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Publication Metadata only Atmospheric pressure plasma jet treatment of human hair fibers(2015) N/A; N/A; Department of Molecular Biology and Genetics; Department of Chemistry; Birer, Özgür; Acar, Erhan; Keleş, Merve; Öngel, Cansu; Researcher; Master Student; Undergraduate Student; Undergraduate Student; Department of Molecular Biology and Genetics; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; Graduate School of Sciences and Engineering; College of Science; College of Science; N/A; N/A; N/A; N/AHuman hair fibers in virgin and dyed forms were treated with atmospheric pressure helium, helium/oxygen, argon, and argon/oxygen plasma jets at 20 W of power. The effects of 10-min plasma treatment on surface morphology and chemistry were studied by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The plasma treatment was quite effective for removing the organic residues from the surface and creating oxidized functional groups. Helium plasma had a mild cleaning effect on the surfaces while argon/oxygen plasma had the strongest corrosive effect. Mild hydrogen peroxide treatment for the same duration had neither the cleaning nor the oxidizing power of the plasma jets. These types of plasma jets have the potential to replace peroxide treatment. The corrosive jets can be used to restore dyed hair fibers. In addition, the jets can be used to clean the surfaces of hair fibers to prepare samples for analytical investigations where the organic residues may induce problems. © 2015, Springer International Publishing AG.Publication Open Access Band alignment engineers faradaic and capacitive photostimulation of neurons without surface modification(American Physical Society (APS), 2019) Department of Electrical and Electronics Engineering; N/A; Department of Chemical and Biological Engineering; Department of Molecular Biology and Genetics; Srivastava, Shashi Bhushan; Melikov, Rustamzhon; Aria, Mohammad Mohammadi; Dikbaş, Uğur Meriç; Kavaklı, İbrahim Halil; Nizamoğlu, Sedat; Researcher; PhD Student; Master Student; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Department of Molecular Biology and Genetics; College of Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; N/A; 40319; 130295Photovoltaic substrates have attracted significant attention for neural photostimulation. The control of the Faradaic and capacitive (non-Faradaic) charge transfer mechanisms by these substrates are critical for safe and effective neural photostimulation. We demonstrate that the intermediate layer can directly control the strength of the capacitive and Faradaic processes under physiological conditions. To resolve the Faradaic and capacitive stimulations, we enhance photogenerated charge density levels by incorporating PbS quantum dots into a poly(3-hexylthiophene-2,5-diyl):([6,6]-Phenyl-C61-butyric acid methyl ester (P3HT:PCBM) blend. This enhancement stems from the simultaneous increase of absorption, well matched band alignment of PbS quantum dots with P3HT:PCBM, and smaller intermixed phase-separated domains with better homogeneity and roughness of the blend. These improvements lead to the photostimulation of neurons at a low light intensity level of 1 mW cm(-2), which is within the retinal irradiance level. These findings open up an alternative approach toward superior neural prosthesis.Publication Open Access Biocompatible quantum funnels for neural photostimulation(American Chemical Society (ACS), 2019) N/A; Department of Chemical and Biological Engineering; N/A; Department of Electrical and Electronics Engineering; Department of Molecular Biology and Genetics; N/A; Jalali, Houman Bahmani; Doğru-Yüksel, Itır Bakış; Eren, Güncem Özgün; Nizamoğlu, Sedat; Karatüm, Onuralp; Melikov, Rustamzhon; Dikbaş, Uğur Meriç; Kavaklı, İbrahim Halil; Sadeghi, Sadra; Yıldız, Erdost; Ergün, Çağla; Şahin, Afsun; PhD Student; Faculty Member; PhD Student; Master Student; Faculty Member; PhD Student; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Department of Electrical and Electronics Engineering; Department of Molecular Biology and Genetics; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; School of Medicine; N/A; N/A; N/A; 130295; N/A; N/A; N/A; 40319; N/A; N/A; N/A; 171267Neural photostimulation has high potential to understand the working principles of complex neural networks and develop novel therapeutic methods for neurological disorders. A key issue in the light-induced cell stimulation is the efficient conversion of light to bioelectrical stimuli. In photosynthetic systems developed in millions of years by nature, the absorbed energy by the photoabsorbers is transported via nonradiative energy transfer to the reaction centers. Inspired by these systems, neural interfaces based on biocompatible quantum funnels are developed that direct the photogenerated charge carriers toward the bionanojunction for effective photostimulation. Funnels are constructed with indium-based rainbow quantum dots that are assembled in a graded energy profile. Implementation of a quantum funnel enhances the generated photoelectrochemical current 215% per unit absorbance in comparison with ungraded energy profile in a wireless and free-standing mode and facilitates optical neuromodulation of a single cell. This study indicates that the control of charge transport at nanoscale can lead to unconventional and effective neural interfaces.Publication Open Access Bulk-heterojunction photocapacitors with high open-circuit voltage for low light intensity photostimulation of neurons(Royal Society of Chemistry (RSC), 2021) Department of Electrical and Electronics Engineering; Department of Molecular Biology and Genetics; N/A; Department of Chemical and Biological Engineering; N/A; Srivastava, Shashi Bhushan; Melikov, Rustamzhon; Yıldız, Erdost; Dikbaş, Uğur Meriç; Sadeghi, Sadra; Kavaklı, İbrahim Halil; Şahin, Afsun; Nizamoğlu, Sedat; Researcher; PhD Student; PhD Student; Master Student; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; School of Medicine; N/A; N/A; N/A; N/A; N/A; 40319; 171267; 130295High-level transduction control of light to bioelectricity is an important goal for the realization of superior neuron-device interfaces that can be used for regulating fundamental cellular processes to cure neurological disorders. In this study, a single-junction, wireless, and capacitive-charge-injecting optoelectronic biointerface with negligible faradaic reactions by using a high open-circuit voltage (0.75 V) bulk heterojunction of PTB7-Th:PC71BM is designed and demonstrated. The biointerface generates a 2-fold higher photocurrent in comparison with P3HT:PC61BM having an open-circuit voltage of 0.55 V. Furthermore, we observed that light intensity is logarithmically correlated with the open-circuit voltage of solar cells, and the photovoltage of the biointerfaces varies the switching speed of capacitive charge-transfer. Finally, pulse trains of capacitive stimuli at a low light intensity of 20 mW cm−2elicit action potential generation in primary hippocampal neurons extracted from E15-E17 Wistar Albino rats. These findings show the great promise of high open-circuit voltage bulk heterojunction biointerfaces for non-genetic, all-optical and safe modulation of neurons.Publication Metadata only Fluorescent protein integrated white LEDs for displays(Iop Publishing Ltd, 2016) N/A; Department of Electrical and Electronics Engineering; N/A; N/A; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; Press, Daniel Aaron; Melikov, Rustamzhon; Çonkar, Deniz; Karalar, Elif Nur Fırat; Nizamoğlu, Sedat; Researcher; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; N/A; N/A; 206349; 130295The usage time of displays (e.g., TVs, mobile phones, etc) is in general shorter than their functional life time, which worsens the electronic waste (e-waste) problem around the world. The integration of biomaterials into electronics can help to reduce the e-waste problem. In this study, we demonstrate fluorescent protein integrated white LEDs to use as a backlight source for liquid crystal (LC) displays for the first time. We express and purify enhanced green fluorescent protein (eGFP) and monomeric Cherry protein (mCherry), and afterward we integrate these proteins as a wavelength-converter on a blue LED chip. The protein-integrated backlight exhibits a high luminous efficacy of 248 lm/W-opt and the area of the gamut covers 80% of the NTSC color gamut. The resultant colors and objects in the image on the display can be well observed and distinguished. Therefore, fluorescent proteins show promise for display applications.Publication Metadata only Laser emission from single, dye-doped microdroplets situated on a superhydrophobic surface(IEEE, 2007) Department of Physics; Department of Physics; Department of Physics; Department of Chemistry; N/A; Department of Physics; Department of Molecular Biology and Genetics; Sennaroğlu, Alphan; Kurt, Adnan; Kiraz, Alper; Demirel, Adem Levent; Dündar, Mehmet Ali; Kalaycıoğlu, Hamit; Doğanay, Sultan; Faculty Member; Teaching Faculty; Faculty Member; Faculty Member; Master Student; PhD Student; Undergraduated Student; Department of Chemistry; Department of Physics; Department of Molecular Biology and Genetics; College of Sciences; College of Sciences; College of Sciences; College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; 23851; 194455; 22542; 6568; N/A; N/A; N/AOptical microcavities are attractive in developing ultralow threshold lasers which hold a great promise for applications in optical communications systems and fundamental studies in cavity quantum electrodynamics. Up to date laser emission has been observed from various different optical microcavities: Microdisks, microspheres, micropillars, photonic crystal defect microcavities, and microdroplets flying in air. Here we report the observation of laser emission from single, stationary, dye-doped microdroplets situated on a superhydrophobic surface. In contrast to the previous demonstrations on microdroplets flying in air, the technique we use allows for the analysis of laser emission from a particular microdroplet over prolonged periods.