Biosensing with nanocube-augmented carbon nanotube networks
Abstract
A porous anodic alumina (PAA) substrate anodized from a metalized wafer acts as a template for subsequent carbon nanotube (CNT) growth. Low density aligned single-walled carbon nanotube (SWCNT) networks are grown from the pores of the PAA via microwave plasma chemical vapor deposition (MPCVD). Electrodeposition of Pd creates Pd nanowires within the pores of the PAA that supply the electrical back contact to the SWCNTs and creates concentric Pd nanocubes at SWCNT defect sites. A thin layer of Au is subsequently electrodeposited onto the Pd nanocubes to enhance the biocompatibility of the Pd nanocubes for biosensing applications. The SWCNT-Au/Pd electrodes are lithographically patterned with Al2O 3 to quantify the sensitivity of the sensor. Field emission scanning electron microscopy (FESEM) and fluorescence microscopy verify the existence and density of the Au/Pd nanocubes decorating the SWCNTs. To analyze the electrochemical efficacy of the Au/Pd nanocube-SWCNT biosensor, hydrogen peroxide (H 2O2) is amperometrically sensed via a three-electrode potentiostat. The biosensor is electrochemically treated with 0.1M H2SO 4 and 0.1M NaOH via cyclic voltammetry to enhance the electrochemical activity of the SWCNT-Au/Pd biosensor towards the oxidation of H2O2. The electrochemical treated Au/Pd nanocube-SWCNT biosensor demonstrated high sensitivity (2.6mA mM-1 cm -2) and a low estimated detection limit (2.3nM) at a signal-to-noise ratio of 3 (S/N = 3) in the amperometric sensing of hydrogen peroxide. To analyze the efficacy of the SWCNT-Au/Pd electrode towards enzymatic electrochemical biosensing, glucose oxidase (GOx) is immobilized on the surface of the Au/Pd nanocubes via a thiol linker [dithiobis (succinimidyl undecanoate)]. The glucose detection limit of 1.3μM (S/N = 3) and linear range (10μM–50mM) of the sensor surpasses similar nanoscale biosensors. These results are further justified through analytical modeling of the mass transfer kinetics of the tethered Au/Pd nanocubes of the Au/Pd nanocube-SWCNT biosensor.
Degree
M.S.M.E.
Advisors
Fisher, Purdue University.
Subject Area
Mechanical engineering
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