Metal ions are physiologically essential, but excessive metal ions may cause severe risk to plants and animals. Here, we prepared gold nanoclusters (Au NCs) protected by 11-mercaptoundecanoic acid (11-MUA), which have excellent fluorescence properties for the detection of metal ions. The results showed that the copper ions (Cu2+) and iron ions (Fe3+) in the solution have obvious quenching effect on the fluorescence intensity of Au NCs. The detection range of Fe3+ was 0.8–4.5 μmol/L (R2 = 0.992) and 4.5–11.0 μmol/L (R2 = 0.997). And Cu2+ has a lower linear range (0.1–1.0 μmol/L, R2 = 0.993). When EDTA was added into the reaction system, it was observed that the quenching effect of Cu2+ and Fe3+ on Au NCs showed different phenomenon. Then, the effect of metal ions on the fluorescence of Au NCs was investigated. The selective detection of Cu2+ was achieved by EDTA masking of Fe3+. In addition, we realized the metal ions detection application of Au NCs in the serumDownload high-res image (265KB)Download full-size imageA facile synthetic fluorescent 11-MUA-Au NCs apply to rapid and quantitative detection of Cu2+ and Fe3+ ions.

•Biological synthesis of gold nanoparticles.•Cytotoxicity and Photo irradiated antimicrobial activities of green nano-gold.•Intra cellular determination of Reactive oxygen species (ROS).The formation of metal nanoparticles is one of the most vast and intensifying research areas in favor of prospective applications for the advancement of new technologies. It is a well-founded, significant feature of green chemistry that making marvelous interconnection between nano-biotechnology and microbial biotechnology. In the present research, the aqueous extract of medicinally important plant Coptis Chinensis (in Chinese called “gold thread”) was applied for the synthesis of gold nanoparticles (Au-NPs). The crystalline structure, size, shape and dispersion of Au-NPs were confirmed by using various characterization techniques i.e. X-ray Diffraction (XRD), High Resolution Transmission Electron Microscope (HRTEM) and Energy Dispersive X-ray (EDX). Well dispersed face centered cubic crystalline structures were obtained in the this contribution. The possible phyto-chemicals involved in the reduction and stabilization of Au-NPs were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). The prepared NPs were tested against highly drug resistance bacterium Escherichia coli both in light and dark. The results illustrated that the antibacterial efficiency of photo irradiated Au-NPs was several times higher than in dark Au-NPs. The zone of inhibition for irradiated Au-NPs was19 ± 0.5 mm, which was higher than in dark 14 ± 0.4 mm. This high antibacterial activity of photo irradiated Au-NPs are due to the production of reactive oxygen species which is responsible for the inhibition of bacteria.

•Synthesis and characterization of Nobel metal nanoparticles•Biological applications•Physical and chemical method to nanoparticle synthesis•Anti-cancer properties of green synthesis nanoparticlesSynthesis of Nobel metal nanoparticles, play a key role in the field of medicine. Plants contain a substantial number of organic constituents, like phenolic compounds and various types of glycosides that help in synthesis of metal nanoparticles. Synthesis of metal nanoparticles by green method is one of the best and environment friendly methods. The major significance of the green synthesis is lack of toxic by-products produced during metal nanoparticle synthesis. The nanoparticles, synthesized by green method show various significant biological activities. Most of the research articles report the synthesized nanoparticles to be active against gram positive and gram negative bacteria. Some of these bacteria include Escherichia coli, Bacillus subtilis, Klebsiella pneumonia and Pseudomonas fluorescens. The synthesized nanoparticles also show significant antifungal activity against Trichophyton simii, Trichophyton mentagrophytes and Trichophyton rubrum as well as different types of cancer cells such as breast cancer cell line. They also exhibit significant antioxidant activity. The activities of these Nobel metal nano-particles mainly depend on the size and shape. The particles of small size with large surface area show good activity in the field of medicine. The synthesized nanoparticles are also active against leishmanial diseases. This research article explores in detail the green synthesis of the nanoparticles and their uses thereof.

Hydroxyl radicals (˙OH) generated by oxygen reduction reaction (ORR) were believed to be responsible for the electrochemical depolymerization of lignin in our previous study. However, the mechanism research was hard to carry out due to the recalcitrant nature of lignin. In this paper, 4-benzyloxyl phenol (PBP) and benzyl phenyl ether (BPE) were employed as lignin model compounds (LMCs). Based on the qualitative and quantitative analysis of the degradation products, a mechanism was put forward, which is that the in situ generated ˙OH selectively attacked the active site opposite to the phenolic hydroxyl group and induced the cleavage of the alkyl-O-aryl ether bond. The proposed mechanism was further verified by the electrochemical degradation of PBP under controlled conditions, which showed a positive correlation between the degradation efficiency of PBP and the concentration of in situ generated ˙OH radicals.

Removing lithium from the Bayer liquor for ensuring good alumina product quality demands a special lithium ion-sieve (LIS) with good stability in a strong alkaline medium. In this study, a three-dimensional porous H2TiO3-type LIS (porous-HTO) prepared by a polystyrene (PS) colloidal microspheres template was applied to adsorb Li+ from the strong alkaline Bayer liquor. XRD and SEM results confirm the fine stability of porous-HTO in strong alkaline medium, and the regeneration tests show that more than 64 mg g−1 lithium adsorption capacity still remains even after 5 cycles of lithiation–delithiation in the simulation Bayer liquor. The lithium adsorption processes of porous-HTO and bare H2TiO3-type LIS (bare-HTO) both fit the pseudo-second-order model, but the adsorption capacity and the adsorption rate of the porous-HTO are much better than those of the bare-HTO. For porous-HTO, the adsorption rate constant is 0.02357 g mg−1 h−1 and the equilibrium adsorption capacity is 76.3 mg g−1, while for bare-HTO, the adsorption rate constant is 0.009682 g mg−1 h−1 and the equilibrium adsorption capacity is only 44.8 mg g−1. The lithium selectivity tests demonstrate that the coexisting ions including Na+, K+, AlO2−, SiO32− in the simulation Bayer liquor have low influence on lithium adsorption. The simulation Bayer liquors with Li+ ions of 56.00, 30.00 and 5.00 mg L−1 are all reduced to below 1.00 mg L−1 by virtue of one-time-adsorption of porous-HTO at various solid to liquid ratios of 1.0, 0.5 and 0.1 g L−1, respectively.

The concentration of 5-hydroxyindole acetic acid (5-HIAA), the major metabolite of serotonin, might be the diagnosis basis for some cranial nerve pathology. An oxidized glassy carbon electrode (named OGCE) was employed to detect 5-HIAA with electrochemical methods. Multi-peaks appeared from the second cycle in range of 0.10–0.55 V (vs. AgCl/Ag) were assigned to the oxidative intermediates and products of 5-HIAA after the electrochemically driven oxidation at over 0.6 V in the first cycle. Kinetics studies show that all of these electrode reactions are adsorption-controlled processes, which are contributed to the strong hydrogen-bond interaction of these intermediates with the negatively charged hydroxyl and carboxyl groups on the surface of OGCE. Based on the square wave voltammetry (SWV) method, the linear relationship was shown between the peak current at 0.7 V and the concentration of 5-HIAA in range of 1.56–58.6 μmol/L, so 5-HIAA could be determined with limit of 0.917 μmol/L (S/N = 3) even certain interference were co-existed.

•Biological synthesis of silver nanoparticles•Optimization of plant extract and time effecting AgNPs synthesis•Photo and chemocatalytic activities of green nanosilver•Antioxidant potency of the prepared AgNPsIn this study, a simple and environmental friendly method was developed for the synthesis of silver nanoparticles (Ag-NPs) using Dimocarpus longan seed extract as a source of reducing and stabilizing agent. The appearance of a surface plasmon resonance peak at 432 nm confirmed the synthesis of silver nanoparticles (UV–visible spectroscopy). The biosynthesized Ag-NPs were face centered cubic structures (XRD) with an approximate particle size of 40 nm (TEM). Optimization study revealed that 10 mL of plant extract (2 mM AgNO3) at 180 min of incubation resulted the optimum product synthesis. Poly-phenolic compounds were majorly involved in the reduction of silver ions into Ag-NPs (FT-IR). The catalytic activities of Ag-NPs were assessed against the photo-catalytic degradation of methylene blue and chemo catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The results indicated that the prepared Ag-NPs have strong chemo catalytic activity with a complete reduction of 4-NP to 4-AP within 10 min. Similarly, Ag-NPs displayed higher photo-catalytic activity (K = 0.12) as compared to commercial Ag-NPs (K = 0.003). In addition, the silver nanoparticles exhibited a promising antioxidant activity in scavenging DPPH radicals. The findings of this study conclude that the biosynthesized Ag-NPs are promising agent possessing strong catalytic and reducing properties.

A three-dimensional (3D) structured electrode in which a compact CeO2-β-PbO2 particle layer on each carbon fiber in the felt (denoted as CF/CeO2-β-PbO2) was fabricated using cyclic voltammetry (CV) method in the presence of CeO2 nanoparticles in the electrolyte and supposed to be used as a sensor for in situ chemical oxygen demand (COD) detection. It was found that CeO2 was codeposited with PbO2 onto the anode, and the deposited crystals were tiny and compacted with each other. The electrochemical behaviors demonstrate that the fabricated CF/CeO2-β-PbO2 electrode possesses larger effective surface area, higher electrochemically catalytic activity, and better mechanical stability as compared with the anode without CeO2 deposited by CV method or constant potential (CP) method. The results of COD determination by the fabricated CF/CeO2-β-PbO2 electrode show a sensitivity of (3.0 ± 0.02) × 10−3 mA cm−2/mg L−1, a detection limit of 3.6 mg L−1 (S/N = 3) and a linear range of 30–8500 mg L−1 with correlation coefficient (R) of 0.9985 and RSD within 5 %.

•Synthesis of silver nano particles using Caruluma edulis plant extract.•Characterizations of silver nanoparticles by UV, FTIR, HRTEM and EDX.•Photo catalytic, antimicrobial and anti-oxidant activity of silver nanoparticles.•Reduction of phenolic compounds at modified GC/AgNP electrode.•Cyclic voltammetric study of bromothymol blue at GC/AgNP modified past electrode.In the present research work a novel, nontoxic and ecofriendly procedure was developed for the green synthesis of silver nano particle (AgNPs) using Caruluma edulis (C. edulis) extract act as reductant as well as stabilizer agents. The formation of AgNPs was confirmed by UV/Vis spectroscopy. The small and spherical sizes of AgNPs were conformed from high resolution transmission electron microscopy (HRTEM) analysis and were found in the range of 2–10 nm, which were highly dispersion without any aggregation. The crystalline structure of AgNPs was conformed from X-ray diffraction (XRD) analysis. For the elemental composition EDX was used and FTIR helped to determine the type of organic compounds in the extract. The potential electrochemical property of modified silver electrode was also studied. The AgNPs showed prominent antibacterial motion with MIC values of 125 μg/mL against Bacillus subtilis and Staphylococcus aureus while 250 μg/mL against Escherichia coli. High cell constituents' release was exhibited by B. subtilis with 2 × MIC value of silver nanoparticles. Silver nanoparticles also showed significant DPPH free radical scavenging activity. This research would have an important implication for the synthesis of more efficient antimicrobial and antioxidant agent. The AgNP modified electrode (GC/AgNPs) exhibited an excellent electro-catalytic activity toward the redox reaction of phenolic compounds. The AgNPs were evaluated for electrochemical degradation of bromothymol blue (BTB) dyes which showed a significant activity. From the strong reductive properties it is obvious that AgNPs can be used in water sanitization and converting some organic perilous in to non-hazardous materials. The AgNPs showed potential applications in the field of electro chemistry, sensor, catalyst, nano-devices and medical.

Electrochemical oxidation of catechols in the presence of 4-mercapto-benzoic acid as nucleophile have been studied in aqueous acetate buffer solution using cyclic voltammetry and control potential coulometry. The cyclic voltammetric results showed that an electro oxidative/Michael type sequential reaction occurs between the 4-mercaptide anion and electrochemically generated o-bezoquinones leading to the corresponding products 4a–4b.The mechanism electrochemical reaction is proved as an EC pathway using controlled-potential coulometry. The antimicrobial activity of these newly synthesized compounds were screened against Gram-positive and Gram-negative bacteria namely, Bacillus subtilis, Staphylococcus aureus, Escherichia coli. These newly syntheses compounds showed good antimicrobial activity.

Lignin, a natural macromolecule containing substantial aromatic rings and abundant hydroxyl groups, was firstly chemically grafted with phosphorus–nitrogen-containing groups via a liquefaction–esterification–salification process to prepare lignin-based phosphate melamine compound (LPMC). And then the LPMC which has remaining hydroxyl groups was used to substitute parts of polyols and copolymerize with isocyanate to produce lignin-modified-PU foam (PU-LPMC) with excellent flame retardancy. Owing to the rigid aromatic structure of lignin and the covalent linkages between LPMC and the polymer–matrix, PU-LPMC showed a nearly 2-fold increase in compression strength and excellent performance of thermal stability, char residue formation, self-extinguishment and inhibition from melt-dripping and smoke generation. Moreover, a large amount of non-flammable gases were released during thermal degradation and a compact and dense intumescent (C–P–N–O)x char layer formed on the surface of the foams after combustion, resulting in the improvement of anti-flaming properties of the polymer by the flame retardancy of both gas phase and condensed phase.

Electrochemical depolymerization of lignin for production of renewable aromatic compounds is presented. In the designed non-diaphragm electrolytic cell, lignin in alkaline electrolyte was directly electro-oxidized on the anode and chemically oxidized by the electro-generated H2O2 formed on the cathode simultaneously. The linkages among C9 units in lignin were broken down and more than 20 kinds of low-molecular-weight (LMW) aromatic compounds containing hydroxyl, aldehyde, carbonyl and carboxyl groups were generated and identified by GC-MS and ESI-MS/MS measurements. The effects of electrolysis conditions on the concentration of H2O2, the decomposition rate of H2O2 into reactive oxygen species (ROS) and the yields of LMW products were investigated in detail. Results show that H2O2 and ROS play very important roles in lignin depolymerization. The electrolysis conditions for producing higher concentrations of H2O2 and ROS are in favor of giving higher yields of LMW products. 59.2% of lignin was depolymerized into LMW products after 1 hour-electrolysis at 80 °C under a current density of 8 mA cm−2 with extra O2 supplement.

Lignin is a natural aromatic macromolecule in huge quantity and might serve as sustainable resources for the chemical industry after being depolymerized. An electrochemical approach combining anode oxidation and electro-generated H2O2 oxidation has been developed for converting lignin into value-added aromatic chemicals in this study. Lignin in alkali solution was electrolyzed in an undivided electrolytic cell with a cylindrical graphite felt cathode and a RuO2–IrO2/Ti mesh anode, in which the by-product O2 on the anode could be efficiently reduced to H2O2 on the cathode in situ. Results display that the depolymerization productivity via the integrated approach obviously surpassed the sum of that by separate H2O2 oxidation and anode oxidation. Moreover, the analysis results of GC-MS, GPC, and C9 expanded formula confirmed that C–C bonds and C–O–C bonds in lignin were cleaved synergistically by direct anodic oxidation and indirect H2O2 oxidation, and the macromolecules are gradually depolymerized into final products of monomers and dimers.

•Pyrite thermo-decomposes to iron monosulfide, pyrrhotite and sulfur.•Iron monosulfide, pyrrhotite or sulfur reduces hematite to magnetite.•Red mud is co-roasted with pyrite.•Iron in red mud is recovered by magnetic separation after roasting.A recycling process of iron from red mud by magnetic separation is proposed, in which iron oxide (Fe2O3) in red mud transforms to magnetite (Fe3O4) by anaerobic co-roasting with pyrite (FeS2). TG-DTA and XRD results showed that hematite was reduced to magnetite by the thermo-decomposed compounds (iron monosulfide, pyrrhotite and element sulfur) of pyrite. The mole ratio of pyrite to hematite and the roasting temperature effected the transformation. In the simulated experiment, 30 g red mud containing 9.24% of iron (13.2% in Fe2O3) mixed with 0.74 g pyrite were roasted at 600 °C under N2 atmosphere for 30 min. 4.5 g magnetic material (with Fe content of 36.9%) was magnetically separated, and the remaining solid only containing 0.61% of Fe (0.87% in Fe2O3), being able to meet the stipulated standard of 2% for refractory material manufacture.

An electrochemical process for producing potassium iodate based on oxidation of KI coupled with oxygen reduction reaction in a newly designed cell is reported. By using an Ag-modified oxygen reduction cathode, the proposed cell needed no ion exchange membrane, and the current efficiency for KIO3 was confirmed to be over 96%, the corresponding cell voltage was only 0.7–0.8 V.

Because the supply of bauxite ores in many countries is becoming deficient, a process of preparing alumina from an alternative resource, namely, kaolin, is proposed in this work. First, kaolin was heated at 600 °C for 2 h before being leached with 1 M citric acid solution, about 75% of the Al in kaolin entered the leachate as aluminum citrate (AlCit) solution. Then, about 50% of the Al(III) in the leachate could be precipitated as ammonium aluminum carbonate hydroxide (AACH) by addition of NH4HCO3 at pH 9.00 ± 0.50. The morphology of AACH characterized by SEM and TEM was spherical particles composed of many nanorods with sizes of about 500 × 25 nm. Finally, mesoporous γ-Al2O3 was obtained by roasting AACH at 700 °C. The Fe and Na contents in the obtained γ-Al2O3 product determined by XRD and ICP-AES were 2 and 0.1 ppm, respectively. The obtained γ-Al2O3 had a morphology similar to that of AACH, and its BET surface area was as high as 235.2 m2/g.

It is a promising technology in the alumina industry using citric acid to extract aluminum from clay or kaolin and obtain the solution of aluminum citrate (AlCit). But the prerequisite of the preparation procedure of alumina started from AlCit is that citric acid should be recycled. A process named AlCit−Dawsonite−alumina is proposed in this paper. By using Dawsonite as an intermediate, citrate groups could be separated and reused. The process was verified in laboratory scale: First, Dawsonite was precipitated from AlCit solution with a satisfied purity and conversion rate. Second, Dawsonite was transformed to alumina with low Na content through the two proposed methods. The structure and purity of the intermediate of Dawsonite and products of alumina were characterized by infrared, thermogravimetric−differential thermal analysis, X-ray diffraction, scanning electron microscopy, and inductively coupled plasma. The results show that the synthesized Dawsonite has a great purity and perfect crystallinity; and the Na content of the final alumina product is lower than 0.2%.

Ionic liquids due to their advantageous properties gain importance in many fields. This study aims to overview the use of ionic liquids in the selective partial fluorination of organic compounds through electrochemical method. In addition to ionic liquid based fluorination, the earlier approaches of fluorination through an electrochemical process have also been highlighted. The factors such as electrode materials (Pt, Ni, and C), types of solvents (CH3CN, DMC, THF, DME, Sulfone, etc.) and type of electrolytes (Et3N·3HF, Et3NF·3HF, py·HF, etc.) which affect the electrochemical fluorination of organic compounds have been reviewed. For electrode preparation, the carbon, platinum and nickel were considered suitable materials to be used as an electrode. In CH3CN media, Et3N·3HF and Et4NF·3HF showed better efficiency during fluorination of organic compounds. Solvent play an important role in electrochemical fluorination of organic compounds, with the change of solvent the percentage yield is highly affected. Py-HF is a convenient solvent-supporting electrolyte medium with a reasonably good conductivity. The electrolyte containing solvents have some side effects on electrochemical fluorination of organic compounds as observed in cyclic voltammetric analysis. Therefore electrochemical fluorination to organic compounds without the use of solvent gained more importance. The ionic liquids have been reported for its dual properties, as solvent as well as a fluorinating agent for organic compounds in electrochemical processes. It has been concluded that solvents free electrochemical fluorination of organic compounds gives good results as compare to solvent based. Ionic liquids due to more oxidative stability were noted to have considerable effect on the yield and selectivity of organic compound fluorination.Download full-size image