Alkalescent Conditions Research Articles

Cookies-like Ag2S/Bi4NbO8Cl heterostructures for high efficient and stable photocatalytic degradation of refractory antibiotics utilizing full-spectrum solar energy

Developing high efficient and stable photocatalysts that extend light-harvesting to near-infrared (NIR) region of solar irradiation is deemed to be critical for the optimization of solar-to-chemical energy conversion. Herein, we report a cookies-like Ag2S/Bi4NbO8Cl, for high efficient photocatalytic processing medical antibiotics waste. By delicately controlling the electrostatic interaction between Ag+ and laminar Bi4NbO8Cl substrate in alkalescent condition, Ag2S nanoparticles are well dispersed, forming a heterostructured photocatalyst. The unique design of the architecture caused photo-induced electrons on the Ag2S migrate to the (001) facet of Bi4NbO8Cl through the type-II heterojunctions, avoiding the photo-induced reduction of Ag+ to metallic Ag species, and stabilizing Ag2S photocatalysts. The impactful spatial separation of photo-induced charges in Ag2S/Bi4NbO8Cl, lead to 13.2-folds enhancement in photocatalytic decomposition towards tetracycline under NIR irradiation as compared to pristine Ag2S, achieving 4.50 × 10−3 min−1. This finding provides a facile approach to make use of full-spectrum sunlight in environmental remediation applications.

Injectable Hydrogel Based on Defect-Rich Multi-Nanozymes for Diabetic Wound Healing via an Oxygen Self-Supplying Cascade Reaction.

Diabetic wound healing remains challenging owing to the risk for bacterial infection, hypoxia, excessive glucose levels, and oxidative stress. Glucose-activated cascade reactions can consume glucose and eradicate bacteria, avoiding the direct use of hydrogen peroxide (H2 O2 ) and wound pH restriction on peroxidase-like activity. However, the anoxic microenvironment in diabetic wounds impedes the cascade reaction due to the oxygen (O2 ) dependence of glucose oxidation. Herein, defect-rich molybdenum disulfide nanosheets loaded with bovine serum albumin-modified gold nanoparticle (MoS2 @Au@BSA NSs) heterostructures are designed and anchored onto injectable hydrogels to promote diabetic wound healing through an O2 self-supplying cascade reaction. BSA decoration decreases the particle size of Au, increasing the activity of multiple enzymes. Glucose oxidase-like Au catalyzes the oxidation of glucose into gluconic acid and H2 O2 , which is transformed into a hydroxyl radical (•OH) catalyzed by peroxidase-like MoS2 @Au@BSA to eradicate bacteria. When the wound pH reaches an alkalescent condition, MoS2 @Au@BSA mimicks superoxide dismutase to transform superoxide anions into O2 and H2 O2 , and decomposes endogenous and exogenous H2 O2 into O2 via catalase-like mechanisms, reducing oxidative stress, alleviating hypoxia, and facilitating glucose oxidation. The MoS2 @Au@BSA nanozyme-anchored injectable hydrogel, composed of oxidized dextran and glycol chitosan crosslinked through a Schiff base, significantly accelerates diabetic wound healing.

Activation mechanisms of quartz flotation with calcium ions and cationic/anionic mixed collectors under alkalescent conditions

High-efficiency flotation of quartz under alkalescent conditions remains challenging owing to the leak of an effective activator. In this research, high quartz flotation recovery was achieved with Ca2+ and cationic/anionic mixed collectors under alkalescency, while activation mechanisms were systematically investigated. Micro-flotation results indicated that 81.60% quartz were floated with 5 × 10−4 mol/L of CaCl2, 2.5 × 10−4 mol/L of sodium oleate (NaOL) and 3.0 × 10−5 mol/L of Dodecylamine (DDA) at pH 9.0. However, under 10% of quartz were recovered without adding CaCl2 or only using CaCl2 and NaOL. Zeta potential, infrared spectroscopy and X-ray photoelectron spectroscopy results confirmed that NaOL adsorbed on calcium-activated quartz surface via chemisorption and DDA could enhance the hydrophobicity of quartz via charge neutralization. Atomic Force Microscope imaging and revealed that Ca2+ could adsorb on quartz in patches, which was subsequently adsorbed with mixed NaOL/DDA. This outcome demonstrated that CaCl2 could promote co-adsorption of cationic/anionic mixed collectors on quartz at mildly basic pH.

Flocculation Efficiency and Mechanism of Carbamazepine by Microbial Flocculant Extracted from Klebsiella pneumoniae J1.

The microbial flocculant (MFX) extracted from Klebsiella pneumoniae J1 was used to remove carbamazepine in prepared wastewater and domestic sewage. The influence factors and flocculation mechanism were studied. The optimal carbamazepine removal conditions for MFX were pH of 7-8, 7 mL of flocculant, 0.1 mL of coagulant, and 35°C, and the removal rate reached 81.75%. MFX was efficient in the removal of carbamazepine in both domestic sewage (75.03%) and secondary sedimentation tank effluent (69.76%). The pseudo-first-order kinetic equation fitted the adsorption process better than the pseudo-second-order kinetic equation, which suggested that the adsorption was not pure chemical adsorption. The analysis of floc size suggested that the repulsive force between carbamazepine and MFX was weakened under alkalescent conditions, which can help the growth and coherence of flocs and increase the carbamazepine removal efficiency. Enough dosage of MFX can generate larger flocs, but excessive dosage of MFX will decrease the carbamazepine removal rate because of increase in electrostatic repulsion. The analysis of 3D-EEM and FTIR suggested that hydroxyl, amino, and carboxyl in MFX played an important role in the removal of carbamazepine. As an eco-friendly and highly efficient microbial flocculant, MFX has potential for practical applications in carbamazepine removal.

Preparation of octopus-like lignin-grafted cationic polyacrylamide flocculant and its application for water flocculation

High efficiency lignin-grafted cationic polyacrylamide (L-CPA) flocculant was synthesized via “grafting to” method using acrylamide (AM), methylacryloyloxyethyltrimethyl ammonium chloride (DMC) and enzymatic hydrolysis lignin (EHL) as raw materials. The linear pre-polymer of cationic polyacrylamide (CPA) terminated with chlorine was first synthesized and then grafted onto EHL via reactions of chlorine with phenolic hydroxyl groups in lignin molecules. The synthesized L-CPA could self-assemble into octopus-like nanospheres with CPA segments dissolved in water and hydrophobic lignin skeletons concentrated in the core, which endowed the L-CPA with excellent flocculation efficiency for kaolin suspension under faintly acid, neutral or alkalescent conditions (pH = 5–9). Only a small dosage between 4.0–4.5 mg/L of L-CPA was needed for flocculation of the kaolin suspension. The charge neutralization and bridging effect was proposed for the flocculation mechanism of the lignin-grafted cationic polyacrylamide. The octopus-like L-CPA was cheap, environmentally friendly and technically feasible, showing a great prospect in wastewater treatment.

Effect of octenyl succinic anhydride starch ester by semi-dry method with vacuum-microwave assistant

Corn starch was esterified with octenyl succinic anhydride (OSA), in which semidry method assisted with vacuum-microwave treatment was used under the alkalescent condition. The effect of vacuum treatment on esterification was studied. The products were characterized by Fourier transform infrared (FT-IR) spectroscopy, 1H nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and X-ray diffraction. And the emulsifying properties were investigated with the emulsifying capacity (EC), emulsion droplet size and confocal laser scanning microscopy (CLSM). The degree of substitution (DS) of OSA starch increased significantly (ρ < 0.05) assisted by the vacuum-microwave treatment with the same dosage of reactant compared with the microwave only. The results confirmed the formation of OSA starch prepared by the method, all reactions occurred mainly on the surface of granules, and had no significant effect on the starch crystallinity. The OSA starch was a good polymeric surfactant with good abilities both in hydrophilic and lipophilic. The emulsifying capacity, degree of substitution of the OSA starch prepared by the method attractively showed vast potential for scale production.

Synchronous removal of CuO nanoparticles and Cu2+ by polyaluminum chloride-Enteromorpha polysaccharides: Effect of Al species and pH

Copper oxide nanomaterials have been extensively applied and can have serious impacts when discharged into the aquatic environment, especially when complexed with humic acid (HA) to form composite contaminants. As an innovative recycled coagulant aid, Enteromorpha polysaccharides (Ep) were associated with polyaluminum chloride (PACl) (denoted as PACl-Ep) to simultaneously remove CuO nanoparticles, Cu2+ and HA in this study. The influence of different Al species coagulants (AlCl3, PAClb and PAClc) and water pH on coagulation performance, floc properties and reaction mechanisms was investigated in detail. Results showed that in the three PACl-Ep systems, PAClb-Ep gave the highest removal efficiencies for turbidity and Cu2+, and the best UV254 removal effect was reached by using PAClc-Ep. Higher contents of Alb and Alc contributed to great coagulation performance because of their stronger bridging and sweeping effects. For all the Al species coagulants, alkalescent conditions were more conducive to removing Cu and HA compared to acidic conditions. Additionally, smaller and more agminated flocs with great recovery ability were formed by PAClb-Ep and PAClc-Ep systems (bridging and enmeshment effects cooperated with the chelated reticular structure formed by the Ep and Al species). Similarly, due to the increased hydrolysis and hydroxide precipitates, flocs formed under the condition of alkalescence were smaller, denser and stronger compared with weakly acidic conditions.

The mechanism change by switching the reactants from water to hydroxyl ions for electrocatalytic water oxidation: a case study of copper oxide microspheres.

Developing noble metal-free water oxidation catalysts is essential for many energy conversion/storage processes (e.g., water splitting). Herein, we report a facile synthesis of CuO microspheres composed of ultrathin, single-crystal-like nanosheets via a simple solution method. The as-obtained CuO microspheres can serve as an active and stable water oxidation catalyst under electrochemical reaction conditions, owing to their unique structural features. In electrochemical water oxidation, this catalyst affords a current density of 10 mA cm-2 (a value related to practical relevance) at an overpotential of ∼0.48 V. Pure CuO was reported as a water oxidation catalyst (WOC) from near-neutral conditions to alkalescent conditions. Electrochemistry values agree with the Nernstian behavior, suggesting ne-/nH+ transfer prior to a chemical rate-determining step. Our results suggest that the delicate nanostructure can offer unique advantages for developing efficient water oxidation catalysts.

ChemInform Abstract: Sequential Michael Addition/Retro‐Claisen Condensation of Aromatic β‐Diketones with α,β‐Unsaturated Esters: An Approach to Obtain 1,5‐Ketoesters.

AbstractThis cascade process involves C—C bond cleavage of aromatic β‐diketones as phenacyl donors under alcoholic alkalescent conditions.

Design and synthesis of a novel fluorescent benzo[g]imidazo[4,5-c]quinoline nucleoside for monitoring base-pair-induced protonation with cytosine: distinguishing cytosine via changes in the intensity and wavelength of fluorescence.

A novel fluorescent benzo[g]imidazo[4,5-c]quinoline nucleoside (BIQ)A (1) comprising a 3-deaza-2'-deoxyadenosine skeleton was developed and used to monitor (BIQ)A-C base-pair formation in oligodeoxynucleotide (ODN) duplexes. The newly synthesized (BIQ)A exhibited distinct photophysical properties associated with its protonated/deprotonated forms (monomer: pKa 6.2) via dramatic changes in its absorption and fluorescence spectra. In ODN duplexes, the induced protonation of (BIQ)A occurred, even under alkalescent conditions when cytosine was the opposite base on the complementary strand; the resulting (BIQ)A-C base pairs were stable. By monitoring the protonation of (BIQ)A under neutral and alkalescent conditions, we could clearly discriminate cytosine through spectral changes in absorption and fluorescence. Similarly, we found that the demonstrated 3-deaza-2'-deoxyadenosine (3z)A forms a stable base pair with cytosine via N(1) protonation in ODN duplexes under neutral and acidic conditions (pH < 7.0). At lower pH values, (3z)A-containing ODNs could clearly discriminate cytosine through melting temperature (Tm) measurements. Therefore, ODN probes containing indicator nucleosides, such as (BIQ)A and (3z)A, exhibit great potential as bioprobes for genetic analysis and structural studies of nucleic acids.

Effects of enzymolysis on the functional ingredient contents and antioxidant activities of aqueous enzymatic extracts from Rice Bran and correlation analysis

Effects of different hydrolytic conditions on functional ingredient contents and antioxidant activities of aqueous enzymatic extracts from rice bran (AEERB) were evaluated and correlations were determined. After trypsin hydrolysis under weak alkalescent conditions, the soluble protein, total phenolic, α-tocopherol, and γ-oryzanol contents of AEERB were increased. Excessively high temperatures (>60°C) and long hydrolysis times (>2.0 h) were not suitable for enzymatic hydrolysis. The free radical scavenging activity, ferric reducing/antioxidant power, lipid peroxidation inhibition activity, and total antioxidant activity were used for evaluation of the antioxidant activity. AEERB displayed an antioxidant activity and correlations of concentration levels of functional ingredients with antioxidant activity were significantly (p<0.05) positive.

Surface‐engineered Saccharomyces cerevisiae cells displaying redesigned CadR for enhancement of adsorption of cadmium (II)

AbstractBACKGROUNDThe use of cell‐surface display technology to express recombinant proteins on a microbial cell surface can enhance metal adsorption to microbial cells. The transcription factor CadR of Pseudomonas putida shows highly selective affinity with Cd2+.RESULTSCadR was genetically engineered by truncating 47 N‐terminal amino acids and 21 C‐terminal amino acids in order to maximize its expression efficiency while maintaining its metal‐binding domain. The redesigned CadR (named T68CadR) was then displayed with Saccharomyces cerevisiae a‐agglutinin cell‐surface display system. This engineering approach enhanced the H+/OH− buffering capacity and the Cd2+ adsorption capacity of yeast cells. The surface‐engineered cells also performed well at mesophilic and higher temperatures (30–50 °C) under neutral or alkalescent conditions. With an initial concentration of 1.0 mg L−1, the Cd2+ removal efficiency remained 85% when the concentration of Na+ changed from 0 to 400 mmol L−1 (pH 7.8). The surface‐engineered cells also showed highly selective adsorption to Cd2+ in the presence of Zn2+ and Pb2+.CONCLUSIONST68CadR displayed yeast cells constructed in this study provide an option to selectively remove Cd in water. It also might be promising as a tool to determine CadR's Cd‐binding mechanism and to improve its selectivity and affinity to Cd2+. © 2015 Society of Chemical Industry

Benzene depletion by Fe2+-catalyzed sodium percarbonate in aqueous solution

In this study, the chemical oxidation of benzene by Fe2+-catalyzed sodium percarbonate (SPC) was conducted. The effects of various factors, such as the SPC/Fe2+/benzene molar ratio, temperature, order of the reagent addition, solution matrix including the presence of anions (Cl−, HCO3−, SO42− and NO3−) and natural organic materials (NOM), and the initial solution pH, were thoroughly investigated. The experimental results showed that benzene can be completely degraded (<0.01mg/L) in 20min with a SPC/Fe2+/benzene molar ratio of 10/10/1 at 20°C, indicating the effectiveness of Fe2+/SPC oxidation for benzene removal. The degradation of benzene is significantly influenced by the SPC/Fe2+/benzene molar ratio as well as the order of the reagent addition, but less affected by the temperature. HCO3− and NOM have significant scavenging effects on benzene degradation, whereas Cl− has a slightly expediting effect at low concentration and a scavenging effect at high concentration. Meanwhile, the influences of SO42− and NO3− are negligible at the tested ionic strength ranges. The degradation of benzene was not apparently inhibited at pH 9.0. This result indicated that Fe2+-catalyzed SPC oxidation is suitable for alkalescent conditions which is superior to the conventional Fenton process. Hydroxyl radical (HO) has been confirmed as the predominant species responsible for benzene degradation by using free radical probe compounds tests, HO scavengers tests and electron paramagnetic resonance (EPR) analysis. In addition, an amazing effective Fe2+-catalyzed SPC oxidation of benzene in actual groundwater was achieved, indicating that Fe2+-catalyzed SPC oxidation is a highly promising technique for the remediation of benzene-contaminated groundwater.

Preparation and properties of konjac glucomannan octenyl succinate modified by microwave method

Konjac glucomannan (KGM) was esterified with octenyl succinic anhydride (OSA) by using microwave method under the alkalescent condition. The structure of the product—konjac glucomannan octenyl succinate (KGOS)—was characterized by means of 1H NMR spectrum, fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction, which drew conclusions that the OSA groups had been grafted onto the KGM molecular, while, incomplete deacetylation reaction occurred. All reactions occurred mainly on the surface of KGM granules, and had no significant effect on the crystallinity of the powder. In the end, the product emulsibility was also assessed, which indicated KGOS was a new kind of polymeric surfactant with good abilities both in hydrophilic and lipophilic.

Interaction among multiple microorganisms and effects of nitrogen and carbon supplementations on lignin degradation

The mutual interactions among the consortium constructed by four indigenous bacteria and five inter-kingdom fusants and the effects of nitrogen and carbon supplementations on lignin degradation and laccase activity were investigated. Analyzed by Plackett-Burman and central composite design, the microbial consortium were optimized, Bacillus sp. (B) and PE-9 and Pseudomonas putida (Pp) and PE-9 had significant interactions on lignin degradation based on a 5% level of significance. The nitrogen and carbon supplementations played an important role in lignin degradation and laccase production. The ultimate lignin degradation efficiency of 96.0% and laccase activity of 268U/L were obtained with 0.5g/L of ammonium chloride and 2g/L of sucrose. Results suggested that a stable and effective microbial consortium in alkalescent conditions was successfully achieved through the introduction of fusants, which was significant for its industrial application.

A bacterial laccase from marine microbial metagenome exhibiting chloride tolerance and dye decolorization ability

Laccases are blue multicopper oxidases with potential applications in environmental and industrial biotechnology. In this study, a new bacterial laccase gene of 1.32 kb was obtained from a marine microbial metagenome of the South China Sea by using a sequence screening strategy. The protein (named as Lac15) of 439 amino acids encoded by the gene contains three conserved Cu(2+)-binding domains, but shares less than 40% of sequence identities with all of the bacterial multicopper oxidases characterized. Lac15, recombinantly expressed in Escherichia coli, showed high activity towards syringaldazine at pH 6.5-9.0 with an optimum pH of 7.5 and with the highest activity occurring at 45 °C. Lac15 was stable at pH ranging from 5.5 to 9.0 and at temperatures from 15 to 45 °C. Distinguished from fungal laccases, the activity of Lac15 was enhanced twofold by chloride at concentrations lower than 700 mM, and kept the original level even at 1,000 mM chloride. Furthermore, Lac15 showed an ability to decolorize several industrial dyes of reactive azo class under alkalescent conditions. The properties of alkalescence-dependent activity, high chloride tolerance, and dye decolorization ability make the new laccase Lac15 an alternative for specific industrial applications.

Co-delivery of PDTC and doxorubicin by multifunctional micellar nanoparticles to achieve active targeted drug delivery and overcome multidrug resistance

Micellar nanoparticles self-assembled from copolymer folate–chitosan (FA–CS) were employed as carriers to co-deliver Pyrrolidinedithiocarbamate (PDTC) and doxorubicin (DOX) to achieve targeted DOX delivery, with a pH responsive drug release, and to overcome DOX multidrug resistance (MDR). The successful synthesis of FA–CS was determined by NMR. Average particle size was small enough to achieve longevity during systemic circulation. Lower CACs in neutral and alkalescent conditions rather than an acid pH may lead to maintenance of good stability of the micellar nanoparticles in the blood stream. DOX and PDTC encapsulating efficiencies of the micellar nanoparticles were 77.64 and 86.54 wt% while loading content was 12.34 and 15.32 wt%, respectively. The release of DOX at neutral or alkalescent pH was slow and sustained, however, in the weak acidic environment, was much faster with close to 75–95% of its total drug content being released within the first 2 h. A lower IC 50 of DOX-loaded micellar nanoparticles suggested that FA–CS micelles greatly enhanced the cellular uptake efficiency. Fluorescence microscopy micrographs further verified that DOX released from CS–FA micelles could be pH sensitive and achieved intracellular targeting. It was confirmed by flow cytometry analysis that co-delivery of PDTC and DOX may further overcome the MDR of DOX besides the folate receptor mediated endocytosis process. This co-delivery system may have important clinical implications against liver cancers.

Dipeptide Formation from Amino Acid Monomer Induced by keV Ion Irradiation: An Implication for Physicochemical Repair by Radiation Itself

An identification of Phe dipeptide from L-phenylalanine monomers after keV nitrogen and argon ion implantation, by using the HPLC (high performance liquid chromatography) and LC-MS(liquid chromatography mass spectrometer) methods is reported. The results showed a similar yield behavior for both ion species, namely: 1) the yield of dipeptides under alkalescent conditions was distinctly higher than that under acidic or neutral conditions; 2) for different ion species, the dose-yield curves tracked a similar trend which was called a counter-saddle curve. The dipeptide formation may implicate a recombination repair mechanism of damaged biomolecules that energetic ions have left in their wake. Accordingly a physicochemical self-repair mechanism by radiation itself for the ion-beam radiobiological effects is proposed.

Synthesis and Characterization of Y-Doped Mesoporous CeO 2 Using A Chemical Precipitation Method

Abstract Using cetyltrimethy lammonium bromide (CTAB) as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO 2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX), transmission electron microscopy (TEM), infrared (IR) absorbance, and the BET method. For the prepared samples with 20% (molar ratio) Y-doped content, a BET specific surface area of 106. 6 m 2 · g −1, with an average pore size of 3.27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N 2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased after mesoporous CeO 2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased.

Surface modification of an up-conversion luminescence material by overcoating with SiO 2 and its characterization

Abstract The surface of an up-conversion luminescence material was modified by overcoating with SiO 2, which was synthesized from a hydrolysis progress of tetraethoxysilane (TEOS) in alkalescent condition. By analyzing the hydrolyzed mechanism of TEOS, it was found that there was not only physical adsorption but also chemical bonding between the up-conversion material and SiO 2. At the same time, some adsorption bands at 1100, 475, 950, and 3500 cm −1 were found by FI-IR, which were the characteristic bands of Si—OH and Si—O—Si. By analyzing the surface elements of the coated material by XPS, it was found that its surface only included Si, O, and C elements, and not F and Y. In the picture of XRD, there was no additional peak after surface modification, suggesting that the silica shell was amorphous. The small peak at 2θ = 23° in the X-ray diffraction pattern of the coated material was caused by the amorphous SiO 2 shell, and the TEM image also proved that the surface of the material was successfully modified by overcoating with SiO 2. The amount of hydroxyls was then increased on the surface of the material, which made it easy to connect with other active groups.