Au Phase Research Articles

Synthesis of Au/Co3O4/PVA hybrid nanocomposites via eco-friendly method based on pulsed laser ablation process for water treatment

A portable nanostructured nanocomposite film, based on cobalt oxide and gold nanoparticles (NPs) embedded in a polyvinyl alcohol structure (PVA), Au/Co3O4/PVA, was prepared via a novel way based on pulsed laser ablation to be applied as an effective catalytic degradation material for a hazardous chemical structure as nitro compounds. Au/Co3O4/PVA was investigated by the techniques of UV–Vis, FT-IR, SEM, and XRD. From XRD, the decrease in crystallinity of PVA is attributed to the intermolecular hydrogen bonding between PVA and Au/Co3O4. In addition, there are five interplanar peaks, with three shared peaks by both phases and one unique peak for each phase of Au and Co3O4. From FT-IR, the modes observed at a 500–1200 cm-1 wavenumber range correspond to the stretching vibration modes of Au/Co3O4. From UV–VIS, as the embedding of Co3O4 on Au-PVA structure increases, the energy band gap is shifted to a lower value. This is due to the embedding of Co3O4 NPs. From SEM, in the case of embedding PVA with Au NPs, the bright semi-spherical shape of the nanostructured materials has a bright semi-spherical light area. Moreover, in the case of the embedded PVA with Co3O4 NPs, the faint semi-spherical form of the nanostructured materials is discernible. Besides, the catalytic activity performance is tested for the degradation of 4-nitrophenol, which reveales that the reaction followed first-order kinetics, as indicated by linear regression analysis. The results shows that the sample completely convertes 4-nitrophenol to 4-aminophenol within 6 min.

Synthesis and performance of PdAu/ITO electrocatalysts in urea oxidation reaction

PdAu electrocatalysts were prepared in different atomic compositions supported on ITO by sodium Borohydride process. XRD results show intense crystalline peaks related to ITO, which may mask the appearance of less crystalline Pd or Au phases. Transmission results indicate agglomeration of palladium and gold nanoparticles on the support, a phenomenon compatible with metal oxide supports. Cyclic voltammograms in the absence of urea display characteristics commonly observed for PdAu electrodes, with an increase in oxygenated species compared to pure Pd or Au. Voltammograms in the presence of urea showed oxidation processes and lower current values, indicating catalyst deactivation processes. PdAu 75:25 demonstrated higher power density values compared to other prepared electrocatalysts, suggesting a synergy between Pd and Au for urea oxidation reaction.

Au–decorated TiO2 nanoparticle photoanode: synthesis, structural, optical properties and photoelectrochemical water splitting performance

This study presents a novel approach to synthesizing Au-decorated TiO2 (Au/TiO2) nanoparticles (NP) using a spin-coating method, showcasing significant advancements in photoanode development. The resulting Au/TiO2 NPs exhibit well-defined crystallite structures comprising Au and TiO2 phases, featuring Au NP sizes ranging from 2.61 nm to 6.10 nm. Notably, the energy bandgap of these Au-decorated TiO2 NPs demonstrates a discernible redshift of 3.22–3.02 eV across various Au concentrations (1%–20%). Photoluminescence spectra reveal three distinct emission peaks at room temperature in the 400–550 nm wavelength range. The water-splitting activity of the Au/TiO2 NPs is investigated through the photoelectrochemical cell (PEC) employing an electrolyte solution with 1.0 M KH2PO4/K2HPO4 buffer. The results demonstrate a substantial photocurrent density of 0.23 mA.cm–2 at a potential of 1.6 V (versus RHE) and a photoconversion efficiency of 0.1% at 0.52 V (vs. RHE), respectively. This pioneering study underscores the potential of Au/TiO2 NP photoanodes as key components in advancing sustainable energy technologies, particularly in the realm of efficient PEC water-splitting applications.

Unveiling the structural behavior of bimetallic AuCu/TiO2 catalysts in the CO oxidation: A combined in-situ spectroscopic and theoretical study

Bimetallic AuCu/TiO2 catalysts were thoroughly studied during the CO oxidation reaction via three in-situ spectroscopic techniques (FTIR, UV–Vis and Raman) and density functional theory (DFT) calculations. Samples were synthesized through the deposition–precipitation with urea (DPU) method, and ex-situ characterized by several techniques. The superior catalytic activity displayed by the AuCu/TiO2 sample was associated with the presence of nanoparticles in the form of heterodimers composed of the Au and CuXO phases in close interaction with the TiO2 support. In-situ DRIFTS results indicated that gold nanoparticles (NPs) presented some restructuration in the monometallic sample, while this event did not occur in the bimetallic one. The better stability on the AuCu/TiO2 catalyst was related to the partial migration of CuXO species to the surface of the NPs, also confirmed through in-situ UV–Vis spectroscopy. The favorable role played by the TiO2 reducibility was established through in-situ Raman spectroscopy. Moreover, findings obtained by DFT confirmed the experimentally evidenced structural modifications.

Crystallographic and electrical properties of mechanically rolled gold backed niobium target

This work demonstrates an excellent and high purity target film, realized by depositing uniformly thick mechanically rolled niobium (Nb) film over gold (Au) foil using indium (In) as adhesive layer (Nb/In/Au). The materials properties of the resulting foil in three layered Nb/In/Au structure, characterized using microscopic and spectroscopic techniques demonstrate presence of pure forms of the material contents and depict crystal phases of pure Au and Nb in Au and Nb/In/Au foils, respectively. This suggests the chemical inertness of Nb film towards oxidation during mechanical rolling and evidences formation of high purity Nb layer with precise crystallinity. The current-voltage (I–V) characteristics of Nb/In/Au foil measured at room temperature through a lateral device structure configuration with silver (Ag) top contacts exhibit ohmic conduction with surface resistivity of 2.5mΩm, indicating 127.3% increment after mechanical rolling of Nb on Au foil. The fabricated gold backed niobium target has been utilized in a recent nuclear level lifetime measurement experiment through Doppler shift attenuation method.

Aqueous Synthesis of Plasmonic Gold-Tin Alloy Nanoparticles.

This protocol describes the synthesis of Au nanoparticle seeds and the subsequent formation of Au-Sn bimetallic nanoparticles. These nanoparticles have potential applications in catalysis, optoelectronics, imaging, and drug delivery. Previously, methods for producing alloy nanoparticles have been time-consuming, require complex reaction conditions, and can have inconsistent results. The outlined protocol first describes the synthesis of approximately 13 nm Au nanoparticle seeds using the Turkevich method. The protocol next describes the reduction of Sn and its incorporation into the Au seeds to generate Au-Sn alloy nanoparticles. The optical and structural characterization of these nanoparticles is described. Optically, prominent localized surface plasmon resonances (LSPRs) are apparent using UV-visible spectroscopy. Structurally, powder X-ray diffraction (XRD) reflects all particles to be less than 20 nm and shows patterns for Au, Sn, and multiple Au-Sn intermetallic phases. Spherical morphology and size distribution are obtained from transmission electron microscopy (TEM) imaging. TEM reveals that after Sn incorporation, the nanoparticles grow to approximately 15 nm in diameter.

Investigating on the microstructure and optical properties of Au, Ag and Cu implanted TiN thin films: The effects of surface oxidation and ion-induced defects

In the present paper, the effects of metal ion implantation on the structural and optical properties of TiN thin films have been investigated. TiN films of 170 nm thickness were grown by d.c. reactive sputtering on Si (100) wafers and then irradiated at 5 × 1016 ions/cm2 with either Au, Ag, or Cu ions by using two different energies per each implanted metal. The results showed that as deposited TiN crystallizes in the form of a fcc cubic structure, with the crystallites preferentially oriented along the (111) plane. For all implanted layers, the cubic structure was preserved, but compared to as deposited TiN the crystallites were smaller and the lattice was contracted. These changes were correlated with the depth distribution of Au, Ag and Cu ions and assigned to implantation-induced damage that was larger when higher ion energies were used. High-resolution XPS spectra of the surface of as deposited sample showed the coexistence of TiN, TiO2 and TiOxNy phases and this was related to the surface oxidation of the films due to the exposure to air. After implantation, the results were almost similar for all metals, showing an increase in TiO2 contribution and the formation of pure metallic Au and Ag phases, while copper is in the Cu2+ state, which is attributed to Cu(II)-oxide and Cu(OH)2. The microstructural characteristics including defect formation, changes in crystallite size and lattice contraction, and also growth of different metallic phases during implantations were correlated with the findings of the optical characterization of the implanted films. For the as deposited film we found an energy gap of 2.91 eV, which was lower than the value typical for TiN. After implantation the gap was shifted to higher energies, while at the visible part of the region, the existence of additional energy levels, at photon energies below 2.9 eV was observed. Besides, all implanted films showed degraded photocatalytic activity compared to as deposited TiN, among which Cu-implanted samples exhibited the best photocatalytic performances. The lower photocatalytic activity of Au and Ag implanted films compared to Cu implantations was ascribed to larger structural defects and the formation of less favorable electronic states.

CO Oxidation Catalyzed by Au Dispersed on SBA-15 Modified with TiO2 Films Grown via Atomic Layer Deposition (ALD)

It has been established that gold, when in nanoparticle (NP) form and in contact with reducible oxides, can promote oxidation reactions under mild conditions. Here, we report results from our exploration of the catalytic oxidation of carbon monoxide using catalysts where Au NPs were combined with thin titanium oxide films deposited on SBA-15 using atomic layer deposition (ALD). Both orders of deposition, with TiO2 added either before or after Au dispersion, were tested for two titania film thicknesses amounting to about half and full TiO2 monolayers. The resulting catalysts were characterized using various techniques, mainly electron microscopy and N2 adsorption–desorption isotherms, and the kinetics of the oxidation of CO with O2 were followed using infrared absorption spectroscopy. A synergy between the Au and TiO2 phases as it relates to the bonding and conversion of CO was identified, the tuning of which could be controlled by varying the synthetic parameters. The ALD of TiO2 films proved to be an effective way to maximize the Au-TiO2 interface sites, and with that help with the activation of molecular oxygen.

Green Synthesis of Au-doped SnO 2 Nanoparticles Using Teucrium Polium Plant Extract for the Evaluation of Their Physicochemical and Antibacterial Properties

Background & Objective: The biological production of nanoparticles (NPs) is a technique that has garnered a lot of interest because it is inexpensive, straightforward, and friendly to the natural environment. This study explores the green synthesis of Au-doped SnO 2 NPs using Teucrium polium plant extract and evaluates their antimicrobial properties in comparison with two commonly used antibiotics.
 Materials & Methods: Initially, an extract of Teucrium polium was made using water, and then it was combined with solutions of tin (II) chloride dehydrate [SnCl 2 .2H 2 O] and gold (III) chloride trihydrate [HAuCl 4 .3H 2 O]. The crystal structure was studied using X-ray diffraction (XRD). The form, structure, and grain size of the NPs were analyzed using scanning electron microscope (SEM) and transmission electron microscope (TEM). The synthesized NPs were tested for their antibacterial properties.
 Results: The XRD and EDS analyses revealed that the SnO 2 : Au phase formed an average crystallite size of 22 nm and an Au dopant content of around 2%. The SEM and TEM investigations demonstrated that the NPs were formed in a regular and nanoscale manner, with diameters ranging from 25 to 30 nm. MIC and MBC of SnO 2 : Au NPs against the studied bacteria (S.aureus ATCC 43300, P.aeruginosa PAO1) were reported 9.6±0.13- 9.6±0.07 μg/mL and 25.9±11.5- 32.5±11.2 μg/mL.
 Conclusion: Green-synthesized NPs exhibit significant antimicrobial activity against both Gram-positive and Gram-negative bacteria, even at low concentrations. The NPs effectively eliminate bacteria and prevent biofilm formation.

Enhanced Plasmonic Photocatalysis of Au-Decorated ZnO Nanocomposites

The rapid development of technological processes in various industrial fields has led to surface water pollution with different organic pollutants, such as dyes, pesticides, and antibiotics. In this context, it is necessary to find modern, environmentally friendly solutions to avoid the hazardous effects on the aquatic environment. The aim of this paper is to improve the photocatalytic performance of zinc oxide (ZnO) nanoparticles by using the plasmonic resonance induced by covering them with gold (Au) nanoparticles. Therefore, we evaluate the charge carriers’ behavior in terms of optical properties and reactive oxygen species (ROS) generation. The ZnO-Au nanocomposites were synthesized through a simple chemical protocol in multiple steps. ZnO nanoparticles (NPs) approximately 20 nm in diameter were prepared by chemical precipitation. ZnO-Au nanocomposites were obtained by decorating the ZnO NPs with Au at different molar ratios through a reduction process. X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) confirmed the simultaneous presence of hexagonal ZnO and cubic Au phases. The optical investigations evidenced the existence of a band-gap absorption peak of ZnO at 372 nm, as well as a surface plasmonic band of Au nanoparticles at 573 nm. The photocatalytic tests indicated increased photocatalytic degradation of the Rhodamine B (RhB) and oxytetracycline (OTC) pollutants under visible light irradiation in the presence of ZnO-Au nanocomposites (60–85%) compared to ZnO NPs (43%). This behavior can be assigned to the plasmonic resonance and the synergetic effects of the individual constituents in the composite nanostructures. The spin-trapping experiments showed the production of ROS while the nanostructures were in contact with the pollutants. This study introduces new strategies to adjust the efficiency of photocatalytic devices by the combination of two types of nanostructures with synergistic functionalities into one single entity. ZnO-Au nanocomposites can be used as stable photocatalysts with excellent reusability and possible industrial applications.

Catalytic Synthesis of Tartaric Acid from Glucose and Gluconic Acid over AuPt/TiO2 Catalysts: Studies on Catalyst Structure–Performance Dependency

Replacing fossil-derived tartaric acid (TA) with sugar-based TA provides a greener route for synthesizing bioplasticizers. However, the detailed mechanism involving C–H and C–C activation of sugar substrates in this area is still under debate. In this work, the plausible reaction mechanism for activation of −CHO (oxidation) and −COOH (decarboxylation) groups in glucose and gluconic acid molecules in the presence of bimetallic AuPt/TiO2 catalysts has been studied and revealed using the UV–vis technique. It is found that Pt and Au phases in bimetallic catalysts selectively promote C–H and C–C cleavage reactions through σ extraction (n−π*) and a π–π (π–π*) coordination mechanism, respectively. The Au2Pt2/TiO2 (Au/Pt: 1/1 atomic ratio) catalyst displays remarkable activity for primary conversion of glucose to gluconic acid (TOF ∼ 20,260 h–1 at 110 °C). Meanwhile, consecutive conversion of gluconic acid to TA can be selectively accelerated by the Au1Pt2/TiO2 (TOF: 3,159 h–1) catalyst. Thus, a record high TA production rate of 12.3 mol/h/molmetal was achieved in this work. Process design and the purification of product mixtures to obtain high quality TA were also proposed and validated at the laboratory scale. The outcome in this work will provide insights for aqueous phase oxidation for synthesis of various valuable sugar-derived carboxylic acids.

Abnormal in-plane epitaxy and formation mechanism of vertically aligned Au nanopillars in self-assembled CeO2-Au metamaterial systems.

Metamaterials present great potential in the applications of solar cells and nanophotonics, such as super lenses and other meta devices, owing to their superior optical properties. In particular, hyperbolic metamaterials (HMMs) with exceptional optical anisotropy offer improved manipulation of light-matter interactions as well as a divergence in the density of states and thus show enhanced performances in related fields. Recently, the emerging field of oxide-metal vertically aligned nanocomposites (VANs) suggests a new approach to realize HMMs with flexible microstructural modulations. In this work, a new oxide-metal metamaterial system, CeO2-Au, has been demonstrated with variable Au phase morphologies from nanoparticle-in-matrix (PIM), nanoantenna-in-matrix, to VAN. The effective morphology tuning through deposition background pressure, and the corresponding highly tunable optical performance of three distinctive morphologies, were systematically explored and analyzed. A hyperbolic dispersion at high wavelength has been confirmed in the nano-antenna CeO2-Au thin film, proving this system as a promising candidate for HMM applications. More interestingly, a new and abnormal in-plane epitaxy of Au nanopillars following the large mismatched CeO2 matrix instead of the well-matched SrTiO3 substrate, was discovered. Additionally, the tilting angle of Au nanopillars, α, has been found to be a quantitative measure of the balance between kinetics and thermodynamics during the depositions of VANs. All these findings provide valuable information in the understanding of the VAN formation mechanisms and related morphology tuning.

Phase constitution and glass formation of U-Pd-Ni-Si alloys

In order to explore U-based alloys having high glass forming ability (GFA), a series of U-Pd-Ni-Si alloys with 60% U were designed on the basis of the eutectic features of U-Ni and U-Pd base systems together with the Si addition. Their ingots and ribbons were prepared by arc-melting and melt-spinning methods and further examined to reveal the phase constitution and amorphization behavior mainly by X-ray diffraction and differential scanning calorimetry. The results show that these alloys can form U6Ni type (NU) and/or α-U type (AU) phases under a quasi-equilibrium or equilibrium condition and amorphous phase, completely for most of them, under a non-equilibrium condition. A possibly Pd-based glassy phase seemed to unexpectedly arise in two Pd-rich alloy ingots, which would be the first observation of glass formation in U-based alloys solidified at low cooling rates. Within all the U-Pd-Ni-Si alloys, the ones with a big Ni/Pd ratio, thus tending to get NU phase, can achieve substantially higher GFA than the others with small Ni/Pd and a tendency to AU phase. Especially, U60Pd7.5Ni25Si7.5 and U60Pd5Ni25Si10 displayed firstly the reduced glass transition temperature Tg/TL of > 0.6 and a wide supercooled liquid region of ~100 K, exhibiting a GFA level superior to the whole reported U-based metallic glasses (MGs) and comparable to some traditional bulk MGs. All the yields reflect that Ni plays stronger roles in both compounding with U and the glass formation than Pd and Si in these alloys, and also offer guidance for creating novel U-based metallic materials including better MGs.

Combinatorial sputter deposition of ultrathick Au-Bi alloy films

Gold-bismuth alloys are of interest as catalysts and catalytic sensing systems, electrochemical sensors, superconductors, and hohlraums for magnetically assisted inertial confinement fusion implosions. Radiation-hydrodynamics simulations with the Lasnex code of laser-driven hohlraums predict higher x-ray drive from Au-Bi alloys compared with cases of Au-Ta or pure Au and Bi hohlraums. Here, we use direct current magnetron sputtering in Ar gas, with co-sputtering from two elemental targets, to deposit Au-Bi alloys with Bi content of 9–77 at.% and thicknesses up to ∼20 µm. Films are characterized by a combination of x-ray diffraction, Rutherford backscattering, scanning electron microscopy, substrate-curvature-based residual stress, and electronic transport measurements. Experiments are complemented by Monte Carlo simulations of ballistic sputtering and gas phase transport of depositing species and Ar gas atoms. Results show that all films are polycrystalline, with three distinct compositional regimes dominated by Au, Au2Bi, and Bi crystallographic phases. A metallic behavior of the temperature dependence of electrical resistivity is observed for all the films. Films with Bi content above ∼30 at.% exhibit porosity, which is tolerable to hohlraum x-ray drive based on Lasnex simulations.

Single-Step Fabrication of Au-Fe-BaTiO3 Nanocomposite Thin Films Embedded with Non-Equilibrium Au-Fe Alloyed Nanostructures.

Nanocomposite thin film materials present great opportunities in coupling materials and functionalities in unique nanostructures including nanoparticles-in-matrix, vertically aligned nanocomposites (VANs), and nanolayers. Interestingly the nanocomposites processed through a non-equilibrium processing method, e.g., pulsed laser deposition (PLD), often possess unique metastable phases and microstructures that could not achieve using equilibrium techniques, and thus lead to novel physical properties. In this work, a unique three-phase system composed of BaTiO3 (BTO), with two immiscible metals, Au and Fe, is demonstrated. By adjusting the deposition laser frequency from 2 Hz to 10 Hz, the phase and morphology of Au and Fe nanoparticles in BTO matrix vary from separated Au and Fe nanoparticles to well-mixed Au-Fe alloy pillars. This is attributed to the non-equilibrium process of PLD and the limited diffusion under high laser frequency (e.g., 10 Hz). The magnetic and optical properties are effectively tuned based on the morphology variation. This work demonstrates the stabilization of non-equilibrium alloy structures in the VAN form and allows for the exploration of new non-equilibrium materials systems and their properties that could not be easily achieved through traditional equilibrium methods.

Electromigration of Au on Ge(111): Adatom and island dynamics

We have observed the motion of two-dimensional phases of Au on Ge(111) under an electric bias by in operando low energy electron microscopy. Electromigration of Au results in a complex dynamics that depends on the nature of the involved mobile phases: two-dimensional adatom gas or two-dimensional islands. We show that the Au adatoms move at the surface in the direction opposite to the electric current. The wind force induced by the electron flow is measured: the effective valence of Au (${Z}^{*}=\ensuremath{-}82\ifmmode\pm\else\textpm\fi{}15$) is directly deduced from the coverage profile of a Au adatom gas spatially retained by a strong Erlich-Schwoebel barrier at a downhill step edge. The velocity of two-dimensional Au islands versus island size reveals a mass transport by terrace diffusion inside the islands. The energy barrier for diffusion above 820 K is $1.16\ifmmode\pm\else\textpm\fi{}0.08$ eV and it strongly increases up to $3.1\ifmmode\pm\else\textpm\fi{}0.6$ eV below. We attribute this change of regime to a modification of diffusing species from single Au atoms at high temperature to Au clusters at low temperature. The strong shape fluctuations of the 2D islands is consistent with a nearly vanishing line tension of $1.2\ifmmode\pm\else\textpm\fi{}0.4$ meV/nm at 800 K.

Evolution of Λ polarization in the hadronic phase of heavy-ion collisions

Using the ampt$+$music$+$urqmd hybrid model, we study the global and local spin polarizations of $\mathrm{\ensuremath{\Lambda}}$ hyperons as functions of the freeze-out temperature of the spin degree of freedom in the hadronic phase of Au$+$Au collisions at $\sqrt{{s}_{NN}}=19.6$ GeV. Including contributions from both the thermal vorticity and thermal shear of the hadronic matter, we find that with the spin freeze-out temperature dropping from the hadronization temperature of 160 MeV to 110 MeV at the kinetic freeze-out, both the global and local spin polarizations of $\mathrm{\ensuremath{\Lambda}}$ hyperons due to the thermal vorticity decrease by a factor of 2, while those due to the thermal shear decrease quickly and become negligibly small at 140 MeV. Our results thus suggest that it is important to take into account the evolution of the spin degree of freedom in the hadronic stage of relativistic heavy-ion collisions when theoretically predicted global and local $\mathrm{\ensuremath{\Lambda}}$ spin polarizations are compared with the experimental measurements.

Green Nanotechnology From Plant Extracts Synthesis And Characterization Of Gold Nanoparticles

The use of plants in green synthesis nanoparticles is becoming increasingly popular when it is easy to manage and has a wide range of metabolites such as antioxidants, nuclear materials, and vitamins. The purpose of this experiment was to know the effects of green tea and zirrorine and palm coconut water as a reducing agent and stabilizer on the synthesis of gold nanoparticles. Gold nanoparticles are determined by spectroscopy, UV absorption, X-ray diffraction (XRD), dynamic light processing (DLS), and electronic electronic analysis (TEM). Their physical stability is measured using a UV-Vis spectrophotometer several days during storage at room temperature. We have noted that green chemical processes for obtaining gold nanoparticles do not require the production of external chemicals for the stability of nanoparticles. Measurements indicate that plasma waveforms occur at about 530 nm. Gold nanoparticles have been shown to have X-rays and rich Au (phases) presence. TEM analysis has generated the same nanoparticles and agglomerates. Differences in nanoparticle size and shape are limited. The potential of AUNP zeta in the presence of eel tea is -33 mm, showing the stability of synthetic nanoparticles.

Gold-Nanoparticle-Deposited TiO2 Nanorod/Poly(Vinylidene Fluoride) Composites with Enhanced Dielectric Performance.

Flexible dielectric polymer composites have been of great interest as embedded capacitor materials in the electronic industry. However, a polymer composite has a low relative dielectric permittivity (ε′ < 100), while its dielectric loss tangent is generally large (tanδ > 0.1). In this study, we fabricate a novel, high-permittivity polymer nanocomposite system with a low tanδ. The nanocomposite system comprises poly(vinylidene fluoride) (PVDF) co-filled with Au nanoparticles and semiconducting TiO2 nanorods (TNRs) that contain Ti3+ ions. To homogeneously disperse the conductive Au phase, the TNR surface was decorated with Au-NPs ~10–20 nm in size (Au-TNRs) using a modified Turkevich method. The polar β-PVDF phase was enhanced by the incorporation of the Au nanoparticles, partially contributing to the enhanced ε′ value. The introduction of the Au-TNRs in the PVDF matrix provided three-phase Au-TNR/PVDF nanocomposites with excellent dielectric properties (i.e., high ε′ ≈ 157 and low tanδ ≈ 0.05 at 1.8 vol% of Au and 47.4 vol% of TNRs). The ε′ of the three-phase Au-TNR/PVDF composite is ~2.4-times higher than that of the two-phase TNR/PVDF composite, clearly highlighting the primary contribution of the Au nanoparticles at similar filler loadings. The volume fraction dependence of ε′ is in close agreement with the effective medium percolation theory model. The significant enhancement in ε′ was primarily caused by interfacial polarization at the PVDF–conducting Au nanoparticle and PVDF–semiconducting TNR interfaces, as well as by the induced β-PVDF phase. A low tanδ was achieved due to the inhibited conducting pathway formed by direct Au nanoparticle contact.

Quantitation of the production cross-section and transition probabilities of the L and M X-ray series in the Au(0) and Au(3+) atomic environments using Total-reflection X-ray fluorescence

This work presents the quantitation of the effects that different chemical environments induced in the transition probabilities of their L and M series spectra working in the particular geometrical and analytical conditions imposed by the Total-reflection X-Ray Fluorescence (TXRF) spectrometry. The evaluated chemical environments were metallic Au(0) and chloride Au(3+) phases, with different oxidation states and different crystal field surroundings. Lines Ll, Lα, Lη, Lβ, Lγ and the overlapped Mα and Mβ, named as Mαβ, were evaluated. Transition probabilities and production cross-section ratios were calculated for both gold environments. The absolute transition probabilities were evaluated as the intensity of each line versus the sum of the set of intensities investigated, i.e. Au L and M lines. Achieved results show significant differences between both gold chemical states and environments higher than uncertainties. TXRF has proven to be sensitive to the transition probabilities induced by different atomic environments. Intensity variations with decrements of −7.3% for Lβ line and increments of 96% for Mαβ lines were measured. In parallel, the same phenomenon observed for gold has been observed qualitatively and for the first time by TXRF in three different phases of lead, metallic Pb(0), nitrate Pb(2+) and sulfide Pb(2+). The achieved results corroborate the ability of TXRF to investigate the, different oxidation states, differents crystalline phases, different environments and in a general way, the different chemical surrounding effect. Finally, the existence of a possible enhancement effect in the Au Mαβ line due to a secondary excitation by the presence of Cl Kα secondary excitation was also checked. Results indicate that the observed change of Mαβ intensities between metallic gold and gold chloride are not due to the Cl Kα enhancement effect.