“Soft” and “hard” laser treatments of noble metals nanoparticles. How do they work in particle size and shape control?

From particle heating-melting-evaporation model, two critical regimes of irradiation of nanocolloid, "hard" and "soft" irradiation, can be determined. The first one corresponds to the conditions when particle into a colloid will be evaporated completely by one laser pulse. The second one corresponds to the conditions when particle into a colloid will be melted completely but not evaporated yet. In other words, if "hard" irradiation corresponds to full evaporation regime, the "soft" one corresponds to the threshold of particle evaporation. Both critical regimes depend on particular noble metal, particle size, shape and laser wavelength. Both ones can be calculated with classical thermodynamics approach.Both "hard" and "soft" irradiation regimes have it\´s own specific applications in nanoparticle synthesis and control processes. ldquoHard" irradiation is very suitable for production of small, spherical, monodisperse nanoparticles from very inhomogeneous mixture of particles with different sizes and shapes. On the other hand, "soft" irradiation can be applied for particle shape control. Some other examples of using these two regimes for particle size and shape control will be demonstrated in this report.