Browsing by Author "Kalay, Mustafa"

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    pH tunable patterning of quantum dots
    (Wiley-VCH Verlag GmbH & Co. KGaA, 2024-01-11) Torun, Ilker; Huang, Conan; Kalay, Mustafa; Shim, Moonsub; Önses, Mustafa Serdar
    Patterning of quantum dots (QDs) is essential for many, especially high-tech, applications. Here, pH tunable assembly of QDs over functional patterns prepared by electrohydrodynamic jet printing of poly(2-vinylpyridine) is presented. The selective adsorption of QDs from water dispersions is mediated by the electrostatic interaction between the ligand composed of 3-mercaptopropionic acid and patterned poly(2-vinylpyridine). The pH of the dispersion provides tunability at two levels. First, the adsorption density of QDs and fluorescence from the patterns can be modulated for pH > ≈4. Second, patterned features show unique type of disintegration resulting in randomly positioned features within areas defined by the printing for pH ≤ ≈4. The first capability is useful for deterministic patterning of QDs, whereas the second one enables hierarchically structured encoding of information by generating stochastic features of QDs within areas defined by the printing. This second capability is exploited for generating addressable security labels based on unclonable features. Through image analysis and feature matching algorithms, it is demonstrated that such patterns are unclonable in nature and provide a suitable platform for anti-counterfeiting applications. Collectively, the presented approach not only enables effective patterning of QDs, but also establishes key guidelines for addressable assembly of colloidal nanomaterials.
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    Silver nanoflowers with SERS activity and unclonable morphology
    (Elsevier, 2023-02-26) Şakir, Menekşe; Torun, Neslihan; Kayacı, Nilgün; Torun, İlker; Kalay, Mustafa; Onses, M. Serdar
    This manuscript presents surface-growth of silver nanoflowers with high surface-enhanced Raman scattering (SERS) activity and unique morphology. The nanoflower morphology is mediated by the seed-mediated growth of silver nanostructures over gold nanoparticles immobilized on hemispherical polymer features. Randomly positioned hemispherical polymer features are self-assembled via surface dewetting of a nanoscopic film of poly (2-vinylpyiridine) (P2VP) film on the polystyrene-grafted substrate. The time-dependent growth study shows that the silver nanoflowers evolve from the circular contact lines separating the P2VP features and underlying substrate. The three-dimensional nature of the underlying feature facilitates growth in a flower like morphology. The silver nanoflowers exhibit high levels of SERS activity allowing for detection of rhodamine 6G at a 100 pM level under 532 nm laser excitation. A feature matching algorithm-based image analysis confirms the unique morphology of every single silver nanoflower. The direct fabrication of silver nanoflowers at random positions with unclonable morphology and high SERS activity is particularly promising for anti-counterfeiting applications.