Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/10—Dispersions; Emulsions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
  • B01J13/0086—Preparation of sols by physical processes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/12—Ketones
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/14—Particulate form, e.g. powders, Processes for size reducing of pure drugs or the resulting products, Pure drug nanoparticles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
  • B23K26/0622—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
  • B23K26/0624—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses using ultrashort pulses, i.e. pulses of 1ns or less
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
  • B23K26/144—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor the fluid stream containing particles, e.g. powder
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
  • B23K26/146—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor the fluid stream containing a liquid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y40/00—Manufacture or treatment of nanostructures
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S977/00—Nanotechnology
  • Y10S977/84—Manufacture, treatment, or detection of nanostructure
  • Y10S977/888—Shaping or removal of materials, e.g. etching
  • Y10S977/889—Shaping or removal of materials, e.g. etching by laser ablation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S977/00—Nanotechnology
  • Y10S977/84—Manufacture, treatment, or detection of nanostructure
  • Y10S977/901—Manufacture, treatment, or detection of nanostructure having step or means utilizing electromagnetic property, e.g. optical, x-ray, electron beamm

Definitions

• This invention relates generally to use of ultrafast pulsed laser ablation to generate stable hydrocolloids of nanoparticles having an average diameter of 100 nanometers or less from organic compounds.
• Curcumin l ,7-bis(4-hydroxy- 3-methoxyphenyl)-l ,6-heptadiene-3,5-dione, is a natural yellow-orange dye extracted from the rhizomes of Curcuma longa L. and it has a variety of biological activities and pharmacological actions.
• curcumin is not water soluble and that limits its' effective bioavailability in many systems. Many attempts have been made to disperse curcumin into water to improve its bioavailability.
• a self-microemulsifying drug delivery system comprising a microemulsion of curcumin with oils and surfactants was reported to improve the solubility of curcumin in water. Jing Cui, Bo Yu, Yu Zhao, Weiwei Zhu, Houli Li, Hongxiang Lou, Guangxi Zhai, "Enhancement of oral absorption of curcumin by self-microemulsifying drug delivery systems", International Journal of Pharmaceutics Vol. 37 1 , 1 48- 1 55. 2009.
• a curcumin-phospholipid complex was reported to greatly increase both the bioavai labi lity and the formation of metabolites as compared to unformulated curcumin.
• a polymeric nanoparticle-encapsulated curcumin, nicknamed “nanocurcumin” was also reported as a novel strategy to improve the bioavailability of curcumin.
• Pulsed laser ablation of metal or metal-alloy targets in liquids is one of the physical methods used to produce metal and metal-alloy nanoparticles.
• a pulsed laser beam is focused on the surface of a target that is submerged in a liquid.
• the ablated material re-nucleates in the liquid and forms nanoparticles.
• this invention provides a method and system for producing chemically pure and stable colloidal suspensions of nanoparticles from organic compounds using laser ablation.
• the method comprises the steps of generating a high repetition rate ultrafast pulsed laser beam; providing an organic compound target and irradiating the organic compound target with the pulsed laser beam, the target positioned in a liquid that is substantially transparent at a wavelength of the pulsed laser beam, the irradiation generating a nanoparticle suspension of the target in the liquid by ablation; and producing one or both of a flow of the liquid relative to a surface of the target and relative motion between the pulsed laser beam and the target.
• the method and system are highly efficient and are capable of high production rates for organic nanoparticle colloidal suspensions.
• the colloidal suspensions are stable at 25° C for at least one week in the absence of any stabilizing agents.
• nanoparticle or “nanoparticles” with respect to particles produced according to the present invention means particles with an average diameter of 100 nanometers or less.
• a poor solvent is defined as a liquid wherein the target organic material has a very low solubility if any solubility at all.
• Figure 1 schematically illustrates a laser-based system for producing organic nanoparticles in a liquid according to the present invention
• Figure 2 schematically illustrates an alternative laser-based system for producing organic nanoparticles in a liquid according to the present invention
• Figure 3 schematically illustrates a laser-based system for producing organic nanoparticles in a liquid according to the present invention by ablating a side surface of a cylindrical target;
• Figure 4 is a plot of absorption versus wavelength of a curcumin nanoparticle hydrocolloidal dispersion
• Figure 5 shows the absorption spectra of a solution of pure curcumin powder dissolved in methanol and the spectra of a curcumin nanoparticle hydrocolloidal prepared according to the present invention mixed with methanol;
• Figure 6 is a transmission electron microscope (TEM) image of a dried sample of a drop of a curcumin nanoparticle hydrocolloidal prepared according to the present invention on a TEM sampling grid;
• TEM transmission electron microscope
• Figure 7A is a mass spectrum of a pure curcumin powder sample
• Figure 7B is a mass spectrum of a curcumin nanoparticle hydrocolloidal sample prepared according to the present invention.
• Figure 8 is a plot of efficiency of nanoparticle production according to the present invention versus laser repetition rate.
• the present invention is directed toward a laser system for producing stable nanoparticle colloidal suspensions from organic materials using an ultrafast pulsed laser ablation process.
• FIG. 1 schematically illustrates a laser-based system for producing organic nanoparticles in a liquid in accordance with the present invention.
• a laser beam 1 is received from a ultrafast pulse source, not shown, and focused by a lens 2.
• the source of the laser beam 1 can be any suitable ultrafast pulsed laser source capable of providing a pulse duration, repetition rate and/or power level as discussed below.
• the focused laser beam 1 then passes from the lens 2 to a guide mechanism 3 for controlling movement of the laser beam 1.
• the guide mechanism 3 can be any of those known in the art including, by way of example only, piezo-mirrors, acousto-optic deflectors, rotating polygons, vibrating mirror, and prisms.
• the guide mechanism 3 is a vibrating mirror 3 to enable controlled and rapid movement of the focused laser beam 1.
• the guide mechanism 3 directs the focused laser beam 1 at a target 4.
• the target 4 is a compressed pellet of an organic compound that is being converted into nanoparticles.
• the compressed pellet can be formed from a variety of powder sources of the organic material. It is preferred to begin with a powdered source of the organic compound that has an average particle size of from submicron to millimeter (mm) size depending on the softness of the starting powder, preferably from submicron to submillimeter size.
• the powdered source material can then be compressed into a pellet using a mold and pressure.
• the pressures used depend on the starting material, but the target 4 pellet must be self sustaining and able to maintain integrity in a container 7 with a flow of a liquid 5 as described below.
• the size of the compressed target 4 is larger than 1 mm in at least one dimension.
• the target 4 can be another source of the organic compound material such as: a film of the organic compound that has been deposited onto a substrate; a bulk material of an organic compound with at least one dimension that is larger than 5 mm; a stream of the bulk organic compound which has been ejected from a nozzle into the liquid 5; or a paste of the bulk organic compound that has been introduced into the liquid 5. Any of these can serve as the target 4 material in the present invention.
• the target 4 is in contact with the liquid 5, preferably the target 4 is submerged a distance of from several millimeters to preferably less than 1 centimeter below the surface of a liquid 5.
• the target 4 is positioned in a container 7 having a removable glass window 6 on top of the container 7.
• An O-ring type of seal 8 is placed between the glass window 6 and the top of the container 7 to prevent the liquid 5 from leaking out of the container 7.
• the container 7 includes an inlet 1 2 and an outlet 14 so the liquid 5 can be passed over the target 4 and so that it can be recirculated.
• the container 7 is optionally placed on a motion stage 9 that can produce translational motion of the container 7 and movement of the liquid 5.
• the liquid 5 is used to carry generated nanoparticles 10 out of the container 7 to be collected elsewhere.
• the flow of liquid 5 over the target 4 also cools the laser focal volume.
• the flow rate and volume of liquid 5 should be sufficient to fill the gap between the target 4 and the glass window 6 as shown. In addition, it must be sufficient to prevent any gas bubbles generated during the laser ablation from staying on the glass window 6.
• the liquid 5 can be any liquid that is largely transparent to the wavelength of the laser beam 1 and that preferably is a poor solvent for the target material 4.
• the liquid 5 is deionized water, preferably having a resistivity of greater than 0.05 MOhm.cm, and more preferably greater than 1 MOhm.cm.
• the ultrafast pulsed laser beam 1 preferably has a pulse duration of 500 picoseconds or less, preferably from about 10 femtoseconds to 500 picoseconds, more preferably from 10 femtoseconds to 200 picoseconds, and most preferably from 100 femtoseconds to 10 picoseconds.
• the pulse repetition rate is preferably from 1 Hz to 100 MHz, more preferably from 10 kHz to 10 MHz, and most preferably from 100 kHz to 5 MHz.
• a preferred wavelength is about 1045 nanometers, however any suitable wavelength of from about 400 nanometers to 4000 nanometers may be used.
• the laser beam 1 has a pulse energy in the range of about 1 nano-Joules to 10 mili-Joules, more preferably in the range from 100 nano-Joules to 1 0 micro-Joules for generation of nanoparticles 10.
• the laser beam 1 has a laser fluence at the focus spot on the surface of target 4 in the range of from about 1 00 micro-Joules/cm" to 1 00 Joules/cm ' , more preferably from 10 milli-JouIes/cm " to 5 Joules/cm " .
• the guide mechanism 3 is a vibrating mirror 3 that is configured for fast rastering or other movement of the laser beam 1 on the surface of the target 4.
• the vibration frequency of mirror 3 is preferably 10 Hz or greater and preferably it has an angular amplitude of 0.1 mrad or greater and more preferably of 1 .0 mrad or greater, such that a rastering speed on the surface of the target 4 is 0.01 meters per second or greater and most preferably 0. 1 meters per second or greater.
• a mirror 3 can be a piezo-driven mirror, a galvanometer mirror, or other suitable apparatus for movement of the laser beam 1 .
• flow of the liquid 5 through the container 7 is carried out by a circulation system, with a flow speed preferably of 1 .0 milliliter per second or greater and more preferably of 10.0 milliliter per second or greater.
• Flow of liquid 5 is necessary to uniformly distribute the generated nanoparticles 10 in the liquid 5 and to remove them from the container 7. It is preferred to maintain a sufficient volume of the liquid 5 to avoid any fluctuations in the thickness of liquid 5 above the target 4. If the liquid 5 thickness varies it can change the optical path properties of the laser beam 1 and cause a broader distribution of sizes of the generated nanoparticles 10.
• the optical window 6 above the flowing liquid 5 helps to keep a constant thickness of liquid 5 above the target 4.
• introducing lateral vibration movement, for example perpendicular to the laser beam 1 , as indicated in Figure 1 , to the motion stage 9 can also cause liquid 5 flow locally across the ablation spot.
• the motion stage 9 preferably has a vibration frequency of several Hz and an amplitude of several millimeters.
• a shaker can also be used to circulate the liquid 5, wherein the circular movement of the shaker causes the liquid 5 in the container 7 to have a circular movement too, therefore the organic nanoparticles 10 can distribute evenly in the liquid 5.
• the glass window 6 is not necessary; however, the use of either will introduce non-uniformity into the thickness of the liquid 5 above the target 4 and will cause a broader size distribution of the nanoparticles 10.
• the present invention provides a system and method for formation of stable and chemically pure nanoparticle colloidal suspensions from organic compounds.
• stable it is meant that the hydrocolloidal, if produced in water, or colloidal suspension if produced in another liquid is stable with no aggregation of the particles after storage at 25° C for at least 7 days and more preferably stable for at least 2 months under these conditions.
• chemically pure it is meant that the colloidal suspension is composed only of the organic materials found in the target 4 and the liquid 5 from which the colloidal suspension is derived. There is no need for added stabilizing agents or surface active agents to maintain the colloid in a stable state.
• the present inventors have discovered that through proper control of laser parameters including pulse duration, pulse energy, pulse repetition rate, and movement of the laser beam 1 over the target 4 such stable nanoparticle colloidal suspensions can be produced.
• Both the laser beam 1 movement rate and the liquid 5 flow rate can be used to aid the process by controlling heat accumulation derived from the preferred high pulse repetition rates used in the present invention.
• ultrashort pulse widths are preferred, it is preferred that the pulse width or pulse duration range from 10 femtoseconds to 200 picoseconds and more preferably from 1 00 femtoseconds to 10 picoseconds. These short duration pulses are believed to enhance ablation efficiency because of a very high peak power and a small heat-affected zone at the ablation site.
• a US patent application serial no. 1 1 /712,924 filed on March 2, 2007 and published on January 10, 2008 as US publication no. 2008/0006524 also teaches a method of generating nanoparticles from metals and metal oxides in a vacuum and ambient gas and depositing them on a substrate.
• the inventors have found that a low pulse energy near the ablation threshold is also preferred for formation of organic nanoparticle colloids. It is preferred for the present invention that the pulses have a pulse energy of from 1 nano-Joules to 10 mili-Joules, more preferably from 100 nano-Joules to 1 0 micro-Joules.
• a high pulse repetition rate is very beneficial for producing nanoparticles according to the present invention from organic source material.
• a preferred pulse repetition rate is in the range of from 1 Hz to 100 MHz, more preferably 10 kHz to 10 MHz and most preferably 100 kHz to 5 MHz. These high repetition rates are beneficial for at least three reasons. First, these rates produce a multiple pulse effect in high repetition rate pulsed laser ablation. With a repetition rate of 100 kHz or greater, for example, the pulse separation is 10 microseconds or less. This period of time is short enough that the ablated material, before drifting away from the laser focal volume, will receive multiple laser pulses and become highly charged.
• the ablation process comprises multiple pulses of the ablated material, fragmentation of initially larger particles can occur, resulting in a final size distribution predominated by nanoparticles.
• the high repetition rate leads to a high production rate of nanoparticles.
• a preferred rastering rate is 0.01 meters per second or greater and more preferred is a rastering rate of 0.1 meters per second or greater. Without such fast rastering of the laser beam 1 , the stream of nanoparticles 10 produced by the leading laser pulses will eventually block the subsequent laser pulses by scattering and absorption of the laser beam 1 . More importantly, accumulated heating of the liquid 5 due to the high repetition rate can also induce coagulation of the nanoparticles 10.
• the inventors have found that movement of the liquid 5 is also useful in making stable nanoparticle colloids. This is primarily because a dispersed colloidal suspension of nanoparticles 10 in a liquid 5 such as water is essentially in a metastable state, i.e., a kinetically stable state and not a thermodynamically stable state. Flow of the liquid 5 during production helps to reduce a nanoparticle's 10 thermal movement, which may overcome the kinetic barrier to coagulation.
• the liquid 5 flow rate is 1 milliliter per second or greater, more preferably 10 milliliter per second or greater.
• a fast rastering of the laser beam 1 is also beneficial in reducing a nanoparticle's 10 thermal motion.
• FIG. 2 schematically illustrates an alternative laser-based system for producing organic nanoparticles in a liquid in accordance with the present invention.
• the laser beam 1 is received from a ultrafast pulse source, not shown, and focused by the lens 2.
• the source of the laser beam 1 can be any suitable pulsed laser source capable of providing a pulse duration, repetition rate and/or power level as discussed above.
• the focused laser beam 1 then passes from the lens 2 to the guide mechanism 3 for controlling movement of the laser beam 1.
• the guide mechanism 3 can be any of those known in the art including by way of example piezo-mirrors, acousto-optic deflectors, rotating polygons, vibrating mirror, and prisms.
• the guide mechanism 3 is a vibrating mirror 3 to enable controlled and rapid movement of the focused laser beam 1 .
• the guide mechanism 3 directs the focused laser beam 1 at the target 4.
• the target 4 is a compressed pellet of the organic compound that is being converted into nanoparticles.
• the compressed pellet can be formed from a variety of powder sources of the organic material.
• the powdered source material is then compressed into a pellet using a mold and pressure.
• the bottom of the container 7 serves as glass window 6 to allow the focused laser beam 1 pass through to ablate the organic compound target 4.
• the target can be submerged into the liquid 5, or the bottom of target 4 can just touch a top surface of the liquid 5.
• the distance between the bottom of target 4 and glass window 6 can be from several millimeters to preferably less than 1 centimeter.
• the container 7 includes the inlet 12 and the outlet 14 so the liquid 5 can be passed over the target 4 and so that it can be re-circulated. Flow of the liquid 5 is used to carry generated nanoparticles 10 out of the container 7 to be collected elsewhere.
• the flow of liquid 5 over the target 4 also cools the laser focal volume.
• the liquid 5 can be any liquid that is largely transparent to the wavelength of the laser beam 1 and that preferably is a poor solvent for the target material 4.
• the target 4 can be mounted on a rotating mechanism and spin during the ablation with the spin speed from several revolutions per minute to a several hundred revolutions per minute as shown by the arrow in the figure. As the target 4 rotates, some of the liquid described as the hydrodynamic boundary layer is dragged by the spinning.
• the sum results are a laminar flow of liquid 5 towards and across the target 4, and distribution of the generated nanoparticles 10 into liquid 5. This also prevents any gas bubbles generated during the laser ablation from staying on the target 4.
• FIG. 3 schematically illustrates another alternative laser-based system for producing organic nanoparticles in a liquid in accordance with the present invention.
• the laser beam 1 is received from a ultrafast pulse source, not shown, and focused by the lens 2.
• the source of the laser beam 1 can be any suitable pulsed laser source capable of providing a pulse duration, repetition rate and/or power level as discussed above.
• the focused laser beam 1 then passes from the lens 2 to the guide mechanism 3 for controlling movement of the laser beam 1.
• the guide mechanism 3 can be any of those known in the art including by way of example piezo-mirrors, acousto-optic deflectors, rotating polygons, vibrating mirror, and prisms.
• the guide mechanism 3 is a vibrating mirror 3 to enable controlled and rapid movement of the focused laser beam 1.
• the guide mechanism 3 directs the focused laser beam 1 at the target 4.
• the target 4 is a compressed cylinder of the organic compound that is being converted into nanoparticles.
• the compressed cylinder can be formed from a variety of powder sources of the organic material.
• the powdered source material is then compressed into a cylinder using a mold and pressure.
• the bottom of the container 7 serves as glass window 6 to allow the focused laser beam 1 to pass through and to ablate the organic compound target 4.
• the target 4 can be submerged into liquid 5, or the side surface of target 4 can just touch the top surface of liquid 5.
• the distance between the side surface of target 4 and glass window 6 can be from several millimeters to preferably less than 1 centimeter.
• the container 7 includes the inlet 12 and the outlet 14 so the liquid 5 can be passed over the target 4 and so that it can be re-circulated. Flow of the liquid 5 is used to carry generated nanoparticles 10 out of the container 7 to be collected elsewhere. The flow of liquid 5 over the target 4 also cools the laser focal volume.
• the liquid 5 can be any liquid that is largely transparent to the wavelength of the laser beam 1 and that preferably is a poor solvent for the target material 4.
• the target 4 is mounted on a rotating mechanism and rotates during the ablation with the rotation speed from several revolutions per minute to a several hundred revolutions per minute as shown by the arrow in the figure.
• the nanoparticles 10 are generated at the side surface of the cylindrical organic compound target 4 instead of at the end surface of the cylindrical target. As the target 4 rotates, it will help to distribute generated nanoparticles 10 into liquid 5, and prevent any gas bubbles generated during the laser ablation from staying on the target 4.
• curcumin powder purchased from Sigma Aldrich, was used as the organic source material.
• the curcumin powder was formed into a pellet of target material by compression in a 0.5 inch in diameter mold using three tons of pressure.
• the curcumin pellet was then ablated according to the present invention using deionized water as the liquid.
• the flow rate of the liquid in the container was about 80 milliliters per second.
• the curcumin pellet was ablated using an ultrafast pulsed laser having a wavelength of 1045 nanometers, using a pulse duration of 500 femtoseconds, a pulse energy of 1 microJoules, a power of 1 W and a pulse repetition rate of 1 MHz.
• the laser focus spot size was about 30 micrometers in diameter and the fluence is calculated at about 0. 14 Joules/cm 2 .
• the frequency of the vibrating mirror was 50 Hz with a 4 mi llimeter trace for 0.4 meters per second.
• the obtained curcumin nanoparticle hydrocoUoidal suspension had a yellow color.
• Figure 4 shows an absorption spectrum of the curcumin nanoparticle hydrocoUoidal which is represented by an absorption peak centered at about 420 nanometers.
• the hydrocoUoidal contains some large particles as evidenced by the spread of the peak and the background absorbance of the curve.
• the y- axis is the absorption and the x-axis is the wavelength. Because curcumin does not dissolve in water there is no curcumin in water spectnim that can be used as a reference to compare to the hydrocoUoidal curcumin nanoparticles.
• Curcumin is dissolvable in methanol, thus the starting curcumin powder was dissolved in methanol at a concentration of 2.5 X 10 "5 M to serve as a standard.
• 0. 1 milliliters of the curcumin nanoparticle hydrocoUoidal prepared according to the present invention was mixed with 1 .0 milliliters of methanol.
• the mixture of prepared nanoparticle hydrocoUoidal and methanol was a clear yellow colored solution as was the solution of curcumin powder dissolved in methanol.
• Figure 5 shows the absorption spectra of each curcumin methanol solution.
• the solid line trace is the hydrocoUoidal sample prepared according to the present invention.
• the dotted line trace is the curcumin standard.
• the two spectra are virtually identical with a major peak at 420 nanometers indicating the existence of curcumin in the hydrocoUoidal sample.
• the trace with the slightly higher peak at 420 nanometers is from the hydrocoUoidal sample prepared according to the present invention.
• the identical nature of the spectra indicates that ablation of a curcumin pellet in water using a low energy ultrafast pulsed laser according to the present invention does not destroy the curcumin structure, instead curcumin nanoparticles are generated and disperse into water forming a stable curcumin nanoparticle hydrocoUoidal suspension.
• Figure 6 is a transmission electron microscope (TEM) image of curcumin nanoparticles generated from a pellet of curcumin in deionized water according to the present invention.
• the average power of the laser used was 0.9W with a repetition rate of 100 kHz, pulse energy of 9 micro-Joules, wavelength of 1045 nanometers, pulse duration of 500 femtoseconds.
• the laser beam had a focal spot diameter of 50 microns and the raster rate was as described above.
• the generated nanoparticle hydrocoiloidal suspension was filtered through Fisher Scientific's P8 filter paper which has a retention size of 25 microns. A drop of the filtrate was transferred to a TEM sampling grid and dried. Although the curcumin nanoparticles aggregate during the drying process, the original nanoparticles are still recognizable and it can be seen that most have a size of less than 100 nanometers.
• Figure 7A is the Mass Spectrum (MS) of pure curcumin starting powder and Figure 7B is the MS of a curcumin hydrocoiloidal sample prepared according to the present invention.
• the curcumin hydrocoiloidal sample was prepared using ultrafast laser ablation according to the present invention in a container with the following laser parameters: 1 Watt of power, repetition rate of 1 MHz, wavelength of 1 045 nanometers, 500 femtosecond pulse duration, and the same raster rate as described above.
• the liquid was deionized water. It is observed that the most intense peaks in both MS tracings are at a mass of 391 for both standard curcumin and the hydrocolloidal sample, which indicates that the curcumin molecules are unchanged during the laser ablation according to the present invention.
• the major peak at mass 391 can be assigned to the complex of curcumin, mass 368, and sodium, mass 23.
• the starting curcumin powder was examined using Energy Dispersed Spectroscopy and no existence of sodium in the curcumin powder was found. This indicates that the sodium is introduced into both samples during the MS process. Despite the appearance of sodium on the MS for both standard curcumin and the hydrocolloidal sample, this does not change the fact that laser ablation of the curcumin pellet in water to form the nanoparticle hydrocolloidal did not destroy the molecular structure of the curcumin.
• the target can be another source of the organic compound material such as: a film of the organic compound that has been deposited onto a substrate; a bulk material of an organic compound with at least one dimension that is larger than 5 mm; a stream of the bulk organic compound which has been ejected from a nozzle into the liquid; or a paste of the bulk organic compound that has been introduced into the liquid. Any of these can serve as the target material in the present invention.
• liquids other than deionized water could be used depending on the desired colloidal suspension.

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• 2010
  • 2010-11-22 US US12/951,496 patent/US8992815B2/en not_active Expired - Fee Related
• 2011
  • 2011-02-03 CN CN2011800089575A patent/CN102802934A/zh active Pending
  • 2011-02-03 DE DE112011100502T patent/DE112011100502T5/de not_active Ceased
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