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Heat and combined pressure-temperature degradation of chlorophyll in broccoli juice have been studied on a kinetic basis. A treatment at 100 °C and atmospheric pressure during 37 min resulted in a 90% decrease in total chlorophyll content of broccoli juice. An extreme pressure stability of both chlorophylls a and b at room temperature was observed. Significant reductions in chlorophyll content were noticed only when pressure was combined with temperatures exceeding 50 °C.Chlorophyll degradation reactions at atmospheric as well as at elevated pressures could be adequately described by assuming a first-order decay. Chlorophyll a degradation occurred more rapidly as compared to chlorophyll b degradation under all pressure-temperature combinations tested (1-800 MPa/50-120 °C). Degradation rates increased with temperature according to the Arrhenius law at all pressures tested.

Graphical abstractHighlights  Ag-polymer-TiO2 composites show ultrastable photocatalytic activity in the long term  Ag-polymer core-shell nanoparticles prepared using affordable layer-by-layer method  Thin polymer shell prevents oxidation and clustering of the silver nanoparticles  Finite element simulations show retention of plasmonic near-field enhancement 3 ABSTRACT Affordable silver-polymer core-shell nanoparticles are prepared using the layer-by-layer (LbL) technique. The metallic silver core is encapsulated with an ultra-thin protective shell that prevents oxidation and clustering without compromising the plasmonic properties. The core-shell nanoparticles retain their plasmonic near field enhancement effect, as studied from finite element numerical simulations. Control over the shell thickness up to the sub-nanometer level is there for key. The particles are used to prepare a plasmonic Ag-TiO2 photocatalyst of which the gas phase photocatalytic activity is monitored over a period of four months. The described system outperforms pristine TiO2 and retains its plasmonic enhancement in contrast to TiO2 modified with bare silver nanoparticles. With this an important step is made toward the development of longterm stable plasmonic (photocatalytic) applications.

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