title: Excess enthalpy and luminescence studies of SnO2 nanoparticles.
abstract: 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 microm) were dropped from room temperature to 987, 936 and 885 K and their H(T)-H298 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 H(T)-H298 values of the nano and the bulk samples were found to be 15.06, 3.05, 2.21 kJ x 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.
authors.affiliation: Chemistry Division, Bhabha Atomic Research Centre, Mumbai 40085, India.
authors.forename: R S
authors.initials: RS
authors.lastname: Ningthoujam
authors.forename: R
authors.initials: R
authors.lastname: Mishra
authors.forename: D
authors.initials: D
authors.lastname: Das
authors.forename: G K
authors.initials: GK
authors.lastname: Dey
authors.forename: S K
authors.initials: SK
authors.lastname: Kulshreshtha