Phototransformation of Alkanethiol-derivatized Noble Metal Nanoparticle

Photon-initiated shape transformation of n-alkanethiol-derivatized noble metal nanoparticles has been studied with variations of metal, alkanethiol, and solvent. Silver nanoparticles undergo fragmentation upon irradiation while gold ones barely do. Silver/gold composite particles follow the case of silver with a reduced efficiency. The efficiency decreases as alkanethiol length or solvent dipole moment increases. Following the conduction of thermalized photon energy, alkanethiol can dissociate in a period of heat dissipation, and some of dethiolated particles fragment within the recombination time. Prior to the thermal conduction, shape transformation via melt and vaporization also occurs for both metals but this effect is less apparent for silver because of more notable fragmentation followed. The difference in the transformation of two metals is ascribed to the differences in work function, oxidation potential, atomization enthalpy, and particle size. Smaller fragmentation efficiency with more polar solvent or longer alkanethiol is attributed mainly to relatively smaller dissociation rate compared with heat dissipation rate.

Energetics of Intramolecular Bonds in 1H-1,2,4-Triazole and 1H-Benzotriazole

This paper deals with a thermodynamic study of 1H-1,2,4-triazole and 1H-benzotriazole (general formula C2H3N3 and C6H5N3 respectively). Investigations were performed by combustion calorimetry of small amounts of substance (a few milligrams), sublimation calorimetry, differential thermal analysis and heat capacity measurements. The experimental combustion, sublimation and fusion enthalpies of the two compounds were determined as well as their triple point temperatures and are as follows: From these results, experimental resonance energies have been obtained and compared with theoretical values. The experimental atomization enthalpy of 1H-1,2,4-triazole is compatible with the calculated value. In the case of 1H-benzotriazole, it was possible to determine from this thermodynamic quantity a value of 298·4 kJ mol-1 for the N=N bond enthalpy.

Energétique des liaisons inter et intramoléculaires dans les trois isomères de l'aminophénol

The prsesent work is concerned with a thermodynamic study of the three aminophenol isomers (general formula: C6H7NO). It was achieved using four techniques: combustion calorimetry of small amounts of substance (a few milligrams), sublimation calorimetry, differential thermal analysis, and heat capacity measurements. From this study, it was possible: to determine the enthalpies of combustion, sublimation, and fusion of these compounds; to discuss the relative stability of the three molecules; to determine the intermolecular enthalpy bonds; to determine the experimental resonance energies and to compare them with the theoretical values; to determine the atomization enthalpies and to compare them with the values calculated from the energetical contributions previously determined in our laboratory; to consider the existence of an intramolecular hydrogen bond in the ortho isomer. Key words: thermodynamics; thermochemistry; calorimetry; differential thermal analysis; 2-aminophenol or ortho-aminophenol; 3-aminophenol or meta-aminophenol; 4-aminophenol or para-aminophenol; enthalpy of combustion, of sublimation, of fusion, of atomization, enthalpy of inter and intramolecular bonds; hydrogen bond; resonance energy; triple point temperature.