title: In situ monitoring, separation, and characterization of gold nanorod transformation during seed-mediated synthesis.
abstract: The control of gold nanorod (GNR) solution-based syntheses has been hindered in part by the inability to examine and control the conversion of precursor seed populations to anisotropic materials, which have resulted in low yields of desired products and limited their commercial viability. The advantages offered by tandem separation and characterization methods utilizing asymmetric-flow field flow fractionation (A4F) are principally achieved as a result of their non-disruptive nature (minimizing artefacts), fast throughput, and in-situ analysis. With hyphenated A4F methods, resolved populations of seeds and secondary products, up to long aspect ratio rods, have been achieved and exemplify progress towards elucidating mechanistic aspects of formation and thus rational design. While there have been previously reported studies on A4F separation of GNRs, to our knowledge, this is the first published investigation of in situ GNR growth, separation, and characterization based on A4F, where its utilization in this capacity goes beyond traditional separation analysis. By using hydroquinone as the reducing agent, the conversion of the initial seed population to a distribution of products, including the GNRs, could be monitored in real time using A4F hyphenated with a diode array detector. Transmission electron microscopy confirms that the number of peaks observed during fractionation corresponds with size and shape dispersity. This proof-of-principle study introduces A4F as a technique that establishes a foundation for future mechanistic studies on the growth of GNRs from gold seeds, including conversion of the seed population to initial products, a topic highly relevant to advancing progress in nanomanufacturing.
authors.affiliation: Materials Measurement Science Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD, 20899-8520, USA.|ANSER, 5727 Leesburg Pike N-5000, Falls Church, VA, 22041, USA.
authors.forename: Thao M
authors.initials: TM
authors.lastname: Nguyen
authors.affiliation: Materials Measurement Science Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD, 20899-8520, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Pettibone
authors.affiliation: Laboratoire de Physico- et Toxico-Chimie de l'Environnement, Université de Bordeaux, CNRS, 351 Cours de la Libe'ration, Talence, 33405, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Gigault
authors.affiliation: Materials Measurement Science Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD, 20899-8520, USA. vince.hackley@nist.gov.
authors.forename: Vincent A
authors.initials: VA
authors.lastname: Hackley
mesh_terms: D031521:Fractionation, Field Flow; D006046:Gold / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D043942:Nanotubes
chemical_list: D006046:Gold
keywords: Field flow fractionation; Gold nanorod; Nanomanufacturing; Nanomaterial; Seed-mediated growth; Separation; Transformation