Graphene was synthesized directly on Si(100) substrates by microwave plasma-enhanced chemical vap... more Graphene was synthesized directly on Si(100) substrates by microwave plasma-enhanced chemical vapor deposition (MW-PECVD). The effects of the graphene structure on the electrical and photovoltaic properties of graphene/n-Si(100) were studied. The samples were investigated using Raman spectroscopy, atomic force microscopy, and by measuring current–voltage (I-V) graphs. The temperature of the hydrogen plasma annealing prior to graphene synthesis was an essential parameter regarding the graphene/Si contact I-V characteristics and photovoltaic parameters. Graphene n-type self-doping was found to occur due to the native SiO2 interlayer at the graphene/Si junction. It was the prevalent cause of the significant decrease in the reverse current and short-circuit current. No photovoltaic effect dependence on the graphene roughness and work function could be observed.
In the present research, hydrogen-free diamond like carbon films with embedded copper nanoparticl... more In the present research, hydrogen-free diamond like carbon films with embedded copper nanoparticles (DLC:Cu) were grown by simultaneous DC magnetron sputtering of the graphite and copper targets. X-ray photoelectron spectroscopy was used to define the composition of the samples. Atomic force microscopy studies of diamond, like carbon films containing different amount of copper, revealed wide range of the surface morphologies as well as sizes and shapes of the embedded copper nanoclusters. Raman scattering spectra of all the DLC:Cu films investigated were typical for diamond-like carbon (including samples containing more than 60 at.% of copper). sp3/sp2 carbon bond ratio in the films decreased with the increase of the Cu amount in the films. According to the optical absorbance measurements, the surface plasmon resonance related absorption peak of DLC:Cu films was only detected in the films containing 28.45 at.% Cu. For the diamond like carbon films containing more than 40 at.% Cu, a ...
SiO x doped diamond-like carbon (DLC) films were synthesized by direct ion beam from hexamethyldi... more SiO x doped diamond-like carbon (DLC) films were synthesized by direct ion beam from hexamethyldisiloxane vapor. Effects of ion beam energy were studied. Variation of atomic concentration of the oxygen versus carbon with ion energy has been observed. Raman scattering spectroscopy didn't indicate essential changes in structure of the films deposited at different ion beam energies. The synthesized films were atomically smooth. Depending on the ion energy the refractive index of the SiO x doped diamond-like carbon films varied within 2.1-2.5 and increased with increase of energy. The contact angle with water for all samples was only 61-64°.
In this study SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H... more In this study SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx (a-C:H:N/SiOx) films were deposited on polyvinylpyrrolidone (PVP) templates of variable thickness using a Hall-type closed drift ion beam source with constant irradiation parameters. A detailed surface characterization was followed using atomic force microscopy (AFM) topography images, surface morphology parameters, height distribution histograms and bearing ratio curves with hybrid parameters. The AFM analysis directly showed that the a-C:H/SiOx/PVP and a-C:H:N/SiOx/PVP composite films represent different morphologies with characteristic surface textures. Surface adhesive properties were evaluated by measuring the force required to separate the AFM tip from the surface by means of AFM force-distance curves. The variance in adhesion force detected was lower for a-C:H/SiOx/PVP composite films due to lower structural homogeneity of the surfaces. Fourier transform infrared spectroscopy analysis was performed to study the blend behavior of PVP upon a-C:H/SiOx and a-C:H:N/SiOx direct ion beam deposition. It was determined that interfacial interactions of PVP with the direct ion beam induced changes in the carbonyl group of the PVP and are dependent on the carrier gas used for the synthesis of the amorphous hydrogenated carbon films.
The morphology and chemical composition of the surface of SiO2 that had been implanted with Zn io... more The morphology and chemical composition of the surface of SiO2 that had been implanted with Zn ions of 60keV and annealed in two different atmospheres, i.e., oxygen gas and a vacuum, were compared. In the as-implanted state, the surface mainly consisted of SiO2 with low roughness due to radiation-induced smoothing. A large number of domelike structures of ZnO appeared on the surface of the SiO2 after annealing in oxygen gas at 600°C for 1h, and the size increased with the annealing temperature up to 800°C. After annealing at 900°C, the surface roughness steeply decreased and the composition changed to Zn2SiO4.
Superhydrophobic and transparent films would be very useful in optoelectronic applications where ... more Superhydrophobic and transparent films would be very useful in optoelectronic applications where non-wetting is desired. Herein, hexamethyldisilazane was used for functionalization of fumed SiO 2 nanoparticles via silylation derivatization reaction. Modified fumed SiO 2 nanoparticle dispersion was used for fabrication of SiO 2-based nanostructured film via drop-casting method. This film exhibited a combination of high optical transmittance in the visible spectrum portion and superhydrophobicity (163 • ± 1 • and hysteresis as low as~2 •). This was possible to achieve due to the submicrometer-scale roughness (R q = 252.7 nm) and branched network structure of the film surface with convenient surface chemistry of hydrophobic methyl groups. The method reported herein is not complicated, allows for obtaining large quantities of modified SiO 2 nanoparticle dispersions and can be used in combination with other deposition methods.
Environmental Technology and Innovation, Aug 1, 2020
Titanium dioxide (TiO 2) based photocatalysis has been among the most popular advanced oxidation ... more Titanium dioxide (TiO 2) based photocatalysis has been among the most popular advanced oxidation processes in environmental applications in past several decades due to its low cost, nontoxicity, and relatively high oxidizing ability, although suffering from relatively low pollutant decomposition efficiency. Here we present a study on the enhancement of efficiency of thin TiO 2 film produced by reactive magnetron sputtering on an interference lithography-processed support, thus increasing the surface area. The efficiency of differently patterned samples was demonstrated by decolorization of methylene blue. The three fold enhancement of the photocatalytic efficiency was observed due to surface area enlargement, and additionally due to multiple UV light reflections.
Materials Research-ibero-american Journal of Materials, 2019
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most successful transp... more Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most successful transparent conductive polymer widely used in functional organic devices. However, its potential in fabrication of highly conductive electrodes still has not been fully explored. This paper is an attempt to fill the existing gap of knowledge on possible post-treatments of dimethyl sulfoxide (DMSO)-doped PEDOT:PSS thin films. In the present study, surface morphology, optical and electrical properties of untreated and sulfuric acid treated DMSO-doped PEDOT:PSS multilayers on the glass coverslip substrates are examined. It is demonstrated that short-time sulfuric acid treatment enhances electrical and optical properties, and smoothens surface of the transparent conductive films. Enhancement of electrical conductivity by more than 30 % can be associated with increase in doping level, removal of excess PSS and accompanied shape alterations of the conjugated PEDOT chains. Acid treatment also results in smoother transmittance spectra and a slight improvement of optical transparency. Hence, sulfuric acid post-treatment can be considered as a simple and inexpensive technique for the complementary doping of DMSO-doped PEDOT:PSS films with the aim to develop the more effective transparent electrodes.
Ag–PVP (silver-polyvinylpyrrolidone) films were spin-coated on silica substrates from Ag–PVP coll... more Ag–PVP (silver-polyvinylpyrrolidone) films were spin-coated on silica substrates from Ag–PVP colloidal solution. Formation of nanoparticles in deposited films was achieved by photoreduction of silver ions due to UV irradiation of prepared samples. Presence of spherical nanoparticles in UV irradiated samples was identified according to the measured absorbance peaks of samples that were observed in the range 410–430nm and were explained by surface plasmon resonance phenomenon. Produced nanocomposite films were further on modified additionally irradiating them with gamma photons within the dose range (2–50) Gy.Plasmonic and mechanical properties of gamma irradiated nanocomposite films have been investigated by UV–vis spectroscopy and AFM and compared to those obtained after prolonged UV irradiation of films.
ABSTRACT Ion beam deposited hydrogenated undoped as well as SiOx (SiOx + N2, SiOx + Ar) doped DLC... more ABSTRACT Ion beam deposited hydrogenated undoped as well as SiOx (SiOx + N2, SiOx + Ar) doped DLC thin films were deposited and evaluated as possible anti-adhesive layers for nanoimprint lithography. Film surface contact angle with water was investigated as a measure of the surface free energy and anti-sticking properties. Contact angle of the DLC films was independent of SiOx doping and ion beam energy. Air-annealing resistance in terms of the contact angle with water of the synthesized diamond like carbon films was investigated. Optical transmittance spectra of the DLC films in UV–VIS range were measured to investigate it as possible anti-sticking layers for UV imprint lithography applications. DLC films with the most promising combination of the UV absorption and anti-sticking properties were revealed. Preliminary imprint tests with uncoated and thin DLC film coated hot imprint stamps were performed.
Microresonators are fundamental components integrated in hosts of MEMS applications: covering the... more Microresonators are fundamental components integrated in hosts of MEMS applications: covering the automotive sector, the telecommunication industry, electronic equipment for surface/material characterization and motion sensing, and etc. The aim of this paper is to investigate the mechanical and electrical properties of PZT film fabricated with three binding materials: polyvinyl butyral (PVB), polymethyl methacrylate (PMMA) and polystyrene (PS) and to evaluate applicability in control of microresonators Q factor. Micro particles of PZT powder were mixed with 20% solution of PVB, PMMA and PS in benzyl alcohol. For investigation of mechanical and electrical properties multilayer cantilevers were made. Obtained PZT and polymer paste was screen printed on copper (thickness 40 μm) using polyester monofilament screen meshes (layer thickness 50 μm) and dried for 30 min at 100°C. Electric dipoles of the PZT particles in composite material were aligned using high voltage generator (5 kV) and a custom–made holder. Electric field was held for 30 min. Surfaces of the applied films were investigated by Atomic Force Microscope NanoWizard(R)3 NanoScience. Dynamic and electrical characteristics of the multilayer were investigated using laser triangular displacement sensor LK-G3000. The measured vibration amplitude and generated electrical potential was collected with USB oscilloscope PicoScope 3424. As the results showed, these cantilevers were able to transform mechanical strain energy into electric potential and, v.v. However, roughness of PZT coatings with PMMA and PS were higher, what could be the reason of the worse quality of the top electrode. However, the main advantage of the created composite piezoelectric material is the possibility to apply it on any uniform or non-uniform vibrating surface and to transform low frequency vibrations into electricity.
This paper reviews recent investigations and achievements in the design of controllable functiona... more This paper reviews recent investigations and achievements in the design of controllable functional components for improving microfluidic systems, its effectiveness, and functionality. The main purpose was to design novel microstructures with piezoelectric properties (microresonators), which enable one to control the effectiveness of fluid flow in micro-hydro-mechanical devices for biomedical/biochemical purposes. Controllable properties were obtained by incorporating different types of binders in a piezoelectric ceramic matrix (lead zirconate titanate): polyvinyl butyral (PVB), poly methyl methacrylate (PMMA), and polystyrene (PS). The change in chemical composition of PZT helps to manipulate the piezoelectric characteristics, surface morphology, mechanical properties, etc., of the designed microfluidic element with the microstructure in it.
ABSTRACT Abstract Graphene oxide (GO) has been recognized as an important intermediate compound f... more ABSTRACT Abstract Graphene oxide (GO) has been recognized as an important intermediate compound for a potential low-cost large-scale graphene-like film fabrication. In this work, graphene oxide multilayer films deposited on glass substrate were reduced using different thermal reduction methods, including low-temperature annealing, flame-induced and laser reduction, and the corresponding surface morphology and structural properties were investigated. These graphene oxide thermal reduction methods strongly affected surface morphology and differently facilitated structural and chemical transformations of graphene oxide. As evidenced by Raman measurements, thermal annealing and laser reduction of graphene oxide produced more ordered graphene-like structure multilayer films. However, surface morphological differences were observed and attributed to the different de-oxidation mechanisms of GO. This Letter provides an important systematic comparison between the GO reduction methods and thermally-driven structural changes they provide to the reduced GO multilayer films obtained.
ABSTRACT In this study, hot embossing by reusable Ni mold with features in the form of rectangula... more ABSTRACT In this study, hot embossing by reusable Ni mold with features in the form of rectangular diffraction gratings of 4μm period was successfully employed for surface texturing of polytetrafluoroethylene (PTFE) film above the glass transition temperature of PTFE amorphous phase with the aim to enhance surface hydrophobicity. Imprint pressure was set to 0.5MPa and it was at least tenfold lower than reported by other authors using cold stamping. Embossed gratings were clearly seen on the surface of all imprinted samples even after the annealing at 140°C and aging for 1 month at room temperature. The best results were achieved when imprint temperature was 150°C. Measurements of the water contact angle on imprinted PTFE surfaces have showed that increase of the average contact angle for the current test setup was 8°. Using imprint stamp with the more favorable features may lead to somewhat higher hydrophobicity.
Graphene was synthesized directly on Si(100) substrates by microwave plasma-enhanced chemical vap... more Graphene was synthesized directly on Si(100) substrates by microwave plasma-enhanced chemical vapor deposition (MW-PECVD). The effects of the graphene structure on the electrical and photovoltaic properties of graphene/n-Si(100) were studied. The samples were investigated using Raman spectroscopy, atomic force microscopy, and by measuring current–voltage (I-V) graphs. The temperature of the hydrogen plasma annealing prior to graphene synthesis was an essential parameter regarding the graphene/Si contact I-V characteristics and photovoltaic parameters. Graphene n-type self-doping was found to occur due to the native SiO2 interlayer at the graphene/Si junction. It was the prevalent cause of the significant decrease in the reverse current and short-circuit current. No photovoltaic effect dependence on the graphene roughness and work function could be observed.
In the present research, hydrogen-free diamond like carbon films with embedded copper nanoparticl... more In the present research, hydrogen-free diamond like carbon films with embedded copper nanoparticles (DLC:Cu) were grown by simultaneous DC magnetron sputtering of the graphite and copper targets. X-ray photoelectron spectroscopy was used to define the composition of the samples. Atomic force microscopy studies of diamond, like carbon films containing different amount of copper, revealed wide range of the surface morphologies as well as sizes and shapes of the embedded copper nanoclusters. Raman scattering spectra of all the DLC:Cu films investigated were typical for diamond-like carbon (including samples containing more than 60 at.% of copper). sp3/sp2 carbon bond ratio in the films decreased with the increase of the Cu amount in the films. According to the optical absorbance measurements, the surface plasmon resonance related absorption peak of DLC:Cu films was only detected in the films containing 28.45 at.% Cu. For the diamond like carbon films containing more than 40 at.% Cu, a ...
SiO x doped diamond-like carbon (DLC) films were synthesized by direct ion beam from hexamethyldi... more SiO x doped diamond-like carbon (DLC) films were synthesized by direct ion beam from hexamethyldisiloxane vapor. Effects of ion beam energy were studied. Variation of atomic concentration of the oxygen versus carbon with ion energy has been observed. Raman scattering spectroscopy didn't indicate essential changes in structure of the films deposited at different ion beam energies. The synthesized films were atomically smooth. Depending on the ion energy the refractive index of the SiO x doped diamond-like carbon films varied within 2.1-2.5 and increased with increase of energy. The contact angle with water for all samples was only 61-64°.
In this study SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H... more In this study SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx (a-C:H:N/SiOx) films were deposited on polyvinylpyrrolidone (PVP) templates of variable thickness using a Hall-type closed drift ion beam source with constant irradiation parameters. A detailed surface characterization was followed using atomic force microscopy (AFM) topography images, surface morphology parameters, height distribution histograms and bearing ratio curves with hybrid parameters. The AFM analysis directly showed that the a-C:H/SiOx/PVP and a-C:H:N/SiOx/PVP composite films represent different morphologies with characteristic surface textures. Surface adhesive properties were evaluated by measuring the force required to separate the AFM tip from the surface by means of AFM force-distance curves. The variance in adhesion force detected was lower for a-C:H/SiOx/PVP composite films due to lower structural homogeneity of the surfaces. Fourier transform infrared spectroscopy analysis was performed to study the blend behavior of PVP upon a-C:H/SiOx and a-C:H:N/SiOx direct ion beam deposition. It was determined that interfacial interactions of PVP with the direct ion beam induced changes in the carbonyl group of the PVP and are dependent on the carrier gas used for the synthesis of the amorphous hydrogenated carbon films.
The morphology and chemical composition of the surface of SiO2 that had been implanted with Zn io... more The morphology and chemical composition of the surface of SiO2 that had been implanted with Zn ions of 60keV and annealed in two different atmospheres, i.e., oxygen gas and a vacuum, were compared. In the as-implanted state, the surface mainly consisted of SiO2 with low roughness due to radiation-induced smoothing. A large number of domelike structures of ZnO appeared on the surface of the SiO2 after annealing in oxygen gas at 600°C for 1h, and the size increased with the annealing temperature up to 800°C. After annealing at 900°C, the surface roughness steeply decreased and the composition changed to Zn2SiO4.
Superhydrophobic and transparent films would be very useful in optoelectronic applications where ... more Superhydrophobic and transparent films would be very useful in optoelectronic applications where non-wetting is desired. Herein, hexamethyldisilazane was used for functionalization of fumed SiO 2 nanoparticles via silylation derivatization reaction. Modified fumed SiO 2 nanoparticle dispersion was used for fabrication of SiO 2-based nanostructured film via drop-casting method. This film exhibited a combination of high optical transmittance in the visible spectrum portion and superhydrophobicity (163 • ± 1 • and hysteresis as low as~2 •). This was possible to achieve due to the submicrometer-scale roughness (R q = 252.7 nm) and branched network structure of the film surface with convenient surface chemistry of hydrophobic methyl groups. The method reported herein is not complicated, allows for obtaining large quantities of modified SiO 2 nanoparticle dispersions and can be used in combination with other deposition methods.
Environmental Technology and Innovation, Aug 1, 2020
Titanium dioxide (TiO 2) based photocatalysis has been among the most popular advanced oxidation ... more Titanium dioxide (TiO 2) based photocatalysis has been among the most popular advanced oxidation processes in environmental applications in past several decades due to its low cost, nontoxicity, and relatively high oxidizing ability, although suffering from relatively low pollutant decomposition efficiency. Here we present a study on the enhancement of efficiency of thin TiO 2 film produced by reactive magnetron sputtering on an interference lithography-processed support, thus increasing the surface area. The efficiency of differently patterned samples was demonstrated by decolorization of methylene blue. The three fold enhancement of the photocatalytic efficiency was observed due to surface area enlargement, and additionally due to multiple UV light reflections.
Materials Research-ibero-american Journal of Materials, 2019
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most successful transp... more Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most successful transparent conductive polymer widely used in functional organic devices. However, its potential in fabrication of highly conductive electrodes still has not been fully explored. This paper is an attempt to fill the existing gap of knowledge on possible post-treatments of dimethyl sulfoxide (DMSO)-doped PEDOT:PSS thin films. In the present study, surface morphology, optical and electrical properties of untreated and sulfuric acid treated DMSO-doped PEDOT:PSS multilayers on the glass coverslip substrates are examined. It is demonstrated that short-time sulfuric acid treatment enhances electrical and optical properties, and smoothens surface of the transparent conductive films. Enhancement of electrical conductivity by more than 30 % can be associated with increase in doping level, removal of excess PSS and accompanied shape alterations of the conjugated PEDOT chains. Acid treatment also results in smoother transmittance spectra and a slight improvement of optical transparency. Hence, sulfuric acid post-treatment can be considered as a simple and inexpensive technique for the complementary doping of DMSO-doped PEDOT:PSS films with the aim to develop the more effective transparent electrodes.
Ag–PVP (silver-polyvinylpyrrolidone) films were spin-coated on silica substrates from Ag–PVP coll... more Ag–PVP (silver-polyvinylpyrrolidone) films were spin-coated on silica substrates from Ag–PVP colloidal solution. Formation of nanoparticles in deposited films was achieved by photoreduction of silver ions due to UV irradiation of prepared samples. Presence of spherical nanoparticles in UV irradiated samples was identified according to the measured absorbance peaks of samples that were observed in the range 410–430nm and were explained by surface plasmon resonance phenomenon. Produced nanocomposite films were further on modified additionally irradiating them with gamma photons within the dose range (2–50) Gy.Plasmonic and mechanical properties of gamma irradiated nanocomposite films have been investigated by UV–vis spectroscopy and AFM and compared to those obtained after prolonged UV irradiation of films.
ABSTRACT Ion beam deposited hydrogenated undoped as well as SiOx (SiOx + N2, SiOx + Ar) doped DLC... more ABSTRACT Ion beam deposited hydrogenated undoped as well as SiOx (SiOx + N2, SiOx + Ar) doped DLC thin films were deposited and evaluated as possible anti-adhesive layers for nanoimprint lithography. Film surface contact angle with water was investigated as a measure of the surface free energy and anti-sticking properties. Contact angle of the DLC films was independent of SiOx doping and ion beam energy. Air-annealing resistance in terms of the contact angle with water of the synthesized diamond like carbon films was investigated. Optical transmittance spectra of the DLC films in UV–VIS range were measured to investigate it as possible anti-sticking layers for UV imprint lithography applications. DLC films with the most promising combination of the UV absorption and anti-sticking properties were revealed. Preliminary imprint tests with uncoated and thin DLC film coated hot imprint stamps were performed.
Microresonators are fundamental components integrated in hosts of MEMS applications: covering the... more Microresonators are fundamental components integrated in hosts of MEMS applications: covering the automotive sector, the telecommunication industry, electronic equipment for surface/material characterization and motion sensing, and etc. The aim of this paper is to investigate the mechanical and electrical properties of PZT film fabricated with three binding materials: polyvinyl butyral (PVB), polymethyl methacrylate (PMMA) and polystyrene (PS) and to evaluate applicability in control of microresonators Q factor. Micro particles of PZT powder were mixed with 20% solution of PVB, PMMA and PS in benzyl alcohol. For investigation of mechanical and electrical properties multilayer cantilevers were made. Obtained PZT and polymer paste was screen printed on copper (thickness 40 μm) using polyester monofilament screen meshes (layer thickness 50 μm) and dried for 30 min at 100°C. Electric dipoles of the PZT particles in composite material were aligned using high voltage generator (5 kV) and a custom–made holder. Electric field was held for 30 min. Surfaces of the applied films were investigated by Atomic Force Microscope NanoWizard(R)3 NanoScience. Dynamic and electrical characteristics of the multilayer were investigated using laser triangular displacement sensor LK-G3000. The measured vibration amplitude and generated electrical potential was collected with USB oscilloscope PicoScope 3424. As the results showed, these cantilevers were able to transform mechanical strain energy into electric potential and, v.v. However, roughness of PZT coatings with PMMA and PS were higher, what could be the reason of the worse quality of the top electrode. However, the main advantage of the created composite piezoelectric material is the possibility to apply it on any uniform or non-uniform vibrating surface and to transform low frequency vibrations into electricity.
This paper reviews recent investigations and achievements in the design of controllable functiona... more This paper reviews recent investigations and achievements in the design of controllable functional components for improving microfluidic systems, its effectiveness, and functionality. The main purpose was to design novel microstructures with piezoelectric properties (microresonators), which enable one to control the effectiveness of fluid flow in micro-hydro-mechanical devices for biomedical/biochemical purposes. Controllable properties were obtained by incorporating different types of binders in a piezoelectric ceramic matrix (lead zirconate titanate): polyvinyl butyral (PVB), poly methyl methacrylate (PMMA), and polystyrene (PS). The change in chemical composition of PZT helps to manipulate the piezoelectric characteristics, surface morphology, mechanical properties, etc., of the designed microfluidic element with the microstructure in it.
ABSTRACT Abstract Graphene oxide (GO) has been recognized as an important intermediate compound f... more ABSTRACT Abstract Graphene oxide (GO) has been recognized as an important intermediate compound for a potential low-cost large-scale graphene-like film fabrication. In this work, graphene oxide multilayer films deposited on glass substrate were reduced using different thermal reduction methods, including low-temperature annealing, flame-induced and laser reduction, and the corresponding surface morphology and structural properties were investigated. These graphene oxide thermal reduction methods strongly affected surface morphology and differently facilitated structural and chemical transformations of graphene oxide. As evidenced by Raman measurements, thermal annealing and laser reduction of graphene oxide produced more ordered graphene-like structure multilayer films. However, surface morphological differences were observed and attributed to the different de-oxidation mechanisms of GO. This Letter provides an important systematic comparison between the GO reduction methods and thermally-driven structural changes they provide to the reduced GO multilayer films obtained.
ABSTRACT In this study, hot embossing by reusable Ni mold with features in the form of rectangula... more ABSTRACT In this study, hot embossing by reusable Ni mold with features in the form of rectangular diffraction gratings of 4μm period was successfully employed for surface texturing of polytetrafluoroethylene (PTFE) film above the glass transition temperature of PTFE amorphous phase with the aim to enhance surface hydrophobicity. Imprint pressure was set to 0.5MPa and it was at least tenfold lower than reported by other authors using cold stamping. Embossed gratings were clearly seen on the surface of all imprinted samples even after the annealing at 140°C and aging for 1 month at room temperature. The best results were achieved when imprint temperature was 150°C. Measurements of the water contact angle on imprinted PTFE surfaces have showed that increase of the average contact angle for the current test setup was 8°. Using imprint stamp with the more favorable features may lead to somewhat higher hydrophobicity.
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Papers by Asta Guobiene