Hierarchically Mesoporous o-Hydroxyazobenzene Polymers: Synthesis and Their Applications in CO2 Capture and Conversion.

The synthesis of hierarchically mesoporous polymers with multiple functionalities is challenging. Herein we reported a template-free strategy for synthesis of phenolic azo-polymers with hierarchical porous structures based on diazo-coupling reaction in aqueous solution under mild conditions. The resultant polymers have surface areas up to 593 m(2) g(-1) with the mesopore ratio of >80 %, and a good ability to complex with metal ions, such as Cu(2+) , Zn(2+) ,Ni(2+) , achieving a metal loading up to 26.24 wt %. Moreover, the polymers complexed with Zn showed excellent performance for catalyzing the reaction of CO2 with epoxide, affording a TOF of 2570 h(-1) in the presence of tetrabutyl ammonium bromide (7.2 mol %). The polymer complexed with Cu could catalyze the oxidation of alcohol with high efficiency.

A chromogenic substrate for solid-phase detection of phospholipase A2.

A method for solid-phase detection of phospholipase A2 (PLA2) was developed. The method uses 1-octanoyloxynaphthalene-3-sulfonic acid, which was found to be a good substrate of PLA2. The substrate is hydrolyzed by PLA2 into 1-naphthol-3-sulfonic acid, which is spontaneously coupled with coexisting diazonium salt to form a red-purple azo dye. Streptomyces and bovine pancreatic PLA2 spotted on a nitrocellulose membrane could be detected by this method with considerable sensitivity. In addition, colonies of recombinant Escherichia coli producing bacterial PLA2 were distinguishable from those producing an inactive mutant PLA2, facilitating high-throughput screening in directed evolution of the enzyme.

Development of a Novel SPME Coating for Efficient Extraction of Organochlorine Pesticides in Liquid Dairy Products.

A sensitive and accurate analysis of organochlorine pesticide (OCP) residues in dairy products poses a significant challenge. Herein, a novel covalent organic polymer, Azo-COP-1, was synthesized for the enhanced extraction of OCPs in dairy products. The solid phase microextraction fiber coated with Azo-COP-1 demonstrated excellent extraction performance for the OCPs via hydrogen bonding, halogen bonding, π-π stacking, and electrostatic interactions. Coupled with gas chromatography-electron capture detection, we developed a facile and reliable method for detecting OCPs in six types of dairy products with low limits of detection (2.0-400 pg g-1) and high method recoveries (82.6-113%). Azo-COP-1 coatings exhibited good stability and durability. The results verified the feasibility of using Azo-COP-1-based SPME to extract OCP residues in dairy product samples, highlighting its potential for routine monitoring of pesticide residues and food safety assessments.

Green synthesis of azo-linked porous organic polymer for enrichment of nitroimidazoles from water, shrimp and Basa fish.

Reliable monitoring of nitroimidazoles (NDZs) is of great significance to public health. Herein, an azo-linked porous organic polymer (Res-POPs) was prepared by green synthesis method using natural resveratrol as monomer for the first time. Using Res-POPs as sorbent, a facile method coupling solid-phase extraction with high performance liquid chromatography-diode array detection was developed for effective detecting NDZs. The method achieved good linearities (0.06 âˆ¼ 100 ng mL-1 for water, 1.8 âˆ¼ 200 ng g-1 for shrimp, and 1.5 âˆ¼ 200 ng g-1 for Basa fish) with determination coefficients above 0.995, low detection limits (0.02 âˆ¼ 0.05 ng mL-1, 0.60 âˆ¼ 1.00 ng g-1 and 0.50 âˆ¼ 0.90 ng g-1 for water, shrimp and Basa fish), high method recovery (85 %∼114 %) and relative standard deviations below 8.2 %. The results demonstrated the superiority and the promising potential of the established method for detection of NDZs compared with the reported method.

Ultrasensitive SERS quantitative detection of antioxidants via diazo derivatization reaction and deep learning for signal fluctuation mitigation.

Synthetic antioxidants serve as essential protectors against oxidation and deterioration of edible oils, however, prudent evaluation is necessary regarding potential health risks associated with excessive intake. The direct adsorption of antioxidants onto conventional surface-enhanced Raman scattering (SERS) substrates is challenging due to the presence of phenolic hydroxyl groups in their molecular structures, resulting in weak Raman scattering signals and rendering direct SERS detection difficult. In this study, a diazo derivatization reaction was employed to enhance SERS signals by converting antioxidant molecules into azo derivatives, enabling the amplification of the weak Raman scattering signals through the strong vibrational modes induced by the N = N double bond. The resulting diazo derivatives were characterized using UV-visible absorption and infrared spectroscopy, confirming the occurrence of diazo derivatization of the antioxidants. The proposed method successfully achieved the rapid detection of three commonly used synthetic antioxidants, namely butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), and propyl gallate (PG) on interfacial self-assembled gold nanoparticles. Furthermore, rapid predictions of BHA, PG, and TBHQ within the concentration range of 1 × 10-6 to 2 × 10-3 mol/L were achieved by integrating a convolutional neural network model. The predictive range of this model surpassed the traditional quantitative method of manually selecting characteristic peaks, with linear coefficients (R2) of 0.9992, 0.9997, and 0.9997, respectively. The recovery of antioxidants in real soybean oil samples ranged from 73.0 % to 126.4 %. Based on diazo derivatization, the proposed SERS method eliminates the need for complex substrates and enables the analysis and determination of synthetic antioxidants in edible oils within 20 min, providing a convenient analytical approach for quality control in the food industry.

Green construction of hydroxyl-functionalized magnetic porous organic framework for effective extraction of triazine herbicides from environmental water and watermelon juice samples.

Triazine herbicides have been widely detected in water resources and food, which poses a potential hazard to both ecosystem and human health. Due to their high polarity, conventional adsorbents have limitations for their extractions. Herein, for the effective magnetic extraction of triazine herbicides, a novel and effective magnetic adsorbent was prepared with a satisfactory extraction performance. In the experiments, five porous organic frameworks (POFs) with hydroxyl functional groups were synthesized by diazo-coupling reactions in aqueous solution with ß-cyclodextrin (ß-CD) as a green monomer. After evaluation of the five POFs, the DDM-CD-POF, which was synthesized with 4'4-diaminodiphenylmethane (DDM) and ß-CD, showed the largest specific surface area and the best adsorption capacity for the five triazine herbicides. Then, it was magnetized by introducing Fe3O4@SiO2 into it to prepare a magnetic adsorbent (M-DDM-CD-POF) to facilitate separation and recycling. Finally, the M-DDM-CD-POF-based magnetic solid-phase extraction in combination with high performance liquid chromatographic detection method was established for the quantitative determination of the triazine herbicides in environmental water and watermelon juice samples. The current strategy showed low limits of detection of 0.03-0.11 ng mL-1 for environmental water and 0.07-0.22 ng mL-1 for watermelon juice sample. The method recoveries for spiked samples ranged from 84.0% to 113.0% with the relative standard deviations ≤8.8%. This work provides a new approach for the detection of the triazine herbicides with good application prospect.

Green adherent spectrophotometric determination of molnupiravir based on computational calculations; application to a recently FDA-approved pharmaceutical dosage form.

Molnupiravir is an oral antiviral drug developed to provide significant benefit in reducing hospitalizations or deaths in mild COVID-19. Integrated green computational spectrophotometric method was developed for the determination of molnupiravir. Theoretical calculations were performed to predict the best coupling agent for efficient diazo coupling of molnupiravir. The binding energy between molnupiravir and various phenolic coupling agents, α-naphthol, ß-naphthol, 8-hydroxyquinoline, resorcinol, and phloroglucinol, was measured using Gaussian 03 software based on the density functional theory method and the basis set B3LYP/6-31G(d). The results showed that the interaction between molnupiravir and 8-hydroxyquinoline was higher than that of other phenolic coupling agents. The method described was based on the formation of a red colored chromogen by the diazo coupling of molnupiravir with sodium nitrite in acidic medium to form a diazonium ion coupled with 8-hydroxyquinoline. The absorption spectra showed maximum sharp peaks at 515 nm. The reaction conditions were optimized. Beer's law was followed over the concentration range of 1-12 µg/ml molnupiravir. Job's continuous variation method was developed and the stoichiometric ratio of molnupiravir to 8-hydroxyquinoline was determined to be 1:1. The described method was successfully applied to the determination of molnupiravir in pure form and in pharmaceutical dosage form. The results showed that the proposed method has minimal environmental impact compared to previous HPLC method.

Intelligently design primary aromatic amines derived carbon dots for optical dual-mode and smartphone imaging detection of nitrite based on specific diazo coupling.

Primary aromatic amines derived carbon dots (PAA-CDs) with the protonated amino groups and high quantum yield of 46% were favorably obtained by one-step solvothermal treatment of m-phenylenediamine (m-PDA) in acidic environment. The interaction between the PAA-CDs and nitrite (NO2-) was inherited the characteristic reaction of m-PDA (a primary aromatic amine) and NO2-, resulting in strong fluorescence quenching and obvious absorption variation of the PAA-CDs. Meanwhile, a chromogenic reaction of diazo coupling can cause significant color changes. Hence, the PAA-CDs were developed for an optical dual-mode and smartphone imaging sensor for NO2- detection in the range of 3.0 ~ 40.0 µM with high selectivity, good sensitivity, and excellent anti-interference capability. A limit of detection (LOD) of 0.024 µM and 0.16 µM was implemented by fluorometry and colorimetry, respectively. For smartphone imaging colorimetry, the LODs of 0.46 µM (visible color) and 0.99 µM (fluorescence color) were acquired. More importantly, the established sensor has been successfully applied for the dynamic detection of NO2- in various food samples with the satisfying results. A smartphone imaging colorimetry method based on the CDs was firstly proposed to visually and quantitatively detect NO2-, which will broaden the application range of the CDs in food safety inspection.

Highly sensitive detection of tryptophan (Trp) in serum based on diazo-reaction coupling with Surface-Enhanced Raman Scattering and colorimetric assay.

Tryptophan plays an important role in the metabolic pathway and tryptophan metabolism is abnormal in tumor tissues. Therefore, Trp and its metabolites in body fluids can be used as tumor markers for cancer monitoring. However, the traditional tryptophan detection method has many shortcomings, such as low sensitivity, time-consuming and so on, which is difficult to meet the clinical needs. Herein, a rapidly, sensitive and reliable method for indirectly detecting Tryptophan (Trp) in serum was proposed by combining diazo-coupling reaction mechanism with surface-enhanced Raman scattering (SERS). The limit of detection (LOD) of Trp can be as low as 20 nM, which is much lower than existing detection methods. In addition, because of obvious change in color in diazo-coupling reaction, a colorimetric detection was applied for convenient determination of Trp in the concentration ranged from 3 × 10-5 - 10-3 M. Furthermore, with the support of good results by SERS assay, the presented method was successfully carried out for the determination of Trp in serum that came from healthy people and colorectal cancer patients. Comparing the difference of Trp content in serum between the two groups, it was found that tryptophan metabolism disorder exists in colorectal cancer patients, which suggested that the accurate detection of tryptophan content may provide important reference for the pathogenesis, prediction and prevention of colorectal cancer.

A simple yet sensitive colorimetric nitrite ions assay based on diazotization with p­Aminobenzoic and coupling with phloroglucinol in acidic medium.

Immoderate intake of nitrite (NO2-) is deleterious human health and may result in causing dangerous diseases. In this study, nitrite detection system was successfully fabricated based on a unique diazo-coupling reaction of p­Aminobenzoic acid (PABA) and phloroglucinol (1, 3, 5­trihydroxybenzene). Upon the presence of NO2- in an acid medium, p­Aminobenzoic acid could not only form diazonium ion easily but also couple with p­Aminobenzoic acid, and results forming yellow water-soluble azo dye that shows maximum absorption at 434 nm. Under the further accurate determination condition, such as acid concentration, amount of reagents and time required, the naked-eye detection of NO2- showed excellent selectivity in compared with some anions. Especially, diazotization and coupling reaction proposed here is very fast and control of pH and temperature are unnecessary. Moreover, the color is stable for several days and Beer's law is obeyed over a wide range. Reliable detection can be made in the range of 0.05 to 1 p.p.m. of nitrite ion. Detection limit was calculated to be 0.024 p.p.m. (0.52 µâ€¯M) by UV-visible spectroscopy and 0.05 p.p.m. (1.09 µâ€¯M) by naked-eye. By using an electrochemical method, IR, SEM, and 1HNMR, the sensing mechanism can be easily verified. More importantly the proposed method was successfully applied for the determination of nitrite in a real water sample.