Synthesis, Characterization And Analytical Application Of Bio-functionalized Carbon Nanotubes

The use of un-functinalized carbon nanotubes(CNTs) as sorbents for separation and preconcentration of trace analytes has received considerable attention.However, little attention has been paid to fuctionalized carbon nanotubes as sorbents for highly selective separation and preconcentration of trace analytes.This dissertation describes the synthesis,characterization and selective sorption capability of bio-functionalized carbon nanotubes in trace analytical application.The main contents are summarized as follows:A selective on-line solid-phase extraction method was developed for the separation and preconcentration of trace Cd using L-cysteine functionalized multi-walled carbon nanotubes(MWCNTs-cysteine) as sorbent.MWCNTs-cysteine were synthesized and characterized by XPS,FT-IR,XRD and TEM.The capability of MWCNTs-cysteine for selective separation and preconcentration of heavy metal ions were statically and dynamically evaluated with Cd²⁺ as a model heavy metal ion. Unlike MWCNTs,the sorption of Cd²⁺ onto MWCNTs-cysteine was not influenced by ionic strength in a wide range.The MWCNTs-cysteine was demonstrated to be good column packings for on-line microcolumn separation and preconcentration of Cd²⁺.Effective preconcentration of Cd²⁺ on the MWCNTs-cysteine packed microcolumn was achieved in a pH range of 5.0 to 6.5.The retained Cd²⁺ was efficiently eluted with 0.5 mol L^-1 HCl for on-line flame atomic absorption spectrometric determination.The MWCNTs-cysteine exhibited fairly fast kinetics for the adsorption of Cd²⁺,and offered up to 1600-fold improvement of the tolerable concentrations of co-existing metal ions over the MWCNTs for on-line solid-phase extraction of Cd²⁺.With a preconcentration time of 60 s at a sample loading flow rate of 5.0 mL min^-1,an enhancement factor of 33 and a sample throughput of 36 h^-1 along with a detection limit(3s) of 0.28μg L^-1 were obtained.The precision(RSD) for 11 replicate measurements was 1.6%at the 10μg L^-1 level.The developed method using the MWCNTs-cysteine as sorbent was successfully applied to determination of trace cadmium in a variety of biological and environmental materials.A selective on-line solid-phase extraction of trace Cu²⁺ and Ni²⁺ was developed using hexhistidine-tagged protein functionalized multi-walled carbon nanotubes (MWCNTs/6His-tagged-protein) as sorbent.The MWCNTs/6His-tagged-protein were prepared and characterized by ultraviolet-visible spectrophotometry,atomic force microscopy and X-ray diffraction spectroscopy.Both static and dynamical adsorption experiments showed that the MWCNTs/6His-tagged-protein served as good sorbent for the solid-phase extraction of Cu²⁺ and Ni²⁺.Effective on-line sorption of Cu²⁺ and Ni²⁺ on the MWCNTs/6His-tagged-protein packed microcolumn was achieved in a pH range of 4.0-5.5 and 5.0-6.5,respectively.The retained Cu²⁺ and Ni²⁺ were efficiently eluted with 0.2 mol L^-1 imidazole-HCl solution for on-line flame atomic absorption spectrometric determination.The MWCNTs/6His-tagged-protein exhibited fairly fast kinetics for the sorption of Cu²⁺ and Ni²⁺,and gave up to 20000 and 1800 times improvement in the tolerable concentrations of co-existing ions over the MWCNTs for solid-phase extraction of Cu²⁺ and Ni²⁺,respectively.On-line solid-phase extraction at a flow rate of 5.0 mL min^-1 for 60 s offered an enhancement factor of 29 for Cu²⁺ and 28 for Ni²⁺,a sample throughput of 40 h^-1,and a detection limit(3s) of 0.31μg L^-1 for Cu²⁺ and 0.63μg L^-1 for Ni²⁺.The precision for 11 replicate measurements was 2.4%for 10μg L^-1 Cu²⁺,and 2.5%for 15μg L^-1 Ni²⁺. The new MWCNTs/6His-tagged protein nanohybrids have been shown to be a promising high selectively sorbent for on-line solid-phase extraction of Cu²⁺ and Ni²⁺ in a variety of environmental and biological samples. An ultrasenstive and rapid method for detection of pathogen Vibrio alginolyticus was developed based on the multi-functional carbon nanotubes. Immuno-magnetic-fluorescence-multiwalled carbon nanotubes were synthesized,and characterized by UV-vis,SEM,FT-IR,VSM and FL.The binding behavior of the multi-functional carbon nanotubes for bacterium was investigated by optical microscope.There were three distinguish functional units of the immuno-magnetic-fluorescence-multiwalled carbon nanotubes.First,the highly specific antibody-antigen interactions and poly(ethylene glycol) was found to be effective in resisting nonspecific adsorption.Second,parts of encapsulated ferromagnetic element Ni in multiwalled carbon nanotubes acted for immunomagnetic separation of pathogenic cells.Third,efficient fluorescent reagent 1-pyrenebutyric acid was conjugated to multi-walled carbon nanotube sidewall via the strongÏ€-Ï€stacking interaction and connected with antibody protein like a "bridge". The nano-fluorescent bioconjuate can be dispersed in water.There was a good linear relationship(R=0.9938) between the enhanced fluorescence intensity and the concentration of V.alginolyticus,with a linear in the range of 3.0×10⁴ to 1.5×10⁷ cfu mL^-1.A detection limit(3s) of 8.4×10³ cfu mL^-1 V.alginolyticus was achieved.The relative standard deviation for 11 replicate detections of 2.0×10⁵ cfu mL^-1 V. alginolyticus was 1.4%(RSD),Immuno-magnetic-fluorescence-multiwalled carbon nanotubes have been shown to be a promising highly selective sorbent for ultrasenstive and rapid detection of pathogen Vibrio alginolyticus.