反应性模板法合成硫化银中空球-银纳米粒子异质结构

以Cu₂S中空球为反应性模板, 通过在水溶液中与银离子的阳离子交换和氧化还原反应制备了大小均匀的Ag₂S中空球-Ag纳米粒子异质结构, 即Ag₂S-Ag异质中空球. 该异质结构中每个Ag₂S中空球的直径约为600 nm, 壁厚约20–30 nm, 其表面均附着一个Ag纳米粒子. 采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)和能量色散X射线谱(EDS)对所得Ag₂S-Ag异质中空球的结构和组成进行了表征. 若以CuS中空球为反应性模板, 在相似转化条件下则主要得到不含Ag粒子的Ag₂S中空球. 该结果表明, Cu₂S中的Cu(I)的还原性在Ag₂S-Ag异质中空球的形成中发挥了重要作用. 通过对所制备的Ag₂S-Ag异质中空球进行二次生长, 还可以得到Ag₂S中空球的半球表面均被Ag膜所包覆的Ag₂S-Ag异质中空球.     

Investigation on the formation and decay of the N,N,N′,N′-tetramethylbenzidine radical cation using various oxidants and reductants by stopped-flow spectrophotometry

N,N,N′,N′-Tetramethylbenzidine (TMB) is an aromatic amine that undergoes oxidation by various oxidizing agents such as Ce⁴⁺, MnO⁻₄, Cr₂O²⁻₇; HSO⁻₅, S₂O⁻₈, H₂O₂, Cl₂, Br₂ and I₂, thereby serving as a reducing substrate. One-electron oxidation of TMB results in a radical cation (TMB^˙+), and on further oxidation leads to the product dication (TMB⁺⁺) were monitored by stopped-flow spectrophotometer at the absorption wavelength of TMB^˙+(λ_max; 460 nm). ESR data was also provided to confirm the formation of radical cation. The rates of both the formation and decay of TMB^˙+ have been followed by a total second-order kinetics, a first-order dependence each on [TMB] (or) [TMB^˙+] and [oxidant]. The kinetic and transition state parameters have been evaluated for the effects of pH and temperature on the formation and decay of TMB^˙+ and discussed with suitable reaction mechanisms. Also, the rate constants for the reactions of the radical cation with various reducing agents such as sulfite (SO²⁻₃), thiosulfate (S₂O²⁻₃), dithionite (S₂O²⁻₄) and disulfite (S₂O²⁻₅) and ascorbic acid (vitamin C, AH₂ were determined. Besides these, this article also explains how TMB acts as a better electron relay than unsubstituted benzidine, even though both of them undergo one-electron oxidation and are used in the chemical routes to solar energy conversions. The observed rate constants for electron transfer were correlated theoretically using Marcus theory. The observed and calculated rate constants have good correlation.     

Coordination‐Driven Hierarchical Assembly of Silver Nanoparticles on MoS2 Nanosheets for Improved Lithium Storage

We report a novel strategy for the hierarchical assembly of Ag nanoparticles (NPs) on MoS₂ nanosheets through coordination by using a multifunctional organic ligand. The presence of Ag NPs on the surface of MoS₂ nanosheets inhibits their agglomeration, thereby providing increased interlayer spacing for easy Li⁺ ion intercalation. Such a unique hybrid architecture also ensures sufficient percolation pathways on the whole surface of the MoS₂ nanosheets. Moreover, the high rigidity and low deformability of the Ag NPs effectively preserve the hybrid architecture during the charge–discharge process, which translates into a high cycle stability. A prominent synergistic effect between MoS₂ and Ag is witnessed. When the Ag content is only 5 wt %, the Ag–MoS₂ hybrid delivers a reversible capacity as high as 920 mA h g^?1 at a current density of 100 mA g^?1, making the Ag–MoS₂ hybrid an attractive candidate for next‐generation LIBs.     

Spectrophotometric FIA methods for determination of hydrogen peroxide: Application to evaluation of scavenging capacity

The determination of hydrogen peroxide (H₂O₂) and the evaluation of scavenging capacity against this species were performed using five colorimetric reactions, which were adapted to flow injection analysis. The reactions chosen were based on the oxidation of iodide (I⁻ method), on the formation of titanium-peroxide complex (TiP method), on the formation of titanium-xylenol orange-peroxide complex (TiXoP method), on the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB method) and on the co-oxidation of phenol-4-sulfonic acid and 4-aminoantipyrine (PSA/4-AAP method). The operational conditions were studied in order to improve the sensitivity of each method. Concerning to the method sensitivity, the ranking order was TMB method > I⁻ method > TiXoP method ∼PSA/4-AAP method > TiP method. All methods showed an excellent repeatability (RSD < 2%) and, except for I⁻ method, relative deviations from the reference method were <1.9%. The FIA manifolds were adapted to perform the determination of scavenging capacity against H₂O₂ and glutathione (GSH) was applied as model compound. TiP and TiXoP methods were not suitable as no inhibition or an increase of analytical signal was attained. PSA/4-AAP method was chosen for further application to dietary phenolics and pharmaceutical compounds, providing IC₅₀ values for those compounds that are fast reacting antioxidants.     

Silver(I) catalyzed oxidation of thiocarboxylic acids into the corresponding disulfides and synthesis of some new Ag(I) complexes of thiophene-2-thiocarboxylate

Aromatic thiocarboxylic acids in presence of a base on treatment with silver nitrate under ambient conditions were oxidized to the corresponding disulfides. The reactions were found to be catalyzed by Ag⁺ ions. The catalytic oxidation is paralleled by the Ag(SCOAr) complex formation reaction which could be considerably subsided by adjustment of the reaction conditions. Attempts to use [Ag(PPh₃)₂]⁺ or [Ag(PPh₃)]⁺ ion as the catalyst were unsuccessful as these resulted in the formation of the corresponding thiocarboxylate complexes. The products, ArCOSSCOAr (1, 2), [Ag(SCOAr)(PPh₃)₂] (3, 4) and [Ag(SCOAr)(PPh₃)]₄ (5) (Ar = C₆H₅, C₄H₃S) were characterized by single crystal X-ray analysis. Compounds 3 and 4 are monomeric while 5 is a cyclic tetramer in the crystalline phase.     

Silver nanoparticles embedded phosphomolybdate–polyaniline hybrid electrode for electrocatalytic reduction of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

Hybrid silver/phosphophomolybdate/polyaniline (Ag/PMo12/PAni) was obtained through one pot synthesis, and then, it was successfully fabricated on the glassy carbon electrode by simple casting method for electrocatalytic reduction of hydrogen peroxide (H₂O₂). The cyclic voltammetric studies of the Ag/PMo12/PAni hybrid electrode suggest that the electronic properties of the phosphomolybdate are retained even after the formation of hybrid material and in addition effectively electro-catalyzing the reduction of H₂O₂ with a less negative over potential. The Ag/PMo12/PAni-modified electrode showed the lowest detection limit (750 nM) for H₂O₂ reduction among the hybrid-modified electrodes already reported with a sensitivity of 4.398 nA μM⁻¹. The prepared hybrid material was well characterized by using UV, XRD and TEM analysis.     

Identification of Epoxide Functionalities in Protonated Monofunctional Analytes by Using Ion/Molecule Reactions and Collision-Activated Dissociation in Different Ion Trap Tandem Mass Spectrometers

A mass spectrometric method has been delineated for the identification of the epoxide functionalities in unknown monofunctional analytes. This method utilizes gas-phase ion/molecule reactions of protonated analytes with neutral trimethyl borate (TMB) followed by collision-activated dissociation (CAD) in an ion trapping mass spectrometer (tested for a Fourier-transform ion cyclotron resonance and a linear quadrupole ion trap). The ion/molecule reaction involves proton transfer from the protonated analyte to TMB, followed by addition of the analyte to TMB and elimination of methanol. Based on literature, this reaction allows the general identification of oxygen-containing analytes. Vinyl and phenyl epoxides can be differentiated from other oxygen-containing analytes, including other epoxides, based on the loss of a second methanol molecule upon CAD of the addition/methanol elimination product. The only other analytes found to undergo this elimination are some amides but they also lose O = B-R (R = group bound to carbonyl), which allows their identification. On the other hand, other epoxides can be differentiated from vinyl and phenyl epoxides and from other monofunctional analytes based on the loss of (CH₃O)₂BOH or formation of protonated (CH₃O)₂BOH upon CAD of the addition/methanol elimination product. For propylene oxide and 2,3-dimethyloxirane, the (CH₃O)₂BOH fragment is more basic than the hydrocarbon fragment, and the diagnostic ion (CH₃O)₂BOH₂⁺ is formed. These reactions involve opening of the epoxide ring. The only other analytes found to undergo (CH₃O)₂BOH elimination are carboxylic acids, but they can be differentiated from the rest based on several published ion/molecule reaction methods. Similar results were obtained in the Fourier-transform ion cyclotron resonance and linear quadrupole ion trap mass spectrometer.     

Formation mechanism of nanostructured Ag films from Ag2O particles using a sonoprocess

Nanostructured Ag films composed of nanoparticles and nanorods can be formed by the ultrasonication of ethanol solutions containing Ag₂O particles. The present work examined the formation process of these films from ethanol solutions by two different agitation methods, including ultrasonication and mechanical stirring. The mass-transfer process from Ag₂O particles to ethanol solvent is accelerated by the mechanical effects of ultrasound. Ag⁺ ions and intermediately reduced Ag clusters were released into the ethanol. These Ag⁺ ions and Ag clusters provide absorption bands at 210, 275 and 300 nm in UV-vis spectra. These bands were assigned to the absorption of Ag⁺, Ag ₄ ²⁺ and Ag_n (n?≈?3). The Ag_n clusters that readily grow to become Ag nanoparticles were formed due to the surface reaction of Ag₂O particles with ethanol under ultrasonication. The reactions of Ag⁺ ions in ethanol to form Ag nanomaterials (through the formation of Ag ₄ ²⁺ clusters) were also accelerated by ultrasonication.     

Dealloying to Nanoporous Silver and Its Implementation as a Template Material for Construction of Nanotubular Mesoporous Bimetallic Nanostructures

Nanoporous silver (NPS) is fabricated by selectively dissolving Al from AgAl alloys in corrosive electrolytes at room temperature. Electron spectroscopy characterizations demonstrate that the NaOH electrolyte is beneficial to the formation of a three‐dimensional bicontinuous porous nanostructure with uniform and tunable pore and ligament dimensions of a few tens of nanometers, while processing in HCl electrolyte easily lead to coarsened porous nanostructures. The high‐surface‐area Ag nanostructures are demonstrated as novel effective template materials to the construction of nanotubular mesoporous Pt/Ag and Pd/Ag alloy structures, which are realized via room temperature galvanic replacement reactions with H₂PtCl₆ and K₂PdCl₄ solutions by adding a high concentration of Cl^? ions as a coordinating agent. Electrochemical measurements indicate that the resulting hollow and porous bimetallic nanostructures show enhanced electrocatalytic activities and CO‐tolerance with better durability toward methanol and formic acid oxidation due to alloying with Ag.     

基于酶标抗体和媒介体共吸附于金胶壳聚糖膜的PSA免疫传感器的制备

本文研制了一种用金胶壳聚糖仿生膜来同时固定四甲基联苯胺（TMB）和酶标抗体的新型电化学免疫传感器,用于检测血清肿瘤标志物前列腺特异性抗原（PSA）的含量。固定的TMB作为电子传递媒介体,在扫速小于45 mV/s时,电极表现为一个表面控制过程,而在扫速大于45 mV/s时则表现为一个扩散控制过程。将固定有酶标抗体和TMB的免疫传感器与待测PSA抗原一起培育,在该传感器上形成的免疫复合物通过TMB-H₂O₂-HRP电化学体系进行了测定。在优化实验条件下,PSA的线性检测范围为5-30 ng·mL^-1,检测限为1.0 ng·mL^-1。该PSA免疫传感器制备方法简单,成本低廉,具有较好的稳定性和重现性。     

Selective and sensitive determination of copper ions in soft drink based on high catalysis of hemin–graphene hybrid nanosheets coupled with enzyme inhibitions

A simple and selective colorimetric biosensor was presented based on high catalysis of hemin–graphene hybrid nanosheets coupled with enzyme inhibitions. Alcohol oxidase (AO) can catalyze the oxidations of methanol to produce hydrogen peroxide (H₂O₂). Subsequently, the resulting H₂O₂ could be catalyzed to oxidize 3,3,5,5-tetramethylbenzidine (TMB) and then produce a blue color reactions by using hemin–graphene hybrid nanosheets with intrinsic peroxidase-like activity. The activity of AO could be selectively inhibited by the copper ions, and therefore, the oxidase-catalyzed reactions of TMB was decreased. Fortunately, other metal ions even at 10 or 100 times copper ions concentrations showed no intensive inhibitions to the AO activity. Based on this functional materials-enzyme inhibitions system, a simple, selective and sensitive colorimetric biosensor was established to determine copper ions in soft drinks. The linear relationship was obtained from 5 nM to 1 μM, and the detections limit was 1.4 nM. The results were in good agreement with those obtained by the classic ICP-MS. It was demonstrated that the proposed method had an excellent practical perspective on the determinations of copper ions in foodstuff samples.     

Mixed Organometallic–Organic Hybrid Assemblies Based on the Diarsene Complex [Cp2Mo2(CO)4(μ,η2-As2)], AgI Salts and N-Donor Organic Molecules

The reaction of the organometallic diarsene complex [Cp₂Mo₂(CO)₄(η²-As₂)] ( 1 ) with Ag[Al{OC(CF₃)₃}₄] (Ag[TEF]) yielded the Ag^I monomer [Ag(η²- 1 )₃][TEF] ( 2 ). This compound exhibits dynamic behavior in solution, which allows directed selective synthesis of unprecedented organometallic–organic hybrid assemblies upon its reaction with N-donor organic molecules by a stepwise pathway, which is supported by DFT calculations. Accordingly, the reaction of 2 with 2,2′-bipyrimidine ( L1 ) yielded the dicationic molecular compound [{(η²- 1 )₂Ag}₂(μ- L1 )][TEF]₂ ( 3 ) or the 1D polymer [{(η²- 1 )Ag}(μ- L1 )]_n[TEF]_n ( 4 ) depending on the ratio of the reactants. However, its reactions with the pyridine-based linkers 4,4′-bipyridine ( L2 ), 1,2-bis(4-pyridyl)ethylene ( L3 ) and 1,2-bis(4-pyridyl)ethyne ( L4 ) allowed the formation of the 2D polymers [{(η²- 1 )Ag}₂(μ- Lx )₃]_n[TEF]_2n [ Lx=L2 ( 5 ), L3 ( 6 ), L4 ( 7 ), respectively]. Additionally, this concept was extended to step-by-step one-pot reactions of 1 , [Ag(CH₃CN)₃][Al{OC(CF₃)₂(CCl₃)}₄] ([Ag(CH₃CN)₃][TEF^Cl]) and linkers L2 – L4 to produce the 2D polymers [{(η²- 1 )Ag}₂(μ, Lx )₃]_n[TEF^Cl]_2n [ Lx = L2 ( 8 ), L3 ( 9 ), L4 ( 10 ), respectively].     

Quantification and Prediction of Imine Formation Kinetics in Aqueous Solution by Microfluidic NMR Spectroscopy

Quantitatively predicting the reactivity of dynamic covalent reaction is essential to understand and rationally design complex structures and reaction networks. Herein, the reactivity of aldehydes and amines in various rapid imine formation in aqueous solution by microfluidic NMR spectroscopy was quantified. Investigation of reaction kinetics allowed to quantify the forward rate constants k₊ by an empirical equation, of which three independent parameters were introduced as reactivity parameters of aldehydes (S_E, E) and amines (N). Furthermore, these reactivity parameters were successfully used to predict the unknown forward rate constants of imine formation. Finally, two competitive reaction networks were rationally designed based on the proposed reactivity parameters. Our work has demonstrated the capability of microfluidic NMR spectroscopy in quantifying the kinetics of label-free chemical reactions, especially rapid reactions that are complete in minutes.     

Self‐Assembling of Hybrid Prussian Blue Units in Cinder Matrix: Characterization and Electrocatalysis

Industrial waste cinder (CFe*) has been utilized as a stable anchoring matrix for self‐assembling of Fe(CN)₆^3? as hybrid Prussian blue units (PB, *Fe³⁺Fe^II(CN)₆) on a screen‐printed carbon electrode (SPE) for efficient catalytic applications. The waste cinder was found to be a composite of calcium and iron silicates similar to glass matrix by X‐ray photoelectron spectroscopic (XPS) study. The hybrid PB formations were confirmed by both FT‐IR and electrochemical methods. Most importantly, the free iron (Fe*) ion bound to the non‐bridging oxygen terminals of the silicates was found to play a key role in the PB formation. The self‐assembled PB hybrid on the cinder‐modified screen‐printed electrodes (designated as PBCFe*‐SPE) improved linear detection range and sensitivity for H₂O₂ mediated oxidation than those obtained at a classical PB‐SPE in 0.1 M, pH 2 KCl/HCl base electrolyte at 0.0 V (vs. Ag/AgCl) by amperometric batch analysis.     

An efficient and easily retrievable dip catalyst based on silver nanoparticles/chitosan-coated cellulose filter paper

Re-use of a catalyst is an important task, which is usually achieved by loading it on easily separable supports such as magnetic substrates. However, we demonstrate here the process of easy and fast catalyst separation from a reaction medium by loading it onto an economically feasible and microscopically high surface substrate of filter paper (FP) made up of cellulose microfibers as catalyst support. To achieve the goal, we coated chitosan (CH) on filter paper (CH-FP) to impart a high affinity of the substrate for metal ion absorption. AgNO₃ dissolved in water with a 0.1 M concentration was used as the Ag ion carrier solution, and CH-FP strips with known rectangular dimensions were submerged into it for the metal ion absorption. The metal ion-laden CH-FP strips were dip treated with sodium borohydride (NaBH₄) aqueous solution to prepare Ag-nanoparticle loaded CH-FP (Ag/CH-FP). X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the formation of the Ag/CH-FP hybrid. Ag/CH-FP morphology was examined through scanning electron microscopy analysis, which showed the presence of Ag nanoparticles attached to the cellulose microfibers. The prepared Ag/CH-FP was employed as a dip catalyst for the degradation of nitroarene compounds of 2-nitophenol (2-NP) and 4-nitrophenol (4-NP) by NaBH₄. Remarkably, the rate constants for 4-NP and 2-NP were 3.9 × 10^?3 and 1.7 × 10^?3 s^?1, respectively. In addition, we discussed the ease of the catalyst retrievability from the reaction mixture and its re-usability.     

Electrochemical Behavior of the LaF3:Eu2+/Me Interface (Me = Sm,Ce, Gd,V, Ag)

The electrochemical behavior of the LaF₃ : Eu²⁺| interface (Me = Sm, Ce, Gd, V, Ag) is studied using stripping voltammetry. Current–voltage curves for cells Ag, AgCl|KCl and KF|LaF₃ : Eu²⁺|Sm (or Ce) may be viewed as background curves for analyzing solid-phase reactions with other metallic electrodes. The substrate material is found to affect properties of interfaces LaF₃ : Eu²⁺/Gd (or V), which are characterized either by solid-phase reactions involving the fluoride ion of a solid electrolyte or by reactions involving oxygen. Regularities, obtained for silver in contact with LaF₃ : Eu²⁺, link electrochemical signals of the reaction of the silver fluoride formation with the contact area.     

Spontaneous Growth of 3D Silver Mesoflowers on Poly(4-vinylpyridine) Brushes-Grafted-Graphene Oxide Films and Facile Creation of Nanoporosities over their Surface

Fabricating three-dimensional (3D) hierarchical noble-metal particles by spontaneous redox reactions between graphene and noble-metal salts still remains a great challenge. Herein, the fact that graphene oxide (GO) itself acts as both a platform for grafting polymer brushes and a reducing agent to reduce [Ag(NH₃)₂]⁺ ions is taken advantages of. 3D flower-like Ag mesoparticles (Ag mesoflowers, Ag MFs) with tunable size and shapes can spontaneous grow on poly(4-vinylpyridine) brushes-grafted-graphene oxide (P4VP-g-GO) films in Ag(NH₃)₂OH solution without the use of any additional reducing agent. The residual Ag(NH₃)₂OH on 3D Ag MFs surface can be further reduced by NaBH₄, causing abundant nanoporosities over the entire Ag MFs. The resulting Ag nanoporous MFs (Ag NMFs) with larger surface-to-volume ratio and higher nanoscale roughness exhibit ultrasensitivity in surface-enhanced Raman spectroscopy (SERS) detection, and the detection limit for 4-aminothiophenol is as low as 10⁻¹³ m .     

Phase equilibrium and thermodynamic properties of silver-saturated compounds BiSI and Bi<Subscript>19</Subscript>S<Subscript>27</Subscript>I<Subscript>3</Subscript> of the AgI–Bi–Bi<Subscript>2</Subscript>S<Subscript>3</Subscript>–BiSI system

The phase composition of alloys in the Ag–Bi–S–I system (in the region AgI–Bi–Bi2S3–BiSI) for Т ≤ 550 K was studied by physicochemical analysis methods. Equations of overall potential-forming reactions involving the BiSI and Bi₁₉S₂₇I₃ phases were composed. The reactions were performed in the C|Ag|glass Ag₃GeS₃I|D|C electrochemical cells (C are inert (graphite) electrodes; Ag, D are the cell electrodes; D are the four-phase alloys of the system; and glass Ag₃GeS₃I is a membrane with pure Ag⁺ ion conductivity). The linear dependences of EMF of the cells in the range 485–525 K were used for calculating the standard thermodynamic properties of saturated solid solutions of the compounds BiSI and Bi₁₉S₂₇I₃ in the AgI–Bi–Bi₂S₃–BiSI system.     

Preparation of Ag Nanowire @ Au Nanoparticle Hybrid Nanowires and their Influence on the Fluorescence Properties of P3HT

In this study, the galvanic displacement reaction between silver and AuCl₄⁻ was carried out to synthesize a series of silver nanowire (Ag NW) @ gold nanoparticle (Au NP) hybrid nanowires. The influence of Ag NW @ Au NP hybrid nanowires on the fluorescence properties of the poly (3‐hexylthiophene) (P3HT) was investigated. The particle sizes of Au NPs on the hybrid nanowires could be adjusted by varying the reaction time and the concentration of the HAuCl₄ solution. Furthermore, steady‐state fluorescence measurements showed that the fluorescence intensity of the P3HT films was higher on various Ag NW @ Au NP hybrid nanowires compared to that on a bare silicon substrate. This was due to the increase in the intensity of electromagnetic field by the localized surface plasmon resonances of Au NPs and surface plasmon polaritons of Ag NWs from the hybrid nanowires. The results were further confirmed by the Raman spectra of the P3HT films on different substrates.     

SO2 Surface Chemistry on Metal Substrates

The surface chemistry, induced by thermal and non-thermal methods, of SO₂ on metal substrates is reviewed. The substrate temperature during dosing is important; regardless of metal, adsorption is dissociative at 300 K and molecular at 100 K. On Ni, Pd, and Pt, molecular adsorption occurs through the S and one O atom, and the molecular plane is perpendicular to the surface. However, on Ag and Cu, adsorption occurs only through the S with the molecular plane perpendicular to the surface. The differences can be attributed to the structure of the metal's molecular orbitals and their interactions with the SO₂ orbitals. Upon heating, SO₂ dissociates on all transition metal surfaces with the exception of Ag, Au, and Cu, where only molecular desorption occurs. On Pt, Fe, and Pd, additional reactions are observed between SO₂ and its dissociation products. The nonthermal reactions induced by photons and electrons for monolayer coverages of SO₂ on Ag (111) are dominated by molecular desorption. Desorption cross sections for 313 nm photons and 50eV electrons were 2.8 × 10^?20 cm² and ?1 × 10^?16 cm², respectively. Nonthermal excitation mechanisms and quenching processes as well as interesting characteristics of SO₂ under irradiation are also reviewed.