Browsing by Author "Demir, Hilmi Volkan"

Now showing 1 - 20 of 21

Citation - WoS: 12
Citation - Scopus: 12
All-Surface Induction Heating With High Efficiency and Space Invariance Enabled by Arraying Squircle Coils in Square Lattice
(IEEE-Inst Electrical Electronics Engineers Inc, 2018) Kilic, Veli Tayfun; Unal, Emre; Yilmaz, Namik; Demir, Hilmi Volkan
This paper reports an all-surface induction heating system that enables efficient heating at a constant speed all over the surface independent of the specific location on the surface. In the proposed induction system, squircle coils are placed tangentially in a two-dimensional square lattice as opposed to commonly used hexagonal packing. As a proof-of-concept demonstration, a simple model setup was constructed using a 3 x 3 coil array along with a steel plate to be inductively heated. To model surface heating, a set of six locations for the plate was designated considering symmetry points. For all of these cases, power dissipated by the system and the plate's transient heating were recorded. Independent from the specific plate position, almost equal heating speeds were measured for the similar levels of dissipated energies in the system. Using full three-dimensional electromagnetic solutions, the experimental results were also verified. The findings indicate that the proposed system is proved to enable energy efficient space-invariant heating in all-surface induction hobs.
Citation - WoS: 48
Citation - Scopus: 49
Colloidal Quantum Dot Light-Emitting Diodes Employing Phosphorescent Small Organic Molecules as Efficient Exciton Harvesters
(Amer Chemical Soc, 2014) Mutlugun, Evren; Guzelturk, Burak; Abiyasa, Agus Putu; Gao, Yuan; Sun, Xiao Wei; Demir, Hilmi Volkan
Nonradiative energy transfer (NRET) is an alternative excitation mechanism in colloidal quantum dot (QD) based electroluminescent devices (QLEDs). Here, we develop hybrid highly spectrally pure QLEDs that facilitate energy transfer pumping via NRET from a phosphorescent small organic molecule-codoped charge transport layer to the adjacent QDs. A partially codoped exciton funnelling electron transport layer is proposed and optimized for enhanced QLED performance while exhibiting very high color purity of 99%. These energy transfer pumped hybrid QLEDs demonstrate a 6-fold enhancement factor in the external quantum efficiency over the conventional QLED structure, in which energy transfer pumping is intrinsically weak.
Citation - WoS: 2
Citation - Scopus: 2
Color Enrichment Solids of Spectrally Pure Colloidal Quantum Wells for Wide Color Span in Displays
(Wiley-VCH Verlag GmbH, 2022) Erdem, Talha; Soran-Erdem, Zeliha; Isik, Furkan; Shabani, Farzan; Yazici, Ahmet Faruk; Mutlugun, Evren; Demir, Hilmi Volkan
Colloidal quantum wells (CQWs) are excellent candidates for lighting and display applications owing to their narrow emission linewidths (<30 nm). However, realizing their efficient and stable light-emitting solids remains a challenge. To address this problem, stable, efficient solids of CQWs incorporated into crystal matrices are shown. Green-emitting CdSe/CdS core/crown and red-emitting CdSe/CdS core/shell CQWs wrapped into these crystal solids are employed as proof-of-concept demonstrations of light-emitting diode (LED) integration targeting a wide color span in display backlighting. The quantum yield of the green- and red-emitting CQW-containing solids of sucrose reach approximate to 20% and approximate to 55%, respectively, while emission linewidths and peak wavelengths remain almost unaltered. Furthermore, sucrose matrix preserves approximate to 70% and approximate to 45% of the initial emission intensity of the green- and red-emitting CQWs after >60 h, respectively, which is approximate to 4x and approximate to 2x better than the drop-casted CQW films and reference (KCl) host. Color-converting LEDs of these green- and red-emitting CQWs in sucrose possess luminous efficiencies 122 and 189 lm W-elect(-1), respectively. With the liquid crystal display filters, this becomes 39 and 86 lm W-elect(-1), respectively, providing with a color gamut 25% broader than the National Television Standards Committee standard. These results prove that CQW solids enable efficient and stable color converters for display and lighting applications.
Citation - WoS: 34
Citation - Scopus: 33
Deep-Red Colloidal Quantum Well Light-Emitting Diodes Enabled Through a Complex Design of Core/Crown Shell Heterostructure
(Wiley-VCH Verlag GmbH, 2022) Shabani, Farzan; Dehghanpour Baruj, Hamed; Yurdakul, Iklim; Delikanli, Savas; Gheshlaghi, Negar; Isik, Furkan; Demir, Hilmi Volkan
Extending the emission peak wavelength of quasi-2D colloidal quantum wells has been an important quest to fully exploit the potential of these materials, which has not been possible due to the complications arising from the partial dissolution and recrystallization during growth to date. Here, the synthetic pathway of (CdSe/CdS)@(1-4 CdS/CdZnS) (core/crown)@(colloidal atomic layer deposition shell/hot injection shell) hetero-nanoplatelets (NPLs) using multiple techniques, which together enable highly efficient emission beyond 700 nm in the deep-red region, is proposed and demonstrated. Given the challenges of using conventional hot injection procedure, a method that allows to obtain sufficiently thick and passivated NPLs as the seeds is developed. Consequently, through the final hot injection shell coating, thick NPLs with superior optical properties including a high photoluminescence quantum yield of 88% are achieved. These NPLs emitting at 701 nm exhibit a full-width-at-half-maximum of 26 nm, enabled by the successfully maintained quasi-2D shape and minimum defects of the resulting heterostructure. The deep-red light-emitting diode (LED) device fabricated with these NPLs has shown to yield a high external quantum efficiency of 6.8% at 701 nm, which is on par with other types of LEDs in this spectral range.
Citation - WoS: 59
Citation - Scopus: 63
Electroluminescence Efficiency Enhancement in Quantum Dot Light-Emitting Diodes by Embedding a Silver Nanoisland Layer
(Wiley-VCH Verlag GmbH, 2015) Yang, Xuyong; Hernandez-Martinez, Pedro Ludwig; Dang, Cuong; Mutlugun, Evren; Zhang, Kang; Demir, Hilmi Volkan; Sun, Xiao Wei
A colloidal quantum dot light-emitting diode (QLED) is reported with substantially enhanced electroluminescence by embedding a thin layer of Ag nanoislands into hole transport layer. The maximum external quantum efficiency (EQE) of 7.1% achieved in the present work is the highest efficiency value reported for green-emitting QLEDs with a similar structure, which corresponds to 46% enhancement compared with the reference device. The relevant mechanisms enabling the EQE enhancement are associated with the near-field enhancement via an effective coupling between excitons of the quantum dot emitters and localized surface plasmons around Ag nanoislands, which are found to lead to good agreement between the simulation results and the experimental data, providing us with a useful insight important for plasmonic QLEDs.
Citation - WoS: 99
Citation - Scopus: 103
Giant Alloyed Hot Injection Shells Enable Ultralow Optical Gain Threshold in Colloidal Quantum Wells
(Amer Chemical Soc, 2019) Altintas, Yemliha; Gungor, Kivanc; Gao, Yuan; Sak, Mustafa; Quliyeva, Ulviyya; Bappi, Golam; Demir, Hilmi Volkan
As an attractive materials system for high- Record-low optical gain threshold in giant-shell COWs performance optoelectronics, colloidal nanoplatelets (NPLs) benefit from atomic-level precision in thickness, minimizing emission inhomogeneous broadening. Much progress has been made to enhance their photoluminescence quantum yield (PLQY) and photostability. However, to date, layer-by-layer growth of shells at room temperature has resulted in defects that limit PLQY and thus curtail the 0.2 performance of NPLs as an optical gain medium. Here, we introduce a hot-injection method growing giant alloyed shells using an approach that reduces core/shell lattice mismatch and suppresses Auger recombination. Near-unity PLQY is achieved with a narrow full-width-at-half-maximum (20 nm), accompanied by emission tunability (from 610 to 650 nm). The biexciton lifetime exceeds 1 ns, an order of magnitude longer than in conventional colloidal quantum dots (CQDs). Reduced Auger recombination enables record-low amplified spontaneous emission threshold of 2.4 mu J cm(-2) under one-photon pumping. This is lower by a factor of 2.5 than the best previously reported value in nanocrystals (6 /kJ cm(-2) for CdSe/CdS NPLs). Here, we also report single-mode lasing operation with a 0.55 mu J cm(-2) threshold under two-photoexcitation, which is also the best among nanocrystals (compared to 0.76 mu J cm(-2) from CdSe/CdS CQDs in the Fabry-Perot cavity). These findings indicate that hot-injection growth of thick alloyed shells makes ultrahigh performance NPLs.
Citation - WoS: 17
Citation - Scopus: 19
High-Efficiency Flow-Through Induction Heating
(Wiley, 2020) Kilic, Veli Tayfun; Unal, Emre; Demir, Hilmi Volkan
This study reports a newly designed induction heating system for efficient, fast, and safe flow-through heating. The system has a very simple architecture, which is composed of a transmitting coil, an isolating plastic pipe, and an embedded metal shell. Wireless energy transfer from the external coil to the internal metal shell through the pipe is essential for decreasing losses. Also, a large contact surface between a fluid and the immersed shell enables rapid heat transfer. The proposed heating system was systematically investigated for different shell geometries and the results were compared with a commercially available conductive flow-through heating device. As a proof-of-concept demonstration, a prototype of the designed induction heating system was manufactured and the heating measurements were conducted with water. Power transfer efficiency of the prototyped induction heating system was measured to be 97%. The comparative study indicates that such high-efficiency induction flow-through heating system offers a great potential for replacing the conventional conductive heating device used in household applications in which the rapid and compact heating is desired.
Citation - WoS: 88
Citation - Scopus: 85
Highly 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) Altintas, Yemliha; Quliyeva, Ulviyya; Gungor, Kivanc; Erdem, Onur; Kelestemur, Yusuf; Mutlugun, Evren; Demir, Hilmi Volkan
Colloidal 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.
Citation - WoS: 24
Citation - Scopus: 26
Management of Electroluminescence From Silver-Doped Colloidal Quantum Well Light-Emitting Diodes
(Cell Press, 2022) Liu, Baiquan; Sharma, Manoj; Yu, Junhong; Wang, Lin; Shendre, Sushant; Sharma, Ashma; Demir, Hilmi Volkan
Impurity doping is a promising strategy to afford colloidal nanocrystals exhibiting novel optical, catalytic, and electronic characteristics. However, some significant properties of noble metal-doped nanocrystals (NMD-NCs) remain unknown. Here, we report the electroluminescence (EL) from NMD-NCs. By doping silver impurity into cad. mium selenide colloidal quantum wells (CQWs), dual-emission emitters are achieved and a light-emitting diode (LED) with a luminance of 1,339 cd m(-2) is reported. In addition, the proposed energy gap engineering to manage exciton recombination is a feasible scheme for tunable EL emissions (e.g., the dopant emission is tuned from 606 to 761 nm). Furthermore, an organic-inorganic hybrid white LED based on CQWs is realized, reaching a color rendering index of 82. Moreover, flexible CQW-LEDs are reported. The findings present a step to unveil the EL property of NMD-NCs, which can be extended to other noble metal impurities, and pave the pathway for NMD-NCs as a class of electronic materials for EL applications.
Citation - WoS: 13
Citation - Scopus: 14
Near-Field Energy Transfer Into Silicon Inversely Proportional to Distance Using Quasi-2D Colloidal Quantum Well Donors
(Wiley-VCH Verlag GmbH, 2021) Humayun, Muhammad Hamza; Hernandez-Martinez, Pedro Ludwig; Gheshlaghi, Negar; Erdem, Onur; Altintas, Yemliha; Shabani, Farzan; Demir, Hilmi Volkan
Silicon 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.
Citation - WoS: 11
Citation - Scopus: 12
Optical Gain in Ultrathin Self-Assembled Bi-Layers of Colloidal Quantum Wells Enabled by the Mode Confinement in Their High-Index Dielectric Waveguides
(Wiley-VCH Verlag GmbH, 2020) Foroutan-Barenji, Sina; Erdem, Onur; Gheshlaghi, Negar; Altintas, Yemliha; Demir, Hilmi Volkan
This study demonstrates an ultra-thin colloidal gain medium consisting of bi-layers of colloidal quantum wells (CQWs) with a total film thickness of 14 nm integrated with high-index dielectrics. To achieve optical gain from such an ultra-thin nanocrystal film, hybrid waveguide structures partly composed of self-assembled layers of CQWs and partly high-index dielectric material are developed and shown: in asymmetric waveguide architecture employing one thin film of dielectric underneath CQWs and in the case of quasi-symmetric waveguide with a pair of dielectric films sandwiching CQWs. Numerical modeling indicates that the modal confinement factor of ultra-thin CQW films is enhanced in the presence of the adjacent dielectric layers significantly. The active slabs of these CQW monolayers in the proposed waveguide structure are constructed with great care to obtain near-unity surface coverage, which increases the density of active particles, and to reduce the surface roughness to sub-nm scale, which decreases the scattering losses. The excitation and propagation of amplified spontaneous emission (ASE) along these active waveguides are experimentally demonstrated and numerically analyzed. The findings of this work offer possibilities for the realization of ultra-thin electrically driven colloidal laser devices, providing critical advantages including single-mode lasing and high electrical conduction.
Citation - WoS: 127
Citation - Scopus: 134
Record High External Quantum Efficiency of 19.2% Achieved in Light-Emitting Diodes of Colloidal Quantum Wells Enabled by Hot-Injection Shell Growth
(Wiley-VCH Verlag GmbH, 2020) Liu, Baiquan; Altintas, Yemliha; Wang, Lin; Shendre, Sushant; Sharma, Manoj; Sun, Handong; Demir, Hilmi Volkan
Colloidal quantum wells (CQWs) are regarded as a highly promising class of optoelectronic materials, thanks to their unique excitonic characteristics of high extinction coefficients and ultranarrow emission bandwidths. Although the exploration of CQWs in light-emitting diodes (LEDs) is impressive, the performance of CQW-LEDs lags far behind other types of soft-material LEDs (e.g., organic LEDs, colloidal-quantum-dot LEDs, and perovskite LEDs). Herein, high-efficiency CQW-LEDs reaching close to the theoretical limit are reported. A key factor for this high performance is the exploitation of hot-injection shell (HIS) growth of CQWs, which enables a near-unity photoluminescence quantum yield (PLQY), reduces nonradiative channels, ensures smooth films, and enhances the stability. Remarkably, the PLQY remains 95% in solution and 87% in film despite rigorous cleaning. Through systematically understanding their shape-, composition-, and device-engineering, the CQW-LEDs using CdSe/Cd0.25Zn0.75S core/HIS CQWs exhibit a maximum external quantum efficiency of 19.2%. Additionally, a high luminance of 23 490 cd m(-2), extremely saturated red color with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.715, 0.283), and stable emission are obtained. The findings indicate that HIS-grown CQWs enable high-performance solution-processed LEDs, which may pave the path for future CQW-based display and lighting technologies.
Citation - WoS: 25
Citation - Scopus: 25
Self-Resonant Microlasers of Colloidal Quantum Wells Constructed by Direct Deep Patterning
(Amer Chemical Soc, 2021) Gheshlaghi, Negar; Foroutan-Barenji, Sina; Erdem, Onur; Altintas, Yemliha; Shabani, Farzan; Humayun, Muhammad Hamza; Demir, Hilmi Volkan
Here, 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.
Citation - WoS: 11
Citation - Scopus: 9
Single-Mode Lasing From a Single 7 nm Thick Monolayer of Colloidal Quantum Wells in a Monolithic Microcavity
(Wiley-VCH Verlag GmbH, 2021) Foroutan-Barenji, Sina; Erdem, Onur; Delikanli, Savas; Yagci, Huseyin Bilge; Gheshlaghi, Negar; Altintas, Yemliha; Demir, Hilmi Volkan
In this work, the first account of monolithically-fabricated vertical cavity surface emitting lasers (VCSELs) of densely-packed, orientation-controlled, atomically flat colloidal quantum wells (CQWs) using a self-assembly method and demonstrate single-mode lasing from a record thin colloidal gain medium with a film thickness of 7 nm under femtosecond optical excitation is reported. Specially engineered CQWs are used to demonstrate these hybrid CQW-VCSELs consisting of only a few layers to a single monolayer of CQWs and are achieved the lasing from these thin gain media by thoroughly modeling and implementing a vertical cavity consisting of distributed Bragg reflectors with an additional dielectric layer for mode tuning. Accurate spectral and spatial alignment of the cavity mode with the CQW films is secured with the help of full electromagnetic computations. While overcoming the long-pending problem of limited electrical conductivity in thicker colloidal films, such ultrathin colloidal gain media can be helpful to enable fully electrically-driven colloidal lasers.
Citation - WoS: 37
Citation - Scopus: 39
Spectrally Wide-Range Efficient, and Bright Colloidal Light-Emitting Diodes of Quasi-2D Nanoplatelets Enabled by Engineered Alloyed Heterostructures
(Amer Chemical Soc, 2020) Altintas, Yemliha; Liu, Baiquan; Hernandez-Martinez, Pedro Ludwig; Gheshlaghi, Negar; Shabani, Farzan; Sharma, Manoj; Demir, Hilmi Volkan
Recently, there has been tremendous interest in the synthesis and optoelectronic applications of quasi-two-dimensional colloidal nanoplatelets (NPLs). Thanks to the ultranarrow emission linewidth, high-extinction coefficient, and high photostability, NPLs offer an exciting opportunity for high-performance optoelectronics. However, until now, the applications of these NPLs are limited to available discrete emission ranges, limiting the full potential of these exotic materials as efficient light emitters. Here, we introduce a detailed systematic study on the synthesis of NPLs based on the alloying mechanisms in core/shell, core/alloyed shell, alloyed core/shell, and alloyed core/alloyed shell heterostructures. Through the engineering of the band gap supported by the theoretical calculations, we carefully designed and successfully synthesized the NPL emitters with continuously tunable emission. Unlike conventional NPLs showing discrete emission, here, we present highly efficient core/shell NPLs with fine spectral tunability from green to deep-red spectra. As an important demonstration of these efficient emitters, the first-time implementation of yellow NPL light-emitting diodes (LEDs) has been reported with record device performance, including the current efficiency surpassing 18.2 cd A(-1), power efficiency reaching 14.8 lm W-1, and record luminance exceeding 46 900 cd m(-2). This fine and wide-range color tunability in the visible range from stable and efficient core/shell NPLs is expected to be extremely important for the optoelectronic applications of the family of colloidal NPL emitters.
Citation - WoS: 5
Citation - Scopus: 6
Tailored Synthesis of Iron Oxide Nanocrystals for Formation of Cuboid Mesocrystals
(Amer Chemical Soc, 2021) Soran-Erdem, Zeliha; Sharma, Vijay Kumar; Hernandez-Martinez, Pedro Ludwig; Demir, Hilmi Volkan
In this work, we systematically studied the shape- and size-controlled monodisperse synthesis of iron oxide nanocrystals (IONCs) for their use as building blocks in the formation of mesocrystals. For this aim, on understanding the influence of the oleic acid concentration, iron-oleate concentration, and heating rate on the synthesis of robust and reproducible IONCs with desired sizes and shapes, we synthesized highly monodisperse similar to 11 nm sized nanocubes and nanospheres. Magnetic measurements of both cubic and spherical IONCs revealed the presence of mixed paramagnetic and superparamagnetic phases in these nanocrystals. Moreover, we observed that the magnetic moments of the nanocubes are more substantial compared to their spherical counterparts. We then demonstrated a simple magnetic-field-assisted assembly of nanocubes into three-dimensional (3D) cuboid mesocrystals while nanospheres did not form any mesocrystals. These findings indicate that small cubic nanocrystals hold great promise as potential building blocks of 3D magnetic hierarchical structures with their superior magnetic properties and mesocrystal assembly capability, which may have high relevance in various fields ranging from high-density data storage to biomedical applications.
Citation - WoS: 53
Citation - Scopus: 59
Thickness-Tunable Self-Assembled Colloidal Nanoplatelet Films Enable Ultrathin Optical Gain Media
(Amer Chemical Soc, 2020) Erdem, Onur; Foroutan, Sina; Gheshlaghi, Negar; Guzelturk, Burak; Altintas, Yemliha; Demir, Hilmi Volkan
We propose and demonstrate construction of highly uniform, multilayered superstructures of CdSe/CdZnS core/shell colloidal nanoplatelets (NPLs) using liquid interface self-assembly. These NPLs are sequentially deposited onto a solid substrate into slabs having monolayer-precise thickness across tens of cm(2) areas. Because of near-unity surface coverage and excellent uniformity, amplified spontaneous emission (ASE) is observed from an uncharacteristically thin film having 6 NPL layers, corresponding to a mere 42 nm thickness. Furthermore, systematic studies on optical gain of these NPL superstructures having thicknesses ranging from 6 to 15 layers revealed the gradual reduction in gain threshold with increasing number of layers, along with a continuous spectral shift of the ASE peak (similar to 18 nm). These observations can be explained by the change in the optical mode confinement factor with the NPL waveguide thickness and propagation wavelength. This bottom-up construction technique for thickness-tunable, three-dimensional NPL superstructures can be used for large-area device fabrication.
Citation - WoS: 1
Citation - Scopus: 1
Ultra-Durable Information-Encoded Anti-Counterfeiting Self-Assembled Nanocrystal Labels
(Wiley-VCH Verlag GmbH, 2025) Haddadifam, Taha; Shabani, Farzan; Kalay, Mustafa; Khaligh, Aisan; Mutlugun, Evren; Onses, Mustafa Serdar; Demir, Hilmi Volkan
Forgery, a serious universal problem, is causing huge economic losses every year. Against forgery, information-encoded labelling systems have attracted significant attention for a diverse range of anti-counterfeiting applications. Here, cost-effective and ultra-durable nanocrystal-based labels are proposed and demonstrated in which information can be encoded as physically unclonable functions (PUFs) of hardware-oriented security systems. The fabrication method of the PUFs is based on the self-assembly of colloidal quantum wells (CQWs) and generation of unclonable features within their pattern at a liquid-liquid interface. These CQW PUFs are analyzed with well-known statistical tests, which show a uniqueness level of 0.5060 +/- 0.0323 and prove their randomness. In addition, a feature-matching algorithm is used to authenticate these information-encoded CQW PUFs. For the safety of the semiconductor chips, a CQW PUF is attached to the surface of the chip to protect against hardware cyber-attacks. Eventually, fabricated labels are examined against high temperatures and moisture environments. The fabricated CQW label is durable for a period of 150 days it is tested, demonstrating ultra-high stability of the label. High stability and durability, cost-effectiveness, and high encoding capacity make these proposed nanocrystal labels extremely attractive for large-scale commercialization.
Citation - WoS: 24
Citation - Scopus: 26
Wireless Measurement of Elastic and Plastic Deformation by a Metamaterial-Based Sensor
(MDPI, 2014) Ozbey, Burak; Demir, Hilmi Volkan; Kurc, Ozgur; Erturk, Vakur B.; Altintas, Ayhan
We report remote strain and displacement measurement during elastic and plastic deformation using a metamaterial-based wireless and passive sensor. The sensor is made of a comb-like nested split ring resonator (NSRR) probe operating in the near-field of an antenna, which functions as both the transmitter and the receiver. The NSRR probe is fixed on a standard steel reinforcing bar (rebar), and its frequency response is monitored telemetrically by a network analyzer connected to the antenna across the whole stress-strain curve. This wireless measurement includes both the elastic and plastic region deformation together for the first time, where wired technologies, like strain gauges, typically fail to capture. The experiments are further repeated in the presence of a concrete block between the antenna and the probe, and it is shown that the sensing system is capable of functioning through the concrete. The comparison of the wireless sensor measurement with those undertaken using strain gauges and extensometers reveals that the sensor is able to measure both the average strain and the relative displacement on the rebar as a result of the applied force in a considerably accurate way. The performance of the sensor is tested for different types of misalignments that can possibly occur due to the acting force. These results indicate that the metamaterial-based sensor holds great promise for its accurate, robust and wireless measurement of the elastic and plastic deformation of a rebar, providing beneficial information for remote structural health monitoring and post-earthquake damage assessment.
Citation - WoS: 18
Citation - Scopus: 21
Wireless Sensing in Complex Electromagnetic Media: Construction Materials and Structural Monitoring
(IEEE-Inst Electrical Electronics Engineers Inc, 2015) Ozbey, Burak; Demir, Hilmi Volkan; Kurc, Ozgur; Erturk, Vakur B.; Altintas, Ayhan
In this paper, wireless sensing in the presence of complex electromagnetic media created by combinations of reinforcing bars and concrete is investigated. The wireless displacement sensing system, primarily designed for use in structural health monitoring (SHM), is composed of a comb-like nested split-ring resonator (NSRR) probe and a transceiver antenna. Although each complex medium scenario is predicted to have a detrimental effect on sensing in principle, it is demonstrated that the proposed sensor geometry is able to operate fairly well in all scenarios except one. In these scenarios that mimic real-life SHM, it is shown that this sensor exhibits a high displacement resolution of 1 mu m, a good sensitivity of 7 MHz/mm in average, and a high dynamic range extending over 20 mm. For the most disruptive scenario of placing concrete immediately behind NSRR, a solution based on employing a separator behind the probe is proposed to overcome the handicaps introduced by the medium. In order to obtain a one-to-one mapping from the measured frequency shift to the displacement, a numerical fit is proposed and used. The effects of several complex medium scenarios on this fit are discussed. These results indicate that the proposed sensing scheme works well in real-life SHM applications.