J. Phys. Chem. C 2010, 114, 2075–2081
2075
Mesoporous In2O3 with Regular Morphology by Nanocasting: A Simple Relation between Defined Particle Shape and Growth Mechanism Stefanie Haffer,†,‡ Thomas Waitz,† and Michael Tiemann*,‡ Institute of Inorganic and Analytical Chemistry, Justus Liebig UniVersity, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany, and Department of Chemistry, UniVersity of Paderborn, Warburger Strasse 100, D-33098 Paderborn, Germany ReceiVed: October 29, 2009; ReVised Manuscript ReceiVed: December 20, 2009
In2O3 with ordered, uniform mesoporosity is prepared by nanocasting, using various porous silica phases (KIT-6, SBA-15) as structure matrices. The In2O3 particles exhibit well-defined morphologies (spherical or ellipsoidal, depending on the choice of silica matrix) and quite uniform sizes in the range of a few hundred nanometers. The regular morphology of the In2O3 particles is not associated with the morphological properties of the silica matrices. Instead, it is the result of the growth mechanism of In2O3 inside the silica pores; this mechanism is investigated in some detail. Hence, the nanocasting method offers a versatile and simple way of creating mesoporous In2O3 with regular morphology; this will be beneficial for many applications that require well-defined morphological properties, such as gas sensing or catalysis. Introduction Over the past few years, the nanocasting concept has become a frequently used method for the synthesis of periodically ordered, mesoporous materials.1-3 In particular, a large number of metal oxides with well-ordered pore systems, large specific surface areas, high thermal stability, and distinguished crystallinity have been prepared that have high potential in heterogeneous catalysis,4,5 electrochemical applications,6 or gas-sensing.7 The latter field of application benefits from well-defined mesoporosity and nanostructural properties of a large variety of semiconducting, mesoporous metal oxides, including In2O3,8-12 SnO2,13-16 ZnO,17-19 or WO3.20,21 In principle, the nanocasting concept is quite simple and very straightforward. Mesoporous silica (e.g., SBA-15,22 KIT-623) or carbon (e.g., CMK-324) is chosen as a structure matrix.1 Its pores are infiltrated with a suitable precursor species, such as a metal salt dissolved in water or in another solvent. Alternatively, the salt can sometimes be used in the molten state without a solvent.25 Infiltration of suitable precursors via the gas phase is also possible.26,27 After the pore system in the structure matrix is homogeneously filled, the solvent (if present) is removed by evaporation, and the metal salt is converted into the respective metal oxide by heating under air atmosphere. Since this process goes along with substantial decrease in volume (from the metal salt solution to the solid-state metal oxide), a large fraction of the pore volume in the structure matrix will not be filled with the metal oxide which is why one or more additional cycles of precursor infiltration and subsequent oxide formation will usually be necessary. Finally, the structure matrix is removed (SiO2 by etching with HF or NaOH solution, carbon by thermal combustion). This procedure yields the mesoporous metal oxide as a negative replica of the original matrix. In addition to the uniform porosity, many applications, such as the above-mentioned field of gas sensing, make it desirable to create mesoporous metal oxides with well-defined particle * Corresponding author. E-mail:
[email protected]. † Justus Liebig University. ‡ University of Paderborn.
morphology. For example, we have recently shown that the sensitivity of mesoporous In2O3 to methane gas depends on its nanostructural properties; such correlation can only be established as long as any impact of different particle morphologies can be ruled out.7,11 Often the morphology of the replica corresponds quite exactly to that of the matrix. This may be desired when the respective matrix itself exhibits a well-defined morphology, such as spherical particles,13,14,16 thin films,15 rodlike particles,16 or monolithic bodies.28,29 In many cases, on the other hand, the morphology of the matrix is ill-defined. For example, many standard synthesis procedures for mesoporous silica deliver irregular particles with nonuniform size and fractallike outer surfaces. In such cases, it would usually be expected that the respective replicas will exhibit just as ill-defined morphologies, but here we present that this is not necessarily the case: Mesoporous silica materials with (SBA-15) or without (KIT-6) defined morphological properties can be used for the synthesis of mesoporous In2O3 replicas with well-defined spherical morphology and quite uniform particle sizes. Furthermore, the average particle size can be varied within certain limits (by varying the number of cycles of precursor infiltration and subsequent oxide formation). We demonstrate how this evolution of well-defined morphology during the nanocasting process can be explained by the growth mechanism of the replica particles inside the silica matrices. Mesoporous In2O3 prepared in this way was recently shown to exhibit very promising gas-sensing properties.11,12 Experimental Section Synthesis of Mesoporous Silica (SBA-15 and KIT-6). The mesoporous silica materials, utilized as the structure matrices for the synthesis of mesoporous In2O3, were synthesized according to a modification of a literature procedure:22,23 12.0 g of P-123 block copolymer (Sigma) were dissolved in a mixture of 360 g deionized water and 43.0 g hydrochloric acid (32%) at 35 °C. In the case of KIT-6, 12.0 g n-butanol was added, and the solution was stirred for 1 h. After addition of 24.0 g of tetraethylorthosilicate (TEOS; Merck), the mixture was stirred at 35 °C for another 24 h. The resulting gel was transferred to
10.1021/jp910336f 2010 American Chemical Society Published on Web 01/15/2010
2076
J. Phys. Chem. C, Vol. 114, No. 5, 2010
Haffer et al.
a Teflon-lined autoclave and kept for 24 h at 80 °C (“SBA-1580” and “KIT-6”) or at 140 °C (“SBA-15-140”). The obtained solid product was filtered off and washed with deionized water. Finally, the removal of P-123 block copolymer was accomplished by calcination at 550 °C for 6 h under air atmosphere (heating rate 2 °C min-1). Synthesis of Mesoporous In2O3. In a typical synthesis, the silica matrix (KIT-6 or SBA-15, respectively) was impregnated with a nearly saturated solution (2.7 mol L-1) of indium nitrate, In(NO3)3 · 5H2O (99%; Sigma) in water by the incipient wetness technique; this means that the amount of indium nitrate solution was chosen in such a way as to exactly match the (analytically determined) total pore volume of the silica matrix. After filtration the sample was dried at ambient temperature, heated under air atmosphere to 300 °C at a constant rate of 2 °C min-1, and kept at that temperature for 2 h to convert indium nitrate to indium oxide. This procedure was repeated three times. Finally the silica matrix was removed by leaching with a NaOH solution (2 mol L-1) for 4 h; this procedure was repeated twice to ensure a complete silica removal. For the investigation of the In2O3 growth by scanning electron microscopy (SEM), aliquots of the samples were taken after each cycle of impregnation/oxide formation, and the silica matrix was removed in the same way as described above. Characterization. Powder X-ray diffraction (XRD) was carried out on a PANalytical X’Pert PRO with an X’Celerator real-time multiple-strip detector using Cu KR radiation (40 kV, 40 mA). The counting time was 25 s for low-angle measurements (2θ < 10°) and 20 s for wide-angle measurements (2θ > 10°) with steps of 2θ ) 0.0167. Nitrogen physisorption was conducted at 77 K on a Quantachrome Autosorb 6; samples were degassed at 60 °C for 24 h prior to measurement. Pore size evaluation was carried out by non-local density functional theory (NLDFT)-based analysis using the cylindrical pore/ equilibrium model data kernel. Scanning electron micrographs were recorded with a HREM EDX Leo Gemini 982; the powdery samples were dispersed in deionized water, placed on carbon foil, adhered to the sample holder, and dried.
Figure 1. Low-angle and wide-angle (inset) powder XRD patterns of silica-free mesoporous In2O3 materials replicated from KIT-6 silica, obtained after consecutive cycles of impregnation and oxide formation.
Results and Discussion
Figure 2. N2 physisorption isotherms and pore size distributions (calculated by using NLDFT data, inset) of the same samples as in Figure 1. (Isotherms are vertically shifted for clarity.)
The aim of this work was the investigation of growth and morphology of In2O3 in a mesoporous silica matrix. For this purpose, three distinct silica matrices were used, which were different from each other with respect to the symmetry of their pore systems and their pore interconnectivity. KIT-6 silica exhibits a cubic arrangement (Ia3jd) of highly branched mesopores with an a priori high degree of pore interconnectivity.23 SBA-15-80 consists of linear mesopores arranged in a twodimensional hexagonal symmetry (p6mm).22 Owing to the low synthesis temperature of 80 °C, the pore walls are comparably thick with only few randomly distributed micropores linking adjacent mesopores; thus, the degree of pore interconnectivity is very low. Contrary to that, SBA-15-140 exhibits the same hexagonal pore arrangement, but substantially thinner pore walls as a consequence of the higher synthesis temperature of 140 °C. This leads to the presence of abundant, small mesopores connecting adjacent linear mesopores;30,31 hence, the degree of pore interconnectivity is higher than that for SBA-15-80, but not as high as for KIT-6.32,33 These differences in pore interconnectivity turn out to have substantial impact on the structure replication. Starting with the KIT-6 silica matrix, we have investigated the silica-free In2O3 replicas obtained after one, two, or three consecutive cycles of impregnation with In(NO3)3 and subse-
quent formation of In2O3. Figure 1 shows the powder XRD diagrams for all three samples; the N2 physisorption isotherms with the respective pore size distributions are shown in Figure 2. The corresponding data of the In2O3-silica composites (i.e., before removal of the silica matrix) are shown in the Supporting Information (Figure S1). A periodically ordered mesoporous In2O3 material is obtained already after one single impregnation/ oxide formation cycle, as confirmed by a weak low-angle XRD reflection (which can be indexed as 211, assuming the cubic (Ia3jd) symmetry) and a physisorption isotherm of type IV.34 (A steep increase of the isotherms close to p/p0 ) 1 suggests an additional pore modus, probably attributable to interparticle voids.) The absence of further XRD reflections indicates that the long-range order of this sample is still rather low. However, after the second and third cycle, additional low-angle reflections can be distinguished one of which can be indexed as 220; the overall intensity of all low-angle reflections increases, and the peaks become narrower after each cycle, indicating larger coherent nanostructural scattering domains after each additional cycle. The same trend is observed for the wide-angle region, which shows the typical diffraction pattern attributable to the atomic-scale crystallinity of the samples (cubic bixbyite); again,
Mesoporous In2O3 with Regular Morphology by Nanocasting
J. Phys. Chem. C, Vol. 114, No. 5, 2010 2077
TABLE 1: Structural Parameters from Powder XRD and N2 Physisorption for KIT-6, As Well As for Mesoporous Silica-Free In2O3 Replicas Obtained after Consecutive Cycles of Impregnation and Oxide Formation
(KIT-6 silica) In2O3 after 1 cycle In2O3 after 2 cycles In2O3 after 3 cycles
d211/nm
average pore width Dh/nm
average pore wall thickness / nm
specific BET surface area / m2g-1
specific pore volume / cm3g-1
(8.1) 7.8 8.1 8.1
(7.0) 5.6 5.6 5.4
(2.9) 4.0 4.3 4.4
(690) 85 80 80
(0.80) 0.25 0.22 0.23
The structural parameters of the corresponding composites before removal of silica are listed in the Supporting Information section; see Table S1.
Figure 3. Schematic drawing of potential growth directions of mesoporous In2O3 inside the pores of the silica structure matrix: along the pore axis (a), perpendicular to the pore axis starting at the pore center (b), and at the pore walls (c).
a certain degree of peak narrowing occurs with each additional cycle, which indicates that the single-crystalline domains might grow slightly; this will be commented on below. (According to the Scherrer method the domains grow from ca. 30 nm to ca. 40 nm; however, for porous materials, the reliability of this method must be regarded as limited. In addition, peak narrowing could also be explained by the occurrence of large, nonporous In2O3 crystals outside the silica pores; the latter, however, has not been observed by transmission electron microscopy (TEM) or SEM.) The type IV characteristics in the corresponding sorption isotherms become more pronounced after each cycle, and a certain degree of H1-type hysteresis occurs.34 The structural data for all three samples obtained from XRD and physisorption are listed in Table 1. Most importantly, the average pore size (ca. 5.6 nm) as well as the pore wall thickness (4.0-4.4 nm; calculated from the d211 value and the pore size as reported in ref 11) of all In2O3 samples remain roughly the same after each cycle of impregnation/oxide formation. This allows for some conclusion regarding the direction of In2O3 growth within the pores of the silica matrix. As depicted in Figure 3, three directions of growth are generally conceivable, namely parallel to the pore axis (a) or perpendicular to the axis (starting from the center, b, or from the pore walls, c). The near-constant values of the average pore size and pore wall thickness of all In2O3 samples indicate that the evolution of In2O3 occurs predominantly along the pore axis (a) and only weakly perpendicular to the pore axis. In the case of the other two possible growth directions (b and c), a pronounced shift of the pore diameters and wall thicknesses would have to occur. This is further confirmed by the fact that, in the respective In2O3-silica composites (i.e., before removal of the silica matrix), the average pore size remains also nearly constant (see Figure S1, Supporting Information). In this context, it needs to be discussed that a remarkable discrepancy exists between the pore size of the KIT-6 silica template (7 nm) and the pore wall thicknesses of the respective In2O3 replicas (between 4.0 and 4.4 nm). Such a discrepancy may be unexpected at first sight since a true structure replication based on complete filling of the silica pores with the precursor (In(NO3)3) should result in a perfect match between the template’s pore width and the replica’s wall thickness and vice versa. However, this situation is usually not observed35 and, on
closer inspection, cannot be expected in the first place: If the pore is completely filled with In(NO3)3 (which is assumed here, see below), then the resulting In2O3 cannot fill out the pore entirely because its molar density with respect to In is much higher than that of In(NO3)3. (The respective mass densities are 7.2 g cm-1 for In2O3 and 2.4 g cm-1 for In(NO3)3 · 5H2O.) In other words, the release of H2O and NOx during the conversion of In(NO3)3 · 5H2O into In2O3 will necessarily result in significant volume shrinkage. Representative SEM images of the respective (abovementioned) three silica-free samples as well as of the original KIT-6 silica matrix before impregnation are shown in Figure 4. For the In2O3 particles, the resolution of the images is sufficient to show the nanometer-scaled periodicity of the mesopore systems at the particles’ outer surfaces (insets). The In2O3 samples exhibit nearly spherical particles and fairly uniform particle sizes (around 200-300 nm, see below), especially after the second and third cycles of impregnation/ oxide formation. This observation is particularly remarkable in light of the fact that the KIT-6 silica particles are irregular in shape and larger than the In2O3 particles by approximately 1 order of magnitude (3.3 ( 2.5 µm in length and 2.2 ( 1.7 µm in width; mean values ( standard deviations). The average size of the (near-spherical) In2O3 replica particles, on the other hand, increases after each cycle of impregnation/oxide formation from 217 ( 60 nm (one cycle), over 317 ( 130 nm (two cycles), to 363 ( 111 nm (three cycles). These values were obtained by measuring the diameter of about 200 particles for each sample. The corresponding particle size distributions are plotted as bar diagrams in Figure 5; the curves represent log-normal distributions, fitted by a least-squares procedure. Apart from the shift of the distribution peaks toward larger particle sizes, it should be noted that the onsets of the distribution curves also shift while the relative fraction of very large particles (with diameters of 350 to 800 nm) increases. These observations clearly indicate that each new cycle of impregnation/oxide formation causes the growth of already existing In2O3 particles, rather than leading to the formation of new particles. These findings, together with the above-made observation that the KIT-6 silica particles are substantially larger than the In2O3 replica particles, show that, in substantial fractions of the silica particles, the pores do not get filled with In2O3 at all, while the pores in other regions seem to get filled completely, as depicted in Figure 6. The spherical shape of the In2O3 particles can only be explained by the formation of “islands” of material within the silica pores, which are assumed to be initially filled with In(NO3)3 solution entirely (since the volume of the solution was chosen in such a way as to correspond exactly to the total pore volume of the matrix; see Experimental Section). The formation of islands would then be caused by surface minimization as the driving force, requiring substantial mass transport, which can only take place in the liquid state. This liquid-phase-based mass transport may occur either before complete removal of the solvent (water) of the
2078
J. Phys. Chem. C, Vol. 114, No. 5, 2010
Haffer et al.
Figure 4. Representative SEM images of mesoporous KIT-6 silica (a), as well as of silica-free mesoporous In2O3 materials replicated from KIT-6 silica, obtained after one (b), two (c), and three (d) cycles of impregnation and oxide formation. Insets show close-up views (4-fold) of selected particles of the same respective samples.
Figure 5. Particle size distribution of mesoporous In2O3 materials replicated from KIT-6 silica, obtained after consecutive cycles of impregnation and oxide formation. The data are based on measuring the diameter of about 200 particles for each sample (bars); the curves represent log-normal distributions, fitted by a least-squares procedure.
In(NO3)3 solution, or afterward, taking into account that the melting point of In(NO3)3 is lower (ca. 100 °C) than the temperature required for the conversion into In2O3. In other
words, this model assumes that either the nitrate solution or nitrate in the molten phase forms droplets inside the pores of the silica; these droplets are larger than the repeat distance of the silica pore system by 1-2 orders of magnitude. The formation of such spherical droplets is facilitated by the high pore interconnectivity present in the KIT-6 silica sample. With each additional “impregnation and conversion into the oxide” cycle, the liquid-phase mass transport leads to attachment of precursor species to the surface of already existing In2O3 particles rather than to nucleation of new droplets; this is consistent with the surface minimization as a driving force. (Interestingly, as briefly mentioned above, the single-crystalline domains on the atomic length scale seem to grow with each cycle, which might indicate that the In2O3 particles grow with a certain degree of epitaxial attachment.) As an alternative explanation, accumulation of In(NO3)3 at distinct spots within the porous silica matrix may occur already in the solution phase prior to solvent evaporation (nonhomogeneous loading of the silica pores). This mechanism would require the occurrence of preferred adsorption sites for the indium cations. The above-described formation of spherical In2O3 particles, caused by droplet formation of a liquid (In(NO3)3 solution and/ or in the molten state) is to a large extent dependent on the high degree of three-dimensional pore interconnectivity in KIT-6 silica. A mesoporous silica matrix with lower pore interconnectivity may therefore be expected to lead to a less well-defined spherical In2O3 particle shape. For this reason we conducted the same studies with SBA-15-80 and SBA-15-140 silica materials serving as the structure matrices. As mentioned above,
Mesoporous In2O3 with Regular Morphology by Nanocasting
J. Phys. Chem. C, Vol. 114, No. 5, 2010 2079
Figure 6. Schematic drawing of the growth of In2O3 particles inside the pores of mesoporous KIT-6 silica. After the first cycle of impregnation with In(NO3)3 and subsequent conversion into In2O3, spherical “islands” are formed inside the silica pore network; additional cycles lead predominantly to the growth of existing In2O3 particles rather than to nucleation of new ones.
Figure 7. Representative SEM images of mesoporous SBA-15-80 silica (a) and SBA-15-140 silica (b), as well as of silica-free mesoporous In2O3 materials replicated from the two silica materials (c,d) after three cycles of impregnation and oxide formation. Insets show close-up views (4-fold) of selected particles of the same respective samples.
TABLE 2: Structural Parameters from Powder XRD and N2 Physisorption for SBA-15-80 and SBA-15-140, As Well As for the Respective Mesoporous Silica-Free In2O3 Replicas Obtained after Three Cycles of Impregnation and Oxide Formation
(SBA-15-80) In2O3 replica (SBA-15-140) In2O3 replica
d100/nm
average pore width Dh/nm
average pore wall thickness / nm
specific BET surface area / m2g-1
specific pore volume / cm3g-1
(8.5) 8.9 (9.4) 9.6
(7.0) 5.6 (10.1) 5.6
(2.8) 4.7 (0.8) 5.4
(840) 60 (438) 73
(0.94) 0.16 (1.10) 0.26
these two materials (especially SBA-15-80) possess lower pore interconnectivity than KIT-6. The structural properties of both SBA-15 materials and their respective replicas are listed in Table 2; the XRD and N2 physisorption isotherms of one system chosen as an example are shown in Figures S2 and S3 in the Supporting Information. Figure 7 shows the SEM images of
SBA-15-80 (a) and SBA-15-140 (b) as well as the respective silica-free In2O3 replicas obtained after three cycles of impregnation/oxide formation (c,d). Both In2O3 replicas show a clearly different shape than the spherical ones originating from the KIT-6 silica matrix. The particles here show an elongated, ellipsoidal shape with an aspect ratio of ca. 1:2 (284 ( 70 nm
2080
J. Phys. Chem. C, Vol. 114, No. 5, 2010
Haffer et al.
Figure 8. Schematic drawing of the growth of In2O3 particles inside the pores of mesoporous SBA-15 silica. Similar to KIT-6 silica (see Figure 6), the formation of “islands” is observed. The near-linear pore shape and low pore interconnectivity lead to ellipsoidal In2O3 particles. The peculiar shape of the SBA-15 silica particles does not affect the morphology of the final In2O3 products.
in length and 141 ( 32 nm in width) for the sample replicated from SBA-15-80 and 1:1.25 (218 ( 90 nm in length and 170 ( 64 nm in width) for the sample replicated from SBA-15140. This is consistent with the substantially lower degree of interconnections between adjacent, parallel mesopores in the SBA-15 silica materials. Instead of spherical droplets (as in the case of the three-dimensionally interconnected pores in KIT-6 silica), only droplets with a preferred orientation along the pore axes are possible, which results in ellipsoidal In2O3 particles. The effect is less pronounced for SBA-15-140 since here the degree of pore interconnectivity is not as low as that for SBA15-80. These results confirm the growth model introduced above for the KIT-6 silica matrix. Interestingly, both SBA-15 silica materials show a fairly welldefined, yet peculiar particle morphology of their own. The particles appear rod-like with an aspect ratio of ca. 1:4, but with a strong curvature of ca. 180°. This curvature also applies to the mesopore axes, as can be distinguished in Figure 7b, which shows sufficient resolution to visualize the nanoscale porosity. The SBA-15 particle sizes are in the approximate region of 1-2 µm in length and 0.5 µm in width, which, as in case of KIT-6 silica, is larger than the size of the In2O3 replica particles by approximately 1 order of magnitude. This means that, similar to the situation found for KIT-6 silica, the particle morphology of In2O3 replicas obtained from SBA-15 silica is well-defined (ellipsoidal) with no relation to the morphology of the silica particles, even though the latter (contrary to KIT-6 silica) show a well-defined morphology of their own. Hence, a similar growth model for In2O3 inside the pores of SBA-15 silica materials can be deduced, which is depicted in Figure 8. Conclusions In summary, this study demonstrates that well-defined particle morphologies and quite uniform particle sizes are generated by nanocasting using distinct mesoporous silica materials as structure matrices. The morphologies of the In2O3 particles are not related to those of the silica particles. The replication takes place at the nanometer (nanocasting of the mesopore system) but not at the micrometer (morphology) scale. The uniform In2O3 morphology can be explained by the growth mechanism inside the silica pores, which is governed by the formation of (presumably) liquid droplets of precursor species prior to oxide formation. Hence, uniform In2O3 particles can be obtained even without paying attention to morphological control during the synthesis of the silica matrices; the uniform morphology comes as a “built-in feature” during the nanocasting process. Similar findings were observed for the synthesis of mesoporous Co3O4
from the same silica matrices, while some other systems (e.g., SnO2) seem to follow different formation mechanisms. Acknowledgment. We thank Christoph Weidmann for valuable help in recording the SEM images. Supporting Information Available: Powder XRD diagrams (low-angle and wide-angle) and N2 physisorption isotherms (with pore size distributions) of In2O3-silica composites (KIT6, SBA-15-80, and SBA-15-140) after consecutive cycles of impregnation/oxide formation; structural data (tables). This material is available free of charge via the Internet at http:// pubs.acs.org. References and Notes (1) Yang, H.; Zhao, D. J. Mater. Chem. 2005, 15, 1217–1231. (2) Lu, A.-H.; Schu¨th, F. AdV. Mater. 2006, 18, 1793–1805. (3) Tiemann, M. Chem. Mater. 2008, 20, 961–971. (4) Trong On, D.; Desplantier-Giscard, D.; Danumah, C.; Kaliaguine, S. J. Appl. Catal., A 2001, 222, 299–357. (5) Taguchi, A.; Schu¨th, F. Microporous Mesoporous Mater. 2005, 77, 1–45. (6) Bruce, P. G.; Scrosati, B.; Tarascon, J.-M. Angew. Chem., Int. Ed. 2008, 47, 2930–2946. (7) Tiemann, M. Chem.sEur. J. 2007, 13, 8376–8388. (8) Yang, H.; Shi, Q.; Tian, B.; Lu, Q.; Gao, F.; Xie, S.; Fan, J.; Yu, C.; Tu, B.; Zhao, D. J. Am. Chem. Soc. 2003, 125, 4724–4725. (9) Tian, B.; Liu, X.; Yang, H.; Xie, S.; Yu, C.; Tu, B.; Zhao, D. AdV. Mater. 2003, 15, 1370–1374. (10) Prim, A.; Pellicer, E.; Rossinyol, E.; Peiro´, F.; Cornet, A.; Morante, J. R. AdV. Funct. Mater. 2008, 17, 2957–2963. (11) Waitz, T.; Wagner, T.; Sauerwald, T.; Kohl, C.-D.; Tiemann, M. AdV. Funct. Mater. 2009, 19, 653–661. (12) Wagner, T.; Sauerwald, T.; Kohl, C. D.; Waitz, T.; Weidmann, C.; Tiemann, M. Thin Solid Films 2009, 517, 6170–6175. (13) Smått, J. H.; Schu¨wer, N.; Ja¨rn, M.; Lindner, W.; Linde´n, M. Microporous Mesoporous Mater. 2008, 112, 308–318. (14) Sturm, M.; Leitner, A.; Smått, J.-H.; Linde´n, M.; Lindner, W. AdV. Funct. Mater. 2008, 18, 2381–2389. (15) Lepoutre, S.; Smått, J. H.; Laberty, C.; Amenitsch, H.; Grosso, D.; Linde´n, M. Microporous Mesoporous Mater. 2009, 123, 185–192. (16) Shon, J. K.; Kong, S. S.; Kim, Y. S.; Lee, J. H.; Park, W. K.; Park, S. C.; Kim, J. M. Microporous Mesoporous Mater. 2009, 120, 441–446. (17) Waitz, T.; Tiemann, M.; Klar, P. J.; Sann, J.; Stehr, J.; Meyer, B. K. Appl. Phys. Lett. 2007, 90, 123108-1. (18) Wagner, T.; Waitz, T.; Roggenbuck, J.; Fro¨ba, M.; Kohl, C.-D.; Tiemann, M. Thin Solid Films 2007, 515, 8360–8363. (19) Schwalm, M.; Horst, S.; Cherniko, A.; Ru¨hle, W. W.; Lautenschla¨ger, S.; Klar, P. J.; Meyer, B. K.; Waitz, T.; Tiemann, M.; Chatterjee, S. Phys. Status Solidi C 2009, 6, 542–545. (20) Rossinyol, E.; Arbiol, J.; Peiro, F.; Cornet, A.; Morante, J. R.; Tian, B.; Zhao, D. Sens. Actuators B 2005, 109, 57–63. (21) Rossinyol, E.; Prim, A.; Pellicer, E.; Arbiol, J.; Ramirez, F.; Peiro, F.; Cornet, A.; Morante, J. R.; Solovyov, L. A.; Tian, B.; Bo, T.; Zhao, D. AdV. Funct. Mater. 2007, 17, 1801–1806.
Mesoporous In2O3 with Regular Morphology by Nanocasting
J. Phys. Chem. C, Vol. 114, No. 5, 2010 2081
(22) Zhao, D.; Huo, Q.; Feng, J.; Chmelka, B. F.; Stucky, G. D. J. Am. Chem. Soc. 1998, 120, 6024–6036. (23) Kleitz, F.; Choi, S. H.; Ryoo, R. Chem. Commun. 2003, 2136– 2137. (24) Jun, S.; Joo, S. H.; Ryoo, R.; Kruk, M.; Jaroniec, M.; Liu, Z.; Ohsuna, T.; Terasaki, O. J. Am. Chem. Soc. 2000, 122, 10712–10713. (25) Yue, W.; Hill, A. H.; Harrison, A.; Zhou, W. Chem. Commun. 2007, 2518–2520. (26) Parmentier, J.; Saadhallah, S.; Reda, M.; Gibot, P.; Roux, M.; Vidal, L.; Vix-Guterl, C.; Patarin, J. J. Phys. Chem. Solids 2004, 65, 139–146. (27) Parmentier, J.; Solovyov, L. A.; Ehrburger-Dolle, F.; Werckmann, J.; Ersen, O.; Bley, F.; Patarin, J. Chem. Mater. 2006, 18, 6316–6323. (28) Smått, J.-H.; Weidenthaler, C.; Rosenholm, J. B.; Linde´n, M. Chem. Mater. 2006, 18, 1443–1450. (29) Lu, A.-H.; Smått, J.-H.; Linde´n, M. AdV. Funct. Mater. 2005, 15, 865–871.
(30) Shin, H. J.; Ryoo, R.; Kruk, M.; Jaroniec, M. Chem. Commun. 2001, 349–350. (31) Joo, S. H.; Ryoo, R.; Kruk, M.; Jaroniec, M. J. Phys. Chem. B 2002, 106, 4640–4646. (32) Ryoo, R.; Ko, C. H.; Kruk, M.; Antochshuk, V.; Jaroniec, M. J. Phys. Chem. B 2000, 104, 11465–11471. (33) Galarneau, A.; Cambon, H.; Di Renzo, F.; Ryoo, R.; Choi, M.; Fajula, F. New J. Chem. 2006, 27, 73–79. (34) Sing, K. S. W.; Everett, D. H.; Haul, R. A. W.; Moscou, L.; Pierotti, R. A.; Rouque´rol, J.; Siemieniewska, T. Pure Appl. Chem. 1985, 57, 603– 619. (35) Ryoo, R.; Joo, S. H.; Jun, S. J. Phys. Chem. B 1999, 103, 7743–7746.
JP910336F
