A bioetching-induced visualized-organic photoelectrochemical transistor dual-signal mode sensor for alkaline phosphatase detection.

A study of an integrated OPECT biosensor gate and the EC color-changing region on the same chip was carried out, achieving sensitive detection through bioetching-induced signal changes. Enzymatic bioetching enables specific alkaline phosphatase (ALP) detection by catalyzing the production of CdS, which modulates the channel current and generates a visual signal.

Synergistic effect of surface metal vacancies and Schottky junction on high-transconductance organic photoelectrochemical transistor aptasensing.

The synergistic effect between surface metal vacancies and a Schottky junction on enhanced transconductance, and the gating effect of an organic photoelectrochemical transistor was reported.

A miniaturized organic photoelectrochemical transistor aptasensor based on nanorod arrays toward high-sensitive T-2 toxin detection in milk samples.

Detection of T-2 toxin is of great significance to environment and human health, as T-2 toxin is one of the main toxins that contaminate crops, stored grain and other food. Herein, a zero-gate-bias organic photoelectrochemical transistor (OPECT) sensor was proposed based on nanoelectrode arrays as gate photoactive materials which can result in the accumulation of photovoltage and preferable capacitance leading to better sensitivity of the OPECT. For comparison, the channel current of OPECT was 100 times higher than photocurrent of conventional photoelectrochemical (PEC) attributing to remarkable signal amplification of OPECT. It was also found that the detection limit of OPECT aptasensor was as low as 28.8 pg/L, lower than 0.34 ng/L of the conventional PEC method, further indicating the advantage of the OPECT devices in T-2 toxin determination. This research has been successfully applied in real sample detection which provided a general platform of OPECT for food safety analysis.

Growth of AgI semiconductors on tailored 3D porous Ti3C2 MXene/graphene oxide aerogel to develop sensitive and selective "signal-on" photoelectrochemical sensor for H2S determination.

Long term exposure to hydrogen sulfide (H2S) even in low concentration poses a serious threat to human health and the ecosystem, pointing to the significance for its effective supervision. In this study, we report a sensitive and selective "signal-on" photoelectrochemical (PEC) sensor for the determination of toxic H2S in aqueous solution by in situ growth of AgI semiconductors on tailored three-dimensional (3D) porous Ti3C2 MXene/graphene oxide aerogel (MGA). Our research demonstrated that the resultant MGA with the starting feeding mass ratio of MXene and graphene oxide (GO) of 1:8 (MGA1:8) possessed the most excellent PEC performance after the growth of AgI semiconductors than their monomers (Ti3C2 MXene and GO) and the MGAs with other starting feeding mass ratio. Such designed PEC sensor based on MGA1:8/AgI heterojunction showed dramatically strengthened PEC responses with increasing concentrations of S2-. Correspondingly, a wide linear range of 5 nM-200 µM, a low limit of detection of 1.54 nM (S/N = 3), and exclusively unique selectivity have been achieved. Our research illustrates that the PEC sensor designed with tailored MGA constitutes is an effective pathway to enhance the overall sensing performance, which will envision to boost more efforts for advanced 3D porous aerogel using in PEC sensors.

A membrane/mediator-free high-power density dual-photoelectrode PFC aptasensor for lincomycin detection in milk and chicken.

Over use of lincomycin (LIN) as antibiotic in animals can lead to multiple harmful impacts to public health, thus detection of LIN at trace level in milk and chicken sample matrixes is vital. In this work, Zinc phthalocyanine nanoparticles sensitized MoS2 (ZnPc/MoS2) was firstly developed as a novel photocathode material combined with nitrogen-doped graphene-loaded TiO2 nanoparticles (TiO2/NG) as photoanode material to construct a dual-photoelectrode photofuel cell (PFC). The as-prepared membrane/mediator-free PFC achieved excellent output performance that the maximum power density (Pmax) reached 11.83 µW cm-2. Specific aptamers are adopted as LIN recognition elements, the as-proposed self-powered aptasensor for LIN exhibited a linear scope in 10-11 -10-5 mol L-1 along with a low detection limit (3S/N) of 3.33 pmol L-1. Consequently, such high-power density dual-photoelectrode PFC aptasensor may be a reassuring candidate electrochemical sensor for the detection of trace contamination in food samples.

Sensitive and stable detection of deoxynivalenol based on electrochemiluminescence aptasensor enhanced by 0D/2D homojunction effect in food analysis.

Sensitive detection for deoxynivalenol (DON) should be developed due to DON as a kind of harmful mycotoxins which can poses health risk to human health even at low concentrations. In this work, an electrochemiluminescence (ECL) DON aptasensor was proposed based on Ti3C2 dots/Ti3C2 nanosheet (TDTN). Compared with Ti3C2 dots and Ti3C2 nanosheet, the ECL intensity of TDTN was 4 times of Ti3C2 dots and 2 times of Ti3C2 nanosheet as emitters. This was attributed to homojunction effect which could provide continuity of band bonding and effectively accelerate charge transfer at the interface. Based on ECL signal changes generated by aptamer and DON fixed on the electrode surface, the ECL aptasensor showed "on-off-on" performances and detected DON specifically in milk, with detection range of 0.001-20 ng/mL and detection limit of 0.3 pg/mL (S/N = 3). Therefore, the constructed ECL aptasensor is a promising detection method for food safety analysis.

Ultrasensitive photoelectrochemical aptasensor for carbendazim detection based on in-situ constructing Schottky junction via photoreducing Pd nanoparticles onto CdS microsphere.

Carbendazim (CBZ) has been widely used in agricultural production to control fruits and vegetables diseases, but it can also destroy the human endocrine system. Therefore, sensitive detection of CBZ has attracted increasing attention worldwide. In this study, Pd nanoparticles (Pd NPs) decorated on CdS microsphere (Pd NPs/CdS) was prepared by the in-situ photoreduced method, and based on the surface plasmon resonance (SPR) effect of noble metal and Schottky junction between Pd nanoparticles (Pd NPs) and CdS microsphere, the photocurrent after introducing Pd NPs is 7.7 times higher than that of bare CdS microsphere. In view of the outstanding photoelectrochemical (PEC) performance of Pd NPs/CdS and the high specificity of the aptamer, the as-fabricated PEC aptasensor for CBZ detection possesses the excellent detection performance including a broad linear ranging from 1.0 × 10-12 to 1.0 × 10-6 mol/L as a low detection limit of 3.3 × 10-13 mol/L (S/N = 3). Furthermore, the PEC aptasensor was used for determination of lettuce samples from actual agricultural products with satisfactory results.

Simultaneous detection of enrofloxacin and ciprofloxacin in milk using a bias potentials controlling-based photoelectrochemical aptasensor.

It is important to develop highly-active photoelectrochemical (PEC) materials and use novel sensing strategy for constructing high-PEC-performance sensors with multiplex detection abilities, owing to the simultaneous presence of multiple antibiotic residues in food. Herein, a bias-potential-based PEC aptasensor was prepared for the trace detection of dual antibiotic analytes, enrofloxacin (ENR) and ciprofloxacin (CIP), which often coexist in milk samples. Here, two materials were developed with excellent PEC performance: three-dimensional nitrogen-doped graphene-loaded copper indium disulfide (CuInS2/3DNG) and Bi3+-doped black anatase titania nanoparticles decorated with reduced graphene oxide (Bi3+/B-TiO2/rGO). By applying different bias potentials to the two materials near one ITO electrode, the cathodic current generated by CuInS2/3DNH and the anodic current generated by Bi3+/B-TiO2/rGO could be clearly distinguished without interfering with each other. Then, ENR and CIP aptamers were respectively modified onto the surface of CuInS2/3DNH and Bi3+/B-TiO2/rGO to construct a PEC aptasensor for the sensitive detection of ENR and CIP. Under optimal conditions, the proposed aptasensor exhibited wide linear ranges of ENR (0.01-10000 ng/mL) and CIP (0.01-1000 ng/mL), and relatively low detection limits of 3.3 pg/mL to ENR and CIP (S/N = 3). The aptasensor was successfully applied to the detection of ENR and CIP in milk samples.

Catalysis-induced performance enhancement of an electrochemical microcystin-LR aptasensor based on cobalt-based oxide on a B, N co-doped graphene hydrogel.

Microcystin detection is of great significance and an urgent need because of its damage to water environments and human health. In this paper, an electrochemical aptasensor was developed by combining a 3D cobalt-based oxide modified boron and nitrogen co-doped graphene hydrogel (3D BNG/Co) with a DNA aptamer for sensitive detection of microcystin (MC-LR) through differential pulse voltammetry (DPV) technology. By using 3D BNG/Co as a catalyst and [Fe(CN)6]3-/4- as a redox probe, the catalytic current signal was 3.8 times higher than that of the bare glassy carbon electrode, which can better monitor the electron conduction on the electrode surface and then improve the sensitivity. The as-fabricated electrochemical aptasensor displayed a wide detection range (0.1-1000 pmol L-1), low detection limit (0.03 pmol L-1), good sensitivity, and repeatability, which has potential applications for the protection of the ecological environment and human health.

Selective and sensitive photoelectrochemical aptasensor for streptomycin detection based on Bi4VO8Br/Ti3C2 nanohybrids.

Sensitive detection of streptomycin (STR) has attracted increasing attention worldwide because of the relationship between food security and human health. In this paper, Bi4VO8Br/Ti3C2 nanohybrids were obtained by one-pot solvent hydrothermal method. It was modified on ITO electrode, and STR aptamer was acted as the recognition element. With excellent photoelectrochemical (PEC) performance of Bi4VO8Br/Ti3C2 nanohybrids, an "on-off-on" PEC aptasensor for STR detection was effectively developed. Compared with pure Bi4VO8Br, the photocurrent intensity of as-prepared Bi4VO8Br/Ti3C2 nanohybrids was about 9 times higher, which ascribed to the highly conductive of Ti3C2, driving the photogenerated electrons transferred to the ITO electrode rapidly, so that the recombination of photogenerated electron and hole pairs was inhibited viably. Furthermore, the constructed "on-off-on" PEC aptasensor accomplished STR detection with high sensitivity, excellent specificity and distinguished repeatability in honey. The photocurrent increased with the increment of STR concentration with the linear range from1 nM to 1000 nM, and the detection limit of 0.3 nM (S/N = 3). Compared with the national standard method (SN/T 1925-2007), the as-constructed PEC sensor showed the consistent results.

A sensitive and stable visible-light-driven photoelectrochemical aptasensor for determination of oxytetracycline in tomato samples.

Sensitive detection of oxytetracycline (OTC) has attracted increasing attention worldwide due to the relationship between food safety and human health problems. In this work, a visible-light-driven photoelectrochemical (PEC) OTC aptasensor was constructed using Bi4VO8Cl/nitrogen-doped graphene quantum dots (Bi4VO8Cl/N-GQDs) nanohybrids as photoactive material and OTC aptamer as identification element. Owing to the well matched heterojunction of Bi4VO8Cl and nitrogen-doped graphene quantum dots (N-GQDs), the photogenerated electron-hole pairs could be separated effectively, so that the photocurrent intensity of as-prepared Bi4VO8Cl/N-GQDs nanohybrids was about 7 times higher than pure Bi4VO8Cl and had higher stability. The constructed "signal-off" PEC aptasensor realized OTC detection in tomato samples with excellent sensitivity, specificity and repeatability. The photocurrent decreased with the increase of OTC concentration in a range from 0.1 nM to 150 nM, and the detection limit was 0.03 nM (S/N = 3). The national standard method was used to compare with our method and the results were consistent.

Design and construction of Z-scheme Bi2S3/nitrogen-doped graphene quantum dots: Boosted photoelectric conversion efficiency for high-performance photoelectrochemical aptasensing of sulfadimethoxine.

Rational design and fabrication of Z-scheme visible-light-driven photoactive materials have drawn much attention owing to their great potential in handling environment and energy crisis. In this work, Z-scheme Bi2S3/nitrogen-doped graphene quantum dots (NGQDs) with superior photoelectric conversion efficiency were designed and fabricated, which demonstrated enhanced photoactivity compared with Bi2S3 owing to the improved separation efficiency of photogenerated electron and hole pairs. The emphasis was put on designing Z-scheme Bi2S3/NGQDs, and then the mechanism of Z-scheme charge transfer mode was verified by the electron spin resonance (ESR) technique. On this basis, the proposed sensor exhibited a wide linear range of 0.1-120 nM and a detection limit of 0.03 nM (S/N = 3) for SDM, with high sensitivity (0.075 µA nM -1), good selectivity and stability. Moreover, the proposed PEC aptasensor using Bi2S3/NGQDs as the photoelectrode achieved sensitive and selective determination of sulfadimethoxine in milk samples. This work could provide some ideas for designing other Z-scheme photoactive species and insights into the charge transfer mechanism of Z-scheme. Furthermore, the promising applicability of PEC aptasensor using photoactive species could be extended to other accurate monitoring for contaminants.

Perovskite-type BiFeO3/ultrathin graphite-like carbon nitride nanosheets p-n heterojunction: Boosted visible-light-driven photoelectrochemical activity for fabricating ampicillin aptasensor.

Developing effective sensing method for trace analysis of ampicillin (AMP) is urgent and significant due to its residue possess serious threats to human health. Herein, a p-n heterojunction, on the basis of p-type BiFeO3 nanoparticles coupled n-typed ultrathin graphite-like carbon nitride (utg-C3N4) nanosheets, has been designed and synthesized via a simple electrostatic interaction strategy. Such p-n heterojunction has two advantages: one is capable to narrow the band gap of photoactive materials from 2.20 eV of BiFeO3 down to 2.04 eV of BiFeO3/utg-C3N4, leading to improve the efficiency of visible light utilization; and the other is to facilitate the charge separation rate, resulting in the boosted photoelectrochemical (PEC) performance of BiFeO3/utg-C3N4. Under visible light illumination, the photocurrent of the resulted BiFeO3/utg-C3N4 was 7.0-fold enhanced than that of pure BiFeO3 nanoparticles, and indeed 2.3-fold enhanced comparing to BiFeO3/bulk-C3N4. Based on excellent PEC properties of BiFeO3/utg-C3N4, an on-off-on PEC aptasensor was successfully fabricated for ampicillin (AMP) determination with highly selectivity and sensitivity. The fabricated PEC aptasensor exhibited excellent PEC performance with a broad linear in the range from 1 × 10-12 mol L-1 to 1 × 10-6 mol L-1 as well as a low detection limit of 3.3 × 10-13 mol L-1 (S/N = 3), and also good feasibility in real sample. The excellent analytical performance indicated that PEC aptasensor on the basis of the visible light driven BiFeO3/utg-C3N4 heterojunction can provide a promising biosensor platform for sensitive detection AMP in food and environment analysis.

A Label-Free and Sensitive Fluorescent Qualitative Assay for Bisphenol A Based on Rolling Circle Amplification/Exonuclease III-Combined Cascade Amplification.

Bisphenol A (BPA) detection in drinking water and food packaging materials has attracted much attention since the discovery that BPA can interfere with normal physiological processes and cause adverse health effects. Here, we constructed a label-free aptamer fluorescent assay for selective and sensitive detection of BPA based on the rolling circle amplification (RCA)/Exonuclease III (Exo III)-combined cascade amplification strategy. First, the duplex DNA probe (RP) with anti-BPA aptamer and trigger sequence was designed for BPA recognition and signal amplification. Next, under the action of BPA, the trigger probe was liberated from RP to initiate RCA reaction as primary amplification. Subsequently, the RCA products were used to trigger Exo III assisted secondary amplification with the help of hairpin probes, producing plenty of "G-quadruplex" in lantern-like structures. Finally, the continuously enriched "G-quadruplex lanterns" were lightened by zinc(II)-protoporphyrin IX (ZnPPIX) generating enhanced fluorescence signals. By integrating the primary RCA and secondary Exo III mediated cascade amplification strategy, this method displayed an excellent sensitivity with the detection limits of 5.4 × 10-17 M. In addition, the anti-BPA aptamer exhibits high recognition ability with BPA, guaranteeing the specificity of detection. The reporter signal probe (G-quadruplex with ZnPPIX) provides a label-free fluorescence signals readout without complicated labeling procedures, making the method simple in design and cost-effective in operation. Moreover, environmental samples analysis was also performed, suggesting that our strategy was reliable and had a great potential application in environmental monitoring.