Move over, graphene. An atomically thin, two-dimensional, ultrasensitive semiconductor material for biosensing developed by researchers at UC Santa Barbara promises to push the boundaries of biosensing technology in many fields, from health care to environmental protection to forensic industries.
Based on molybdenum disulfide or molybdenite (MoS2), the biosensor material—used commonly as a dry lubricant—surpasses graphene's already high sensitivity, offers better scalability and lends itself to high-volume manufacturing. Results of the researchers' study have been published in ACS Nano.
"This invention has established the foundation for a new generation of ultrasensitive and low-cost biosensors that can eventually allow single-molecule detection—the holy grail of diagnostics and bioengineering research," said Samir Mitragotri, co-author and professor of chemical engineering and director of the Center for Bioengineering at UCSB. "Detection and diagnostics are a key area of bioengineering research at UCSB and this study represents an excellent example of UCSB’s multifaceted competencies in this exciting field."
The key, according to UCSB professor of electrical and computer engineering Kaustav Banerjee, who led this research, is MoS2’s band gap, the characteristic of a material that determines its electrical conductivity.
Semiconductor materials have a small but nonzero band gap and can be switched between conductive and insulated states controllably. The larger the band gap, the better its ability to switch states and to insulate leakage current in an insulated state. MoS2’s wide band gap allows current to travel but also prevents leakage and results in more sensitive and accurate readings.
While graphene has attracted wide interest as a biosensor due to its two-dimensional nature that allows excellent electrostatic control of the transistor channel by the gate, and high surface-to-volume ratio, the sensitivity of a graphene field-effect transistor (FET) biosensor is fundamentally restricted by the zero band gap of graphene that results in increased leakage current, leading to reduced sensitivity, explained Banerjee, who is also the director of the Nanoelectronics Research Lab at UCSB.