From colloidal dispersions to aerogels: How to master nanoparticle gelation

Matter, Fabian; Luna, Ana L.; Niederberger, Markus

doi:10.1016/j.nantod.2019.100827

Cited by 143 publications

(143 citation statements)

References 109 publications

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“…Thus, the mechanisms of SF-G and VPS-G should be useful for designing gel materials (8)(9)(10)(11)(12). SF-G may also allow us to form a stable soft colloidal gel free from network shrinkage since it does not suffer from the self-generated internal mechanical stress, which is inevitable for VPS-G (26) and causes network shrinkage (9,52). The colloid volume fraction separating between SF-G and VPS-G also provides the border of the settling behavior between cluster deposition and collective settling under gravity (9).…”

Section: Discussionmentioning

confidence: 99%

“…SF-G may also allow us to form a stable soft colloidal gel free from network shrinkage since it does not suffer from the self-generated internal mechanical stress, which is inevitable for VPS-G (26) and causes network shrinkage (9,52). The colloid volume fraction separating between SF-G and VPS-G also provides the border of the settling behavior between cluster deposition and collective settling under gravity (9). Our work also reveals how the character of the interparticle attractions affects aggregation, phase separation, and gelation.…”

Section: Discussionmentioning

confidence: 99%

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A unique route of colloidal phase separation yields stress-free gels

2020

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Phase separation often leads to gelation in soft and biomatter. For colloidal suspensions, we have a consensus that gels form by the dynamical arrest of phase separation. In this gelation, percolation of the phase-separated structure occurs before the dynamical arrest, leading to the generation of mechanical stress in the gel network. Here, we find a previously unrecognized type of gelation in dilute colloidal suspensions, in which percolation occurs after the local dynamical arrest, i.e., the formation of mechanically stable, rigid clusters. Thus, topological percolation generates little mechanical stress, and the resulting gel is almost stress-free when formed. We also show that the selection of these two types of gelation (stressed and stress-free) is determined solely by the volume fraction as long as the interaction is short-ranged. This universal classification of gelation of particulate systems may have a substantial impact on material and biological science.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

A unique route of colloidal phase separation yields stress-free gels

2020

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“…The as-synthesized NPs exhibit the advantage of being already crystalline (anatase), without the use of heat treatment, and controlled crystallite size (only a few nm size) and surface composition, displaying photocatalytic performance. [11] To further increase their photocatalytic efficiency, they have been assembled into an aerogel, [12] which allows them to be connected without agglomeration, but still with a high surface area and high accessibility of the active surfaces. Moreover, advanced aerogels have been developed, by co-assembling spherical Au, Pd, and PdAu NPs with those TiO 2 NPs and applying them for gas-phase H 2 generation.…”

Section: Introductionmentioning

confidence: 99%

Porous Silica Microspheres with Immobilized Titania Nanoparticles for In‐Flow Solar‐Driven Purification of Wastewater

et al. 2021

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In this paper, inorganic silica microspheres with interconnected macroporosity are tested as a platform for designing robust and efficient photocatalytic systems for a continuous flow reactor, enabling a low cost and straightforward purification of wastewater through solar‐driven photocatalysis. The photocatalytically active microspheres are prepared by wet impregnation of porous silica scaffolds with Trizma‐functionalized anatase titania (TiO 2 ) nanoparticles (NPs). NPs loading of 22 wt% is obtained in the form of a thin and well‐attached layer, covering the external surface of the microspheres as well as the internal surface of the pores. The TiO 2 loading leads to an increase of the specific surface area by 26%, without impacting the typically interconnected macroporosity ( ≈ 60%) of the microspheres, which is essential for an efficient flow of the pollutant solution during the photocatalytic tests. These are carried out in a liquid medium for the decomposition of methyl orange and paracetamol. In addition to photocatalytic activity under continuous flow, the microspheres offer the advantage that they can be easily removed from the reaction medium, which is an appealing aspect for industrial applications. In this work, the typical issues of TiO 2 NPs photocatalysts are circumvented, without the need for elaborate chemistries, and for low availability and expensive raw materials.

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“…The development of NC-based gels 6 as well as the different methods and underlying theory 35 have been widely reviewed already. Accordingly, this Account focuses on recent achievements that go a different way, using the variety and customizability of NC chemistry and the assembly of these NCs.…”

Section: Introductionmentioning

confidence: 99%

Control over Structure and Properties in Nanocrystal Aerogels at the Nano-, Micro-, and Macroscale

2020

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Conspectus The assembly of individual colloidal nanocrystals into macroscopic solvogels and aerogels introduced a new exciting type of material into the class of porous architectures. In these so-called nanocrystal gels, the structure and properties can be controlled and fine-tuned to the smallest details. Recently it was shown that by employing nanocrystal building blocks for such gel materials, the interesting nanoscopic properties can be conserved or even expanded to properties that are available neither in the nanocrystals nor in their respective bulk materials. In general, the production of these materials features the wet-chemical synthesis of stable nanocrystal colloids followed by their carefully controlled destabilization to facilitate arrangement of the nanocrystals into highly porous, interconnected networks. By isolation of the synthesis of the discrete building blocks from the assembly process, the electronic structure, optical properties, and structural morphology can be tailored by the myriad of procedures developed in colloidal nanocrystal chemistry. Furthermore, knowledge and control over the structure–property correlation in the resulting gel structures opens up numerous new ways for extended and advanced applications. Consequently, the amount of different materials converted to nanocrystal-based gel structures is rising steadily. Meanwhile the number of methods for assembly initiation is likewise increasing, offering control over the overall network structure and porosity as well as the individual nanocrystal building block connection. The resulting networks can be dried by different methods to obtain highly porous air-filled networks (aerogels) or applied in their wet form (solvogels). By now a number of different applications profiting from the unique advantages of nanocrystal-based gel materials have been realized and exploited in the areas of photocatalysis, electrocatalysis, and sensing. In this Account, we aim to summarize the efforts undertaken in the structuring of nanocrystal-based network materials on different scales, fine-tuning of the individual building blocks on the nanoscale, the network connections on the microscale, and the macroscale structure and shape of the final construct. It is exemplarily demonstrated how cation exchange reactions (at the nanoscale), postgelation modifications on the nanocrystal networks (microscale), and the structuring of the gels via printing techniques (macroscale) endow the resulting nanocrystal gel networks with novel physicochemical, mechanical, and electrocatalytic properties. The methods applied in the more traditional sol–gel chemistry targeting micro- and macroscale structuring are also reviewed, showing their future potential promoting the field of nanocrystal-based aerogels and their applications.

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From colloidal dispersions to aerogels: How to master nanoparticle gelation

Cited by 143 publications

References 109 publications

A unique route of colloidal phase separation yields stress-free gels

A unique route of colloidal phase separation yields stress-free gels

Porous Silica Microspheres with Immobilized Titania Nanoparticles for In‐Flow Solar‐Driven Purification of Wastewater

Control over Structure and Properties in Nanocrystal Aerogels at the Nano-, Micro-, and Macroscale

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