CC BY
1The 30th International Conference on Advanced Laser Technologies LM-I-11
ALT'23
Laser synthesis of gold and carbon chains in liquid media
K. Ashikkalieva1, V. Kononenko1, N. Arutyunyan1, E. Akhlyustina2, E. Zavedeev1,
A. Vasiliev3'4, V. Konov1
1-Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia
2- National Research Nuclear University "MEPhI", Moscow, Russia
3-National Research Centre "Kurchatov Institute ", Moscow, Russia 4- FRSC Crystallography and Photonics RAS, Moscow, Russia
Main author email address: [email protected]
Ultrashort intense pulses are known to cause processes of nonlinear multiphoton and avalanche ionization in liquid [1]. This initiates structural transformations in liquid media, leading to occurrence radically new compounds and structures (molecules, nanoparticles of different shape, chains etc.). However general physical regularities of laser synthesis in liquid media have been studied, the problem of controlling morphology and sizes of the synthesized structures is not well understood. In particular, the most important problem is to control the shape of synthesized structures by changing the irradiation conditions (the number of laser pulses, pulse duration and repetition rate). Here, we report on synthesizing gold and carbon chains under multiple laser irradiation of liquid solutions.
The materials under study were hydrochloroauric acid (HAuCU) aqueous solutions (5X10-4 mol/L) and colloid solutions of graphite microparticles in ethanol (0.4 mg/ml). The gold ion solutions were irradiated with femtosecond (fs) irradiation of Ti-sapphire laser "Spectra Physics" (x=120-fs, ^=800 nm, f=1 kHz). The graphite colloid solutions were treated with picosecond (ps) irradiation of hybrid laser "Huaray-Olive-1064-40" (x=10-ps, A,=1064 nm, f=10 kHz). The solutions were irradiated at a fixed pulse energy (E = 800 pJ and E = 16 pJ for fs- and ps-pulses, respectively) by varying the number of laser pulses. Optical absorption spectra in the range from UV to near-IR were measured with a double-beam spectrophotometer Perkin Elmer Lambda 950. The morphology of synthesized nanostructures was studied by analyzing their images obtained in a transmission electron microscope (TEM).
It was found that high-intensity femtosecond pulses along with single gold nanoparticles caused formation of numerous elongated (chain) particles [2]. As TEM shows, individual gold nanoparticles can have triangle and round shape, whereas chain structures (up to several nanometers in length) can have linear or dendrite structure. The synthesis of chain structures depended on the pulse number: the maximum concentration of gold chains are observed at the pulse number N«Ncr=4x105; under further irradiation the chains almost completely disappeared. Apparently, elongated nanostructures disintegrated into individual nanoparticles due to the melting and evaporation processes. The thermal disintegration of gold chains during multiple fs-laser irradiation was accompanied with their repeated formation upon switching off the laser (cooling the liquid).
According to the preliminary experiment on picosecond irradiation of pure ethanol, in spectra of the irradiated liquid there were no distinguishable absorption peaks attributed to linear carbon chains (polyynes). This means that ethanol is likely to be resistant to laser irradiation in the range of the processing parameters studied (E=20 pJ, N < 4*107). This is why ethanol was chosen as a solvent for graphite microparticles. It has been found that optical absorption spectra of the ps-irradiated graphite solutions contain a set of lines (216— 297 nm), which are corresponding to polyynes. Among synthesized linear carbon chains there were short (C6H2, C8H2) and longer (C10H2, C12H2, C14H2) ones. It has been found that absorption lines in the spectra become clearly distinguished at N>2*106. Further increase in the number of laser pulses causes the rise in intensity of the absorption peaks related to the polyynes.
This work was supported by the Russian Science Foundation (project no. 19-12-00255-P).
[1] V. Kononenko , K. Ashikkalieva, N. Arutyunyan, et al., Femtosecond laser-produced plasma driven nanoparticle formation in gold aqueous solution, Journal of Photochemistry & Photobiology, A: Chemistry, vol. 426, P.113709 (2022)
[2] K. Ashikkalieva, V.Kononenko, N. Arutyunyan, et al., Laser Synthesis of Gold Nanochains from Hydrochloroauric Acid Aqueous Solutions, Physics of Wave Phenomena, vol. 31, pp. 44-50, (2023)
