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1.
Ting Li Brian Albee Matti Alemayehu Rocio Diaz Leigha Ingham Shawn Kamal Maritza Rodriguez Sandra Whaley Bishnoi 《Analytical and bioanalytical chemistry》2010,398(2):689-700
A comparative assessment of the 48-h acute toxicity of aqueous nanoparticles synthesized using the same methodology, including
Au, Ag, and Ag–Au bimetallic nanoparticles, was conducted to determine their ecological effect in freshwater environments
through the use of Daphnia magna, using their mortality as a toxicological endpoint. D. magna are one of the standard organisms used for ecotoxicity studies due to their sensitivity to chemical toxicants. Particle suspensions
used in toxicity testing were well-characterized through a combination of absorbance measurements, atomic force or electron
microscopy, flame atomic absorption spectrometry, and dynamic light scattering to determine composition, aggregation state,
and particle size. The toxicity of all nanoparticles tested was found to be dose and composition dependent. The concentration
of Au nanoparticles that killed 50% of the test organisms (LC50) ranged from 65–75 mg/L. In addition, three different sized Ag nanoparticles (diameters = 36, 52, and 66 nm) were studied
to analyze the toxicological effects of particle size on D. magna; however, it was found that toxicity was not a function of size and ranged from 3–4 μg/L for all three sets of Ag nanoparticles
tested. This was possibly due to the large degree of aggregation when these nanoparticles were suspended in standard synthetic
freshwater. Moreover, the LC50 values for Ag–Au bimetallic nanoparticles were found to be between that of Ag and Au but much closer to that of Ag. The bimetallic
particles containing 80% Ag and 20% Au were found to have a significantly lower toxicity to Daphnia (LC50 of 15 μg/L) compared to Ag nanoparticles, while the toxicity of the nanoparticles containing 20% Ag and 80% Au was greater
than expected at 12 μg/L. The comparison results confirm that Ag nanoparticles were much more toxic than Au nanoparticles,
and that the introduction of gold into silver nanoparticles may lower their environmental impact by lowering the amount of
Ag which is bioavailable. 相似文献
2.
A. V. Bukhtiyarov I. P. Prosvirin I. A. Chetyrin A. A. Saraev V. V. Kaichev V. I. Bukhtiyarov 《Kinetics and Catalysis》2016,57(5):704-711
The formation of Ag–Au, Cu–Au, and Ag–Cu bimetallic particles on the surface of highly oriented pyrolytic graphite was studied by X-ray photoelectron spectroscopy. Samples with the core–shell structure of particles were prepared by sequential thermal vacuum deposition. The thermal stability of the samples was studied over a wide range of temperatures (25-400°C) under ultrahigh-vacuum conditions. The heating of the samples to ~250°C leads to the formation of bimetallic alloy particles with a relatively uniform distribution of metals in the bulk. The thermal stability of the samples with respect to sintering depends on the nature of the supported metals. Thus, the Ag–Au particles exhibited the highest thermal resistance (~350°C) under ultrahigh-vacuum conditions, whereas the Ag–Cu particles agglomerated even at ~250°C. 相似文献
3.
Masato Takenaka Yoshikazu Hashimoto Takeshi Iwasa Tetsuya Taketsugu Gediminas Seniutinas Armandas Balčytis Saulius Juodkazis Yoshiaki Nishijima 《Journal of computational chemistry》2019,40(8):925-932
First principles electrodyanmics and quantum chemical simulations are performed to gain insights into the underlying mechanisms of the surface enhanced Raman spectra of 22BPY adsorbed on pure Au and Ag as well as on Au–Ag alloy nanodiscs. Experimental SERS spectra from Au and Ag nanodiscs show similar peaks, whereas those from Au–Ag alloy reveal new spectral features. The physical enhancement factors due to surface nano-texture were considered by numerical FDTD simulations of light intensity distribution for the nano-textured Au, Ag, and Au–Ag alloy and compared with experimental results. For the chemical insights of the enhancement, the DFT calculations with the dispersion interaction were performed using Au20, Ag20, and Au10Ag10 clusters of a pyramidal structure for SERS modeling. Binding of 22BPY to the clusters was simulated by considering possible arrangements of vertex and planar physical as well as chemical adsorption models. The DFT results indicate that 22BPY prefers a coplanar adsorption on a (111) face with trans-conformation having close energy difference to cis-conformation. Binding to pure Au cluster is stronger than to pure Ag or Au–Ag alloy clusters and adsorption onto the alloy surface can deform the surface. The computed Raman spectra are compared with experimental data and assignments for pure Au and Ag models are well matching, indicating the need of dispersion interaction to reproduce strong Raman signal at around 800 cm–1. This work provides insight into 3D character of SERS on nanorough surfaces due to different binding energies and bond length of nanoalloys. © 2018 Wiley Periodicals, Inc. 相似文献
4.
This work deals with the prediction and experimental measurements of the (solid + liquid) equilibrium (SLE) in acid medium for industrial purposes. Specific systems including KCl–ethanol–water–HCl and K2SO4–water–H2SO4 were analyzed. At first, a critical discussion of SLE calculations was given, based on the well-known UNIQUAC extended and LIQUAC models. Two new proposals were derived, considering the explicit necessity of a new reference state for SLE calculations for the studied (solvents + acid) mixtures. The solubility of KCl in water–ethanol–HCl mixed solvents was measured in the temperature range of 300.15 to 315.15 K using an analytical gravimetric method. These results combined with some other experimental data reported in the open literature let us to propose a set of parameters for the new models. They included the interaction parameters between ethanol and the H+ ion. The prediction capability of the new models, for calculations in acid medium, was illustrated. Experimentally, it was observed that the (K2SO4 + water + H2SO4) system presented the unusual behavior of increasing K2SO4 solubility with an increase in the sulfuric acid concentration. This was accurately predicted by the newly proposed models. 相似文献
5.
本文利用旋转圆盘电极系统研究了酸性介质中H2O2在Au(100)和Au(111)电极表面的电化学行为. 实验发现在Au电极上H2O2难以发生还原,但是当电位稍微正于H2O2氧化为O2的平衡电势时即可发生氧化. 在Au(111)上H2O2氧化的起始电位比在Au(100)正0.1 V左右. Au(100)上的双桥位位点能增强反应中间体*OOH的吸附,可能是导致Au(100)上H2O2氧化反应超电势比Au(111)低的主要原因. 在较正电位区(E>1.2 V), 当电极表面被氧物种覆盖时,H2O2在两个电极上的氧化都会受到一定程度的抑制,这种影响在Au(111)上比Au(100)上更加明显,这与Au(111)上氧物种的生成与逆向还原可逆性差的趋势一致. 最后还将Au与Pt单晶电极上H2O2氧化的行为进行了对比分析. 相似文献
6.
有关用于各种氧化反应中Au-Ag双金属催化剂存在显著协同效应的来源有两种观点:(1) AgOx块与体相Au表面的接触界面起重要作用,体相Au的表面是催化活性位;(2) Au-Ag双金属催化剂中形成的Au-Ag合金中电荷从Ag转移到Au上,可能对催化剂活性起作用。因此,确定Au表面上Ag是以氧化物还是以金属合金形式存在可能是深度理解该协同效应的关键。
为了检测和验证催化剂活性的增加是由于Ag2O与Au纳米粒子的紧密接触,在密闭循环反应体系中比较研究了Au/Ag2O和Ag2O催化剂上CO氧化反应。将CO/O2摩尔比为2的混合气通入到这二个催化剂上来跟踪压力降低的速率。因而检测了气体的消耗量和CO2的生成量。结果发现,在稳态下Au/Ag2O和Ag2O催化剂的压力降低的速率不存在差别。这两个催化剂上压力的降低是由于Ag2O中表面晶格氧被混合气中CO的还原所致。 Au/Ag2O催化剂上得到的结果与以前研究的具有氧化表面的Ag掺杂的Au粉末(Ag/Au-b)上的一致,也表明AgOx块与体相Au表面界面周边不大可能是CO氧化反应催化活性位。基于具有稳态表面的Ag/Au-b样品上的研究结果,我们认为AgOx物种被还原为0价态Ag而形成的Ag-Au合金很可能是催化活性位。 相似文献
为了检测和验证催化剂活性的增加是由于Ag2O与Au纳米粒子的紧密接触,在密闭循环反应体系中比较研究了Au/Ag2O和Ag2O催化剂上CO氧化反应。将CO/O2摩尔比为2的混合气通入到这二个催化剂上来跟踪压力降低的速率。因而检测了气体的消耗量和CO2的生成量。结果发现,在稳态下Au/Ag2O和Ag2O催化剂的压力降低的速率不存在差别。这两个催化剂上压力的降低是由于Ag2O中表面晶格氧被混合气中CO的还原所致。 Au/Ag2O催化剂上得到的结果与以前研究的具有氧化表面的Ag掺杂的Au粉末(Ag/Au-b)上的一致,也表明AgOx块与体相Au表面界面周边不大可能是CO氧化反应催化活性位。基于具有稳态表面的Ag/Au-b样品上的研究结果,我们认为AgOx物种被还原为0价态Ag而形成的Ag-Au合金很可能是催化活性位。 相似文献
7.
在无额外的添加剂和保护剂的情况下,以柠檬酸钠还原氯金酸制得链状金纳米粒子,使用扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察样品. 层层自组装技术可将金纳米粒子自组装,并分别以L-甲硫氨酸(L-Methionine,L-Met)、硫脲(Thiourea,TU)、丙烯基硫脲(Allyl thiourea,ATU)和聚乙烯吡咯烷酮(Polyvinylpyrrolidone,PVP)交联剂自组装于玻碳基底,即得金纳米粒子修饰电极. 以[Fe(CN)6]3-/4-氧化还原电对为探针,考察该修饰电极的电化学性质. Au/L-Met/GC电极有最佳电化学性能,循环伏安曲线和计时电流曲线测试表明,Au/L-Met/GC电极的H2O2电催化氧化有较高的灵敏度,线性范围2×10-7 ~ 3×10-3 mol·L-1,检出限6.67×10-8 mol·L-1. 相似文献
8.
Gorobinskii L. V. Chernyavskii A. S. Solntsev K. A. Kuznetsov N. T. 《Russian Journal of Coordination Chemistry》2001,27(3):147-149
Reactions of iodination of monosubstituted derivatives of B12H11X2–anion (X = OC(O)CH3, OH, SCN) were studied. The reactions were shown to proceed smoothly to give B12H10(OC(O)CH3)I2–((carboxy)(iodo)[decahydro[I
h1551-20-closo]dodecaborate(2–)] anion), B12H10(OH)I2–((hydroxo)(iodo)[decahydro[I
h1551-20-closo]dodecaborate(2–)] anion), and B12H10(SCN)I2–((thiocyanato)(iodo)[decahydro[I
h1551-20-closo]dodecaborate(2–)] anion) in high yields, irrespective of the solvent used (benzene, H2O–ROH, where R = C2H5, CH2CH2CH3).1 相似文献
9.
Yu. Trach V. Sydorchuk O. Makota S. Khalameida R. Leboda J. Skubiszewska-Zi?ba V. Zazhigalov 《Journal of Thermal Analysis and Calorimetry》2012,107(2):453-461
Deposited catalysts composition H3PMo12O40/SiO2 and Ag/H3PMo12O40/SiO2 have been synthesized on the basis of fumed silica, including milling technique. Physical–chemical characteristics of prepared
catalysts have been studied by means of XRD, DTA-TG, FTIR, UV–Vis spectroscopy, and adsorption of nitrogen. Catalysts possess
meso- or meso-macroporous structure and contain deposited Keggin heteropolycompounds. Deposition of heteropolycompounds on
support with high specific surface area results in increase of selectivity to epoxide in epoxidation reactions. The use of
milling during catalyst synthesis leads to further growth of selectivity of epoxides formation. 相似文献
10.
Keskinov V. A. Semenov K. N. Gol’tsov T. S. Charykov N. A. Podol’skii N. E. Kurilenko A. V. Shaimardanov Zh. K. Shaimardanova B. K. Kulenova N. A. 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2019,93(12):2555-2558
Russian Journal of Physical Chemistry A - Isothermal phase diagrams of ternary systems fullerenol-d–LaCl3–H2O and fullerenol-d–GdCl3–H2O at 25°C are studied via... 相似文献
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12.
《Journal of Coordination Chemistry》2012,65(15):2724-2731
A new coordination polymer, {[Ag(H3bptc)(bpe)]?·?2H2O} n (1) (H4bptc?=?3,3′,4,4′-benzophenonetetracarboxylic acid, bpe?=?1,2-bis(4-pyridyl)ethene), has been synthesized through a hydrothermal technique and structurally characterized. The crystal structure of 1 exhibits a 2-D hydrogen-bonding sheet between H3bptc? and two free water molecules. Fluorescent property, TG analysis, and X-ray powder diffraction for 1 were also measured and discussed. 相似文献
13.
Sangeetha K Babu RR Ramamurthi K Prakash J Khan SA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(5):884-888
L-arginine hydrochloride monohydrate and L-arginine hydrobromide monohydrate single crystals are irradiated by 100 MeV Ag8+ swift heavy ions. The residual gases liberated from the irradiated samples are monitored as a function of ion fluence using quadrupole mass analyzer. The C2H3+, C2H2, N2, CO, HCl and CO2 are the dominant gases liberated. Fourier transform infrared spectra of irradiated crystals explain the breaking of bonds in a localized region of the crystals. The crystallinity of irradiated crystals is analyzed by powder X-ray diffractions. 相似文献
14.
Wen Yao Zhang Li Xiao Ping Yang Lei Sang Shi Hua 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2019,93(6):1032-1037
Russian Journal of Physical Chemistry A - The solubility data for ternary systems Na2SO4–Na2B4O7–H2O and Li2B4O7–Na2B4O7–H2O at 273 K were obtained experimentally by the... 相似文献
16.
以银离子、3,3 ',4,4'-二苯硫酮四羧酸阴离子(tdpc)和4,4'-联吡啶(bipy),合成了一种新型化合物[十二水合(3,3',4,4'-二苯硫酮四羧酸)(4,4'-联吡啶)水合银][ Ag2 (tdpc)(bipy)2][ Ag2 (bipy)2 (H2O)]·12H2O,该化合物为链状结构,Ag…Ag相互... 相似文献
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19.
Magda F. Fathalla 《Journal of solution chemistry》2011,40(7):1258-1270
The kinetics of alkaline hydrolysis of 2-chloroquinoxaline (QCl) with hydroxide ion was investigated spectrophotometrically
at different percentages of aqueous–organic solvent mixtures with acetonitrile (10–60% v/v) and with dimethylesulphoxide (10–80%)
over the temperature range from 25 to 45 °C. The reaction was performed under pseudo first order conditions with respect to
2-chloroquinoxaline (QCl). An increase in the percentage of organic solvent (v/v) has different effects on the reaction rate
constants, presumably due to hydrogen bond donor and acceptor differences of the media and other solvatochromic parameters.
The data were discussed in terms of the Kamelt-Taft parameter and E
T(30). A nonlinear relation between the logarithm of the rate constant and reciprocal of the dielectric constant suggests the
presence of selective solvation by the polar water molecules. Activation parameters ΔH
#, ΔS
# and ΔG
# were determined and discussed. 相似文献
20.
Khoma R. E. Gelmboldt V. O. Baumer V. N. Ennan A. A. Vodzinskii S. V. Ishkov Yu. V. Rakipov I. M. 《Russian Journal of General Chemistry》2021,91(2):173-180
Russian Journal of General Chemistry - An original procedure was proposed for the synthesis of a series of aminomethanesulfonic acids AlkNHCH2SO3 (Alk = n-Bu, n-Hept, n-Oct, Bn) and... 相似文献