Colloidal Nanocrystals: A Toolbox for Materials Chemistry

Abstract

Colloidal nanocrystals are the ideal building blocks for the fabrication of functional materials. Using various assembly, patterning or processing techniques, the nanocrystals can be arranged with unprecedented flexibility in 1-, 2- or 3-dimensional architectures over several orders of length scales, providing access to ordered or disordered, porous or non-porous, and simple as well as hierarchical structures. Careful selection of colloidal nanocrystals allows the properties of the final materials to be predefined. Moreover, by combining different nanocrystals, these properties can be fine-tuned for a specific application, opening up fascinating opportunities to create new materials for energy storage and conversion, catalysis, photocatalysis, biomedicine or optics. Indeed, functional materials made of preformed nanoparticles have been realized for metals, polymers, semiconductors, and ceramics, as well as for composites and organic-inorganic hybrids. In this review article, we introduce some concepts for the fabrication of colloidal nanocrystals and their assembly into dense and porous 3-dimensional structures. Porosity is a particularly important material property that strongly influences its application potential. Therefore, we pay special attention to this aspect and compare porous materials synthesized from nanoparticles with those from molecular routes. An additional focus is set on the degree of structural order that can be achieved on different length scales.

The Importance of the Macroscopic Geometry in Gas‐Phase Photocatalysis

“…Reproduced under the terms of the Creative Commons Attribution License CC BY 4‐0. [ 44 ] Copyright 2021, The Authors, publisched by Swiss Chemical Society. b) Examples of single‐ and multi‐component nanoparticle‐based aerogels obtained by gelation of metal, metal oxide, metal nitride, metal phosphide, and metal chalcogenide nanoparticles.…”

Robust Antibacterial Activity of Xanthan-Gum-Stabilized and Patterned CeO2–x–TiO2 Antifog Films

“…Such an effect would be enhanced by the increased Ce 3+ /Ce 4+ ratio. ,, Furthermore, due to its tunable electronic configuration of Ce 4+ and Ce 3+ , cerium can form mid-band gap in TiO 2, which assists the absorption in the visible region of 400–500 nm (Figure S-10). − This also partially explains that S7-containing CeO 2– x –TiO 2 possesses excellent antibacterial activity against Gram-negative and Gram-positive bacteria (Figure ). The ROS level produced by S2 (CeO 2– x ) and S7 (CeO 2– x –TiO 2 ) further confirmed this point of view.…”

“…The 25 mol % CeO 2– x –TiO 2 and 50 mol % CeO 2– x –TiO 2 systems led to transmission electron microscopy (TEM) images and X-ray diffraction (XRD) similar to the 75 mol % CeO 2– x –TiO 2 . The loose CeO 2– x –TiO 2 nanoparticles benefit the Ce 3+ preservation and the related photocatalytic effect, which are the advantages of using the microwave reaction method in the benzyl alcohol bath. With an increasing ratio of CeO 2– x , TiO 2 crystallinity became lower (Figure g), displaying an amorphous-like structure (Figure f).…”

Nanoparticle-Based Aerogels and Their Prospective Future Applications

“…Reviewed were the history of synthesis, design strategies, gelation mechanisms, and applications, especially for NMAs. NMAs have emerged as ideal candidates with excellent performance, especially for electrocatalysis and biosensors, which benefit from their high specific surface areas, highly porous nanostructures, and the self-supporting property. ,,,,,,, The diagnosis is made that the field is currently gradually shifting from material accumulation to more in-depth investigations, e.g., toward a closer look at gelation mechanisms and the elaboration of synthesis methods from a “6D design” perspective (i.e.., initiators, precursors, reducing agents, ligands, solvents, and external fields) . In this context also detailed descriptions of the two main parameters involved in the gelation; namely, the concentration of the NP dispersion and the strength of the attractive force between the particles is given.…”

“…Those include but are not limited to work by Arachchige and Brock on the assembly of metal chalcogenide quantum dots, Cai et al on electrocatalysis on aerogels and on multimetallic hierarchical aerogels with shape engineered building blocks, − Zhu et al on NMAs, Wen et al on enzymatic biofuel cells with metal gels and on NMAs in biosensing, , Milliron et al on thermodynamic aspects of NPAs and very recently on the assembling of NPAs, , Bigall et al on the control over structure and properties in NPAs on different length scales, Niederberger et al with the titles “Synthesis of aerogels: from molecular routes to 3-dimensional nanoparticle assembly”, “Multiscale Nanoparticle Assembly: From Particulate Precise Manufacturing to Colloidal Processing“, “From colloidal dispersions to aerogels: How to master nanoparticle gelation” (cf. Figure ), and “Colloidal Nanocrystals: A Toolbox for Materials Chemistry”, − Liu et al on synthesis and characterization of NMAs and their applications as electrocatalysts and on versatile aerogels for sensors, , Du et al on the engineering of self-supported noble metal foams toward electrocatalysis and beyond, on the state of the art of emerging NMAs, and on providing a roadmap for 3D metal aerogels with respect to materials design and application attempts, − and finally Ziegler et al entiteled “Modern Inorganic Aerogels” . From the last paper, Figure is reprinted because it illustrates at a glance the variety of possible materials and material combinations that become achievable through NPA formation.…”