U.S. patent application number 10/525654 was filed with the patent office on 2006-05-18 for process for producing nanoparticle apparatus therefor and method of storing nanoparticle.
This patent application is currently assigned to HAMAMATSU PHOTONICS K.K.. Invention is credited to Mitsuo Hiramatsu, Tomonori Kawakami, Bo Li.
Application Number | 20060103060 10/525654 |
Document ID | / |
Family ID | 31972929 |
Filed Date | 2006-05-18 |
United States Patent
Application |
20060103060 |
Kind Code |
A1 |
Kawakami; Tomonori ; et
al. |
May 18, 2006 |
Process for producing nanoparticle apparatus therefor and method of
storing nanoparticle
Abstract
With this invention, in a nanoparticle production method,
wherein nanoparticles are produced by irradiating a laser light
irradiation portion 2a of a to-be-treated liquid 8 with a laser
light, in which suspended particles are suspended, to pulverize the
suspended particles in laser light irradiation portion 2a, laser
light irradiation portion 2a of to-be-treated liquid 8 is cooled.
In this case, by the cooling of to-be-treated liquid 8, the
respective suspended particles are cooled in their entireties. When
the portion 2a of this to-be-treated liquid 8 is irradiated with
the laser light, the laser light is absorbed at the surfaces of the
suspended particles at portion 2a. Since to-be-treated liquid 8 is
cooled during this process, significant temperature differences
arise between the interiors and surfaces of the suspended particles
and between the surfaces of the suspended particles and the
to-be-treated liquid at laser light irradiation portion 2a, and
highly efficient nanoparticulation is realized.
Inventors: |
Kawakami; Tomonori;
(Hamamatsu-shi, JP) ; Li; Bo; (Wuhan City, CN)
; Hiramatsu; Mitsuo; (Hamamatsu-shi, JP) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Assignee: |
HAMAMATSU PHOTONICS K.K.
1126-1, Ichino-cho Hamamatsu-shi
Shizuoka 435-8558
JP
|
Family ID: |
31972929 |
Appl. No.: |
10/525654 |
Filed: |
August 28, 2003 |
PCT Filed: |
August 28, 2003 |
PCT NO: |
PCT/JP03/10962 |
371 Date: |
September 16, 2005 |
Current U.S.
Class: |
266/202 |
Current CPC
Class: |
B01J 19/121 20130101;
B01J 2219/0879 20130101; B01J 2219/0877 20130101; B01J 2219/00063
20130101; B01J 2219/00137 20130101; C01P 2004/64 20130101; B01J
19/0013 20130101; B01J 2219/0871 20130101; B01J 2219/00094
20130101; B01J 2219/00126 20130101; C09C 3/00 20130101 |
Class at
Publication: |
266/202 |
International
Class: |
C21C 1/00 20060101
C21C001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 30, 2002 |
JP |
2002-255973 |
Claims
1. A nanoparticle production method comprising: a nanoparticle
production step of producing nanoparticles by irradiating a laser
light irradiation portion of a to-be-treated liquid with a laser
light, wherein suspended particles are suspended, to pulverize the
suspended particles in the laser light irradiation portion; and
wherein the laser light irradiation portion of the to-be-treated
liquid is cooled prior to irradiation of the laser light
irradiation portion with the laser light.
2. The nanoparticle production method according to claim 1, further
comprising, after the nanoparticle production step, a rapid cooling
solidification step of rapidly cooling and solidifying the laser
light irradiation portion.
3. The nanoparticle production method according to claim 2, wherein
in the rapid cooling solidification step, the rapid cooling
solidification is carried out at a cooling rate with which the rate
of progress of solidification of the laser light irradiation
portion is higher than the rate of Brownian motion of the
nanoparticles.
4. The nanoparticle production method according to claim 1, further
comprising: a cooling solidification step of, prior to the
nanoparticle production step, cooling and solidifying the
to-be-treated liquid and thereby obtaining a solidified body; a
thawing step of irradiating the laser light irradiation portion of
the solidified body with a thawing laser light and thawing the
laser light irradiation portion; and an optical trapping step of
irradiating the laser light irradiation portion with an optical
trapping laser light and gathering the suspended particles to the
center of the laser light irradiation portion by the optical
trapping action of the optical trapping laser light.
5. The nanoparticle production method according to claim 4, further
comprising, after the nanoparticle production step, a laser
irradiation stopping step of stopping the irradiations with the
thawing laser light, the optical trapping laser light, and the
nanoparticle production laser light.
6. A nanoparticle production device comprising: a treatment
chamber, containing a to-be-treated liquid; a nanoparticle
production laser device, irradiating a laser light irradiation
portion of the to-be-treated liquid with a nanoparticle production
laser light; and a temperature adjustment device, enabled to cool
the laser light irradiation portion of the to-be-treated liquid;
and wherein nanoparticles are produced by irradiating the laser
light irradiation portion of the to-be-treated liquid with the
nanoparticle production laser light, wherein suspended particles
are suspended, to pulverize the suspended particles in the laser
light irradiation portion.
7. The nanoparticle production device according to claim 6; further
comprising: a thawing laser device, irradiating the laser light
irradiation portion with a thawing laser light when the laser light
irradiation portion is made into a solidified body by cooling
solidification of the to-be-treated liquid and thereby thawing the
laser light irradiation portion; and an optical trapping laser
device, irradiating the laser light irradiation portion with an
optical trapping laser light and thereby gathering the suspended
particles to the center of the laser light irradiation portion.
8. A nanoparticle preservation method, wherein a to-be-treated
liquid, in which nanoparticles are suspended, is preserved in a
solid-phase state.
Description
TECHNICAL FIELD
[0001] This invention concerns a nanoparticle production method and
production device and a nanoparticle preservation method, and to be
more specific, concerns a nanoparticle production method and
production device, with which nanoparticles are produced by
irradiating a laser light irradiation portion of a to-be-treated
liquid with a laser light, wherein suspended particles are
suspended, to pulverize the suspended particles in the laser light
irradiation portion, and a nanoparticle preservation method.
BACKGROUND ART
[0002] Nanoparticulation brings about extreme increase of surface
area. Thus with nanoparticles, the reactivity with the surroundings
is thus high and properties unique to a substance are exhibited
readily. Also, in the case where the particles are of a poorly
soluble or insoluble substance, by nanoparticulation, the
nanoparticles can be put in state of pseudo-dissolution in a
solvent (a state wherein the nanoparticles, though being suspended
in the solvent, appear to be pseudo-dissolved due to the lack of
light scattering).
[0003] Nanoparticulation arts thus have the possibility of
providing methods of preparing new substances, and applications are
anticipated in a wide range of fields.
[0004] As a prior-art nanoparticulation method, there is known the
method disclosed in Japanese Patent Application Laid-open No.
2001-113159. This document discloses a nanoparticulation method,
wherein after dispersing an organic compound in a solvent,
microparticles (nanoparticles) of this organic compound are
obtained by irradiation with a laser light.
DISCLOSURE OF THE INVENTION
[0005] However, with the nanoparticulation method described in the
above prior document, the efficiency of nanoparticulation was still
inadequate.
[0006] This invention has been made in view of the above
circumstance and an object thereof is to provide a nanoparticle
production method and production device, with which
nanoparticulation of high efficiency can be realized, and a
nanoparticle preservation method.
[0007] The present inventors have found, as a result of diligent
research towards resolving the above issue, that the efficiency of
nanoparticulation is increased extremely by cooling a laser light
irradiation portion and irradiating the portion with a laser light,
and have thus come to complete the present invention.
[0008] That is, this invention's nanoparticle production method
comprises: a nanoparticle production step of producing
nanoparticles by irradiating a laser light irradiation portion of a
to-be-treated liquid with a laser light, wherein suspended
particles are suspended, to pulverize the suspended particles in
the laser light irradiation portion; and wherein the laser light
irradiation portion of the to-be-treated liquid is cooled prior to
irradiation of the laser light irradiation portion with the laser
light.
[0009] With this invention, by the to-be-treated liquid being
cooled, the respective suspended particles are cooled in their
entireties. When the cooled laser light irradiation portion of the
to-be-treated liquid is irradiated with the laser light, the laser
light is absorbed at the surfaces of the suspended particles in the
laser light irradiation portion. Since the to-be-treated liquid is
cooled at this time, significant temperature differences arise
between the interiors and surfaces of the suspended particles and
between the surfaces of the suspended particles and the
to-be-treated liquid at the laser light irradiation portion. The
suspended particles are thus pulverized readily and
nanoparticulation of high efficiency is carried out.
[0010] Also, this invention's nanoparticle production device
comprises: a treatment chamber, containing a to-be-treated liquid;
a nanoparticle production laser device, irradiating a laser light
irradiation portion of the to-be-treated liquid with a nanoparticle
production laser light; and a temperature adjustment device,
enabled to cool the laser light irradiation portion of the
to-be-treated liquid; and wherein nanoparticles are produced by
irradiating the laser light irradiation portion of the
to-be-treated liquid with the nanoparticle production laser light,
wherein suspended particles are suspended, to pulverize the
suspended particles in the laser light irradiation portion.
[0011] With such a device, the above-described nanoparticle
production method can be carried out effectively. That is, with
this invention's device, by the to-be-treated liquid being set to a
low temperature by the temperature adjustment device, the
respective suspended particles are cooled in their entireties. When
the laser light irradiation portion of the to-be-treated liquid is
then irradiated with the nanoparticle production laser light by the
nanoparticle production laser device, the nanoparticle production
laser light is mainly absorbed at the surfaces of the suspended
particles in the laser light irradiation portion. Since the
to-be-treated liquid is cooled at this point, significant
temperature differences arise between the interiors and surfaces of
the suspended particles and between the surfaces of the suspended
particles and the to-be-treated liquid at the laser light
irradiation portion. The suspended particles are thus pulverized
readily and nanoparticulation of high efficiency is carried
out.
[0012] Also, this invention's nanoparticle preservation method is
characterized in that a to-be-treated liquid, in which
nanoparticles are suspended, is preserved in a solid-phase state.
By this preservation method, the state in which nanoparticles are
suspended can be preserved over a long period of time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic view showing an embodiment of a
nanoparticle production device.
[0014] FIG. 2 is a schematic view showing another embodiment of a
nanoparticle production device.
[0015] FIG. 3 is a perspective partial view of a treatment
chamber.
[0016] FIG. 4 is a graph showing absorbance measurement results of
an Example 1 and Comparative Examples 1 and 2.
BEST MODE FOR CARRYING OUT THE INVENTION
[0017] Embodiments of this invention shall now be described in
detail.
[0018] FIG. 1 is a schematic view showing a first embodiment of
this invention's nanoparticle production device. As shown in FIG.
1, a nanoparticle production device 1 is equipped with a treatment
chamber 2, containing a to-be-treated liquid 8 in which suspended
particles are suspended, a constant-temperature device (temperature
adjustment device) 3, which can cool to-be-treated liquid 8 in
treatment chamber 2 to a low temperature no more than room
temperature and can rapidly cool to-be-treated liquid 8, and a
stirring device (not shown), which stirs to-be-treated liquid 8
inside treatment chamber 2.
[0019] Nanoparticle production device 1 is also equipped with a
nanoparticle production laser device 5, which irradiates a laser
light irradiation portion 2a of treatment chamber 2 with a
nanoparticle production laser light 9 to thereby pulverize the
suspended particles and produce nanoparticles, and a control device
6, controlling constant-temperature device 3 and laser device 5. As
to-be-treated liquid 8, for example, a suspension of vanadyl
phthalocyanine (referred to hereinafter as "VOPc") particles in
water, is used.
[0020] As treatment chamber 2, one that is formed of quartz or
other material, which is transparent to the wavelength of laser
light 9 emitted from nanoparticle production laser device 5, is
used. The stirring device comprises, for example, a magnetic
stirrer and a stirring element. Also as constant-temperature device
3, for example, a cooling device that makes use of a Peltier
element or a rapid cooling device that makes use of liquid
nitrogen, etc., is favorably used.
[0021] Nanoparticle production laser device 5 is preferably one
that emits laser light of a wavelength in the range of 400 to 180
nm. If the wavelength is longer than 400 nm, the nanoparticulation
efficiency tends to decrease, and if the wavelength is shorter than
180 nm, the optical energy of laser irradiation tends to be
absorbed by the solvent, which for example is water. Nanoparticle
production laser device 5 is equipped with a laser light source.
If, for example, an Nd:YAG laser is to be used as the laser light
source, since the fundamental wavelength of an Nd:YAG laser is 1064
nm, laser device 5 must be equipped furthermore with a higher
harmonic unit that includes the nonlinear optic crystal KDP, in
order to convert the light of fundamental wavelength to a light of
the third harmonic (wavelength: 355 nm). Also, an excimer laser
(193 nm, 248 nm, 308 nm, 351 nm) or a nitrogen laser (337 nm) may
be used as the laser light source.
[0022] Control device 6 performs temperature control of the
to-be-treated liquid, on/off control of laser irradiation, control
of the irradiation time etc., for example, by activating laser
device 5 when the temperature of constant-temperature device 3
falls to a predetermined value or less and stopping laser device 5
when the temperature of constant-temperature device 3 exceeds a
predetermined value to thereby constantly maintain the
nanoparticulation treatment at high efficiency.
[0023] A nanoparticle production method using the above-described
nanoparticle production device 1 shall now be described.
[0024] First, to-be-treated liquid 8, in which the suspended
particles to be subject to nanoparticulation are suspended, is
loaded into treatment chamber 2. To-be-treated liquid 8 is then
stirred by the stirring device. The suspended state of suspended
particles in to-be-treated liquid 8 is thereby maintained.
[0025] To-be-treated liquid 8 is then cooled by
constant-temperature device 3. The respective suspended particles
are thereby cooled in their entireties. In this process,
to-be-treated liquid 8 is cooled to room temperature or less and
preferably to 10.degree. C. or less.
[0026] When the temperature has dropped to a predetermined
temperature or less, laser device 5 is activated by control device
6, and the laser light irradiation portion 2a of to-be-treated
liquid 8, contained inside treatment chamber 2, is irradiated with
laser light 9 from laser device 5 (nanoparticle production step).
In this step, the laser light is mainly absorbed at the surfaces of
the suspended particles in laser light irradiation portion 2a.
Since the to-be-treated liquid is set to a low temperature no more
than the predetermined temperature, significant temperature
differences arise between the interiors and surfaces of the
suspended particles and between the surfaces of the suspended
particles and the to-be-treated liquid. The suspended particles are
thus pulverized readily and nanoparticulation of high efficiency is
carried out.
[0027] As nanoparticles are thus formed, since the nanoparticles
become less likely to scatter light, a pseudo-dissolution state, in
other words, a transparent state is achieved as nanoparticulation
progresses. The formation of nanoparticles can thus be judged by
the transparency of the to-be-treated liquid.
[0028] Also, the pulse repetition frequency is preferably a high
repetition frequency in consideration of the treatment efficiency.
However, since the to-be-treated liquid is heated at high
frequency, the pulse repetition frequency must be set so as to be
of a heating energy with which the performance of the
constant-temperature device can be maintained.
[0029] The nanoparticles that are formed as described above are
normally active. Thus when laser device 5 is stopped after
nanoparticle formation and the nanoparticles are left as they are
in this state for some time, the nanoparticles aggregate. The
aggregation of nanoparticles must thus be prevented to maintain the
dispersed state of the nanoparticles.
[0030] For this purpose, after nanoparticle formation,
to-be-treated liquid 8 is subject to rapid cooling solidification
(rapid cooling solidification step) by constant-temperature device
3. The suspended state of the nanoparticles can thereby be
maintained over a long period of time.
[0031] Here, "rapid cooling" refers to a state of cooling with
which the rate of progress of solidification of the laser light
irradiation portion is higher than the rate of Brownian motion of
the nanoparticles. With gradual cooling solidification that does
not meet this state, the probability that the nanoparticles will be
captured inside the solidified solid phase will be low and the
nanoparticles will tend to aggregate in the non-solidified liquid
phase.
[0032] To preserve the nanoparticles, to-be-treated liquid 8 is
maintained at a temperature no more than its solidification point
after rapid cooling solidification. That is, to-be-treated liquid 8
is maintained in the solid phase state. Thus after rapid cooling
solidification, storage in a normal freezer is adequate. The
nanoparticles can thereby be preserved in the suspended state over
a long period of time.
[0033] A second embodiment of this invention's nanoparticle
production device shall now be described.
[0034] FIG. 2 is a schematic view showing the second embodiment of
this invention's nanoparticle production device. As shown in FIG.
2, this embodiment's nanoparticle production device 10 differs from
nanoparticle production device 1 of the first embodiment firstly in
being further equipped with an XYZ stage 11 for moving treatment
chamber 2, a thawing laser device 12, which, when to-be-treated
liquid 8 inside treatment chamber 2 is made a solidified body,
thaws laser light irradiation portion 2a of that solidified body,
an optical trapping laser device 13, which gathers suspended
particles to the center of the thawed laser light irradiation
portion 2a by the optical trapping action of a laser light, and an
optical system 16, which irradiates the same portion of the to-be
treated liquid with the respective laser lights from thawing laser
device 12, optical trapping laser device 13, and nanoparticle
production laser device 5.
[0035] Here as thawing laser device 12, a laser device that emits
laser light of a wavelength at which absorption by the
to-be-treated liquid or the suspended particles occurs is
preferable. For example, in the case where the suspended particles
are VOPc, since VOPc absorbs light in the wavelength range of 500
to 900 nm, an argon ion laser (488 nm, 514 nm) is used for example
as thawing laser device 12. Also as optical trapping laser device
13, a laser device that emits laser light of a wavelength at which
there is no absorption by the to-be-treated liquid or the suspended
particles is preferable. For example, in the case where the
suspended particles are VOPc, since VOPc absorbs light in the
wavelength range of 500 to 900 nm, a YAG laser (1064 nm) is for
example used as optical trapping laser device 13.
[0036] Also, along the line joining nanoparticle production laser
device 5 and laser light irradiation portion 2a of treatment
chamber 2, that is, along an optical axis 17, a first half-mirror
14 and a second half-mirror 15 are disposed, for example, as
optical system 16. The thawing laser light that is emitted from
thawing laser device 12 is arranged to be reflected by first
half-mirror 14, pass along optical axis 17 of nanoparticle
production laser device 5, and the same portion as the
above-mentioned laser light irradiation portion 2a is irradiated
with the thawing laser light. Also, the optical trapping laser
light emitted from optical trapping laser device 13 is arranged to
be reflected by second half-mirror 15, pass along optical axis 17
of nanoparticle production laser device 5, and the same portion as
the above-mentioned laser light irradiation portion 2a is
irradiated with the optical trapping laser light.
[0037] Furthermore with nanoparticle production device 10, by
moving XYZ stage 11, laser light irradiation position 2a in
treatment chamber 2 can be changed freely.
[0038] Secondly, nanoparticle production device 10 differs from
nanoparticle production device 1 of the first embodiment in that
control device 6 controls nanoparticle production laser device 5,
thawing laser device 12, and optical trapping laser device 13 in
association with constant-temperature device 3 and XYZ stage
11.
[0039] With nanoparticle production device 10 of the present
embodiment, nanoparticulation of suspended particles is carried out
in the following manner.
[0040] That is, first, XYZ stage 11 is moved to set laser light
irradiation portion 2a in treatment chamber 2. As shown in FIG. 3,
laser irradiation portion 2a is the region through which laser
light passes. The entirety of to-be-treated liquid 8 is then cooled
and solidified and made into a solidified body by means of
constant-temperature device 3 (cooling solidification step).
Thereafter, this temperature is maintained.
[0041] Next, thawing laser device 12 is activated and made to emit
the thawing laser light. The thawing laser light is reflected by
first half-mirror 14 and the laser light irradiation portion 2a of
the solidified body is irradiated with the thawing laser light. The
thawing laser light is thus absorbed by to-be-treated liquid 8 or
the suspended particles in laser light irradiation portion 2a, heat
is thereby generated, and laser light irradiation portion 2a is
thawed by this heat (thawing step).
[0042] Then while keeping thawing laser device 12 activated,
optical trapping laser device 13 is activated and made to emit the
optical trapping laser light. The optical trapping laser light is
reflected by second half-mirror 15 and the laser light irradiation
portion 2a is irradiated with the optical trapping laser light
(optical trapping step). In this process, suspended particles of
large particle diameter that exist in the thawed laser irradiation
portion 2a gather along optical axis (center of the laser
irradiation portion) 17 due to the optical trapping action of the
optical trapping laser light. The optical trapping action is
stronger the larger the particle diameter of a particle, and
selective positioning of particles of large particle diameter along
optical axis 17 is thereby enabled. The concentration of suspended
particles along optical axis 17 of laser light irradiation portion
2a thus increases. Such an art provides the merits of preventing
the aggregation of nanoparticles with each other at portions
outside the laser light irradiation portion and enabling a cooling
treatment to be carried out in a comparatively simple manner since
thawing of just a localized portion is performed.
[0043] Lastly, with thawing laser device 12 and optical trapping
laser device 13 being kept activated, nanoparticle production laser
device S is activated. The nanoparticle production laser light is
transmitted successively through first half-mirror 14 and second
half-mirror 15 and the laser light irradiation portion 2a is
irradiated with the nanoparticle 6 production laser light
(nanoparticle production step). At this point, the suspended
particles in laser light irradiation portion 2a are in a state of
high concentration. Also, the laser light intensity is normally
high at the center of laser light irradiation portion 2a. Thus when
the laser light irradiation portion 2a is irradiated with the
nanoparticle production laser light by nanoparticle production
laser device 5, light pulverization of even higher efficiency can
be realized.
[0044] After the nanoparticulation treatment, the irradiations with
laser light by thawing laser device 12, optical trapping laser
device 13, and nanoparticle production laser device 5 are stopped
(laser irradiation stopping step). The cooling of the thawed
portion thus begins, and since this portion is localized, rapid
cooling solidification occurs naturally. By then keeping this
solidified body at a low temperature no more than the
solidification point of the to-be-treated liquid, the suspended
state of the nanoparticles can be maintained over a long period of
time.
[0045] This invention is not limited to the above-described first
and second embodiments. For example, though with the
above-described embodiments, VOPc, which is an organic compound, is
used as the suspended particles, the suspended particles are not
limited to those of VOPc and may be those of other organic
compounds. Ibuprofen, clobetasone butyrate, etc., which are
insoluble medical agents, can be cited as examples.
[0046] Also, though with the above-described embodiments, water is
used as the solvent for suspending VOPc, the combination of
suspended particles and solvent is not limited thereto, and any
combination with which suspended particles are suspended in a
solvent may be used.
[0047] Furthermore with the above-described embodiments, a
surfactant (for example, SDS or other ionic surfactant, Igepal or
other nonionic surfactant -that does not become ionized, Tween,
which is permitted to be added to medical products, etc.) is
preferably added to the to-be-treated liquid prior to the
irradiation with the nanoparticle production laser light. In this
case, nanoparticulation of higher efficiency is carried out when
the to-be-treated liquid is irradiated with the nanoparticle
production laser light. Also, after the laser light irradiation,
the aggregation of the nanoparticles formed is prevented
adequately.
[0048] Also, though with the above-described embodiment,
nanoparticles produced by the above described nanoparticle
production methods are used as the nanoparticles to be preserved,
the nanoparticles preserved by this invention's nanoparticle
preservation method is not limited to just the nanoparticles
produced by the above-described nanoparticle production methods and
may instead be nanoparticles that have been produced by a
production method other than the above-described nanoparticle
production methods.
[0049] Though the details of this invention shall now be described
more specifically by way of examples, this invention is not limited
to the following examples.
EXAMPLE 1
[0050] 3 ml of a sample solution, prepared by suspending a VOPc
powder in water (VOPc: 0.5 mg/ml), were dispensed in a 10
mm.times.10 mm.times.40 mm rectangular quartz cell, and thereafter
the temperature of the sample solution was lowered to 5.degree. C.
using a constant-temperature device (131-0040 Constant-Temperature
Cell Holder with Temperature Display, made by Hitachi).
[0051] The sample solution was then irradiated with the third
harmonic of an Nd:YAG laser (80 mJ/cm.sup.2pulse, FWHM=4 ns, 20 Hz)
for 15 minutes. As a result, the entirety of the sample solution
became transparent. It is thus considered that nanoparticulation
VOPc progressed and pseudo-dissolution of the nanoparticles
occurred.
[0052] The absorbance of the sample solution after laser light
irradiation was then measured by an absorbance measuring device.
The result is shown in FIG. 4. As shown in FIG. 4, the absorbance
was found to be significantly high in the vicinity of 500 to 900
nm, which is the absorbance wavelength range of VOPc. Since when
VOPc particles that are suspended in a to-be-treated liquid are
made fine, the inherent light absorption of the particles increase
due to the increase of surface area, the above result shows that
nanoparticles were formed efficiently by the light irradiation
treatment. Of the four absorbance curves, the absorbance curve at
the lowest position is that prior to laser light irradiation.
[0053] Next, in order to maintain the pseudo-dissolution state of
the nanoparticles in the sample solution, rapid cooling by liquid
nitrogen was performed so that the rate of progress of
solidification of the sample solution by the constant-temperature
device will be higher than the rate of Brownian motion of the
nanoparticles. As a result, the sample solution solidified while
remaining transparent. It is thus considered that by performing
such rapid cooling, it was possible to maintain the
pseudo-dissolution state of the nanoparticles and adequately
prevent the aggregation of the nanoparticles.
[0054] When the sample solution subject to laser light irradiation
in this Example was cooled by placing the sample solution in a
normal refrigerator, the formation of a non-transparent portion at
the interface between the solidified body and the to-be-treated
liquid was seen, indicating that the obtained pseudo-dissolution
state of the nanoparticles was greatly degraded. It is thus
considered that with normal cooling, the rate of progress of
solidification of the to-be-treated liquid is slower than the rate
of Brownian motion of the nanoparticles, the probability of the
nanoparticles becoming captured in the solidified solid phase is
low, and the aggregation of the nanoparticles occurs in the
non-solidified liquid phase.
COMPARATIVE EXAMPLE 1
[0055] Besides setting the temperature of the sample solution to
35.degree. C., nanoparticulation of VOPc was carried out in the
same manner as in Example 1. The absorbance of the sample solution
was then measured in the same manner as in Example 1. The result is
shown in FIG. 4. As shown in FIG. 4, the absorbance is considerably
lower in comparison to Example 1. It is thus considered that the
efficiency of formation of nanoparticles after light irradiation
treatment is inadequate.
COMPARATIVE EXAMPLE 2
[0056] Besides setting the temperature of the sample solution to
70.degree. C., nanoparticulation of VOPc was carried out in the
same manner as in Example 1. The absorbance of the sample solution
was then measured in the same manner as in Example 1. The result is
shown in FIG. 4. As shown in FIG. 4, the absorbance is not only
considerably lower in comparison to Example 1 but is also
considerably lower in comparison to Comparative Example 1. It is
thus considered that the efficiency of formation of nanoparticles
after light irradiation treatment is inadequate.
EXAMPLE 2
[0057] In this Example, nanoparticulation treatment of VOPc was
carried out as follows using the device of FIG. 2.
[0058] First, XYZ stage 11 was moved to set the laser light
irradiation portion in the 10 mm.times.10 mm.times.40 mm
rectangular quartz cell. 3 ml of a sample solution, prepared by
suspending VOPc powder in water (VOPc: 0.5 mg/ml), was then
dispensed in the rectangular quartz cell. Thereafter, using the
same constant-temperature device as in Example 1, the sample
solution was cooled to and solidified at -5.degree. C., thereby
obtaining a solidified body.
[0059] Then using an argon ion laser (514 nm) as thawing laser
device 12, the above-mentioned laser light irradiation portion was
irradiated with a thawing laser light.
[0060] Then using a YAG laser (1064 nm) as optical trapping laser
device 13, an optical trapping laser light was emitted and the
above-mentioned laser light irradiation portion was irradiated with
the optical trapping laser light.
[0061] Lastly, using the third harmonic light (wavelength: 355 nm)
of an Nd:YAG laser as nanoparticle production laser device 5, the
laser light irradiation portion was irradiated with a nanoparticle
production laser light. After 10 seconds of irradiation, the laser
light irradiation portion of the solidified body became
transparent. Comparison of this result with that of Example 1 in
consideration of the cross-section of the irradiation laser shows
that, since the treatment of making the entire to-be-treated liquid
of 3 ml transparent was completed in 15 minutes with Example 1 and
in 7 to 8 minutes with Example 2, nanoparticulation occurred at is
a higher efficiency than in the case of Example 1.
[0062] After the nanoparticulation treatment, the irradiations with
laser light by the argon ion laser, YAG laser, and the third
harmonic of the Nd:YAG laser were stopped. As a result, the laser
light irradiation portion remained transparent. It is thus
considered that by rapid cooling of the thawed portion, it was
possible to maintain the pseudo-dissolution state of the
nanoparticles and adequately prevent the aggregation of the
nanoparticles.
INDUSTRIAL APPLICABILITY
[0063] As described above, this invention's nanoparticle production
method and production device can be used as a production method and
production device that can realize nanoparticulation of high
efficiency by lowering of the temperature of the to-be-treated
liquid. Furthermore, long-term maintenance of the suspended state
of the nanoparticles is enabled by rapid cooling solidification
after the nanoparticulation treatment.
[0064] Also, this invention's nanoparticle preservation method can
be used as a preservation method that enables long term
preservation of the state in which nanoparticles are suspended.
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