Organic functionalization of sidewall of carbon nanotubes

Carbon nanotubes ornamented hollow polymethyl methacrylate microspheres for turbidity removal from water

Novel materials with low density are being synthesized with great interest owing to their effectiveness in water purification systems. Materials of micro/nano-scale provide outstanding results in miniature point-of-use devices because of their high surface-to-volume ratio. In this study, we report the successful synthesis of hollow polymethyl methacrylate microspheres (HPM) coated with functionalized carbon nanotubes (f-CNTs) (CHPM) by employing solvent evaporation and in situ coating techniques. The surface coating of HPM with the f-CNTs was visually confirmed by the surface roughness recorded in scanning electron microscopy. Furthermore, characterization with Fourier transform infrared spectroscopy substantiated the presence of hydroxyl and carboxyl groups of f-CNTs on the CHPM. The efficiency of CHPM to remove the turbidity from surface water was evaluated. The CHPM was effective in bringing down the turbidity of the water from 500 NTU to <1 NTU (>97%) which was within the desirable limit of the Bureau of Indian Standards. The temperature and pH for maximum reduction in turbidity were optimized to 49.5 °C and 4.5, respectively. Moreover, kinetic studies of CHPM indicated that the material followed the Langmuir isotherm model with regeneration efficiency lasting more than 10 cycles. From the results, we propose a simple, facile, and cost-effective synthetic route for the synthesis of CHPM for water purification, especially for turbidity removal. The synthesized CHPM with low density and relatively large surface area offer huge potential in water treatment applications and related fields.

Chemical Functionalization of Boron−Nitride Nanotubes with NH3and Amino Functional Groups

We have investigated properties of chemically modified boron nitride nanotubes (BNNTs) with NH(3) and four other amino functional groups (NH(2)CH(3), NH(2)CH(2)OCH(3), NH(2)CH(2)COOH, and NH(2)COOH) on the basis of density functional theory calculations. Unlike the case of carbon nanotubes, we found that NH(3) can be chemically adsorbed on top of the boron atom, with a charge transfer from NH(3) to the BNNT. The minimum-energy path calculation shows that a small energy barrier is encountered during the adsorption. Similarly, a small energy barrier (about 0.42 eV) is also involved in the desorption, suggesting that both adsorption and desorption can be realized even at room temperature. For chemically modified BNNTs with various amino functional groups, the adsorption energies are typically less than that of NH(3) on the BNNT. The trend of adsorption-energy change can be correlated with the trend of relative electron-withdrawing or -donating capability of the amino functional groups. Overall, the chemical modification of BNNTs with the amino groups results in little changes in the electronic properties of BNNTs. However, the chemical reactivity of the BNNTs can be enhanced by the chemical modification with the amino group containing -COOH.