Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 13Citation - Scopus: 15Effect of Silicon Nitride Coating Thickness on Silicon Wafer Substrates for Signal Enhancement in Laser-Induced Breakdown Spectroscopic Analysis of Liquids(Elsevier, 2022) Kaplan, Dilara; Yalçın, Şerife HanımIt has been shown by previous studies of our group that the use of nitride-coated silicon wafer surfaces as a sample loading substrate in dried-droplet LIBS analysis provided enhancement in plasma emission signal and better detection limits compared to uncoated or oxide-coated silicon wafer surfaces. To further investigate the effect of coating thickness for enhanced sensitivity in dried nano-droplet analysis of liquids, silicon-wafer substrates of different nitride coating thicknesses; 75, 300, 450, and 1000 nm, were comparatively studied. With 75 nm silicon nitride coating, the thin-film effect due to the anti-reflective behavior of the silicon nitride film is observed, and plasma emission signal is enhanced up to three times compared to 300 nm coated substrates. With coating thicknesses of 450 nm and 1000 nm, on the other hand, thermophysical and mechanical properties of the silicon nitride material, like thermal conductivity and hardness, become more dominant factors, leading to higher emission signals for all the elements studied. With 1000 nm coating thickness, enhancement factors of 4.8, 6.4, and 3.7 were obtained for the elements of Pb, Cu, and Cr, respectively. Optimization of the experimental LIBS parameters was conducted, calibration curves were constructed, and analytical figures of merits were determined. Sub-picogram amounts absolute detection limits; 0.7 pg Pb, 0.6 pg Cr, and 0.4 pg Cu, in 500 nanoliter droplets were obtained from the slopes of the calibration curves. The nitride-coated substrates' analytical performance was tested using certified reference solutions, standard water, and real water samples. The materials and the methodology developed can be used for waste-water monitoring of environmental samples by LIBS.Article Citation - WoS: 29Citation - Scopus: 29Investigating Silicon Wafer Based Substrates for Dried-Droplet Analysis by Laser-Induced Breakdown Spectroscopy(Elsevier Ltd., 2019) Aras, Nadir; Yalçın, ŞerifeThis work communicates a critical assessment on the analytical capability of the three silicon wafer-based substrates; crystalline silicon (c-Si), oxide-coated silicon (SiO2-Si), and nitride-coated silicon (Si3N4-Si), for dried-droplet analysis by laser-induced breakdown spectroscopy. The methodology consists of loading, drying and analyzing steps. First, nanoliter volume of droplets are manually loaded onto the substrate and dried at room temperature. Then, the dry residue is subjected to high peak power (1.15 GW/cm(2)) laser pulses focused outside the minimum focal point condition and luminescent plasma is spectroscopically analyzed. Results revealed that nitride-coated substrate exhibits strong enhancements in signal intensity for most emission lines of the analyte species investigated: Cd, Cr, Cu, Mn, and Pb. Surface reflectivity and surface morphology were comparatively investigated to explore enhanced analytical performance of nitride-coated substrates. Experimental conditions were optimized and growth curves for all the elements are found linear with minimum regression constant of 0.96. LOD's of 62 pg Cd, 1.5 pg Cr, 0.5 pg Cu, 2 pg Mn and 11 pg Pb, in absolute amounts, were obtained. The accuracy and precision of the methodology were tested on certified reference water sample (CRM-TMDW), and ICP-multi-element standard sample (ICP-MES). The surface enhancement effect observed on Si3N4 coated substrates has improved the analytical capability of laser-induced breakdown spectroscopy for liquid analysis.Article Citation - WoS: 62Citation - Scopus: 64Ultrasonic Nebulization-Sample Introduction System for Quantitative Analysis of Liquid Samples by Laser-Induced Breakdown Spectroscopy(Elsevier Ltd., 2012) Aras, Nadir; Ünal Yeşiller, Semira; Ateş Arıca, Dilek; Yalçın, ŞerifeIn this study, design and optimization studies of a sample introduction system based on ultrasonic nebulization of metal salts in aqueous environment for laser-induced breakdown spectroscopic detection were presented. The system consisted of an ultrasonic nebulizer connected to a tandem heater-condenser- membrane dryer unit that produces sub-micron size aerosols. Results indicate improvements in detection limits for some elements with the use of membrane dryer. Optimization studies were performed by systematical investigation of LIBS emission signal with respect to laser energy, carrier gas flow rate and detector timing parameters. Under optimized conditions, calibration graphs for Na, K, Mg, Ca, Cu, Al, Cr, Cd, Pb and Zn were constructed and detection limits were calculated. The applicability of the ultrasonic nebulization-LIBS system was tested on real water samples. This system establishes LIBS as an effective analytical tool for both qualitative and quantitative determination of metal aerosols in aqueous environments. This technique is sufficiently rapid to provide real-time monitoring of toxic metals.Article Citation - WoS: 23Citation - Scopus: 22Optimization of Chemical and Instrumental Parameters in Hydride Generation Laser-Induced Breakdown Spectrometry for the Determination of Arsenic, Antimony, Lead and Germanium in Aqueous Samples(Elsevier Ltd., 2013) Ünal Yeşiller, Semira; Yalçın, ŞerifeA laser induced breakdown spectrometry hyphenated with on-line continuous flow hydride generation sample introduction system, HG-LIBS, has been used for the determination of arsenic, antimony, lead and germanium in aqueous environments. Optimum chemical and instrumental parameters governing chemical hydride generation, laser plasma formation and detection were investigated for each element under argon and nitrogen atmosphere. Arsenic, antimony and germanium have presented strong enhancement in signal strength under argon atmosphere while lead has shown no sensitivity to ambient gas type. Detection limits of 1.1mgL-1, 1.0mgL-1, 1.3mgL-1 and 0.2mgL-1 were obtained for As, Sb, Pb and Ge, respectively. Up to 77 times enhancement in detection limit of Pb were obtained, compared to the result obtained from the direct analysis of liquids by LIBS. Applicability of the technique to real water samples was tested through spiking experiments and recoveries higher than 80% were obtained. Results demonstrate that, HG-LIBS approach is suitable for quantitative analysis of toxic elements and sufficiently fast for real time continuous monitoring in aqueous environments.Article Citation - WoS: 17Citation - Scopus: 162-D Analysis of Ge Implanted Sio2 Surfaces by Laser-Induced Breakdown Spectroscopy(Elsevier Ltd., 2008) Yalçın, Şerife; Örer, Sabiha; Turan, Raşit2-D elemental distribution of Ge in silicon oxide substrates with differing implantation doses of between 3 × 1016 cm- 2 and 1.5 × 1017 cm- 2 has been investigated by Laser-Induced Breakdown Spectroscopy (LIBS). Spectral emission intensity has been optimized with respect to time, crater size, ablation depth and laser energy. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) coupled with Energy-Dispersive X-Ray Spectroscopy (EDX) have been utilized to obtain crater depth, morphology and elemental composition of the sample material, respectively. LIBS spectral data revealed the possibility of performing 2-D distribution analysis of Ge atoms in silicon oxide substrate. EDX analysis results confirmed that LIBS is capable to detect Ge atoms at concentrations lower than 0.2% (atomic). LIBS as a fast semi-quantitative analysis method with 50 μm lateral and 800 nm depth resolution has been evaluated. Results illustrate the potential use of LIBS for rapid, on-line assessment of the quality of advanced technology materials during the manufacturing process. © 2008 Elsevier B.V. All rights reserved.