Simple Replacement Reaction Research Articles

Ultrasensitive electrochemiluminescence immunosensor using PtAg@carbon nanocrystals composites as labels and carbon nanotubes-chitosan/gold nanoparticles as enhancer

An ultrasensitive electrochemiluminescence (ECL) immunosensor was developed using PtAg@carbon nanocrystals (CNCs) as excellent labels based on carbon nanotubes-chitosan/AuNPs (CNT-CHIT/AuNPs) composite modified screen-printed carbon electrodes (SPCEs) for prostate protein antigen (PSA) detection. The CNCs were obtained simply by electro-oxidation of graphite with abundant carboxyl groups at their surfaces. The PtAg bimetallic nanocomposites with hierarchically hollow structures were fabricated through simple replacement reaction using dealloyed nanoporous silver (NPS) as both a template and reducing agent. Structure characterization was obtained by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) images. The PtAg@CNCs composites exhibit a 6 times higher ECL intensity than the pure CNCs labeled anti-PSA. The as-prepared CNT-CHIT/AuNPs composite can attach more antibody than pure CNTs. Due to the dual-amplification techniques, the concentrations of PSA were obtained in the range from 1 pg mL(-1) to 50 ng mL(-1) with a detection limit of 0.6 pg mL(-1). Finally, the as-proposed ECL immunosensor has the advantages of high sensitivity, specificity and stability and could become a promising technique for tumor marker detection.

Ultrasensitive electrochemiluminescence detection of DNA based on nanoporous gold electrode and PdCu@carbon nanocrystal composites as labels

A sensitive electrochemiluminescence (ECL) DNA biosensor based on nanoporous gold (NPG) electrode and PdCu@carbon nanocrystals (CNCs) composites is developed. The CNCs were obtained simply by electrooxidation with abundant carboxyl groups at their surfaces. The NPG can be easily prepared by a selective dissolution of silver from silver-gold alloy in nitric acid, which has free-standing noble metal membranes with controllable three-dimensional (3D) porosity. The PdCu bimetallic nanocomposites with hierarchically hollow structures were fabricated through a simple replacement reaction using dealloyed nanoporous copper (NPC) as both a template and reducing agent. Structure characterization was obtained by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) images. The PdCu@CNCs composites exhibit 6 times higher ECL intensity than the pure CNC-labeled reporter DNA. Taking advantage of dual-amplification effects of the developed probe, a limit of detection as low as 18 aM can be achieved and the assay exhibits excellent selectivity for single-mismatched DNA detection even in human serum. The proposed ECL based method should have wide applications in diagnosis of genetic diseases due to its simplicity, low cost, and high sensitivity at extremely low concentrations.

Novel urchin-like Pd nanostructures prepared by a simple replacement reaction and their catalytic properties

Novel urchin-like Pd nanostructures were firstly synthesized using a simple replacement reaction between Al and PdCl2 aqueous solution at room temperature without the assistance of any surfactant or ligand. Their phase structure, morphology, specific surface area, and catalytic property were characterized by XRD, TEM, EDS, BET and DSC/TG. The results show numerous one-dimensional Pd nanorods radiate from the center of the aluminum templates to form an urchin-like shape with a diameter of ∼0.5–1.0μm. The as-prepared urchin-like Pd nanostructures can serve as a promising additive to accelerate the thermal decomposition of ammonium perchlorate (AP), a key oxidizer in composite solid propellants.

Superhydrophobicity and surface enhanced Raman scattering activity of dendritic silver layers

Dendritic silver nanostructured surface has been prepared on copper substrate by a simple replacement reaction. It was observed that morphology of the silver surface became much rough with reaction time, from initial nanosized clusters to nanostructured dendrites. The silver surface modified with dodecanethiol showed great superhydrophobicity. It was also found that the dendritic silver nanostructured surface demonstrated highly sensitive surface enhanced Raman scattering (SERS) character. It is expected that the dendritic silver surface may be applied as molecular probe and biological sensing.

Surface‐enhanced Raman spectroscopy coupled with dendritic silver nanosubstrate for detection of restricted antibiotics

AbstractSurface‐enhanced Raman spectroscopy (SERS) coupled with dendritic silver nanosubstrates was used in this study for rapid detection and characterization of restricted antibiotics. Dendritic silver nanosubstrates were prepared through a simple replacement reaction and stored in deionized water for months. SERS methods with near‐IR excitation at 785 nm using silver nanosubstrates were evaluated for detection of three restricted antibiotics (i.e. enrofloxacin, ciprofloxacin, and chloramphenicol) prepared in standard solutions. SERS was capable of identifying and characterizing three antibiotics quickly and accurately. Silver dendrites exhibit satisfactory and consistent performance with an analytical enhancement factor of ∼104. The limit of detection and limit of quantification for antibiotics could reach the level of 20 ppb. Silver dendrites can be kept in deionized water for up to 6 months with no signs of degradation in SERS performance. These results demonstrate a great potential of using SERS coupled with silver dendrites for rapid detection, classification, and quantification of chemical contaminants. Copyright © 2009 John Wiley & Sons, Ltd.

Characterization of chitin–metal silicates as binding superdisintegrants

When chitin is used in pharmaceutical formulations, processing of chitin with metal silicates is advantageous, from both an industrial and pharmaceutical perspective, compared to processing using silicon dioxide. Unlike the use of acidic and basic reagents for the industrial preparation of chitin–silica particles, coprecipitation of metal silicates is dependent upon a simple replacement reaction between sodium silicate and metal chlorides. When coprecipitated onto chitin particles, aluminum, magnesium, or calcium silicates result in nonhygroscopic, highly compactable/disintegrable compacts. Disintegration and hardness parameters for coprocessed chitin compacts were investigated and found to be independent of the particle size. Capillary action appears to be the major contributor to both water uptake and the driving force for disintegration of compacts. The good compaction and compression properties shown by the chitin–metal silicates were found to be strongly dependent upon the type of metal silicate coprecipitated onto chitin. In addition, the inherent binding and disintegration abilities of chitin–metal silicates are useful in pharmaceutical applications when poorly compressible and/or highly nonpolar drugs need to be formulated. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4887–4901, 2009

Synthesis of Ag-Mn<SUB>3</SUB>O<SUB>4</SUB> Core–Shell Nanorods and Mn<SUB>3</SUB>O<SUB>4</SUB> Nanotubes from Sacrificial Ag Nanorod Templates

Our research focuses on the preparation of Ag-Mn3O4 core-shell nanorods and Mn3O4 nanotubes which have various engineering applications. Hausmannite manganese oxide (Mn3O4) nanotubes were synthesized via a galvanic replacement reaction at mild reaction conditions. The Mn3O4 nanotubes were prepared by solidification of manganese ions on a sacrificial silver nanorod due to the standard reduction potential difference between solid silver and manganese ions. The Mn ions were reduced to solid while the solid Ag rod was oxidized to ions. Ag-Mn3O4 core-shell nanorods and Mn3O4 nanotubes were simply prepared by changing the amount of manganese ions. The Mn3O4 layer in the nanorods and nanotubes had a Hausmannite crystalline structure and showed weak hysteresis of magnetism. This weak magnetism is likely due to the diamagnetic property of silver and multiple magnetic domain of Mn3O4. This simple replacement reaction could be applied to various oxide nanotube fabrications with exact shape control.

Controllable growth of silver nanostructures by a simple replacement reaction and their SERS studies

Hierarchical silver nanostructures, consisting of dendritic (symmetric branched) and fractal patterns (randomly ramified), were synthesized very easily by dropping a droplet of AgNO 3-HF solution on silicon wafers. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and open circuit potential-time (Ocp-t) measurement demonstrated that the two nanostructures converted with the reaction composition. The structural evolution was tentatively explained with the theory that oriented growth was determined by the anisotropy of the solid–liquid interfacial energy and the oriented attachment-based aggregation mechanism. Results on surface-enhanced Raman scattering (SERS) signals of the silver films with hierarchical nanostructures demonstrate that SERS is sensitive to silver nanostructures.

Preparation and Catalytic Activity of Monolayer-Dispersed Pt/Ni Bimetallic Catalyst for C=C and C=O Hydrogenation

Abstract The monolayer-dispersed Pt/Ni bimetallic catalyst was prepared through a simple replacement reaction, and its catalytic activity for the hydrogenation of cyclohexene, styrene, acetone, and butyl aldehyde was also tested. The Pt/Ni catalyst that was prepared by the replacement reaction showed much higher activity than Pt/Ni and Pt/Al 2 O 3 catalysts with the same Pt loading prepared by the conventional impregnation method.

Synthesis and Reactivity of Labile MeCN Adducts of Diruthenium Bis(μ-methylene) Species, Cp2Ru2(μ-CH2)2(CO)n(MeCN)2-n(n= 1, 2): Reaction with H Sources, H−X (X = SiR3, SnR3, H), and C−C Coupling with Alkynes and Diazoalkanes

Irradiation of the diruthenium bis(μ-methylene) complex Cp2Ru2(μ-CH2)2(CO)2 (1), in acetonitrile gives the mono- and bis(acetonitrile) species Cp2Ru2(μ-CH2)2(CO)(MeCN) (2) and Cp2Ru2(μ-CH2)2(MeCN)2 (3) in a successive manner. The mono-MeCN species 2 has been characterized spectroscopically and crystallographically, but the bis-MeCN species 3 is too unstable to be fully characterized. Reaction of 2 with hydrosilanes and hydrostannanes results in oxidative addition of the H−Si and H−Sn bond to give hydrido−μ-methylene complexes, Cp2Ru2(μ-CH2)2(H)(mR3)(CO) (m = Si (7), Sn (9)). In the case of the reactions with dihydrosilane, phenylsilane, and triphenylstannane, one of the two methylene bridges is eliminated as methane (and benzene from phenylsilane) to give μ-methylene−μ-silylene complexes, Cp2Ru2(μ-CH2)(μ-SiR2)(H)(SiR3)(CO) (8), and a tristannyl−μ-methylene complex, Cp2Ru2(μ-CH2)(μ-H)(SnPh3)3(CO) (10). Treatment of 2 with alkynes (R1C⋮CR2) and diphenyldiazomethane produces the metallacyclic products Cp2Ru2[μ-η3-C(R1)C(R2)CH2](μ-CH2)(CO) (12), and the vinylidene complex Cp2Ru2(μ-CCPh2)(μ-η3-CPh2) (14), respectively, via C−C coupling. In contrast to 2, corresponding reactions of the bis-MeCN species 3 are sluggish and only the simple MeCN replacement reaction proceeds in a selective manner.

Short DNA fragments induce site specific recombination in mammalian cells

A defective hprt gene was corrected by homologous recombination in a lymphocyte cell line deficient in Hypoxanthine-phosphoribosyl-transferase activity (hprt). In a novel approach, only a fragment of a cDNA clone of the functional hprt gene was used to induce homologous recombination. The mutation that was corrected corresponds to a single base change in exon III of the hprt gene. Two transfection methods, electroporation and the previously unreported use of polyoma capsids containing only short DNA fragments, were able to induce the recombinational event. After transfection cells with a functional hprt gene were selected and homologous recombination events were identified using polymerase chain reaction. Double stranded fragments and both coding and non-coding single stranded fragments resulted in conversion to a functional gene. Analysis of the resulting hprt positive cells revealed that most cells had undergone a simple replacement reaction. Interestingly, however, some cells had lost an intron adjacent to the site of mutation. Potential mechanisms for this phenomenon, including the possible involvement of RNA in DNA repair, are discussed.