Fabrication of carbon-nanotube-based sensor array and interference study

Abstract

An array of 32 sensor elements with single-walled carbon nanotubes (SWCNTs) as the sensing medium has been fabricated. The microfabrication approach used allows reduction of the chip size and increases the number of sensor elements in a chip and is amenable for large wafer scale-up. The sensor array chip is designed as an electronic nose for use with the aid of a pattern recognition algorithm. The sensor chips were tested for NO 2 sensing and interfering effects from humidity and a background of chlorine. The results indicate that NO 2 can be detected at low concentration levels of 0.5 ppm in the presence of chlorine at 30 times higher concentrations. The sensor response is affected by humidity, which implies that the training data set for NO 2 detection needs to be generated for multiple humidity levels for interpolation purposes during field use.

Toward Highly Sensitive and Energy Efficient Ammonia Gas Detection with Modified Single-Walled Carbon Nanotubes at Room Temperature

“…This way an ultrasensitive device able to reliably detect ammonia in the whole ppb range of concentrations can be fabricated. This makes the SWCNT based ammonia sensors attractive as components of a single-chip sensor array for the analysis of gas mixtures with a little fraction of ammonia. Such arrays can be potentially used for noninvasive and fast medical diagnostics such as exhaled gas mapping that can be employed for the detection of particular disease fingerprints (liver cirrhosis, kidney failure, or diseases caused by Helicobacter pylori ).…”

A carbon nanotube based ammonia sensor on cellulose paper

“…Several mechanisms have been suggested to understand the humidity effect in CNT-based sensors including electron donation, bonding of hydrogen with the oxygen defects, and direct H 2 O adsoption. 15,24 The cross sensitivity with the analyte of NH 3 and background humidity can be even more complex. Calibration curves produced in Fig.…”

“…change in resistance due to humidity) may not be linear as seen in the case of NO 2 . 24 In order to investigate the impact of relative humidity, the NH 3 responses of the layer-bylayer structures were measured under three additional relative humidity levels as shown in Fig. 5.…”

A Sensor Array for the Detection and Discrimination of Methane and Other Environmental Pollutant Gases

“…Sensor technologies suitable for deploying in real world applications require additional features such as ruggedness, reliability, long term stability, sensor refreshing protocols and understanding and accounting for the environmental impact [ 10 ]. For example, we have previously considered the effect of humidity as an interferant in NO 2 sensing [ 52 ] and found that it affects the sensor response requiring response curves of the type in Figure 1 and calibration curves to be generated for multiple humidity levels for later field use in interpolation and PCA. The demonstration in this work represents additional steps towards realizing the potential of long investigated CNT based sensors for gas/vapor detection.…”