Yan Yueming, Spear Nathan J, Cummings Adam J, Khusainova Karina, Macdonald Janet E, Haglund Richard F
Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 USA.
Vanderbilt Institute of Nanoscale Science and Engineering, Vanderbilt University, Nashville, TN 37235, USA.
Sci Adv. 2025 Jun 6;11(23):eadv1822. doi: 10.1126/sciadv.adv1822. Epub 2025 Jun 4.
Heterostructures combining two or more metal and/or semiconductor nanoparticles exhibit enhanced upconversion arising from localized nanoparticle resonances. However, plasmon-exciton coupling in semiconductor-metal nanostructures exhibits nanosecond relaxation times, and multi-plasmon metallic heterostructures are not broadly tunable. Here, we develop a biplasmonic heterostructure in which CuS and Au nanoparticle layers, separated by an alumina spacer of variable thickness, exhibit enhanced second- and third-harmonic generation due to dipole-dipole coupling between Au and CuS plasmons, as seen in the characteristic inverse sixth-power dependence of their separation in the measured harmonic enhancement and confirmed by numerical simulations of near-field CuS-Au nanoparticle coupling. Transient-absorption spectroscopy shows faster relaxation in Au/CuS (690 femtoseconds) compared to CuS heterostructures (929 femtoseconds). Moreover, nonlinear absorption measurements provide evidence for harmonic-induced plasmonic resonant energy transfer between the narrow Au and broad, tunable CuS plasmon resonances. This prototype for ultrafast upconversion showcases a strategy for high-efficiency, tunable plasmonic nonlinear devices with promising applications in photocatalysis, parametric down-conversion, and biomedical imaging.
结合两种或更多种金属和/或半导体纳米颗粒的异质结构，由于局部纳米颗粒共振而表现出增强的上转换。然而，半导体-金属纳米结构中的等离子体激元-激子耦合表现出纳秒级的弛豫时间，并且多等离子体金属异质结构的可调谐性不强。在这里，我们开发了一种双等离子体异质结构，其中由可变厚度的氧化铝间隔层隔开的硫化铜（CuS）和金纳米颗粒层，由于金和硫化铜等离子体之间的偶极-偶极耦合，表现出增强的二次和三次谐波产生，这在测量的谐波增强中其间隔的特征性六次方反比关系中可见，并通过近场硫化铜-金纳米颗粒耦合的数值模拟得到证实。瞬态吸收光谱表明，与硫化铜异质结构（929飞秒）相比，金/硫化铜结构中的弛豫更快（690飞秒）。此外，非线性吸收测量为窄金等离子体和宽可调谐硫化铜等离子体共振之间的谐波诱导等离子体共振能量转移提供了证据。这种用于超快上转换的原型展示了一种用于高效、可调谐等离子体非线性器件的策略，在光催化、参量下转换和生物医学成像方面具有广阔的应用前景。
