Chromophoric thin film based on cellulose triacetate blends for sensing metal ions

Chromophoric sensors were made based on 8-hydroxyquinoline immobilized onto a thin film of a polymer blend matrix. The thin films were made by the solution casting method using cellulose triacetate and polyethylene glycol (PEG 600) as plasticizer and pore-forming agent. Different contents of PEG 600 additive were investigated. The prepared films were characterized by FTIR and thermal analysis. The absorption and fluorescence spectra of different films were dependent on the content of PEG 600 with clear quenching of the fluorescence of the film that contains PEG 600 compared to that with zero content. This behavior was attributed to the collective effect of hydrogen bonding (intra- and intermolecular hydrogen bonding) that enhances the process of excited-state proton transfer. This result is favorable to a responsive sensor that shows fluorescence off in the absence of metal ions and fluorescence on upon metal ion chelation. The detection of 5 × 10⁻⁵ M of Al³⁺, Zn²⁺ and thallium (I) in aqueous solution has been observed with the fluorescence method. The result obtained is consistent with the enhancing effect of PEG 600 in the detectability of metal ions. Compared with the detection of Al³⁺ and Zn²⁺, the sensor shows better detection of thallium (I), with clear fluorescence spectra.     

Fabrication of spiropyran-containing thin film sensors used for the simultaneous identification of multiple metal ions

In this article, a methacrylate-based spiropyran-containing copolymer was used as a colorimetric sensor to identify multiple metal ions simultaneously. Through UV-vis absorption spectroscopy, the relative binding affinity of merocyanine to each metal ion was investigated by displacement studies of a bound metal ion with a second metal ion of a higher binding affinity. We also show that because each metal ion gives rise to a distinct spectral response, partial least-squares discriminant analysis (PLS-DA) can be used to analyze the UV-vis absorbance spectra to identify the two metal ions that are present in solution at varying concentrations simply by dipping a coated polymer substrate into solution after irradiation. Partial least-squares regression analysis (PLS) was used to determine the metal ions in solution for several binary mixtures quantitatively. We also demonstrate that the quantitative determination depends on the relative binding preference of merocyanine to each metal ion.     

Electrodeposited three dimensional tin nano wire anode for thin film Li-Ion micro batteries

The tin wire grown over anodic aluminium oxide template is used as anode for Li ion batteries. This work entails porous template formation through double step electrochemical oxidation method optimized by design of experiment and Tafel polarization. The X-ray diffraction results of different anodized specimens show amorphous alumina layer formation. The pores in alumina matrix and the filamentous outward projection of Sn wires are observed from micrographs. The initial discharge capacity of Sn wire and Sn planar thin film is observed to be around 850 and 531 mA h/g respectively. The 50th cycle capacity of Sn wire is observed to be around 494 mA h/g which is very high when compared to theoretical capacity of graphite anodes.     

Deposition of acrylonitrile cluster ions on solid substrates: thin film formation by intracluster polymerization products

Cluster anions of acrylonitrile (AN), known to give intracluster anionic polymerization products, were deposited on solid substrates. The obtained films were examined by using infrared absorption spectroscopy, X-ray photoemission spectroscopy, and gel permeation chromatography with the aid of quantum chemical calculations. The acquired spectroscopic data are similar to those of polyacrylonitrile (PAN), while the normal polymerization of AN or reactions related to PAN seemed not to occur noticeably. On the contrary, the product analysis shows that most of the constituent molecules of the films are formed via cyclohexane-1,3,5-tricarbonitrile (CHTCN), a dominant product of the intracluster polymerization of AN, accompanied by fragmentation and dimerization.     

Organic thin film pyrosensors

Recent developments in sensor technology show the suitability of thin pyroelectric films for the construction of pyroelectric sensor devices made from polymer materials. These materials are used for its advantageous thermal properties and also for its suitable frequency behaviour. Pyroelectrical measurements have been provided on thin films based upon poly(vinyl alcohol)s and poly(siloxane)s with azobenzene side chains. Relaxation behaviour and stability of poled pyroelectric polymers are discussed and related to the results of dipole relaxation measurements provided at our laboratories.     

Fe/Si multi-layer thin film anodes for lithium rechargeable thin film batteries

Fe/Si multi-layer thin films were prepared by alternate deposition using an electron-beam evaporation method. Electrochemical results through galvanostatic charge–discharge experiments are presented. It appears that the volumetric expansion of silicon during cycling can be effectively suppressed by forming a Fe layer between Si layers. The electrochemical characteristics of Fe/Si multi-layer film electrode can be controlled by the thickness, and number of stacked Si layers, and post-annealing.     

Fabrication and electrochemical behaviors of thin film three electrode-measurement unit with microdisk array as working electrode

A three electrode-measurement unit with 33 microdisk electrode-array (MDA) as working electrode was constructed by lithography.Its electrochemical behavior was observed.The results of the oxidation of ferrocene in CH3CN-H2O mixed media demonstrate that high quality electrochemical data for the system without supporting electrolyte can be achieved with the MDA unit constructed in the present work.     

Incipient CdS thin film formation

The quality of a final thin film is essentially determined by the processes taking place at incipient CdS deposition, which in turn are strongly influenced by the physicochemical properties of the substrate and liquid in contact. SEM pictures of deposits formed through steady flow of a supersaturated (with respect to CdS) solution suggest that initially nuclei are continuously generated on the substrate and grow as discrete "surface" particles. With time, these particles tend to "coalesce" with neighboring ones, while new nuclei keep forming and growing, leading to the formation of a coherent film. There is evidence that similar growth patterns prevail in CdS deposition via the chemical bath deposition (CBD) process. Based on experimental observations, a simple model is developed, which is capable of predicting macroscopically determined film characteristics such as the temporal thickness evolution including the "induction period." Two cases of the growth pattern are examined theoretically; one based on instantaneous surface nucleation (due to its simplicity) and another with a constant surface nucleation rate, which appears to be closer to experimental observations.     

Pyroelectricity of Cd-doped telluride thin film

The crystalline structure, electrical conductivity and pyroelecricity of freshly prepared Hg_0.7Cd_0.3Te thin film have been investigated in detail.

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Zusammenfassung Kristallstruktur, elektrische Leitfähigkeit und Pyroelektrizität einer frisch präparierten Hg_0.7Cd_0.3Te Filmschicht wurden ausführlich untersucht.

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, Hg_0.7Cd_0.3Te.

     

Evaporation of a thin liquid film

Evaporation of a thin (submicrometer size) liquid film confined between two solid substrates is studied using diffuse interface hydrodynamic model supplemented by the van der Waals equation of state. The time and space evolution of the basic thermodynamic quantities such as temperature, density, entropy, chemical potential, and entropy production is presented. The values of numerical parameters chosen correspond to those of argon. The time and space scales studied range from picoseconds to microseconds and from nanometers to micrometers correspondingly.     

Standardless quantitation of thin film specimens

This paper reviews the procedures available for the X-ray microanalysis of specimens in the form of thin self-supporting films without the use of standards. Standardless analysis refers to the procedure in which there is no requirement to prepare standards and then measure them during the course of the current analysis. The factors by which the measured X-ray intensities are converted to compositions are calculated for the elements of interest after the experimental measurements have been completed. These calculations are based on published tabulated data for the physical constants required, or evaluated from theoretical or empirical models. The physical parameters which are required to evaluate the characteristic X-ray production in the specimen are the fluorescence yield, the partition function and the X-ray production cross-section. Most analytical procedures ensure that other variables such as the specimen thickness and electron beam current are not required. Of the parameters mentioned, the first two have been examined and extensively tabulated in the literature. This paper focuses primarily on methods of evaluating the X-ray cross-sections for both the characteristic and bremsstrahlung production.The way in which the physical parameters are incorporated into the standardless quantitation methods for materials samples is described. A new standardless version of the continuum normalisation method for quantitative analysis for samples with organic matrices is introduced. Some techniques for making corrections for absorption to the observed intensities are discussed, and formulae are given for X-ray absorption and fluorescence which it may be necessary to use with thicker specimens.     

Dewetting of a sol-gel-derived thin film

We report on the dewetting of a thin film produced by the sol-gel method. In the early stages of dynamic morphological instability, the drying stress in the capillary wave model determines the linearly scaling behaviors of the characteristic wavelength with the initial film thickness and the square law dependence of the number density of the dewetted holes on the film thickness. These power law dependences are weaker than those observed in the case of the spinodal dewetting of a polymer thin film. The wavelength determined in the early stages also dominates the scaling behaviors of the average length of the sides and number density of the polygons and the diameter of the droplets of the dewetting pattern with the film thickness in the final stages of the dynamic instability. We also observed that further drying eventually induces wrinkles in the droplets, rim, and film, which have a characteristic wavelength that can be theoretically predicted.     

Pattern formation in draining thin film suspensions

We demonstrate the emergence of complexity from remarkably simple and ubiquitous systems: draining thin-film suspensions exhibiting a striking transition between two classes of self-organizing patterns. Vertical channels form when attractive forces lead to transient gelation, while horizontal bands result from granular mixtures. We propose an explanation whereby the generic physical mechanisms require only the existence of viscous and excluded-volume couplings among the particles, solvent, and substrate. System-specific, small inhomogeneities trigger large-scale pattern formation, through collective dynamics, where jamming plays a crucial role. Our results shed light on emergent complexity in bio- and geophysical processes and have implications for coatings and food industries.     

Bistability in doped organic thin film transistors

Organic thin film transitors (TFTs) with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid), PEDOT:PSS, as the active layer and cross-linked, layer-by-layer assembled poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) multilayers as the gate dielectric layer were investigated. A combination of spectroscopic data and device performance characteristics was used to study the behavior of these TFT devices under a variety of controlled environmental test conditions. It was shown that depletion and recovery of the device can be induced to occur by a means that is consistent with the electrochemical oxidation and reduction of water contained in the film. In addition to acting as a reactant, moisture also acts as a plasticizer to control the mobility of other species contained in the film and thereby permits bistable operation of these devices. Raman spectroscopy was used to show that the observed device switching behavior is due to a change in the PEDOT doping level.     

Application of thin metal film elements in bioanalysis

Advanced metal deposition and microfabrication techniques enable preparation of metal surfaces with high precision and excellent control over their size and shape with subnanometer resolution. Thin metal films of different types and functions can be found in many analytical instruments. Surfaces with high optical quality serve as mirrors, beam splitters, antireflective coatings etc. Smooth metal coating is crucial in electron microscopy. Unique properties of the thin metal films are widely used in optical systems, as tools for sample manipulation but also for chemical sensing and detection. While some of the applications are widespread and belong to the basic curriculum in analytical chemistry, the newer or less common uses of thin metal films are well known only to the experts in the field. The purpose of this critical review is to highlight the role of thin metal films in bioanalysis and summarize some of their main applications in current bioanalytical instrumentation.     

Wetting of a particle in a thin film

When a particle is placed in a thin liquid film on a planar substrate, the liquid either climbs or descends the particle surface to satisfy its wetting boundary condition. Analytical solutions for the film shape, the degree of particle immersion, and the downward force exerted by the wetting meniscus on the particle are presented in the limit of small Bond number. When line tension is significant, multiple solutions for the equilibrium meniscus position emerge. When the substrate is unyielding, a dewetting transition is predicted; that is, it is energetically favorable for the particle to rest on top of the film rather than remain immersed in it. If the substrate can bend, the energy to drive this bending is found in the limits of slow or rapid solid deflection. These results are significant in a wide array of disciplines, including controlled delivery of drugs to pulmonary airways, the probing of liquid film/particle interface properties using particles affixed to AFM tips and the positioning of small particles in thin films to create patterned media.     

Absorption spectra of thin film of polyaniline

The absorption spectra of thin film of polyaniline (PANI) on slide glass coated by a spin coater were measured as a function of the protonation state of PANI, the concentration of solution of PANI in NMP, drying temperature, and atmosphere. The absorbance value of the 950 nm peak and the ratio of the absorbance value at 950 nm to that of the 630 nm peak increases with increasing the protonation state of PANI. This is consistent with the observation of varying the conductivity with the protonation state. A modified molecular structure of PANI is proposed: where y and x are defined as the oxidation and the protonation states of PANI, respectively.