Afterglow-Assistant Surface-Enhanced Raman Scattering on Cr3+:ZnGa2O4@Au

Surface-enhanced Raman scattering (SERS) has been widely investigated in recent years. The subtle design and synthesis of SERS substrates, including the semiconductor–metal composites, are the key but difficult points. To date, only the short-lived semiconductors are involved, and no research has been conducted concerning the long-lived ones although the persistent luminescence semiconductors have great potential of charge transfer in relatively long durations. Herein, we present a concept of afterglow-assistant SERS (AASERS) on the long-lived gold shell-capped Cr3+-doped ZnGa2O4 (CZGO@Au) substrate. The normal SERS, AASERS acquired immediately after 2 min illuminating of a 633 nm laser, AA-1 min SERS acquired 1 min after 2 min illuminating of a 633 nm of the typical analytes on CZGO@Au, ZnGa2O4@Au (ZGO@Au), and gold nanostars (GNSs) with the same UV–vis absorption wavelength are systematically compared. The CZGO@Au owns the SERS signals that are 1.8 times of ZGO@Au and 3.4 times of GNSs. A higher AASERS than the corresponding SERS (1.65 times) is only observed on CZGO@Au, and the AASERS on CZGO@Au is 2.8 times of that on ZGO@Au and 5.2 times of that on GNSs. Because of the afterglow decay of CZGO@Au, the AA-1 min SERS on CZGO@Au returns to its SERS. These data demonstrate that the AASERS on long-lived substrates is a promising way for further enhancing SERS signals just by laser illuminating the substrates, and thus affords alternatives for reducing the difficulties in the complicated synthesis of the exquisite substrates. The AASERS mechanism and the application of CZGO@Au in SERS imaging of living U87MG cells are also discussed.