Fig. 2: Quenching mechanism of TEMPO.
a Initiation and matter confining mechanism in MC-MPL. ET energy transfer, ISC inter-system crossing. b ESR spectra of DETC in dichloromethane after 10 min irradiation by a 365 nm light, in which N-tert-Butyl-α-phenylnitrone (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) are employed as trapping agents. The hyperfine coupling constants of the PBN-based radical adduct are αN = 13.6 G and αH = 1.8 G, suggesting the generation of C-centered radicals. The ESR spectra of the DMPO-based radical adduct imply the formation of N-centered cation radicals. c ESR spectra of TEMPO (0.2 mM) and TEMPO (0.2 mM) + DETC (1 mM) in dichloromethane before UV irradiation and after UV irradiation (placed in the dark for 0, 20 or 60 min). The irradiation duration is 10 min by a 365 nm light. d The fluorescence emission spectra (λex = 263 nm) of the photoresists (DETC) with different concentrations (0–40 mM) of TEMPO. The concentration of TEMPO in Pr2 is about 40 mM. e Typical Stern–Volmer plots,\(\frac{{I}_{0}}{I}=1+{K}_{{{\rm {SV}}}}Q\), for the quenching process of DETC by TEMPO in the photoresist, where I0 and I is the fluorescence intensity in the presence and absence of quenchers, Q is the concentration of quenchers. f Fluorescence decays spectra of the photoresists (DETC) with different concentrations (0–40 mM) of TEMPO. g The Stern–Volmer plots of fluorescence lifetime for the quenching process of DETC by TEMPO in photoresist, where τ0 and τ is the fluorescence lifetime in the presence and absence of quenchers.
