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: 8Citation - Scopus: 8Analytical Performance Characteristics of Micro-Structured Surfaces for Laser-Induced Breakdown Spectroscopic Analysis of Liquids(Pergamon-elsevier Science Ltd, 2024) Kaplan, Dilara; Yaman, Iayda; Yalcin, SerifeWe have previously shown the design and fabrication studies of 3-D micro -structured surfaces, to be used as a sample loading substrate for liquids analysis via dried -droplet LIBS methodology. Among the three designs, the substrate structured with 20-mu m diameter cylinders, CYL-20, has shown the highest signal enhancement for the elements, Cu, Cr, and Pb, compared to 5-mu m diameter cylinders, CYL-5, and 5-mu m side -length triangular prisms, TAP -5, surfaces. Here, in this study, the analytical performance characteristics (LOD, accuracy, and precision) of these micro -structured Si -wafer surfaces are presented in comparison with unstructured surfaces. The drieddroplet residue of aqueous heavy metal solutions of Pb, Cr, and Cu were analyzed at their respective emission wavelengths under optimized experimental conditions. The results obtained from CYL-20 structured surfaces in comparison to 300 nm thin-film coated surfaces indicate up to 17, 11, and 7 -fold increases in LIBS signal strength for Cu, Cr, and Pb, respectively. The experiments were performed using single and multi -element standards, and certified reference water samples. Sub-picogram absolute detection limits, 0.8 pg Pb, 0.5 pg Cu, and 0.45 pg Cr were obtained from the analysis of 500 nanoliters standard solutions, via dried -droplet methodology. Results with 70-75% accuracy and 95% precision were obtained from the repeated measurements. Though the results are promising, more extensive fabrication and application studies are required to find optimum structures of different sizes and shapes.Article Citation - WoS: 13Citation - Scopus: 13Design, Fabrication, and Application of Micro-Structured Surfaces for Laser-Induced Breakdown Spectroscopic Analysis of Liquids: a Sample-Loading Target Development Studies(Elsevier, 2024) Kaplan, Dilara; Aras, Nadir; Yalcin, SerifeIn this paper, design, fabrication, and application studies of a sample loading target patterned with periodical micro-structures were presented. Two different geometrical shapes; triangular prisms and cylinders of two different feature sizes; 5-mu m, and 20-mu m, were photo-lithographically patterned on Si-wafer substrates, and dry etched to 10 mu m height. Followed by a 1-mu m thick silicon nitride film coating over micro-patterned substrates, final products were obtained after dicing into one-inch size squares, each containing 36 patterned sample loading areas. Among the three different patterns studied; a geometric design with 20-mu m diameter cylinders exhibited a more effective task in increasing the LIBS signal strength, compared to the other two patterns. The characterization of the surface morphology and the size-shape distribution of the micro-patterns were carried out through optical and scanning electron microscopic measurements. SEM images proved a more effective ablation occur-ring on triangular prism micro-structured surfaces that can be associated with an increased path length and enhanced absorption of the laser beam on the flat surfaces of triangular prism via multiple reflections. The results of structured surfaces were also compared with the ones from non-structured surfaces of 300 nm and 1000 nm thicknesses of silicon nitride-coating. The applications of micro-structured surfaces for heavy metals analysis were performed with Cr and Pb solutions via dried-droplet LIBS methodology. The enhancement factor of 4 for Pb(I) 405.8 nm, and 8 for Cr(I) 428.9 nm were observed from the 20-mu m diameter cylinder, CYL-20, surfaces compared to 300 nm thick Si3N4 surfaces, respectively. This study of micro-structuring substrate surfaces with an emphasis on the signal enhancement effect is promising in terms of improving the capacity and limitations of the dried-droplet methodology by LIBS.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.