Photon-gated persistent spectral hole burning by electron transfer from a doped donor to an acceptor branched to a host polymer matrix

Abstract

Two-color photon-gated persistent spectral hole burning (PSHB) via donor-acceptor electron transfer is reported in systems where the acceptor, 10-chloroanthracene, was intentionally branched to a side chain of the poly(methylmethacrylate) (PMMA) host polymer while the donor, metal-free tetraphenylporphine, was dispersed in the polymer. The systems, which had an acceptor concentration of up to 10−1 M, were prepared without aggregation of the acceptor. Spectral holes were burnt in the Qx(0,0) absorption band of the donor when the systems were simultaneously irradiated with a frequency-selective excitation (duration: 500 ps; energy: 200 nJ/cm2) and a gating excitation (wavelength: 514.5 nm; duration: 33 ms; energy: 14 μJ/cm2). The difference absorption spectrum between the unburned absorption spectrum and one recorded after photon-gated PSHB has confirmed that the hole formation mechanism is donor-acceptor electron transfer from a photoexcited donor to a ground-state branched acceptor. The thermal stability of burnt holes measured with a temperature cycling experiment increased when the acceptor was branched into PMMA. The effect of acceptor branching on the PSHB characteristics is discussed with reference to those for an acceptor-doped system.