Synthesis of Au nanorod-embedded and graphene oxide-wrapped microporous ZIF-8 with high electrocatalytic activity for the sensing of pesticides

Preparation of W-N-C single atom catalyst and Cu3(HHTP)2 metal-organic framework dual-decorated graphene nanoplatelet flexible electrode arrays for the rapid detection of carbendazim in vegetables

It is highly desirable to develop a low-cost and rapid detection method for trace levels of carbendazim fungicide residues, which would be beneficial for improving human health and mitigating environmental issues. Herein, isolated single tungsten atoms were implanted onto well-organized metal-organic framework (MOF)-derived N-doped carbons to form W-N-C single-site heterojunctions with ultrahigh electrocatalytic activity. The coupling of W-N-C with Cu3(HHTP)2, an electronically conductive MOF with a large surface area and porous structure, exhibited enhanced electrocatalytic performance for the oxidation of carbendazim (CBZ) when they were used for decorating graphene nanoplatelet flexible electrode arrays fabricated via template-assisted scalable filtration. A wide linear range (3.0 nM-50 μM) with an ultra-low detection limit of 0.97 nM and fast response was achieved for CBZ analysis. Moreover, the sensing platform has been utilised to monitor CBZ levels in vegetable samples with satisfactory recovery rates of 97.2-102% and a low relative standard deviation of 1.9%.

2D/1D VSe2/MWCNT hybrid-based electrochemical sensor for carbendazim quantification of environmental, food, and biological samples

For the first time the sensitive determination of carbendatim (CRB) is reported utilizing a well-designed sensing architecture based on vanadium diselenide-multiwalled carbon nanotube (VSMC). FTIR, XRD, FESEM, EDS, and EIS were employed to evaluate the sensor's structural integrity, and the results demonstrated the successful integration of nanomaterials, resulting in a robust and sensitive electrochemical sensor. Cyclic voltammetry (CV) and chronoamperometric (CA) investigations showed that the sensor best performed at pH 8.0 (BRB) with an excellent detection limit of 9.80 nM with a wide linear range of 0.1 to 10.0 µM. A more thermodynamically viable oxidation of CRB was observed at the VSMC/GCE, with a shift of 200 mV in peak potential towards the less positive side compared with the unmodified GCE. In addition, the sensor demonstrated facile heterogeneous electron transfer, favorable anti-fouling traits in the presence of a wide range of interferents, good stability, and reproducible analytical performance. Finally, the developed sensor was validated for real-time quantification of CRB from spiked water, food, and bio-samples, which depicted acceptable recoveries (98.6 to 101.5%) with RSD values between 0.35 and 2.23%. Further, to derive the possible sensing mechanism, the valence orbitals projected density of states (PDOS) for C, H, and N atoms of an isolated CRB molecule, VSe2 + CNT and VSe2 + CNT + CRB were calculated using density functional theory (DFT) calculations. The dominant charge transfer from the valence 2p-orbitals of the C and N atoms of CRB to CNT is responsible for the electrochemical sensing of CRB molecules.

"Multi-in-One" Yolk-Shell Structured Nanoplatform Inducing Pyroptosis and Antitumor Immune Response Through Cascade Reactions

Pyroptosis, a new mode of regulatory cell death, holds a promising prospect in tumor therapy. The occurrence of pyroptosis can trigger the release of damage-associated molecular patterns (DAMPs) and activate the antitumor immune response. Moreover, enhancing intracellular reactive oxygen species (ROS) generation can effectively induce pyroptosis. Herein, an integrated nanoplatform (hCZAG) based on zeolitic imidazolate framework-8 (ZIF-8) with Cu2+ and Zn2+ as active nodes and glucose oxidase (GOx) loading is constructed to evoke pyroptosis. GOx can effectively elevate intracellular hydrogen peroxide (H2O2) levels to regulate the unfavorable tumor microenvironment (TME). Cu2+ can be reduced to Cu+ by endogenous overexpressed GSH and both Cu2+ and Cu+ can exert Fenton-like activity to promote ROS generation and amplify oxidative stress. In addition, the accumulation of Cu2+ leads to the aggregation of lipoylated dihydrolipoamide S-acetyltransferase (DLAT), thus resulting in cuproptosis. Notably, the outburst of ROS induced by hCZAG activates Caspase-1 proteins, leads to the cleavage of gasdermin D (GSDMD), and induces pyroptosis. Pyroptosis further elicits an adaptive immune response, leading to immunogenic cell death (ICD). This study provides effective strategies for triggering pyroptosis-mediated immunotherapy and achieving improved therapeutic effects.

A Review on Recent Trends and Future Developments in Electrochemical Sensing

Electrochemical methods and devices have ignited prodigious interest for sensing and monitoring. The greatest challenge for science is far from meeting the expectations of consumers. Electrodes made of two-dimensional (2D) materials such as graphene, metal-organic frameworks, MXene, and transition metal dichalcogenides as well as alternative electrochemical sensing methods offer potential to improve selectivity, sensitivity, detection limit, and response time. Moreover, these advancements have accelerated the development of wearable and point-of-care electrochemical sensors, opening new possibilities and pathways for their applications. This Review presents a critical discussion of the recent developments and trends in electrochemical sensing.

Electroanalytical overview: the sensing of carbendazim

Carbendazim is a broad-spectrum systemic fungicide that is used to control various fungal diseases in agriculture, horticulture, and forestry. Carbendazim is also used in post-harvest applications to prevent fungal growth on fruits and vegetables during storage and transportation. Carbendazim is regulated in many countries and banned in others, thus, there is a need for the sensing of carbendazim to ensure that high levels are avoided which can result in potential health risks. One approach is the use of electroanalytical sensors which present a rapid, but highly selective and sensitive output, whilst being economical and providing portable sensing platforms to support on-site analysis. In this minireview, we report on the electroanalytical sensing of carbendazim overviewing recent advances, helping to elucidate the electrochemical mechanism and provide conclusions and future perspectives of this field.

MWCNTs and ZnO-based Ce-MOF nanocomposites as enhanced sensing platform for electrochemical detection of carbendazim in Chinese traditional herbs samples

A facile and novel Ce-MOF@MWCNTs@ZnO-modified glassy carbon electrode was prepared through drop coating and used for accurate and sensitive electrochemical detection of carbendazim. The modification of ZnO nanospheres and Ce-based metal-organic frameworks (Ce-MOFs), which possess vast surface/bulk ratio, large surface area, and excellent catalytic ability, provided more active sites for reaction. The combination of multi-walled carbon nanotubes endowed the modified electrode with excellent conductivity and greatly accelerated the electron transfer. The promotion of electrochemical response and the significant improvement of peak current indicated the outstanding electrocatalytic ability of the modified electrode. The oxidation peak current of carbendazim which was measured by DPV in a potential range from 0.5 to 1.0 V produced a good linear relationship in the concentration ranges 0.05-10.0 μM and 10.0-50.0 μM under  optimized experimental conditions. The detection limit was 13.2 nM (S/N = 3). The constructed electrode was successfully applied to the detection of carbendazim in Lithospermum and Glycyrrhiza uralensis real samples and exhibited satisfactory RSD (2.7-3.6% and 1.6-4.8%, respectively) and recovery (102-106% and 97.7-107%, respectively).

Monitoring of trace aquatic sulfonamides through hollow zinc-nitrogen-carbon electrocatalysts anchored on MXene architectures

Herein, we designed and fabricated hollow N-doped carbon polyhedrons with atomically dispersed Zn species (Zn@HNCPs) through a topo-conversion strategy by utilising metal-organic frameworks as precursors. Zn@HNCPs achieved efficient electrocatalytic oxidation of sulfaguanidine (SG) and phthalyl sulfacetamide (PSA) sulfonamides through the high intrinsic catalytic activity of the Zn-N₄ sites and excellent diffusion from the hollow porous nanostructures. The combination of the novel Zn@HNCPs with two-dimensional Ti₃C₂T_x MXene nanosheets resulted in improved synergistic electrocatalytic performance for the simultaneous monitoring of SG and PSA. Therefore, the detection limit of SG for this technique is much lower than those of other reported techniques; to the best of our knowledge, this is the first detection approach for PSA. Moreover, these electrocatalysts show promise for the quantification of SG and PSA in aquatic products. Our insights and findings can serve as guidelines for the development of highly active electrocatalysts for application in next-generation food analysis sensors.

ZIF-8-derived Zn, N-codoped porous carbon as a high-performance piezocatalyst for organic pollutant degradation and hydrogen production

The development of highly efficient piezocatalysts has attracted widespread attention for energy conversion and pollution abatement. This paper reports for the first time exceptional piezocatalytic properties of a Zn- and N-codoped porous carbon piezocatalyst (Zn-N_x-C) derived from the zeolitic imidazolium framework-8 (ZIF-8) for both hydrogen production and degradation of organic dyes. The Zn-N_x-C catalyst has a high specific surface area of 810.6 m²/g and retains the dodecahedron structure of ZIF-8. Under ultrasonic vibration, the hydrogen production rate of Zn-N_x-C has achieved 6.29 mmol/g/h, surpassing most recently reported piezocatalysts. Additionally, the Zn-N_x-C catalyst demonstrates a 94% degradation efficiency for organic rhodamine B (RhB) dye during 180 min of ultrasonic vibration. This work sheds new light on the potential of ZIF-based materials in the field of piezocatalysis and provides a promising avenue for future developments in the area.

A scientometric study on application of electrochemical sensors for detection of pesticide using graphene-based electrode modifiers

Pesticide testing is an important topic in environmental protection and food safety. The development of green, accurate and reliable pesticide residue detection methods is an important technical support for implementing of agricultural quality supervision. Electrochemical sensors are a very promising analytical method for pesticide detection due to their high sensitivity, speed, low cost and portability. Performance enhancement of electrochemical sensors is often accompanied by research advances in materials science. Among them, carbon material is a very important electrode material for the fabrication of electrochemical sensors. The discovery of graphene makes it the most promising candidate among carbon materials for sensor performance enhancement. The topic of this review is the use of graphene-modified electrochemical sensors for pesticide detection in the last decade. Traditional literature summaries and bibliometric analyses were used for an in-depth analysis of this topic. In addition to the introduction of different sensor types and performance comparisons, this review also parses the authors' country, keywords and publication frequency. The related research experienced rapid growth several years ago and has now reached a relatively stable stage. We also discuss the perspectives on this topic.

Recent advancements in metal-organic frameworks composites based electrochemical (bio)sensors

Metal-organic frameworks (MOFs) are a novel class of crystalline materials which find widespread applications in the field of microporous conductors, catalysis, separation, biomedical engineering, and electrochemical sensing. With a specific emphasis on the MOF composites for electrochemical sensor applications, this review summarizes the recent construction strategies on the development of conductive MOF composites (post-synthetic modification of MOFs, in situ synthesis of functional materials@MOFs composites, and incorporating electroactive ligands). The developed composites are revealed to have excellent electrochemical sensing activity better than their pristine forms. Notably, the applicable functionalized MOFs to electrochemical sensing/biosensing of various target species are discussed. Finally, we highlight the perspectives and challenges in the field of electrochemical sensors and biosensors for potential directions of future development.

Metal organic frameworks for electrochemical sensor applications: A review

Metal-organic frameworks (MOFs) are broadly known as porous coordination polymers, synthesized by metal-based nodes and organic linkers. MOFs are used in various fields like catalysis, energy storage, sensors, drug delivery etc., due to their versatile properties (tailorable pore size, high surface area, and exposed active sites). This review presents a detailed discussion of MOFs as an electrochemical sensor and their enhancement in the selectivity and sensitivity of the sensor. These sensors are used for the detection of heavy metal ions like Cd²⁺, Pb²⁺, Hg²⁺, and Cu²⁺ from groundwater. Various types of organic pollutants are also detected from the water bodies using MOFs. Furthermore, electrochemical sensing of antibiotics, phenolic compounds, and pesticides has been explored. In addition to this, there is also a detailed discussion of metal nano-particles and metal-oxide based composites which can sense various compounds like glucose, amino acids, uric acid etc. The review will be helpful for young researchers, and an inspiration to future research as challenges and future opportunities of MOF-based electrochemical sensors are also reported.

A novel electrochemical sensor based on β-cyclodextrin functionalized carbon nanosheets@carbon nanotubes for sensitive detection of bactericide carbendazim in apple juice

Carbendazim (CBZ) abuse always causes the over-standard of pesticide residues in agricultural products, which has adverse effects on human health. Herein, a novel electrochemical sensor was firstly fabricated based on the β-cyclodextrin (β-CD) functionalized carbon nanosheets@carbon nanotubes (CNS@CNT) for the CBZ determination. CNS@CNT combined large surface area of CNS and excellent electrical conductivity of CNT, which significantly enhanced the electrocatalytic performance. Moreover, β-CD possessed excellent host-gest supramolecular recognition ability, which could improve the selective recognition and enrichment capability of CBZ. Thanks to the synergistic interaction of CNS@CNT and β-CD, the β-CD/CNS@CNT/GCE sensor exhibited a low limit of detection of 9.4 nM in the linear CBZ concentration range of 0.03-30 μM. The fabricated sensor presented favorable stability, high sensitivity (30.86 μA μM^-1 cm^-2), and reliable reproducibility (RSD = 3.6%). Especially, the β-CD/CNS@CNT/GCE sensor could show pretty practical feasibility for the detection of CBZ in apple juice with recoveries of 97.1%-99.4%.

Target-Responsive Smart Nanomaterials via a Au-S Binding Encapsulation Strategy for Electrochemical/Colorimetric Dual-Mode Paper-Based Analytical Devices

Target-responsive nanomaterials attract growing interest in the application of drug delivery, bioimaging, and sensing due to the responsive releasing of guest molecules by the smart molecule gate. However, it remains a challenge to develop smart nanomaterials with simple assembly and low nonspecific leakage starting from encapsulation strategies, especially in the sensing field. Herein, Au nanoclusters (Au NCs) were first grown on porous carbon derived from ZIF-8 (PCZIF) to be employed as nanocarriers. By employing the Au NCs as linkers and aptamer (Apta) double-strand hybrids (target Apta and SH-complementary DNA) as capping units, we reported the novel target-responsive nanomaterials of Apta/Au NCs-PCZIF/hemin through Au-S binding encapsulation for sensing assays. The Au-S binding encapsulation strategy simplified the packaging procedure and reduced non-target responsive leakage. As a proof, ochratoxin A (OTA) as a model target participates in the double-strand hybrid competitive displacement reaction and triggered Apta conformation switches from a coil to a G-quadruplex structure accompanied by the dissociation of the gatekeeper. Simultaneously, the released hemin can initiate a self-assembly to form G-quadruplex/hemin DNAzyme. Interestingly, owing to DNAzyme providing electron transfer mediators and peroxidase-like activity, we proposed an electrochemical/colorimetric dual-mode paper-based analytical device (PAD) that provided self-verification to enhance reliability and accuracy, benefiting from independent signal conversion and transmission mechanism. As a consequence, the proposed dual-mode PAD could achieve sensitive electrochemical detection and visual prediction of OTA in the range of 1 pg/mL to 500 ng/mL and 50 pg/mL to 500 ng/mL, respectively. The electrochemical detection limit for OTA was as low as 0.347 pg/mL (S/N = 3). We believe that this work provides point-of-care testing (POCT) tools for a broad spectrum of applications.

Elucidating the roles of oxygen functional groups and defect density of electrochemically exfoliated GO on the kinetic parameters towards furazolidone detection

Using electrochemically exfoliated graphene oxide (GO)-modified screen-printed carbon electrodes for the detection of furazolidone (FZD), a nitrofuran antibiotic, was explored. In this study, we designed some GO samples possessing different oxygen functional group content/defect density by using ultrasonic irradiation or microwave techniques as supporting tools. The difference in physical characteristics of GO led to the remarkable change in kinetic parameters (electron transfer rate constant (k_s) and transfer coefficient (α)) of electron transfer reactions at K₃/K₄ probes as well as the FZD analyte. Obtained results reveal that the GO-ultrasonic sample showed the highest electrochemical response toward FZD detection owing to the increase in defect density and number of edges in the GO nanosheets under ultrasonic irradiation. The proposed electrochemical nanosensor enabled the monitoring of FZD in the linear range from 1 μM to 100 μM with an electrochemical sensitivity of 1.03 μA μM⁻¹ cm⁻². Tuning suitable electronic structures of GO suggests the potentiality of advanced GO-based electrochemical nanosensor development in food-producing animal safety monitoring applications.

In this study, we have investigated the role of changes in the microstructure of graphene oxide (GO) on the analytical kinetic parameters of GO-based electrochemical sensors for detection of furazolidone (FZD) antibiotic drug.

Electrochemical characterization of and theoretical insight into a series of 2D MOFs, [M(bipy)(C4O4)(H2O)2]·3H2O (M = Mn (1), Fe (2), Co (3) and Zn (4)), for chemical sensing applications

The electrochemical sensing applications of a series of water-stable 2D metal–organic framework (MOF)-modified screen-printed carbon electrodes (SPCEs) are reported. The MOF materials in this study are [M(bipy)(C₄O₄)(H₂O)₂]·3H₂O, in which bipy = 4,4′-bipyridine and M = Mn, Fe, Co and Zn. The MOF materials are characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), showing that the MOFs have a layer-by-layer rod structure with a smooth surface. We use the nitrofurazone molecule as a probe to investigate the influence of the metal ions of MOFs on electrochemical sensing ability. Cyclic voltammetry demonstrated that the Mn-MOF electrode of interest delivered stronger signals than that of other electrodes. Through first-principles calculations, we also revealed that the change in the spin polarization of divalent metal ions passing from the free ion state to the MOF environment appeared to be significantly correlated with the enhancement in the peak response current. The theoretical and experimental results consistently indicate that Mn-MOF has the smallest bandgap and good sensitivity among these MOF materials. Accordingly, we proposed a simple model to illustrate this observation and disclosed the importance of the electron configuration of the transition metal constructing the MOF materials used in improving electrochemical sensing applications.

Framework-to-metal charge transfer of the MOF materials results in enhancing electrochemical sensing ability to nitrofurazone.

In situ growth of ZIF-8 on gold nanoparticles/magnetic carbon nanotubes for the electrochemical detection of bisphenol A

We herein report a facile and scalable strategy for the fabrication of a metal-organic framework (MOF) based composite by in situ growing ZIF-8 on gold nanoparticle (AuNP) loaded magnetic carbon nanotubes (mCNTs). AuNPs were firstly loaded on PEI (polyethylenimine) modified mCNTs by electrostatic forces, and then AuNPs/mCNTs were encapsulated into the ZIF-8 frame through in situ self-assembling of zinc ions and 2-methylimidazole. The morphology, spectroscopy and structural properties of the AuNP/mCNT@ZIF-8 nanocomposites were systematically characterized. The conductivity-strain tests revealed that the in situ insertion of AuNPs/mCNTs in ZIF-8 could not only shorten the electron transfer distance between active sites and mCNTs, but also increase the dispersion of mCNTs, which would benefit the electron and mass transfer. Besides, by adopting the AuNP/mCNT@ZIF-8 nanocomposite-modified glassy carbon electrode (GCE) as the working electrode, a novel electrochemical sensor was successfully developed for the detection of bisphenol A (BPA). A linear range of BPA detection from 1 μM to 100 μM with a limit of detection of 690 nM was favorably obtained. Moreover, the developed sensor exhibited satisfactory reproducibility and superior stability with excellent anti-interference ability, and was successfully applied in the detection of BPA in real samples.

Metal-organic framework for the extraction and detection of pesticides from food commodities

Pesticide residues in food matrices, threatening the survival and development of humanity, is one of the critical challenges worldwide. Metal-organic frameworks (MOFs) possess excellent properties, which include excellent adsorption capacity, tailorable shape and size, hierarchical structure, numerous surface-active sites, high specific surface areas, high chemical stabilities, and ease of modification and functionalization. These promising properties render MOFs as advantageous porous materials for the extraction and detection of pesticides in food samples. This review is based on a brief introduction of MOFs and highlights recent advances in pesticide extraction and detection through MOFs. Furthermore, the challenges and prospects in this field are also described.

Introducing reticular chemistry into agrochemistry

For survival and quality of life, human society has sought more productive, precise, and sustainable agriculture. Agrochemistry, which solves farming issues in a chemical manner, is the core engine that drives the evolution of modern agriculture. To date, agrochemistry has utilized chemical technologies in the form of pesticides, fertilizers, veterinary drugs and various functional materials to meet fundamental demands from human society, while increasing the socio-ecological consequences due to inefficient use. Thus, more useful, precise, and designable scaffolding materials are required to support sustainable agrochemistry. Reticular chemistry, which weaves molecular units into frameworks, has been applied in many fields based on two cutting-edge porous framework materials, namely metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs). With flexibility in composition, structure, and pore chemistry, MOFs and COFs have shown increasing functionalities associated with agrochemistry in the last decade, potentially introducing reticular chemistry as a highly accessible chemical toolbox into agrochemical technologies. In this critical review, we will demonstrate how reticular chemistry shapes the future of agrochemistry in the fields of farm sensing, agro-ecological preservation and reutilization, agrochemical formulations, smart indoor farming, agrobiotechnology, and beyond.

Metal Organic Framework steered electrosynthesis of anisotropic gold nanorods for specific sensing of organophosphate pesticides in vegetables collected from the field

The uncontrolled use of organophosphate (OP) group of pesticides has led to their accumulation in food and vegetables, causing major health issues. Hence, the development of a reliable sensor is imperative for the detection of neurotoxic organophosphates (OP). In the present study, we have intertwined the interfaces of a Metal Organic Framework (MOF), MOF-directed rapid electrochemically grown gold nanorods (aAuNR), cysteamine (Cys) functionalization, and the neurotransmitter acetylcholinesterase (AChE) to fabricate a novel electrochemical bioprobe AChE/Cys/aAuNR/MOF/ITO for sensing OP pesticides with an ultra-low detection limit of 3 ng L-1 over a linear range of 30 to 600 ng L-1. Prior to sensing, in silico docking studies were employed for tracking the structural aspects of the molecular recognition of specific OP as potential inhibitors. The sensor can quantify residues of sprayed OP (chlorpyrifos, malathion, parathion, methyl parathion, ethion) in field vegetables (Abelmoschus esculentus, Solanum melongena, Capsicum annuum, Momordica charantia Linn) using a single calibration curve designed using chlorpyrifos, and the results were validated via gas chromatography-electron capture detector (GC-ECD) measurements. The inhibition rate kinetics of structurally different OP (chlorpyrifos, malathion, methyl parathion) were studied via the bioprobe and further validated using the standard Ellman method, confirming the practical applicability of the sensor for the detection of a specific group of OP. The bioprobe AChE/Cys/aAuNR/MOF/ITO offers good stability, specificity, and anti-interference properties for the detection of OP in real samples.

Facile synthesis of Vulcan XC-72 nanoparticles-decorated halloysite nanotubes for the highly sensitive electrochemical determination of niclosamide

We report a scalable and controllable ultrasound-assisted strategy for the preparation of Vulcan XC-72 nanoparticles-decorated halloysite nanotubes (HNTs@VXC-72), which was applied to modify glassy carbon electrode (GCE) for the highly sensitive electrochemical determination of niclosamide (NA). For the HNTs@VXC-72 nanocomposite, VXC-72 nanoparticles with excellent electrical conductivity and good dispersing property contributed to the formation of the interconnected conductive network; HNTs possessed good adsorption performance and promoted the electrochemical redox reaction. The research results showed that the combination of VXC-72 nanoparticles and HNTs produced the effect of synergistic enhancement. The HNTs@VXC-72/GCE sensor could show a relatively low detection limit of 3.28 nM in the great linear NA concentration range of 0.01-1 µM. When used for the NA determination in food samples, the HNTs@VXC-72/GCE sensor exhibited good practical feasibility with low RSD and acceptable recoveries, which provided a promising NA determination approach to ensure food safety.

Recent advances in metal-organic frameworks for pesticide detection and adsorption

The large-scale use of pesticides such as organophosphate pesticides (OPPs) and organochlorine pesticides (OCPs) has led to serious environmental problems worldwide, and their high toxicity could cause serious damage to human health. It is crucial to remove and track them precisely in the environment and food resources. As novel nanomaterials, metal-organic frameworks (MOFs) have attracted significant attention in the fields of adsorption and luminescence sensing due to their rich topology, tunable pore size and shape, high surface area, and abundant active sites. Luminescent metal-organic frameworks (LMOFs) have sprung up as great potential chemical sensors to detect pesticides with fast response, high sensitivity, high selectivity and easy operation. Therefore, in this highlight, we focus on recent progress of MOFs in sensing and adsorbing pesticides, as well as in the possible mechanism of sensing, so as to attract more attention to pesticide detection and adsorption.

Synthesis of a CdS-decorated Eu-MOF nanocomposite for the construction of a self-powered photoelectrochemical aptasensor

A composite of CdS nanoparticles and a europium metal organic framework (Eu-MOF) (CdS/Eu-MOF) was synthesized. The unique properties of MOFs help to improve the photoelectrochemical (PEC) properties of CdS by reducing charge carrier recombination and utilizing a broader spectrum for light harvesting. Under visible light illumination, the photocurrent of the CdS/Eu-MOF composite modified electrode was about 2.5-fold higher than that of the CdS modified electrode. When an ampicillin (AMP)-binding aptamer was immobilized on the CdS/Eu-MOF modified electrode as a recognition element, a self-powered PEC aptasensor exhibiting a specific photocurrent response to AMP was constructed. Several experimental conditions such as the ratio of CdS to MOF, the coating amount of the CdS/Eu-MOF suspension and the concentration of the aptamer were studied. Under optimum conditions, the photocurrent of the developed sensor was linearly related to the logarithm AMP concentration in the range of 1 × 10-10 to 2 × 10-7 M, with a detection limit (3S/N) of 9.3 × 10-11 M. Moreover, this sensor exhibited excellent selectivity, good repeatability and desirable stability. It was successfully applied to the detection of AMP in lake water and milk samples.