Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
Browse
6 results
Search Results
Article Citation - WoS: 3Citation - Scopus: 3The Electronic and Optical Properties of a Triexciton in CdSe/ZnS Core/Shell Quantum Dot Nanocrystals(Taylor & Francis Ltd, 2016-02-21) Akturk, Abdurrahman; Tas, Hatice; Koksal, Koray; Sahin, MehmetIn the study, we aim to investigate the electronic and optical properties of single excitons, biexcions and triexcitons in a CdSe/ZnS core/shell quantum dot nanocrystal. The electronic structure has been determined by solving of the Poisson-Schrodinger equations self-consistently. In calculations, the exchange-correlation effects between identical particles have been taken into account in the frame of the local density approximation. We have demonstrated that the optical properties of triexciton systems are remarkably different from the single and biexciton systems. Absorption peaks or transition energies of the triexciton system are well separated from those of single- and bi-exciton systems. We have observed that the core-radius dependent transition energy variations of triexcitons are higher when compared with single- and bi-excitonic systems. The transition energy shifts of double and triple excitons with respect to the single exciton have been calculated as a function of the core radius and we have shown that the energy shifts are inversely proportional with the radius. We have also investigated the radius-dependent changes in binding energies and lifetimes of the structures and the comparative results have been discussed in a detail manner.Article Citation - WoS: 23Citation - Scopus: 21Tattoo-Like Multi-Color Physically Unclonable Functions(Wiley-VCH Verlag GmbH, 2023-12-07) Kiremitler, N. Burak; Esidir, Abidin; Drake, Gryphon A.; Yazici, Ahmet Faruk; Sahin, Furkan; Torun, Ilker; Onses, M. SerdarAdvanced anti-counterfeiting and authentication approaches are in urgent need of the rapidly digitizing society. Physically unclonable functions (PUFs) attract significant attention as a new-generation security primitive. The challenge is design and generation of multi-color PUFs that can be universally applicable to objects of varied composition, geometry, and rigidity. Herein, tattoo-like multi-color fluorescent PUFs are proposed and demonstrated. Multi-channel optical responses are created by electrospraying of polymers that contain semiconductor nanocrystals with precisely defined photoluminescence. The universality of this approach enables the use of dot and dot-in-rod geometries with unique optical characteristics. The fabricated multi-color PUFs are then transferred to a target object by using a temporary tattoo approach. Digitized keys generated from the red, green and blue fluorescence channels facilitate large encoding capacity and rapid authentication. Feature matching algorithms complement the authentication by direct image comparison, effectively alleviating constraints associated with imaging conditions. The strategy that paves the way for the development of practical, cost-effective, and secure anticounterfeiting systems is presented. Tattoo-like multi-color encoding layers based on random processing of semiconductor nanocrystals of varied composition and geometry are reported. Additive deposition via chaotic electrospraying enables randomness and multiplexing, whereas the tattoo approach provides substrate independence.imageArticle Citation - WoS: 25Citation - Scopus: 25Self-Resonant Microlasers of Colloidal Quantum Wells Constructed by Direct Deep Patterning(Amer Chemical Soc, 2021-05-24) Gheshlaghi, Negar; Foroutan-Barenji, Sina; Erdem, Onur; Altintas, Yemliha; Shabani, Farzan; Humayun, Muhammad Hamza; Demir, Hilmi VolkanHere, the first account of self-resonant fully colloidal mu-lasers made from colloidal quantum well (CQW) solution is reported. A deep patterning technique is developed to fabricate well-defined high aspect-ratio on-chip CQW resonators made of grating waveguides and in-plane reflectors. The fabricated waveguide-coupled laser, enabling tight optical confinement, assures in-plane lasing. CQWs of the patterned layers are closed-packed with sharp edges and residual-free lifted-off surfaces. Additionally, the method is successfully applied to various nanoparticles including colloidal quantum dots and metal nanoparticles. It is observed that the patterning process does not affect the nanocrystals (NCs) immobilized in the attained patterns and the different physical and chemical properties of the NCs remain pristine. Thanks to the deep patterning capability of the proposed method, patterns of NCs with subwavelength lateral feature sizes and micron-scale heights can possibly be fabricated in high aspect ratios.Article Citation - WoS: 13Citation - Scopus: 14Near-Field Energy Transfer Into Silicon Inversely Proportional to Distance Using Quasi-2D Colloidal Quantum Well Donors(Wiley-VCH Verlag GmbH, 2021-09-12) Humayun, Muhammad Hamza; Hernandez-Martinez, Pedro Ludwig; Gheshlaghi, Negar; Erdem, Onur; Altintas, Yemliha; Shabani, Farzan; Demir, Hilmi VolkanSilicon is the most prevalent material system for light-harvesting applications; however, its inherent indirect bandgap and consequent weak absorption limits its potential in optoelectronics. This paper proposes to address this limitation by combining the sensitization of silicon with extraordinarily large absorption cross sections of quasi-2D colloidal quantum well nanoplatelets (NPLs) and to demonstrate excitation transfer from these NPLs to bulk silicon. Here, the distance dependency, d, of the resulting Forster resonant energy transfer from the NPL monolayer into a silicon substrate is systematically studied by tuning the thickness of a spacer layer (of Al2O3) in between them (varied from 1 to 50 nm in thickness). A slowly varying distance dependence of d(-1) with 25% efficiency at a donor-acceptor distance of 20 nm is observed. These results are corroborated with full electromagnetic solutions, which show that the inverse distance relationship emanates from the delocalized electric field intensity across both the NPL layer and the silicon because of the excitation of strong in-plane dipoles in the NPL monolayer. These findings pave the way for using colloidal NPLs as strong light-harvesting donors in combination with crystalline silicon as an acceptor medium for application in photovoltaic devices and other optoelectronic platforms.Article Citation - WoS: 2Citation - Scopus: 3Magnetically Controlled Anisotropic Light Emission of DNA-Functionalized Supraparticles(Springer Heidelberg, 2022-08-23) Erdem, Talha; Zupkauskas, Mykolas; O'Neill, Thomas; Cassiagli, Alessio; Xu, Peicheng; Altintas, Yemliha; Eiser, Erika; O’Neill, ThomasIn this article, we show the DNA-functionalization of supraparticles, form their network, and manipulate the optical features of these networks by applying a magnetic field. We start with preparing the supraparticles (SPs) of semiconducting InP/ZnSeS/ZnS quantum dots (QDs), plasmonic silver nanoparticles, and superparamagnetic iron oxide nanoparticles. These SPs are prepared by employing azide-functionalized amphiphilic diblock or triblock copolymers as well as by using their combinations. Subsequently, we attached single-stranded DNAs to these SPs by employing copper-free click chemistry. Next, we hybridized DNA-coated QD SPs with the iron oxide SPs and formed a network. By applying a magnetic field, we restructured this network such that the iron oxide SPs are aligned. This led to an anisotropic emission from the QD SPs with a polarization ratio of 1.9. This study presents a proof-of-concept scheme to control the optical features of a self-assembled supraparticle system using an external interaction. We believe that our work will further contribute to the utilization of smart self-assembly techniques in optics and photonics.Article Citation - WoS: 88Citation - Scopus: 85Highly Stable, Near-Unity Efficiency Atomically Flat Semiconductor Nanocrystals of CdSe/ZnS Hetero-Nanoplatelets Enabled by ZnS-Shell Hot-Injection Growth(Wiley-VCH Verlag GmbH, 2019-01-30) Altintas, Yemliha; Quliyeva, Ulviyya; Gungor, Kivanc; Erdem, Onur; Kelestemur, Yusuf; Mutlugun, Evren; Demir, Hilmi VolkanColloidal semiconductor nanoplatelets (NPLs) offer important benefits in nanocrystal optoelectronics with their unique excitonic properties. For NPLs, colloidal atomic layer deposition (c-ALD) provides the ability to produce their core/shell heterostructures. However, as c-ALD takes place at room temperature, this technique allows for only limited stability and low quantum yield. Here, highly stable, near-unity efficiency CdSe/ZnS NPLs are shown using hot-injection (HI) shell growth performed at 573 K, enabling routinely reproducible quantum yields up to 98%. These CdSe/ZnS HI-shell hetero-NPLs fully recover their initial photoluminescence (PL) intensity in solution after a heating cycle from 300 to 525 K under inert gas atmosphere, and their solid films exhibit 100% recovery of their initial PL intensity after a heating cycle up to 400 K under ambient atmosphere, by far outperforming the control group of c-ALD shell-coated CdSe/ZnS NPLs, which can sustain only 20% of their PL. In optical gain measurements, these core/HI-shell NPLs exhibit ultralow gain thresholds reaching approximate to 7 mu J cm(-2). Despite being annealed at 500 K, these ZnS-HI-shell NPLs possess low gain thresholds as small as 25 mu J cm(-2). These findings indicate that the proposed 573 K HI-shell-grown CdSe/ZnS NPLs hold great promise for extraordinarily high performance in nanocrystal optoelectronics.