Self-assembled monolayer of carboxyl-terminated poly(amido amine) dendrimer

Adlayer formation and adsorption structure of 2.5th-generation poly(amido amine) dendrimer with carboxyl-terminated groups on solid substrates were investigated by atomic force microscopy, surface plasmon resonance spectroscopy, and surface enhanced infrared absorption spectroscopy. Dendrimer molecules are not uniformly adsorbed on solid surface but form aggregates with a width of approximately 100 nm and a height less than 1 nm. Adsorption reaches in equilibrium at 100-1000 sec, depending on the dendrimer concentration. The adsorption-desorption process is considerably reproducible and repeatable. Although the adsorption at equilibrium increases with dendrimer concentration and reaches maximum at neutral pH, monolayer is always maintained after the desorption with solvent. This indicates the formation of self-assembled monolayer. Such monolayer is preserved even at the variation of pH. Although most carboxylates are protonated at acidic pH, small amount of carboxylate remains even at acidic pH. The adsorption structure of dendrimer was illustrated.     

Quantum size effect in TiO2 nanoparticles prepared by finely controlled metal assembly on dendrimer templates

The use of dendrimer templates to make metal-based nanoparticles of controlled size has attracted much interest. These highly branched macromolecules have well-defined structures that enable them to bind metal ions to generate precursors that can be converted into nanoparticles. We describe the sub-nanometre size control of both anatase and rutile forms of TiO2 particles with phenylazomethine dendrimers, leading to samples with very narrow size distributions. Such fine tuning is possible because both the number and location of metal ions can be precisely controlled in these templates. Quantum size effects are observed in the particles, and the energy gap between the conduction and valence bands exhibits a blueshift with decreasing particle size and is dependent on the crystal form of the material. The dependency of the bandgap energy on these factors is explained using a semi-empirical effective mass approximation.     

Kinetic and equilibrium binding analysis of protein-ligand interactions at poly(amidoamine) dendrimer monolayers

The interaction of streptavidin (SA) with a biotinylated surface has been of great interest in the development of an interfacial layer for protein immobilization based on self-assembled monolayers (SAMs) and polymeric layers. Here, we demonstrate the unique characteristics of protein-ligand interactions on dendrimer monolayers based on kinetic and equilibrium binding analyses. With amine-ended poly(amidoamine) dendrimers from the first (G1) to fourth (G4) generation, the formation of even, compact dendrimer monolayers on gold was confirmed using FT-IR spectroscopy and ellipsometry. For the SA-biotin interaction, quantitative analysis of bound SA using surface plasmon resonance showed that the saturation binding level of SA was fairly higher in all dendrimer layers when compared to other tested systems of 11-mercaptoundecylamine SAMs and a poly(L-lysine) layer. Kinetic studies revealed that the initial binding rate of SA up to the saturation level was 2-fold higher in all dendrimer layers than in the SAMs regardless of the surface density of functionalized biotin. Concurrently, the dendrimer layers led to much higher values of sticking probability, which is defined as the probability that the SA molecule adsorbs upon collision with a biotinylated surface, at a fixed SA coverage, and prolonged the significant levels around the maximum probability with increasing SA coverage. Plots of the saturation coverage of SA versus the SA concentration in solution showed that SA binding onto the biotinylated G1 and G3 layers fit to a Langmuir isotherm model. Taken together, faster binding of SA and highly ordered packing of the molecules seems to be achieved through typical properties of the dendrimer monolayers such as surface distribution of functionalized biotin, surface corrugation, and flexibility of highly branched larger dendrimers, which provides a guideline for the construction and analysis of an interfacial layer in biosensing applications.     

On amine treated polyoxymethylene (POM) blends with low formaldehyde emission for metal injection moulding (MIM)

Journal of Materials Science - When polyoxymethylene (POM)—a common polymer used in metal injection moulding feedstock—is exposed to heat and oxygen during compounding, it can be easily...     

Characterization of bimetallic Au-Pt(111) surfaces

Structural and electronic properties of ultrathin Au films deposited on Pt(111) and annealed at different temperatures have been studied by ultraviolet photoelectron spectroscopy (UPS), photoemission of adsorbed xenon (PAX) and low energy electron diffraction (LEED). The LEED measurements indicate an initial pseudomorphic growth of the Au films. The UPS and PAX experiments show a strong temperature dependence of the surface morphology. The surface covered with Au at 150 K is quite rough but smoothens significantly above room temperature. At a temperature of 750 K intermixing and the formation of an Au-Pt surface alloy start at the interface. The electronic properties of this surface alloy seem to be nearly independent from the originally deposited Au amount in the investigated range of 1-10 monolayers. The removal of Au from the surface regions has also been verified by scanning tunneling microscopy. Adsorption experiments with CO as a titration agent show a significantly lower affinity of the Au-Pt surface alloy in comparison with the clean Pt surface.     

分光光度法测定铬(Ⅵ)

研究了在4.1～7.0mol.L~(-1)磷酸介质中于溴化十六烷基三甲铵及锰(Ⅱ)存在下铬(Ⅵ)与二安替比林苯乙烯基甲烷显色反应。该显色体系最大吸收波长位于541nm,摩尔吸光系数(?)_(541nm)=2.11×10~6L·mol~(-1)·cm~(-1)。铬(Ⅵ)在2.0～20ng·mL~(-1)范围内遵守比尔定律。建立了硝酸铬中铬(Ⅵ)及废水中总铬的分光光度测定新方法。     

Spectrophotometric determination of Ce(IV) usingo-phenylenediamine in steels

A simple and sensitive spectrophotometric method for the determination of cerium(IV) was developed. Witho-phenylenediamine cerium(IV) gives an orange-red colour with an absorption maximum at 470 nm. The system obeys Beer’s law in the range 7 ppm to 500 ppm with a molar absorptivity of 2·4 × 10³l mol⁻¹ cm⁻¹ and Sandell sensitivity of 0·5 ppm. Interference by various ions was studied. This method was used for the determination of cerium in low-alloy steels and the results are in good agreement with the certified values.     

胺基端基树状分子在铜纳米粒子形成过程中的模板及稳定化作用

通过Micheal加成和胺解的交替反应,制得末端基为氨基的聚酰胺-胺型树状分子（PAMAM）;研究了第7代PAMAM（G7-NH2）在制备铜纳米粒子过程中的模板作用,通过紫外光谱和透射电镜表征了铜粒子的形成过程以及所得铜粒子的大小。结果表明,铜离子不仅与G7-NH2内部叔胺基形成络合物,还与树状分子外部的伯胺基形成络合物;在得到铜粒子的过程中,G7-NH2具有内模板和外模板作用,铜纳米粒子的尺寸随着铜离子与G7-NH2浓度比例的提高而增大;同时,由于铜纳米粒子为G7-NH2模板所包裹,使其在水中具有良好的分散均匀性和稳定性。但在有氧条件下,铜粒子很容易被氧化为G7-NH2（Cu^2＋）n络合离子。     

Spectrophotometric determination of osmium (IV) ions in intermetallic compounds

We have developed, for the first time, a simple spectrophotometric method for the determination of osmium (IV) ions, based on the reaction of formation of a complex of this metal with Congo Red. We have established the optimal conditions of formation of this complex. The interaction of Os(IV) with Congo Red proceeds with complex formation for the ratio Me: R = 1: 1 at pH 3.5. The complex obtained is characterized by the maximum light absorption on λ_max = 340 nm. Our method enables one to determine from 0.09 to 6.7 mg / liter of osmium. We have also investigated the influence of foreign ions on the spectrophotometric determination of Os(IV). Our method was verified in the course of analysis of synthetic solutions and alloys. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 2, pp. 82–86, March–April, 2008.     

Synthesis and characterization of new bimetallic transition metal oxynitrides: MI-MII-O-N (MI,MII=V,Mo, W and Nb)

A new class of materials, M_I-M_II-O-N (where M_I, M_II = V, Mo, W, and Nb), has been synthesized by nitriding bimetallic oxide precursors with ammonia gas via a temperature programmed reaction. The oxide precursors are prepared by conventional solid state reaction between two appropriate monometallic oxides. The synthesis of the oxynitrides involves passing NH₃ gas over the oxide precursors at a flow rate of 6.80×10² mols^–1 (1000 cm³ min^–1), and raising the temperature at a rate of 8.3×10^–2 Ks^–1 (5K min^–1) to a final temperature which is held constant for a short period of time. The oxynitrides thus obtained are pyrophoric and need to be passivated before exposing them to air. All these new bimetallic oxynitrides have a face centered cubic (f.c.c.) metal arrangement and high values of surface area. Their surface activity is assessed from their ability to chemisorb CO.     

Synthesis of single crystal metal sulfide nanowires and nanowire arrays by chemical precipitation in templates

Single crystal metal sulfide nanowires and nanowire arrays were synthesized by chemical precipitation reaction in the channels of anodic aluminum oxide templates under ambient conditions with simple inorganic salts as precursors. Aligned metal sulfide arrays were achieved by dissolving the template. This template-directed synthesis yielded well-defined nanowires of varied lengths and diameters for almost all precursors. The crystal quality of metal sulfide nanowires was concentration-dependent, high single crystal nanowires were achieved at low concentrations.     

Electrical and magnetic properties of electro-oxidative polymerized poly(tris(thienylphenyl)amine)s

Electro-oxidative polymerized poly(tris(thienylphenyl)amine)s, which have the hyperbranched (dendritic) structure (PTPA) and linear type (PMeTPA), were investigated for their electrical and magnetic properties. The conductivity PTPA showed was almost one order higher than that of PMeTPA. From the solid state ESR measurements of the polymers, observation of ESR signal at g = 2.0027 and 2.0030 indicated the formation of a triphenylamine cation radical. The normalized magnetization plots (M/M_s) for PTPA and PMeTPA are close to the theoretical Brillouin curves for S = 1, indicating a magnetic interaction between the spin centers in PMeTPA. The spin concentrations determined by the M_s values of PTPA and PMeTPA were 7.3–7.4 and 1.3–1.4%, respectively. This large difference in the spin concentration of the polymers according to the structure resulted from a different spin conformation by the radical structure.     

Spectrophotometric determination of Sb(III) and Sb(V) in biological samples after micelle-mediated extraction

This work presents a micelle-mediated extraction method for simultaneous preconcentration and determination of Sb(III) and Sb(V) species in biological samples as a prior preconcentration step to their spectrophotometric determination. The analytical system is based on the selective reaction between Sb(III) and bromopyrogallol red (BPR) in the presence of cetyltrimethylammonium bromide (CTAB) and potassium iodide at pH 6.4. Total Sb concentration was determined after reduction of Sb(V) to Sb(III) in the presence of potassium iodide and ascorbic acid. The optimal extraction and reaction conditions were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration factor, and improvement factors) were obtained. Linearity for Sb(III) and Sb(V) were obeyed in the range of 0.2–20.0 ng mL⁻¹ and 0.4–25.0 ng mL⁻¹, respectively. The detection limit for the determination of Sb(III) and Sb(V) were 0.05 ng mL⁻¹ and 0.08 ng mL⁻¹, respectively. The interference effect of some anions and cations was also studied. The method was applied to the determination of Sb(III) in the presence of Sb(V) and total antimony in blood plasma and urine samples.     

Synthesis of Poly(ether ether ketone)s containing tertiary amine

A functional or reactive PEEK-Poly(ether ether ketone)s containing tertiary amine was synthesized. The product was determined by ¹H NMR, ¹³C NMR, IR spectra and elemental analysis. Thermal analysis of the polymer revealed the glass-transition temperatures (T_g = 119.57 °C), a 5% weight loss in air at 386 °C. An M_n of 10.4 kD, M_w of 20.2 kD, Polydispersity of 1.95 was obtained from GPC. The Poly(ether ether ketone)s containing a tertiary amine structure can be synthesized as a scaffolds for post-polymerization reaction.     

棓花青褪色光度法测定镀铬液中的铬

在硫酸混酸介质 ,10 0℃恒温水浴中 ,铬 (Ⅵ )能氧化花青 ,使其显著褪色 ,据此建立了测定铬 (Ⅵ )的新方法。铬 (Ⅵ )的浓度在 0～ 1.0 4 μg/mL范围内 ,符合比耳定律 ,表观摩尔吸光系数为 1.90× 10 4 L/ (mol·cm)。此法用于测定镀铬液中铬 (Ⅵ )的含量 ,结果令人满意     

催化动力学光度法测定镀铬液中的铬(Ⅵ)

在pH=5.7的HAc-NaAc缓冲介质、90℃恒温水浴中,铬(Ⅵ)能显著催化过氧化氢氧化胭脂红的褪色反应.研究了影响催化反应速度的最佳条件,建立了测定铬(Ⅵ)的新方法,铬(Ⅵ)的浓度在0.5～1.5μg/mL范围内符合比耳定律,表观摩尔吸光系数为3.905×103L/mol·cm.该方法的检出限量为0.045μg/mL,此法用于镀铬液中铬(Ⅵ)的测定,结果令人满意.