The energetics of pure-phase rutile nanorods and spherical anatase nanoparticles have been studied by high-temperature drop solution calorimetry in 3Na 2 O‚4MoO 3 solvent at 975 K and water adsorption calorimetry in a wide range of particle sizes (surface area) from 6 to 40 nm (5-270 m 2 /g). The calorimetric surface enthalpies for rutile and anatase, calculated as 2.22 ( 0.07 and 0.74 ( 0.04 J/m 2 , respectively, are in general agreement with Ranade et al. 's results (Proc. Natl. Acad. Sci. U.S.A., 2002, 99, 6476), although their numerical values are somewhat different because of impurities and unaccounted bound water in the previous work. This study supports the energy crossovers previously proposed for the TiO 2 polymorphs. The energetics of water adsorption were measured using a commercial Calvet microcalorimeter coupled with a gas dosing system. This permitted the calculation of differential and integral enthalpies of water adsorption that characterize how tightly water binds to rutile and anatase surfaces and the calculation of adsorption entropies, which reflect the surface mobility of adsorbed water. The integral enthalpy of tightly bound water (relative to liquid H 2 O standard state) is -18 kJ/mol for anatase and -40 kJ/mol for rutile. As seen previously for Al 2 O 3 , the TiO 2 polymorphs with higher surface energy bind water more tightly. The calculated entropy changes for the adsorption of water on TiO 2 are more negative than the entropy changes for the condensation of gaseous water to hexagonal ice. This finding suggests highly restricted mobility of molecules adsorbed at initial stages of adsorption (low coverage) and, possibly, dissociative adsorption on both rutile and anatase surfaces. However, nanoparticles contain both tightly bound water and loosely bound water. The latter is characterized by energetics of bulk water. The stabilizing water contribution to the overall energy of the system makes the hydrated nanophase samples more stable. The recommended transformation enthalpy for bulk anatase to bulk rutile is -1.7 ( 0.9 kJ/mol.

Contents 1. Introduction 3885 2. Zeolites 3887 2.1. General Remarks 3887 2.2. Anhydrous High-Silica Zeolites 3889 2.3. Anhydrous Aluminosilicate Zeolites 3891 2.4. Zeolite Hydration and Cation Exchange 3891 3. Mesoporous Silica 3895 4. Interactions with Structure-Directing Agents 3895 5. Zeotypes 3896 6. Synthesis and Transformations of Zeolites and Related Materials 3897 7. Concluding Remarks 3899 8. References 3900

Supporting Information.Element maps were taken for the x = 0.6 single crystal sample, and are shown in SFigure 1. These maps show that the distribution of Al and Mn across the crystal is homogeneous. The random light and dark specks on the images are surface imperfections or dust since the crystal was measured as-is, not polished or sanded. SFigure 2 shows the microprobe back scattered electron (BSE) images from the pressed pellets: the light-grey regions are identified as the Yb 14 Mn 1-x Al x Sb 11 phase. There are a few minor small medium-grey regions that were identified as Sn inclusions and a very few dark regions which are voids or Yb inclusions.

The formation enthalpies by in situ direct synthesis calorimetry for a series of silver alkanethiolates, AgS(CH 2 ) n CH 3 , with various long chain-length substituents (n ) 9, 11, 15, and 17) are reported. The calorimetric results support a mechanism of stepwise hierarchical assembly involving primary directional interactions between Ag and S forming the inorganic core and secondary stacking facilitating the formation of the three-dimensional structure. The formation enthalpy data are chain-length dependent, indicating an energy of -4 ( 0.5 kJ/mol per methyl group due to alkyl chain interactions. The chain independent component of the enthalpy associated with bonding between Ag and S is -137 ( 6 kJ/mol, which is consistent with previous experimental data and ab initio calculations for these and related materials. A new recrystallization method offers significantly improved structural consistency across the chain-length series. Larger purified crystals, prepared by this method, were used to probe the structure, thermodynamics of phase transitions, and thermal stability, using a combination of differential scanning and solution calorimetry, thermogravimetric analysis, evolved gas Fourier transform infrared spectroscopy, and temperature-dependent X-ray diffraction. The DSC data show that the temperature of the main phase transition at 131°C is essentially independent of the length of the alkyl chain substituents for recrystallized samples. This chain-length independence does not reflect constant enthalpy of transition but rather a complex interplay between enthalpic and entropic contributions. In agreement with previous studies, this phase transition is assigned to a fully reversible transformation from the layered crystalline structure to a columnar mesophase, characterized by structural rearrangements of the inorganic framework and partial conformational disordering of the chain substituents. In situ scanning calorimetry in toluene upon slow heating from room temperature to 110°C, where the sample appeared to dissolve in the toluene near 100°C, gives insight into chain assembly and crystal growth. The second reaction seen in DSC at 210°C is an irreversible transformation to an amorphous derivative, ultimately leading to the formation of silver and silver sulfide crystals resulting from the chemical decomposition of alkyl chains.