2-aminoterephthalic Acid Research Articles

One-pot synthesis of Ni(Ⅱ)-doped UiO-66-NH2 for enhanced photocatalytic CO2 reduction to CO with efficient charge transfer

Introducing a new metal into the metal center of metal–organic framework materials (MOFs) to alter their original electron transfer pathway to improve photocatalytic performance is a promising approach at present. Here, we report a one-pot method to introduce Ni2+ into the metal-centered Zr-O clusters of UiO-66-NH2 (UN) to create a series of Ni2+-doped bimetallic materials (xNi-UN). Experimental results showed that the 0.5Ni-UN exhibited the highest photocatalytic CO2 reduction activity, with a CO yield of 9.01 µmol g-1h−1 under visible light irradiation, which was 2.46 times higher than that of UN (3.67 µmol g-1h−1). Through a number of characterization analyses, we find that the doped Ni2+ replaced the part of original metal center Zr4+ to form a bimetallic UiO-66-NH2 (Zr/Ni), which changed the energy band gap of UiO-66-NH2 and improved the charge transfer. More importantly, the introduction of Ni2+ enhanced the efficiency of interfacial charge transfer from the organic ligand (2-aminoterephthalic acid) to the Zr-O cluster, enabling a metal-to-metal charge transfer (MMCT) pathway, which exhibited higher photocatalytic CO2 to CO reduction activity.

Water sorption studies with mesoporous multivariate monoliths based on UiO-66.

Hierarchical linker thermolysis has been used to enhance the porosity of monolithic UiO-66-based metal-organic frameworks (MOFs) containing 30 wt% 2-aminoterephthalic acid (BDC-NH2) linker. In this multivariate (i.e. mixed-linker) MOF, the thermolabile BDC-NH2 linker decomposed at ∼350 °C, inducing mesopore formation. The nitrogen sorption of these monolithic MOFs was probed, and an increase in gas uptake of more than 200 cm3 g-1 was observed after activation by heating, together with an increase in pore volume and mean pore width, indicating the creation of mesopores. Water sorption studies were conducted on these monoliths to explore their performance in that context. Before heating, monoUiO-66-NH2-30%-B showed maximum water vapour uptake of 61.0 wt%, which exceeded that reported for either parent monolith, while the highly mesoporous monolith (monoUiO-66-NH2-30%-A) had a lower maximum water vapour uptake of 36.2 wt%. This work extends the idea of hierarchical linker thermolysis, which has been applied to powder MOFs, to monolithic MOFs for the first time and supports the theory that it can enhance pore sizes in these materials. It also demonstrates the importance of hydrophilic functional groups (in this case, NH2) for improving water uptake in materials.

One-step solvothermal synthesis of full-color fluorescent carbon dots for information encryption and anti-counterfeiting applications.

Multicolor fluorescent carbon dots (CDs) have received extensive attention due to their excellent fluorescence tunable performance. In this study, multicolor CDs with color tunable and high fluorescence quantum yields (QYs) were successfully prepared under the same conditions by a one-step solvothermal method using 2-aminoterephthalic acid (ATA) and Nile Blue A (NBA) as reaction reagents, achieving a wide color field coverage. Detailed studies on the relevant mechanisms have been carried out for blue, green and red CDs, indicating that the regulating mechanism of multicolor luminescence is determined by the size of the sp2 conjugated domains, which is due to the increase of particle size that causes an increase in the size of the sp2 conjugated domains, resulting in the narrowing of the band gap and the red-shift of the emission wavelength. It was found that the CDs have the advantages of simple preparation, high photostability and high quantum yield. They were used as fluorescent ink and mixed with polyvinyl alcohol (PVA) to form CD/PVA composites, which were successfully applied in the field of information encryption and anti-counterfeiting. This work provides a new strategy for the synthesis of panchromatic tunable fluorescent CDs and their application in the field of information encryption and anti-counterfeiting.

Novel nitrogen-doped carbon-coated SnSe2 based on a post-synthetically modified MOF as a high-performance anode material for LIBs and SIBs.

SnSe2 with high theoretical capacity has been identified as an emerging anode candidate for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). However, the rate performance and cycling performance of this material in practical applications are still limited by unavoidable volume expansion and low conductivity. In this work, we designed and synthesized nitrogen-doped carbon-coated SnSe2/C-N composites using 2-aminoterephthalic acid (C8H7NO4) as a nitrogen-containing compound for modification by hydrothermal and vacuum calcination methods to achieve efficient utilization of active sites and optimization of the electronic structure. The carbon skeleton inherited from the Sn-MOF precursor can effectively improve the electronic conduction properties of SnSe2. N-doping in the Sn-MOF can increase the positive and negative electrostatic potential energy regions on the molecular surface to further improve the electrical conductivity, and effectively reduce the binding energy with Li+/Na+ which was determined by Density Functional Theory (DFT) methods. In addition, the N-doped carbon skeleton also introduces a larger space for Li+/Na+ intercalation and enhances the mechanical properties. In particular, the post-synthetically modified MOF-derived SnSe2/C-N materials exhibit excellent cyclability, with a reversible capacity of 695 mA h g-1 for LIBs and 259 mA h g-1 for SIBs after 100 cycles at 100 mA g-1.

The Gore-Tex® effect in externally hydrophobic Metal–Organic Frameworks

UiO-66-NH2 ([Zr6O4(OH)4(NH2-bdc)], NH2-bdc = 2-aminoterephthalic acid) was post-synthetically modified using four strategies to improve its external hydrophobicity.

A smartphone-intergrated dual-emission fluorescent nanoprobe for visual and ratiometric detection of anthrax biomarkers

A novel dual-emission fluorescent nanoprobe based on rare-earth nanosheets was fabricated to detect 2,6-pyridine dicarboxylic acid (DPA), which is the biomarker of Bacillus anthracis. 2-amino terephthalic acid (BDC-NH2) and surfactant sodium dodecyl sulfate (SDS) were co-intercalated into layered europium hydroxide (LEuH) to prepare the organic/inorganic composite, which was delaminated to obtain the rare-earth nanosheets. The ratio detection of DPA is possible due to the antenna effect between DPA and Eu3+. The nanoprobe shows high accuracy and sensitivity due to the large specific surface area of the rare-earth nanosheets. The limit of detection (LOD) is 4.4 nM for DPA in the range of 0–20 μM. In addition, a more convenient and faster smartphone-based visual detection platform was established based on the obvious color change. This work offers an effective way for developing visual sensing platforms, which opens a new path for designing fluorescent probes with superior sensing capabilities.

Tuning the Fluorometric Sensing of Phosphate on UiO-66-NH2(Zr, Ce, Hf) Metal Nodes.

Metal-organic frameworks (MOFs) with intrinsic luminescent properties, modular structure, and tunable electronic properties, provide unique opportunities for designing target-specific molecular sensors by systematically choosing their constituent building blocks. We report a simple one-step MOF-based sensing platform for phosphate (P) detection that combines the luminescent properties of 2-aminoterephthalic acid (ATA) with the affinity of rationally selected nodes in UiO-66-NH2 to bind with P. This MOF possesses an electron-donating amine group that controls the light-harvesting characteristics of the linkers. Substituting Zr6 node with Ce6 or Hf6 results in a series of isostructural MOFs with distinct optical properties that are nonexistent in the unsubstituted MOF. We have utilized these MOFs to quantitatively measure P, using its ability to bind strongly to metal nodes inhibiting the LMCT process and altering the linker's photon emission. Using this system, detection limits of 4.5, 7.2 and 10.5 μM were obtained for the UiO-66-NH2(Ce), UiO-66-NH2, and UiO-66-NH2(Hf) respectively, adopting a straightforward single step procedure. These results demonstrate that the selection of metal nodes in a series of isostructural MOFs can be used to modulate their electronic properties and create sensing probes possessing the desired characteristics needed for the detection of environmental contaminants.

Efficient photocatalysis-Fenton for degradation of rhodamine B and inhibition of bacteria by core-shell Fe3O4 @UiO-66-NH2 nanospheres

Core-shell Fe3O4 @UiO-66-NH2 nanospheres with superior photocatalytic activity and photo-Fenton performance were synthesized using a layer-by-layer growth strategy. The synthesis involved the use of FeCl3, trisodium citrate, sodium acetate, ZrCl4, and 2-aminoterephthalic acid as raw materials, with mercaptoacetic acid serving as a modifier. Fe3O4 @UiO-66-NH2 demonstrated improved visible-light-driven photocatalytic performance in the oxidation degradation of Rhodamine B (RhB) in the presence of trace amounts of H2O2 under visible light irradiation. The Fe(II)/Fe(III) cycle was accelerated by the transfer of the photogenerated electrons (e-) from UiO-66-NH2 to Fe3O4, which in turn encouraged the Fenton reaction to produce hydroxyl radicals (•OH). With only 10 mmol/L H2O2, the removal rate of RhB approached 94% in 120 min. Furthermore, when exposed to visible light, Fe3O4 @UiO-66-NH2 exhibited 99% efficacious antibacterial activity against Escherichia coli and Staphylococcus aureus. Overall, the as-prepared Fe3O4 @UiO-66-NH2 core-shell nanospheres show promise for practical applications as photocatalysts for the degradation of organic pollutants and the inactivation of bacteria in wastewater.

Real-time intelligent detection of ethephon based on a high-throughput ratiometric fluorescent probe

Ethephon (ETH) is a common pesticide, and its overuse has resulted in a variety of health problems for humans. However, the existing ETH detection methods are tedious and time-consuming, and real-time ETH identification remains a significant difficulty. To mitigate this concern, a dual-emission ratiometric fluorescent probe Ru@ZrMOF was rationally synthesized for the detection of ETH. In the presence of ETH, the emission peak at 435 nm gradually increased, while the peak at 600 nm remained constant, accompanied by the fluorescence color change from red, pink, blue-violet to blue. The fluorescence intensity ratio (F435/F600) demonstrated two linear relations with the ETH concentration ranges at 3 − 50 μM and 50 − 500 μM, with a lowest detection limit at 1 μM. This was attributed to the formation of Zr−O−P bonds which attenuated the ligand-metal charge transfer (LMCT) process, resulting in the recovery of blue fluorescence of the ligand 2-Aminoterephthalic acid (2-APDC). To validate the practical application of the developed platform, a YOLO v5x-based WeChat applet "96 Speckles" was developed, and a 96-well plate and smartphone-embedded 3D-printed portable toolbox was designed for the real-time intelligent detection of ETH. This smart platform allows for real-time and efficient ETH analysis in various real samples including apples, pears and tomatoes.

Atomically dispersed Fe sites on hierarchically porous carbon nanoplates for oxygen reduction reaction

Developing cost-effective, robust and stable non-precious metal catalysts for oxygen reduction reaction (ORR) is of paramount importance for electrochemical energy conversion devices such as fuel cells and metal-air batteries. Although Fe-N-C single atom catalysts (SACs) have been hailed as the most promising candidate due to the optimal binding strength of ORR intermediates on the Fe-N4 sites, they suffer from serious mass transport limitations as microporous templates/substrates, i.e., zeolitic imidazolate frameworks (ZIFs), are usually employed to host the active sites. Motivated by this challenge, we herein develop a hydrogen-bonded organic framework (HOF)-assisted pyrolysis strategy to construct hierarchical micro/mesoporous carbon nanoplates for the deposition of atomically dispersed Fe-N4 sites. Such a design is accomplished by employing HOF nanoplates assembled from 2-aminoterephthalic acid (NH2-BDC) and p-phenylenediamine (PDA) as both soft templates and C, N precursors. Benefitting from the structural merits inherited from HOF templates, the optimized catalyst (denoted as Fe-N-C SAC-950) displays outstanding ORR activity with a high half-wave potential of 0.895 V (vs. reversible hydrogen electrode (RHE)) and a small overpotential of 356 mV at 10 mA cm−2 for the oxygen evolution reaction (OER). More excitingly, its application potential is further verified by delivering superb rechargeability and cycling stability with a nearly unfading charge–discharge gap of 0.72 V after 160 h. Molecular dynamics (MD) simulations reveal that micro/mesoporous structure is conducive to the rapid mass transfer of O2, thus enhancing the ORR performance. In situ Raman results further indicate that the conversion of O2 to *O2− the rate-determining step (RDS) for Fe-N-C SAC-950. This work will provide a versatile strategy to construct single atom catalysts with desirable catalytic properties.

Metal-organic framework assisted preparation of α-Fe2O3 for selective catalytic reduction of NOX with NH3

Fe-MIL-101-NH2 was prepared by solvothermal method with ferric nitrate and 2-Aminoterephthalic Acid (DBC-NH2), and Fe-MIL-101-NH2 as precursor was calcined to prepare α-Fe2O3 catalyst. The optimum synthesis condition and the NO conversion efficiency of α-Fe2O3 were systematically investigated, and its crystallinity, micro-morphology and surface acidity were characterized. The results showed that α-Fe2O3 over calcination at 400 °C for 1 h had excellent catalytic activity, SO2 tolerance, water resistance, and stability. When an initial NO concentration of 500 ppm, the gas hourly space velocity (GHSV) of 35000 h−1, and a reaction temperature of 350 °C, the NO conversion efficiency of α-Fe2O3 remained above 90 %. The crystal structure of the catalyst was α-Fe2O3 which retained the original octahedral morphology of Fe-MIL-101-NH2 and increased a lot of new pores, leading to more abundant Lewis acid sites for promoting NO conversion efficiency.

Fluorescence and absorbance dual-mode immunoassay for detection of Ochratoxin A based on 2-aminoterephthalic acid and p-nitrophenol

In this work, a dual-mode immunoassay to detect Ochratoxin A (OTA) was developed relied on p-nitrophenyl phosphate (PNPP) and 2-aminoterephthalic acid (PTA-NH2). This proposed immunoassay based on microplate immunoenzyme technique used alkaline phosphatase (ALP) as a label for forming immune complexes. The ALP was used to catalyze the dephosphorization of PNPP to generate yellow p-nitrophenol (PNP). Since the absorption wavelength of PNP overlapped with the fluorescence emission of PTA-NH2, the fluorescence of PTA-NH2 can be quenched by PNP. The color of PNP and the fluorescence of PTA-NH2 were used as double signals to detect OTA. In this dual-mode immunoassay, the limit of detection (LOD) and the linear detection range of fluorescence mode were 0.57 ng/mL (about 0.57 μg/kg) and 1.56–50.00 ng/mL (about 1.56–50.00 μg/kg), respectively. For absorbance mode, the LOD and linear range were 0.07 ng/mL (about 0.07 μg/kg) and 0.39–25.00 ng/mL (about 0.39–25.00 μg/kg), respectively. Both detection modes showed good selectivity for OTA. The recoveries rates of fluorescence mode and absorption mode in maize flours were 91.80–128.85% and 100.10–114.00%, respectively.

Dual-function sensor based on NH2-MIL-101(Fe)@Cu/CeO2 nanozyme for colorimetric and fluorescence detection of heavy metals

Heavy metal ions exhibit significant toxicity and pose threats to ecosystems and human health. Therefore, the development of sensitive detection methods is crucial. Nanozyme-based heavy metal sensors have garnered attention, yet existing nanozymes often suffer from low catalytic activity, limited functionality, and unclear mechanisms. To address these issues, this study successfully synthesized an organic-inorganic hybrid nanozyme (NH2-MIL-101(Fe)@Cu/CeO2) using doping and composite techniques, creating a dual-functional sensor. It's worth noting that in NH2-MIL-101(Fe)@Cu/CeO2, copper doping and heterojunction formation may increase oxygen vacancy concentration, promoting electron transfer. Compared to individual components like amino-terephthalic acid iron (III) metal-organic framework (NH2-MIL-101(Fe)) and copper-doped cerium dioxide (Cu/CeO2), this composite material exhibited enhanced peroxidase-like activity (oxidase-like, peroxidase-mimic, catalase-mimic, and superoxide dismutase-mimic). Particularly, NH2-MIL-101(Fe)@Cu/CeO2 displayed outstanding peroxidase-like activity, with Km values of 0.02 mM for TMB and 0.49 mM for H2O2, surpassing most nanozymes, along with high reaction rate (Vmax = 3.82 × 10−5 mM/s). Leveraging NH2-MIL-101(Fe)@Cu/CeO2's peroxidase-like behavior, TMB oxidation turned blue, inhibited by glutathione causing fading. Importantly, Hg2+ complexed with glutathione's thiol group forming GSH-Hg2+, restoring the blue color. Utilizing these properties, a colorimetric sensor for Hg2+ detection was developed. Furthermore, NH2-MIL-101(Fe)@Cu/CeO2 also exhibited remarkable fluorescence performance; Cu2+ binding with amino groups quenched fluorescence. Exploiting this phenomenon, a fluorescent sensor for Cu2+ detection was devised. Results demonstrated this dual-functional sensor's advantages: high sensitivity (LODHg2+ = 0.7 nM, LODCu2+ = 0.1 µM), strong selectivity, wide linear range (0.01 ∼ 4 µM and 8 ∼ 600 µM), and robust stability (90 % activity retained after three cycles).

The cactus bulb-shaped metal-S-C/N nanoparticles supported by highly conductive channels for efficient electrocatalytic hydrogen evolution reaction

Accelerating electron transfer and exposing active sites are key factors that could improve electrocatalytic hydrogen evolution reaction (HER). In this study, Co3S4-Ni3S2-C/N, the cactus bulb-shaped nanoparticles based on metal-organic frameworks (MOFs), were successfully prepared. The catalyst requires only 101 and 227 mV overpotential to reach current densities of 20 and 100 mA cm−2, respectively, in 1 M KOH. The high catalytic activity is attributed to the confinement effect achieved by introducing 2-aminoterephthalic acid as a precursor, allowing the catalyst to have a small particle size and fully exposed metal active sites. Moreover, the catalyst has a highly conductive metal-S-C/N channel that effectively reduces the intrinsic charge transfer resistance of the catalytic electrode, improves its conductivity, and modulates the electron density at the metal active site. Furthermore, compared to other crystal planes, the exposed (111) crystal plane of Co3S4 provides the most octahedral coordination of high spin state Co3+, which is highly catalytically active. This makes it the dominant crystal plane for catalysis. Through spatial confinement effect to limit metal sulfide particle size and introducing an organic backbone to create highly conductive metal-S-C/N channels, our study provides a general approach to developing highly active catalytic materials.

Environment-friendly organic coordination design of Z-scheme heterojunction N-BOB/BiOIO3 for efficient LED-light-driven photocatalytic and electrochemical performance

As the climate seriously changes, ecofriendly nanomaterials have attracted tremendous interest in renewable energy as photocatalysis. Herein, we designed a new green bismuth-based Z-scheme Bi2O22+ slabs coordinate with 2-aminoterephthalic acid (N-BOB)/BiOIO3 through a simple anion exchange and postsynthetic hydrothermal reaction. FTIR, XRD, FESEM and TEM were employed to characterize the functional groups, structure, and morphologies. UV-DRS revealed the difference in band energy of the N-BOB and N-BOB/BiOIO3. Toward Rh B, TC and CIP degradation tests, 1-N-BOB/BiOIO3 manifests the best photocatalytic degradation (52.3%, 63.6% and 30.2%) efficiency. Also, 1-N-BOB/BiOIO3 possesses high durability in photocatalytic reactions and can inhibit 32.3% of bacterial growth. The results indicate that the synergistic effect between surface amine groups and Z-scheme heterojunction harvests light absorption to increase solar-to-energy (STE) efficiency, accelerate the charge separation, and increases the active sites with high photoredox potential, thus improving the photocatalytic performance. ROS scavenging tests further elucidated that photogenerated holes and hydroxyl radicals play a critical role. In addition, the surface amine groups and benzene rings can be utilized for supercapacitors and other multidisciplinary applications. 0.5 N-BOB/BiOIO3/GO impressively showed 5 times higher specific capacitance than pure GO electrode. We hope this work provides new sight into designing green nanomaterials to relieve environmental pollution and leave behind a clean future for the next generation.

Carbon quantum dots modified NH2-MIL-125(Ti) acid-etching derived TiO2-based photocatalysts and efficient removal of high concentrations of dyes from wastewater under visible light

TiO2 is considered one of the most promising photocatalysts for photocatalytic treatment of dye wastewater. However, TiO2 only responds to ultraviolet light, with a small specific surface area and weak photogenerated carrier separation ability, which limit its application in the treatment of high concentration dye wastewater. In this paper, 2-amino terephthalic acid (NH2-BDC) modified TiO2 photocatalyst (NH2BDCX-TiO2) were prepared for the first time through in situ acid-etching strategy of NH2-MIL-125(Ti), and then YCQDs/NH2BDC10-TiO2 composite photocatalysts were synthesized by loading carbon quantum dots (CQDs) on its surface. The results indicated that the NH2BDCX-TiO2 photocatalyst had excellent visible light response and enhanced adsorption capacity. In addition, the successful loading of CQDs on its surface effectively enhanced the separation of photogenerated carriers and further expanded the light absorption range of the composite photocatalyst to the near-infrared region. The adsorption and photocatalytic degradation efficiency of 5CQDs/NH2BDC10-TiO2 composite photocatalyst for high concentration RhB solution (80 mg/L) reached 24.8 % and 87.1 %, respectively, which were 2.0 times and 435.5 times higher than commercial P25, respectively. Moreover, the optimum concentration of RhB solution, photocatalyst dosage and initial pH of RhB solution were also explored. Finally, based on active species capture experiments and energy band structure analysis, a possible mechanism for photocatalytic degradation of high concentration RhB solution by 5CQDs/NH2BDC10-TiO2 was also proposed. This work provided a new insight into the design of TiO2-based composite photocatalysts for the practical treatment of highly concentrated dye wastewater.

Fe-MOF-based fluorescent sensor with on/off capabilities for the highly sensitive detection of tert-butylhydroquinone in edible oils

In this work, a “turn off-on” fluorescent sensor was developed for highly sensitive determination of tert-butylhydroquinone (TBHQ) based on an Fe(III)-based metal-organic framework (Fe-MOF). An Fe-MOF with an octahedral structure was synthesized via a simple hydrothermal method using ferric chloride hexahydrate and 2-aminoterephthalic acid (NH2-BDC) as raw materials. The fluorescence of Fe-MOF is extremely weak owing to ligand-to-metal charge transfer (LMCT) and internal filtration effect (IFE). When the system contained TBHQ, the binding of TBHQ to Fe(III) inhibited the LMCT of the fluorescent ligand NH2-BDC to Fe(III), releasing the fluorescence of NH2-BDC and thus restoring the fluorescence. With this as the basis, a rapid, sensitive, and selective fluorescence sensor is developed for the detection of TBHQ. Under the optimal conditions, TBHQ showed good linearity with fluorescence intensity in the range of 0–1.5 × 102 μmol L−1 and a detection limit of 0.0030 μmol L−1 (S/N = 3). The selectivity, reproducibility, and stability of the developed Fe-MOF-based sensors are comprehensively studied. Finally, the practicality of the method is verified by examining the detection of TBHQ in soybean oil; the results are consistent with those obtained using conventional high-performance liquid chromatography.

Investigating charge transportation and photo-responsive outcome of a Schottky diode fabricated by 2-amino terephthalic acid directed supramolecular Mn(II)-metallogel

This study investigates a supramolecular metallogel formed using an ultrasonication technique and employing manganese acetate tetrahydrate as a metal salt, 2-amino terephthalic acid (ATA) as an organic gelator, and N,N′-dimethyl formamide and dimethyl sulfoxide as mixed solvents. The mechanical toughness and viscoelastic parameters of the metallogel material were well demonstrated by rheology-based experimental values of storage and loss moduli with rotational frequency, shear strain, and shear stress of the Mn(II)-metallogel (Mn-ATA). The microstructural analysis along with chemical composition were shown using field emission scanning electron microscopy and energy dispersive X-ray analysis-based elemental research. Analysis of the infrared spectrum aided in determining how Mn-ATA was formed. Electrospray ionization mass investigation of Mn-ATA demonstrated the existence of several metallogel components and their engagement in producing the metallogel structure. Different diode parameters (i.e. photosensitivity, photoconductivity sensitivity, responsivity, specific detectivity, ideality factor, barrier height, and series resistance were measured, revealing the semiconducting property of the metallogel. The current–voltage characteristics of a Mn-ATA-based thin-film type metal–semiconductor junction device demonstrated non-linear rectifying behavior, indicating Schottky diode behavior with dominating electronic-charge transport features. The device displayed an improved rectifying property under illumination, which also implied higher conductivity. The device's measured conductivity in the low-voltage domain (equivalent to ohmic behavior) was 1.03 × 10−5 and 4.12 × 10−5 Sm−1 under darkness and illumination, respectively, implying photo-responsive behavior.

Ratiometric fluorescence aptasensor for the detection of patulin in apple juice based on the octahedral UiO-66-TCPP metal-organic framework and aptamer systems

Patulin (PAT) is a potentially harmful mycotoxin to human health and is known to contaminate apple juice. In this work, we developed a ratiometric fluorescence aptasensor using tetrakis(4-carboxyphenyl)porphyrin (H2TCPP)-treated octahedral UiO-66-NH2 (defined as UiO-66-TCPP) to detect PAT. This 2-aminoterephthalic acid and H2TCPP functionalized metal-organic framework showed multiple adsorption effects (hydrogen bonding and π–π stacking) on the aptamer (Apt) and served as a quenching material. When the target PAT bound specifically to the Apt, the fluorescence of the 6-carboxyfluorescein-labeled Apt would recover, and the fluorescence of the H2TCPP ligand remained unchanged. This ratiometric fluorescence property improved the accuracy of PAT detection. Moreover, the introduction of the H2TCPP ligand enhanced the quenching efficiency of UiO-66-NH2, thus improving the sensitivity of the fluorescent aptasensor (UiO-66-TCPP vs. UiO-66-NH2: 0.0162 ng/mL vs. 1.8 ng/mL). In addition, we used UiO-66-TCPP to detect PAT in apple juice samples. This work provides a good paradigm for the construction of ratiometric fluorescence aptasensors with high sensitivity and accuracy.

A Y-shape-structured electrochemiluminescence biosensor based on carbon quantum dots and locked nucleic acid probe for microRNA determination with single-base resolution

Since microRNAs (miRNAs) are predictors of tumorigenesis, accurate identification and quantification of miRNAs with highly similar sequences are expected to reflect tumor diagnosis and treatment. In this study, a highly selective and sensitive electrochemiluminescence (ECL) biosensor was constructed for miRNAs determination based on Y-shaped junction structure equipped with locked nucleic acids (LNA), graphene oxide-based nanocomposite to enrich luminophores, and conductive matrix. Specifically, two LNA-modified probes were designed for specific miRNA recognition, that is, a dual-amine functionalized hairpin capture probe and a signal probe. A Y-shaped DNA junction structure was generated on the electrode surface upon miRNA hybridizing across the two branches, so as to enhance the selectivity. Carbon quantum dots-polyethylene imine-graphene oxide (CQDs-PEI-GO) nanocomposites were developed to enrich luminophores CQDs, and thus enhancing the ECL intensity. For indirect signal amplification, an electrochemically activated poly(2-aminoterephthalic acid) (ATA) film decorated with gold nanoparticles was prepared on electrode as an effective matrix to accelerate the electron transfer. The fabricated ECL biosensor achieved sensitive determination of miRNA-222 with a limit-of-detection (LOD) as low as 1.95 fM (S/N = 3). Notably, Y-shaped junction structures equipped with LNA probes endowed ECL biosensor with salient single-base discrimination ability and anti-interference capacity. Overall, the proposed Y-shaped ECL biosensor has considerable promise for clinical biomarker determination.