Dr Ben Miles, Ph.D.

Fluorescently labelled nanoparticles are routinely used in Correlative Light Electron Microscopy (CLEM) to combine the capabilities of two separate microscope platforms: fluorescent light microscopy (LM) and electron microscopy (EM). The
inherent assumption is that the fluorescent label observed under LM colocalises well with the electron dense nanoparticle observed in EM. Herein we show, by combining single molecule fluorescent imaging with optical detection of the scattering from single… Show more

Fluorescently labelled nanoparticles are routinely used in Correlative Light Electron Microscopy (CLEM) to combine the capabilities of two separate microscope platforms: fluorescent light microscopy (LM) and electron microscopy (EM). The
inherent assumption is that the fluorescent label observed under LM colocalises well with the electron dense nanoparticle observed in EM. Herein we show, by combining single molecule fluorescent imaging with optical detection of the scattering from single gold nanoparticles, that for a commercially produced sample of 10 nm gold nanoparticles tagged to Alexa-633 there is in fact no colocalisation between the fluorescent signatures of Alexa-633 and the scattering associated with the gold nanoparticle. This shows that the attached gold nanoparticle quenches the fluorescent signal by ∼ 95%, or less likely that the complex has dissociated. In either scenario, the observed fluorescent signal in fact arises from a large population of untagged fluorophores; rendering these labels potentially ineffective and misleading to the field. Show less

3D printing and actively switchable redox-active oligo(aniline)-based materials are combined to create novel tuneable 3D photonic materials. By a direct laser writing process, switchable functional structures with submicrometer features are fabricated. Reversible changes in the refractive index of the written materials are generated with negligible size changes.

Nitrogen-vacancy (NV-) defects embedded in nanodiamond have attracted attention for their useful photonic and spin properties, and their exceptional photo-stability. Efficiently detecting nanodiamonds that possess colour centres and discriminating from any background fluorescent contamination is essential for nanodiamond-based technologies, and so necessitates the detection of both the nanoparticle and the fluorescent signature. However, optically detecting small nanodiamonds (<40 nnm)… Show more

Nitrogen-vacancy (NV-) defects embedded in nanodiamond have attracted attention for their useful photonic and spin properties, and their exceptional photo-stability. Efficiently detecting nanodiamonds that possess colour centres and discriminating from any background fluorescent contamination is essential for nanodiamond-based technologies, and so necessitates the detection of both the nanoparticle and the fluorescent signature. However, optically detecting small nanodiamonds (<40 nnm) proves difficult due to the low absorption and scattering cross section of nanodiamonds. Here we demonstrate an all optical method capable of simultaneous colocalising scattered signal from individual nanodiamonds (~10nm) with the fluorescent signature from NV- centres. Show less

We address the sensitivity of Interferometric Cross-Polarisation Microscopy by comparing scattering and absorption by spherical 10nm nanoparticles through a combination of modelling and experiment. We show that orthogonality of light in the two polarisation branches of Cross-Polarisation Microscopy ensures that only light that has interacted with a nanoparticle is interferometrically enhanced. As a result background-free shot noise-limited detection is achieved for sub-μW optical powers at the… Show more

We address the sensitivity of Interferometric Cross-Polarisation Microscopy by comparing scattering and absorption by spherical 10nm nanoparticles through a combination of modelling and experiment. We show that orthogonality of light in the two polarisation branches of Cross-Polarisation Microscopy ensures that only light that has interacted with a nanoparticle is interferometrically enhanced. As a result background-free shot noise-limited detection is achieved for sub-μW optical powers at the sample. Our modelling in particular shows that in the near-infrared regime, above the plasmon resonance frequency of spherical nanoparticles, the cross-polarisation approach is several orders of magnitude more sensitive than conventional extinction based detection. This enhanced near-infrared sensitivity for spherical nanoparticles is promising for applications requiring low absorption and low power imaging of nanoparticles in cells. Show less

The ability to characterize the Point Spread Function(PSF) is crucial in practical microscopy, but requires knowledge of the complex PSF for approaches that detect fields instead of intensities. Here we experimentally measure and theoretically model the volumetric amplitude and phase response of an Interferometric Cross-polarisation Microscope to demonstrate the technique’s capability to provide confocal-like images of weakly birefringent structures in living cells. We find the axial FWHM of… Show more

The ability to characterize the Point Spread Function(PSF) is crucial in practical microscopy, but requires knowledge of the complex PSF for approaches that detect fields instead of intensities. Here we experimentally measure and theoretically model the volumetric amplitude and phase response of an Interferometric Cross-polarisation Microscope to demonstrate the technique’s capability to provide confocal-like images of weakly birefringent structures in living cells. We find the axial FWHM of the amplitude PSF to be 0.70 ± 0.01 μm and 0.83 μm for model and measurement, respectively, on par with confocal microscopy. Ultimately retaining both amplitude and phase information will however enable approaches for improved localisation of objects. Show less