Synthesis of different gold nanostructures by solar radiation and their SERS spectroscopy

In this article, a simple and novel photochemical synthesis of different gold nanostructures is proposed using solar radiation. This method is rapid, convenient and of low cost, and can be performed under ambient conditions. By adjusting the concentration of sodium acetate (NaAc), different morphologies of the products can be easily obtained. Without NaAc, the products obtained are mainly polyhedral gold particles; lower concentration of NaAc (0.05 and 0.1 M) accelerates the formation of flowerlike gold nanostructures; while higher concentration of NaAc (0.5 M) facilitates the formation of a variety of gold nanowires and nanobelts. It is found that the morphology change of gold nanaostructures is the result of the synergistic effect of poly(diallyl dimethylammonium) chloride (PDDA), Ac- ions, and the pH value. In addition, the different gold nanostructures thus obtained were used as substrates for surface-enhanced Raman scattering (SERS) with p-aminothiophenol (p-ATP) as the probe molecule.

Preparation of Polyacrylamide Aqueous Dispersions Using Poly(sodium acrylic acid) as Stabilizer

High-solids, low-viscosity, stable polyacrylamide (PAM) aqueous dispersions were prepared by dispersion polymerization of acrylamide in aqueous solution of ammonium sulfate (AS) using Poly (sodium acrylic acid) (PAANa) as the stabilizer, ammonium persulfate (APS) or 2,2'-Azobis (N,N'-dimethyleneisobutyramidine) dihydrochloride (VA-044) as the initiator. The molecular weight of the formed PAM, ranged from 710, 000 g/mol to 4,330,000 g/mol, was controlled by the addition of sodium formate as a conventional chain-transfer agent. The progress of a typical AM dispersion polymerization was monitored with aqueous size exclusion chromatography. The influences, of the AS concentration, the poly(sodium acrylic acid) concentration, the initiator type and concentration, the chain-transfer agent concentration and temperature Oil the monomer conversion, the dispersion viscosity, the PAM molecular weight and distribution, the particle size and morphology were systematically investigated.

Direct dissolution of Au nanoparticles induced by potassium ferricyanide

In this work, we studied the reaction between Au nanoparticles (Au NPs) and [Fe(CN)(6)](3-) by the UV-vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy. The absorption peak of Au NPs disappeared after adding [Fe(CN)(6)](3-) and the XPS data conformed the formation of [Au(CN)(2)](-). The results demonstrated that [Fe(CN)(6)](3-) could induce the dissolution of Au NPs, where the CN- from the dissociation of [Fe(CN)(6)](3-) played an important role.

Solid-state electrochemiluminescence sensor based on the Nafion/poly(sodium 4-styrene sulfonate) composite film

An effective electrochemiluminescence (ECL) sensor based on Nafion/poly(sodium 4-styrene sulfonate) (PSS) composite film-modified ITO electrode was developed. The Nafion/PSS/Ru composite film was characterized by atomic force microscopy, UV-vis absorbance spectroscopy and electrochemical experiments. The Nafion/PSS composite film could effectively immobilize tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) via ion-exchange and electrostatic interaction. The ECL behavior of Ru(bpy)(3)(2+) immobilized in Nafion/PSS composite film was investigated using tripropylamine (TPA) as an analyte. The detection limit (S/N = 3) for TPA at the Nafion/PSS/Ru composite-modified electrode was estimated to be 3.0 nM, which is 3 orders of magnitude lower than that obtained at the Nafion/Ru modified electrode. The Nafion/PSS/Ru composite film-modified indium tin oxide (ITO) electrode also exhibited good ECL stability. In addition, this kind of immobilization approach was simple, effective, and timesaving.

Research on various factors influencing the moisture absorption property of sodium polyacrylate

Sodium polyacrylate was synthesized with acrylic acid as the monomer, and sodium bisulfate and ammonium persulfate as the initiator, by means of aqueous solution polymerization. The factors influencing the properties of moisture absorption, such as monomer concentration, dosage of initiator, and reaction temperature were systematically investigated. The experimental results indicate that the moisture-absorbing property of this polymer was better than other traditional material, such as silica gel, and molecular sieve. The best reaction condition and formula are based on the orthogonal experiment design. The optimum moisture absorbency of sodium polyacrylate reaches 1.01 g/g. The mathematical correlation of this polymer with various factors and moisture absorbency is obtained based on the multiple regression analysis. The moisture content intuitive analysis table shows that neutralization degree has the most significant influence on moisture absorbency, followed by monomer concentration and reaction temperature, while other factors have less influence.

A General Route to Construct Diverse Multifunctional Fe3O4/Metal Hybrid Nanostructures

We have developed a simple, efficient, economical, and general approach to construct diverse multifunctional Fe3O4/metal hybrid nanostructures displaying magnetization using 3-aminopropyltrimethoxysilane (APTMS) as a linker. High-density Au nanoparticles (NPs) could be supported on the surface of superparamagnetic Fe3O4 spheres and used as seeds to construct Au shell-coated magnetic spheres displaying near-infrared (NIR) absorption., which may make them promising in biosensor and biomedicine applications. High-density flower-like Au/Pt hybrid NPs could be supported on the surface of Fe3O4 spheres to construct multifunctional hybrid spheres with high catalytic activity towards the electron-transfer reaction between potassium ferricyanide and sodium thiosulfate. High-density Ag or Au/Ag core/shell NPs could also be supported on the surface of Fe3O4 spheres and exhibited pronounced surface-enhanced Raman scattering (SERS), which may possibly be used as an optical probe with magnetic function for application in high-sensitivity bioassays.

Bimolecular quadruplexes and their transitions to higher-order molecular structures detected by ESI-FTICR-MS

Four individual quadruplexes, which are self-assembled in ammonium acetate solution from telomeric sequences of closely related DNA strands - d(G(4)T(4)G(4)), d(G(3)T(4)G(4)), d(G(3)T(4)G(3)), and d(G(4)T(4)G(3)) - have been detected in the gas phase using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS). The bimolecular quadruplexes associate with the same number of NH4+ in the gas phase as NMR shows that they do in solution. The quadruplex structures formed in solution are maintained in the gas phase. Furthermore, the mass spectra show that the bimolecular quadruplexes generated by the strands d(G(3)T(4)G(3)) and d(G(4)T(4)G(3)) are unstable, being converted into trimolecular and tetramolecular structures with increasing concentrations of NH4+ in the solution. Circular dichroism (CD) spectra reveal structural changes during the process of strand stoichiometric transitions, in which the relative orientation of strands in the quadruplexes changes from an antiparallel to a parallel arrangement. Such changes were observed for the strand d(G(4)T(4)G(3)), but not for the strand d(G(3)T(4)G(3)). The present work provides a significant insight into the formation of various DNA quadruplexes, especially the higher-order species.

Narion/Poly(sodium 4-styrenesulfonate) mixed coating modified bismuth film electrode for the determination of trace metals by anodic stripping voltammetry

To improve the reproducibility, stability, and sensitivity of bismuth film electrode (BiFE), we studied the performances of a mixed coating of two cation-exchange polymers, Nafion (NA) and poly(sodium 4-styrenesulfonate) (PSS), modified glassy carbon BiFE (GC/NA-PSS/BiFE). The characteristics of GC/NA-PSS/BiFE were investigated by scanning electron microscopy and cyclic voltammetry. Various parameters were studied in terms of their effect on the anodic stripping voltarnmetry (ASV) signals. Under optimized conditions, the limits of detection were 71 ng L-1 for Cd(II) and 93 ng L-1 for Pb(II) with a 10 min preconcentration. The results exhibited that GC/NA-PSS/BiFE can be a reproducible and robust toot for monitor of trace metals by ASV rapidly and environmentally friendly, even in the presence of surface-active compounds.

Synthesis, structure and electrochemical property of calixarene potassium polyoxometalates

One inorganic-organic hybrid and two host-guest complexes were synthesized from calix[4] arene tetra acetic ether derivative( C60H80O12, L) and potassium polyoxometalates. The structures of the complexes were characterized with the elemental analysis, IR, TG-DTA and X-crystallographic. X-ray crystallographic studies reveal the formation of an ionic crystal, which contains a calix-cluster and calix-cluster-calix line array, and belongs to a typical inorganic-organic hybrid ( complex 1) or has a host-guest structure ( complex 2 and 3). The results of cyclic voltammograms at different scanning rates showed that the anode peak current of complex 1 was proportional to the square root of the scanning rate and the charge transfer process was controlled by pervasion. The anode peak current of complexes 2 and 3 was proportional to the scanning rate and the charge transfer process was controlled by the surface. The results suggest that there are consanguineous relationship between the anode reaction and the structure.

Facilitated ion-transfer of sodium cation by (anthraquinone-1-yloxy) methane-15-crown-5 across the water/1,2-dichloroethane microinterface

The transfer of sodium cation facilitated by (anthraquinone-1-yloxy) methane-15-crown-5(L) has been investigated at the water/1,2-dichloroethane microinterface supported at the tip of a micropipette. The diffusion coefficient of (anthraquinone-1-yloxy) methane-15-crown-5 obtained was (3.42 +/- 0.20) x 10(-6) cm(2) s(-1). The steady-state voltammograms were observed for forward and backward scans due to sodium ion transfer facilitated by L with 1:1 stoichiometry. The mechanism corresponded to an interfacial complexation (TIC) and interfacial dissociation (TID) process. The association constant was calculated to be log beta(o) = 11.08 +/- 0.03 in the DCE phase. The association constant of other alkali metals (Li+, K+, Rb+) were also obtained.

Investigation of facilitated ion-transfer reactions at high driving force by scanning electrochemical Microscopy

The kinetics of facilitated ion-transfer (FIT) reactions at high driving force across the water/1,2-dichloroethane (W/DCE) interface is investigated by scanning electrochemical microscopy (SECM). The transfers of lithium and sodium ions facilitated by dibenzo-18-crown-6 (DB18C6) across the polarized W/DCE interface are chosen as model systems because they have the largest potential range that can be controlled externally. By selecting the appropriate ratios of the reactant concentrations (Kr c(M)+/c(DB18C6)) and using nanopipets as the SECM tips, we obtained a series of rate constants (k(f)) at various driving forces (Delta(O)(W) phi(ML+)(0') - Es, Delta(O)(W) phi(ML+)(0') is the formal potential of facilitated ion transfer and Es is the potential applied externally at the substrate interface) based on a three-electrode system. The FIT rate constants k(f) are found to be dependent upon the driving force. When the driving force is low, the dependence of 1n k(f) on the driving force is linear with a transfer coefficient of about 0.3. It follows the classical Butler-Volmer theory and then reaches a maximum before it decreases again when we further increase the driving forces. This indicates that there exists an inverted region, and these behaviors have been explained by Marcus theory.

Sequential deprotonation of meso-(p-hydroxyphenyl)porphyrins in DMF: From hyperporphyrins to sodium porphyrin complexes

Sequential deprotonations of meso-(p-hydroxyphenyl)porphyrins (p-OHTPPH2) in DMF + H2O (V/V = 1:1) mixture have been verified to result in the appearance of hyperporphyrin spectra. However, when the deprotonations of these p-OHTPPH2 are carried out in DMF, the spectral changes differ considerably from those in the mixture mentioned above. At low [OH-], the optical spectra in the visible region are still considered to have characteristics of hyperporphyrin spectra. Further deprotonation at much higher basicity makes the optical spectra form three-banded spectra similar to those in the acidic solution. To clarify the molecular origins of these changes, UV-vis, resonance Raman (RR), proton nuclear magnetic resonance (H-1 NMR) experiments are carried out. Our data give evidence that p-OHTPPH2 in DMF can be further deprotonated of pyrrolic-H by higher concentrated NaOH, due to an aprotic medium like DMF effectively weakening the basicity of the porphyrin relative to that of the NaOH, and coordinates with two sodium ions (except the sodium ions that interact with the peripherial phenoxide anions) to form the sodium complexes of p-OHTPPH2 (Na2P, to lay a strong emphasis on the sodium ions that coordinate with the central nitrogen atom), which can be regarded as the porphyrin anions being perturbed by the sodium cations due to their highly ionic character.

Electrogenerated chemiluminescence biosensor based on Ru(bpy)(3)(2+) and dehydrogenase immobilized in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) composite material

A new electrogenerated chemiluminescence biosensor was fabricated by immobilizing ECL reagent Ru(bPY)(3)(2+) and alcohol dehydrogenase in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) (PSS) organically modified composite material. The component PSS was used to immobilize ECL reagent Ru(bpy)(3)(2+) by ion-exchange, while the addition of chitosan was to prevent the cracking of conventional sol-gel-derived glasses and provide biocompatible microenvironment for alcohol dehydrogenase. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate and it was much simpler than previous double-layer design. The detection limit was 9.3 x 10(-6) M for alcohol (S/N = 3) with a linear range from 2.79 x 10(-5) to 5.78 x 10(-2) M. With ECL detection, the biosensor exhibited wide linear range, high sensitivity and good stability.

In situ electrochemical SERS studies on electrodeposition of aniline on 4-ATP/Au surface

The electrochemical polymerization of 0.01 M aniline in 1 M H2SO4 aqueous solution on roughened Au surface modified with a self-assembled monolayer (SAM) of 4-aminothiophenol (4-ATP) has been investigated by in situ electrochemical surface-enhanced Raman scattering spectroscopy (SERS). The repeat units and possible structures of the electrodeposited polyaniline (PANI) film were proposed; i.e., aniline monomer is coupled in head-to-tail predominately at the C-4 of aniline and amine of 4-ATP, and the thin PANI film is orientated vertically to substrate surface. Simultaneous Raman spectra during potential scanning indicate clearly that the ultrathin PANI film (in initial growth of the film) consists of semiquinone radical cation (IP+), para-disubstituted benzene (IP and IP+) and quinine diimine (NP) while it is oxidized, and without quinine diimine and semiquinone radical cation while reduced. Meanwhile, the results confirm that 4-ATP monolayer shows a strong promotion on the electrodeposition of aniline monomer, and a possible polymerization mechanism was proposed.