The epitaxial graphene-on-silicon carbide (SiC-G) has advantages of high quality and large area coverage owing to a natural interface between graphene and SiC substrate with dimension up to 100 mm. It enables cost effective and reliable solutions for bridging the graphene-based sensors/devices from lab to industrial applications and commercialization. In this work, the structural, optical and electrical properties of wafer-scale graphene grown on 2’’ 4H semi-insulating (SI) SiC utilizing sublimation process were systemically investigated with focus on evaluation of the graphene’s uniformity across the wafer. As proof of concept, two types of glucose sensors based on SiC-G/Nafion/Glucose-oxidase (GOx) and SiC-G/Nafion/Chitosan/GOx were fabricated and their electrochemical properties were characterized by cyclic voltammetry (CV) measurements. In addition, a few similar glucose sensors based on graphene by chemical synthesis using modified Hummer’s method were also fabricated for comparison.
Zinc oxide tetrapods (ZnO-Ts) were synthesized by flame transport synthesis using Zn microparticles. This work herein reports a systematical study on the structural, optical and electrochemical properties of the ZnO-Ts. The morphology of the ZnO-Ts was confirmed by scanning electron microscopy (SEM) as joint structures of four nano-microstructured legs, of which the diameter of each leg is 0.7-2.2 μm in average from the tip to the stem. The ZnO-Ts were dispersed in glucose solution to study the luminescence as well as photocatalytic activity in a mimicked biological environment. The photoluminescence (PL) intensity in the ultraviolet (UV) region quenches with linear dependence to increased glucose concentration up to 4 mM. The ZnO-Ts were also attached with glucose oxidase (GOx) and over coated with a thin film of Nafion to form active layers for electrochemical glucose sensing. The attachment of GOx and coating of Nafion were confirmed by infrared spectroscopy (FT-IR). Furthermore, the current response of the active layers based on ZnO-Ts was investigated by cyclic voltammetry (CV) in various glucose concentrations. Stable current response of glucose was detected with linear dependence to glucose concentration up to 12 mM, which confirms the potential of ZnO-Ts for biomolecule sensing applications.
ZnO nanorods (NRs) sensors utilizing hybrid or monolithic integration of the NRs on nanoscale or microscale
interdigitated electrodes (IDEs) were fabricated and characterized. The IDEs with their finger electrode width ranging
from 50 nm to 3 μm were formed on SiO<sub>2</sub>/Si substrates by nanoimprint lithography or conventional photolithography
and metallization techniques, whereas the ZnO NRs were grown by chemical synthesis method. The average diameter of
the ZnO NRs is about 100 nm, and their length can be varied from 2 to 5 μm by controlling growth time. When sensing
targets, such as molecules or nanoparticles, bind onto the ZnO NRs, the conductance between IDEs will change. As
probing test, II-VI quantum dots (QDs) were attached on the ZnO NRs, and clear responses were obtained by measuring
and comparing current-voltage (I-V) characteristic of the sensor before and after binding the QDs.