Ag Precursor Research Articles

Mixing performance and continuous production of nanomaterials in an advanced-flow reactor

The Corning Advanced-FlowTM Reactor (AFR) whose productivity is ready for scale-up with limited loss of transport properties was implemented in the continuous synthesis of Ag nanoparticles (NPs). To demonstrate the effect of mixing on Ag NPs, the flow pattern and mixing characteristic (mainly on the meso- and macroscale) in AFR were studied by flow visualisation and computational fluid dynamics simulation first. It was found that increasing the total flow rate from 1 to 9 mL·min−1 could enhance mixing by the synergetic combination of secondary flows created by different mechanisms. The flow rate ratio in the range of 0.25–8 affected the degree of mixing by changing the initial concentration distribution profile across the combined stream. The highest degree of mixing was obtained at the flow rate ratios of 0.25 and 8. Subsequently, the micromixing performance was quantified by Villermaux-Dushman method. The micromixing time decreased from 17 to 4 ms as the total flow rate increased from 1 to 9 mL·min−1, while the micromixing time was nearly independent of the flow rate ratio. At last, the link between the mixing characteristics and average size and particle size distribution (PSD) of Ag NPs was established. As the total flow rate increased, the average particle size decreased, and PSD became narrower due to better micromixing efficiency. When the flow rate ratio varied, the PSD of Ag NPs was dependent on the width of the Ag precursor stream rather than the degree of mixing, because an excessive amount of NaBH4 was used.

Conductive PEDOT: PSS-Based Organic/Inorganic Flexible Thermoelectric Films and Power Generators.

We present a simple thermoelectric device that consists of a conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based inorganic/organic thermoelectric film with high thermoelectric performance. The PEDOT:PSS-coated Se NWs were first chemically synthesized in situ, and then mixed with an Ag precursor solution to produce the PEDOT:PSS-coated Ag2Se NWs. The PEDOT:PSS matrix was then treated with dimethyl sulfoxide (DMSO) prior to the production of flexible PEDOT:PSS-coated Ag2Se NW/PEDOT:PSS composite films with various weight fractions of Ag2Se via a simple drop-casting method. The thermoelectric properties (Seebeck coefficient, electrical conductivity, and power factor) of the composite films were then analyzed. The composite film with 50 wt.% NWs exhibited the highest power factor of 327.15 μW/m·K2 at room temperature. The excellent flexibility of this composite film was verified by bending tests, in which the thermoelectric properties were reduced by only ~5.9% after 1000 bending cycles. Finally, a simple thermoelectric device consisting of five strips of the proposed composite film was constructed and was shown to generate a voltage of 7.6 mV when the temperature difference was 20 K. Thus, the present study demonstrates that that the combination of a chalcogenide and a conductive composite film can produce a high-performance flexible thermoelectric composite film.

Incorporation of Ag into Cu(In,Ga)Se2 films in low-temperature process

Chalcopyrite Cu(In,Ga)Se2 (CIGS) thin films deposited in a low-temperature process (450°C) usually produce fine grains and poor crystallinity. Herein, different Ag treatment processes, which can decrease the melting temperature and enlarge band gap of the CIGS films, were employed to enhance the quality of thin films in a low-temperature deposition process. It is demonstrated that both the Ag precursor and Ag surface treatment process can heighten the crystallinity of CIGS films and the device efficiency. The former is more obvious than the latter. Furthermore, the Urbach energy is also reduced with Ag doping. This work aims to provide a feasible Ag-doping process for the high-quality CIGS films in a low-temperature process.

Seeded Growth of Au@PdAg Alloy Core‐Shell Nano‐Dendrites with Tunable Size and Composition

AbstractWe report a facile synthesis of Au@PdAg alloy core‐shell nanocrystals in dendrite form, having tunable size and composition. In particular, using spherical Au nanoparticles as seeds, the co‐reduction of Pd and Ag precursor in growth stage results in the formation of PdAg alloy shells with a dendrite shape. Their size and elemental composition can be tuned by varying the seed amount and feeding ratio in Pd and Ag precursor, respectively, illustrating the versatility of the current synthetic strategy. The size, morphology, and elemental composition of the products have been characterized using a set of techniques, including SEM, TEM, XRD, XPS, HAADF‐STEM, and EDX‐STEM mapping. When working as electrocatalysts, the current Au@PdAg alloy core‐shell nanocrystals supported by carbon black exhibit enhanced activity and excellent operation stability for electroxidation of ethanol as compared to commercial Pd/C. The current work offers a feasible strategy to preparation of multi‐metallic core‐shell dendritic nanocrystals with controllable size and composition and could find important use in fuel cells and related fields.

Bimetallic AgPd/UiO-66 Hybrid Catalysts for Propylene Glycol Oxidation into Lactic Acid.

Different methods (the wetness impregnation of Ag and Pd precursors dissolved in water or acetonitrile solution, and the double solvent impregnation technique) were employed to immobilize Ag–Pd nanoparticles (NPs) into the pores of the microporous zirconium-based metal-organic framework known as UiO-66. The obtained materials were characterized by using nitrogen adsorption-desorption at −196 °C, powder X-ray diffraction, UV-Vis diffusion reflectance spectroscopy, and transition electron microscopy measurements. Special attention was paid to the acid and redox properties of the obtained materials, which were studied by using temperature-programmed desorption of ammonia (TPD-NH3) and temperature-programmed reduction (TPR-H2) methods. The use of a drying procedure prior to reduction was found to result in metallic NPs which, most likely, formed on the external surface and were larger than corresponding voids of the metal-organic framework. The formation of Ag–Pd alloy or monometallic Ag and Pd depended on the nature of both metal precursors and the impregnation solvent used. Catalytic activity of the AgPd/UiO-66 materials in propylene glycol oxidation was found to be a result of synergistic interaction between the components in AgPd alloyed NPs immobilized in the pore space and on the external surface of UiO-66. The key factor for consistent transformation of propylene glycol into lactic acid was the proximity between redox and acid-base species.

Eco-friendly synthesis of lignin mediated silver nanoparticles as a selective sensor and their catalytic removal of aromatic toxic nitro compounds.

The development of an eco-friendly and reliable process for the production of nanomaterials is essential to overcome the toxicity and exorbitant cost of conventional methods. As such, a facile and green synthesis method is introduced for the preparation of lignin mediated silver nanoparticles (L-Ag NPs). This is produced by reducing Ag precursors using lignin biopolymers which are formulated by pulsed laser irradiation and an ultrasonication process. Lignin operates as both a reducing and stabilizing agent. The various analytical techniques of ultraviolet-visible spectroscopy, transmission electron microscope and X-ray diffractometer studies were employed to verify the formation of non-aggregated spherical L-Ag NPs with an average size as small as 7-8nm. The selective sensing capability of the synthesized L-Ag NPs was examined for the detection of hydrogen peroxide and mercury ions in an aqueous environment. Furthermore, the superior catalytic performance of L-Ag NPs was demonstrated by the rapid conversion of toxic 4-nitrophenol and nitrobenzene as targeted pollutants to the corresponding amino compounds. A plausible catalytic reduction mechanism for the removal of toxic nitro-organic pollutants over L-Ag NPs is proposed. This research coincides with existing studies and affirms that L-Ag NPs are an effective sensor that be applied as a catalytic material within environmental remediation and also alternative biomedical applications.

Synthesis of Silver Nanocatalysts Using Microwave Irradiation in Ionic Liquid for Reduction of Carbon Dioxide to CO By Solar-Driven Electrochemical

Over the last few decades electrochemical CO2 reduction has attracted attention as a promising technology for greenhouse gas reduction. The Carbon monoxide product from CO2 reduction is of interest as a component of syngas for methanol synthesis. Silver is a reactive electrocatalyst toward carbon dioxide reduction to Carbon monoxide among single metals (Au, Zn etc.). In order to carry out CO2 reduction reaction effectively, it is require to nano-sized electro catalyst for wide active area. However, there is aggregation issue of nano-sized particle in liquid phase reduction method from metal precursor. It can be solved simply using of ionic liquid as a solvent and capping agent to suppress aggregation of nano-particle. In addition, Microwave-assisted fabrication has much potential due to their distinctive characteristics such as rapid heating ability, efficient and uniform internal heating, and relatively short process time.Here we describe its use as a single electrocatalyst made in Microwave method with Ionic liquid for reduction of CO2 to CO. We have simply synthesized Ag nanoparticles with an ultra-fine size (~20nm) by microwave irradiation process using Ag precursors dissolve in Ionic liquid. Silver carbonate (Ag2CO3, purchased from Sigma Aldrich) as a precursor was dissolved in Ionic liquid, Butyl-3-methylimidazolium tetrafluoroborate (BMIM BF4-, purchased from C-TRI). The 5mL mixture solutions with a concentration of 10, 20 and 30mM were prepared by stirring under atmosphere at room temperature. Each mixture solution was heated by microwave irradiation system (CEM Co.,Ltd Discover) at the power of 10~30W within just 10min.Characterization of synthesized silver nanoparticles was analyzed by Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) to confirm the morphology, chemical state, and crystal structure of the samples. XRD analysis showed (111), (200), (220), (311), and (222) diffractions of Ag metal with a face-centered cubic structure, confirming that the silver nanoparticles could be synthesized. TEM images showed that the nanoparticles have ultra-fine sized silver, less than 20nm without aggregation. Based on CO2 reduction reaction (CO2RR) response, the elctrocatalystic performance of synthesized silver was evaluated. In order to compare the performance, the same mass of commercial Ag and carbon black were used in three electrode system with 0.5M KHCO3 aqueous solution saturated with CO2. The catalytic potential reduced 0.374eV compared to carbon black.In order to confirm the efficiency of Solar-driven electrochemical carbon dioxide reduction, synthsized silver nano catalyst of 9mg/cm2 was loaded at the cathode(6.25cm2) in electrochemical reactor which is a closed two-component separated by anion exchange membrane (Sustainion® X37-50, Dioxide Materials). The anode was IrOx (purchased from Dioxide materials) sprayed on Carbon paper (9cm2). A Si solar cell of series connection solar panels supplied electric power to electrochemical reactor. We achieved the Faradaic Efficiency of 92% to Carbon monoxide conversion by synthesized silver catalyst. We obtained 8.81% to Power conversion efficiency employing series connected Si photovoltaics for CO2 conversion to CO.

Single atom Fe in favor of carbon disulfide (CS2) adsorption and thus the removal efficiency

Carbon disulfide (CS2) is a typical organic sulfur compound emitted from many industrial processes, such as petrochemical, smelting, et al. Chemical adsorption is a promising method for CS2 removal and Fe based adsorbents usually show excellent performance. Single-atom catalysts (SACs) always perform magical effects in various heterogeneous reactions. In this work, pyrolyzing coordinated polymer (PCP) strategy was adopted to synthesize Fe single-atom catalyst. HAADF-STEM and XAFS results show that among several support precursor (Zn, Ce, Ag and Al), single-atom Fe only appears successfully on Al coordinated catalyst Fe-C/Al2O3, which also performs the optimal adsorption efficiency. The contrast with Fe2O3-C/Al2O3 catalyst shows that single-atom Fe catalyst has remarkable advantage and the agglomeration of iron atoms decreases the adsorption capacity. DFT calculation results finally reveal that the strong interaction between Fe atom and C atom (in CS2) induces the increment of CS2 adsorption capacity on Fe single-atom catalyst Fe-C/Al2O3.

SYNTHESIS OF SILVER NANOPARTICLES USING AQUEOUS EXTRACT OF PERGULARIA DAEMIA AND ANALYSIS OF ANTIMICROBIAL ACTIVITY

The present work deals with the green synthesis of silver nanoparticle from aqueous extract of Pergularia daemia as reducing agent and evaluation of the antimicrobial potential of synthesized green nanoparticles (GNPs). The synthesized silver nanoparticles (SNPs) were characterized by UltravioletVisible absorption spectroscopy (UV-Vis) and high-resonance transmission electron microscopy (TEM) analysis. Visual observation showed that the color of the fresh leaf extracts of P. daemia turned into dark brown after incubation of 24 h with Ag precursors. The TEM analysis showed that nanoparticles were spherical in shape and the size was found to be in the range of 7-22 nm. The green synthesized nanoparticles showed concentration dependent (25 µg/mL, 50 µg/mL and 100 µg/mL) noteworthy antimicrobial activity against E. coli, S. aureus and B. subtilis with ciprofloxacin as a standard. Research findings conclude that GNPs possess superior antimicrobial potential and it is a new option to combat antibiotic resistance.

Cubic-shape hematite decorated with plasmonic Ag-Au bimetals for enhanced photocatalysis under visible light irradiation

Cubic-shape hematite (C-Fe2O3) was facilely prepared by hydrothermal autoclave reaction of Fe3+ in the presence of 1,12-diaminododecane at 130 °C for 10 h. The surface of C-Fe2O3 was decorated with nanosilvers through the sonochemical reduction of Ag precursor (0.1–0.4 ml of 1.0 wt.% AgNO3), so-called C-Fe2O3@Ag. After then, the C-Fe2O3@Ag was plated with Au layer via galvanic-assisted reduction of Au precursor (0.04–0.14 ml of 1.0 wt.% HAuCl4), so-called C-Fe2O3@Ag-Au. Scanning electron microscopy demonstrated the formation of cubic-shape hematite deposited with plasmonic nanometals. X-ray photoelectron spectroscopy analysis confirmed the existence of Ag and Au crystals. Photocatalytic performance of the hematite samples was estimated towards the degradation of methylene blue (MB) under visible light. The C-Fe2O3@Ag (0.2 ml) exhibited the five-fold increase of photocatalytic activity to that of the pristine C-Fe2O3. Furthermore, Au-deposited C-Fe2O3@Ag (0.2 ml), i.e., C-Fe2O3@Ag-Au, exhibited the 200% increase of photocatalytic activity to that of the C-Fe2O3@Ag (0.2 ml), owing to the plasmonic coupling effect on the extended visible light absorbance and enhanced separation efficiency of electron-hole pairs on the hematite surface.

Synthesis Study of Silver-Doped Zinc Oxide for Near-Infrared Shielding Applications

Undoped ZnO and Ag-doped ZnO were prepared to use as near-infrared (NIR) shielding by simple precipitation method with zinc acetate and zinc nitrate as Zn precursor and silver nitrate as Ag precursor. The Ag-doped ZnO and undoped ZnO were characterized by XRD, SEM, and UV-vis-NIR spectrophotometer. The NIR reflectance performance reveals that Ag-doping improves the NIR shielding and optical property of pure ZnO. The 10 mol% Ag loading shows the lowest reflection in the visible region of about 15% and the highest reflection in the NIR region of about 50%. It not only shows the best NIR reflection but also exhibits the best thermal insulation. It reduces the inner temperature of the in-lab setup to mimic a house by 7.5°C when compared to the uncoated glass window. It is concluded that 10 mol% Ag-doped ZnO nanoparticles can result in UV-NIR shielding coatings.

Rationally designed in-situ fabrication of thin film nanocomposite membranes with enhanced desalination and anti-biofouling performance

Silver nanoparticle (AgNP)-incorporated thin film nanocomposite (Ag-TFN) membranes with enhanced reverse osmosis (RO) separation and anti-biofouling performance were fabricated via a rationally designed in-situ hybridization technique based on the dual action of reactant materials: (1) m-phenylenediamine (MPD) monomer, conventionally employed to form a polyamide (PA) selective layer, can also reduce Ag precursors (AgNO3) to form AgNPs; (2) sodium dodecyl sulfate (SDS) surfactant, widely used to facilitate PA formation, can also stabilize AgNPs and transfer them to the interface where the PA layer is formed. The simple addition of AgNO3 to an MPD solution containing SDS during interfacial polymerization enabled the simultaneous formation of the PA layer and AgNPs, which led to the uniform incorporation of AgNPs into the PA matrix, creating the PA-AgNP interfacial free volume (nanovoids) without impairing PA crosslinking. Hence, the Ag-TFN membrane exhibited remarkably higher water permeance with similar NaCl rejection in comparison with the pristine thin film composite (TFC) and commercial membranes, mainly owing to its enhanced interfacial free volume and increased hydrophilicity. The Ag-TFN membrane also exhibited better anti-biofouling performance than control TFC owing to the antibacterial ability of AgNPs and reinforced anti-adhesion enabled by its reduced surface roughness and enhanced surface hydrophilicity.

Synthesis and Characterization of Silver Nanoparticles from <I>Ashyranthus aspera</I> Extract for Antimicrobial Activity Studies

Development of biologically inspired experimental processes for the synthesis of nanoparticles is evolving into an important branch of nanotechnology. Plant-mediated synthesis of nanomaterials has been increasingly gaining popularity due to its eco-friendly nature and cost-effectiveness. In the present study, we were synthesized silver (Ag) nanoparticles using aqueous extracts of fresh leaves of Ashyranthus aspera medicinal plants as bio-reducing agents. UV-Vis spectrometer used to monitor the reduction of Ag ions and the formation of AgNPs in the medium. UV-Vis spectra and visual observation showed that the color of the fresh leaf extracts of Ashyranthus aspera turned into grayish-brown respectively, after treatment with Ag precursors. XRD and SEM have been used to investigate the morphology of prepared AgNPs. The peaks in the XRD pattern are associated with that of the Face-Centered-Cubic (FCC) form of metallic silver. TGA/DTA results associated with weight loss and exothermic reaction due to the desorption of chemisorbed water. FTIR was performed to identify the functional groups which form a layer covering AgNPs and stabilize the AgNPs in the medium. Moreover, silver nanoparticles using aqueous leaf extracts of Ashyranthus aspera were separately tested for their antibacterial activity against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Enterobacter). The results showed that the bacterial growth was inhibited by the extracts containing AgNPs Nanoparticles. The biosynthesized nanoparticle was prepared from Ashyranthus aspera leaf extracts exhibits potential applications as broad-spectrum antimicrobial agents
 Keywords: Ashyranthus aspera, Silver Nanoparticles, Plant extracts, Bacteria, Antibacterial activity.

Fabrication of photoanodes using sol-gel synthesized Ag-doped TiO2 for enhanced DSSC efficiency

A simple, less time consuming, the cost-ineffective sol-gel method was used to synthesis TiO2 nanoparticles (TiO2) and Ag-doped TiO2 nanocomposites (Ag-TiO2) by using titanium tetra isopropoxide as TiO2 and silver nitrate as Ag precursors, respectively. The XRD results show that the doping of Ag reduces the grain size from 19 nm to 12 nm. From the UV–Visible, the blue shift in absorbance was confirmed, and there is an increase in bandgap from 3.3 eV to 3.5 eV while increasing the Ag doping in TiO2. SEM analysis of pure TiO2 and 10% Ag doped TiO2 self assembled grains composed of small TiO2 particles and EDX confirms the presence of Ag in the TiO2 system. The TEM analysis of 10% Ag doped TiO2 sample shows that all the particles are in the nanometer range. The power conversion efficiency (PCE) was found to be 4.09%, and 5.6% for N3 (cis-di(thiocyanato)bis(2,2′-bipyridyl 4,4′-di carboxylate ruthenium (II)) containing acetonitrile dye) sensitized TiO2 and Ag-TiO2 nanocomposites respectively.

Controlling synthesis of Au@AgPd core–shell nanocubes and in situ monitoring SERS of their enhanced catalysis

Surface-enhanced Raman spectroscopy (SERS) displays extraordinary application value in studying chemical reaction mechanism catalyzed by noble metal nanocomposites in recent years by identifing ‘‘fingerprint” information of molecules from their vibrational transitions. Herein, we successfully fabricated Au@AgPd core-shell nanocomposites with integration of catalytic and SERS activities, via a facile process by simultaneously reducing Ag and Pd precursors (AgNO3 and PdCl2) in the presence of Au nanocubes. By easily adjusting the amount of AgNO3 and PdCl2, we can optimize the SERS and catalytic activities of Au@AgPd core-shell nanocomposites. Various spectroscopic and microscopic techniques were employed to characterize the nanocomposites. The optimal Au@AgPd core-shell nanocomposites were used to follow the catalytic reduction process of 4-nitrothiophenol in the presence of NaBH4 by SERS. The prepared Au@AgPd core-shell nanocomposites are effective and suitable for sensitively investigating the catalytic reaction process by in situ SERS.

Silver nanoplate-pillared mesoporous nano-clays for surface enhanced raman scattering

Due to characteristic properties of silver (Ag), Ag nanoparticles have attracted unprecedented attention in various scientific fields such as sensors, catalysts, antibacterial materials, and so on. To obtain tailor-made functionalities of Ag nanoparticles with desired physicochemical properties, proper fabrication process is needed to control their sizes, morphologies or arrangements by hybridization with different components, immobilization on solid struts, and etc. Herein, we suggest a facile synthetic route to obtain Ag-pillared mesoporous nanoclays through simultaneous crystal growth and arrangement of Ag nanoplates with the help of a 2-dimensional inorganic template. To obtain Ag-pillars, layered silver-thiolate self-assembly was exfoliated to monolayers (Ag precursor) and then in-situ hybridized with layered double hydroxide in a layer-by-layer manner. Through reductive calcination, silver thiolate transformed to Ag-pillars which grew in nanoplate morphology with well-arrangement in confined space of nanoclays. Crystal structure, morphology, and pore structure of Ag-pillars in nanoclays were systematically characterized. Surface enhanced Raman scattering effect of arranged Ag-pillars on metal oxide substrate obtained upon calcination was also investigated with rhodamine 6G.

Photodeposition of Ag Nanocrystals onto TiO2 Nanotube Platform for Enhanced Water Splitting and Hydrogen Gas Production

Current work reports the study of Ag nanocrystals (NCs) decorated doubly anodized (DA) TiO2 nanotubes (NTs) thin film as an efficient photoelectrode material for water splitting and photocatalytic hydrogen gas production. DA process has been shown to be capable of producing less defective NTs and creating additional spacious gaps in between NT bundles to allow efficient and uniform integration of Ag NCs. By employing photoreduction method, Ag NCs can be deposited directly onto NTs, where the size and density of coverage can be maneuvered by merely varying the concentration of Ag precursors. Field emission scanning electron microscope (FESEM) images show that the Ag NCs with controllable size are homogeneously decorated onto the walls of NTs with random yet uniform distribution. X-ray diffraction (XRD) results confirm the formation of anatase TiO2 NTs and Ag NCs, which can be well indexed to standard patterns. The decoration of metallic Ag NCs onto the surface of NTs demonstrates a significant enhancement in the photoconversion efficiency as compared to that of pristine TiO2 NTs. Additionally, the as-prepared nanocomposite film also shows improved efficiency when used as a photocatalyst platform in the production of hydrogen gas. Such improvement in the performance of water splitting and photocatalytic hydrogen gas production activity can be credited to the surface plasmonic resonance of Ag NCs present on the surface of the NTs, which renders improved light absorption and better charge separation. The current work can serve as a model of study for designing more advanced nanoarchitecture photoelectrode for renewable energy application.

Co-delivery of superfine nano-silver and solubilized sulfadiazine for enhanced antibacterial functions.

For the effective treatment of bacterial infection, it is essential to find a new strategy to deliver antibacterial agents. In the present study, the co-delivery of superfine nano-silver with solubilized sulfadiazine (SD) using cyclodextrin metal-organic frameworks (CD-MOF) as a carrier exhibited superior antibacterial efficacy to insoluble silver sulfadiazine. The abundant hydroxyl moieties in CD-MOF were utilized to reduce Ag precursor into silver nanoparticles (Ag NPs) of 4-5nm and immobilized within the nano-sized cavities. Microporous CD-MOF facilitated the inclusion of SD molecules in the hydrophobic cavities of γ-cyclodextrin (γ-CD) molecular pairs. The hydrophilic CD-MOF can easily dissolve within exudates at the wound region to release the drug. This approach improved the aqueous solubility of SD by 50 folds which subsequently enhanced SD release and their antibacterial activity. The CD framework also prevented the aggregation of nano-silver particles, stabilizing the particle size and enhancing the curative effects. Hence, the incorporation of superfine nano-silver with solubilized SD using CD-MOF could be an alternate strategy to co-deliver silver and SD with higher efficacy.

Catalytic ozonation of toluene using Mn–M bimetallic HZSM-5 (M: Fe, Cu, Ru, Ag) catalysts at room temperature

We investigated the catalytic efficiency of Mn-based bimetallic oxides in degrading toluene and ozone at room temperature. The room temperature-active bimetallic oxide catalysts were prepared by the addition of Fe, Cu, Ru, and Ag precursors to Mn/HZSM-5. We obtained H2-temperature-programmed reduction (H2-TPR) profiles, X-ray diffraction patterns, and X-ray photoelectron spectra to investigate the characteristics of the prepared catalysts. The catalytic efficiency of Mn-based bimetallic oxide catalysts in degrading toluene and ozone at room temperature was mostly improved by the addition of the secondary metals. The prepared bimetallic oxide catalysts, Cu-Mn/HZSM-5, Fe-Mn/HZSM-5, Ru-Mn/HZSM-5, and Ag-Mn/HZSM-5, enhanced efficiency for toluene removal compared to Mn/HZSM-5. The H2-TPR profiles of the Mn-based bimetallic oxide catalysts showed stronger and broader adsorption-desorption bands at lower temperatures than the profile of Mn/HZSM-5. Additionally, the ratio of the surface defective oxygen over the lattice oxygen on the bimetallic oxide catalysts was higher than that of Mn-only catalysts; the ratio of Mn3+ over Mn4+ was higher for all bimetallic oxide catalysts, as well. Among the bimetallic oxide catalysts, Ru-Mn/HZSM-5 showed the highest efficiency for the removal of toluene to COx due to the synergetic effect of the oxidation state and reducible potential at room temperature.

Antibacterial composite paper with corn stalk-based carbon spheres immobilized AgNPs.

Silver nanoparticles (AgNPs) have been widely used for sterilization due to their broad-spectrum bactericidal properties. However, there exist the problems of premature releasing and accumulative toxicity when free AgNPs are applied. This study proposed a one-pot hydrothermal strategy to synthesize carbon spheres immobilized silver nanoparticles (AgNPs@CS). The synthesis involves with silver ammonia solution as Ag precursor, and corn stalk as green reducing agent and carbon precursor. Furthermore, AgNPs@CS was anchored by cellulose nanofibers (CNF) to obtain the antibacterial composite paper. The obtained CNF/AgNPs@CS paper exhibited superior antibacterial properties against E. coli and S. aureus. Notably, the accumulative release rate of AgNPs from AgNPs@CS was 10.2% in 9days, while that from CNF/AgNPs@CS paper was only 6.7% due to the anchoring effect of both CS and CNF, which was low for avoiding the cumulative toxicity problem. In addition, the mechanical and barrier properties of CNF/AgNPs@CS paper were also improved by 29.4% (tensile index), 2.7% (tear index), 7.4% (burst index), 10% (folding endurance), 0.8% (water vapor transmission) and 9.4% (oxygen transmission rate), respectively. Therefore, the composite paper has potential application as a medical antibacterial material.