Reaction pH Value Research Articles

Chitosan-Based Charge-Controllable Supramolecular Carrier for Universal Immobilization of Enzymes with Different Isoelectric Points.

Electrostatic adsorption is an enzyme immobilization method that effectively maintains enzyme activity and exhibits considerable binding efficiency. However, enzymes carry different charges at their respective reaction pH levels, which prevents the use of the same carrier to immobilize enzymes with different charges. In this study, we employed a template-mediated polysaccharide-enzyme coupling self-assembly strategy to develop a charge-controllable supramolecular immobilization carrier by regulating the charge properties of carboxymethyl chitosan, enabling the universal immobilization of enzymes with different charge levels across a range of reaction pH values. By using silica nanoparticles of certain sizes as templates, the size of the carrier can be precisely controlled and the hollow network structure formed after removing the template can effectively reduce mass transfer resistance. Trypsin and papain are used as model enzymes, and the experimental results show that the supramolecular self-assembly immobilization strategy does not disrupt the secondary structure of the enzyme molecules. After 2 h of reaction, the enzyme activities of immobilized papain and immobilized trypsin are 13.2% and 7.7% higher than those of the free enzymes, respectively. After 10 consecutive reactions, the enzyme activities of immobilized papain and immobilized trypsin retained 56.3% and 64.3% of their initial values, respectively.

Phase evolution and performance of sodium sulfate-activated slag cement pastes

This study evaluates the reaction kinetics, phase assemblage, and microstructure evolution of Na2SO4-activated slag cements produced with three commercial slags. The main reaction products identified are ettringite and calcium aluminosilicate hydrates, alongside a poorly crystalline SO42- intercalated Mg-Al-layered double hydroxide (LDH) phase. Results revealed that the Al2O3 slag content alone does not correlate with the cement performance. While pastes made with a higher Al2O3 content slag exhibit faster reaction kinetics, those made with a slag with a higher Mg/Al ratio developed superior compressive strength and reduced porosity over extended curing periods. Thermodynamic modelling simulations indicate that sulfate consumption occurs via ettringite and LDH phase formation, influencing the slag reaction degree, pH value, and porosity reduction in these cements. This research highlights the critical role of slag composition in controlling microstructure and, consequently, performance of sodium sulfate activated slag cement pastes.

A new UiO-66-NH2 MOF-based nano-immobilized DFR enzyme as a biocatalyst for the synthesis of anthocyanidins

Anthocyanidins and anthocyanins are one subclass of flavonoids in plants with diverse biological functions and have health-promoting effects. Dihydroflavonol 4-reductase (DFR) is one of the important enzymes involved in the biosynthesis of anthocyanidins and other flavonoids. Here, a new MOF-based nano-immobilized DFR enzyme acting as a nano-biocatalyst for the production of anthocyanidins in vitro was designed. We prepared UiO-66-NH2 MOF nano-carrier and recombinant DFR enzyme from genetic engineering. DFR@UiO-66-NH2 nano-immobilized enzyme was constructed based on covalent bonding under the optimum immobilization conditions of the enzyme/carrier ratio of 250 mg/g, 37 °C, pH 6.5 and fixation time of 10 min. DFR@UiO-66-NH2 was characterized and its catalytic function for the synthesis of anthocyanidins in vitro was testified using UPLC-QQQ-MS analysis. Compared with free DFR enzyme, the enzymatic reaction catalyzed by DFR@UiO-66-NH2 was more easily for manipulation in a wide range of reaction temperatures and pH values. DFR@UiO-66-NH2 had better thermal stability, enhanced adaptability, longer-term storage, outstanding tolerances to the influences of several organic reagents and Zn2+, Cu2+ and Fe2+ ions, and relatively good reusability. This work developed a new MOF-based nano-immobilized biocatalyst that had a good prospect of application in the green synthesis of anthocyanins in the future.

Efficient calcium sulfite oxidation treatment by a highly active iron-manganese bimetallic metal-organic frameworks (MOFs)

Calcium sulfite (CaSO3) oxidation is the key step in the resource utilization of flue gas desulfurization (FGD) ash waste. However, under natural conditions the oxidation rate of CaSO3 is very low, limiting its conversion into calcium sulfate, an acceptable product for construction material. This study was devoted to the investigation of the synthesis and performance of a bimetallic MOFs with potential catalytic activity, namely, Fe/Mn(BDC)(DMF,F) catalysts. A combination of techniques including SEM, EDS, XRD, FT-IR, etc. were used to characterize the catalysts. The excellent catalytic performance examined in a gas-liquid-solid three-phase oxidation system are due to the special flexible respiratory architecture and homogeneous distribution of active sites, which allows the reactants to fully contact with the catalyst. Mn incorporated in the backbone of the metal-organic framework significantly enriches the catalytic active species that participate in a radical chain reaction with activated SO32- as ·SO3-, which in turn generates the key radical ·SO5- that reacts with SO32- to form SO42-. In the presence of Fe/Mn(BDC)(DMF, F)-13, the oxidation ratio of CaSO3 could reach 90.71%, which is more than 30-fold compared to non-catalytic oxidation and almost 5 times the effects of the single metal Fe(BDC)(DMF, F) catalyst. In addition, the study of kinetics shows that the oxidation rate of Fe/Mn(BDC)(DMF,F)-13 can reach 0.042 mmol·L-1·s-1 with an apparent activation energy of 10.86 kJ/mol. The oxidation rate is mainly affected by reaction temperature, pH value, catalyst concentration, and air flow rate. This study provides a potentially sustainable way for utilization of CaSO3-containing desulfurization ash.

Solidification and Release Characteristics of Heavy Metals in Gypsum from Coal-Fired Power Plants

Heavy metals in flue gas desulfurization (FGD) gypsum from coal-fired power plants are at risk of releaching during the processes of stockpiling and resource utilization. In this study, the effects of organosulfur chelators dithiocarbamate (DTC) and trisodium trithiocyanate-15 (TMT-15) on the solidification characteristics of heavy metals in desulphurized gypsum under different mass fractions, pH values, water contents and reaction times were investigated. The chemical composition and morphology were analyzed by inductively coupled plasma atomic emission spectrometer (ICP-AES) and scanning electron microscope (SEM). The experiments showed that both DTC and TMT-15 were effective at stabilizing the heavy metals in the FGD gypsum, with more than a 50% curing effect for all the heavy metals except Pb. DTC showed a better stabilization for Pb, Hg, Cu, Zn, and Cr, and TMT-15 showed a better curing effect for Cd. The solidified gypsum had good heavy metal stability in low-water-content environments. Increasing the mass fraction, reaction time, and pH decreased the heavy metal leaching, and the mass fraction had the greatest effect on the total heavy metal leaching concentration, followed by the reaction time and pH value.

Asparagine-Glucose Amadori Compounds: Formation, Characterization, and Analysis in Dry Jujube Fruit.

Amadori rearrangement products of asparagine with glucose (Asn-Glc-ARP) were first prepared through Maillard model reactions and identified via liquid chromatography-mass spectroscopy. With the study on the effect of the reaction temperature, pH values, and reaction time, the ideal reaction condition for accumulation of Asn-Glc-ARP was determined at 100 °C for 40 min under pH 7. Asparagine (Asn) was prone to degrade from Asn-Glc-ARP in alkaline pH values within a lower temperature range, while in an acidic environment with high temperatures, deamidation of Asn-Glc-ARP to Asp-Glc-ARP (Amadori rearrangement products of aspartic acid with glucose) was displayed as the dominant pathway. The deamidation reaction on the side chain of the amide group took place at Asn-Glc-ARP and transferred it into the hydroxyl group, forming Asp-Glc-ARP at the end. Considering that lyophilization as pretreatment led to limited water activity, a single aspartic acid was not deamidated from Asn directly nor did it degrade from Asp-Glc-ARP even at 120 °C. The degradation of Asn-Glc-ARP through tandem mass spectrometry (MS/MS) analysis showed the obvious fragment ion at m/z 211, indicating that the stable oxonium ion formed during fragmentation. The structure of Asn-Glc-ARP was proposed as 1-deoxy-1-l-asparagino-d-fructose after separation and purification. Also, the content of Asn-Glc-ARP within dry jujube fruit (HeTianYuZao) was quantitated as high as 8.1 ± 0.5 mg/g.

Synthesis of manganese oxide from manganese ore of bajaur agency khyber Pakhtunkhwa (KPK), Pakistan

In the present work manganese sulphate developed from the Bajaur (KPK, Pakistan) manganese ore was utilized successfully for the synthesized Manganese Oxide chemically by an alkali-oxidation of manganese sulphate using the co-precipitation method. The advantages of this eco-friendly co-precipitation method include quick and easy preparation, simple control of particle size, and cost-effective composition using local ore. Because of the readily available raw materials and the controlled reaction conditions, this method is widely used in industry. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the synthetic manganese oxide. Fourier transforms infrared spectroscopy (FTIR) Infrared reveals that the O-Mn-O vibrational mode occurs in pure manganese oxide at wavelengths between 600 and 500 cm-1. The chemical composition was obtained by EDX analysis and confirmed the presence of Mn and O in the sample. Experimental optimization was done for the manganese oxide precipitation conditions. The findings show that a variety of parameters have an impact on the product yield; the precursor ratio and reaction temperature are the most important variables, and the reaction time and pH value have the greatest impact on the quality of crystallization. Bangladesh J. Sci. Ind. Res. 58(4), 221-230, 2023

Nano-Si for On-Demand H2 Production: Optimization of Yield and Real-Time Visualization of Si─H2O Reaction Using Liquid-Phase Transmission Electron Microscopy.

Hydrogen (H2), the most abundant element in the universe, has the potential to address the challenges of energy security and climate change. However, due to the lack of a safe and efficient method for storing and delivering hydrogen, its practical application is still in its infancy stages. To overcome this challenge, a promising solution is demonstrated in the form of on-demand production of H2 using nano-Silicon (Si) powders. The method offers instantaneous production of H2, yielding a volume of 1.3 L per gram of Si at room temperature. Moreover, the H2 production yield and the rate can be effectively controlled by adjusting the reaction pH value and temperatures. Additionally, liquid-phase transmission electron microscopy (LPTEM) is utilized in situ to demonstrate the entire reaction in real-time, wherein H2 bubble formation is observed and illustrated the gradual conversion of crystalline Si particles into amorphous oxides. Moreover, it is confirmed that the purity of the generated gas is 99.5% using gas chromatography mass spectrometry (GC-MS). These findings suggest a viable option for instant H2 production in portable fuel cells using Si cartridges or pellets.

Syntheses, Structures, Structural Transformation, and Properties of Neodymium Sulfate Based Inorganic Networks

AbstractTwo neodymium sulfate based purely inorganic networks, [NH4][Nd(SO4)2(H2O)3] ⋅ H2O (1) and [Nd2(SO4)3(H2O)4] ⋅ H2O (2) have been synthesized at different reaction temperatures and pH values. The structure of 1 features a two‐dimensional (2D) anionic corrugated sheet with an sql topological net built up by linking NdO8 units and μ2‐SO42− anions, in which the NH4+ charge‐compensating/templating cations occupy the intersheet layers. While 2 possesses a 3D neutral framework with an unprecedented (3,42,7‐c) net constructed by NdO9 units and μ4‐ and μ6‐SO42− linkers. They exhibit thermally induced irreversible structural transformation associated with the dehydration and the changes in coordination geometry and dimensionality. Both compound 1 and 2 display typical antiferromagnetic interactions between the Nd3+ centres. In addition, the CO2 adsorption isotherms of the desolvated samples 1 and 2 were also investigated.

Electrolysis characterization of saline wastewater discharged from a subsurface pipe in saline-alkali land

We improved the design of an ion membrane electrolysis device to assess its use for electrolytic desalination and hydrogen production utilizing wastewater discharged from a subsurface drainage pipe in saline-alkali land. The device can reduce the waste of water resources and agricultural non-point source pollution. The electrolysis performance is low due to the low concentration of salts and complex ionic species in the drainage water from subsurface pipes of farmland. A one-factor quantitative experimental study was conducted to assess the influence of the electrolysis parameters on the electrolytic characteristics. Multifactor synergistic optimization of the parameters was performed. The results indicate different degrees of linear correlations between the hydrogen and chlorine gas production rates and the current density (CD) for different process parameters. Different factors have different degrees of influence on the electrolysis characteristics, and factor interactions occur. The optimization model describing the effects of multiple factors on the final current density (FCD), pH value after reaction (ARP), and energy consumption rate (ECR) is reliable and stable. The optimized operating parameters included a brine concentration (BC) of 3.6 mol·L−1, before reaction pH (BRP) value of 9, working voltage (WV) of 12.2 V, and electrode immersion depth (EID) of 22.5 cm. Under these conditions, the FCD is 183.03 mA·cm−2, the ARP is 13.99, and the ECR is 24,586.50 kW·h/kg. The proposed method substantially improves the electrolysis performance. The results provide theoretical and technical support for utilizing saline wastewater discharged from saline-alkaline land.

Chloride-induced corrosion propagation of alkali-activated slag mortar with pulverized fuel ash and metakaolin replacements

Alkali-activated materials have great potential in reducing CO2 emissions in cement production industry. This study aims to investigate the corrosion propagation performance of alkali-activated slag mortars with various pulverized fuel ash (PFA) and metakaolin (MK) replacements subject to chloride-induced corrosion. The corrosion propagation performances including corrosion potential, corrosion rate and mortar electrical resistivity under wetting and drying cycles in seawater are studied. Scanning electron microscope (SEM), mercury intrusion porosimetry (MIP) and pH value measurement were conducted to analyze the effects of PFA and MK replacements on the relationship between reaction degree, pore structure, pH value and corrosion propagation performances. The results show that the MK replacement can enhance the corrosion propagation resistance of slag-based alkali-activated mortars under high activator concentration while the PFA replacement reduces the resistance to metallic corrosion of alkali-activated mortars. Mechanisms controlling the corrosion propagation are discussed.

Preparation and Performance Study of ZnO Nanorod Array with Anti-Ultraviolet and Superhydrophobic Surface

A two-step low-temperature hydrothermal method was used to construct an aluminum-nickel compound network structure on the substrate surface, followed by a secondary hydrothermal synthesis of ZnO nanorod array. After low surface energy material modification, a superhydrophobic and superoleophobic surface was obtained. The aluminum-nickel compound network structure plays a key guiding role in the growth of ZnO nanorod arrays. The uniformly shaped and densely arranged ZnO nanorod arrays have high roughness and exhibit excellent hydrophobic properties after modification. The surface of the ZnO nanorod array is improved in terms of UV resistance due to the size effect. The effects of hydrothermal reaction temperature, hydrothermal reaction time, hydrothermal reaction pH value, and Zn[Formula: see text] concentration on the surface structure, morphology, and properties of the ZnO nanorod array were also studied.

Effects of Processing Conditions on the Properties of Monoammonium Phosphate Microcapsules with Melamine-Formaldehyde Resin Shell.

To develop monoammonium phosphate (MAP) as a novel acid source for durable intumescent fire retardants (IFR), MAP microcapsules (MCMAPs) containing MAP as the internal core and melamine-formaldehyde (MF) as the external shell were prepared by in situ polymerization in this study. The influences of synthesis conditions (including reaction temperature, polymerization time, and reaction pH value) on the properties of obtained MCMAPs (MAP content, yield, morphologies, and thermal properties) were then investigated systematically. The morphologies, chemical structures, and thermal properties were characterized by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetry analyzer (TGA). The results show that MAP was well encapsulated by MF resin. No microcapsules are obtained at <55 °C or with polymerization times <1 h. Optimal preparation conditions of reaction temperature, polymerization time, and reaction pH value are 75 °C, 3 h, and 5.5, respectively. Those results provide process reference and theoretical basis for preparing MCMAPs and could promote the application of MAP microcapsules in wood flame-retardant materials.

Catalytic MnWO4 Nanorods for Chemodynamic Therapy Synergized Radiotherapy of Triple Negative Breast Cancer

AbstractNanomedicine‐based synergy of chemodynamic therapy (CDT) and radiotherapy (RT) modulated by tumor microenvironment enables rapid tumor ablation, which holds great hope for the refractory and recurrent cancers, such as triple negative breast cancer (TNBC). The clinical translation of hafnium oxide (HfO2), commercially named as NBTXR3, has aroused new research focus on single‐component inorganic nanomedicines as clinical candidates. Herein, the single‐component MnWO4 is first reported as a new kind of Fenton‐like agent yet radiosensitizer for TNBC treatment undergoing the synergistic CDT/RT mechanism. MnWO4 nanorods are synthesized via a simple one‐pot hydrothermal method and then undergo a layer‐by‐layer PEGylation to obtain bioavailable MnWO4‐PEG (MWP). MWP‐based Fenton‐like reaction efficacy depends on reaction time, temperatures, pH values, and MWP concentrations. Mn‐triggered chemodynamic effect delays RT‐induced DNA damage repair and sorts cell cycles distribution toward radiosensitive phases, while W‐mediated radiosensitization improves the tumoral H2O2 overexpression to enhance CDT, remarkably amplifying of the intracellular oxidative stress to boost 4T1 cell apoptosis. In vitro and in vivo evaluations further demonstrate the effectiveness and biosafety of MWP‐based synergistic therapy. Considering the potential magnetic resonance and computed tomography imaging capabilities, MWP can be expected as an intelligent cancer theranostics for imaging‐guided cancer therapy in clinic in the future.

Effects of reaction temperature, pH and duration on conversion of tea catechins and formation of theaflavins and theasinensins

Theaflavins (TFs) and theasinensins (TSs) are the key components formed from the enzymatic oxidation of tea catechins, contributing significantly to the biological activities and taste of black and Oolong teas. In this study, we aimed to reveal the catechin conversion and the enzymatic synthesis of TFs and TSs under reaction temperatures and pH values using polyphenol oxidase (PPO) from potato tuber (Solanum tuberosum L.). The results indicated that different temperatures, pH values and durations had significant effects on the conversion of catechins and the formation of TFs and TSs. During the reaction, the most of catechin substrates was consumed at 60–90 min after reaction initiation, and large amounts of the products TFs (0.04–0.41 mg/mL) and TSs (0.51–1.52 mg/mL) were obtained. The content of TSs was significantly higher and the maximum content of TSs was more than three times that of TFs. Reaction at a lower temperature (20 °C) is suitable for producing dimers, especially for TFs. Higher pH value resulted in higher catechin consumption and higher TSs content, while the maximum of TFs was obtained at pH 5.0. The present results provided a theoretical basis and practical guidance for the targeted processing of tea catechin dimers in vitro.

Flocculation performance of PCFA composite coagulant for removing nanoparticles

In this study, red mud was used as the main raw material to prepare polyaluminum-ferric chloride (PCFA) with high added value. The effects of the liquid–solid ratio, reaction temperature, reaction time, hydrochloric acid concentration during acid leaching, polymerization time, OH−/Fe molar ratio, and polymerization temperature on the preparation of PCFA were investigated and determined by conducting single-factor optimization experiments under optimal preparation conditions. Characterization results show that the surface of the PCFA flocculant has compact and dense porosity and a dense sheet-like structure, and PCFA contains hydroxyl-bridged iron–aluminum polymers. When the settling time was 30 min, the stirring intensity was 200 rpm; the initial concentration of Nano-titanium dioxide（TiO2-NPs） was 30 mg·L−1; the pH value was 7.0; the dosage of PCFA was 25 mg·L−1, and the optimum removal rates of TiO2-NPs and turbidity were 84.8% and 81.3%, respectively. The flocs produced by PCFA treatment of TiO2-NPs were large and dense. Under optimal flocculation conditions, the average particle size of PCFA-TiO2-NP flocs was 2.98 µm, and the fractal dimension was 1.66. Based on the abovementioned flocculation experimental data, a Grey correlation method was established to evaluate the degree of correlation among factors such as ionic strength, settling time, stirring strength, kaolin concentration, initial concentration, reaction pH value, and dosage and the performance of PCFA coagulation to remove TiO2-NP-containing wastewater. In the reaction system of the PCFA coagulation of TiO2-NPs, the dosage is the most important factor.

Expression of β-Glucosidases from the Yak Rumen in Lactic Acid Bacteria: A Genetic Engineering Approach.

β-glucosidase derived from microorganisms has wide industrial applications. In order to generate genetically engineered bacteria with high-efficiency β-glucosidase, in this study two subunits (bglA and bglB) of β-glucosidase obtained from the yak rumen were expressed as independent proteins and fused proteins in lactic acid bacteria (Lactobacillus lactis NZ9000). The engineered strains L. lactis NZ9000/pMG36e-usp45-bglA, L. lactis NZ9000/pMG36e-usp45-bglB, and L. lactis NZ9000/pMG36e-usp45-bglA-usp45-bglB were successfully constructed. These bacteria showed the secretory expression of BglA, BglB, and Bgl, respectively. The molecular weights of BglA, BglB, and Bgl were about 55 kDa, 55 kDa, and 75 kDa, respectively. The enzyme activity of Bgl was significantly higher (p < 0.05) than that of BglA and BglB for substrates such as regenerated amorphous cellulose (RAC), sodium carboxymethyl cellulose (CMC-Na), desiccated cotton, microcrystalline cellulose, filter paper, and 1% salicin. Moreover, 1% salicin appeared to be the most suitable substrate for these three recombinant proteins. The optimum reaction temperatures and pH values for these three recombinant enzymes were 50 °C and 7.0, respectively. In subsequent studies using 1% salicin as the substrate, the enzymatic activities of BglA, BglB, and Bgl were found to be 2.09 U/mL, 2.36 U/mL, and 9.4 U/mL, respectively. The enzyme kinetic parameters (Vmax, Km, Kcat, and Kcat/Km) of the three recombinant strains were analyzed using 1% salicin as the substrate at 50 °C and pH 7.0, respectively. Under conditions of increased K+ and Fe2+ concentrations, the Bgl enzyme activity was significantly higher (p < 0.05) than the BglA and BglB enzyme activity. However, under conditions of increased Zn2+, Hg2+, and Tween20 concentrations, the Bgl enzyme activity was significantly lower (p < 0.05) than the BglA and BglB enzyme activity. Overall, the engineered lactic acid bacteria strains generated in this study could efficiently hydrolyze cellulose, laying the foundation for the industrial application of β-glucosidase.

Site-specific isotope fractionation during Zn adsorption onto birnessite: Insights from X-ray absorption spectroscopy, density functional theory and surface complexation modeling

Birnessite minerals help control the fate of Zn in surface environments and readily fractionate Zn isotopes through adsorption reactions, yet little is known about the role played by various reactive sites in stable isotopic fractionation. Here we present the Zn isotope fractionation data cause by adsorption on birnessite under different reaction times, pH values, and Zn concentrations. We observe that isotopic equilibrium of Zn is attained after ∼120 h of reaction time at pH 6. At pH 3–5 and Zn concentrations of 0.05–0.3 mM, the isotopic fractionation (Δ66Znadsorbed-aqueous) is around −0.46 ± 0.04‰, and gradually increases to −0.09 ± 0.05‰ at pH 6–8 and Zn concentrations of 0.2 mM. The change in Zn isotopic compositions as a function of pH and Zn concentration is well described using the surface complexation model, where two binding sites are involved: external edge sites and interlayer vacancies. According to this model, two different isotopic fractionation factors of Zn are calculated: Δ66Znadsorbed-aqueous = −0.46 ± 0.04‰ for adsorption on vacancy sites and Δ66Znadsorbed-aqueous = 0.52 ± 0.04‰ for binding to edge sites. Extended X-ray absorption fine structure spectroscopy (EXAFS) demonstrates that Zn forms triple-corner-sharing (TCS) octahedral complex on birnessite vacancies at pH 3 and Zn concentrations of 0.05–0.2 mM, where Zn is coordinated on one side to three oxygen atoms of the Mn vacancy (∼2.03 Å) and to three water molecules on the other side (∼2.15 Å), suggesting the formation of distorted ZnO octahedra (average bond length: ∼2.09 Å). At pH 6 and 8, double-corner-sharing (DCS) complexes on layer edges formed in addition to the TCS octahedral complex on vacancies. Density functional theory (DFT) optimisations suggest that DCS Zn complex exist in tetrahedral coordination. Based on EXAFS spectroscopy, DFT optimisations and surface complexation modeling, the distinct isotopic fractionation of Zn is related to the differences in Zn local structure at different reactive sites of birnessite. Our results provide a molecular-scale understanding of Zn isotopic fractionation in natural birnessite-containing settings, as well as new insights into predicting the links between adsorption and fractionation of other similar metals.

Mechanism and degradation pathways insight of photocatalytic oxidation antibiotics by geometrical Ag/AgNbO3/BiVO4 plasmon Z-type heterojunction

Three-dimensions geometry-like plasmon Ag/AgNbO3/BiVO4 (Ag/ANO/BVO) Z-type heterojunction photocatalyst was synthesized by electrostatic self-assembly and photo-deposition method. Levofloxacin hydrochloride (LEF) became the target degradation object to evaluate photocatalytic activity. The 3-Ag/ANO/BVO showed the best photocatalytic properties compared with other as-synthesized catalysts. The apparent rate constant of 3-Ag/ANO/BVO was 0.0235 min−1, which separately was 47.00, 5.22, and 1.85 times higher than that of AgNbO3 (ANO), BiVO4 (BVO), and 40%-AgNbO3/BiVO4 (40-ANO/BVO). Several reaction parameters including catalyst dosage, initial LEF concentration, and reaction pH values were filtrated to investigate optimal photocatalytic reaction conditions of the 3-Ag/ANO/BVO composite. The elevated photocatalytic activity can be attributed to the effective migration and separation of photo-induced carriers on the contact interface due to the formation of Z-type heterojunction and broadened visible light absorption range by localized surface plasmon resonance (LSPR) in 3-Ag/ANO/BVO composite. Furthermore, formed intermediates during the photocatalytic oxidation of LEF molecules were detected via high-performance liquid chromatography-mass spectrometry (HPLC-MS). Ultimately, a plasmonic Z-type photocatalytic mechanism was verified through a variety of characterization tests and simulations method (finite difference time domain, FDTD).

One-pot synthesis of gold-copper nanoparticles mediated by silk fibroin peptides: Peroxidase-like properties and its application in antioxidant detection

SFP@Au-CuNPs were synthesized by the one-pot reduction method using silk fibroin peptides as reductants and stabilizers. The synthesis process was simple, safe, and environmentally friendly. The synthesized SFP@Au-CuNPs showed effective peroxidase mimicking activity through colorimetric analysis and had a catalytic effect. The reaction pH value, temperature, time, and concentration were optimized to determine the best method for achieving the inherent catalytic activity in practical application. According to the double reciprocal curve, the Michaelis–Menten constants of TMB and H2O2 substrates were calculated to study the affinity of the SFP@Au-CuNPs using TMB and H2O2 substrates. The Km of H2O2 was 0.240 mM, and the TMB was 0.040 mM. SFP@Au-CuNPs had a strong affinity for the H2O2 and TMB substrates. The peroxidase-like characteristics of the SFP@Au-CuNPs were used to detect antioxidants, in which ascorbic acid LOD was 0.059 μM, gallic acid LOD was 0.010 μM, and LOD was 0.040 μM. Colorimetric analysis using UV-spectrophotometer was used to observe the color changes. The R2 values of the ascorbic acid, gallic acid, and l-cysteine were 0.998, 0.996, and 0.990, respectively, indicating that the curve has a good linear relationship in the detection range and the assay was successfully used to evaluate the antioxidant content of real fruits. This study provides a broader prospect for the preparation of nanozymes for relevant applications.