Production Of Organic Compound Nanoparticles With High Repetition Rate Ultrafast Pulsed Laser Ablation In Liquids

Abstract

Disclosed is a method of producing a chemically pure and stably dispersed organic nanoparticle colloidal suspension using an ultrafast pulsed laser ablation process. The method comprises irradiating a target of an organic compound material in contact with a poor solvent with ultrashort laser pulses at a high repetition rate and collecting the nanoparticles of the organic compound produced. The method may be implemented with a high repetition rate ultrafast pulsed laser source, an optical system for focusing and moving the pulsed laser beam, an organic compound target in contact with a poor solvent, and a solvent circulating system to cool the laser focal volume and collect the produced nanoparticle products. By controlling various laser parameters, and with optional poor solvent flow movement, the method provides stable colloids of dispersed organic nanoparticles in the poor solvent in the absence of any stabilizing agents.

We claim: 
     
         1 . A method of producing nanoparticle colloidal suspensions of organic materials in poor solvents, comprising the steps of:
 a) irradiating a shaped bulk target of an organic compound material with an ultrashort pulsed laser beam having a pulse duration of 500 picoseconds or less, at least a portion of the shaped bulk target in contact with a liquid, the liquid being substantially transparent at a wavelength of the pulsed laser beam, the irradiation generating a stable nanoparticle suspension of the organic compound material in the liquid by ablation; and   b) producing one or both of relative movement of the liquid relative to a surface of the target and relative motion between the pulsed laser beam and the target.   
     
     
         2 . The method of  claim 1 , wherein step a) comprises irradiating with a pulsed laser beam having a repetition rate in the range of about 1 Hz to 100 MHz. 
     
     
         3 . The method of  claim 2 , wherein step a) comprises irradiating with a pulsed laser beam having a pulse duration ranging from 10 femtosecond to 500 picosecond. 
     
     
         4 . The method of  claim 1 , wherein step a) comprises irradiating with a pulsed laser beam having a pulse energy ranging from 1 nano-Joule to 10 mili-Joule. 
     
     
         5 . The method of  claim 1 , wherein step a) comprises irradiating with a pulsed laser beam having a laser fluence on the target surface of from 10 milli-Joules/cm 2  to 5 Joules/cm 2 . 
     
     
         6 . The method of  claim 1 , further comprising providing deionized water having a resistance of 0.05 M Ohm·cm or greater as the liquid. 
     
     
         7 . The method of  claim 1 , wherein step b) comprises flowing the liquid across a surface of the target at a rate of 1 milliliter per second or greater. 
     
     
         8 . The method of  claim 1 , further comprising providing a vibrating mirror having a frequency of 10 Hz or greater and an angular amplitude of 0.1 mrad or greater, said vibrating mirror moving said laser beam over said target. 
     
     
         9 . The method of  claim 8 , comprising guiding the laser beam movement on the target such that a focal spot of the laser beam moves at a speed of 0.1 meters per second or greater over the target. 
     
     
         10 . A nanoparticle colloidal suspension prepared according to the method of  claim 1 . 
     
     
         11 . A colloidal suspension of nanoparticles in a liquid comprising nanoparticles having an average diameter of 100 nanometers or less, wherein said colloidal suspension is stable at 25° C. for at least 7 days in the absence of any stabilizing agents or surface active agents with no aggregation of said nanoparticles. 
     
     
         12 . The colloidal suspension as recited in  claim 11  wherein said colloidal suspension is stable at 25° C. for at least 2 months. 
     
     
         13 . The colloidal suspension as recited in  claim 11  wherein said colloidal suspension consists essentially of said nanoparticles and said liquid. 
     
     
         14 . The colloidal suspension as recited in  claim 11  wherein said liquid is deionized water have a resistivity of greater than 0.05 MOhm·cm. 
     
     
         15 . The colloidal suspension as recited in  claim 11  wherein said liquid is deionized water having a resistivity of greater than 1 mOhm·cm. 
     
     
         16 . The colloidal suspension as recited in  claim 11  wherein said nanoparticles have a charge. 
     
     
         17 . The colloidal suspension as recited in  claim 11  wherein said nanoparticles comprise curcumin. 
     
     
         18 . The colloidal suspension as recited in  claim 11  wherein said nanoparticles are poorly soluble in said liquid. 
     
     
         19 . The colloidal suspension as recited in  claim 11  wherein said nanoparticles are insoluble in said liquid. 
     
     
         20 . The colloidal suspension as recited in  claim 11  wherein said nanoparticles are an organic material.