Tuning the Morphology of Spray‐Dried Supraparticles: Effects of Building Block Size and Concentration

Abstract

fields, such as photonic devices, [5,6] biomaterials, [7][8][9][10] energy conversion, [11,12] and smart, interactive, and "communicating" materials. [13][14][15] Moreover, the resulting properties of supraparticles can be strongly affected not only by the properties of the single nanoparticle building blocks but also by the structures of their hierarchical units. Therefore, different assembled morphologies resulting in supraparticles providing distinct properties, lead to diverse applications. [5,[16][17][18][19][20] For example, shape-anisotropic (e.g., doughnut-like structure) particles were proposed to be utilized in catalysis due to their high surface area and hierarchical porosity, while composition-anisotropic ones (e.g., single-patch magnetic particles) were suggested as, for example, promising drug delivery systems due to their easy manipulation with a magnet. [19,20] There are many developed experimental methods to fabricate supraparticles. The surface-templated evaporationdriven method is a frequently used one, assembling nanoparticles to supraparticles on liquid-repellent surfaces, [21] such as superhydrophobic [19,22] and superamphiphobic one. [23] Another technique is the emulsion-templated self-assembly, in which nanoparticles dispersed in oil droplets within an oil-in-water emulsion (or other phase combinations), arrange themselves into supraparticles. [24] In addition, lately, the microfluidic technique has been applied for the self-assembly of colloids into well-defined structures. [25,26] Apart from the above mentioned approaches, spray-drying also widely draws attention to itself as a fast, economic method to fabricate micron-scale particle powders from solutions or suspensions. [27][28][29][30] It permits to influence the obtained supraparticles by varying the feeding materials or adapting process parameters. Thus, it is a flexible way of assembling single nanoparticles into hierarchical supraparticles.The morphology of the product is strongly influenced by process parameters, such as the drying gas temperature, [10,28,31] the gas flow rate, [10] and the type of nozzle. [30,31] Exemplarily, it varies from spherical to non-spherical structures as a result of fast evaporation of the solvent at high-temperature conditions. [10,28,31,32] Furthermore, the resulting size of the particles can be reduced by increasing the flow rate of the drying gas, which breaks up the dispersion into droplets. [10] Controlling the morphology of spray-dried supraparticles via adjustments at the nanoparticle dispersion level has also been Tuning the morphology of supraparticles can crucially influence their final properties and is, thus, important for their application in chemical, pharmaceutical, and food industries. The present study reveals how varied nanoparticle sizes, concentrations, and weight ratios in multicomponent dispersions influence the morphology of supraparticles assembled by these nanoparticle building blocks via spray-drying. In a droplet containing monodisperse nanoparticles, smaller nanoparticles ...

Versatile Mesoporous Microblocks Prepared by Pattern‐Induced Cracking of Colloidal Films

“…We conceptually demonstrated the preparation of anti-counterfeiting films by inserting colored microblocks randomly rotated in microwells, the separation of desired chemicals by using different electro-static interactions with microblocks, and the elimination of undesired chemicals by the photocatalytic effect after separation. Compared to other methods used to produce microparticles, such as microfluidic and spray-drying approaches, [15,19,22,23] the proposed method has advantages such as excellent control of sizes and shapes of particles with multiple functions and good uniformity. Environmentally friendly methods of producing multifunctional versatile mesoporous microscale fragments can be used in various fields, such as catalytic processes, biomedical engineering, energy, and display devices.…”

“…[ 1–6 ] They have potential uses in various fields, such as catalysis, [ 7–9 ] energy conversion, [ 6,10,11 ] environmental purification, [ 12–14 ] biomedical applications [ 15 ] and smart communication. [ 16–18 ] To fabricate supraparticles of a uniform size, spray‐drying process, [ 15,19 ] self‐assembly with an emulsion, [ 20,21 ] or use of microfluidic devices [ 22,23 ] were suggested. These solvent‐based methods are suitable for mass production; however, they require additional stabilizers or emulsifiers and entail waste problems after processing.…”

Multifunctional, Hybrid Materials Design via Spray‐Drying: Much more than Just Drying

“…The self-assembly of building blocks, such as nanoparticles and molecules within a single droplet upon solvent evaporation [8,15] can produce a variety of compositions (e.g., single-component, [16] multi-component, [17,18] inorganic-organic hybrid, [19] metal oxide hybrid [20,21] ) and structures (e.g., solid, [22] hollow, [23] core-shell [23] ) with unique properties and potential applications. Recently, many types of unique building blocks such as nanofibers, [24] nanorods, [25] and metal-organic frameworks (MOFs) [26,27] have become available and offer potential advantages.…”

From Meso to Macro: Controlling Hierarchical Porosity in Supraparticle Powders

“…For any application requiring large amounts of SPs, it is therefore important to establish how the internal structure and pore system of such spray‐dried SPs can be controlled. [ 44–47 ]…”

“…For any application requiring large amounts of SPs, it is therefore important to establish how the internal structure and pore system of such spray-dried SPs can be controlled. [44][45][46][47] Here, we focus on controlling the pore system in hierarchical SPs fabricated via spray drying. We combine approaches to tailor pore structures over multiple length scales, as outlined in Figure 1.…”