A chemical modification process was developed to functionalize graphene with specific groups. Graphene oxide (GO) was successfully functionalized with thionyl bromide which can be used as precursors for further functionalization. Amino terminated-polyethylene glycol (PEG-NH2) molecules were linked to single-layer graphene sheets through covalent bond. FT-IR, SEM and UV-vis spectroscopy techniques were used to characterize PEG modified graphene oxide and PEG modified reduced graphene oxide (PEG-RG). PEG-RG could disperse in water, tetrahydrofuran and ethylene glycol, with individual, single-layer graphene sheets spontaneously. The dispersion behavior of PEG-RG in an aqueous solvent has been investigated. A series of solutions of PEG-RG with concentrations of 0.001% to 1.5% were prepared and the PEG-RG dispersions exhibited long-term stability. In addition, a PEG-RG film with layered structure and high conductivity has been successfully prepared by filtration.

Blood-cell-free serum is required for most clinical chemistry tests. At present bend micro channel and polymeric pillars are used in polymer based microfluidic devices (such as PMMA) for the blood filtration. In this study, we have fabricated carbon nanotube (CNT) pillars on silicon from 20-50 μm in diameter with ˜10 μm spacing and integrate them inside the microfluidic channel with a view of using these for blood plasma filtration from whole blood, with passive capillary flow. Our main objective is to design a novel sensor, comprising CNT arrays, to filter/control whole blood flow, with an integrated micro patterned gold electrode which will be sealed by bonding into microfluidics structures. We have characterized the microfluidic channel by measuring the meniscus movement profiles. Also gold inter-digitated electrodes (IDEs) were fabricated on glass and immobilized with an antibody. These IDEs were used as an impedance-based biosensor using label-free antigen – antibody interaction. At a fixed frequency, the IDEs gave a linear response across the range of concentrations of secondary antibodies investigated (0 to 500 μg/mL).

Layer-by-layer (LbL) assembly was used to deposit transparent, highly conductive thin films using aqueous solutions of nanotubes stabilized by deoxycholate (DOC) and poly(diallyl-dimethylammonium chloride) (PDDA). Three different types of carbon nanotubes (CNTs) were used: (1) multi-walled carbon nanotubes (MWNTs), (2) a mixture of single, di- and tri-walled nanotubes (XM grade) and (3) purified HiPCO single-walled carbon nanotubes (SWNTs). SWNTs produced the most transparent (> 85 %T across visible spectrum) and electrically conductive (˜ 150 S/cm) 20-bilayer films with 42 nm thickness. Moreover, optoelectronic performance of SWNT-based thin films was improved with heat treatment due to the removal of PDDA. A 20-bilayer SWNT LbL film achieved a conductivity of 369 S/cm with a 5 min exposure to 400 °C. This study demonstrates the ability of the LbL technique to produce highly transparent and conductive nanotube-based thin films, which may be useful for a variety of large area electronics applications.

Infrared spectroscopy is used to monitor the evolution of CO2 (2330-2350 cm-1) and CO (2050-2200 cm-1) generated during thermal reduction of graphite oxide. The appearance of CO2 at low temperatures (≤200°C) is associated with oxygen removal in species such as anhydrides, esters, lactols, carboxylic acids and lactones either at the edges or in the distorted basal plane of the GO sheets. At higher temperatures (250°C-750°C), release of CO is observed and may be due to decomposition of CO2 or oxygen-containing species like ethers, carbonyls, phenols or quinones. Observation of these gases is possible in multilayer GO because they are trapped in between the interlayer spacing of GO stacks for a time sufficient for detection.

We have fabricated top-gated field effect transistors (FETs) using graphene synthesized by chemical vapor deposition directly on a SiO2/Si substrate without using any transferring processes. Graphene was synthesized on an Fe catalyst film on the substrate at 650°C. The catalyst film was then etched after both ends of the graphene were fixed by source and drain electrodes, leaving the graphene channel connecting the two electrodes. Top-gated FETs were then made by covering graphene channels with HfO2 and depositing top electrodes. The drain current was successfully modulated by the gate voltage and exhibited the bipolar behavior that is characteristic of graphene. Also, it has been shown that graphene channels can sustain an electric current with a density of 107–108 /cm2. Our newly developed fabrication process paves a way to fabricate graphene transistors all over large substrates including Si and glass.

Conductive Atomic Force Microscopy was applied to study the lateral uniformity of current transport at the interface between graphene and 4H-SiC, both in the case of epitaxial graphene (EG) grown on the Si face of 4H-SiC and in the case of graphene exfoliated from HOPG and deposited (DG) on the same substrate. This comparison is aimed to investigate the role played by the C-rich buffer layer present at EG/4H-SiC interface and absent in the case of DG/4H-SiC. The distribution of the local Schottky barrier heights at EG/4H-SiC interface (ΦEG) was compared with the distribution measured at DG/4H-SiC interface (ΦDG), showing that ΦEG (0.36±0.1eV ) is ˜0.49eV lower than ΦDG (0.85 ± 0.06eV). This difference is explained in terms of the Fermi level pinning ˜0.49eV above the Dirac point in EG, due to the presence of positively charged states at the interface between the Si face of 4H-SiC and the buffer layer.

Carbon nanotube (CNT) has emerged as potential candidate for replacement of conventional metal patch in antenna application. The principal objective of our research is to develop nanostructured flexible patch antenna array for multi- frequency operation in industrial, scientific and medical (ISM) band. Patch antenna design using CNT on flexible cotton sheets has been simulated with cotton as a substrate and CNT as conductive patch and ground plane. Due to high conformability and conductivity of CNT all antenna parameters like VSWR, return loss, gain and radiation pattern obtained using FEKO EMSS software meet design criteria. Our simulated antenna design shows a return loss less than -10 dB and VSWR less than 2 at 2.06 GHz, 2.38 GHz and 2.49 GHz. We have also simulated a versatile and conformable antenna design where the whole geometry is rolled up like patch array on cylindrical surface. Conformability to curved surfaces and integration with the structure brings about a unique antenna design. An inset fed square patch array is also proposed for RF energy harvesting operating in the 2.45 GHz ISM band that can harvest and store energy from the surrounding environment. Simulation result shows that dc voltage of 0.215 V can be achieved at -6 dbm received energy level at 2.45 GHz IEEE 802.11b band. This would correspond to potential working distance of 10m.