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With their nanoscalar, superparamagnetic Gd3-ion clusters (1 × 5 nm) confined within ultrashort (20−80 nm) single-walled carbon nanotube capsules, gadonanotubes are high-performance T1-weighted contrast agents for magnetic resonance imaging (MRI). At 1.5 T, 37 °C, and pH 6.5, the r1relaxivity (ca. 180 mM-1s-1per Gd3ion) of gadonanotubes is 40 times greater than any current Gd3ion-based clinical agent. Herein, we report that gadonanotubes are also ultrasensitive pH-smart probes with their r1/pH response from pH 7.0−7.4 being an order of magnitude greater than for any other MR contrast agent. This result suggests that gadonanotubes might be excellent candidates for the development of clinical agents for the early detection of cancer where the extracellular pH of tumors can drop to pH 7 or below. In the present study, gadonanotubes have also been shown to maintain their integrity when challenged ex vivo by phosphate-buffered saline solution, serum, heat, and pH cycling. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy (XPS) along with inductively coupled plasma analysis (ICP-AE) and Raman spectroscopy have been used to define the location and to quantify the amount of iodine in HiPco SWNT samples loaded with molecular I2via sublimation (I2-SWNTs). The exterior-adsorbed I2can be removed (as I-) by reducing the sample of filled nanotubes with Na0/THF or by heating the I2-SWNTs to 300 °C (without reduction), leaving I2contained only within the interior of the SWNTs (I2SWNTs) as proven by XPS. These I2SWNTs contain ∼25 wt % of I2and are stable without the loss of I2even after exposure to additional reduction with Na0/THF or upon heating to ca. 500 °C. [ABSTRACT FROM AUTHOR]