Photoelectrochemical study of organic–inorganic hybrid thin films via electrostatic layer-by-layer assembly

The stepwise assembly of negatively charged organic molecules (poly(sodium 4-styrenesulfonate) (PSS) or tetrasodium-meso-tetra(4-sulfonatophenyl) porphine (TPPS)) and positively charged TiO₂ colloids on pretreated substrate surfaces utilizing the layer-by-layer (LbL) approach was investigated. The step-by-step formation of these films was studied by UV–vis spectrophotometry and electrochemistry. Photocurrent was generated upon light irradiation of the hybrid thin films assembled on fluorine-doped tin oxide (FTO) conducting glass, which increased linearly as the deposited bilayers increased. In addition, compared to PSS/TiO₂ hybrid thin films, the enhancement of the generated photocurrent and the photocurrent response within the wavelength range from 400 to 450 nm were observed in the TPPS/TiO₂ hybrid thin films. This was attributed to the dye-sensitized effect of the layered TPPS molecules. It was demonstrated that electrostatic LbL films were attractive systems for the photoelectrochemical investigation, and the control of the generated photocurrent could be achieved by the structure of the multilayered films.     

Patterning of spontaneous rolling thin polymer films for versatile microcapillaries

We investigate the spontaneous rolling of polydimethylsiloxane (PDMS) thin films and demonstrate the fabrication of capillaries with topographical and chemical patterns on the inner wall. Thin films of PDMS are either coated by a layer of hard material or have their surface hardened by plasma oxidation. They are then driven out of equilibrium by selective solvent swelling in vapor phase resulting in a tubular rolled‐up system. The inner diameter of those is measured as a function of layer thickness for different solvents and capping types. Those results are shown to be in good agreement with Timoshenko theory. Before rolling, the future inner surface can be characterized and functionalized. We demonstrate topographical and chemical patterning, respectively by embossing and microcontact printing. These methods are very simple and can easily produce cylindrical capillaries with inner diameter between 20 and some hundreds of microns with fully functionalized inner surface, overcoming many difficulties encountered in conventional soft lithography techniques. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 721–728     

Retention of poly(N-isopropylacrylamide) thin films on polycarbonate via polymer interdiffusion

This study explored the possibility of polymer interdiffusion for retaining thermoresponsive poly(N-isopropylacrylamide) (pNIPAAm) on polycarbonate (PC). It was hypothesized that interdiffusion could be facilitated either by increasing the annealing temperature or by treating PC using air plasma (AP) and ultra-violet ozone (UVO). The results showed that increasing annealing temperature only moderately improved pNIPAAm retention. Treating PC with AP led to an increase in surface-active groups and a greatly enhanced retention of pNIPAAm. UVO treatment, however, severely damaged the PC layer with no noticeable enhancement on pNIPAAm retention. The retained pNIPAAm films on PC exhibited thermoresponsive behavior as evidenced by water contact angle and desired cell attachment/detachment behaviors. These results illustrate the simplicity of using polymer interdiffusion to successfully retain pNIPAAm films on a polymer, and the resulting substrates would be less expensive and more versatile than those retained on brittle supports (e.g., glass) for applications that require resilient thermoresponsive substrates.     

Phase formation process of sputtered NiCr(37:63) thin films

The phase formation process of NiCr(37:63) thin films has been investigated using the x-ray diffraction method. The films were deposited onto Si-wafers by means of d.c. magnetron sputtering. The structure of the as-deposited layers was amorphous. As a result of subsequent thermal annealing the crystallization process took place characterized by the formation of b.c.c. Cr-rich solid solution, metastable σ-NiCr-phase, and f.c.c. Ni-rich solid solution, respectively. Besides lattice constants, grain sizes and texture of the formed phases were determined.     

Semicrystalline morphology in thin films of poly(3-hexylthiophene)

The thermodynamic phase behavior and the morphology in thin films of poly(3-hexylthiophene) (P3HT) has been studied using calorimetry, X-ray scattering, and scanning force microscopy (AFM). Around 225 °C a phase transition from the crystalline state to a layered, liquid crystalline structure occurs in regioregular P3HT, while the regiorandom counterpart material is disordered at all temperatures and displays a glass transition temperature T_g–3 °C. Regioregular P3HT is semicrystalline and forms needle or plate like crystallites which in solution cast thin films are oriented with respect to the substrate. Films produced by spin coating display a non-equilibrium structure with reduced order and orientation. Annealing of these films in the liquid crystalline state leads to the formation of a morphology similar to the one observed in solution cast films.

Generation of paramagnetic hybrid inorganic/organic thin films

There is a growing interest in developing advanced materials for thin film applications in biology, electronics, photonics and engineering. We report the development of hybrid inorganic/organic thin films containing nickel, iron and cobalt paramagnetic materials. By etching the resist in oxygen plasma after processing, most of the organic component of the resist was removed. The elemental chemical composition of the films was confirmed by energy dispersive X‐ray spectroscopy. This process can potentially lead to patterning paramagnetic thin films containing paramagnetic materials by following standard photolithography protocols, obviating the need for a wet or vacuum metal deposition. Copyright © 2010 John Wiley & Sons, Ltd.     

Thermoanalytical methods in the study of inorganic thin films

Thermoanalytical (TA) methods are relatively seldom applied for assessing the physical and chemical proeprties of thin films, but they can be used in studies of composition, phase transitions and film—substrate interactions. In the present paper the possibilities of TA methods in thin film studies are reviewed. The thermoanalytical methods considered are the classical TG and DTA/DSC methods but some complementary methods will also be briefly mentioned. The main emphasis is given to true thin films. Details of sample preparation are also given. An important application of TA methods is characterization of precursors for the CVD growth of thin films, and this is also discussed.     

Structure of friction-transferred highly oriented poly(3-hexylthiophene) thin films

Oriented thin films of P3HT were obtained by a friction-transfer technique. The morphology and structure of the film were studied by means of optical microscopy, atomic force microscopy and transmission electron microscopy. Optical microscopy observation indicates that large size well-ordered P3HT thin films can be produced by a friction-transfer technique. Highly ordered lamellae were observed in P3HT friction-transferred films by electron microscopy. Electron diffraction results confirm the existence of high orientation with the a- and c-axes of P3HT crystals aligned in the film plane while the c-axis parallel to the friction-transfer direction. The atomic force microscopy observation of the as-prepared P3HT thin film shows, however, a featureless top surface morphology, indicating the structure inhomogeneity of the obtained film. To get highly oriented P3HT thin films with homogenous structure, high temperature annealing, solvent vapor annealing and self-seeding recrystallization of the friction-transferred film were performed. It is confirmed that solvent vapor annealing and self-seeding recrystallization methods are efficient in improving the surface morphology and structure of the frictiontransferred P3HT thin film. Highly oriented P3HT films with unique structure can be obtained through friction-transfer with subsequent solvent vapor annealing and self-seeding recrystallization.     

Nanoscale current modulations in Pr(0.7)Ca(0.3)MnO(3) thin films

Many theoretical and experimental efforts have been focused on the origin of the electric-pulse-induced resistance change effect. However, there are still various reports of the origin supporting either the bulk nature or the interface nature. To resolve the controversies, nanoscale electronic measurements may provide essential clues. In this work, we report microscopic electrical properties of Pr(0.7)Ca(0.3)MnO(3) thin films. The resistance of a single-crystalline grain is not homogeneous in nanometer scale. We deduce that nanoscale inhomogeneity is related to the periodic relaxation of substrate-induced strain, which is caused by the lattice mismatch between the substrate and the thin film.     

Reactive epoxy-functionalized thin films by a pulsed plasma polymerization process

A novel plasma functionalization process based on the pulsed plasma polymerization of allyl glycidyl ether is reported for the generation of robust and highly reactive epoxy-functionalized surfaces with well-defined chemical properties. Using a multitechnique approach including X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and ellipsometry, the effect of the plasma deposition parameters on the creation and retention of epoxy surface functionalities was characterized systematically. Under optimal plasma polymerization conditions (duty cycle: 1 ms/20 ms and 1 ms/200 ms), reactive uniform films with a high level of reproducibility were prepared and successfully used to covalently immobilize the model protein lysozyme. Surface derivatization was also carried out with ethanolamine to probe for epoxy groups. The ethanolamine blocked surface resisted nonspecific adsorption of lysozyme. Lysozyme immobilization was also done via microcontact printing. These results show that allyl glycidyl ether plasma polymer layers are an attractive strategy to produce a reactive epoxy functionalized surface on a wide range of substrate materials for biochip and other biotechnology applications.     

Tunable dielectric thin films by aqueous, inorganic solution-based processing

Sub-micron, nanolaminated, dielectric thin films comprised of amorphous aluminum oxide phosphate (AlPO) and hafnium oxide sulfate (HafSOx) layers were fabricated in open-air conditions from aqueous inorganic precursors by spin coating with minimal thermal processing. These nanolaminated thin film insulators display an averaging effect of effective dielectric permittivity in devices with controlled AlPO:HafSOx thickness ratios, enabling tunable dielectric properties. X-ray reflectivity measurements were used to characterize film thickness, smoothness, and uniformity. Scanning electron microscopy was used to analyze final nanolaminated devices. Electrical characterization of metal-insulator-insulator-metal capacitors revealed tunable relative dielectric constants ranging from approximately 5–10 with loss tangents less than 2% at 10 kHz in devices with approximately 300 nm total dielectric thickness. The results suggest a simple, inexpensive processing approach for fabricating devices that require insulating layers with specific dielectric properties.     

Design of precursors for the CVD of inorganic thin films

Applications of inorganic thin films in the electronics industry have spurred activity in the area of chemical vapor deposition (CVD). This article discusses the increasingly sophisticated design strategies for precursor complexes through a series of case studies on CVD of metal oxide and metal nitride films.     

Patterning of sol gel thin films by capillary force assisted soft lithographic technique

Patterning of sol gel based silica and silica–titania films has been developed at room temperature by soft lithographic technique. Corresponding metal alkoxides have been utilized for the preparation of precursor sols. Elastomeric stamps of polydimethylsiloxane (PDMS) are used to emboss patterns of a master grating on the as-prepared silica and silica–titania films obtained by sol gel process. Pressure-less capillary force lithography has been used to fabricate both 1-D and 2-D ordered structures of simple stripe patterns. A modified solvent assisted lithography and micro-molding in capillaries yielded stable and high fidelity 1-D structures for silica and silica–titania films over a large area.     

Infrared analysis of thin inorganic and organic films on metals

Infrared spectroscopy is shown to be an adequate method for qualitative and quantitative characterization of technical surface layers for corrosion protection. The measuring conditions for each type of sample have to be selected carefully. For the sake of reliability a certain redundancy in the evaluated data might be useful. It is the aim of this work to gather experience for routine quality control of steel and aluminium surfaces.Duridine, Granodine and Alodine used in this work are registered trademarks of Collardin GmbH     

Wavelength dependence of nanoscale photodegradation in poly(3-octylthiophene) thin films

The use of conducting polymers in optoelectronic devices is subject to the understanding of the electro-optical processes that take place at the nanoscale. One of the photo-induced processes that limit their application is the photodegradation, which reduces the device working life. In this work the photodegradation of poly(3-octylthiophene) thin films was studied by combining Kelvin probe microscopy and optical microscopy. In this way, a direct correlation between morphological and contact potential changes with optical density changes as a function of the irradiation wavelength and intensity can be made. These results, complemented with Raman spectra help to clarify the degradation processes that are taking place. We find that the photodegradation strongly depends on the irradiation wavelength blue light being much more aggressive than UV. In addition, the optical properties change abruptly before any substantial change in the morphology is observed.     

Biomimetic assembly of polypeptide-stabilized CaCO(3) nanoparticles

In this paper, we report a simple polypeptide-directed strategy for fabricating large spherical assembly of CaCO(3) nanoparticles. Stepwise growth and assembly of a large number of nanoparticles have been observed, from the formation of an amorphous liquidlike CaCO(3)-polypeptide precursor, to the crystallization and stabilization of polypeptide-capped nanoparticles, and eventually, the spherical assembly of nanoparticles. The "soft" poly(aspartate)-capping layer binding on a nanoparticle surface resulted in the unusual soft nature of nanoparticle assembly, providing a reservoir of primary nanoparticles with a moderate mobility, which is the basis of a new strategy for reconstructing nanoparticle assembly into complex nanoparticle architectures. Moreover, the findings of the secondary assembly of nanoparticle microspheres and the morphology transformation of nanoparticle assembly demonstrate a flexible and controllable pathway for manipulating the shapes and structures of nanoparticle assembly. In addition, the combination of the polypeptide with a double hydrophilic block copolymer (DHBC) allows it to possibly further control the shape and complexity of the nanoparticle assembly. A clear perspective is shown here that more complex nanoparticle materials could be created by using "soft" biological proteins or peptides as a mediating template at the organic-inorganic interface.     

Adsorbates on thin iron(100) films

The electronic and magnetic properties of different kinds of adsorbates on thin magnetized Fe(100) films have been investigated by means of spin resolving photoelectron spectroscopy. The study has been carried out with atomically physisorbed xenon, the molecule carbon monoxide, and metallic gold. The spin splitting of the Xe 5p signal can be explained by magnetic interactions with the final ionic hole state. By spin analysis, it could be shown that at room temperature for low exposures the adsorption of CO is dissociative and with increasing exposure additionally molecular. The Au related features for the monolayer show different line shapes in both spin channels but no splittings due to an sp-like behavior of this interface state being dominated by minority character.