Fractionation and purification of antioxidant peptides from Chinese sturgeon (Acipenser sinensis) protein hydrolysates prepared using papain and alcalase 2.4L

Protein hydrolysates have the potential to be natural and safer sources of bioactive peptides. In this study, two proteases were used to hydrolyze Chinese sturgeon (Acipenser sinensis) protein, and the hydrolysates were then purified to yield antioxidant peptides. The degree of hydrolysis of 23.56 % and 18.14 % was obtained using papain and alcalase 2.4L, respectivly, and hydrolysates had 96.80 % and 87.24 % total amino acid content, respectivly. The papain hydrolysate (PH) and alcalase 2.4L hydrolysate (AH) showed good antioxidant activity against DPPH^? (IC₅₀ of 3.64 and 3.15 mg/mL) and ABTS^?+ (IC₅₀ of 1.92 and 1.58 mg/mL), respectively. The low-molecular-weight (<1000 Da) fraction of both hydrolysates demonstrated the highest antiradical activity (IC₅₀ of 2.59 and 2.31 mg/mL, DPPH) and (IC₅₀ of 1.54 and 1.36 mg/mL, ABTS), respectively. Nine peptides were separated from both hydrolysates using reverse phase high performance liquid chromatography (RP-HPLC). The IC₅₀ for ABTS^?+ scavenging activity of peptide P5 with valine, glycine and asparagine (MW of 282.13 Da) from PH, and peptide P3 with histidine, glycine and alanine (MW of 302.74 Da) from AH was 0.89 and 0.72 mg/mL, respectively. The fractions and purified peptides obtained from Chinese sturgeon hydrolysates could be utilized as natural antioxidant substitutes in pharmaceuticals and food products.     

Eco-friendly synthesis of size-controlled silver nanoparticles by using Areca catechu nut aqueous extract and investigation of their potent antioxidant and anti-bacterial activities

Silver nanoparticles (AgNPs) have attracted considerable attention owing to their unique biological applications. AgNPs synthesized by plant extract is considered as a convenient, efficient and eco-friendly material. In this work, the aqueous extract of Areca catechu L. nut (ACN) was used as the reducing and capping agents for one-pot synthesis of AgNPs, and their antioxidant and antibacterial activities were investigated. UV (Ultra Violet)-visible spectrum and dynamic light scattering (DLS) analysis revealed that the size of AgNPs was sensitive to the synthesis conditions. The synthesized AgNPs were composed of well-dispersed particles with an small size of about 10 nm under the optimal conditions (pH value of extract was 12.0; AgNO₃ concentration was 1.0 mM; reaction time was 90 min). In addition, scanning electron microscope with energy dispersive X-ray (SEM-EDX), transmission electron microscopy (TEM) and X-ray diffraction (XRD) results further verified that the synthesized AgNPs had a stable and well-dispersed form (Zeta potential value of ?30.50 mV and polydispersity index of 0.328) and a regular spherical shape (average size of 15–20 nm). In addition, Fourier transform infrared spectrometry (FTIR) results revealed that phytochemical constituents in ACN aqueous extract accounted for Ag⁺ ion reduction, capping and stabilization of AgNPs. The possible reductants in the aqueous extract of Areca catechu L. nut were identified by high-performance liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry (HPLC-ESI-qTOF/MS) method. More importantly, the synthesized AgNPs indicated excellent free radical scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH, IC₅₀ = 11.75 ± 0.29 μg/mL) and 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS⁺, IC₅₀ = 44.85 ± 0.37 μg/mL), which were significant higher than that of ascorbic acid. Moreover, AgNPs exhibited an enhanced antibacterial activity against six selected common pathogens (especially Escherichia coli and Staphylococcus aureus) compared with AgNO₃ solution. In a short, this study showed that the Areca catechu L. nut aqueous extract could be applied for eco-friendly synthesis of AgNPs.     

Green synthesis of copper oxide nanoparticles CuO NPs from Eucalyptus Globoulus leaf extract: Adsorption and design of experiments

The study is concerned with synthesizing copper oxide nanoparticles with leaf extract Eucalyptus Globoulus. The results of scanning electron microscopy (SEM) and dynamic light scattering (DLS) revealed that the green synthesized copper oxide nanoparticles are spherical and have a mean particle size of 88 nm, with a negative zeta potential of ?16.9 mV. The XRD graph showed the crystalline and monoclinic phases of CuO nanoparticles. The average crystalline size around 85.80 nm was observed by the Debye–Scherrer formula. The adsorption characteristics of the nano-adsorbents were investigated using methyl orange, and the adsorption efficiency at room temperature attained 95 mg/g. Copper oxide nanoparticles (CuO NPs) adsorb methyl orange dye most effectively at pH 4.5 when the dye is applied in quantities of 0.04 g/50 mL. Box–Behnken design (BBD) in response surface methodology (RSM) was used to optimize various process parameters, such as pH solution (X₁: 2 – 11), adsorbing dose (X₂: 0.01 – 0.08 g/L), [MO] dye concentration (X₃: 10 – 80 mg/L). Overall, the adjusted coefficient of determination (R²) value of 0.99 demonstrated that the used model was quite appropriate, and the chosen RSM was effective in optimization the decolorization conditions of MO.     

Application of stress induces ascorbate peroxidases of S. polyrhiza for green-synthesis Cu nanoparticles

The objective of this study was to assess the effects of stress on physiology/biochemical component of S. polyrhiza and its impact on CuNPs synthesis and bioethanol production. NaCl with RV5 provokes oxidative stress in S. polyrhiza and significantly increase MAD, Proline, H₂O₂, ROS, SOD and APX activity compare to control condition. Starch accumulation in S. polyrhiza was found 354% higher and correspond 4.4 times higher ethanol yield under stress condition compare to control. CuNPs were synthesized with an average size of 23–26 nm by purified fraction of APX having 37 KDa MW, 1.44 IU specific activity. Synthesized CuNPs were stable up to 15 consecutive cycles and potency against wide range of reactive dyes. The maximum remedial efficiency of synthesized CuNPs for COD and BOD was 55263.3 ± 3298.5 mg/m³min. and 30560.3 ± 1987.5 mg/m³min. respectively for RV5 wastewater. 0.072 mg/g of bioethanol was produced from the wet pulp remaining after nanoparticles synthesis. High efficiency of CuNPs and significant production of Ethanol, indicate that the feasibility for circular model for continuous industrial wastewater treatment.     

Controlling the diffusion of micro-volume Pb solution on hydrophobic polyurethane membrane for quantitative analysis using laser-induced breakdown spectroscopy (LIBS)

This work reports a novel controlling mechanism of analyte diffusion in a micro volume solution (100 μL) into a hydrophobic membrane. This study was designed to facilitate the liquid–solid conversion using membrane for laser-induced breakdown spectroscopy (LIBS) in quantitatively analyzing aqueous lead (Pb) pollutant. Herein, we used the same analyte (Pb) solution applied on one side of the membrane (back side) to enhance the diffusion of the analyte administered from the other side (front side). The membrane was confirmed hydrophobic with contact angles ranged from 104.6°±1.3° to 106.28°±1.7°, where its morphology had smooth surface and randomly distributed small pores. We found the limit of detection (LOD) to reach 184.2 mg/L derived from a calibration curve with Pb I (405.7 nm) line intensity as the dependent variable, where the root-mean-square-errors (RMSE) and correlation (R²) were 1.08 M and 0.999, respectively. In comparison, the membrane back side with distilled water achieved LOD as low as 134.53 mg/L obtained from the similar calibration curve (RMSE = 5.8 M; R² = 0.986). Further analysis using the LIBS spectra confirmed the role of the analyte ion on the back side of the membrane in enhancing the analyte diffusion.     

Antitubercular and antioxidant activities of hydroxy and chloro substituted chalcone analogues: Synthesis,biological and computational studies

A series of chalcone analogues (1–15) were synthesized by Claisen-Schmidt condensation in good yields (70–95%) and characterized by FT-IR, ¹H NMR and mass spectral methods. Additionally, compounds 3 and 7 were characterized by ¹³C NMR. Antitubercular and antioxidant activities of the chalcones were evaluated by MABA and DPPH free radical assays. In MABA assay analogues 3 (MIC = 14 ± 0.11 µM) and 11 (MIC = 14 ± 0.17 µM) bearing fluorine and methoxy groups at para and meta positions were 1.8-times more active than the standard pyrazinamide (MIC = 25.34 ± 0.22 µM). The chalcone analogues such as compound 7 (IC₅₀ = 4 ± 1 µg/mL) containing electron releasing groups such as OH at ortho position had slightly more antioxidant activity than Gallic acid (IC₅₀ = 5 ± 1 µg/mL). The potential compounds 3, 7, 9 and 11 were less selective and toxic against human live cell lines-LO2. Further, molecular docking results of chalcones against anti-tubercular drug target isocitrate lyase (PDB ID: 1F8M) revealed that compound 3 and 11 shown least binding energies as ?7.6, and ?7.5 kcal/mol are in line with in vitro MABA assay, suggesting that these compounds 3 and 11 are strong inhibitor of isocitrate lyase. SwissADME programme estimated the drug likeliness properties of compounds 3, 7, 9 and 11. The lead molecules arisen through this study helps to develop new antitubercular and antioxidant agents.     

Preparation of carbon-aerogel polypyrrole composite for desalination by hybrid capacitive desalination method

Capacitive Deionization (CDI) is an emerging technology with great potential applications. Most researchers view it as a viable water treatment alternative to reverse osmosis. This research reports the preparation and application of a carbon aerogel polypyrrole (CA-PPy) composite for the desalination of NaCl solution by the hybrid CDI method. The carbon aerogel (CA) was prepared from a Resorcinol / Formaldehyde precursor by the sol–gel method. The aerogel obtained from the sol–gel was then pyrolysed in a tube furnace to form CA. Polypyrrole (PPy) was prepared by the Oxidative chemical polymerisation of pyrrole, ferric chloride hexahydrate (oxidant), and sodium dodecyl sulfate (dopant). A composite of CA and PPy was then prepared and used to modify carbon electrodes. The CA-PPy composite was characterised to verify its composition, morphology, thermal properties, and functional groups. The electrochemical properties of the material were determined by Cyclic voltammetry (CV) and Electrochemical impedance spectroscopy (EIS) tests. The electrochemical tests were done using a GAMRY potentiostat electrochemical workstation, a 1.0 M KCl was used as the electrolyte, and the applied potential window was (-0.2 to + 0.6) V for the CV test. The EIS test was done with the same concentration of KCl electrolyte at an applied potential of 0.22 V and at a frequency range of (0.1 – 100, 000) Hz. The optimal specific capacitance of the CA is 115F/g, and that of the composite is 360.1F/g, they were both obtained at a scan rate of 5 mV/s. The CDI desalination study of the CA-PPy composite showed a salt adsorption capacity (SAC) of 10.10 mg/g (300 mg/L NaCl solution) – 15.7 mg/g (800 mg/L NaCl solution) at 1.2 V applied voltage. The salt recovery efficiency of the electrode material in the 300 mg/L solution is 27 %, in the 500 mg/L solution, it is 20.12 %, and in the 800 mg/L solution, it is 15.41 %. The electrode material also showed good electrochemical stability after nine cycles of ion adsorption/desorption study.     

Bioprospecting Dodonaea viscosa Jacq.; a traditional medicinal plant for antioxidant,cytotoxic, antidiabetic and antimicrobial potential

Purpose of studyDodonaea viscosa Jacq. is an ethnomedicinal plant that has been extensively used for the treatment of gout, rheumatism and pain. Current study was undertaken to mine its antioxidant, antimicrobial, cytotoxic and antidiabetic potential. Chromogenic assays were employed to establish plant’s multimode antioxidant profile whereas HPLC fingerprinting was performed to quantify polyphenols. Standard brine shrimp lethality, MTT and SRB assays proved its cytotoxicity potential.ResultsAmong all the extracts (flower, leaf, stem and root), maximum extract recovery (22% w/w), gallic acid equivalent total phenolic content (20.11 ± 0.11 ug GAE/mg DW), ascorbic acid equivalent total antioxidant capacity (22.5 ± 0.07 µg/mg DW) and total reducing power (31.1 ± 1.13 µg/mg DW) were recorded in the distilled water + acetone extract of leaf. The acetone extract of leaf showed maximum quercetin equivalent total flavonoid content (4.78 ± 0.13 µg/mg DW). HPLC-DAD analysis revealed significant amount of rutin, vanillic acid, coumaric acid, ferulic acid, gallic acid, syringic acid, cinnamic acid, gentisic acid, catechin, caffeic acid, apigenin and myricetin in the different plant parts. Maximum scavenging potential was exhibited by methanol + ethyl acetate stem extract (IC₅₀ = 23.8 µg/ml). The highest antibacterial potential was found in flower (85.7%) and root (71.4%) extracts. The ethanol + ethyl acetate (1:1) leaf extract showed noteworthy toxicity against brine shrimps (LC₅₀ = 95.46 µg/ml) while a notable antiproliferative activity against THP-1 (IC₅₀ = 3.4 µg/ml) and Hep G2 (IC₅₀ = 20 µg/ml) cell lines was shown by ethanol + ethyl acetate extracts (1:1) of stem and root, respectively. A moderate inhibition of α-amylase enzyme was observed in all parts of the plant.ConclusionThe results of the present study suggest D. viscosa as a potential source of antioxidant, anticancer and α-amylase inhibitory phytochemicals.     

Cyclometalated complexes containing ferrocenyl Schiff base: Preparation,characterization, DFT calculations,application in cancer and biological researches and MOE studies

A series of transition metal (II/III) complexes containing organometallic Schiff base ligand (H₂L) had been synthesized and characterized by using elemental analysis (C, H, N, M), molar conductivity, IR, UV–Vis, ¹H NMR and mass spectral analysis. Also, their TG and DTG behaviors were investigated. The ligand was prepared by condensation of 4-aminosalicylic acid with 2-acetylferrocene in 1:1 M ratio. The data of elemental analysis indicated that the prepared complexes were synthesized also in a 1:1 M ratio. The ligand behaved as neutral bidentate ligand that coordinated to metal ions through protonated O-phenolic and protonated carboxylic-OH groups. All complexes had octahedral structure. DFT calculations for H₂L ligand were determined with some parameters such as HOMO-LUMO energy gab, electronegativity and chemical hardness–softness. Antimicrobial activity of both H₂L Schiff base ligand and its metal complexes was tested against different strains of bacteria and fungi species. Furthermore, all compounds had been screened for their anticancer activities against breast cancer (MCF-7) cell line. [Cu(H₂L)(H₂O)₂Cl₂]·2H₂O complex had the lowest IC₅₀ value = 47.3 µg/mL. For determining the more effective and probable binding mode between the H₂L ligand, Co(II) and Zn(II) complexes with different active sites of 4K3V, 2YLB and 3DJD receptors, so molecular docking studies were investigated.     

Response surface methodology for the optimization of the ultrasonic-assisted rhamnolipid treatment of oily sludge

This study investigates the recovery of oily sludge using ultrasound-assisted rhamnolipids and uses oil recovery yield as an evaluation index. The Box–Behnken response surface method was employed to investigate the individual and interactive effects of four different operating factors: frequency, dosage, liquid–solid ratio, and stirring speed. The model optimization results showed that the order of degree of influence of these four factors is frequency > liquid–solid ratio > dosage > stirring speed. The mathematical model predicted the highest oil recovery yield as 92.27%, which was highly accurate (in the 95% confidence interval) as from the experimental results, the highest oil recovery yield was 89.95% under optimal reaction conditions (frequency = 25.58 kHz, dosage = 150.45 mg/L, liquid–solid ratio = 4.1:1 mL/g, and stirring speed = 407 rpm). Thus, the deviation from the prediction model was only 2.32%, indicating that this method provides a theoretical basis for the treatment of oily sludge and can be implemented for practical application in Huaidong in the Xinjiang Province.     

Synthesis,antifungal activity and in vitro mechanism of novel 1-substituted-5-trifluoromethyl-1H-pyrazole-4-carboxamide derivatives

Inspired by the wide application of amides in plant pathogens, a series of novel 1-substituted-5-trifluoromethyl?1H?pyrazole-4-carboxamide derivatives were designed and synthesized. Bioassay results indicated that some target compounds exhibited excellent and broad-spectrum in vitro and certain in vivo antifungal activities. Among them, the in vitro EC₅₀ values of Y₁₃ against G. zeae, B. dothidea, F. prolifeatum and F. oxysporum were 13.1, 14.4, 13.3 and 21.4 mg/L, respectively. The in vivo protective activity of Y₁₃ against G. zeae at 100 mg/L was 50.65%. SAR analysis revealed that the phenyl on the 1-position of the pyrazole ring was important for this activity. An antifungal mechanism study of Y₁₃ against G. zeae demonstrated that this compound may disrupt the cell membrane of mycelium, thus inhibiting the growth of fungi. These mechanistic study results were inconsistent with those for traditional amides and may provide a novel view for deep study of this series of pyrazole carboxamide derivatives.     

Identification of the roselle root rot pathogen and its sensitivity to different fungicides

Root rot is the main disease affecting roselle plantings and production and can seriously affect the yield and quality of calyces. Thus, it is urgent to identify the pathogen causing roselle root rot and screen effective pesticides to control the disease. In the present study, morphological observation, pathogenicity assays and molecular biology methods were used to identify the pathogen causing roselle root rot in Nanning, Guangxi Province, and four biological and four chemical fungicides were evaluated for their effects on the mycelial growth rate of the pathogen. The results showed that the pathogen causing roselle root rot in Nanning, Guangxi, was Fusarium solani, marking the first report of this fungus causing root rot of roselle in China. The fungicidal activity screening revealed differences in the inhibitory effects of the eight fungicides on the colony growth of F. solani. For the biofungicides, Bacillus amyloliquefaciens exhibited the best fungistatic effect, with an IC₅₀ of 1.10 mg/mL. When the mass concentration was 2.5 mg/mL, the mycelial growth of the pathogen was 100% inhibited, while Bacillus subtilis had the worst inhibitory effect, with an IC₅₀ of 46.78 mg/mL. When its mass concentration was 80 mg/mL, mycelial growth was only inhibited by 74.67%. For the chemical fungicides, carbendazim and thiophanate-methyl presented the strongest effects on F. solani, with IC₅₀ values of 0.0082 mg/mL and 0.0243 mg/mL, respectively. When the mass concentrations were 0.03 mg/mL and 0.075 mg/mL, mycelial growth was inhibited by 100%. These results provide a scientific basis for rationally selecting fungicides to control roselle root rot in field production.     

An ultrasensitive electrochemical immunosensor for CA72-4 based on a signal amplification strategy of MoS2 nanoflower-supported Au nanoparticles

Accurate detection of cancer antigen 72-4 (CA72-4), a tumor-associated glycoprotein, is of great significance for gastric cancer diagnosis and immunotherapy monitoring. Modification of noble metal nanoparticles on transition metal dichalcogenides can significantly enhance functions, such as electron transport. Molybdenum disulfide gold nanoparticles nanocomposites (MoS₂-Au NPs) were prepared in this study and a series of characterization studies were carried out. In addition, a label-free, highly sensitive electrochemical immunosensor molybdenum disulfide -Au nanoparticles/Glassy carbon electrode (MoS₂-Au NPs/GCE) was also prepared and used for the detection of CA72-4. The electrochemical performance of the immunosensor was characterized by electrochemical techniques, such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The results indicated that better MoS₂-Au NPs nanomaterials have been synthesized, and the prepared electrochemical immunosensor, MoS₂-Au NPs/GCE, showed excellent electrochemical performance. The sensor exhibited high detection sensitivity under optimal conditions, including an incubation time of 30 min, an incubation temperature of 25 °C, and a pH of 7.0. The electrochemical immunosensor also had a low detection limit of 2.0 × 10^?5 U/mL (S/N = 3) in a concentration range of 0.001–200 U/mL, with good selectivity, stability, and repeatability. In conclusion, this study provided a theoretical basis for the highly sensitive detection of tumor markers in clinical biological samples.     

Ethanol leaf extract of Ruspolia hypocrateriformis abrogated hepatic redox imbalance and oxidative damage induced by heavy metal toxicity in rats

Humans and animals are frequently exposed to heavy metals in the environment, which are highly toxic to the physiological milieu and organs of the body. We investigated the ameliorative potentials of ethanol leaf extract of Ruspolia hypocrateriformis against redox imbalance due to exposure of rats to heavy metals. The in vitro study explored the antioxidant potentials of the ethanol leaf extract using 1,1-diphenyl-2-picryl hydrazyl, nitric oxide and ferric reducing antioxidant potential assays respectively. HPLC was used to quantify the amount of flavonoids and phenolic acids in the extract. For in vivo study, 30 rats were randomly divided into 5 groups. Group A received normal saline. Group B received combined solution of Lead Nitrate and Mercury Chloride (11.25 mg/kg and 0.4 mg/kg) per Bwt/day. Group C, D and E were administered with the leaf extract at doses of 200, 400 and 600 mg/kg body weight respectively for 28 consecutive days. Biomarkers of hepatic dysfunctions and oxidative stress were investigated in the study rats. The HPLC study revealed high amount of gallic and ferulic acids (17.86 ± 2.68), which are the major phenolic compounds found in the extract. The extract further exhibited high antioxidant potentials in inhibiting the scavenging activity of free radicals produced in vitro. Interestingly, 600 mg/kg dosage of the leaf extract successfully ameliorated the distorted redox imbalance and oxidative damage in the liver of the rats caused by exposure to the heavy metals. Leaf extract of Ruspolia hypocrateriformis demonstrated strong antioxidant potentials, which could be exploited in pharmaceutical preparations.     

Fast simultaneous determination of 23 veterinary drug residues in fish,poultry, and red meat by liquid chromatography/tandem mass spectrometry

The misuses of veterinary drugs can result in the accumulation of residues in food of animal origin that can make its way to the final consumer. Herein we describe a simple method for the accurate determination of beta-lactams, quinolones, sulphonamides, and tetracyclines in fish, poultry, and red meat. No extraction cartridges were used; instead, the extraction process consisted of the addition of an organic solvents, shaking, centrifugation, and dilution. An extensive validation process demonstrated an excellent linearity (R² ≥ 0.99) for 23-drug residues. The recovery of drugs in different matrices at two concentration levels (n = 6) was in the range of 82–119%. The method was proved to be repeatable and reproducible with intra/inter-day measurements (RSDs lower than 20%). The quantification limits of drug residues were in the range of 0.8 to 45.3 ug/kg, which is well below the maximum residue limits set by most regulatory authorities. This method was successfully applied to the routine analysis of 20 fish, poultry, and red meat samples (n = 60).     

Design,synthesis, docking and mechanistic studies of new thiazolyl/thiazolidinylpyrimidine-2,4-dione antiproliferative agents

In this article, we display on the synthesis and biological evaluation of a new series of thiazolylpyrimidine 3a-l and thiazolidinylpyrimidine derivatives 5a-e. The structures of the new compounds were confirmed by using different spectral techniques including NMR, IR, mass spectroscopy in addition to elemental analyses. The cell viability of the new compounds was assessed against normal human mammary gland epithelial (MCF-10A) cell line. Data revealed that none of the compounds examined exhibited cytotoxic effects, and the cell viability for the compounds examined at 50 µM was greater than 87%. The antiproliferative activity of 3a-l and 5a-e was evaluated against four human cancer cell lines where the compounds showed promising activity. The most potent derivatives were compounds 3a, 3c, 3f, 3i, and 5b with GI₅₀ values ranging from 0.90 µM to 1.70 µM against the four cancer cell lines in comparison to doxorubicin (GI₅₀ = 1.10 µM). Compounds 3a, 3c and 3i showed potent antiproliferative activity with dual inhibitory action against EGFR and BRAF^V600E. Compounds 3a, 3c, and 3i demonstrated promising AutoDock scores towards EGFR and BRAF^V600E with values of ? 9.1 and ? 8.6, ?9.0 and ? 8.5, and ? 8.4 and ? 8.0 kcal/mol, respectively. The physicochemical and pharmacokinetic characteristics of 3a, 3c, and 3i were anticipated, demonstrating their oral bioavailability.     

Ascorbic acid supported Carboxymethyl cellulose stabilized silver nanoparticles as optical nanoprobe for Au3+ detection in environmental sample

Heavy metals (HMs), pollution of major environmental matrices and its attendant effects on human health and the environment, continue to generate huge scientific interest, particularly in monitoring and detection. Herein, the optical property of carboxymethyl cellulose stabilized silver nanoparticles (CMC-AgNPs), supported with ascorbic acid, is exploited as a colorimetric probe for the detection of toxic Au³⁺ ion in solution. The as-synthesized CMC-AgNPs showed sharp absorption maximum at 403 nm, with sparkling yellow color and average particles size distribution less than 10 nm. It was further characterized using ATR-FTIR, TEM, FESEM/EDS, XRD and DLS/zeta potential analyzer. Au³⁺ ion detection strategy involves the addition of ascorbic acid (AA) to a pH adjusted CMC-AgNPs, followed by the analyte addition. AA would facilitate the reduction of Au³⁺ on CMC-AgNPs (seed), with resultant color perturbations from light yellow to yellow, orange, ruby red and purple red, under 8 min incubation, at room temperature (RT). The CMC-AgNPs could also serve as a catalyst, by promoting AA mediated reduction of Au³⁺, in-situ. Moreover, we propose, that the color and the absorption spectra change is attributed to the deposition of gold nanoparticles (AuNPs), on the CMC-AgNPs/AA probe, to form (CMC-Ag@Au) nanostructures, depending on the analyte concentration. Absorbance ratio (A₅₄₀/A₄₀₃) showed good linearity with Au³⁺ concentration from 0.25 to 100.0 µM, and an estimated LOD of 0.061 µM. The assay was applied to Au³⁺ detection in environmental wastewater sample, showing satisfactory real sample detection potentiality.     

Pathway and mechanism study on improvement of N2 selectivity of catalytic denitrification

Recently, nitrate pollution has attracted more public attention. In order to truly remove nitrate and reduce total nitrate content (TN) in water body, more harmless N₂ should be converted from nitrate. Studies on catalytic removal of nitrate in wastewater have been carried out. However, the catalytic performance still needs to be significantly improved, especially the N₂ selectivity. According to these, strategies that enable to efficiently improve N₂ selectivity of catalytic denitrification were explored in this paper. Results implied that the catalyst with composite carrier that possesses porous structure, large surface area, excellent electronic properties, and stable physical–chemical property tends to have better catalytic performance. It is suggested that acid washing by 2 mol/L HCl for certain carriers be applied to enhancement of N₂ selectivity. Additionally, higher N₂ conversion was also achieved by addition of sodium bis-2-ethylhexyl sulphosuccinate (AOT) onto Pd with the formation of Pd_AOT-Cu catalyst, which may be ascribed to the AOT that partially shields Pd active sites and inhibits hydrogen spillover from Pd to Cu. Response Surface Methodology (RSM) was utilized for experimental design and prediction of the optimal parameters. More N₂ was obtained under the predicted optimal conditions: 5.0 pH, 135 min time, 3.1 Pd: Cu, and 3.1 g/L Fe⁽⁰⁾.