Exploitation of a photoelectrochemical sensing platform for catechol quantitative determination using BiPO4 nanocrystals/BiOI heterojunction

In-situ synthesized MgIn2S4/CdWO4 type-II heterojunction as a light-driven photoelectrochemical sensor for ultrasensitive detection of catechol in environmental water samples

As an essential chemical intermediate, catechol (CC) residues may have adverse effects on human health. Herein, an effective and facile photoelectrochemical sensor platform based on MgIn2S4/CdWO4 composite is constructed for monitoring CC. MgIn2S4 increases light absorption range and activity, while CdWO4 enhances photoelectronic stability, and the type-II heterojunction formed can significantly enhance photocurrent response. Due to the autoxidation process, CC is converted into oligomeric products, which increase the spatial site resistance and attenuate the overall photocurrent response. It is worth noting that the cauliflower-like structure of MgIn2S4 can provide a large specific surface area, and the presence of Mg2+ promotes autoxidation, thus providing a suitable condition for detecting CC. Under optimal conditions, the MgIn2S4/CdWO4/GCE photoelectrochemical sensor has a prominent linear relationship in the range of CC concentration from 2 nM to 7 μM, with a limit of detection of 0.27 nM. With satisfactory selectivity, excellent stability, and remarkable reproducibility, this sensor provides a crucial reference value for effectively and rapidly detecting pollutants in environmental water samples.

Carbon quantum dots(CQDs)-sensitized CdS/CuInS2 heterojunction as a photoelectrochemical biosensing platform for highly sensitive detection of prostate-specific antigen

Sensitive and quantitative detection of prostate-specific antigen (PSA) has been determined to be indispensable for clinical diagnostics of prostate cancer, whereas such detection is quite challenging due to the extremely low concentration of biomarkers in human serum samples. In this study, a photoelectrochemical (PEC) sensor was effectively developed for the high-sensitivity analysis of prostate-specific antigen (PSA) using a signal amplification method utilizing sensitized carbon quantum dots (CQDs). In this experiment, cadmium sulfide quantum dots were employed as the substrate materials, and indium copper sulfide quantum dots were loaded on their surfaces. Moreover, the efficient matching of energy levels in these two materials contributed to the generation of photocurrents. The aforementioned heterojunction semiconductor QDs were thus combined with CQDs to produce CQDs on their surfaces. As a result of the presence of CQDs, the ability of heterojunction materials to absorb light was remarkably enhanced, increasing the photocurrent by over ten times. Consequently, in this study, CQDs were combined with PEC sensors, and the developed PEC biosensors exhibited excellent optical performance, sensitivity, repeatability, and stability. The results obtained from the analysis of actual samples were satisfactory and have promising application prospects.

A photoelectrochemical immunosensing platform for ultrasensitive detection of alpha-fetoprotein based on a signal amplification strategy

For the first time, a PEC immunosensor based on a signal amplification strategy is successfully constructed to quantitatively detect alpha-fetoprotein in serum sample. Three favorable factors explain the ultra-high sensitivity of this method. Firstly, compared with pure BiPO₄, the BiPO₄/BiOBr heterojunction has a narrower band gap, which expands the light absorption range and enables the light energy to be fully utilized. Secondly, the separation of photogenerated electrons and hole pairs during PEC detection is due to the efficient matching of energy levels among BiPO₄, BiOBr and CdS, inhibiting the recombination of photogenerated electrons, which improves the performance of PEC immunosensor. Thirdly, due to the presence of CdS, the light absorption capability of the sensor is enhanced, more electron-hole pairs are generated, and the photocurrent signal is increase. Under the optimal conditions, the PEC immunosensor shows a wide linear range of 0.001-1000 ng/mL for AFP and a low detection limit of 0.82 pg/mL. The PEC immunosensor developed in this experiment has excellent reproducibility, stability and high sensitivity, and also achieves satisfactory results in the analysis of human serum samples, establishing a new analytical method for biomarker detection.

A mechanothermal approach for the synthesis of Fe3O4 nanoparticles as dopant on mesoporous TiO2 for electrochemical determination of catechol

The subject of water contamination and how it gets defiled to the society and humans is confabulating from the past decades. Phenolic compounds widely exist in the water sources and it is emergent to determine the toxicity in natural and drinking water, because it is hazardous to the humans. Among these compounds, catechol has sought a strong concern because of its rapid occurrence in nature and its potential toxicity to humans. The present work aims to develop an effective electrochemical sensing of catechol using mesoporous structure of Fe₃O₄-TiO₂ decorated on glassy carbon (GC) electrode. The creation of pure TiO₂ using the sol-gel technique was the first step in the synthesis protocol for binary nanocomposite, which was then followed by the loading of Fe₃O₄ nanoparticles on the surface of TiO₂ using the thermal decomposition method. The resultant Fe₃O₄-TiO₂ based nanocomposite exhibited mesoporous structure and the cavities were occupied with highly active magnetite nanoparticles (Fe₃O₄) with high specific surface area (90.63 m²/g). When compared to pure TiO₂, catechol showed a more prominent electrochemical response for Fe₃O₄-TiO₂, with a significant increase in anodic peak current at a lower oxidation potential (0.387 V) with a detection limit of 45 μM. Therefore, the prepared magnetite binary nanocomposite can serve as an efficient electroactive material for sensing of catechol, which could also act as a promising electrocatalyst for various electrocatalytic applications.

New Aptamer/MoS2/Ni-Fe LDH Photoelectric Sensor for Bisphenol A Determination

Here, a new type of PEC aptamer sensor for bisphenol A (BPA) detection was developed, in which visible-light active MoS₂/Ni-Fe LDH (layered double hydroxide) heterostructure and aptamer were used as photosensitive materials and biometric elements, respectively. The combination of an appropriate amount of MoS₂ and Ni-Fe LDH enhances the photocurrent response, thereby promoting the construction of the PEC sensor. Therefore, we used a simple in situ growth method to fabricate a MoS₂/Ni-Fe LDH sensor to detect the BPA content. The aptasensor based on aptamer/MoS₂/Ni-Fe LDH displayed a linear range toward a BPA of 0.05-10 to 50-40,000 ng L^-1, and it has excellent stability, selectivity and reproducibility. In addition, the proposed aptamer sensor is effective in evaluating real water samples, indicating that it has great potential for detecting BPA in real samples.

Enhanced the photoelectrochemical performance of Bi2XO6 (X = W, Mo) for detecting hexavalent chromium by modification of CuS

In this work, Bi₂XO₆ (X = W, Mo) are synthesized at different temperatures. The results of tests find the optimal temperatures of Bi₂WO₆ and Bi₂MoO₆ are 180 and 160°C (BW-180, BM-160). Then, BW-180 and BM-160 are further compounded with different contents of CuS. The results of photoelectrochemical (PEC) tests show that CuS can improve the PEC performance of semiconductor materials, and it has better performance when CuS mass fraction is 5%. These maybe the photoelectron potentials generated by CuS/Bi₂XO₆ (X = Mo, W) heterojunction reduce the combination of photogenerated electrons and holes. When the PEC sensor based on 5%-CuS/BW-180 detects Cr(VI), it has a linear range of 1-80 μmol/L with detection limit of 0.95 μmol/L, while the PEC sensor based on 5%-CuS/BM-160 detects Cr(VI) has a linear range of 0.5-230 μmol/L and a detection limit of 0.12 μmol/L. Thus, 5%-CuS/Bi₂XO₆ has potential application in hexavalent chromium detection.

Designing of CuS growing on Bi2WO6 nanosheet heterostructures based on a photoelectrochemical aptasensor for detecting ofloxacin

Bi2WO6 (BW) was compounded with different contents of copper sulfide (CuS) by a two-step procedure. The chemical composition and morphology of the materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results of photoelectrochemical (PEC) tests showed that CuS can improve the PEC performance of semiconductor materials and it has the best performance when the CuS mass fraction is 5%. Therefore, CuS/BW-5% nanocomposite has been constructed as ofloxacin (OFL) drug PEC aptasensors by binding of aptamer receptors. The PEC aptasensor based on CuS/BW-5% has a linear relationship for OFL of 1-12,000 nM and a determination limit of 0.35 nM. Since the photoelectron potential generated by CuS/BW-5% heterojunction reduces the combination of photogenerated electrons and holes CuS/BW-5% has a better photoelectrocatalytic performance. Graphical abstract Schematic presentation of a photoelectrochemical aptasensor based on CuS/Bi2WO6 for the determination of OFL.

The design and growth of peanut-like CuS/BiVO4 composites for photoelectrochemical sensing

In this study, the CuS/BiVO₄-X (where X represents the mass percentage of CuS associated with CuS/BiVO₄; X = 2%, 5% and 7%) p–n heterostructures were fabricated using a two-step hydrothermal method.

Strain engineered biocompatible h-WO3 nanofibers based highly selective and sensitive chemiresistive platform for detection of Catechol in blood sample

In this work, we demonstrate a simple, low-cost biocompatible 1D-WO₃ electrospun nanofibers based strain-induced high-performance chemiresistive catechol sensor. WO₃ nanofibers were synthesized using e-spinning, annealed and drop-casted on to flexible PET substrate. X-Ray Diffraction (XRD) studies confirm the formation of Hexagonal phase-WO₃ and Raman spectroscopy proved the presence of O-W-O bending modes. Field emission scanning electron microscopy (FESEM) images displayed the random orientation of dense WO₃ nanofibers on PET substrate. Hall measurements confirmed the formation of n-type WO₃ nanofibers with carrier density of 10¹⁹ cm^-3. The sensor responded to a broad dynamic range of catechol concentrations from 1 μM to 100 μM with sensitivity of 51.29 μM^-1 cm^-2 and limit of detection of 0.52 μM which are better than previously reported catechol sensors. Interestingly, upon application of compressive strain to the flexible sensor, a remarkable increase in sensitivity to 88.34 μM^-1 cm^-2 was observed with further reduction of the limit of detection to 42 nM. Upon subjecting the sensor to strain ranging from 3.14% to 47.6%, an increase in sensitivity to catechol was observed due to the increase in the exposed surface area of interconnected WO₃ nanofibers which enhances the active sites for catechol oxidation by enhancing the tunneling current. The sensor could detect catechol in simulated blood samples with excellent selectivity against AA, UA, Na⁺, Ca⁺, hydroquinone and glucose.

Novel Bi3O5I2 Hollow Microsphere and Its Enhanced Photocatalytic Activity

A new type of I-deficient bismuth oxyiodide Bi3O5I2 with a hollow morphology was prepared by the solvothermal process. The structure, composition, morphology, optical property and photoelectric property of the as prepared photocatalyst were investigated through some characterization methods. Those characterization results showed that Bi3O5I2 displayed a larger specific surface area, promising band structure and lower recombination of photoinduced carriers than pure BiOI. Bi3O5I2 had a higher photocatalytic activity than BiOI on the decomposition of methyl orange (MO) under simulated solar light irradiation. The superoxide (·O2−) and hole (h+) were the dominating active species during the degradation of MO. Its stability and reusability performance showed its great promising application in the degradation of organic pollutant.

Integrated BiPO4 nanocrystal/BiOBr heterojunction for sensitive photoelectrochemical sensing of 4-chlorophenol

A sensor platform was constructed by using a BiPO₄ nanocrystal/BiOBr heterojunction, which displayed superior performance for monitoring 4-chlorophenol.