Multidimensional Ultrasensitive Whey-Protein Sensor Based on Graphene Composite Metal Metamaterial

Protein is an essential substance for human growth and development. Here, a graphene composite metal metamaterial sensor (GM) for multidimensional ultrasensitive detection of whey protein is presented. Its terahertz (THz) transmission spectrum features a transparent peak at a frequency of 1.14 THz due to hybridization. The amplitude of this peak shows obvious change with the increasing whey-protein concentration. Based on the change in amplitude of the resonant peak, solutions with trace amounts of 207 fg/mL can be detected. In addition, the dimension of phase difference (PD) is introduced. PD curves exhibit quasi-linear characteristics against frequency at all concentrations. The slope of PD curves combining with the peak amplitude can detect the concentration of the analyte quantitatively. More interestingly, plant and whey proteins are distinguished successfully using hexagonal radar maps of amplitude variation and the slope of PD curves at different polarization angles. This device provides a research prospect for the detection of proteins using a THz biosensor.