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Reversible Assembly and Disassembly of Gold Nanoparticles Directed by a Zwitterionic Polymer
Author(s) -
Ding Ya,
Xia XingHua,
Zhai HeSheng
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601013
Subject(s) - colloidal gold , polymer , nanoparticle , nanomaterials , colloid , rational design , nanotechnology , ligand (biochemistry) , materials science , chemistry , stabilizer (aeronautics) , nanoscopic scale , chemical engineering , organic chemistry , mechanical engineering , biochemistry , receptor , engineering
Herein, we have successfully introduced the stimuli‐response concept into the controllable synthesis of gold nanoparticles (AuNPs) with designed properties. We used a pH‐responsive zwitterionic polymer that acted as a template and a stabilizer. Gold colloids prepared in situ from the polymer solution have a narrow size distribution of about 5 nm. The assembly and disassembly of AuNPs can be finely tuned by modulating the net charges of the zwitterionic polymer so that they are either positive or negative as a function of the solution pH. Different aggregates and colors appear on altering the solution pH. In acidic solutions, gold colloids form large symmetrical aggregates, while the AuNPs disperse in solutions with a pH≈9.6. However, as the solution pH increases (>9.6), needle‐like aggregates with a small interparticle distances are formed. On the basis of TEM, SEM, 1 H NMR and UV/Vis measurements, we attribute pH‐triggered aggregation and color changes of the gold colloids to the ionization process and conformational change of the polymer. The ionization process governs the choice of ligand anchored on the surface of AuNPs, and the conformational change of the polymer modulates the interspaces between AuNPs. The present approach, which is based on a rational design of the physicochemical properties of the template used in the synthesis process, provides a powerful means to control the properties of the nanomaterial. Furthermore, the colorimetric readout can be visualized and applied to future studies on nanoscale switches and sensors.