U.S. patent application number 12/322389 was filed with the patent office on 2009-08-13 for composite phosphors based on coating porous substrates.
Invention is credited to Eve Bauer, Anthony K. Burrell, Quanxi Jia, Thomas Mark Mccleskey.
Application Number | 20090200561 12/322389 |
Document ID | / |
Family ID | 40938141 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090200561 |
Kind Code |
A1 |
Burrell; Anthony K. ; et
al. |
August 13, 2009 |
Composite phosphors based on coating porous substrates
Abstract
A composite material is provided including a phosphor material
of at least one of among hafnium oxide, niobium oxide, tantalum
oxide or zirconium oxide as a conformal coating on a porous
substrate, the composite characterized as exhibiting
photoluminescence at room temperature. Also provided is a composite
material including a phosphor material of at least one of among
hafnium oxide, niobium oxide, tantalum oxide, zinc oxide or
zirconium oxide as a conformal coating on a porous substrate, the
composite characterized as exhibiting photoluminescence at room
temperature and as having a broad emission spectrum having a width
at 1/2 maximum greater than 80 nm.
Inventors: |
Burrell; Anthony K.; (Los
Alamos, NM) ; Mccleskey; Thomas Mark; (Los Alamos,
NM) ; Jia; Quanxi; (Los Alamos, NM) ; Bauer;
Eve; (Los Alamos, NM) |
Correspondence
Address: |
LOS ALAMOS NATIONAL SECURITY, LLC
LOS ALAMOS NATIONAL LABORATORY, PPO. BOX 1663, LC/IP, MS A187
LOS ALAMOS
NM
87545
US
|
Family ID: |
40938141 |
Appl. No.: |
12/322389 |
Filed: |
January 30, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61063154 |
Jan 30, 2008 |
|
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61063153 |
Jan 30, 2008 |
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Current U.S.
Class: |
257/80 ; 257/98;
257/E31.001; 257/E33.061; 257/E33.068; 428/158 |
Current CPC
Class: |
H01L 31/055 20130101;
Y10T 428/249978 20150401; C09K 11/54 20130101; Y10T 428/24149
20150115; C09K 11/671 20130101; H01L 31/02322 20130101; Y10T
428/24999 20150401; Y10T 428/12479 20150115; Y10T 428/249953
20150401; Y10T 428/24997 20150401; Y10T 428/24496 20150115; Y10T
428/24942 20150115; Y10T 428/268 20150115; Y10T 428/249969
20150401; Y10T 428/249967 20150401 |
Class at
Publication: |
257/80 ; 257/98;
428/158; 257/E33.061; 257/E33.068; 257/E31.001 |
International
Class: |
H01L 33/00 20060101
H01L033/00; H01L 31/00 20060101 H01L031/00; B32B 3/12 20060101
B32B003/12 |
Goverment Interests
STATEMENT REGARDING FEDERAL RIGHTS
[0002] This invention was made with government support under
Contract No. DE-AC52-06NA25396 awarded by the U.S. Department of
Energy. The government has certain rights in the invention.
Claims
1. A composite comprising: a phosphor material of at least one of
among hafnium oxide, niobium oxide, tantalum oxide or zirconium
oxide as a conformal coating on a porous substrate, the composite
characterized as exhibiting photoluminescence at room
temperature.
2. The composite of claim 1 wherein the porous substrate is of
silica.
3. The composite of claim 2 wherein the porous silica substrate is
an inverse opal structure.
4. The composite of claim 2 wherein the porous silica substrate is
a zeolite.
5. The composite of claim 1 wherein the composite is further
characterized as having a broad emission spectrum having a width at
1/2 maximum greater than 80 nm.
6. The structure of claim 1 further including a material with a
pre-selected index of refraction within pores of said porous
substrate adapted to minimize light scattering from said
structure.
7. The composite of claim 6 wherein said material with a
pre-selected index of refraction is a liquid, gel or solid.
8. The composite of claim 6 wherein said index of refraction is
either greater than 1.0 or is approximately equal to the index of
refraction of the porous substrate.
9. A composite comprising: a phosphor material of at least one of
among hafnium oxide, niobium oxide, tantalum oxide, zinc oxide or
zirconium oxide as a conformal coating on a porous substrate, the
composite characterized as exhibiting photoluminescence at room
temperature and as having a broad emission spectrum having a width
at 1/2 maximum greater than 80 nm.
10. The composite of claim 9 wherein the porous substrate is of
silica.
11. The composite of claim 10 wherein the porous silica substrate
is an inverse opal structure.
12. The composite of claim 10 wherein the porous silica substrate
is a zeolite.
13. The composite of claim 9 further including a material with a
pre-selected index of refraction within pores of said porous
substrate adapted to minimize light scattering from said
structure.
14. The composite of claim 13 wherein said material with a
pre-selected index of refraction is a liquid, gel or solid.
15. The composite of claim 13 wherein said index of refraction is
either greater than 1.0 or is approximately equal to the index of
refraction of the porous substrate.
16. A light-emitting device comprising: a mesoporous silicon or
silica support structure having pores, an interior surface, and an
exterior surface, and a conformal metal-oxide-containing film that
coats said interior surface and exterior surface of said mesoporous
silicon or silica support structure without substantially blocking
the pores of said mesoporous silicon support structure.
17. The light-emitting device of claim 16, wherein the pores of
said mesoporous silicon or silica support structure have sizes in a
range of from 1 to 20 nm.
18. The light-emitting device of claim 16, wherein said mesoporous
silicon or silica support structure comprises an inverse opal or a
photonic crystal.
19. The light-emitting device of claim 16, wherein said metal
oxide-containing film that coats the interior and exterior surfaces
of said mesoporous silicon or silica support structure comprises a
transition metal oxide or a lanthanide oxide.
20. The light-emitting device of claim 16, wherein said metal
oxide-containing film that coats the interior and exterior surfaces
of said mesoporous silicon or silica support structure comprises a
group-4 transition metal or a group-5 transition metal.
21. The light-emitting device of claim 16, wherein said metal
oxide-containing film that coats the interior and exterior surfaces
of said mesoporous silicon or silica support structure includes
titanium, zirconium, hafnium, or zinc.
22. The light-emitting device of claim 16, wherein the pores of
said mesoporous silicon or silica support structure are filled with
an index matching material.
23. A radiation detector comprising: a light-emitting device that
comprises a mesoporous silicon or silica support structure having
pores, an interior surface, and an exterior surface, and a
conformal metal-oxide-containing film that coats said interior
surface and exterior surface of said mesoporous silicon or silica
support structure without substantially blocking the pores of said
mesoporous silicon support structure.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 61/063,154 entitled "Composite Phosphors Based
on Coating Porous Substrates," filed Jan. 30, 2008, and U.S.
Provisional Application Ser. No. 61/063,153 entitled
"Polymer-Assisted Deposition of Conformal Films on Porous
Materials," both hereby incorporated by reference.
FIELD OF THE INVENTION
[0003] The present invention relates to a new series of metal oxide
phosphors having a broad emission in the visible light region. In
particular these phosphors can be deposited onto silica inverse
opal structures or silica-based zeolites. The phosphors can be
deposited as films by a polymer assisted deposition technique and
can result in a luminescent composite material.
BACKGROUND OF THE INVENTION
[0004] Phosphors find applications in many LED devices. Thin films
of phosphors are used in many imaging and LED applications from
radiation detection to solid state lighting. The key properties of
phosphors include quantum yield, stability, emission wavelength and
lifetime. In particular for LEDs the efficiency of conversion of
high energy blue excitation light to the white light is a key
factor for the overall LED efficiency. Phosphors are an integral
part of any LED, and unfortunately contribute significantly to
efficiency losses. The loss mechanisms include fundamental losses
innate to the phosphor conversion material (nonradiative decay
paths that lead to reduced quantum yields) and reduced extraction
efficiency. The reductions in extraction efficiency include radial
emission from the phosphor and wave guiding at interfaces.
Phosphors are often applied in an epoxy layer over the high energy
emitting GaN light source. If smooth layers are applied effective
wave guiding can occur that channels light to the sides of the
device. Efforts have been made to reduce this effect through
surface roughening but extraction efficiencies remain at or near
60% in the best cases. Typically phosphors are only available as
powders or as thin film coatings.
[0005] One of the major obstacles in the development of high
efficiency systems is loss due to wave guiding when thin film
phosphors are used. Thin films help to minimize losses from self
absorption, but the planar interface between the phosphor layer and
other layers in the device lead to interfaces with different
refractive indexes. At these interfaces all light from the phosphor
that hits the interface at an angle > than the critical angle as
defined by Snell's Law is effectively reflected at the surface and
wave guided to the edges of the film. One way to avoid this problem
is to place the phosphor as a thin film on a three dimensional
structure with vertical structures that allow the light to
propagate in the desired direction. As the surface area of the
3-dimensional structure increases more phosphor can be excited
resulting in higher light yield. Nanoporous structures offer great
potential, but they are very difficult to coat. These nanoporous
structures can include porous alumina anodiscs that consist of a
honeycomb structure with straight channels having pore diameters
from 20 to 200 nm, porous inverse opals structures having well
defined connected cavities that can be readily controlled to the
hundreds of nanometers, and well known silica-bases zeolite systems
such as MCM-41 with pores on the dimensions of 3 to 100 nm in
diameter. All of these structures have high surface areas but the
nanometer scale porosity with openings or cavities less than about
1000 nm make them very difficult to coat by traditional
line-of-site techniques.
[0006] Over the past 10 years, photonic crystal ("PC") structures
have emerged as perhaps the ultimate platform for microdevices that
can manipulate light in all three dimensions. These artificial
microstructures consist of a periodic repetition of dielectric
elements, which creates forbidden and allowed energy bands for
photons. PCs represent a major new frontier in optoelectronics due
to their ability to coherently manipulate light. This manipulation
is essential for enabling new concepts such as producing negative
indices of refraction, tailoring the photonic density of states,
controlling spontaneous emission rates, and modifying and
controlling black-body radiation. It has been predicted [Shanhui
Fan, et al., Phys. Rev. Lett. 78, 3294 (1998)] that a weakly
penetrating etched photonic lattice on the surface of an LED can
suppress all lateral modes, causing the light to be emitted
primarily in the vertical direction.
[0007] PCs have been restricted to a subset of materials that can
be formed in the sol-gel processing. Inverse opals represent one
common form of PC in which a metal oxide is formed around
closed-packed monodisperse polymer beads, and then the beads are
subsequently removed by heat treatment to yield a metal oxide with
interconnected cavities that reflect the size of the polymer beads.
It is not possible to make PCs from just any material, which limits
their potential properties. Coating is one way to add
functionality, but traditional techniques such as pulsed laser
deposition ("PLD") and chemical vapor deposition ("CVD") cannot
coat the complex porous structures. Sol-gel can penetrate the pores
but does not result in conformal coatings since metal oxide
oligomers form in the bulk solution. The primary technique used for
effective coating of 3-D materials such as inverse opals structures
is atomic laser deposition ("ALD"). ALD is limited in that thicker
coatings require many steps and only single component coatings can
be readily applied. PAD can deposit conformal coatings of complex
metal oxides on nano-structured 3-D supports.
[0008] PAD is a unique alternative coating method based on
solutions that access the interior of porous substrates. The
coating solution used in PAD is made by adding the metal precursor
to the polymer. The polymer actively binds the metal, encapsulating
it to prevent chemical reactions that may lead to undesired phases
of metal oxide. PAD is a low-cost chemical solution method and
effectively eliminates problems such as uneven distribution of the
metal oxide on the substrate, unwanted reactivity of the metal
resulting in the formation of undesired phases, and the difficulty
of obtaining the desired metal/metal ratios when coating a
substrate with more than one metal oxide. The PAD technique is a
bottom-up growth technique that enables coating complex 3-D
structures.
[0009] New thermally stable phosphors with high quantum yields
and/or short lifetimes are highly desirable. These phosphors can be
used in solid state lighting where broad emissions that mimic the
solar spectrum to generate warm white light are highly
advantageous. They can also be used as scintillator for radiation
detection where a combination of high quantum yields, short
lifetimes and emission bands that matches the PMT detector
sensitivity are all figures of merit.
[0010] Chemical solution deposition techniques have been generally
viewed as less capital intensive (see, Lange, "Chemical Solution
Routes to Single-Crystal Thin Films", Science, vol. 273, pp.
903-909, 1996 and Schwartz, "Chemical Solution Deposition of
Perovskite Thin Films", Chemistry of Materials, vol. 9, pp.
2325-2340, 1997). Also, chemical solution techniques are not
generally limited to flat surfaces.
[0011] A scintillator is a material that is transparent in the
scintillation or emission wavelength range and that responds to
incident radiation by emitting a light pulse. From such materials,
generally single crystals, it is possible to manufacture detectors
in which the light emitted by the crystal that the detector
comprises is coupled to a light-detection means and produces an
electrical signal proportional to the number of light pulses
received and to their intensity. Such detectors are used especially
in industry for thickness or weight measurements and in the fields
of nuclear medicine, physics, chemistry and oil exploration. A
family of known scintillator crystals widely used is of the
thallium-doped sodium iodide Tl:NaI type. This scintillating
material, discovered in 1948 by Robert Hofstadter and which forms
the basis of modern scintillators, still remains the predominant
material in this field in spite of almost 50 years of research on
other materials. However, these crystals have a scintillation decay
which is not very fast. A material that is also used is CsI that,
depending on the applications, may be used pure or doped either
with thallium ("Tl") or with sodium ("Na"). One family of
scintillator crystals that has undergone considerable development
is of the bismuth germanate ("BGO") type. The crystals of the BGO
family have high decay time constants, which limit the use of these
crystals to low count rates. A more recent family of scintillator
crystals was developed in the 1990s and is of the cerium-activated
lutetium oxyorthosilicate Ce:LSO type. However these crystals are
very heterogeneous and have very high melting points (about 2200
degrees Celsius). The development of new scintillating materials
for improved performance is the subject of many studies. One of the
parameters that it is desired to improve is the energy resolution.
This is because in the majority of nuclear detector applications,
good energy resolution is desired. The energy resolution of a
nuclear radiation detector actually determines its ability to
separate radiation energies which are very close. It is usually
determined for a given detector at a given energy, such as the
width at mid-height of the peak in question on an energy spectrum
obtained from this detector, in relation to the energy at the
centroid of the peak. The smaller the value of the energy
resolution, the better the quality of the detector.
[0012] Nevertheless, lower values of resolution are of great
benefit. For example, in the case of a detector used to analyze
various radioactive isotopes, improved energy resolution enables
improved discrimination of these isotopes. While thin film
scintillators have limited utility in applications where energy
resolution is needed in radiation detection, they have major
applications in imaging systems such as X-ray imaging device.
[0013] X-ray imaging devices in which the scintillator for
converting an X-ray into visible light, or the like, and the
imaging devices for receiving the visible light, or the like, are
used in combination and more particularly a resolution-variable
X-ray imaging device whose resolution can be changed as occasion
demands and an X-ray CT apparatus. As the X-ray imaging device for
capturing an image by visualizing an X-ray, there are some devices
that can sense directly an X-ray and others that can visualize an
X-ray by using the scintillator and then capture an image by using
the imaging device such as CCD, or the like. In this case high
quantum yield and very short lifetimes are desirable.
[0014] Conventional neutron detectors typically include devices
that operate as ionization chambers or proportional counters. Each
of the available methods demonstrates different strengths, but all
share the common goals of high neutron efficiency, minimum
gamma-ray sensitivity or gamma/neutron discrimination. Other
systems, including scintillators doped with .sup.6Li, or .sup.10B,
have been examined with mixed results. One of the prime
difficulties in these systems is the gamma-ray rejection
characteristics of the system. In addition, many of the detector
materials are air and water sensitive or the scintillators employ
heavy elements that limit gamma-ray rejection or have slow response
times thanks to the long relaxation times. Scintillators have the
added complication that often single crystals are required to avoid
light loss, making it difficult to add large amounts of boron or
lithium to increase the neutron cross-section absorption. While
there are obvious advantages to the use of solid-state neutron
detectors, to date these are outweighed by their disadvantages.
Coating scintillators onto three dimensional structures which can
then be filled with neutron stooping material may provide a new
class of neutron detector.
SUMMARY OF THE INVENTION
[0015] To achieve the foregoing and other objects, and in
accordance with the purposes of the present invention, as embodied
and broadly described herein, the present invention provides for a
new series of phosphors including oxides of hafnium ("Hf"),
zirconium ("Zr"), zinc ("Zn"), tantalum ("Ta"), or niobium ("Nb")
deposited as thin conformal films onto porous metal oxide supports.
The resulting composites can have the property of observable
photo-luminescence ("PL") at room temperature.
[0016] The present invention further provides for a new series of
phosphors composed metal oxide mixtures containing at least one of
the following: Hf, Zr, Zn, Ta, or Nb deposited as thin conformal
films onto porous metal oxide supports. The resulting composite has
the property of observable photo-luminescence ("PL") at room
temperature. In particular porous silica structures serve as the
substrate. Further, the emission band of the resulting phosphors is
generally very broad having a width at 1/2 max of greater than 80
nm.
[0017] This invention further involves filling a porous substrate
with a homogenous solution, said solution containing a soluble
metal precursor and a soluble polymer in a suitable solvent, to
form a polymer and metal containing layer thereon, said polymer
characterized as having metal binding properties, and heating said
substrate in a controlled atmosphere at temperatures and for time
characterized as sufficient to remove said polymer from said
polymer and metal containing layer and form a conformal film on the
porous support.
[0018] The resulting coated porous structure has observable PL at
room temperature and maintains porosity which may be subsequently
filled with a liquid, gel, or solid. Filling the cavities with
materials of refractive index that match the substrates refractive
index can lead to enhanced light output which is important for many
applications.
[0019] The invention also includes a light-emitting device
comprising a mesoporous silicon or silica support structure having
pores, an interior surface, and an exterior surface, and a
conformal metal-oxide-containing film that coats said interior
surface and exterior surface of said mesoporous silicon or silica
support structure without substantially blocking the pores of said
mesoporous silicon support structure.
[0020] The invention also includes a radiation detector having a
light-emitting device that comprises a mesoporous silicon or silica
support structure having pores, an interior surface, and an
exterior surface, and a conformal metal-oxide-containing film that
coats said interior surface and exterior surface of said mesoporous
silicon or silica support structure without substantially blocking
the pores of said mesoporous silicon support structure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 shows the emission spectra of a hafnium-containing
solid composite phosphor from Example 5 upon 350 and 420 nm
excitation.
[0022] FIG. 2 shows the emission spectra of a hafnium-containing
solid composite phosphor from Example 5 filled with CCl.sub.4 upon
330 and 390 nm excitation.
[0023] FIG. 3 shows the emission spectra of a zinc-containing solid
composite phosphor from Example 7 filled with CCl.sub.4 upon 330 nm
excitation.
[0024] FIG. 4 shows the emission spectra of a hafnium-containing
solid composite phosphor from Example 4 filled with CCl.sub.4 upon
330 and 390 nm excitation.
[0025] FIG. 5 shows the emission spectra of a hafnium-containing
solid composite phosphor from Example 2 filled with CCl.sub.4 upon
330 and 390 nm excitation.
[0026] FIG. 6 shows the emission spectra of a zirconium-containing
solid composite phosphor filled with CCl.sub.4 upon 330 and 390 nm
excitation.
[0027] FIG. 7 shows the emission spectra of a
hafnium-zinc-containing solid composite phosphor from Example 12
upon 365 nm excitation.
[0028] FIG. 8 shows the emission spectra of a
hafnium-zinc-containing solid composite phosphor from Example 12
filled with CCl.sub.4 upon 390 nm excitation.
[0029] FIG. 9 shows emission spectra of hafnium, zirconium and zinc
oxide on silica inverse opal filled dry and filled with
CCl.sub.4.
[0030] FIG. 10 shows emission spectra of zirconium oxide on silica
MCM-41.
[0031] FIG. 11 shows emission spectrum from HfO.sub.2 coated
inverse opals irradiated with Mo K.alpha. radiation.
DETAILED DESCRIPTION
[0032] The present invention describes a new class of phosphors
that have desirable characteristics for a variety of applications
including LEDs, solid state lighting, scintillation-based imaging,
and scintillation-based detection of radiation. A series of new
phosphors have been prepared by coating nanoporous substrates with
metal oxide coatings using the PAD process, for example 2 coats of
hafnium oxide on 360 nm silica inverse opals gives bright emission,
as shown in FIG. 1. The substrates coated include silica inverse
opals, and the silica zeolite MCM-41. Coating the nanoporous
substrates via PAD with Hf, Zr, Ta, Nb, or Zn solutions or a
solution mixture of more than 1 metal containing Hf, Zr, Ta, Nb, or
Zn produces a thin conformal coating on the porous material.
Filling the pores with index-matched material increases the light
output. The filling of the pores reduces the light scattering. FIG.
2 shows the 360 nm pore diameter silica inverse opals coated with 2
coats of hafnium filled with carbon teterachloride. When zinc oxide
is coated on the 320 nm pore diameter silica inverse opals and the
pores are filled with carbon tetrachloride the emission, seen in
FIG. 3, is at much lower energy. Interestingly, the number of coats
also has an effect on the emission maxima. When the 2 coats of
hafnium is applied onto 360 nm pore diameter silica inverse opals
the emission maxima for 390 nm excitation is .about.455 nm, see
FIG. 2. When the only 1 coat of hafnium is applies onto 390 nm pore
diameter silica inverse opals the emission maxima for 390 nm
excitation is .about.440 nm, see FIG. 4. The size of the pores also
has an effect. When hafnium is coated onto 320 nm pore diameter
silica inverse opal the emission maxima for 330 nm excitation is
.about.410 nm, see FIG. 5. Whereas, the hafnium coated onto 360 nm
pore diameter silica inverse opal the emission maxima for 330 nm
excitation is .about.390 nm, see FIG. 5. Zirconium coated onto
inverse opals with a pore diameter of 320 nm, give an emission
maxima of 450 nm, seen in FIG. 6. The porous substrates coated with
Hf, Zr, Ta, Zn and a 50:50 mixture of Zn and Hf all show strong PL
at room temperature, as shown in FIG. 7. Filling the pores of the
mixed hafnium-zinc material with an index-matched solvent as shown
in FIG. 8 also results in increased light output. The
photoluminescent material may include a single phosphor or multiple
phosphors mixed together. The structure of the conformal film can
be amorphous, composite, polycrystalline, nanocrystalline, or
microcrystalline depending upon the chemistry of the solution, the
substrate used for the film deposition and growth and the
post-thermal treatment conditions. Hafnium oxide has been proposed
as a potential high refractive index layer for coatings in a
variety of materials and is used as a optical coating on glass, but
it has never been shown to significant visible PL at room
temperature. The observation of visible PL at room temperature for
films of Hf, Zr, Ta, and Nb oxide films is unprecedented to our
knowledge. Zinc oxide has long been known to have observable PL at
room temperature via oxygen defects that lead to emissive states at
energies below the bandgap of ZnO. Zinc oxide has also been
deposited by a variety of techniques including spray pyrolysis and
ALD onto many substrates including silica inverse opals. All of
these materials show two emission bands: a blue band centered near
380 nm and a second green (structured) band centered near 540 nm.
In general the green band is less intense than the blue band.
Strong PL is typically only observed when the ZnO is prepared in a
reducing atmosphere.
[0033] In particular Hf, Zr, Ta, Nb, Zn and combinations with more
than one metal in combination such as Hf:Zn can be deposited as
oxide films onto nanoporous structures or can be deposited onto
various photonic crystal structures such as an inverse opal
structure. The resulting composite materials are luminescent at
room temperature with broad emission bands greater than 80 nm at
1/2 the maximum. The exact emission spectrum of each element is
different as shown by FIG. 9. This is important for white light
applications and for matching photomultiplier tubes.
[0034] In the present invention the zinc oxide coated porous silica
materials are unique in their structure as evidenced by the PL. In
these new materials the PL shows only one extremely broad emission
band centered near 490 nm with a bandwidth at 1/2 max of 150 rm. At
1/2 the maximum emission intensity the emission band is 150 nm wide
extending from 400 to 550 nm. This type of emission from ZnO has
not been observed before to our knowledge. Another unique feature
of these composite ZnO phosphors is that they can be prepared by
simple annealing in air. No reducing atmosphere is required for
strong PL at room temperature.
[0035] Similar broad emission from defect sites below the bandgap
energy of either the substrate or the coating is observed with Zr,
Hf, Ta and a 1:1 mixture of Hf:Zn. All of the resulting phosphors
show intense PL at room temperature with quantum yields greater
than about 0.05. The lifetime of the hafnium coated silica inverse
opals is extremely short at less than about 5 ns (the resolution of
the instrument used). The combination of the short lifetime with a
high quantum yield and a thermal stability of at least 500.degree.
C. is extremely rare in a phosphor system. Many metal oxide
phosphor systems such as europium have microsecond or millisecond
lifetimes that limit their applications. Organic phosphors with
intense singlet to singlet state emission can have high quantum
yields and very short lifetimes but they are not thermally stable
at temperatures greater than about 250.degree. C. and they are
often toxic. Many of the phosphors described here are based on
simple metal oxide coatings that should limited or no adverse
health effects. Emission from coated porous silicon (silica) new
with no examples of titanium, zirconium, hafnium, tantalum or
niobium coated silica producing photoluminescence ever being
reported. The effect is not just restricted to inverse opals.
MCM-41 when coated with these metals also emits light, when
excited, as seen in FIG. 10.
[0036] The present invention uses a soluble polymer to assist in
the deposition of the desired metal containing film. The process
can be referred to as a polymer assisted deposition ("PAD")
process. Inclusion of a soluble polymer with a single metal
precursor or multiple metal precursors promotes better distribution
of the materials during the deposition. The metal bound polymer
solution can be completely infused into a porous material by simple
capillary action. This effect can be enhanced by exposing the
porous material to the solution and then reducing the pressure in
the system (by placing it in a partial vacuum) to cause the
solution to fill the porous volume of the substrate. The volume of
the metal bound polymer solution should not be significantly
greater than the volume of the porous substrate. The solvent and
polymer can be removed subsequently by heating at sufficiently high
temperatures to first eliminate the solvent and then the polymer
and leave a conformal metal containing film. By using a soluble
polymer in conjunction with one or more metal precursors, single or
mixed compound/complex metal containing films can be prepared. In
one embodiment, the overall process can be an aqueous process that
can be organic solvent free. Formation of the metal containing film
depends upon the proper selection of precursor and atmosphere
during heating. The polymer cannot only control the desired
viscosity for the process, but also binds the metal ions to prevent
premature precipitation and formation of metal oxide oligomers. As
the solvent is removed the polymer bound metal will preferentially
stick to the walls of the porous support when there are good
adhesive forces between the polymer and the porous support. The
results are found to be a homogeneous distribution of the metal
precursors in the solution and the formation of conformal metal
containing films throughout the porous support. PAD can grow highly
conformal films with no clogging of the porous structure and
minimal loss in surface area.
[0037] The heating of the polymer and metal layer is generally
carried out in air for simple metal oxide films, but can also be
carried out under a variety of controlled atmospheres such as
reducing atmosphere to maintain lower oxidation states in the
films.
[0038] By the process of the present invention, the metal
containing film may be prepared with an amorphous structure or a
nanocrystalline structure, polycrystalline structure or crystalline
structure by suitable treatment after deposition of the polymer and
metal containing layer upon a substrate or by suitable selection of
the substrate. Such amorphous or polycrystalline structures may be
preferred for some applications, while crystalline structures are
required for some phosphors to emit light efficiently.
[0039] The metal oxide-containing films of the present invention
are conformal films, i.e., they are homogeneous films throughout
the internal pores of the porous supports that do not greatly
reduce the surface area by clogging pore openings.
[0040] In one embodiment of the present invention the porous
substrate can be an inverse opals structure based on an oxide
framework. The oxide framework can consist of silica, borate,
zirconium oxide, titanium oxide and the like. The size of the
cavities of the inverse opals framework can be varied from hundred
of microns down to tens of nanometers.
[0041] In one embodiment of the present invention the porous
substrate can be a porous silica zeolite. The size of the pores can
be varied from 100 nm down to 3 nanometers depending on the
framework structure.
[0042] The starting solution can be deposited on a desired
substrate by infusion as a result of capillary forces, infusion
through reduced pressure and the like. After deposition of the
starting solution on a substrate, the deposited coating must be
heated under a suitable atmosphere at high temperatures of from
about 250.degree. C. to about 1300.degree. C., preferably from
about 400.degree. C. to about 1200.degree. C. for a period of time
sufficient to remove the polymer and to form only the metal
containing film. Heating times may be varied and may be longer
depending upon the thickness of the deposited film.
[0043] The coating is done by simply adding a volume of solution
that is less than or equal to the volume of the porous support
used. The solution wets into the pores by capillary action.
Alternatively a reduced pressure atmosphere can be used to drive
the solution into the porous substrate
[0044] The post-thermal treatment conditions such as post-annealing
temperature and ambient change in a wide range depending on the
objectives of the materials deposited. For most of the phosphors
described here there thermal treatment was carried out by heating
in air at a ramp rate of 10.degree. C./min to 120.degree. C., held
for 1 hour, heated at a ramp rate of 10.degree. C. to 450.degree.
C., held for 1 hour, and then heated at a ramp rate of 10.degree.
C. to 500.degree. C., and held for 1 hour. The material was then
allowed to cool to room temperature. In one embodiment of the
present invention the resulting porous nanostructure with the metal
containing coating from the PAD deposition may be subsequently
filled with a liquid, gel or solid. The conformal coating does not
fill the pore volume so that the pores may be filled with a
subsequent step to add functionality including high Z materials for
gamma-ray absorption, boron containing materials for neutron
absorption, materials with a refractive index to match the
substrate in order to increase the light output of the phosphor and
the like.
[0045] It has been found that not all materials have this
photoluminescence. Coating of other high refractive index metal
oxides such as tungsten and bismuth onto the inverse opals does not
yield material with PL at room temperature. In addition the inverse
opals themselves have no PL at room temperature.
[0046] Preliminary results from irradiation with X-Rays show that
P1 gives no response, while the Hf coated P1 yields PL upon X-ray
irradiation. These results indicate that these new phosphors are
potential scintillators for radiation detection.
[0047] The coating of hafnium, zirconium, titanium and zinc on the
silica inverse opals, which are an ordered nanoporous structure
made up of mesoporous silica, and the mesoporous silica in the form
of MCMs, results in a new material composition that emits light
when excited with light of any energy greater that 420 nm. The
potential utility of the coated silica inverse opals as
scintillators in radiation detection is shown in FIG. 11 where the
light emission is stimulated by X-ray radiation.
[0048] The present invention is more particularly described in the
following examples which are intended as illustrative only, since
numerous modifications and variations will be apparent to those
skilled in the art.
[0049] Examples A-F describe the preparation of metal-containing
solutions used in the deposition and formation of the metal
containing films, e.g., metal oxide containing films. Examples 1-12
describe the synthesis of the composite phosphor materials in
accordance with the present invention. Polyethylenimine was
obtained from BASF as a water free, branched, polymer with an
average MW of 50,000. Water was deionized via reverse osmosis
(having a resistivity >16 Ohms).
Example A
[0050] A hafnium coating solution was prepared by mixing 1.0 g of
HfOCl.sub.2 (ALDRICH, 99.99% pure), 1.0 g K.sub.2EDTA (ALDRICH,
99.995% pure), and 1 grams BASF polyethyleneimine polymer in
deionized (18 M.OMEGA.) H.sub.2O. The resulting solution was
filtered through a 0.45 micron filter, diluted to 200 mL with nano
pure water, and purified by Amicon filtration with a 3,000 MW
cut-off filter. The final concentrated solution was 144 mM hafnium,
determined by ICP/AES. The potassium concentration was 11 mM, also
determined by ICP/AES.
Example B
[0051] A hafnium coating solution was prepared by mixing 2.0 g of
HfOCl.sub.2 (ALDRICH, 99.99% pure), 2.0 g HEDTA (ALDRICH, 99.995%
pure) and 2 grams BASF polyethyleneimine polymer and concentrated
ammonium hydroxide, NH.sub.4OH (Fisher) in deionized (18 M.OMEGA.)
H.sub.2O. The resulting solution was filtered through a 0.45 micron
filter, diluted to 200 mL with nano pure water, and purified by
Amicon filtration with a 3,000 MW cut-off filter. The final
concentrated solution was 163 mM hafnium, determined by ICP/AES.
This solution was rotovapped to further concentrate it, resulting
in a final concentration of 250 mM hafnium.
Example C
[0052] A zinc solution was prepared by mixing 3.7 g zinc nitrate
hexahydrate, Zr(NO.sub.3).sub.2 6H.sub.2O, (ALPHA AESAR, 99.998%
pure), 5.0 g HEDTA (ALDRICH, 99.995% pure) and 5 grams BASF
polyethyleneimine polymer in deionized (18 M.OMEGA.) H.sub.2O. The
resulting solution was filtered through a 0.45 micron filter,
diluted to 200 mL with nano pure water, and purified by Amicon
filtration with a 3,000 MW cut-off filter. The final concentrated
solution was 179 mM zinc, determined by ICP/AES.
Example D
[0053] A zirconium solution was prepared by mixing 2.04 g of
Zirconyl Nitrate, ZrO(NO.sub.3).sub.2, (Aldrich 35 wt % Zr), 2.0 g
HEDTA (Aldrich 99.995% pure) and 2 grams BASF polyethyleneimine
polymer and concentrated ammonium hydroxide, NH.sub.4OH (FISHER) in
deionized (18 M.OMEGA.) H.sub.2O. The resulting solution was
filtered through a 0.45 micron filter, diluted to 200 mL with nano
pure water, and purified by Amicon filtration with a 3,000 MW
cut-off filter. The final concentrated solution was 225 mM
zirconium, determined by ICP/AES.
Example E
[0054] A bismuth solution was prepared by mixing 3.0 g bismuth
nitrate hydrate, Bi(NO.sub.3).sub.3 X H.sub.2O, (ALPHA AESAR,
99.999% pure), 2.0 g HEDTA (ALDRICH, 99.995% pure) and 2 grams BASF
polyethyleneimine polymer in deionized (18 M.OMEGA.) H.sub.2O. The
resulting solution was filtered through a 0.45 micron filter,
diluted to 200 mL with nano pure water, and purified by Amicon
filtration with a 3,000 MW cut-off filter. The final concentrated
solution was 153 mM bismuth, determined by ICP/AES.
Example F
[0055] A tungsten solution was prepared by mixing 3.0 g of sodium
tungstate, and 3.0 grams BASF polyethyleneimine polymer in
deionized (18 M.OMEGA.) H.sub.2O at pH 7 (by addition of HCl). The
resulting solution may be pH adjusted to >4 by addition of an
ammonium hydroxide solution. The solution was filtered through a
0.45 micron filter, diluted to 200 mL with nano pure water, and
purified by Amicon filtration with a 3,000 MW cut-off filter. The
final concentrated solution was 211 mM tungsten, determined by
ICP/AES.
Example 1
[0056] Silica inverse opals were coated with hafnium oxide using
the PAD method of coating. 334 mg of the solution from example A
was diluted with 105 mg of deionized (18 M.OMEGA.) H.sub.2O. The
solution was then dropped onto 30 mg of P1 photonic inverse opals
in a 20-mL scintillation vial. The vial was rotated to ensure total
coverage of the inverse opals by the coating solution. The coated
inverse opals were then rotovapped under negative pressure in order
to cause the solution to penetrate the cavities within the photonic
inverse opals and remove excess water.
[0057] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
Example 2
[0058] P1-Silica inverse opals with one coat of Hf were prepared as
follows. SiO.sub.2 inverse opals were coated with hafnium oxide
using the PAD method of coating. Two hundred mg of the solution
from example B was diluted with 100 mg of deionized (18 M.OMEGA.)
H.sub.2O. The solution was then dropped onto 32 mg of P1 photonic
inverse opals in a 20-mL scintillation vial. The vial was rotated
to ensure total coverage of the inverse opals by the coating
solution. The coated inverse opals were then rotovapped under
negative pressure in order to cause the solution to penetrate the
cavities within the photonic inverse opals and remove excess
water.
[0059] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour. FIG. 9 shows
the PL of the P1 inverse opal and P1 inverse opal coated with
hafnium as in Example 2. FIG. 5 shows the emission spectra of the
hafnium-containing solid composite phosphor filled with CCl.sub.4
upon 330 and 390 nm excitation.
Example 3
[0060] P1-Photonic Inverse opals with two coats of Hf were prepared
as follows. SiO.sub.2 inverse opals were coated with hafnium oxide
using the PAD method of coating. 211 mg of the solution from
example B was diluted with 109 mg of deionized (18 M.OMEGA.)
H.sub.2O. The solution was then dropped onto 31 mg of P1 photonic
inverse opals in a 20-mL scintillation vial. The vial was rotated
to ensure total coverage of the inverse opals by the coating
solution. The coated inverse opals were then rotovapped under
negative pressure in order to cause the solution to penetrate the
cavities within the photonic inverse opals and remove excess
water.
[0061] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
[0062] The inverse opals were removed from the crucible and placed
in a scintillation vial. Another solution of 213 mg Hf solution
plus 115 mg H.sub.2O was dropped onto the P1 inverse opals with 1
coat of Hf. The vial was rotated to ensure total coverage of the
inverse opals by the coating solution. The coated inverse opals
were then rotovapped under negative pressure in order to cause the
solution to penetrate the cavities within the photonic inverse
opals and remove excess water.
[0063] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
Example 4
[0064] P3-Photonic Inverse opals with one coat of Hf were prepared
as follows. SiO.sub.2 inverse opals were coated with hafnium oxide
using the PAD method of coating. Two hundred mg of the solution
from example B was diluted with 100 mg of deionized (18 M.OMEGA.)
H.sub.2O. The solution was then dropped onto 32 mg of P3 photonic
inverse opals in a 20-mL scintillation vial. The vial was rotated
to ensure total coverage of the inverse opals by the coating
solution. The coated inverse opals were then rotovapped under
negative pressure in order to cause the solution to penetrate the
cavities within the photonic inverse opals and remove excess
water.
[0065] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
[0066] The inverse opals were removed from the crucible and placed
in an NMR tube to investigate emissions of the coated inverse
opals. FIG. 4 shows the emission spectra of the hafnium-containing
solid composite phosphor filled with CCl.sub.4 upon 330 and 390 nm
excitation.
Example 5
[0067] P3--Photonic Inverse opals with two coats of Hf were
prepared as follows. SiO.sub.2 inverse opals were coated with
hafnium oxide using the PAD method of coating. 211 mg of the
solution from example B was diluted with 109 mg of deionized (18
M.OMEGA.) H.sub.2O. The solution was then dropped onto 34 mg of P3
photonic inverse opals in a 20-mL scintillation vial. The vial was
rotated to ensure total coverage of the inverse opals by the
coating solution. The coated inverse opals were then rotovapped
under negative pressure in order to cause the solution to penetrate
the cavities within the photonic inverse opals and remove excess
water.
[0068] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
[0069] The inverse opals were removed from the crucible and placed
in a scintillation vial. Another solution of 213 mg Hf solution
plus 115 mg H.sub.2O was dropped onto the P1 inverse opals with 1
coat of Hf. The vial was rotated to ensure total coverage of the
inverse opals by the coating solution. The coated inverse opals
were then rotovapped under negative pressure in order to cause the
solution to penetrate the cavities within the photonic inverse
opals and remove excess water.
[0070] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour. FIG. 1 shows
the emission spectra of the hafnium-containing solid composite
phosphor upon 350 and 420 nm excitation. FIG. 2 shows the emission
spectrum when the pores are filled with CCl.sub.4.
Example 6
[0071] P3--Photonic Inverse opals with three coats of Hf were
prepared as follows. SiO.sub.2 inverse opals were coated with
hafnium oxide using the PAD method of coating. 219 mg of the
solution from example B was diluted with 112 mg of deionized (18
M.OMEGA.) H.sub.2O. The solution was then dropped onto 36 mg of P3
photonic inverse opals in a 20-mL scintillation vial. The vial was
rotated to ensure total coverage of the inverse opals by the
coating solution. The coated inverse opals were then rotovapped
under negative pressure in order to cause the solution to penetrate
the cavities within the photonic inverse opals and remove excess
water.
[0072] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
[0073] The inverse opals were removed from the crucible and placed
in a scintillation vial. Another solution of 206 mg Hf solution
plus 109 mg H.sub.2O was dropped onto the P3 inverse opals with 1
coat of Hf. The vial was rotated to ensure total coverage of the
inverse opals by the coating solution. The coated inverse opals
were then rotovapped under negative pressure in order to cause the
solution to penetrate the cavities within the photonic inverse
opals and remove excess water.
[0074] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
[0075] The inverse opals were removed from the crucible and placed
in a scintillation vial. Another solution of 220 mg Hf solution
plus 115 mg H.sub.2O was dropped onto the P3 inverse opals with 2
coats of Hf. The vial was rotated to ensure total coverage of the
inverse opals by the coating solution. The coated inverse opals
were then rotovapped under negative pressure in order to cause the
solution to penetrate the cavities within the photonic inverse
opals and remove excess water.
[0076] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
Example 7
[0077] P1--Photonic Inverse opals with one coat of Zn were prepared
as follows. SiO.sub.2 inverse opals were coated with zinc oxide
using the PAD method of coating. 200 .mu.L of the solution from
Example C was diluted with 100 .mu.L of deionized (18 M.OMEGA.)
H.sub.2O. The solution was then dropped onto 31 mg of P1 photonic
inverse opals in a 20-mL scintillation vial. The vial was rotated
to ensure total coverage of the inverse opals by the coating
solution. The coated inverse opals were then rotovapped under
negative pressure in order to cause the solution to penetrate the
cavities within the photonic inverse opals and remove excess
water.
[0078] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
[0079] FIG. 3 shows the emission spectra of the zinc-containing
solid composite phosphor filled with CCl.sub.4 upon 330 nm
excitation.
Example 8
[0080] P3--Photonic Inverse opals with two coats of Zn were
prepared as follows. SiO.sub.2 inverse opals were coated with zinc
oxide using the PAD method of coating. 200 .mu.L of the solution
from example C was diluted with 100 .mu.L of deionized (18
M.OMEGA.) H.sub.2O. The solution was then dropped onto 31 mg of P3
photonic inverse opals in a 20-mL scintillation vial. The vial was
rotated to ensure total coverage of the inverse opals by the
coating solution. The coated inverse opals were then rotovapped
under negative pressure in order to cause the solution to penetrate
the cavities within the photonic inverse opals and remove excess
water.
[0081] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
[0082] The inverse opals were removed from the crucible and placed
in a scintillation vial. Another solution of 200 .mu.L Zn solution
plus 100 .mu.L H.sub.2O was dropped onto the P3 inverse opals with
1 coat of Zn. The vial was rotated to ensure total coverage of the
inverse opals by the coating solution. The coated inverse opals
were then rotovapped under negative pressure in order to cause the
solution to penetrate the cavities within the photonic inverse
opals and remove excess water.
[0083] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
Example 9
[0084] P1--Photonic Inverse opals with one coat of Zr were prepared
as follows. SiO.sub.2 inverse opals were coated with zirconium
oxide using the PAD method of coating. 192 mg of the solution from
example D was diluted with 107 mg of deionized (18 M.OMEGA.)
H.sub.2O. The solution was then dropped onto 32 mg of P1 photonic
inverse opals in a 20-mL scintillation vial. The vial was rotated
to ensure total coverage of the inverse opals by the coating
solution. The coated inverse opals were then rotovapped under
negative pressure in order to cause the solution to penetrate the
cavities within the photonic inverse opals and remove excess
water.
[0085] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
[0086] The temperature was ramped to 120.degree. C. at
10.degree./min and held for 1 hour.
The temperature was ramped to 450.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 500.degree. C. at
10.degree./min and held for 1 hour.
Example 10
[0087] P3--Photonic Inverse opals with two coats of Zr were
prepared as follows SiO.sub.2 inverse opals were coated with
zirconium oxide using the PAD method of coating. 238 mg of the
solution from example D was diluted with 135 mg of deionized (18
M.OMEGA.) H.sub.2O. The solution was then dropped onto 30 mg of P3
photonic inverse opals in a 20-mL scintillation vial. The vial was
rotated to ensure total coverage of the inverse opals by the
coating solution. The coated inverse opals were then rotovapped
under negative pressure in order to cause the solution to penetrate
the cavities within the photonic inverse opals and remove excess
water.
[0088] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
[0089] The inverse opals were removed from the crucible and placed
in a scintillation vial. Another solution of 238 mg Zr solution
plus 135 mg H.sub.2O was dropped onto the P3 inverse opals with 1
coat of Zr. The vial was rotated to ensure total coverage of the
inverse opals by the coating solution. The coated inverse opals
were then rotovapped under negative pressure in order to cause the
solution to penetrate the cavities within the photonic inverse
opals and remove excess water.
[0090] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
Example 11
[0091] P3--Photonic Inverse opals with one coat of Zr were prepared
as follows. SiO.sub.2 inverse opals were coated with zirconium
oxide using the PAD method of coating. 192 mg of the solution from
example D was diluted with 107 mg of deionized (18 M.OMEGA.)
H.sub.2O. The solution was then dropped onto 32 mg of P3 photonic
inverse opals in a 20-mL scintillation vial. The vial was rotated
to ensure total coverage of the inverse opals by the coating
solution. The coated inverse opals were then rotovapped under
negative pressure in order to cause the solution to penetrate the
cavities within the photonic inverse opals and remove excess
water.
[0092] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour.
Example 12
[0093] P1--Photonic inverse opals with one coat of a mixed Zn:Hf
coating 1:1 ratio were prepared as follows. SiO.sub.2 inverse opals
were coated with tungsten oxide using the PAD method of coating. A
solution of a 1:1 molar ratio of Zn:Hf was prepared by combining
the solutions from example B and example C in the appropriate
ratios. The solution was then dropped onto 32 mg of P1 photonic
inverse opals in a 20-mL scintillation vial. The vial was rotated
to ensure total coverage of the inverse opals by the coating
solution. The coated inverse opals were then rotovapped under
negative pressure in order to cause the solution to penetrate the
cavities within the photonic inverse opals and remove excess
water.
[0094] When the inverse opals appeared dry, the inverse opals were
transferred to a ceramic crucible. The inverse opals were then
annealed in air with the following heating program:
The temperature was ramped to 120.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 450.degree. C. at
10.degree./min and held for 1 hour. The temperature was ramped to
500.degree. C. at 10.degree./min and held for 1 hour. FIG. 7 shows
the emission spectra of a hafnium-containing solid composite
phosphor upon 365 nm excitation. FIG. 8 shows the emission spectra
of the hafnium-zinc-containing solid composite phosphor filled with
CCl.sub.4 upon 390 nm excitation.
Example 13
[0095] The zirconium-coated mesoporous silica was prepared by
taking 192 mg of the zirconium solution and diluting with 100 mg of
deionized (18 M.OMEGA.) H.sub.2O. The solution was then dropped
onto 32 mg of the silica photonic crystals in a 20-mL scintillation
vial. The vial was rotated to ensure total coverage of the crystals
by the coating solution. The coated crystals were then rotovapped
under negative pressure in order to cause the solution to penetrate
the cavities within the photmic crystals and remove excess water.
When the crystals appeared dry, the crystals were transferred to a
ceramic crucible. The crystals were then annealed in air with the
following heating program: The temperature was ramped to
120.degree. C. at 10.degree./min and held for 1 hour. The
temperature was ramped to 450.degree. C. at 10.degree./min and held
for 1 hour. The temperature was ramped to 500.degree. C. at
10.degree./min and held for 1 hour. The resulting zirconium-coated
mesoporous silica was very bright under UV light.
Example 14
[0096] The hafnium coated mesoporous silica was prepared by taking
200 mg of the hafnium solution and diluting with 100 mg of
deionized (18 M.OMEGA.) H.sub.2O. The solution was then dropped
onto 32 mg of the titanium oxide photonic crystals in a 20-mL
scintillation vial. The vial was rotated to ensure total coverage
of the crystals by the coating solution. The coated crystals were
then rotovapped under negative pressure in order to cause the
solution to penetrate the cavities within the photonic crystals and
remove excess water. When the crystals appeared dry, the crystals
were transferred to a ceramic crucible. The crystals were then
annealed in air with the following heating program: The temperature
was ramped to 120.degree. C. at 10.degree./min and held for 1 hour.
The temperature was ramped to 450.degree. C. at 10.degree./min and
held for 1 hour. The temperature was ramped to 500.degree. C. at
10.degree./min and held for 1 hour.
[0097] The foregoing description of the invention has been
presented for purposes of illustration and description and is not
intended to be exhaustive or to limit the invention to the precise
form disclosed, and obviously many modifications and variations are
possible in light of the above teaching. The embodiments were
chosen and described in order to best explain the principles of the
invention and its practical application to thereby enable others
skilled in the art to best utilize the invention in various
embodiments and with various modifications as are suited to the
particular use contemplated. It is intended that the scope of the
invention be defined by the claims appended hereto.
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