Chemical Detection in Water by Single-Walled Carbon Nanotubes-Based Optical Fiber Sensors

In this letter, the possibility to use single-walled carbon nanotubes (SWCNTs) as sensitive nanostructured material for the development of an optoelectronic sensor that can perform chemical detection in water has been investigated and demonstrated for the first time. The fabricated sensor has been employed in a reflectometric system involving single wavelength reflectance measurements. The good stability of the steady-state signal, the high sensitivity, as well as the good response dynamics obtained in the case of toluene detection confirm the potentiality of SWCNTs to be employed in a water environment.

I. Introduction

Carbon nanotubes have been studied intensively due to their importance as building blocks in nanotechnology. A number of chemical sensors based on carbon nanotubes have been proposed in the recent years, especially for Volatile Organic Compound (VOC), , , and detection in gaseous environments [1]. The main drawback in using such materials is that due to their low selectivity against given chemical species, no straightforward information about the analytes present in the test environment is achievable in case of a multicomponent gas mixture. However, the use of pattern recognition methods is very useful in these cases, where the correlation between data obtained by complementary transducers is used to enhance the discrimination capability of the whole hybrid system. Single-Walled Carbon Nanotubes (SWCNTs) have already been exploited as highly sensitive materials by the authors for the development of high-performance VOC Silica Optical Fiber (SOF) sensors [2], [3]. In this work, for the first time (to our best knowledge), the excellent sensing properties of carbon nanotubes have been used for the detection of chemical pollutants in aqueous environments at room temperature. As matter of fact, experimental results reveal the stability of the SWCNTs film within the aqueous environment as well as the capability of SWCNTs-based SOF sensors to detect low concentrations of toluene in water.