Browsing by Subject "Enhancement"

Now showing 1 - 11 of 11

Open Access
Biomaterial-integrated metasurfaces for biomarker detection
(2022-08) Derin, Esma
Today, healthcare system is in the midst of a crucial transition from centralized care to self-monitoring approaches, aiming to reach more individuals; to reduce the workload in hospitals; and to minimize healthcare costs. In this regard, biosensor platforms play a mainstay role in disease diagnostics as an alternative or complementary to current interventions. However, integrating existing biosensing systems into the point-of-care (POC) settings is mostly hampered by the need for bulky instrumentation, lengthy assay procedures, and high-cost platforms. In this thesis, we aim to develop a new biosensing strategy that integrates biomaterials with metasurfaces for this manner. To achieve this aim, optical disks were recycled to obtain their inherent nanograting surfaces as the plastic substrates. Accordingly, two different types of metasurfaces were fabricated (i) by coating the plastic substrates with titanium (Ti), silver (Ag) and gold (Au), and (ii) the latter one was coated with Ag only. Poly-L-Lysine (PLL) was then integrated onto these surfaces to construct a biopolymeric adlayer. To enhance sensing characteristics, biomaterial (PLL)-integrated metasurfaces were decorated with gold nanoparticles (AuNPs), and also, nanoislands (NI) were formed on these surfaces through a chemical reduction reaction of chloroauric acid and hydroxylamine hydrochloride. To benchmark analytical performance of sensors, bulk sensitivity analysis was performed with 1%-70% glycerol solutions. In addition, exosomes were employed as model biomarkers in this study since they are released from kidneys to renal space dynamically, and they carry critical information on disease conditions, holding pivotal impact to be employed for early diagnosis of kidney diseases. With the aforementioned sensing scheme, minute concentrations of exosomes were detected over a wide-sensing area decorated with either anti-CD81 antibodies or anti-CD63 antibodies. In sum, we anticipate that this platform would resolve overwhelming challenges in cost- and complex fabrication-related challenges, and consequently, it would offer an affordable and facile-to-use diagnostic platform for this realm.
Open Access
Enhancement of polycrystalline silicon solar cells efficiency using indium nitride particles
(Institute of Physics Publishing Ltd., 2015) Alkis, S.; Chowdhury, F. I.; Alevli, M.; Dietz, N.; Yalızay, B.; Aktürk, S.; Nayfeh, A.; Okyay, Ali Kemal
In this work, we present a hybrid indium nitride particle/polycrystalline silicon solar cell based on 230 nm size indium nitride particles (InN-Ps) obtained through laser ablation. The solar cell performance measurements indicate that there is an absolute 1.5% increase (Δη) in the overall solar cell efficiency due to the presence of InN-Ps. Within the spectral range 300-1100 nm, improvements of up to 8.26% are observed in the external quantum efficiency (EQE) and increases of up to 8.75% are observed in the internal quantum efficiency (IQE) values of the corresponding solar cell. The enhancement in power performance is due to the down-shifting properties of the InN-Ps. The electrical measurements are supplemented by TEM, Raman, UV/VIS and PL spectroscopy of the InN-Ps. © 2015 IOP Publishing Ltd.
Open Access
Fabrication and characterization of high speed resonant cavity enhanced Schottky photodiodes
(1996) Islam, M. Saiful
High speed, high external quantum efficiency and narrow spectral linewidth make resonant cavity enhanced (RC E) Schottky photodetector a good candidate for telecommunication applications. In this thesis, we present our work for the design, fabrication and characterization of a RCE Schottky photodiode with high quantum efficiency and high speed. We present experimental results on a RCE photodiode having an operating wavelength of 900 nm. The absorption takes place in a thin InGaAs layer placed inside the GaAs cavity. The active region was grown above a highreflectivity GaAs/AIAs quarter-wavelength Bragg reflector. The top mirror consisted of a 200A thin Au layer which also acted as Schottky metal of the device. An external quantum efficiency of 55% was obtained from our devices. We demonstrate that the spectral response can be tailored by etching the top surface of the microcavity. Our high speed measurements yielded a FW HM of 30 ps, which is the record response for any RCE Schottky photodiode ever reported.
Open Access
Generalized theory of förster-type nonradiative energy transfer in nanostructures with mixed dimensionality
(American Chemical Society, 2013-04-16) Hernandez-Martinez, P. L.; Govorov, A. O.; Demir, Hilmi Volkan
Forster-type nonradiative energy transfer (NRET) is widely used, especially utilizing nanostructures in different combinations and configurations. However, the existing well-accepted Forster theory is only for the case of a single particle serving as a donor together with another particle serving as an acceptor. There are also other special cases previously studied; however, there is no complete picture and unified understanding. Therefore, there is a strong need for a complete theory that models Forster-type NRET for the cases of mixed dimensionality including all combinations and configurations. We report a generalized theory for the Forster-type, NRET, which includes the derivation of the effective dielectric function due to the donor in different confinement geometries and the derivation of transfer rates distance dependencies due to the acceptor in different confinement geometries, resulting in a complete picture and understanding of the mixed dimensionality.
Open Access
Highly directional enhanced radiation from sources embedded inside two and three-dimensional photonic crystals
(SPIE, 2005) Çağlayan, Hümeyra; Bulu, İrfan; Özbay, Ekmel
In this work, we have experimentally and theoretically studied the emission of radiation from a monopole source embedded in a two and three dimensional photonic crystal. We have demonstrated the enhancement of radiation at the band edges and at the cavity modes including coupled cavity modes. We have shown that the emission of radiation from a source depends on the group velocities of the modes and on the electric field intensities of the modes at the source location. Moreover, we have studied the angular distribution of power emitted from a radiation source embedded inside a photonic crystal. Our results show that it is possible to obtain highly directive radiation sources operating at the band edge of the photonic crystal.
Open Access
Hyperbolic metamaterials based on quantum-dot plasmon resonator nanocomposites
(Optical Society of America, 2014) Zhokovsky, S. V.; Ozel, T.; Mutlugun, E.; Gaponik, N.; Eychmuller, A.; Lavrinenko, A. V.; Demir, Hilmi Volkan; Gaponenko, S. V.
We theoretically demonstrate that nanocomposites made of colloidal semiconductor quantum dot monolayers placed between metal nanoparticle monolayers can function as multilayer hyperbolic metamaterials. Depending on the thickness of the spacer between the quantum dot and nanoparticle layers, the effective permittivity tensor of the nanocomposite is shown to become indefinite, resulting in increased photonic density of states and strong enhancement of quantum dot luminescence. This explains the results of recent experiments [T. Ozel et al., ACS Nano 5, 1328 (2011)] and confirms that hyperbolic metamaterials are capable of increasing the radiative decay rate of emission centers inside them. The proposed theoretical framework can also be used to design quantum-dot/nanoplasmonic composites with optimized luminescence enhancement. (C) 2014 Optical Society of America
Open Access
Luminescence of Gold Nanorod-Quantum Dots Complexes
(World Scientific Publishing Company, 2019) Trotsiuk, L. L.; Muravitskaya, A. O.; Kulakovich, O. S.; Gaponenko, S. V.; Demir, Hilmi Volkan
The photoluminescence of gold nanorod-quantum dots complexes was investigated in order to find optimal conditions for the luminescence enhancing. The number of quantum dots and polyelectrolyte layers on the gold nanorod surface in these complexes were considered as main factors in the enhancement.
Open Access
Nanoantenna coupled UV subwavelength photodtectors based on GaN
(Optical Society of America, 2012) Butun, S.; Cinel, N. A.; Özbay, Ekmel
The integration of nano structures with opto-electronic devices has many potential applications. It allows the coupling of more light into or out of the device while decreasing the size of the device itself. Such devices are reported in the VIS and NIR regions. However, making plasmonic structures for the UV region is still a challenge. Here, we report on a UV nano-antenna integrated metal semiconductor metal (MSM) photodetector based on GaN. We designed and fabricated Al grating structures. Well defined plasmonic resonances were measured in the reflectance spectra. Optimized grating structure integrated photodetectors exhibited more than sevenfold photocurrent enhancement. Finite difference time domain simulations revealed that both geometrical and plasmonic effects played role in photocurrent enhancement. (C) 2012 Optical Society of America
Open Access
Plasmonic backcontact grating for P3HT:PCBM organic solar cells enabling strong optical absorption increased in all polarizations
(Optical Society of America, 2011) Sefunc, M. A.; Okyay, Ali Kemal; Demir, Hilmi Volkan
In P3HT:PCBM based organic solar cells we propose and demonstrate numerically plasmonic backcontact grating architectures for strong optical absorption enhanced in both transverse-magnetic and transverse-electric polarizations. Even when the active material is partially replaced by the metallic grating (without increasing the active layer film thickness), we show computationally that the light absorption in thin-film P3HT:PCBM is increased by a maximum factor of similar to 21% considering both polarizations under AM1.5G solar radiation and over a half-maximum incidence angle of 45 degrees (where the enhancement drops to its half) compared to the same cell without a grating. This backcontact grating outperforms the typical plasmonic grating placed in PEDOT:PSS layer. (C)2011 Optical Society of America.
Open Access
Plasmonic light-sensitive skins of nanocrystal monolayers
(IOP Publishing, 2013) Akhavan, S.; Gungor, K.; Mutlugun, E.; Demir, Hilmi Volkan
We report plasmonically coupled light-sensitive skins of nanocrystal monolayers that exhibit sensitivity enhancement and spectral range extension with plasmonic nanostructures embedded in their photosensitive nanocrystal platforms. The deposited plasmonic silver nanoparticles of the device increase the optical absorption of a CdTe nanocrystal monolayer incorporated in the device. Controlled separation of these metallic nanoparticles in the vicinity of semiconductor nanocrystals enables optimization of the photovoltage buildup in the proposed nanostructure platform. The enhancement factor was found to depend on the excitation wavelength. We observed broadband sensitivity improvement (across 400-650 nm), with a 2.6-fold enhancement factor around the localized plasmon resonance peak. The simulation results were found to agree well with the experimental data. Such plasmonically enhanced nanocrystal skins hold great promise for large-area UV/visible sensing applications.
Open Access
Three-dimensional study of planar optical antennas made of split-ring architecture outperforming dipole antennas for increased field localization
(Optical Society of America, 2012-01-09) Kilic, V. T.; Erturk, V. B.; Demir, Hilmi Volkan
Optical antennas are of fundamental importance for the strongly localizing field beyond the diffraction limit. We report that planar optical antennas made of split-ring architecture are numerically found in three-dimensional simulations to outperform dipole antennas for the enhancement of localized field intensity inside their gap regions. The computational results (finite-difference time-domain) indicate that the resulting field localization, which is of the order of many thousandfold, in the case of the split-ring resonators is at least 2 times stronger than the one in the dipole antennas resonant at the same operating wavelength, while the two antenna types feature the same gap size and tip sharpness.