Rigved Epur

Gold-coated carbon nanotube electrode arrays: Immunosensors for impedimetric detection of bone biomarkers

C-terminal telopeptide (cTx), a fragment generated during collagen degradation, is a key biomarker of bone resorption during the bone remodeling process. The presence of varying levels of cTx in the bloodstream can hence be indicative of abnormal bone metabolism. This study focuses on the development of an immunosensor utilizing carbon nanotube (CNT) electrodes coated with gold nanoparticles for the detection of cTx, which could ultimately lead to the development of an inexpensive and rapid point-of-care (POC) tool for bone metabolism detection and prognostics. Electrochemical impedance spectroscopy (EIS) was implemented to monitor and detect the antigen-antibody binding events occurring on the surface of the gold-deposited CNT electrode. Type I cTx was used as the model protein to test the developed sensor. The sensor was accordingly characterized at various stages of development for evaluation of the optimal sensor performance. The biosensor could detect cTx levels as low as 0.05 ng/mL. The feasibility of the sensor for point-of-care (POC) applications was further demonstrated by determining the single frequency showing maximum changes in impedance, which was determined to be 18.75 Hz.

A simple and scalable approach to hollow silicon nanotube (h-SiNT) anode architectures of superior electrochemical stability and reversible capacity

Strain engineered unique architectures of silicon nanotubes have garnered tremendous attention as high capacity and stable lithium-ion battery (LIB) anodes. However, the expensive nature of the hitherto synthesis techniques used to produce the silicon nanotubes combined with the inferior yield and poor loading densities have rendered these unique morphologies unattractive for commercial LIB systems. In this study, we report for the first time, a simple, facile, and more importantly, recyclable sacrificial template based approach involving magnesium oxide (MgO) nanorods for producing scalable quantities of hollow silicon nanotubes (h-SiNTs) architectures. Electrodes fabricated from these h-SiNTs derived from this novel scalable approach exhibit equitable loadings and reversible capacities in excess of 1000 mA h g−1 at a high current density of 2 A g−1 for nearly 400 cycles, combined with a very low fade rate of only 0.067% loss per cycle. The high capacity, good current rate characteristics combined with excellent charge-transfer kinetics as well as the long cycle life of these engineered h-SiNTs render this approach viable for industry scale while also boding promise for practical applications.

Ferrocene and Inconel assisted growth of dense carbon nanotube forests on copper foils

Aligned growth of carbon nanotubes on copper substrates has been achieved using a nickel-based catalyst, Inconel, which is first deposited on the copper foil substrate before the growth of nanotubes via thermal chemical vapor deposition (CVD). An additional catalyst, iron, is supplied by mixing ferrocene with the carbon feedstock, xylene, during the CVD growth. For specific ranges of the film thickness, 10–12 nm, and under certain growth conditions, dense, aligned growth of carbon nanotubes is observed. This technique represents a relatively simple process for direct growth of carbon nanotubes on copper substrates without the need for additional barrier layers and plasma-enhanced CVD techniques. Scanning electron microscopy was used to qualitatively evaluate the density of the nanotubes and the tendency to align in a direction perpendicular to the substrates. Transmission electron microscopy and Raman spectroscopy were used to examine the structure and quality of the nanotubes, as well as the composition ...

Growth of Carbon Nanotubes on Copper Substrates Using a Nickel Thin Film Catalyst

Carbon nanotubes with their attractive properties, one-dimensional geometry, and their large aspect ratio are ideal candidates for a variety of applications including energy storage, sensing, nanoelectronics, among others. We have studied the growth of carbon nanotubes on copper substrates using a nickel thin film as a catalyst. The catalyst was sputtered in a chamber with a base pressure in the ultra-high-vacuum regime. By adjusting the sputtering parameters, the effects of the morphology and the thickness of the nickel catalyst on the growth of carbon nanotubes have also been investigated. Multiple hydrocarbon sources as carbon feedstock (methane, acetylene and m-xylene), corresponding catalyst precursors and varying temperature conditions were used during chemical vapor deposition (CVD) process to understand and determine the best conditions for growth of carbon nanotubes on copper. Correlation between the thickness of the thin film nickel catalyst and the carbon nanotube diameter is also presented in the study. Characterization techniques used to study the morphology of the CNTs grown on copper include SEM, TEM, HRTEM, Raman Spectroscopy. Results of these studies are outlined and discussed.