Browsing by Subject "Plasma applications"

Now showing 1 - 4 of 4

Open Access
Characterization of denture acrylic resin surfaces modified by glow discharges
(Sage Publications, Inc., 1997) Süzer, Ş.; Özden, N.; Akaltan, F.; Akovali, G.
Resin samples prepared by compression molding using a poly (methyl methacrylate) (PMMA) denture base material were exposed to radio-frequency (rf) glow discharges to improve the wettability of the material. Fourier transform infrared (FT-IR) reflectance, X-ray photoelectron spectroscopy (XPS), and contact-angle measurements have been employed to characterize the changes introduced by the glow discharge plasma. FT-IR measurements cannot detect any modification. XPS reveals an increase in the O/C atomic ratio. Contact angles of the plasma-treated samples are always lower when compared with untreated ones. The increased O atomic concentration is attributed to formation of -COH groups on the surface during plasma treatment. The O/C atomic ratio decreases upon heating the samples in vacuum to 100 °C for 1-2 min and exposing the samples to liquid CH2Cl2 for 1-2 min. Exposure to distilled water for prolonged periods causes a slight decrease during the initial 1-20 days but levels off to a constant value up to a period of 60 days. Plasma treatment seems to offer a durable increase in the wettability for these materials left in air or distilled water.
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Microcavity enhanced amorphous silicon photoluminescence
(IEEE, 1997) Serpengüzel, Ali; Aydınlı, Atilla; Bek, Alpan
A microcavity enhancement of room temperature photoluminescence (PL) of a hydrogenated amorphous silicon (a-Si:h) was performed. A quantum confinement model was developed to describe the occurrence of the PL in the bulk a-Si:H. According to the model, small a-Si clusters are in a matrix of a-Si:H. The regions with Si-H, having larger energy gaps due to strong Si-H bonds, isolate these clusters, and form barrier regions around them. The PL originates from these a-Si clusters.
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Rapid and alternative fabrication method for microfluidic paper based analytical devices
(Elsevier B.V., 2016) Malekghasemi, S.; Kahveci, E.; Duman, M.
A major application of microfluidic paper-based analytical devices (µPADs) includes the field of point-of-care (POC) diagnostics. It is important for POC diagnostics to possess properties such as ease-of-use and low cost. However, µPADs need multiple instruments and fabrication steps. In this study, two different chemicals (Hexamethyldisilazane and Tetra-ethylorthosilicate) were used, and three different methods (heating, plasma treatment, and microwave irradiation) were compared to develop µPADs. Additionally, an inkjet-printing technique was used for generating a hydrophilic channel and printing certain chemical agents on different regions of a modified filter paper. A rapid and effective fabrication method to develop µPADs within 10 min was introduced using an inkjet-printing technique in conjunction with a microwave irradiation method. Environmental scanning electron microscope (ESEM) and x-ray photoelectron spectroscopy (XPS) were used for morphology characterization and determining the surface chemical compositions of the modified filter paper, respectively. Contact angle measurements were used to fulfill the hydrophobicity of the treated filter paper. The highest contact angle value (141°±1) was obtained using the microwave irradiation method over a period of 7 min, when the filter paper was modified by TEOS. Furthermore, by using this method, the XPS results of TEOS-modified filter paper revealed Si2p (23%) and Si-O bounds (81.55%) indicating the presence of Si–O–Si bridges and Si(OEt) groups, respectively. The ESEM results revealed changes in the porous structures of the papers and decreases in the pore sizes. Washburn assay measurements tested the efficiency of the generated hydrophilic channels in which similar water penetration rates were observed in the TEOS-modified filter paper and unmodified (plain) filter paper. The validation of the developed µPADs was performed by utilizing the rapid urease test as a model test system. The detection limit of the developed µPADs was measured as 1 unit ml−1 urease enzyme in detection zones within a period of 3 min. The study findings suggested that a combination of microwave irradiation with inkjet-printing technique could improve the fabrication method of µPADs, enabling faster production of µPADs that are easy to use and cost-effective with long shelf lives.
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Visible photoluminescence from low temperature deposited hydrogenated amorphous silicon nitride
(Pergamon Press, 1996) Aydınlı, A.; Serpengüzel, A.; Vardar, D.
Hydrogenated amorphous silicon nitride (a-SiNx:H) samples have been prepared by plasma enhanced chemical vapor deposition (PECVD) using a mixture of silane (SiH4), nitrogen and ammonia (NH3). Most films exhibit visible photoluminescence (PL) and some emit strong PL after annealing. While films grown without NH3 exhibit PL in the deep red, those grown with NH3 show PL in the green. The PL properties of these films with no oxygen (O) content are similar to those of silicon oxide (SiOx) films and porous Si. Using infrared and X-ray Photoelectron Spectroscopy, we suggest that PL from a-SiNx:H films originate from Si clusters which form during PECVD and crystallize upon annealing. We propose that the presence of O is not necessary for efficient PL.