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.

Development of a highly sensitive colloidal gold semiquantitative method for the determination of difenoconazole residues in citrus.

Introduction: Difenoconazole (DIFE) is a common pesticide used in citrus cultivation; excessive intake can cause neurological damage to the organism, and the existing colloidal gold immunochromatographic test strips cannot meet the requirements for the detection of citrus samples. Methods: Difenoconazole test strip was prepared based on the colloidal gold immunochromatographic technique (GICT), and its application in citrus samples was investigated; with colloidal gold (CG) as the probe, the optimization of GICT parameters, and the determination of reaction method, the immunochromatographic test strips for the detection of DIFE in citrus was developed, and the limit of detection (LOD), specificity, accuracy, and stability of the test strips were verified. Results: The results showed that the visual detection limit of the prepared colloidal gold immunochromatographic test strips was 0.2 mg/kg and the quantitative range was 0.06-0.6 mg/kg, and the test strips could specifically identify DIFE and have no cross-reaction with other common triazole pesticides. The detection method established in this study was verified by the GC-MS method, and the detection results achieved good consistency (R2 > 0.98). Conclusion: The test strips developed in this study have good performance and can be used for highly sensitive detection of citrus samples.

Highly selective detection and removal of mercury ions in the aquatic environment based on magnetic ZIF-71 multifunctional composites with sufficient chlorine functional groups.

The development of both detection and removal technologies for heavy metal ions is of great importance. Most of the existing adsorbents that contain oxygen, nitrogen or sulfur functional groups can remove heavy metals, but achieving both selective detection and removal of a single metal ion is difficult because they bind to a wide range of heavy metal ions. Herein, we selected zeolite imidazolium hydrochloride framework-71 (ZIF-71) with sufficient chlorine functional groups to fabricate magnetic ZIF-71 multifunctional composites (M-ZIF-71). M-ZIF-71 had a large specific surface area, excellent water stability, and good magnetic properties, which made M-ZIF-71 conducive to the separation and recovery of adsorbents and the assembly of electrodes. M-ZIF-71 exhibited high selectivity, wide linear range (1-500 µg/L), and low detection limit (0.32 µg/L) for electrochemical detection of mercury ions (Hg2+). Meanwhile, M-ZIF-71 demonstrated rapid Hg2+ adsorption with a high capacity of 571.2 mg/g and excellent recyclability. The high selectivity for Hg2+ was attributed to the powerful affinity of highly electronegative chlorine and Hg2+. Moreover, XPS spectra demonstrated the interaction between chlorine and Hg2+. This work provides a new inspiration for applications in the targeted monitoring and removal of heavy metal pollution.

Ce/Zr-MOF with Dual Cycle Synergistic Catalysis Pathway Enabling Enhanced Peroxidase-like Performance for Wearable Hydrogel Patch Visualization Sensing Platform.

Engineering the activity of enzyme-like catalysts should be a top priority to make them superior substitutes for natural enzymes. Herein, a Ce/Zr bimetal-organic framework (Ce/Zr-MOF) was designed and synthesized by a one-pot hydrothermal method, which has enhanced performance in mimicking peroxidase (POD) than its single-metal counterparts. To further comprehend the mechanism of activity enhancement, the role of the bimetallic synergistic catalysis process in H2O2 decomposition and reactive oxygen species formation was elucidated, and the possible dual cycle synergistic catalysis pathway of bimetallic catalysis is proposed for the first time. The enhanced POD-like activity mainly depends on the introduction of Ce, which improved the conductivity and electron-transfer capability of Ce/Zr-MOF and promoted the generation of •OH. Integrated with a hydrogel substrate, a wearable all-solid-state H2O2 sensor for early diagnosis of plant health was produced. The detection limit can be as low as 3.3 µM, which is lower than that of some instrument-based colorimetric methods and has great potential in the development of visualized sensing applications. The concept of dual cycle synergistic catalysis pathway we proposed not only deepens the comprehension regarding sensing and catalytic mechanisms but also provides novel perspectives into the design of enzyme-like catalysts for extensive usage.

Coordination Construction of the Dual Superoxide Dismutase Catalytic Center Nanozyme: Synergistic Contribution of the Site, Structure, and Electron Transfer Pathway.

Superoxide dismutase (SOD) mimics are limited by a single active center, and their performance is difficult to achieve the activity level of natural SOD. Herein, we exhibit the coordination construction of different SOD active centers (Cu and Mn) and structural regulation of framework carbonization in MOFs. The obtained catalytic activity and excellent biocompatibility are comparable to Cu/Zn-SOD. The improvement of catalytic performance was attributed to the bimetallic sites' synergistic catalysis (enhancing the substrate affinity and accelerating the reaction process) on the one hand and the contribution of framework carbonization on the other hand, which not only regulate the relative position and valence of metal nodes but improve the spatial adaptability of the reaction and reduce the reaction barrier, and the increased conductivity of the framework accelerates the electron transfer process in the reaction. The excellent biocompatibility results from the fixing effect of the carbonized framework on the metal nodes. Mn/Cu-C-N2 was encapsulated in a chitosan film as an antioxidant compared with a pure chitosan film; the anthocyanin content of blueberries increased 2 times after being stored at room temperature for 7 days, and the content was 83% of the fresh blueberries, providing exciting potential for biological applications limited by the performance of SOD nanozymes.

Soft integration of a neural cells network and bionic interfaces.

Both glial cells and neurons can be considered basic computational units in neural networks, and the brain-computer interface (BCI) can play a role in awakening the latency portion and being sensitive to positive feedback through learning. However, high-quality information gained from BCI requires invasive approaches such as microelectrodes implanted under the endocranium. As a hard foreign object in the aqueous microenvironment, the soft cerebral cortex's chronic inflammation state and scar tissue appear subsequently. To avoid the obvious defects caused by hard electrodes, this review focuses on the bioinspired neural interface, guiding and optimizing the implant system for better biocompatibility and accuracy. At the same time, the bionic techniques of signal reception and transmission interfaces are summarized and the structural units with functions similar to nerve cells are introduced. Multiple electrical and electromagnetic transmissions, regulating the secretion of neuromodulators or neurotransmitters via nanofluidic channels, have been flexibly applied. The accurate regulation of neural networks from the nanoscale to the cellular reconstruction of protein pathways will make BCI the extension of the brain.

Simulation design of a binding-pocket structure of natural enzymes in MOFs for enhanced catalytic activity.

We demonstrated that the activity gap between metal-organic frameworks (Fe) and horseradish peroxidase could be bridged by simulating the binding-pocket structure and adding active centers. This customized structure promoted the activation and enrichment of substrates, and addition of gold nanoparticles led to activity superposition and synergistic enhancement.

Hierarchical Regulation of LaMnO3 Dual-Pathway Strategy for Excellent Room-Temperature Organocatalytic Oxidation Performance.

The performance-enhancing strategy of a single pathway for perovskite has been widely studied. In this work, the dual-pathway strategy of A-site Ce substitution and nitric acid selective dissolution was proposed. The catalytic oxidation performance of LaMnO3 exhibits the characteristic of hierarchical regulation, that is, a steplike improvement, which avoids the limitation of performance improvement of the single pathway. The B-site Mn with catalytic activity was in situ reconstituted on the surface to build a Mn-rich surface. The obtained sdLa0.7Ce0.3MnO3 has the advantages of good oxygen mobility, high Mn4+/Mn3+ molar ratio, and large specific surface area, and this material showed excellent catalytic oxidation performance for organics, which can realize colorimetric chemical oxygen demand detection at room temperature. Here, Ce substitution improved the oxidation capacity by improving the oxygen mobility and the ratio of Mn4+/Mn3+, and further nitric acid treatment not only accelerated the in situ reconstruction of B-site Mn but also increased the specific surface area.

Ultrasensitive photoelectrochemical aptasensor for carbendazim detection based on in-situ constructing Schottky junction via photoreducing Pd nanoparticles onto CdS microsphere.

Carbendazim (CBZ) has been widely used in agricultural production to control fruits and vegetables diseases, but it can also destroy the human endocrine system. Therefore, sensitive detection of CBZ has attracted increasing attention worldwide. In this study, Pd nanoparticles (Pd NPs) decorated on CdS microsphere (Pd NPs/CdS) was prepared by the in-situ photoreduced method, and based on the surface plasmon resonance (SPR) effect of noble metal and Schottky junction between Pd nanoparticles (Pd NPs) and CdS microsphere, the photocurrent after introducing Pd NPs is 7.7 times higher than that of bare CdS microsphere. In view of the outstanding photoelectrochemical (PEC) performance of Pd NPs/CdS and the high specificity of the aptamer, the as-fabricated PEC aptasensor for CBZ detection possesses the excellent detection performance including a broad linear ranging from 1.0 × 10-12 to 1.0 × 10-6 mol/L as a low detection limit of 3.3 × 10-13 mol/L (S/N = 3). Furthermore, the PEC aptasensor was used for determination of lettuce samples from actual agricultural products with satisfactory results.

A colorimetric biosensor for simultaneous ochratoxin A and aflatoxins B1 detection in agricultural products.

Colorimetric biosensors have been widely applied to mycotoxins testing. However, the colorimetric assay previously reported used a single color to detect one mycotoxin, and there were few reports on the simultaneous detection of multiple mycotoxins. In this work, a colorimetric biosensor for dual mycotoxins detection was developed. A Fe3O4/GO based platform for aflatoxins B1 (AFB1) detection and a Fe3O4@Au based platform for ochratoxin A (OTA) detection were fabricated. The quantification of OTA and AFB1 was respectively achieved by the release of thymolphthalein under alkaline conditions and 3,3',5,5'-tetramethylbenzidine was catalyzed by Au NPs under acidic conditions. Because of different conditions, two sensing methods didn't interfere with each other but could provide a higher detection efficiency. The detection range of AFB1 is 5-250 ng·ml-1 and that of OTA is 0.5-80 ng·ml-1. This biosensor has been successfully applied in real sample detection, which has a broad application prospect in fields of food safety.

Highly active metal-free peroxidase mimics based on oxygen-doped carbon nitride by promoting electron transfer capacity.

A heteroatom oxygen doping strategy was developed to prepare oxygen-doped carbon nitride (OCN). The performance and mechanism of its peroxidase-like activity were studied for the first time. The greatly improved peroxidase-like activity could be attributed to the promoted electron transferability.

Oxygen Vacancy Engineering in Europia Clusters/Graphite-Like Carbon Nitride Nanostructures Induced Signal Amplification for Highly Efficient Electrochemiluminesce Aptasensing.

Oxygen vacancy is an intrinsic defect in metal oxide semiconductors and has a crucial influence on their physicochemical and electronic properties. To boost the electrochemiluminescence (ECL) efficiency of the graphite-like carbon nitride (g-C3N4), the wet-chemical-calcination method was developed to introduce an oxygen vacancy in Eu-doped g-C3N4 nanostructures for the first time. The morphology and structure characterization suggest that the Eu element was present in the matrix of the europia (Eu2O3) clusters. Because of the effect of oxygen vacancy promoting catalytic activity, the doping of Eu caused a great positive shift of onset potential and large signal amplification in cathodic ECL signals compared with pure g-C3N4. Furthermore, a novel and ultrasensitive ECL aptasensor was realized with 17ß-estradiol (E2) as a prototype target by adsorption of E2 aptamer onto the Eu2O3-doped g-C3N4 (Eu2O3- g-C3N4) surface via van der Waals force. Given the specific recognition between aptamer and E2, the ECL signal decreased with the increasing concentration of E2, because the formation of E2-aptamer complex impeded the diffusion of luminophor molecules and the electrons approaching the surface of the electrode. Under the optimal cases, the as-prepared ECL aptasensor showed superior performances and also manifested outstanding selectivity toward E2. The present conceptual strategy offers a novel methodology to boost the sensitivity of the ECL sensor and promote the activity of ECL reagents.