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Publication Probing molecular interactions on carbon nanotube surfaces using surface plasmon resonance sensors(AIP Publishing, 2012-11-26) Nurbek Kakenov; Osman Balci; Sinan Balci; Coskun KocabasIn this work, we present a method to probe molecular interactions on single-walled carbon nanotube (SWNT) surfaces using a surface plasmon sensor. SWNT networks were synthesized by chemical vapor deposition and transfer-printed on gold surfaces. We studied the excitation of surface plasmon-polaritons on nanotube coated gold surfaces with sub-monolayer, monolayer, and multilayer surface coverage. Integrating the fabricated sensor with a microfluidic device, we were able to obtain binding dynamics of a bovine serum albumin (BSA) protein on SWNT networks with various tube densities. The results reveal the kinetic parameters for nonspecific binding of BSA on SWNT coated surfaces having various tube densities.Publication Plexcitonic crystals: a tunable platform for light-matter interactions(The Optical Society, 2014-09-02) Ertugrul Karademir; Sinan Balci; Coskun Kocabas; Atilla AydinliPublication Erratum: Probing molecular interactions on carbon nanotube surfaces using surface plasmon resonance sensors [Appl. Phys. Lett. 101, 223114 (2012)](AIP Publishing, 2015-11-02) Nurbek Kakenov; Osman Balci; Sinan Balci; Coskun KocabasPublication Weighing graphene with QCM to monitor interfacial mass changes(AIP Publishing, 2016-08-01) Nurbek Kakenov; Osman Balci; Omer Salihoglu; Seung Hyun Hur; Sinan Balci; Coskun KocabasIn this Letter, we experimentally determined the mass density of graphene using quartz crystal microbalance (QCM) as a mechanical resonator. We developed a transfer printing technique to integrate large area single-layer graphene on QCM. By monitoring the resonant frequency of an oscillating quartz crystal loaded with graphene, we were able to measure the mass density of graphene as ∼118 ng/cm2, which is significantly larger than the ideal graphene (∼76 ng/cm2) mainly due to the presence of wrinkles and organic/inorganic residues on graphene sheets. High sensitivity of the quartz crystal resonator allowed us to determine the number of graphene layers in a particular sample. Additionally, we extended our technique to probe interfacial mass variation during adsorption of biomolecules on graphene surface and plasma-assisted oxidation of graphene.Publication Graphene as a Reversible and Spectrally Selective Fluorescence Quencher(Springer Science and Business Media LLC, 2016-09-22) Omer Salihoglu; Nurbek Kakenov; Osman Balci; Sinan Balci; Coskun KocabasAbstractWe report reversible and spectrally selective fluorescence quenching of quantum dots (QDs) placed in close proximity to graphene. Controlling interband electronic transitions of graphene via electrostatic gating greatly modifies the fluorescence lifetime and intensity of nearby QDs via blocking of the nonradiative energy transfer between QDs and graphene. Using ionic liquid (IL) based electrolyte gating, we are able to control Fermi energy of graphene in the order of 1 eV, which yields electrically controllable fluorescence quenching of QDs in the visible spectrum. Indeed, our technique enables us to perform voltage controllable spectral selectivity among quantum dots at different emission wavelengths. We anticipate that our technique will provide tunable light-matter interaction and energy transfer that could yield hybrid QDs-graphene based optoelectronic devices with novel functionalities and additionally, may be useful as a spectroscopic ruler, for example, in bioimaging and biomolecular sensing. We propose that graphene can be used as an electrically tunable and wavelength selective fluorescence quencher.Publication Hybrid J-Aggregate–Graphene Phototransistor(American Chemical Society (ACS), 2019-12-11) Ozan Yakar; Osman Balci; Burkay Uzlu; Nahit Polat; Ozan Ari; Ilknur Tunc; Coskun Kocabas; Sinan Balci