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Chemical fabrication of ZnO nanostructures and their emission properties: Cholesterol biosensing applications utilizing ZnO and Graphene
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
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 [en]
Zinc oxide, aqueous chemical synthesis, nanostructures, light emitting diode, electrochemical biosensor.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-71323ISBN: 978-91-7393-101-4 (print)OAI: oai:DiVA.org:liu-71323DiVA: diva2:447380
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
List of papers
1. Trimming of aqueous chemically grown ZnO nanorods into ZnO nanotubes and their comparative optical properties
Open this publication in new window or tab >>Trimming of aqueous chemically grown ZnO nanorods into ZnO nanotubes and their comparative optical properties
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2009 (English)In: APPLIED PHYSICS LETTERS, ISSN 0003-6951, Vol. 95, no 7, 073114- p.Article in journal (Refereed) Published
Abstract [en]

Highly oriented ZnO nanotubes were fabricated on a silicon substrate by aqueous chemical growth at low temperature (andlt; 100 degrees C) by trimming of ZnO nanorods. The yield of nanotubes in the sample was 100%. Photoluminescence spectroscopy of the nanotubes reveals an enhanced and broadened ultraviolet (UV) emission peak, compared with the initial nanorods. This effect is attributed to whispering gallery mode resonance. In addition, a redshift of the UV emission peak is also observed. Enhancement in the deep defect band emission in the nanotubes compared to nanorods was also manifested as a result of the increased surface area.

Keyword
crystal growth from solution, II-VI semiconductors, nanofabrication, red shift, semiconductor growth, semiconductor nanotubes, whispering gallery modes, wide band gap semiconductors, zinc compounds
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-20618 (URN)10.1063/1.3211124 (DOI)
Available from: 2009-09-16 Created: 2009-09-15 Last updated: 2015-03-09
2. White Electroluminescence Using ZnO Nanotubes/GaN Heterostructure Light-Emitting Diode
Open this publication in new window or tab >>White Electroluminescence Using ZnO Nanotubes/GaN Heterostructure Light-Emitting Diode
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2010 (English)In: NANOSCALE RESEARCH LETTERS, ISSN 1931-7573, Vol. 5, no 6, 957-960 p.Article in journal (Refereed) Published
Abstract [en]

We report the fabrication of heterostructure white light-emitting diode (LED) comprised of n-ZnO nanotubes (NTs) aqueous chemically synthesized on p-GaN substrate. Room temperature electroluminescence (EL) of the LED demonstrates strong broadband white emission spectrum consisting of predominating peak centred at 560 nm and relatively weak violet-blue emission peak at 450 nm under forward bias. The broadband EL emission covering the whole visible spectrum has been attributed to the large surface area and high surface states of ZnO NTs produced during the etching process. In addition, comparison of the EL emission colour quality shows that ZnO nanotubes have much better quality than that of the ZnO nanorods. The colour-rendering index of the white light obtained from the nanotubes was 87, while the nanorods-based LED emit yellowish colour.

Place, publisher, year, edition, pages
Springer Science Business Media, 2010
Keyword
ZnO nanotubes, Light-emitting diodes, Electroluminescence, Lightning, White light sources
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-57167 (URN)10.1007/s11671-010-9588-z (DOI)000278096000008 ()
Available from: 2010-06-11 Created: 2010-06-11 Last updated: 2014-09-25
3. Natural oxidation based controlled synthesis and characterization of ZnO nanodisks through structural transition of ZnO nanorods at 55 °C
Open this publication in new window or tab >>Natural oxidation based controlled synthesis and characterization of ZnO nanodisks through structural transition of ZnO nanorods at 55 °C
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

A novel, reproducible and natural oxidation based low temperature (55 °C) synthesis of ZnO nanodisks has been carried out using metallic zinc foil and formamide solution. The concentration of the formamide and the reaction duration are optimized to achieve the controlled fabrication. The morphological evolution of the ZnO nanodisks has been observed using scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy. It is observed that ZnO nanodisks are of a good crystalline quality and have hexagonal wurtzite structure. The mechanism behind the growth and the breaking of nanorods into nanodisks is also suggested. Microphotoluminescence spectrum exhibits a strong ultraviolet emission and a very weak deep level related emission. In addition, temperature dependent studies reveal a decrease in the emission intensity of the ultraviolet peak combined with a red shift with increasing temperature from 20 to 300 K.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-71321 (URN)
Available from: 2011-10-11 Created: 2011-10-11 Last updated: 2014-01-15Bibliographically approved
4. Potentiometric cholesterol biosensor based on ZnO nanorods chemically grown on Ag wire
Open this publication in new window or tab >>Potentiometric cholesterol biosensor based on ZnO nanorods chemically grown on Ag wire
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2010 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 3, 1106-1109 p.Article in journal (Refereed) Published
Abstract [en]

An electrochemical biosensor based on ZnO nanorods for potentiometric cholesterol determination is proposed. Hexagon-shaped ZnO nanorods were directly grown on a silver wire having a diameter of 250 mu m using low temperature aqueous chemical approach that produced ZnO nanorods with a diameter of 125250 nm and a length of similar to 1 mu m. Cholesterol oxidase (ChOx) was immobilized by a physical adsorption method onto ZnO nanorods. The electrochemical response of the ChOx/ZnO/Ag biosensor against a standard reference electrode (Ag/AgCl) was investigated as a logarithmic function of the cholesterol concentration (1 x 10(-6)M to 1 x 10(-2)M) showing good linearity with a sensitivity of 35.2 mV per decade and the stable output signal was attained at around 10 s.

Place, publisher, year, edition, pages
Elsevier Science B.V., Amsterdam., 2010
Keyword
Potentiometric biosensor; Cholesterol; Cholesterol oxidase; Electrostatic immobilization; ZnO nanorods
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-63930 (URN)10.1016/j.tsf.2010.08.052 (DOI)000285075300032 ()
Available from: 2011-01-11 Created: 2011-01-10 Last updated: 2017-12-11
5. Chemically fashioned ZnO nanowalls and their potential application for potentiometric cholesterol biosensor
Open this publication in new window or tab >>Chemically fashioned ZnO nanowalls and their potential application for potentiometric cholesterol biosensor
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2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 25, 253705- p.Article in journal (Refereed) Published
Abstract [en]

Chemically fashioned zinc oxide (ZnO) nanowalls on aluminum wire have been characterized and utilized to fabricate a potentiometric cholesterol biosensor by an electrostatic conjugation with cholesterol oxidase. The sensitivity, specificity, reusability, and stability of the conjugated surface of ZnO nanowalls with thickness of similar to 80 nm have been investigated over a wide logarithmic concentrations of cholesterol electrolyte solution ranging from 1x10(-6)-1x10(-3) M. The presented biosensor illustrates good linear sensitivity slope curve (similar to 53 mV/decade) corresponding to cholesterol concentrations along with rapid output response time of similar to 5 s.

Place, publisher, year, edition, pages
American Institute of Physics, 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-69852 (URN)10.1063/1.3599583 (DOI)000292039900075 ()
Note
Original Publication: M.Q. Israr, J.R. Sadaf, Omer Nur, Magnus Willander, S. Salman and B. Danielsson, Chemically fashioned ZnO nanowalls and their potential application for potentiometric cholesterol biosensor, 2011, Applied Physics Letters, (98), 25, 253705. http://dx.doi.org/10.1063/1.3599583 Copyright: American Institute of Physics http://www.aip.org/ Available from: 2011-08-10 Created: 2011-08-08 Last updated: 2017-12-08
6. Structural characterization and biocompatible applications of graphene nanosheets for miniaturization of potentiometric cholesterol biosensor
Open this publication in new window or tab >>Structural characterization and biocompatible applications of graphene nanosheets for miniaturization of potentiometric cholesterol biosensor
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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).

Keyword
Graphene nanosheets; Cholesterol; Potentiometric; Biosensor
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-71322 (URN)10.4172/2155-6210.1000109 (DOI)
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

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