Electromagnetic resonance analysis of asymmetric carbon nanotube dimers for sensing applications

Abstract

In this work, we study the electromagnetic scattering characteristics of asymmetric carbon nanotube (CNT) dimers with rigorous computational experiments. We show that the configurational asymmetry in the CNT dimer assembly creates a unique field distribution in the vicinity of the dimer, which in turn generates two distinct resonances representing the bonding and anti-bonding modes. The sensitivity of these two modes towards CNT lengths, orientations, and shapes, is studied. We also show the ability of asymmetric CNT dimer for the contactless detection of nanoparticles (NP). The presence of a NP in the vicinity of the CNT dimer perturbs the dimer’s field distribution and causes unequal shifts in the bonding and anti-bonding resonances depending on the NP location, material, size and shape. By studying the differences in these resonance shifts, we show that the relative location and orientation of the NP can be reconstructed. The computational experiments performed in this work have the potential to guide the use of asymmetric CNT dimers for novel sensing applications.

SARS-CoV-2 Detection Using Colorimetric Plasmonic Sensors: A Proof-of-Concept Computational Study

“…For example, gold nanorods are asymmetric which causes them to exhibit both longitudinal and/or transverse resonances based on their orientation [6], [8]. Therefore, the orientation of each gold nanorod on the surface of the virus needs to be varied to follow what happens in This randomness in orientation might enhance the bandwidth of the broadband absorption similar to what was reported in other kinds of nanostructures [35], [36]. Finally, for gold nanorods, the surface area and the aspect ratio play a significant role in their optical characteristics [6], [8].…”

Method of Moment Analysis of Carbon Nanotubes Embedded in A Lossy Dielectric Slab Using A Multilayer Dyadic Green’s Function

“…To evaluate the scattered electric fields we first need to evaluate the DGFs present in integrals ( 12) and (13). For planar stratified media, the DGFs are laterally invariant and thus while deriving G xx (R,R ) and G zz (R,R ) in layer 2 we consider the source point located atR (x = 0, y = 0, z ), and choose an arbitrary observation pointR(x, y, z).…”

“…To satisfy the ATW condition with reasonable accuracy, the discretization should be optimized. At least 20 segments per wavelength is desired, but individual segment length should not fall below twice the diameter of the CNT [13], [16]. This sets an upper and lower limit on the choice of segment number (S), (31) 20 l λ < S < l 4 r cnt Substituting (30) into (1) results in a matrix equation as given below that needs to be solved for each operating frequency [31],…”

“…The total axial current (Ī cnt ) flowing in the CNT is determined by solving the matrix equation (32). Once the current is solved, we can finally calculate the total extinction power (P ext ), absorbed power (P abs ), and scattered power (P scat ) for the embedded CNTs following the given relations [13], (33a)…”

Method of Moment Analysis of Carbon Nanotubes Embedded in a Lossy Dielectric Slab Using a Multilayer Dyadic Green’s Function

“…Several factors control the electromagnetic response of CNT composites, such as the spatial distribution of CNTs [8]- [10], CNT volume fraction [11], average length of embedded CNTs [12], [13], interaction among CNTs [13], [14], conductivity of CNTs (single wall/multi wall) [11], [15], waviness of CNTs (nearly straight to highly crumpled) [16], [17], CNT interaction with matrix, matrix properties, and dimensions [18], [19]. Thus, finding an efficient method capable of accurately quantifying the interactions among CNTs, interactions of CNTs with the embedding layers, and with the incident electromagnetic excitation is critical for understanding and optimizing the electromagnet response of CNT reinforced composites.…”