U.S. patent application number 11/315209 was filed with the patent office on 2007-06-28 for mesoporous membranes with complex functional architectures and methods for making.
Invention is credited to Anthony Yu-Chung Ku, Sergio Paulo Martins Loureiro, Mohan Manoharan, James Anthony Ruud, Seth Thomas Taylor.
Application Number | 20070148415 11/315209 |
Document ID | / |
Family ID | 38194165 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070148415 |
Kind Code |
A1 |
Ku; Anthony Yu-Chung ; et
al. |
June 28, 2007 |
Mesoporous membranes with complex functional architectures and
methods for making
Abstract
In some embodiments, the present invention is directed to
methods of making structures with complex functional architectures,
where such structures generally comprise at least two mesoporous
regions comprising different chemical activity, and where such
methods afford spatial control over the placement of such regions
of differing chemical activity. In some embodiments, the present
invention is also directed to the structures formed by such
methods, where such structures are themselves novel.
Inventors: |
Ku; Anthony Yu-Chung;
(Rexford, NY) ; Taylor; Seth Thomas; (Niskayuna,
NY) ; Manoharan; Mohan; (Niskayuna, NY) ;
Loureiro; Sergio Paulo Martins; (Saratoga Springs, NY)
; Ruud; James Anthony; (Delmar, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
PATENT DOCKET RM. BLDG. K1-4A59
NISKAYUNA
NY
12309
US
|
Family ID: |
38194165 |
Appl. No.: |
11/315209 |
Filed: |
December 23, 2005 |
Current U.S.
Class: |
428/195.1 ;
502/439 |
Current CPC
Class: |
B01D 2323/24 20130101;
B01D 2325/08 20130101; B01D 67/0069 20130101; Y10T 428/24802
20150115; Y10S 977/893 20130101; B01D 67/0093 20130101; C04B
38/0064 20130101; B01D 71/024 20130101; C04B 38/0064 20130101; C04B
35/00 20130101; C04B 38/0054 20130101 |
Class at
Publication: |
428/195.1 ;
502/439 |
International
Class: |
B01J 21/04 20060101
B01J021/04 |
Claims
1. A structure comprising at least two chemically-distinct
mesoporous ceramic regions, wherein at least one such region
comprises organic functionality, wherein the regions are in fluid
communication with each other, and wherein the regions are further
differentiated by at least one property selected from the group
consisting of pore morphology, bulk chemical composition, and
combinations thereof.
2. The structure of claim 1, wherein the organic functionality
emanates from organic-based molecules covalently-integrated into
the at least one region comprising such functionality.
3. The structure of claim 1, wherein pore morphology is
differentiable between regions if the average pore size of such
regions differs by at least about 10 percent.
4. The structure of claim 1, wherein the bulk chemical composition
of the mesoporous ceramic regions is selected from the group
consisting of SiO.sub.2, TiO.sub.2, Al.sub.2O.sub.3, ZrO.sub.2,
Y.sub.2O.sub.3:ZrO.sub.2, Y.sub.2O.sub.3, and combinations
thereof.
5. The structure of claim 1, wherein the organic functionality
comprises moieties selected from the group consisting of alkyl,
mercapto, carboxyl, vinyl, amine, benzyl, and combinations
thereof.
6. The structure of claim 5, wherein the organic functionality
further comprises organometallic functionality.
7. The structure of claim 1, wherein the mesoporous ceramic regions
comprise pores having an average pore size of between about 1 nm
and about 40 nm.
8. The structure of claim 7, wherein the average pore size
comprises a standard deviation of between about .+-.0.1 nm and
about .+-.10 nm.
9. A structure comprising at least two mesoporous ceramic regions
of substantially similar bulk chemical composition and pore
morphology, wherein the regions are in fluid communication with
each other, wherein at least one such region comprises organic
functionality, and wherein at least one such region is
substantially devoid of organic functionality.
10. The structure of claim 9, wherein the organic functionality
emanates from organic-based molecules covalently-integrated into
the at least one region comprising such functionality.
11. The structure of claim 10, wherein the organic functionality
comprises moieties selected from the group consisting of alkyl,
mercapto, carboxyl, vinyl, amine, benzyl, and combinations
thereof.
12. The structure of claim 11, wherein the organic functionality
further comprises organometallic functionality.
13. A structure comprising at least two morphologically-distinct
mesoporous ceramic regions, wherein the regions are in fluid
communication with each other, and wherein at least one such region
comprises organic functionality.
14. The structure of claim 13, wherein the organic functionality
emanates from organic-based molecules covalently-integrated into
the at least one region comprising such functionality.
15. The structure of claim 14, wherein the organic functionality
comprises moieties selected from the group consisting of alkyl,
mercapto, carboxyl, vinyl, amine, benzyl, and combinations
thereof.
16. The structure of claim 15, wherein the organic functionality
further comprises organometallic functionality.
17. The structure of claim 13, wherein the at least two
morphologically-distinct mesoporous ceramic regions are deemed
morphologically-distinct if the average pore size of such regions
differs by at least about 10 percent.
18. A method comprising the steps of: a) providing a framework in
which a mesoporous ceramic can be generated; b) depositing, in a
first region of the framework, a first precursor mixture; c)
treating the first precursor mixture so as to form a region of
mesoporous ceramic substructure comprising a first chemical
activity; d) depositing, in a second region of the framework
adjacent to the region of mesoporous ceramic substructure
comprising a first chemical activity, a second precursor mixture;
and e) treating the second precursor mixture so as to form a region
of mesoporous ceramic substructure comprising a second chemical
activity, wherein the regions of mesoporous ceramic substructure of
first and second chemical activity provide for a mesoporous
membrane structure comprising regions of mesoporous ceramic,
wherein such regions are differentiable by at least one property
selected from the group consisting of chemical activity, pore
morphology, bulk chemical composition, and compositions thereof;
wherein both of the first and second precursor mixtures comprise a
quantity of a self-assembling surfactant species, a quantity of
ceramic precursor, and wherein at least one of the first and second
precursor mixtures comprises a species for imparting organic-based
chemical activity to the region in which it is present.
19. The method of claim 18, wherein the method provides for a
mesoporous membrane structure comprising regions of mesoporous
ceramic of different chemical activity.
20. The method of claim 19, further comprising a step of depositing
additional precursor mixtures into additional regions of the
framework, wherein such additional precursor mixtures are treated
so as to form additional regions of mesoporous ceramic substructure
comprising additional chemical activities, and wherein this
additional precursor mixture deposition and treatment provides for
a structure comprising at least three chemically-distinct
mesoporous ceramic regions.
21. The method of claim 19, wherein the method provides positional
control over the deposition of the first and second precursor
mixtures and over placement of the regions of mesoporous ceramic
substructure so formed.
22. The method of claim 19, further comprising a step of removing
at least part of the framework.
23. The method of claim 22, wherein the framework is completely
removed to yield mesoporous ceramic nanorods.
24. The method of claim 23, wherein the chemical activity varies
within individual nanorods.
25. The method of claim 23, wherein the chemical activity varies
between individual nanorods.
26. The method of claim 19, wherein at least one of the first and
second chemical activities is at least partially-derived from
organic-based molecules covalently-integrated with the region of
mesoporous ceramic substructure with which it is associated.
27. The method of claim 26, wherein the organic-based molecules
comprise functional moieties selected from the group consisting of
alkyl, mercapto, carboxyl, vinyl, amine, benzyl, and combinations
thereof.
28. The method of claim 27, further comprising a step of chemically
modifying the functional moieties so as to alter the chemical
activity of the mesoporous region in which they are present.
29. The method of claim 28, wherein step of chemically modifying
involves treating at least some of the functional moieties in the
mesoporous regions in which they are present with a species
selected from the group consisting of organic species,
organometallic species, metallic species, and combinations
thereof.
30. The method of claim 19, wherein the regions of mesoporous
ceramic substructure comprise a bulk composition selected from the
group consisting of SiO.sub.2, TiO.sub.2, Al.sub.2O.sub.3,
ZrO.sub.2, Y.sub.2O.sub.3:ZrO.sub.2, Y.sub.2O.sub.3, and
combinations thereof.
31. A method comprising the steps of: a) depositing, on a
substrate, a layer of a first mesoporous ceramic precursor mixture;
b) treating the first precursor mixture so as to form a mesoporous
ceramic substructure layer comprising a first chemical activity; c)
depositing, on the mesoporous ceramic substructure layer comprising
a first chemical activity, a second precursor mixture; and d)
treating the second precursor mixture so as to form a mesoporous
ceramic substructure layer comprising a second chemical activity,
wherein the mesoporous ceramic substructure layers of first and
second chemical activity collectively provide for a mesoporous
membrane structure comprising mesoporous ceramic regions
differentiable by at least one property selected from the group
consisting of chemical activity, pore morphology, bulk chemical
composition, and combinations thereof.
32. The method of claim 31, wherein the method provides for a
mesoporous membrane structure of mixed chemical activity.
33. The method of claim 32, further comprising a step of removing
the mesoporous ceramic structure of mixed chemical activity from
the substrate on which it was formed.
34. The method of claim 32, further comprising a step of forming at
least one additional mesoporous ceramic substructure layer within
the mesoporous ceramic structure of mixed chemical activity,
wherein adjacent layers possess different chemically activity.
35. The method of claim 34, wherein the mesoporous ceramic
structure of mixed chemical activity comprises at least three
chemically-distinct mesoporous ceramic substructure layers.
36. The method of claim 34, wherein the mesoporous ceramic
substructure layer comprising a first chemical activity at least
partially derives its chemical activity from organic molecules that
are covalently integrated with the mesoporous ceramic substructure
layer.
37. The method of claim 36, wherein the organic molecules comprise
functional moieties selected from the group consisting of alkyl,
mercapto, carboxyl, vinyl, amine, benzyl, and combinations
thereof.
38. The method of claim 36, further comprising a step of chemically
modifying the organic molecules so as to alter the chemical
activity of the mesoporous regions with which they are
associated.
39. The method of claim 38, wherein step of chemically modifying
involves treating at least some of the organic molecules in the
mesoporous regions with which they are associated with a species
selected from the group consisting of organic species,
organometallic species, metallic species, and combinations
thereof.
40. The method of claim 32, wherein the mesoporous ceramic
substructure layers comprise a bulk composition selected from the
group consisting of SiO.sub.2, TiO.sub.2, Al.sub.2O.sub.3,
ZrO.sub.2, Y.sub.2O.sub.3:ZrO.sub.2, Y.sub.2O.sub.3, and
combinations thereof.
41. The method of claim 34, wherein the first and second chemical
activities are differentiable and at least partially derived from
differences in bulk composition between the substructure layers.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to mesoporous
structures, and more specifically to complex mesoporous
architectures comprising ceramic/organic hybrid structures with
distinct mesoporous domains having different chemical
functionalities.
BACKGROUND INFORMATION
[0002] There is a well-established need for mesoporous oxide
structures with tunable chemical activity for use as filters,
reactors or sensors. One way to impart specific chemical
functionality to such structures is to embed organic
functionalities into the walls or onto the surfaces of the
mesoporous oxides. These groups are either chemically active or can
be further reacted to form chemically-active sites. Mesoporous
ceramic structures with organic functionalities embedded in the
walls and on the pore surfaces have been produced (Dag et al.,
"Oriented Periodic Mesoporous Organosilica (PMO) Film with Organic
Functionality Inside the Channel Walls," Adv. Funct. Mater. 11,
213-217 (2001); and Asefa et al., "Periodic mesoporous
organosilicas with organic groups inside the channel walls,"
Nature, 402, 867-871 (1999)). Commonly referred to as periodic
mesoporous organosilicas (PMOs), these materials are generally
formed as powders. Usually, aqueous based processing methods are
used in their fabrication, although there are some references to
alcohol-based processing methods which can produce such mesoporous
films.
[0003] The primary limitation with the current above-described PMO
methods is that the materials produced are structurally
homogeneous. There is a need for multiple organic functionalities
within a mesoporous structure and also for spatial separation of
the mesoporous regions with these sites-needs that the
above-described PMO methods do not currently meet.
[0004] Presently, organic groups can be incorporated into the walls
of mesoporous silica in two ways. The first approach is a
sequential process in which the mesoporous structure is formed,
followed by deposition of a layer containing the desired organic
groups. It is difficult to use this approach to produce regions
with distinct organic groups because methods for selective
deposition into targeted pore regions without simultaneous
deposition onto other regions is considerably difficult. One method
for accomplishing this was detailed in Doshi et al., "Optically
Defined Multifunctional Patterning of Photosensitive Thin-Film
Silica Mesophases," Science, 290, 107-111 (2000), which describes
the incorporation of a photoacid into a mesoporous structure and
where ultraviolet (UV) light was used to selectively activate the
structure in illuminated regions. However, this method cannot be
universally applied because not all groups are responsive to
photopatterning. The second approach is a single step process in
which a precursor for the functional groups is incorporated into
the precursor solution for the mesoporous oxide. Again, with this
second approach, spatial control of the functional groups is
lacking.
[0005] As a result of the foregoing, a more universal method of
imparting differential chemical activity to pre-defined mesoporous
regions within a structure so as to afford spatial control over the
placement of such regions would be highly desirable.
BRIEF DESCRIPTION OF THE INVENTION
[0006] In some embodiments, the present invention is directed to
methods of making mesoporous membrane structures with complex
functional architectures, where, in some such embodiments, such
structures generally comprise at least two mesoporous regions
comprising different chemical activity, and where such methods
afford spatial control over the placement of such regions of
differing chemical activity within the overall structure. In some
embodiments, the present invention is also directed to the
mesoporous structures formed by such methods, where such structures
are themselves novel.
[0007] In some embodiments, the present invention is directed to
methods of a first type comprising the steps of: (a) providing a
framework in which a mesoporous ceramic can be generated; (b)
depositing, in a first region of the framework, a first precursor
mixture; (c) treating the first precursor mixture so as to form a
region of mesoporous ceramic substructure comprising a first
chemical activity; (d) depositing, in a second region of the
framework adjacent to, or separated from, the region of mesoporous
ceramic substructure comprising a first chemical activity, a second
precursor mixture; and (e) treating the second precursor mixture so
as to form a region of mesoporous ceramic substructure comprising a
second chemical activity, wherein the regions of mesoporous ceramic
substructure of first and second chemical activity provide for a
mesoporous membrane structure comprising regions of mesoporous
ceramic of different chemical activity; wherein both of the first
and second precursor mixtures comprise a quantity of a
self-assembling surfactant species, a quantity of ceramic
precursor, and wherein at least one of the first and second
precursor mixtures comprises a species for imparting organic-based
chemical activity to the region in which it is present.
[0008] In some embodiments, the present invention is directed to
methods of a second type comprising the steps of: (a) depositing,
on a substrate, a layer of a first mesoporous ceramic precursor
mixture; (b) treating the first precursor mixture so as to form a
mesoporous ceramic substructure layer comprising a first chemical
activity; (c) depositing, on the mesoporous ceramic substructure
layer comprising a first chemical activity, a second precursor
mixture; and (d) treating the second precursor mixture so as to
form a mesoporous ceramic substructure layer comprising a second
chemical activity, wherein the mesoporous ceramic substructure
layers of first and second chemical activity provide for a
mesoporous membrane structure of mixed chemical activity.
[0009] In some embodiments, the present invention is directed to
mesoporous membrane structures comprising at least two
chemically-distinct mesoporous ceramic regions, wherein at least
one such region comprises organic functionality, wherein the
mesoporous regions are in fluid communication with each other, and
wherein the regions are further differentiated by at least one
property selected from the group consisting of pore morphology,
bulk chemical composition, and combinations thereof.
[0010] In some embodiments, the present invention is directed to
mesoporous membrane structures comprising at least two mesoporous
ceramic regions of substantially similar bulk chemical composition
and pore morphology, wherein the regions are in fluid communication
with each other, wherein at least one such region comprises organic
functionality, and wherein at least one such region is
substantially devoid of organic functionality.
[0011] In some embodiments, the present invention is directed to
mesoporous membrane structures comprising at least two
morphologically-distinct mesoporous ceramic regions, wherein the
regions are in fluid communication with each other, and wherein at
least one such region comprises organic functionality.
[0012] The foregoing has outlined rather broadly the features of
the present invention in order that the detailed description of the
invention that follows may be better understood. Additional
features and advantages of the invention will be described
hereinafter which form the subject of the claims of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a more complete understanding of the present invention,
and the advantages thereof, reference is now made to the following
descriptions taken in conjunction with the accompanying drawings,
in which:
[0014] FIG. 1 depicts, in flow diagram form, methods of a first
type for making mesoporous membrane structures with complex
architectures comprising regions of differential chemical activity,
in accordance with some embodiments of the present invention;
[0015] FIG. 2 depicts, in flow diagram form, methods of a second
type for making mesoporous membrane structures with complex
architectures comprising regions of differential chemical activity,
in accordance with some embodiments of the present invention;
[0016] FIGS. 3A-3C schematically illustrate a mesoporous membrane
structures with complex architecture comprising regions of
differential chemical activity and morphology, in accordance with
some embodiments of the present invention;
[0017] FIG. 4 illustrates an anodized aluminum oxide (AAO) template
which is useful as a framework in the fabrication of mesoporous
membrane structures with complex architectures comprising regions
of differential chemical activity, in accordance with some
embodiments of the present invention;
[0018] FIGS. 5A and SB show cross-sectional (B) and plan view (A)
SEM images of an AAO membrane that has been filled with
F127-templated mercaptosilane;
[0019] FIG. 6 shows a plan view TEM image of an AAO template
containing a P123-templated SiO.sub.2/F127-templated mercaptosilane
composite structure, where complete filling of the AAO is realized,
in accordance with some embodiments of the present invention;
[0020] FIGS. 7A and 7B are enlarged views of the structure shown in
FIG. 6;
[0021] FIGS. 8A and 8B show cross-sectional (B) and plan view (A)
SEM images of an AAO membrane that has been filled with
F127-templated vinylsilane;
[0022] FIG. 9 shows a plan view TEM image of an AAO template
containing a P123-templated SiO.sub.2/F127-templated vinylsilane
composite structure, where complete filling of the AAO is realized,
in accordance with some embodiments of the present invention;
[0023] FIG. 10 is magnified region of the structure shown in FIG.
9;
[0024] FIGS. 11A and 11B show cross-sectional (B) and plan view (A)
SEM images of an AAO membrane that has been filled with
F127-templated methylsilane;
[0025] FIG. 12 depicts TGA (trace a) and DTA (trace b) thermal
analysis data for templated silica;
[0026] FIG. 13 depicts TGA (trace a) and DTA (trace b) thermal
analysis data for templated silica and templated methylsilica
[0027] FIG. 14 depicts TGA (trace a) and DTA (trace b) thermal
analysis data for templated vinylsilica;
[0028] FIG. 15 depicts TGA (trace a) and DTA (trace b) thermal
analysis data for templated mercaptosilica; and
[0029] FIG. 16 shows partial IR spectra for methyl-functionalized
silica (trace a), mercapto-functionalized silica (trace b), and
templated vinylsilica (trace c), where in this region the vinyl
peaks in the templated vinylsilica sample (trace c) appear as a
shoulder peak at around 1600 cm.sup.-1.
DETAILED DESCRIPTION OF THE INVENTION
[0030] In some embodiments, the present invention is directed to
methods of making mesoporous membrane structures with complex
functional architectures, where, in some such embodiments, such
structures generally comprise at least two mesoporous regions
comprising different chemical activity, and where such methods
afford spatial control over the placement of such regions of
differing chemical activity within the overall structure. In some
embodiments, the present invention is also directed to the
mesoporous membrane structures formed by such methods, wherein such
structures are themselves novel.
[0031] In the following description, specific details are set forth
such as specific quantities, sizes, etc. so as to provide a
thorough understanding of embodiments of the present invention.
However, it will be obvious to those skilled in the art that the
present invention may be practiced without such specific details.
In many cases, details concerning such considerations and the like
have been omitted inasmuch as such details are not necessary to
obtain a complete understanding of the present invention and are
within the skills of persons of ordinary skill in the relevant
art.
[0032] Referring to the drawings in general, it will be understood
that the illustrations are for the purpose of describing a
particular embodiment of the invention and are not intended to
limit the invention thereto.
[0033] "Mesoporous," as defined herein, refers to porous materials
comprising ordered, accessible pores with free diameters of less
than 50 nm.
[0034] Referring to FIG. 1, in some embodiments, the present
invention is directed to methods of a first type comprising the
steps of: (Step 101) providing a framework in which a mesoporous
ceramic can be generated; (Step 102) depositing, in a first region
of the framework, a first precursor mixture; (Step 103) treating
the first precursor mixture so as to form a region of mesoporous
ceramic substructure comprising a first chemical activity; (Step
104) depositing, in a second region of the framework adjacent to,
or separated from, the region of mesoporous ceramic substructure
comprising a first chemical activity, a second precursor mixture;
and (Step 105) treating the second precursor mixture so as to form
a region of mesoporous ceramic substructure comprising a second
chemical activity, wherein the regions of mesoporous ceramic
substructure of first and second chemical activity provide for a
mesoporous membrane structure comprising regions of mesoporous
ceramic of different chemical activity; wherein both of the first
and second precursor mixtures comprise a quantity of a
self-assembling surfactant species, a quantity of ceramic
precursor, and wherein at least one of the first and second
precursor mixtures comprises a species for imparting organic-based
chemical activity to the region in which it is present.
[0035] Herein, when referring to a particular region, such a
region, in accordance with invention embodiments, need not be
continuous, but generally comprises common physical and chemical
characteristics, and, if physically separated into discrete
sub-regions, such sub-regions are maintained in fluid communication
with each other (vide infra).
[0036] In some of the above-described embodiments involving methods
of a first type, there exists a further step of depositing
additional precursor mixtures into additional regions of the
framework, wherein such additional precursor mixtures are treated
so as to form additional regions of mesoporous ceramic substructure
comprising additional chemical activities, and wherein this
additional precursor mixture deposition and treatment provides for
a structure comprising at least three chemically-distinct
mesoporous ceramic regions.
[0037] In some of the embodiments involving the first type of
methods, the methods provide positional (i.e., spatial) control
over the depositional placement of the first and/or second
precursor mixtures and over spatial positioning of the regions of
mesoporous ceramic substructure so formed. Such positional control
can provide for a variety of complex architectures.
[0038] In some of the above-described embodiments involving methods
of a first type, there exists a further step of removing at least
part of the framework. In some such embodiments, the framework is
completely removed to yield mesoporous ceramic nanorods. In some
such embodiments, the chemical activity varies within individual
nanorods. In some such embodiments, the chemical activity varies
between individual nanorods.
[0039] In some of the above-described embodiments involving methods
of a first type, the framework comprises a material such as, but
not limited to, polymeric materials, ceramic materials,
semiconductor materials, metals, glasses, and combinations thereof.
In some such embodiments, the framework is a templated material. An
exemplary such material is anodized aluminum oxide (AAO), also
referred to as "anodic alumina."
[0040] In some of the above-described embodiments involving methods
of a first type, the first and second precursor mixtures comprise a
liquid medium in which the self-assembling surfactant species and
the ceramic precursor are dispersed and/or dissolved. In some such
embodiments, the liquid medium(s) comprises an aqueous and/or
alcohol solvent. In some such embodiments, the liquid medium(s)
comprise additional additive such as, but not limited to, acids,
bases, salts, and combinations thereof. Exemplary self-assembling
surfactant species include, but are not limited to, PEO-PPO block
co-polymers such as F127, P123, and the like. Exemplary ceramic
precursor species include, but are not limited to, colloidal
silica, silanes (e.g., tetraethoxyorthosilicate,
tetramethyoxyorthosilicate), and the like.
[0041] In some of the above-described embodiments involving methods
of a first type, the domain size of the mesoporous regions is
tunable. Such tunability is also possible with regard to the size
of the pores in a particular mesoporous region. In some embodiments
involving the latter case, such tunability is afforded by judicious
selection of the self-assembling surfactant species.
[0042] In some of the above-described embodiments involving methods
of a first type, at least one of the first and second chemical
activities is at least partially-derived from organic-based
molecules covalently-integrated with the region of mesoporous
ceramic substructure with which it is associated. In some such
embodiments, the organic-based molecules comprise functional
moieties selected from the group consisting of alkyl, mercapto,
carboxyl, vinyl, amine, benzyl and combinations thereof.
[0043] In some of the above-described embodiments involving methods
of a first type, the regions of mesoporous ceramic substructure
comprise a bulk composition selected from the group consisting of
SiO.sub.2, TiO.sub.2, Al.sub.2O.sub.3, ZrO.sub.2,
Y.sub.2O.sub.3:ZrO.sub.2, Y.sub.2O.sub.3, and combinations
thereof.
[0044] Chemical activity can be native to the material of the
ceramic substructure layer, or it can be imparted through the
addition of organic additives. As mentioned above, to impart
organic-based chemical activity to at least one of the first and/or
second precursor mixtures, an organic additive is added to one or
both of the first and/or second precursor mixtures. Exemplary
organic additives include, but are not limited to,
mercaptopropyltriethoxysilane, triethoxyvinylsilane, and the
like.
[0045] In some embodiments involving methods of a first type, the
ceramic precursor species itself comprises organic functional
groups which impart organic-based chemical activity to the
resulting mesoporous membrane structure. Exemplary such species
include, but are not limited to, organosilanes, e.g.,
mercaptosilane.
[0046] In the above-described embodiments involving methods of a
first type, treating the first and second precursor mixtures so as
to form regions of mesoporous ceramic substructure typically
comprise a solvent removal procedure. Such solvent removal can be
enhanced by heat and/or vacuum. Such treatment generally further
comprises removal of the self-assembling surfactant species and
conversion of the ceramic precursor species to a ceramic species,
the latter possessing mesoporosity by virtue of the self-assembling
surfactant species previously present. To achieve these latter
outcomes, sufficient heat (so as to effect the decomposition of the
self-assembling surfactant species and convert the ceramic
precursor into a ceramic) and/or a suitable chemical species may be
added.
[0047] Referring to FIG. 2, in some embodiments, the present
invention is directed to methods of a second type comprising the
steps of: (Step 201) depositing, on a substrate, a layer of a first
mesoporous ceramic precursor mixture; (Step 202) treating the first
precursor mixture so as to form a mesoporous ceramic substructure
layer comprising a first chemical activity; (Step 203) depositing,
on the mesoporous ceramic substructure layer comprising a first
chemical activity, a second precursor mixture; and (Step 204)
treating the second precursor mixture so as to form a mesoporous
ceramic substructure layer comprising a second chemical activity,
wherein the mesoporous ceramic substructure layers (i.e., layered
regions) of first and second chemical activity provide for a
mesoporous membrane structure of mixed chemical activity.
[0048] In some of the above-described embodiments involving methods
of a second type, the step of depositing comprises a casting or
printing process. In some such embodiments, the depositing involves
spin casting.
[0049] In some of the above-described embodiments involving methods
of a second type, there exists a further step of removing the
mesoporous ceramic structure of mixed chemical activity from the
substrate on which it was formed.
[0050] In some of the above-described embodiments involving methods
of a second type, there exists a further step of forming at least
one additional mesoporous ceramic substructure layer within the
mesoporous ceramic membrane structure of mixed chemical activity,
wherein adjacent layers possess different chemically activity. In
some such embodiments, the mesoporous ceramic membrane structure of
mixed chemical activity comprises at least three
chemically-distinct mesoporous ceramic substructure layers.
[0051] In some of the above-described embodiments involving methods
of a second type, the mesoporous ceramic substructure layer
comprising a first chemical activity at least partially derives its
chemical activity from organic molecules that are covalently
integrated with the mesoporous ceramic substructure layer. In some
such embodiments, the organic molecules comprise functional
moieties selected from the group consisting of alkyl, mercapto,
carboxyl, vinyl, amine, benzyl, and combinations thereof. In some
such embodiments, the first and second chemical activities are
differentiable and at least partially derived from differences in
bulk composition between the substructure layers.
[0052] In some of the above-described embodiments involving methods
of a second type, the mesoporous ceramic substructure layers
comprise a bulk composition selected from the group consisting of
SiO.sub.2, TiO.sub.2, Al.sub.2O.sub.3, ZrO.sub.2,
Y.sub.2O.sub.3:ZrO.sub.2, Y.sub.2O.sub.3, and combinations
thereof.
[0053] For embodiments involving methods of a second type,
mesoporous ceramic precursor mixtures are generally as described
above for methods of a first type and generally comprise
self-assembling surfactant species and ceramic precursor species in
like manner. Also in like manner, organic-based chemical activity,
and species for imparting same, are generally as described above
for methods of a first type.
[0054] For embodiments involving methods of a second type, methods
of treating precursor mixtures are generally performed as described
above for methods of a first type.
[0055] Variations on method embodiments of a first or second type
include, but are not limited to, scenarios where the chemical
activity can be the same or different from mesoporous region to
mesoporous region, but wherein such regions are differentiable by
pore morphology and/or bulk chemical composition.
[0056] In any of the above-described method embodiments, wherein
the mesoporous membrane structures so produced comprise regions
that comprise organic functionality, the structure can be further
modified by treating the organic functionality with a second
organic, organometallic, or metallic substance. For example,
vinylsilica can be modified with an organic compound that forms a
covalent bond through reaction with the vinylic double bond.
Another example is the adsorption of cis-platin (CP,
cis-[Pt(NH.sub.3).sub.2Cl.sub.2]) onto the mercaptosilica. A third
example is the adsorption of gold nanoparticles onto
mercaptosilicas or the binding of platinum (Pt) or palladium (Pd)
nanoparticles onto amine-functionalized silica. Another example is
the incorporation of platinum-containing organometallic species
comprising a vinyl moiety, such as
platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane. Both Pt and
Pd can be incorporated as organometallic functionality through
alkyl-alkyl or vinyl-vinyl complexes.
[0057] In some embodiments, the present invention is directed to
mesoporous membrane structures of a first type comprising at least
two chemically-distinct mesoporous ceramic regions, wherein at
least one such region comprises organic functionality, wherein the
mesoporous regions are in fluid communication with each other, and
wherein the regions are further differentiated by at least one
property selected from the group consisting of pore morphology,
bulk chemical composition, and combinations thereof.
[0058] In some embodiments, the present invention is directed to
mesoporous membrane structures of a second type comprising at least
two mesoporous ceramic regions of substantially similar bulk
chemical composition and pore morphology, wherein the regions are
in fluid communication with each other, wherein at least one such
region comprises organic functionality, and wherein at least one
such region is substantially devoid of organic functionality.
[0059] In some embodiments, the present invention is directed to
mesoporous membrane structures of a third type comprising at least
two morphologically-distinct mesoporous ceramic regions, wherein
the regions are in fluid communication with each other, and wherein
at least one such region comprises organic functionality.
[0060] In some such above-described structural embodiments, the
organic functionality emanates from organic-based molecules
covalently-integrated into the at least one region comprising such
functionality. In some such embodiments, pore morphology is
differentiable between regions if the average pore size of such
regions differs by at least about 10 percent or if the pore
organization is different (e.g., as determined by small angle X-ray
scattering).
[0061] In some such above-described embodiments directed to
mesoporous membrane structures, the bulk chemical composition of
the mesoporous ceramic regions is selected from the group
consisting of SiO.sub.2, TiO.sub.2, Al.sub.2O.sub.3, ZrO.sub.2,
Y.sub.2O.sub.3:ZrO.sub.2, Y.sub.2O.sub.3, and combinations thereof.
In some such embodiments, the organic functionality comprises
moieties selected from the group consisting of alkyl, mercapto,
carboxyl, vinyl, amine, benzyl, and combinations thereof. In some
such embodiments, the mesoporous ceramic regions comprise pores
having an average pore size of between about 1 nm and about 40 nm.
In some such embodiments, the average pore size comprises a
standard deviation of between about .+-.0.1 nm and about .+-.10
nm.
[0062] "Fluid communication," as defined herein, refers to an
ability to transport fluids between two mesoporous regions. Fluid
transport through and between the mesoporous regions generally
occurs within the pores. The rate of transport within a region
depends on the identity of the fluid, the pore morphology, and,
optionally, the bulk chemical structure and organic functionality
of the mesoporous regions. For example, the relative Knudsen
diffusion rates of two gases within a mesoporous region will depend
on the square root of the molecular weight ratio. The rate of
transport between regions depends on the identity of the fluid, the
pore morphologies of the regions, the macroscopic size and shape of
the regions, and, optionally, on the bulk chemical structures and
organic functionalities. For example, the time scale associated
with the diffusion of a gas from one region into a second region
depends on the mechanism of diffusion and the size of the regions.
Transport from the center of a region with a macroscopic size of 10
.mu.m to a second region with a macroscopic size of 10 .mu.m would
take longer than transport from region with a macroscopic size of
100 nm to a second region with a macroscopic size of 100 nm.
[0063] FIG. 3(A) schematically illustrates an exemplary mesoporous
membrane structure 300 comprising mesoporous areas 301 in a
structural framework 302, in accordance with some embodiments of
the present invention. Referring to FIG. 3(C), mesoporous areas 301
can be seen to comprise a first mesoporous region 301a comprising a
first chemical activity and second mesoporous region 301b
comprising a second chemical activity. In FIG. 3, mesoporous
regions 301a and 301b are interspersed with each other, region 301a
comprising a pore morphology of cubic organization provided by the
Type 2 structural elements depicted in FIG. 3(C). In contrast,
region 301b comprises a pore morphology of hexagonal organization
provided by the Type 1 structural elements depicted in FIG.
3(C).
[0064] Methods of the present invention permit the formation of
mesoporous membrane structures with spatially-controlled placement
of distinct chemical groups within the mesoporous structure. It is
important to note that the chemical activity of the mesoporous
regions, particularly the spatial positioning of such chemical
activity and wherein such chemical activity is organic-based, is
not dependent upon photoactivation to impart variations thereof.
Such methods and structures enable applications related to fluid
filtration and chemical reactivity/cataylsis such as metal removal
from water streams, pre-concentration of chemical species in gas
streams, multi-step catalytic membranes, and biosensors (glucose
oxidase) with separate pores to transport the reagents (glucose and
oxygen). The applications described above serve as mere examples,
since the method of making such structures is flexible enough to
impart the desired level of differential functionality (chemical,
catalytic, optical, electrical, etc.) into a structure.
[0065] The following examples are included to demonstrate
particular embodiments of the present invention. It should be
appreciated by those of skill in the art that the methods disclosed
in the examples that follow merely represent exemplary embodiments
of the present invention. However, those of skill in the art
should, in light of the present disclosure, appreciate that many
changes can be made in the specific embodiments described and still
obtain a like or similar result without departing from the spirit
and scope of the present invention.
EXAMPLE 1
[0066] This Example serves to illustrate the synthesis of a
F127-templated mercaptosilane in an AAO template (Sample 1), as
shown in FIG. 4 where AAO template 400 comprises hollow channels
401 in a Al.sub.2O.sub.3 matrix 402.
[0067] Sample 1 was prepared using the following procedure: 3 g of
F127polymer was completely dissolved in 18 g ethanol and 6 g 0.4 M
HCl. To this solution was added 7.7 g of tetraethoxysilane (TEOS),
followed by 3.6 g of mercaptopropyltriethoxysilane after an hour of
stirring. The solution was poured into a Petri dish containing AAO
membranes (Whatman, 25 mm diameter, 50 .mu.m thick, 200 nm pores)
supported on polydimethylsiloxane (PDMS) blocks. Initially, the
solution completely covered the membranes. The solution was allowed
to evaporate at room temperature until the membranes were exposed
by the receding fluid line. After 24 hours, the membranes were
sealed in a jar with 100 g of ethanol and 1 g of KCl. The jar was
heated to 80.degree. C. for 2 days to remove the F127 template.
[0068] FIGS. 5A and 5B show cross-sectional (B) and plan view (A)
scanning electron microscopy (SEM) images of the resulting AAO
membrane filled with F127-templated mercaptosilane (Sample 1).
EXAMPLE 2
[0069] This Example serves to illustrate P123-templated silica and
F127-templated mercaptosilane in an AAO template (Sample 2),
thereby providing two mesoporous regions of different chemical
activity.
[0070] Sample 2 was prepared using the following procedure: 3 g of
P123polymer was completely dissolved in 18 g ethanol and 6 g 0.4 M
HCl. To this solution, 7.7 g of TEOS was added. The solution (first
precursor mixture) was poured into a Petri dish containing AAO
membranes (framework) (Whatman, 25 mm diameter, 50 .mu.m thick, 200
nm pores) supported on PDMS blocks. Initially, the solution
completely covered the membranes. The solution was allowed to
evaporate at room temperature until the membranes were exposed by
the receding fluid line. The membrane was then heated to
600.degree. C. for 4 hours at a ramp rate of 1.degree. C./min to
treat the first precursor mixture.
[0071] The membrane was subjected to a second deposition step in
which 3 g of F127polymer was completely dissolved in 18 g ethanol
and 6 g 0.4 M HCl. To this solution 7.7 g of TEOS was added,
followed by 3.6 g of mercaptopropyltriethoxysilane after an hour of
stirring. The solution (second precursor mixture) was poured into a
Petri dish containing AAO membranes (Whatman, 25 mm diameter, 50
.mu.m thick, 200 nm pores) supported on PDMS blocks. Initially, the
solution completely covered the membranes. The solution was allowed
to evaporate at room temperature until the membranes were exposed
by the receding fluid line. After 24 hours, the membranes were
sealed in a jar with 100 g of ethanol and 1 g of KCl. The jar was
heated to 80.degree. C. for 2 days to remove the F127template and
form the mesoporous membrane structures.
[0072] FIG. 6 shows a plan view transmission electron microscopy
(TEM) image of the resulting AAO template containing a
P123-templated SiO.sub.2F127-templated mercaptosilane composite
structure (Sample 2), where complete filling of the AAO is
realized. FIGS. 7A and 7B are enlarged views of the structure shown
in FIG. 6.
EXAMPLE 3
[0073] This Example serves to illustrate F127-templated vinylsilane
in AAO (Sample 3).
[0074] Sample 3 was prepared using the following procedure: 3 g of
F127polymer was completely dissolved in 18 g ethanol and 6 g 0.4 M
HCl. To this solution 7.7 g of TEOS was added, followed by 3.6 g of
triethoxyvinylsilane after an hour of stirring. The solution was
poured into a Petri dish containing AAO membranes (Whatman, 25 mm
diameter, 50 .mu.m thick, 200 nm pores) supported on PDMS blocks.
Initially, the solution completely covered the membranes. The
solution was allowed to evaporate at room temperature until the
membranes were exposed by the receding fluid line. After 24 hours,
the membranes were sealed in a jar with 100 g of ethanol and 1 g of
KCl. The jar was heated to 80.degree. C. for 2 days to remove the
F127 template.
[0075] FIGS. 8A and 8B show cross-sectional (B) and plan view (A)
SEM images of the resulting AAO membrane that has been filled with
F127-templated vinylsilane (Sample 3).
EXAMPLE 4
[0076] This Example serves to illustrate P123-templated silica and
F127-templated vinylsilane in AAO (Sample 4).
[0077] Sample 4 was prepared using the following procedure: 3 g of
P123 polymer was completely dissolved in 18 g ethanol and 6 g 0.4 M
HCl. To this solution, 7.7 g of TEOS was added. The solution (first
precursor mixture) was poured into a Petri dish containing AAO
membranes (Whatman, 25 mm diameter, 50 .mu.m thick, 200 nm pores)
supported on PDMS blocks. Initially, the solution completely
covered the membranes. The solution was allowed to evaporate at
room temperature until the membranes were exposed by the receding
fluid line. The membrane was then heated to 600.degree. C. for 4
hours at a ramp rate of 1.degree. C./min.
[0078] The membrane was subjected to a second deposition step in
which 3 g of F127 polymer was completely dissolved in 18 g ethanol
and 6 g pH 0.4 HCl. To this solution 7.7 g of TEOS was added,
followed by 3.6 g of triethoxyvinylsilane after an hour of
stirring. The solution (second precursor mixture) was poured into a
Petri dish containing AAO membranes (Whatman, 25 mm diameter, 50
.mu.m thick, 200 nm pores) supported on PDMS blocks. Initially, the
solution completely covered the membranes. The solution was allowed
to evaporate at room temperature until the membranes were exposed
by the receding fluid line. After 24 hours, the membranes were
sealed in a jar with 100 g of ethanol and 1 g of KCl. The jar was
heated to 80.degree. C. for 2 days to remove the F127 template.
[0079] FIG. 9 shows a plan view TEM image of the resulting AAO
template containing a P123-templated SiO.sub.2/F127-templated
vinylsilane composite structure (Sample 4), where complete filling
of the AAO is realized. FIG. 10 is magnified region of the
structure shown in FIG. 9.
EXAMPLE 5
[0080] This Example serves to illustrate F127-templated
methylsilane in AAO (Sample 5).
[0081] Sample 5 was prepared by using the following procedure: 3 g
of F127 polymer was completely dissolved in 18 g ethanol and 6 g
0.4 M HCl. To this solution 7.7 g of TEOS was added, followed by
3.6 g of methyltrichlorosilane after an hour of stirring. The
solution was poured into a Petri dish containing AAO membranes
(Whatman, 25 mm diameter, 50 .mu.m thick, 200 nm pores) supported
on PDMS blocks. Initially, the solution completely covered the
membranes. The solution was allowed to evaporate at room
temperature until the membranes were exposed by the receding fluid
line. After 24 hours, the membranes were sealed in a jar with 100 g
of ethanol and 1 g of KCl. The jar was heated to 80.degree. C. for
2 days to remove the F127 template.
[0082] FIGS. 11A and 11B show cross-sectional (B) and plan view (A)
SEM images of the resulting AAO membrane that has been filled with
F127-templated methylsilane (Sample 5).
EXAMPLE 6
[0083] This Example serves to illustrate thermal gravimetric
analysis (TGA) and differential thermal analysis (DTA) for some of
the Samples generated in the previously-described Examples (and
similar samples).
[0084] FIG. 12 depicts TGA (trace a) and DTA (trace b) thermal
analysis data for templated silica. FIG. 13 depicts TGA (trace a)
and DTA (trace b) thermal analysis data for templated silica and
templated methylsilica. FIG. 14 depicts TGA (trace a) and DTA
(trace b) thermal analysis data for templated vinylsilica (EXAMPLES
3 and 4). FIG. 15 depicts TGA (trace a) and DTA (trace b) thermal
analysis data for templated mercaptosilica (EXAMPLES 1 and 2).
EXAMPLE 7
[0085] This Example serves to illustrate infrared spectral data for
form of the samples generated in the previously described
Examples.
[0086] FIG. 16 shows partial infrared (IR) spectra for methylsilica
(trace a), mercapto (trace b), and templated vinylsilica (trace c),
where in this region the vinyl peaks in the templated vinylsilica
sample (trace c) appear as a shoulder peak at around 1600
cm.sup.-1.
[0087] It will be understood that certain of the above-described
structures, functions, and operations of the above-described
embodiments are not necessary to practice the present invention and
are included in the description simply for completeness of an
exemplary embodiment or embodiments. In addition, it will be
understood that specific structures, functions, and operations set
forth in the above-described referenced patents and publications
can be practiced in conjunction with the present invention, but
they are not essential to its practice. It is therefore to be
understood that the invention may be practiced otherwise than as
specifically described without actually departing from the spirit
and scope of the present invention as defined by the appended
claims.
* * * * *