Nanohole Size Research Articles

Influence of surface effect of the edge of a half-plane on the stress concentration around a nearby nanosized hole of arbitrary shape

Influence of surface effect of the edge of a half-plane on the stress concentration around a nearby nanosized hole of arbitrary shape

Photon transport through a nanohole by a moving atom

We have proposed and investigated for the first time an efficient way of photon transport through a subwavelength hole by a moving atom. The transfer mechanism is based on the reduction of the wave packet of a single photon due to its absorption by an atom and, correspondingly, its localization in a volume is smaller than both the radiation wavelength and the nanohole size. The scheme realizes the transformation of a single-photon single-mode wave packet of the laser light into a single-photon multimode wave packet in free space.

Modeling Graphene with Nanoholes: Structure and Characterization by Raman Spectroscopy with Consideration for Electron Transport

Recent advances in controlled synthesis and characterization of single-layer graphene nanostructures with defects provide the basis for gaining an understanding of the complex nanomaterials by theoretical investigation. In this work, we modeled defective single-layer graphene (DSLG), where nanostructures with divacancy, trivacancy, tetravacancy, pentavacancy, hexavacancy, and heptavacancy defects, having pore sizes from 0.1 to 0.5 nm, were considered. Nanostructures with molecular oxygen adsorption to mimic experimental conditions were also investigated. On the basis of calculated formation energies of the optimized nanostructures, a few DSLGs were selected for theoretical characterization of the defect-induced I(D)/I(D′) Raman intensity ratios. We found that the I(D)/I(D′) ratio decreases with an increase in the nanohole size and in the number of adsorbed oxygens, which explains an experimental observation of a decrease in this characterization signature with an increase in exposure time to oxygen plasma...

Optical Filters Based on Nano-Sized Hole and Slit Patterns in Aluminum Films

Optical Filters Based on Nano-Sized Hole and Slit Patterns in Aluminum Films

Design and fabrication of a 3D-structured gold film with nanopores for local electric field enhancement in the pore

Three-dimensionally structured gold membrane films with nanopores of defined, periodic geometries are designed and fabricated to provide the spatially localised enhancement of electric fields by manipulation of the plasmons inside nanopores. Square nanopores of different size and orientation relative to the pyramid are considered for films in aqueous and air environments, which allow for control of the position of electric fields within the structure. Designs suitable for use with 780 nm light were created. Here, periodic pyramidal cavities produced by potassium hydroxide etching to the {111} planes of (100) silicon substrates are used as templates for creating a periodic, pyramidal structured, free-standing thin gold film. Consistent with the findings from the theoretical studies, a nano-sized hole of 50 nm square was milled through the gold film at a specific location in the cavity to provide electric field control which can subsequently used for enhancement of fluorescence or Raman scattering of molecules in the nanopore.

Plasmonic Gold Nanohole Arrays for Surface-Enhanced Raman Scattering Biosensing

Gold nanohole arrays can serve as promising substrates for construction of surface-enhanced Raman scattering (SERS) biosensors. Gold nanohole arrays support tunable localized surface plasmon resonance (LSPR) and propagating surface plasmon polariton (SPP). However, it is a great challenge to optimize their performance due to coexistence of LSPR and SPP. Here, finite difference time domain (FDTD) simulation is used in combination with measured transmission and reflection to discern which resonance mode leads to the electromagnetic field enhancement. The SERS peak signal intensity has been mapped with the nanohole size, which shows that the “gap” between neighboring nanoholes in the array pattern and the absorption play an important role in SERS enhancement. Optimization of hole size and pitch is necessary for development of nanohole array based SERS biosensors.

Surface effects in nanoscale structures investigated by a fully-nonlocal energy-based quasicontinuum method

Surface effects in nanoscale mechanical systems such as nanoporous solids or small-scale structures can have a significant impact on the effective material response which deviates from the material behavior of bulk solids. Understanding such phenomena requires modeling techniques that locally retain atomistic information while transitioning to the relevant macroscopic length scales. We recently introduced a fully-nonlocal energy based quasicontinuum (QC) method equipped with new summation rules. This technique accurately bridges across scales from atomistics to the continuum through a thermodynamically-consistent coarse-graining scheme. Beyond minimizing energy approximation errors and spurious force artifacts, the new method also qualifies to describe free surfaces, which is reported here. Surfaces present a major challenge to coarse-grained atomistics, which has oftentimes been circumvented by costly ad hoc extensions of the traditional QC method. We show that our new coarse-graining scheme successfully and automatically reduces spurious force artifacts near free surfaces. After discussing the computational model, we demonstrate its benefits in the presence of free surfaces by several nanomechanical examples including surface energy calculations, elastic size effects in nano-rods and in plates with nano-sized holes. Overall, we demonstrate the importance of surface effects as well as a new strategy to accurately capture those computationally via coarse-grained atomistics.

폴리스티렌 나노 비드를 이용한 플라즈모닉 나노 구조체의 광학 특성

We proposed and demonstrated the double layered metallic nano-hole structure using polystyrene beads process to enhance the sensitivity of surface plasmon resonance (SPR). The double layered SPR structures are calculated using the finite-difference time-domain (FDTD) method for the width, thickness, and period of the metallic nano-hole structures. The thickness of the metal film and the metallic nano-hole is 30 and 20 nm in the 214 nm wide nano-hole size, respectively. The double layered SPR structures are fabricated with monolayer polystyrene beads of 420 nm wide. The sensitivities of the conventional SPR sensor and the double layered SPR sensor are obtained to 42.2 and 52.1 degree/RIU, respectively.

Effect of the Size and Position of Ion-Accessible Nanoholes on the Specific Capacitance of Single-Walled Carbon Nanohorns for Supercapacitor Applications

We explore the importance of the size and position of nanoholes on the electrochemical performance of single-walled carbon nanohorn (SWCNH)-based supercapacitors using an ionic liquid electrolyte. The oxidized sample at 673 K showed a low specific capacitance per unit of internal specific surface area (4.0 μF cm–2), as the nanoholes created on the tips of SWCNHs via a selective chemical attack are too small to introduce electrolyte ions. For a sample oxidized at 723 K, the enlarged diameter of the nanoholes on the tips allows electrolyte ions to penetrate into the internal spaces of the SWCNHs, thereby resulting in a 2-fold capacitance improvement (8.6 μF cm–2). However, the abrupt decrease in the capacitance of the oxidized SWCNHs at 823 K (3.8 μF cm–2) can be explained by the selective formation of nanoholes on the sidewalls of the SWCNHs, where the small interstitial pores restrict ion diffusion to deeply positioned nanoholes on the sidewalls of the SWCNHs. Our study clearly reveals that the size and p...

Effects of the molecular level dispersion of graphene oxide on the free volume characteristics of poly(vinyl alcohol) and its impact on the thermal and mechanical properties of their nanocomposites.

Poly(vinyl alcohol), PVA, reinforced with carbon nanofillers has shown drastic variations in thermal as well as mechanical properties. In order to establish structure-property correlations, these variations have been correlated with modifications in the hydrogen bonding structure as well as the crystallinity of the PVA matrix without paying much attention to molecular packing in the amorphous region of this semicrystalline polymer. In order to investigate the molecular packing in PVA-graphene oxide (GO) nanocomposites, free volume characterization of PVA-GO nanocomposites has been carried out using ortho-positronium (o-Ps) probe. The variations in free volume size, density and size distribution have been determined through o-Ps lifetime and the corresponding intensity as well as its lifetime distribution. The variation in hydrogen bonding and its effect on crystallinity has been determined by Fourier Transform Infra Red (FTIR) and X-ray diffraction (XRD) measurements. The variation in the thermal (glass transition temperature) and mechanical (Young's modulus, tensile strength and percentage strain at break) properties of the nanocomposites is explained in view of the free volume structure and crystallinity of the PVA matrix which are severely modified due to the molecular-level dispersion of GO sheets in the PVA matrix.

Optimized Sensitivity and Electric Field Enhancement by Controlling Localized Surface Plasmon Resonances for Bowtie Nanoring Nanoantenna Arrays

The surface plasmon resonances of gold bowtie nanoring antenna arrays were simulated using the finite-difference time-domain method in the present study. Both the local field and transmission spectra of bowtie nanoring antennas with various nanohole sizes were examined to find the optimum conditions to induce the greatest local electromagnetic field enhancement and sensitivity compared to the solid bowtie antenna. With the optimized nanohole size of bowtie nanoring, the local electromagnetic field enhancement, the decay length of the electric field, and the bulk sensitivity were increased as high as about 73, 349, and 63 %, respectively, compared to the solid bowtie antenna. The electric field enhancement profile and the charge distribution of the bowtie nanoring antennas were studied to characterize the coupled plasmon configurations, and it was used to explore the mechanism of enhanced sensitivity and resonance-wavelength shift of bowtie nanoring array with different surrounding dielectric media. This highly localized electromagnetic field enhancement and sensitive bowtie nanoring array system can be applied in the field of surface-enhanced Raman scattering and bio-sensing.

Interaction of a screw dislocation with a nano-sized, arbitrarily shaped inhomogeneity with interface stresses under anti-plane deformations.

We propose an elegant and concise general method for the solution of a problem involving the interaction of a screw dislocation and a nano-sized, arbitrarily shaped, elastic inhomogeneity in which the contribution of interface/surface elasticity is incorporated using a version of the Gurtin-Murdoch model. The analytic function inside the arbitrarily shaped inhomogeneity is represented in the form of a Faber series. The real periodic function arising from the contribution of the surface mechanics is then expanded as a Fourier series. The resulting system of linear algebraic equations is solved through the use of simple matrix algebra. When the elastic inhomogeneity represents a hole, our solution method simplifies considerably. Furthermore, we undertake an analytical investigation of the challenging problem of a screw dislocation interacting with two closely spaced nano-sized holes of arbitrary shape in the presence of surface stresses. Our solutions quite clearly demonstrate that the induced elastic fields and image force acting on the dislocation are indeed size-dependent.

Fabrication of size‐tunable hierarchical CrN nanohole arrays for two‐dimensional nanomould using modified nanosphere lithography

This Letter presents a low-cost, high-throughput strategy for fabricating size-tunable hierarchical CrN nanohole arrays for a nanomould using a magnetron sputtering approach with nanosphere lithography (NIL)-based technology. The size of the polystyrene nanospheres has a direct influence on the diameter and period of the CrN nanohole structure. The reactive ion etching and magnetron sputtering process can easily control the nanohole size and depth. The hole depth generally depends on the film thickness. The contact angles were measured by the sessile drop method using distilled water, ethylene glycol and diiodomethane. The surface-free energy of the CrN nanomould was calculated using the Owens–Wendt geometric mean approach. This Letter reports the successful fabrication of a series of nanoholes with diameters decreased from 347 ± 9.6 to approximately 166 ± 11.8 nm with a depth of 100 ± 5.6 nm. The corresponding surface-free energy decreased from 40.83 to approximately 24.58 mN/m. The diameter of nanoholes has an obvious effect on the surface-free energy and there is tendency for the surface-free energy to decrease with the decrease in the diameter of the nanoholes. This new approach of ordered CrN nanohole array structures can be used to create a two-dimensional nanomould for NIL.

Gold Nano Particles (GNPs): An Emerging Solution of Cancer

Cancer, one of the leading causes that bring confirm death, is the subject of widespread fear and taboos. Although the complete elimination of cancer hasn’t been discovered yet, “the war against cancer” has already been declared worldwide and research works are ongoing for cancer medicines. This paper presents a review on “Gold Nano Particle (GNP)”, a magic bullet which might be the timely solution to bring win against cancer malignancy. GNPs can be used as cancer drug carriers, contrast agent or in target cancer therapy etc. Because cancer cell membrane has Nano size holes, the Nano structure of GNP would help it to enter the cancer cells. It has also the dissolving abilities, so no harm would be done to other parts of the body. By using near infrared LASER, localized heating of GNPs is also possible to destroy cancer cells. Test on rats using GNPs is found successful and the implementation on human is a matter of time. In Vitro and In Vivo observations on GNPs show much promises in near future.

Fabrication of Ag nanodot array over large area for surface-enhanced Raman scattering using hybrid nanoimprint mold made from AAO template

We demonstrated the fabrication of dense hexagonal arrays of Ag nanodots over a large area using a novel nanoimprint-based fabrication technique for surface-enhanced Raman spectroscopy. Flexible imprint molds with sub-10 nm features were duplicated from AAO templates using a novel hybrid mold technique. This method solves the nonflatness-induced defect issue in the conventional thermal nanoimprint technique, and allows high-quality duplications of nanometer features from rigid nonflat templates. Moreover, with the help of the excellent tunability of the size of nanoholes on AAO templates, we were able to tune the size of Ag nanodots, and consequently to tailor the resonance frequency of the Ag nanodot arrays. Finally, surface-enhanced Raman scattering of Rhodamine-123 on Ag nanodot arrays was measured, and large signal enhancement was observed on the 70 nm Ag nanodots. We numerically simulated the optical properties of those Ag nanodot arrays, and excellent agreement was found with the experimental results.

Preparation and electrochemical performance of a porous polymer-derived silicon carbonitride anode by hydrofluoric acid etching for lithium ion batteries

Porous silicon carbonitride (SiCN) ceramics were pyrolyzed from poly(silylcarbondiimide) derivatives, followed by etching with different concentrations of HF aqueous solution (5, 10, 15 and 20 wt%). The morphologies, structures and electrochemical performances of the HF-etched SiCN materials were investigated. The results indicated that the surface of the HF-etched SiCN composites became rough and porous. SiCN-10-HF, one of four HF-etched SiCN samples, showed excellent electrochemical properties as an anode for lithium ion batteries. Charge–discharge measurements indicated that the SiCN-10-HF anode exhibited a high initial specific discharge capacity of 681 mA h g−1 at a current density of 40 mA g−1, which was 2.4 times that of the unetched SiCN anode. After 100 cycles, the discharge capacity of SiCN-10-HF anode delivered 229.3 mA h g−1, which was 5.0 times that of the unetched SiCN anode (45.6 mA h g−1). Additionally, the SiCN-10-HF anode exhibited high rate performance. At a current density of 190 mA g−1, the discharge capacity of the anode was 160 mA h g−1. It was deduced that the formation of nano-sized pores or holes on the surface of the SiCN materials in the HF-etching process not only offered new channels for the intercalation of Li+ but also relieved the volume expansion during the charge and discharge process, resulting in improved capacity, stable cycling and good rate capability.

Enhanced detection limit by dark mode perturbation in 2D photonic crystal slab refractive index sensors

We demonstrate for the first time a 300nm thick, 300μm × 300μm 2D dielectric photonic crystal slab membrane with a quality factor of 10,600 by coupling light to slightly perturbed dark modes through alternating nano-hole sizes. The newly created fundamental guided resonances greatly reduce nano-fabrication accuracy requirements. Moreover, we created a new layer architecture resulting in electric field enhancement at the interface between the slab and sensing regions, and spectral sensitivity of >800 nm/RIU, that is, >0.8 of the single-mode theoretical upper limit of spectral sensitivity.

Surface effects in the deformation of an anisotropic elastic material with nano-sized elliptical hole

We examine the effect of surface energy on an anisotropic elastic material weakened by an elliptical hole. A closed-form, full-field solution is derived using the standard Stroh formalism. In particular, explicit expressions for the hoop stress, normal, in-plane tangential and out-of-plane displacement components along the edge of the hole are obtained. These expressions clearly demonstrate the effect of elastic anisotropy of the bulk material on the corresponding field variables. When the material becomes isotropic, the hoop stress agrees with the well-known result in the literature while both the in-plane tangential and out-of-plane displacements vanish and the normal displacement is constant along the entire boundary of the elliptical hole.

Morphology of CD4+T Lymphocytes Bound on Nano-Patterened Substrates for Sensing the Size of Nanoholes

We report on direct finding of how the morphology (i.e. filopodia width) of <TEX>$CD4^+$</TEX> T lymphocytes correlates with the size of the quartz nanohohole arrays (QNHAs, 140, 200, 270, and 550 nm in diameter) via scanning electron microscopy (SEM). This research exhibits that the filopodia of <TEX>$CD4^+$</TEX> T-lymphocytes extended on the QNHA substrates were observed to increase in width by increasing the size of QNHA in diameter from 140 to 550 nm. This strong linear response (<TEX>$R^2$</TEX>=0.988, n = 6) in filopodia's width of surface-bound <TEX>$CD4^+$</TEX> T-cells with topographical structures of QNHA can be explained by contact guidance between the cells and solid-state substrates. Furthermore, this research suggests that the protruded filopodia of surface-bound T-lymphocytes can be used as a biosensor for sensing the topographical information of the nano-patterned substrates.

Revealing the Nano‐Level Molecular Packing in Chitosan–NiO Nanocomposite by Using Positron Annihilation Spectroscopy and Small‐Angle X‐ray Scattering

Chitosan-NiO nanocomposite (CNC) is shown to be a potential dielectric material with promising properties. CNCs containing NiO nanoparticles (0.2, 0.6, 1, 2, 5 wt %) are prepared through chemical methods. The inclusion of NiO nanoparticles in the chitosan matrix is confirmed by scanning electron microscopy (SEM) and X-ray diffraction. The morphology of the NiO nanoparticles and the nanocomposites is investigated by transmission electron microscopy and SEM, respectively. Positron annihilation lifetime spectroscopy (PALS) and the coincidence Doppler broadening (CDB) technique are used to quantify the free volume and molecular packing in the nanocomposites. The triplet-state positronium lifetime and the corresponding intensity show the changes in nanohole size, density, and size distribution as a function of NiO loading. Small-angle X-ray scattering indicates that the NiO aggregates are identical in all the CNCs. The momentum density distribution obtained from CDB measurements excludes the possibility of a contribution of vacant spaces (pores) available in NiO aggregates to the free volume of nanocomposites upon determination by using PALS. The results show systematic variation in free-volume properties and nano-level molecular packing as a function of NiO loading, which is presumed to play a vital role in determining the various properties of the nanocomposites.