Signal amplified sandwich-type photoelectrochemical sensing assay based on rGO-Znln2S4 functionalized Au–WO3 IOPCs Z-scheme heterojunction

Photocurrent polarity switching photoelectrochemical aptasensor for oxytetracycline based on BiOBr/Ag2S/PDA//CuO: CuO-induced II-type to dual Z-scheme system

BACKGROUND

As a broad-spectrum tetracycline antibiotic, Oxytetracycline (OTC) was widely used in a variety of applications. But, the overuse of OTC had led to the detection of it in food, water and soil, which could present significance risk to human health and cause damage to ecosystem. It was of great significance to develop sensitive detection methods for OTC. Herein, an environmentally friendly photoelectrochemical (PEC) aptasensor was constructed for the sensitive detection of OTC based on CuO-induced BiOBr/Ag2S/PDA (Polydopamine) photocurrent polarity reversal.

RESULTS

BiOBr/Ag2S/PDA composites modified electrode not only produced stable initial anodic photocurrent but also provided attachment sites for the aptamer S1 of OTC by the strong adhesion of PDA. On the other hand, CuO loaded OTC aptamer S2 (Cu-S2) was got through Cu-S bonds. After the target OTC was identified on the electrode surface, CuO was introduced to the surface of ITO/BiOBr/Ag2S/PDA through the specific binding of OTC to S2. This identification process formed dual Z-type heterojunctions and resulted in a remarkable reversal of photocurrent polarity from anodic to cathodic. Under optimization conditions, the PEC aptasensor showed a wide linear range (50 fM ∼ 100 nM), low detection limit (1.9 fM), excellent selectivity, stability and reproducibility for the detection of OTC. Moreover, it was successfully used for the analysis of OTC in real samples of tap water, milk and honey, and had the potential for practical application.

SIGNIFICANCE

This work developed an environmentally friendly photocurrent-polarity-switching PEC aptasensor with excellent selectivity, reproducibility, stability, low LOD and wide linear range for OTC detection. This sensitive system, which was including BiOBr, Ag2S, PDA and CuO were low toxicity, not only reduced the risk of traditional toxic semiconductors to operators and the environment, but can also be used for the detection of real samples, broadening the wider range of applications for BiOBr, Ag2S, PDA and CuO.

Photoelectrochemical sensor based on AuNPs@WO3@TpPa-1-COF for quantification of DNA methylation levels

A "signal-off" photoelectrochemical (PEC) sensing platform has been designed for the ultrasensitive detection of DNA methylation levels and multiple methylated sites. The platform employs tungsten trioxide and TpPa-1-COF loaded by gold nanoparticle (AuNPs@WO3@TpPa-1-COF) composite material as the photoactive component and p-type reduced graphene (rGO) as an efficient quencher. The PEC signal of AuNPs@WO3@TpPa-1-COF composite is effectively quenched in the presence of p-type rGO, because p-type rGO can compete with AuNPs@WO3@TpPa-1-COF to deplete light energy and electron donors. In addition, a hybrid strand reaction (HCR) amplification strategy fixes more target DNA and then combines with rGO-modified anti-5-methylcytosine antibody to facilitate ultrasensitive DNA methylation detection. Under optimal conditions, DNA methylation can be measured within a linear concentration range of 10-14 to 10-8 M, with an exceptionally low detection limit of 0.19 fM (S/N = 3). At the same time, the platform can conduct quantitative determination of multi-site methylation, with the linear equation △I = 44.19LogA + 61.43, and the maximum number of methylation sites is 5. The sensor demonstrates high sensitivity, excellent selectivity, and satisfactory stability. Furthermore, the proposed signal-off PEC strategy was successfully employed to detect DNA methylation in spiked human serum samples, with recoveries ranging from 93.17 to 107.28% and relative standard deviation (RSD) ranging from 1.15 to 5.49%.

Constructed a novel of Znln2S4/S-C3N4 heterogeneous catalyst for efficient photodegradation of tetracycline

Despite S-doped C3N4 can exhibit more efficient photo-reactivity than pure C3N4, there is still some space to further improve the detaching efficiency of electron-hole and enhance the photocatalytic efficiency of S-C3N4. The construction of heterojunction is an effective method to promote the photocatalytic efficiency. ZnIn2S4, as a novel photocatalyst, its VB (1.37 V) and CB (- 1.09 V) can match with S-C3N4. Therefore, we hope to construct the ZnIn2S4/S-C3N4 heterojunction for boosting the photocatalytic activity of S-C3N4. In this paper, ZnIn2S4/S-C3N4 heterojunction was prepared through hydrothermal method using S-C3N4, ZnCl2, InCl3·4H2O, and thioacetamide as raw materials and heated at 160 °C for 16 h. The optimum 18% ZnIn2S4/S-C3N4 nanocomposites exhibit dramatically enhanced photocatalytic performance for degradation of tetracycline with 86.3% removal rate within 120 min, higher than 50% degradation efficiency of pure S-C3N4. And in the process of photodegradation for tetracycline, the largest contribution rate is the photo-excited cavity (h+), followed by ·O2- and ·OH. Herein, we have provided a good example for removing antibiotic residues by using S-C3N4-based heterojunction towards environmental remediation.

An ultrasensitive photo-driven self-powered aptasensor for microcystin-RR assay based on ZnIn2S4/Ti3C2 MXenes integrated with a matching capacitor for multiple signal amplification

A photo-driven self-powered aptasensor was constructed based on a matching capacitor and the ZnIn2S4/Ti3C2 heterojunction as the photoanode and Cu2O as the photocathode in a dual-photoelectrode sensing matrix for multiple signal amplification for the ultrasensitive detection of microcystin-RR (MC-RR). The introduction of Ti3C2 MXene nanosheets on the photoanode surface can not only accelerate the transfer and separation of photoinduced electron/hole pairs, thus enhancing the output signal of the photo-driven self-powered system, but also provide a larger specific surface area for the immobilization of the bio-recognition unit aptamer. More importantly, for a portable and miniaturized device, a micro-workstation with the size of a universal serial bus (USB) disk and a novel short-circuit current access was proposed to capture the instantaneous output electrical signal for real-time data tracking. In such a way, a sensitivity of 2.7 mA pM-1 was achieved when the matching capacitor was integrated into the self-powered system, which was 22 times that without a capacitor. After the interaction between MC-RR and the corresponding aptamer, a 'signal-off' detection configuration was formed via the steric hindrance effect. Therefore, such a multiple signal amplification system realized the ultrasensitive and selective determination of MC-RR successfully. Under optimal conditions, the linear range of the self-powered aptasensor was 0.1 to 100 pM and the detection limit was 0.033 pM (S/N = 3). The aptasensor was applied to the detection of MC-RR in fish, exhibiting good reproducibility (≈3.88%), paving the way for detecting microcystins in real-life samples.

Engineered inverse opal structured semiconductors for solar light-driven environmental catalysis

Inverse opal (IO) macroporous semiconductor materials with unique physicochemical advantages have been widely used in solar-related environmental areas. In this minireview, we first summarize the synthetic methods of IO materials, emphasizing the two-step and three-step approaches, with the typical physicochemical properties being compared where applicable. We subsequently discuss the application of IO semiconductors (e.g., TiO₂, ZnO, g-C₃N₄) in various photo-related environmental techniques, including photo- and photoelectro-catalytic organic pollutant degradation in water, optical sensors for environmental monitoring, and water disinfection. The engineering strategies of these hierarchical structures for optimizing the activities for different catalytic reactions are discussed, ranging from heterojunction construction, cocatalyst loading, and heteroatom doping, to surface defect construction. Structure-activity relationships are established correspondingly. With a systematic understanding of the unique properties and catalytic activities, this review is expected to orient the design and structure optimization of IO semiconductor materials for photo-related performance improvement in various environmental techniques. Finally, the challenges of emerging IO structured semiconductors and future development directions are proposed.

Self-powered photoelectrochemical aptasensor based on MIL-68(In) derived In2O3 hollow nanotubes and Ag doped ZnIn2S4 quantum dots for oxytetracycline detection

A self-powered photoelectrochemical (PEC) aptasensor was constructed based on MIL-68(In) derived indium oxide hollow nanotubes (In₂O₃ HNs) and Ag-doped ZnIn₂S₄ quantum dots (QDs) as sensing matrix for the ultrasensitive detection of oxytetracycline (OTC). The hollow tube structure of the designed photoelectric active platform provided abundant active sites and a larger specific surface area for the immobilization of target recognition unit. The coupling of Ag:ZnIn₂S₄ QDs and In₂O₃ HNs can accelerate the transmit and separation of photoinduced charge, and thus greatly increasing the intensity of photocurrent signal. Then, the well-constructed OTC-aptamer was anchored on the modified photoelectrode as an accurate capturing element, achieving the specific detection of analyte. Under optimal conditions, the photocurrent intensity of the PEC aptasensor decreases linearly, with a linear response range of 10^-4 -10 nmol/L, and a limit of detection (LOD) of 3.3 × 10^-5 nmol/L (S/N = 3). The developed self-powered aptasensor with excellent reproducibility, stability, and selectivity, provides a potential way to detect antibiotic residues in environmental media.