UC Santa Barbara researchers recently engineered a 2-D next-generation field-effect transistor (FET) biosensor using molybdenum disulfide (MoS2), a compound 75 times more sensitive than graphene in detecting single molecules.
Flexible and transparent, molybdenum disulfide — whose mineral ore is molybdenite — holds potential use as a diagnostic tool in point-of-care analyses of disease. It is a highly effective detecting apparatus, essentially providing greater breadth and sensitivity in detecting pH levels in cells.
FET biosensors are devices that can detect any molecule with a charge by using an electric field to directly translate interactions of a target molecule on a semiconductor material. They are applied frequently in biomedical, security and environmental fields. Examples include glucose-level biosensors and sensors used by miners to detect toxic gas levels.
Kaustav Banerjee, a professor of electrical and chemical engineering and principle investigator of the research, said that designing biosensors requires high sensitivity to a molecule’s charge.
“When you try to design a biosensor, it is essentially reading off the charge to these bio-molecules,” Banerjee said. “You will not be able to get as high sensitivity (with graphene) as the other material (molybdenite).”
Generally separated into two categories, 1-D FET biosensors include silicon and carbon nanotubes, while 2-D sensors often contain graphene. Yet 1-D materials are difficult to fabricate and most 2-D FET tools are not supersensitive.
Until now, graphene has been a key material in biosensors despite its flaws. These include a lack of a band gap in the biosensor, which creates a level of low conductivity, and the high cost of production.
Banerjee said that semi-conductive capabilities and prominent band gap of molybdenite convinced his team of its incredible abilities even before they began experiments.
“We actually knew right away, even without doing the experiments, that we could use molybdenite for bio-sensing. It would actually be a superior material compared to graphene because graphene does not have a band gap,” Banerjee said. “Because graphene has a zero band gap, it will keep leaking a charge and will give you a leakage charge even when it is off.
Not only does molybdenite’s large band gap make it a more cost-effective choice as a biosensor, but it is also provides more precise readings.
According to Deblina Sarkar , a Ph.D. student working with Banerjee, the new biosensor may soon be used for early detection of cancer.
“They are not only good for electronics and computer chips, but they could also have a great indication in the biological area,” Sarkar said. “Biosensors are very important in our daily life because if anyone has a certain disease, we can use biosensors to detect an increase in bio-molecules faster — to detect, for example, a type of cancer.”
Banerjee believes FET biomaterials will play an essential role in the molecular sensing world, noting that molybdenite will soon be the key material used in this field.
“Many other groups around the world are also trying to do the same with molybdenite and I believe in the next few years people will be working with this material in bio-sensing.”
If Banerjee’s predictions prove true, scientists can hope to see more of these new-era biosensors in the near future. To access more information on the researcher’s findings, their paper “MoS2 Field-Effect Transistor for Next-Generation Label-Free Biosensors” is available online in ACS Nano.
This story appeared on page 13 of Thursday, September 25, 2014’s print edition of the Daily Nexus.