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China has undergone rapid urbanisation over the last few decades, involving both migration into urban areas and the geographical expansion of urban areas. While we know that both migration and urbanisation have a bidirectional relationship with health, this relationship has only been studied to a limited extent in China. In particular, the exiting literature has neglected the effects of migration and urbanisation on health and well-being in later life, instead focusing on the relationship between these outcomes over the short term in relation to temporary rural-to-urban movements. Using an inter-disciplinary approach, drawing literature from economics, epidemiology and sociology, this thesis conceptualises and examines the association between different forms of migration and their relationship with later life health and well-being. It then compares these relationships with the impact of the geographical expansion of urban areas on those who do not migrate, but consequently become urbanised. It then attempts to draw conclusions on likely causal processes. To do this, I use the China Health and Retirement Longitudinal Study (CHARLS), a nationally representative and multi-disciplinary dataset that examines the circumstances of the Chinese population aged over 45 years old. Moreover, using the structure of the dataset, this thesis is able to independently study migration and urbanisation processes. The results show that there are strong associations between migration status and later life health and well-being in China, with migrations to or within urban areas having the largest positive effects, these hold even after accounting for selective features of migration. Moreover, the results show there are no significant differences in health and well-being in later life between return migrants and non-migrants; although return migration seems to positively relate to risky health behaviours in later life. In addition, the results show that urbanisation in China has largely exogenous and positive impacts on health and well-being. This thesis contributes to the literature by examining different forms of migrations in China and showing how these migrations may relate to health and well-being in later life. The results highlight the need to study return migration and urbanisation along with studying migration in China in order to understand the impacts of migration on health and well-being, as these processes may have impacts on the relationship between migration and health and well-being too.

A surge in the developments in nanoscience in recent years has opened the door to new possibilities in the field of semiconductors, in particular the fabrication of high quality semiconductor nanocrystals. These materials are important to the semiconductor photovoltaics and photo induced water splitting devices. The aim of this thesis is to advance understanding regarding the band edge energy level (Eedge) alignment of as-fabricated nanoscale semiconductors (such as quantum dots, QDs) through 'hot injection' methodologies, as well as investigation of the chemical reaction mechanisms behind this synthetic approach. Eedge evolution of binary and ternary cadmium chalcogenide QDs were studied electrochemically, employing an ultramicroelectrode. It was found that, with change in particle size or composition, variations in the band gap were mainly attributed to changes in the conduction Eedge; a non-linear conduction Eedge bowing phenomenon also revealed when tuning the composition of alloyed QDs. A radical reaction during the phosphine-free QDs synthetic approach was detected through NMR, FTIR. and mass spectroscopy, which further led to studies of the chemical reaction mechanism of formation of quaternary CuZnSnS(Se4) (CZTS, CZTSe) and binary iron chalcogenide nanocrystals. By employing a modified electrode approach, Eedge of as-prepared quaternary CZTS(Se) and binary ion chalcogenide nanocrystals were also determined. It was discovered that the conductivity of CZTSe is three orders of magnitude higher than the CZTS nanocrystals; the detection of metallic copper (formed in the precursor preparation step) and different oxidative power of S and Se species, are found to be the reasons behind the- difference in charge transport ability. The scientific contributions reported in this thesis add precious value to the picture of energy level distribution of semiconductors, and the chemical mechanism study provides guidance for scale up production and new material synthesis, which are crucial factors in the fabrication of electrochemical semiconductor devices.