Relaxivity tuning of nanomaterials with the intrinsic T- T dual-contrast ability has great potential for MRI applications. Until now, the relaxivity tuning of T and T dual-modal MRI nanoprobes has been accomplished through the dopant, size, and morphology of the nanoprobes, leaving room for bioapplications. However, a surface engineering method for the relaxivity tuning was seldom reported. Here, we report the novel relaxivity tuning method based on the surface engineering of dual-mode T- T MRI nanoprobes (DMNPs), along with protein interaction monitoring with the DMNPs as a potential biosensor application. Core nanoparticles (NPs) of europium-doped iron oxide (EuIO) are prepared by a thermal decomposition method. As surface materials, citrate (Cit), alendronate (Ale), and poly(maleic anhydride- alt-1-octadecene)/poly(ethylene glycol) (PP) are employed for the relaxivity tuning of the NPs based on surface engineering, resulting in EuIO-Cit, EuIO-Ale, and EuIO-PP, respectively. The key achievement of the current study is that the surface materials of the DMNP have significant impacts on the r and r relaxivities. The correlation between the hydrophobicity of the surface material and longitudinal relaxivity ( r) of EuIO NPs presents an exponential decay feature. The r relaxivity of EuIO-Cit is 13.2-fold higher than that of EuIO-PP. EuIO can act as T- T dual-modal (EuIO-Cit) or T-dominated MRI contrast agents (EuIO-PP) depending on the surface engineering. The feasibility of using the resulting nanosystem as a sensor for environmental changes, such as albumin interaction, was also explored. The albumin interaction on the DMNP shows both T and T relaxation time changes as mutually confirmative information. The relaxivity tuning approach based on the surface engineering may provide an insightful strategy for bioapplications of DMNPs and give a fresh impetus for the development of novel stimuli-responsive MRI nanoplatforms with T and T dual-modality for various biomedical applications.

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Improvement of polycarbazole-based organic bulk-heterojunction solar cells using 1,8-diiodooctane Appl.External-biased potential distributions of a polymer bulk-heterojunction (BHJ) solar cell, incorporated with electron/hole transporting layers, were directly obseved through a cross-sectional Kelvin probe force microscopy. The bulk electric field of BHJ was found to be nearly field-free even under reverse biases, and the field-free region was probed to expand with the incorporation of TiO x electron transporting layer; as a result, inducing a decrease of quasi-Fermi level splitting region in obtaining a high fill factor in the TiO x -interlayered junction photodiodes. V C 2012 American Institute of Physics. [http://dx.

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