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Structural characterization and biocompatible applications of graphene nanosheets for miniaturization of potentiometric cholesterol biosensor
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.ORCID iD: 0000-0001-5365-6140
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2011 (English)In: Journal of Biosensors & Bioelectronics, ISSN 2155-6210, Vol. 2, no 3Article in journal (Refereed) Published
Abstract [en]

The potentiometric cholesterol biosensor based on graphene nanosheets has been successfully miniaturized. Cholesterol oxidase (ChOx) has been immobilized onto graphene nanosheets exfoliated on copper wire through the process of physical adsorption,. The presented potentiometric biosensor renders effective selectivity and sensitivity (~82 mV/decade) for the detection of cholesterol biomolecules in 1 × 10−6 M to 1 × 10−3 M logarithmic range and quick output response within ~ 4 sec. The stability and reusability of the biosensor has also been investigated for the above mentioned range of cholesterol concentrations. The enzyme activity measurements on graphene nanosheets are studied using UV-Visible and FTIR spectrophotometers. Additionally, the functioning of the presented biosensor is studied for a range of temperatures (15-70 °C) and pH values (4-9).

Place, publisher, year, edition, pages
2011. Vol. 2, no 3
Keyword [en]
Graphene nanosheets; Cholesterol; Potentiometric; Biosensor
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-71322DOI: 10.4172/2155-6210.1000109OAI: oai:DiVA.org:liu-71322DiVA: diva2:447371
Note

On the day of the defence day the status of this arcile was "Manuscript".

Available from: 2011-10-11 Created: 2011-10-11 Last updated: 2014-11-24Bibliographically approved
In thesis
1. Chemical fabrication of ZnO nanostructures and their emission properties: Cholesterol biosensing applications utilizing ZnO and Graphene
Open this publication in new window or tab >>Chemical fabrication of ZnO nanostructures and their emission properties: Cholesterol biosensing applications utilizing ZnO and Graphene
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Zinc oxide (ZnO) is an inorganic compound, owing to wide band gap and large binding energy, and holds promising potential in the fields of semiconducting as well as piezoelectric applications with excellent stability and reliability. In addition, ZnO has a plenteous number of nanoscale structures containing unique physical, chemical, electrical, sensing and optical properties. These properties of nanostructures are being unrevealed extensively since last two decades and have become a prominent field of research in nanoscience and nanotechnology.

More specifically, the present dissertation deals with the low temperature synthesis of ZnO nanostructures (nanorods, nanotubes, nanodisks and nanowalls) on a variety of substrates such as silicon, gallium nitride, zinc foil, silver and aluminum; structural characterization and study of their luminescence properties. In paper 1 we investigated the synthesis mechanism of chemically fashioned ZnO nanotubes and their superior emission capability compared to ZnO nanorods with significant enhancements in ultraviolet and visible regions has been studied. These chemically synthesized ZnO nanotubes are further utilized to fabricate a heterostructure with p-GaN thin film in order to achieve white emission (Paper 2). The aim of Paper 3 is to understand the synthesis of ZnO nanorods and their transition into ZnO nanodisks at 55 °C along with temperature dependent micro-photoluminescence studies. However, the second half of the dissertation is devoted to the fabrication of potentiometric cholesterol biosensors through the conjugation of ZnO nanostructures and graphene nanosheets with a thin film of cholesterol oxidase. Paper 4 contains the fabrication of cholesterol biosensor by the deposition of ZnO nanorods on thin silver wire followed by their functionalization under the physical adsorption method. The specificity, reproducibility and stability of the biosensor have been investigated with good linearity slope curve of ~35 mV/ decade. The purpose of papers 5 and 6 is to enhance the sensitivity of the cholesterol biosensor by using ZnO nanowalls and graphene nanosheets as a matrix where the sensitivity of the slope curve is achieved as ~53 and ~82 mV/ decade, respectively.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 67 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1387
Keyword
Zinc oxide, aqueous chemical synthesis, nanostructures, light emitting diode, electrochemical biosensor.
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-71323 (URN)978-91-7393-101-4 (ISBN)
Public defence
2011-09-23, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2011-10-11 Created: 2011-10-11 Last updated: 2014-01-15Bibliographically approved
2. Graphene and ZnO Nanostructures for Nano- Optoelectronic & Biosensing Applications
Open this publication in new window or tab >>Graphene and ZnO Nanostructures for Nano- Optoelectronic & Biosensing Applications
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There has been a remarkable excitement in graphene research since the famous discovery in 2004 by isolating a monolayer with the help of scotch tape. Graphene, merely a single layer of carbon atoms, is progressively making inroads into a wide range of applications, from ballistic electronics to biosensors to flexible/transparent displays. Graphene is a matchless material that is strong, light, transparent, and an excellent conductor of heat and electricity. On the other hand, zinc oxide (ZnO) is a wide band semiconductor that demonstrates excellent electrical, optical, catalytic and sensing properties and has numerous applications in various fields. ZnO is a natural n-type semiconductor due to the presence of intrinsic defects such as Zn interstitials and O vacancies that also contribute strongly to optical emissions in the visible region.

The amalgamation of the exceptional properties of graphene with good semiconducting properties of ZnO can pave the way towards the realization of future devices (LED, biosensors, photovoltaics etc.).

In this thesis, graphene nanosheets and zinc oxide (ZnO) nanostructures have beensuccessfully synthesized by using chemical vapor deposition (CVD), vapor liquidsolid (VLS) or wet chemistry routines. These nanostructures were used to fabricatenano and optoelectronic devices, including field effect transistors (FETs), lightemitting diodes (LEDs), UV detectors and biosensors. Both nanomaterial’s propertiesand performances of the devices have been characterized and reported.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 80 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1458
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-78697 (URN)978-91-7519-869-9 (ISBN)
Public defence
2012-05-29, K3, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:15 (English)
Opponent
Supervisors
Available from: 2012-06-18 Created: 2012-06-18 Last updated: 2014-01-15Bibliographically approved

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Israr, Muhammad Qadirul Hasan, KamranSadaf, Jamil RanaEngquist, IsakNour, OmerWillander, Magnus

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Israr, Muhammad Qadirul Hasan, KamranSadaf, Jamil RanaEngquist, IsakNour, OmerWillander, Magnus
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