Synthesis, characterization, and biosensing application of novel hybrid nanomaterials

Hybrid nanomaterials consisting of nanoparticles (NPs) distributed on the surface of the carbon nanotube (CNT)/graphene represent a new class of materials. These materials could potentially display not only the unique properties of NPs and those of the CNT/graphene, but also additional novel properties due to the interaction between the NP and the CNT/graphene. This thesis entails the synthesis and characterization of NP-CNT/graphene hybrid nanomaterials and the demonstration of their use for biosensors.;A simple method that combines an electrospray technique with electrostatic force directed assembly (ESFDA) was developed for successful functionalization of the CNT/thermally-reduced graphene oxide (TRGO) with NPs. Colloidal CdSe NPs, Au NPs, and Au NP-antibody conjugates were electrosprayed and assembled onto random CNTs, vertically-aligned CNT arrays, and TRGO sheets in a controlled manner. CNT and TRGO field-effect transistors (FETs) were fabricated; and novel electronic protein biosensors based on the CNTFET/TRGO FET and Au NP-antibody conjugates were demonstrated. The electrical detection of the protein binding was accomplished by the introduction of Au NP-antibody conjugates in the CNTFET/TRGO FET, in which the Au-coated CNT/TRGO serves as the electrical conducting channel. Antibody (anti-horseradish peroxidase/anti-Immunoglobulin G) and antigen (horseradish peroxidase/Immunoglobulin G) binding events led to the change in the CNT/TRGO conductivity, which was sensitively detected by FET and direct current (dc) measurements.;The CNTFET biosensor had a detection limit of 0.2 mg/ml (∼4.5 microM, horseradish peroxidase) while the TRGO FET biosensor exhibited a detection limit of 2 ng/ml (∼13 pM, Immunoglobulin G), which is among the best of carbon nanomaterial (e.g., CNT, graphene, GO)-based protein sensors. The dependence of the sensor response on the TRGO resistance and the antibody areal density on the TRGO sheet was systematically studied, and the sensor response was more significant with larger TRGO resistance and higher antibody areal density. The detection limit of the TRGO FET biosensor could be improved to 0.2 ng/ml level by tuning the TRGO resistance and the antibody areal density. The hybrid nanomaterial-based biosensing platforms are thus useful for in vitro diagnostics as they can be used to detect various target biomolecules by functionalizing the CNT/TRGO with desired Au NP-antibody conjugates.