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You searched for subject:(Fe3O4 TiO2). Showing records 1 – 2 of 2 total matches.

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Indian Institute of Science

1. Chalasani, Rajesh. Functionalized Nanostructures : Iron Oxide Nanocrystals and Exfoliated Inorganic Nanosheets.

Degree: PhD, Faculty of Science, 2018, Indian Institute of Science

This thesis consists of two parts. The first part deals with the magnetic properties of Fe3O4 nanocrystals and their possible application in water remediation. The second part is on the delamination of layered materials and the preparation of new layered hybrids from the delaminated sheets. In recent years, nanoscale magnetic particles have attracted considerable attention because of their potential applications in industry, medicine and environmental remediation. The most commonly studied magnetic nanoparticles are metals, bimetals and metal oxides. Of these, magnetite, Fe3O4, nanoparticles have been the most intensively investigated as they are, non-toxic, stable and easy to synthesize. Magnetic properties of nanoparticles such as the saturation magnetization, coercivity and blocking temperature are influenced both by size and shape. Below a critical size magnetic particles can become single domain and above a critical temperature (T B , the blocking temperature) thermal fluctuations can induce random flipping of magnetic moments resulting in loss of magnetic order. At temperatures above the blocking temperature the particles are superparamagnetic. Magnetic nanocrystals of similar dimensions but with different shapes show variation in magnetic properties especially in the value of the blocking temperature, because of differences in the surface anisotropy contribution. The properties of magnetic nanoparticles are briefly reviewed in Chapter 1. The objective of the present study was to synthesize Fe3O4 nanocrystals of different morphologies, to understand the difference in magnetic properties associated with shape and to explore the possibility of using Fe3O4 nanocrystals in water remediation. In the present study, oleate capped magnetite (Fe3O4) nanocrystals of spherical and cubic morphologies of comparable dimensions (∼10nm) have been synthesized by thermal decomposition of FeOOH in high-boiling octadecene solvent (Chapter 2). The nanocrystals were characterized by XRD, TEM and XPS spectroscopy. The nanoparticles of different morphologies exhibit very different blocking temperatures. Cubic nanocrystals have a higher blocking temperature (T B = 190 K) as compared to spheres (T B = 142 K). From the shift in the hysteresis loop it is demonstrated that the higher blocking temperature is a consequence of exchange bias or exchange anisotropy that manifests when a ferromagnetic material is in physical contact with an antiferromagnetic material. In nanoparticles, the presence of an exchange bias field leads to higher blocking temperatures T B because of the magnetic exchange coupling induced at the interface between the ferromagnet and antiferromagnet. It is shown that in these iron oxide nanocrystals the exchange bias field originates from trace amounts of the antiferromagnet wustite, FeO, present along with the ferrimagnetic Fe3O4 phase. It is also shown that the higher FeO content in nanocrystals of cubic morphology is responsible for the larger exchange bias fields that in turn lead to a higher blocking temperature.… Advisors/Committee Members: Vasudevan, S (advisor).

Subjects/Keywords: Nanostructures; Iron Oxide Nanocrystals; Exfoliated Inorgnaic Nanosheets; Iron Oxide Nanocrystals; Magnetic Nanocrystals; Magnetic Nanoparticles; Magnetic Iron Oxide Nanocrystals; Magnetic Nanoparticles; Surfactant Intercalation; Layered Materials - Delamination; [email protected]; Inorganic Nanosheets; Layered Double Hydroxide; Oleate Capped Magnetite Nanocrystals; Nanotechnology

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Chalasani, R. (2018). Functionalized Nanostructures : Iron Oxide Nanocrystals and Exfoliated Inorganic Nanosheets. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/3463

Chicago Manual of Style (16th Edition):

Chalasani, Rajesh. “Functionalized Nanostructures : Iron Oxide Nanocrystals and Exfoliated Inorganic Nanosheets.” 2018. Doctoral Dissertation, Indian Institute of Science. Accessed January 18, 2021. http://etd.iisc.ac.in/handle/2005/3463.

MLA Handbook (7th Edition):

Chalasani, Rajesh. “Functionalized Nanostructures : Iron Oxide Nanocrystals and Exfoliated Inorganic Nanosheets.” 2018. Web. 18 Jan 2021.

Vancouver:

Chalasani R. Functionalized Nanostructures : Iron Oxide Nanocrystals and Exfoliated Inorganic Nanosheets. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2018. [cited 2021 Jan 18]. Available from: http://etd.iisc.ac.in/handle/2005/3463.

Council of Science Editors:

Chalasani R. Functionalized Nanostructures : Iron Oxide Nanocrystals and Exfoliated Inorganic Nanosheets. [Doctoral Dissertation]. Indian Institute of Science; 2018. Available from: http://etd.iisc.ac.in/handle/2005/3463

2. Strandqvist, Carl. The Functionalization of Epitaxial Graphene on SiC with Nanoparticles towards Biosensing Capabilities.

Degree: Faculty of Science & Engineering, 2015, Linköping UniversityLinköping University

Graphene has been shown to be very powerful as a transducer in many biosensor applications due to its high sensitivity. This enables smaller surfaces and therefore less material consumption when producing sensors and concequently cheaper and more portable sensors compared to the commercially available sensors today. The electrical properties of graphene are very sensitive to gas exposure why presence of molecules or small changes in concentration could easily be detected when using graphene as a sensing layer. Graphene is sensitive towards many molecules and in order to detect and possibly identify gas molecules the surface needs to be functionalized. The intention of this project was to use nanoparticles (NPs) to further increase sensitivity and specificity towards selected molecules and also enable biofunctionalization of the NPs, and by that tune the electrical properties of the graphene. This study proposes the use of Fe3O4 and TiO2 NPs to enable sensitive detection of volatile gases and possibly further functionalization of the NPs using biomolecules as a detecting agent in a liquid-phasebiosensor application. The interaction between graphene and NPs have been investigated using several surface charactarization methods and electrical measurements for detection of gaseous molecules and also molecules in a liquid solution. The characterizing methods used are XPS, AFM with surface-potential mapping and Raman spectroscopy with reflectance mapping in order to investigate the NPs interaction with the graphene surface. Sensors where manufactured for gas-phase detection of CO, formaldehyde, benzene and NH3 specifically and display differences in sensitivity and behavior of the Fe3O4 and TiO2 NPs respectively. For liquid measurements the difference in behavior in two buffers was investigated using an in-house flow-cell setup. The surface charecterizing measurements indicated that just a small difference could be found between the two NPs, however a significant change in sensor response could be detected as a function of coverage. The liquid and gas-phase measurements rendered information on differences in sensitivity between the NPs and between analytes where TiO2 showed a higher level of sensitivity towards most of the gases investigated. Both Fe3O4 and TiO2 NP coated graphene showed capability to detect formaldehyde and benzene down to 50 ppb and 5 ppb respectively. The sensitive gas detection could help protecting individuals being exposed to a hazardous level of volatile gases if concentrations increase rapidly or at a long term exposure with lower concentrations, improving saftey and health where these gases are present.

Subjects/Keywords: Graphene; Epitaxial; Silicon carbide; SiC; Nanoparticles; NPs; TiO2; Fe3O4; Functionalization; Gas sensing; CO; CH2O; C6H6; NH3; Carbon monoxide; Formaldehyde; Benzene; Ammonia; WHO; Hollow cathode; plasma sputtering; AFM; XPS; Raman spectroscopy; Surface characterization; Surface potential; Biosensor; Biosensing

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Strandqvist, C. (2015). The Functionalization of Epitaxial Graphene on SiC with Nanoparticles towards Biosensing Capabilities. (Thesis). Linköping UniversityLinköping University. Retrieved from http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-120502

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Strandqvist, Carl. “The Functionalization of Epitaxial Graphene on SiC with Nanoparticles towards Biosensing Capabilities.” 2015. Thesis, Linköping UniversityLinköping University. Accessed January 18, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-120502.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Strandqvist, Carl. “The Functionalization of Epitaxial Graphene on SiC with Nanoparticles towards Biosensing Capabilities.” 2015. Web. 18 Jan 2021.

Vancouver:

Strandqvist C. The Functionalization of Epitaxial Graphene on SiC with Nanoparticles towards Biosensing Capabilities. [Internet] [Thesis]. Linköping UniversityLinköping University; 2015. [cited 2021 Jan 18]. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-120502.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Strandqvist C. The Functionalization of Epitaxial Graphene on SiC with Nanoparticles towards Biosensing Capabilities. [Thesis]. Linköping UniversityLinköping University; 2015. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-120502

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

.