Clusters of iron oxide nanoparticles encapsulated in a pH-responsive hydrogel are synthesized and studied for their ability to alter the T 2 -relaxivity of protons. Encapsulation of the clusters with the hydrophilic coating is shown to enhance the transverse relaxation rate by up to 85% compared to clusters with no coating. With the use of pH-sensitive hydrogel, difficulties inherent in comparing particle samples are eliminated and a clear increase in relaxivity as the coating swells is demonstrated. Agreement with Monte Carlo simulations indicates that the lower diffusivity of water inside the coating and near the particle surface leads to the enhancement. This demonstration of a surface-active particle structure opens new possibilities in using similar structures for nanoparticle-based diagnostics using magnetic resonance imaging.

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/jp809990aAccess and use of this website and the material on it are subject to the Terms and Conditions set forth at Single-sized CdSe nanocrystals with bandgap photoemission via a noninjected one-pot approach Yu, Kui; Ouyang, Jianying; Zaman, Md. Badruz; Johnston, Dennis; Yan, Fu Jian; Li, Grace; Ratcliffe, Christopher I.; Leek, Donald M.; Wu, Xiaohua; Stupak, Jacek; Jakubek, Zygmunt; Whitfield, Dennis 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=08c76c5f-73da-4536-8c4e-8c0a4441510d http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=08c76c5f-73da-4536-8c4e-8c0a4441510d The manuscript addresses the synthesis and characterization of one colloidal CdSe single-sized nanocrystal ensemble exhibiting bandgap absorption and emission peaking at 463 and 465 nm, respectively, with full width at half-maximum of ca. 8 nm. This ensemble is called Family 463; also, these single-sized quantum dots (QDs) are termed as magic-sized quantum dots (MSQDs). A magic-sized quantum dot (MSQD) ensemble is similar to a regular quantum dot (RQD) ensemble but consisting of single-sized nanocrystals; meanwhile, MSQDs do not grow in size any more with longer reaction periods or higher temperature, after their well development during synthesis. The CdSe MSQDs were synthesized via a noninjection one-pot approach with long reaction periods at elevated temperature, with cadmium acetate dihydrate (Cd(OAc) 2 · 2H 2 O) and elemental selenium as Cd and Se sources, respectively, one long-chain fatty acid as ligands, and 1-octadecene (ODE) as a reaction medium. Different carboxylic acids with the carbon-chain length ranging from C2 to C24, the number of which refers to the total number of carbons, were inve...

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CdS magic-sized nanocrystals (MSNs) exhibiting both band gap absorption and emission at 378 nm with a narrow bandwidth of ∼9 nm and quantum yield (QY) of ∼10% (total QY ∼28%, in hexane) were synthesized via a one-pot noninjection approach. This CdS MSN ensemble is termed as Family 378. It has been acknowledged that magic-sized quantum dots (MSQDs) are single-sized, and only homogeneous broadening contributes to their bandwidth. The synthetic approach developed is ready and highly reproducible. The formation of the CdS MSQDs was carried out at elevated temperatures (such as 90−140 °C) for a few hours in a reaction flask containing bis(trimethylsilyl)sulfide ((TMS)2S) and Cd(OAc)(OA) in situ made from cadmium acetate dihydrate (Cd(OAc)2·2H2O) and oleic acid (OA) in 1-octadecene (ODE). Low OA/Cd and high Cd/S feed molar ratios favor this formation, whose mechanism is proposed to be thermodynamically driven. 13C solid-state cross-polarization magic-angle spinning (CP/MAS) nuclear magnetic resonance (NMR) demonstrates that the capping ligands are firmly attached to the nanocrystal surface via carboxylate groups. With the cross-polarization from 1H of the alkyl chains to surface 113Cd, 113Cd NMR is able to distinguish the surface Cd (471 ppm) bonding to both −COO− and S and the bulk Cd (792 ppm) bonding to S only. DOSY-NMR was used to determine the size of Family 378 (∼1.9 nm). The present study provides strategies for the rational design of various MSNs.