Exhaled breath of cancer patients contains certain nonpolar volatile organic compounds (VOCs)
which are not present in the breath of a healthy person. An electronic nose composed of an array
of random network (RN) of carbon nanotube (CNT) sensors could in principle detect cancer from
breath, but the notoriously low sensitivity of CNT sensors to nonpolar VOCs limits their accuracy.
We have achieved a marked improvement of the RN-CNT chemiresistors' response to the nonpolar
VOCs found in the breath of lung cancer patients by functionalizing them with different types of
nonpolymeric organic films as well as discontinuous films composed of sponge-like wires of
hexaperi-hexabenzocoronene (HBC) molecules. By monitoring the changes in conductance, work
function and organic film thickness during exposure we show that the enhanced sensitivity of the
functionalized RN-CNTs to nonpolar cancer biomarkers stems from carrier scattering induced by
swelling of the organic film. Based on these findings, we show that an array of RN-CNT sensors
can discriminate between the VOCs found in the breath of patients with lung cancer and in healthy
controls. Hence, controlling the carrier scattering in RN-CNTs via deliberate functionalization
with suitable organic films could become an important factor in the design of sensors for nonpolar
VOCs, which have hitherto been difficult to trace. The results presented here are an important
step towards the development of a robust, cost effective electronic nose for sniffing out nonpolar
VOCs as biomarkers for cancer in patients' breath.
We show here that an array of random network of carbon nanotubes coated with non-polymeric organic materials and
conjugated with pattern recognition algorithms has a high potential for diagnosis of lung cancer via breath samples. The
results indicate that the sensors array allow excellent discrimination between the volatile organic compounds (VOCs)
found in the breath of patients with lung cancer, relative to healthy controls, especially if the sensors array is preceded
with either water extractor and/or pre-concentrator of VOCs.