Scholarly Publications - UNAM
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Item Open Access Zn-MOF as a saturable absorber for thulium/holmium-doped fiber laser(Institute of Physics Publishing Ltd., 2024-09-19) Ahmad, H.; Chiam, J. W.; Samion, M. Z.; Thambiratnam, K.; Mutlu, S.; Yilmaz, S. S.; Arsu, N.; Ortaç, BülendMetal–organic framework (MOF) is a class of material that is highly porous and modular. Due to their unique properties, MOFs have found applications in gas storage, gas separation, sensing, and supercapacitors. [Zn2(H2L)2(1,2-Bis(4-pyridyl)ethene)4]n, zinc (Zn)-based MOF was used in this work to achieve mode-locked operation in a thulium/holmium-doped fiber laser due to its excellent optical absorption at a wavelength of 1925 nm. The saturable absorber (SA) was fabricated by drop-casting a mixture of Zn-MOF and isopropanol on an arc-shaped fiber. The center wavelength of the mode-locked laser is 1906.75 nm, with a maximum average output power of 3.251 mW. The fundamental repetition rate and the pulse width were 12.89 MHz and 1.772 ps. At the same time, the pulse energy and peak power were 252 pJ and 142 W, respectively. To the authors' knowledge, this is the first time an MOF has been used for mode-locked pulse generation in a thulium/holmium-doped all-fiber laser. This work extends the use of MOF material as a saturable absorber for mode-locking applications in near-infrared fiber lasers.Item Open Access Modifying NiTi shape memory alloys to reduce nickel ions release through ethylenediamine plasma polymerization for biomedical applications(Elsevier BV, 2024-04) Sağdıc, Kutay; İnci, Fatih; Durukan, Barkan Kagan; Kockar, BenatShape memory alloys (SMAs)-a type of smart materials- offer unique benefits for constructing unique medical implants, especially for heart stents, vertebral nails, and braces. One of the widespread SMAs is nitinol (NiTi) which exhibits extraordinary shape memory ability to recover its initial form. However, due to the result of nickel (Ni2+) ions release, long-term usage of NiTi alloys would pose allergic and carcinogenic risks in orthopedics and clinical applications. To tackle these hurdles, we here demonstrate a surface modification technique via plasma polymerization in order to minimize Ni2+ ions release. NiTi substrates were initially exploited by plasma polymerization of ethylenediamine (EDA) with varying power values (25-50-75-100 W) and time rates (5-10-15 min) in order to assess the most efficient parameters for minimal toxic metal release. The samples were then tested for 14 days in a biomimicked media. As a result, 75 W-10 min plasma polymerized sample reduced Ni2+ ions release by 57.18 % compared to the base specimen. These results offer a significant outcome in deploying NiTi alloys into the biomedical field more safely through surface modifications using the plasma polymerization technique.Item Open Access Productivity enhancement in top-down VPP via concurrent grayscaling and platform speed profile optimization for symmetrical parts having micro scale features(Springer, 2024-06-14) Güven, Ege; Karpat, Yiğit; Çakmakcı, MelihVat Photopolymerization (VPP), a widely adopted additive manufacturing technique, has revolutionized the domain of 3D printing by enabling the precise fabrication of complex structures, including intricate details. However, challenges remain in achieving optimal print quality while improving speed. Conventionally, grayscaling has been used to improve part accuracy in continuous VPP systems as the build platform speed remains constant. Considering a detailed photocurable resin solidification model, together with grayscaling, this study aims to improve productivity by optimizing platform speed profile while maintaining the build quality. While the optimization formulation presented here can be applied to any part, the computational limitations due to the employment of a voxel-based approach and the nonlinear nature of the resulting optimization problem are simplified by adopting a novel discretization methodology utilizing the symmetric properties of the target 3D part. By employing ring elements instead of voxels for cylindrical symmetrical parts, the computational load of the optimization algorithm is dramatically reduced. Experimental results show the proposed concurrent optimization reduces print time by 56% while maintaining superior print surface quality on an hourglass-shaped test part having micro scale features.Item Embargo Enhancing polarization maintenance and spectral filtering in negative curvature hollow-core fibers(Elsevier BV, 2023-12-09) Siddiqui, Muhammad Zain; Ahmet E. Akosman; Mustafa OrduA new design of polarization-maintaining and spectral filtering negative curvature hollow-core fiber tailored for the telecommunication bands in the near-infrared region is presented. The optical fiber, consisting of a six-tube silica structure, incorporates vertically nested tubes anchored radially by a pole structure. By contrast, standard nested tubes in the horizontal direction form the asymmetric fiber structure, which encounters birefringence. This unique fiber design not only preserves the polarization states of light but also exhibits frequency selective transmission exclusively in the vertical direction due to the pole structure. Through fiber design optimization, a transmission loss below 0.1 dB/km for spectrally filtered wavelengths is achieved, with birefringence on the order of 10−5 within the wavelength range of 1.45 µm to 1.60 µm. These results demonstrate significant improvements in terms of birefringence, distinct loss separation between horizontally and vertically polarized states, and a reduced number of spectrally filtered wavelengths compared to previously reported findings. The proposed fiber design holds untapped potential for applications requiring selective transmissions with specific polarization.Item Embargo Roadmap to DILI research in Europe. A proposal from COST action ProEuroDILINet(Academic Press, 2023-12-28) Lucena, M. I.; Villanueva-Paz, M.; Alvarez-Alvarez, I.; Aithal, G. P; Bjornsson, E. S.; Cakan-Akdogan, G.; Cubero, F. J.; Esteves, F.; Falcon-Perez, J. M.; Fromenty, B.; Garcia-Ruiz, C.; Grove, J. I.; Konu, Özlen; Kranendonk, M.; Kullak-Ublick, G. A.; Miranda, J. P.; Remesal-Doblado, A.; Sancho-Bru, P.; Nelsons, L.; Andrade, R. J.; Daly, A. K.; Fernandez-Checa, J. C.In the current article the aims for a constructive way forward in Drug-Induced Liver Injury (DILI) are to highlight the most important priorities in research and clinical science, therefore supporting a more informed, focused, and better funded future for European DILI research. This Roadmap aims to identify key challenges, define a shared vision across all stakeholders for the opportunities to overcome these challenges and propose a high-quality research program to achieve progress on the prediction, prevention, diagnosis and management of this condition and impact on healthcare practice in the field of DILI. This will involve 1. Creation of a database encompassing optimised case report form for prospectively identified DILI cases with well-characterised controls with competing diagnoses, biological samples, and imaging data; 2. Establishing of preclinical models to improve the assessment and prediction of hepatotoxicity in humans to guide future drug safety testing; 3. Emphasis on implementation science and 4. Enhanced collaboration between drug-developers, clinicians and regulatory scientists. This proposed operational framework will advance DILI research and may bring together basic, applied, translational and clinical research in DILI.Item Open Access Cooperative engulfment of nanoparticles by membranes and vesicles(Institute of Physics Publishing Ltd., 2024-10-01) Bahrami, Arash; Bahrami, Amir HoushangCellular uptake and expulsion of nanoparticles and viruses often involves a substantial particle concentration at the cell membrane. These particles, many of which are distributed across the cell at relatively large distances, cooperate to enter or exit the cell, highlighting the importance of engulfment cooperativity. Here, we explore the cooperative entry and exit of two and multiple distant nanoparticles to and from curved vesicles, representing cellular endocytosis and exocytosis, respectively. We discover indirect engulfment cooperativity between distant nanoparticles wrapped by vesicles, driven by vesicle curvature, which is absent for particles engulfed by a flat bilayer. For the cooperative entry of two identical particles into the vesicle, we identify a counter-intuitive symmetry-breaking in which one fully-engulfed and one non-engulfed particle is more likely than two fully-engulfed or two non-engulfed particles. As a result, with a high concentration of closely-sized external particles, only half of the particles are expected to be successfully internalized by the vesicle, while the remaining half remains unwrapped, and partially engulfed particles are unlikely. In contrast, the cooperative exit of internal particles from the vesicle is characterized by the simultaneous partial engulfment of the particles that are continuously wrapped by the vesicle. This explains how evolution has harnessed membrane curvature for the simultaneous budding of multiple viral particles, a crucial step in viral infection. Our findings for the cooperative entry of multiple particles have significant implication for achieving efficient drug concentration in drug delivery applications.Item Open Access Delivering broadband light deep inside diffusive media(NATURE PORTFOLIO, 2024-05-23) McIntosh, Rohin; Goetschy, Arthur; Bender, Nicholas; Yamilov, Alexey; Hsu, Chia Wei; Yılmaz, Hasan; Cao, HuiWavefront shaping enables the targeted delivery of coherent light into random-scattering media, such as biological tissue, by the constructive interference of scattered waves. However, broadband waves have short coherence times, weakening the interference effect. Here we introduce a broadband deposition matrix that identifies a single input wavefront that maximizes the broadband energy delivered to an extended target deep inside a diffusive system. We experimentally demonstrate that long-range spatial and spectral correlations result in sixfold energy enhancement for targets containing 1,700 speckle grains and located at a depth of up to ten transport mean free paths, even when the coherence time is an order of magnitude shorter than the diffusion dwell time of light in the scattering sample. In the broadband (fast decoherence) limit, enhancement of energy delivery to extended targets becomes nearly independent of the target depth and dissipation. Our experiments, numerical simulations and analytic theory establish the fundamental limit for broadband energy delivery deep into a diffusive system, which has important consequences for practical applications. Owing to spectral long-range correlation, broadband energy can be delivered to extended targets deep inside a multiple-scattering system, greatly broadening the scope of controlling wave transport in disordered systems.Item Open Access Laser nanofabrication inside silicon with spatial beam modulation and anisotropic seeding(NATURE PORTFOLIO, 2024-07-16) Sabet, Rana Asgari; Ishraq, Aqiq; Saltık, Alperen; Bütün, Mehmet; Tokel, OnurNanofabrication in silicon, arguably the most important material for modern technology, has been limited exclusively to its surface. Existing lithography methods cannot penetrate the wafer surface without altering it, whereas emerging laser-based subsurface or in-chip fabrication remains at greater than 1 mu m resolution. In addition, available methods do not allow positioning or modulation with sub-micron precision deep inside the wafer. The fundamental difficulty of breaking these dimensional barriers is two-fold, i.e., complex nonlinear effects inside the wafer and the inherent diffraction limit for laser light. Here, we overcome these challenges by exploiting spatially-modulated laser beams and anisotropic feedback from preformed subsurface structures, to establish controlled nanofabrication capability inside silicon. We demonstrate buried nanostructures of feature sizes down to 100 +/- 20 nm, with subwavelength and multi-dimensional control; thereby improving the state-of-the-art by an order-of-magnitude. In order to showcase the emerging capabilities, we fabricate nanophotonics elements deep inside Si, exemplified by nanogratings with record diffraction efficiency and spectral control. The reported advance is an important step towards 3D nanophotonics systems, micro/nanofluidics, and 3D electronic-photonic integrated systems. The authors report controlled laser nanofabrication inside silicon. The dimensional barrier is overcome by spatially modulated lasers and anisotropic feedback from preformed structures. Features down to 100 nm is achieved, improving the state-of-the-art by an order-of-magnitude.Item Open Access Optical signatures of lattice strain in chemically doped colloidal quantum wells(NATURE PORTFOLIO, 2025-01-18) Yu, Junhong; Demir, Hilmi Volkan; Sharma, ManojLattice strain plays a vital role in tailoring the optoelectronic performance of colloidal nanocrystals (NCs) with exotic geometries. Although optical identifications of lattice strain in irregular-shaped NCs or hetero-structured NCs have been well documented, less is known about optical signatures of the sparsely distributed lattice mismatch in chemically-doped NCs. Here, we show that coherent acoustic phonons (CAPs) following bandgap optical excitations in Cu-doped CdSe colloidal quantum wells (CQWs) offer a unique platform for indirectly measuring the dopant-induced lattice strain. By comparing the behavior of CAPs in Cu-doped and undoped CQWs (i.e., vibrational phase/lifetime/amplitude), we have revealed the driving force of CAPs related to the optical screening of lattice strain-induced piezoelectric fields, which thus allows to determine the strain-induced piezoelectric field of similar to 10(2) V/m in Cu-doped CdSe CQWs. This work may facilitate a detailed understanding of lattice strain in chemically-doped colloidal NCs, which is a prerequisite for the design of favorable doped colloids in optoelectronics.Item Open Access Ion transport induced room-temperature insulator-metal transition in single-crystalline Cu2Se(Royal Society of Chemistry, 2024-05-09) Suleiman, Abdulsalam Aj; Parsi, Amir; Razeghi, Mohammadali; Başçı, Uğur; Pehlivanoğlu, Doruk; Jeong, Hu Young; Kang, Kibum; Kasırga, Talip Serkan; Oh, SaeyoungCu2Se is a superionic conductor above 414 K, with ionic conductivities reaching that of molten salts. The superionic behavior results from hopping Cu ions between different crystallographic sites within the Se scaffold. However, the properties of Cu2Se below 414 K are far less known due to experimental limitations imposed by the bulk or polycrystalline samples that have been available so far. Here, we report the synthesis of ultra-thin, large-area single crystalline Cu2Se samples using a chemical vapor deposition method. The as-synthesized Cu2Se crystals exhibit optically and electrically detectable and controllable robust phases at room temperature and above. We demonstrate that Cu ion vacancies can be manipulated to induce an insulator-metal transition, which exhibits 6 orders of magnitude change in the electrical resistance of two terminal devices, accompanied by an optical change in the phase configuration. Our experiments show that the high mobility of the liquid-like Cu ion vacancies in Cu2Se causes macroscopic ordering in the Cu vacancies. Consequently, phase distribution over the crystals is not dictated by the diffusive motion of the ions but by the local energy minima formed due to the phase transition. As a result, long-range vacancy ordering of the crystal below 414 K becomes optically observable at a micrometer scale. This work demonstrates that Cu2Se could be a prototypical system where long-range ordering properties can be studied via electrical and optical methods.Item Open Access Strongly polarized color conversion of isotropic colloidal quantum dots coupled to fano resonances(Royal Society of Chemistry, 2024-07-24) Güngör, Kıvanç; Erdem, Onur; Güzeltürk, Burak; Ünal, Emre; Jun, Shinae; Jang, Eunjoo; Demir, Hilmi VolkanColloidal quantum dots (QDs) offer high color purity essential to high-quality liquid crystal displays (LCDs), which enables unprecedented levels of color enrichment in LCD-TVs today. However, for LCDs requiring polarized backplane illumination in operation, highly polarized light generation using inherently isotropic QDs remains a fundamental challenge. Here, we show strongly polarized color conversion of isotropic QDs coupled to Fano resonances of v-grooved surfaces compatible with surface-normal LED illumination for next-generation QD-TVs. This architecture overcomes the critically oblique excitation of surface plasmon coupled emission by using v-shapes imprinted on the backlight unit (BLU). With isotropic QDs coated on the proposed v-BLU surface, we experimentally measured a far-field polarization contrast ratio of similar to 10. Full electromagnetic solution shows Fano line-shape transmission in transverse magnetic polarization allowing for high transmission as an indication for forward-scattering configuration. Of these QDs coupled to the surface plasmon-polariton modes, we observed strong modifications in their emission kinetics revealed by time-resolved photoluminescence spectroscopy and via dipole orientations identified by back focal plane imaging. This collection of findings indicates conclusively that these isotropic QDs are forced to radiate in a linearly polarized state from the patterned planar surface under surface-normal excitation. For next-generation QD-TVs, the proposed polarized color-converting isotropic QDs on such v-BLUs can be deployed in bendable electronic displays. We demonstrate a novel backlight unit utilizing the plasmonic interaction of quantum dots with v-shaped metallic grooves, which are capable of enhancing the emission in the desired polarization while suppressing the unwanted polarization component.Item Open Access Deterministic positioning of few aqueous colloidal quantum dots(Royal Society of Chemistry, 2024-08-27) Pambudi, Muhammad Tegar; Arora, Deepshikha; Liang, Xiao; Sain, Basudeb; Ranganath, Anupama Sargur; Chua, Matthew R; Vu, Cam Nhung; Zamiri, Golnoush; Rahman, Md. Abdur; Demir, Hilmi VolkanEmerging quantum technologies that critically require the integration of quantum emitters on photonic platforms are hindered by the control over their position, quantity, and scalability. Herein, we describe a facile strategy to deposit aqueous silica-coated quantum dots (QDs) in a template of polymethyl methacrylate (PMMA) nanoholes that leverages saturated ethanol vapor drop-casting and subsequent lift-off of the template. Ethanol vapor incorporation into water droplets during the drying process reduces the meniscus contact angle, which increases capillary forces and enhances particle confinement within the pinning contact region. Furthermore, induced Marangoni flow controls the particle transport dynamics inside the droplets, making large-scale deposition possible. Controlling the hole diameter of the template demonstrates changes in the number of QDs per hole, which is consistent with the Poissonian distribution with the best results of similar to 40% single-particle yield from an similar to 80% total site occupancy. This method employs a simple setup, eliminating the need for intricate optimization, yet offers the potential for deterministic patterning within complex photonic platforms.Item Open Access Microfluidic vs. batch synthesis of fluorescent poly(GMA-co-EGDMA) micro/nanoparticles for biomedical applications(Springer Nature, 2024-09-25) Kılınçlı, Betül; Çınar, Ayşe Duru; Çetin, Barbaros; Kibar, GüneşFluorescent particles play a crucial role in nanomedicine and biological applications such as imaging, diagnostic tools, drug delivery, biosensing, multimodal imaging, and theranostics. This report presents a novel synthesis method and comparative study for synthesizing fluorescent particles in microfluidic continuous and batch-type reactors. Glycidyl methacrylate (GMA) and ethylene glycol dimethyl acrylate (EGDMA) are well-known monomers for synthesizing functional particles for biomedical applications. Several methods exist to obtain fluorescent poly(GMA-co-EGDMA) (p(GMA-EGDMA))particles through various polymerization techniques. Unlike existing methods, we developed a green approach for synthesizing fluorescent p(GMA-EGDMA) particles via UV-initiated one-step emulsion polymerization by comparing microfluidic and batch synthesis. Moreover, as a fluorescent dye, fluorescein isothiocyanate (FITC) was directly incorporated with p(GMA-EGDMA) particles at various concentrations to achieve tunable fluorescent functionality. While the batch synthesis resulted in polydisperse fluorescent p(GMA-EGDMA)microparticles with spherical shapes ranging from 25 μm to 1.0 μm in size, the microfluidic synthesis produced nonspherical nanoparticles. Fluorescent FITC@p(GMA-EGDMA) particles were characterized by scanning electron microscope (SEM), fluorescent microscope, and Fourier-transform infrared spectroscopy (FTIR). The synthesized particles have potential for fluorescence imaging applications, specifically bio-detection in array systems.Item Open Access Molten Salt Assisted Assembly (MASA) of novel mesoporous Ni0.5Mn0.5Co2O4 for high-performance asymmetric supercapacitors(Elsevier Science Inc., 2024-11) Özkaynak, Mert Umut; Türker, Yurdanur; Dönmez, Koray Bahadır; Dağlar, Selin; Çobandede, Zehra; Çelenk, Merve Metin; Karatepe, Nilgi; Güner, F. Seniha; Dağ, ÖmerMesoporous transition metal oxides (TMO) are immensely investigated as electrode materials in supercapacitors. The molten salt assisted self-assembly (MASA) process enables a facile route for the synthesis of the mesoporous TMO. In this study, mesoporous nickel manganese cobaltite (Ni0.5Mn0.5Co2O4) is synthesized for the first time using a MASA process and is evaluated as a novel electrode-active material for asymmetric supercapacitors. The objective of this work is to quantitatively measure the performance improvement in the Ni0.5Mn0.5Co2O4 electrode based on its composition and reveal the improvement mechanism through electrochemical methods. The electrochemical performance of the NiCo2O4 and MnCo2O4 prepared by MASA is also investigated, in order to understand the synergistic effect of Ni and Mn elements in the same cobaltite structure. In line with the data obtained from half cells, a full asymmetric cell is prepared by assembling the appropriate amount of Ni0.5Mn0.5Co2O4 and activated carbon through the charge balance theory. The test results show that the specific capacitance CA (Cs) values are 2.62F/cm2 (92.1F/g) for mesoporous NiCo2O4, 0.26F/cm2 (9.8F/g) for mesoporous MnCo2O4, and 9.53F/cm2 (338.5F/g) for mesoporous Ni0.5Mn0.5Co2O4 under the test conditions of 5 mA/cm2. The asymmetric supercapacitor assembled with Ni0.5Mn0.5Co2O4 and activated carbon demonstrates a superior energy density of 79.52 Wh/kg at 1 mA/cm2. The findings of the study highlight the importance of substituting the electrode with Ni0.5Mn0.5Co2O4 to enhance the CA (Cs) by achieving proper surface properties and electrochemical activity.Item Embargo Recent advances in the synthesis and applications of fluoranthenes(Royal Society of Chemistry, 2025-03-04) Turkmen, Yunus EmreAs an important subclass of polycyclic aromatic hydrocarbons (PAHs), fluoranthenes continue to attract significant attention in synthetic organic chemistry and materials science. In this article, an overview of recent advances in the synthesis of fluoranthene derivatives along with selected applications is provided. First, methods for fluoranthene synthesis with a classification based on strategic bond disconnections are discussed. Then, the total syntheses of natural products featuring the benzo[j]fluoranthene skeleton are covered. Finally, examples of important applications of a variety of fluoranthenes are summarized.Item Open Access Polariton lasing in Mie-resonant perovskite nanocavity(Editorial Office of Opto-Electronic Advances, 2024-01-19) Masharin, Mikhail A.; Khmelevskaia, Daria; Kondratiev, Valeriy I.; Markina, Daria I.; Utyushev, Anton D.; Dolgintsev, Dmitriy M.; Dmitriev, Alexey D.; Shahnazaryan, Vanik A.; Pushkarev, Anatoly P.; Isik, Furkan; Iorsh, Ivan V.; Shelykh, Ivan A.; Demir, Hilmi V.; Samusev, Anton K.; Makarov, Sergey V.Deeply subwavelength lasers (or nanolasers) are highly demanded for compact on -chip bioimaging and sensing at the nanoscale. One of the main obstacles for the development of single -particle nanolasers with all three dimensions shorter than the emitting wavelength in the visible range is the high lasing thresholds and the resulting overheating. Here we exploit exciton-polariton condensation and mirror -image Mie modes in a cuboid CsPbBr 3 nanoparticle to achieve coherent emission at the visible wavelength of around 0.53 mu m from its ultra -small ( approximate to 0.007 mu m 3 or approximate to lambda 3 / 2 0) semiconductor nanocavity. The polaritonic nature of the emission from the nanocavity localized in all three dimensions is proven by direct comparison with corresponding one-dimensional and two-dimensional waveguiding systems with similar material parameters. Such a deeply subwavelength nanolaser is enabled not only by the high values for exciton binding energy ( approximate to 35 meV), refractive index (>2.5 at low temperature), and luminescence quantum yield of CsPbBr 3 , but also by the optimization of polaritons condensation on the Mie resonances with quality factors improved by the metallic substrate. Moreover, the key parameters for optimal lasing conditions are intermode free spectral range and phonons spectrum in CsPbBr 3 , which govern polaritons condensation path. Such chemically synthesized colloidal CsPbBr 3 nanolasers can be potentially deposited on arbitrary surfaces, which makes them a versatile tool for integration with various on -chip systems.Item Open Access Laser-written wave plates inside the silicon enabled by stress-induced birefringence(Optica, 2024-01-01) Saltik, Alperen; Tokel, OnurLaser writing enables optical functionality by altering the optical properties of materials. To achieve this goal, efforts generally focus on laser -written regions. It has also been shown that birefringence surrounding the modified regions can be exploited for achieving functionality. The effect has been used to fabricate wave plates in glass, with significant potential for other materials. Here, we establish analogous stress control and birefringence engineering inside silicon. We first develop a robust analytical model enabling the prediction of birefringence maps from arbitrary laser -written patterns. Then, we tailor three-dimensional laser lithography to create the first, to the best of our knowledge, polarization -control optics inside silicon. (c) 2023 Optica Publishing GroupItem Open Access Quasi-bound states in the continuum for electromagnetic induced transparency and strong excitonic coupling(Optica, 2024-05-20) Hajian, Hodjat; Zhang, Xia; Mccormack, Oisin; Zhang, Yongliang; Dobie, Jack; Rukhlenko, Ivan d.; Ozbay, Ekmel; Bradley, A. LouiseAdvancing on previous reports, we utilize quasi-bound states in the continuum (q-BICs) supported by a metasurface of TiO2 meta-atoms with broken inversion symmetry on an SiO2 substrate, for two possible applications. Firstly, we demonstrate that by tuning the metasurface’s asymmetric parameter, a spectral overlap between a broad q-BIC and a narrow magnetic dipole resonance is achieved, yielding an electromagnetic induced transparency analogue with a 50 µs group delay. Secondly, we have found that, due to the strong coupling between the q-BIC and WS2 exciton at room temperature and normal incidence, by integrating a single layer of WS2 to the metasurface, a 37.9 meV Rabi splitting in the absorptance spectrum with 50% absorption efficiency is obtained. These findings promise feasible two-port devices for visible range slow-light characteristics or nanoscale excitonic coupling.Item Embargo Quantum Beats between Spin-Singlet and Spin-Triplet Interlayer Exciton Transitions in WSe2-MoSe2 Heterobilayers(American Chemical Society, 2024-04-19) Durmuş, Mehmet Atıf; Sarpkaya, İbrahimThe long-lived interlayer excitons (IXs) of semiconducting transition metal dichalcogenide heterobilayers are prime candidates for developing various optoelectronic and valleytronic devices. Their photophysical properties, including fine structure, have been the focus of recent studies, and the presence of two spin states, namely, spin-singlet and spin-triplet, has been experimentally confirmed. However, the existence of the interaction between these states and their nature remains unknown to date. Here, we demonstrate the presence of coherent coupling between the spin-singlet and spin-triplet IXs of a WSe2-MoSe2 heterobilayer utilizing quantum beat spectroscopy via a home-built Michelson interferometer. As a clear signature of coherent coupling, the quantum beat signal has been observed for the first time between closely spaced transitions of IXs. The observed strong damping of the quantum beat signals with fast dephasing times of 270-400 fs indicates that fluctuations giving rise to inhomogeneous broadening in the photoluminescence emission of these states are uncorrelated.Item Open Access Gastroenteropancreatic neuroendocrine neoplasms: current development, challenges, and clinical perspectives(BioMed Central, 2024-06-24) Ertaş, Yavuz NuriNeuroendocrine neoplasms (NENs) are highly heterogeneous and potentially malignant tumors arising from secretory cells of the neuroendocrine system. Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are the most common subtype of NENs. Historically, GEP-NENs have been regarded as infrequent and slow-growing malignancies; however, recent data have demonstrated that the worldwide prevalence and incidence of GEP-NENs have increased exponentially over the last three decades. In addition, an increasing number of studies have proven that GEP-NENs result in a limited life expectancy. These findings suggested that the natural biology of GEP-NENs is more aggressive than commonly assumed. Therefore, there is an urgent need for advanced researches focusing on the diagnosis and management of patients with GEP-NENs. In this review, we have summarized the limitations and recent advancements in our comprehension of the epidemiology, clinical presentations, pathology, molecular biology, diagnosis, and treatment of GEP-NETs to identify factors contributing to delays in diagnosis and timely treatment of these patients.