In Situ Control of Crystallinity of 3D Colloidal Crystals by Tuning the Growth Kinetics of Nanoparticle Building Blocks

Abstract

Colloidal crystals (CCs) constructed from inorganic nanoparticle (NP) building blocks exhibit properties that cannot be realized from isolated NPs or corresponding bulk counterparts. Because the arrangement of NPs in CCs is crucial in the CC’s collective properties, development of a procedure to modulate the assembly of NP constituents is important. We demonstrate rapid formation of nickel (phosphide) CCs with tunable crystallinity through van der Waals force-driven spontaneous self-assembly of NPs in a facile one-pot colloidal synthesis. The quantity of size-regulating reagent (tri-n-octylphosphine) modulates the assembly of NPs from ordered close-packed to a disordered configuration in CCs. Synchrotron-based in situ small-angle X-ray scattering revealed that the size uniformity of the NPs determines the crystallinity of CCs, indicating the importance of regulating the growth kinetics of NPs during the synthesis. Our work will be useful for universal scalable preparation of CCs from a variety of materials and structures, with tunable concerted properties.

Growth and Self-Assembly of CsPbBr3 Nanocrystals in the TOPO/PbBr2 Synthesis as Seen with X-ray Scattering

“…At this surface-to-surface distance, van der Waals attractions can trigger the superstructure crystallization. This is consistent with previous observations of spontaneous crystallization triggered by interparticle interactions. ,− …”

Quantifying Structural Heterogeneity in Individual CsPbBr3 Quantum Dot Superlattices

“…These SL structural trends are congruent with previous studies on SL growth dynamics during evaporative self-assembly using other nanocrystal cores. , Many factors are known to influence nanocrystal assembly dynamics in solution, including size, shape and faceting, ligand density, concentration, and solubility. − Among these factors, the starting nanocrystal size likely plays an important role in our CsPbBr 3 SL assemblies because the other factors remain constant in a single growth experiment. Several studies utilizing in situ X-ray scattering and theoretical modeling have elucidated how nanocrystal size impacts attractive (van der Waal’s) and repulsive (ligand sterics and osmotic pressure) interactions between individual nanocrystals in SL growth. − These studies show that larger nanocrystals begin to assemble into ordered SLs at earlier time points and lower solution concentration than smaller nanocrystals due to their stronger attractive interactions.…”

Functionalized nanoparticles: Tailoring properties through surface energetics and coordination chemistry for advanced biomedical applications

“…The monitoring of nucleation and self-assembly of fNPs can be done in situ via small-angle X-ray scattering (SAXS) and surface fea-tures can be observed through TEM and SEM analysis. 98 To study colloidal reactions, synchrotron-based methods, X-ray absorption spectroscopy (XAS) or powdered X-ray diffraction (PXRD) can be considered. Moreover, to track complex changes in chemical and electronic properties during complex reactions, more advanced high-energy-resolution fluorescencedetected X-ray absorption near edge structure (HERFD-XANES) is required to capture subtle changes in the near chemical environment of absorbing atoms.…”

“…The magnetic dipole–dipole forces are two magnitudes smaller than the other two, and particles eventually self-assemble when they reach within the interaction influence region of each other. 98 Debye lengths in water–2,6-lutidine mixtures can be controlled from a nanometer to a hundred nanometers, which indicates an ion concentration between 1 M and 1 μM at room temperature.…”