Atmospheric Pressure Plasma Fabrication Of Conjugated Polymer Fluorescent Nanoparticles

Having excellent fluorescent intensity and photostability, fluorescent nanomaterials have widespread applications in chemical sensor, optical material and biological detecting and labeling. However, it is still a significant challenge to achieve controllable synthesis of fluorescent nanomaterials with large amount and desired morphologies, structures and properties, whichi is a foundation and perquisite for the applications of fluorescent nanomaterials. Fluorescent polymer nanoparticles have remarkably high and tailorable fluorescence and were proposed as an alternative to inorganic quantum dots, with their potential cytotoxicity, and to dye-loaded colloids. This dissertation primarily aim at atmospheric pressure plasma vapor synthesis of polymer nanoparticles with emphasis on the control of morphology, structure and chemical composition and their optical properties of the obtained materials by plasma parameters. The research work presented can be categorized into four parts:1) Characterization of plasma dischargeDuring atmospheric pressure plasma polymerization functional nanomaterial process, plasma parameters are closed related to the growth of nanoparticles, it also have great impact on the morphology, chemical structure and optical properties of polymer nanoparticles. The discharge characteristics of our plasma setup are investigated with electrical measurements and numerical simulation. The measured waveforms of applied voltage and discharge current suggest that the discharge show a multi current peak uniform discharge mode under frequency of 7 kHz. The reaction and dynamic process of monomer in the plasma phase can be easily controlled under this uniform discharge mode, so we can tune the size of nanoparticles by plasma parameters. The lower energy of plasma species under atmospheric pressure helps the monomer keep a better chemical structure integrity during plasma reaction process, thus obtain fluorescent polymer nanoparticles.2) Fabrication and manipulation of morphology and size of polypyrrole nanoparticlesPolypyrrole nanoparticles with different morphology and size were synthesized by a comb-like atmospheric pressure plasma. Discharge power was the key role in controlling the morphology of polypyrrole nanoparticles, however the size of polypyrrole nanoparticles could be manipulated with gas residence time and monomer partial pressure. Chemical structure analysis show that discharge power and gas residence could tuned the chemical structure of polypyrrole nanoparticles, lower discharge power and high Ar flow rate could guarantee the chemical structure integrity of most monomer in plasma polymerization process. Combined the experiment result and simulation results, we proposed the "activation-nucleation-condensation-discharging-surface growth" model of polymer nanoparticles in atmospheric pressure plasma. Under the directing of this model, we fabricated polypyrrole nanoparticles by parallel plate plasma.3) Optical properties of polypyrrole nanoparticlesThe polypyrrole nanoparticles show a blue fluorescent with exciting laser with wavelength of 350 nm. Optical properties of polypyrrole nanoparticles were tuned with plasma parameters. Based on the size, chemical structure and optical properties of polypyrrole nanoparticles, we put forward the fluorescent mechanism of polypyrrole nanoparticles.4) Fabrication of polythiophene-rhodamine B copolymer nanoparticlesPolythiophene and polythiophene-rhodamine B copolymer nanoparticles were fabricated by comb-like plasma. We obtained high fluorescent polymer nanoparticles by adjust Forster energy transfer between thiophene and rhodamine B molecule. The quantum yield of pothiophene fabricated by plasma is 0.0599, which is higher than the 0.00943 of quantum yield of polypyrrole. By doped with rhodamine B, the quantum yield of copolymer nanoparticles reaches to 0.114. Due to Forster energy transfer between rhodamine B and thiophene, the fluorescent peak of copolymer nanoparticles red shift from 460 nm to 550 nm.