4-nitrophenol Research Articles

Synthesis of iron oxide nanoparticles encapsulated poly(styrene‐co‐4‐vinyl pyridine) nanocomposites for column adsorption and photocatalytic degradation of para nitrophenol from water

AbstractStyrene (St), 1,4 vinyl pyridine (4VP) monomers and divinyl benzene (DVB) monomer‐cum‐crosslinker at different molar ratios were subjected to emulsion polymerization in the presence of FeCl2, 6H2O/FeCl3⋅4H2O followed by the treatment with an aqueous ammonia solution to produce several iron oxide nanoparticles (IONs) impregnated crosslinked copolymer composites. The resulting polymer metal nanocomposites (PMNCs) were characterized by FTIR, proton and 13C NMR, UV–visible spectroscopy, XRD, XPS, DLS, magnetic properties, SEM and TEM. The PMNCs were used for batch and column adsorption and photocatalytic degradation of p‐nitrophenol (PNP) from water. The PMNC4 composite prepared with an styrene:4VP molar ratio of 5:1 (16.7 mol% 4VP), 4 wt.% DVB crosslinker and 0.025/0.05 molar ratios of Fe(II)/Fe(III) salts leads to an optimum batch equilibrium adsorption (qe, mg/g)/removal% of 496.36/99.3 PNP from aqueous PNP of concentration 100 mg/L. The same composite showed an equilibrium PNP adsorption (qe) of 114.2 mg/g polymer and a removal% of 26.8 for an inlet feed concentration (Ci, mg/L)/flow rate (Qt, mL/min)/bed height (h, mm) of 100/30/30 in a fixed bed. The PMNC4 polymer showed a photodegradation efficiency of 98% with a 1st order rate constant of 0.029 min−1 after 70 min of degradation of 100 mg/L PNP in solar light.Highlights Copolymer network of styrene, 4 vinyl pyridine and DVB were synthesized. Iron oxide nanoparticles were introduced into the network in‐situ during synthesis. The metal polymer nanocomposites (PMNCs) were characterized. Synthesis parameters were optimized with respect to batch adsorption of PNP. PMNCs showed excellent fixed bed adsorption and photocatalytic degradation of PNP.

Urinary concentrations of environmental phenol among pregnant women in the Japan Environment and Children’s Study

Humans are exposed to various bisphenols, alkylphenols and nitrophenols through dietary intake, food packaging and container materials, indoor and outdoor air/dust. This study aimed to evaluate exposure of Japanese pregnant women to environmental phenols by measuring target compounds in urine samples. From a cohort of the Japan Environment and Children’s Study, 4577 pregnant women were selected. Bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF), bisphenol AF (BPAF), para-nitrophenol (PNP), 3-methyl-4-nitrophenol (PNMC), branched 4-nonylphenol (4-NP), linear 4-nonylphenol and 4-tert-octylphenol (4-t-OP) were analysed using a high-performance liquid chromatograph coupled to a triple-quadrupole mass spectrometer. The urinary metabolite data were combined with a questionnaire to examine the determinants of phenol exposure by machine learning. The estimated daily intake (EDI) and hazard quotient (HQ) of BPA were calculated. PNP (68.2%) and BPA (71.5%) had the highest detection frequencies, with median concentrations of 0.76 and 0.46 μg/g creatinine, respectively. PNMC, BPS, BPF and 4-NP were determined in 24.9%, 11.9%, 1.3% and 0.4% of samples, respectively, whereas BPAF (0.02%) and 4-t-OP (0.02%) were only determined in a few samples. The PNP concentrations measured in this study were comparable with those reported in previous studies, whereas the BPA concentrations were lower than those reported previously worldwide. The EDI of BPA was 0.014 μg/kg body weight/day. Compared with the tolerable daily intake set by the German Federal Institute for Risk Assessment, the median (95th percentile) HQ was 0.044 (0.2). This indicates that the observed levels of BPA exposure pose a negligible health risk to Japanese pregnant women. Determinants of bisphenol and nitrophenol exposure could not be identified by analysing the questionnaire solely, suggesting that biological measurement is necessary to assess exposure of pregnant women to bisphenols and nitrophenols. This is the first study to report environmental phenol exposure of Japanese pregnant women on a nationwide scale.

Development and validation of chemometric-assisted spectrophotometric models for efficient quantitation of a binary mixture of supportive treatments in COVID-19 in the presence of its toxic impurities: a comparative study for eco-friendly assessment

The use of sustainable solvents has increased significantly in recent years due to advancements in green analytical methods. The number of impurities in the drug substance determines how safe the finished product is. Therefore, during the whole medication planning process, contaminants need to be closely watched. Using chemometric models, the concentrations of hyoscine N-butyl bromide (HYO) and paracetamol (PAR) were determined in the presence of three PAR impurities [P-nitrophenol (PNP), P-aminophenol (PAP), and P-chloroacetanilide (PCA), as well as DL-tropic acid (TRO) as a HYO impurity]. It was possible to isolate and measure these dangerous impurities. Fever and spasms associated with COVID-19 are reported to be considerably reduced when PAR and HYO are taken together. Artificial neural networks, principal component regression, multivariate curve resolution-alternating least squares, and partial least squares are the four chemometric-assisted spectrophotometric models that were created and verified. All of the proposed methods’ quantitative analytical potency was assessed using recoveries%, root mean square error of prediction, and standard error of prediction. For PAR, HYO, PNP, PCA, TRO, and PAP, respectively, the indicated approaches were used in the ranges of 4.00–8.00, 16.00–24.00, 1.00–5.00, 0.40–0.80, 4.00–12.00, and 2.00–6.00 µg/mL. They are able to get around difficulties like collinearity and spectral overlaps. After statistical testing, there was no discernible difference between the recommended methods and the published one. The degree of greenness of the established models was evaluated using three different green assessment methods. In the presence of their harmful impurities, PAR and HYO could be identified using the recommended methods.

A poly(2,6-diaminopyridine) functionalized magnetic porous carbon nanomaterial for extraction and determination of phenol, nitrophenols, and chlorophenols in water samples

Herein, for the first time, a new method for the simultaneous extraction of phenol (Ph), nitrophenols (NPs), and chlorophenols (CPs) as the priority pollutants was proposed using a magnetic porous carbon coated with poly(2,6-diaminopyridine). The analytes were separated/determined by an HPLC device coupled to a diode array detector. Magnetic porous carbon was obtained by the pyrolysis of MIL-53(Fe) as a precursor and then functionalized with a layer of poly(2,6-diaminopyridine). Next, the synthesized adsorbent was identified by various methods, including FT-IR, XRD, SEM, VSM, surface analysis, and TEM techniques. After that, the design of the experiment strategy was used to identify and optimize the extraction variables. The LODs and linear range were obtained in the range of 0.04–0.15 µg/L and 0.1–500 µg/L, respectively. The one-day RSDs and day-to-day RSDs were gained in the range of 4.2–9.5 % and 5.0–12.5 %, respectively. The enrichment factors and extraction recoveries were obtained in the range of 208–378 and 41.6–75.6 %, respectively. Eventually, the outlined method was employed to analyze diverse water/wastewater samples satisfactorily.

A Multifunctional Co-Based Metal-Organic Framework as a Platform for Proton Conduction and Ni trophenols Reduction.

The design and development of proton conduction materials for clean energy-related applications is obviously important and highly desired but challenging. An ultrastable cobalt-based metal-organic framework Co-MOF, formulated as [Co2(btzip)2(μ2-OH2)] (namely, LCUH-103, H2btzip = 4, 6-bis(triazol-1-yl)-isophthalic acid) had been successfully synthesized via the hydrothermal method. LCUH-103 exhibits a three-dimensional framework and a one-dimensional microporous channel structure with scu topology based on the binuclear metallic cluster {Co2}. LCUH-103 indicated excellent chemical and thermal stability; peculiarly, it can retain its entire framework in acid and alkali solutions with different pH values for 24 h. The excellent stability is a prerequisite for studying its proton conductivity, and its proton conductivity σ can reach up to 1.25 × 10-3 S·cm-1 at 80 °C and 100% relative humidity (RH). In order to enhance its proton conductivity, the proton-conducting material Im@LCUH-103 had been prepared by encapsulating imidazole molecules into the channels of LCUH-103. Im@LCUH-103 indicated an excellent proton conductivity of 3.18 × 10-2 S·cm-1 at 80 °C and 100% RH, which is 1 order of magnitude higher than that of original LCUH-103. The proton conduction mechanism was systematically studied by various detection means and theoretical calculations. Meanwhile, LCUH-103 is also an excellent carrier for palladium nanoparticles (Pd NPs) via a wetness impregnation strategy, and the nitrophenols (4/3/2-NP) reduction in aqueous solution by Pd@LCUH-103 indicated an outstanding conversion efficiency, high rate constant (k), and exceptional cycling stability. Specifically, the k value of 4-NP reduction by Pd@LCUH-103 is superior to many other reported catalysts, and its k value is as high as 1.34 min-1 and the cycling stability can reach up to 6 cycles. Notably, its turnover frequency (TOF) value is nearly 196.88 times more than that of Pd/C (wt 5%) in the reaction, indicating its excellent stability and catalytic activity.

Ratiometric fluorescence immunoassay based on silver nanoclusters and calcein-Ce3+ for detecting ochratoxin A

Ochratoxin A (OTA), a dangerous mycotoxin, is found in many crops. It is essential to create sensitive OTA detection techniques to ensure food safety. Based on the principle of p-nitrophenol (PNP) quenched the fluorescence of bovine serum albumin silver nanocluster (BSA-AgNCs) through an internal filtering effect, and phosphate activated fluorescence of calcein-Ce3+ system, a ratiometric fluorescence immunoassay for OTA detection was developed. In this strategy, the value of F518/F640 was used as a signal for response of OTA concentration. The detection range of this strategy was 0.625–25 ng/mL, the limit of detection (LOD) was 0.04 ng/mL. This new immunoassay offered a brand-new platform for detecting OTA.

One-step synthesis of Ag-loaded Co3O4 as an efficient catalyst for the reduction of p-nitrophenol

The composite comprised of noble metal and non-precious metal oxide as a catalyst offers both low cost and high performance. To obtain this structure, a two-step approach is usually performed, which is time and energy consuming. In this paper, a one-step hydrothermal method was proposed to prepare the Ag/Co3O4 composites with variable silver loadings, using cobalt acetate, silver nitrate, and l-arginine as the reductant. The catalytic activities of these Ag/Co3O4 composites were investigated taking p-nitrophenol (PNP) reduction using NaBH4 as the reducing agent. The results demonstrated that the Ag/Co3O4 composite exhibited superb catalytic reduction capacity towards PNP benefiting from the even dispersion of elemental Ag particles on the surface of Co3O4 microspheres. A reduction ratio of 89.33 % and a reaction rate of 0.1558 min−1 for PNP were obtained within 15 min under the optimal reaction conditions: Ag0.008/Co3O4 amount of 0.01 g·L−1, NaBH4 dosage of 7 mmol·L−1, PNP concentration of 0.108 mmol·L−1, a total reaction volume of 1000 mL and a temperature of 25 °C. Besides, the composite showed stable catalytic performance after five continuous uses, maintaining a PNP reduction rate above 82 %. This work presents an effective way for the facile preparation of noble metal-loaded composite catalysts.

Removal of p-nitrophenols by BC@nZVI activated persulfate: A study of key factors and mechanisms

Straw biochar loaded zero-valent iron nanoparticles were prepared by co-precipitation method using agricultural waste straw biochar as a carrier for the removal of p-nitrophenol (PNP) by activated sodium persulfate (PS). The physicochemical properties of BC@nZVI were characterized using SEM, EDS, FTIR, BET, and RAMAN. The effects of PS concentration, catalyst concentration, initial pH, coexisting anions, and different activation systems on the degradation of PNP were investigated. The results showed that the best activation effect was exhibited at pH= 7, BC@nZVI dosage of 2 g/L, and PS concentration of 1 mM, and the removal of 40 mg/L PNP reached 91.7 % in 10 min. The high concentration of PS (4 mM) triggered free radical competition to inhibit the degradation, and the removal rate was only 74.5 % at 1 mM. In addition, bicarbonate ions (0–20 M) had a significant inhibitory effect on this system. Electron spin resonance (ESR) demonstrated that SO4⋅− and·OH were the major radicals, and SO4⋅− was preferentially generated. The intermediate products were identified by LC-MS, XRD and XPS characterization, which showed that adsorption and redox were the main degradation mechanisms, with p-benzoquinone was the oxidized product and substances such as 4-heptanone and propionic acid were the reduced products. This study proves that BC@nZVI activated PS is an efficient and excellent means of removing PNP and a good way to reuse agricultural waste.

In-situ growth of Ni3S2@Mo2S3 catalyst on Mo-Ni foam for degradation of p-nitrophenol with a good synergetic effect by using ozone

In this study, Ni3S2@Mo2S3 composites were grown on the surface of molybdenum-nickel (Mo-Ni) foam in situ by a one-step hydrothermal method. With p-nitrophenol (PNP) as the target pollutant, the catalyst can produce a good synergistic effect with ozone, and the degradation rate of PNP is more than 96%. Even after five cycles, Ni3S2@Mo2S3-NF/O3 was able to degrade PNP efficiently and stably. In addition, the unique three-dimensional structure of Ni3S2@Mo2S3-NF solves the separation and recycling problem of traditional powder catalysts by maintaining the structural stability during the use process and thus, may reduce the cost of water treatment. The degradation process is mainly dominated by non-radical pathways, and the radical pathway, which work synergistically. This work reveals the influencing factors and degradation mechanism of Ni3S2@Mo2S3-NF/O3 system for PNP degradation, which provides a new idea for water treatment and broadens its potential application.

Supramolecular Fe3O4-gluconic acid@β-cyclodextrin magnetic composite: green synthesis using sucrose and application in removal of p-nitrophenol

A two-pot method is reported for the synthesis of ferric oxide-gluconic acid/β-cyclodextrin (Fe3O4-GA@β-CD). The proposed approach is a green one as the raw material is a natural product (sucrose) and no organic solvent is involved. Meanwhile, this novel composite was demonstrated for catalytic degradation of p-nitrophenol (PNP), a prototype toxic with high toxicity and low degradability. This is realized by H2O2 activation induced by the heterogeneous Fenton-like catalysis of the as-prepared Fe3O4-GA@β-CD nano-microspheres. The results showed that the reaction rate constants of PNP degradation catalyzed by Fe3O4-GA@β-CD and Fe3O4-GA were 0.0879 and 0.0514 min−1, respectively, suggesting improved catalytic performance of Fe3O4-GA@β-CD compared with Fe3O4-GA. This can be attributed to the cavity of β-CD, which can capture and include PNP molecules. The effects of pH value, H2O2 concentration, catalyst load and hydroxyl radical quenching on the Fenton-like catalysis were explored and the optimized conditions (pH value = 2.0, H2O2 concentration = 50 mM, and catalyst load = 1.0 g/L) were determined. Additionally, Fe3O4-GA@β-CD exhibited excellent reusability (catalytic degradation rate = 95.1% after five recycling times) as it can be recycled under external magnetic field owing to its good magnetic response (up to 18.41 emu/g).

Hydroxylamine-assisted retarding surface passive layer of zero-valent iron for highly efficient p-nitrophenol removal via direct electron transfer

Zerovalent iron (ZVI) has been widely used in groundwater remediation due to its excellent reducibility. However, the passivation layer on ZVI surface limits the reactivity of ZVI. In this work, hydroxylamine hydrochloride (HA) has been selected to assist to improve the remediation efficiency of ZVI, and the removal rate constant of p-nitrophenol (PNP) increased nearly 90 times than that of ZVI alone. The effect of HA concentration on the degradation efficiency of PNP by ZVI was also discussed. The concentrations of Fe(Ⅱ) and Fe(Ⅲ) in reaction solution and on ZVI surface during the processes were measured. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) of fresh and used ZVI were characterized, which elucidated that HA could facilitate the reduction of Fe(Ⅲ) to Fe(Ⅱ), retard passivation, and extend the pH range of reaction. The mechanism of high degradation efficient in ZVI/HA system was studied through a series of probing experiments. Fe0 directly donated electron to reduce PNP, which was the fundamental reason. The contribution of Fe(Ⅱ) and active hydrogen generated on ZVI surface to the degradation efficiency of PNP could be negligible. It can be concluded that the addition of HA was an effective strategy to improve the reduction efficiency of ZVI.

Linear and nonlinear regression analysis of phenol and P-nitrophenol adsorption on a hybrid nanocarbon of ACTF: kinetics, isotherm, and thermodynamic modeling

This study aimed to create activated carbon thin film (ACTF) as a hybrid nanocarbon via a simple and efficient method through a single-step mixing process using thermal functionalization techniques. TEM, BET, BJH, FTIR, XRD, and TGA analyses were used to investigate the prepared ACTF. The results exhibited that ACTF has a porous structure with a high surface area of 318 m2/g and important functional groups, which are considered significant adsorption sites. The adsorption performance of ACTF for phenol and p-nitrophenol (PNP) removal from aqueous solutions using batch adsorption mode was studied. Evaluations were conducted on experimental factors influencing the adsorption process, such as pH, initial phenol and PNP concentrations, adsorbent dose, contact time, and temperature. Under the optimized conditions, the phenol and PNP were removed with a maximum efficiency of 89.98% and 92.5%, respectively. The results of linear and nonlinear isotherms and kinetic models of phenol and PNP showed that both pollutants were well fitted with the Freundlich model (R2 = 0.99, χ2 = 0.13, RMSE = 1.6), (R2 = 0.99, χ2 = 0.42, RMSE = 2.8), and the pseudo-second-order model (R2 = 0.999, χ2 = 0.03, RMSE = 0.31), (R2 = 0.99, χ2 = 0.01, RMSE = 0.24), for phenol and PNP, respectively. According to the calculated thermodynamic results, the adsorption of phenol and p-nitrophenol onto the ACTF surface was a spontaneous and exothermic reaction. The regeneration experiments showed that the spent ACTF could be reused up to the fifth cycle while maintaining noteworthy removal efficiency.

Facile one-pot combustion synthesis of CuCo2S4 binary nanocomposite for synergetic photodegradation of CR dye and reduction of nitroarenes

A one-pot combustion method was employed for the synthesis of branch-like CuCo2S4 (CCS) without any surfactant, polymerizing, or capping agent. Most of the studies were conducted on CCS material for electrochemical performances. Herein, we demonstrated CCS is an efficient catalyst for the photodegradation of toxic CR dye and also, the reduction of nitroarenes. The cubic structural phase of the symphonized material was confirmed by using XRD analysis. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results interpret that the uniform skull-like structures were formed during the combustion method. The bandgap was about 1.41 eV, which was analyzed from UV–Vis DRS analysis. FT-IR confirms the presence of Cu-S, Co-S, and Cu-Co bonding. Photoluminescence (PL spectrofluorometer) is evidence, of the ability of electrons and hole recombination. A significant surface area and the pore diameter were found to be 4.072 m2/g and 34.75 nm respectively, by BET (Brunauer -Emmett-Teller) and BJH (Barret-Joyner-Halenda) analysis. Herein, we report CCS material, for the photodegradation of Congo red (CR) dye with a photodegradation efficiency of 91.2 % in 80 min (min). And retains its stability for up to 4- cycles. Further, CCS material also exhibits a good catalyst for the reduction of nitrobenzene and 4- nitro phenol (4-NP) with reduction rate constants of 0.07056 min−1 and 0.194 min−1. The degradation products were confirmed by using LC-MS, and TOC (Total Organic Carbon) analysis. These reports are evident that the synthesized CCS nanostructures are latent material for the removal of hazardous dyes from wastewater as well as catalyzed the reduction of nitrobenzene and 4-NP.

Influences of Mg-activation on sugarcane bagasse biochar characteristics and its PNP removing potentials from contaminated water

Biochar as a substitute eco-friendly and low-cost adsorbent is introduced for removing p-nitrophenol (PNP) one of the most important chemical contaminant that recognized as the main metabolite in many pesticides and an intermediate compound in many industries. Physicochemical characteristics of sugarcane bagasse biochar (SCBB) and its Mg-activation (ASCBB) generated at 500 °C for 30 min were investigate. Batch kinetic experiment was conducted (200 mg L−1 PNP) to evaluate sorption efficiency of both tested biochars. To study the reaction behavior of PNP adsorption on ASCBB, solution pH and isotherm experiment of different concentrations and dosages were as investigated. The results show that ASCBB had a higher biochar yield, ash content, pH, molar ratios (H/C and O/C), surface area, pore volume, mean pore diameter, and specific and thick wall structure than SCBB. The efficiency of ASCBB to remove PNP was higher than SCBB which reached 51.98% in the first 1 min., and pH 7 achieved the optimum adsorption. Pseudo-second-order model examination exhibited well fitted to explain the adsorption results depending on R2 value (1.00). The adsorption isotherm results were well described by the Elovich and Freundlich models depending on the R2, qm and n values, which means the formation of a multilayer of PNP on the ASCBB surface through the chemisorption reaction. The calculated qm (144.93 mg g−1) of 1g L−1 was relatively close with experimental value (142.03 mg g−1). The PNP adsorption mechanism on both biochar types was electrostatic attraction, hydrogen bonding, and π-π stacking interactions, which were confirmed by studying the surface reactions before and after adsorption. Overall, the current study provided a successful waste biomass-derived biochar as a conducive alternative eco-sorbent to eliminate p-nitrophenol from wastewater.

Magnetite nanoparticles decorated on cellulose aerogel for p-nitrophenol Fenton degradation: Effects of the active phase loading, cross-linker agent and preparation method

Magnetite nanoparticles (Fe3O4 NPs) are among the most effective Fenton-Like heterogeneous catalysts for degrading environmental contaminants. However, Fe3O4 NPs aggregate easily and have poor dispersion stability because of their magnetic properties, which seriously decrease their catalytic efficiency. In this study, a novel environmentally friendly method for synthesising Fe3O4@CA was proposed. Fe3O4 NPs were immobilized on the 3D cellulose aerogels (CAs) in order to augment the degradation efficiency of p-nitrophenol (PNP) treatment and make the separation of the catalyst accessible by vacuum filtration method. Besides, CAs were fabricated from a cellulose source extracted from water hyacinth by using different cross-linking agents, such as kymene (KM) and polyvinyl alcohol–glutaraldehyde system (PVA–GA), and other drying methods, including vacuum thermal drying and freeze drying, were evaluated in the synthesis process. As-synthesized samples were analysed by various methods, including Powder X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray analysis and Brunauer–Emmett–Teller. Then, using ultraviolet–visible spectroscopy, the difference in the degradability of PNP of the obtained material samples was also investigated to determine their potential applications. Results highlighted that the Fe3O4-3@CA-KF catalyst with an Fe3O4 loading of 0.40 g/gCA used KM as a cross-linker and the freeze-drying method demonstrated the highest PNP removal efficiency (92.5 %) in all Fe3O4@CA samples with a H2O2 content of 5 g/L. The degradation kinetics and well-fitted pseudo-first-order model were investigated. Notably, after five successive PNP degradation experiments, this catalyst retained ∼80 % of the ability to degrade PNP, indicating its outstanding reusability. In environmental remediation, this study provides valuable insights into the development of simply separated and high-efficiency catalysts for heterogeneous catalytic reactions.

Metal-/carboxylate-directed four d10 piperazine-amide-based coordination polymers for the fluorescent detection of nitrophenol and nitroaniline in various water environments

Four piperazine-amide-bridged d10 metal-organic coordination polymers, namely, [Zn(L)0.5(1,3-BDC)∙H2O]∙H2O (1), [Cd(L)(1,3-BDC)] (2), [Zn(L)0.5(5-MIP) ∙H2O]·H2O (3), [Cd(L)(5-MIP)] (4) were synthesized by the L ligand [N, N'-bis[(3-pyridin)acrylophenone] piperazine (L)] and two carboxylic acids with Zn/Cd(II) chloride under hydrothermal conditions. The title complexes were characterized by IR spectroscopy, powder X-ray diffraction and single-crystal X-ray diffraction. Complex 1 is a 1D ladder-like structure. Complex 2 is a 3D NaCl type framework. Complexes 3 and 4 are 63 and 44 connected 2D structures. The different structural details of the title complexes directed by caroxylates and the central metals were compared. The complexes 1–4 can be used as excellent fluorescent sensors toward nitrophenol (NOP) and nitroaniline (NA) with a low limit of detection and a high quenching constant, and have good anti-interference and recyclable characteristics. The feasibility of actual sample detection was verified by tap water, river water and wastewater samples. Taking complex 3 as an example, the mechanism was also explored by fluorescence lifetime experiment and the UV-visible absorption spectroscopy. The 3-modified visual detection cloth and test paper were also prepared by solid phase deposition method.

Design and synthesis of bifunctional conjugated microporous polymers containing tetraphenylethene and bisulfone units for energy storage and fluorescent sensing of p-nitrophenol

In this study, we successfully used the Suzuki-Miyaura reaction to prepare three novel conjugated microporous polymers (CMPs) that include tetraphenylethene (TPE): TPE-Ph-Th, TPE-Ph-Tha, and TPE-Ph-BSu. Using methods like FTIR and solid-state NMR, we examined the chemical composition and functional groups in the TPE-Ph CMPs. The TPE-Ph-BSu CMP's thermal characteristics were also examined, and they showed remarkable features with a decomposition temperature (Td10) of 535 °C and a char yield of 73 wt%. We also looked at TPE-Ph-Th CMP, which had a pore size of 2.0 nm and a surface area (SBET) of 67 m2 g−1. We carried out photoluminescence (PL) and electrochemical investigations to evaluate the potential of TPE-Ph CMPs for supercapacitor applications and their capability to detect p-nitrophenol (PNP). According to our electrochemical investigation, the TPE-Ph-Tha and TPE-Ph-BSu CMPs both exhibited exceptional capacitance, reaching 51 and 52 F g−1 at a current density of 0.5 A g−1, respectively. Furthermore, even after 5000 cycles, these CMPs still retained 80% of their capacitance, demonstrating their remarkable capacitance retention. In conclusion, synthetic TPE-Ph CMPs have several benefits, including outstanding electrochemical performance and thermal stability. Additionally, they successfully detect PNP using fluorescence-based sensing without interference, making them adaptable materials suited for a variety of applications, including the detection of pollutants (as PNP has shown) and the usage of supercapacitors.

Electrochemical surface plasmon resonance approach to probe redox interactions between microbial extracellular polymeric substances and p-nitrophenol

Microbial extracellular polymeric substances with redox functional groups play a crucial role in the bio-conversion of pollutants, which can affect their reactivity toward diverse pollutants. However, the redox interactions between microbial EPS and pollutants have not addressed in depth due to the absence of essential analytical methodologies. In this study, we have developed an electrochemical-surface plasmon resonance (EC-SPR) system to investigate the interactions between EPS and p-nitrophenol (PNP) by simultaneously monitoring the electrochemical reaction and the binding kinetics. Moreover, in vitro PNP degradation experiments were performed in the presence of EPS across varying redox states to provide further verification of PNP reduction by EPS. The results indicated that direct electrochemical treatment successfully converted raw EPS (EPSraw) into reductive EPS (EPSred) and oxidized EPS (EPSox), respectively. The EC-SPR system served as a powerful tool for probing redox interactions between EPS at distinct redox states and PNP. The binding affinity of EPS to PNP was related to the redox states of EPS, following the order of EPSred > EPSraw > EPSox. EPS exhibited the capability to reduce PNP to p-aminophenol by donating electrons, and the reductive process highly depended on the redox states of EPS, primarily determined by their electron donating capacity. Importantly, direct electrochemical reduction treatment of EPS leads to a substantial improvement in the PNP removal efficiency from 33.8% (EPSraw) to 56.9% (EPSred). This work contributes to a comprehensive understanding of the critical role of EPS redox property in the conversion of refractory pollutants in aquatic environments.

Co-removal of P-nitrophenol and nitrate in sulfur-based autotrophic and methanol-fed heterotrophic denitrification bioreactors

P-nitrophenol (PNP) can co-occur with nitrate (NO3-) in industrial and municipal wastewater due to effluent discharges from industry and agricultural activities. In this study, the simultaneous removal of PNP and NO3- was investigated under autotrophic and heterotrophic denitrifying conditions in two bioreactor columns at laboratory scale. Autotrophic denitrification with elemental sulfur showed efficient elimination of both PNP (85 % on average for 5–50 mg/L) and NO3- (99 % on average) even at feed PNP concentration of 50 mg/L. In contrast, the heterotrophic column showed significantly lower PNP removal (53 % on average for 5–50 mg/L) despite denitrification efficiency being ≥ 95 %. ORP was identified as a possible control parameter to modulate PNP removal efficiency. The autotrophic column showed better resiliency than the heterotrophic one under intermittent feeding of 50 mg/L of PNP. Absorbance spectra and HPLC results revealed no accumulation of PNP by-products, i.e., aminophenol, in the autotrophic column during transient feeding conditions.

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.