(Invited) Microenvironment Responsiveness of Defect Photoluminescence of Locally Functionalized Single-Walled Carbon Nanotubes and Its Sensing Applications

Abstract

Photoluminescence (PL) of single-walled carbon nanotubes (SWCNTs) in the near infrared (NIR) region is applicable to advanced optical applications such as bio-imaging and sensing. Local chemical functionalization (slight amount of chemical modification) of SWCNTs has been developed to introduce sp3 carbon defects in the sp2 carbon network of the tube walls for the luminescent defect formation.[1-3] The resultant locally functionalized SWCNTs (lf-SWCNTs) show defect PL (E 11* PL) with red-shifted wavelengths and increased quantum yields compared to original E 11 PL of pristine SWCNTs. For lf-SWCNTs, molecularly designed modifier molecules have enabled the defect PL wavelength modulation[4] and the sensing function creation.[5,6]Recently, we have reported the unique microenvironment responsiveness of defect PL of lf-SWCNTs; namely, the greater wavelength shifts of E 11* PL than E 11 PL by dielectric effects[7] and the PL shifting behavior modulation based on the chemical structure difference of the functionalized sites and the exciton localization effects[8] were observed. The microenvironment responsiveness of the defect PL was applied to the biological sensing application development.[9] To investigate protein detection/recognition functions of lf-SWCNTs, we introduced an avidin-biotin interaction with a selective and strong binding fashion at the functionalized sites of lf-SWCNTs. The lf-SWCNTs tethering biotin groups (lf-SWCNTs-b) were synthesized through diazonium chemistry, followed by its subsequent-modification. When neutravidin was mixed with a lf-SWCNTs-b solution, E 11* PL peak was red-shifted, indicating the higher polarity environment formation by the neutravidin adsorption on lf-SWCNTs-b. When avidin or streptavidin was used, wavelength shifting behaviors of E 11* PL of lf-SWCNTs-b were clearly changed depending on the used avidin derivatives. The results indicate the different polarity environment formation deriving from structural differences of each avidin derivative. Moreover, the detection signal enhancement was observed in a film device using lf-SWCNTs-b. Therefore, lf-SWCNTs have a high potential for development of advanced protein detection/recognition systems using NIR PL.[1] T. Shiraki et al. Acc. Chem. Res., 53, 1846 (2020). [2] S. Tretiak et al., Acc. Chem. Res., 53, 1791(2020) [3] Y. Wang et al. Nat. Rev. Chem., 3, 375 (2019). [4] T. Shiraki et al. ACS Nano, DOI: 10.1021/acsnano.2c09897 (2022). [5] T. Shiraki et al. Chem. Commun., 52, 12972 (2016). [6] S. Kruss et al, Angew. Chem. Int. Ed., 59, 17732 (2020). [7] T. Shiraki et al. Chem. Commun., 55, 3662 (2019). [8] T. Shiraki et al. J. Phys. Chem. C, 125, 12758 (2021). [9] T. Shiraki et al. Nanoscale, 14, 13090 (2022). Figure 1