Tuning the properties of quantum nanocrystals and magnetic nanoparticles using spherical ligands: carboranes and metallacarboranes.

Abstract

The research presented in this thesis has been summarized as a compendium of articles published and to be published in the future. There are five chapters dealing with the results and discussions. The results and discussions are preceded by a general introduction and objectives. The summary of each chaper of the results is given below. The 1st chapter deals with aqueous quantum dots (QDs) capped with meta-carboranyl phosphinate which gives us a brand new architecture of QDs named as core-canopy QDs. This is the first time spherical ligands have been experimentally used to cap QDs. Due to this architecture, we obtained a new luminescence property in these QDs, called the kinetic fluorescence switching (KFS) which has never been reported before. It is a new phenomenon in which the luminescence fades with time but upon application of kinetic energy regains the full intensity of emission. These core-canopy QDs can trap anions and act like capacitors, they are compared with other QDs and characterized. The next chapter deals with synthesis of QDs in water using a new set up developed by us. It produces QDs with high PL, QY and longer lifetime of emission in water medium. The set up used is different to the reflux based method used to synthesize QDs in water at 100oC. Here we used a cork insulated sand bath, with ace pressure tubes of glass. The QDs are generated in these pressure tubes at 150oC under autogeneous pressure produced by the tubes. They have been compared to the traditional water based QDs and charaterized. These QDs combine the advanatge of high QY and different luminescence colours of organometallic synthesized QDs and the easy and cheap production of a water based synthesis. The next chapter deals with quantum nanocrystals (QNCs) being synthesized in water for the first time. We have demonstrated an easy synthetic route and setup design using which quantum rods (Qrods) and quantum rings (QRs) can be easily synthesized in a water medium. This is the first time that this has been experimentally synthesized and studied. These QNCs could be easily stored in powdered form, remain suspended in various solvents for more than 18 months, without degradation in their colloidal stability or luminescence properties. Moreover, they can be used to form nancomposites using polymers. These polymeric films containing the QNCs showed luminescence which lasted over a year and could also show electroluminescence, hence making them viable for QLED applications in the future. The 4th chapter of the results and discussions deals with magnetic nanoparticles (MNPs) coated with meta-carboranyl phosphinate. These give rise to new nano-hybrids which can be used for biological application of boron neutron capture therapy (BNCT). These nanohybrids have been synthesized, characterized and used in biological applications. Their magnetic properties and stability has been studied after autoclave sterilization, further their colloidal stability in different biological culture mediums has also been studied. Then their cellular uptake has been studied and quantified. The uptake of the MNPs by the glioblastoma tumor cells has been visualized and also studied in vivo for BNCT applications. Finally, the last chapter deals with the synthesis of MNPs and coating with inorganic silica shell. These coated MNPs are further functionalzied with amino and carboxylic groups for them to be attached with antibodies for biosensing applications. MWCNTs are also used in conjugation with these MNPs to generate magnetic nanocomposites (MNCs). Both the MNPs and MNCs are used to generate for the first time a non-bonded complex with H[COSAN]. H[COSAN] being a redox specie can be used to manipulate the HOMO-LUMO levels, thus enabling these MNPs and MNCs as effective sensing layer materials.

Date of Award	12 Sept 2019
Original language	English
Supervisor	Francesc Teixidor Bombardó (Director), Clara Viñas Teixidor (Director) & Joan Suades Ortuno (Tutor)