Kinetics, mechanisms and ionic liquids in the uptake of n-butylamine onto low molecular weight dicarboxylic acids

Atmospheric particles adversely affect visibility, health, and climate, yet the kinetics and mechanisms of particle formation and growth are poorly understood. Multiphase reactions between amines and dicarboxylic acids (diacids) have been suggested to contribute. In this study, the reactions of n-butylamine (BA) with solid C3-C8 diacids were studied at 296 ± 1 K using a Knudsen cell interfaced to a quadrupole mass spectrometer. Uptake coefficients for amines on the diacids with known geometric surface areas were measured at initial amine concentrations from (3-50) × 1011 cm-3. Uptake coefficients ranged from 0.7 ± 0.1 (2σ) for malonic acid (C3) to <10-6 for suberic acid (C8), show an odd-even carbon number effect, and decrease with increasing chain length within each series. Butylaminium salts formed from evaporation of aqueous solutions of BA with C3, C5 and C7 diacids (as well as C8) were viscous liquids, suggesting that ionic liquids (ILs) form on the surface during the reactions of gas phase amine with the odd carbon diacids. Predictions from the kinetic multi-layer model of aerosol surface and bulk chemistry (KM-SUB) were quantitatively consistent with uptake occurring via dissolution of the underlying diacid into the IL layer and reaction with amine taken up from the gas phase. The butylaminium salts formed from the C4 and C6 diacids were solids, and their uptake coefficients were smaller. These experiments and kinetic modeling demonstrate the unexpected formation of ILs in a gas-solid reaction, and suggest that ILs should be considered under some circumstances in atmospheric processes

Cytotoxicity of Phenol Red in Toxicity Assays for Carbon Nanoparticles

To explore the novel properties of carbon nanoparticles (CNPs) in nanotoxicity assays, the adsorption of phenol red (a pH indicator for culture medium) by multi-walled carbon nanotubes (MWNTs) and three kinds of carbon blacks (CBs) with nanosize, and its effects on cytotoxicity were studied. Results indicated that the phenol red adsorbed and delivered into cells by CBs was responsible for the toxicity to Hela cells in the medium without serum. The cellular uptake of phenol red was verified using 125I-labeling techniques. The size-dependent cytotoxicity of CBs was found to closely correlate to adsorption of phenol red, cellular uptake of phenol red-CB complexes and the amount of phenol red delivered into the cells by CBs. Although the CBs were either nontoxic or slightly toxic, as vehicles of phenol red, they played an essential role in the cytotoxicity induced by phenol red. However, MWNTs showed an intrinsic cytotoxicity independent of phenol red. The implications associated with these findings are discussed