Gordel-Wójcik Marta, Kołkowski Radosław, Nyk Marcin, Samoć Marek
Faculty of Chemistry, University of Wrocław, 14.p F. Joliot-Curie Street, 50-383 Wrocław, Poland.
Department of Applied Physics, Aalto University, P.O.Box 13500, FI-00076 Aalto, Finland.
ACS Appl Mater Interfaces. 2025 May 14;17(19):28484-28494. doi: 10.1021/acsami.5c00984. Epub 2025 May 3.
Hybrid nanosystems, such as those combining plasmonic, dielectric, and quantum-confined nanostructures, have long been of interest for enhancing and tailoring diverse light-matter interactions. Here, we present a series of hybrid nanomaterials exhibiting strongly enhanced nonlinear optical (NLO) properties, fabricated by combining silver sulfide quantum dots (AgS QDs) with silica and gold nanostructures. We studied their NLO properties (two-photon absorption and saturable absorption) in colloidal solutions over a wide spectral range (500-1600 nm) using the femtosecond Z-scan technique. Embedding AgS QDs into silica nanospheres gives rise to remarkable enhancement of two-photon absorption (up to a factor of 16 increase in the merit factor σ/ compared to bare QDs), whereas covering such QD-doped silica nanospheres with gold nanoparticles or attaching the QDs to the surface of gold nanoshells (NSs) leads to even further enhancement (up to 73-fold increase in σ/), accompanied by a competing effect of saturable absorption. Furthermore, in the case of QD-doped silica spheres covered with a continuous gold layer, we observe a previously unreported saturation of extinction in the near-infrared region that follows an unusual intensity dependence, suggesting the involvement of two-photon absorption as the pumping mechanism. In addition to the experimental studies, we have performed numerical simulations, revealing the plasmonic origin of the observed spectral dependences of the NLO properties, with the underlying enhancement mechanisms involving local field enhancement and, possibly, also coupling between plasmon modes and QD excitons, giving rise to a double peak in the σ spectrum. Our findings demonstrate the unique potential of hybrid NLO nanomaterials combining quantum-confined, plasmonic, and dielectric components.
混合纳米系统，例如那些结合了等离子体、介电和量子限制纳米结构的系统，长期以来一直是增强和定制各种光与物质相互作用的研究热点。在此，我们展示了一系列通过将硫化银量子点（AgS QDs）与二氧化硅和金纳米结构相结合而制备的具有强烈增强的非线性光学（NLO）特性的混合纳米材料。我们使用飞秒Z扫描技术在宽光谱范围（500 - 1600 nm）内研究了它们在胶体溶液中的NLO特性（双光子吸收和饱和吸收）。将AgS QDs嵌入二氧化硅纳米球中可显著增强双光子吸收（与裸量子点相比，品质因数σ/增加高达16倍），而用金纳米颗粒覆盖此类掺杂量子点的二氧化硅纳米球或将量子点附着到金纳米壳（NSs）表面会导致进一步增强（σ/增加高达73倍），同时伴随着饱和吸收的竞争效应。此外，在覆盖有连续金层的掺杂量子点的二氧化硅球的情况下，我们观察到近红外区域中消光的一种先前未报道的饱和现象，其遵循不寻常的强度依赖性，这表明双光子吸收作为泵浦机制参与其中。除了实验研究外，我们还进行了数值模拟，揭示了所观察到的NLO特性的光谱依赖性的等离子体起源，潜在的增强机制包括局部场增强，并且可能还包括等离子体模式与量子点激子之间的耦合，从而在σ光谱中产生双峰。我们的研究结果证明了结合量子限制、等离子体和介电成分的混合NLO纳米材料的独特潜力。
