A graphene oxide enhanced terahertz metamaterial for ultra-sensitive detection of D-aspartic acid solution

Trace biological solution detection is currently of great interest in the terahertz (THz) field. Graphene oxide (GO) is an amphiphilic graphene-like material with favorable biocompatibility, showing good potential applicability in THz liquid detection. In this work, a GO enhanced THz metamaterial liquid biosensor with a polyimide capillary as the microfluidic channel is proposed. The experimental results reveal that the capillary structure can avoid the large absorption of THz waves by controlling the amount of water. In the biosensor, GO is demonstrated to play an important role in enhancing the THz response, improving surface adsorption, and facilitating signal transmission. It is able to enhance the immobilization of D-Asp, which was confirmed by both Raman spectra and XRD scans, thus resulting in the structural changes of GO. The transmission amplitude variation of THz waves indicates that the electromagnetic response of GO varies with the adsorbed D-Asp concentration. The proposed biosensor achieves an ultra-low detection limit of 3 pg mL−1 and a maximum transmission change of about 12.5%. Thus, with their robust resistance to water interference and outstanding detection performance, the proposed biosensors show potential advantages for the expanded application of THz metamaterials in the ultra-sensitive detection of trace biological samples in liquid environments.