Metallointercalated-DNA Nanotubes as Functional Light Antenna for Organic Photoelectrochemical Transistor Biosensor with Minimum Background

Organic photoelectrochemical transistor based on titanium dioxide nanorods for detection of Microcystin-LR

A more efficient signal amplification strategy is needed to improve the performance of promising photoelectrochemical sensors (PEC). Organic photoelectrochemical transistor (OPECT) sensors are of growing interest in many fields, but their potential has not yet been widely exploited and remains a challenge. In this study, a novel organic photoelectrochemical transistor aptamer (OPECT) biosensor combining photoelectrochemical analysis and organic electrochemical transistor with AgI-TiO2 (AgI-TNs) as photoreactive material and target-specific DNA chain reaction hybridization as signal amplifier for microcystin-LR detection was developed. The developed sensor performs highly sensitive detection with a linear range of 0.1 fg mL-1-10 pg mL-1 and a low detection limit of 0.079 fg mL-1. The development of the biosensitive OPECT platform is a promising tool for MC-LR detection, meanwhile it can also be used to detect other contaminants in freshwater environments.

Organic photoelectrochemical transistor biosensor based on BiVO4-ZnIn2S4 material for efficient and sensitive detection of MCF-7 cells

Recently, organic photoelectrochemical transistor (OPECT) has become a very interesting biological measurement method in photoelectrochemical (PEC) bioanalysis and future bio-related applications. OPECT is expected to be a powerful tool for disease detection and early warning. Circulating tumor cells (CTCs) are generally deemed to be the dominant factor of tumor metastasis, and 90 % of cancer patients die from this metastatic disease. Therefore, there is an imminent need to develop a highly sensitive CTCs detection sensing system to improve the survival rate of cancer patients. Here, we use a DNA tetrahedrons (DNA NTH) with an aptamer at the top to immobilize on the surface of the photoelectric material to capture cells (MCF-7). Specifically, the BiVO4-ZnIn2S4 hybrid was synthesized by a simple hydrothermal method, which can effectively modulated devices with high current gain. Au NPs were directly integrated on the electrode surface to construct an OPECT photoelectric sensing platform. Subsequently, the aptamer which is thiol-functionalized (SH-Apt) was immobilized on the electrode surface. Because of the overexpression of MUC1 protein on the cell membrane, it can specifically capture MCF-7 cells. The introduction of MCF-7 cells resulted in a significant decrease in the current signal. There is a relationship between the change of photocurrent and the logarithm of MCF-7 cell concentration, which is a good linear relationship ranging from 50 to 5 × 105 cell mL-1. The obtained detection limit is 43 cell mL-1. The biosensor has high selectivity and sensitivity, and achieves sensitive detection of MCF-7.

Lattice atom-bridged chemical bond interface facilitates charge transfer for boosted photoelectric response

The construction of chemical bonds at heterojunction interfaces currently presents a promising avenue for enhancing photogenerated carrier interfacial transfer. However, the deliberate modulation of these interfacial chemical bonds remains a significant challenge. In this study, we successfully established a p-n junction composed of atomic-level Pt-doped CeO2 and 2D metalloporphyrins metal-organic framework nanosheets (Pt-CeO2/CuTCPP(Fe)), which enables the realization of photoelectric enhancement by regulating the interfacial Fe-O bond and optimizing the built-in electric field. Atomic-level Pt doping in CeO2 leads to an increased density of oxygen vacancies and lattice mutation, which induces a transition in interfacial Fe-O bonds from adsorbed oxygen (Fe-OA) to lattice oxygen (Fe-OL). This transition changes the interfacial charge flow pathway from Fe-OA-Ce to Fe-OL, effectively reducing the carrier transport distance along the atomic-level charge transport highway. This results in a 2.5-fold enhancement in photoelectric performance compared with the CeO2/CuTCPP(Fe). Furthermore, leveraging the peroxidase-like activity of the p-n junction, we employed this functional heterojunction interface to develop a photoelectrochemical immunoassay for the sensitive detection of prostate-specific antigens.

3D Z-scheme conjugated polymer/Cu2O for organic photoelectrochemical transistor bioassay

Organic photoelectrochemical transistor (OPECT) is an emerging technology studying photo-electric-biological recognition events. Here, this work reports the three-dimensional (3D) Z-scheme poly (1,4-diethynylbenzene) (pDEB)@Cu2O heterojunction as a high-efficacy photogating module and its application for OPECT bioassay. Specifically, 3D Z-scheme pDEB@Cu2O heterojunction enabled fast charge transport and ion diffusion in the system, achieving remarkable amplification capability with a current gain as high as ca. 9.6 × 103. By linking with GOx-labeled sandwich immunorecognition, the impact of GOx-generated H2O2 on the OPECT made possible the sensitive bioassay. Exemplified by carcinoembryonic antigen (CEA) as the model target, the OPECT device achieved a linear detection range spanning from 100 fg/mL to 100 ng/mL and coupled with a detection limit as low as 72 fg/mL. This work provided a generic and extensible platform for the designation of novel bioassay systems.

A split organic photophotochemical transistor/vision sensing platform based on MNZ composite and ZIF-67/CuCoO nanospheres for ultra-sensitive detection of CEA

In this study, a novel organic photophotochemical transistor (OPECT) biosensing platform was proposed for dual-mode detection of CEA. The dual-mode detecting system is achieved benefit from the exceptional photoelectric performance of MIL-53(Fe) -NH2@ZnIn2S4 (MNZ) and the peroxidase enzyme (POD) activity of ZIF-67/Cu0.76Co2.24O4 (ZIF-67/CuCoO). Ab2- ZIF-67/CuCoO probe was immobilized on a 96-well plate by enzyme-linked immunosorbent assay, which accelerated the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide and thus successfully realized visual detection of CEA. Additionally, in OPECT biosensing mode, the oxidized form of TMB (oxTMB·) serves as a consumptive agents of the electron donor AA, which cause the photocurrent change of MNZ heterojunction, leading to a decrease in the channel current of poly (ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) organic transistor. The integration of nanobiocatalysts and the OPECT system demonstrates excellent detection performance for CEA, with a detection limit as low as 3.24 fg mL-1 and expanded their prospective applications for clinical detection of nucleic acids, proteins, and other tumor markers.

Photoactive gate material-based organic photoelectrochemical transistor sensors: working principle and representative applications

Organic photoelectrochemical transistor (OPECT)-based sensors that use light-sensitive semiconductor materials as the gate have recently garnered increasing interest in various fields ranging from biological analysis to environmental monitoring. However, so far, the working principle and representative applications of OPECT sensors have not been discussed and reviewed systematically. In this review, we aim to present a comprehensive overview of the working principle and sensing mechanisms of OPECT-based sensors and various inorganic and organic photoactive gate materials used in OPECTs, with a focus on the representative applications and recent progress of these sensors in the fields of enzyme sensing, immunoassays, and nucleic acid-based sensing. Moreover, the challenges and outlooks that need to be addressed for future advancements in this field are summarized and discussed. This review will assist researchers in gaining a more comprehensive understanding and cognition of new OPECT-based sensing methods and devices.

Ultrasensitive Organic Photoelectrochemical Transistor Biosensor Based on DNA as Nanocarrier for Efficient Immobilization of Signal Probe with Pimping Background

Organic photoelectrochemical transistor (OPECT) assays are mainly focused on the improvement of photoactive materials at the gating interface, which leads to an enhanced initial signal alongside significant background noise. This phenomenon can cause considerable deviations and impose limits on target detection. In this study, we achieved sensitive and low-background detection of alkaline phospholipase (ALP) activity using single-stranded DNA (ssDNA) as a nanocarrier to effectively immobilizing CdS quantum dots (QDs) sensitizing UiO-66. Specifically, ssDNA-labeled CdS QDs could be connected to UiO-66 via Zr-O-P bonds, while sodium tripolyphosphate (STPP) interfered with the binding of CdS QD-ssDNA to UiO-66 due to an occupancy effect. The hydrolysis of STPP, catalyzed by ALP, diminished this occupancy effect, allowing for increased binding of CdS QDs-ssDNA to UiO-66 and thereby enhancing the responsive signal. The competitive dynamic between STPP and ssDNA allowed for controlled binding of CdS QDs-ssDNA photosensitizers on UiO-66, thus realizing sensitive detection of ALP. This organic integration of biological modulation and signal amplification in OPECT has led to the creation of a novel sensing platform for detecting ALP concentrations ranging from 0.005 to 100 U·L-1, and the detection limit is 0.0012 U·L-1, thus paving the way for innovative approaches to sensitively monitor ALP activity.

Photoelectrochemical transistors based on semiconducting polymers: an emerging technology for future bioelectronics

In recent years, organic electrochemical transistors (OECTs) have attracted widespread attention due to their significant advantages such as low-voltage operation, biocompatibility, and compatibility with flexible substrates. Organic photoelectrochemical transistors (OPECTs) are OECTs with photoresponse capabilities that achieve photoresponse and signal amplification in a single device, demonstrating tremendous potential in multifunctional optoelectronic devices. In this mini-review, we briefly introduce the channel materials and operation mechanisms of OECTs/OPECTs. Then different types of OPECTs are discussed depending on their device-architecture-related photoresponse generation. Following this, we summarize recent advances in OPECT applications across various fields including biomedical sciences, optoelectronics, and sensor technologies. Finally, we outline the current challenges and explore future research prospects, aiming at extending their further development and applications.

Research Progress of Biosensor Based on Organic Photoelectrochemical Transistor

In order to solve the food safety problem better, it is very important to develop a rapid and sensitive technology for detecting food contamination residues. Organic photoelectrochemical transistor (OPECT) biosensor rely on the photovoltage generated by a semiconductor upon excitation by light to regulate the conductivity of the polymer channels and realize biosensor analysis under zero gate bias. This technology integrates the excellent characteristics of photoelectrochemical (PEC) bioanalysis and the high sensitivity and inherent amplification ability of organic electrochemical transistor (OECT). Based on this, OPECT biosensor detection has been proven to be superior to traditional biosensor detection methods. In this review, we summarize the research status of OPECT biosensor in disease markers and food residue analysis, the basic principle, classification, and biosensing mechanism of OPECT biosensor analysis are briefly introduced, and the recent applications of biosensor analysis are discussed according to the signal strategy. We mainly introduced the OPECT biosensor analysis methods applied in different fields, including the detection of disease markers and food hazard residues such as prostate-specific antigen, heart-type fatty acid binding protein, T-2 toxin detection in milk samples, fat mass and objectivity related protein, ciprofloxacin in milk. The OPECT biosensor provides considerable development potential for the construction of safety analysis and detection platforms in many fields, such as agriculture and food, and hopes to provide some reference for the future development of biosensing analysis methods with higher selectivity, faster analysis speed and higher sensitivity.

Foldable paper-based photoelectrochemical biosensor based on etching reaction of CoOOH nanosheets-coated laser-induced PbS/CdS/graphene for sensitive detection of ampicillin

Timely and rapid detection of antibiotic residues in the environment is conducive to safeguarding human health and promoting an ecological virtuous cycle. A foldable paper-based photoelectrochemical (PEC) sensor was successfully developed for the detection of ampicillin (AMP) based on glutathione/zirconium dioxide hollow nanorods/aptamer (GSH@ZrO2 HS@apt) modified cellulose paper as a reactive zone with laser direct-writing lead sulfide/cadmium sulfide/graphene (PbS/CdS/LIG) as photoelectrode and cobalt hydroxide (CoOOH) as a photoresist material. Initially, AMP was introduced into the paper-based reaction zone as a biogate aptamer, which specifically recognized the target and then left the ZrO2 HS surface, releasing glutathione (GSH) encapsulated inside. Subsequently, the introduction of GSH into the reaction region and etching of CoOOH nanosheets to expose the PbS/CdS/LIG photosensitive material increased photocurrent. Under optimal conditions, the paper-based PEC biosensor showed a linear response to AMP in the range of 5.0 - 2 × 104 pM with a detection limit of 1.36 pM (S/N = 3). In addition, the constructed PEC sensing platform has excellent selectivity, high stability and favorable reproducibility, and can be used to assess AMP residue levels in various real water samples (milk, tap water, river water), indicating its promising application in environmental antibiotic detection.

Signal Modulation Induced by a Hole Transfer Layer Participant Photoactive Gate: A Highly Sensitive Organic Photoelectrochemical Transistor Sensing Platform

It is urgent to pursue appropriate gate photoactive materials for gate-to-channel signal modulation to achieve superior transconductance performances of organic photoelectrochemical transistor (OPECT) sensors. Notably, a hole transfer layer (HTL) participant CdZnS/sulfur-doped Ti3C2 MXene (S-MXene) gate was designed and developed in this work, which exhibited a remarkable signal modulation performance by up to 3 orders of magnitude. Because of the incorporation of S-MXene with an enhanced electrical conductivity as the effective HTL, the signal modulation capabilities of the CdZnS/S-MXene photoactive gate were superior to those of CdZnS and CdZnS/MXene. This incorporation inhibited the recombination of the interfacial charge and facilitated the transfer of photogenerated holes, thus enhancing the photoelectric conversion performance. This enhancement facilitated fast electron transfer with a larger effective photovoltage to augment the dedoping ability of channel ions. Based on these findings, an aptasensing platform that exhibited good performance was constructed using the proposed OPECT device, with ofloxacin as a model target and an aptamer for specific recognition. The developed OPECT aptasensor had various advantages, including a high sensitivity, good linear range (1.0 × 10-13 to 1.0 × 10-6 M), and low limit of detection (3.3 × 10-15 M). This study provided a proof-of-concept for the generalized development of HTL participant gates for OPECT sensors and other related applications.

Organic photoelectrochemical transistor based on cascaded DNA network structure modulated ZnIn2S4/MXene Schottky junction for sensitive ATP detection

Organic photoelectrochemical transistor (OPECT) biosensor is now appearing in perspective of public, which characterized by amplified the grating electrode potential by ion transport. In this study, the DNA network formed by the hybridization chain reaction (HCR) detects the target adenosine triphosphate (ATP) by adjusting the surface potential of the new heterojunction of ZnIn2S4/MXene. The formation of DNA network amplifies the detection signal of ATP. Significantly, OPECT biosensor could further amplify the signal, which calculated the gain achieved 103, which is consistent with the gain signal of the previously reported OPECT biosensor. Furthermore, the OPECT biosensor achieved a highly sensitivity detection of the target ATP, which the linear detection range is 0.03 pM-30 nM, and the detection limit is 0.03 pM, and illustrated a high selectivity to ATP. The proposed OPECT biosensor achieved signal amplification by adjusting the surface potential of ZnIn2S4/MXene through cascade DNA network, which provides a new direction for the detection of biomolecules.

Dynamics of Polyalkylfluorene Conjugated Polymers: Insights from Neutron Spectroscopy and Molecular Dynamics Simulations

The dynamics of the conjugated polymers poly(9,9-dioctylfluorene) (PF8) and poly(9,9-didodecylfluorene) (PF12), differing by the length of their side chains, is investigated in the amorphous phase using the temperature-dependent quasielastic neutron scattering (QENS) technique. The neutron spectroscopy measurements are synergistically underpinned by molecular dynamics (MD) simulations. The probe is focused on the picosecond time scale, where the structural dynamics of both PF8 and PF12 would mainly be dominated by the motions of their side chains. The measurements highlighted temperature-induced dynamics, reflected in the broadening of the QENS spectra upon heating. The MD simulations reproduced well the observations; hence, the neutron measurements validate the MD force fields, the adopted amorphous model structures, and the numerical procedure. As the QENS spectra are dominated by the signal from the hydrogens on the backbones and side chains of PF8 and PF12, extensive analysis of the MD simulations allowed the following: (i) tagging these hydrogens, (ii) estimating their contributions to the self-part of the van Hove functions and hence to the QENS spectra, and (iii) determining the activation energies of the different motions involving the tagged hydrogens. PF12 is found to exhibit QENS spectra broader than those of PF8, indicating a more pronounced motion of the didodecyl chains of PF12 as compared to dioctyl chains of PF8. This is in agreement with the outcome of our MD analysis: (i) confirming a lower glass transition temperature of PF12 compared to PF8, (ii) showing PF12 having a lower density than PF8, and (iii) highlighting lower activation energies of the motions of PF12 in comparison with PF8. This study helped to gain insights into the temperature-induced side-chain dynamics of the PF8 and PF12 conjugated polymers, influencing their stability, which could potentially impact, on the practical side, the performance of the associated optoelectronic active layer.

Dual Engine Boosts Organic Photoelectrochemical Transistor for Enhanced Modulation and Bioanalysis

Organic photoelectrochemical transistor (OPECT) has shown substantial potential in the development of next-generation bioanalysis yet is limited by the either-or situation between the photoelectrode types and the channel types. Inspired by the dual-photoelectrode systems, we propose a new architecture of dual-engine OPECT for enhanced signal modulation and its biosensing application. Exemplified by incorporating the CdS/Bi2S3 photoanode and Cu2O photocathode within the gate-source circuit of Ag/AgCl-gated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) channel, the device shows enhanced modulation capability and larger transconductance (gm) against the single-photoelectrode ones. Moreover, the light irritation upon the device effectively shifts the peak value of gm to zero gate voltage without degradation and generates larger current steps that are advantageous for the sensitive bioanalysis. Based on the as-developed dual-photoelectrode OPECT, target-mediated recycling and etching reactions are designed upon the CdS/Bi2S3, which could result in dual signal amplification and realize the sensitive microRNA-155 biodetection with a linear range from 1 fM to 100 pM and a lower detection limit of 0.12 fM.

Tailoring Charge Flow in Carbon-Defective Cu-MOF with Pd Nanoparticles: A Boost for Visible Light Organic Photoelectrochemical Transistor in Bioanalysis

The photoactive material was of significant importance in organic photoelectrochemical transistor (OPECT) bioanalysis as it influences the photoinduced voltage and the μC* product, resulting in a varying sensor sensitivity. The utilization of metal-organic frameworks (MOFs) as photoactive materials in OPECT analysis is promising, yet it remains a grand challenge due to the inherently narrow light absorption range and high electron-hole recombination rate. Herein, Pd NPs were encapsulated as electron acceptors into the Cu-MOF using a double-solvent method, followed by pyrolysis at the proper temperature. After pyrolysis, Cu-MOF transformed into a carbon defect-rich composite of CuO and Cu2O while retaining its high porosity and structural morphology. The resulting carbon defect-rich pyrolysis Cu-MOF (p-Cu-MOF) served as an active support, facilitating the separation of electrons and holes. The photoelectrons trigger the electron transfer of adjacent active metal components and the formation of a Schottky junction between Pd and the MOFs. This effect induces the electron donation from the MOFs. Moreover, Pd/pyrolysis Cu-MOF exhibits significantly higher visible light absorption, better water stability, and higher electrical conductivity compared to Cu-MOF and Pd/Cu-MOF. An OPECT sensor was fabricated by utilizing Pd/p-Cu-MOF as the photoactive material and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the channel material on an integrated laser-etched FTO. The aptamer was used as the recognition element, enabling sensitive and efficient detection of residual isocarbophos.

Piezoelectric Applications of Low-Dimensional Composites and Porous Materials

Low-dimensional (LD) materials, with atomically thin anisotropic structures, exhibit remarkable physical and chemical properties, prominently featuring piezoelectricity resulting from the absence of centrosymmetry. This characteristic has led to diverse applications, including sensors, actuators, and micro- and nanoelectromechanical systems. While piezoelectric effects are observed across zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) LD materials, challenges such as effective charge separation and crystal structure imperfections limit their full potential. Addressing these issues requires innovative solutions, with the integration of LD materials with polymers, ceramics, metals, and other porous materials proving a key strategy to significantly enhance piezoelectric properties. This review comprehensively covers recent advances in synthesizing and characterizing piezoelectric composites based on LD materials and porous materials. The synergistic combination of LD materials with other substances, especially porous materials, demonstrates notable performance improvements, addressing inherent challenges. The review also explores future directions and challenges in developing these composite materials, highlighting potential applications across various technological domains.

Photoresponsive Hydrogen-Bonded Organic Frameworks-Enabled Organic Photoelectrochemical Transistors for Sensitive Bioanalysis

A facile route for exponential magnification of transconductance (gm) in an organic photoelectrochemical transistor (OPECT) is still lacking. Herein, photoresponsive hydrogen-bonded organic frameworks (PR-HOFs) have been shown to be efficient for gm magnification in a typical poly(ethylene dioxythiophene):poly(styrenesulfonate) OPECT. Specifically, 450 nm light stimulation of 1,3,6,8-tetrakis (p-benzoic acid) pyrene (H4TBAPy)-based HOF could efficiently modulate the device characteristics, leading to the considerable gm magnification over 78 times from 0.114 to 8.96 mS at zero Vg. In linkage with a DNA nanomachine-assisted steric hindrance amplification strategy, the system was then interfaced with the microRNA-triggered structural DNA evolution toward the sensitive detection of a model target microRNA down to 0.1 fM. This study first reveals HOFs-enabled efficient gm magnification in organic electronics and its application for sensitive biomolecular detection.