Abstract
Emerging nanotechnologies demand the manipulation of nanoscale components with the same predictability and programmability as is taken for granted in molecular synthetic methodologies. Yet installing appropriately reactive chemical functionality on nanomaterial surfaces has previously entailed compromises in terms of reactivity scope, functionalization density, or both. Here, we introduce an idealized dynamic covalent nanoparticle building block for divergent and adaptive post‐synthesis modification of colloidal nanomaterials. Acetal‐protected monolayer‐stabilized gold nanoparticles are prepared via operationally simple protocols and are stable to long‐term storage. Tunable surface densities of reactive aldehyde functionalities are revealed on‐demand, leading to a wide range of adaptive surface engineering options from one nanoscale synthon. Analytically tractable with molecular precision, interfacial reaction kinetics and dynamic surface constitutions can be probed in situ at the ensemble level. High functionalization densities combined with rapid equilibration kinetics enable environmentally adaptive surface constitutions and rapid nanoparticle property switching in response to simple chemical effectors.
Highlights
Nanoscale components with programmable chemical reactivity can form the basis of a comprehensive synthetic toolkit that fully integrates nanomaterials with current-day molecular and supramolecular technologies
Dynamic covalent exchange reactions are emerging as a powerful tool for post-synthesis surface engineering of nanoparticles in colloidal solution.[1c,d] We have recently developed metal nanoparticles stabilized by hydrazone-functionalized surface monolayers
The stability of covalently bonded systems, is accompanied by relatively slow exchange kinetics, which we have found to be further retarded by surface confinement when applied for nanoparticle surface engineering.[2b]. We report a “best-of-both-worlds” dynamic covalent nanoparticle (DCNP) synthon that addresses the shortcomings of both our previous technology and the alternative functionalization approaches
Summary
Nanoscale components with programmable chemical reactivity can form the basis of a comprehensive synthetic toolkit that fully integrates nanomaterials with current-day (macro) molecular and supramolecular technologies. We previously accessed high-density aldehyde-derived electrophilic monolayers on metal (Au) nanoparticles using hydrazones, which could be modified post synthesis with either nucleophilic hydrazides to achieve dynamic covalent hydrazone exchange, or with an electrophilic scavenger to reveal surface-bound aldehydes.[2b] Here, we report that introducing the carbonyl species masked as an acetal provides a convenient, rapid and tunable route to dense, single-component monolayers of nanoparticle-bound acetals From these optimized electrophilic nanoparticle starting points, precisely controlled surface densities of aldehydes can be rapidly revealed without requiring addition (and subsequent removal) of scavengers. Facile synthetic access to high densities of kinetically labile exchangeable units opens up a new domain of nanoparticle-bound dynamic covalent reactivity for tuning functionalization, properties and assembly
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