Mono- and bi-functional arenethiols as surfactants for gold nanoparticles: synthesis and characterization

Stable gold nanoparticles stabilized by different mono and bi-functional arenethiols, namely, benzylthiol and 1,4-benzenedimethanethiol, have been prepared by using a modified Brust's two-phase synthesis. The size, shape, and crystalline structure of the gold nanoparticles have been determined by high-resolution electron microscopy and full-pattern X-ray powder diffraction analyses. Nanocrystals diameters have been tuned in the range 2 ÷ 9 nm by a proper variation of Au/S molar ratio. The chemical composition of gold nanoparticles and their interaction with thiols have been investigated by X-ray photoelectron spectroscopy. In particular, the formation of networks has been observed with interconnected gold nanoparticles containing 1,4-benzenedimethanethiol as ligand

NEXAFS study of a Pt-containing rod-like organometallic polymer (Pt-DEBP). Molecular orientation onto HOPG, Au/Si(111), Cr/Si(111) AND Si(111) surfaces

The influence of different substrates on the molecular orientation of organometallic polymer Pt-DEBP, [Pt(PBu 3) 2CCC 12H 8CC] n, has been investigated by NEXAFS spectroscopy. Thin films were deposited on HOPG, Au/Si(1 1 1), Cr/Si(1 1 1), Si(1 1 1) and stainless steel. The assignment of the spectral features has been carried out on the basis of previous STEX calculations performed on phenylacetylene model molecule in gas phase and adsorbed on Pt(1 1 1) and Cu(1 0 0). Angular dependent analysis of the π* resonance occurring at 285.50 eV photon energy deriving by the benzene carbon orbitals showed a polarisation effect for all substrates. A preferential molecular orientation at nearly 40°to the surface normal was observed. This result might be explained by the strong interaction between sp and sp 2 carbons of the organic diethynylbiphenyl DEBP moiety contained in close chains, leading to polymer self-assembling

Phase synchronization of oxygenation waves in the frontal areas of children with attention-deficit hyperactivity disorder detected by optical diffusion spectroscopy correlates with medication.

The beneficial effects of pharmacotherapy on children with attention-deficit hyperactivity disorder (ADHD) are well documented. We use near-infrared spectroscopy (NIRS) methodology to determine reorganization of brain neurovascular properties following the medication treatment. Twenty-six children with ADHD (ages six through 12) participated in a modified laboratory school protocol to monitor treatment response with lisdexamfetamine dimesylate (LDX; Vyvanse®, Shire US Inc.). All children refrained from taking medication for at least two weeks (washout period). To detect neurovascular reorganization, we measured changes in synchronization of oxy (HbO2) and deoxy (HHb) hemoglobin waves between the two frontal lobes. Participants without medication displayed average baseline HbO2 phase difference at about -7-deg. and HHb differences at about 240-deg.. This phase synchronization index changed after pharmacological intervention. Medication induced an average phase changes of HbO2 after first medication to 280-deg. and after medication optimization to 242-deg.. Instead first medication changed of the average HHb phase difference at 186-deg. and then after medication optimization to 120-deg. In agreement with findings of White et al., and Varela et al., we associated the phase synchronization differences of brain hemodynamics in children with ADHD with lobe specific hemodynamic reorganization of HbO2- and HHB oscillations following medication status

Self Assembling Monolayers of dialkynyl bridged Pd(II) thiols obtained by thermally induced multilayer desorption: thermal and chemical stability investigated by SR-XPS

""Self assembling monolayers (SAMs) of organometallic thiols trans-[HS–Pd(PBu3)2–SH], trans-[HS–Pd(PBu3)2(–CC–C6H5)] and trans,trans-[HS–Pd(PBu3)2(–CC–C6H4–C6H4–CC–Pd(PBu3)2–SH] on gold were obtained from the corresponding multilayers through thermally induced desorption. Temperature-dependent synchrotron radiation-induced X-ray photoelectron spectroscopy (SR-XPS) measurements were carried out on the heated multilayers during the annealing process, in order to investigate the thermal and chemical stability of the systems. SAMs of the same organometallic thiols were also obtained by rinsing the thick films with appropriate solvents. SR-XPS was used to ascertain that the molecular and electronic structure of the two series of SAMs are not influenced by the rinsing or thermal desorption process, i.e. both strategies allow for obtaining well ordered monolayers of organometallic thiols."

NEXAFS and XPS investigation of self-assembling biomaterial

Some of the most promising new synthetic biomaterial scaffolds are composed of self-assembling peptides that can be modified to contain biologically active motifs. The development of synthetic materials promoting cell growth aims at the realization of systems suitable for implantology or sensoristic applications. The final goal is to establish methodologies to control the adsorption/anchoring of special oligopeptide sequences capable to give self-organised layers on suitable surfaces. Peptide-based biomaterials can be fabricated to give rise to two- and three-dimensional structures. In this contribution we present results obtained by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption spectroscopy (NEXAFS), concerning the electronic structure of a 16 units peptide as deposited onto Au and TiO2 substrates. The peptide has been synthesized on purpose to give rise to a special sequence of the constituting amino acids (L-Alanine, L-Glutammic acid and L-Lysine). The TiO2 substrate has been grown onto a Si(111) disk; XPS data confirmed the surface stoichiometry. Data concerning some basic amino acids used in the sequence are also presented. XPS spectra have been measured either for the substrate and for the adsorbed peptide, at the C1s, N1s, O1s, Ti2p and Au4f core levels. Angular dependent NEXAFS has been performed at both C-K and N-K. Feature assignment is discussed and preliminary considerations concerning the angular dependence of specific resonances are also reported. Static exchange ab initio (STEX) calculations are in progress, in order to simulate the expected NEXAFS spectra and their polarization dependence

Self Assembling behaviour of self-complementary oligopeptides on biocompatible substrates

Self-complementary amphiphilic oligopeptides, consisting of an alternation of hydrophobic and hydrophilic amino acids and of positively and negatively charged groups can generate extended ordered structures by self-assembling (SA) from aqueous solutions, and have been successfully tested as promising candidates for scaffolds in several fields of tissue engineering. In this paper we present a systematic XPS, NEXAFS and FTIR investigation carried out on a series of SA peptides consisting of different selected sequences of 16 residues, with the aim of determining the effect of side chains length on molecular arrangement and orientation. Peptides were immobilized on the surface of titanium, a well known biocompatible material, or deposited as thick films on inert gold surfaces. FTIR analysis yields information on the backbone conformation. XPS spectroscopy was used to investigate the peptide adsorption on the TiO2 surface. The orientation of the peptide chains was studied by angular-dependent NEXAFS. The performed spectroscopical characterization leads to widely investigate the physical properties of biopolymers–peptide coatings

SELF ASSEMBLING BEHAVIOUR OF SELF-COMPLEMENTARY OLIGOPEPTIDES ON BIOCOMPATIBLE SUBSTRATES

Self-complementary amphiphilic oligopeptides, consisting of an alternation of hydrophobic and hydrophilic amino acids and of positively and negatively charged groups can generate extended ordered structures by self-assembling (SA) from aqueous solutions, and have been successfully tested as promising candidates for scaffolds in several fields of tissue engineering. In this paper we present a systematic XPS, NEXAFS and FTIR investigation carried out on a series of SA peptides consisting of different selected sequences of 16 residues, with the aim of determining the effect of side chains length on molecular arrangement and orientation. Peptides were immobilized on the surface of titanium, a well known biocompatible material, or deposited as thick films on inert gold surfaces. FTIR analysis yields information on the backbone conformation. XPS spectroscopy was used to investigate the peptide adsorption on the TiO2 surface. The orientation of the peptide chains was studied by angular-dependent NEXAFS. The performed spectroscopical characterization leads to widely investigate the physical properties of biopolymers–peptide coatings