Abstract
Understanding interfacial phenomena in soft materials such as wetting, colloidal stability, coalescence, and friction warrants non-invasive imaging with nanometer resolution. Super-resolution microscopy has emerged as an attractive method to visualize nanostructures labeled covalently with fluorescent tags, but this is not amenable to all interfaces. Inspired by PAINT we developed a simple and general strategy to overcome this limitation, which we coin 'iPAINT: interface Point Accumulation for Imaging in Nanoscale Topography'. It enables three-dimensional, sub-diffraction imaging of interfaces irrespective of their nature via reversible adsorption of polymer chains end-functionalized with photo-activatable moieties. We visualized model dispersions, emulsions, and foams with ∼20 nm and ∼3° accuracy demonstrating the general applicability of iPAINT to study solid/liquid, liquid/liquid and liquid/air interfaces. iPAINT thus broadens the scope of super-resolution microscopy paving the way for non-invasive, high-resolution imaging of complex soft materials.
Highlights
Interfaces play an essential role in physical, biological and chemical processes, ranging from colloidal stability, energy conversion, and phase-transfer catalysis to signal-transduction, molecular recognition, and molecular transport across membranes
Emulsions, and foams with ∼20 nm and ∼3° accuracy demonstrating the general applicability of iPAINT to study solid/liquid, liquid/liquid and liquid/air interfaces. iPAINT broadens the scope of super-resolution microscopy paving the way for non-invasive, high-resolution imaging of complex soft materials
To evaluate the possibilities and limitations of iPAINT as a complementary tool to visualize interfaces with high precision, we start off by imaging aqueous dispersions of monodisperse, spherical hydrophilic silica nanoparticles, which are broadly applied as biomaterials and in food formulations, photonics, coatings, and responsive materials.[15,16]
Summary
Interfaces play an essential role in physical, biological and chemical processes, ranging from colloidal stability, energy conversion, and phase-transfer catalysis to signal-transduction, molecular recognition, and molecular transport across membranes. This is a direct consequence of their ubiquitous presence, especially in nanostructured materials with high surfaceto-volume ratios due to the small dimensions of the building blocks. In the last decade super-resolution microscopy emerged as an attractive technique complementary to X-ray diffraction, electron microscopy (EM), and atomic force microscopy (AFM) to study interfaces with nanometer resolution in 3D.1–4 It is suited for dynamic, soft materials where minimal sample perturbation is essential and differences in electron density are small. Recent STORM experiments unravelling the self-assembly mechanism and architecture of complex synthetic molecular systems[8,9] demonstrate that super-resolution microscopy offers unique insights into man-made materials
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