Sun Mengqi, Fu Xiaoqi, Chen Kexun, Wang Hui
Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States.
School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013, China.
ACS Appl Mater Interfaces. 2020 Oct 14;12(41):46146-46161. doi: 10.1021/acsami.0c13420. Epub 2020 Sep 30.
Although the intriguing plasmonic properties of noble metal nanoparticles originate from the collective oscillations of free electrons in the conduction band, nanoparticles of doped semiconductors may also exhibit metal-like, plasmonic features that are dictated by the resonantly excited free hole oscillations in the valence band. Here, we combine Au, a representative free electron metal, with copper sulfides, a class of plasmonic -type semiconductors, in a core-shell nanoparticle geometry to construct dual-plasmonic hetero-nanostructures displaying unique multiplex optical characteristics dominated by plasmonic hole oscillations in the semiconductor shells, plasmonic electron oscillations in the metallic cores, and interband electronic transitions from the valence to conduction bands. Through deliberately designed colloidal synthesis, we are able to selectively grow nanoshells comprising copper sulfides of specifically targeted crystalline phases and Cu/S stoichiometries, such as covellite (CuS), digenite (CuS), and nonstoichiometric CuS, on the surfaces of Au nanoparticle cores. Our synthetic approach enables us not only to finely control the core and shell dimensions but also to systematically adjust the free hole concentrations in the semiconductor shells, which forms the keystone for the fine tuning of multiple optical resonance modes supported by these hybrid hetero-nanostructures. The dual-plasmonic Au@copper sulfide core-shell nanoparticles exhibit unique multimodal photothermal and photocatalytic behaviors upon selective photoexcitations of different optical transitions at their characteristic resonant frequencies, allowing us to quantitatively evaluate and rigorously compare the intrinsic photothermal and photocatalytic efficacies of multiple types of hot charge carriers, all photoexcited in the same hybrid nanoparticles but with distinct photophysical origins, excited-state lifetimes, energy distributions, and transfer pathways.
尽管贵金属纳米颗粒引人入胜的等离子体特性源于导带中自由电子的集体振荡，但掺杂半导体纳米颗粒也可能表现出类似金属的等离子体特征，这些特征由价带中共振激发的自由空穴振荡决定。在这里，我们将具有代表性的自由电子金属金与一类等离子体半导体硫化铜以核壳纳米颗粒的几何结构相结合，构建了双等离子体异质纳米结构，该结构展示出独特的多重光学特性，这些特性由半导体壳层中的等离子体空穴振荡、金属核中的等离子体电子振荡以及从价带到导带的带间电子跃迁主导。通过精心设计的胶体合成方法，我们能够在金纳米颗粒核的表面选择性地生长出包含特定目标晶相和铜硫化学计量比的硫化铜纳米壳，例如辉铜矿（CuS）、蓝辉铜矿（Cu₂S）和非化学计量比的CuₓS。我们的合成方法不仅使我们能够精确控制核壳尺寸，还能系统地调节半导体壳层中的自由空穴浓度，这构成了微调这些混合异质纳米结构所支持的多种光学共振模式的关键。双等离子体金@硫化铜核壳纳米颗粒在其特征共振频率下对不同光学跃迁进行选择性光激发时，表现出独特的多模态光热和光催化行为，这使我们能够定量评估并严格比较多种类型热载流子的固有光热和光催化效率，所有这些热载流子都在同一混合纳米颗粒中被光激发，但具有不同的光物理起源、激发态寿命、能量分布和转移途径。
