Size-Discriminative Self-Assembly of Nanospheres in Evaporating Drops

Abstract

Evaporation of liquid drops containing nanospheres resulted in circular deposition patterns. The circularity of the patterns depended on the uniformity of the surface tension on the substrate. By employing binary suspensions, containing two differently sized nanospheres, it was possible to modulate the fine structure of such rings. Slow evaporation on mirror-polished substrates resulted in well-ordered distributions, where larger particles self-assembled in dense hexagonal packages, forming apparently an external ring, deposited around the massive inner ring. Deposition started at the air/liquid/solid-contact line. Results could inspire principles for the fabrication of optical devices and may be fruitfully used to design biomaterials with cell-selective properties. A simple model is employed to predict the radial arrangement of nanospheres in rings. Deviations from a standard order (predicted by the model) may be useful to detect biologically active nanoparticles.

The influence of gravity on the distribution of the deposit formed onto a substrate by sessile, hanging, and sandwiched hanging drop evaporation

“…Other reports [21] present the influence of gravity on the shape of a sessile or a hanging drop. For colloidal suspensions, to the best of the authors knowledge, there are only two references suggesting that gravity could influence considerably the structure of the ring patterns [22], the width of the ring, and the amount of material deposited in the area enclosed by the ring [23]. The latter reference also suggests that gravitational effects become negligible for droplets less than 1 mm in size.…”

Controllable size, shape and morphology of molybdic acid self-aggregated with rhodamine B to construct functional material

“…Various shapes and morphologies including disks [8], nanorods [9,10], nanowires [11][12][13], networks [14][15][16], tubes [17][18][19], rings [20,21], etc., have been achieved in the past decade. Much research has been focused on the preparation and the properties of the architectures.…”

“…Much research has been focused on the preparation and the properties of the architectures. Recently, the ordered aggregates constructed with nanosubunits attract much interest in fabrication of functional materials [21][22][23][24]. However, the normal concept for crystal growth, which is typically thought to occur via atom-atom addition to an existing nucleusor template, has been challenged by the aggregation-based growth of nanosubunits.…”

“…On the one hand, the temperature, nucleation and growth, components and concentrations are important ways to fabrication of the aggregates. On the other hand, the aggregation process is also an important factor to fabricate the morphologies of the colloidal particles, for example, the self-aggregation proceeded in bulk solution, in which has been acting as an important synthetic route for preparation of nanoscale functional materials with specific shapes, sizes, orientations and properties [26,34], is quite different from that of happened under the interfaceevaporated conditions [35][36][37][38]. Firstly, the critical concentration of colloidal particles is easy to exceed and the incipient crystal nucleation is ready to formation with the evaporation of solvent at air-water interface.…”

Ink‐Jet Printing of Metallic Nanoparticles and Microemulsions

“…Highly ordered structures obtained upon drying of colloidal droplets were described for aqueous polymeric nanoparticles, [50][51][52] metallic nanoparticles dispersed in organic solvents, [53][54][55] and semiconductor nanoparticles. [56] The mechanism of rings formation has been explained in terms of correlation between wetting properties, surface tension, evaporation-driven convective flows, [52,54] and capillary flow (and pinned contact line) as described by Deegan et al for stains from dried liquid drops. [57] Printing on a glass slide of a microemulsion containing 0.5 wt.-% of colorant, results in the formation of a rim surrounding the dried droplet ( Figure 5).…”