纳米银粒子对[Ru(bpy)_3]~(2+)光谱学性质的影响及电解质效应

研究了[Ru(bpy)3]2+溶液中引入纳米银粒子的光谱学性质变化规律以及[Ru(bpy)3]2+与纳米银粒子所构成的溶液体系([Ru(bpy)3]2+-Ag)的电解质效应.研究结果表明,[Ru(bpy)3]2+吸附在纳米银粒子表面使纳米银粒子相互桥连形成规则的类链状网络聚集体.纳米银粒子造成[Ru(bpy)3]2+溶液荧光猝灭,且大尺寸的纳米银粒子引起的荧光猝灭程度较大.在[Ru(bpy)3]2+-Ag体系中引入电解质造成纳米银粒子不同程度的聚集和生长.电解质对纳米银聚集影响为:CaCl2MgCl2Ca(NO3)2KClKNO3.随着[Ru(bpy)3]2+-Ag体系中引入电解质含量的增加,溶液的荧光强度先降低而后又逐渐增强,直至达到定值,表明一定量的电解质可产生荧光猝灭释放效应.电解质对荧光强度影响顺序为:Ca(NO3)2CaCl2MgCl2KClKNO3.采用透射电子显微镜、紫外-可见吸收分光光度计和荧光分光光度计等手段从分子间相互作用和能量传输等方面初步探讨了纳米银粒子对表面吸附[Ru(bpy)3]2+溶液光谱学性质的影响机制以及电解质效应.     

电解质对吸附于纳米银粒子表面荧光素的光谱学性质的影响

在含有纳米银的荧光素溶液(Fl-Ag)中引入KNO₃、KCl、Ca(NO₃)₂和CaCl₂电解质,利用透射电子显微镜、紫外-可见分光光度计和荧光分光光度计等技术研究电解质对Fl-Ag溶液的显微结构和光谱学性质的影响。结果表明,电解质离子与纳米银粒子间存在较强的相互作用,这种强的相互作用造成纳米银粒子不同程度的聚集和生长。各电解质引起的纳米银粒子的聚集程度关系为CaCl₂＞Ca(NO₃)₂＞KCl＞KNO₃。随着电解质加入量的增加,溶液的荧光强度先下降,而后又逐渐增强,直至达到定值。各电解质对Fl-Ag溶液的荧光强度影响强弱关系为Ca(NO₃)₂＞CaCl₂＞KCl＞KNO₃。本文从分子间的相互作用、能量传输等方面探讨了电解质离子对含有纳米银的荧光素溶液的显微结构和光学性能影响机理。     

可控纳米银胶体的稳定性

纳米银胶体(AgNPs)长期储存不稳定性问题是本研究的中心,着重考察了不同前驱体对纳米银胶体的稳定性影响。分别以银氨([Ag(NH3)2]OH)溶液和Ag NO3溶液为前驱体制备了多份纳米银胶体样品并通过UV-Vis、FE-SEM、EDS、ZETA电位仪等现代分析测试手段研究了纳米银胶的形貌、粒径大小以及稳定性。对比分析发现,以[Ag(NH3)2]OH溶液为前驱体,制备的纳米银胶体具有粒径可控,尺寸均一,分散性良好等特点;而且经过一个月的常温储存,表现出比用Ag NO3溶液为前驱体制备的纳米银胶体具有更高的储存稳定性。     

不同电性的纳米银对甲基橙光谱学性质的影响

通过吸收光谱和荧光光谱等手段研究了正/负电性纳米银对不同pH值的甲基橙(MO)溶液光谱学性质的影响.研究结果表明,正电性纳米银(P-Ag)与甲基橙作用形成新的复合物,吸收光谱表现为复合物体系的性质.负电性纳米银(N-Ag)与甲基橙静电排斥作用,相互作用较弱,吸收光谱仅表现为两者简单叠加.在正电性纳米银-甲基橙体系中,S1→S0荧光明显增强.当溶液pH=2.1时,荧光增强比率最大,当pH=4.8时,荧光增强比率最小;S2→S0荧光减弱,且与体系的pH值关系不大.在负电性纳米银-甲基橙体系中,仅少量纳米银存在条件下,S1→S0荧光略增强.在溶液pH=2.1时,荧光增强比率最大;S2→S0荧光明显减弱,且与体系的pH值关系不大.分析认为,不同电性的纳米银对甲基橙光谱学性质影响不同,与纳米银与甲基橙分子间相互作用、纳米银的局域场增强效应以及无辐射能量转移作用等密切相关.     

纳米银对表面吸附镝配合物的荧光增强效应研究

研究了不同粒径的纳米银对镝配合物(乙二胺四乙酸配合物)的光谱学性质影响。当配合物溶液的pH值范围为4.0～6.0时,加入纳米银,可观察到大量的纳米银聚集体形成,而在吸收光谱的长波处出现一个新的吸收峰,随着纳米银浓度的增加,该吸收峰逐渐红移,同时,镝配合物的荧光强度增强。实验结果表明,纳米银粒子对镝配合物的荧光增强效应及荧光增强因子与纳米银粒子的浓度和粒径密切相关。随着纳米银浓度的增加,配合物的荧光强度先增强而后又逐渐降低。小粒径的纳米银对镝配合物的荧光增强因子较小。本文从纳米银粒子的聚集效应、局部电磁场增强效应及光吸收效应等方面探讨了纳米银对表面吸附镝配合物的+荧光增强效应机理。     

均匀铁氧化物（含水）胶体粒子的制备

均匀胶体具有广阔的应用前景,开展这种胶体的研究具有重要的理论和实际意义。铁氧化物(含水)均匀胶体粒子首先在Matijevi’c的实验室制得。不久前,我们在无防尘设备的一般实验室条件下成功地制得了二种直径为0.090μm的球状α-Fe_2O_3胶体粒子,并开展了均匀胶体的性质研究。为了进一步开展均匀胶体特性及其表面性质的研究,就要制取不同大小和不同形状的胶体粒子,并掌握其制备规律。本文旨在探讨制备铁氧化物胶体粒子对反应液铁离子的浓度、盐酸量以及陈化时间等因素对粒子物相、形状等的影响。     

可控纳米银胶体的稳定性研究

纳米银胶体(AgNPs)长期储存不稳定性问题是本研究的中心,着重考察了不同前驱体对纳米银胶体的稳定性影响.分别以银氨([Ag(NH₃)₂]OH)溶液和AgNO₃溶液为前驱体制备了多份纳米银胶体样品并通过UV-Vis、FE-SEM、EDS、ZETA电位仪等现代分析测试手段研究了纳米银胶的形貌、粒径大小以及稳定性.对比分析发现,以[Ag(NH₃)₂]OH溶液为前驱体,制备的纳米银胶体具有粒径可控,尺寸均一,分散性良好等特点;而且经过一个月的常温储存,表现出比用AgNO₃溶液为前驱体制备的纳米银胶体具有更高的储存稳定性.     

碱性品红分子在正、负电性纳米银上的吸附取向

制备了两种不同电性的纳米银粒子的胶体,发现当碱性品红分子分别吸附在这两种纳米银上时,其表面增强拉曼谱在谱线的强度及谱线数目上均有有明显的不同.在正电性纳米银上,主要是面内模式得到增强,且碱性品红特征峰的强度是I1589>I1524>I1371.而在负电性纳米银上,面内伸缩模式及面外弯曲模式均得到增强,且碱性品红特征峰的强度是I1588相似文献   

银纳米粒子的形貌可调控研究

在聚乙烯吡咯烷酮(PVP)保护下,以乙二醇(EG)为还原剂制备银纳米粒子.探讨了反应物浓度、反应温度对制备的纳米银粒子形貌的影响.采用X射线衍射(XRD)和透射电镜(TEM)来表征纳米银粒子的结构和形貌.结果表明,AgNO3和PVP的浓度,AgNO3和PVP的比例以及反应温度对纳米银粒子有较大影响,反应温度控制在140 ℃至160 ℃之间,易于控制纳米银粒子的形貌.     

香豆素改性透明质酸颗粒乳化剂的制备及应用

利用7-(2-羟基乙氧基)-4-甲基香豆素(HEMC)疏水改性透明质酸(HA)制得光敏双亲大分子(HA-HEMC),并通过自组装形成了HA-HEMC胶体粒子。通过核磁共振氢谱和紫外分光光度计确定了HA-HEMC的结构及取代度;采用动态激光光散射、纳米粒度仪和透射电镜等手段对胶体粒子的性质及形貌进行了表征。进一步以HA-HEMC胶体粒子作为颗粒乳化剂稳定油水界面,研究了胶体粒子质量浓度、油相类型、水相pH和盐浓度对胶体粒子乳化性能的影响。结果表明:HA-HEMC可以在选择性溶剂中自组装形成粒径约为236nm的球形胶体粒子;该胶体粒子能够在较宽的pH范围内(3~11)稳定水包油型乳液且所得乳液有良好的耐盐性;此外,HAHEMC胶体粒子还能稳定多种油-水体系。     

Effect of the polarity of silver nanoparticles induced by ionic liquids on facilitated transport for the separation of propylene/propane mixtures

The effect of ionic liquids on the formation of a partial positive charge on the surface of silver nanoparticle and its subsequent effect on facilitated olefin transport were investigated. Three different ionic liquids of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM⁺BF₄⁻), 1-butyl-3-methylimidazolium triflate (BMIM⁺Tf⁻), and 1-butyl-3-methylimidazolium nitrate (BMIM⁺NO₃⁻) were employed to control the positive charge density of the surface of silver nanoparticles. The positive charge density of the silver nanoparticles, as characterized by the binding energy of the silver atom, was in the following order: BMIM⁺BF₄⁻/Ag ? BMIM⁺Tf⁻/Ag > BMIM⁺NO₃⁻/Ag. This order was consistent with the tendency of ionic liquids to form free ions. The best separation performance for the propylene/propane mixtures was a mixed gas selectivity of 17 and a permeance of 7 GPU through a composite membrane consisting of BMIM⁺BF₄⁻/Ag. A better separation performance for olefin/paraffin mixtures was observed with a higher positive charge density of the silver nanoparticles. It was therefore concluded that facilitated olefin transport was a direct consequence of the surface positive charge of the silver nanoparticles induced by ionic liquids.     

<Emphasis Type="Italic">In situ</Emphasis> XPS study of the size effect in the interaction of NO with the surface of the model Ag/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/FeCrAl catalysts

The interaction of NO with the surface of model Ag/Al₂O₃/FeCrAl catalysts containing Ag nanoparticles of different size (1 and 3 nm) was studied. The use of the Auger parameter α_Ag (E _b(Ag3d_5/2) + E _kin(Ag MVV)) made it possible to reliably identify the change in the chemical state of silver cluster upon their interaction with О₂ and NO. The oxygen treatment leads to the oxidation of small Ag nanoparticles (1 nm) and formation of AgO _x clusters resulted in the intensive formation of nitrite—nitrate structures on the step of the interaction with NO. These structures are localized on both the silver clusters and Al₂O₃ surface. An increase in the size of Ag⁰ nanoparticles to 3 nm results in an increase in the stability of these structures and impedes the Ag⁰ → AgO _x transition, due to which the formation of surface groups NO₂ ^–/NO₃ ^– is suppressed. The data obtained make it possible to explain the dependence of the activity of the Ag/Al₂O₃ catalysts in the selective reduction of NO on the Ag nanoparticle size.     

Thermodynamic properties and solution equilibria of aqueous bivalent transition metal nitrates and magnesium nitrate

Osmotic coefficients for Mn(NO₃)₂, Co(NO₃)₂, Ni(NO₃)₂, Cu(NO₃)₂, Zn(NO₃)₂, and Mg(NO₃)₂ in aqueous solution have been determined by the isopiestic method at 25°C, and activity coefficients have been derived. The results agree with the literature data for Zn(NO₃)₂, while they are significantly different for Co(NO₃)₂, Cu(NO₃)₂, and Mg(NO₃)₂, and those for Mn(NO₃)₂ and Ni(NO₃)₂ are new. The concentration dependence of the osmotic coefficients for the bivalent metal nitrates is similar to that for the trifluoroacetates, while it differs from those for the other salts of the same series of metals. The results are discussed in terms of the inner-sphere and outer-sphere association of ions, auxiliary information being derived from the concentration effects in the visible spectra of the coloured metal nitrates.     

Synthesis and Properties of Copper,Mercury, and Silver (2-Naphthyl)acetylenides

(Z)-2-Naphthylacetylene was synthesized by the reaction of (Z)-3-(2-naphthyl)-3-chloropropenal (prepared from 2-acetylnaphthalene) with aqueous NaOH in dioxane. The reactions of 2-naphthylacetylene with CuCl, [Ag(NH₃)₂]NO₃, and K₂[HgI₄] gave copper, silver, and mercury 2-naphthylacetylenides, respectively. Silver naphthylacetylenide reacts with iodine to give the iodoethynyl derivative, which readily takes up bromine across the triple bond.     

Paper chromatographie studies on periodic precipitation

Summary An investigation of the nature of the rhythmic patterns obtained by diffusing the reactant solution on the circular filter papers impregnated with precipitating agents and a protective colloid (2% agar agar) has been made. The systems: AgNO₃–K₂CrO₄, Pb(NO₃)₂–K₂CrO₄, Ba(NO₃)₂–K₂CrO₄, Co(NO₃)₂–K₄Fe(CN)₆, and Co(NO₃)₂–K₃Fe(CN)₆ have been studied. An attempt has been made to explain the radial and ring rhythmicity on filter papers on the basis of coagulation theory ofDhar andChatterji.     

Gravimetric determination of cobalt as presumed k3co(no2)6

The composition of 'potassium cobaltinitrite' precipitated under the usual conditions from a slightly acid solution containing a large excess of potassium nitrite, and finally dried at 110°, has been determined. When a relatively small quantity of cobalt is precipitated the dried precipitate consists of a mixture of anhydrous and hydrated K₃Co(NO₂)₆. With large amounts of cobalt the precipitate also contains a salt of cobalt(II) (probably K₂Co(NO₂)₄) due to incomplete oxidation of the cobalt(II). Because the formula weight of K₂Co(NO₂)₄ is smaller than that of K₃Co(NO₂)₆. whereas that of hydrated K₃Co(NO₂)₆ is larger, the weight of the precipitate is actually not very different than if it were pure K₃Co(NO₂)₆. Quantities of cobalt from 40 to 300 mg can be determined with an error within ±1 % by weighing the dried precipitate as presumed K₃Co(NO₂)₆, and, if desired, the error can be decreased to a few tenths of a percent by employing an empirical factor. This simple method rivals in accuracy the more laborious electrogravimetric method.     

Biogenic fabrication of silver nanoparticles,oxidative dissolution and antimicrobial activities

Metallic silver nanoparticles (AgNPs) were prepared by using Foeniculum vulgare Mill seeds extract. The silver nitrate was used as silver precursor in an aqueous solution. The photooxidative dissolution of AgNPs with persulfate (K₂S₂O₈) under UV light was investigated. Effects of initial concentration of K₂S₂O₈, AgNPs, initial solution pH, and temperature were studied on dissolution of AgNPs. The 100% AgNPs dissolution was achieved in 60 min under typical conditions (pH = 4.0, 1.2 mM K₂S₂O₈, and 30 ⁰C). The experimental results showed higher temperature brought faster dissolution rate, and the activation energy was 65.2 kJ/mol. The effects of ethanol, tertiary butanol, and nitrobenzene were studied to establish the role of SO₄^? and HO radical species. AgNPs dissolution was inhibited by Cl^?, Br^?, I^?, and NO₃^? ions. Staphylococcus auerus (s. aureus), Escherichia coli (E. coli) and Candida albicans (C. albicans) were the effective human pathogens against the AgNPs. The lag phase, growth kinetics, minimum bactericidal concentration, death rate, and antimicrobial efficacy depend on the concentration of AgNPs.     

Studies on the thermal decomposition of the silver group of alkali metal nitritocobaltates(III)

The thermal decomposition of nitritocobaltate(III) of the silver group of general formula M₂Ag[Co(NO₂)₆] (where M = K⁺, NH⁺₄, Rb⁺ or Cs⁺) has been investigated. Based on the thermal curves of the investigated compounds and chemical and diffractometric analysis, the mechanism of thermal decomposition has been determined. The results obtained indicate that the decomposition proceeds in three stages. As a result of decomposition in the first stage (300°C), nitrates of alkali metals, metallic silver and Co₃O₄ are formed. In the second stage (500°C), a partial decomposition of nitrates to alkali metal oxides occurs, and in the third stage the products are alkali metal oxides, silver and Co₃O₄. This paper also presents the dependence of the decomposition temperature of nitritocobaltates(III) of the silver group on the ionic radius of the outer-sphere cation.     

Polymorphism in Alkali Metal Uranyl Nitrates: Synthesis and Crystal Structure of γ‐K(UO2)(NO3)3

Single crystals of γ‐K(UO₂)(NO₃)₃ were prepared from aqueous solutions by evaporation. The crystal structure [orthorhombic, Pbca (61), a = 9.2559(3) Å, b = 12.1753(3) Å, c = 15.8076(5) Å, V = 1781.41(9) Å³, Z = 8] was determined by direct methods and refined to R₁ = 0.0267 on the basis of 3657 unique observed reflections. The structure is composed of isolated anionic uranyl trinitrate units, [(UO₂)(NO₃)₃]^–, that are linked through eleven‐coordinated K⁺ cations. Both known polymorphs of K(UO₂)(NO₃)₃ (α‐ and γ‐phases) can be considered as based upon sheets of isolated complex [(UO₂)(NO₃)₃]^– ions separated by K⁺ cations. The existence of polymorphism in the two K[UO₂(NO₃)₃] polymorphs is due to the different packing modes of uranyl trinitrate clusters that adopt the same two‐dimensional but different three‐dimensional arrangements.     

Comparative study of ionic interactions of 1 : 1 and 1 : 2 electrolytes of nitrates salts solutions with water analysed with physicochemical data

Densities (ρ), viscosities (η) and surface tension (γ) as function of the molarity of 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 for LiNO₃, NaNO₃, KNO₃, Sr(NO₃)₂, Ba(NO₃)₂ and Pb(NO₃)₂ electrolytes are reported at 32°C. Data were regressed for limiting values for solute–solvent interactions and effects of shell numbers and electronic configurations. A confidence variance of 95.5% at Gaussian distribution was noted. Densities explained ionic forces and sizes, and viscosities defined frictional forces while the surface tension focused surface energies of hydrated ions. Slopes of densities, viscosities and surface tensions explained the concentration effects on ionic interactions. Limiting densities from Li⁺ to Ba²⁺ increased with increase in sizes. Pb²⁺ smaller in size than the Ba²⁺ had lower limiting densities. The ρ ⁰ are Ba^2+?>?Sr^2+?>?Pb^2+?>?K^+?>?Na^+?>?Li⁺ with 3.24, 2.98, 4.53, 2.109, 2.257 and 2.38?×?10^3?kg?m^?3 densities of nitrate salts, respectively, in the solid state.