Institute of Materials Science and Nanotechnology (UNAM)

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Open Access
High external quantum efficiency light-emitting diodes enabled by advanced heterostructures of type-ii nanoplatelets
(American Chemical Society, 2023-03-13) Durmusoglu, Emek G.; Hu, Sujuan; Hernandez-Martinez, Pedro Ludwig; Izmir, Merve; Shabani,Farzan; Guo, Min; Gao, Huayu; Isik, Furkan; Delikanli, Savas; Sharma, Vijay Kumar; Liu, Baiquan; Demir, Hilmi Volkan; Demir, Hilmi Volkan; Shabani, Farzan; Işık, Furkan; Delikanli, Savaş
Colloidal quantum wells (CQWs), also known as nanoplatelets (NPLs), are exciting material systems for numerous photonic applications, including lasers and light-emitting diodes (LEDs). Although many successful type-I NPL-LEDs with high device performance have been demonstrated, type-II NPLs are not fully exploited for LED applications, even with alloyed type-II NPLs with enhanced optical properties. Here, we present the development of CdSe/CdTe/CdSe core/crown/crown (multi-crowned) type-II NPLs and systematic investigation of their optical properties, including their comparison with the traditional core/crown counterparts. Unlike traditional type-II NPLs such as CdSe/CdTe, CdTe/CdSe, and CdSe/CdSexTe1–x core/crown heterostructures, here the proposed advanced heterostructure reaps the benefits of having two type-II transition channels, resulting in a high quantum yield (QY) of 83% and a long fluorescence lifetime of 73.3 ns. These type-II transitions were confirmed experimentally by optical measurements and theoretically using electron and hole wave function modeling. Computational study shows that the multi-crowned NPLs provide a better-distributed hole wave function along the CdTe crown, while the electron wave function is delocalized in the CdSe core and CdSe crown layers. As a proof-of-concept demonstration, NPL-LEDs based on these multi-crowned NPLs were designed and fabricated with a record high external quantum efficiency (EQE) of 7.83% among type-II NPL-LEDs. These findings are expected to induce advanced designs of NPL heterostructures to reach a fascinating level of performance, especially in LEDs and lasers.
Open Access
On-chip flow rate sensing via membrane deformation and bistability probed by microwave resonators
(Springer Link, 8-04-2023) Seçme, Arda; Pisheh, Hadi Sedaghat; Tefek, Uzay; Uslu, H. Dilara; Küçükoğlu, Berk; Alataş, Ceren; Kelleci, Mehmet; Hanay, Mehmet Selim; Seçme, Arda; Pisheh, Hadi Sedaghat; Tefek, Uzay; Uslu, H. Dilara; Küçükoğlu, Berk; Alataş, Ceren; Kelleci, Mehmet; Hanay, Mehmet Selim
Precise monitoring of fluid flow rates constitutes an integral problem in various lab-on-a-chip applications. While off-chip flow sensors are commonly used, new sensing mechanisms are being investigated to address the needs of increasingly complex lab-on-a-chip platforms which require local and non-intrusive flow rate sensing. In this regard, the deformability of microfluidic components has recently attracted attention as an on-chip sensing mechanism. To develop an on-chip flow rate sensor, here we utilized the mechanical deformations of a 220 nm thick Silicon Nitride membrane integrated with the microfluidic channel. Applied pressure and fluid flow induce different modes of deformations on the membrane, which are electronically probed by an integrated microwave resonator. The flow changes the capacitance, and in turn resonance frequency, of the microwave resonator. By tracking the resonance frequency, liquid flow was probed with the device. In addition to responding to applied pressure by deflection, the membrane also exhibits periodic pulsation motion under fluid flow at a constant rate. The two separate mechanisms, deflection and pulsation, constitute sensing mechanisms for pressure and flow rate. Using the same device architecture, we also detected pressure-induced deformations by a gas to draw further insight into the sensing mechanism of the membrane. Flow rate measurements based on the deformation and instability of thin membranes demonstrate the transduction potential of microwave resonators for fluid–structure interactions at micro- and nanoscales.
Open Access
Microfluidics-integrated microwave sensors for single cells size discrimination
(Institute of Electrical and Electronics Engineers, 2021-04-01) Seçme, Arda; Pisheh, Hadi Sedaghat; Uslu, H. Dilara; Akbulut, Özge; Erdoğan, R. Tufan; Hanay, M. Selim; Akbulut, Özge; Erdoğan, R. Tufan; Seçme, Arda; Pisheh, Hadi Sedaghat; Uslu, H. Dilara; Hanay, M. Selim
The size of a cell is one of the most fundamental biophysical parameters it possesses. Traditionally size measurements are done by using optical microscopy and quantitative phase imaging. However, a sensor with higher resolution, high throughput and lower cost is still needed. Here, a novel microfluidics-integrated microwave sensor is demonstrated to characterize single cells in real-time without labelling. Coplanar waveguide resonator is designed with a bowtie-shaped sensing electrodes separated by 50 μm. Cells are transported to sensing region by microfluidic channels and their sizes are measured simultaneously by the microwave sensors and optical microscopy. To enhance the microwave resolution, the microwave resonator is equipped with external heterodyne measurement circuitry detecting each and every cell passing through the sensing region. By comparing quantitative microscopic image analysis with frequency shifts, we show that microwave sensors can effectively measure cellular size. Our results indicate that microfluidics-integrated microwave sensors (MIMS) can be used for detecting.
Open Access
Classification of dielectric microparticles by microwave impedance cytometry
(Cold Spring Harbor Laboratory, 2022-09-28) Hanay, M. Selim; Sarı, Burak; Tefek, Uzay; Hanay, M. Selim; Sarı, Burak; Tefek, Uzay
AbstractCoulter counters and impedance cytometry are commonly used for counting microscopic objects, such as cells and microparticles flowing in a liquid, as well as to obtain their size distribution. However, the ability of these techniques to provide simultaneous material information — via dielectric permittivity measurements — has been limited so far. The challenge stems from the fact that the signals generated by microparticles of identical size, but different material composition, are close to each other. The similarity in impedance signals arises because the material-dependent factor is determined mainly by the volume of aqueous solution displaced by the microparticles, rather than the microparticles themselves. To differentiate between materially distinct particles with similar geometry and size, another measurement mode needs to be implemented. Here, we describe a new microfluidics-based sensor that provides material classification between microparticles with similar sizes by integrating impedance cytometry with microwave resonator sensors on the same chip. While low-frequency impedance cytometry provides the geometric size of particles, the microwave sensor operating at three orders-of-magnitude higher frequency provides their electrical size. By combining these two measurements, the Clausius-Mossotti factors of microparticles can be calculated to serve as a differentiation parameter. In addition to distinguishing dielectric materials from cells and metals, we classified two different dielectric microparticles with similar sizes and electrical characteristics: polystyrene and soda lime glass, with 94% identification accuracy. The proposed technique can serve as an automated monitoring system for quality control of manufactured microparticles and facilitate environmental microplastic screening.
Open Access
On-chip liquid and gas flow rate sensing via membrane deformation and bistability probed by microwave resonators
(Springer, 2022-11-15) Seçme, Arda; Pisheh, Hadi Sedaghat; Uslu, H. Dilara; Tefek, Uzay; Küçükoğlu, Berk; Alataş, Ceren; Kelleci, Mehmet; Hanay, M. Selim; Seçme, Arda; Pisheh, Hadi Sedaghat; Uslu, H. Dilara; Tefek, Uzay; Küçükoğlu, Berk; Alataş, Ceren; Kelleci, Mehmet; Hanay, M. Selim
Abstract Precise monitoring of fluid flow rates constitutes an integral problem in various lab-on-a-chip applications. While off-chip flow sensors are commonly used, new sensing mechanisms are being investigated to address the needs of increasingly complex lab-on-a-chip platforms which require local and non-intrusive flow rate sensing. In this regard, the deformability of microfluidic components has recently attracted attention as an on-chip sensing mechanism. To develop an on-chip flow rate sensor, here we utilized the mechanical deformations of a 220 nm thick Silicon Nitride membrane integrated with the microfluidic channel. Fluid flow induces deformations on the membrane, which is electronically probed by the changes in the capacitance and resonance frequency of an overlapping microwave resonator. By tracking the resonance frequency, both liquid and gas flows were probed with the same device architecture. For liquid flow experiments, a secondary sensing mechanism emerged when it was observed that steady liquid flow induces periodic deformations on the membrane. Here, the period of membrane deformation depends on the flow rate and can again be measured electronically by the microwave sensor. Flow rate measurements based on the deformation and instability of thin membranes demonstrate the transduction potential of microwave resonators for fluid-structure interactions at micro and nanoscales.
Open Access
Erratum: Specialty optical fiber modeling, fabrication, and characterization feature issue
(Optica, 2022) Ortaç, Bülend; Jain, Deepak; Jha, Rajan; Hu, Jonathan; Ung, Bora; Ortaç, Bülend
Two articles [1,2] appearing in the “Specialty optical fiber modeling, fabrication, and characterization” feature issue should have been labeled as invited.
Open Access
Erratum: α -MoO3-SiC metasurface for mid-IR directional propagation of phonon polaritons and passive daytime radiative cooling (Applied Physics Letters (2022) 121 (182201) DOI: 10.1063/5.0128110)
(AIP Publishing LLC, 2022-11-21) Erçağlar, Veysel; Hajian, Hodjat; Rukhlenko, I.D.; Özbay, Ekmel; Erçağlar, Veysel; Hajian, Hodjat; Özbay, Ekmel
This article was originally published online on 31 October 2022 with errors in the Author Contributions section and Refs. 24 and 41. The Author Contributions section and references are shown correctly below. All online and printed versions of the article were corrected on 1 November 2022. AIP Publishing apologizes for this error. © 2022 Author(s).
Open Access
Radiation shielding tests of crosslinked polystyrene-b-polyethyleneglycol block copolymers blended with nanostructured selenium dioxide and boron nitride particles
(MDPI, 2022-02-01) Cinan, Zehra Merve; Erol, Burcu; Baskan, Taylan; Mutlu, Saliha; Ortaç, Bülend; Savaskan Yilmaz, Sevil; Yilmaz, Ahmet Hakan; Ortaç, Bülend
In this work, gamma-ray shielding features of crosslinked polystyrene-b-polyethyleneglycol block copolymers (PS-b-PEG) blended with nanostructured selenium dioxide (SeO2 ) and boron ni-tride (BN) particles were studied. This research details several radiation shielding factors i.e., mass attenuation coefficient (µm ), linear attenuation coefficient (µL ), radiation protection efficiency (RPE), half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP). The irradiation properties of our nanocomposites were investigated with rays from the152 Eu source (in the energy intervals from 121.780 keV to 1408.010 keV) in a high-purity germanium (HPGe) detector system, and analyzed with GammaVision software. Moreover, all radiation shielding factors were determined by theoretical calculus and compared with the experimental results. In addition, the morphological and thermal characterization of all nanocomposites was surveyed with various techniques i.e., nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). Acceptable compatibility was revealed and observed in all nanocomposites between the experimental and theoretical results. The PS-b-PEG copolymer and nanostructured SeO2 and BN particles exerted a significant effect in enhancing the resistance of the nanocomposites, and the samples with high additive rates exhibited better resistance than the other nanocomposites. From the achieved outcomes, it can be deduced that our polymer-based nanocomposites can be utilized as a good choice in the gamma-irradiation-shielding discipline. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
Open Access
A recombinase-based genetic circuit for heavy metal monitoring
(MDPI, 2022-02-16) Akboğa, Doğuş; Saltepe, Behide; Akboğa, Doğuş; Saltepe, Behide
Rapid progress in the genetic circuit design enabled whole-cell biosensors (WCBs) to become prominent in detecting an extensive range of analytes with promise in many fields, from medical diagnostics to environmental toxicity assessment. However, several drawbacks, such as high background signal or low precision, limit WCBs to transfer from proof-of-concept studies to real-world applications, particularly for heavy metal toxicity monitoring. For an alternative WCB module design, we utilized Bxb1 recombinase that provides tight control as a switch to increase dose-response behavior concerning leakiness. The modularity of Bxb1 recombinase recognition elements allowed us to combine an engineered semi-specific heat shock response (HSR) promoter, sensitive to stress conditions including toxic ions such as cadmium, with cadmium resistance regulatory elements; a cadmium-responsive transcription factor and its cognitive promoter. We optimized the conditions for the recombinase-based cadmium biosensor to obtain increased fold change and shorter response time. This system can be expanded for various heavy metals to make an all-in-one type of WCB, even using semi-specific parts of a sensing system. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
Open Access
Uncovering the non-radiative thermal characteristics of a passive radiative cooler under real operating conditions
(Institute of Physics Publishing Ltd., 2022-12-12) Koçer, Hasan; Durna, Yılmaz; Işık, Halil; Soydan, Mahmut Can; Khalichi, Bahram; Ghobadi, Amir; Kurt, H.; Özbay, Ekmel; Koçer, Hasan; Durna, Yılmaz; Işık, Halil; Soydan, Mahmut Can; Khalichi, Bahram; Ghobadi, Amir; Özbay, Ekmel
Passive radiative cooling (PasRadCool), which emits thermal energy from objects to deep cold space through atmospheric transparency, offers complementary and alternative green energy solutions for passive cooling of buildings, clothing, and renewable energy harvesting. Depending on the spectral emissive/absorptive properties of the unit under test (UUT), radiative heat exchanges occur between the UUT, atmosphere, and sun, while at the same time non-radiative heat exchange occurs. The performance of the PasRadCool is determined by the combined thermal and thermodynamic effects of both exchange mechanisms. Although the non-radiative heat exchange, which consists of conductive and convective processes to the outer surfaces of the UUT and the surrounding air fluid, is very sensitive to environmental changes, the actual performance is not fully determined since this feature is considered statically in many studies. Herein, we propose a method that reveals the non-radiative thermal characteristics of the PasRadCool under real operating conditions. With a photonic radiative cooler structure, which we manufacture as a proof of concept, we perform nighttime field test measurements in varying non-radiative thermal conditions. The proposed method extracts the time-dependent non-radiative heat transfer coefficient of the UUT as accurately as possible. We also confirm that our experimental result shows good agreement with both numerical and analytical methods. The proposed approach, which highlights the realistic thermal management of PasRadCool, is not specific to the circumstances of our study and can be applied to all PasRadCool situations with different geometry, material, and environmental conditions.
Open Access
Microfluidic methods in janus particle synthesis
(Dove Medical Press Ltd, 2022-09-19) Saqib, Muhammad; Tran, Phong A.; Ercan, Batur; Yegan Erdem, Emine; Saqib, Muhammad; Yegan Erdem, Emine
Janus particles have been at the center of attention over the years due to their asymmetric nature that makes them superior in many ways to conventional monophase particles. Several techniques have been reported for the synthesis of Janus particles; however, microfluidic-based techniques are by far the most popular due to their versatility, rapid prototyping, low reagent consumption and superior control over reaction conditions. In this review, we will go through microfluidic-based Janus particle synthesis techniques and highlight how recent advances have led to complex functionalities being imparted to the Janus particles. © 2022 Saqib et al.
Open Access
An outline of contributing vaccine technologies for SARS CoV2 advancing in clinical and preclinical phase-trials
(Bentham Science Publishers, 2022-04-21) Naz, Sheikh Saba; Munir, Iqra; Munir, Iqra
Background: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV2) is an RNA virus involving 4 structural and 16 non-structural proteins, and exhibiting high transmission potential and fatality. The emergence of this newly encountered beta coronavirus-SARS CoV2 has brought over 2 million people to death, and more than 10 billion people got infected across the globe as yet. Consequently, the global scientific community has contributed to the synthesis and design of effective immunization technologies to combat this virus. Objectives: This literature review was intended to gather an update on published reports of the vaccines advancing in the clinical trial phases or preclinical trials, to summarize the foundations and implications of contributing vaccine candidates inferring their impact in the pandemic repression. In addition, this literature review distinctly facilitates an outline of the overall vaccine effectiveness at current doses. Methods: The reported data in this review was extracted from research articles, review articles and patents published from January 2020 to July 2021, available on Google Scholar, Pubmed, Pubmed Central, Research Gate, Science direct, and Free Patent Online Database by using combination of keywords. Moreover, some information is retrieved from native web pages of vaccine manufacturing companies' due to progressing research and unavailability of published research papers. Conclusion: Contributing vaccine technologies include: RNA (Ribonucleic acid) vaccines, DNA (Deoxyribonucleic acid) vaccines, viral vector vaccines, protein-based vaccines, inactivated vaccines, viruses-like particles, protein superglue, and live-attenuated vaccines. Some vaccines are prepared by establishing bacterial and yeast cell lines and as self-assembling adenovirus- derived multimeric protein-based self-assembling nanoparticle (ADDOmer). On May 19, WHO has issued an emergency use sanction of Moderna, Pfizer, Sinopharm, AstraZeneca, and Covishield vaccine candidates on account of clinical credibility from experimental data.
Open Access
Second generation Pichia pastoris strain and bioprocess designs
(BioMed Central Ltd, 2022-12-29) Ergün, Burcu Gündüz; Ergün, Burcu Gündüz
Yeast was the first microorganism used by mankind for biotransformation processes that laid the foundations of industrial biotechnology. In the last decade, Pichia pastoris has become the leading eukaryotic host organism for bioproduct generation. Most of the P. pastoris bioprocess operations has been relying on toxic methanol and glucose feed. In the actual bioeconomy era, for sustainable value-added bioproduct generation, non-conventional yeast P. pastoris bioprocess operations should be extended to low-cost and renewable substrates for large volume bio-based commodity productions. In this review, we evaluated the potential of P. pastoris for the establishment of circular bioeconomy due to its potential to generate industrially relevant bioproducts from renewable sources and waste streams in a cost-effective and environmentally friendly manner. Furthermore, we discussed challenges with the second generation P. pastoris platforms and propose novel insights for future perspectives. In this regard, potential of low cost substrate candidates, i.e., lignocellulosic biomass components, cereal by-products, sugar industry by-products molasses and sugarcane bagasse, high fructose syrup by-products, biodiesel industry by-product crude glycerol, kitchen waste and other agri-food industry by products were evaluated for P. pastoris cell growth promoting effects and recombinant protein production. Further metabolic pathway engineering of P. pastoris to construct renewable and low cost substrate utilization pathways was discussed. Although, second generation P. pastoris bioprocess operations for valorisation of wastes and by-products still in its infancy, rapidly emerging synthetic biology tools and metabolic engineering of P. pastoris will pave the way for more sustainable environment and bioeconomy. From environmental point of view, second generation bioprocess development is also important for waste recycling otherwise disposal of carbon-rich effluents creates environmental concerns. P. pastoris high tolerance to toxic contaminants found in lignocellulosic biomass hydrolysate and industrial waste effluent crude glycerol provides the yeast with advantages to extend its applications toward second generation P. pastoris strain design and bioprocess engineering, in the years to come. Graphical Abstract: [Figure not available: see fulltext.]. © 2022, The Author(s).
Open Access
Roadmap on wavefront shaping and deep imaging in complex media
(Institute of Physics, 2022-10) Gigan, Sylvain; Katz, Ori; De Aguiar, Hilton B.; Andresen, Esben Ravn; Aubry, Alexandre; Bertolotti, Jacopo; Bossy, Emmanuel; Bouchet, Dorian; Brake, Joshua; Brasselet, Sophie; Bromberg, Yaron; Cao, Hui; Chaigne, Thomas; Cheng, Zhongtao; Choi, Wonshik; Čižmár, Tomáš; Cui, Meng; Curtis, Vincent R.; Defienne, Hugo; Hofer, Matthias; Horisaki, Ryoichi; Horstmeyer, Roarke; Ji, Na; LaViolette, Aaron K.; Mertz, Jerome; Moser, Christophe; Mosk, Allard P; Pégard, Nicolas C; Piestun, Rafael; Popoff, Sebastien; Phillips, David B.; Psaltis, Demetri; Rahmani, Babak; Rigneault, Hervé; Rotter, Stefan; Tian, Lei; Vellekoop, Ivo M.; Waller, Laura; Wang, Lihong; Weber, Timothy; Xiao, Sheng; Xu, Chris; Yamilov, Alexey; Yang, Changhuei; Yılmaz, Hasan; Yılmaz, Hasan
The last decade has seen the development of a wide set of tools, such as wavefront shaping, computational or fundamental methods, that allow us to understand and control light propagation in a complex medium, such as biological tissues or multimode fibers. A vibrant and diverse community is now working in this field, which has revolutionized the prospect of diffraction-limited imaging at depth in tissues. This roadmap highlights several key aspects of this fast developing field, and some of the challenges and opportunities ahead. © 2022 The Author(s). Published by IOP Publishing Ltd.
Open Access
Compartmentalizing and sculpting nanovesicles by phase-separated aqueous nanodroplets
(Royal Society of Chemistry, 2022-11-08) Sabet, Fatemeh Kazemi; Bahrami, Arash; Bahrami, Amir Houshang; Bahrami, Amir Houshang
Phase-separated liquid droplets inside giant vesicles have been intensely studied as biomimetic model systems to understand cellular microcompartmentation and molecular crowding and sorting. On the nanoscale, however, how aqueous nanodroplets interact with and shape nanovesicles is poorly understood. We perform coarse-grained molecular simulations to explore the architecture of compartmentalized nanovesicles by phase-separated aqueous nanodroplets, and their morphological evolution under osmotic deflation. We show that phase separation of a biphasic liquid mixture can form both stable two-compartment and meta-stable multi-compartment nanovesicles. We identify morphological transitions of stable two-compartment nanovesicles between tube, sheet and cup morphologies, characterized by membrane asymmetry and phase-separation propensity between the aqueous phases. We demonstrate that the formation of local sheets and in turn cup-shaped nanovesicles is promoted by negative line tensions resulting from large separation propensities, an exclusive nanoscale phenomenon which is not expected for larger vesicles where energetic contributions of the line tensions are dominated by those of the membrane tensions. Despite their instability, we observe long-lived multi-compartment nanovesicles, such as nanotubules and branched tubules, whose prolonged lifetime is attributed to interfacial tensions and membrane asymmetry. Aqueous nanodroplets can thus form novel membrane nanostructures, crucial for cellular processes and forming cellular organelles on the nanoscale. © 2022 The Royal Society of Chemistry.
Open Access
Design and robustness improvement of high-performance LNA using 0.15 μm GaN technology for X-band applications
(John Wiley & Sons Ltd., 2022-07) Zafar, Salahuddin; Çankaya Akoğlu, Büşra; Aras, Erdem; Yılmaz, Doğan; Nawaz, Muhammad İmran; Kashif, Ahsanullah; Özbay, Ekmel; Zafar, Salahuddin; Çankaya Akoğlu, Büşra; Aras, Erdem; Yılmaz, Doğan; Nawaz, Muhammad İmran; Kashif, Ahsanullah; Özbay, Ekmel
In this paper, we present a highly robust GaN-based X-band low-noise amplifier (LNA) showing promising small-signal and noise performance as well as good linearity. The LNA is fabricated using in-house 0.15 μm AlGaN/GaN on a SiC HEMT process. Owing to the optimum choice of HEMT topologies and simultaneous matching technique, LNA achieves a noise figure better than 2 dB, output power at 1 dB gain compression higher than 19 dB, input and output reflection coefficients better than −9 and −11 dB, respectively. The small-signal gain of LNA is more than 19 dB for the whole band, and NF has a minimum of 1.74 dB at 10.2 GHz. LNA obtains an OIP3 up to 34.2 dBm and survives input power as high as 42 dBm. Survivability is investigated in terms of gain compression and forward gate current. Reverse recovery time (RRT), a crucial parameter for radar front-ends, is explored with respect to the RC time constant and trap phenomenon. The analysis shows that the significant contribution in RRT is due to traps while the RC time constant is in the nanoseconds range. Moreover, this study also addresses the requirement and choice of a DC gate feed resistor for the subsequent stages in a multi-stage design. The size of the designed LNA chip is 3 mm (Formula presented.) 1.2 mm only.
Open Access
Polarization insensitive phase change material-based nanoantenna array for thermally tunable infrared applications
(Institute of Electrical and Electronics Engineers, 2022-09-21) Khalichi, Bahram; Omam, Zahra Rahimian; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, Ekmel; Khalichi, Bahram; Omam, Zahra Rahimian; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, Ekmel
Thermal radiation management is an emerging application of metamaterials owing to their exotic electromagnetic radiative properties. Herein, a thermally tunable phase change material-based nanoantenna array is reported to manipulate electromagnetic waves for potential applications in radiative cooling and multispectral camouflage from thermal infrared detectors. The simulation results show that the proposed nanoantenna array possesses high reflectance exceeding at least 60% within the 3−5 µm and 8−12 µm wavelength ranges, indicating low thermal emissivity, while the reflectance value increases as the temperature rises. Additionally, the wavelength-selective nanoantenna emitter operates with high absorption and therefore emission within the non-atmospheric window (5−8 µm). The thermally tuning feature leads to further controlling the absorption and, therefore, the emission performance of the nanoantenna and corresponding infrared signatures detected by thermal cameras.
Open Access
A Transmissive all-dielectric metasurface-based nanoantenna array for selectively manipulation of thermal radiation
(Institute of Electrical and Electronics Engineers, 2022-09-21) Khalichi, Bahram; Omam, Zahra Rahimian; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, Ekmel; Khalichi, Bahram; Omam, Zahra Rahimian; Osgouei, Ataollah Kalantari; Ghobadi, Amir; Özbay, Ekmel
In this study, a wavelength-selective thermal nanoantenna emitter based on metamaterial design with heat radiation signature management and radiative cooling property is proposed. The design can be considered as a multifunctional window by reducing the heat signature and releasing the heat energy within the non-atmospheric window. The approach relies on the indium tin oxide cubic-shaped unit cell coated on a flexible and transparent substrate (polystyrene). The spectral behaviors of the proposed structure are obtained using the finite difference time domain method, where the power calculation model is utilized to demonstrate the radiative cooling efficiency and low power detection on infrared cameras.
Open Access
Transmissive terahertz metasurfaces with vanadium dioxide split-rings and grids for switchable asymmetric polarization manipulation
(Nature Research, 2022-12) Serebryannikov, Andriy E.; Lakhtakia, Akhlesh; Vandenbosch, Guy A. E.; Özbay, Ekmel; Özbay, Ekmel
Metasurfaces containing arrays of thermally tunable metal-free (double-)split-ring meta-atoms and metal-free grids made of vanadium dioxide (VO2), a phase-change material can deliver switching between (1) polarization manipulation in transmission mode as well as related asymmetric transmission and (2) other functionalities in the terahertz regime, especially when operation in the transmission mode is needed to be conserved for both phases of VO2. As the meta-atom arrays function as arrays of metallic subwavelength resonators for the metallic phase of VO2, but as transmissive phase screens for the insulator phase of VO2, numerical simulations of double- and triple-array metasurfaces strongly indicate extreme scenarios of functionality switching also when the resulting structure comprises only VO2 meta-atoms and VO2 grids. More switching scenarios are achievable when only one meta-atom array or one grid is made of VO2 components. They are enabled by the efficient coupling of the geometrically identical resonator arrays/grids that are made of the materials that strongly differ in terms of conductivity, i.e. Cu and VO2 in the metallic phase. © 2022, The Author(s).
Open Access
Enhanced photoresponse of PVP:GaSe nanocomposite thin film based photodetectors
(Institute of Physics Publishing Ltd., 2022-02-21) Demirtaş, T.; Odacı, C.; Aydemir, Umut; Aydemir, Umut
Two-dimensional materials have become the focus of attention of researchers in recent years. The demand for two-dimensional materials is increasing day by day, especially with the inadequacy of graphene in optical applications. In this context, the optical and electrical characteristics of the PVP:GaSe thin film nanocomposites were investigated. The surface morphologies of the samples were characterized by SEM, the thin film thicknesses and refractive index parameters were measured by the Ellipsometer method, the structural characteristics were obtained by XRD, and Raman and PL spectroscopy was used to determine the optical characteristics. Critical parameters of Au/PVP:GaSe/n-Si photodetector were calculated under various illumination intensities. It is observed that photodetector with PVP:%5GaSe thin film has the best performance results. According to the experimental results, its responsivity, external quantum efficiency, and detectivity values are 0.485 A W−1, %86, and 1.14 × 107 cm Hz1/2 W−1 respectively.