Zhu Xiao Lei. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (p. 116-121). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Efficient delivery into cells is essential for many applications. However, cellular access of “cell-impermeable” molecules, such as drugs, sensors, proteins and oligonucleotides, can often be severely limited due to the plasma membrane which protects cells from unregulated influx of hydrophilic materials. In order to solve this issue, several physical techniques and bio-chemical products are today available. One of them is called peptoids (N-alkylglycines). These compounds are peptidomimetics which are resistant to enzymatic degradation, non-immunogenic and are readily prepared by an Fmoc chemical approach. Peptoids based on the "TAT"-peptide (RKKRRQRRR) offer rapid cellular uptake/delivery and low cytotoxicity. In this thesis, based on previous works using fluorescein-cationic peptoids, various fluorescent N-substitued glycines (lysine-like) were prepared by the monomer method followed by solid-phase synthesis. Their cellular uptakes in vitro into several cell lines (such as HeLa, B16F10, HEK293T and primary immune cells) were examined via flow cytometry and microscopy. The cellular delivery of small molecules mediated by the 9mer polymer achieved an efficient and rapid penetration. These results open up a vast number of applications for delivery of macromolecules using nonalysine-like peptoid. In order to demonstrate this ability, the nonalysinelike carrier was used to deliver various biopolymer molecules such as peptides, GFP protein and DNA (in collaboration with Dr. Stefano Caserta). In addition, thanks to the non-cytotoxicity of this cellular transpoter (MTT assays); experiments were carried out in vivo in mice using peptoids labelled near-infrared dyes. The first results have shown that the peptoid is not toxic for the mouse and does not block cell movements. These results allowed the use of 9mer-peptoid as a cellular tracking agent. Based on the development on antimicrobial peptides, the polylysine-like peptoid was also tested as an antibiotic. Recent experiments carried out in collaboration with Dr. Kevin Dhaliwal have revealed a new antimicrobial property of the peptoids. In vitro and in vivo studies have been carried out using both gram positive and negative bacteria. These results present a promising alternative to conventional antibiotics and antimicrobial peptides (AMPs).

It Should Be Familiar is an artist’s book and collection of copper and steel intaglio printing plates. Together they examine shifts in external and internal identities, personal symbols, and perceptions of trauma over time. The book is printed with a plant-based dye mixture that reacts differently to each metal plate. As a parallel to the mentioned personal shifts, images in the book will change color with exposure to the metals as well as UV light.

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The subject of this thesis is the development of a laser light source which could be used in an air pollution monitor to measure the average concentration of sulfur dioxide gas over long paths (>1 km). Many of the problems encountered in designing a long-path pollutant monitor such as instrument cost and reliability, the selection of an optimum spectral region for making the measurement, and light losses due to scattering and turbulence, are considered. The result of these considerations together with a survey of available laser light sources suggested that a frequency- doubled dye laser possessed several advantages over other laser light sources.

<p>The properties relevant for electron transfer processes between dye molecules and semiconductor substrates, titanium dioxide (TiO₂) and zinc oxide (ZnO), have been studied by means of photoelectron spectroscopy, PES, near edge X-ray absorption spectroscopy, NEXAFS, and resonant photoemission, RPES.</p><p>For dye-sensitized solar cells, the currently used dyes are ruthenium polypyridine complexes adsorbed to the semiconductor via carboxyl linker groups. A series of such complexes has been investigated, and the most efficient dye so far, cis-bis(4,4'-dicarboxy-2,2'-bipyridine)-bis(isothiocyanato)ruthenium(II), RuL'₂(NCS)₂, was studied in more detail. The results revealed a high content of thiocyanate orbitals in the highest occupied molecular orbital, HOMO, of this complex, which partly explains its efficiency in the solar cell. The thiocyanate ligands were found to be highly influenced by the substrate when the dye is adsorbed onto ZnO, which is not the case for the corresponding TiO₂ system. </p><p>A bridge bonding between TiO₂ and the L' ligand was proposed, where the carboxyl groups are deprotonated and all oxygens interact with surface titanium ions. For ZnO, the results indicate a different bonding geometry, involving protonated carboxyl groups.</p><p>For the display system a dye molecule, which shifts color upon electrochemical treatment, was adsorbed on TiO₂ and studied in its reduced and oxidized states. The major electronic difference between the two states was shown to occur on the nitrogen atom. In addition, a reversible photoreduction process during the measurements was observed.</p>

This thesis focuses on liquid redox electrolytes in dye-sensitized solar cells (DSCs). A liquid redox electrolyte, as one of the key constituents in DSCs, typically consists of a redox mediator, additives and a solvent. This thesis work concerns all these three aspects of liquid electrolytes, aiming through fundamental insights to enhance the photovoltaic performances of liquid DSCs. Initial attention has been paid to the iodine concentration effects in ionic liquid (IL)-based electrolytes. It has been revealed that the higher iodine concentration required in IL-based electrolytes can be attributed to both triiodide mobility associated with the high viscosity of the IL, and chemical availability of triiodide. The concept of incompletely solvated ionic liquids (ISILs) has been introduced as a new type of electrolyte solvent for DSCs. It has been found that the photovoltaic performance of ISIL-based electrolytes can even rival that of organic solvent-based electrolytes. And most strikingly, ISIL-based electrolytes provide highly stable DSC devices under light-soaking conditions, as a result of the substantially lower vapor pressure of the ISIL system. A significant synergistic effect has been observed when both guanidinium thiocyanate and N-methylbenzimidazole are employed together in an IL-based electrolyte, exhibiting an optimal overall conversion efficiency. Tetrathiafulvalene (TTF) has been investigated as an organic iodine-free redox couple in electrolytes for DSCs. An unexpected worse performance has been observed for the TTF system, albeit it possesses a particularly attractive positive redox potential. An organic, iodine-free thiolate/disulfide system has also been adopted as a redox couple in electrolytes for organic DSCs. An impressive efficiency of 6.0% has successfully been achieved by using this thiolate/disulfide redox couple in combination with a poly (3, 4-ethylenedioxythiophene) (PEDOT) counter electrode material under full sunlight illumination (AM 1.5G, 100 mW/cm2). Such high efficiency can even rival that of its counterpart DSC using a state-of-the-art iodine-based electrolyte in the systems studied.The cation effects of lithium, sodium and guanidinium ions in liquid electrolytes for DSCs have been scrutinized. The selection of the type of cations has been found to exert quite different impacts on the conduction band edge (CB) of the TiO2 and also on the electron recombination kinetics, therefore resulting in different photovoltaic behavior. / QC 20120124

The properties relevant for electron transfer processes between dye molecules and semiconductor substrates, titanium dioxide (TiO2) and zinc oxide (ZnO), have been studied by means of photoelectron spectroscopy, PES, near edge X-ray absorption spectroscopy, NEXAFS, and resonant photoemission, RPES. For dye-sensitized solar cells, the currently used dyes are ruthenium polypyridine complexes adsorbed to the semiconductor via carboxyl linker groups. A series of such complexes has been investigated, and the most efficient dye so far, cis-bis(4,4'-dicarboxy-2,2'-bipyridine)-bis(isothiocyanato)ruthenium(II), RuL'2(NCS)2, was studied in more detail. The results revealed a high content of thiocyanate orbitals in the highest occupied molecular orbital, HOMO, of this complex, which partly explains its efficiency in the solar cell. The thiocyanate ligands were found to be highly influenced by the substrate when the dye is adsorbed onto ZnO, which is not the case for the corresponding TiO2 system. A bridge bonding between TiO2 and the L' ligand was proposed, where the carboxyl groups are deprotonated and all oxygens interact with surface titanium ions. For ZnO, the results indicate a different bonding geometry, involving protonated carboxyl groups. For the display system a dye molecule, which shifts color upon electrochemical treatment, was adsorbed on TiO2 and studied in its reduced and oxidized states. The major electronic difference between the two states was shown to occur on the nitrogen atom. In addition, a reversible photoreduction process during the measurements was observed.

This project employs the biological compounds hemin, melanin, and retinoic acid as photoactive dyes in dye-sensitized solar cells (DSSCs). These dyes are environmentally and economically superior to the standard ruthenium-based dyes currently used in DSSCs because they are nontoxic and widely available. Characterization by linear sweep voltammetry yielded averaged maximum overall conversion efficiency values of 0.059% for retinoic acid, 0.023% for melanin, and 0.015% for hemin. Absorption spectra of hemin and retinoic acid suggest that they would complement each other well when used in tandem in one cell because hemin has a secondary maximum absorption peak at 613nm and retinoic acid has maximum absorption at 352nm. Cells made with hemin or melanin performed better with the use of lower temperatures to seal the cells, and hemin cells performed exceptionally well with exclusion of the sealing procedure. These biologically-derived cells have the potential to advance the development of inexpensive and safer solar energy sources, which promise to serve as clean energy sources in the near future.

The objective of this work was to study the addition of fluorescent whitening agents (FWAs) for efficient use on pigment coating of paper substrates with low grammage and the goal was to achieve high optical response by using low amount of FWAs. A commercial light-weight coated (LWC) paper grade was provided by Stora Enso Corbehem Mill and isotropic laboratory sheets were produced at Stora Enso Research Centre using PFI sheet former. Optical properties such as brightness, whiteness and L, a* and b* colour space values were evaluated using Minolta spectrophotometer with D65 illuminant for both types of substrate using different types and amounts of FWA while the effect of the addition of dye was evaluated in both isotropic sheets and as well as in the coating. The results showed that brightness and whiteness of double-coated paper increased by increasing the amount of fluorescent whitening agent in the coating layer. Also, higher brightness and whiteness was achieved by introducing a higher amount of fluorescent whitening agent in the top coating rather than in a pre-coating. The addition of a shading colorant in the paper substrate had a positive influence not only on the brightness but also on the whiteness of coated paper. / Syftet med denna studie var att studera tillsatsen av fluorescerande vitmedel (FWA) för att effektivisera användningen i pigmentbestrykning av papper med låg ytvikt. Målet var att nå en hög optisk respons men ändå använda en låg mängd FWA. Ett kommersiellt LWC-papper erhölls från Stora Enso, Corbehems pappersbruk, och isotropa laboratorieark tillverkades med PFI-arkformerare på Stora Enso Research Centre. Optiska egenskaper, såsom ljushet, vithet och färgrymd (L, a* och b* värden), hos samtliga prover med varierande mängd och typ av FWA uppmättes med hjälp av en Minolta spektrofotometer med D65 ljuskälla. Effekten av färgnyanstillsats utvärderades både hos handgjorda ark och hos bestrykningslager. Resultaten visade att både ljushet och vithet hos dubbelbestrukna ark ökade med ökad mängd FWA i bestrykningslagren. Högre ljushet och vithet nåddes också när FWA placerades i toppbestrykningen. Tillsats av nyanseringsfärg i papperssubstratet ökade både ljushet och vithet hos de bestrukna arken.