Solid-state reference electrodes based on carbon nanotubes and polyacrylate membranes

A novel potentiometric solid-state reference electrode containing single-walled carbon nanotubes as the transducer layer between a polyacrylate membrane and the conductor is reported here. Single-walled carbon nanotubes act as an efficient transducer of the constant potentiometric signal originating from the reference membrane containing the Ag/AgCl/Cl− ions system, and they are needed to obtain a stable reference potentiometric signal. Furthermore, we have taken advantage of the light insensitivity of single-walled carbon nanotubes to improve the analytical performance characteristics of previously reported solid-state reference electrodes. Four different polyacrylate polymers have been selected in order to identify the most efficient reservoir for the Ag/AgCl system. Finally, two different arrangements have been assessed: (1) a solid-state reference electrode using photo-polymerised n-butyl acrylate polymer and (2) a thermo-polymerised methyl methacrylate:n-butyl acrylate (1:10) polymer. The sensitivity to various salts, pH and light, as well as time of response and stability, has been tested: the best results were obtained using single-walled carbon nanotubes and photo-polymerised n-butyl acrylate polymer. Water transport plays an important role in the potentiometric performance of acrylate membranes, so a new screening test method has been developed to qualitatively assess the difference in water percolation between the polyacrylic membranes studied. The results presented here open the way for the true miniaturisation of potentiometric systems using the excellent properties of single-walled carbon nanotubes

Bilateral multifocal Warthin's tumors in upper neck lymph nodes. report of a case and brief review of the literature

Cystadenolymphomas (Warthin's tumors) are the second most frequent lesions of the parotid gland. Due to their benign clinical behavior, the low rates of recurrence and malignant transformation they were classified as tumor-like lesions. In addition, a polyclonal growth of the epithelial components of the tumor could be detected. Warthin's tumors occur bilateral in 7-10%, whereas a multifocal appearance is extremely rare. Even if the pathogenesis is still unclear a heterotopia of salivary tissue during embryogenesis is the most likely explanation for the origin of these tumors in the upper neck and periparotideal region. Here we present a rare case of bilateral, multifocal, extraglandular Warthin's tumors in lymph nodes of the upper neck and give a brief review of the literature. If a primary malignancy can be excluded by a careful staging procedure prior to the operation an isolated excision of the lesions of the neck is the adequate treatment

Annealing impacts on microstructural, optical, mechanical properties of sputtered CrN thin film coatings: Experimental studies and finite element modeling

Chromium nitride (CrN) coatings were deposited by magnetron sputtering onto Si(100) substrates. The coatings were then annealed at different temperatures (500–800 °C in steps of 100 °C) in air for 1 h. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, nanoindentation tests and finite element modeling (FEM) were conducted in order to investigate their structural, morphological, optical and mechanical properties. XRD patterns show that the crystallinity of the CrN phase increases with the rise in annealing temperatures together with its preferred orientations along (111) and (200) diffraction planes. The lattice constants were slightly reduced from 4.19 to 4.11 nm at 800 °C. The lattice micorstrains and residual stresses were also reduced as the annealing temperatures rose as a result of reduced defects, dislocations and vacancies. Smooth grain-like surfaces with grain sizes ranging between ∼50 and 250 nm were confirmed by FESEM micrographs. XPS studies indicated the existence of Cr and N on the coating systems. Optical studies showed that with the rise in annealing temperature of up to 700 °C, the solar absorptance of CrN coatings is increased from 61% to 89% and slightly decreased at 800 °C, while the optical band-gap energy dropped from 2.62 to 1.38 eV and slightly increased to 1.48 eV at 800 °C. A gradual increase of dielectric constants of CrN films were realized with the subsequent annealing progression. Nanoindentation results indicated that as the annealing progresses, the hardness and elastic modulus values are lowered

Evidence for fungi and gold redox interaction under Earth surface conditions

Microbial contribution to gold biogeochemical cycling has been proposed. However, studies have focused primarily on the influence of prokaryotes on gold reduction and precipitation through a detoxification-oriented mechanism. Here we show, fungi, a major driver of mineral bioweathering, can initiate gold oxidation under Earth surface conditions, which is of significance for dissolved gold species formation and distribution. Presence of the gold-oxidizing fungus TA_pink1, an isolate of Fusarium oxysporum, suggests fungi have the potential to substantially impact gold biogeochemical cycling. Our data further reveal that indigenous fungal diversity positively correlates with in situ gold concentrations. Hypocreales, the order of the gold-oxidizing fungus, show the highest centrality in the fungal microbiome of the auriferous environment. Therefore, we argue that the redox interaction between fungi and gold is critical and should be considered in gold biogeochemical cycling

N-donor functionalised ionic liquids: their thermo-physical, electrochemical and transport properties

Two functionalised room temperature ionic liquids 1-ethyl-1,4-dimethyl piperazinium bis{(trifluoromethyl)sulfonyl}amide (1) and 1-(2-dimethylaminoethyl)dimethylethylammonium bis{(trifluoromethyl)sulfonyl}amide (2) were synthesised. Properties measured were the electrochemical window, melting point, glass and decomposition temperatures, density, thermal expansivity, viscosity, conductivity and ion self-diffusion coefficients. These were compared with those of 1-butyl-1-methylpyrrolidinium bis{(trifluoromethyl)sulfonyl}amide (3), as a benchmark salt. A marked difference in thermal stability was observed between the two tertiary amine functionalised salts and the non-functionalised benchmark system, the former being up to 170 K less stable than the latter. The compounds of this study also have narrower electrochemical windows than structural counterparts lacking a tertiary amine function, by about 3 V. The ion self-diffusion coefficients and conductivities are higher for the open chain (2) than for the cyclic (1) at each temperature, and the viscosity less. The transport properties are examined using fractional Stokes – Einstein and Nernst – Einstein relations and the velocity correlation coefficients (VCC) calculated. The fractional Stokes – Einstein exponents range from (0.95 to 0.98). The Nernst – Einstein equation deviation parameters (Δ) are such that the mean of the like-ion VCCs is greater than that for the unlike ions: Δ = (0.36 and 0.42) respectively, values typical for ionic liquids. The VCCs are analysed in terms of the anti-correlated motion of ions, a feature of one-component molten salts, that contrasts with the correlated motions of ions in electrolyte solutions. According to the VCC analysis, the distinct diffusion coefficients follow the order D--

A holistic analysis of surface, chemical bonding states and mechanical properties of sol-gel synthesized CoZn-oxide coatings complemented by finite element modeling

This article presents a comprehensive study on surface chemical bonding states, morphological features, mechanical properties, finite element modeling, and water contact angle measurements of wet chemical based dip-coated CoZn-oxide thin film coatings. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Nanoindentation, finite element method (FEM) modeling, and drop shape analysis techniques were used to carry out the detailed measurements. AFM studies showed that the surface roughness values of all the coatings sturdily increased with the increase in sol concentrations. The gradual increase in sol concentrations and annealing temperature also had a remarkable influence over the Co, and Zn-contents of these coatings given by XPS analysis. The deconvolution of Co 2p3/2 photoelectron lines revealed the formation of Co(OH)2, CoO, Co2O3, and Co3O4 phases from the coatings surface while low intensity satellite peaks developed due to a partial spinel lattice structure of Co-ions. The occurrence of Co3O4, CoO, and ZnO phases were also confirmed from the deconvolution of O 1s photoelectron lines. The elastic modulus, E, of CoZn-oxide thin film coating, varied within the range of 43.7–69.2 GPa was comparable with that in CoCuO thin film coatings. The maximum stress level induced was estimated to be in the range of 4.0–6.5 GPa. However, as the thickness of the coatings is increased, the maximum stress level slightly decreased. The coatings were moderately hydrophobic

Electrochemically substituted metal phthalocyanines, e-MPc (M = Co, Ni), as highly active and selective catalysts for CO(2) reduction

Metal-oxide nanoclusters (NCs) such as FeOₓ, CoOₓ, and NiOₓ are incorporated into iron phthalocyanine (FePc) supported on graphene, MOₓ/FePc, via a facile self-assembly method. MOₓ/FePc electrocatalysts show high activity, selectivity and stability for the electrochemical CO₂ reduction reaction (CO₂RR) as compared with the corresponding metal phthalocyanines, i.e., FePc, CoPc and NiPc, under identical test conditions. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy reveals that MOₓ/FePc undergoes a metal ion replacement of the iron center of Pc, forming electrochemically substituted metal Pc, e-MPc where M = Co and Ni, co-existing with the replaced FeOₓ nanoparticles (NPs) in the vicinity of the e-MPc. The results indicate that the e-MPc with in situ dispersed FeOₓ NPs, FeOₓ/e-CoPc and FeOₓ/e-NiPc exhibits excellent activity, high selectivity and stability for the CO₂RR.Yi Cheng, Jean-Pierre Veder, Lars Thomsen, Shiyong Zhao, Martin Saunders, Raffaella Demichelis, Chang Liu, Roland De Marco and San Ping Jian

Sol-gel derived ITO-based bi-layer and tri-layer thin film coatings for organic solar cells applications

In this investigation, ITO-based bi-layer and tri-layer thin film coatings (~130 nm) were synthesized via a sol-gel spin-coating process and annealed at 500 °C. Thin layers of Au, Au-NPs, Ag-NPs and AgO were inserted underneath ITO films to form bi-layer thin film systems and/or encapsulated between two thin ITO layers to form tri-layer thin film systems. The effects of incorporating these layers with ITO thin films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), UV–Vis spectroscopy, four-point probes and Hall effect. XRD results confirmed the presence of a body-centred cubic structure of indium oxide for all synthesized ITO-based coatings with an average grain size ~30 nm. FESEM images of all fabricated films revealed the formation of dense surfaces with grain-like morphologies confirming the formation of a polycrystalline structure of ITO. Optical studies on the Ag-NPs and Au-NPs colloidal solutions resulted in absorption peaks featured at wavelengths 405 and 531 nm, indicating the formation of 10–14 nm and 48 nm Ag and Au nanoparticles, respectively. The highest optical transparency and band gap energy were found to be ~91.5% and 3.75 eV for (AgO)I and (I(AgO)I) thin films, respectively. The lowest electrical resistivity of 1.2 × 10−4 Ω·cm, along with the highest carrier concentration of 11.4 × 1020 cm−3 and mobility 40 cm2/V.s were obtained from the IAuI thin film. An improvement in the power conversion efficiency (PCE) from 3.8 to 4.9% was achieved in an organic solar cell by replacing the conventional pure ITO electrode with the (I(AgO)I) electrode

Physico-chemical properties of CrMoN coatings - combined experimental and computational studies

In this study, Cr−Mo−N thin films with different Mo contents were synthesised via closed field unbalanced magnetron sputtering ion plating. The effects of Mo content on the microstructure, chemical bonding state, and optical properties of the prepared films were investigated by X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy, and ultraviolet-visible spectrophotometry. XRD results determined the face centered cubic (fcc) structure of pure CrN film. The incorporation of molybdenum (Mo) in the CrN matrix was confirmed by both XRD and XPS analyses. The CrMoN coatings demonstrate various polycrystalline phases including CrN, γ-Mo2N, Cr with oxides layers of MoO3, CrO3, and Cr2O3. Microstructural results of the Cr-Mo-N coatings show that the grain size increased with an increase in Mo content due to the formation of MoN phase, in which the Mo atoms interact with N atoms around the grain boundaries of the CrN phase. XPS investigations confirmed the presence of Cr, Mo, N, C and O elements in the studied coatings. The optical results revealed that the synthesised coatings exhibit low reflection magnitudes in the visible region of the solar spectrum indicating good antireflection surfaces. Mo doped thin coatings improve the solar absorptance by ~76% in the wavelength range of 200–800 nm with a low thermal emittance of ~ 20% in the infrared range (up to 4000 nm). Furthermore, by applying density functional theory, the computational simulation provides similar trends as the experimental finding of absorption coefficient in the wavelength range