چكيده به لاتين
Nanoparticles play a major role in some applications such as biology medicine, energy conversion and storage, electronics, and information storage. Nanoparticles have large surface to volume ratio. Such size-dependent characteristics provide unique physical and chemical properties for nanoparticles. Within the last two decades, several techniques have been developed for producing nanoparticles with controlled sizes, phases, shapes, and some other properties. These techniques include chemical method, thermal evaporation and condensation, milling, and sputtering. unfortunately, these synthesis methods are relatively expensive and often agglomerated particles with sizes up to several micrometers are formed. in addition, in some of these techniques, harmful and toxic materials are used. furthermore, they may also induce impurities to the nanoparticles by some catalysts.
In recent years, pulsed laser ablation in liquids (PLAL) attracts much attention as a new technique for nanoparticle synthesis. It has been demonstrated that relatively more stable colloidal nanoparticles can be produced by this method. Compared with other techniques, PLAL is an effective, clean, and safe method for synthesis of nanoparticles. Recent investigations show that in PLAL method, size properties of produced nanoparticles significantly depend on laser characteristics such as wavelength, fluence, and pulse duration. It has been also shown that nanoparticle characteristics strongly depend on both target material properties and liquid environment in which ablation occurs. The size of the produced nanoparticles can be tuned to some extent by properly selecting laser and material parameters. Within the last few years, many articles were published in the field of nanoparticles synthesis by PLAL, but only a limited number of them investigated size properties of the nanoparticles produced by PLAL. The effects of liquid environment, laser fluence, liquid depth and number of laser pulses on size properties of nanoparticles produced by PLAL have also been investigated only by a few numbers of authors. Investigation on size properties of the nanoparticles produced by nanosecond laser ablation in various water depths (in the range of a few millimeters) and effect of the number of laser pulses (specifically, within the range of a few thousand to tens of thousands) on mean size and size distribution of colloidal nanoparticles have not been reported yet. Additionally, to the best of our knowledge, the production of nanoparticles by double PLAL with inter-pulse delay times within the range of a few nanoseconds to a few tens of nanoseconds has not yet been reported.
In this thesis, we have reported the synthesis of colloidal aluminum, titanium and silver nanoparticles by single pulse mode and collinear double-pulse laser ablation in liquid medium. The effects of target type, liquid medium, laser fluence, number of laser pulses, liquid depth and inter-pulse delay times between two collinear sequential pulses on the productivity and size properties (mean size and size distribution) of the prepared colloidal nanoparticles was discussed in detail. UV–vis absorption spectroscopy and scanning electron microscopy, inductively coupled-plasma mass spectrometry and image processing techniques were used for the characterization of the produced nanoparticles.
