Tetramethylbenzidine Research Articles

Core-shell structured carbon nanofiber-supported bristlegrass-like conductive metal‐organic framework Cu3(HHTP)2 nanorod arrays for electrochemical and colorimetric dual-mode detection of dopamine in serum

Dopamine (DA) is a central neurotransmitter that plays a crucial role in human metabolism. Its precise detection is of great importance in disease diagnosis. Compared with single-signal detection methods, colorimetric and electrochemical dual-signal outputs can self-validate the measured data and counteract interference effects, which is expected to provide more reliable detection results. In this paper, carbon nanofiber-supported 3D bristlegrass-like π-conjugated conducting metal–organic frameworks (cMOF) Cu3(HHTP)2 nanorod arrays (Cu3(HHTP)2 NRAs/CNF) catalyst with core–shell structure are synthesized by electrospinning and solvothermal reaction. The obtained catalyst possesses remarkable peroxidase-like activity which can catalyze the colorless 3,3′,5,5′ −tetramethylbenzidine (TMB) to blue oxTMB. The mechanism study showes that ·OH radicals are the main active substances. Meanwhile, the core–shell structure between π-conjugated cMOF and CNF can effectively inhibit the aggregation of Cu3(HHTP)2 nanorods and generate more catalytic active sites, resulting in strong electrocatalytic activity of Cu3(HHTP)2 NRAs/CNF. As a result, a novel dual-mode sensor based on colorimetric and electrochemical are constructed for detecting dopamine (DA) with a good linear relationship ranging from 2.5-60 μM and 0.1–106 μM, and the limit of detection (LOD) are 0.27 μM and 10.1 nM (S/N=3), respectively. This study opens up a new idea for the application of cMOF peroxidase-like enzyme in sensing field.

Fluorescent Iron-Doped Polymer Dot Nanozyme-Based Cascade System for Dual-Mode Detection of Acetylcholinesterase Activity and Its Inhibitors.

The advancement of acetylcholinesterase (AChE) activity and its inhibitor assays is crucial for clinical diagnosis, drug screening, and environmental monitoring. A nanozyme-mediated cascade reaction system could offer promising prospects for a wide range of applications in such biosensing; however, the creation of nanozyme catalysts with diverse functionalities remains a significant challenge. Herein, we have proposed a multifunctional iron-doped polymer dots (Fe-PDs) nanozyme possessing excellent fluorescence and peroxidase (POD)-mimicking activity. Notably, the Fe-PDs nanozyme is capable of catalyzing H2O2 to produce a series of reactive oxygen species, which can simultaneously quench the fluorescence of Fe-PDs and induce a chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB), enabling the dual-mode detection of H2O2 through both fluorescence turn-off and absorbance turn-on signals. Furthermore, by integrating acetylcholine (ACh) and choline oxidase (ChOx), we have developed a three-enzyme (AChE-ChOx-POD) cascade-based fluorometric and colorimetric dual-mode sensing platform for monitoring AChE activity and its inhibitors. The sensitive and convenient dual-mode sensor has achieved low limits of detection with 0.5 mU/mL (fluorometry) and 0.014 mU/mL (colorimetry) for AChE, respectively, which are superior to the traditional Ellman's assay. More significantly, this sensor can also be extended to detect the reversible and irreversible inhibitors of AChE, such as tacrine (IC50 = 23.3 nM) and carbaryl (LOD = 0.8 nM). We firmly believe that this innovative dual-mode nanozyme-involved multienzyme cascade system-based sensing strategy will stimulate further exploration and serve as a versatile and practical tool for biochemical sensing applications.

In Situ Formed 3,3',5,5'-Tetramethylbenzidine-Cu(I/II) Charge-Transfer Complex Intermediates Promoting Colorimetric Assay of Cr6.

Developing a synthesis-free, multifunctional, and effective colorimetric assay system based on 3,3',5,5'-tetramethylbenzidine (TMB) oxidation is attractive yet challenging. Herein, we established a synergetic Cu2+/Cr6+-promoting strategy for TMB-based colorimetric detection of Cr6+. By introducing Cu2+, critical TMB·+···Cu(I/II)···TMB charge transfer complex (TMC) intermediates were in situ formed to reduce the activation energy of TMB oxidation, thereby accelerating Cr6+-mediated TMB oxidation. TMC intermediates also played a pivotal role in H2O2-participated TMB oxidation, clarifying the secondary responsibility of reactive oxygen species frequently caused by Fenton-like reactions. Leveraging the synergetic capacity between Cu2+ and Cr6+ for TMB oxidation, we demonstrated sensitive and specific colorimetric detections for Cr6+ with a limit of detection of 0.006 μM. With its convenient operation and rapid responsiveness, this strategy successfully enabled the practical detection of Cr6+ in real water samples. This work not only enhances the understanding of the internal acceleration mechanism in colorimetric sensing but also provides valuable opportunities to advance synthesis-free detection platforms.

Sensitive colorimetric detection of glutathione in human serum based on peroxidase-like activity of chitosan-stabilized gold nanoparticles.

Acolorimetric sensor for the rapid and sensitive detection of GSH was developed. The hydrothermal method was utilized to synthesize chitosan-stabilized gold nanoparticles (CS-AuNPs). The synthesized CS-AuNPs were characterized by UV-vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffractograms (XRD), and Fourier transform infrared spectroscopy (FTIR). The CS-AuNPs arewell-dispersed and possess aspherical shapewith an average particle size of 10.05 ± 2.26nm in aqueous solution. Theyshow an intrinsic peroxidase-like activity, which could efficiently catalyze the decomposition of H2O2 to produce •OH radicals. These radicals then oxidized 3, 3´, 5, 5´-tetramethylbenzidine (TMB), resulting in the formation of the blue oxidizedproduct oxTMB, observed a visible color change (from colorless to blue), and oxTMB had an obvious absorption peak at 652nm. The presence of GSH could inhibit the peroxidase-like activity of CS-AuNPs, thereby reducing the formation of oxTMB. The solution's blue hue underwent a reduction in absorption intensity. Based on this fact, a novel and sensitive colorimetric sensor for detection of GSH was constructed. Under optimal conditions, the results of detection had an excellent linear relationship between the concentration of GSH and ∆A within the range 0.5 ~ 50.0 × 10-6mol/L. The limit of detection (LOD) for GSH was 2.10 × 10-7mol/L, which was much lower than those in most previous works. Furthermore, for detection in real human serum samples, the recoveries of GSH and the relative standard deviations (RSD) in the serum were in the range 98.40 ~ 103.32% and 1.85 ~ 3.54%, respectively. Thus, this visual colorimetric method has good precision and can be used for GSH detection in practical applications, promising in the fields of bioanalysis and illness diagnostics.

Janus Separation-Sensing Membrane Hosted with Enzyme@MOF Nanoreactor for Real-Time Blood Sensing.

Plasma separation, rich in biomarkers crucial for diagnosis, is conventionally achieved via high-speed centrifugation, a method hindered by its blood usage, lengthy processes, and complex operations, which delays detection. We introduced a novel real-time blood sensing method based on a Janus membrane and enzymes @MOFs. Asymmetric driving of the janus membrane can realize spontaneous separation of plasma and prevent hemolysis during direct separation. Glucose oxidase (GOx), uric acid oxidase (UOx) and horseradish peroxidase (HRP) were encapsulated in a hydrophilic organometallic framework (MOFs) to construct an enzyme cascade nanoreactor. Embedding enzyme in hydrophilic MOFs not only retains the natural conformation of free enzyme but also improves the brittleness of enzyme, endows MOFs with new biological functions, and expands its sensing application. Using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogen and a custom app for color interpretation, we achieved real-time visualization of glucose (Glu) and uric acid (UA) at a 50 μM limit. The system accurately analyzed serum samples, matching commercial kits and showing promise for portable, personalized diagnostics.

Sensitive colorimetric detection of heparin using reverse modulation of peroxidase- and oxidase-mimetic activities in Fe3O4@PDA@MnO2 nanocomposites

Heparin, a widely studied glycosaminoglycan, plays crucial roles in the regulation of various physiological and pathological processes. Therefore, it's important to develop highly selective and sensitive methods for convenient monitoring of heparin levels in biological systems. We report the design and synthesis of Fe3O4@PDA@MnO2 nanoparticles (FPM-NPs), which exhibit dual enzymatic activities, enabling quantitative detection of heparin. The FPM-NPs feature a unique tri-layer spherical shell structure, possessing both peroxidase-like and oxidase-like activities, and catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence or absence of H2O2. Remarkably, upon co-incubated with heparin, the oxidase activity of FPM-NPs decreases, while the peroxidase activity increases. By leveraging these dual enzymatic properties of FPM-NPs, a highly sensitive and specific colorimetric detection of heparin is achieved, with a detection limit reaching 6.51 nM and a good linear response to quantify heparin ranging 10–800 nM. Additionally, the developed FPM-NPs are successfully applied to measure heparin in fetal bovine serum samples. We also extend this detection method to a paper-based chip, enabling portable detection of heparin through grayscale analysis of mobile phone photographs. The multi-nanozyme-based heparin detection approach provides a new perspective for future research on expanding the application of nanocomposite materials in biomedical detection and analysis.

Cu-MoOx-based nanozyme with enhanced peroxidase like activity for quinolone antibiotics detection

The abuse of antibiotics has seriously threatened human health and living environment. Nevertheless, the detection of quinolones is currently mainly performed by high-cost and cumbersome means, such as High-Performance Liquid Chromatography (HPLC). Herein, we reported a novel method based on copper-doped MoOx nanoparticles (Cu-MoOx NPs) with peroxidase-like enhancement activity for the easy preparation, sensitive and rapid visualization of quinolone detection. Cu-MoOx NPs can make the chromogenic substrate 3,3′,5,5′-Tetramethylbenzidine (TMB) change from colorless to blue. Moreover, the addition of quantitative quinolone antibiotics can significantly accelerate the TMB oxidation reaction. Based on this phenomenon, a colorimetric method for detecting quinolone antibiotics was established with a good linear relationship ranging from 1 × 10−6 M to 1.3 × 10−4 M, and the detection limit was 0.310 μM for ciprofloxacin (CIP) and 0.520 μM for levofloxacin (LVFX). Furthermore, the mechanism was also explored, and the results showed that the peroxidase-like activity of Cu-MoOx NPs was probably derived from the generated OH, 1O2, oxygen vacancies and partially reduced Cu+, and on the other hand was derived from quinolone antibiotics and nanozymes electrostatic interaction between them.

Ferroelectric BaTiO3 nanoparticles as peroxidase mimics for colorimetric detection of glutathione S-transferase at physiological pH

The long-standing challenges in peroxidase-mimicking nanozymes catalysis lie in their generally lower catalytic activity in comparison to natural enzymes, as well as only exhibiting specific activities within acidic environments. Herein, BaTiO3 nanoparticles (BTO NPs) operated optimally at a physiological pH and exhibited excellent peroxidase-like activity with the catalytic constant (Kcat) up to 1.99×104 s⁻1 and 9.41×103 s⁻1 for 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2 substrate, respectively, which is fourfold and twofold that of horseradish peroxidase (4.00×103 s⁻1 and 3.48×103 s⁻1). Mechanism studies suggested that BTO NPs generated internal electric fields due to spontaneous polarization, which drove free carrier separation in different directions. The free carriers led to redox reactions with H2O2 and dissolved oxygen, which produced a variety of reactive oxygen species (ROS), such as•OH, 1O2 and O2•⁻, thus effectively oxidizing the chromogenic substrates. Furthermore, due to its strong reducing property, glutathione (GSH) can inhibit the oxidation of TMB. Conversely, glutathione S-transferase (GST) reduces the inhibition of GSH by facilitating the reaction between GSH and 1-chloro-2,4-dinitrobenzene. Ultimately, a colorimetric method was established for the detection of GST at physiological pH, with a linear range of 0.025 − 5.0 U·L⁻1. This work demonstrated the great promise of screening novel peroxidase mimics with super activities from ferroelectric materials.

Cu2O nanoparticles with morphology-dependent peroxidase mimic activity: a novel colorimetric biosensor for deoxynivalenol detection.

Different morphological Cu2O nanoparticles including cube, truncated cube, and octahedron were successfully prepared by a selective surface stabilization strategy. The prepared cube Cu2O exhibited superior peroxidase-like activity over the other two morphological Cu2O nanoparticles, which can readily oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to form visually recognizable color signals. Consequently, a sensitive and simple colorimetric biosensor was proposed for deoxynivalenol (DON) detection. In this biosensor, the uniform cube Cu2O was employed as the vehicle to label the antibody for the recognition of immunoreaction. The sensing strategy showed a detection limit as low as 0.01ng/mL, and a wide linear range from 2 to 100ng/mL. Concurrently, the approximate DON concentration can be immediately and conveniently observed by the vivid color changes. Benefiting from the high sensitivity and selectivity of the designed biosensor, the detection of DON in wheat, corn, and tap water samples was achieved, suggesting the bright prospect of the biosensor for the convenient and intuitive detection of DON in actual samples.

Colorimetric detection of benzoate in the beverage using the peroxidase-like properties of single-atom Fe-N-C nanozymes

Overuse of benzoate as a preservative is bad for human health. Therefore, we need to achieve quantitative detection of benzoate. Colorimetric nanozyme sensors have garnered significant interest owing to their exceptional efficacy and affordability. In this article, Fe-N-C dodecahedral nanozymes with superior peroxidase-like catalytic activity are prepared using ZIF-8 as a precursor. Therefore, we construct a colorimetric sensor for benzoate detection with a detection limit of 0.33 μM through integrating the inhibitory impact of benzoate on D-amino acid oxidase activity with the Fe-N-C-catalyzed 3,3′,5,5′-tetramethylbenzidine (TMB)–H2O2 system, and this reaction is completed within 10 min. It is noteworthy that a recovery rate of 96.8–109 % has been attained for the detection of benzoate in beverages.

Performance-complementary colorimetric/electrochemical bimodal detection of Hg2+ based on analyte-accelerated peroxidase-mimicking activity of GO-AuNPs

As a highly toxic heavy metal pollutant, mercury ions cause substantial risks to the environment and human health, and developing high-performance and convenient analytical approaches becomes quite important. Here we propose a performance-complementary colorimetric/electrochemical dual-mode Hg2+ sensing method based on the analyte accelerating the peroxidase-mimetic activity of gold nanoparticles (AuNPs) loaded on graphene oxide (GO). The GO-AuNPs composite was readily fabricated via mechanically mixing AuNPs and GO with controllable proportions, exhibiting a weak peroxidase-like activity in catalyzing the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB). Upon the introduction of Hg2+, it combined with AuNPs rapidly, significantly enhancing the peroxidase-mimicking activity of GO-AuNPs. By capturing the color signal of the generated blue oxTMB and the electro-oxidation response of residual TMB, a “turn-on” colorimetric and “turn-off” electrochemical bimodal method was established for Hg2+ measurement, providing a linear range of 10–60 μg/L in colorimetric detection and 0.001–20 μg/L in electrochemical analysis. Different from common bimodal assays mainly improving detecting reliability due to their cross-validation ability, our dual-mode sensor exhibits the unique feature of complementary sensitivity and detection range, thus enabling its flexible use in analyzing different levels of the target in a broad scope with no requirement for sample enrichment and dilution.

Enhancing colorimetric efficiency: nanozyme-activated peroxymonosulfate for in situ 3-aminophenol detection.

Anovel colorimetric approach specifically designed to effectively identify the presence of 3-aminophenol (3-AP) in environmental water isintroduced. Briefly, a nitrogen-doped carbon-supported cobalt nanozyme (Co@CN-1) was synthesized and utilized to improve the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of peroxymonosulfate (PMS). Comparative catalytic reactions confirmed that the performance of PMS as an activator exceeds that of hydrogen peroxide catalytically by a factor of 3.5. The catalytic reaction parameters underwent optimization, further resulting in the derivation of a linear detection equation for 3-AP, expressed as inhibition rate (IR%) = 3.35[3-AP]-4.36 (0-20μM, R2 = 0.994) and IR% = 1.43[3-AP] + 31.87 (20-36μM, R2 = 0.992), with the limit of detection (LOD) of 2.84μM. The linear relationship between 3-AP concentration and the conversion of color to grayscale value (GSV) was established by smartphones, expressed as GSV = 1.28[3-AP] + 147.10 (R2 = 0.972). Density functional theory calculations revealed that Co acts as the preferred active site for donating electrons in PMS activation. This work provides a rapid and accurate approach for monitoring 3-AP concentration, enabling real-time analysis and potentially contributing to environmental and ecological studies.

Nitrogen-doped polydopamine manganese nanoparticles with excellent oxidase-like activity for ultrafast detection of glutathione at room temperature

Glutathione (GSH) is an essential natural antioxidant, and plays a crucial role in the prevention of various diseases. Herein, a nitrogen-doped polydopamine manganese nanoparticle (N-PDA@Mn) was prepared and used as nanozyme sensor for the rapid and colorimetric detection of GSH. N-PDA@Mn demonstrated excellent oxidase-like activity (Km = 0.0841 mM and Vmax = 3.6 × 10-7 MS-1), exhibiting a rapid balance period of < 100 s. N-PDA@Mn could activate dissolved oxygen to primarily generate singlet-oxygen (1O2), which oxidized colorless 3,3′, 5, 5′-tetramethylbenzidine (TMB) to blue oxidized (ox-TMB). Because GSH could rapidly deplete 1O2, an ultrafast and colorimetric strategy was developed for GSH detection based on N-PDA@Mn. The GSH detection range was 0.5–100 μM, and the detection limit was 0.28 µM. Importantly, at room temperature, the detection time was only 30 s, which was short than that of previously reported GSH detection methods. Furthermore, a point-of-care testing (POCT) platform was designed by combining the N-PDA@Mn colorimetric sensor with a smartphone. Use the POCT platform, a broad linear detection range of 0.5–100 μM and a detection limit of 0.40 μM were obtained. Subsequently, the N-PDA@Mn colorimetric sensor and POCT platform were successfully used in the real-time and on-site quantification of GSH in human serum, achieving a high accuracy and good recovery. Therefore, the N-PDA@Mn-based methods could realize the rapid, on-site visualization, and economical detection of GSH, demonstrating their substantial potential for application in practical testing in fields of food and medicine.

Enhanced peroxidase-like activity via Pt loading of Ni-MOF for colorimetric and smartphone-based bimodal determination of antioxidant capacity in aging cells

Total antioxidant capacity (TAC) serves as a vital indicator for evaluating cell senescence. Here, we synthesized a platinum-loaded nickel-based metal–organic framework material (Ni-MOF@Pt) via a solvothermal method for bimodal determination of TAC in aging cells. The Pt nanoparticle incorporation substantially enhanced the peroxidase-like catalytic activity of Ni-MOF. Ni-MOF@Pt exhibited a strong affinity for 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2, with lower Km values compared to horseradish peroxidase (HRP). The Ni-MOF@Pt-TMB-H2O2 system was successfully applied for detecting antioxidants, including glutathione (GSH), ascorbic acid (AA), and cysteine (Cys) with impressive detection limits (121 nM for GSH, 119 nM for AA, 72 nM for Cys), highlighting the high sensitivity of this system. Additionally, a smartphone-assisted visual detection sensor was established using Ni-MOF@Pt for rapid, sensitive, and on-site TAC detection. Moreover, our established Ni-MOF@Pt method effectively determined the TAC of aging cells and demonstrated its ability to differentiate between normal, senescent, and cancerous cells. This research offers novel insight on fabricating nanozymes with potent peroxidase-like properties and manifests their practicality in TAC analysis.

A colorimetric sensor based on multiple elements doped carbon dot nanozyme for rapid detection of 1-naphthol in human urine samples

The residual carbaryl in crops can cause serious damage to the human kidney and nervous system after entering the human body, which may be metabolized to 1-naphthol (1-NAP) and excreted through urine. 1-NAP is often used as the biomarker for carbaryl exposure, so the intake or leakage of carbaryl can be monitored by detecting the concentration of 1-NAP. Herein, Co, N, P ternary co-doped carbon dots (CoNP-CDs) derived from vitamin B12 were synthesized by a facile hydrothermal method. CoNP-CDs exhibited oxidase-like activity and excellent peroxidase-like activity, which was attributed to the Fenton-like reaction of Co2+/Co3+ and the presence of pyrrole N and P elements, which together provided multiple active sites for chromogenic substrates. Due to the dual enzyme-like activity of CoNP-CDs, hydroxyl radicals (OH) and superoxide radicals (O2−) were generated during the catalytic process, which could rapidly oxidize colorless 3,3′,5,5′-tetramethyl benzidine (TMB) to blue oxidation products (oxTMB). The α-carbon in 1-NAP can be attacked by OH, and the catalytic oxidation process of TMB can be inhibited by the consumption of OH, so that the blue color of the solution became lighter. Based on this principle, a smartphone-assisted colorimetric sensing platform was constructed for the detection of 1-NAP, and which resulted in a linear range of 1.07–37.3 μM and a visual detection limit of 0.68 μM. Moreover, the colorimetric sensing system showed satisfactory recoveries in the detection of human urine samples. The colorimetric sensing system owned the advantages of fast response, strong selectivity and simple operation, and provided a potential strategy for the on-site detection of 1-NAP.

Highly sensitive assaying study based on three-dimensional graphene/cerium oxide nanoparticle nanozyme for the detecting of organophosphate pesticides in vegetable

As an important chemical pollutant affecting the safety of agricultural products, the on-site and efficient detection of pesticide residues has become a global trend and hotspot in research. Herein, this work present a highly sensitive assaying study based on three-dimensional graphene/cerium oxide nanoparticle nanozyme for the detection of organophosphate pesticides (OPs) in vegetable. The detection mechanism is because OPs can inhibit the activity of alkaline phosphatase (ALP). Cerium oxide nanoparticles exhibited intrinsic biomimetic oxidase activity and catalyzed the oxidation of the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue oxidized oxTMB. Upon the introduction of ALP, L-ascorbic acid-2-phosphate can be dephosphorylated to ascorbic acid, which aroused the disintegration of cerium oxide nanoparticles into Ce3+ ions. This disintegration weakened the enzyme-mimicking activity, thus impeding the oxidation of TMB. The absorbance at 652 nm exhibited a linear relationship with the concentration of phorate in the range of 0.15–50 μg/mL, generating a limit of detection of 0.13 μg/mL, Phorate recovery in the spiked samples for the absorption detection mode was 81.0 %–96.7 %. The relative standard deviations (RSD) of the absorption were in the range of 2.18 %–4.12 %. The results in terms of detecting pesticide residues collected from food samples via this method satisfactorily agree with those obtained via gas chromatography–mass spectrometry. This simple assay is therefore suitable for sensing pesticides in complex samples, especially in combination with other portable platforms.

Adenosine triphosphatase synergetic cobalt metal-organic frameworks with enhanced peroxidase-like activity for L-cystine detection

The role of metal–organic frameworks (MOFs) in the field of enzyme-like materials is significant, and they have been successfully applied to various peroxidase-like studies involving catalytic oxidation of the substrate 3,3′,5,5′-tetramethylbenzidine (TMB). However, the limited chemical stability of MOFs in aqueous environments hampers their catalytic applications. To address this inherent drawback and enhance the peroxidase-like activity of MOFs, a method involving adenosine triphosphate (ATP) bonding was proposed. In this study, collaborative materials comprising cobalt MOFs (Co-MOFs) and ATP were utilized as model catalysts for TMB catalysis. The presence of ATP significantly improved the catalytic capability of Co-MOFs over a pH range from 3 to 9 and temperatures ranging from 25 to 60 °C. Notably, at pH 7 and 60 °C, the catalytic efficiency increased by approximately 100 times and an impressive enhancement rate of up to 4600 % was achieved respectively. This peroxidase-like catalytic system offers a colorimetric detection assay that selectively detects L-cysteine with a limit of detection as low as 76.2 nM. Incorporating ATP into Co-MOFs presents a novel approach for utilizing MOFs in catalysis that is convenient, straightforward, and gentle.

Constructing novel metal-free HCOF-Ph@g-C3N4 heterojunctions through molecular expansion to enhance photogenerated carrier involved molecular oxygen activation and photocatalytic hydrogen evolution

Modification of covalent organic frameworks (COFs) have exceptional stability as well as tunable structures is the key to efficient photocatalysts. In this study, hyper-crosslinked COF-Ph was constructed with g-C3N4 to obtain a novel HCOF-Ph@g-C3N4 heterojunction, and the lamellar mesoporous of g-C3N4 was successfully embedded into the pores of 3D HCOF-Ph. The synthetic strategy greatly enhanced the photocatalytic properties and molecular oxygen activation capability of the catalyst. 10 mg of HCOF-Ph@g-C3N4 heterojunction could completely degrade 30 mg/L of tetracycline (TC) within 14 min, and the rate of hydrogen generation reached 9214.69 μmol g−1 h−1. The active species in this process of photocatalysis were verified through tests with free radical trapping and ESR spectra. In addition, the molecular oxygen activation capacity of heterojunction interface and the yield of superoxide radicals were examined by 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation and degradation of nitrotetrazolium nlue chloride (NBT) experiments, respectively. We found that the molecular expansion strategy can change molecule energy band structure to improve absorption of sunlight, and the efficient segregation of the photogenerated charge were ensured by the complementary energy band structure between g-C3N4 and HCOF-Ph. This study created an efficient molecular expansion method for the synthesis of COF-based catalysts with potential uses in the energy and environmental fields.

A Versatile Visual Molecular Imprinting-Driven Switchable Nanozyme Activity-Based Trimodal Assay and Logic Gate Circuits of Ethyl Carbamate.

Concerns regarding the hazard of the carcinogenic ethyl carbamate (EC) have driven attempts to exploit efficient, timely, straightforward, and economic assays for warning early food safety. Here, we proposed a novel molecularly imprinted polymer Co@MOF-MIP, with a high peroxidase (POD)-like activity and a bright blue fluorescence emission, to develop a versatile visual assay for colorimetric, fluorescent, and photothermal trimodal detection and logic gate outputting of EC. Briefly, the POD-like activity of Co@MOF-MIP made it to decompose H2O2 into ·OH for oxidizing colorless 3,3',5,5'-tetramethylbenzidine (TMB) into a blue oxTMB, resulting in a 660 nm irradiated photothermal effect and bursting the blue fluorescence of Co@MOF-MIP via inner filter effect, observing a decreased fluorescence signal together with an increased colorimetric and 660 nm irradiated photothermal signals. However, EC could specifically fill the imprinted cavities of Co@MOF-MIP to block the catalytic substrates TMB and H2O2 out of Co@MOF-MIP for further reacting with the inside catalytic center of Co2+, resulting in the transformation suppressing of TMB into oxTMB, yielding an EC concentration-dependent trimodal responses in fluorescence signal enhancement, colorimetric, and 660 nm irradiated photothermal signal decreases. Assisted by the portable devices such as smartphones and hand-held thermal imagers, a visual onsite portable trimodal analytical platform was proposed for EC fast and accurate detection with the low detection limits of 1.64, 1.24, and 1.78 μg/L in colorimetric, fluorescent, and photothermal modes, respectively. Interestingly, these reactive events could be programmed by the classical Boolean logic gate analysis to offer a novel promising avenue for the big data Internet of Things monitoring and warning early residual EC in a more intelligent, dynamical, fast, and accurate manner, safeguarding food safety.

Glucose Oxidase Coupling with Pistol-Like DNAzyme Based Colorimetric Assay for Sensitive Glucose Detection in Tears and Saliva.

Non-invasive monitoring of glucose levels in tears and saliva is crucial for diagnosing and predicting various illnesses, such as diabetic nephropathy. However, the capability of the current glucose detection methods to identify small amounts of glucose with a high sensitivity remains a significant obstacle. This study proposes a simple, visual technique for sensitively detecting glucose levels from tears and saliva using glucose oxidase (GOx) to catalyze glucose and pistol-like DNAzyme (PLDz) to enhance the signal. In particular, the β-D-glucose present in the samples serves as the initial molecule that GOx identifies and catalyzes to generate gluconic acid and hydrogen peroxide (H2O2). The H2O2 induces the self-cleavage of PLDz, activating the "part b" sequence. This activation initiates catalytic hairpin assembly (CHA) and releases the DNAzyme section in the H1 probe. The DNAzyme acts as a peroxidase analog, facilitating the catalysis of the 3,3',5,5'-tetramethylbenzidine (TMB)-hydrogen peroxide (H2O2) system and resulting in color changes. The proposed method exhibits a broad detection range of six orders of magnitude and a low limit of 0.32μM for glucose detection. Furthermore, the proposed method was highly effective in detecting glucose in saliva and tears, suggesting that it could potentially diagnose hyperglycemia-related disorders in clinical environments.