Improving the adhesion of polymethacrylate thin films onto indium tin oxide electrodes using a silane-based “Molecular Adhesive”

Indium tin oxide (ITO) is the most commonly used transparent conducting substance. It has been used in numerous applications such as light-emitting diodes. In most applications and studies, the ITO surface is further coated with additional layers. The interface between the ITO and the coating is of utmost importance since it affects the physical and chemical properties of the final device. Improving the adhesion between ITO and a coating layer can be achieved by applying a “molecular adhesive” as an inter-phasing molecular layer. In this study, we used 3-(trimethoxysilyl)propyl methacrylate as a “molecule adhesive” for better connection between ITO and a polymethacrylate layer. The samples were studied by electrochemistry, contact angle goniometry, atomic force microscopy, and nano scratch microscopy. These studies clearly show that a simple silanization process formed a thin molecular adhesive layer, which did not influence the physical and chemical properties of the final coated electrode and at the same time increased significantly the adhesion between the ITO and the polymethacrylate coating.

     

Modified procedure for the sol–gel processing of indium–tin oxide (ITO) films

Dispersions of crystalline nanoscaled ITO and solutions of amorphous precursors were used for the preparation of transparent conductive films on glass both by large area dip-coating (30 × 30 cm²) and pad-printing. The advantages of both types of coating materials regarding single layer thickness and conductivity were combined by a coating-infiltration procedure. The resulting films showed a specific resistivity down to 1.77 10E−03 Ω cm after treatment in reducing atmosphere and an increased resistance to subsequent storage in air.     

Mediated spectroelectrochemical determination of holo-transferrin reduction potential using a flow cell with disposable screen-printed indium‑tin oxide electrode

A convenient spectroelectrochemical method for the determination of holo-transferrin reduction potential is described. All materials and accessories are commercially available and the results are in agreement with previous reports that required custom-built hardware. The method requires minimal preparation with simple sample handling, small solution volume, cost-effective electrode replacement and automated measurement. This method can easily be applied to the study of similar systems in aqueous media and might be of particular importance in the momentous field of glycomics, where large numbers of protein isoforms need to be characterized.     

Effect of sintering temperature on the structural, optical and electrical properties of sol–gel derived indium oxide thin films

Sol gel derived indium oxide, In₂O₃; films were prepared by spin coating technique. The films were dried and sintered at different sintering temperatures (300, 400, 450 and 500 °C) in air. The effect of sintering temperature on the structural, optical and electrical properties of In₂O₃ thin films was studied. The morphology and structure of the films were analyzed by scanning electron microscope and X-ray diffraction. The films showed a bcc structure that changes its 400-preferential orientation to 222 orientation as the sintering temperature increases from 300 to 500 °C. The optical behavior of the films was studied by measuring the transmission spectra in the wavelength range 200–2,500 nm. Different optical models have been proposed for fitting the transmittance data and simulate the optical constants as well as the film thickness of In₂O₃ films. The best fitting of the data was obtained by combining the classical Drude and OJL models coupled with the Bruggeman effective medium approximation. The optical parameters of Drude model (plasma frequency and damping constant) are used calculate the electrical properties of the films. The calculated values of the electrical sheet resistance were compared with those measured experimentally by four probes. The correlation between the film orientation change and its optical and electrical properties was discussed.     

Structural,electrical and optical properties of tin doped cadmium oxide thin films obtained by sol–gel

Transparent and conducting tin doped cadmium oxide thin films were obtained by mixing cadmium oxide and tin oxide precursor solutions by the sol–gel method. Different tin contents in solution were studied: 0, 0.5, 1, 2, 3, 5 and 10 at.%. The films were sintered at 550 °C and, after that, annealed in N₂/H₂ gas mixture, in order to decrease their resistivity. X-ray diffraction patterns showed that doping of tin diminishes the [111] light preferred orientation of films and provokes a decrease of the average crystallite size from 30 to 12 nm. Atomic force microscopy images revealed morphological changes with the addition of tin content. All the films showed a high transmission around 75 % in the 600 < λ < 1,700 nm range and a shift of the absorption edge towards the blue region as the tin concentration was increased. The cadmium oxide films doped with 1 at.% of tin showed the lowest resistivity of 5.7 × 10^?4 Ω cm and a band gap energy value of 2.7 eV. For their characteristics, these CdO:Sn films are good candidates as transparent conductive electrodes in CdS/CdTe and CdS/CIGS type solar cells.     

Comparison of the influence of titanium and chromium adhesion layers on the properties of sol–gel derived NKN thin films

Lead-free (Na_0.5K_0.5)NbO₃ (NKN) thin films were prepared on Pt/X/SiO₂/Si substrates (with the adhesion promoters X = Ti, Cr) by a sol–gel process with and without post-annealing treatment. The effect of the diffusion of the adhesion layer elements Ti and Cr into the NKN film was analysed by secondary ion mass spectrometry, scanning electron microscopy pictures, X-ray diffraction (XRD), and leakage current measurements. It turned out that Cr diffuses into the films to a higher extent than Ti. The high amount of Cr diffusion led to the formation of a secondary phase, as seen in the XRD pattern, and to pore formation on the surface of the NKN films. In contrast, the films with Ti adhesion layer were single phase NKN without pore formation. Also, the leakage current measurements showed a strong influence of the Cr diffusion. The leakage current of the films with Cr adhesion layer was about four orders of magnitude higher than that of the films with Ti adhesion layer. The study shows the strong influence of the adhesion layer of the substrate on the properties of NKN films.     

Optical and structural properties of aluminium oxide thin films prepared by a non-aqueous sol–gel technique

Clear aluminium oxide sols without precipitation were synthesized via a non-aqueous sol–gel technique using three different alcohols (ethanol, isopropanol and n-butyl alcohol) as solvent, aluminium sec-butoxide as a precursor and acetyl acetone as a chelating agent. Although all sols could be successfully used to prepare thin films, the most stable one was prepared with n-butyl alcohol. Highly transparent, homogenous and amorphous aluminium oxide thin films were obtained on Si substrates after a heat treatment at 500 °C. X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared absorption (FT-IR) spectroscopy revealed all films were hydroxide free. The optical and structural properties of the films were particularly investigated. Any significant difference except from thickness on the film properties was not observed by changing the alcohol. Refractive index was used as an indication of the porosity of the films and ranged from 1.54 to 1.60.     

Distereoselective one-pot synthesis of pyrimidopyrimidines using sulfated tin oxide as a reusable catalyst： An extension of Biginelli-type reaction

The Biginelli-type compounds 4,5,8a-triarylhexahydropyrimido[4,5-d]pyrimidine-2,7（1H,3H）-diones were synthesized by a one-pot three-component reaction using sulfated tin oxide as a reusable catalyst. This method has the advantages of high yields, short reaction time, simple starting materials and reusability of catalyst for several times.     

Comparative characterisation of zinc oxide thin films prepared from zinc acetate with or without water of hydration via the sol–gel method

Zinc oxide thin films were prepared using either zinc acetate dihydrate or anhydrous zinc acetate via the sol–gel method. Comparative characterisation of the crystallographical, morphological, optical/spectroscopical and electrical properties of the so-obtained films was performed. The idea of one- (in the case of the anhydrous precursor), and two- (in the other case) stage hydrolysis/condensation was postulated, which was supported by the characterisation results. The film prepared using the anhydrous precursor had a more pronounced c-axis crystal orientation preference, with a larger average crystallite size and more porous morphology. The transparency of this film was significantly lower over the UV/visible region due to its more porous morphology, which also resulted in lower intensity of the ‘near band edge emission’, and higher electrical resistivity. The overall results also suggested that anhydrous zinc acetate could be employed as a precursor for the sol–gel synthesis of zinc oxide thin films, which might have potential advantages in microelectronic and optoelectronic applications.     

Photoemission study on the valence band of a β-FeSi2 thin film using synchrotron radiation

Resonant and constant-initial state photoemission spectroscopies using synchrotron radiation were applied to investigate the valence-band electronic structure of a semi-conducting β-type iron-disilicide (β-FeSi(2)) thin film. The results clearly indicated that the component elements, iron (Fe) and silicon (Si), contribute differently to the valence band features; the Fe 3d orbitals mainly concentrate in the top region of the valence band while the Si 3s and 3p orbitals spread over the wide region of the valence band. The β-FeSi(2) thin film showed a typical p-type semi-conducting nature with a work function of 4.78 eV. The β-FeSi(2) film showed the Fe M(1)VV Auger lines around the kinetic energy of 88 eV. It would be expected from these observations that there exist strong interactions between iron and silicon atoms in the β-FeSi(2) film resulting in orbital mixing and band formation.     

Improving the fluorometric determination of the cancer biomarker 8-hydroxy-2′-deoxyguanosine by using a 3D DNA nanomachine

The authors describe a fluorometric method for improving the determination of the cancer biomarker 8-hydroxy-2′-deoxyguanosine (8-OHdG). A nicking endonuclease (NEase)-powered 3-D DNA nanomachine was constructed by assembling hundreds of carboxyfluorescein-labeled single strand oligonucleotides (acting as signal reporter) and tens of swing arms (acting as single-foot DNA walkers) on a gold nanoparticle (AuNP). The activity of this DNA nanomachine was controlled by introducing the protecting oligonucleotides. In the presence of aptamer against 8-OHdG, the protecting oligonucleotides are removed from the swing arms by toehold-mediated strand displacement reaction. In the next step, detached DNA walker hybridizes to the labelled DNA so that the DNA nanomachine becomes activated. Special sequences of signal reporter in the formed duplex can be recognized and cleaved by NEase. As a result, the DNA walker autonomously and progressively moves along the surface of the AuNP, thereby releasing hundreds of signal reporters and causing a rapid increase in green fluorescence. This 3-D nanomachine is highly efficient because one aptamer can release hundreds of signal reporters. These unique properties allowed for the construction of a DNA nanomachine-based method for sensitively detecting 8-OHdG in concentrations as low as 4 pM. This is three orders of magnitude lower compared to previously reported methods.

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Graphical abstract Schematic of a fluorometric method for determination of the cancer biomarker 8-hydroxy-2′-deoxyguanosine. A nicking endonuclease powered 3D-DNA nanomachine was used to improve the sensitivity. Limit of detection is three orders of magnitude lower than reported methods.

     

Description of the state of deformation of ethylene–tetrafluoroethylene alternating copolymer films estimated by using a model proposed in terms of orientation of crystallites within a rod

To study the deformation mechanism of ethylene–tetrafluoroethylene alternating copolymer films caused by elongation, a model relating crystal orientation to the orientation of the rods was proposed. The orientation distribution of crystallites within the rod was given as the correlation with the rod orientation. The distribution functions of a given reciprocal lattice vector of the crystal plane were derived from the two functions of the crystallites and of rods with several parameters representing the orientation of rods and the rotation of crystallites within a rod. By choosing suitable values of the parameters, the calculated functions were in good agreement with the results of X-ray diffraction experiments. From the values of the parameters to give the best fit between calculated and observed results, it turned out that the characteristic orientation of the c-axis is mainly due to the preferential orientation of the rod with respect to a stretching direction and is hardly affected by the rotation of crystallites within the rod. Using the two orientation functions concerning rods and crystallites, Hv light scattering was formulated by introducing an interparticle interference effect of the rods. The calculated results assumed the characteristic profile of the observed patterns as the superposition of broadleaf lobes and a sharp pattern of streaks. Received: 28 April 2000 Accepted: 30 September 2000     

Determination of the state of charge of TCNQ0/− mixed-valence complexes based on a spectroscopic model. Application to thin films of electrocrystallised tetraethylammonium complexes

A simple and inexpensive method is proposed as a powerful and rapid tool for the determination of the state of charge of mixed-valence compounds. Based on UV-spectrometry and integration of voltammetric peaks, the stoichiometric ratio between both oxidation states of TCNQ (that is TCNQ^0/−) has been determined for thin films obtained by electrocrystallisation on a glassy carbon electrode. This method permits such determination, regardless of the experimental conditions and, thus, it can be used to establish the reproducibility of the methods of synthesis of mixed-valence compounds by using simple spectroscopic measurements. The method has been validated with the well-known Cs₂TCNQ₃ system and applied to ethylammonium salts of unknown structure.     

Voltammetric determination of the anti-cancer drug nilutamide using a screen-printed carbon electrode modified with a composite prepared from β-cyclodextrin,gold nanoparticles and graphene oxide

The authors describe an electrochemical method for the determination of the anti-cancer drug nilutamide. The method is based on the use of a composite prepared from β-cyclodextrin, gold nanoparticles and graphene oxide (β-CD-AuNP/GO). An alkaline solution of glucose was used as a reducing agent to reduce the gold ions, rather than citric acid and a harmful reducing agent such as hydrazine and sodium borohydride. The structure and surface morphology of the β-CD-AuNP/GO composite was characterized by Raman spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. A screen printed carbon electrode was modified with the nanocomposite, and the resulting electrode used as a disposable sensor for the determination of nilutamide by differential pulse voltammetry. Best operated at a working voltage of 0.43 V (vs Ag/AgCl), it exhibits excellent electrocatalytic activity and a detection limit as low as 0.4 nM. The sensor was applied to the determination of nilutamide in (spiked) human serum, as well as in a tablet, where it displays good recovery and accuracy. The sensor is repeatable, reproducible, stable and selective even in the presence of other aromatic nitro compounds.

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Graphical abstract An electrochemical method for the determination of the anti-cancer drug nilutamide is described. A screen printed carbon electrode is modified with the nanocomposite prepared from β-cyclodextrin, gold nanoparticles and graphene oxide (β-CD-AuNP/GO). Best operated at a working voltage of 0.43 V (vs Ag/AgCl), it exhibits excellent electrocatalytic activity and a detection limit as low as 0.4 nM. The sensor was applied to the determination of nilutamide in (spiked) human serum and a tablet where it displays good recovery and accuracy.

     

Simultaneous determination of germanium,arsenic, tin and antimony with total-reflection X-ray fluorescence spectrometry using the hydride generation technique for matrix separation—first steps in the development of a new application

This paper introduces a new perspective for total-reflection X-ray fluorescence analysis (TXRF), that is the simultaneous determination of Ge, As, Sn and Sb in seawater. As is well known from atomic absorption spectroscopy (AAS) and inductively coupled plasma techniques (ICP) compounds of these elements can be reduced by sodium borohydride to their hydrides and thus separated from the matrix. In this work the hydride generation is used for matrix separation in TXRF measurements. For this purpose the following procedures are considered: (1) Preconcentration of hydrides by absorption in solvents, and evaporation of some μl of this solution on the sample carrier. (2) Decomposition of hydrides in a heated thin silica tube, or at rough and/or catalytically active surfaces, e.g. in adequately prepared columns, eluting of the species by acid and evaporation of some μl of this solution on the sample carrier. (3) Decomposition of hydrides directly on the surface of a heated silica sample carrier as a thin amorphous film. (4) Combustion of hydrides in the hydrogen flame and deposition of an elemental film on the sample carrier. Basically, all four ways have been tested and the results are promising. © 1997 Elsevier Science B.V.     

Local optical emission spectroscopy of excited species effused from an evaporation cell and a sputter source into dense plasmas – Basic studies for the deposition of thin gradient films

Space resolved optical emission spectroscopy has been applied to determine the distribution of excited species in dense plasmas which are used for the deposition of thin coatings. Typical electron densities and electron temperatures in the plasma facility PETRA ( Plasma Engineering and Technology Research Assembly) are in the range of n(e) = 10(12) cm(-3) and T(e) = 10 eV. During the deposition process material (Al) is evaporated from a vapour cell under controlled conditions. The vapour stream is guided into a dense plasma which is composed of inert gas, Ar or He, and hydrocarbon species produced from the dissociation of C(2)H(2). The evaporated Al-stream which travels with thermal velocity into a plasma of high electron density, is nearly completely ionized due to the short mean free path for electron impact ionization in the above mentioned parameter range. Optical emission spectroscopy has been applied to investigate the interaction processes between the vapour stream and the plasma as well as the transport of the ionized Al along the applied magnetic field. For the measurements space resolved optical emission spectroscopy with an in-situ translation mechanism of the optical fibre has been used to measure the local concentrations of excited Al neutrals and ions as well as the concentration of the background plasma species.     

Synthesis and characterization of novel InVO<Subscript>4</Subscript>–TiO<Subscript>2</Subscript> thin films using the low temperature sol

The InVO₄ sol was obtained by a mild hydrothermal treatment (the precursor precipitation solution at 423 K, for 4 h). Novel visible-light activated photocatalytic InVO₄–TiO₂ thin films were synthesized through a sol–gel dipping method from the composite sol, which was obtained by mixing the low temperature InVO₄ sol and TiO₂ sol. The photocatalytic activities of the new InVO₄–TiO₂ thin films under visible light irradiation were investigated by the photocatalytic discoloration of methyl orange aqueous solution. The thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and UV–Vis absorption spectroscopy (UV–Vis). The results revealed that the InVO₄ doped thin films enhanced the methyl orange degradation rate under visible light irradiation, 3.0 wt% InVO₄–TiO₂ thin films reaching 80.1% after irradiated for 15 h.     

Preparation and characterization of In<Subscript>2</Subscript>S<Subscript>3</Subscript> semiconductor thin films using the sol–gel method

This study describes the In₂S₃ semiconductor thin film coating on glass substrate by sol–gel method. The In₂S₃ thin film samples were prepared and examined by the X-ray diffraction (XRD), the UV–visible optical absorption and transmission study, and the Scanning Electron Microscope (SEM) image analyses. The XRD analysis results show that the In₂S₃ semiconductor thin films prepared by sol–gel method is formed at T~360–520 °C temperature interval. Band gap energy and optical absorption spectrum analysis of the In₂S₃ thin films reveal that Eg~2.51 eV for the In₂S₃ thin films. According to the EDX result the film was In-rich with the In/S = 1.42 ratio. The thickness of prepared In₂S₃ layer is about 400 nm.     

Stabilization of TiO<Subscript>2</Subscript>–Co<Subscript>3</Subscript>O<Subscript>4</Subscript> thin films on a glass fiber material by introduction of silica into the matrix

The TiO₂–Co₃O₄–SiO₂ oxide system supported on glass fiber was synthesized and studied. The oxide layers attached to the glass fiber surface have a porous structure. Characteristics of thin-film coatings on the glass fiber substrate (oxide layer phase composition and adhesion to the glass fiber surface) depend on the silica concentration. The obtained materials are catalytically active towards the exhaustive oxidation of propane.