Abstract:The assembly of nanomaterials into thin films is an important area in the nanofabrication of novel devices. The monodispersity of nanoparticles plays an essential role in the resulting quality of the assembled mono-and multilayers. Larger polydispersity leads to smaller lateral correlation lengths and smaller domains of aligned nanoparticles, thus resulting in more point and line defects. Perfectly monodisperse nanoparticles should therefore minimize the number of defects in the assembled films. Despite tremen… Show more
“…We conducted in situ grazing-incidence small-angle X-ray scattering (GISAXS) measurements to investigate a real-time change in the nanoscopic arrangement of GNP films. GISAXS measurements provide high accuracy in determining interparticle gap distances with robust statistics thanks to the large-area sampling nature. ,,− Figure c shows a GISAXS pattern of a free-floating GNP film on acetonitrile before and after the ligand exchange with C2DT, respectively. Due to the low absorption of the X-ray in acetonitrile, we could observe the scattering pattern of both the reflected and transmitted beams .…”
Nanoparticle superlattices produced with controllable interparticle gap distances down to the subnanometer range are of superior significance for applications in electronic and plasmonic devices as well as in optical metasurfaces. In this work, a method to fabricate large-area (∼1 cm 2 ) gold nanoparticle (GNP) superlattices with a typical size of single domains at several micrometers and high-density nanogaps of tunable distances (from 2.3 to 0.1 nm) as well as variable constituents (from organothiols to inorganic S 2− ) is demonstrated. Our approach is based on the combination of interfacial nanoparticle self-assembly, subphase exchange, and free-floating ligand exchange. Electrical transport measurements on our GNP superlattices reveal variations in the nanogap conductance of more than 6 orders of magnitude. Meanwhile, nanoscopic modifications in the surface potential landscape of active GNP devices have been observed following engineered nanogaps. In situ optical reflectance measurements during free-floating ligand exchange show a gradual enhancement of plasmonic capacitive coupling with a diminishing average interparticle gap distance down to 0.1 nm, as continuously red-shifted localized surface plasmon resonances with increasing intensity have been observed. Optical metasurfaces consisting of such GNP superlattices exhibit tunable effective refractive index over a broad wavelength range. Maximal real part of the effective refractive index, n max , reaching 5.4 is obtained as a result of the extreme field confinement in the high-density subnanometer plasmonic gaps.
“…We conducted in situ grazing-incidence small-angle X-ray scattering (GISAXS) measurements to investigate a real-time change in the nanoscopic arrangement of GNP films. GISAXS measurements provide high accuracy in determining interparticle gap distances with robust statistics thanks to the large-area sampling nature. ,,− Figure c shows a GISAXS pattern of a free-floating GNP film on acetonitrile before and after the ligand exchange with C2DT, respectively. Due to the low absorption of the X-ray in acetonitrile, we could observe the scattering pattern of both the reflected and transmitted beams .…”
Nanoparticle superlattices produced with controllable interparticle gap distances down to the subnanometer range are of superior significance for applications in electronic and plasmonic devices as well as in optical metasurfaces. In this work, a method to fabricate large-area (∼1 cm 2 ) gold nanoparticle (GNP) superlattices with a typical size of single domains at several micrometers and high-density nanogaps of tunable distances (from 2.3 to 0.1 nm) as well as variable constituents (from organothiols to inorganic S 2− ) is demonstrated. Our approach is based on the combination of interfacial nanoparticle self-assembly, subphase exchange, and free-floating ligand exchange. Electrical transport measurements on our GNP superlattices reveal variations in the nanogap conductance of more than 6 orders of magnitude. Meanwhile, nanoscopic modifications in the surface potential landscape of active GNP devices have been observed following engineered nanogaps. In situ optical reflectance measurements during free-floating ligand exchange show a gradual enhancement of plasmonic capacitive coupling with a diminishing average interparticle gap distance down to 0.1 nm, as continuously red-shifted localized surface plasmon resonances with increasing intensity have been observed. Optical metasurfaces consisting of such GNP superlattices exhibit tunable effective refractive index over a broad wavelength range. Maximal real part of the effective refractive index, n max , reaching 5.4 is obtained as a result of the extreme field confinement in the high-density subnanometer plasmonic gaps.
“…Microstructural analysis of monolayers prepared via fluid interface-assisted assembly typically relies on microscopy (atomic force and electron microscopy) and scattering (X-ray and light scattering). , The application of such techniques assumes the microstructure is conserved during transfer to a solid interface and subsequent drying, which might be untrue. Combining ex situ (i.e., after the deposition of the monolayer on the solid substrate) with in situ analysis – revealed significant changes in the microstructure . This study covers only micron-sized core-shell NCs.…”
We explore the potential of nanocrystals (a term used
equivalently
to nanoparticles) as building blocks for nanomaterials, and the current
advances and open challenges for fundamental science developments
and applications. Nanocrystal assemblies are inherently multiscale,
and the generation of revolutionary material properties requires a
precise understanding of the relationship between structure and function,
the former being determined by classical effects and the latter often
by quantum effects. With an emphasis on theory and computation, we
discuss challenges that hamper current assembly strategies and to
what extent nanocrystal assemblies represent thermodynamic equilibrium
or kinetically trapped metastable states. We also examine dynamic
effects and optimization of assembly protocols. Finally, we discuss
promising material functions and examples of their realization with
nanocrystal assemblies.
“…For Au 32 ( n Bu 3 P) 12 Cl 8 nanoclusters, uniform chlorine ligands may induce anisotropic interactions. Together with the dipolar interaction between chlorine ligands and water molecules, the AuNCs can assemble into a multilayer Langmuir film . Flat films serve as substrates, facilitating their effective integration of structures and functions.…”
Gold nanoclusters (AuNCs), with customized structures and diverse optical properties, are promising optical materials. Constructing composite systems by the assembly and incorporation of AuNCs can utilize their optical properties to achieve diagnostic and therapeutic applications in the biological field. Therefore, the exploration of the assembly behaviors of AuNCs and the enhancement of their performance has attracted widespread interest. In this review, we introduce multiple interactions and assembly modes that are prevalent in nanocomposites and microcomposites based on AuNCs. Then, the functions of AuNC composites for bioapplications are demonstrated in detail. These composite systems have inherited and enhanced the inherent optical performances of the AuNCs to meet diverse requirements for biological sensing and optical treatments. Finally, we discuss the prospects of AuNC composites and highlight the challenges and opportunities in biomedical applications.
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