Laser Ablation and Photo-Fragmentation Processes

In the late 1990, research into the LA synthesis of Cu nanostructures followed two roads (i) depositions in vacuum or imder an inert gas and (ii) LA in the liquid phase. 

A brief description of NP formation with LA in an inert gas atmosphere (route i) is as follows. Initially, interaction between the laser and metal target generates a plume of evaporated atoms that collide with gas molecules at the front of the expanding plume. This causes the plume atoms to thermalize, and a shock wave 

Although, during recent years, several interesting studies on the fundamental aspects have been conducted [282], and papers providing evidence of Cu NPs formahon [281, 283] from gas-phase processes have been prepared, during the past few years the technique has mainly evolved towards solution-based strategies. 

The first examples of nonoxidized Cu NPs produced by LA in soluhon were provided by Yeh and collaborators, who converted an isopropanol suspension of CuO powder into Cu NPs by using a Nd YAG laser [both fundamental (1064nm) and second harmonic wavelengths were investigated] [284]. A few years later the same authors investigated the effect of thiols on the system [285], while Tsuji et al. studied the influence of laser wavelength on the efficiency of ablation of metallic copper targets immersed in an aqueous solution [286]. 

Subsequently, many studies have been conducted on the Nd YAG laser ablation of bulk copper [287-289] or Cu ° powder [290, 291], and on targets in solvents such as water [287, 291], isopropanol [289, 290], acetone [287] and polysiloxane [288]. In Ref. [289], PVP was investigated for the LA preparation of polymer-protected Cu NPs. 

---