immunosensor

The construction of an immunosensor based on ultralong chemiluminescence is challenged due to the shortage of highly efficient initiator for long and stable catalysis. Herein, the heterogeneous Au/Pt@CuO/Cu₂O catalyst was used to investigate the structure-activity relationship, while Au/Pt significantly promotes the activity of CuO/Cu₂O to catalyze H₂O₂ and thus produces ·OH and O₂^•- radicals in highly alkaline solutions, resulting in the strong and long chemiluminescence in the reaction with luminol (10 mL, more than 4 min with 1 μg catalyst). By using the Au/Pt@CuO/Cu₂O as the label in the immunoassay, the strong and long chemiluminescence could initiate the photocurrent of the photoelectrochemical (PEC) substrate, and the luminescence time could influence the photocurrent extinction time, thus a self-powered time-resolved PEC immunosensor was developed to detect furosemide, showing a linear relationship between the extinction time and the logarithm of concentrations from 10^-3 to 1 μg/L. This work not only experimentally verifies that the Pt-O-Cu bond in heterogeneous catalysts breaks the pH limitation of the Fenton reaction, but also realizes the chemiluminescence for self-powered time-resolved immunosensor, thereby expanding the portable applicability of chemiluminescence in food safety inspection, health monitoring, and biomedical detection without external light source.

Codoping g-C3N4 with boron and graphene quantum dots: Enhancement of charge transfer for ultrasensitive and selective photoelectrochemical detection of dopamine

The development of superior photoelectrochemical (PEC) sensors for biosensing has become a major objective of PEC research. However, conventional PEC-active materials are typically constrained by a weak photocurrent response owing to their limited surface-active sites and high electron-hole recombination rate. Here, a boron and graphene quantum dots codoped g-C₃N₄ (named GBCN) as PEC sensor for highly sensitive dopamine (DA) detection was fabricated. GBCN exhibited the greatest photocurrent response and PEC activity compared to free g-C₃N₄ and g-C₃N₄ doped with boron. The proposed PEC sensor for DA determination exhibited a broad linear range (0.001-800 μM) and a low detection limit (0.96 nM). In particular, a sensitivity up to 10.3771 μA/μM/cm² was seen in the case of GBCN. The high PEC activity can be attributed to the following factors: (1) the boron and graphene quantum dots co-doping significantly increased the specific surface area of g-C₃N₄, providing more adsorption sites for DA; (2) the dopants extended the absorption intensity of g-C₃N₄, red-shifting the absorption from 470 to 540 nm; and (3) the synergism of boron and graphene quantum dots efficiently boosted the photogenerated electrons migration from the conduction band of g-C₃N₄ to graphene quantum dots, facilitating charge separation. In addition, GBCN also exhibited good anti-interference ability and stability. This research may shed light on the creation of a highly sensitive and selective PEC platform for detecting biomolecules.

Photoelectrochemical and visual dual-mode sensor for efficient detection of Cry1Ab protein based on the proximity hybridization driven specific desorption of multifunctional probe

Currently, the development of sensitive and visual strategy for Cry1Ab detection, particularly using a switchable dual-mode detection system based on a single component, remains a great challenge. Here, a photoelectrochemical (PEC) and visual dual-mode sensor was designed for Cry1Ab detection based on a proximity hybridization driven multifunctional probe. In the presence of Cry1Ab, specific desorption of the antibody-DNA conjugate was achieved via sufficient proximity hybridization, leading to the selective release of the multifunctional signal probe, i.e., antibody-labeled single-stranded DNA-gold nanoparticles (Ab₁-S1-AuNPs). The released Ab₁-S1-AuNPs reduced the photocurrent signal and produced a colored response, thereby achieving PEC and visual dual-mode detection based on a single component. Owing to the different signal generation mechanisms, two independent signals were obtained simultaneously, which provided self-verification to improve reliability and accuracy. Taking advantage of the PEC sensitive detection and visual prediction, the dual-mode sensor achieved efficient detection of the Cry1Ab protein. The developed sensor was successfully used to determine Cry1Ab in corn, wheat, and soil samples with satisfactory results. This method offers a promising biosensing platform for the on-site detection of Cry1Ab protein.

Self-powered photoelectrochemical aptasensor based on AgInS2@Co/Ni-UiO-66@CDs photoelectrode for estradiosl detection

A self-powered photoelectrochemical (PEC) aptasensor was constructed to sensitively detect 17β-estradiol (E₂). Firstly, a reasonable AgInS₂@Co/Ni-UiO-66@Carbon Nanodots (CDs) photoelectrode with excellent photoelectrochemical performance was built by a simple two-step preparation method. The Co and Ni doping markedly improved the activity of UiO-66; the matched energy level of AgInS₂ and Co/Ni-UiO-66 promoted the separation of electron-hole pairs, and the coupling of CDs further enhanced the conductivity and light utilization. Therefore, a steady anode-photocurrent signal output was obtained in 0.0 V bias voltage, providing a reliable photoelectric translating platform for assembling a self-powered PEC aptasensor. The E₂-aptamer was adopted as a recognition unit to enhance the selectivity and sensitivity of the proposed aptasensor. The specific recognition reaction between E₂ and aptamer administering to a raised photocurrent signal and the concentration of E₂ was quantified by counting the fluctuation of the anode-photocurrent signal. The linear response range of the PEC aptasensor was 1.0 × 10^-5-10 nmol/L, and the detection limit (S/N = 3) was lower than 3.0 fmol/L under optimal conditions. The fabricated aptasensor exhibited admirable selectivity, high sensitivity, rapid response, and wide linear range, demonstrating an extensive application prospect for environmental endocrine disruptor detection.

Self-powered photoelectrochemical biosensor with inherent potential for charge carriers drive

Self-powered photoelectrochemical (PEC) sensing platform without external voltage has provided a breakthrough in the development of biosensors, however, it is necessary to find suitable Fermi energy level difference between photoanode materials and photocathode materials as the driving force. Herein, the self-powered PEC sensor was developed to combine the advantages of both the photoanode (SnS₂/In₂S₃) and the photocathode (CuInS₂). The sufficient Fermi level differentiation between the photoanode with the photocathode not only resulted in an evident photocurrent response vis tuning the electron transfer but avoided redox reactions of extra electron donors/acceptors to enhance the accuracy of the sensor. The biological target was immobilized on the photocathode, which allowed the sensor to possess a good anti-interference capability for the detection of real samples. The proposed PEC sensor exhibits good sensitivity for the cytokeratin 19 fragment (CYFRA21-1) detection and a low limit of detection (LOD) of 6.57 fg mL^-1. Moreover, the as-purposed PEC system with good anti-interference capability and accuracy has implications for the detection of other biomarkers.