Controllable optical activity of non-spherical Ag and Co SERS substrate with different magnetic field**Project supported by the Key Science and Technology Research Project of Henan Province, China (Grant No. 162102210164), the Natural Science Foundation of Henan Educational Committee, China (Grant No. 17A140002), the National Natural Science Foundations of China (Grant Nos. 11574276, 11404291, and 11604079), and the Program for Science

Abstract

We experimentally fabricate a non-spherical Ag and Co surface-enhanced Raman scattering (SERS) substrate, which not only retains the metallic plasmon resonant effect, but also possesses the magnetic field controllable characteristics. Raman detections are carried out with the test crystal violet (CV) and rhodamine 6G (R6G) molecules with the initiation of different magnitudes of external magnetic field. Experimental results indicate that our prepared substrate shows a higher SERS activity and magnetic controllability, where non-spherical Ag nanoparticles are driven to aggregate effectively by the magnetized Co and plenty of hot-spots are built around the metallic Ag nanoparticles, thereby leading to the enhancement of local electromagnetic field. Moreover, when the external magnetic field is increased, our prepared substrate demonstrates excellent SERS enhancement. With the 2500 Gs and 3500 Gs (1 Gs = 10−4 T) magnetic fields, SERS signal can also be obtained with the detection limit lowering down to 10−9 M. These results indicate that our proposed magnetic field controlled substrate enables us to freely achieve the enhanced and controllable SERS effect, which can be widely used in the optical sensing, single molecule detection and bio-medical applications.