Tahir Iqbal

Reinforcement of high performance polystyrene/polyamide/polythiophene with multi-walled carbon nanotube obtained through various routes

In this endeavor, four simple methods (ball milling (BM), high temperature graphite (HG), graphene oxide (GO), and simple chemical (SC) route) were employed for the preparation of multi-walled carbon nanotube (MWCNT). These methods involved the in situ alteration of graphite to carbon nanotubes. Structure of MWCNTBM, MWCNTHG, MWCNTGO, and MWCNTSC was confirmed using transmission electron microscopy and X-ray diffraction. A triply blended material consisting of polystyrene, polyamide, and polythiophene (PS/PA/PTh) was used as matrix. According to field emission scanning electron microscopy, curled polymer-coated nanotubes were seemed to be dispersed in PS/PA/PTh matrix. The composites decompose in a single-step beginning around 320–360 °C. Maximum decomposition temperature of PS/PA/PTh/MWCNTHG composites (HG route) was found higher in the range of 415–439 °C. The electrical conductivity of PS/PA/PTh/MWCNT was observed between 0.09 and 0.15 Scm−1. Among all the composites prepared, PS/PA/PTh/MWCNTHG 0.3 showed higher electrical conductivity of 0.15 Scm−1. Better thermal and electrical profile for PS/PA/PTh/MWCNTHG series depicted the success of HG route.

Plasmonic Bandgap in 1D Metallic Nanostructured Devices

This research work reports the excitation of surface plasmon polaritons (SPPs) in a 1D grating device in a gold film on glass substrate. Various grating structures have been modelled using finite element analysis (FEA) in comsol RF module. The periodicity in such devices remains constant, whereas slit width is changed for each structure. We have studied the effects of slit width on SPP resonances and formation of the plasmonic bandgap. The trend shows that bandgap energy increases with increasing slit width and reaches a maximum value for slit width nearly equal to half of the periodicity in the grating structure and then decreases which is a new and important observation. The possible reason for this optimum value of the slit width corresponds to the absence of higher plasmonic modes and the sinusoidal nature of the slit.

Plasmonic Band Gap: Role of the Slit Width in 1D Metallic Grating on Higher Refractive Index Substrate

This paper reports the excitation of surface plasmon polaritons (SPPs) and associated plasmonic band gap (PBG) while using TM plane wave interacting with 1D metallic grating on higher refractive index GaP substrate. A simple method is introduced to estimate the PBG which is crucial for many plasmonic devices. The PBG is estimated by measuring the transmission spectra obtained through the plasmonic grating structures when slit width is varied while periodicity and the thickness of the gold (Au) film remained fixed. The PBG is observed for the grating devices whose slit width is less than one third of the periodicity which is caused by the presence of a higher plasmonic mode. The PBG is absent for the grating device whose slit width is slightly less than half and greater than one third of the periodicity. Such grating devices support only a fundamental plasmonic mode because the profile/shape of the slit in the grating device is more like a sinusoidal nature. Furthermore, such grating offers intermediate scattering to the incident light and the SPP as well which in turn couple more incident energy to the SPPs. Far-field modelling results also support the results obtained through experiment.

Trends in Conducting Polymer and Hybrids of Conducting Polymer/Carbon Nanotube: A Review

ABSTRACT Several conducting polymers, including polyaniline, polypyrrole, polythiophene, polyvinylpyrrolidone, poly(3,4-ethylenedioxythiophene), poly(m-phenylenediamine), polynaphthylamine, poly(p-phenylene sulfide), and their carbon nanotube reinforced nanocomposites are discussed in this review. The physical, electrical, structural and thermal properties of polymers along with synthesis methods are discussed. A concise note on carbon nanotubes regarding their purification, functionalization, properties and production are reported. Moreover, the article focuses upon synthesis methods, properties and applications of conducting polymer/carbon nanotube nanocomposites are focused. Nanotube dispersion, loading concentration and alignment within conducting polymer/carbon nanotube nanocomposite affect their performance and morphology. The conducting polymer/carbon nanotube nanocomposites are substantially used in sensors, energy storage devices, supercapacitors, solar cells, EMI materials, diodes, and coatings. GRAPHICAL ABSTRACT

Non-universal behavior of leaky surface waves in a one dimensional asymmetric plasmonic grating

We report on a non-universal behavior of leaky surface plasmon waves on asymmetric (Si/Au/analyte of different height) 1D grating through numerical modelling. The occurrence of the leaky surface wave was maximized (suppressing the Fabry–Perot cavity mode), which can be identified in a reflection spectrum through characteristic minimum. Beyond a specific analyte height (h), new sets of surface waves emerge, each bearing a unique reflection minimum. Furthermore, all of these minima depicted a red-shift before saturating at higher h values. This saturation is found to be non-universal despite the close association with their origin (being leaky surface waves). This behavior is attributed to the fundamental nature and the origin of the each set. Additionally, all of the surface wave modes co-exit at relatively higher h values.

Clinical and molecular characteristics in three families with biallelic mutations in IGHMBP2

Biallelic mutations in IGHMBP2 cause spinal muscular atrophy with respiratory distress type 1 (SMARD1) or Charcot-Marie-Tooth type 2S (CMT2S). We report three families variably affected by IGHMBP2 mutations. Patient 1, an 8-year-old boy with two homozygous variants: c.2T>C and c.861C>G, was wheelchair bound due to sensorimotor axonal neuropathy and chronic respiratory failure. Patient 2 and his younger sister, Patient 3, had compound heterozygous variants: c.983_987delAAGAA and c.1478C>T. However, clinical phenotypes differed markedly as the elder with sensorimotor axonal neuropathy had still unaffected respiratory function at 4.5 years, whereas the younger presented as infantile spinal muscular atrophy and died from relentless respiratory failure at 11 months. Patient 4, a 6-year-old girl homozygous for IGHMBP2 c.449+1G>T documented to result in two aberrant transcripts, was wheelchair dependent due to axonal polyneuropathy. The clinical presentation in Patients 1 and 3 were consistent with SMARD1, whereas Patients 2 and 4 were in agreement with CMT2S.

Attributes of Polymer and Silica Nanoparticle Composites: A Review

ABSTRACT In this article, polymer microspheres and silica nanoparticles have been discussed as important filler in polymer composites. Their synthesis methods, properties, and application were particularly stressed. Silica is usually used as nucleating agent, surface enhancement mediator, and as templates and cores. Among polymer/silica composites, various categories including polyaniline, polypyrrole, polystyrene, epoxy, rubber, and acrylate polymer were discussed in detail. It was observed that silica nanoparticles enhanced mechanical strength and overall performance of composites. Furthermore, composites having carbon nanotube along with silica particles possess high electrical and mechanical performance. These composites are important in nanoelectronic devices, nanomedicines, and defense-related applications. GRAPHICAL ABSTRACT

Coupling Efficiency of Surface Plasmon Polaritons: Far- and Near-Field Analyses

The excitation of surface plasmon polaritons (SPPs) through one-dimentional (1D) metallic (Au) grating on higher refractive index -GaP substrate is investigated. Such grating devices find potential applications in real world, only if the coupling efficiency (η) of a free-space transverse-magnetic plane-wave into a SPPs mode is maximum. A simple and robust technique is used to estimate the η, by simply measuring the transmission through the grating while varying slit width (a) but period (Λ) and the thickness (t) remain fixed. When the wave vector (k0) of the incident light is matched to that of SPP, highest η is achieved. It is found that Λ/3 < a < Λ/2 yields a maximum η where the intermediate scattering couples more incident energy to SPPs. These gratings are designed in such a way that they support only the fundamental plasmonic mode yielding higher η. Scanning near-field optical measurements also confirm and corroborate the observations of far-field and near-field modeling (COMSOL multiphysics) results.

Structure, morphology, thermal, and electro-magnetic shielding properties of polystyrene microsphere/polyaniline/multi-walled carbon nanotube nanocomposite

In this work, polystyrene microspheres (PSMS) and PSMS-based polymer nanocomposites have been prepared. PSMS were first synthesized by dispersion polymerization of styrene monomer. The microsphere-coated-multi-walled carbon nanotube (PSMS/MWCNT) nanocomposite was prepared by incorporating MWCNT into PSMS matrix. Aniline monomer was then introduced by means of in situ oxidative polymerization (PANI) route to PSMS, MWCNT, and PSMS/MWCNT. Fourier transform infrared spectroscopy depicted the composite formation of PANI and MWCNT with PSMS matrix. PANI polymer was successfully polymerized in PSMS matrix and on carbon nanotube walls. According to scanning electron microscopy, all nanocomposites exhibited core-shell morphology. Glass transition temperature (Tg) of PSMS/PANI, PANI/MWCNT, and PSMS/PANI/MWCNT were found as 245℃, 287℃, and 289℃, while maximum decomposition temperature (Tmax) was 387℃, 575℃, and 580℃, respectively. Tetrahydrofuran was shown to be a suitable solvent for dispersing the nanocomposite. Toluene can also be used as suitable solvent for these nanocomposites. X-ray diffraction analysis depicted amorphous form of PSMS; however, PANI and MWCNT reduced the amorphous nature of the microspheres. PANI/MWCNT showed the highest crystallinity among all nanocomposites. Moreover, PSMS/PANI/MWCNT nanocomposite revealed electromagnetic interference shielding effectiveness of ∼23.2 dB.

Wet Chemical Co-precipitation Synthesis of Nickel Ferrite Nanoparticles and Their Characterization

In this study, wet chemical co-precipitation method was employed for the synthesis of pure and doped nickel ferrite nanoparticles at low temperature whereas the concentration of nickel varies from 2, 4, 6 and 8%. Optical absorption and transmission, Surface morphology, and structural properties of material are characterized by Fourier-transform infrared spectrometer, ultra-violet visible spectroscopy, scanning electron microscopy and powder X-ray diffraction respectively. It is observed that the transmission, size and band gap energy increases by increasing the amount of nickel. Red shift of the peaks is observed in the UV–visible spectra which is associated with the increase in size of the nickel ferrite. It can be used to fabricate devices intended to store data, for the classification of inorganic materials which plays a very important role in the different aspects of life due to their outstanding magnetic, electronic and optical properties.