Universal Gelation of Metal Oxide Nanocrystals via Depletion Attractions

Cabezas, Camila A. Saez; Sherman, Zachary M.; Howard, Michael P.; Domínguez, M.; Cho, Shin Hum; Ong, Gary K.; Green, Allison; Truskett, Thomas M.; Milliron, Delia J.

doi:10.1021/acs.nanolett.0c01311

Cited by 19 publications

(26 citation statements)

References 72 publications

(115 reference statements)

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“…To demonstrate depletion gelation for NCs, we assembled gels from three different NCs of varying composition and shape: FeO x spheres, Sn:In 2 O 3 spheres, and F,Sn:In 2 O 3 cubes, all of which were roughly σ ≈ 10 nm across. 2 The NCs were electrostatically stabilized by stripping them of their native, hydrophobic ligands, leaving a positive charge. We then added incremental concentrations of poly(ethylene glycol) (PEG, R g ≈ 1 nm) depletant.…”

Section: Laboratorymentioning

confidence: 99%

“…J. Saez Cabezas, C. A. Sherman, Z. M. Howard, M. P. Dominguez, M. N. Cho, S. H. Ong, G. K. Green, A. M. Truskett, T. M. Milliron, D. J. Nano Lett.20202040074013 . Reversible gels were assembled from a variety of different nanocrystals through nonspecific, polymer-induced depletion attractions.…”

Section: Key Referencesmentioning

confidence: 99%

“…Despite this effective paradigm for MP gels, thermodynamic principles are not commonly employed to design NC gels. This is problematic because gelation times can span days to months, , making trial-and-error materials discovery time-consuming. A major challenge is that it is more difficult to precisely tune interactions between NCs than it is for MPs.…”

Section: Introductionmentioning

confidence: 99%

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Colloidal Nanocrystal Gels from Thermodynamic Principles

et al. 2021

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Conspectus Gels assembled from solvent-dispersed nanocrystals are of interest for functional materials because they promise the opportunity to retain distinctive properties of individual nanocrystals combined with tunable, structure-dependent collective behavior. By incorporating stimuli-responsive components, these materials could also be dynamically reconfigured between structurally distinct states. However, nanocrystal gels have so far been formed mostly through irreversible aggregation, which has limited the realization of these possibilities. Meanwhile, gelation strategies for larger colloidal microparticles have been developed using reversible physical or chemical interactions. These approaches have enabled the experimental navigation of theoretically predicted phase diagrams, helping to establish an understanding of how thermodynamic behavior can guide gel formation in these materials. However, the translation of these principles to the nanoscale poses both practical and fundamental challenges. The molecules guiding assembly can no longer be safely assumed to be vanishingly small compared to the particles nor large compared to the solvent. In this Account, we discuss recent progress toward the assembly of tunable nanocrystal gels using two strategies guided by equilibrium considerations: (1) reversible chemical bonding between functionalized nanocrystals and difunctional linker molecules and (2) nonspecific, polymer-induced depletion attractions. The effective nanocrystal attractions, mediated in both approaches by a secondary molecule, compete against stabilizing repulsions to promote reversible assembly. The structure and properties of the nanocrystal gels are controlled microscopically by the design of the secondary molecule and macroscopically by its concentration. This mode of control is compelling because it largely decouples nanocrystal synthesis and functionalization from the design of interactions that drive assembly. Statistical thermodynamic theory and computer simulation have been applied to simple models that describe the bonding motifs in these assembling systems, furnish predictions for conditions under which gelation is likely to occur, and suggest strategies for tuning and disassembling the gel networks. Insights from these models have guided experimental realizations of reversible gels with optical properties in the infrared range that are sensitive to the gel structure. This process avoids time-consuming and costly trial-and-error experimental investigations to accelerate the development of nanocrystal gel assemblies. These advances highlight the need to better understand interactions between nanocrystals, how interactions give rise to gel structure, and properties that emerge. Such an understanding could suggest new approaches for creating stimuli-responsive and dissipative assembled materials whose properties are tunable on demand through directed reconfiguration of the underlying gel microstructure. It may also make nanocrystal gels amenable to computationally guided design using inve...

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Section: Laboratorymentioning

confidence: 99%

Section: Key Referencesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Colloidal Nanocrystal Gels from Thermodynamic Principles

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“…[ 1–3 ] NP gels have attracted interest for applications in photonics, [ 4,5 ] photovoltaics, [ 6,7 ] catalysis, [ 8–11 ] thermoelectrics, [ 1,12,13 ] and other applications that can benefit from combination of porosity, quantum confinement, and simplicity of their synthesis. The universal ability of nanoscale components to self‐organize make possible their preparation from a wide range of nanoscale solids including noble metals, [ 8,9,14,15 ] metal oxides, [ 16–20 ] and chalcogenide semiconductors. [ 1,4,5,13,21,22 ]…”

Section: Introductionmentioning

confidence: 99%

“…

from combination of porosity, quantum confinement, and simplicity of their synthesis. The universal ability of nanoscale components to self-organize make possible their preparation from a wide range of nanoscale solids including noble metals, [8,9,14,15] metal oxides, [16][17][18][19][20] and chalcogenide semiconductors. [1,4,5,13,21,22] Pre-formed colloidal NPs can be assembled into gels by reducing electrostatic and steric repulsion between individual NPs, [2,4,11] which is achieved by controlled colloidal destabilization.

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confidence: 99%

Spanning Network Gels from Nanoparticles and Graph Theoretical Analysis of Their Structure and Properties

et al. 2022

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Gels self‐assembled from colloidal nanoparticles (NPs) translate the size‐dependent properties of nanostructures to materials with macroscale volumes. Large spanning networks of NP chains provide high interconnectivity within the material necessary for a wide range of properties from conductivity to viscoelasticity. However, a great challenge for nanoscale engineering of such gels lies in being able to accurately and quantitatively describe their complex non‐crystalline structure that combines order and disorder. The quantitative relationships between the mesoscale structural and material properties of nanostructured gels are currently unknown. Here, it is shown that lead telluride NPs spontaneously self‐assemble into a spanning network hydrogel. By applying graph theory (GT), a method for quantifying the complex structure of the NP gels is established using a topological descriptor of average nodal connectivity that is found to correlate with the gel's mechanical and charge transport properties. GT descriptions make possible the design of non‐crystalline porous materials from a variety of nanoscale components for photonics, catalysis, adsorption, and thermoelectrics.

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Self‐assembled Micro‐nanorobots: From Assembly Mechanisms to Applications

et al. 2021

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Due to the extremely tiny size, micro‐nanorobots hold promise in performing tasks at the micro‐nanoscale, which is impossible for macroscale robots. However, the massive fabrication of micro‐nanorobots is of crucial challenge and has been attracting extensive attention among academics. Active colloids can be self‐assembled into ordered structures, and offer a promising solution to this largescale manufacture challenge. Here, we summarize the development and mechanisms of different assembly technologies in the past two decades, and introduce the applications of micro‐nanorobots using self‐assembly strategies in biomedical and physical fields. For clarification, the self‐assembly mechanisms are presented in three categories: chemical, physical and biological. The manufacture of micro‐nanorobots through self‐assembly not only solves the problem of large‐scale manufacturing, but also increases the reconfigurability of structure and improves their adaptability to the environment, which promises further development as microsurgeons and the application of micro‐nanorobots in other fields, such as environmental restoration and micro‐manipulation.

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Universal Gelation of Metal Oxide Nanocrystals via Depletion Attractions

Cited by 19 publications

References 72 publications

Colloidal Nanocrystal Gels from Thermodynamic Principles

Colloidal Nanocrystal Gels from Thermodynamic Principles

Spanning Network Gels from Nanoparticles and Graph Theoretical Analysis of Their Structure and Properties

Self‐assembled Micro‐nanorobots: From Assembly Mechanisms to Applications

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