Foam films in the presence of functionalized gold nanoparticles

Dry aqueous foams made of anionic surfactant (SDS) and spherical gold nanoparticles are studied by small angle X-ray scattering and by optical techniques. To obtain stable foams, the surfactant concentration is well above the critical micelle concentration. The specular reflectivity signal obtained on a very thin film (thickness 20 nm) shows that functionalized nanoparticles (17 nm typical size) are trapped within the film in the form of a single monolayer. In order to isolate the film behavior, investigations are made on a single film confined in a tube. The film thinning according to the ratio of functionalized nanoparticle and SDS micelles (1:1, 1:10, 1:100) is mainly governed by the structural arrangement of SDS micelles. In thick films, nanoparticles tend to form aggregates that disappear during drainage. In particular self-organization of nanoparticles (with different surface charge) inside the film is not detected.     

Self-organization in the chitosan-clay nanoparticles system regulated through polysaccharide macromolecule charging. 1. Hydrogels

Scanning and transmission electron microscopy and dynamic rheology are used to thoroughly characterize the morphology and mechanical properties of bionanocomposite hydrogel prepared by mixing cationic chitosan with negatively charged particles of a synthetic clay (saponite) followed by gradual increasing of the charge of chitosan macromolecules by decreasing the pH of a medium. Gelation of the system is found to be due to the formation of a fibrillar three-dimensional network structure. It is shown that the size fibrils, the density of the network structure, and its mechanical properties are determined by the concentration ratio between the polysaccharide and saponite particles.     

Synthesis of CeO2@SiO2 core-shell nanoparticles by water-in-oil microemulsion. Preparation of functional thin film

Synthesis of nanoparticles under restricted environment offered by water-in-oil (W/O) microemulsions provides excellent control over particle size and shape, and inter-particle spacing. Such an environment has been involved to synthesize silica nanoparticles with a CeO2 core, so-called CeO2@SiO2. Aqueous fluids made up of ceria nanoparticles with a size close to 5 nm have been used as the water phase component. The starting CeO2 sols and obtained CeO2@SiO2 nanoparticles have been characterized by dynamic light scattering (DLS), X-ray diffraction, scanning and transmission electron microscopy, and specific surface area measurements. The microemulsion process has been characterized by DLS. Preliminary results on CeO2@SiO2 thin films are presented.     

The influence of local structure of nanocrystalline Ni films on the catalytic activity

The aim of our investigation was to study the influence of the nanoparticles size (the local structure) in sputter deposited Ni films on hydrogen evolution kinetics. The grain size of Ni-particles (11–100 nm) was controlled by the substrate temperature (from 35 °C to 300 °C). The dependence of the kinetic parameters on the temperature at which the films were deposited was measured in alkaline solution by electrochemical impedance spectroscopy (EIS). It correlates well with the change of the ratio between the nanocrystalline and non-homogenous disordered fraction of the nc-Ni film observable by Grazing incidence small angle X-ray scattering (GISAXS) analysis and ascribed to the intercrystalline matter. The catalytic activity of nanocrystalline nickel (nc-Ni) on the hydrogen evolution reaction (h.e.r.) is markedly greater at larger fraction of the spherical inhomogeneities inside the film. This effect is especially strongly pronounced for the nc-Ni films prepared on the substrates at lower temperatures.     

Raman and Brillouin scattering spectroscopy studies of atomic layer-deposited ZrO(2) and HfO(2) thin films

Atomic layer-deposited ZrO(2) (zirconia) and HfO(2) (hafnia) films with various thicknesses, ranging from 112 to 660 nm, have been studied by Raman scattering spectroscopy. Spectral analysis of the excellent quality Raman data obtained by using freestanding edges of the films has unambiguously demonstrated that a metastable tetragonal t-ZrO(2) is coexisting with the stable monoclinic phase in zirconia films. Even though the Raman spectrum signal-to-noise ratio was high, only the monoclinic phase was positively identified from the observed spectral patterns of hafnia films. X-ray diffraction patterns are used to define the structure of metastable phases. Complementary Brillouin light scattering measurements of the freestanding edges are also employed in constraining elastic properties of the 405 nm HfO(2) thin film.     

Growth of TiC films by Pulsed Laser Evaporation (PLE) and characterization by XPS and AES

Summary Thin films of TiC with a thickness of some 100 nm have been grown on Si(100) substrates by Pulsed Laser Evaporation (PLE). Advantages of PLE in comparison with more conventional growth methods e. g. PVD or CVD are reported. The feasibility of growing stoichiometric thin films of TiC by PLE was investigated. These films produced have been analysed in situ by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). XPS results and Auger sputter depth profiles indicate that the films grown between RT and 500°C are stoichiometric TiC. Film/substrate interdiffusion is observed at 600°C substrate temperature and higher.     

Nanosilica-supported polyethoxyamines as low-cost, reversible carbon dioxide sorbents

Nanoparticles capped with amine ligands with different steric properties, dodecylamine and oleylamine, respectively, are investigated in the solid state as well as in solution. A combined X-ray diffraction, small angle X-ray scattering and electron microscopy investigation showed that the nanoparticles exhibit the sphalerite modification of ZnS as crystal phase with a diameter of 3-5 nm. A close packing of the monocrystalline nanoparticles in the solid state is observed. However, in the dodecylamine sample, besides spherical particles, a fraction of the nanoparticles is elongated. The nanoparticles are readily resoluble in apolar solvents like hexane. Dynamic light scattering (DLS) and SAXS investigations of the solutions reveal that the nanoparticles are dissolved as singular particles. In the case of oleylamine-capped ZnS, a defined core-shell structure with a ZnS core with a diameter of 4 nm and an organic shell with a thickness of approximately 2 nm have been found. Dodecylamine-capped nanoparticles slightly tend to form agglomerates with a diameter of approximately 40 nm.     

Controlling the Surface Functionalization of Ultrasmall Gold Nanoparticles by Sequence-Defined Macromolecules

Ultrasmall gold nanoparticles (diameter about 2 nm) were surface-functionalized with cysteine-carrying precision macromolecules. These consisted of sequence-defined oligo(amidoamine)s (OAAs) with either two or six cysteine molecules for binding to the gold surface and either with or without a PEG chain (3400 Da). They were characterized by ¹H NMR spectroscopy, ¹H NMR diffusion-ordered spectroscopy (DOSY), small-angle X-ray scattering (SAXS), and high-resolution transmission electron microscopy. The number of precision macromolecules per nanoparticle was determined after fluorescent labeling by UV spectroscopy and also by quantitative ¹H NMR spectroscopy. Each nanoparticle carried between 40 and 100 OAA ligands, depending on the number of cysteine units per OAA. The footprint of each ligand was about 0.074 nm² per cysteine molecule. OAAs are well suited to stabilize ultrasmall gold nanoparticles by selective surface conjugation and can be used to selectively cover their surface. The presence of the PEG chain considerably increased the hydrodynamic diameter of both dissolved macromolecules and macromolecule-conjugated gold nanoparticles.     

Preparation and Characterization of CdTe Nanoparticles in Zirconia Films Prepared by the Sol Gel Method

Two methods for the synthesis of CdTe nanoparticles in zirconia sol-gel films are demonstrated. The nanoparticles were obtained by chemical reduction of Te(IV) using reducing agent (hydrazine) or tin chloride. Particle sizes ranging from 6 to 20 nm in diameter could be prepared by varying the experimetal parameters. The size and crystalline structure of the particles were characterized by optical absorption, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The film morphology was characterized by scanning force microscopy.The film obtained by SnCl₂ method is smooth and homogeneous. The dense structure of CdTe nanoparticles of a few nm in diameter is revealed. The films prepared with hydrazine are porous as a result of evolution of the decomposition gaseous products during the reduction.Advantages and disadvantages of the two methods are discussed.     

Structure of carbon nanoparticles synthesized by adiabatic compression of acetylene and their application in supercapacitors

The work reports the study of the structure of carbon nanoparticles prepared by the pyrolysis of heliumdiluted acetylene under adiabatic compression in a piston reactor. At a pushing gas pressure of 0.5 MPa, 0.7 MPa, and 0.9 MPa the reaction gas was heated to temperatures of 400 °C, 600 °C, and 750 °C. By transmission electron microscopy it is found that carbon nanoparticles have a spherical shape and their size varies from 20 nm to 60 nm. The structural features of carbon nanoparticles are determined from the X-ray photoelectron spectroscopy data and the analysis of the near-edge X-ray absorption fine structure spectroscopy. Carbon nanoparticles prepared at a pushing gas pressure of 0.5 MPa have an amorphous structure and consist of hydrogenated carbon with impurities of polycyclic aromatic fragments. At a stronger compression ratio, carbon nanoparticles with a layered structure consisting mainly of sp² hybridized carbon atoms are formed. The capacitance behavior and electrochemical impedance of carbon nanoparticle-based supercapacitors are compared.     

Notable shift of ultraviolet intensity on Sn-doped ZnO nanostructure fabricated by sol–gel method

Sn-doped ZnO (SZO) thin films are deposited by sol–gel dip-coating method with Sn content at 0 at.% and 1–15 at.% with an increment of 2 at.%. The structure and luminescence of the films are investigated. X-ray diffraction results indicate that all the SZO samples show preferential orientation along the (002) direction, and the scanning electron microscope exhibits that the surface morphology of the films change from nanoparticles to nanorods with increasing Sn concentration. X-ray photoelectron spectroscopy reveals that Sn exists as valence of +4 in the matrix. The photoluminescence peaks at 381 and 398 nm are observed in all the samples. The ratio of intensity of peak at 381 nm to that of peak at 398 nm differed markedly. The intensity of peak at 398 nm might be due to the response for the Sn atoms, while the intensity of peak at 381 nm is probably related to the quantum size effect.     

Layer-by-layer deposition of open-pore mesoporous TiO<Subscript>2</Subscript>-Nafion® film electrodes

The formation of variable thickness TiO₂ nanoparticle-Nafion® composite films with open pores is demonstrated via a layer-by-layer deposition process. Films of about 6 nm diameter TiO₂ nanoparticles grow in the presence of Nafion® by “clustering” of nanoparticles into bigger aggregates, and the resulting hierarchical structure thickens with about 25 nm per deposition cycle. Film growth is characterized by electron microscopy, atomic force microscopy, and quartz crystal microbalance techniques. Simultaneous small-angle X-ray scattering and wide-angle X-ray scattering measurements for films before and after calcination demonstrate the effect of Nafion® binder causing aggregation. Electrochemical methods are employed to characterize the electrical conductivity and diffusivity of charge through the TiO₂-Nafion® composite films. Characteristic electrochemical responses are observed for cationic redox systems (diheptylviologen^2+/+, \({\text{Ru}}{\left( {{\text{NH}}_{3} } \right)}^{{3 + /2 + }}_{6} \), and ferrocenylmethyl-trimethylammonium^2+/+) immobilized into the TiO₂-Nafion® nanocomposite material. Charge conduction is dependent on the type of redox system and is proposed to occur either via direct conduction through the TiO₂ backbone (at sufficiently negative potentials) or via redox-center-based diffusion/electron hopping (at more positive potentials).     

Characterization of nanocrystalline anatase TiO<Subscript>2</Subscript> thin films

Nanoporous thin films were deposited onto glass substrates by painting with a solution of nanocrystalline anatase TiO(2) particles (with a size of either 6 nm or 16 nm) suspended in an organic solvent. Upon drying in air for about 1 day, the films were tempered at 450 degrees C in air for 1 h. This procedure results in stoichiometric TiO(2) films with a thickness of several micro m and a milky whitish appearance. Scanning force microscopy of the surface revealed that the nanoparticles of the films agglomerated into structures with lateral dimensions of some 100 nm. Transmission electron microscopy was utilized to investigate the structural arrangement of the crystallites in the films. High-resolution electron diffraction and X-ray diffraction analyses demonstrated, furthermore, that the material consists exclusively of a single TiO(2) phase, namely anatase, and that the films do not exhibit any preferential texture. The elemental stoichiometry and the possible presence of impurities were monitored throughout the films by means of secondary-ion mass spectrometry depth profiling. Electrical measurements have been carried out as a function of both the sample temperature T and the ambient oxygen partial pressure p(O(2)). From these data the electrical conductivity sigma of the porous films was determined in dependence of those parameters.     

XPS investigations on boron nitride fibre coatings prepared by chemical vapour deposition in comparison to their hydrolytic rate

Investigations on CVD boron nitride films on fibres by means of photoelectron and X-ray spectroscopy resulted in B/N ratios above the stoichiometric value 1 and oxygen contents up to 25 at%. Compared to the hydrolytic rate of the films an apparent dependence was found on the deposition rate and some evidence of the oxygen concentration. CVD fibre coatings exhibit a hexagonal turbostratic structure with extremely small atomic layer plane dimensions, which was proved by transmission electron microscopy. Corresponding to oxygen concentrations in pyrolytic carbon films with similar structure a model is proposed, where the small atomic layers with dimensions of some nanometers cause a relatively high oxygen concentration in the boron nitride films. The oxygen atoms saturate the dangling bonds. Moreover the B/N ratio extents the expected stoichiometric ratio due to the oxygen atoms at nitrogen sites. Received: 15 July 1997 / Revised: 29 January 1998 / Accepted: 2 February 1998     

Modification of the structure of cellulose triacetate films in the course of solvent vapor sorption

Intermolecular interaction and structure of cellulose triacetate films in the course of sorption of dimethylsulfoxide, nitromethane, and tetrachloroethane vapors were studied by Fourier IR spectroscopy, X-ray diffraction analysis, and polarization microscopy. Quantitative ratio of different types of intra- and intermolecular hydrogen bonds in polymer films was estimated. Changes in the structure of cellulose triacetate films in the course of solvent vapor sorption were discussed from the viewpoint of competition between the interchain interactions via OH and C=O groups of the macromolecules and their solvation with the solvent molecules.     

Polymer-nanoparticle complexes: from dilute solution to solid state

We report on the formation and the structural properties of "supermicellar" aggregates made from mineral nanoparticles and polyelectrolyte-neutral block copolymers in aqueous solutions. The mineral particles put under scrutiny are ultrafine and positively charged yttrium hydroxyacetate nanoparticles. Combining light, neutron, and X-ray scattering experiments, we have characterized the sizes and the aggregation numbers of the organic-inorganic complexes. We have found that the hybrid aggregates have typical sizes in the range of 100 nm and exhibit a remarkable colloidal stability with respect to ionic strength and concentration variations. Solid films with thicknesses up to several hundreds of micrometers were cast from solutions, resulting in a bulk polymer matrix in which nanoparticle clusters are dispersed and immobilized. It was found in addition that the structure of the complexes remains practically unchanged during film casting.     

Removal of permethrin pesticide from water by chitosan–zinc oxide nanoparticles composite as an adsorbent

Synthesis of chitosan–ZnO nanoparticles (CS–ZnONPs) composite beads was performed by a polymer-based method. The resulting bionanocomposite was characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) spectroscopy and infrared spectroscopy (FT-IR). Adsorption applications for removal of pesticide pollutants were conducted. The optimum conditions, including adsorbent dose, agitating time, initial concentration of pesticide and pH on the adsorption of pesticide by chitosan loaded with zinc oxide nanoparticles beads were investigated. Results showed that 0.5 g of the bionanocomposite, in room temperature and pH 7, could remove 99% of the pesticide from permethrin solution (25 ml, 0.1 mg L⁻¹), using UV spectrophotometer at 272 nm. Then, the application of the adsorbent for pesticide removal was studied in the on-line column. The column was regenerated with NaOH solution (0.1 M) completely, and then reused for adsorption application. The CS–ZnONPs composite beads appear to be the new promising material in water treatment application with 56% regeneration after 3 cycles.     

Rapid green synthesis of gold nanoparticles using Rosa hybrida petal extract at room temperature

This study reports a green method for the synthesis of gold nanoparticles using the aqueous extract of rose petals. The effects of gold salt concentration, extract concentration and extract quantity were investigated on nanoparticles synthesis. Gold nanoparticles were characterized with different techniques such as UV-vis spectroscopy, FT-IR spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, dynamic light scattering and transmission electron microscopy. Transmission electron microscopy experiments showed that these nanoparticles are formed with various shapes. FT-IR spectroscopy revealed that gold nanoparticles were functionalized with biomolecules that have primary amine group (-NH2), carbonyl group, -OH groups and other stabilizing functional groups. X-ray diffraction pattern showed high purity and face centered cubic structure of gold nanoparticles. Dynamic light scattering technique was used for particle size measurement, and it was found to be about 10nm. The rate of the reaction was high and it was completed within 5 min.     

Structural stability and phase transitions in WO3 thin films

Tungsten oxide (WO3) thin films have been produced by KrF excimer laser (lambda = 248 nm) ablation of bulk ceramic WO3 targets. The crystal structure, surface morphology, chemical composition, and structural stability of the WO3 thin films have been studied in detail. Characterization of freshly grown WO3 thin films has been performed using X-ray diffraction (XRD), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy (RS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) measurements. The results indicate that the freshly grown WO3 thin films are nearly stoichiometric and well crystallized as monoclinic WO3. The surface morphology of the resulting WO3 thin film has grains of approximately 60 nm in size with a root-mean-square (rms) surface roughness of 10 nm. The phase transformations in the WO3 thin films were investigated by annealing in the TEM column at 30-500 degrees C. The phase transitions in the WO3 thin films occur in sequence as the temperature is increased: monoclinic --> orthorhombic --> hexagonal. Distortion and tilting of the WO6 octahedra occurs with the phase transitions and significantly affects the electronic properties and, hence, the electrochemical device applications of WO3.     

Structural variety of CdS in films synthesized by vapor deposition polymerization

Poly(p-xylylene)—CdS (PPX—CdS) nanocomposite films with different thicknesses (～0.2, ～0.5, ～1, and ～1.5 μm) and concentrations of CdS from 5 to 90 vol.%, as well as single-component CdS and PPX films with various thicknesses were studied by X-ray diffraction. The films were synthesized on polished silicon or quartz substrates by low-temperature vapor deposition method. It was shown that CdS nanoparticles in PPX—CdS films, depending on their thickness and CdS content, can have an X-ray amorphous structure, a defect crystal structure (RCP structure), or a wurtzite-type crystal structure. Similar structures were observed for single-component CdS films of the corresponding thickness. The sizes of the coherent scattering regions of CdS were determined for some nanocomposite and single-component films. Poly(p-xylylene) in the studied nanocomposite films was characterized by an X-ray amorphous structure.