Sensors that sniff out chemicals in the air to warn us about everything from fires to carbon monoxide to drunk drivers to explosive devices hidden in luggage have improved so much that they can even detect diseases on a person’s breath. Researchers from Drexel University and the Korea Advanced Institute of Science and Technology have made a discovery that could make our best “chemical noses” even more sensitive.
The team describes how a two-dimensional, metallic material called MXene can be used as a highly sensitive detector of gaseous chemicals. Their paper suggests that MXene can pick up chemicals, such as ammonia and acetone, which are indicators of ulcers and diabetes, in much lower traces than sensors currently being used in medical diagnostics.
The key to its excellent scent-sleuthing capabilities is that MXene is both highly conductive and undergoes a measurable change of electrical conductivity in the presence of the chemical it’s designed to detect — and only when that particular chemical is present.
This discernment is called signal-to-noise ratio in the world of chemical sensors and it is used to rank the quality of sensors — picking up more signal and less noise is the goal. The ones in use today, mostly in medical settings to detect chemicals like acetone, ethanol, and propanol, or in breathalyzers to detect alcohol, have a signal-to-noise ratio between 3 and 10 — MXene’s is between 170 and 350, depending on the chemical.
This level of sensitivity could be extremely important for detection of disease. In addition to ulcers and diabetes, breath analysis is currently being developed for early diagnosis of multiple types of cancer, cirrhosis, multiple sclerosis, and kidney disease. If the chemical indicators for these diseases can be spotted in lower concentrations, they are more likely to be diagnosed and treated at earlier stages.
MXene’s advantage over conventional sensor materials lies in its porous structure and chemical composition. The material is good at both allowing gas molecules to move across its surface, and snagging, or adsorbing, certain ones that are chemically attracted to it, showing good selectivity.
The researchers believe that in the future, MXene sensors could play an important role in environmental monitoring, energy harvesting and storage, as well as health care.