Magnetic resonance force microscopy (MRFM) is a new measurement technique combining scanning probe microscopy (SPM) and MR spectroscopy, offering the potential of high resolution chemical specific imaging. MRFM is based on the principle of force detection of magnetic resonance (FDMR) in which the magnetisation of a sample in a magnetic field is coupled to an atomic force microscopy cantilever via a field gradient. Magnetic resonance is used to modulate the sample magnetisation at the cantilever resonant frequency and the resulting oscillating force on the cantilever leads to oscillations which may be detected optically. The high sensitivity of force detection offers the potential for single electron spin sensitivity. This thesis describes instrumental aspects of ESR based FDMR experiments and presents the first results at high fields (3.3T). High fields are advantageous for sensitivity and spectral resolution. However, they pose significant technical challenges. FDMR measurements on the organic conductor (fluoranthene)2PF6 were carried out in experiments based around an existing quasi-optical high field ESR spectrometer. Further measurements on (FA)2PF6 and DPPH are presented together with progress towards the construction of a high field MRFM system, based on a commercial SPM instrument. Experiments were performed with both magnet-on-cantilever and sample-on-cantilever configurations with the former the favoured method for potential imaging applications. Signal detection uses a novel fibre-optic interferometer. Cantilever magnets of low conductivity ferrite appear to be more promising for high Q measurements than the metallic magnets favoured by most other groups. Experiment sensitivities are estimated at around 4.4 x 10⁸ polarised electron spins, comparable to conventional commercial ESR spectrometers. Experimental consistency was difficult, especially regarding the positioning of probe and sample, an area in which refinement is essential for repeatable and sensitive experiments. The potential for imaging is attractive and the prospect of single spin detection is discussed.

published_or_final_version / abstract / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

The best for PhD thesis in the Faculties of Arts, Architecture, Business & Economics, Education, Law and Social Sciences (Universityof Hong Kong), Li Ka Shing prize, 2006-2007 / published_or_final_version / abstract / Psychology / Doctoral / Doctor of Philosophy

Coherent transient effects are the optical analogs of the many transient phenomena seen in pulsed nuclear magnetic resonance experiments on spin systems. For example, photon-echo and optical nutation are the respective optical equivalents of spin echo and transient nutation of nuclear magnetic resonance. In Stark-switching and frequency-switching techniques the laser field and the molecules are brought into resonance in a sequence of pulses, the rest of the time they remain well off-resonance. So far it has been assumed that the off-resonance field does not have any measureable influence on the experimental results and is utilized to implement a very efficient detection scheme. This work discusses how the off-resonance field affects the coherent transient effects. It is shown here how this field, by inducing changes in the index of refraction as small as 10⁻⁶ produces easily observable effects in photon echo and delayed optical nutation.

Magnetic resonance imaging (MRI) is an imaging technique that is used in hospitals worldwide. The images are acquired through the use of an MRI scanner and the clinical information is provided through the image contrast, which is based on the magnetic properties in biological tissue. By altering the scanner settings, images with different contrast properties can be obtained. Conventional MRI is a qualitative imaging technique and no absolute measurements are performed. At Center for Medical Imaging and Visualization (CMIV) researchers are developing a new MRI technique named synthetic MRI (SyMRI). SyMRI is based on quantitative measurements of data and absolute values of the magnetic properties of the biological tissue can be obtained. The purpose of this master thesis has been to take the development of SyMRI a step further by developing and implementing a visualization studio for SyMRI imaging of the human brain. The software, SyMRI Brain Studio, is intended to be used in clinical routine. Input from radiologists was used to evaluate the imaging technique and the software. Additionally, the requirements of the radiologists were converted into technical specifications for the imaging technique and SyMRI Brain Studio. Additionally, validation of the potential in terms of replacing conventional MRI with SyMRI Brain Studio was performed. The work resulted in visualization software that provides a solid formation for the future development of SyMRI Brain Studio into a clinical tool that can be used for validation and research purposes. A list of suggestions for the future developments is also presented. Future clinical evaluation, technical improvements and research are required in order to estimate the potential of SyMRI and to introduce the technique as a generally used clinical tool.

In the work undertaken here, NMR has been used to ascertain the structure of some 1,2,4-triazoles. The investigation provides information concerning the structure of potentially tautomeric triazoles such as hydroxy- and aminotriazole. Connected with this aspect of triazole chemistry is the larger problem of mesohydric tautomerism. The present study also yields information for a comparison of substituent effects in triazoles, N-heteroaromatic substances and benzene.

The ligands 2-(bis(2-(octahydro-2-oxobenzo[b][1,4]oxazin-4-yl)ethyl)amino)acetic acid trihydrochloride and bis(2-(octahydro-2-oxobenzo[b][1,4]oxazin-4-yl)ethyl)amine trihydrochloride are synthesized for the formation of Gd(III) complexes, potentially useful as MRI contrast agents. Speciation and hydration numbers of the Gd(III) complexes of 1,7- bis(2-hydroxycyclohexyl)-1,4,7-tris(carboxymethyl)-1,4,7-triazaheptane (Cy2DETA.3A) and 1,7-bis(2-hydroxycyclohexyl)-1,7-bis(carboxymethyl)-1,4,7-triazaheptane (Cy2DETA.2A) can be inferred from spectroscopic studies of the analogous Eu(III) complexes, due to their similar ionic radii, charge and coordination geometry. The phosphorescence emission spectra for the Eu(III) complexes are recorded as function of pH, in buffered and aqueous media. Modulation of the relative intensities of the emission bands is observed for both Eu(III) complexes. Spectroscopically determined pKa values are used to determine potential solution speciation. Ligand pKa values were determined potentiometrically. Attempts were made to correlate results from potentiometric titrations with that of lanthanide luminescent titrations of these complexes. Hydration states (q) were determined for the Eu(III) complexes at spectroscopically significant pH values, in buffered and aqueous media. The results confirm the formation of a octadentate complex between Eu(III) and Cy2DETA.3A, with the inclusion of one H2O molecule in the inner sphere. The complex has high stability and is responsive towards changes in pH and analyte concentration (o-phthalate); potentially suitable as a luminescent sensor. The heptadentate complex formed between Cy2DETA.2A and Eu(III) is substantially weaker, with precipitation of Eu(OH)3 observed at neutral pH, that limits its potential application as a luminescent sensor.

No description available.

Law Wing Cheung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.I / Acknowledgements --- p.V / List of Publications related to this project --- p.VI / Contents --- p.VII / Chapter Chapter 1 --- Introduction --- p.1-1 / Chapter Chapter 2 --- Literature Review / Chapter 2.1 --- Surface Plasmon Waves --- p.2-2 / Chapter 2.2 --- Excitation of Surface Plasmon --- p.2-4 / Chapter 2.2.1 --- Surface Plasmon Coupling Schemes --- p.2-6 / Chapter 2.3 --- Detection Techniques used in SPR sensors --- p.2-13 / Chapter 2.3.1 --- Angular Interrogation --- p.2-14 / Chapter 2.3.2 --- Wavelength Interrogation --- p.2-15 / Chapter 2.3.3 --- Intensity Interrogation --- p.2-16 / Chapter 2.3.4 --- Phase Interrogation --- p.2-16 / Chapter 2.3.5 --- Commercial SPR biosensors --- p.2-18 / Chapter 2.3.6 --- Comparison between Detection Techniques --- p.2-19 / Chapter 2.4 --- Applications of SPR biosensors --- p.2-21 / Chapter Chapter 3 --- Principle of Surface Plasmon Resonance Sensing Technology / Chapter 3.1 --- SPR Phenomenon --- p.3-1 / Chapter 3.2 --- Conditions for Surface Plasmon Resonance --- p.3-5 / Chapter 3.3 --- Wave-vectors --- p.3-7 / Chapter 3.4 --- Surface Plasmon Resonance described by Fresnel's Theory --- p.3-8 / Chapter 3.5 --- Concept of Surface Plasmon Resonance Biosensing --- p.3-10 / Chapter Chapter 4 --- Experiments / Chapter 4.1 --- Highly sensitive differential phase-sensitive surface plasmon resonance biosensor based on Mach-Zehnder configuration --- p.4-1 / Chapter 4.1.1 --- Materials required --- p.4-1 / Chapter 4.1.2 --- Experimental Setup --- p.4-2 / Chapter 4.1.3 --- Principle of Differential Phase Measurement --- p.4-3 / Chapter 4.1.4 --- Photodetector Circuitry --- p.4-6 / Chapter 4.1.5 --- Digital Signal Processing --- p.4-7 / Chapter 4.1.6 --- Polymer based Micro-fluidic System Integrated with SPR Biosensor --- p.4-9 / Chapter 4.2 --- Phase-sensitive Surface Plasmon Resonance Biosensor using the Photoelastic Modulation Technique --- p.4-12 / Chapter 4.2.1 --- Materials required --- p.4-12 / Chapter 4.2.2 --- Experimental Setup --- p.4-13 / Chapter 4.2.3 --- Principle of Photoelastic Modulation Technique and Signal Processing --- p.4-14 / Chapter 4.2.4 --- Operation Principle of Photoelastic Modulator --- p.4-17 / Chapter 4.3 --- Sample Preparations --- p.4-18 / Chapter 4.3.1 --- Glycerin-water Mixtures --- p.4-18 / Chapter 4.3.2 --- "PBS, BSA and BSA antibody" --- p.4-19 / Chapter 4.3.3 --- "RPMI, Trypsin, Cells and SDS" --- p.4-20 / Chapter Chapter5 --- Results amd Discussions / Chapter 5.1 --- Experimental setup I: Highly sensitive differential phase-sensitive surface plasmon resonance biosensor based on Mach-Zehnder configuration --- p.5-1 / Chapter 5.1.1 --- Measuring various glycerin-water concentration mixture with silver-gold sensing layer --- p.5-1 / Chapter 5.1.2 --- Comparison between the sensitivity of our setup and reported setup based on phase detection --- p.5-4 / Chapter 5.1.3 --- Discussion on 0.01° system resolution --- p.5-7 / Chapter 5.1.4 --- Experiment on monitoring BSA-BSA antibody binding reaction --- p.5-9 / Chapter 5.1.5 --- Matching oil and glass slide --- p.5-11 / Chapter 5.1.6 --- Experiments on monitoring BSA-BSA antibody binding reaction with integrated microfluidic system --- p.5-12 / Chapter 5.1.7 --- Experiment on observing cell adhesion properties on gold surface under the influence of trypsin --- p.5-14 / Chapter 5.1.8 --- Discussion on the non-specific binding between trypsin and gold surface --- p.5-16 / Chapter 5.1.9 --- Modifying the gold surface with BSA layer --- p.5-17 / Chapter 5.1.10 --- Experiment on observing cell adhesion properties on the gold surface under the influence Sodium Dodecyl Sulfate (SDS) --- p.5-18 / Chapter 5.2 --- Experimental setup II: Phase-sensitive surface plasmon resonance biosensor using the photoelastic modulation technique --- p.5-21 / Chapter 5.2.1 --- Measurement on difference glycerin-water concentration mixture --- p.5-21 / Chapter 5.2.2 --- Experiment on monitoring BSA-BSA antibody binding reaction --- p.5-23 / Chapter Chapter 6 --- Conclusions and Future Works / Chapter 6.1 --- Conclusions --- p.6-1 / Chapter 6.2 --- Future Works --- p.6-2 / References --- p.R-1 / Appendix / Chapter A. --- Phase Extraction Routine written by Matlab --- p.A-1 / Chapter B. --- Mathematical expressions for calculating the phase angle in the experiment of SPR biosensor using the Photoelastic Modulation Technique --- p.A-6 / Chapter C. --- Relationship between Concentration and Refractive Index of Glycerin-Water Mixture --- p.A-11 / Chapter D. --- Physical Properties of Bovine Serum Albumin --- p.A-12 / Chapter E. --- Simulation Curve written by Matlab --- p.A-13

Detection of oligonucleotide target has been performed with a sandwich assay scheme. We compare the detection performance of strategies using probe oligonucleotide with or without gold nanoparticles (Au-NPs, 20nm) capped on 3'. Our experimental results reveal that while the DNA detection implemented with NIS can provide high sensitivity, both dynamic range and detection limit can be amplified with the aid of Au-NPs on 3' of the probes. The current detection limits of NIS with and without Au-NPs are 0.4 femtomole and 1 nanomole respectively. (Abstract shortened by UMI.) / Finally, this work presents a systematic study of the surface-enhanced Raman-scattering (SERS) properties of nanoparticle island substrates (NIS) and their application for oligonucleotide target detection. To effectively implement SERS on NIS and identify an optimal condition for DNA detection, the relationship between extinction maximum (lambdamax) and SERS enhancement factor (EF) will be explored in detail. This work demonstrates high S/N ratio SERS spectra can be achieved with NIS that has lambdamax located within a spectral window (∼60nm) defined by the excitation wavelength (514nm) and the scattered Raman wavelength. The highest EF measured is about 4x10 8 with a thickness of Ag being 50 A. / In addition, a surface plasmon enhanced ellipsometry (SPEE) biosensor scheme based on the use of a photoelastic modulator (PEM) has been explored. We showed that the polarization parameters of a laser beam, tan psi, cos Delta and ellipse orientation angle &phis;, can be directly measured by detecting the modulation signals at the 1st and 2nd harmonics of the modulation frequency under a certain birefringence geometry. This leads to an accurate measurement of refractive index variations within the evanescent field region close to the gold sensor surface, thereby enabling biosensing applications. Our experimental results confirm that the new scheme offers a decent detection limit of 2x10-7 refractive index unit (RIU) or 5ng/ml of biomolecule solute concentration without any compromise in dynamic range. / We have demonstrated that the sensitivity limit of intensity-based SPR biosensors can be enhanced when we combine the contributions from phase with that of amplitude instead of just detecting the amplitude or phase variation only. Experimental results indicate that an enhancement factor of as much as 20 times is achievable, yet with no compromise in measurement dynamic range. While existing SPR biosensor systems are predominantly based on the angular scheme, which relies on detecting intensity variations associated with amplitude changes only, the proposed scheme may serve as a direct system upgrade approach for these systems. / We have developed a novel design of multi-pass surface plasmon resonance (SPR) biosensor with differential phase interrogation based on multi-pass interferometry. This new configuration provides an intrinsic phase amplification effect of over two-fold by placing the SPR sensor head in a signal arm of the interferometer so that the interrogating optical beam will traverse the sensor surface infinite number of times. Experimental interferometers based on the Michelson and Fabry-Perot configurations have been employed to experimentally verify this amplification effect through the comparison with the Mach-Zehnder configuration. Results obtained from the salt-water mixtures, antibody-antigen, and protein-DNA binding reaction have confirmed the expected phase measurement enhancement. / Yuan, Wu. / Adviser: H. P. Ho. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3582. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 115-132). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.