scholarly journals Preparation of Au-Ag Bimetals and Large-Size Porous Gold Nanostructured Materials

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Xuewen Chen
Keyword(s):  
Catalytic Reduction ◽  
Chemical Properties ◽  
Precious Metals ◽  
Size Composition ◽  
Molar Ratio ◽  
Porous Gold ◽  
Large Size ◽  
Gold Silver ◽  
Average Size ◽  
Gold Nanomaterials

Gold, silver, and other precious metals are very important nonferrous metals and have been widely applied in fields such as electronics, medicine, metallurgy, pharmaceuticals, and transportation. Adjustable properties of precious metals are mainly attributed to controlled synthesis of precious metals by structure, size, composition, and morphology. Synthesis of binary metals focuses on coordination of physical and chemical properties of metal elements in components, with the aim to give full play to the advantages of the two metals. Gold (Au) and silver (Ag) have similar lattice constants, which provide important theoretical basis for obtaining the binary bimetallic nanostructure of the two metals by coreduction at room temperature. Ag–Au alloy was prepared at different molar ratios of Ag+/AuIII, and the bimetallic nanomaterials obtained had similar Ag/Au ratios to the molar ratio at reaction. This suggested that the bimetallic nanomaterials reacted completely, with the maximum average size in Ag90.1–Au9.9 and the minimum average size in Ag83.2–Au16.8 and Ag66.9–Au33.1. Due to the deficiency of conventional etching agents, the “regrowth etching” method was proposed in this study. Specifically, with AuI as the etching agent, the porous gold nanomaterials with the size of more than 300 nm were successfully prepared, achieving the regrowth etching effect and a good structural stability. According to the analysis based on the catalytic reduction reaction with p-nitrophenol, the properties of the large-size porous gold nanomaterials were related to the quantity and size of pores.

ULTRAFINE AU NANODOTS ON GRAPHENE OXIDE FOR CATALYTIC REDUCTION OF 4-NITROPHENOL

NANO ◽  
2013 ◽  
Vol 08 (03) ◽  
pp. 1350034 ◽  
Author(s):  
JIANLI CHEN ◽  
GANG CHENG ◽  
ZHUANGNAN LI ◽  
FUJUN MIAO ◽  
XIAOQIANG CUI ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Catalytic Activity ◽  
Catalytic Reduction ◽  
Synthesis Method ◽  
Chemical Properties ◽  
Electrochemical Sensing ◽  
Graphene Oxide Nanosheet ◽  
Average Size ◽  
Physical And Chemical ◽  
Au Nanodots

Graphene oxide nanosheet is an ideal platform to capture nanoparticles for highly efficient catalysis, electrochemical sensing and biosensing. In this work, we have described a simple synthesis method for preparation graphene oxide– Au nanohybrid. Au nanodots with an average size of 1.6 nm uniformly dispersed on the surface of graphene oxide. The well-defined nanostructure has been characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The nanohybrid also exhibits enhanced catalytic activity toward the reduction of 4-nitrophenol by NaBH4 . Comparing with pure Au nanodots and graphene oxide, graphene oxide– Au nanohybrid shows the highest catalytic activity. This approach not only suggests a wide potential application of graphene oxide nanosheet as a host material for supporting a variety of nanoparticles, but also provides a new approach for the fabrication of graphene-based nanohybrids with multiple physical and chemical properties.

Physical and Chemical Properties of the Waste Electronic Circuit Board

2013 ◽  
Vol 699 ◽  
pp. 900-903 ◽  
Author(s):  
Hong Fen Wang
Keyword(s):  
Printed Circuit Boards ◽  
Electronic Circuit ◽  
Chemical Properties ◽  
Precious Metals ◽  
Circuit Board ◽  
Physical And Chemical Properties ◽  
Gold Silver ◽  
Waste Pcbs ◽  
Physical And Chemical ◽  
And Chemical Properties

Printed circuit boards (PCBs) and copper-clad laminate (CCLs) are the foundation of the electronic industry, and the core components of all kinds of electronic products. With the accelerated pace of information equipment replacement, waste PCBs and CCLs increase every year, and generated a lot of e-waste. Sweden Ronnskar smelter made an analysis on elements of the PCBs used in the personal computer, the results showed that the PCBs generally contain precious metals gold, silver and non-ferrous metals such as copper, wherein the mass fraction of copper is up to 26.8%, the mass concentration of gold and silver respectively reached 80 g/t and 3300 g/t, which much higher than the average gold grade and having high recycling value. Waste PCBs also contain heavy metals such as lead, cadmium, chromium, which have a great deal of harm to the environment and human body. This paper focuses on the physical and chemical properties of the electronic circuit board such as calorific value and moisture, on the content measurement and analysis of gold, copper and other precious metals so that the physical and chemical properties of the ingredients in waste PCBs and CCLs are determined from a qualitative and quantitative point of view, which is very important for looking for recyclable value of the waste PCBs and CCLs and for determining the best method of recycling them. The test results showed that the waste PCBs and CCLs had very high recycling value.

scholarly journals Effects of serpentinite fertilizer on the chemical properties and enzyme activity of young spruce soils

2016 ◽  
Vol 30 (4) ◽  
pp. 401-414 ◽  
Author(s):  
Ewa Błońska ◽  
Kazimierz Januszek ◽  
Stanisław Małek ◽  
Tomasz Wanic
Keyword(s):  
Enzyme Activity ◽  
Chemical Properties ◽  
Molar Ratio ◽  
Tree Roots ◽  
Forest Zone ◽  
Negative Effect ◽  
Phosphorus And Potassium ◽  
One Year ◽  
Nitrogen Phosphorus ◽  
Experimental Plots

AbstractThe experimental plots used in the study were located in the middle forest zone (elevation: 900-950 m a.s.l.) on two nappes of the flysch Carpathians in southern Poland. The aim of this study was to assess the effects of serpentinite in combination with nitrogen, phosphorus, and potassium fertilizers on selected chemical properties of the soil and activity of dehydrogenase and urease in the studied soils. All fertilizer treatments significantly enriched the tested soils in magnesium. The use of serpentinite as a fertilizer reduced the molar ratio of exchangeable calcium to magnesium, which facilitated the uptake of magnesium by tree roots due to competition between calcium and magnesium. After one year of fertilization on the Wisła experimental plot, the pH of the Ofh horizon increased, while the pH of the mineral horizons significantly decreased. Enrichment of serpentinite with nitrogen, phosphorus, and potassium fertilizers stimulated the dehydrogenase activity in the studied organic horizon. The lack of a negative effect of the serpentinite fertilizer on enzyme activity in the spruce stand soil showed that the concentrations of the heavy metals added to the soil were not high enough to be toxic and indicated the feasibility of using this fertilizer in forestry.

scholarly journals Contributions to Management Strategies in the NE Atlantic Regarding the Life History and Population Structure of a Key Deep-Sea Fish (Mora moro)

Biology ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 522
Author(s):  
Régis Santos ◽  
Wendell Medeiros-Leal ◽  
Osman Crespo ◽  
Ana Novoa-Pabon ◽  
Mário Pinho
Keyword(s):  
Population Structure ◽  
Life History ◽  
Deep Sea ◽  
Management Strategies ◽  
Size Composition ◽  
Large Size ◽  
The Common ◽  
Fishing Impacts ◽  
Sea Fish

With the commercial fishery expansion to deeper waters, some vulnerable deep-sea species have been increasingly captured. To reduce the fishing impacts on these species, exploitation and management must be based on detailed and precise information about their biology. The common mora Mora moro has become the main deep-sea species caught by longliners in the Northeast Atlantic at depths between 600 and 1200 m. In the Azores, landings have more than doubled from the early 2000s to recent years. Despite its growing importance, its life history and population structure are poorly understood, and the current stock status has not been assessed. To better determine its distribution, biology, and long-term changes in abundance and size composition, this study analyzed a fishery-dependent and survey time series from the Azores. M. moro was found on mud and rock bottoms at depths below 300 m. A larger–deeper trend was observed, and females were larger and more abundant than males. The reproductive season took place from August to February. Abundance indices and mean sizes in the catch were marked by changes in fishing fleet operational behavior. M. moro is considered vulnerable to overfishing because it exhibits a long life span, a large size, slow growth, and a low natural mortality.

scholarly journals Green Synthesis of N/Zr Co-Doped TiO2 for Photocatalytic Degradation of p-Nitrophenol in Wastewater

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 235
Author(s):  
Hayette Benkhennouche-Bouchene ◽  
Julien G. Mahy ◽  
Cédric Wolfs ◽  
Bénédicte Vertruyen ◽  
Dirk Poelman ◽  
...  
Keyword(s):  
Visible Light ◽  
Tio2 Nanoparticles ◽  
Sol Gel ◽  
Visible Region ◽  
Chemical Properties ◽  
Pure Tio2 ◽  
Molar Ratio ◽  
Xps Spectra ◽  
Doped Tio2 ◽  
Co Doped

TiO2 prepared by a green aqueous sol–gel peptization process is co-doped with nitrogen and zirconium to improve and extend its photoactivity to the visible region. Two nitrogen precursors are used: urea and triethylamine; zirconium (IV) tert-butoxide is added as a source of zirconia. The N/Ti molar ratio is fixed regardless of the chosen nitrogen precursor while the quantity of zirconia is set to 0.7, 1.4, 2, or 2.8 mol%. The performance and physico-chemical properties of these materials are compared with the commercial Evonik P25 photocatalyst. For all doped and co-doped samples, TiO2 nanoparticles of 4 to 8 nm of size are formed of anatase-brookite phases, with a specific surface area between 125 and 280 m2 g−1 vs. 50 m2 g−1 for the commercial P25 photocatalyst. X-ray photoelectron (XPS) measurements show that nitrogen is incorporated into the TiO2 materials through Ti-O-N bonds allowing light absorption in the visible region. The XPS spectra of the Zr-(co)doped powders show the presence of TiO2-ZrO2 mixed oxide materials. Under visible light, the best co-doped sample gives a degradation of p-nitrophenol (PNP) equal to 70% instead of 25% with pure TiO2 and 10% with P25 under the same conditions. Similarly, the photocatalytic activity improved under UV/visible reaching 95% with the best sample compared to 50% with pure TiO2. This study suggests that N/Zr co-doped TiO2 nanoparticles can be produced in a safe and energy-efficient way while being markedly more active than state-of-the-art photocatalytic materials under visible light.

Positive effects of a halloysite-supported Cu/Co catalyst fabricated by a urea-driven deposition precipitation method on the CO-SCR reaction and SO2 poisoning

2021 ◽  
Author(s):  
Wei-Jing Li ◽  
Shu Tsai ◽  
Ming-Yen Wey
Keyword(s):  
Co Oxidation ◽  
Catalytic Reduction ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Halloysite Nanotube ◽  
Co Catalyst ◽  
Reduction Of No ◽  
Co Catalysts ◽  
Positive Effects ◽  
So2 Poisoning

Cu/Co catalysts were prepared on halloysite nanotube supports by a urea-driven deposition-precipitation method for CO oxidation and the selective catalytic reduction of NO (CO-SCR). First, the Cu/NH3 molar ratio was...

Silver nanoparticles induce cytotoxicity, but not cell transformation or genotoxicity on Balb3T3 mouse fibroblasts

2013 ◽  
Vol 14 (1-2) ◽  
pp. 49-60 ◽  
Author(s):  
Francesca Broggi ◽  
Jessica Ponti ◽  
Guido Giudetti ◽  
Fabio Franchini ◽  
Vicki Stone ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Cell Transformation ◽  
Micronucleus Test ◽  
Chemical Properties ◽  
Neoplastic Transformation ◽  
Research Centre ◽  
Ag Nps ◽  
Joint Research ◽  
Ic50 Values ◽  
Average Size

AbstractSilver nanoparticles (Ag NPs) are one of the most common nanomaterials present in nanotechnology-based products. Here, the physical chemical properties of Ag NPs suspensions of 44 nm, 84 nm and 100 nm sizes synthesized in our laboratory were characterized. The NM-300 material (average size of 17 nm), supplied by the Joint Research Centre Nanomaterials Repository was also included in the present study. The Ag NPs potential cytotoxicity was tested on the Balb3T3 cell line by the Colony Forming Efficiency assay, while their potential morphological neoplastic transformation and genotoxicity were tested by the Cell Transformation Assay and the micronucleus test, respectively. After 24 h of exposure, NM-300 showed cytotoxicity with an IC50 of 8 µM (corresponding to 0.88 µg/mL) while for the other nanomaterials tested, values of IC50 were higher than 10 µM (1.10 µg/mL). After 72 h of exposure, Ag NPs showed size-dependent cytotoxic effect with IC50 values of 1.5 µM (1.16 µg/mL) for NM-300, 1.7 µM (1.19 µg/mL) for Ag 44 nm, 1.9 µM (0.21 µg/mL) for Ag 84 nm and 3.2 µM (0.35 µg/mL) for Ag 100 nm. None of the Ag NPs tested was able to induce either morphological neoplastic transformation or micronuclei formation.

scholarly journals Effect of Crosslinking Type on the Physical-Chemical Properties and Biocompatibility of Chitosan-Based Electrospun Membranes

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 831
Author(s):  
Andrea Dodero ◽  
Sonia Scarfi ◽  
Serena Mirata ◽  
Alina Sionkowska ◽  
Silvia Vicini ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Biological Properties ◽  
Diglycidyl Ether ◽  
Chemical Crosslinking ◽  
Electrospinning Technique ◽  
Vapour Permeability ◽  
Phosphate Ions ◽  
Physically Crosslinked ◽  
Mechanical Performances ◽  
Average Size

Chitosan nanofibrous membranes are prepared via an electrospinning technique and explored as potential wound healing patches. In particular, the effect of a physical or chemical crosslinking treatment on the mat morphological, mechanical, water-related, and biological properties is deeply evaluated. The use of phosphate ions (i.e., physical crosslinking) allows us to obtain smooth and highly homogenous nanofibers with an average size of 190 nm, whereas the use of ethylene glycol diglycidyl ether (i.e., chemical crosslinking) leads to rougher, partially coalesced, and bigger nanofibers with an average dimension of 270 nm. Additionally, the physically crosslinked mats show enhanced mechanical performances, as well as greater water vapour permeability and hydrophilicity, with respect to the chemically crosslinked ones. Above all, cell adhesion and cytotoxicity experiments demonstrate that the use of phosphate ions as crosslinkers significantly improves the capability of chitosan mats to promote cell viability owing to their higher biocompatibility. Moreover, tuneable drug delivery properties are achieved for the physically crosslinked mats by a simple post-processing impregnation methodology, thereby indicating the possibility to enrich the prepared membranes with unique features. The results prove that the proposed approach may lead to the preparation of cheap, biocompatible, and efficient chitosan-based nanofibers for biomedical and pharmaceutical applications.

Synthesis and characterization of Au, Pt supported on graphene aerogel catalysts for CO oxidation at low temperature

2021 ◽  
Vol 11 (1) ◽  
pp. 118-122
Author(s):  
Chuyen Phan Thi ◽  
Hang Tran Thi Thanh ◽  
Phong Pham Nam ◽  
Ha Vu Thi Thu
Keyword(s):  
Low Temperature ◽  
Ambient Temperature ◽  
Co Oxidation ◽  
Pt Nanoparticles ◽  
Molar Ratio ◽  
Synthesis And Characterization ◽  
Graphene Aerogel ◽  
Highly Dispersed ◽  
Average Size

Au, Pt supported on graphene aerogel catalysts (PtAu/rGOA) with molar ratio of Pt and Au of 1:1, and total metal concentration of 5 % were successfully synthesized by hydrothermal method.  The obtained catalysts were characterized by Raman, XRD, XPS, HR-TEM, BET. It revealed that Au and Pt nanoparticles with average size of 3 – 5 nm were highly dispersed on aerogel graphene. The activity of these catalysts was tested  in CO oxidation. The results showed that the conversion of CO at ambient temperature was 100% during 25 minutes. Accordingly, PtAu/rGOA could be considered as a potential catalysts for CO oxidation at low temperature.

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