Research Project: Novel Nanoengineered Optoelectronic Biointerfaces
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Contributors
Funders
ID
EC.00079
Authors
Nizamoğlu, Sedat
Faculty Member
Publications
Stokes-shift-engineered indium phosphide quantum dots for efficient luminescent solar concentrators
(American Chemical Society (ACS), 2018) Aria, Mohammad Mohammadi; Jalali, Houman Bahmani; Kumar, Baskaran Ganesh; Melikov, Rustamzhon; Nizamoğlu, Sedat; Sadeghi, Sadra; Ow-Yang, Cleva W.; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
Luminescent solar concentrators (LSCs) show promise because of their potential for low-cost, large-area, and high-efficiency energy harvesting. Stokes shift engineering of luminescent quantum dots (QDs) is a favorable approach to suppress reabsorption losses in LSCs; however, the use of highly toxic heavy metals in QDs constitutes a serious concern for environmental sustainability. Here, we report LSCs based on cadmium-free InP/ZnO core/shell QDs with type-II band alignment that allow for the suppression of reabsorption by Stokes shift engineering. The spectral emission and absorption overlap was controlled by the growth of a ZnO shell on an InP core. At the same time, the ZnO layer also facilitates the photostability of the QDs within the host matrix. We analyzed the optical performance of indium-based LSCs and identified the optical efficiency as 1.45%. The transparency, flexibility, and cadmium-free content of the LSCs hold promise for solar window applications.
Cadmium-free and efficient Type-II InP/ZnO/ZnS quantum dots and their application for LEDs
(American Chemical Society (ACS), 2021) Eren, Güncem Özgün; Han, Mertcan; Jalali, Houman Bahmani; Melikov, Rustamzhon; Nizamoğlu, Sedat; Önal, Asım; Öz, Fatma; Sadeghi, Sadra; Sennaroğlu, Alphan; Baylam, Işınsu; Ritter, Maximilian; Şahin, Mehmet; Ow-Yang, Cleva W.; Lechner, Rainer T.; Department of Electrical and Electronics Engineering; Department of Physics; Graduate School of Sciences and Engineering; KUBAM (Koç University Boron and Advanced Materials Application and Research Center); KUYTAM (Koç University Surface Science and Technology Center); Yes; College of Engineering; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center
It is a generally accepted perspective that type-II nanocrystal quantum dots (QDs) have low quantum yield due to the separation of the electron and hole wavefunctions. Recently, high quantum yield levels were reported for cadmium-based typeII QDs. Hence, the quest for finding non-toxic and efficient type-II QDs is continuing. Herein, we demonstrate environmentally benign type-II InP/ZnO/ZnS core/shell/shell QDs that reach a high quantum yield of similar to 91%. For this, ZnO layer was grown on core InP QDs by thermal decomposition, which was followed by a ZnS layer via successive ionic layer adsorption. The small-angle Xray scattering shows that spherical InP core and InP/ZnO core/ shell QDs turn into elliptical particles with the growth of the ZnS shell. To conserve the quantum efficiency of QDs in device architectures, InP/ZnO/ZnS QDs were integrated in the liquid state on blue light-emitting diodes (LEDs) as down-converters that led to an external quantum efficiency of 9.4% and a power conversion efficiency of 6.8%, respectively, which is the most efficient QD-LED using type-II QDs. This study pointed out that cadmium-free type-II QDs can reach high efficiency levels, which can stimulate novel forms of devices and nanomaterials for bioimaging, display, and lighting.
Bulk-heterojunction photocapacitors with high open-circuit voltage for low light intensity photostimulation of neurons
(Royal Society of Chemistry (RSC), 2021) Dikbaş, Uğur Meriç; Kavaklı, İbrahim Halil; Melikov, Rustamzhon; Nizamoğlu, Sedat; Sadeghi, Sadra; Şahin, Afsun; Srivastava, Shashi Bhushan; Yıldız, Erdost; Department of Electrical and Electronics Engineering; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; KUTTAM (Koç University Research Center for Translational Medicine); School of Medicine; Yes; College of Engineering; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center; SCHOOL OF MEDICINE
High-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.
Perovskite-based optoelectronic biointerfaces for non-bias-assisted photostimulation of cells
(Wiley, 2019) Aria, Mohammad Mohammadi; Dikbaş, Uğur Meriç; Kavaklı, İbrahim Halil; Nizamoğlu, Sedat; Özdemir, Yasemin Gürsoy; Sadeghi, Sadra; Şekerdağ, Emine; Srivastava, Shashi Bhushan; Cameron, Petra J.; Pering, Samuel R; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; School of Medicine; KUTTAM (Koç University Research Center for Translational Medicine); Department of Molecular Biology and Genetics; Yes; College of Engineering; GRADUATE SCHOOL OF HEALTH SCIENCES; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; SCHOOL OF MEDICINE; Research Center; College of Sciences
Organohalide perovskites have attracted significant attention for efficient solar energy harvesting. They boost the photoelectrical conversion efficiency of the solution-processable solar cells because of having a nearly 100% internal quantum efficiency, operating in both narrow- and broadband spectral regimes, near-infrared sub-bandgap absorption, and high diffusion length. At the same time, these optoelectronic properties make it an ideal candidate for photostimulation of neurons. However, the biocompatibility of perovskite and its longevity in a cell medium constitute a major limitation to use it for biological interfaces. Here, high-level perovskite stability and biocompatibility are shown by forming hydrophobic perovskite microcrystals and encapsulating them within a polydimethylsiloxane layer. For effective and safe photostimulation of cells perovskite microcrystals are interfaced with poly(3-hexylthiophene-2,5-diyl) (P3HT) polymer for dissociation of the photogenerated charge carriers, which leads to non-bias-assisted cell stimulation. The results point out a new direction for the use of perovskite for photomedicine.
Band alignment engineers faradaic and capacitive photostimulation of neurons without surface modification
(American Physical Society (APS), 2019) Aria, Mohammad Mohammadi; Dikbaş, Uğur Meriç; Kavaklı, İbrahim Halil; Melikov, Rustamzhon; Nizamoğlu, Sedat; Srivastava, Shashi Bhushan; Department of Electrical and Electronics Engineering; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Yes; College of Engineering; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
Photovoltaic 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.
