No description available.

by Lam King Shun. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (p. 103-107). / 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. / by Lam King Shun.

DNA has been widely studied in a variety of solvents. The majority of these solvents consist of either aqueous or organic components. The presence of ions or salts in these solvents can further alter DNA properties by changing the melting point or helical structure. The size, charge, and concentration of these additional components can all affect the behaviour of DNA. A new class of solvents, known as ionic liquids have recently gained popularity. Ionic liquids are comprised of entirely of ions and can be liquid at room temperature. Due to their low volatility and ability to dissolve both polar and non-polar substances, they are generating high levels of interest as ‘green solvents’. Although the interaction between DNA and ionic liquids has been characterized, the potential of this interaction is still being studied. It was discovered that when DNA mixed with DNA intercalating dyes was added to ionic liquids, there was a large reduction in fluorescence. Although this fluorescence drop was believed to occur to removal of the dye molecule from the helix, the strength of this interaction has not been researched. In this thesis, the interaction between different intercalating dyes and different ionic liquids was evaluated. We reasoned that perhaps the difference in interaction could be used as a method of separating the DNA-dye complex, which has previously never been accomplished. For example, it has been established that both DNA and cationic dyes have an affinity for ionic liquids. The relative strength of this affinity is undetermined, as well as the comparison to normal aqueous mediums. Although ionic liquids can drastically alter the stability of the DNA duplex by either raising or decreasing the melting point depending on the ionic liquid chosen, we found that the DNA actually has a higher affinity for the aqueous phase. Conversely, intercalating dyes prefer to partition into the ionic phase. The relative affinities of the two components are strong enough for their respective phases that the complex can be split apart and each component can be extracted, allowing for separation of the two.

Stora Enso, a big Swedish-Finnish forest industry company, wants to find a substitute for the dye that is used in their edge wick analyzes. The dye amaranth, that is used today, is a classified substance that is unhealthy and hazardous. It causes irritation to the eyes, skin and respiratory system. Edge wick is a method to determine the amount of penetrated liquid into the unprotected edges of a packaging board (the surfaces are covered with plastic). It is important to analyze liquid penetration to know that the board will sustain the liquids that it might be exposed to, for example sterilizing liquid (hydrogen peroxide), juice or wine. The dye is used as coloring agent for colorless solutions to enable visual evaluation of the penetration. In the present study several colorants were screened and evaluated in edge wick tests with the standard test liquids used at Stora Enso. Machine, pilot and handmade boards were used in the tests. Surface tension of some test liquids was also determined, as it is important to know if the dyes change the liquid properties since this may influence the penetration. The result of the tests was that a new dye was found, Allura red AC. It has a similar chemical structure to amaranth and seems to act in the same way in different type of test conditions. The recommendation is that amaranth be substituted for allura red AC, since the latter is less hazardous and is not a classified substance.

In developing countries many industries use dyes to colour their products, such as textiles, rubber, paper, cosmetics, leather, plastics, and food industries. Such a wide range of using dyes in many industries increases the demand of dye, and currently 100,000 dyes are commercially available with a rough estimated production of 10⁶ tones/year. Without proper treatment, dye effluent can be mixed with surface and ground water system and it may finally enter the drinking water system. Therefore, the treatment of dye effluents before discharge to the environment has become an global challenge due to the stability and adverse effects of dyes. Among the present methods, adsorption has been preferred to other conventional techniques due to the simple design and operation, low initial investment,effectiveness and insensitivity to toxic substances. The high surface area and the presence of permanent negative charge on the surface makes cellulose nanocrystal (CNC) an excellent candidate for the adsorption of basic (cationic) dyes. The objective of this project is to evaluate the adsorption properties of CNC for the removal of methylene blue from aqueous solution by changing the parameters, such as adsorbent dosage, initial dye concentration, pH, temperature and salt concentration. It was found that the adsorption is independent of pH, however increase in temperature and ionic strength decreased the removal percentage slightly. The Langmuir and Freundlich isotherms were used to evaluate the feasibility of the adsorption process. The adsorption capacity of CNC was determined using the linearized form of Langmuir model. It possessed a value of 118 mg/g at pH 9 and 25 °C. To enhance the adsorption, CNC was oxidized with TEMPO reagent to convert primary hydroxyl groups to carboxyl groups that provides more negative charge. After the oxidation, the adsorption capacity increased from 118 to 769 mg/g.

In developing countries many industries use dyes to colour their products, such as textiles, rubber, paper, cosmetics, leather, plastics, and food industries. Such a wide range of using dyes in many industries increases the demand of dye, and currently 100,000 dyes are commercially available with a rough estimated production of 10⁶ tones/year. Without proper treatment, dye effluent can be mixed with surface and ground water system and it may finally enter the drinking water system. Therefore, the treatment of dye effluents before discharge to the environment has become an global challenge due to the stability and adverse effects of dyes. Among the present methods, adsorption has been preferred to other conventional techniques due to the simple design and operation, low initial investment,effectiveness and insensitivity to toxic substances. The high surface area and the presence of permanent negative charge on the surface makes cellulose nanocrystal (CNC) an excellent candidate for the adsorption of basic (cationic) dyes. The objective of this project is to evaluate the adsorption properties of CNC for the removal of methylene blue from aqueous solution by changing the parameters, such as adsorbent dosage, initial dye concentration, pH, temperature and salt concentration. It was found that the adsorption is independent of pH, however increase in temperature and ionic strength decreased the removal percentage slightly. The Langmuir and Freundlich isotherms were used to evaluate the feasibility of the adsorption process. The adsorption capacity of CNC was determined using the linearized form of Langmuir model. It possessed a value of 118 mg/g at pH 9 and 25 °C. To enhance the adsorption, CNC was oxidized with TEMPO reagent to convert primary hydroxyl groups to carboxyl groups that provides more negative charge. After the oxidation, the adsorption capacity increased from 118 to 769 mg/g.

In my study, I attempted to use the high electrical conductivity of graphite modified TiO2 nanoparticles to study the effect of graphite modification to the performance of dye-sensitized solar cell. Graphite oxide (GO) was successfully prepared by the improved Hummer¡¦s method. Graphenes that from the as-prepared GO reduced with hydrazine hydrate and sodium borohydride were characterized by Fourier transform infrared spectroscopy (FT-IR) and UV-visible spectroscopy. The performance of TiO2 based DSSC revealed a short-circuit photocurrent density of 11.24 mA/cm2, an open-circuit voltage of 0.66 V, and a fill factor of 0.48, yielding an overall conversion efficiency of 4.50%. The TiO2 / r-GO composite based DSSC showed higher efficiency than those standard DSSC, revealed a short-circuit photocurrent density of 18.48 mA/cm2, an open-circuit voltage of 0.68 V, and a fill factor of 0.51, yielding an overall conversion efficiency of 7.83%. On the other hand, we found the DSSC that treated with small amount of alcohol in making the TiO2 paste showed superior performance to that with untreated photoanode, the ratio of energy conversion efficiency being 7.11% to 4.50%.

The laser-induced holographic gratings in the azo-dye-doped liquid crystals have been investigated by changing the temperature, and the concentration of the sample, the intensity of the two writing beams, and the polarization of probe beams. The cw Nd:YAG laser has been employed as the writing beams and the cw He-Ne laser has been employed as a real-time probe beam to detect the first order diffraction singals. The gratings are the results of photo-isomerization of azo dye and the structure alignment of liquid crystals. The model has been established to explain the first order diffraction signals, the mechanism of gratings formation and the temperature dependence.

Two experimental rainfall simulation plots in the Edwards Aquifer region of Texas were established to measure the effects of brush clearing on surface and subsurface water movement pathways. Multi-stage rainfall simulations were carried out at a site with Juniperus ashei (ashe juniper) cover both before and after brush removal, with three replications of a particular rainfall event for each vegetation condition. Similar simulations were carried out on a plot with a longstanding grass cover. Both plots included trenches at their downhill ends for observation of shallow lateral subsurface flow. Canopy interception was found to represent a major water loss, with interception of 32.7 mm for an average 166 mm, 5.25 hr rainfall event. Brush clearing had little impact on surface runoff, with no overland flow occurring at the juniper plot for either vegetation condition, while 31.9 percent of applied rainfall moved as overland flow at the grass plot. This difference was attributed to differences in the structure and permeability of the epikarst. Brush removal caused significant (90 percent confidence level) reduction in shallow lateral subsurface flow into the trench after brush removal, with 56.7 percent of water reaching the surface entering the trench for the pre-cut condition and only 43.4 percent for the post-cut condition. However, subsurface water movement through other pathways increased from 31.0 to 54.1 percent after brush removal. This additional water, due to removal of canopy interception, could either move off-site through conduit and fracture flow or remain on site as storage in conduits, unconsolidated caliche/marl layers, or in soil pockets. Two tracer tests with fluorescent dyes were also conducted using simulated rainfall to assess discrete flow paths discharging into the trench at the downhill end of the juniper plot. Analysis of samples from sixteen outlet locations revealed that not all areas of the plot were connected hydraulically to the trench. Additionally, subsurface flow paths were found to have a high degree of interconnection, linking conduit flow outlets with multiple inlet locations on the plot surface. Conduits showed strong connection with an area surrounding juniper vegetation, with rapid water flow (up to 2.4 m/h) from this area.

In this work, we study the technique of Titanium Dioxide(TiO2) work electrode of the dye sensitized solar cells. The research contained four parts. (I)Fabrication of porous TiO2 with sol-gel method. (II)Compare the efficiency between dense layer non-dense layer. (III)Study the characteristics of nanometer photocatalyzer layer with silver atom on porous layer. (IV)Replace the commercial dye with the novel Discotic Liquid Crystal(DLC) material which we synthesized. We compared different TiO2 particle size, and discovered the efficiency of 20nm particle which made Degussa reached 3.31%. After joining dense layer, the efficiency can be up to 3.75%. Finally, we sprayed a silver atom layer, the device efficiency increase to 4.13%. Because of the cost of the commercial dye, we replace the dye with DLC which were synthesized by ourselves. The efficiency is up to 0.46%. We offer a feasible direction in low cost and high-efficiency at present.