Probing pH-Tuned Morphological Changes in Core−Shell Nanoparticle Assembly Using Atomic Force Microscopy

This paper reports novel findings of an investigation of pH-tuned morphological changes in a core−shell gold nanoparticle assembly derived from hydrogen-bonding at the encapsulating shells. Our strategy couples the selective assembly of such hydrogen-bonding-linked nanoparticles at patterned substrates with the capability of atomic force microscopy to detect the nanostructural changes in the pH-tuned interfacial process. The selective assembly on a monolayer-patterned substrate provided an ideal imaging platform with an internal standard from the unassembled areas. The detection of significant and reversible changes of both friction and height in the nanoparticle-assembled areas provided new insights into understanding of ionic fluxes and solvation effect within the nanoporous structure, which have important implications to the design of nanoparticle-based interfaces for nanostructured catalysis and molecular recognition.