JP2008285384A - Fluorescent glass particles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide fluorescent glass particles exhibiting excellent stability, which is a characteristic different from that of NaYF<SB>4</SB>. <P>SOLUTION: The fluorescent glass particles are comprises Bi<SB>2</SB>O<SB>3</SB>-SiO<SB>2</SB>based glass containing at most 3 mole% of Er<SB>2</SB>O<SB>3</SB>and have particle diameters of at most 300 nm. Also provided are the above fluorescent glass particles, wherein the Bi<SB>2</SB>O<SB>3</SB>-SiO<SB>2</SB>based glass further contains Yb<SB>2</SB>O<SB>3</SB>and has a content of Er<SB>2</SB>O<SB>3</SB>+Yb<SB>2</SB>O<SB>3</SB>of 0.2-3 mole%; and the above fluorescent glass particles, wherein the Bi<SB>2</SB>O<SB>3</SB>-SiO<SB>2</SB>based glass contains 30-55% of Bi<SB>2</SB>O<SB>3</SB>, 15-45% of SiO<SB>2</SB>and at most 35% of Al<SB>2</SB>O<SB>3</SB>+Ga<SB>2</SB>O<SB>3</SB>by mole%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to fluorescent glass fine particles that exhibit up-conversion fluorescence in the visible range when excited with near infrared light and are suitably used in the fields of biological tagging and imaging.

For the purpose of tagging and imaging of cells, proteins, DNA, and bioreagents, development of fluorescent nanoparticles is in progress.
As a tagging or imaging method, a method of irradiating fluorescent nano-particles with ultraviolet light and detecting fluorescence in the visible region having a wavelength longer than the irradiation light is common. As materials for such fluorescent nanoparticles, organic dyes doped with rare earth elements, quantum dots (see Non-Patent Document 1), and the like are used.

  However, when organic dyes are used for tagging and imaging of living cells and bioreagents, the intensity of the detection light tends to decrease when the ultraviolet light continues to be irradiated, and the detection is difficult because the wavelengths of the irradiation light and the detection light are close There was a problem.

Quantum dots are superior to organic dyes in terms of resistance to ultraviolet light. However, since the emission wavelength of a quantum dot changes depending on its size, there is a problem that when this is used for tagging or imaging, strict control of the size is necessary and it is difficult to manufacture, and the material of quantum dots is generally selenium. Since compounds and sulfur compounds are used, there was concern in terms of biotoxicity.
Furthermore, since both organic dyes and quantum dots are irradiated with ultraviolet light, the living cells are damaged, and the living cells themselves emit light, so that noise is mixed into the detection light.

Therefore, a method for irradiating fluorescent nanoparticles with infrared light and detecting fluorescence in the visible range having a shorter wavelength than the irradiated light, for example, irradiating a nanoparticle doped with Er ³⁺ ions with a laser having a wavelength of 980 nm or 800 nm and green A method for detecting the up-conversion fluorescence is proposed. As such a nanoparticulate material emitting up-conversion fluorescence, for example, a fluoride crystal such as NaYF ₄ doped with Er ³⁺ ions and Yb ³⁺ ions has been proposed (see Non-Patent Document 2).

Bruchez et al. , Science vol. 281, 1998, pp2013 Heer et al. , Advanced Materials vol. 16, 2004, pp2102

The up-conversion fluorescent material has an advantage that ultraviolet light does not have to be used for irradiation light.
Fluoride nanocrystals emitting up-conversion fluorescence are produced, for example, by dissolving NaYF ₄ doped with Er ³⁺ ions and Yb ³⁺ ions in a high-temperature liquid and precipitating the crystals while lowering the temperature of the liquid.

However, since such crystals are easily soluble, there is a problem that the material itself lacks stability even after it is in a final form.
An object of the present invention is to provide fluorescent glass fine particles having excellent stability unlike NaYF ₄ .

The present invention provides fluorescent glass fine particles made of Bi ₂ O ₃ —SiO ₂ glass containing Er ₂ O ₃ in a range of 3 mol% or less and having a particle size of 300 nm or less.

According to the present invention, it is possible to obtain fluorescent fine particles that emit up-conversion fluorescence in the visible range when irradiated with infrared light and are made of oxide glass.
Since the fluorescent glass fine particles of the present invention are oxides, the fluorescence intensity is stable over a long period of time, and the chemical durability is high and there is little damage to the living body.
Further, in an embodiment in which Er ³⁺ ions and Yb ³⁺ ions are co-doped, highly efficient up-conversion light emission can be obtained. Therefore, this embodiment is suitable as a fluorescent material used for tagging and imaging of biological cells and bioreagents.

First, components of Bi ₂ O ₃ —SiO ₂ glass (hereinafter referred to as glass of the present invention) in the present invention will be described. In addition, the content of each component in the glass is expressed as a mole percentage. For example, the Er ₂ O ₃ content refers to the case where all of the Er in the glass exists in the form of Er ₂ O _3. .

Er ₂ O ₃ is an optically active component for obtaining upconversion fluorescence and is essential. If Er ₂ O ₃ exceeds 3%, vitrification becomes difficult, or the intensity of up-conversion fluorescence decreases due to concentration quenching of Er ³⁺ ions. Preferably it is 2.5% or less, typically 2% or less. Further, _Er 2 _{O 3} is preferably at least 0.2%. If it is less than 0.2%, sufficient up-conversion fluorescence intensity may not be obtained. Preferably it is 0.3% or more, More preferably, it is 0.5% or more.

Yb ₂ O ₃ is not essential, but is preferably contained when it is desired to sensitize Er ₂ O ₃ upconversion fluorescence.
When Yb ₂ O ₃ is contained, the content is preferably 0.2 to 3%. If it is less than 0.2%, a sufficient sensitizing effect may not be obtained. More preferably, it is 0.3% or more, and typically 0.5% or more. If it exceeds 3%, vitrification may be difficult. More preferably, it is 2.5% or less, and typically 2% or less.

The total Er ₂ O ₃ + Yb ₂ O ₃ of Yb ₂ O ₃ and Er ₂ O ₃ content is preferably 0.2 to 5%. If it is less than 0.2%, sufficient up-conversion fluorescence intensity may not be obtained. More preferably, it is 0.4% or more, and typically 1% or more. If it exceeds 5%, vitrification may be difficult. Typically 2% or less.

The content ratio Yb / Er of Yb ₂ O ₃ and Er ₂ O ₃ is preferably 0.2 to 5. If it is less than 0.2, a sufficient sensitizing effect may not be obtained. Typically 0.8 or more. If it exceeds 5, the upconversion fluorescence intensity may be lowered. Typically 3 or less.

Bi ₂ O ₃ is a component for obtaining up-conversion fluorescence and is essential.
The content of Bi ₂ O ₃ is preferably 30 to 55%. If it is less than 30%, it is difficult to obtain up-conversion fluorescence intensity. Typically 35% or more. If it exceeds 55%, vitrification tends to be difficult, or nano-sized fine particles are hardly obtained. More preferably, it is 50% or less, and typically 45% or less.

SiO ₂ is a network former and is an essential component that suppresses crystal precipitation during glass production and facilitates glass formation.
The content of SiO ₂ is preferably 15 to 45%. If it is less than 15%, vitrification may be difficult. More preferably, it is 20% or more, and typically 25% or more. If it exceeds 45%, the maximum energy of the lattice vibration of the network former in the glass becomes large, and there is a risk that it is difficult to obtain up-conversion fluorescence, or a sufficient amount of fine particles are obtained during laser irradiation in the laser ablation method described later. There is a risk that it will be difficult to be. Typically 40% or less.

Al ₂ O ₃ is not essential, but may be contained up to 10% in order to suppress crystal precipitation during glass production and facilitate glass formation, or to increase upconversion fluorescence intensity. . If it exceeds 10%, vitrification may be difficult. Preferably it is 8% or less, typically 5% or less.
When Al ₂ O ₃ is contained, its content is preferably at least 0.1%, more preferably at least 1%, typically at least 2%.

Ga ₂ O ₃ is not essential, but may be contained up to 30% in order to increase the upconversion fluorescence intensity. If it exceeds 30%, vitrification becomes difficult. Preferably it is 25% or less, typically 20% or less.
When Ga ₂ O ₃ is contained, its content is preferably at least 0.1%. If it is less than 0.1%, the effect of increasing the intensity of up-conversion fluorescence becomes small. More preferably, it is 5% or more, and typically 10% or more.

It is preferable to contain at least one of Al ₂ O ₃ and Ga ₂ O ₃ in order to suppress crystal precipitation during glass production and facilitate glass formation, or to increase upconversion fluorescence intensity. In this case, the total Al ₂ O ₃ + Ga ₂ O ₃ of these contents is preferably 35% or less. If it exceeds 35%, vitrification may be difficult, or nano-sized fine particles may not be obtained. Typically 25% or less. Further, Al ₂ O ₃ + Ga ₂ O ₃ is preferably 3% or more, more preferably 7.5% or more, and typically 11% or more.

La ₂ O ₃ has an effect of making concentration quenching less likely to occur or an effect of increasing the up-conversion fluorescence intensity, and may be contained up to 10%. If it exceeds 10%, vitrification becomes difficult. Preferably it is 7% or less, typically 5% or less.
When La ₂ O ₃ is contained, its content is preferably at least 0.1%. If it is less than 0.1%, the effect is small. Preferably it is 0.2% or more, typically 0.5% or more. In the case where the Er ₂ O ₃ content is 1% or more and concentration quenching is to be suppressed, La ₂ O ₃ is preferably contained at 1% or more, and the typical content is 2.5% or more.

CeO ₂ is not essential, but Bi ₂ O ₃ may be contained up to 2% in order to prevent Bi ₂ O ₃ from being deposited as metal bismuth in the glass melt and reducing the transmittance of the glass. is there. If it exceeds 2%, it may not vitrify. Preferably it is 1% or less, typically 0.5% or less. When CeO ₂ is contained, the content is preferably 0.05% or more. If it is less than 0.05%, the content effect is small.

The glass of the present invention may contain components other than those listed above as long as the object of the present invention is not impaired. Examples of such components include GeO ₂ , SnO ₂ , TiO ₂ , WO ₃ , TeO ₂ , Ta and the like for facilitating vitrification or for suppressing crystal precipitation in the annealing process. _{2 O 5, In 2 O 3} , Y 2 O 3, Gd 2 O 3, MgO, CaO, SrO, BaO, Na 2 O, K 2 O, ZrO 2, ZnO, CdO, PbO , and the like.

As a preferable aspect of the glass of the present invention, Bi ₂ O ₃ 30-55%, SiO ₂ 15-45%, Al ₂ O ₃ + Ga ₂ O ₃ 3-35%, La ₂ O ₃ 0-10%, CeO ₂ 0 ˜2%, Er ₂ O ₃ 0.2-3%, Yb ₂ O ₃ 0-3%. Here, for example, “La ₂ O ₃ 0-10%” means that La ₂ O ₃ is not essential but may be contained up to 10%, and “consisting essentially of” means these enumerated components Other components may be contained within a range not impairing the object of the present invention. When components other than the above listed components are contained, the total amount of the components or these components is preferably 10% or less, and typically 5% or less.

  The fluorescent glass fine particles of the present invention have a particle size of 300 nm or less so that they can be applied to biological cells, proteins, DNA tagging, imaging, and the like. Preferably it is less than 100 nm, More preferably, it is 30 nm or less.

  As infrared light irradiated to the fluorescent glass fine particles of the present invention when used for tagging or imaging of living cells, for example, light from a commercially available semiconductor laser having a wavelength of 800 nm or 980 nm can be used.

  The fluorescent glass fine particles of the present invention are obtained by applying a laser ablation method to bulk glass produced using, for example, a melting method, that is, a method of obtaining nano-sized glass fine particles by causing high-power laser irradiation to cause ablation. Can be manufactured.

  When producing bulk glass by the melting method, the raw materials are prepared and mixed, placed in a gold crucible, alumina crucible, quartz crucible or iridium crucible, and melted in the air at 800 to 1300 ° C. Can be manufactured by casting into a predetermined mold. In order to reduce cracking during laser irradiation in the laser ablation method, it is preferable to heat-treat the cast glass at 400 to 600 ° C.

When the laser ablation method is used, examples of the laser used for causing ablation include a carbon dioxide gas laser having a wavelength of 10.6 μm and a Yb laser having a wavelength of 1.05 μm.
The laser may be irradiated with a continuous wave, or a pulse may be generated and irradiated.
Laser irradiation is usually performed in air.
The powder produced by ablation is collected by being deposited on a glass or silicon substrate in the air.

A glass (bulk glass) having a composition represented by mol% in the columns from Bi ₂ O ₃ to Yb ₂ O _{3 in} Table 1 was produced by a melting method. Incidentally, _{Bi 2 O} 3 -SiO 2 based glass in Examples 1-8 is a glass of the present invention, was dissolved in 1200 ° C..

  Next, a laser ablation method was applied to the bulk glasses of Examples 1 to 9 to produce glass fine particles. That is, the bulk glass of Examples 1 to 7 and 9 was irradiated with a carbon dioxide laser (10 W) having a wavelength of 10.6 μm with a continuous wave, and the beam was condensed near the surface of the bulk glass with a lens of f = 100 mm. Glass particles generated by such ablation were collected on a commercially available slide glass. For the bulk glass of Example 8, a Yb fiber laser with a wavelength of 1045 nm was irradiated with a pulse wave (pulse width 375 fs, repetition 1 MHz, pulse energy 500 nJ), and the beam was irradiated near the surface of the bulk glass with a lens of f = 3.5 mm. The glass particles collected by such ablation were collected on a silicon substrate. The laser irradiation and the collection of glass fine particles were both performed in air.

  The glass fine particles of Examples 1 to 9 thus obtained were subjected to powder X-ray diffraction (Cu-Kα ray, irradiation intensity 40 mA, 50 kV). Was not recognized.

Each of 150 glass fine particles of Examples 1 to 4 and 9 was observed by SEM (S-4300 manufactured by Hitachi, Ltd.) at a magnification of 50000 times, and the particle size (unit: nm) of each 150 fine particles was measured. The largest particle size is shown in the column of maximum particle size in Table 1, and the average particle size calculated by particle analysis is shown in the column of average particle size in the same table.
Moreover, TEM observation was performed about 200 glass fine particles of Example 8, and the maximum particle diameter and the average particle diameter were calculated | required. The average particle size was calculated by particle analysis with n = 200.
In addition, about the glass fine particles of Examples 5-7, the estimated value of the maximum particle diameter and an average particle diameter was described in Table 1.

  When the glass fine particles of Examples 1 to 9 were irradiated with a semiconductor laser having a wavelength of 980 nm or 800 nm, strong green up-conversion fluorescence was visually observed for the glass fine particles of Examples 1 to 8, but for the glass fine particles of Example 9 Up-conversion fluorescence could not be observed visually.

In order to compare the up-conversion fluorescence intensities of Examples 1 to 5 and 9, the following measurements were performed using 20 mm × 15 mm × 3.5 mm mirror-polished bulk glass as a sample. That is, a spectroscope (light receiving slit 0.5 mm) in which a sample was irradiated with a semiconductor laser (1 W) having a wavelength of 980 nm, and light emitted and scattered light from the glass was collected using a lens of f = 100 mm and dispersed at a wavelength of 550 nm. ).
The dispersed light was detected by a photomultiplier tube connected to the spectrometer.
The detection light was amplified using a preamplifier and a lock-in amplifier, and the voltage value (unit: mV) displayed on the lock-in amplifier was used as the up-conversion fluorescence intensity.

  The fluorescence intensity is shown in Table 1. In addition, the detection light of Example 9 was below the detection sensitivity of a photomultiplier tube. Moreover, the up-conversion fluorescence intensity of Examples 6-8 of Table 1 is an estimated value.

  Examples 10 to 19 shown in Table 2 are other examples of the glass of the present invention, but the fluorescence intensity is an estimated value from the composition.

  It can be used for tagging and imaging of living cells.

Claims (10)

Fluorescent glass fine particles made of Bi ₂ O ₃ —SiO ₂ glass containing Er ₂ O ₃ in a range of 3 mol% or less and having a particle size of 300 nm or less. The fluorescent glass fine particles according to claim 1, wherein the Bi ₂ O ₃ —SiO ₂ based glass contains Yb ₂ O ₃ and Er ₂ O ₃ + Yb ₂ O ₃ is 0.2 to 5 mol%. The fluorescent glass particle according to claim 2, wherein the Bi ₂ O ₃ —SiO ₂ glass has a Yb ₂ O ₃ content to Er ₂ O ₃ content ratio of 0.2 to 5. The _Bi 2 _O 3 according to claim 1, 2 or 3 of the fluorescent glass particles _Er 2 _{O 3} content of -SiO ₂ based glass is at least 0.2 mol%. The Bi ₂ O ₃ —SiO ₂ glass contains, in mol%, Bi ₂ O ₃ in a range of ₃₀ to 55%, SiO ₂ in a range of 15 to 45%, and Al ₂ O ₃ + Ga ₂ O ₃ in a range of 35% or less. The fluorescent glass fine particles according to any one of claims 1 to 4. The fluorescent glass fine particles according to claim 5, wherein the Bi ₂ O ₃ —SiO ₂ glass has a SiO ₂ content of 15 to 40 mol%. The fluorescent glass fine particles according to claim 5 or 6, wherein the Bi ₂ O ₃ —SiO ₂ glass contains La ₂ O ₃ in a range of 10 mol% or less. The fluorescent glass fine particles according to claim 5, 6 or 7, wherein the Bi ₂ O ₃ —SiO ₂ glass contains CeO ₂ in a range of 2 mol% or less.   The fluorescent glass particle according to any one of claims 1 to 8, which has a particle size of less than 100 nm.   The fluorescent glass particle according to any one of claims 1 to 9, which is produced by a laser ablation method.