scholarly journals Advantages of the Surface Structuration of KBr Materials for Spectrometry and Sensors

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 3013 ◽  
Author(s):  
Natalia Kamanina ◽  
Svetlana Likhomanova ◽  
Pavel Kuzhakov
Keyword(s):  
Carbon Nanotubes ◽  
Refractive Index ◽  
Electric Fields ◽  
Matrix Material ◽  
Small Diameter ◽  
Main Idea ◽  
Potassium Bromide ◽  
Material Surface ◽  
Vertical Position ◽  
Output Window

A potassium bromide (KBr) material, which has been widely used as the key element in Fourier spectrometers and as the output window of the IR-lasers, was studied via applying carbon nanotubes in order to modify the potassium bromide surface. The laser-oriented deposition method was used to place the carbon nanotubes at the matrix material surface in the vertical position at different electric fields varying from 100 to 600 V × cm−1. The main idea of the improvement of the spectral properties of the potassium bromide structure is connected with the fact that the refractive index of the carbon nanotubes is substantially less than the refractive index of the studied material, and the small diameter of the carbon nanotubes allows one to embed these nano-objects in the voids of the lattice of the model matrix systems. Moreover, the mechanical characteristics and wetting features of potassium bromide structures have been investigated under the condition mentioned above. Analytical and quantum-chemical simulations have supported the experimental results.

scholarly journals Advantages of the Surface Structuration of the KBr Materials for the Spectrometry and Sensors

2018 ◽  
Author(s):  
Natalia Kamanina ◽  
Svetlana Likhomanova ◽  
Pavel Kuzhakov
Keyword(s):  
Carbon Nanotubes ◽  
Refractive Index ◽  
Matrix Material ◽  
Small Diameter ◽  
Main Idea ◽  
Potassium Bromide ◽  
Material Surface ◽  
Vertical Position ◽  
Output Window ◽  
The Matrix

A potassium bromide KBr material, which has been widely used as the key element in the Fourier spectrometers and as the output window of the IR-lasers, has been studied with good advantage via applying the carbon nanotubes in order to modify the potassium bromide surface. The laser oriented deposition method has been used to place the carbon nanotubes at the matrix material surface in the vertical position at the different electric field varied from 100 to 600 V×cm-1. The main idea of the improvement of the spectral properties of the potassium bromide structure is connected with the fact that the refractive index of the carbon nanotubes is substantially less than the refractive index of the studied material, and the small diameter of the carbon nanotubes allows one to embed these nano-objects in the voids of the lattice of the model matrix systems. Moreover, the mechanical characteristics and wetting features of the potassium bromide structures have been investigated under the condition mentioned above. Analytical and quantum-chemical simulations have supported the experimental results.

Electron-Phonon Interaction and Joule Heating in Nanostructures

2008 ◽  
Author(s):  
Eric Pop
Keyword(s):  
Carbon Nanotubes ◽  
Electric Fields ◽  
Joule Heating ◽  
Optical Phonon ◽  
Phonon Transport ◽  
Phonon Energy ◽  
Strained Silicon ◽  
Vibrational Modes ◽  
Optical Phonons ◽  
Ambient Gas

The electron-phonon energy dissipation bottleneck is examined in silicon and carbon nanoscale devices. Monte Carlo simulations of Joule heating are used to investigate the spectrum of phonon emission in bulk and strained silicon. The generated phonon distributions are highly non-uniform in energy and momentum, although they can be approximately grouped into one third acoustic (AC) and two thirds optical phonons (OP) at high electric fields. The phonon dissipation is markedly different in strained silicon at low electric fields, where certain relaxation mechanisms are blocked by scattering selection rules. In very short (∼10 nm) silicon devices, electron and phonon transport is quasi-ballistic, and the heat generation domain is much displaced from the active device region, into the contact electrodes. The electron-phonon bottleneck is more severe in carbon nanotubes, where the optical phonon energy is three times higher than in silicon, and the electron-OP interaction is entirely dominant at high fields. Thus, persistent hot optical phonons are easily generated under Joule heating in single-walled carbon nanotubes suspended between two electrodes, in vacuum. This leads to negative differential conductance at high bias, light emission, and eventual breakdown. Conversely, optical and electrical measurements on such nanotubes can be used to gauge their thermal properties. The hot optical phonon effects appear less pronounced in suspended nanotubes immersed in an ambient gas, suggesting that phonons find relaxation pathways with the vibrational modes of the ambient gas molecules. Finally, hot optical phonons are least pronounced for carbon nanotube devices lying on dielectrics, where the OP modes can couple into the vibrational modes of the substrate. Such measurements and modeling suggest very interesting, non-equilibrium coupling between electrons and phonons in solid-state devices at nanometer length and picoseconds time scales.

scholarly journals Synthetic electric fields and phonon damping in carbon nanotubes and graphene

2009 ◽  
Vol 80 (7) ◽  
Author(s):  
Felix von Oppen ◽  
Francisco Guinea ◽  
Eros Mariani
Keyword(s):  
Carbon Nanotubes ◽  
Electric Fields

The Influence of Fe/Al Molar Ratio on Microreactor-Based Catalyst Preparation and Carbon Nanotube Preparation

2021 ◽  
Vol 1036 ◽  
pp. 130-136
Author(s):  
Ting Qun Tan ◽  
Lei Geng ◽  
Yan Lin ◽  
Yan He
Keyword(s):  
Carbon Nanotubes ◽  
Catalytic Activity ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Small Diameter ◽  
High Specific Surface Area ◽  
Detection Methods ◽  
Molar Ratio ◽  
High Catalytic Activity

In order to prepare carbon nanotubes with high specific surface area, small diameter, low resistivity, high purity and high catalytic activity, the Fe-Mo/Al2O3 catalyst was prepared based on the microreactor. The influence of different Fe/Al molar ratios on the catalyst and the carbon nanotubes prepared was studied through BET, SEM, TEM and other detection methods. Studies have shown that the pore structure of the catalyst is dominated by slit pores at a lower Fe/Al molar ratio. The catalytic activity is the highest when the Fe/Al molar ratio is 1:1, reaching 74.1%. When the Fe/Al molar ratio is 1:2, the catalyst has a higher specific surface area, the maximum pore size is 8.63 nm, and the four-probe resistivity and ash content of the corresponding carbon nanotubes are the lowest. The higher the proportion of aluminum, the higher the specific surface area of the catalyst and the carbon nanotubes, and the finer the diameter of the carbon nanotubes, which gradually tends to relax. The results show that when the Fe/Al molar ratio is 1:2, although the catalytic activity of the catalyst is not the highest, the carbon nanotubes prepared have the best performance.

Enhancement of Mechanical Properties by Reinforcing Magnesium With Ni-Coated Carbon Nanotubes

2010 ◽  
Author(s):  
M. H. Nai ◽  
C. S. Goh ◽  
S. M. L. Nai ◽  
J. Wei ◽  
M. Gupta
Keyword(s):  
Carbon Nanotubes ◽  
Load Transfer ◽  
Matrix Material ◽  
Strength Based ◽  
The Matrix ◽  
Rapid Sintering ◽  
Reinforcing Material ◽  
Coated Carbon ◽  
Strength And Ductility ◽  
Walled Cnts

In this study, carbon nanotubes (CNTs) are coated with nickel (Ni) to improve the wettability of the CNT surface and metal matrix, and allow an effective load transfer from the matrix to nanotubes. Pure magnesium is used as the matrix material and different weight percentages of Ni-coated multi-walled CNTs are incorporated as the reinforcing material. The nanocomposite materials are synthesized using the powder metallurgy route followed by microwave assisted rapid sintering. Mechanical property characterizations reveal an improvement of 0.2% yield strength, ultimate tensile strength and ductility with the addition of Ni-CNTs. As such, Ni-coated CNTs can be used as a reinforcement in magnesium to improve the formability of the material for light-weight, strength-based applications.

scholarly journals Photoluminescence of CdSe/ZnS quantum dots in nematic liquid crystals in electric fields

2018 ◽  
Vol 9 ◽  
pp. 1544-1549 ◽  
Author(s):  
Margarita A Kurochkina ◽  
Elena A Konshina ◽  
Daria Khmelevskaia
Keyword(s):  
Quantum Dots ◽  
Liquid Crystals ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electric Fields ◽  
Dielectric Anisotropy ◽  
Vertical Position ◽  
Decay Times ◽  
Pl Intensity

We have experimentally investigated the effect of the reorientation of a nematic liquid crystal (LC) in an electric field on the photoluminescence (PL) of CdSe/ZnS semiconductor quantum dots (QDs). To the LC with positive dielectric anisotropy, 1 wt % QDs with a core diameter of 5 nm was added. We compared the change of PL intensity and decay times of QDs in LC cells with initially planar or vertically orientated molecules, i.e., in active or passive LC matrices. The PL intensity of the QDs increases four-fold in the active LC matrix and only 1.6-fold in the passive LC matrix without reorientation of the LC molecules. With increasing electric field strength, the quenching of QDs luminescence occurred in the active LC matrix, while the PL intensity did not change in the passive LC matrix. The change in the decay time with increasing electric field strength was similar to the behavior of the PL intensity. The observed buildup in the QDs luminescence can be associated with the transfer of energy from LC molecules to QDs. In a confocal microscope, we observed the increase of particle size and the redistribution of particles in the active LC matrix with the change of the electric field strength. At the same time, no significant changes occurred in the passive LC matrix. With the reorientation of LC molecules from the planar in vertical position in the LC active matrix, quenching of QD luminescence and an increase of the ion current took place simultaneously. The obtained results are interesting for controlling the PL intensity of semiconductor QDs in liquid crystals by the application of electric fields.

The Generation of a Carbon Nanotube- Cyclodextrin Complex

2001 ◽  
Vol 703 ◽  
Author(s):  
G.F. Farrell ◽  
G. Chambers ◽  
A.B Dalton ◽  
E. Cummins ◽  
M. McNamara ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Aqueous Solution ◽  
Raman Spectroscopy ◽  
Carbon Nanotube ◽  
Intermolecular Interaction ◽  
Intermolecular Interactions ◽  
Small Diameter ◽  
Cyclodextrin Complex ◽  
Yellow Solution ◽  
Single Wall Nanotubes

ABSTRACTIn this study the intermolecular interactions of small diameter (∼0.7nm) carbon nanotubes and γ-cyclodextrin were examined. Four samples of γ cyclodextrin and HiPco carbon nanotubes were prepared. The first, by grinding the tubes and the cyclodextrin (1:30 ratio) together in a dry mixture, the second was prepared in a similar fashion but was ground in the presence of water (1ml). Finally an aqueous solution of γ-cyclodextrin (0.3M) and HiPco carbon nanotubes (5mg) was prepared by refluxing for ∼100 hours, forming a pale yellow solution from which a number of crystals were produced, both the solution and the recrystallised material were analysed. The samples were analysed using UV-Vis-NIR and Raman spectroscopy. The results presented are the first spectroscopic evidence of an intermolecular interaction between γ-cyclodextrin and single wall nanotubes.

Encapsulation of copper and zinc oxide nanoparticles inside small diameter carbon nanotubes

2015 ◽  
Vol 202 ◽  
pp. 189-197 ◽  
Author(s):  
Dennis Großmann ◽  
Axel Dreier ◽  
Christian W. Lehmann ◽  
Wolfgang Grünert
Keyword(s):  
Carbon Nanotubes ◽  
Zinc Oxide ◽  
Zinc Oxide Nanoparticles ◽  
Small Diameter ◽  
Oxide Nanoparticles ◽  
Copper And Zinc

scholarly journals Refractive index sensing and surface-enhanced Raman spectroscopy using silver–gold layered bimetallic plasmonic crystals

2017 ◽  
Vol 8 ◽  
pp. 2492-2503 ◽  
Author(s):  
Somi Kang ◽  
Sean E Lehman ◽  
Matthew V Schulmerich ◽  
An-Phong Le ◽  
Tae-woo Lee ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Refractive Index ◽  
Electric Fields ◽  
Surface Enhanced Raman Spectroscopy ◽  
Plasmonic Crystals ◽  
Metal Thickness ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Difference Time

Herein we describe the fabrication and characterization of Ag and Au bimetallic plasmonic crystals as a system that exhibits improved capabilities for quantitative, bulk refractive index (RI) sensing and surface-enhanced Raman spectroscopy (SERS) as compared to monometallic plasmonic crystals of similar form. The sensing optics, which are bimetallic plasmonic crystals consisting of sequential nanoscale layers of Ag coated by Au, are chemically stable and useful for quantitative, multispectral, refractive index and spectroscopic chemical sensing. Compared to previously reported homometallic devices, the results presented herein illustrate improvements in performance that stem from the distinctive plasmonic features and strong localized electric fields produced by the Ag and Au layers, which are optimized in terms of metal thickness and geometric features. Finite-difference time-domain (FDTD) simulations theoretically verify the nature of the multimode plasmonic resonances generated by the devices and allow for a better understanding of the enhancements in multispectral refractive index and SERS-based sensing. Taken together, these results demonstrate a robust and potentially useful new platform for chemical/spectroscopic sensing.

Sign in / Sign up

Export Citation Format

Share Document