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Identifier 000452389
Title 1. Synthesis of perovskite nanoparticles and evaluation of their cytotoxicity 2. Room temperature synthesis of hydrophilic, highly-fluorescent metal halide perovskite nanocrystals for biomedical applications
Alternative Title 1. Σύνθεση περοβσκιτικών νανοσωματιδίων και αξιολόγηση της κυτταροτοξικότητάς τους 2. Σύνθεση σε θερμοκρασία δωματίου υδρόφιλων, υψηλού – φθορισμού μεταλλικών νανοκρυστάλλων περοβσκίτη αλογονιδίου για βιοϊατρικές εφαρμογές
Author Σπληνάκη, Μαρκέλλα
Thesis advisor Στρατάκης, Εμμανουήλ
Reviewer Βαμβακάκη, Μαρία
Ρανέλλα, Ανθή
Abstract

1st Inorganic semiconducting nanocrystals are unique materials with interesting optoelectronic properties for various applications. Their unique size- and shape- dependent properties together with their easy colloidal synthesis render them promising materials for multiple applications in photonics and energy storage or conversion. Over the last five years, metal halide perovskite nanocrystals, a new material family which has the formula ABX3, where the cation “A” occupies the corner positions of the unit cell, cation “B” is situated at the center of the cell and anion “X” (X= F, Cl, Br and I) located at the unit cell faces, seems to exist in some of these applications. Some of the important features that make the metal halide nanocrystals important nanoscale materials are: i) they have crystal structure that is tolerant to defects, ii) they present a narrow and symmetric FWHM, iii) they present a low rate of non-radiative recombination and thus high PL quantum yield (PLQY), iv) they present a long free-carrier diffusion length, v) they have an easy-tunable bandgap and v) are able to emit to all visible spectrum with low fluorescence blinking. Despite of the important features of the metal halide nanocrystals, they have also some important drawbacks. Their instability in aqueous dispersions is one of them, limiting their application in non-biological applications. This master thesis aims to contribute to this research field. Its main scope is to fabricate stable hydrophilic perovskite nanocrystals well dispersed in aqueous media using room temperature protocols. The metal halide nanocrystals will be covered with a silica shell and these core-shell particles will be used in imaging of cells exploiting their fluorescence properties. More specifically, the first part of this thesis will include the development of stable CsPbBr3@SiO2 nanocrystals in aqueous environment. Ligand-assisted re-precipitation (LARP) colloidal method will be used for the synthesis of the core-shell structures and different silica precursors will be evaluated in order to obtain the optimum robust silica shell that fully covers the CsPbBr3 perovskite-cores. Then the stability of these core-shell nanocrystals in water will be proved through the optical characterization (PL and absorbance spectroscopies) in successive time intervals. Transmission Electron Microscopy (TEM) will be used for the determination of the morphological and structural features of the nanocrystals, while the x-ray diffraction (XRD) will be carried out to characterize the crystallinity and quality of the nanocrystals. Then in the second part of the thesis the toxicity of the core-shell nanocrystals and their imaging capability will be investigated.

2nd. Inorganic semiconducting nanocrystals are unique materials with interesting properties that are size- and shape- dependent and in combination with their easy colloidal synthesis render them promising tools for multiple applications. Recently, metal halide perovskite nanocrystals, a new material family which has the formula ABX3, where the cation “A” occupies the corner positions of the unit cell, cation “B” is situated at the center of the cell and anion “X” (X= F, Cl, Br and I) located at the unit cell faces, have gained attention for their potential medical applications in the fields of bio-imaging, bio-sensing and drug delivery. Since metal halide nanocrystals offer important advantages compared to the established methods of the aforementioned fields due to their unique features: i) their crystal structure is defect tolerant, ii) they present a low rate of non-radiative recombination and thus high photoluminescence (PL) quantum yield (PLQY) and narrow and symmetric PL FWHM, iii) they present a long free-carrier diffusion length, iv) their bandgap can be tuned easily and v) are able to emit in all the visible spectrum with low fluorescence blinking. Despite of the important optoelectronic properties of the metal halide nanocrystals, they also present significant drawbacks. Their instability in aqueous dispersions and biological buffers of different pH are some of them that lead to serious cytotoxicity issues, limiting their use in medical applications. An effective way to overcome these issues is the encapsulation of the fluorescent nanocrystals into an inert silica (SiO2) shell which is non-toxic and transparent to the visible. This master thesis aims to contribute to this research field. Its main scope is to fabricate stable hydrophilic perovskite nanocrystals well dispersed in aqueous and biological media using room temperature protocols. More specifically, this thesis will include the development of stable CsPbBr3@SiO2 nanocrystals in aqueous environment. Ligand-assisted re-precipitation (LARP) colloidal method will be used for the synthesis of the core-shell structures and two different silica precursors will be investigated in order to obtain a robust SiO2 shell around the perovskite cores (CsPbBr3). The proposed precursors are: a) TMOS (Si(OCH3)4) in which the hydrolysis takes place rapidly in four directions (-OCH3) resulting in a denser matrix and b) MPTMS (HS(CH2)3Si(OCH3)3) with two functional groups, the -OCH3 (hydrolysis -> denser shell) and –SH (-PbS bond -> stability between the shell and the core).The optimum precursor quantities as well as the appropriate order of the precursors injection in the reactant solution will be investigated. Then the stability through the time of the-perovskite-based core-shell nanocrystals in water and biological media will be studied through Photoluminescence spectroscopy. The degradation mechanism of the nanocrystals in the aqueous-based dispersions will be explored in order to improve the initially-synthesized core-shell nanocrystals. Transmission Electron Microscopy (TEM) will be used for the determination of the morphological and structural features of the nanocrystals, while the X-ray diffraction (XRD) will be carried out to characterize the crystallinity and quality of the nanocrystals. In a later stage, the cytotoxicity and the imaging capability of the optimum nanocrystals in terms of fluorescence and stability will be considered.

Language English, Greek
Issue date 2022-12-07
Collection   School/Department--School of Medicine--Department of Medicine--Post-graduate theses
  Type of Work--Post-graduate theses
Permanent Link https://elocus.lib.uoc.gr//dlib/0/5/3/metadata-dlib-1673432601-149382-16035.tkl Bookmark and Share
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Synthesis of perovskite nanoparticles and evaluation of their cytotoxicity

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Room temperature synthesis of hydrophilic, highly-fluorescent metal halide perovskite nanocrystals for biomedical applications

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It won't be available until: 2025-12-07