Platelike WO3 sensitized with CdS quantum dots heterostructures for photoelectrochemical dynamic sensing of H2O2 based on enzymatic etching

Photoelectrochemical sensor for nitrite determination based on the etching of BiOCl/Zn0.5Cd0.5S

A rapid photoelectrochemical (PEC) sensor was constructed for nitrite detection in food based on the one-step chemical etching strategy of BiOCl/Zn0.5Cd0.5S (BOC/ZCS) nanocomposites by nitrite. BOC/ZCS heterojunction was prepared by a simple coprecipitation method, and it was found that BOC/ZCS showed significant photoelectrochemical (PEC) activity. The results of this study confirmed that the decrease in the photocurrent of the sensor was linked to the etching of ZCS by nitrite under acidic conditions. Under optimized conditions, the BOC/ZCS-based PEC sensor showed good analytical properties for detecting nitrite, with linear ranges of 1-100 μM and 100-600 μM. The detection limit of the sensor was 0.41 μM (S/N = 3). Excellent repeatability, reproducibility, low background noise, and immunity to interference were demonstrated using the proposed system, and satisfactory results were achieved for the nitrite assay using real samples. These results demonstrate a new method for nitrite detection developed using the proposed PEC sensor.

CRISPR/Cas12a-Derived Photoelectrochemical Aptasensor Based on Au Nanoparticle-Attached CdS/UiO-66-NH2 Heterostructures for the Rapid and Sensitive Detection of Ochratoxin A

The sensitive and accurate detection of ochratoxin A (OTA) is crucial for public health due to its high toxicity. Herein, using Au nanoparticle (NP)-attached CdS/UiO-66-NH2 heterostructures as photoactive materials, a photoelectrochemical (PEC) aptasensor was presented for the ultrasensitive assay of OTA based on a competitive displacement reaction triggering the trans-cleavage ability of CRISPR/Cas12a. In this sensing strategy, methylene blue-labeled single-stranded DNA (MB-ssDNA) was immobilized on the Au NPs/CdS/UiO-66-NH2 electrode to accelerate the separation of the photogenerated carrier, thus producing a significantly increased PEC response. In the presence of OTA, it specifically bound with the aptamer (Apt) and resulted in the release of the activation chain, triggering the trans-cleavage characteristics of CRISPR/Cas12a. MB-ssDNA was cut randomly on the electrode surface to convert the PEC signal from the "on" to the "off" state, thereby achieving a quantitative and accurate detection of OTA. The CRISPR/Cas12a-derived PEC aptasensor exhibited excellent sensitivity and specificity, with a linear range from 100 to 50 ng/mL and a detection limit of 38 fg/mL. Overall, the proposed aptasensor could provide a rapid, accurate, and sensitive method for the determination of OTA in actual samples.

Progress in Electrochemical Immunosensors with Alkaline Phosphatase as the Signal Label

Electrochemical immunosensors have shown great potential in clinical diagnosis, food safety, environmental protection, and other fields. The feasible and innovative combination of enzyme catalysis and other signal-amplified elements has yielded exciting progress in the development of electrochemical immunosensors. Alkaline phosphatase (ALP) is one of the most popularly used enzyme reporters in bioassays. It has been widely utilized to design electrochemical immunosensors owing to its significant advantages (e.g., high catalytic activity, high turnover number, and excellent substrate specificity). In this work, we summarized the achievements of electrochemical immunosensors with ALP as the signal reporter. We mainly focused on detection principles and signal amplification strategies and briefly discussed the challenges regarding how to further improve the performance of ALP-based immunoassays.

Alkaline Phosphatase-Mediated Bioetching of CoOOH/BiVO4 for Signal-On Organic Photoelectrochemical Transistor Bioanalysis

Organic photoelectrochemical transistor (OPECT) bioanalytics has recently appeared as a promising route for biological measurements, which has major implications in both next-generation photoelectrochemical (PEC) bioanalysis and futuristic biorelated implementations. Via biological dissociation of materials, bioetching is a useful technique for bio-manufacturing and bioanalysis. The intersection of these two domains is expected to be a possible way to achieve innovative OPECT bioanalytics. Herein, we validate such a possibility, which is exemplified by alkaline phosphatase (ALP)-mediated bioetching of a CoOOH/BiVO₄ gate for a signal-on OPECT immunoassay of human immunoglobulin G (HIgG) as the model target. Specifically, target-dependent bioetching of the upper CoOOH layer could result into an enhanced electrolyte contact and light accessibility to BiVO₄, leading to the modulated response of the polymeric poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) channel that could be monitored by the channel current. The introduced biosensor achieves sensitive detection of HIgG with high selectivity and sensitivity. This work features bioetching-enabled high-efficacy OPECT bioanalysis and is anticipated to serve as a generic protocol, considering the diverse bioetching routes.

Tungsten-based Nanomaterials in the Biomedical Field: A Bibliometric Analysis of Research Progress and Prospects

Tungsten-based nanomaterials (TNMs) with diverse nanostructures and unique physicochemical properties have been widely applied in the biomedical field. Although various reviews have described the application of TNMs in specific biomedical fields, there are still no comprehensive studies that summarize and analyze research trends of the field as a whole. To identify and further promote the development of biomedical TNMs, a bibliometric analysis method is used to analyze all relevant literature on this topic. First, general bibliometric distributions of the dataset by year, country, institute, referenced source, and research hotspots are recognized. Next, a comprehensive review of the subjectively recognized research hotspots in various biomedical fields, including biological sensing, anticancer treatments, antibacterials, and toxicity evaluation, is provided. Finally, the prospects and challenges of TNMs are discussed to provide a new perspective for further promoting their development in biomedical research.

Photoelectrochemical Detection of Exosomal miRNAs by Combining Target-Programmed Controllable Signal Quenching Engineering

MicroRNAs extracted from exosomes (exosomal miRNAs) have recently emerged as promising biomarkers for early prognosis and diagnosis. Thus, the development of an effective approach for exosomal miRNA monitoring has triggered extensive attention. Herein, a sensitive photoelectrochemical (PEC) biosensing platform is demonstrated for exosomal miRNA assay via the target miRNA-powered λ-exonuclease for the amplification strategy. The metal-organic framework (MOF)-decorated WO₃ nanoflakes heterostructure is constructed and implemented as the photoelectrode. Also, a target exosomal miRNA-activatable programmed release nanocarrier was fabricated, which is responsible for signal control. Hemin that acted as the electron acceptor was prior entrapped into the programmed control release nanocarriers. Once the target exosomal miRNAs-21 was introduced, the as-prepared programmed release nanocarriers were initiated to trigger the release of hemin, which enabled the quenching of the photocurrent. Under the optimized conditions, the level of exosomal miRNAs-21 could be accurately tracked ranging from 1 fM to 0.1 μM with a low detection limit of 0.5 fM. The discoveries illustrate the possibility for the rapid and efficient diagnosis and prognosis prediction of diseases based on the detection of exosomal miRNAs-21 and would provide feasible approaches for the fabrication of an efficient platform for clinical applications.

Photoelectrochemical sensing and mechanism investigation of hydrogen peroxide using a pristine hematite nanoarrays

In this paper, a facile hydrothermal combined with subsequent two-step post-calcination method was used to fabricate hematite (α-Fe₂O₃) nanoarrays on fluorine-doped SnO₂ glass (FTO). The morphology, crystalline phase, optical property and surface chemical states of the fabricated α-Fe₂O₃ photoelectrode were characterized by scanning electron microscopy, X-ray diffraction, ultraviolet visible spectroscopy and X-ray photoelectron spectroscopy correspondingly. The α-Fe₂O₃ photoelectrode exhibits excellent photoelectrochemical (PEC) response toward hydrogen peroxide (H₂O₂) in aqueous solutions, with a low detection limit of 20 μM (S/N = 3) and wide linear range (0.01-0.09, 0.3-4, and 6-16 mM). Additionally, the α-Fe₂O₃ photoelectrode shows satisfying reproducibility, stability, selectivity and good feasibility for real samples. Mechanism analysis indicates, comparing with H₂O, H₂O₂ possesses much more fast reaction kinetics over α-Fe₂O₃ surface, thus the recombination of photogenerated charges are reduced, followed by much more photogenerated electrons are migrated to the counter electrode via external circuit. The insight on the enhanced photocurrent, which is corelative to the concentration of H₂O₂ in aqueous solution, will stimulate us to further optimize the surface structure of α-Fe₂O₃ to gain highly efficient α-Fe₂O₃ based sensors.

Etching reaction of carbon quantum dot-functionalized MnO2 nanosheets with an enzymatic product for photoelectrochemical immunoassay of alpha-fetoprotein

An etching reaction-based photoelectrochemical (PEC) immunoassay was developed to monitor alpha-fetoprotein (AFP) by coupling with the enzymatic product toward the dissolution of MnO2 nanosheets.

Highly Sensitive Amperometric Detection of Hydrogen Peroxide in Saliva Based on N-Doped Graphene Nanoribbons and MnO2 Modified Carbon Paste Electrodes

Four different graphene-based nanomaterials (htGO, N-htGO, htGONR, and N-htGONR) were synthesized, characterized, and used as a modifier of carbon paste electrode (CPE) in order to produce a reliable, precise, and highly sensitive non-enzymatic amperometric hydrogen peroxide sensor for complex matrices. CPE, with their robustness, reliability, and ease of modification, present a convenient starting point for the development of new sensors. Modification of CPE was optimized by systematically changing the type and concentration of materials in the modifier and studying the prepared electrode surface by cyclic voltammetry. N-htGONR in combination with manganese dioxide (1:1 ratio) proved to be the most appropriate material for detection of hydrogen peroxide in pharmaceutical and saliva matrices. The developed sensor exhibited a wide linear range (1.0–300 µM) and an excellent limit of detection (0.08 µM) and reproducibility, as well as high sensitivity and stability. The sensor was successfully applied to real sample analysis, where the recovery values for a commercially obtained pharmaceutical product were between 94.3% and 98.0%. Saliva samples of a user of the pharmaceutical product were also successfully analyzed.

CdS/TiO2 Nanocomposite-Based Photoelectrochemical Sensor for a Sensitive Determination of Nitrite in Principle of Etching Reaction

The CdS/TiO₂ nanocomposite (NC) photoelectrochemical (PEC) sensor was constructed based on a new sensing strategy for nitrite assay. The CdS etching process caused by nitrite-in-acid solution was confirmed and applied to nitrite sensing. The CdS etching phenomenon occurring on the sensor led to an obvious reduction in the photocurrent response under visible-light irradiation, which responded to the nitrite concentration. The CdS/TiO₂ NC-based PEC sensor exhibited excellent performance on nitrite detection. The linear range for nitrite determination was from 1-100 and 100-500 μM, and the sensitivity of the PEC sensor was 2.91 and 0.186 μA μM^-1 cm^-2, respectively. The detection limit of the sensor was 0.56 μM (S/N = 3). In addition, the PEC sensor was also equipped with advantages such as good selectivity, excellent stability, low background, and recyclability. Satisfying results were obtained for the nitrite assay in real samples by such a PEC sensor. In summary, this work contributed a fresh idea to precisely determinate nitrite through PEC sensing.

Detection of pollutants in water bodies: electrochemical detection or photo-electrochemical detection?

The massive discharge of pollutants including endocrine-disrupting chemicals (EDCs), heavy metals, pharmaceuticals and personal care products (PPCPs) into water bodies is endangering the ecological environment and human health, and needs to be accurately detected. Both electrochemical and photo-electrochemical detection methods have been widely used for the detection of these pollutants, however, which one is better for the detection of different environmental pollutants? In this feature article, different electrochemical and photo-electrochemical detection methods are summarized, including the principles, classification, common catalysts, and applications. By summarizing the advantages and disadvantages of different detection methods, this review provides a guide for other researchers to detect pollutants in water bodies by using electrochemical and photo-electrochemical analysis.

A self-powered photoelectrochemical biosensor for H2O2, and xanthine oxidase activity based on enhanced chemiluminescence resonance energy transfer through slow light effect in inverse opal TiO2

TiO₂ inverse opal photonic crystals (IOPCs) were fabricated by using polystyrene template. TiO₂ IOPCs based photoelectrochemical (PEC) biosensor was fabricated for the precise and stable detection of Heme without external irradiation. Then, the sensitization of TiO₂ IOPCs was fulfilled with CdS quantum dots (QDs) by SILAR method to form ITO-TiO₂ IOPCs-CdS:Mn electrode, which in turn was used to construct a PEC biosensor. The uniform porous structure of IOPCs with a large surface area is conducive to the excellent electronic transmission and QDs deposition. Also, the energy level matching between the conduction bands of CdS QDs and TiO₂ IOPCs widened the range of light absorption, allowing for electron injection from excited CdS QDs to TiO₂ upon luminol chemiluminescence, which enhanced the photocurrent. Furthermore, when the red edge of the photonic stop band of TiO₂ IOPCs overlapped with the band gap of TiO₂, and chemiluminescence emission of luminol, a substantial photocurrent increment was observed due in part to the slow light effect. The biosensor possesses a large linear detection range of 0.063-4 mM with a LOD of 19 μM for H₂O₂. Also, xanthine oxidase activity was determined with a linear measurement range of 0.01-15 mU/mL. Our strategy opens a new horizon to IOPCs based and QDs sensitized PEC sensing, which could be more sensitive, convenient and inexpensive for clinical and biological analysis. As far as we know, the largest photocurrent generation by luminol chemiluminescence was observed thanks to the use of semiconducting hybrid IOPCs material even at 0 V.

Recent developments of photoelectrochemical biosensors for food analysis

Recent developments of photoelectrochemical biosensors for food analysis are summarized and the future prospects in this field are discussed.

Ultrafine Pt NPs-Decorated SnO2/α-Fe2O3 Hollow Nanospheres with Highly Enhanced Sensing Performances for Styrene

Styrene, a chronic toxic gas, is of great harm to human health. It is urgently required to develop a portable, efficient, and inexpensive method to detect this toxic gas. Chemiresistive gas sensor based on semiconductor metal-oxides is considered as one of the best candidate suited to above features, while its sensitivity and selectivity are not enough high for the applications. Herein, the ultrafine Pt NPs embellished SnO₂/α-Fe₂O₃ hollow nanoheterojunctions were achieved by in-situ reduction and subsequent calcination treatment. Particularly, such yielding products exhibited excellent styrene sensing performances with a detection limit of 50 ppb and extremely fast response/recovery time (3/15 s, respectively). More importantly, this SnO₂/α-Fe₂O₃/Pt sensing platform revealed improved styrene selectivity against other malodorous gases. Additionally, the significant enhancement for styrene sensing response was also obtained compared to other two sensors (pristine SnO₂ and SnO₂/α-Fe₂O₃, respectively). Further studies demonstrated that such enhanced performances possibly be owing to the "catalytic sensitization" effect driven by Pt NPs and "electronic sensitization" effect triggered through the formation of Schottky junction as well as n-n nanoheterojunction. Based on these sensing features, it is probably great promising in the detection of styrene gas in the future.

A review on visible-light induced photoelectrochemical sensors based on CdS nanoparticles

Discovering the distinctive photophysical properties of semiconductor nanoparticles (NPs) has made these a popular subject in recent advances in nanotechnology-related analytical methods.

Three-Dimensional WO3 Nanoplate/Bi2S3 Nanorod Heterojunction as a Highly Efficient Photoanode for Improved Photoelectrochemical Water Splitting

The rational design of semiconductor photoanodes with sufficient light absorption, efficient photogenerated carrier separation, and fast charge transport is crucial for photoelectrochemical (PEC) water splitting. Incorporating a small-band-gap semiconductor to a large-band-gap material with matched energy band position is a promising route to improve the light harvesting and charge transport. Herein, we report the fabrication of a three-dimensional heterojunction with uniform Bi₂S₃ nanorods on WO₃ nanoplates by hydrothermal process and chemical bath deposition. The seed layer strategy was used to assist the growth of Bi₂S₃ nanorods for perfect interface contact between WO₃ and Bi₂S₃. The as-prepared WO₃/Bi₂S₃ composite exhibited a much enhanced photocurrent (5.95 mA/cm² at 0.9 V vs reversible hydrogen electrode), which is 35 and 1.4 times higher than those of pristine WO₃ and WO₃/Bi₂S₃ composite without a seed layer, respectively. In addition, higher incident photon-to-current conversion efficiency (68.8%) and photoconversion efficiency (1.70%) were achieved. The enhancement mechanism was investigated in detail, and the sufficient light absorption, efficient charge transport, and high carrier density simultaneously contribute to the improved PEC activity. These findings will open up new opportunities to develop other highly efficient heterostructures as photoelectrodes for PEC applications.

Fabrication of photo-electrochemical biosensors for ultrasensitive screening of mono-bioactive molecules: the effect of geometrical structures and crystal surfaces

The controlled design of hierarchical CN-ST flowers is a key feature for creating biosensor surface electrodes for photo-electrochemical, ultrasensitive screening of mono-bioactive molecules.

Bismuth ferrite-based photoactive materials for the photoelectrochemical detection of disease biomarkers coupled with multifunctional mesoporous silica nanoparticles

A photoelectrochemical sensing system was designed to detect CEA on bismuth ferrite photoactive materials with target-controlled glucose release from mesoporous silica nanoparticles.