Ph. D. THESIS 2009

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Our goal is to develope a lasser asisted technique to fabricate continuous and well defined gold nanostructures inspiring by the iron-based photographic technique in gold and its photochemical process. Taking in account that the process has been validated both in solution and in the solid state, preliminary two-photon induced photoprecipitation experiments have been performed. 4.3.1. PSS- matrix for gold microfabrication The TPA iradiation of a gold salt aqueous solution can form gold nanoparticles, insoluble in water, which aggregate short time after generation. On Figure 44 can be seen the optical image of two huge gold colloids obtained in a 0.1 M gold salt solution, when irradiating by a femtosecond laser at 40 mW. Figure 13. Optical image recorded in transmitted light for two huge gold colloids generated in aqueous solution of gold salt at 40 mW. The key point of our experiment was to increase the solution viscosity using different matrices such as xanthane, polyethyleneoxide, gelatine, and poly (4styrenesulfonate acid) as stabilizers. These compounds allow to controll the rate of reduction and to keep the metallic deposition localized in the small volume at the focal point during the laser action and after it stops. From this point of view is required a hydrosoluble and relative chemical stable polymer host, good electrons donor which allow an homogeneus dispersion of high gold salt concentrations without phase separation in the solid state. In this respect we chose the poly (4-styrenesulfonic acid), denoted PSS, which embodies all these properties, as a system stabilizer. Thus, it offers the possibility to fabricate continuous and well defined silver nanostructures by two-photon absorption. Figure 14a) shows gold lines fabricated by TPA at the same laser power when PSS matrix is added to the previous gold salt aqueous solution. 9
a b Figure 14. Gold lines fabricated by laser in thick film of: a) a PSS aqueous solution of gold salt at 30 mW; b) a PSS, gold salt and ammonium ferric citrate aqueous solution of in 40-50 mW range. It is therefore important to study the photochemical reactions of gold salt in polymer matrices. Thus, we created a chemical system that contains tetrachloroauric acid as active specie and ammonium ferric citrate as sensitiser, dispersed into a PSS matrix. The structures are thiner and more regular by adding of sensitizer and required less energy to be written, as can be seen in Figure 14b. That means PSS induces the decrease of size and number of the nanoparticles generated by photoreduction by reducing the reaction rate. The contribution of the polymer film in the photoreduction reaction is not yet elucidated. 4.3.2. Double-line effect in thin PSS matrix The TPA photoreduction process in thin films allows us to fabricate various kinds of 2D structures such as nanodots and nanowires networks. Within our research we have studied the fabrication of metallic wires with dimensions varying from a few hundred nanometers to one micron for their widths, and ranging from a few to several hundred microns for their lengths (see figure 15a). a b 10
Page 1 and 2:
“BABES-BOLYAI” UNIVERSITY CLUJ-
Page 3 and 4:
General Introduction OUTLINE Part A
Page 5 and 6:
3.6.1. Dots 188 3.6.2. 3D structure
Page 7 and 8: Part A: Synthesis and Structural An
Page 9 and 10: H 3C H 3C O O O C C O O 1a O O C C
Page 11 and 12: The two forms are in equilibrium an
Page 13 and 14: Figu re 4 . Th e 13 C-NMR APT (CDCl
Page 15 and 16: set used , the anarmonicities that
Page 17 and 18: Figure 9. ORTEP diagram for the bic
Page 19 and 20: 1.5.1. Tetramethyl 3,7-dihydroxybic
Page 21 and 22: Table 7. The selected molecular par
Page 23 and 24: a b Figure 14. 1 H NMR spectrum (CD
Page 25 and 26: Figure 16. 13 C NMR spectrum APT (C
Page 27 and 28: Absorbance (a. u.) Absorbance (a.u.
Page 29 and 30: icyclo[3.3.1]nonane-3,7-dione solut
Page 31 and 32: m u lt ip let a t a t δ ==1 .7 6 p
Page 33 and 34: Figure 22. 13 C NMR APT spectrum of
Page 35 and 36: Figure 24. NMR investigation of the
Page 37 and 38: (mol·l -1 ) syn 8.8 x10 -3 1.4373
Page 39 and 40: a b Figure 29. 3D FTIR spectra in s
Page 41 and 42: Figure 32. ORTEP diagram for the cy
Page 43 and 44: H2 … N3 = 1.839 Å H5 … N6 = 1.
Page 45 and 46: 2. Conclusions of the part A Differ
Page 47: 20. L. J. Bellamy, “Advanced in I
Page 50 and 51: 2. Experimental part: fabrication a
Page 52 and 53: 3 m 30 m a b Figure 4. Optical imag
Page 54 and 55: (NA 1.25) in phase-contrast (a) and
Page 56 and 57: was chosen instead of an aqueous on
Page 60 and 61: Figure 15. a Optical image of gold
Page 62 and 63: the power as parameter exhibits a m
Page 64 and 65: a b Figure 21 a) Optical image of g
Page 66: 4.5.3. 3D structures The 3D structu
Page 69 and 70: Selected References 1. E. S. Wu, J.
Page 71: VIII. J. Bosson-Ehoomann, A. Mihut,
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Ph. D. THESIS 2009

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