Surface-enhanced Raman scattering (SERS) nanotags have garnered much attention for in vivo and intraoperative imaging due to their high sensitivity and intrinsic fingerprint spectrum. Recently, in vivo bioimaging at the second biological near-infrared (NIR-II) window has demonstrated significant advances with better spatial resolution and deeper tissue penetration. The development of SERS nanotags at the NIR-II window are therefore highly desired. The resonant strategy, i.e., the use of resonant substrates and resonant molecules, can be helpful in fabricating bright SERS nanotags at the NIR-II window; however, this strategy has not been demonstrated with the lack of quantitative assessments. Here we report a quantitative study on the Raman enhancements of the resonant strategy in preparing NIR-II SERS nanotags. By comparing the resonant and nonresonant plasmonic nanorod substrates, the resonant substrates have been shown to provide an enhancement factor of up to 4 orders of magnitude. When using the resonant Raman reporter molecules, SERS intensities can be further increased by 25–546 times. This work demonstrates the potential of the resonant strategy in fabricating ultrasensitive NIR-II SERS nanotags and provides insights into the design of related plasmonic devices.
Huanhuan Li,Chang Liu,Xin Wang,Jiangchao Wang,Ping Li,Gaozhan Xie,Yunbo Jiang,Runfeng Chen,Ye Tao
Developing high-performance host materials is one of the biggest challenges for blue and white thermally activated delayed-fluorescence (TADF) organic light-emitting diode (OLED) technology due to the rigorous requirements of both efficient carrier flux ability and high triplet energy (ET) levels in static donor–acceptor molecules. Here, with the aid of a dual-resonance strategy, a host molecule showing dynamic adaption features in the acceptor–resonance–donor–resonance–acceptor (A–r–D–r–A) molecular configuration has been successfully developed through the implantation of two acceptors of diphenylphosphine oxide into electron-donating 5,10-dihydrophenazine with N–P═O resonance linkages. Owing to the dual enantiotropic N+═P–O– resonances, the designed A–r–D–r–A molecule exhibits an extraordinarily balanced charge flux transportation attribute at high ET (2.96 eV). Excitingly, blue and warm-white TADF OLEDs hosted by the A–r–D–r–A molecule exhibit outstanding external quantum efficiencies of 14.7 and 20.3%, respectively. Our studies not only broaden the scope of resonance molecules but also indicate that a resonance structure is an effective linkage to develop optoelectronic materials with dynamically adaptive properties.
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