title: High colloidal stability of gold nanorods coated with a peptide-ethylene glycol: Analysis by cyanide-mediated etching and nanoparticle tracking analysis.
abstract: The stability of gold nanorods was assessed following coating with various charged or uncharged ligands, mostly peptides. Highly stable monodispersed gold nanorods were obtained by coating CTAB-stabilized gold nanorods with a pentapeptide with C-terminal ethylene glycol units (peptide-EG). UV-vis spectroscopy of these nanorods suspended in saline solutions indicated no signs of aggregation, and they were easily purified using size-exclusion chromatography. A more stringent measure of nanorod stability involved observing changes in the UV-vis absorbance of gold nanorods subjected to etching with cyanide. The λmax absorbance of peptide-EG coated nanorods red-shifted in etchant solution. The hypothesis that changes in the nanorod aspect ratio led to this red-shift was confirmed by TEM analysis, which showed pit formation along the transverse axis. The etching process was followed in solution using nanoparticle tracking analysis. The red-shift was shown to occur while the particles remained mono-dispersed, and so was not due to aggregation. Adding both etchant solution and peptide-EG to the nanorods was further shown to allow modulation of the Δλmax red-shift and increase the etchant resistance of peptide-EG nanorods. Thus, very stable gold nanorods can be produced using the peptide-EG coating approach and their optical properties modulated with etchant.
authors.affiliation: Institute of Materials Research and Engineering, Agency for Science, Technology & Research (A*STAR), 2 Fusionopolis Way, Innovis, #08-03, 138634, Singapore. Electronic address: freepf@imre.a-star.edu.sg.
authors.forename: Paul
authors.initials: P
authors.lastname: Free
authors.affiliation: Division of Bioengineering, Nanyang Technological University, 637141, Singapore.
authors.forename: Gao
authors.initials: G
authors.lastname: Conger
authors.affiliation: Institute of Materials Research and Engineering, Agency for Science, Technology & Research (A*STAR), 2 Fusionopolis Way, Innovis, #08-03, 138634, Singapore.
authors.forename: Wu
authors.initials: W
authors.lastname: Siji
authors.affiliation: Advanced Environmental & Biotechnology Centre, Nanyang Environment & Water Research Institute, Nanyang Technological University, 637141, Singapore.
authors.forename: Jing Bo
authors.initials: JB
authors.lastname: Zhang
authors.affiliation: Department of Biochemistry, Institute of Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK.
authors.forename: David G
authors.initials: DG
authors.lastname: Fernig
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003486:Cyanides / Q000737:chemistry*; D004573:Electrolytes; D005026:Ethylene Glycols / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D043942:Nanotubes / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry*; D012996:Solutions; D013499:Surface Properties
chemical_list: D003102:Colloids; D003486:Cyanides; D004573:Electrolytes; D005026:Ethylene Glycols; D010446:Peptide Fragments; D012996:Solutions; D006046:Gold
keywords: Colloidal stability; Etching; Gold nanorods; Nanoparticle tracking analysis; Peptides; Red-shift; Sodium cyanide