The graphene market continues to expand across a range of applications including consumer electronics, sensors, flexible wearables, supercapacitors, conductive inks and coatings. Thanks to graphene’s extraordinary electrical and mechanical properties a new generation of rapid, sensitive, low-cost bio/chemical sensors can be envisaged with impact upon healthcare, drug discovery, and bio/chemical detection applications.
Here we present the graphene-related R&D work at RISE Acreo with focus upon three objectives: graphene materials including wafer scale graphene-on-SiC, chemically synthesized graphene oxide (GO), reduced graphene oxide (RGO) and graphene quantum dots (or carbon nano particles); design and fabrication of the graphene devices, especially on their multiplexed sensing capability for enabling detection of multiple targets on a miniature integrated chip; and analysis of sensing mechanisms.
A few sensor examples will be described in this work, one is a graphene sensor to monitor glucose for diabetes. Another is a dopamine (DA) sensor utilizing graphene/ZnO-tetrapod hybrids for early diagnosis of Parkinson diseases (PD). DA is an important biomarker in the serum of patients with PD. The third one is a proton transmission detector utilizing 3D graphene onto SiC, which can initiate a new application for the detection of ionizing particle irradiation onto living cells. Finally, graphene sensors for forensic applications will be addressed; for instance, detection of amphetamine and TNT has been explored, aiming at rapid onsite crime scene analysis. In addition, a comprehensive analysis of the market and commercial opportunities of these devices will be presented.
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.
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.