More Like this

1. Hierarchical assemblies of superparamagnetic colloids in time-varying magnetic fields

   https://doi.org/10.1039/D0SM01878C  

   Spatafora-Salazar, Aldo; Lobmeyer, Dana M.; Cunha, Lucas H.; Joshi, Kedar; Biswal, Sibani Lisa (February 2021, Soft Matter)

   null (Ed.)

   Magnetically-guided colloidal assembly has proven to be a versatile method for building hierarchical particle assemblies. This review describes the dipolar interactions that govern superparamagnetic colloids in time-varying magnetic fields, and how such interactions have guided colloidal assembly into materials with increasing complexity that display novel dynamics. The assembly process is driven by magnetic dipole–dipole interactions, whose strength can be tuned to be attractive or repulsive. Generally, these interactions are directional in static external magnetic fields. More recently, time-varying magnetic fields have been utilized to generate dipolar interactions that vary in both time and space, allowing particle interactions to be tuned from anisotropic to isotropic. These interactions guide the dynamics of hierarchical assemblies of 1-D chains, 2-D networks, and 2-D clusters in both static and time-varying fields. Specifically, unlinked and chemically-linked colloidal chains exhibit complex dynamics, such as fragmentation, buckling, coiling, and wagging phenomena. 2-D networks exhibit controlled porosity and interesting coarsening dynamics. Finally, 2-D clusters have shown to be an ideal model system for exploring phenomena related to statistical thermodynamics. This review provides recent advances in this fast-growing field with a focus on its scientific potential. 

   more » « less
2. Microscopic origins of the crystallographically preferred growth in evaporation-induced colloidal crystals

   https://doi.org/10.1073/pnas.2107588118  

   Ling, Li; Goodrich, Carl; Yang, Haizhao; Phillips, Katherine R.; Jia, Zian; Chen, Hongshun; Wang. Lifeng; Zhong, Jinjin; Liu, Anhui; Lu, Jianfeng; et al (August 2021, Proceedings of the National Academy of Sciences)

   Significance Self-assembly is one of the central themes in biologically controlled synthesis, and it also plays a pivotal role in fabricating a variety of advanced engineering materials. In particular, evaporation-induced self-assembly of colloidal particles enables versatile fabrication of highly ordered two- or three-dimensional nanostructures for optical, sensing, catalytic, and other applications. While it is well known that this process results in the formation of the face-centered cubic (fcc) lattice with the close-packed {111} plane parallel to the substrate, the crystallographic texture development of colloidal crystals is less understood. In this study, we show that the preferred <110> growth in the fcc colloidal crystals synthesized through evaporation-induced assembly is achieved through a gradual crystallographic rotation facilitated by mechanical stress-induced geometrically necessary dislocations. 

   more » « less
3. Disorder and demixing in bidisperse particle systems assembling bcc crystals

   https://doi.org/10.1063/5.0219037  

   Kennard, Jasmin J; Zelaya_Solano, H Jonathan; Biddulph, Caleb D; Prager, Ryan C; Dshemuchadse, Julia (August 2024, The Journal of Chemical Physics)

   Colloidal and nanoparticle self-assembly enables the creation of ordered structures with a variety of electronic and photonic functionalities. The outcomes of the self-assembly processes used to synthesize such structures, however, strongly depend on the uniformity of the individual nanoparticles. Here, we explore the simplest form of particle size dispersity—bidispersity—and its impact on the self-assembly process. We investigate the robustness of self-assembling bcc-type crystals via isotropic interaction potentials in binary systems with increasingly disparate particle sizes by determining their terminal size ratio—the most extreme size ratio at which a mixed binary bcc crystal forms. Our findings show that two-well pair potentials produce bcc crystals that are more robust with respect to particle size ratio than one-well pair potentials. This suggests that an improved self-assembly process is accomplished with a second attractive length scale encoded in the particle–particle interaction, which stabilizes the second-nearest neighbor shell. In addition, we document qualitative differences in the process of ordering and disordering: in bidisperse systems of particles interacting via one-well potentials, we observe a breakdown of order prior to demixing, while in systems interacting via two-well potentials, demixing occurs first and bcc continues to form in parts of the droplet down to low size ratios. 

   more » « less
4. Shape-driven entropic self-assembly of an open, reconfigurable, binary host–guest colloidal crystal

   https://doi.org/10.1039/d0sm02073g  

   Moore, Timothy C.; Anderson, Joshua A.; Glotzer, Sharon C. (March 2021, Soft Matter)

   null (Ed.)

   Entropically driven self-assembly of hard anisotropic particles, where particle shape gives rise to emergent valencies, provides a useful perspective for the design of nanoparticle and colloidal systems. Hard particles self-assemble into a rich variety of crystal structures, ranging in complexity from simple close-packed structures to structures with 432 particles in the unit cell. Entropic crystallization of open structures, however, is missing from this landscape. Here, we report the self-assembly of a two-dimensional binary mixture of hard particles into an open host–guest structure, where nonconvex, triangular host particles form a honeycomb lattice that encapsulates smaller guest particles. Notably, this open structure forms in the absence of enthalpic interactions by effectively splitting the structure into low- and high-entropy sublattices. This is the first such structure to be reported in a two-dimensional athermal system. We discuss the observed compartmentalization of entropy in this system, and show that the effect of the size of the guest particle on the stability of the structure gives rise to a reentrant phase behavior. This reentrance suggests the possibility for a reconfigurable colloidal material, and we provide a proof-of-concept by showing the assembly behavior while changing the size of the guest particles in situ . Our findings provide a strategy for designing open colloidal crystals, as well as binary systems that exhibit co-crystallization, which have been elusive thus far. 

   more » « less
5. Accelerating ion transport in polycrystalline conductors: On pores and grain boundaries

   https://doi.org/10.1126/sciadv.adt7795  

   Truong, Erica; Patel, Sawankumar V; Liu, Haoyu; Chen, Yudan; Lacivita, Valentina; Zhang, Chi; Oyekunle, Ifeoluwa P; Ojelade, Islamiyat; Jin, Yongkang; Jones, Brendon T; et al (May 2025, Science Advances)

   Polycrystalline ion conductors are widely used as solid electrolytes in energy storage technologies. However, they often exhibit poor ion transport across grain boundaries and pores. This work demonstrates that strategically tuning the mesoscale microstructures, including pore size, pore distribution, and chemical compositions of grain boundaries, can improve ion transport. Using LiTa₂PO₈as a case study, we have shown that the combination of LiF as a sintering agent with Hf⁴⁺implantation improves grain-grain contact, resulting in smaller, evenly distributed pores, reduced chemical contrast, and minimized nonconductive impurities. A suite of techniques has been used to decouple the effects of LiF and Hf⁴⁺. Specifically, LiF modifies particle shape and breaks large pores into smaller ones, while Hf⁴⁺addresses the chemical mismatches between grains and grain boundaries. Consequently, this approach achieves nearly two orders of magnitude improvement in ion conduction. Tuning mesoscale structures offers a cost-effective method for enhancing ion transport in polycrystalline systems and has notable implications for synthesizing high-performance ionic materials. 

   more » « less