Browsing by Subject "Nanofabrication"

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A coherent coupling between graphene plasmon and molecular vibration in strong coupling regime
(2024-08) Hossain, Md Faysal
Manipulating the energy states of atoms or molecules is of great interest due to its unlimited potential in spectroscopy, analytical chemistry, atomic structural analysis, imaging, chemical and biological sensing, and many other fields of micro-nanotechnology. Various ways of atomic or molecular energy modulation have been employed to date, such as electric or magnetic field excitation, molecular vibrational or rotational excitation, quantum tunneling, and laser excitation. When electromagnetic wave interacts with materials, it may fall into either a weak, i.e., Fano resonance and Purcell effect, or strong coupling regime depending on the coupling strength. The formation of hybridized polaritonic states in the strong coupling regime opens up a new way to modify materials' physical and chemical properties by altering energy levels of the material excitation. While the formation of polaritonic states has been demonstrated for excitonic transitions, the same phenomenon can also take place with molecular vibrations. In general, a Fabry-Pérot (FP) cavity having two parallel metal or dielectric mirrors is used to induce strong coupling as a cavity optical mode interacts with molecular vibrations of a material placed in the cavity. However, a planar optical cavity has a limited spatial resolution for monitoring polaritonic states. Moreover, strong coupling in the FP cavity represents an ensemble-average due to spatially-varied optical fields inside the FP cavity. To address some of the limitations of the FP cavity, I used a deep metal grating as a new optical resonator to demonstrate vibrational strong coupling (VSC). First, I simulated the optical properties of the deep metal grating and found that the hybridization between localized surface plasmon resonances and magnetic polaritons is responsible for generating strong mid-infrared optical resonances. When single-layer graphene was integrated into the grating, the grating resonances showed Fano line shapes as a result of a weak coupling between discrete graphene plasmon modes and continuum grating resonances. In addition, with the addition of a molecular absorber to the deep metal grating, VSC was achieved with tunability in polaritonic energy states by changing the system parameters including the grating height and widths, as well as the chemical potential applied to the graphene. In parallel with simulations, I generated a large area of double-layer graphene by chemical vapor deposition and fabricated deep metal grating structures by electron-beam lithography and inductively-coupled plasma etching.
Open Access
Antibacterial electrospun zein nanofibrous web encapsulating thymol/cyclodextrin-inclusion complex for food packaging
(Elsevier, 2017-10) Aytac Z.; Ipek, S.; Durgun, Engin; Tekinay, T.; Uyar, Tamer
Thymol (THY)/γ-Cyclodextrin(γ-CD) inclusion complex (IC) encapsulated electrospun zein nanofibrous webs (zein-THY/γ-CD-IC-NF) were fabricated as a food packaging material. The formation of THY/γ-CD-IC (1:1 and 2:1) was proved by experimental (X-ray diffraction (XRD), thermal gravimetric analysis (TGA), 1H NMR) and computational techniques. THY/γ-CD-IC (2:1) exhibited higher preservation rate and stability than THY/γ-CD-IC (1:1). It is worth mentioning that zein-THY/γ-CD-IC-NF (2:1) preserved much more THY as observed in TGA and stability of THY/γ-CD-IC (2:1) was higher, as shown by a modelling study. Therefore, much more THY was released from zein-THY/γ-CD-IC-NF (2:1) than zein-THY-NF and zein-THY/γ-CD-IC-NF (1:1). Similarly, antibacterial activity of zein-THY/γ-CD-IC-NF (2:1) was higher than zein-THY-NF and zein-THY/γ-CD-IC-NF (1:1). It was demonstrated that zein-THY/γ-CD-IC-NF (2:1) was most effective in inhibiting the growth of bacteria on meat samples. These webs show potential application as an antibacterial food packaging material.
Open Access
Design and construction of protein and peptide-based self-assembled nanostructures
(Elsevier, 2022-01-01) Yuca, Esra; Khan, Anooshay; Hacıosmanoğlu, Nedim; Şeker, Urartu Özgür Şafak; Pandya, A.; Singh, V.; Bhosale, R. S.
Self-assembly is the driving force for the formation of biological materials. From nucleic acid conformations to more complex cellular organizations, self-assembling structures shape biological functionality. So, the design of self-assembling biomolecular structures holds a great advantage for enhanced material properties. In biological processes, inorganic structures are created in a hierarchical fashion utilizing biomolecule-based templates. Since they have recognition and self-assembly properties, biomolecules can control highly organized inorganic material formation in nature. The bio-templating approach takes advantage of biomolecules’ self-assembly properties to develop new nanostructures with superior chemical and physical properties. Here, peptides and proteins including β-sheets, β-hairpins, α-helix, amyloid, capsid, ferritin, and albumin, used in the formation of nanostructures with desired functionality under mild environmental conditions, and their applications are discussed.
Open Access
Design, fabrication, and applications of multi-mode nanoelectromechanical systems
(2017-07) Arı, Atakan Bekir
Miniaturization of systems allowed wide spread consumer use of microelectronics, integrated circuits and MEMS based sensors. Thanks to the advancement in microfabrication methods, it is possible to build structures with submicron dimensions. The integration of electronic control to these submicron structures started the NEMS eld. Due to their minuscule dimensions and very high frequency response, NEMS can sense external perturbations with unprecedented sensitivity. This made NEMS excellent candidates for sensor applications. NEMS are starting to evolve from academic research tools to become mass produced and large scale integrated sensing devices. Information extracted from the higher order modes further increase the capabilities of NEMS. In order to attain this extra information, we fabricated NEMS that can reach higher order mechanical modes. Every step of fabrication was done at Bilkent University research facilities such as UNAM and ARL. To pattern the submicron feature sizes, we relied on electron beam lithography. Thermal and electron beam evaporators were deployed for metallization of contacts and etch mask. In order to suspend the doubly clamped beams, we developed anisotropic silicon nitride and isotropic silicon dry etch recipes. At each step of the fabrication, tools such as SEM and stylus pro lometer was utilized for characterization. Fabricated NEMS were wirebonded to printed circuit boards for detection. Electrothermal actuation, an integrated method, was chosen to drive the nanomechanical resonator to its higher order modes. Piezoresistive down-mixing, another integrated method to complement the actuation, was used to detect the resulting nanomechanical motion. We used high frequency electronic equipment to detect RF range responses of our NEMS. Using these NEMS, we studied two novel applications on intermodal and mechanical coupling. First, we investigated intermodal coupling e ect of doubly clamped beams in order utilize this coupling e ect in higher order mode detection. When a doubly clamped beam is excited at its resonance frequency, every other mode of the device gets tuned. This occurs due to the clamping on both sides preventing longitudinal elongation and causing a stress on the beam. Using intermodal coupling method, we probed higher order modes of a nanomechanical resonator while tracking the fundamental frequency at the same time. We were able to detect mechanical modes up to 840 MHz, well out of the detection limit of our setup. We propose intermodal coupling as a novel detection method to acquire frequency response of NEMS at higher order modes which can not be detected with conventional methods. Finally, we studied nano scale energy sinks that absorb energy from a another structure. Energy sinks are linear oscillators that can trap the energy of a nearby structure within their phase space. When the natural frequency of these sinks are distributed optimally, nite number of sinks can mimic absorption of in nite sinks. We envisioned a real time dissipation controlled NEMS platform by deploying energy sinks. In order to test energy sink performance at nano scale, we devised an experimental setup, comparing identical nanomechanical resonators with and without energy sinks. We have shown that energy sinks successfully absorb energy of a resonator at nanoscale.
Open Access
The effect of gadolinium doping on the structural, magnetic and photoluminescence properties of electrospun bismuth ferrite nanofibers
(Elsevier Ltd, 2015) George Philip G.; Senthamizhan, A.; Srinivasan Natarajan, T.; Chandrasekaran G.; Annal Therese H.
Gadolinium (Gd) doped Bismuth ferrite (BFO) nanofibers (Bi1-xGdxFeO3 (x=0.0, 0.05, 0.10, 0.15 and 0.20)) were synthesized via electrospinning. Scanning Electron Microscope (SEM) analysis showed that the diameter of the nanofibers ranged from 150 to 250 nm. X-Ray Diffraction (XRD) analysis revealed a structural phase transition with varying 'x', the compositions with x≤0.10 have crystal structures with space group R3c, while the compositions with x > 0.10 have crystal structures with space group Pnma. Vibrating Sample Magnetometer (VSM) analysis exhibited the weak ferromagnetic nature of the BFO nanofibers. However an increase in the saturated magnetic moment with increase in Gd dopant concentration was observed. The Photoluminescence (PL) spectra of the Bi:1-x :x nanofibers show enhanced Near Band Emission (NBE) intensity at x=0.10 due to the passivation of oxygen vacancies by Gd doping. © 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Open Access
Laser nano-structuring deep inside silicon using bessel beams
(2021-01) Ishraq, Aqiq
Current nano-fabrication methods for silicon (Si), while excellent, are limited to its surface. Novel laser-lithography methods are emerging to introduce subsurface (inchip) functionality to Si, however, the state-of-the-art is at the microfabrication level, with resolution limited to > 1 µm. Multiple challenges exist for breaking this fabrication barrier, such as the diffraction-limit and complex limiting nonlinear effects inside silicon. This thesis demonstrates the first nanofabrication capability deep inside silicon, achieved without altering the wafer above or below fabricated structures, with confinement in one- and two-dimensions at the nanoscale. We achieve this by exploiting nonlinear energy localization due to structured laser beams and also a new seeding-type effect. The approach is based on pre-formed laser-written inchip structures enabling the controlled formation of even smaller features. We also demonstrate laser polarization as a new parameter for in-chip fabrication control. Further, by exploiting a combination of parameters, including pulse energy, Bessel beam phase pattern, polarization and the laser focusing conditions, we demonstrate the first in-chip structures that are beyond the diffraction limit in terms of feature size, with resolution down to 120 nm ± 25 nm, thus, improving the state-of-the-art by about an order of magnitude. In order to demonstrate a proof-of-concept optical element, we fabricated the first in-chip nano-gratings, shown to be operating with an efficiency approaching 90%. This new nanofabrication capability, demonstrated for the important technological material silicon, may have significant implications for nano-photonics, micro/nano-fluidics, photonic-electronic integration, and micro/nano-electromechanical systems (MEMS/NEMS)-type systems.
Open Access
Mass and stiffness spectrometry of nanoparticles and bio-molecules by nanoelectromechanical systems
(2018-08) Orhan, Ezgi
Mass spectrometry (MS) is a technique used frequently in mass measurements in order to identify mass of the molecules. Nanoelectromechanical systems are highly sensitive to adhered species, thus using NEMS devices, it is possible to perform NEMS-MS where not only the inertial mass of the molecules but also the position of the adhered particle can be found out by resolving the adsorbateinduced frequency shifts in the first two modes.By using frequency shifts obtained from three mechanical modes, it is possible to obtain stiffness of the adsorbate in addition to its mass and position on the resonator when the Youngs modulus of the analyte and the resonant structure are comparable. For soft analytes, multimode information can be used to obtain shape properties of analytes and allows for image reconstruction from global image features. In order to conduct our experiments, we fabricate NEMS resonators whose transduction method is electrothermal actuation and piezoresistive detection. Fabrications of the devices are completed in National Nanotechnology Research Center (UNAM) in Bilkent University and Sabancı University Nanotechnology Research and Application Center (SUNUM).Initially, low vacuum apparatus is built to perform NEMS-MS using Electrospray Ionization(ESI) for molecule delivery. In order to direct particles to resonator, the fabrication of a doubly clamped beam is planned in a way that the orifice was etched through silicon wafer from the backside with KOH etch.This fabrication method, however, is tedious and hard to fabricate consistently.Then, Matrix Assisted Laser Desorption and Ionization (MALDI) is implemented to deliver particles towards the resonator.Different analyte types which are gold nanoparticles, centrosome organelles of HeLa cells and M13ke bacteriophages are used in the experiments.We use first four out-of-plane modes of the doublyclamped beam resonator for real-time study of the adsorbates. For biomolecule detection, care was taken to prevent uniform coverage of matrix molecules. Phaselocked-loop(PLL) operation is simultaneously performed for the first four modes of the resonator.Using frequency shifts of the four modes due to the adsorption, we propose a method in which we assume the analytes adhered on the beam are hemispherical to obtain mass and stiffness, size and positions of the analytes. Using three mechanical modes, stiffness, mass and position vaues are calculated.
Open Access
Monitoring micromechanical buckling at high-speed for sensing and transducer applications
(IEEE, 2021-08-06) Demiralp, Berke; Pisheh, Hadi Sedaghat; Küçükoğlu, Berk; Hatipoğlu, Utku; Hanay, Mehmet Selim
Controlling the amount and direction of buckling at micro- and nano-scale efficiently opens up avenues for novel actuation and sensor applications. Earlier platforms that can achieve a full and non-thermal control of microscopic buckling operated only with a time resolution of 40 ms. Here, we have measured the buckling amount of a beam starting from unbuckled position and reaching to large post-buckling deformations by collecting secondary electrons under scanning electron microscope. Line mode is used for ultrafast measurements with 33kHz scan frequency, and a displacement noise floor of 40pm/√Hz was obtained. Moreover, by further reduction in the device dimensions, the buckling threshold voltage was reduced by a factor of three compared to similar platforms.
Open Access
Monolayer-thick light-sensitive nanocrystal skins of oriented colloidal quantum wells
(2023-05) Bozkaya, Taylan
Colloidal quantum wells (CQWs), a two-dimensional member of semiconductor nanocrystals, featuring very tight vertical quantum confinement, possess giant oscillator strengths. Also, CQWs exhibit remarkably large absorption cross-sections, thanks to their oscillator strengths combined with their laterally large geometries. Additionally, as a powerful tool of fabrication, CQWs lend themselves to be conveniently self-assembled into monolayer-thick films in a single orientation of our choice: either face-down (lying down on their large lateral surfaces and side by side leaving no large gap between them similar to a mosaic pattern) or edge-up (standing up on their thin edges and facing each other in a very dense superstructure formation of repeating chains). In this thesis, to make use of the attractive absorption properties of CQWs and leverage on our ability to construct their orientation-controlled self-assemblies, we show the first account of monolayer-thick light-sensitive nanocrystal skins (LS-NS) that employ self-oriented CQWs as their active absorptive layer. These CQW LS-NS devices operate on the principle of strong optical absorption of the monolayered assembly of CQWs and the subsequent photogenerated potential build-up across their strongly capacitive thin device for sensing in the visible to ultraviolet. Such oriented CQWs in the LS-NS device architecture yield profoundly reduced surface roughness in their monolayer-thick films, essential to high device performance. Here, specifically, we developed and demonstrated two groups of LS-NS devices: one group consisting of all face-down oriented CQWs and the other, of all edge-up ones. We systematically studied their photocharging effect, spectral sensitivity and decay times. We observed in all LS-NS devices that the spectral sensitivity complies with the first (heavy-hole) and second (light hole) excitonic peaks of the absorption of the CQWs. We also found that, as the excitation power is increased, the peak photovoltage readout increases while the sensitivity decreases. The photocharging effect was further observed as the excitation was turned off. Finally, using the edge-up orientation, we identified a profound peak photovoltage signal enhancement. These findings of the thesis indicate that the proposed LS-NS devices of the orientation-controlled CQW monolayers hold great promise for applications in photos-sensing facades over larger surfaces.
Open Access
Pd nanocube decoration onto flexible nanofibrous mats of core-shell polymer-ZnO nanofibers for visible light photocatalysis
(Royal Society of Chemistry, 2017) Arslan, O.; Topuz, F.; Eren, H.; Bıyıklı, Necmi; Uyar, Tamer
Plasmonic enhancement for electron-hole separation efficiency and visible light photocatalysis was achieved by Pd nanocube decoration on a ZnO nanolayer coated onto electrospun polymeric (polyacrylonitrile (PAN)) nanofibers. Since exciton formation and sustainable electron-hole separation have a vital importance for realizing better solar energy in photovoltaic and photocatalytic devices, we achieved visible light photocatalysis by Pd nanocube decoration onto well designed core-shell nanofibers of ZnO@PAN-NF. By controlling the cubic Pd nanoparticle size and the thickness of the crystalline ZnO nanolayer deposited onto electrospun PAN nanofibers via atomic layer deposition (ALD), defect mediated visible light photocatalysis efficiency can be increased. By utilizing nanofabrication techniques such as thermal decomposition, electrospinning and ALD, this fabricated template became an efficient, defect mediated, Pd nanocube plasmon enhanced photocatalytic system. Due to the enhanced contact features of the Pd nanocubes, an increase was observed for the visible light photocatalytic activity of the flexible and nanofibrous mat of Pd@ZnO@PAN-NF.
Open Access
Single, binary and successive patterning of charged nanoparticles by electrophoretic deposition
(Springer, 2021-11-19) Sopubekova, Eliza; Kibar, G.; Yegan Erdem, Emine
Deposition of nanoparticles on a substrate in a controlled manner leads to the formation of multifunctional surfaces and therefore devices. Electrostatic forces can be utilized to manipulate different types of materials such as magnetic, insulating, conducting, semiconducting, organic and inorganic, without altering the chemistry of the surface. However, simultaneous and successive electrophoretic deposition (EPD) methods are not fully utilized for nanoparticles with different characteristics. In this work, electrostatic forces are applied to direct and position charged nanoparticles suspended in aqueous dispersions on desired areas of the surface. Assemblies of particles are obtained by electrostatic attraction generated by gold electrodes of sizes from 500 nm to 50 µm that are fabricated by thermal evaporation. Different types of charged nanoparticles were simultaneously attracted towards different locations of the surface by means of EPD; as a result, alternating nanoparticle patterns and particle deposition on the same designated areas for forming composite areas are obtained. Assemblies formed from positively charged silver nanoparticles and negatively charged fluorescent latex and silica nanoparticles are demonstrated. The position of metallic-, polymeric- and inorganic-based nanoparticles is controlled by the design of electrode geometry.
Open Access
Surface integrated membrane nanomechanical and microwave coplanar waveguide based biosensors
(2018-08) Aslanbaş, Levent
Nanoelectromechanical Systems, or NEMS, is the further miniaturized extension of novel devices of 40 years ago, Microelectromechanical Systems or MEMS in short. Nano scale devices first appeared at the dawn of 21st century and they are well established and elaborated by this time to a point which it shapes the technological paradigm of the current decade with various applications such as gene sequencing, improved computers and single molecule detection. The rapid improvement of miniaturization tecniques owes a great deal to the hard work of scientists and engineers of previous generation. Fabrication methods which were limited to a small number which disallowed sub-micron features are improved and new methods have been discovered within the previous decades. This has paved the way for creation of very sensitive sensors in NEMS domain. In this study, a novel biosensor is designed and attempted to be created out of coplanar waveguide resonators which is constructed on top of a nanometers thick membrane and at the sensory region of the resonator a nanopore is proposed to be created. The nanopore is suggested in order to allow nano-particle carrier fluids to pass through the most sensitive region of the resonator, causing a change in its resonant frequency due to electrical property of the nano-particle. The frequency shift caused by particles is suggested to be used to detect and characterize the particles. The particles in this case are planned to be exosomes which are sub-micron packages with cytoplasmic content, naturally secreted by cells for various reasons. Contents of the exosomes may carry diagnostic information about the cell. Exosomes themselves are still being investigated for their uses and benefits within the context of microbiology which makes the proposed device very crucial for ongoing exosome research effort which is still on the rise.
Open Access
Synthesis of iron oxide core chitosan nanoparticles in a 3D printed microfluidic device
(Springer, 2021-03-02) Aşık, M.D.; Kaplan, M.; Çetin, Barbaros; Sağlam, N.
Nanostructures are capable of major changes in our life. However, the game changing properties of experimental nanostructures mostly are not repeatable for the industry and it is not easy to produce the amount of nanoparticles necessary for the industrial world. Repeatable methods, which do not require highly trained personnel, for industrial-scale production should be developed to transfer the academic research to the use of people. Although there are various successful microfluidics devices that have been designed for microstructures synthesis, the synthesis of the nanostructures is not an enlightened area and there is a need for research to reach a better state. Especially, the development and design of microfluidics devices for biopolymeric nanoparticles are very important. The biopolymeric nanoparticles have uses in both nanotechnology and nanomedicine especially as theragnostic tools. In this study, a microfluidic device has been modeled, designed, and manufactured for especially iron oxide core chitosan nanoparticles. The microfluidics channels were manufactured by 3D printing. After nanoparticles synthesized by manufactured device, these particles were characterized, and their properties were examined. In addition to the flow rate, chemical concentrations, and pH, the structure of the microfluidics channel and hurdles have effects on the particle size and particle size distribution. Best results were obtained with 120-120ml/h flow rates and 0.06-0.03% concentrations at pH 4.5 for chitosan-tripolyphosphate couple. The nanoparticles that were produced in microchannels with hurdles under these conditions have a DLS measurement of 190±15 nm in diameter with 69% intensity. In conclusion, the 3D printed microfluidic channels are able to synthesize nanoparticles in a reproducible way with or without iron oxide core.
Open Access
Tailoring self-organized nanostructured morphologies in kilometer-long polymer fiber
(Nature Publishing Group, 2014-05-06) Khudiyev, T.; Tobail, O.; Bayındır, Mehmet
While nanowires and nanospheres have been utilized in the design of a diverse array of nanoscale devices, recent schemes frequently require nanoscale architectures of higher complexity. However, conventional techniques are largely unsatisfactory for the production of more intricate nanoscale shapes and patterns, and even successful fabrication methods are incompatible with large-scale production efforts. Novel top-down, iterative size reduction (ISR)-mediated approaches have recently been shown to be promising for the production of high-throughput cylindrical and spherical nanostructures, though more complex architectures have yet to be created using this process. Here we report the presence of a hitherto-undescribed transitory region between nanowire and nanosphere transformation, where a diverse array of complex quasi one-dimensional nanostructures is produced by Rayleigh-Plateau instability-mediated deformation during the progress of a combined ISR/thermal instability technique. Temperature-based tailoring of architecturally diverse, indefinitely long, globally parallel, complex nanostructure arrays with high uniformity and low size variation facilitates the development of in-fiber or free-standing nanodevices with significant advantages over on-chip devices.
Open Access
Tunable nano devices fabricated by controlled deposition of gold nanoparticles via focused ion beam
(Elsevier, 2009-12-16) Shahmoon, A.; Limon, O.; Girshevitz, O.; Fleger, Y.; Demir, Hilmi Volkan; Zalevsky, Z.
In this paper, we present the fabrication procedures as well as the preliminary experimental results of a novel method for significantly simplified deposition of charged nanoparticles at specific patterns based on focused ion beam (FIB) technology. The deposition method relies on the implantation of positive gallium ions on an insulated material which creates the basis for attracting the nanoparticles to the substrate. In order to substantiate the theory two patterns were generated on a silicon on insulator (SOI) chip with an upper layer of silicon of 200 nm. The two patterns are as follows: resolution target - consisting of six squares and 400 nm × 400 nm circular sinusoidal tunnel. In addition, we demonstrate the utilization and applicability of the aforementioned method in a tunable radiation nano device as well as show its experimental characterization.