Form Of Solid Film Research Articles

Tracing Poly(Vinyl Acetate) Emulsions by Infrared and Raman Spectroscopies: Identification of Spectral Markers.

Vinyl emulsions started to be used by artists in paintings at least since the early 1960s, being now present in several artworks worldwide. However, different vinyl formulations can result in distinct behaviours over time, and if some artworks are currently showing a good condition, others already show damages due to the use of compositions more susceptible to degradation. For this reason, it is fundamental to identify the main components in the vinyl acetate-based (VAc-based) emulsion. This work focuses on the molecular study of VAc-based emulsions by infrared and Raman spectroscopies. It aims at deepening the knowledge on the variability of the composite formulation and on the identification of characteristic bands and spectral profiles (identified as spectral markers) for both polymer and additives. To this end, a broad set of vinyl emulsions was gathered, including reference materials, historical commercial brands in use by Portuguese artists, and commercial brands collected from industrial companies. The entire set includes vinyl homopolymers produced for the purpose of the study and known formulations of vinyl homopolymers and copolymers, with and without plasticisers, according to technical data sheets and previous studies. Furthermore, unknown formulations have been included to validate the usefulness of the identified spectral markers. This set has been studied in the form of solid films deposited in glass slides by infrared spectroscopy in attenuated total reflection mode (ATR-FTIR) and micro-Raman spectroscopy (µ-Raman), both conducted in situ. As conclusions, the combined use of ATR-FTIR and µ-Raman proved to be very useful as different spectral markers were detected by each technique, confirming their complementarity. Besides the clear identification of vinyl acetate-based emulsions by both techniques, it was also possible to suggest spectral markers for the copolymerisation of vinyl acetate with vinyl versatate by µ-Raman, the stabilisation of the emulsion with poly(vinyl alcohol) by ATR-FTIR, and the addition of phthalates or benzoates plasticisers by both ATR-FTIR and µ-Raman.

Structural, electrical, and nonlinear optical performance of PVAL embedded with Li+‐ions for multifunctional devices

In this paper, pure and 0.04%, 0.19%, 0.4%, 1.9%, and 4% LiNO3‐doped PVAL (polyvinyl alcohol) electrolyte were fabricated in the form of solid films by the casting process. The influence of Li+‐ions on PVAL was identified by some characterization tools such as X‐ray diffraction, FT‐IR (Fourier transform infrared), scanning electron microscope (SEM), thermal gravimetric analysis (TGA), UV‐visible‐NIR spectroscopy, dielectric, and conductivity measurements. X‐ray diffraction studies indicate that the semicrystalline of PVAL and the calculated crystallize size from Gaussian fitting were decreased with Li+‐ions concentration. FT‐IR results indicate that there is strong interaction among doping ions and the matrix. The surface morphology of the electrolyte films was studied via SEM. The optical studies demonstrate that the transmittance of films decreased with the rising of Li+‐ions. Urbach's energy and bandgap are also reduced with adding more ions. Different empirical equations were used to study the relation between the energy gap and the refractive index. The index of refraction of the films has average values in 2.024 to 2.078 range. Li+‐ion concentrations critically influenced the factors of nonlinearity. The calculated values of nonlinear optical susceptibility χ(3) and refractive index n2 were increased from 8.6 × 10−13 esu and 1.55 × 10−11 to 20.56 × 10−10 esu and 2.05 × 10−11, respectively. The dielectric constant and loss measurements of the PVAL embedded with 4% of LiNO3 (SPL‐5) were decreased exponentially with increasing the incident frequency. The AC electrical conductivity (σAC) and nonlinear I‐V curves are enhanced by increasing the Li+‐ion contents. The electrical current was increased with small resistivity for SPL‐5 film. The studied films have an inimitable result in various fields, such as nonlinear optical and varistor devices.

Simulation of Patterned Glass Film Formation in the Evaporating Colloidal Liquid under IR Heating

The paper theoretically studies the method of evaporative lithography in combination with external infrared heating. This method makes it possible to form solid microstructures of the required relief shape as a result of evaporation of the liquid film of the colloidal solution under the mask. The heated particles are sintered easier, so there are no cracks in the obtained structure, unlike the structure obtained employing the standard method of evaporative lithography. The paper puts forward a modification of the mathematical model which allows to describe not only heat and mass transfer at the initial stage of the process, but also the phase transition of colloidal solution into glass. Aqueous latex is taken as an example. The resulting final form of solid film is in good agreement with the experimental data of other authors.

Stable Dispersion of Iodide-Capped PbSe Quantum Dots for High-Performance Low-Temperature Processed Electronics and Optoelectronics

Here, we present a ligand exchange of long insulating molecules with short, robust, and environmentally friendly iodide ions via a mild flocculation of PbSe nanocrystals (NCs). This ligand exchange leads to the formation of stable colloidal solutions in various polar solvents and in a broad concentration range via electrostatic repulsion. The iodide capping ligands preserve the electronic structure and maintain the optical properties of the PbSe NCs, both in solution and in the form of solid films. The spin-coated PbSe NC solids exhibit good transport characteristics with electron mobilities in the linear and saturation regimes reaching (2.1 ± 0.3) cm2/(V·s) and (2.9 ± 0.4) cm2/(V·s), respectively. This opens up opportunities for the low-cost and low-temperature fabrication of NC thin films being attractive for applications in the fields of electronics and optoelectronics.

Photo-Electrochemical Investigation of Inorganic/Organic Interfaces Assembly Consisting of Zn-Doped WO3 /Poly 4-(Thiophen-3-yl) Aniline

Photoactivities at inorganic/Organic/Interfaces (IOI) consisting of Zn-doped WO3 (Zn-WO3) /Poly 4-(Thiophen-3-yl) aniline (P3ThA) assemblies were investigated in nanoparticle suspensions and in thin solid film forms. The effects of P3ThA modifier on the photoelectrochemical behavior of the IOI were investigated using [Fe(CN)6]4- as a photoactive donor of hydrated electrons. Results show that the adsorption process of [Fe(CN)6]3- (photolysis product) controls the photoactivity outcomes of the IOI assemblies. P3ThA shows a greater heterogeneous photochemical response than native Zn-WO3. The band alignment between Zn-WO3 and P3ThA is of a p-p junction straddling gap type, where the charge transfer process is achieved through a hole transfer mechanism. The interface activities were explained by analyzing the IOI junction characteristics such as electron affinity, work function and hole/electron barrier heights. The creation of hybrid sub-band states close to the Fermi energy level at the interface was suggested. The aqueous nano-systems retained moderate stability as indicated by the reproducibility of their photocatalytic activities. Both [Fe(CN)6]4- and P3ThA contributed to the stability of the native Zn-WO3 surfaces.

Photoelectrochemical Studies on CdS/Poly Ethyl-Aniline Interfaces

An inorganic/organic/interface (IOI) consisting of CdS/poly ethyl aniline (PEA) assemblies was subjected to photoelectrochemical studies in nanoparticle suspensions and in thin solid film forms . The effects that PEA modifiers have on the photoelectrochemical behavior of the IOI were investigated using [Fe(CN)6]4-as a photoactive hydrated electron donor agent. Results show that the adsorption process of [Fe(CN)6]3- (the photolysis product) controls the photoactivity outcome of IOI assemblies. CdS/PEA shows lower heterogeneous photochemical response than native CdS. Native CdS amorphous nanoparticles adsorb more [Fe(CN)6]3- with a very steady adsorption/desorption process than the CdS/PEA. The interface activities were explained by analyzing the IOI junction’s properties such as electron affinity, work function and hole/electrons barrier heights. The lower hole barrier height versus electron barrier height suggests that charge injection is mediated at the IOI interface through hole transfer. The aqueous nano systems retained moderate stability as indicated by the reproducibility of their photocatalytic activities. Both [Fe(CN)6]4- and PEA contributed to the stability of native CdS surfaces.

Photoelectrochemical Studies at CdS/PTTh Nanoparticles Interfaces

Photo-activities at Inorganic/Organic/Interfaces (IOI) consisting of CdS/ Polyterthiophine (PTTh) assemblies were investigated in nanoparticle suspension and in thin solid film forms. The effects PTTh modifier cause on the photoelec-trochemical behavior of the IOI were investigated using [Fe(CN)6]4- as photoactive hydrated electron donor agent. Results show that the adsorption process of [Fe(CN)6]3- (photolysis product) control the photoactivity outcome of IOI assemblies. CdS/PTTh shows lower heterogeneous photochemical response than native CdS. Native CdS amorphous nanoparticles adsorb more [Fe(CN)6]3- with very steady adsorption /desorption process than the modified ones. The interface activities were explained by analyzing the IOI junctions’ characteristics, such as electron affinity, work function and hole/electrons barrier heights. The aqueous nano-systems retained moderate stability as indicated by the reproducibility of their photocatalytic activities. Both [Fe(CN)6]4- and PTTh contributed to the stability of native CdS surfaces.

Asymmetric indolylmaleimides as non-dopant type red color emitting dyes

The photophysical properties of asymmetric indolylmaleimide derivatives ( 4a–4f) with a variety of aryl substituents at C(4) were analyzed. Their absorption spectra vary in the region of aryl substituents, whereas their emission spectra are nearly identical. The red emission is derived from a charge transfer transition along the indole-maleimide chromophore, which is not significantly disturbed by the introduction of a nearby aryl substituent at C(4). All compounds displayed intensive emissions both in solutions as well as in the form of solid films. Light emitting diodes (LED) were fabricated successfully by using the neat film of these materials as emitters. The performance of devices among the series varied slightly as a result of different film morphology. The best performance was found on the compound with a pyrene substituent, which exhibited optimal external quantum efficiency of 1.1%. This device could be turned on at 4 V and reached to optimal brightness of 9750 cd/m 2. The red color, according to the Commission Internationale de l’Eclairage (CIE) coordinates at (0.65, 0.34), was very close to pure red (0.67, 0.33).

Bis(trifluoromethyl)carbinol-Substituted Polynorbornenes: Dissolution Behavior

Alicyclic polymers, such as substituted polynorbornene (PNB), are expected to be one potential material solution for providing transparent photoresist polymer resins for photolithography at 193 and 157 nm wavelengths. In this work, the dissolution behavior of bis(trifluoromethyl)carbinol-substituted polynorbornene (HFAPNB) in aqueous alkaline solutions as a function of polymer molecular weight is explored. Surprisingly, it was found that the dissolution rate of bis(trifluoromethyl)carbinol-substituted polynorbornene increased with increasing molecular weight over the range from approximately 10,000 to 100,000 Mw. Experimental results show that this polymer displays strong hydrogen bonding in the solid film form and that such hydrogen bonding is disrupted as the polymer molecular weight is increased. On the basis of this evidence, an explanation for this unusual dissolution behavior based upon disruption of hydrogen bonding is presented.

Amorphous Thin Films of Chiral Binaphthyls for Photonic Waveguides

The synthesis of chiral nonracemic materials and the polarization properties of chiral optical waveguides fabricated from them are presented. These materials are based on binaphthyl compounds designed to produce a glassy isotropic optically active material in a thin solid film form. Chiral‐core optical waveguides may find use as novel elements in integrated optic devices for photonics applications.

Whisker Formation in the Presence of Anthraquinone

IT has been shown1 that nitrogen-substituted amino-anthraquinone compounds prepared by vacuum deposition in the form of solid films on quartz can crystallize when stored in the dark at room temperature. Similar experiments with impure aminoanthraquinone derivatives containing anthraquinone showed that whiskers2 also grow from the surface of the film. When these substances were purified and freed from anthraquinone before deposition, however, no whiskers were formed when the solid films were stored; nor was it possible to grow whiskers from films containing only anthraquinone. Subsequent attempts to investigate whisker formation were made with films prepared from mixtures of the purified aminoanthraquinone compound and pure anthraquinone.