title: Monitoring Early-Stage Nanoparticle Assembly in Microdroplets by Optical Spectroscopy and SERS.
abstract: Microfluidic microdroplets have increasingly found application in biomolecular sensing as well as nanomaterials growth. More recently the synthesis of plasmonic nanostructures in microdroplets has led to surface-enhanced Raman spectroscopy (SERS)-based sensing applications. However, the study of nanoassembly in microdroplets has previously been hindered by the lack of on-chip characterization tools, particularly at early timescales. Enabled by a refractive index matching microdroplet formulation, dark-field spectroscopy is exploited to directly track the formation of nanometer-spaced gold nanoparticle assemblies in microdroplets. Measurements in flow provide millisecond time resolution through the assembly process, allowing identification of a regime where dimer formation dominates the dark-field scattering and SERS. Furthermore, it is shown that small numbers of nanoparticles can be isolated in microdroplets, paving the way for simple high-yield assembly, isolation, and sorting of few nanoparticle structures.
authors: Department of Chemistry, University of Cambridge, Lensfield Rd, Cambridge, CB2 1EW, UK.|Department of Physics, University of Cambridge, Cavendish Laboratory, JJ Thompson Avenue, Cambridge, CB3 0HE, UK.
authors: Andrew R
authors: AR
authors: Salmon
authors: Materials Physics Center (CSIC-UPV/EHU) and DIPC, Paseo Manuel de Lardizabal 4, Donostia-San Sebastian, ES, 20018, Spain.
authors: Ruben
authors: R
authors: Esteban
authors: Department of Physics, University of Cambridge, Cavendish Laboratory, JJ Thompson Avenue, Cambridge, CB3 0HE, UK.
authors: Richard W
authors: RW
authors: Taylor
authors: Department of Physics, University of Cambridge, Cavendish Laboratory, JJ Thompson Avenue, Cambridge, CB3 0HE, UK.|ICFO, The Barcelona Institute of Science and Technology, Barcelona, 08860, Spain.
authors: James T
authors: JT
authors: Hugall
authors: Sphere Fluidics Limited, Babraham Research Campus, Cambridge, CB22 3AT, UK.
authors: Clive A
authors: CA
authors: Smith
authors: Heriot-Watt University, School of Engineering and Physical Sciences, David Brewster Building, Edinburgh, EH14 4AS, UK.
authors: Graeme
authors: G
authors: Whyte
authors: Department of Chemistry, University of Cambridge, Lensfield Rd, Cambridge, CB2 1EW, UK.
authors: Oren A
authors: OA
authors: Scherman
authors: Materials Physics Center (CSIC-UPV/EHU) and DIPC, Paseo Manuel de Lardizabal 4, Donostia-San Sebastian, ES, 20018, Spain.
authors: Javier
authors: J
authors: Aizpurua
authors: Department of Chemistry, University of Cambridge, Lensfield Rd, Cambridge, CB2 1EW, UK.
authors: Chris
authors: C
authors: Abell
authors: Department of Physics, University of Cambridge, Cavendish Laboratory, JJ Thompson Avenue, Cambridge, CB3 0HE, UK.
authors: Jeremy J
authors: JJ
authors: Baumberg
mesh_terms: D006046:Gold / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D044085:Microfluidics / Q000379:methods*; D055620:Optical Phenomena; D012031:Refractometry; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D006046:Gold
keywords: SERS; dark-field spectroscopy; microdroplets; nanoparticle