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  • Küçük Resim
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    Femtosecond laser ablation synthesis of nanoparticles and nano-hybrides in ethanol medium
    (ELSEVIER, 2019) Gündoğdu, Yasemin.; Kepceoğlu, Abdullah.; Yiğit Gezgin, Serap.; Küçükçelebi, Hayrettin.; Kılıç, Hamdi Şükür.
    The nanoparticle production has a significant importance because of its unique optical properties in molecular biology and medicine. Plasmonic metallic nanoparticles are widely used in cancer monitoring studies as contrast agents on the account of their surface plasmon resonance (SPR) effect. Beside, silicon (Si) semiconductor nanoparticles can provide several beneficial properties that they are used commonly intensifying the detecting signals. Nanoalloys/Nanohybides/Nanocomposites are more functional materials than a single material structure and having many restrictions. At that point, the application of Pulsed Laser Ablation (PLA) technique has many advantages if applied in the liquid. Since no any chemical technique is applied, this procedure promises a clean synthesis process; it is a simple and economical technique in the production process. It provides some possibilities to generate particles in the desired size, shape and density, and these properties of nanoparticles produced can be controlled by controlling the laser parameters. In this work, we have focused on the production of nanoparticles to rid off chemical processes using femtosecond laser ablation technique, and this technique presents a process to reach the fast and reliable results for production of nanoshells, nanocomposites and all nanoforms of particles. We have produced Si@Au nanohybrids in ethanol medium using femtosecond laser ablation depending on laser pulse energy. Absorption spectra were recorded day by day to determine the optical characteristics of produced nanoparticles within these time durations, Transmission Electron Microscopy (TEM) images were obtained for monitoring and determining the size/structure of nanoparticles, energy dispersive spectroscopy (EDS) for material compositions were produced, these results obtained are presented in the scope of this paper. (C) 2019 Elsevier Ltd. All rights reserved.
  • Küçük Resim
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    Real-Time distinguishing of the xylene isomers using photoionization and dissociation mass spectra obtained by femtosecond laser mass spectrometry (FLMS)
    (TAYLOR & FRANCIS INC, 2020) Kepceoğlu, Abdullah.; Gündoğdu, Yasemin.; Ledingham, Kenneth William David.; Kilic, Hamdi Sukur.
    Distinguishing chemicals and improvement on analytical methods has a direct impact on modern chemical analysis. In this work, the dissociative ionization of xylene isomers was investigated using a femtosecond laser mass spectrometry (FLMS) method with a custom-built linear time-of-flight (TOF) instrument. Laser beams at 800 nm and 400 nm were used and intensity-dependent analysis of the obtained mass spectra was performed using principal component analysis (PCA) to distinguish the xylene isomers, which give identical mass spectra in appearance that cannot be distinguished using normal mass spectrometry methods. The results show that there is a statistically highly significant difference between the xylene isomers for two principal components (1 - alpha > 99.99%) and minimal information loss (<5%) took place during the PCA procedure. Also, the use of the k-medoid clustering method showed that the isomers may be distinguished in real-time for a wide range of ionization laser pulse powers with approximately 99% accuracy. The results suggest that real-time isomer analysis by the FLMS method is suitable for mass spectral identification applications. The FLMS method has been shown to be an important alternative to other mass spectrometric methods that use different ionization mechanisms.