Dr Andrei Sapelkin Project Abstracts
BSc Project Abstracts
Spectroscopic signal separation in super-resolution microscopy
Over the last two decades, there has been significant progress in achieving optical resolution below the diffraction limit of around 250 nm, which most famously culminated in the award of the Nobel Prize in Chemistry in 2014 "for the development of super-resolved fluorescence microscopy". These advances have enabled to study fixed biological samples in unprecedented details, but significant challenges remain in the area of super-resolution (SR) microscopy when applied to study live cells. The vast majority of SR methods and are based on temporal separation of signals emitted by organic fluorophores and come at a significant time cost (seconds to minutes) as only a small part of the overall picture is collected at a time making live cell SR challenging. The aim of this project is test a methodology for SR biological imaging based on spectral rather than temporal signal separation of light emission from quantum dots (QDs). The proposed methodology relies on size-dependent emission (tuneable from ultra-violet to infra-red range) from QDs due to the quantum confinement effect for the purpose of imaging below the diffraction limit. The methodology will be tested using sub diffraction reference standards (e.g. DNA-based rulers and DNA origami) and will be used to investigate the effects of spectral overlap and of S/N ration on image resolution and precision of localisation of single quantum dots.
Structure and electronic properties of standard and magic-sized semiconductor nanoclusters
It has been long observed, based on the optical properties during and after a reaction, that colloidal semiconductor quantum dots (QDs) within the same batch could be readily divided into a regular nanoclusters and magic-sized nanoclusters (MSNCs). The latter are particles with well-defined sizes that exhibit narrow fluorescence emission peaks with homogeneous broadening of no more than ~ 10 nm (narrow emission bandwidth is desirable for a number of applications). This suggests that the model of particle nucleation and growth in a colloidal solution may not be strictly applicable to these systems. Within this project we will use x-ray absorption data collected at a synchrotron radiation source to explore the relationship between the structure and electronic properties of nanoclusters.
The local structure of liquids
Structural characterisation of liquids has been a significant challenge due to lack of periodicity and hence of the long-range order. We will use x-ray absorption data collected using synchrotron radiation to develop an approach for structural characterisation of liquids using short-range order information. We will then apply this approach to investigate structural evolution of liquid gallium in a wide temparture range.
MSci Review Project Abstracts
Future quantum dot systems
Quantum dots – materials reduced in size down to just a few nanometers possess a range of interesting physical properties due to effect of quantum confinement of the charge carriers (electrons and holes) and a large surface- to-volume ratio. These properties can be used in variety of applications including tagging of living cells and observation of communication in neuron networks. This project aims to review the current trends in quantum dot applications in bio-related areas and identify possible future directions and potential materials.
MSci Research/Investigative Project Abstracts
Spectroscopic signal separation for super-resolution microscopy
Over the last two decades, there have been significant progress in achieving optical resolution below the diffraction limit of around 250 nm, which most famously culminated in the award of the Nobel Prize in Chemistry in 2014 "for the development of super-resolved fluorescence microscopy". The aim of this project is test a methodology for SR biological imaging based on spectral rather than temporal signal separation of light emission from quantum dots (QDs). The proposed methodology relies on size-dependent emission (tuneable from ultra-violet to infra-red range) from QDs due to the quantum confinement effect for the purpose of imaging below the diffraction limit. Within this project we will set up a laser–based system for spectral signal separation and develop software to control data acquisition. The system will be tested using sub diffraction reference standards (e.g. DNA-based rulers and DNA origami) and will be used to investigate the effects of spectral overlap and of S/N ration on image resolution and precision of localisation of single quantum dots.
Single quantum dot structure and light emission
Quantum dots – materials reduced in size down to just a few nanometers possess a range of interesting physical properties due to effect of quantum confinement of charge carriers (electrons and holes) and a large surface-to- volume ratio. These properties can be used in variety of applications including tagging of living cells and observation of communication in neuron networks. This experimental project involves investigation and correlation of structural, electronic and optical properties of quantum dots. Experimental work will include electron microscopy, Raman and photoluminescence measurements.
Structural and optical characterisation of low dimensional and molecular systems
Relationships between structural, electronic and optical properties of low dimensional systems (e.g. quantum dots, molecules, etc.) is one of the central problems in materials charcterisation. Lack of periodicity and small system size presents significant problems for standards structural characterisation techniques such as x-ray diffraction, Raman, etc. Within this project we will investigate capabilities of x-ray absorption and electron energy loss spectroscopies to provide information on structure and electronic properties in non-periodic systems.
