WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
Browse
8 results
Search Results
Now showing 1 - 8 of 8
Article Selective Growth of Fapbbr3 Nanocrystals With Precisely Tailored Optical Properties for Advanced Optoelectronic Applications(Amer Chemical Soc, 2025) Guvenc, C. Meric; Polat, Nahit; Arica, Tugce A.; Balci, SinanUnderstanding the evolution of semiconductor nanocrystals (NCs) during their colloidal synthesis is essential for achieving improved control over their physical and chemical properties. The fast reaction kinetics and concurrent nucleation and growth periods of lead halide perovskite NCs pose significant challenges in controlling the synthesis. Here, we present the room-temperature colloidal synthesis of FAPbBr3 NCs with physically decoupled nucleation and growth periods by using the common oleylamine and oleic acid ligand pair for lead halide perovskite NCs. Importantly, in this method, the nucleation and growth phases are entirely decoupled by halting the reaction at a metastable state, where the FAPbBr3 nuclei are formed. Subsequently, preformed FAPbBr3 nuclei are selectively grown by increasing supersaturation. This is achieved by reducing the monomer solubility through the injection of oleic acid into the solution. Notably, two-dimensional perovskite nanostructures form as intermediate products during the synthesis. Furthermore, the size of the FAPbBr3 NCs is tuned from 5.7 to 13.5 nm by controlling the injected oleic acid amount. Photoluminescence quantum yields of the FAPbBr3 perovskite NCs synthesized by using this method reached up to 95%. These findings demonstrate a robust strategy for the controlled synthesis of FAPbBr3 perovskite NCs, providing precisely tailored optical properties for advanced applications such as solar cells, photodetectors, and light-emitting diodes.Article Citation - WoS: 2Citation - Scopus: 2Temperature-Dependent Spectral Properties of Hexagonal Boron Nitride Color Centers(Amer Chemical Soc, 2025) Ari, Ozan; Polat, Nahit; Firat, Volkan; Cakir, Ozgur; Ates, SerkanColor centers in hexagonal boron nitride (hBN) are emerging as a mature platform for single-photon sources in quantum technology applications. In this study, we investigate the temperature-dependent spectral properties of a single defect in hBN to understand the dominant dephasing mechanisms due to phonons. We observe a sharp zero-phonon line (ZPL) emission accompanied by Stokes and anti-Stokes optical phonon sidebands assisted by the Raman-active low-energy (approximate to 6.5 meV) interlayer shear mode of hBN. The shape of the spectral lines around the ZPL is measured down to 78 K, at which the line width of the ZPL is measured as 211 mu eV. Using a quadratic electron-phonon interaction, the temperature-dependent broadening and the lineshift of the ZPL are found to follow a temperature dependence of T + T 5 and T + T 3, respectively. Furthermore, the temperature-dependent line shape around the ZPL at low-temperature conditions is modeled with a linear electron-phonon coupling theory, which results in a 0 K Debye-Waller factor of the ZPL emission as 0.59. Our results provide insights into the underlying mechanisms of electron-phonon coupling in hBN, which is critical to enhance their potential for applications in quantum technologies.Article Citation - WoS: 1Citation - Scopus: 1Hyperspectral Imaging of Exciton Polaritons in Optical Microcavities(Amer Chemical Soc, 2024) Polat, Nahit; Yakar, Ozan; O''zdemir, Sahin K.; Balci, SinanPhotons can be confined in optical microcavities both spectrally and spatially, which allows us to study the light-matter interaction in both weak and strong coupling regimes. While the former is identified by the Purcell factor, which quantifies the suppression or enhancement of the spontaneous emission rate of the quantum emitters coupled to the cavity modes, the latter is identified by the formation of hybrid photon-matter modes called exciton polaritons and thus represents an avoided crossing in the spectra. Until now, various imaging and spectroscopic techniques have been extensively used to study exciton polariton formation in optical microcavities, and the coupling between excitons and photons has been statically and dynamically tuned. Herein, we demonstrate the hyperspectral imaging of exciton polaritons in optical microcavities. Two thin metal films acting as reflectors and a polymer matrix containing a collection of quantum emitters form a hybrid system for polariton imaging. We show a strong exciton-photon interaction between photons confined in the microcavity and Frenkel excitons of dye molecules placed inside the optical microcavity. We find that exciton polaritons can be imaged and spatially mapped in the optical microcavity by using hyperspectral imaging in the visible region. We envision that our findings will help us to understand exciton polariton formation in the spectral and spatial domains at the same time across different coupling regimes.Article Citation - WoS: 17Citation - Scopus: 19Strong Coupling of Carbon Quantum Dots in Liquid Crystals(American Chemical Society, 2022) Sarısözen, Sema; Polat, Nahit; Mert Balcı, Fadime; Güvenç, Çetin Meriç; Kocabaş, Çoşkun; Yağlıoğlu, Halime Gül; Balcı, SinanCarbon quantum dots (CDs) have recently received a tremendous amount of interest owing to their attractive optical properties. However, CDs have broad absorption and emission spectra limiting their application ranges. We herein, for the first time, show synthesis of water-soluble red emissive CDs with a very narrow line width (∼75 meV) spectral absorbance and hence demonstrate strong coupling of CDs and plasmon polaritons in liquid crystalline mesophases. The excited state dynamics of CDs has been studied by ultrafast transient absorption spectroscopy, and CDs display very stable and strong photoluminescence emission with a quantum yield of 35.4% and a lifetime of ∼2 ns. More importantly, we compare J-aggregate dyes with CDs in terms of their absorption line width, photostability, and ability to do strong coupling, and we conclude that highly fluorescent CDs have a bright future in the mixed light-matter states for emerging applications in future quantum technologies.Article Citation - WoS: 2Citation - Scopus: 2Room Temperature Emission From Single Defects in Wo3 Enhanced by Plasmonic Nanocrystals(American Institute of Physics, 2021) Özçeri, Elif; Polat, Nahit; Balcı, Sinan; Tarhan, EnverRoom temperature light emission from optically active defect centers in two-dimensional layered materials has attracted great interest in recent years owing to the critical applications in the field of quantum information technologies. Therefore, efficient generation, detection, characterization, and manipulation of spatially localized emission from the defect centers are of crucial importance. Here, we report localized, stable, and bright room temperature photoluminescence (PL) emission from defects in WO3. In particular, the experimentally observed polarized and power dependent PL emission shows single photon characteristics. In addition, density functional theory calculations indicate that the source of the emission is most probably oxygen vacancy defects in WO3. The PL emission obtained from the localized defect centers in WO3 at room temperature has been, further, enhanced more than 20 times by using plasmonic gold nanoparticles.Article Citation - WoS: 13Citation - Scopus: 15Hybrid J-aggregate-graphene phototransistor(American Chemical Society, 2020) Yakar, Ozan; Balcı, Osman; Uzlu, Burkay; Polat, Nahit; Arı, Ozan; Tunç, İlknur; Balcı, SinanJ-aggregates are fantastic self-assembled chromophores with a very narrow and extremely sharp absorbance band in the visible and near-infrared spectrum, and hence they have found many exciting applications in nonlinear optics, sensing, optical devices, photography, and lasing. In silver halide photography, for example, they have enormously improved the spectral sensitivity of photographic process due to their fast and coherent energy migration ability. On the other hand, graphene, consisting of single layer of carbon atoms forming a hexagonal lattice, has a very low absorption coefficient. Inspired by the fact that J-aggregates have carried the role to sense the incident light in silver halide photography, we would like to use Jaggregates to increase spectral sensitivity of graphene in the visible spectrum. Nevertheless, it has been an outstanding challenge to place isolated J-aggregate films on graphene to extensively study interaction between them. We herein noncovalently fabricate isolated J-aggregate thin films on graphene by using a thin film fabrication technique we termed here membrane casting (MC). MC significantly simplifies thin film formation of water-soluble substances on any surface via porous polymer membrane. Therefore, we reversibly modulate the Dirac point of graphene in the J-aggregate/graphene van der Waals (vdW) heterostructure and demonstrate an all-carbon phototransistor gated by visible light. Owing to the hole transfer from excited excitonic thin film to graphene layer, graphene is hole-doped. In addition, spectral and power responses of the all-carbon phototransistor have been measured by using a tunable laser in the visible spectrum. The first integration of J-aggregates with graphene in a transistor structure enables one to reversibly write and erase charge doping in graphene with visible light that paves the way for using J-aggregate/graphene vdW heterostructures in optoelectronic applications.Article Citation - WoS: 13Citation - Scopus: 14Strong Plasmon-Exciton Coupling in Colloidal Halide Perovskite Nanocrystals Near a Metal Film(Royal Society of Chemistry, 2020) Güvenç, Çetin Meriç; Polat, Nahit; Balcı, SinanAll inorganic colloidal halide perovskite nanoplatelets and nanowires are highly anisotropic shaped semiconductor nanocrystals with highly tunable optical properties in the visible spectrum. These nanocrystals have large exciton binding energies and high oscillator strengths due to their strongly quantum confined natures. The optical properties of the halide perovskites are tunable by variation of halide composition and morphology of the nanocrystals. We herein demonstrate that colloidal perovskite nanocrystals (NCs) placed in close proximity to chemically functionalized metal films show mixed plasmon-exciton formation, plexciton formation, in the strong coupling regime. The optical properties of all-inorganic lead halide perovskite NCs were controlled by colloidally synthesizing NCs with different morphologies such as nanowires and nanoplatelets or by controlling the composition of the halides in the NCs. The experimentally observed Rabi splitting energies are around 90 meV, 70 meV, and 55 meV for CsPbI3 nanoplatelets, CsPbI3 nanowires, and CsPb(Br/I)(3) nanoplatelets, respectively. In addition, the numerical simulations are in good agreement with the experimentally obtained data. The results show that colloidal all-inorganic halide perovskite NCs are promising and strong candidates for studying light-matter interaction at nanoscale dimension.Article Citation - WoS: 9Citation - Scopus: 9Fourier Transform Plasmon Resonance Spectrometer Using Nanoslit-Nanowire Pair(American Institute of Physics, 2019) Uulu, Doolos Aibek; Ashirov, Timur; Polat, Nahit; Yakar, Ozan; Balcı, Sinan; Kocabaş, CoşkunIn this paper, we present a nanoscale Fourier transform spectrometer using a plasmonic interferometer consisting of a tilt subwavelength slit-nanowire pair on a metallic surface fabricated by the focused ion beam microfabrication technique. The incident broadband light strongly couples with the surface plasmons on the gold surface, and thus, surface plasmon polaritons (SPPs) are generated. The launched SPPs interfere with the incident light and generate high contrast interference fringes in the nanoslit. The transmitted SPPs through the metal nanoslit can decouple into free space and are collected by an objective in the far field. The spectroscopic information of the incidence light is obtained by fast Fourier transform of the fringe pattern of the SPPs. In our design, there is no need for a bulky dispersive spectrometer or dispersive optical elements. The dimension of the spectrometer is around 200 mu m length. Our design is based on inherent coherence of the SPP waves propagating through the subwavelength metal nanoslit structures etched into an opaque gold film.