| Abstract
| - A direct calorimetric measurement of the dependence of the surface enthalpy of nanophase ZnO on morphology is reported. The surface enthalpies of nanoparticle are the same as those of nanoporous composites, and both of them are much lower than those of nanorods and nanotetrapods, which are also close to each other.
- A direct calorimetric measurement of the dependence of the surface enthalpy of nanophase ZnO onmorphology is reported. Nanoparticles, nanoporous composites, nanorods, and nanotetrapods were preparedwith various sizes, and their surface enthalpies were derived from their drop solution enthalpies in moltensodium molybdate. Water adsorption calorimetry for nanoparticles and nanorods was carried out tocharacterize the stabilization effect of surface hydration. The surface enthalpies of hydrated surfaces fornanoparticles, nanoporous composites, nanorods, and nanotetrapods are 1.31 ± 0.07, 1.42 ± 0.21, 5.19± 0.56, and 5.77 ± 2.50 J/m2, respectively, whereas those of the anhydrous surfaces are 2.55 ± 0.23,2.74 ± 0.16, 6.67 ± 0.56, and 7.28 ± 2.50 J/m2, respectively. The surface enthalpies of nanoparticlesare the same as those of nanoporous composites and are much lower than those of nanorods andnanotetrapods, which also are close to each other. The dependence of surface enthalpy on morphologyis discussed in terms of exposed surface structures. This is the first time that calorimetry on nanocrystallinepowders has been able to detect differences in surface energetics of materials having different morphologies.
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