Manipulating the surface properties of polyacrylamide with nitrogen plasma

Polyacrylamide (PAL) was physically adsorbed onto a hydroxylated silicon surface to form a uniform PAL film and the up-top PAL thin film was treated by nitrogen (N₂) plasma for surface modification. The atomic composition of the modified surface of the PAL film adsorbed on silicon substrate was analyzed with Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The surface energy of PAL film was calculated from the data of contact angle of three-probe liquid. The FTIR results show an increase of peak intensity at 1214 cm⁻¹ (NH₂ stretch vibration) after the nitrogen plasma treatment, which confirms that the nitrogen was grafted to the PAL surface in the process of N₂-plasma treatment. The XPS results show that the ratio of relative intensity of N1s to O1s increases with increasing the plasma treatment time, which further affirms the formation of the amine groups on the PAL surface after the nitrogen plasma treatment. The surface tension increases with increasing the plasma grafting time. However, the surface energy decreases rapidly at the early stage when stored in air and approaches to an equilibrium value. It suggests that some physically-adsorbed ions and alkyl radicals on PAL surface can rapidly lose their activities. The increase of the surface tension of the plasma treated PLA films is due to the amine groups covalently grafted to PAL surface.     

Photochromism of dihydroindolizines. Part 16: Tuning of the photophysical behavior of photochromic dihydroindolizines in solution and in polymeric thin film

In this work, photochromic materials based on the dihydroindolizine (DHI) system were synthesized in multistep reactions using chemical and photochemical methods. Some of the synthesized photochromic dihydroindolizine derivatives were substituted on the fluorene (region A) and pyridazine (region C) moieties in order to provide the appropriate functionality for optimal tuning of the photochromic properties of the system. Irradiation of the photochromic DHIs with polychromatic light led to ring opened colored betaines, which underwent thermal 1,5-electrocyclization. The red to green colored betaines produced after UV irradiation returned back through 1,5-electrocyclization to the corresponding DHIs with different rate constants depending on the substituents in both fluorene and pyridazine regions. The kinetic measurements of the thermal 1,5-electrocyclization under different temperatures that ranged from −10 to 25 °C showed that the half-lives of the colored betaines fall in the second to hours domain. Interestingly, these materials showed a very good photochromic behavior not only in solution but also in the PMMA matrix. Irradiation of a slide prepared by the deep-coating method led to the formation of the colored betaine and the kinetics of the thermally reversible 1,5-electrocyclization and the AFM image of the film has been recorded. Indeed, the chemical and thermal stability of the investigated betaines in polymer (PMMA) will render such species useful for a plethora of new of applications.     

Stress evolution on gel-to-ceramic thin film conversion

In situ cracking observation, uncracking critical thickness evaluation and in situ stress measurement were conducted during heating for alkoxide-derived gel coating films. Higher water-to-alkoxide ratios and lower heating rates were shown to cause cracking at lower temperatures. The in situ stress measurement suggested that higher water-to-alkoxide ratios in solutions and lower heating rates result in larger in-plane tensile stress to be generated in the heating-up stage, which was thought to cause the cracking at lower temperatures. Methyltriethoxysilane, chelating agents and polyvinylpyrrolidone were shown to be effective in increasing uncracking critical thickness and/or thick film formation. The in situ stress measurement suggested that these additives or components are effective in suppressing the stress evolution during heating.     

Synthesis, characterization and photochromic studies in film of heterocycle-containing spirooxazines

A series of novel heterocycle-containing spirooxazines have been designed and synthesized, and their photochromic properties were investigated under flash photolysis and continuous irradiation in particular regard to the fatigue resistance, the lifetime of the colored merocyanine form in various solutions and polymers. Especially, the characteristics of two UV-sensitive spirooxazines dispersed polymethylmethacrylate thin-films were extensively studied. Detailed studies showed that general significant shifts in the λ_max of the absorption spectra of the open forms, interesting fatigue resistances and emission fluorescene properties were observed.     

Synthesis and conductivity of hybrid materials based on germanium-containing polyoxometalates and ionic liquids

Three new compounds, [MIMPS]₅GeW₁₁VO₄₀, [MIMPS]₅GeW₁₀MoVO₄₀, and [MIMPS]₅GeMo₁₁VO₄₀, have been synthesized from 1-(3-sulfonic group) propyl-3-methyl imidazolium (MIMPS, C₇H₁₃N₂O₃) and germanium-containing heteropoly acids H₅GeW₁₁VO₄₀, H₅GeW₁₀MoVO₄₀, and H₅GeMo₁₁VO₄₀. IR spectra indicate the formation of the hybrid molecular compounds showing fingerprint vibrational bands of both heteropolyanions and MIMPS cations. The products exhibit high conductivity and small conductive activation energies; conductivities increase with higher temperature. Their conductivities are as follows: [MIMPS]₅GeW₁₁VO₄₀?>?[MIMPS]₅GeW₁₀MoVO₄₀?>?[MIMPS]₅GeMo₁₁VO₄₀. The sequence is opposite for their conductive activation energies. The results show that the conductivity and conductive activation energies are closely related to their component elements. The W-containing material exhibits higher conductivity and smaller conductive activation energy than Mo-containing material.     

Effect of thermal annealing on the microstructure of P3HT thin film investigated by RAIR spectroscopy

The influence of thermal annealing on the structural ordering and orientation rearrangement of as cast P3HT thin film (<100 nm) has been studied by reflection absorption infrared spectroscopy (RAIR). In order to erase the effect of temperature on the spectral intensity, two thermal procedures have been used to investigate the annealing-induced structural change of P3HT thin film. One is the continuous heating mode, in which the RIAR spectra were in situ collected during the heating process. The other is the stepwise heating mode, that is the isothermal annealing, and the spectra were ex situ collected at room temperature after the thermal treatment. It is found that thermal annealing can enhance the π–π interaction in P3HT crystal domain, whereas the improvement on the degree of crystallinity is not so obviously. Meanwhile, our results suggest that annealing-induced structural rearrangement on π–π stacking is irreversible, whereas the change on hexyl side chain packing is reversible.     

Surface oxidation and thin film preparation of AlCuFe quasicrystals

This paper reviews the work carried out over the last decade by the Nancy team on surface oxidation and thin film preparation of AlCuFe icosahedral quasicrystals. After discussing the problems linked with the surfaces of these quasicrystals, this review addresses the issue of the preparation of quasicrystalline surfaces and the first steps of oxidation under very low pressure of oxygen. This paper compares the nucleation and growth of oxide on i-AlCuFe quasicrystal and on a classical crystalline phase of this alloy: ω-AlCuFe. Aluminium diffusion is studied through the aluminium segregation on the surface that occurs during exposure to oxygen. Some surface properties of quasicrystals are reviewed with regard to oxidation. The evolution of physical parameters such as surface energy, friction coefficient and optical emissivity is described. This review also deals with the preparation of i-AlCuFe thin films. Two protocols to make i-AlCuFe thin films with free surfaces are described and discussed. The mechanical resistance and the tribological behaviour of these thin films, the oxygen and carbon influence on the final crystalline structure, and the quasicrystallization kinetics are presented.     

Synthesis of block copolymers based on poly(2,3-epithiopropylmethacrylate) via RAFT polymerization and preliminary investigations on thin film formation

New block copolymers with narrow molecular weight distribution based on (2,3-epithiopropylmethacrylate) (ETMA), methylmethacrylate (MMA) and n-butylmethacrylate (nBMA) have been successfully synthesized via reversible addition-fragmentation transfer (RAFT) polymerization. First, RAFT homopolymerization of ETMA and MMA was carried out using 2-(2-cyanopropyl) dithiobenzoate (CPDB) as the chain transfer agent (CTA) and 2,2-azobisisobutyronitrile (AIBN) as the initiator. PETMA-b-P(nBMA) copolymers were synthesized using PETMA homopolymers as the macro-chain transfer agent (MCTA), while PMMA-b-PETMA diblock copolymers were synthesized using PMMA as the MCTA. The evolution of the molecular weight and molecular weight distribution of the homo- and co-polymers were compatible with the RAFT polymerization features. Thin films from the block copolymers were prepared by spin coating a 1 wt% polymer solution from toluene, chloroform or THF. After the preparation, the films were annealed under 80% vapor pressure of chloroform for 1, 2 and 4 h and investigated with scanning electron microscopy (SEM). The most interesting results were found in the films prepared using PETMA-b-P(nBMA) copolymers (). The observed images suggested the formation of hybrid lamellar structures, ascribed to the combination of its higher molecular weight and solvents viscosity.     

Syntheses, structures and properties of a series of photochromic hybrids based on Keggin tungstophosphates

Three inorganic-organic hybrids based on Keggin tungstophosphates and lanthanides, [Pr(NMP)₆(PW₁₂O₄₀)]_n (1), [Eu(NMP)₆(PW₁₂O₄₀)]_n (2), and [Er₂(NMP)₁₂(PW₁₂O₄₀)][PW₁₂O₄₀] (3) (NMP=N-methyl-2-pyrrolidone), have been synthesized and characterized by elemental analysis, IR, UV-vis, and single-crystal X-ray diffraction. Compounds 1 and 2 exhibit 1D infinite zigzag chain structures, while compound 3 exhibits an ionic asymmetric structure due to lanthanide contraction. The three compounds are all photochromic. The magnetic susceptibility for 1 measured over the range 2-300 K shows that there is the dominant antiferromagnetic interaction in the compound. The results of luminescent properties show that compound 2 displays an interesting selectivity for Zn²⁺ ions.     

The influence of electrode metals and its configuration on the response of tin oxide thin film CO sensor

Thin films of tin oxide were deposited by electron beam evaporation. The effects of the electrode materials (Ag, Al, Au and Pt) and different electrode configurations on the CO-sensing of tin oxide thin films were investigated. The Pt and Au electrodes with bottom electrode configuration show much higher response than Ag and Al electrodes. The sensor response and recovery times have also been measured. The films were characterized using X-ray diffraction and X-ray photoelectron spectroscopy. All the films were found to be amorphous. It was found that the CO-sensing properties depend both on the electrode materials and configuration.     

The adsorption structure of nonionic surfactant on the sessile mercury electrode in a thin liquid film

In relation to a colloid stability, the adsorption structure of the Stern layer on a sessile mercury electrode in a thin liquid film of nonionic surfactant was investigated by measuring the double layer capacitance. The Stern capacitance on the electrode in the film could be detected when the measuring frequency used was low, for the resistance of the film was not extremely high but of the order of several thousand ohm. It was found that the adsorption structure of nonionic surfactant in the thin liquid film shows a stratification different from that of bulk.     

Novel chemical synthesis of polypyrrole thin film electrodes for supercapacitor application

Present investigation describes the cost-effective, novel and simple chemical synthesis of polypyrrole (PPy) thin films for supercapacitor application. These PPy films are characterized by different techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The XRD pattern reveals the amorphous nature of PPy thin film, which is highly feasible for supercapacitors. Further, FTIR study confirms the formation of PPy. The surface morphological study exhibit the coverage of uniform and smooth morphology on thin film. The electrochemical supercapacitive properties of PPy thin films are evaluated using cyclic voltammetry (CV) in 0.5 M H₂SO₄ electrolyte, which exhibits the maximum specific capacitance of 329 Fg⁻¹ at the scan rate of 5 mV s⁻¹. Additionally, an equivalent series resistance (ESR) of PPy thin films is found to be 1.08 Ω using electrochemical impedance measurement.     

Novel preparation of NaA/carbon nanocomposite thin films with high permeance for CO2/CH4 separation

Novel NaA/carbon nanocomposite thin films were successfully prepared on a porous a-Al2O3 substrate by incorporatingnanosized NaA zeolite into novolak-type phenolic resin.The prepared films were characterized by XRD,SEM and single gaspermeation tests.The NaA zeolite/carbon nanocomposite thin films exhibited that the ideal separation factor of CO2/CH4 was 28.4and the carbon dioxide flux was 3.39*10-7mol/(Pa m2s)at room temperature and under a pressure difference of 100 kPa,whichwas two orders of magnitude higher than that of pure carbon membrane prepared at the same procedures and conditions as those ofcomposite films.From the SEM images,the films were continuous and highly intergrown.Compared with carbon membranes,thethickness of nanocomposite films was drastically decreased,which was helpful to reduce the diffusion resistance and increase theflux of gas permeance.     

In-situ preparation and electrochromic properties of TiO2/PTPA-HTAN core-shell nanocomposite film

A new star-shaped structure conjugated microporous polymers, poly (2,8,14-tri[4-diphenyl-benzene]-hexaazatrinaphthylene) (PTPA-HATN), was designed and in-situ electrochemically polymerized on the surfaces of FTO electrodes with a directional alignment TiO₂ nanorod array to obtain TiO₂/PTPA-HATN core-shell nanocomposite films. Compared with the PTPA-HATN film, the TiO₂/PTPA-HATN composite film exhibits higher optical contrast and faster response time, with contrast of 57% at 783 nm, coloring time of 3.62 s and discoloring time of 2.55 s (43%, 4.63 s and 4.77 s for PTPA-HATN film, respectively). After 400 cycles, the contrast of nanocomposite film decreased by 28%, while the PTPA-HATN film basically lost its electrochromic properties. A simple three-layer EC prototype device based on TiO₂/PTPA-HATN nanocomposite film constructed with hydrogel electrolyte clearly shows color changes at different voltages. On the one hand, the formation of core-shell porous nanostructure of TiO₂/PTPA-HATN composite film provides a larger ion doping/de-doping interface, shortening the average diffusion length of ions. On the other hand, the large indented polymer-nanorods contact interface makes it difficult for the polymer to detach from the electrode, thus significantly improving the cyclic stability of the composite film.     

AFM,ellipsometry, XPS and TEM on ultra-thin oxide/polymer nanocomposite layers in organic thin film transistors

Here we report on the fabrication and characterization of ultra-thin nanocomposite layers used as gate dielectric in low-voltage and high-performance flexible organic thin film transistors (oTFTs). Reactive sputtered zirconia layers were deposited with low thermal exposure of the substrate and the resulting porous oxide films with high leakage currents were spin-coated with an additional layer of poly-α-methylstyrene (PαMS). After this treatment a strong improvement of the oTFT performance could be observed; leakage currents could be eliminated almost completely. In ellipsometric studies a higher refractive index of the ZrO₂/PαMS layers compared to the “as sputtered” zirconia films could be detected without a significant enhancement of the film thickness. Atomic force microscopy (AFM) measurements of the surface topography clearly showed a surface smoothing after the PαMS coating. Further studies with X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) also indicated that the polymer definitely did not form an extra layer. The polymer chains rather (self-)assemble in the nano-scaled interspaces of the porous oxide film giving an oxide–polymer “nanocomposite” with a high oxide filling grade resulting in high dielectric constants larger than 15. The dielectric strength of more than 1 MV cm⁻¹ is in good accordance with the polymer-filled interspaces.     

Self-repairing and superhydrophobic film of gold nanoparticles and fullerene pyridyl derivative based on the self-assembly approach

In this paper, we report that thin gold films can be prepared on the water/toluene interface by self-assembly of gold nanoparticles (NPs) and fullerene pyridyl derivatives. The assembled films were characterized using UV–vis spectroscopy and transmission electron microscope (TEM). The films show self-repairing and superhydrophobic properties.     

Effect of surfactants on the stability of thin liquid film flow on a rotating disk

The effect of surfactants on surface instabilities of thin liquid film flow on a rotating disk was studied at different flow rates Q (0.5相似文献   

Low dielectric constant nanocomposite thin films based on silica nanoparticle and organic thermosets

Low dielectric constant (low-k) nanocomposite thin films have been prepared by spin coating and thermal cure of solution mixtures of one of two organic low-k thermoset prepolymers and a silica nanoparticle with an average diameter of about 8 nm. The electrical, the mechanical, and the thermomechanical properties of these low-k nanocomposite thin films have been characterized with 4-point probe electrical measurements, nanoindentation measurements with an atomic force microscope, and specular X-ray reflectivity. Addition of the silica nanoparticle to the low-k organic thermosets enhances both the modulus and the hardness and reduces the coefficient of thermal expansion of the resultant nanocomposite thin films. The enhancements in the modulus of the nanocomposite thin films are less than those predicted by the Halpin-Tsai equations, presumably due to the relatively poor interfacial adhesion and/or the aggregation of the hydrophilic silica nanoparticles in the hydrophobic organic thermoset matrices. The addition of the silica nanoparticle to the low-k organic thermoset matrices increases the relative dielectric constant of the resultant nanocomposite thin films. The relative dielectric constant of the nanocomposite thin films has been found to agree fairly well with an additive formula based on the Debye equation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1482–1493, 2007     

Fluorescence spectroscopic study of dip coated sol-gel thin film internal environment using fluorescent probes Hoechst33258 and Pyranine

The characterization of physicochemical properties of the internal environment of sol-gel thin films is required for understanding and designing applications in optical biosensors. We have investigated the dip coated tetraethyl-orthosilicate (TEOS) derived sol-gel thin films deposited on microscopic glass cover slips using molar ratio (water or ethanol / TEOS) R=32 using fluorescence spectroscopic measurements (emission, lifetime and anisotropy) on entrapped fluorescent probes. The effect of water and/or ethanol was studied as a function of storage (60 days) using fluorescent probes Hoechst 33258 (H258) and Pyranine (PY). Distribution of fluorescent probes in thin film was studied using confocal microscope. Emission maxima of H258 entrapped thin films from sol prepared using water as solvent showed emission maximum at 503 nm indicating the presence of water like environment which did not change during storage. On the contrary, PY entrapped thin films depicted emission bands at 434 nm and 513 nm, characteristics of ethanol and water respectively, up to the first few weeks and then the band at 434 nm prevailed (60 days), suggesting heterogeneous internal environment. Thin films from sol prepared using ethanol as solvent showed presence of ethanol through out storage. Fluorescence lifetime data of these probes in both sol-gel and thin films also suggested presence of heterogeneous internal environment. Thin films prepared from sol-gel using water as solvent suggested release of ethanol in the pores during hydrolysis and condensation reaction, which were clearly indicated by PY. The effect of sodium phosphate buffer was also studied in sol-gel and thin films. The results of these measurements showed that both the probes H258 and PY could be used effectively in monitoring the physicochemical properties of internal environment of thin films and sol-gel as a function of storage.     

Controllable preparation of nanosized TiO_2 thin film and relationship between structure of film and its photocatalytic activity

~~Controllable preparation of nanosized TiO_2 thin film and relationship between structure of film and its photocatalytic activity@魏刚$College of Material Science and Engineering,Beijing University of Chemical Technology! Beijing 100029,China @张元晶$College of Material Science and Engineering,Beijing University of Chemical Technology! Beijing 100029,China @熊蓉春$College of Material Science and Engineering,Beijing University of Chemical Technology! Beijing 100029,China~…