Journal
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY
Volume 8, Issue 8, Pages 4176-4180Publisher
AMER SCIENTIFIC PUBLISHERS
DOI: 10.1166/jnn.2008.AN29
Keywords
Excess Surface Energy; Nanoparticles; Enthalpy; Luminescence; Surface Trap
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The extra reactivity of nano materials is attributed to the excess surface energy stored in the sample. The excess enthalpy of SnO2 nano-particles were measured as a function of particle size using a calvet calorimeter. SnO2 with particle size 11, 27, 47 nm and bulk samples (1 pm) were dropped from room temperature to 987, 936 and 885 K and their H-T-H-298 values were determined. The excess enthalpies for SnO2 samples with particle sizes 11, 27 and 47 nm compared to the bulk sample calculated from the difference between HT-H-298 values of the nano and the bulk samples were found to be 15.06, 3.05, 2.21 kJ.mol(-1) respectively. Luminescence experiments reveal that the surface trap electron density decreases with increase of particle size. The excess enthalpy is related to the surface trap intensity.
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