Research Project: Full name of the project
Loading...
Contributors
Funders
ID
EC.00164
Authors
Nizamoğlu, Sedat
Faculty Member
Publications
Emergence of near-infrared photoluminescence via ZnS shell growth on the AgBiS2 nanocrystals
(American Chemical Society, 2024) Metin, Önder; Önal, Asım; Kaya, Tarık Safa; Nizamoğlu, Sedat; Department of Electrical and Electronics Engineering; Department of Chemistry; Graduate School of Sciences and Engineering; Yes; College of Engineering; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
AgBiS2 nanocrystals (NCs), composed of nontoxic, earth-abundant materials and exhibiting an exceptionally high absorption coefficient from visible to near-infrared (>105 cm(-1)), hold promise for photovoltaics but have lack of photoluminescence (PL) due to intrinsic nonradiative recombination and challenging shell growth. In this study, we reported a facile wet-chemical approach for the epitaxial growth of ZnS shell on AgBiS2 NCs, which triggered the observation of PL emission in the near-infrared (764 nm). Since high quality of the core is critical for epitaxial shell growth, we first obtained rock-salt structured AgBiS2 NCs with high crystallinity, nearly spherical shape and monodisperse size distribution (<6%) via a dual-ligand approach reacting Ag-Bi oleate with elemental sulfur in oleylamine. Next, a zincblende ZnS shell with a low-lattice mismatch of 4.9% was grown on as-prepared AgBiS2 NCs via a highly reactive zinc (Zn(acac)(2)) precursor that led to a higher photoluminescence quantum yield (PLQY) of 15.3%, in comparison with a relatively low reactivity precursor (Zn(ac)(2)) resulting in reduced PLQY. The emission from AgBiS2 NCs with ultrastrong absorption, facilitated by shell growth, can open up new possibilities in lighting, display, and bioimaging.
Emergence of near-infrared photoluminescence via ZnS shell growth on the AgBiS2 nanocrystals
(American Chemical Society, 2024) Önal, Asım; Kaya, Tarık Safa; Metin, Önder; Nizamoğlu, Sedat; Department of Chemistry; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Yes; College of Engineering; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
AgBiS2 nanocrystals (NCs), composed of nontoxic, earth-abundant materials and exhibiting an exceptionally high absorption coefficient from visible to near-infrared (>105 cm(-1)), hold promise for photovoltaics but have lack of photoluminescence (PL) due to intrinsic nonradiative recombination and challenging shell growth. In this study, we reported a facile wet-chemical approach for the epitaxial growth of ZnS shell on AgBiS2 NCs, which triggered the observation of PL emission in the near-infrared (764 nm). Since high quality of the core is critical for epitaxial shell growth, we first obtained rock-salt structured AgBiS2 NCs with high crystallinity, nearly spherical shape and monodisperse size distribution (<6%) via a dual-ligand approach reacting Ag-Bi oleate with elemental sulfur in oleylamine. Next, a zincblende ZnS shell with a low-lattice mismatch of 4.9% was grown on as-prepared AgBiS2 NCs via a highly reactive zinc (Zn(acac)(2)) precursor that led to a higher photoluminescence quantum yield (PLQY) of 15.3%, in comparison with a relatively low reactivity precursor (Zn(ac)(2)) resulting in reduced PLQY. The emission from AgBiS2 NCs with ultrastrong absorption, facilitated by shell growth, can open up new possibilities in lighting, display, and bioimaging.
Capacitive and efficient near-infrared stimulation of neurons via an ultrathin AgBiS2 nanocrystal layer
(American Chemical Society, 2024) Balamur, Rıdvan; Hasanreisoğlu, Murat; Kaleli, Humeyra Nur; Karatüm, Onuralp; Nizamoğlu, Sedat; Önal, Asım; Pehlivan, Çiğdem; Şahin, Afsun; Oh, Jae Taek; Wang, Yongjie; Konstantatos, Gerasimos; Department of Electrical and Electronics Engineering; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; KUTTAM (Koç University Research Center for Translational Medicine); School of Medicine; Yes; College of Engineering; GRADUATE SCHOOL OF HEALTH SCIENCES; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center; SCHOOL OF MEDICINE
Colloidal nanocrystals (NCs) exhibit significant potential for photovoltaic bioelectronic interfaces because of their solution processability, tunable energy levels, and inorganic nature, lending them chemical stability. Silver bismuth sulfide (AgBiS2) NCs, free from toxic heavy-metal elements (e.g., Cd, Hg, and Pb), particularly offer an exceptional absorption coefficient exceeding 10(5) cm(-1) in the near-infrared (NIR), surpassing many of their inorganic counterparts. Here, we integrated an ultrathin (24 nm) AgBiS2 NC layer into a water-stable photovoltaic bioelectronic device architecture that showed a high capacitive photocurrent of 2.3 mAcm(-2) in artificial cerebrospinal fluid (aCSF) and ionic charges over 10 mu Ccm(-2) at a low NIR intensity of 0.5 mWmm(-2). The device without encapsulation showed a halftime of 12.5 years under passive accelerated aging test and did not show any toxicity on neurons. Furthermore, patch-clamp electrophysiology on primary hippocampal neurons under whole-cell configuration revealed that the device elicited neuron firing at intensity levels more than an order of magnitude below the established ocular safety limits. These findings point to the potential of AgBiS2 NCs for photovoltaic retinal prostheses.
Optical neuromodulation at all scales: from nanomaterials to wireless optoelectronics and integrated systems
(Royal Society of Chemistry (RSC), 2023) Karatüm, Onuralp; Nizamoğlu, Sedat; Önal, Asım; Gwak, Min-Jun; Hyun, Junghun; Koirala, Gyan Raj; Kim, Tae-Il; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
Light-based neuromodulation systems offer exceptional spatiotemporal resolution combined with the elimination of physical tether to communicate with neurons. Currently, optical neuromodulation systems ranging from the nano to the centimeter scale enable neural activity control from the single cell to the organ level in retina, heart, spinal cord, and brain, facilitating a wide range of experiments in intact and freely moving animals in different contexts, such as during social interactions and behavioral tasks. Nanotransducers (e.g., metallic nanoparticles, silicon nanowires, and polymeric nanoparticles) and microfabricated photodiodes convert light to electrical, thermal, and mechanical stimuli that can allow remote and non-contact stimulation of neurons. Moreover, integrated devices composed of nano and microscale optoelectronic components comprise fully implantable and wirelessly powered smart optoelectronic systems that exhibit multimodal and closed-loop operation. In this review, we first discuss the material platforms, stimulation mechanisms, and applications of passive systems, i.e., nanotransducers and microphotodiodes. Then, we review the use of organic and inorganic light-emitting diodes for optogenetics and implantable wireless optoelectronic systems that enable closed-loop optogenetic neuromodulation through the use of light-emitting diodes, wireless power transfer circuits, and feedback loops. Exploration of materials and mechanisms together with the presented applications from both research and clinical perspectives in this review provides a comprehensive understanding of the optical neuromodulation field with its advantages and challenges to build superior systems in the future.
Photovoltaic nanoassembly of nanowire arrays sensitized with colloidal nanocrystals for near-infrared retina photostimulation
(American Association for the Advancement of Science, 2026) Kaya, Tarık Safa; Yılmaz, Alp; Kaleli, Humeyra Nur; Pehlivan, Çiğdem; Çalışkan, Uğur Berkay; Balamur, Rıdvan; Nizamoğlu, Sedat; Önal, Asım; Tekinay, Eren; Mohajeri, Roya; Kaleli, Humeyra Nur; Çalışkan, Uğur Berkay; Önal, Asım; Balamur, Rıdvan; Kaya, Tarık Safa; Yılmaz, Alp; Chaffiol, Antoine; Corna, Andrea; Joffrois, Corentin; Cetin, Arif E.; Zeck, Gunther; Picaud, Serge; Graduate School of Sciences and Engineering; KUTTAM (Koç University Research Center for Translational Medicine); Department of Electrical and Electronics Engineering; Yes; Tekinay, Eren; Pehlivan, Çiğdem; College of Engineering; Research Center; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
Nanowires have served as a transformative platform for advanced neural and tissue interfaces. While their photovoltaic properties hold exceptional promise for neural modulation, existing photostimulation approaches predominantly rely on visible light-activated photoelectrochemical mechanisms. Here, we present a solution-processed photovoltaic nanoassembly comprising a ZnO nanowire array sensitized with AgBiS2 nanocrystals that enables efficient near-infrared (NIR) neural stimulation through capacitive photocurrents. By optimizing nanowire morphology and nanocrystal interdigitation, the platform achieves high charge injection densities (tens of microcoulombs per square centimeter) at low NIR intensities (<1 milliwatt per square millimeter). The nanoassembly was subretinally placed in an ex vivo blind rat retina, where it elicited repeatable and robust responses in retinal ganglion cells under NIR pulses. Notably, these responses were achieved at light intensities substantially below established ocular safety limits. The nexus of neuronal systems and nanoassemblies offers potential for enabling unconventional visual prosthetics and advanced neuromodulation therapies.
