Abstract
Abstract Time-of-flight secondary ion mass spectrometer (TOF-SIMS) is capable of simultaneously analyzing trace organic molecules and inorganic elements in mass ranging from hydrogen atom to synthetic and natural polymers with molecular weight up to ten thousands and more. TOF-SIMS could distinguish analytes with mass resolution different by 10000 at ppma to ppba sensitivity. Top monolayer atomic or molecular information could be determined by adjusting primary ion current density. Chemical images with lateral resolution 100 nm or less can be obtained by using Ga+ ion gun. The nm-scale depth profile and sub-□m area analysis capabilities inherent in TOF-SIMS extend its applicability to broad fields such as microelectronics, nano-technology, polymer science, life science technology, environmental analysis, \medical technology and clinical diagnostics. TOF-SIMS could simultaneously provide critical chemical information and is a multi functional state-of-the-art instrument. In chapter 2, the round robin study of reference standards of Cl, S and C implanted into Cu films with known energy and dosage using five SIMS instruments was attempted in this work. Quantifying these impurities and comparing the results in terms of relative sensitivity factor (RSF) was the objective to check the discrepancy in results. Significant differences in RSFs but similarity in maximum peak concentration among different instruments was observed. Each sample was tested for the background level of C, O, S and Cl before being ion-implanted. The extent of uncertainty due to sample inhomogeneities was estimated using analytical results from a single instrument run by an operator. Relative standard deviations (RSDs) of maximum peak concentration 5.5 % and of peak position for Cl (1x1015 ions/cm2) were obtained, respectively. The detection limit and dynamic range were estimated from the depth profiles. In chapter 3, use of TOF-SIMS to analyze plasticiser like bis(2-ethylhexyl) phthalate (DEHP) from the inner surface of the blood bags and their migration into the blood is discussed. Food packing materials were also analyzed for DEHP. The simplicity of using TOF-SIMS with improved mass resolution as an aid in the identification and analysis are discussed. The TOF-SIMS results, the fragmentation pattern and the ratio of ions were comparable to those obtain from traditional GC-MS analysis, indicates that TOF-SIMS could be a promising technique for direct analysis of DEHP, and phthalates in general, in blood bags and food packagings made of polymeric materials In chapter 4, an easy and rapid method to doped biotin into polypyrrole thin film by electro-polymerization was demonstrated. The results of fluorescence and TOF-SIMS image have an agreement with each other. Modification of Ppy/Biotin surface could be made for further application. Degradation study shows biotin doped polypyrrole was stable in the PBS solution. No significant decay was found after two week. Applying 0.5 mA constant current for 5 min for electro-polymerization could form approximately 4 μm thick polypyrrole thin film on gold electrode. Electro-polymerization at 25 oC showed higher ion intensity than 4 oC of m/z 227(532:444). It might be due to the increasing of the diffusion coefficient of biotin toward the electrode surface. In chapter 5, four different polymers for DNA delivery and three polymers for siRNA delivery into cells were synthesized. All these four polymers for DNA delivery showed promising result compared with C32 polymer from previous screening. They also show good transfection efficiency in the presence of serum in vitro. They might have great potential to delivery gene in vivo also. siRNA delivery showed better efficiency compared with commercial transfection reagent Lipofatamine 2000. Cytotoxicity of these polymers at low concentration is acceptable. For DNA delivery, compared with viral vector, non-viral cationic polymer vectors provide a lot of advantages; most significant is safe and easy to produce. These polymers might further conjugate with functional peptides and PEG to increase their tranfection efficiency and specific cell targeting. In chapter 6, Polypyrrole(dodecylbenzene sulfonate) (PPy(DBS)) was electro-polymerized on indium tin oxide (ITO) glass using different concentration of sodium dodecylbenzene sulfonate (NaDBS) ranging from 0.002M to 0.2M in aqueous solution. The PPy(DBS) films were studied using time of flight secondary ion mass spectrometry (TOF-SIMS) in which the cation and anion doping concentrations were monitored on surface and along the thickness of the film. TOF-SIMS depth profiles showed interesting variations of sodium concentration along the thickness of electro-polymerized PPy(DBS) films. The morphology of the PPy(DBS) films was characterized using field emission scanning electron microscope (FE-SEM) and correlate with conductivity study.