Photoelectrochemical Response Research Articles

A novel “signal-off” photoelectrochemical sensing platform for selective detection of rutin based on Cu2SnS3/TiO2 heterojunction

In this study, a novel and ultrasensitive photoelectrochemical (PEC) sensor was developed for highly selective detection of rutin with a “signal-off” pattern based on Cu2SnS3-modified TiO2 nanotube arrays (NTAs) under UV light irradiation. Herein, the highly ordered TiO2 nanotube arrays were grown on the surface of Ti foil using an anodization process, and then Cu2SnS3 nanoparticles (NPs) were deposited on TiO2 NTAs by electrodeposition method. It was found that the Cu2SnS3/TiO2 NTAs/Ti electrode exhibited a much-increased photocurrent response compared to the bare TiO2 NTAs/Ti electrode owing to the synergistic effect between Cu2SnS3 nanoparticles and TiO2 NTAs, which could accelerate the separation of electron-hole pairs. In the presence of rutin,the PEC response was reduced due to the steric hindrance effect caused by the interaction between Cu2SnS3 nanoparticles and rutin. Under optimum conditions, the fabricated PEC sensor indicated a widespread linear range of 0.001 nM–100 µM toward rutin with an extremely low detection limit (LOD) of 0.0007 nM. Moreover, the experimental results revealed that the proposed PEC sensor possessed good stability, favorable selectivity, outstanding repeatability, and reproducibility. Meanwhile, the proposed PEC sensor was successfully used to determine rutin content in real samples, and satisfactoryresults were obtained.

Visible light active Fe2O3/SnS heterojunction decorated with graphene oxide layer for improved photoelectrochemical performance

Tin monosulfide, also known as SnS, is a significant IV-VI group semiconductor that has acquired considerable emphasis owing to its good absorption in visible range. In the present work, nanostructured thin films of pure SnS, Fe2O3, and Fe2O3/SnS heterojunction were synthesized using cost effective thermal evaporation and Rf sputtering method, respectively. Furthermore, to enhance the sample's photoelectrochemical activity, a homogenous thin film of graphene oxide (GO) is coated on Fe2O3/SnS heterojunction sample. All samples were well characterized and their photoelectrochemical response was investigated. The maximum photocurrent density was observed for Fe2O3/SnS/GO heterojunction i.e. 1.0 ​mA/cm2 which is much higher than pure SnS (0.3 ​mA/cm2) and Fe2O3 (0.02 ​mA/cm2) at 0.95 ​V vs. Ag/AgCl. The role of graphene layer is being examined for the improved photoresponse. Remarkable photoresponse and stability of the Fe2O3/SnS/GO heterojunction sample may be attributed to better charge separation at the interfacial junction of SnS and Fe2O3 and excellent electron density of GO layer.

Enhanced photoelectrochemical response of reduced graphene oxide covered inexpensive TiO2-BiFeO3 composite photoanodes

We show enhanced photoelectrochemical response of reduced graphene oxide covered inexpensive TiO2-BiFeO3 composite photoanodes for photoelectrochemical water splitting reaction. The photoelectrochemical activity of TiO2-BiFeO3 composite electrode is increased by creating heterojunction of TiO2-BiFeO3 and rGO. Structural, optical and morphological analysis of pristine and composite samples was done by characterizing them using X-ray diffraction, UV–vis spectrometry and scanning electron microscopy. The photoelectrochemical water splitting reaction revealed that composite TiO2-BiFeO3 with 20 wt.% BiFeO3 has higher photocurrent density. Further this composite electrode with rGO layer exhibits more than tenfold photocurrent density at onset and as well as higher potential. Graphene oxide layer acts as rich source of electrons caused better separation of the photogenerated electron hole pairs at heterojunction. Finally, this system shows high photocurrent density of 3.5 mA cm−2 at 0.95 V/Ag/AgCl with good stability under light conditions.

TiO2 nanotube arrays as a photoelctrochemical platform for sensitive Ag+ ion detection based on a chemical replacement reaction

Silver ions (Ag+) are essential for living organisms; however, they are toxic at high concentrations. Herein, a photoelectrochemical (PEC) platform is constructed using TiO2 nanotube arrays (TiNTs) prepared by electrochemical anodization of electrode substrate, with high photocurrent response in visible-light region by coating PbS nanocrystals (NCs) through continuous chemical bath deposition (CBD) technique. Combining the low band-gap of PbS with the improved photogenerated electron-hole separation at PbS/TiO2 heterojunctions, the resulting PbS/TiNTs electrode possesses a highly improved PEC response under visible light. Owing to an efficient chemical replacement of Pb(II) in PbS by targeted Ag+ ions, the formed Ag2S components become the new recombination centers for charge carriers, leading to decreased PEC response. Based on photocurrent reduction, the PEC electrode demonstrated an excellent sensing ability for trace Ag+ in solution with a linear range of 5.0 × 10−3 ∼ 5.0 × 10−8 mol L−1 and a limit of detection reaching 1.5 × 10−8 M (S/N = 3). The semiconductor hybrid nanotubes-based photoelectrochemical platform provides a promising route to design highly sensitive and selective sensors for directly detecting ions or molecules.

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.

Tailoring enzymatic loading capacity on CdS nanorods@ZnIn2S4 nanosheets 1D/2D heterojunctions: Toward ultrasensitive photoelectrochemical bioassay of tobramycin

Despite advances in the development of photoelectrochemical (PEC) sensor, modulating the PEC response of assembled heterostructure interface is still a great challenge. Here, an ultrasensitive PEC aptasensor for tobramycin (TOB) assay was conducted based on one-dimensional/two-dimensional CdS nanorods@ZnIn2S4 nanosheets (1D/2D CdS NRs@ZnIn2S4 NSs) heterojunctions by tailoring enzymatic loading capacity. Firstly, alkaline phosphatase modified TOB aptamer (ALP-Apt) was linked via specific base complementary pairing, and insoluble precipitations were then produced through the ALP-triggered catalytic reaction with the aid of Ag+, which prevented the charge transfer and resulted in the decrement of photocurrent. In the presence of TOB, partial ALP-Apt detached from the electrode surface due to the strong affinity between TOB and its aptamer, leading to a reduction in the amount of ALP and insoluble precipitate, in turn the PEC response partially recovered. The photocurrents exhibited a wider linear range towards the TOB concentration of 1.0–5.0 × 104 pg mL−1, with a low detection limit of 0.96 pg mL−1. The constructed PEC aptasensor gained satisfactory results for TOB assay in milk samples as well, which also offered significant promise for other pollutants in environmental analysis.

Van der Waals Black Phosphorus/Bi10O6S9 Heterojunction Harvesting Ambient Electric Field Energy for Enhanced Photoelectrochemical Sense

Ingenious utilization of ambient energy is a vigorous issue for heterostructure-type devices in evoking their performance in various applications. Using the van der Waals effect, two-dimensional black phosphorus is developed to bond with a unique Bi10O6S9 layer, which then forms a type-II heterostructure based on a truncated pyramidal Si/Ag/WO3 substrate. It is demonstrated that the ambient electric field can not only promote the separation and transfer of the electrons (and holes) excited by light irradiation but also induce additional electrons (and holes) to migrate in the same direction as that of those excited by light irradiation. Under the action of a 1100 V m–1 ambient electric field, the photoelectrochemical response current of light irradiation is increased 1.6 times, while the stability of the photoelectrochemical response current can retain 81.06% of the initial value even after 6000 s. The thin black phosphorus layer alone contributes 1.75 times the response current. On this basis, a sensitive device for monitoring the weak physiological electric field of a human arm assisted by light irradiation was developed, which shows wide application prospects in wearable devices.

In-depth interpretation of aptamer-based sensing on electrode: Dual-mode electrochemical-photoelectrochemical sensor for the ratiometric detection of patulin

Electrochemical aptasensors have been extensively used to quantify food contaminants (e.g., mycotoxin) by using high-affinity aptamer for target recognition. Yet, analytical performance of aptasensors using different aptamers can be varied for the same target. Here, four aptamers with different sequences (i.e., A22, A34, A42, and A45) of patulin (PAT) were selected to estimate sensing behaviors at electrodes with electrochemical (EC) and photoelectrochemical (PEC) assays. Synergistic effect of steric hindrance and electron transfer distance was found to significantly affect EC and PEC response for PAT at aptasensors fabricated with A22, A34, A42, or A45. Eventually, A22 emerged to be the optimal aptamer for aptasensing, despite the highest affinity of A42 to PAT. The A22-based EC-PEC dual-mode ratiometric aptasensor offered a linear range of 50 fg mL−1 – 500 ng mL−1 with a detection limit of 30 fg mL−1 for PAT, and it was applied to apple product (i.e., juice, puree) analysis.

PEC/Colorimetric Dual-Mode Lab-on-Paper Device via BiVO4/FeOOH Nanocomposite In Situ Modification on Paper Fibers for Sensitive CEA Detection.

A dual-mode lab-on-paper device based on BiVO4/FeOOH nanocomposites as an efficient generating photoelectrochemical (PEC)/colorimetric signal reporter has been successfully constructed by integration of the lab-on-paper sensing platform and PEC/colorimetric detection technologies for sensitive detection of carcinoembryonic antigen (CEA). Concretely, the BiVO4/FeOOH nanocomposites were in situ synthesized onto the paper-working electrode (PWE) through hydrothermal synthesis of the BiVO4 layer on cellulose fibers (paper-based BiVO4) which were initially modified by Au nanoparticles for improving the conductivity of three dimensional PWE, and then the photo-electrodeposition of FeOOH onto the paper-based BiVO4 to construct the paper-based BiVO4/FeOOH for the portable dual-mode lab-on-paper device. The obtained nanocomposites with an FeOOH needle-like structure deposited on the BiVO4 layer exhibits enhanced PEC response activity due to its effective separation of the electron-hole pair which could further accelerate the PEC conversion efficiency during the sensing process. With the introduction of CEA targets onto the surface of nanocomposite-modified PWE assisted by the interaction with the CEA antibody from a specific recognition property, a signal-off PEC signal state with a remarkable photocurrent response decreasing trend can be achieved, realizing the quantitative detection of CEA with the PEC signal readout mode. By means of a smart origami paper folding, the colorimetric signal readout is achieved by catalyzing 3,3',5,5'-tetramethylbenzidine (TMB) to generate blue oxidized TMB in the presence of H2O2 due to the satisfied enzyme-like catalytic activity of the needle-like structure, FeOOH, thereby achieving the dual-mode signal readout system for the proposed lab-on-paper device. Under the optimal conditions, the PEC and colorimetric signals measurement were effectively carried out, and the corresponding linear ranges were 0.001-200 ng·mL-1 and 0.5-100 ng·mL-1 separately, with the limit of detection of 0.0008 and 0.013 ng·mL-1 for each dual-mode. The prepared lab-on-paper device also presented a successful application in serum samples for the detection of CEA, providing a potential pathway for the sensitive detection of target biomarkers in clinical application.

Photoelectrochemical C-H Activation Through a Quinacridone Dye Enabling Proton-Coupled Electron Transfer.

Dye-sensitized photoanodes for C-H activation in organic substrates are assembled by vacuum sublimation of a commercially available quinacridone (QNC) dye in the form of nanosized rods onto fluorine-doped tin oxide (FTO), TiO2 , and SnO2 slides. The photoanodes display extended absorption in the visible range (450-600 nm) and ultrafast photoinduced electron injection (<1 ps, as revealed by transient absorption spectroscopy) of the QNC dye into the semiconductor. The proton-coupled electron-transfer reactivity of QNC is exploited for generating a nitrogen-based radical as its oxidized form, which is competent in C-H bond activation. The key reactivity parameter is the bond-dissociation free energy (BDFE) associated with the N⋅/N-H couple in QNC of 80.5±2.3 kcal mol-1 , which enables hydrogen atom abstraction from allylic or benzylic C-H moieties. A photoelectrochemical response is indeed observed for organic substrates characterized by C-H bonds with BDFE below the 80.5 kcal mol-1 threshold, such as γ-terpinene, xanthene, or dihydroanthracene. This work provides a rational, mechanistically oriented route to the design of dye-sensitized photoelectrodes for selective organic transformations.

Influence of manganese concentration on photoelectrochemical response of TiO2 nanotube decorated with Mn/CdS as photoanode

Influence of manganese concentration on photoelectrochemical response of TiO2 nanotube decorated with Mn/CdS as photoanode

Zero-Biased and Visible Light-Driven Immunosensing of Cardiac Troponin I Biomarker Based on a BiOI/S-g-C3N4/Bi-NaTaO3 Photoelectrochemical Platform

This work describes the development of a platform based on bismuth oxyiodide (BiOI), sulfur-doped graphitic carbon nitride (S-g-C3N4), and bismuth-doped sodium tantalate perovskite (Bi-NaTaO3) for zero-biased photoelectrochemical immunosensing of cardiac troponin I (cTnI) biomarker. The spectroscopic, structural, morphological, and compositional characteristics of the photoelectrochemical (PEC) materials were evaluated by Raman and Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Electrochemical impedance (EI) measurements were performed under the incidence and absence of light to investigate the effects of photons on the charge transfer resistance of the photoelectrochemical platform. The influence of the cTnI biomarker on the photoelectrochemical response of the anti-cTnI antibody-modified photoelectrochemical platform (anti-cTnI/BiOI/S-g-C3N4/Bi-NaTaO3/FTO) was evaluated by measuring the photocurrent of the system. The immunosensor presented a linear response range from 1 pg mL-1 to 50 ng mL-1, mean recovery percentage between 95.98 and 99.78% in real human serum samples, and selectivity for the cTnI biomarker.

A novel TAPP-DHTA COF cathodic photoelectrochemical immunosensor based on CRISPR/Cas12a-induced nanozyme catalytic generation of heterojunction

The level of Interleukin-4 (IL-4, a classical anti-inflammatory cytokine) in cerebrospinal fluid is in response to brain injury, infection and neurodegenerative diseases. For early prevention and treatment of related diseases, sensitive and reliable monitoring of IL-4 is urgently needed. Herein, by employing 5,10,15,20-tetrakis(4-aminophenyl)porphyrin-2,5-dihydroxyterephthaldeyde COF (TAPP-DHTA COF) as an efficient photocathode and in situ generated-polyaniline (PANI) as the signal label, we establish an immuno-HCR assisted CRISPR/Cas12a-based bioassay platform for IL-4 determination. The TAPP-DHTA COF provides an outstanding cathodic photoelectrochemical (PEC) response, profiting from the unique structural feature and high light harvesting capability. The immuno-HCR-CRISPR/Cas12a system magnifies the target signal multiply, through initiation of the unique trans-cleavage function of CRISPR/Cas12a. During the trans-cleavage process, the nanozyme that consists of MoS2 QDs@Cu nanowires (MQD@CNW) is released and a PANI layer is in situ catalytically deposited onto the porphyrin COF, leading to significantly enhanced photocurrent. As a result, an ultralow detection limit of 0.32 fg mL−1 and wide linear range of 2 fg mL−1 to 0.2 μg mL−1 are obtained. This work exemplifies a high performance 2D porphyrin-COF cathodic PEC sensing platform with a promise of biomedical applications.

Flow cell for operando X-ray photon-in-photon-out studies on photo-electrochemical thin film devices.

Background: Photo-electro-chemical (PEC) water splitting represents a promising technology towards an artificial photosynthetic device but many fundamental electronic processes, which govern long-term stability and energetics, are not yet fully understood. X-ray absorption spectroscopy (XAS), and particularly its high energy resolution fluorescence-detected (HERFD) mode, emerges as a powerful tool to study photo-excited charge carrier behavior under operating conditions. The established thin film device architecture of PEC cells provides a well-defined measurement geometry, but it puts many constraints on conducting operando XAS experiments. It remains a challenge to establish a standardized thin film exchange procedure and concurrently record high-quality photoelectrochemical and X‑ray absorption spectroscopy data that is unperturbed by bubble formation. Here we address and overcome these instrumental limitations for photoelectrochemical operando HERFD-XAS. Methods: We constructed a novel operando photo-electro-chemical cell by computer numerical control milling, guided by the materials' X‑ray and visible light absorption properties to optimize signal detection. To test the cell's functionality, semiconducting thin film photoelectrodes have been fabricated via solution deposition and their photoelectrochemical responses under simulated solar light were studied using a commercial potentiostat in a three-electrode configuration during HERFD-XAS experiments at a synchrotron. Results: We demonstrate the cell's capabilities to measure and control potentiostatically and in open‑circuit, to detect X‑ray signals unperturbed by bubbles and to fluently exchange different thin film samples by collecting high-resolution Fe K-edge spectra of hematite ( α -Fe 2O 3) and ferrite thin film ( MFe 2O 4, M= Zn, Ni) photoelectrodes during water oxidation. Conclusions: Our cell establishes a measurement routine that will provide experimental access of photo-electro-chemical operando HERFD-XAS experiments to a broader scientific community, particularly due to the ease of sample exchange. We believe to enable a broad range of experiments which acquired fundamental insights will spur further photoelectrochemical research and commercialization of water splitting technologies.

Photoelectrochemical determination of cardiac troponin I based on rod-like g-C3N5@MnO2 heterostructure.

Rod-like graphite carbon nitride@MnO2 (R-g-C3N5@MnO2) heterostructure was prepared by in situ self-anchored growth of MnO2 nanosheet on the surface of R-g-C3N5. The synthesized R-g-C3N5@MnO2 heterostructure as photoactive material exhibited excellent photoelectrochemical (PEC) performance, and the prepared heterostructure-aptamer probe displayed sensitive PEC response to cTnI. Therefore, the PEC method was developed to detect cTnI based on the R-g-C3N5@MnO2 heterostructure. It was found that the linear response to cTnI was in the range 0.001-30ng/mL under optimized conditions, and the detection limit of the proposed sensor was 0.3pg/mL. The PEC method displays stable photocurrent response up to 8 cycles and exhibited outstanding selectivity and sensitivity. The PEC method was successfully applied to detect cTnI in serum samples. The recoveries of cTnI detection in serums reach 95.5-104%, and the relative standard deviations range from 3.20 to 4.45%.

Signal-On Near-Infrared Photoelectrochemical Aptasensors for Sensing VEGF165 Based on Ionic Liquid-Functionalized Nd-MOF Nanorods and In-Site Formation of Gold Nanoparticles

The low photon energy and deep penetrating ability of near-infrared (NIR) light make it an ideal light source for a photoelectrochemical (PEC) immunosensing system. Absorption wavelengths of the metal-organic frameworks (MOFs) can be regulated by adjusting the metal ions and the conjugation degree of the ligands. Herein, an ionic liquid with a large conjugated structure was synthesized and was used as a ligand to coordinate with Nd ions to prepare Nd-MOF nanorods with a band gap of 1.26 eV. The Nd-MOF rods show a good photoabsorption property from 200 to 980 nm. A PEC platform was constructed by using Nd-MOF nanorods as the photoelectroactive element. A detachable double-stranded DNA labeled with alkaline phosphatase (ALP), which is specific to VEGF165, was immobilized onto the PEC sensing interface. After blocking unspecific active sites with bovine albumin, an NIR PEC aptasensing system was developed for VEGF165 detection. After being incubated in a mixture of VEGF165, l-ascorbic acid 2-phosphate (magnesium salt hydrate) (AAP), and chloroauric acid, the aptamers for VEGF165 were detached from the PEC aptasensing interface, thus resulting in the decrease of the charge-transfer resistance and the increase of the photocurrent response. The shedding of the aptamers also makes the ALP approach the electrode surface, thus catalyzing the reduction of AAP to produce ascorbic acid (AA). Subsequently, AA reduces in situ chloroauric acid to produce AuNPs on the Nd-MOF-based sensing interface. With the excellent conductivity and localized surface plasmon resonance effect, the AuNPs can accelerate the separation of electron-hole pairs generated from Nd-MOF nanorods, thus promoting the photoelectric conversion efficiency and achieving signal amplification. Under optimized conditions, the PEC responses were linearly related to the VEGF165 concentrations in the range of 0.01-100 ng mL-1 and exhibit a low detection limit of 3.51 pg mL-1 (S/N = 3). VEGF165 in human serum samples was detected by the NIR PEC aptasensor. Their concentrations were found to be well consistent with that obtained from ELISA. Furthermore, the PEC aptasensor demonstrated recoveries from 96.07 to 103.8%. The relative standard deviations were within 5%, indicating good accuracy and precision. The results further verify its practicability for clinical diagnosis.

Nickel-doped TiO2 and thiophene-naphthalenediimide copolymer based inorganic/organic nano-heterostructure for the enhanced photoelectrochemical urea oxidation reaction

To overcome the global challenges of energy crises and environmental threats, urea oxidation is a hopeful route to utilize urea-rich wastewater as an energy source for hydrogen production. Herein, we report an inorganic/organic type of nano-heterostructure (NHs–Ni-TiO2/p-NDIHBT) as a photoanode with excellent urea oxidation efficiency driven by visible light. This heterostructured photoanode consists of nickel (Ni)-doped TiO2 nanorods (NRs) arrays as an inorganic part and a D-A-D type organic polymer i.e p-NDIHBT as an organic part. The as-prepared photoanode was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The morphological studies of TEM confirm the coating of p-NDIHBT on Ni–TiO2 NPs (∼1 μm). The consequence of heterostructure formation on optical and photoelectrochemical (PEC) properties of photoanode were explored through photoelectrochemical responses under visible light irradiation. The photoelectrochemical activity of Ni–TiO2 and Ni–TiO2/p-NDIHBT photoanode from linear sweep voltammetry (LSV) shows the ultrahigh photocurrent density of 0.36 mA/cm2 and 2.21 mA/cm2, respectively measured at 1.965 VRHE. Electrochemical impedance spectroscopy (EIS) of both photoanodes shows a highly sensitive nature toward the urea oxidation reaction. The hybrid photoanode also exhibits high photostability, good solar-to-hydrogen conversion efficiency, and high faradaic efficiency for urea oxidation.

Synthesis of crystalline BaZrO3 thin films over preferred-oriented ZrN by a hydrothermal-galvanic couple method for photoelectrochemical evaluations

Crystalline barium zirconate (BaZrO 3 ; BZO) films which could be applied to photoelectrochemical cells and fuel cells were synthesized by a hydrothermal-galvanic couple (HT–GC) method using preferred-oriented ZrN thin-film electrodes. The HT–GC synthesis was carried out at 90°C in alkaline solutions. Substantial galvanic currents were detected without applying any external power sources throughout the synthesis. X-ray diffraction patterns reveal that BZO films with different crystallinities were achieved by such a facile synthesis. Moreover, the BZO films that grew on close-packed (200)-preferred oriented ZrN underlayer exhibited higher crystallinity and growth rates than on the (111)-preferred oriented ZrN. The obtained BZO films exhibited fast on-off photoelectrochemical responses while the BZO films with higher crystallinity over the (200)-ZrN possessed better photoelectrochemical responses. • Crystalline BaZrO3 films could be synthesized on ZrN by a hydrothermal-galvanic couple method • Crystallinity and photoelectrochemical performance of the films were tailored through ZrN • Galvanic effects were enhanced by using (200)-oriented ZrN rather than (111) oriented ZrN • Higher crystallinity of the films could be achieved by a more close-packed (200)-ZrN • Better and fast on-off photoelectrochemical responses of the films were obtained by (200)-ZrN

Photoelectrochemical Biosensor for Histone Deacetylase Sirt1 Detection Based on Polyaspartic Acid-Engaged and Triggered Redox Cycling Amplification and Enhanced Photoactivity of BiVO4 by Gold Nanoparticles and SnS2.

A photoelectrochemical (PEC) biosensor was established for histone deacetylase Sirt1 detection based on the polyaspartic acid (PASP)-mediated redox cycling amplification and Sirt1 catalysis deacetylation-triggered recognition of the deacetylated substrate peptide, using PASP as the recognition reagent. After BiVO4 was composited with gold nanoparticles and SnS2, the photoactivity of the composite was greatly enhanced due to the matched energy band structure. Under the catalysis of Sirt1 enzyme, the acetylated substrate peptide was deacetylated to obtain a positive peptide, which was recognized by negative PASP. In addition to the recognition function, PASP also played other triple roles. First, PASP interacted with the positive peptide to form a double-stranded structure, which led to the electrode interface changing from irregular to regular, resulting in an improved PEC response. Second, PASP was involved into redox cycle amplification due to its reduction to dehydroascorbic acid. Further, it was used for repeated preparation of ascorbic acid to provide electron donors. This process enhanced the PEC response. Third, based on the matched energy band with BiVO4, PASP effectively improved the photoactivity of BiVO4. With multiplex signal amplification, the PEC biosensor showed a wide linear range (1.83-1830 pM) and high detection sensitivity with a low detection limit of 0.732 pM (S/N = 3). The applicability of this method was evaluated by studying the effects of a known inhibitor of nicotinamide and the heavy metal ions of Cd2+ and Pb2+ on Sirt1 enzyme activity, and the results showed that this method not only provided a new platform for screening Sirt1 enzyme inhibitors but also provided new biomarkers for evaluating the ecotoxicological effects of environmental pollutants.

Bismuth-Based BiOBrxI1–x/Ti3C2 MXene Schottky Nanocomposites for Hg2+ Photoelectrochemical Sensors

BiOBrxI1–x/Ti3C2 Schottky heterojunction nanocomposites were prepared through a simple electrostatic adsorption and self-assembly method. The Schottky heterojunction was used as a sensitive material in the fabrication of a photoelectrochemical (PEC) sensor for mercury ion detection. Due to the large specific surface area, excellent electrical conductivity, and abundant surface chemical groups of the 2D nano Ti3C2 in the Schottky heterojunction, the in situ growth of solid solution BiOBrxI1–x on its surface enabled the nanocomposites to form a high Schottky barrier to improve the sensitivity of the PEC response. The addition of glutathione (GSH) caused it to adhere to the surface of the nanocomposites where it hindered the transfer of electrons and reducing the photocurrent by reacting with the bismuth ions on their surface through its carboxyl groups. During the Hg2+ assay, Hg2+ ions reacted to GSH on the surface of the heterojunction nanocomposites, and then captured more GSH in a solution to form a complex with 3D structure. This complex further hindered electron transfer and led to a sharp decrease in photocurrent. A trace amount of Hg2+ was detected based on the change of photocurrent, with a linear range of 1.0 × 10–10 mol/L to 1.0 × 10–6 mol/L and a detection limit of 4.21 × 10–11 mol/L. This method was one of the most sensitive methods reported for Hg2+ detection. The sensor had been applied to determine trace mercury in environmental water samples.