RESUMO
The photothermal effect of nanoparticles has proven efficient for driving diverse physical and chemical processes; however, we know of no study addressing the dependence of efficacy on nanoparticle size. Herein, we report on the photothermal effect of three different sizes (5.5 nm, 10 nm and 15 nm in diameter) of magnetite nanoparticles (MNP) driving the decomposition of poly(propylene carbonate) (PPC). We find that the chemical effectiveness of the photothermal effect is positively correlated with particle volume. Numerical simulations of the photothermal heating of PPC supports this observation, showing that larger particles are able to heat larger volumes of PPC for longer periods of time. The increased heating duration is likely due to increased heat capacity, which is why the volume of the particle functions as a ready guide for the photothermal efficacy.
Assuntos
Nanopartículas de Magnetita/química , Polipropilenos/química , Estrutura Molecular , Tamanho da Partícula , Processos Fotoquímicos , TemperaturaRESUMO
Magnetite nanoparticles (MNPs) show remarkable stability during extreme photothermal heating (≥770 K), displaying no change in size, crystallinity, or surfactants. The heat produced is also shown as chemically useful, driving the high-barrier thermal decomposition of polypropylene carbonate. This suggests MNPs are better photothermal agents (compared to gold nanoparticles), for photothermally driving high-barrier chemical transformations.
RESUMO
The structure and torsional properties of oxalyl chloride fluoride in the gas phase have been measured by electron diffraction at temperatures of 22, 81, 158, and 310 °C. The molecule may be regarded as a hybrid of oxalyl chloride and oxalyl fluoride. Since the former exists as a more stable periplanar anti form (Ï = 180°) in equilibrium with a less stable gauche form (Ï ≃ 60°) and the latter as an equilibrium between two periplanar forms, anti and syn, the second form of oxalyl chloride fluoride is an interesting question. It was found to be gauche. The system was modeled as two rotational conformers related by a potential of the form 2V = V(1)(1 + cos Ï) - V(2)(1 - cos 2Ï) + V(3)(1 + cos 3Ï). The anti/gauche bond distances and bond angles (r(g)/Angstroms, â (α)/degrees) with estimated 2σ uncertainties at 22 °C are