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The objective of my research is to develop new surface optochemical sensors for studying cellular processes by investigating techniques to modify surface properties. The spectral characteristics of the modified surfaces and coatings are designed to show remarkable changes after interaction with analytes from biological fluids and cells. My studies focused on pancreatic cells and addressed the need for improved techniques to measure zinc release from pancreatic cells (chapter 3, 4) and to measure the metastasis potential of cancerous pancreatic cells (chapter 5). Chapter 3 describes the development of zinc sensing glass slides by conjugating a carboxylmodified ZnAF-2 to an amino functionalized glass surface. The sensor was used for the measurement of glucose-stimulated zinc ion release from cultured beta pancreatic cells with impact in diabetes research. In chapter 4 is described conjugation of the carboxyl-modified ZnAF-2 to antibody molecules (A2B5) that specifically recognize pancreatic cells. This enabled for the first time the use of targeted zinc sensors to monitor zinc release events from pancreatic cells. Chapter 5 describes development for the first time of a fluorescence sensor to measure the proteolysis activity of pancreatic cancer cells in microfluidic systems. The sensor was fabricated using a Layer by layer (LbL) deposition of polyelectrolyte. The sensor was based on Fluorescence Resonance Energy Transfer (FRET) between luminescent quantum dots (serve as donors) and rhodamine molecules (serve as acceptors) that are separated by multi-layers of polyelectrolytes. The microfluidic platform enables precise delivery of reactants to assemble the sensor and facilitate unique cellular assays of enzymatic activity and enzymatic expression on pancreatic cancer cells.

聚（N-異丙基丙烯酸醯胺）（PNIPAM）微凝膠是一種内部有化学交联的三維網絡結構的軟膠體。這種微凝膠的物理性質是介於硬球膠體和超軟軟的星形聚合物或者膠束之間的。根據微粒的柔軟程度，微凝膠可以發生網絡互穿或者形變。因此塞滿微凝膠的體系的有效體積分數可以遠遠超過硬球系統裏的緊密堆積體積分數。這樣的系統會出現比硬球系统更加豐富的相行為。然而現在仍然缺乏對軟膠體系統在超過緊密堆積體積分數時變現的機構和性質的研究。特別是有些理論預測出的相行為仍然還沒被實際的實驗觀測的到。 / 本論文採用了一種新穎的方式去研究微凝膠體系的微流變，這種方法結合了粒子追蹤微流變和磁鑷系統。這種方法本質上是通過一種消逝波（產生於全內反射顯微鏡（TIRM）中的固液介面）作為入射光來探測靠近平直表面上事先植入的探針微粒（直徑為幾個微米）的位移。這個儀器通過記錄來自探針微粒的散射光強度來追蹤植入的探針微粒在垂直於固體水平面上的熱運動。對於位移的記錄可以達到十個納米的精度，使得它成為很靈敏的空間位置探測器。再者，通過添加了磁鑷系統，使得我們能夠有效地通過震蕩的力來在三維空間裏操控植入的微粒。通過控制探針微粒的運動，可以測量微凝膠懸浮液裏局部原位的粘彈性質。我們研究了濃度依賴和溫度依賴的PNIPAM微凝膠懸浮液的結構變化和相行為。 通過微流變的研究，讓我們第一次通過分析微凝膠懸浮液的粘彈性，確認觀測到了由有效體積分數導致的可逆轉的流體態-玻璃態-劉體態的相轉變過程。 / Soft colloids such as poly(N-isopropylamide) (PNIPAM)-based microgels are colloidal particles that consist of chemically cross-linked three-dimensional polymer networks. The physical nature of these microgel particles thus lies in between that of hard-sphere colloids, and ultrasoft star polymers as well as micelles. Due to the softness of the particles, microgels can interpenetrate or compress. As a result, microgels can be packed to effective volume fractions far above solid particles close packing, leading to the existence of much richer phase behavior when compared to simple hard colloidal particles. However, there is still a lack of knowledge on the structure and properties of soft colloid suspensions at and above close packing, and in particular some theoretically predicted phase behavior has not yet been reproduced by the experimental studies. / This thesis presents a novel approach to study the rheological properties of soft microgel suspensions using a combination of particle-tracking microrheology and magnetic tweezers. We essentially employ an evanescent wave (generated by a solid/liquid interface in the total internal reflection microscopy (TIRM)) as the incident light source to probe the displacement of an embedded probe particle (of a few micrometers diameter) near a flat surface. By measuring the scattered intensity, this technique allows tracking of the thermal motion of the embedded particle perpendicular to the solid surface to a precision of tens of nanometers, making it a highly sensitive spatial detector. Moreover, the integration of a magnetic driving force into the TIRM enables us to effectively manipulate the embedded particle in three dimensions by an oscillatory force so that the local viscoelastic properties of the microgel suspensions can be measured by resolving the particle motion. We investigated the concentration- and temperature-dependent on the structural ordering and phase behavior of PNIPAM microgel suspensions. Microrheology allows us, at a first time, to identify an effective volume fraction driven re-entrant liquid-glass-liquid phase transition by looking at the viscoelastic properties of the suspensions. We show that this result is related to the softness of the microgel particles under a confined condition, and discuss our findings in view of the existing theoretical predictions for soft particles. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Hua, Li. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references. / Abstracts also in Chinese. / 摘要 --- p.i / Abstract --- p.ii / Acknowledgement --- p.iv / Chapter 1 --- p.1 / Chapter 1.1 --- Introduction to colloids --- p.1 / Chapter 1.1.1 --- Phase transition in hard colloidal system --- p.2 / Chapter 1.1.2 --- Phase transition in soft colloidal system --- p.3 / Chapter 1.2 --- Overview of phase transition in microgels --- p.4 / Chapter 1.3 --- Simulation of soft colloids’ phase diagram --- p.8 / Chapter 1.4 --- Reference and Notes --- p.12 / Chapter 2 --- p.15 / Chapter 2.1 --- Overview of the microrheology methods --- p.15 / Chapter 2.1.1 --- Passive techniques of microrheology --- p.16 / Chapter 2.1.2 --- Active techniques for microrheology --- p.23 / Chapter 2.2 --- Microrheometer based on incorporating Magnetic Tweezers to Total Internal Reflection Microscopy --- p.29 / Chapter 2.2.1 --- Particle tracking system - TIRM --- p.30 / Chapter 2.2.2 --- Magnetic Tweezers as driven force --- p.32 / Chapter 2.2.3 --- Calibration of the magnetic force --- p.35 / Chapter 2.3 --- Reference and Notes --- p.37 / Chapter 3 --- p.44 / Chapter 3.1 --- Overview of the series of experiments --- p.44 / Chapter 3.2 --- PNIPAM microgel synthesis and characterization --- p.44 / Chapter 3.3 --- Microrheology of PNIPAM microgels suspension --- p.47 / Chapter 3.3.1 --- Volume Fraction dependence measurements --- p.49 / Chapter 3.3.2 --- Temperature depended measurements --- p.53 / Chapter 3.4 --- References and Notes --- p.55 / Chapter 4 --- p.56 / Chapter 4.1 --- Discussion and Conclusion --- p.56 / Chapter 4.2 --- Future Perspectives --- p.59 / Chapter 4.3 --- References and Notes --- p.61

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Surface spectroscopic techniques have been applied to facets of the flotation beneficiation and hydrometallurgical extraction of sulfide minerals to enhance the fundamental understanding of these industrially important processes. As a precursor to the determination of surface chemical composition, the sub-surface properties of some sulfide minerals that have not previously been fully characterised were also investigated. The electronic properties of ??-NiS and ??-NiS (millerite), Ni3S2 (heazlewoodite), (Ni,Fe)9S8 (pentlandite), CuFe2S3 (cubanite), CuFeS2 (chalcopyrite), Cu5FeS4 (bornite) and CuS (covellite) were investigated by conventional and synchrotron X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy augmented by ab initio density of state calculations and NEXAFS spectral simulations. Particular aspects studied included the relationship between sulfur coordination number and core electron binding energies, the higher than expected core electron binding energies for the sulfur in the metal-excess nickel sulfides, and the formal oxidation states of the Cu and Fe in Cu-Fe sulfides. It was concluded that the binding energy dependence on coordination number was less than previously believed, that Ni-Ni bonding was the most likely explanation for the unusual properties of the Ni sulfides, and that there was no convincing evidence for Cu(II) in sulfides as had been claimed. Most of the NEXAFS spectra simulated by the FEFF8 and WIEN2k ab initio codes agreed well with experimental spectra, and the calculated densities of states were useful in rationalising the observed properties. XPS, static secondary ion mass spectrometry (SIMS) and NEXAFS spectroscopy were used to investigate thiol flotation collector adsorption on several sulfides in order to determine the way in which the collector chemisorbs to the mineral surface, to differentiate monolayer from multilayer coverage, and to characterise the multilayer species. It was found that static SIMS alone was able to differentiate monolayer from multilayer coverage, and together with angle-resolved NEXAFS spectroscopy, was also able to confirm that 2-mercaptobenzothiazole interacted through both its N and exocyclic S atoms. The altered layers formed on chalcopyrite and heazlewoodite during acid leaching were examined primarily by means of threshold S KLL Auger electron spectroscopy, but no evidence for buried interfacial species was obtained.

Probing the surface chemistry of thiol ligand binding to cadmium chalcogenide nanoparticles is important to clarify factors involved in quantum dot stability and surface functionalisation. This research is a spectroscopic investigation aimed at gaining a better understanding of the interaction/bonding of various ligands to CdS, with respect to the use of CdS in biological imaging. The findings of this research are important to the more general field of cadmium chalcogenide materials as biological imaging agents. Deposited CdS nanoparticle films were used in this work as model quantum dot surfaces for ligand adsorption studies. The adsorption of the monothiol-containing ligands, mercaptoacetic acid, mercaptopropionic acid, and mercaptoethanol, to CdS thin films were studied in situ using attenuated total reflectance infrared spectroscopy. The absence of an S-H stretch absorption for the adsorbed species showed that adsorption occurred via the deprotonated thiol group. The adsorption of the dithiol-containing ligands α-lipoic acid, dihydrolipoic acid, and dithiothreitol to CdS nanoparticle films was investigated. The adsorption of dihydrolipoic acid and dithiothreitol was found to occur via both thiol functional groups and an additional interaction between the carboxylate group and the CdS surface. The adsorption of α-lipoic acid to CdS in the presence of light proceeded with photo-oxidation of the CdS surface and reductive cleavage of the disulfide bond of α-lipoic acid to produce some adsorbed dihydrolipoic acid and thiosulfate. The adsorption of α-lipoic acid to CdS in the absence of visible light showed no photo-oxidation, and suggested adsorption occurred via retention of the disulfide bond. The kinetics of adsorption and desorption of oxalic acid on deposited anatase TiO₂ films were studied to investigate the feasibility of extracting molecular information from attenuated total reflectance infrared spectroscopic kinetic data of ligand processes on deposited particle films. Oxalic acid adsorbed on anatase TiO₂ is a well-studied example and is reported to result in three different surface species. The profile of the desorption data indicated contributions from three different components. Different component contributions were unable to be obtained from the adsorption data which is attributed to adsorption occurring much faster than desorption and thus being relatively insensitive to the presence of different adsorbed species. The kinetics of adsorption and desorption of mercaptoacetic acid on CdS were investigated. The desorption data profile indicated the presence of two adsorbed species with different affinities for the CdS surface, the exact chemical nature of which can only be speculated upon given the absence of distinguishing IR spectral features. Ligand exchange reactions at the surface of oleate and trioctylphosphine oxide-capped CdS quantum dot films were investigated. Adsorbed oleate was coordinated to the CdS in a chelating bidentate manner through the carboxylate functional group, while adsorbed trioctylphosphine oxide was coordinated though the P=O functional group. Ligand exchange reactions on the oleate and trioctylphosphine-capped CdS films were studied, and exchange with monothiol-containing ligands was observed only at solution pH where the exchanging ligand was uncharged. Avidin-biotin bioconjugation reactions were carried out on CdS films, which involved the sequential adsorption of mercaptoacetic acid, the protein avidin, and the subsequent binding of the ligand biotin. The spectral data suggested that avidin underwent a conformational change upon adsorption to the CdS surface. This conformation appeared to be perturbed again upon binding of biotin, and it is speculated that the conformation partially reverted back to the native solution conformation.

Monolayer protected nanoparticles (MPNs) display fascinating size-dependent electronic, optical and catalytic properties. They are promising candidates to be used as building blocks with which to construct new generation nanoarchitectures and nanodevices for sensing, electronic and optoelectronic applications. The aggregation and dispersion of colloidal nanoparticles is one of the key issues closely related to their potential applications. Our knowledge of the colloid stability of nanoparticle dispersions with small sizes is still in its infancy, however, thymine is one of the bases in DNA, and is a pH sensitive and chromatic molecule. In the present study, thymine-functionalized self-assembled monolayer protected gold nanoparticles were synthesized. Their morphology and surface structure were characterized using TEM, UV-vis, FTIR, DSC-TGA and XPS techniques. The colloid stability of thymine-capped gold nanoparticle dispersions as a function of the type and concentration of monovalent salt, pH and particle size in alkaline aqueous solution were investigated. The manipulation of colloid stability with light was further explored. The results and conclusions are summarized inthis thesis.

Quartz particles of various discrete particle size ranges have been methylated to varying known mounts using trimethylchlorosilane and their flotation behaviour has been assessed in a modification of the Hallimond tube. For each particle size there is a definite degree of. surface coverage below which the particles do not float. A 'flotation domain' is identified which shorvs that both coarse (-100pm) and fine (-10pm) particles require a greater degree of surface coverage to initiate flotation than do intermediate (-40pm) particles. Water contact angles have been measured on quartz plates and powders which have been methylated (under the same conditions) with trimethylchlorosilane. Both advancing and receding water contact angles measured on quartz plates as a function of degree of surface methylationare in good agreement with the angles predicted by the Cassie equation. Advancing water contact angles measured on quartz particles as a function of degree of surface methylation are also in good agreement with angles predicted by the Cassie equation up to surface coverages of'about 70%. The angles measured at higher surface coverages are less than those anticipated by the Cassie equation. The flotation behaviour of the particles has been compared with that predicted by existing flotation theories. It has been shown that coarse particle behaviour is predicted by the kinetic theory of flotation proposed by Schulze. Fine particle behaviour, however, only qualitatively agrees with Scheludko's theory of fine particle behaviour. Calculated induction times, in conjunction with observed flotation behaviour, indicate that the bubble-particle attachment process is most efficient for particles of about 38pm in diameter ander the set experimental conditions used in this study. Flotation rate trials were performed for three particle size ranges and rate constants were evaluated for the various degrees of surface coverage. It was found that the dependence of rate constant on particle size is essentially linear.

Ellipsometry was used to study the effects of surface energetics and temperature on the equilibrium adsorptive behavior exhibited by β-lactoglobulin. β-Lactoglobulin isotherms at 25, 37, and 55°C were constructed for this purpose. The surfaces of acrylic, polycarbonate, polyester, glass, and #304 stainless steel were contacted with protein solutions of varying concentration, buffered at pH 6.7 with mono- and dibasic sodium phosphate. After three hours, the surfaces were mildly rinsed with deionized water and dried overnight. Optical properties of each film were ellipsometrically measured and the adsorbed mass was calculated as a function of film thickness and refractive index. Contact angle methods were used to measure the hydrophobicity exhibited by each of the five solid surfaces. However, interpretation of protein adsorption results based solely on solid surface hydrophobicity proved unworkable. For polymers (low-energy surfaces), the adsorbed mass of protein was explained with reference to the degree of extensibility of molecular structure. Glass (a high-energy surface) was observed to adsorb the greatest mass of β-lactoglobulin. Stainless steel was observed to adsorb the least mass of β-lactoglobulin and the plateau values of protein adsorption were found to be consistent with those reported elsewhere, and to lie within the range of adsorbed mass on metal surfaces in general. The temperature dependence of β-lactoglobulin adsorption could not be clearly quantified. Apparently, any differences in adsorbed mass were too small to be detected by the instrument. In any event, other investigators have not detected any significant difference in adsorbed mass as long as the temperature was below the denaturation temperature of the protein. / Graduation date: 1991

Scanning Tunneling Microscopy (STM) has been used to study the physisorption and chemisorption behaviour for three simple organic haloalkanes; 1,5 Dichloropentane (DCP), Bromomethane (CH3Br) and Chloromethane (CH3Cl)) on Si(100) 2x1, at temperatures ranging from 270 K to room temperature. The results were interpreted by Density Functional Theory (DFT) performed by collaborators at McGill University and the University of Liverpool. Physisorbed molecules of DCP were found to self assemble into stable lines aligned predominantly perpendicular to the Si dimer pair rows on the surface. A novel mechanism for line formation of Dichloropentane, termed, Dipole Directed Assembly (DDA), was elucidated by DFT calculations. For CH3Br three different patterns of dissociative attachment of reaction products (CH3 and Br/Cl) were observed, and assigned to three reaction pathways. These experimentally determined relative yields were used to obtain differences in reaction activation energy, Delta Ea, between the reaction pathways. These, in turn, were compared with computed differences in reaction barriers, Delta Eb, obtained ab initio for the same pathways by DFT. For CH3Cl, two single-molecule patterns of attachment were found, and a new reaction pathway for attaching CH3Cl in long chains of alternating CH3 and Cl was discovered. The mechanisms for chain growth were determined experimentally by examination of single molecular steps. This mechanism was explained ab initio by DFT to be the result of relative barrier heights for the possible chain-growth pathways.