Researcher:
Çelebi, Serdar

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Master Student

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Serdar

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Çelebi

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Çelebi, Serdar

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2007 - 200922010 - 20141

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Researcher Of Publications: search.filters.isAuthorOfPublication.3e90c2c8-ee25-4537-ab7f-0bdebc79f7e1

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    Development of highly stable and luminescent aqueous CdS quantum dots with the poly(acrylic acid)/mercaptoacetic acid binary coating system
    (Amer Scientific Publishers, 2009) Lieberwirth, I.; Department of Chemistry; N/A; Department of Chemical and Biological Engineering; Acar, Havva Funda Yağcı; Çelebi, Serdar; Serttunalı, Nazlı İpek; Faculty Member; Master Student; Undergraduate Student; Department of Chemistry; Department of Chemical and Biological Engineering; College of Sciences; Graduate School of Sciences and Engineering; College of Engineering; 178902; N/A; N/A
    Highly stable and luminescent CdS quantum dots (QD) were prepared in aqueous solutions via in situ capping of the crystals with the poly(acrylic acid) (PAA) and mercaptoacetic acid (MAA) binary mixtures. The effect of reaction temperature and coating composition on the particle size, colloidal stability and luminescence were investigated and discussed in detail. CdS QDs coated with either PAA or MAA were also prepared and compared in terms of properties. CdS-MAA QDs were highly luminescent but increasing reaction temperature caused an increase in the crystal size and a significant decrease in the quantum yield (QY). Although less luminescent and bigger than CdS-MAA, CdS-PAA QDs maintained the room temperature size and QY at higher reaction temperatures. CdS-MAA QDs lacked long term colloidal stability whereas CdS-PAA QDs showed excellent stability over a year. Use of PAA/MAA mixture as a coating for CdS nanoparticles during the synthesis provided excellent stability, high QY and ability to tune the size and the color of the emission. Combination of all of these properties can be achieved only with the mixed coating. CdS coated with PAA/MAA at 40/60 ratio displayed the highest QY (50% of Rhodamine B) among the other compositions.
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    Synthesis and characterization of poly(acrylic acid) stabilized cadmium sulfide quantum dots
    (Amer Chemical Soc, 2007) N/A; N/A; Department of Physics; Department of Physics; Department of Chemistry; Çelebi, Serdar; Erdamar, Ahmet Koray; Sennaroğlu, Alphan; Kurt, Adnan; Acar, Havva Funda Yağcı; Master Student; Master Student; Faculty Member; Teaching Faculty; Faculty Member; Department of Physics; Department of Chemistry; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; College of Sciences; N/A; N/A; 23851; 194455; 178902
    Cadmium sulfide (CdS) nanoparticles (NPs) capped with poly(acrylic acid) (PAA) were prepared in aqueous solutions from Cd(NO3)(2) and NaS. Influence of the COOH/Cd ratio (0.8-12.5), reaction pH (5.5 and 7.5), and PAA molecular weight (2100 and 5100 g/mol) on the particle size, colloidal stability, and photoluminescence were investigated. A Cd/S ratio of < 1 causes ineffective passivization of the surface with the carboxylate and therefore results in a red shift of the absorption band and a significant drop in photoluminescence. Therefore, the Cd/S ratio was fixed at 1.1 for all experiments studying the mentioned variables. PAA coating provided excellent colloidal stability at a COOH/Cd ratio above 1. Absorption edges of PAA-coated CdS NPs are in the range of 460-508 nm. The size of the NPs increases slightly with increasing PAA molecular weight and COOH/Cd ratio at pH 7.5. It is demonstrated that there is a critical COOH/Cd ratio (1.5-2) that maximizes the photoluminescence intensity and quantum yield (QY, 17%). Above this critical ratio, which corresponds to smaller crystal sizes (3.7-4.1 nm) for each reaction set, the quantum yield decreases and the crystal size increases. Moreover, US NPs prepared at pH 7.5 have significantly higher QY and absorb at lower wavelengths in comparison with those prepared at pH 5.5. Luminescence quenching has not been observed over 8 months.
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    PublicationOpen Access
    Preface of the "1st symposium on multiscale, multiphysics and turbulent flow simulations"
    (American Institute of Physics (AIP) Publishing, 2014) Department of Mathematics; Çelebi, Serdar; Çağlar, Mine; Faculty Member; Department of Mathematics; College of Sciences; N/A; 105131