Modification And Applications Of Single-walled Carbon Nanotubes

Non-covalent modification of carbon nanotubes with cyanine dyes can be used for detecting the concentration of bovine serum albumin (BSA) and surfactant (SDBS). Methine chain of different lengths and different types of substituents in the same series will effect quenching efficiency of SWCNTs and the sensitivity of detection. The longer chain of Methine, the greater the degree of quenching efficiency and fluorescence recovery; cyanine dyes with electron donor groups is better than cyanine dyes with electron-withdrawing groups in the quenching efficiency of carbon nanotubes and the fluorescence recovery after the addition of certain amount of BSA.Acridine orange (AO) can easily intercalate into the DNA base pair, leading to a significant fluorescence enhancement, which it is often used as a commercially available DNA probe. Unfortunately, AO itself has a strong fluorescence emission, leading to an intense auto-fluorescence background. Single-walled carbon nanotubes (SWCNTs) was used to solve this problem. AO can be absorbed on the surface of SWCNTs via physisorption, owing to a π-π stacking interaction between the organic dye and the SWCNTs sidewalls, and SWCNTs can be employed as an efficient quencher here. The fluorescence of acridine orange (AO) can be quenched significantly with addition of the single-wall carbon nanotubes (SWCNTs) solution, due to the formation of a hybrid complex between AO and SWCNTs. A fluorescence enhancement of approximately18x can be observed after the addition of certain amount of DNA into the above mentioned solution. The fluorescence increase was linearly proportional to the amount of DNA added in the concentration range of0-50.75μM, and the DNA detection limit was down to8.56x10-8M. This method can be used to detect DNA in vitro.RB-2, RB-6, and the RB-0were used for covalent modification of carbon nanotubes, The structures were prove to be correct. When pH value is less than3.6in aqueous solution, the fluorescence intensity of the three compounds were significantly enhanced; When pH value is more than3.6in aqueous solution, the fluorescence intensity was relatively weak. The electrochemical luminescence intensity of three compounds are663.8、805.land868.8respectively. The longer the carbon chain, the greater ECL intensity. RB-2-CNT, was used for staining of Hela cells. It is noticed that there is no fluorescence in vitro, but there is fluorescence within the Hela cells. A common inhibitor of carboxylesterase (AEBSF) was used to study mechanism of intracellular fluorescence. The intracellular carboxylesterase opened lactone-ring of rhodamine,at the same time RB-2was separated from SWCNTs, which explained intracellular fluorescence.