Researcher:
Türker, Yurdanur

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Yurdanur

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Türker

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Türker, Yurdanur

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2017 - 20192

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    Green synthesis of strongly luminescent, ultrasmall pbs and pbse quantum dots
    (Amer Chemical Soc, 2017) N/A; Department of Chemistry; Department of Chemistry; Durmuşoğlu, Emek Göksu; Türker, Yurdanur; Acar, Havva Funda Yağcı; PhD Student; Researcher; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 178902
    Although size tunable synthesis of PbS between 3 and 10 nm with emission in the NIR. II region is well-known, there is no well-established method to produce smaller particles with emission below 1000 nm, which is easier to detect with less costly and more widely available Si and extented PMT-detectors. Here, we demonstrate synthesis of PbS QDs in sizes between 2.4 and 3.2 nm using PbCl2, elemental S, dodecanethiol (DT), and a toluene/oleylamine mixture at low temperatures (65-80 C-omicron). It was shown that addition of DT enhances the solubility of S and DT binds to the crystal surface during the growth, hence reducing the size with enhanced luminescence intensity. Use of toluene as a cosolvent reduces the viscosity and provides an additional reduction in the size. Using these variables, size tunable synthesis of highly luminescent QDs were achieved. Furthermore, we applied additional DT ligand exchange as a postprocess that increases the long-term stability of particles. The photoluminescence lifetime investigation provided insight into the luminescence properties of OLA/DT and DT-capped PbS QDs. Finally, we successfully expanded our synthesis method to the synthesis of small PbSe QDs.
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    PublicationOpen Access
    Luminescent PbS and PbS/CdS quantum dots with hybrid coatings as nanotags for authentication of petroleum products
    (American Chemical Society (ACS), 2019) Durmuşoğlu, Emek Göksu; Türker, Yurdanur; Acar, Havva Funda Yağcı; Faculty Member; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/A; 178902
    There is an urgent need to tag some valuable liquid products, such as petroleum products, for authentication. However, it is a challenging task because of the strong autofluorescence of liquid petroleum products in the visible range and the chemically active and harsh medium. Therefore, strongly luminescent, near-infrared (NIR) fluorophores with long-term stability are needed. The use of NIR quantum dots (QDs), such as lead chalcogenides, seems to be the best approach; however, most widely used coatings do not provide enough stability, and QDs are quenched in a short time in liquid petroleum products. Here, we report for the first time the synthesis of highly luminescent, ultrasmall, NIR-emitting PbS and PbS/CdS QDs with a hybrid coating consisting of oleylamine (OLA), 1-dodecanethiol (DT), and poly(methacrylic acid) (PMAA), adopting a simple, greener synthetic method. The photoluminescence (PL) emission wavelengths of these QDs were tuned between 700 and 1100 nm for detection with low-cost, widely used silicon detectors, which allows easy translation of such QDs as luminescent nanotags to serve as a means for the authentication of goods, such as petroleum. In the nanoparticle design, a thin layer of a CdS shell deposited by a cation-exchange process was adopted to enhance the emission intensity and stability of PbS QDs. The influence of postsynthetic ligand exchange of OLA with DT on the stability is also shown. PMAA in the coating provided a significant blue shift in the peak maxima, enhanced the luminescence intensity, and, most importantly, improved the long-term stability of QDs, especially in liquid petroleum products (oil, gasoline, and diesel). Such stability and size tunability was utilized to create binary barcodes. Hence, these QDs are shown as promising luminescent nanotags for liquid petroleum products. The development of such stable QD-based nanotags offers an invaluable use of nanotechnology for optical barcode generation.