A commercial Ion Mobility Spectrometer that is designed to detect Chemical Warfare Agents (CWAs), is modified by the addition of a second ion gate, and connected to a commercial Ion Trap Mass Spectrometer (ITMS). The addition of the second gate allows selection of individual ion mobility peaks for m/z analysis in the ITMS. This was demonstrated with the organophosphorus ester ions (CWA nerve gas simulants). The ITMS was used to perform isolation and fragmentation of the CWA simulants ions produced in the IMS. For the organophosphates dimethyl methylphosphonate, diethyl methylphosphonate and diisopropyl methylphosphonate, two ion mobility peaks were observed, which are shown to be the ammoniated monomer and ammoniated dimer ions. Using an ElectroSpray Ionisation (ESI) - ITMS, the fragmentation pathway of dimethyl ethylphosphonate (DMEP) is investigated. The isotopomers of DMEP have unusual fragmentations, and density functional theory calculations are used to aid in the interpretation of the mechanisms involved in these fragmentations. Of note, it is shown that entropy must be taken into consideration, and hence the free energy of the final transition involved in the mechanism, so that the true rate-limiting steps can be determined. Preliminary fragmentations using ESI-ITMS of eighteen other organophosphorus esters have been undertaken. These give an insight as to which fragmentations will require further investigations involving Density Functional Theory (DFT) calculations and deuterated isotopomers to fully understand the mechanisms involved.

The work presented in this thesis deals with two important low dimensional nanostructures: carbon nanotubes (CNTs) and quantum dots (QDs). In the part of the work related to CNTs a novel method for growing CNTs without the need of metal catalyst is presented. The as produced CNTs were grown by means of chemical vapour deposition on Si-Ge islands and on Ge dots grown with the Stransky — Krastanow method on top of silicon substrates. Through rigorous characterisation products of the method were identified as single wall carbon nanotubes (SWCNTs) with diameters of 1.6 and 2.1 nm. Acquired Raman spectra showed very low intensity or none D — band while the G’ band was of high intensity indicating that the as produced CNTs may be of high quality. A by-product of this method is amorphous fibres which can be easily eliminated when exposed to HF vapour. As this method does not employ metal particles it is fully compatible with the front end silicon processing and therefore opens up the prospect of merging carbon nanotubes with silicon technology. Furthermore CNTs were utilised as probes for atomic force microscopy (AFM). For the fabrication of the CNT probes two methods were applied successfully: the surface growth method and the pick up method. The latter was found to be substantially more efficient than the former and although not proper for mass production it is ideal for laboratory use as it can potentially generate thousands of CNT probes. The as fabricated CNT probes, had diameters in the range of 4 to 7 nm. Using CNT probes the surface of a mesoporous material with pore diameter of 7 to 12 nm and repeated distance of 15 to 18 nm was imaged, proving the high resolution that can be achieved with such probes and that AFM can be applied successfully to mesoporous materials. The latter has the potential to considerably expand the knowledge and the control of such materials to the nanoscale. In the part of the work related to QDs a time resolved two colour pump photoluminescence (PL) technique was applied, with the aim to probe the coherent properties of the excitonic ground state of a single Stransky-Krastanow InGaAs QD. The method comprises of two pulses of different energy; a delayed blue pulse that pumps the GaAs barrier and an infrared (IR) pulse that pumps the excitonic ground state of the QD. The PL of the 1st excitonic excited state of the QD is used in order to probe the occupancy of the ground state. The detection is carried out at zero laser background and thus having a considerably higher signal to noise ratio than other pump and probe methods. A PL intensity variation and a red shift in the energy of the I excitonic excited state were observed, with both effects being dependant upon the intensity of the JR pulse but independent of the time delay and its energy. Further investigations showed that the IR excitation causes all PL and absorption lines of the QD to red shift, induces broadening of the absorption lines and increases the background absorption. Comparison with temperature dependent PL measurements showed that although heating might contribute to the above effects it cannot be the sole reason for their occurrence. Because of the above effects the time resolved two colour pump method cannot be applied as such for probing the coherence of QD ground excitonic state and needs to be modified further.

This thesis describes experimental and theoretical studies of interrogation systems for determining fluorescent decays of order a few microseconds. The studies have enabled optimised design of interrogators for sensing oxygen using a fluorescent polymerencapsulated ruthenium complex. Two basic interrogation methods were explored, using blue LED excitation. The Rapid Lifetime Detection (RLD) scheme, a fluorescence interrogation method based on direct interrogation of the decay curve following pulsed excitation was generalised, and a novel method for optimising measurement precision derived. The effect of background light on the optimum was quantified. Dissolved (aqueous) oxygen concentration was measured to a precision of 1 part per billion using a 1 second response time (the peak fluorescence power was only 12.5±0.5pW). A second interrogation method, where the phase delay between an intensity modulated excitation source and the resultant fluorescence is processed to make measurements, was for the first time, fully analysed for measurement of exponential decays. When measuring fluorescence lifetimes in the range 2.9-3.3μs, a precision of 2.3 x 10-10 s Hz-0.5 was achieved. (The peak fluorescence power was 500±25pW). A novel combination of ruby optical temperature sensor insert and oxygen sensing layer was demonstrated as a simultaneous temperature and oxygen sensor. A new fluorescence calibration standard consisting of thermally stabilised titanium-dopedsapphire sample was constructed to calibrate and test the indicators. This work was sponsored by a BRITE EuRam European project, which helped determine the priorities of the research.

This thesis presents an investigation into the morphology of palladium (Pd) size selected clusters and industrial Pd catalysts using high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) technique. The driving force of this work is to establish reliable and efficient methods for the structural characterisation of nanostructures. The characterisation of nanostructures is essential to our fundamental understanding of cluster use within applications, such as catalysis. The complexity of the morphology of industrial catalysts presents a significant challenge to rapid screening techniques. This thesis presents an efficient method which uses size selected clusters as mass standards in STEM based mass spectrometry. Size selected clusters were created using a radio frequency magnetron sputtering cluster beam source in conjunction with a lateral time of ight mass selector, Pd clusters were soft-landed onto amorphous carbon grids between the size range of N = 454 to 10,000 (\(\pm\)4%), with a deposition energy of 500 eV. The quantitative image analysis allows one to gain insight into each catalytic Pd particle and, in combination with two-dimensional diameter measurements, evaluate the three dimensional morphology of the particles. The use of the cluster source has also allowed investigation into the formation mechanisms of nanostructures, finding specific size-dependant morphological features for Pd clusters. Elongation of Pd clusters has been observed for cluster sizes of \(\geq\) 2000 atoms, as well as the onset of voids within the cluster structure for sizes \(\geq\) 2622. HAADF-STEM analysis has proved to be an invaluable tool in the determination of cluster size, independent of morphology, as well as enabling specific structural features within clusters to be revealed. An investigation into the atomic structure of supported Pd\(_{887}\) clusters is also presented. Specific structural motifs are identified using aberration corrected STEM within the sample range via direct comparison with simulated HAADF-STEM images of structures simulated using global minimum techniques.