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1. Materials. Triton X-100, GdCl3· 6H2O, 1-hexanol, hexanes, cyclohexane, tetraethyl orthosilicate (TEOS), pyridine, diethylenetriamine pentaacetic acid dianhydride, methanol, and aqueous NH4+ OH-were purchased from Aldrich and used without further purification. 3-aminopropyl triethoxysilane (APS) and 3-(trimethoxysilylpropyl) diethylene triamine were purchased from Gelest. Thermogravimetric analysis (TGA) was performed using a Shimadzu TGA-50 equipped with a platinum pan and heated at a rate of 3 oC/min under air. A Hitachi 4700 field emission scanning electron microscope (SEM) and a JEM 100CX-II transmission electron microscope were used to determine particle size and morphology. SEM images of the nanoparticles were taken on glass substrate. A Cressington 108 Auto Sputter Coater equipped with a Au/Pd (80/20) target and MTM-10 thickness monitor was used to coat the sample with approximately 5 nm of conductive layer before taking SEM images. Gd3+ ion concentration was measured on an Applied Research Laboratories (ARL) SpectraSpan7 Direct Current Plasma (DCP) Spectrometer. Emission and excitation data were collected on a Shimadzu RF-5301PC Spectrofluorophotometer. T1 and T2 values were determined on a Bruker 3.0 Tesla full body Magnetic Resonance Imaging (MRI) scanner. Confocal laser scanning microscope images were taken with a Zeiss LSM5 Pascal Confocal Laser Scanning Microscope or a Leica SP2 Laser Scanning Confocal Microscope with 488 nm excitation and a 530 LP emission filter. Fluorescence microscope images were taken with a Zeiss Axiovert 100 TV Fluorescence …