Temperature-dependent uptake and release of small molecules within porous silica nanoparticles has been achieved by treatment of preformed, thiol-functionalized micro-to-mesoporous silica nanoparticles (MSN) with pyridyl disulfide-terminated poly(N-isopropylacrylamide) (PNIPAM−S−S−Py). The resulting nanoparticle−polymer composites show uptake and release of fluorescein at room temperature (below the lower critical solution temperature, LCST, of the polymer) and a low level of leakage at 38 °C (above LCST, <2% after 2 h). The data are consistent with a mode of action in which fluorescein diffusion occurs readily when the polymer is in the random coil conformation but is significantly retarded when the polymer adopts the globule conformation. This mode of action is opposite to that observed for systems in which the PNIPAM is grown from the porous silica surface or co-condensed with silica and is accompanied by a greater than 10-fold improvement in fluorescein retention in the “pore-closed” conformation.

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Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://doi.org/10.1021/jp103157tAccess and use of this website and the material on it are subject to the Terms and Conditions set forth at Pore structure and interconnectivity of CdS aerogels and xerogels by hyperpolarized xenon NMR Pawsey, Shane; Kalebaila, Kennedy K.; Moudrakovski, Igor; Ripmeester, John A.; Brock, Stephanie L.http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/droits L'accès à ce site Web et l'utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D'UTILISER CE SITE WEB. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=4601cacd-09be-4467-82ec-1e7011c292cf http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=4601cacd-09be-4467-82ec-1e7011c292cf ReceiVed: April 7, 2010; ReVised Manuscript ReceiVed: June 30, 2010 Metal chalcogenide aerogels and xerogels are unique materials that combine semiconducting nanostructures with porosity and are thus of interest for photocatalysis and sensing. To assess the feasibility for applications dependent on molecular transport, the pore structure and interconnectivity in CdS aerogels and xerogels were probed by a combination of conventional techniques and hyperpolarized (HP) 129 Xe NMR. HP 129 Xe NMR of the aerogels was consistent with two distinct types of accessible pores (adsorption sites), and 2-D EXSY NMR data suggest that these are connected. In contrast, a single resonance of low intensity with a temperature dependence consistent with the dissolution of Xe within a polymer matrix, that is, transport facilitated at high temperatures due to chain motion, is observed in xerogels. 13C NMR and thermal gravimetric analysis data reveal the presence of residual organics in both xerogels and aerogels, but a relatively higher proportion in the former, due, in part, to the surfactant used in their preparation. These data, combined with the absence of any meaningful adsorption isotherm for N 2 at 77 K (wh...