Graphene based materials: Past, present and future

Graphene oxide: preparation, functionalization, and electrochemical applications.

Graphene, a two-dimensional, single-layer sheet of sp(2) hybridized carbon atoms, has attracted tremendous attention and research interest, owing to its exceptional physical properties, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Other forms of graphene-related materials, including graphene oxide, reduced graphene oxide, and exfoliated graphite, have been reliably produced in large scale. The promising properties together with the ease of processibility and functionalization make graphene-based materials ideal candidates for incorporation into a variety of functional materials. Importantly, graphene and its derivatives have been explored in a wide range of applications, such as electronic and photonic devices, clean energy, and sensors. In this review, after a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.

Graphene-Based Materials: Synthesis, Characterization, Properties, and Applications

Recent advances in graphene-based biosensors

Graphene has proved to be an excellent nanomaterial for applications in electrochemistry. We review progress in constructing high-performance electrochemical sensors and biosensors. We also discuss: different routes for graphene fabrication; graphene-modified electrodes and graphene-composite electrodes for sensing, including those based on ionic liquids; incorporation of biorecognition elements into graphene-based electrodes; and, graphene-supported electrocatalytic nanoparticle-based electrochemical sensors and biosensors.

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Graphene for electrochemical sensing and biosensing

A novel and facile technique for the rapid synthesis of few layered graphene sheets via hydrogen induced reduction–exfoliation of graphite oxide at a low temperature of ∼200 °C is reported.

Graphene synthesis via hydrogen induced low temperature exfoliation of graphite oxide

Amperometric glucose biosensors have been fabricated by using platinum–gold (Pt–Au) and gold (Au) nanoparticle spacers decorated graphene nanosheets. Functionalized graphene (f-G) sheets have been prepared by exfoliation of graphitic oxide and it has been decorated with crystalline (Pt–Au)/Au metal nanoparticles using a simple chemical reduction method. The immobilization of glucose oxidase (GOD) over Nafion-solubilized metal nanoparticles dispersed graphene f-G-(Pt–Au) and f-G-(Au) electrode has been achieved by physical adsorption. The resultant bioelectrode retains its biocatalytic activity and offers fast and sensitive glucose quantification. The performances of the biosensor have been investigated by electrochemical method at an optimum potential of +0.8 V in pH 7.0 phosphate buffer. The fabricated f-G-(Au) based glucose biosensor exhibits best sensing performance with a linear response up to 30 mM with an excellent detection limit of 1 μM. The elimination of restacking of f-G by using (Pt–Au) and (Au) nanoparticle spacers resulted in the increase in the surface area and glucose sensing performance.

Metal decorated graphene nanosheets as immobilization matrix for amperometric glucose biosensor

We report for the first time, the synthesis of highly stable exfoliated graphene based nanofluids with water and ethylene glycol as base fluids with out any surfactant and the subsequent studies on their thermal and electrical conductivities. Graphene was synthesized by thermal exfoliation of graphene oxide at 1050 °C in Ar atmosphere. The as-synthesized graphene has been suitably functionalized and further dispersed it in the base fluids without any surfactant. Thermal and electrical conductivities of these nanofluids were measured for varying volume fractions and at different temperatures. An enhancement in thermal conductivity by about 14% has been achieved at 25 °C with deionized water (DI) as base fluid at a very low volume fraction of 0.056% which increases to about 64% at 50 °C. Electrical conductivity measurements for these nanofluids indicate an enormous enhancement at 25 °C for a volume fraction of 0.03%in DI water.

Investigation of thermal and electrical conductivity of graphene based nanofluids

The present work investigates the structural stability, dispersion, viscosity, and convective heat transfer properties of nanofluids based on multiwalled carbon nanotubes (MWCNT). Oxidative acid refluxation on MWCNT was examined for different time periods in order to achieve good dispersibility and thermal enhancement. Structural stability and efficient chemical functionalization was investigated by thermogravimetric analysis. Fourier transform infrared spectroscopy was conducted to ascertain the formation of chemical functional groups on covalently modified MWCNT. Raman band study on oxidized MWCNT was analyzed by Raman scattering measurements. Dispersion of functionalized MWCNT was studied by ultraviolet–visible spectroscopy. Field emission scanning electron microscopy and transmission electron microscopy have been performed to ascertain the structural durableness of nanomaterials in fluids. Viscosity and thermal conductivity behavior of DI water and ethylene glycol based MWCNT nanofluids were studied w...

Investigation of Structural Stability, Dispersion, Viscosity, and Conductive Heat Transfer Properties of Functionalized Carbon Nanotube Based Nanofluids

In the present work we describe a novel synthesis procedure for silver decorated functionalized hydrogen induced exfoliated graphene (Ag/HEG) and preparation of nanofluids using this material. Further, thermal conductivity and convective heat transfer studies are carried out for these nanofluids. A simple chemical reduction method is implemented to synthesize uniformly coated Ag/HEG and characterized by different experimental techniques. Ag/HEG is used for making nanofluids considering the high thermal conductivity of graphene and silver nanoparticles. Ag/HEG has been dispersed in deionized water and ethylene glycol using ultrasonic agitation and proper dispersion is achieved without any surfactant. Thermal conductivity and heat transfer studies on Ag/HEG dispersed nanofluids show an enhancement in the corresponding values compared to the base fluid. The level of enhancement depends on the volume fraction and temperature at which the measurement is performed. Ag/HEG dispersed deionized water based nanofluid shows an enhancement of ∼25% for 0.05% volume fraction at 25 °C. Similarly, the heat transfer coefficient of Ag/HEG based nanofluids also shows a large enhancement compared to the base fluid. The synthesized nanofluid is stable for more than three months.

Tessy Theres Baby

Papers

Graphene synthesis via hydrogen induced low temperature exfoliation of graphite oxide

Metal decorated graphene nanosheets as immobilization matrix for amperometric glucose biosensor

Investigation of thermal and electrical conductivity of graphene based nanofluids

Investigation of Structural Stability, Dispersion, Viscosity, and Conductive Heat Transfer Properties of Functionalized Carbon Nanotube Based Nanofluids

Synthesis and nanofluid application of silver nanoparticles decorated graphene