Ultrasensitive biosensors for probing protein structures could greatly improve the depth of diagnosis for a wide variety of diseases extending to both humans and animals. These include Alzheimer’s disease, Chronic Wasting Disease, and mad cow disease — disorders related to protein misfolding. Such biosensors could also lead to improved technologies for developing new pharmaceutical compounds.
Graphene, a material made of a single layer of carbon atoms, was discovered more than a decade ago. It has enthralled researchers with its range of amazing properties that have found uses in many new applications, including creating better sensors for detecting diseases. Significant attempts have been made to improve biosensors using graphene, but the challenge exists with its remarkable single-atom thickness. This means it does not interact efficiently with light when shined through it. Light absorption and conversion to local electric fields is essen tial for detecting small amounts of molecules when diagnosing diseases. Previous research utilizing similar graphene nanos-tructures has only demonstrated a light absorption rate of less than 10 percent.
Researchers have combined graphene with nano-sized metal ribbons of gold. Using sticky tape and a nanofabrication technique called “template stripping,” they were able to create an ultra-flat base layer surface for the graphene. The energy of light was then used to generate a sloshing motion of electrons in the graphene, called plasmons, which are like ripples or waves spreading through a sea of electrons. Similarly, these waves can build in intensity to giant tidal waves of local electric fields.
By shining light on the single-atom-thick graphene layer device, a plasmon wave was created with unprecedented efficiency at a near-perfect 94 percent light absorption into tidal waves of electric field. When protein molecules were inserted between the graphene and metal ribbons, enough energy was harnessed to view single layers of protein molecules.