Alternating Binary Multilayers of Alkanethiol-Modified Gold Nanoparticles and Quantum Dots with Artificial Three-Dimensional Structures and Rational Photoluminescence

The formation of periodic arrangements of two types of nanoparticles (NPs), i.e., binary NP superlattices (BNSLs), provides a versatile approach to control their physical properties through interparticle interactions. However, achieving highly ordered BNSLs is still challenging because of the difficulty of combining two distinct NPs without phase segregation. In this work, plasmonic Au NPs and CdS quantum dots (QDs) modified with dodecanethiol ligands were assembled into binary multilayered structures by alternately laminating their monolayers onto a single substrate. Grazing-incidence small-angle X-ray scattering analysis confirmed the long-range ordered arrangement of the NPs, demonstrating the successful fabrication of 3D structures with Au NPs and CdS QDs. The formation of close-packed monolayers and entropic stabilization by surface ligands were identified as key factors in artificially constructing such 3D arrays via multilayering. The formation of defect-free BNSLs was also optically identified by a systematic increase in the intensities of the photoluminescence (PL) and plasmon extinction intensities, as well as perfect control of respective band positions. Based on finite-difference time-domain simulations, this PL behavior was attributed to the formation of a layered superstructure with a homogeneous dielectric function in the repeat unit of a Au NP-CdS QD-Au NP layer. This work demonstrates that simple alternative lamination of NP monolayers offers a facile yet effective strategy to obtain BNSLs with well-defined physical properties for broader application of NP array-based materials.