Search

Funder: Isaac Newton Trust, Funder: Leverhulme Trust, Surface-enhanced Raman spectroscopy (SERS) is considered an attractive candidate for quantitative and multiplexed molecular sensing of analytes whose chemical composition is not fully known. In principle, molecules can be identified through their fingerprint spectrum when binding inside plasmonic hotspots. However, competitive binding experiments between methyl viologen (MV2+) and its deuterated isomer (d8-MV2+) here show that determining individual concentrations by extracting peak intensities from spectra is not possible. This is because analytes bind to different binding sites inside and outside of hotspots with different affinities. Only by knowing all binding constants and geometry-related factors, can a model revealing accurate concentrations be constructed. To collect sufficiently reproducible data for such a sensitive experiment, we fully automate measurements using a high-throughput SERS optical system integrated with a liquid handling robot (the SERSbot). This now allows us to accurately deconvolute analyte mixtures through independent component analysis (ICA) and to quantitatively map out the competitive binding of analytes in nanogaps. Its success demonstrates the feasibility of automated SERS in a wide variety of experiments and applications.

Bottom-up assembly of nanoparticle-on-mirror (NPoM) nanocavities enables precise inter-metal gap control down to ≈ 0.4 nm for confining light to sub-nanometer scales, thereby opening opportunities for developing innovative nanophotonic devices. However limited understanding, prediction, and optimization of light coupling and the difficulty of controlling nanoparticle facet shapes restricts the use of such building blocks. Here, an ultraprecise symmetry-breaking plasmonic nanocavity based on gold nanodecahedra is presented, to form the nanodecahedron-on-mirror (NDoM) which shows highly consistent cavity modes and fields. By characterizing > 20 000 individual NDoMs, the variability of light in/output coupling is thoroughly explored and a set of robust higher-order plasmonic whispering gallery modes uniquely localized at the edges of the triangular facet in contact with the metallic substrate is found. Assisted by quasinormal mode simulations, systematic elaboration of NDoMs is proposed to give nanocavities with near hundred-fold enhanced radiative efficiencies. Such systematically designed and precisely-assembled metallic nanocavities will find broad application in nanophotonic devices, optomechanics, and surface science.

Additional file 1: Figure S1. The quantitative of ApoE-/- mice carotid artery HE staining longitudinal and transversal section. Quantitative analysis of media area (A) and adventitia area (B) in carotid artery longitudinal section. The quantitative analysis of media area (C) and adventitia area (D) in carotid artery transversal section. (E) Quantitative analysis of inner diameter in carotid artery longitudinal section. (F) Quantitative analysis of inner diameter in carotid artery transversal section. n= 5 , *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001. Figure S2. Biosafety of PLGA NPs administration and restenosis manipulation. (A) The plasma lipid and lipoprotein levels were measured in Sham group, SO 30 % and SO 70 % with or without NPs treatment (n = 5), *p < 0.05. From top to bottom are triglycerides, total cholesterol, HDL-C, LDL-C. (B) The HE staining of main organs from different groups were representative. Scale bars, 50 μm.

Charge carriers trapped at localized surface defects play a crucial role in quantum dot (QD) photophysics. Surface traps offer longer lifetimes than band-edge emission, expanding the potential of QDs as nanoscale light-emitting excitons and qubits. Here, we demonstrate that a nonradiative plasmon mode drives the transfer from two-photon-excited excitons to trap states. In plasmonic cavities, trap emission dominates while the band-edge recombination is completely suppressed. The induced pathways for excitonic recombination not only shed light on the fundamental interactions of excitonic spins, but also open new avenues in manipulating QD emission, for optoelectronics and nanophotonics applications.

Slurry uniform flow can ensure uniform slurry distribution, temperature distribution, mechanical and chemical reactions, and timely residue removal, which is conducive to the stability of the machining process. Surface pattern of a polishing pad is one of the main factors to control the flow of slurry. To achieve the slurry uniform flow, the hydrodynamics of the slurry were calculated to design the surface grooves on polishing pad. Finite element technology was adopted to simulate the flow field distribution of the designed polishing pad. Particle image velocimetry experiments were conducted to verify the uniformity of slurry flow on the designed pad surface. The polishing experiments with designed and groove-diffused pads were conducted to obtain the high surface quality in the same polishing conditions. The results show that the spiral surface pattern established by a curve equation with 2-mm-width and 1.5-mm-depth grooves was obtained for the slurry uniform flow. The experiments reveal that the new surface pattern retards the slurry flow, causing the radial velocity of slurry to be uniform. Surface roughness Sa of CaF2 crystal polished by the designed pad is 0.251 nm, which is much better than that by the groove-diffused pad. Therefore, the slurry uniform flow is conducive to obtain a better surface quality.

This thesis focuses on how self-assembled optical nanostructures can play a crucial role in nanochemistry. It starts with an introduction to the fundamental plasmonic properties of metal nano-architectures, followed by various self-assembly strategies I explored to form controlled plasmonic aggregates. I then discuss in detail how these structures can be combined with optics to control and probe chemical and physical processes at the nanoscale. Chain aggregates of metal nanoparticles are used to optically control thermally-activated redox processes. These aggregates are further dressed by core-shell quantum dots through direct self-assembly and the resultant hybrid aggregates are used to probe the chemical kinetics using surface-enhanced Raman spectroscopy during heterogenous photo-catalytical reaction induced by quantum dots. Single quantum dots are further sandwiched in individual plasmonic cavities. Manipulation of excitonic nonlinear excitation and relaxation pathways of quantum dots is realised through the coupling between two-photon excited excitons and a plasmon mode provided by the plasmonic cavity. Single atomic features within these plasmonic nanocavities are shown to further enhance the field-confinement. Such extremely confined light is then utilised to monitor single-molecule surface coordination dynamics in real-time. From bulk solution down to single-molecule, a range of systems are demonstrated to illustrate the powerful interplay between plasmonics and nanochemistry.