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Experimental measurement and modelling of reactive species generation in TiO2 nanoparticle photocatalysis.

ABSTRACT: The generation of reactive species in titanium dioxide (TiO2) nanoparticle photocatalysis was assessed in a laboratory scale setup, in which P25 Aeroxide TiO2 suspensions were photoactivated by means of UV-A radiation. Photogenerated holes and hydroxyl radicals were monitored over time by observing their selective reaction with probe compounds, iodide and terephthalic acid, respectively. TiO2 aggregate size and structure were characterized over the reaction time. Reactive species quenching was then described by a model, accounting for radiative phenomena, TiO2 nanoparticle aggregation and kinetic reactions. The interaction between iodide and photogenerated holes was influenced by iodide adsorption on TiO2 surface, described by a Langmuir-Hinshelwood mechanism, whose parameters were studied as a function of TiO2 concentration and irradiation time. Iodide oxidation was effectively simulated by modelling the reaction volume as a completely stirred two-dimensional domain, in which irradiation phenomena were described by a two-flux model and the steady state for reactive species was assumed. The kinetic parameters for iodide adsorption and oxidation were estimated and successfully validated in a different experimental setup. The same model was adapted to describe the oxidation of terephthalic acid by hydroxyl radicals. The kinetic parameters for terephthalic acid oxidation were estimated and validated, while the issues in investigating the interaction mechanisms among the involved species have been discussed. The sensitivity of operating parameters on model response was assessed and the most relevant parameters were highlighted.

SUBMITTER: Turolla A

PROVIDER: S-EPMC5119892 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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Experimental measurement and modelling of reactive species generation in TiO2 nanoparticle photocatalysis.

Turolla Andrea A Piazzoli Andrea A Budarz Jeffrey Farner JF Wiesner Mark R MR Antonelli Manuela M

Chemical engineering journal (Lausanne, Switzerland : 1996) 20150309

The generation of reactive species in titanium dioxide (TiO2) nanoparticle photocatalysis was assessed in a laboratory scale setup, in which P25 Aeroxide TiO2 suspensions were photoactivated by means of UV-A radiation. Photogenerated holes and hydroxyl radicals were monitored over time by observing their selective reaction with probe compounds, iodide and terephthalic acid, respectively. TiO2 aggregate size and structure were characterized over the reaction time. ...[more]

PMID: 27885321

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Project description:Astrocytes are increasingly recognized as critical contributors to multiple sclerosis pathogenesis. We have previously shown that lack of Response Gene to Complement 32 (RGC-32) alters astrocyte morphology in the spinal cord at the peak of experimental autoimmune encephalomyelitis (EAE), suggesting a role for RGC-32 in astrocyte differentiation. In this study, we analyzed the expression and distribution of astrocytes and astrocyte progenitors by immunohistochemistry in spinal cords of wild-type (WT) and RGC-32-knockout (KO) mice with EAE and of normal adult mice. Our analysis showed that during acute EAE, WT astrocytes had a reactive morphology and increased GFAP expression, whereas RGC-32 KO astrocytes had a morphology similar to that of radial glia and an increased expression of progenitor markers such as vimentin and fatty acid binding protein 7 (FABP7). In control mice, GFAP expression and astrocyte density were also significantly higher in the WT group, whereas the number of vimentin and FABP7-positive radial glia was significantly higher in the RGC-32 KO group. In vitro studies on cultured neonatal astrocytes from WT and RGC-32 KO mice showed that RGC-32 regulates a complex array of molecular networks pertaining to signal transduction, growth factor expression and secretion, and extracellular matrix (ECM) remodeling. Among the most differentially expressed factors were insulin-like growth factor 1 (IGF1), insulin-like growth factor binding proteins (IGFBPs), and connective tissue growth factor (CTGF); their expression was downregulated in RGC-32-depleted astrocytes. The nuclear translocation of STAT3, a transcription factor critical for astrogliogenesis and driving glial scar formation, was also impaired after RGC-32 silencing. Taken together, these data suggest that RGC-32 is an important regulator of astrocyte differentiation during EAE and that in the absence of RGC-32, astrocytes are unable to fully mature and become reactive astrocytes.

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Experimental measurement and modelling of reactive species generation in TiO2 nanoparticle photocatalysis.

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Experimental measurement and modelling of reactive species generation in TiO<sub>2</sub> nanoparticle photocatalysis.

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