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Graphene and ZnO Nanostructures for Nano- Optoelectronic & Biosensing Applications
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
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: urn:nbn:se:liu:diva-78697ISBN: 978-91-7519-869-9 (print)OAI: oai:DiVA.org:liu-78697DiVA: diva2:534778
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
List of papers
1. Polycation stabilization of graphene suspensions
Open this publication in new window or tab >>Polycation stabilization of graphene suspensions
2011 (English)In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 6, no 493Article in journal (Refereed) Published
Abstract [en]

Graphene is a leading contender for the next-generation electronic devices. We report a method to produce graphene membranes in the solution phase using polymeric imidazolium salts as a transferring medium. Graphene membranes were reduced from graphene oxides by hydrazine in the presence of the polyelectrolyte which is found to be a stable and homogeneous dispersion for the resulting graphene in the aqueous solution. A simple device with gold contacts on both sides was fabricated in order to observe the electronic properties.

Place, publisher, year, edition, pages
SpringerOpen, 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-72038 (URN)10.1186/1556-276X-6-493 (DOI)000296254800001 ()
Available from: 2011-11-11 Created: 2011-11-11 Last updated: 2017-12-08Bibliographically approved
2. Controlled Growth of ZnO Nanowires on Graphene surface
Open this publication in new window or tab >>Controlled Growth of ZnO Nanowires on Graphene surface
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Graphene, a perfect two-dimensional (2D) and completely p-conjugated honeycomb network of carbon, can potentially be a platform to serve as a substrate for growth of semiconductor nanostructures. High quality graphene films are prepared by sublimation on semiinsulating SiC grown by high temperature chemical vapor deposition (HTCVD) and on SiO2 by wet chemistry routine. Selective growth of ZnO nanowires (NWs) is performed on the graphene surface by the hydrothermal method. Mechanical stability of the graphene-ZnO heterojunction is tested by a utilizing a very simple technique. 1D ZnO NWs exhibit strong binding with 2D graphene surface and the NWs grown on graphene are of high crystal quality. This result can be very important for realizing the ultimate goal of 3D assembly at the nanoscale. The electrical contact between graphene and ZnO was analyzed by current vs. voltage (I-V) characteristics. The graphene-ZnO junction behaved as a typical metal-semiconductor ohmic contact lacking a contact barrier. These combined graphene-ZnO 3D heterojunction can pave the way for the next-generation of nano and optoelectronic devices.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-78675 (URN)
Available from: 2012-06-18 Created: 2012-06-18 Last updated: 2014-01-15Bibliographically approved
3. Recent progress on growth and device development of ZnO and CuO nanostructures and graphene nanosheets
Open this publication in new window or tab >>Recent progress on growth and device development of ZnO and CuO nanostructures and graphene nanosheets
Show others...
2012 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 6, 2337-2350 p.Article in journal (Refereed) Published
Abstract [en]

Recent progress on the growth of zinc oxide (ZnO), copper oxide (CuO) and graphene nanosheets is presented and discussed. We here restrict the discussion to the hydrothermal low temperature growth regime. In view of this the most critical and important parameters for obtaining nanostructures with desired morphology are discussed and presented. Among all parameters, the temperature and the pH during growth were chosen due to their strong role in affecting the produced nanostructures. The application of this method to non-conventional substrates e. g. paper, is demonstrated. Different devices are fabricated using the grown material and their performance is discussed.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-75118 (URN)10.1039/c1jm15152e (DOI)000299178500001 ()
Available from: 2012-02-21 Created: 2012-02-17 Last updated: 2017-12-07
4. 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
5. Needle-Type Glucose Sensor Based on Functionalized Graphene
Open this publication in new window or tab >>Needle-Type Glucose Sensor Based on Functionalized Graphene
2012 (English)In: Journal of Biosensors and Bioelectronics, ISSN 2155-6210, Vol. 3, no 1Article in journal (Refereed) Published
Abstract [en]

We demonstrate a novel, highly efficient glucose sensor based on functionalized graphene. Glucose oxidase (GOD) immobilization has been apprehendedbythe direct interaction between carboxyl acid groups of the reduced graphene oxide (RGO) and amines of GOD together with the electrostatic interactions existing between the positively charged polymeric ionic liquid (PIL) and GOD. This combined system can provide a favorable microenvironment for the GOD to retain its good bioactivity. The enzyme-coated graphene biosensor exhibited glucose-dependent electrochemical measurements against an Ag/AgCl reference electrode. The resulting sensor show broad range detection, up to 100 mM glucose concentration, with a sensitivity of 5.59 μA/ decade. It was found that glucose biosensor based on functionalized graphene can be seen as an effective candidate for the detection of sugar concentration in clinical diagnoses.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-78677 (URN)10.4172/2155-6210.1000114 (DOI)
Available from: 2012-06-18 Created: 2012-06-18 Last updated: 2014-01-15Bibliographically approved
6. Graphene-based Biosensor for Intracellular Glucose Measurements
Open this publication in new window or tab >>Graphene-based Biosensor for Intracellular Glucose Measurements
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper, we report a novel graphene-based glucose micro sensor for measuring intracellular glucose. A borosilicate glass capillary (0.7 um diameter) is coated first with a graphene ink and then with a graphene-enzyme conjugate. The functional groups, presumably on the edge plane of graphene, assist binding with the free amine terminals of the glucose oxidase enzyme to result in a better immobilization. The as-prepared graphene biosensor exhibits a glucose-dependent electrochemical potential difference versus an Ag/AgCl reference microelectrode. The potential difference is linear over the concentration range of interest (10–1000μM). The measured glucose concentration in human adipocytes by using our graphene based sensor is consistent with reported values of glucose concentration. This device demonstrates a simple technique to measure intracellular glucose concentration.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-78679 (URN)
Available from: 2012-06-18 Created: 2012-06-18 Last updated: 2014-01-15Bibliographically approved
7. Single nanowire-based UV photodetectors for fast switching
Open this publication in new window or tab >>Single nanowire-based UV photodetectors for fast switching
Show others...
2011 (English)In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 6, no 348Article in journal (Refereed) Published
Abstract [en]

Relatively long (30 mu m) high quality ZnO nanowires (NWs) were grown by the vapor-liquid-solid (VLS) technique. Schottky diodes of single NW were fabricated by putting single ZnO NW across Au and Pt electrodes. A device with ohmic contacts at both the sides was also fabricated for comparison. The current-voltage (I-V) measurements for the Schottky diode show clear rectifying behavior and no reverse breakdown was seen down to -5 V. High current was observed in the forward bias and the device was found to be stable up to 12 V applied bias. The Schottky barrier device shows more sensitivity, lower dark current, and much faster switching under pulsed UV illumination. Desorption and re-adsorption of much smaller number of oxygen ions at the Schottky junction effectively alters the barrier height resulting in a faster response even for very long NWs. The NW was treated with oxygen plasma to improve the switching. The photodetector shows high stability, reversibility, and sensitivity to UV light. The results imply that single ZnO NW Schottky diode is a promising candidate for fabricating UV photodetectors.

Place, publisher, year, edition, pages
Springer Science Business Media, 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-69918 (URN)10.1186/1556-276X-6-348 (DOI)000292290700003 ()
Available from: 2011-08-09 Created: 2011-08-08 Last updated: 2017-12-08
8. Screen printed ZnO UV photoconductive sensor on pencil drawn circuitry over paper
Open this publication in new window or tab >>Screen printed ZnO UV photoconductive sensor on pencil drawn circuitry over paper
2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 21, 211104- p.Article in journal (Refereed) Published
Abstract [en]

Many applications require a low-cost and large-scale mode of flexible electronics with reasonably high photoresponse that can be detected without high precision measurement systems. We demonstrate a very easy to fabricate ZnO UV sensor, made on common pencil drawn circuit over a paper. ZnO nanocrystals were extracted in a high throughput via a simple and green route. This sensor is well capable of detecting UV light and demonstrates features comparable to those of made with complex and expensive techniques.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-78686 (URN)10.1063/1.4720179 (DOI)000304489900004 ()
Available from: 2012-06-18 Created: 2012-06-18 Last updated: 2017-12-07Bibliographically approved
9. Electro-optical and Cathodoluminescence properties of low temperature grown ZnO nanorods/p-GaN white light emitting diodes
Open this publication in new window or tab >>Electro-optical and Cathodoluminescence properties of low temperature grown ZnO nanorods/p-GaN white light emitting diodes
Show others...
2010 (English)In: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, ISSN 1862-6300, Vol. 207, no 1, 67-72 p.Article in journal (Refereed) Published
Abstract [en]

Vertically aligned ZnO nanorods (NRs) with a diameter in the range of 160-200 nm were grown on p-GaN/sapphire substrates by aqueous chemical growth technique and white light emitting I diodes (LEDs) are fabricated. The properties of this LED were investigated by parameter analyzer, cathodoluminescence (CL), electroluminescence (EL), and photoluminescence (PL). The I-V characteristics of the fabricated ZnO/GaN heterojunction revealed rectifying behavior and the LED emits visible EL when bias is applied. From the CL it was confirmed that both the ZnO NRs and the p-GaN are contributing to the observed peaks. The observed EL measurements showed two emission hands centered at 450 nm and a second broad deep level defect related emission centered at 630 nm and extending from 500 rim and up to over 700 rim. Moreover, the room temperature PL spectrum of the ZnO NRs/p-GaN reveals an extra peak at the green color wavelength centered at 550 nm. Comparison of the PL, CL, and EL data suggest that the blue and near red emissions in the EL spectra are originating from Mg acceptor levels in the p-GaN and from the deep levels defects present in the ZnO NRs, respectively. The mixture of high and low energy colors, i.e., blue, green, and red, has led to the white observed luminescence.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-54058 (URN)10.1002/pssa.200925393 (DOI)000274280900010 ()
Available from: 2010-02-22 Created: 2010-02-22 Last updated: 2014-01-15

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