Abstract
Laser ablation with the use of ultra-short laser pulses is a widely used technique for the fabrication of nanoparticles of metals, inorganic and hybrid materials. However, fabrication of fragile organic nanocrystals via laser ablation is rarely used due to easy photodegradation of molecules. The method employing laser irradiation of the target material is beneficial as no other chemicals are used in the production of nanoparticles, except for a given material and a solvent. In this work, we test the concept of formation of nonlinear optical (NLO) organic nanocrystals dispersion in water by irradiation of the microcrystals of the NLO material with nonabsorbed infrared nanosecond light pulses. These pulses, due to a nonlinear optical process active in a noncentrosymmetric organic crystal, such as those studied in this work, DCNP dye (3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole), produce nanosecond pulses of second-harmonic (SH) light. Due to doubling of photon energy, they are reabsorbed in the volume of DCNP microcrystals and thermal shocks fracture them into nanometer size crystals. To the best of our knowledge, such process and its interpretation have not been described yet in the literature.
Highlights
Organic nanoparticles, like their inorganic or hybrid organic− inorganic counterparts, may find several applications in biosensing, bioimaging, optical and nonlinear optical devices, material science and medicine.[1−7] They are produced by various methods of chemical synthesis including precipitation,[8] reprecipitation and solvent-vapor annealing,[9] milling,[10] sonication technique,[11] laser ablation,[12−16] size-isolation effect of dendrimers,[17] growth in sol−gel coatings,[18] etc
The target material is suspended in liquid and laser ablation in liquids (LAL) proceeds via cycles of heating and cooling mediated by a liquid[39] that is regarded as mild conditions when compared with laser ablation in vacuum
This method can be applied for organic solids to fragment them into nanoparticles. This technique was pioneered for organic material treatment already in the middle of 1990s by Masuhara group and its coworkers.[22−28] LAL is usually performed by the impact of short laser light pulses on dispersion of larger particles in liquids, free liquid jets, or aerosols,[29−36] leading to the formation of nanoparticle colloids
Summary
Like their inorganic or hybrid organic− inorganic counterparts, may find several applications in biosensing, bioimaging, optical and nonlinear optical devices, material science and medicine.[1−7] They are produced by various methods of chemical synthesis including precipitation,[8] reprecipitation and solvent-vapor annealing,[9] milling,[10] sonication technique,[11] laser ablation,[12−16] size-isolation effect of dendrimers,[17] growth in sol−gel coatings,[18] etc. The target material is suspended in liquid (e.g. water) and laser ablation in liquids (LAL) proceeds via cycles of heating and cooling mediated by a liquid[39] that is regarded as mild conditions when compared with laser ablation in vacuum. This method can be applied for organic solids to fragment them into nanoparticles. When light intensity level exceeds that of ODT an irreversible material damage (melting, decomposition, photodegradation, cracking, etc.) may occur This generally unwanted effect, if well controlled, can be Received: October 22, 2020 Accepted: April 5, 2021 Published: April 15, 2021
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