# Radially Aligned Carbon Nanotube Glass Fiber Composites as Ion-Selective Microelectrodes

## TL;DR

Researchers developed a new type of microelectrode using carbon nanotubes on glass fibers to detect ions more effectively and selectively.

## Contribution

The novel use of radially aligned carbon nanotube-glass fiber composites as a solid contact material for ion-selective microelectrodes is introduced.

## Key findings

- The μISE using RACNT-GF showed improved detection limits and selectivity for ammonium ions.
- The device's high surface area and durability enhance ionophore accommodation in the membrane.
- The μISE demonstrated potential for selective and sensitive ion detection with specific ionophores.

## Abstract

Detection of ions is challenging due to their small size,
rapid
diffusion, and high mobility, especially for assaying in samples of
low volumes. Among the traditional analytical methods, potentiometric
ion-selective electrodes (ISE) have become a popular choice for detecting
ions as they are cost-effective, user-friendly and can be miniaturized,
making them useful for on-site analysis. In this context, radially
aligned carbon nanotubes (RACNT) directly grown on glass fibers (GF)
via the chemical vapor deposition method is investigated as a solid
contact material for the fabrication of ion-selective microelectrodes
(μISE) upon incorporating specific ionophores within a polymeric
encapsulation membrane. As an illustration, sensitive detection of
ammonium ions is accomplished by the fabricated μISE (plasticized
PVC membrane containing nonactin ionophores), which yielded a LOD
and a linear response range between 7.5 × 10–6 and 1.0 × 10–5 to 1.0 × 10–1 M, respectively. The μISE fabricated with RACNT-GF as an interface
material exhibited improvements in LOD and enhanced the detection
selectivity as compared to a conventional ISE fabricated using planar
solid contact materials such as graphite. We hypothesize that the
fabricated μISE with a high surface area and mechanical durability
maximize the accommodation of ionophores in the barrier membrane for
yielding improved potentiometric responses. Experimental results illustrate
that the μISE possesses the potential to be utilized for the
fabrication of selective and sensitive ISE upon incorporation of specific
ionophores with RACNT-GF composites.