Morphological Transitions in Patchy Nanoparticles

Abstract

Nanoparticles (NPs) decorated with topographically or chemically distinct surface patches are an emerging class of colloidal building blocks of functional hierarchical materials. Surface segregation of polymer ligands into pinned micelles offers a strategy for the generation of patchy NPs with controlled spatial distribution and number of patches. The thermodynamic nature of this approach poses a question about the stability of multiple patches on the NP surface, as the lowest energy state is expected for NPs carrying a single patch. In the present work, for gold NPs end-grafted with thiol-terminated polymer molecules, we show that the patchy surface morphology is preserved under conditions of strong grafting of the thiol groups to the NP surface (i.e., up to a temperature of 40 °C), although the patch shape changes over time. At higher temperatures (e.g., at 80 °C), the number of patches per NP decreases, due to the increased lateral mobility and coalescence of the patches as well as the ultimate loss of the polymer ligands due to desorption at enhanced solvent quality. The experimental results were rationalized theoretically, using a scaling approach. The results of this work offer insight into the surface science of patchy nanocolloids and specify the time and temperature ranges of the applications of patchy NPs.

Nanoscopic morphological effect on the optical properties of polymer-grafted gold polyhedra

“…6c), conrming that the PS-graed concave cube could express enhanced spectral responses to changes in the temperature. It appears that such a blue-shi in the LSPR spectra could be attributed to the local refractive index change due to partial detachment of the PS shell 35 and decrease in the refractive index of the surrounding medium at the elevated temperatures, 36 which could be supported with dynamic light scattering (DLS) spectra ( Fig. 6d) as well as our observation in irreversible LSPR spectral shi without the core morphology being changed.…”

The Effect of Chemical Structure of OEG Ligand Shells with Quaternary Ammonium Moiety on the Colloidal Stabilization, Cellular Uptake and Photothermal Stability of Gold Nanorods

“… 15 , 79 , 80 In contrast to the formerly accepted view, recent research demonstrating that the gold-sulfur coupling in gold–thiol self-assembled monolayers (SAMs) has a physisorbed rather than chemisorbed (or covalent) character supports the possibility of ligand release. 81 , 82 Moreover, a ligand desorption can be caused by heating 83 and by an intensive fs-laser irradiation of GNPs, leading to their reshaping and melting that trigger the breaking of the S-Au bond. 84 , 85 In the blood stream, the released free ligands can then cause toxicity or induce tissue pathology.…”

Engineering heterogeneity of precision nanoparticles for biomedical delivery and therapy

“…Nanostructures with topographically or chemically distinctive surface patches. They include such as inorganic NPs modified with ligand patches, 25d,29 multicompartment polymer micelles obtained from phase separation, 22,30 etc.…”

“…DNA‐based strategy allows for fabricating patchy NPs with high precision and complexity, but the method suffers from its high cost, low yield, and poor scalability. Phase‐segregation of end‐grafted polymers on NPs provides a simple yet inexpensive approach to the preparation of NPs with surface patterns of polymers 29a‐e,36 . For instance, when water was added into polystyrene‐grafted AuNPs in DMF, the end‐grafted polymer chains collapsed and segregated to form pinned micelles on the surface of NPs and hence defined polymeric patches (Figure 2D).…”

“…This strategy allows for effective control over the dimensions, spatial distribution and surface density of patches on NPs. When anisotropic NPs with different shapes are used, the formation of patches on NPs strongly depends on the shapes of inorganic NPs 29b,37 . For Au nanocubes, polymeric patches are preferentially formed on the high‐curvature regions (e.g., vertices and edges) of the NPs 29b …”