We assembled small gold NPs at the LLI. The films were analysed with x-ray reflectivity and GISAXS to determine the coverage and interparticle spacing of the NPs at the interface and correlated with optical reflectance measurements in order to produce a “plasmon ruler”.
Large (42 nm) gold NPs were assembled at the LLI. The citrate concentration in the aqueous phase was varied to control the assembly of the NPs. I studied the optical properties of the films made at different citrate concentration with transmission spectroscopy. The spacing between the NPs could be increased or decreased in situ depending on whether the amount of citrate was increased or decreased respectively. The reversibility of this process was studied.
The 42 nm gold NPs were then tagged with a Raman reporter (4-MBA) and similar modulation of the spacing with citrate concentration was carried out while simultaneously monitoring the SERS and optical response.
I performed a study on the assembly of gold nanorods at the LLI where I decreased the spacing between the rods in situ by adding acid to the organic phase. During this transition to a close packed GNR array, I monitored the optical and SERS response of 4-MBA which was adsorbed onto the GNRs. The Raman signal increased 40 fold.
Shaped NPs were assembled at the liquid-air interface (LAI). The arrays formed at the LAI were extracted and dried onto glass substrates to form a device. Their Raman and optical response was measured, determining the optimum geometry and composition of NPs which presented enhanced Raman signals. Spherical gold NPs, nanorods, stars, triangles and spherical silver NPs were studied.
We investigated the detection of CEA, a biomarker for colorectal cancer. A NP sandwich immunoassay approach was used using crumpled gold substrate with silver NPs tagged with a Raman reporter. To form the sandwich immunoassay, the gold substrates were incubated for 2h in serum or buffer samples containing CEA down to concentrations of 10 ng/mL. A concentration above 10 ng/mL indicates that colorectal cancer may be present. The CEA binds to the CEA antibody on the gold substrate. The substrate is them incubated in the silver NP solution. Due to the CEA antibody on the surface of the silver NPs they can bind with the CEA protein attached to the gold surface. Only samples containing CEA presented a signal for the 4-MBA tagged NPs.
Exploitation and dissemination of results:
Publications:
D1.2 “Tuneable 2D self-assembly of plasmonic nanoparticles at liquid | liquid interfaces. Nanoscale 2016, 8, 19229-19241.”
D1.3 Manuscript under preparation “The effect of citrate on the assembly of gold nanoparticles at liquid-liquid interfaces. 2017.”
D1.4 Manuscript under preparation: “Controlling the SERS response of 2D gold nanoparticle films at the liquid-liquid interface. 2017.”
D1.5 Manuscript (submitted to Nature Materials): “Electrotuneable Nanoplasmonic Liquid Mirror, 2017.”
D2.1 Manuscript under preparation. “A simple, fast, upscalable method to assemble plasmonic NPs into arrays at a liquid interface for application as SERS substrates, 2017”
D 2.2 Publication (accepted), “Monitoring plasmon coupling and SERS enhancement through in situ nanoparticle spacing modulation, Faraday Discussions, 2017. Article ID: FD-ART-05-2017-000162.R1”
Seminars and conferences:
Oral presentation at the SERS Faraday Discussions, 2017 (Glasgow, UK). “Monitoring plasmon coupling and SERS enhancement through in situ nanoparticle spacing modulation”
London Centre of Nanotechnology seminar series, Imperial College London, 2017. “Tuneable 2D self-assembly of plasmonic nanoparticles at liquid interfaces”
King’s College London, Physics department, invited seminar, 2016. “Precise control on the self-assembly of plasmonic nanoparticles at liquid interfaces tailored for SERS applications”
