Understanding the interactions of carbon nanotubes with environmentally-relevant ions and hydrogen peroxide for optical sensing

• Main Author: Kamel, Azhar Abdul kareem
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2013
• Subjects: Physical chemistry
• ISBN: 1321871724; 9781321871722

Single-walled carbon nanotubes (SWNTs) have drawn great attention in chemical and biological optical sensor applications due to their novel near infrared (NIR) optical properties that are extremely sensitive to the surrounding environment. This dissertation is devoted to four research areas: 1) Redox chemistry of sodium dodecyl sulfate (SDS)-encased SWNTs with mercuric ions in an aqueous environment for optical sensing: Various factors including SDS and SWNT concentrations, different pH levels, and buffer constituents, have been systematically examined. SWNTs show high selectivity and sensitivity to Hg2+ concentration over eleven other metal ions. The determined detection limit is 0.6 nM, lower than 10.0 nM, the maximum contaminant level for mercuric ions in drinking water. 2) DNA-encased SWNTs for optically sensing mercuric ions in aqueous solution: A monotonic SWNT NIR peak shift with Hg2+ concentration in both dsDNA-SWNT suspensions and ssDNA-SWNT suspensions has been observed. The peak shift is caused by the direct interaction between mercuric ions and DNA strands by forming metal-base complexes. The peak shift is buffer-dependent, and can be affected by buffer concentrations. SWNTs show high selectivity on Hg2+ concentration over seven other metal ions. The results from both area 1 and 2 show that the functionalization of SWNTs plays an important role in the interactions between metal ions and carbon nanotubes. 3) DsDNA-encased SWNTs for detecting hydrogen peroxide in a biological environment: SWNTs have been used as a probe for optical detection of H 2O2 in a blood model matrix (BMM) and serum, where the effects of key blood components on the reactivity of SWNTs with H2O 2 have been systematically investigated. Three different sensing methods for H2O2 detection have been developed. A detection limit of 2.9 µM is determined, providing improved sensitivity for detecting physiological and environmental H2O2. 4) DsDNA-encased SWNTs-BMM-hydrogen peroxide sensing matrix for detecting nitrite and nitrate ions in aqueous solution: The redox reaction of the SWNT matrix has been studied with nitrite ions. The reaction is pH and H2 O2 concentration dependent. The matrix has high selectivity on nitrite over nine other ions, with a limit of detection of 18.0 nM. By reducing nitrate to nitrite using a Cu-Cd reduction method, the matrix is able to measure nitrate ions with similar sensitivity. This dissertation may advance the SWNT-based optical sensor research to a new level for environmental, chemical, and biological applications.