Paramagnetic behaviour of silver nanoparticles generated by decomposition of silver oxalate

Silver oxalate Ag₂C₂O₄, was already proposed for soldering applications, due to the formation when it is decomposed by a heat treatment, of highly sinterable silver nanoparticles. When slowly decomposed at low temperature (125 °C), the oxalate leads however to silver nanoparticles isolated from each other. As soon as these nanoparticles are formed, the magnetic susceptibility at room temperature increases from −3.14 10⁻⁷ emu.Oe⁻¹.g⁻¹ (silver oxalate) up to −1.92 10⁻⁷ emu.Oe⁻¹.g⁻¹ (metallic silver). At the end of the oxalate decomposition, the conventional diamagnetic behaviour of bulk silver, is observed from room temperature to 80 K. A diamagnetic-paramagnetic transition is however revealed below 80 K leading at 2 K, to silver nanoparticles with a positive magnetic susceptibility. This original behaviour, compared to the one of bulk silver, can be ascribed to the nanometric size of the metallic particles.     

Synthesis of Stable Silver Nanoparticles with Antimicrobial Activities in Room-temperature Ionic Liquids

Stable silver nanoparticles was successfully synthesized by chemical reduction of silver nitrate in an ionic liquid,1-n-butyl-3-methylimidazolium tetrafluoroborate([BMIM]·BF4) at room temperature.Results of UV-Vis diffuse reflectance spectroscopy show as-prepared Ag nanoparticles exhibit a typical emission peak at 400―430 nm.By varying the reaction temperature and the precursor concentration,the size and the shape of the silver nanoparticles could be easily controlled under mild conditions.Analyses of trans...     

Molecular Precursors for the Phase‐Change Material Germanium‐Antimony‐Telluride,Ge2Sb2Te5 (GST)

This review provides an overview of the precursor chemistry that has been developed around the phase‐change material germanium‐antimony‐telluride, Ge₂Sb₂Te₅ (GST). Thin films of GST can be deposited by employing either chemical vapor deposition (CVD) or atomic layer deposition (ALD) techniques. In both cases, the success of the layer deposition crucially depends on the proper choice of suitable molecular precursors. Previously reported processes mainly relied on simple alkoxides, alkyls, amides and halides of germanium, antimony, and tellurium. More sophisticated precursor design provided a number of promising new aziridinides and guanidinates.     

Chemical solution deposited silver tantalate niobate, Ag x (Ta0.5Nb0.5)O3? y , thin films on (111)Pt/Ti/SiO2/(100)Si substrates

Silver tantalate niobate films are candidates for temperature stable microwave dielectrics. In this work, a chemical solution deposition synthesis method was developed for Ag _x (Ta_0.5Nb_0.5)O_3−y films on Pt-coated Si substrates. Stable solutions with a range of silver stoichiometries were prepared using 2-methoxyethanol and pyridine as solvents, from AgNO₃ and Nb and Ta ethoxide precursors. It was extremely difficult to prepare phase-pure perovskite films of Ag(Ta_0.5Nb_0.5)O₃ on Pt-coated Si subtrates; instead a mixture of perovskite and natrotantite phases was identified. Such mixed phase films had dielectric constant ɛ _r and dielectric loss tanδ values ranging from 200±20 to 270±25 and 0.006±0.002 to 0.002±0.001 at 100 kHz, respectively, depending on the firing temperature. For Ag₂(Ta_0.5Nb_0.5)₄O₁₁, Ag_0.8(Ta_0.5Nb_0.5)O_2.9, Ag_0.85(Ta_0.5Nb_0.5)O_2.925 and Ag_0.9(Ta_0.5Nb_0.5)O_2.95 films, mainly the natrotantite phase was observed. The ɛ _r values of these films were between 70±10 and 130±15 with tan δ values of 0.008±0.002 at 100 kHz.     

Te,CdTe,HgCdTe的电沉积及其成核机理

应用自装微机联用恒电位系统研究了在玻璃碳或铁电极上Te、CdTe、HgCdTe的电沉积及其电结晶成核机理。结果表明,在酸性溶液中,HTeO_2~+的阴极还原符合4电子还原机理,其电结晶生长表现为由HTeO_2~+扩散控制的三维瞬时成核机理;CdTe沉积层的形成是亚碲酸还原的延续,其电结晶成核机理因电位阶跃值、沉积温度及溶液pH值的改变而由HTeO_2~+扩散控制的三维瞬时成核转变为二维瞬时成核机理;对HgCdTe,其电沉积过程的动力学步骤可设想为: Hg~(2+)+2e—→Hg,HTeO_2~++3H~++4e—→Te+2H_2O xHg+Te—→Hg_2Te,Hg_2Te+(1—x)Cd~(2+)+2(1—x)e—→Hg_2Cd_(1-2)Te 相关的结晶生长除受各种实验因素影响外,还与CdTe的成核过程有关。在本文实验条件下,大体遵循二维瞬时成核机理。     

Characterization of the transient species generated by the photoionization of Berberine: A laser flash photolysis study

Using 266 nm laser flash photolysis it has been demonstrated that Berberine (BBR) in aqueous solution is ionized via a mono-photonic process giving a hydrated electron, anion radical that formed by hydrated electron react with steady state of BBR, and neutral radical that formed from rapid deprotonation of the radical cation of BBR. The quantum yield of photoionization is determined to be 0.03 at room temperature with KI solution used as a reference. Furthermore utilizing pH changing method and the SO₄⁻ radical oxidation method, the assignment of radical cation of BBR was further confirmed, the pK_a value of it was calculated, and the related set up rate constant was also determined.     

Vanadium(IV) oxide thin films on glass and silicon from the atmospheric pressure chemical vapour deposition reaction of VOCl3 and water

The dual source atmospheric pressure chemical vapour deposition (APCVD) reaction of VOCl₃ and H₂O was used to prepare thin films of vanadium oxides on glass and silicon substrates. The thin films were characterised by X-ray diffraction, Raman spectroscopy X-ray photoelectron spectroscopy and scanning electron microscopy. At reactor temperatures above 600 °C with a gas-phase excess of water over VOCl₃, vanadium(IV) oxide thin films were produced which show a thermochromic transition temperature of 67 °C. The APCVD process is directly compatible with high throughput float-glass production enabling the use of a thin film of VO₂ as an intelligent window coating. With reactor temperatures below 600 °C or with a gas-phase excess of VOCl₃ over water, V₂O₅ thin films were produced. Vanadium(IV) oxide thin films could also be prepared on silicon substrates from the APCVD reaction of VOCl₃ and H₂O, which opens up further technological applications for the APCVD of VO₂ thin films.     

Sulfur ylides generated from the reaction of adamantylidene and phenylcarbene with sulfur substrates

Reaction of adamantylidene and phenylcarbene with ethylthiol, ethylene dithiol, allylethylsulfide, allylphenylsulfide, and trimethylenesulfide involves the formation of a sulfur ylide intermediate, followed by H-migration, 2,3-sigmatropic shift, or ring opening to give sulfides. The sulfur ylide formed in the reaction of phenylcarbene with trimethylenesulfide is directly observed by laser flash photolytic techniques.     

微接触印刷法构造金属银的二维和准三维微图纹结构

以聚二甲基硅氧烷（PDMS）有机硅橡胶为弹性印章，以十八烷基三氯硅烷（OTS）正已烷溶液为“墨水”，用微接触印刷分别在普通盖玻片表面和直径为20 mm的试管外表面直接盖印，以及在直径为10 mm的玻璃棒表面进行滚动式微接触印刷盖印.将这些盖好印的基材放在化学镀银液中进行选择性镀银沉积，得到金属银在平面上的二维微结构和在曲面上的准三维微结构.这些微结构的显微照片显示，采用微接触印刷法制备的微图纹结构，图纹转移效率高，精细度很好，特别是微接触印刷操作方法灵活多变，适用于多种形态的表面，是一类实用的微制造方法.     

Voltammetric behavior and trace determination of Pb at a mercury-free screen-printed silver electrode

Screen-printed silver electrodes (AgSPEs), without chemical modification, has been investigated as disposable sensors for the measurement of trace levels of Pb²⁺. Potential segment analysis indicates that the formation of underpotential and bulk depositions of Pb is not strongly coupled on the AgSPE. The possibility of determining Pb²⁺ at trace levels using the reversible underpotential deposition peak was examined by square-wave anodic stripping voltammetry without removal of oxygen. Under the optimized analytical conditions, the obtained sensitivity, linearity, and detection limit are 0.355 μA/ppb, 5-80 ppb (r=0.9992), and 0.46 ppb (S/N=3), respectively. The electrode is quite stable for repetitive measurements. The interference effect was thoroughly studied with various metals and no significant change in current was found in the determination of 5 ppb Pb²⁺. The practical applications were demonstrated to measure trace Pb²⁺ in natural waters.     

Tuning the size of silver deposits by templated electrodeposition using agarose gels

Tuning the size of electrochemically deposited silver crystals is possible by using template layers of agarose gels of certain concentrations on platinum electrodes. The size of the silver crystals can be controlled in the range of 100 to 400 nm by choosing the appropriate agarose concentration. The obtained crystal sizes match very well with the size of the pores that have been reported in literature for the used agarose concentrations. This is also a good proof of the correctness of the earlier pore-size estimations applying other techniques.     

A silver(I)-catalyzed reaction of 2-alkynylbenzaldoxime with arylsulfonyl chloride

A silver-catalyzed reaction of 2-alkynylbenzaldoxime with arylsulfonyl chloride proceeds smoothly at room temperature to afford 4-tosyloxyisoquinolines in moderate to good yields. Additionally, the resulting 4-tosyloxyisoquinolines could be further elaborated through palladium-catalyzed coupling reactions leading to diverse isoquinolines.     

Pyrolysis and film growth studies of phosphinoborane compounds

Chemical vapor deposition experiments were conducted using phosphinoborane compounds of the type [R₂BPR′₂]_n, where R = CH₂CH₃ (1) or CH₃ (2), R′= C(CH₃)₃, and R = CH₂CH₃ (3) or CH₃ (4), R′ = Si(CH₃)₃. Thin films were deposited on Si substrates at 300–850°C under vacuum using 1–3, while no film formed using 4. All films contained considerable carbon (C/B = 0.67–7) and were deficient in phosphorus (P/B = 0-0.5) according to Auger electron spectroscopy. For 3, silicon was incorporated in the films (Si/B = 0.9–2). The preferential loss of phosphorus was nearly complete at higher pyrolysis temperatures that favor formation of carbon-rich films. Volatile products of the decompositions were observed by in situ mass spectroscopy and by ¹H nuclear magnetic resonance analysis of the condensate in a liquid nitrogen cooled trap. The products indicate that β-hydrogen elimination of alkene from boron is a preferred reaction pathway, while concerted elimination reactions appear to be inefficient. Although these phosphinoborane compounds do not appear to be suitable precursors for pure boron phosphide, the B-P-C films obtained are chemically inert and may be of interest as protective coatings.     

Ionic liquid-assisted synthesis of silver nanorods by polyol reduction

<正>Silver nanorods have been successfully synthesized in large scale by the ethylene glycol(EG) reduction in the presence of ionic liquid(IL) 1-butyl-3-methylimidazolium tetrafluoroborate(bmimBF_4) and polyvinyl-pyrrolidone(PVP).The silver nanorods were characterized by scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),transmission electron microscopy(TEM),electron energy disperse spectroscopy(EDS) and UV-vis spectroscopy.The results showed that the uniform silver nanorods have an average diameter of about 100 nm and the aspect ratio from 15 to 20.IL,bmimBF_4 may play a role of capping agent together with PVP in the formation of silver nanorods.On the other band,bmimBF_4 may accelerate nucleation and improve the stability of the resulting Ag nanorods due to the low interface tension of IL.     

New aspects of the reaction of silver(I) cations with the ethylenediaminetetraacetate ion

The highly neutralized ethylenediaminetetraacetate (EDTA) titrant (95–99% as Y⁴⁻ anion) precipitates with Ag⁺ cations to form the Ag₄Y species, in aqueous medium, which is well characterized from conductometric titration, thermal analysis and potentiometric titration of the silver content of the solid. The precipitate dissolves in excess Y⁴⁻ to form a complex, AgY³⁻. Equilibrium studies at 25°C and ionic strength 0.50 M (NaNO₃) have shown from solubility and potentiometric measurements that the formation constant (95% confidence level) β₁ = (1.93 ± 0.07) × 10⁵ M⁻¹ and the solubility products are K_S0 = [Ag +]⁴[Y⁴⁻] = (9.0 ± 0.4) × 10⁻¹⁸ M⁵ and K_S1 = [Ag +]³[AgY³⁻] = (1.74 ± 0.08) × 10⁻¹² M⁴. The presence of Na⁺, rather than ionic strength, markedly affects the equilibrium; the data at ionic strength 0.10 M are: β₁ = (1.19 ± 0.03) × 10⁶ M⁻¹, K_S0 = (1.6 ± 0.4) × 10⁻¹⁹ M⁵ and K_S1 = (1.9 ± 0.5) × 10⁻¹³ M⁴; at ionic strength tending to zero; β₁ = (1.82 ± 0.05) × 10⁷ M⁻¹, K_S0 = (2.6 ± 0.8) × 10⁻²² M⁵ and K_S1 = (5 ± 1) × 10⁻¹⁵ M⁴. The intrinsic solubility is 2.03 mM silver (I) in 0.50 M NaNO₃. Well-defined potentiometric titration curves can be taken in the range 1–2 mM with the Ag indicator electrode. Thermal analysis revealed from differential scanning calorimetry a sharp exothermic peak at 142°C; thermal gravimetry/differential thermal gravimetry has shown mass loss due to silver formation and a brown residue, a water-soluble polymeric acid (decomposition range 135–157°C), tending to pure silver at 600°C, consistent with the original Ag₄Y salt.     

ICP-AES determination of silver after chemical separation from uranium matrix

The separation of silver from a uranium matrix has been carried out using Cyanex-471X (triisobutylphosphine sulphide) in xylene. The effects of various parameters such as the Cyanex-471X concentration, the nitric acid molarity, the contact time and the nitrate ion concentration on the extraction of silver have been studied. The silver metal ion species extracted into the organic phase was found to be Ag(NO₃)·2S (where S is Cyanex-471X). The stripping of silver into an aqueous medium was carried out with 5% NaHSO₃, followed by its determination using ICP-AES.     

Chemical vapour deposition of selenium and tellurium films by UV laser photolysis of selenophene and tellurophene

Excimer laser‐induced photolysis of gaseous selenophene and tellurophene affords gaseous 1‐buten‐3‐yne and ethyne (as major products) and butadiyne (a very minor product) and results in chemical vapour deposition of selenium and tellurium films. The film properties were characterized by XPS and SEM techniques and by UV spectroscopy. Copyright © 2000 John Wiley & Sons, Ltd.     

Photochemistry in the Low-Temperature Processing of Metal Oxide Thin Films by Solution Methods

Photochemistry has emerged in the last few years as a powerful tool for the low-temperature processing of metal oxide thin films prepared by solution methods. Today, its implementation into the fabrication procedure makes possible the integration of amorphous semiconductors or functional crystalline oxides into flexible electronic systems at temperatures below 350 °C. In this review, the effects of UV irradiation at the different stages of the chemical solution deposition of metal oxide thin films are presented. These stages include from the synthesis of the precursor solution to the formation of the amorphous metal-oxygen network in the film and its subsequent crystallization into the oxide phase. Photochemical reactions that can be induced in both the solution deposited layer and the irradiation atmosphere are first described, highlighting the role of the potential reactive chemical species formed in the system under irradiation, such as free radicals or oxidizing compounds. Then, the photochemical effects of continuous UV light on the film are shown, focusing on the decomposition of the metal precursors, the condensation and densification of the metal-oxygen network, and the nucleation and growth of the crystalline oxide. All these processes are demonstrated to advance the formation and crystallization of the metal oxide thin film to an earlier stage, which is ultimately translated into a lower temperature range of fabrication. The reduced energy consumption of the process upon decreasing the processing temperature, and the prospect of using light instead of heat in the synthesis of inorganic materials, make photochemistry as a promising technique for a sustainable future ever more needed in our life.     

Low Temperature Activation of Tellurium and Resource-Efficient Synthesis of AuTe2 and Ag2Te in Ionic Liquids

The low temperature syntheses of AuTe₂ and Ag₂Te starting from the elements were investigated in the ionic liquids (ILs) [BMIm]X and [P₆₆₆₁₄]Z ([BMIm]⁺=1-butyl-3-methylimidazolium; X = Cl, [HSO₄]⁻, [P₆₆₆₁₄]⁺ = trihexyltetradecylphosphonium; Z = Cl⁻, Br⁻, dicyanamide [DCA]⁻, bis(trifluoromethylsulfonyl)imide [NTf₂]⁻, decanoate [dec]⁻, acetate [OAc]⁻, bis(2,4,4-trimethylpentyl)phosphinate [BTMP]⁻). Powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy revealed that [P₆₆₆₁₄]Cl is the most promising candidate for the single phase synthesis of AuTe₂ at 200 °C. Ag₂Te was obtained using the same ILs by reducing the temperature in the flask to 60 °C. Even at room temperature, quantitative yield was achieved by using either 2 mol % of [P₆₆₆₁₄]Cl in dichloromethane or a planetary ball mill. Diffusion experiments, ³¹P and ¹²⁵Te-NMR, and mass spectroscopy revealed one of the reaction mechanisms at 60 °C. Catalytic amounts of alkylphosphanes in commercial [P₆₆₆₁₄]Cl activate tellurium and form soluble phosphane tellurides, which react on the metal surface to solid telluride and the initial phosphane. In addition, a convenient method for the purification of [P₆₆₆₁₄]Cl was developed.     

Sensitivity enhancement of SPR biosensor with silver mirror reaction on the Ag/Au film

Based on well-known silver mirror reaction the Ag film was formed on Au film modified by self-assembled monolayer (SAM) of 1,6-hexanedithiol (HDT). The sensitivity of the biosensor based on this Ag/Au film is enhanced compared to that based on Au film. When the surface plasmon resonance (SPR) biosensor based on this Ag/Au film was used to determine human IgG, the range of concentrations of human IgG that could be determined is 0.30-40.00 μg mL⁻¹. The lowest concentration (0.30 μg mL⁻¹) that could be detected was about 8 times lower than that obtained by the biosensor without modification by Ag film (2.50 μg mL⁻¹), which demonstrated that the biosensor based on Ag/Au film could make the resonant wavelength move to longer wavelength following with the sensitivity enhancement of the SPR biosensor.