Plasmon-Assisted Activation and Grafting by Iodonium Salt: Functionalization of Optical Fiber Surface

In this paper, the utilization of plasmon-induced cleavage of CI bond in the structure of iodonium salt followed by grafting of organic radicals to Au surface is proposed. The plasmon is excited by the coupling of Au-covered optical fiber with the laser light source, with wavelength corresponding to the plasmon absorption band, and immersion of fiber in the solution of iodonium salt. Grafting procedure is monitored through the shift of surface plasmon resonanse (SPR) position during the laser light transmission. Further verifications are performed using the surface enhanced Raman spectroscopy (SERS) and scanning electron microscopy and energy-dispersive X-ray spectroscopy methods. Only in the case of coincidence of coupled laser emission and initial SPR absorption band wavelengths efficient activation of diaryliodonium salt (IS) is observed. With the aim to introduce hydrophobic and repellent surface properties the di-[3,5-bis(trifluoromethyl)phenyl]iodonium tetrafluoroborate salt is used. Surface functionality is further tested using the wettability and antifouling test. Proposed method for the first time utilizes the plasmonic phenomenon as an effective tool for initiating the iodonium salt heterophase reaction and can be considered as extremely effective approach in the case of surface activation, in terms of energy and materials harvesting.