Biosensors are instrumental in the detection of analytes in a wide range of areas including enzyme kinetics and disease diagnosis. A proof-of-principle upconversion nanophosphor (UCNP) based biosensor based on luminescence energy transfer between UCNPs, acting as the energy transfer donor, and enzymes and biologically relevant proteins, the energy transfer acceptor is reported here. Analyte detection has been performed by ratiometric sensing by monitoring the change in the multiple emission bands of the UCNPs. Chapter 1 is an introduction into the emerging field of UCNPs as biosensing agents. These nanoparticles offer numerous advantages over current biosensing agents (namely organic dyes and quantum dots) including resistance to photobleaching and photoblinking, long emissive lifetimes, a large anti-Stokes' shift and near infrared (nIR) excitation to eliminate autofluoresence, and multiple characteristic emission bands for sensing multiple analytes. Chapter 2 describes the synthesis and characterisation of Yb3+/Tm3+ and Yb3+/Er3+ co-doped UCNPs via a range of different preparative methods; thermal decomposition, microwave irradiation and a one-step solvothermal process to produce hydrophilic UNCPs. In addition, commercial UCNPs, kindly donated by Phosphor Technology, were also characterised and used as a benchmark for characterisation of the newly synthesised UCNPs. Chapter 3 describes the detection of the enzyme pentaerythritol tetranitrate reductase (PETNR), through energy transfer between the commercial Yb3+/Tm3+ doped UCNPs and the enzyme using ratiometric sensing. These proof-of-principle results were published in Dalton Transactions. In addition, ratiometric change of the UCNP emission bands was able to monitor the enzyme-substrate turnover in a two electron redox reaction. Chapter 4 describes techniques for increasing the scope and sensitivity of the proof-of-principle UCNP-enzyme biosensing system. Small, hydrophilic Yb3+/Tm3+ and Yb3+/Er3+ doped UCNPs, synthesised in chapter 2, were able to detect glucose oxidase and cytochrome c, in addition to PETNR. Covalent attachment of PETNR to Yb3+/Tm3+ doped UCNPs was additionally achieved. Chapter 5 describes the incorporation of UCNPs into optical ring resonators (ORRs) in order to develop a lost cost, label-free, rapid response biosensor. Drop casting and inkjet printing methods for the deposition of UCNPs onto these devices were investigated and emission of UCNPs was achieved, for the first time, by ORR excitation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:728224 |
| Date | January 2017 |
| Creators | Oakland, Chloe |
| Contributors | Natrajan, Louise |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/lanthanide-upconversion-nanophosphors-as-platforms-for-luminescent-biosensing-applications(5a40bf86-83bb-455e-93c9-7ac488955c45).html |
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