Facile deposition of copper-doped diamond-like carbon nanocomposite films by a liquid-phase electrochemical route

Copper-doped diamond-like carbon nanocomposite films have been facilely deposited by a liquid-phase electrochemical route from an acetonitrile solution of [Cu(CH(3)CN)(4)]ClO(4).     

Plasma-enhanced deposition of diamond-like carbon films on high temperature tolerant polymers

The feasibility of depositing carbon films with a diamond-like structure on high temperature polymers, using established plasma-enhanced chemical vapor deposition techniques, is explored. Potential uses for such a film will depend upon the adhesion of the film to the substrate, the properties of the deposited film, and the effect of the deposition process on the bulk properties of the polymer substrate. Amorphous carbon (diamond-like carbon) coatings with thicknesses ranging from 2 to 18 μm were deposited on polyimide substrates at temperatures below 420°C. Extended exposure to the plasma processing conditions caused no visible damage but halved the room-temperature tensile strength of the polymer films. Diamond-like carbon, graphitic carbon, and a precursor to the diamond-like carbon structure, attributed to an aromatic carbon ring structure, were observed. The optical transparency of the coated polymer film was attenuated uniformly across the spectral range, 2.5-22 μm. Static oxidation and limited thermal cycling of the coated polymer produced no widespread delamination of the coating from the substrate: neither the deposited film nor the coated regions of the polymer showed any effect when oxidized at 370°C, for 450 h. © 1994 John Wiley & Sons, Inc.     

Simultaneous fabrication of superhydrophobic and superhydrophilic polyimide surfaces with low hysteresis

Polyimide is of great interest in the field of MEMS and microtechnology. It is often used for its chemical, thermal, mechanical, and optical properties. In this paper, an original study is performed on controlled variation of polyimide film wettability. A two-step microtexturing method is developed to transform hydrophilic polyimide surfaces into a superhydrophobic surface with low magnitude of hysteresis (Δθ ≈ 0° and contact angle θ ≈ 158°). This method is based on the conception of a new kind of fakir surface with triangular cross-section micropillars, the use of a two-scale roughening, and a C(4)F(8) coating. We demonstrate that the absence of hysteresis is related to a combination of two scales of structuring and the pillar shape. The technology that has been developed results in the simultaneous fabrication of adjacent superhydrophobic and superhydrophilic small areas, which allows an effect of self-positioning of water droplets when deposited on such a checkerboard-like surface.     

Long-lasting hydrophilicity on nanostructured Si-incorporated diamond-like carbon films

We investigated the long-lasting hydrophilic behavior of a Si-incorporated diamond-like carbon (Si-DLC) film by varying the Si fraction in DLC matrix through oxygen and nitrogen plasma surface treatments. The wetting behavior of the water droplets on the pure DLC and Si-DLC with the nitrogen or oxygen plasma treatment revealed that the Si element in the oxygen-plasma-treated Si-DLC films played a major role in maintaining a hydrophilic wetting angle of <10° for 20 days in ambient air. The nanostructured patterns with a roughness of ～10 nm evolved because of the selective etching of the carbon matrix by the oxygen plasma in the Si-DLC film, where the chemical component of the Si-Ox bond was enriched on the top of the nanopatterns and remained for over 20 days.     

Electrochemical properties of diamond-like carbon electrodes prepared by the pulsed laser deposition method

Diamond-like carbon electrodes (DLCEs) have been synthesized by the pulsed laser deposition method. The surface structure of the DLCEs has been studied by atomic force microscopy and the root-mean-square roughness has been established as R _ms≥81 ?. Electrochemical impedance spectroscopy and cyclic voltammetry data show that DLCEs are nearly ideally polarizable in the potential region –0.4<E<1.1 V (vs. Ag|AgCl|sat. KCl in H₂O) in 0.1 M NaF+H₂O solution. Various equivalent circuits have been used for fitting the complex plane and Bode plots. A very good agreement between experimental and calculated Nyquist curves has been established if the charge transfer and double layer charging at the surface, intercalation of the H⁺ and (or) Na⁺ ions and solid phase diffusion inside the nanoparticle, as well as the effect of an insulating film at the surface (i.e. surrounding the nanoparticles), are taken into account.     

Formation of superhydrophobic surfaces by the deposition of coatings from supercritical carbon dioxide

The deposition of uniform coatings of fluorinated polymers from solutions in supercritical carbon dioxide on a number of rough substrates allowed superhydrophobic (ultrahydrophobic) properties to be imparted to their surfaces, and, namely, to increase the value of the contact angle for water droplet to 150° and greater. The dynamics of changing of geometry of a drying droplet on a substrate is studied. A procedure is developed that permits the penetration of water into the substrate to be detected. Original Russian Text & M.O. Gallyamov, L.N. Nikitin, A.Yu. Nikolaev, A.N. Obraztsov, V.M. Bouznik, A.R. Khokhlov, 2007, published in Kolloidnyi Zhurnal, 2007, Vol. 69, No. 4, pp. 448–462.     

The unusual tribological behavior of diamond-like carbon films under high vacuum

We fabricate F-doped and F-S-codoped diamond-like carbon (DLC) films using plasma-enhanced chemical vapor deposition system. The hardness, Raman spectra, and high-vacuum tribological behaviors indicate that the films are DLC films. The hardness is close related to the tribological properties of DLC films under high vacuum. The high hardness of DLC films would be helpful for obtaining the long lifetime under high vacuum. The lifetimes of F-S-codoped DLC films are about 120 and 140 seconds, which is attributed to the fast graphitization under high vacuum. The lifetime of F-doped DLC films is prolonged to the value of around 300 and 440 seconds, X-ray photoelectron spectroscopy analysis exhibits the existence of the “adsorption” F, and transmission electron microscopy analysis shows that the “adsorption” F could react with Fe to form layered FeF₂ nanocrystal at the initial sliding, which could be helpful for prolonging the lifetime of F-doped DLC films under high vacuum. This investigation opens a new window to overcome the disadvantage of F, S-doped DLC films under high vacuum.     

Ultralow hysteresis superhydrophobic surfaces by excimer laser modification of SU-8

We present a new and simple method to produce superhydrophobic surfaces with ultralow hysteresis. The method involves surface modification of SU-8 using an excimer laser treatment. The modified surface is coated with a hydrophobic plasma-polymerized hexafluoropropene layer. The advancing and receding water contact angles were measured to be approximately 165 degrees . The achieved water contact angle hysteresis was below the measurement limit. This low hysteresis can be ascribed to nanoscale debris generated during the excimer laser process.     

Structural and electrical characterization of boron-containing diamond-like carbon films deposited by femtosecond pulsed laser ablation

The present study investigates the influence of the incorporation of boron in Diamond-Like Carbon (DLC) films deposited by femtosecond laser ablation, on the structure and electrical properties of the coatings within the temperature range 70–300 K. Doping with boron has been performed by ablating alternatively graphite and boron targets. The film structure and composition have been highlighted by coupling Atomic Force Microscopy (AFM), Scanning Electron Microscopy equipped with a field emission gun (SEM-FEG) and High Resolution Transmission Electron Microscopy (HRTEM). Boron dilution ranges between 2 and 8% and appears as nanometer size clusters embedded in the DLC matrix. Typical resistivity values are 100 W cm for pure a-C films, down to few W cm for a-C:B films at room temperature. The resistance decreases exponentially when the temperature increases in the range 70–300 K. The results are discussed considering the classical model of hopping conduction in thin films. Some coatings show temperature coefficients of resistance (TCR) as high as 3.85%. TCRs decrease when the doping increases. Such high values of TCR may have interests in the use of these films as thermometer elements in micro and nanodevices.     

Vertical alignment of single-walled carbon nanotube films formed by electrophoretic deposition

Films of chemically shortened and functionalized single-walled carbon nanotubes (SWNTs) have been formed on a gold electrode by electrophoretic deposition. Applying ultrasonic energy resulted in dramatic changes of the film morphology; the deposited SWNT bundles reassembled and oriented normal to the electrode. Oriented SWNT bundles with high density (more than 250 bundles/microm (2)) not only presented narrow size distributions, but uniformly spread on the electrode. We discuss the mechanism of SWNT orientation by analyzing the variation in the film morphology with ultrasonication time. In addition, we suggest that the 3D displays of AFM images can lead to misjudgment of nanotube alignment. The method for aligning SWNTs normal to the electrode may be competitive with chemical vapor deposition or screen printing, the predominant methods by which vertically aligned SWNT films have been fabricated to date.     

Surface enhanced Raman spectroscopic characterization of molecular structures in diamond-like carbon films

Vibrational bands associated with the out of plane bending modes of CH groups attached to various aromatic ring structures have been identified in surface enhanced Raman spectra of diamond-like amorphous carbon films deposited by femtosecond laser ablation of graphite. The appearance of enhanced modes associated with specific ring structures is assigned to solo-, duo-, trio- and quartet-CH groups and to pendant rings. Analysis of these bands provides insight into the nature of the molecular ring components of fs-DLC films. The resulting composition consists of polycyclic aromatic carbon (PAH)-like ring molecules and polyyne chains stabilized in a sp³-bonded network.     

Facile transformation of hydrophilic cellulose into superhydrophobic cellulose

Superhydrophobic cellulose-based materials coupled with transparent, stable and nanoscale polymethylsiloxane coating have been successfully achieved by a simple process via chemical vapor deposition, followed by hydrolyzation and polymerization.     

Droplet compression and relaxation by a superhydrophobic surface: contact angle hysteresis

In this article, the contact angle hysteresis (CAH) of acrylic glass is experimentally and theoretically studied through the compression-relaxation process of droplets by using a superhydrophobic surface with negligible CAH effect. In contrast to the existing technique in which the volume of the droplet changes during the measurement of CAH, this procedure is carried out at a constant volume of the droplet. By observing the base diameter (BD) and the contact angle (CA) of the droplet during the compression-relaxation process, the wetting behavior of the droplet can be divided into two regimes, the contact line withdrawal and the contact line pinning regimes, depending on the gap thickness (H) at the end of the compression process. During the compression process, both regimes possess similar droplet behavior; the contact line will move outward and the BD will expand while the CA remains at the advancing angle. During the relaxation process, the two regimes are significantly different. In the contact line withdrawal regime, the contact line will withdraw with the CA remaining at the receding angle. In the contact line pinning regime, however, the contact line will be pinned at the final position and the CA will decline to a certain value higher than the receding angle. Furthermore, the advancing pinning behavior can also be realized through a successive compression-relaxation process. On the basis of the liquid-induced defects model, Surface Evolver simulations are performed to reproduce the behavior of the droplet during the compression-relaxation process; both contact line withdrawal and pinning regimes can also be identified. The results of the experiment and simulation agree with each other very well.     

Reversible switching on superhydrophobic TiO2 nano-strawberry films fabricated at low temperature

Superhydrophobic TiO2 nano-strawberry rutile films, on which superhydrophobicity and superhydrophilicity can be reversibly switched by alternation of ultraviolet (UV) irradiation and dark storage, were fabricated on a large scale from aqueous solution via a seeded growth method at low temperature without any pressure equipment.     

Stable superhydrophobic organic-inorganic hybrid films by electrostatic self-assembly

Organic-inorganic hybrid films were prepared through layer-by-layer (LBL) deposition of poly(allylamine hydrochloride) (PAH) and ZrO(2) nanoparticles coated with poly(acrylic acid) (PAA), allowing facile control of surface roughness and hydrophobicity. Superhydrophobic behavior was observed after deposition of silica nanoparticles and a simple fluorination of the surface. The structure of films was controlled by the number of deposition cycles using PAA-coated 100 nm ZrO(2) nanoparticles, the particle size, and the prelayer with PAH and PAA. The change in the apparent water contact angle of (PAH/PAA-coated ZrO(2)n surfaces without fluorination of the surface agrees with Cassie and Baxter's model for nonwetted surfaces even though the outermost surface itself is hydrophilic. Superhydrophobic surfaces were then successfully developed by the deposition of hydrophilic silica nanoparticles on a 10 bilayer surface of PAH/PAA-coated ZrO(2), and a simple fluorination. Moreover, the chemical stability of the film was greatly increased by heat-induced cross-linking of the film. The incorporation of ZrO(2) nanoparticles in superhydrophobic films promises better mechanical properties than the organic film.     

Thermodynamic aspects of fibroblastic spreading on diamond-like carbon films containing titanium dioxide nanoparticles

The combination of low friction, wear resistance, high hardness, biocompatibility, and chemical inertness makes diamond-like carbon (DLC) films suitable in numerous applications in biomedical engineering. The cytotoxicity of DLC films containing TiO₂ nanoparticles was practical and theoretically evaluated. The films were grown on 316L stainless steel substrates from a dispersion of TiO₂ nanopowder in hexane. Raman spectroscopy shows that the presence of TiO₂ increased the graphite-like bonds in the films. The incorporation of TiO₂ nanoparticles into DLC films increases surface roughness, decreases water contact angle (increased hydrophilic character), and increases the total free surface energy due to the higher polar component. As the concentration of TiO₂ increased, the films increased the cell viability (MTT assay), becoming more thermodynamically favorable to cell spreading (??F _Adh values became more negative). This was evidenced through the increasing number of projections (philopodia and lamellipodia), indicating a higher adhesion between the L929 cells and the films. The practical and theoretical findings of this study show that the incorporation of TiO₂ into DLC films is effective in enhancing cell viability. These results show the potential use of DLC and TiO₂-DLC films in biomedical applications.     

Si-doped carbon nanostructured films by pulsed laser deposition from a liquid target

Ablation of a silicone oil, Dow Corning's DC-705 with laser pulses of sub-ps duration in high vacuum is a novel approach to fabrication of Si-doped carbon nanocomposite films. Gently focused, temporally clean 700 fs pulses @ 248 nm of a hybrid dye/excimer laser system produce power densities of the order of 10¹¹–10¹² W cm^?2 on the target surface. The evolution of the chemical structure of film material is followed by comparing Fourier Transformed Infrared and X-ray Photoelectron spectra of films deposited at temperatures between room temperature and 250 °C. Despite the low thermal budget technique, in the spectrum of films deposited at room temperature the fingerprint of the silicone oil can clearly be identified. With increasing substrate temperature the contribution of the features characteristic of the oil gradually diminishes, but does not completely disappear even at 250 °C. This result is intriguing since the chance of oil droplets to survive in their original liquid form on the hot surface should be minimal. The results of the X-ray Photoelectron Spectroscopy suggest that the chemical structure of the film material resembles that of the oil. Both reflection mode optical microscopy and low magnification Scanning Electron Microscopy reveal that the films are inhomogeneous: areas of lateral dimensions ranging from a few to tens of micrometers, characterized by different contrasts can be identified. On the other hand, surface mapping by Scanning Electron and Atomic Force Microscopy unambiguously proves that all films possess a solid surface consisting of nanoparticles of less than 100 nm dimension, without the presence of any drop of oil. Possible explanations of the puzzling results can be that the films are polymers consisting mainly of the molecules of the target material, or composites of solid C:Si nanoparticles and oil residues.     

Preparation of superhydrophobic composite paper mulching film

To study the influence of different concentrations of zinc oxide (ZnO)/silicon dioxide (SiO₂) composite coating on hydrophobic property and mechanical stability of paper mulch film, three kinds of ZnO/SiO₂ composite coating paper mulch films (2%, 4%, 6%) with different coating substance contents were prepared by brush coating method. Through particle size analysis, contact angle, rolling angle and mechanical stability test, combined with scanning electron microscope, three-dimensional morphology and roughness measuring instrument, the optimal concentration of ZnO/SiO₂ composite coated paper mulch film was screened out. Through acid-base salt corrosion test, silver mirror reaction and surface self-cleaning, the optimal concentration of composite coated paper mulch film was compared with the original paper mulch film to prove its excellent chemical stability and hydrophobicity. The results show that the paper mulch film with 4% coating material has excellent hydrophobicity and mechanical stability, can effectively reduce the surface roughness of paper mulch film, and has remarkable effects in resisting acid, alkali and salt and self-cleaning.     

Spectroscopic characterization of carbon chains in nanostructured tetrahedral carbon films synthesized by femtosecond pulsed laser deposition

A comparative study of carbon bonding states and Raman spectra is reported for amorphous diamondlike carbon films deposited using 120 fs and 30 ns pulsed laser ablation of graphite. The presence of sp(1) chains in femtosecond carbon films is confirmed by the appearance of a broad excitation band at 2000-2200 cm(-1) in UV-Raman spectra. Analysis of Raman spectra indicates that the concentrations of sp(1)-, sp(2)-, and sp(3)-bonded carbon are approximately 6%, approximately 43%, and approximately 51%, respectively, in carbon films prepared by femtosecond laser ablation. Using surface enhanced Raman spectroscopy, specific vibrational frequencies associated with polycumulene, polyyne, and trans-polyacetylene chains have been identified. The present study provides further insight into the composition and structure of tetrahedral carbon films containing both sp(2) clusters and sp(1) chains.