BODIPY dyes for singlet oxygen and optical limiting applications
- Authors: Harris, Jessica
- Date: 2018
- Subjects: Photosensitizing compounds , Active oxygen -- Physiological effect , Photochemotherapy , Cancer -- Treatment , Nonlinear optics , BODIPY (Boron-dipyrromethene)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/58002 , vital:27014
- Description: A series of structurally related BODIPY dyes were synthesised and characterised. Their photophysical properties were studied in order to determine whether they would be suitable candidates for use as photosensitisers in the photodynamic therapy (PDT) treatment of cancer. The synthesis of two highly fluorescent BODIPY cores was achieved via the acid-catalysed condensation of a pyrrole and a functionalised aldehyde. In order to promote intersystem crossing, and hence improve the singlet oxygen generation of these dyes, bromine atoms were added at the 2,6-positions of the BODIPY core. These dibrominated analogues showed good singlet oxygen quantum yields, and excellent photostability in ethanol. In order to red-shift the main spectral bands of the BODIPY dyes towards the therapeutic window, vinyl/ styryl groups were introduced at the 3-, 5-, and 7-positions via a modified Knoevengal condensation reaction. The addition of vinyl/ styryl groups to the BODIPY core caused an increase in fluorescence quantum yield as well as a decrease in singlet oxygen quantum yield with respect to the dibrominated analogues. However, two of the red-shifted BODIPY dyes still showed moderate singlet oxygen quantum yields. The use of BODIPY dyes in nonlinear optics (NLO) was explored. The nonlinear optical characterisations and optical limiting properties of a series of 3,5-dithienylenevinylene BODIPY dyes were studied, both in dimethylformamide (DMF) solution and when embedded in poly(bisphenol A carbonate) (PBC) as thin films. The 3,5-dithienylenevinylene BODIPY dyes showed typical nonlinear absorption behaviour, with reverse saturable absorption (RSA) profiles, indicating that they have potential as optical limiters. The second-order hyperpolarizability (Y), and third-order nonlinear susceptibility (/m[/(3)]) values are also reported for these dyes. The optical limiting values of one of the BODIPY dyes in solution, and two of the BODIPY-embedded PBC films, were below the maximum threshold of 0.95 J-cm-2. The effect of addition of substituents on the electronic structure of the BODIPY dyes was investigated using TD-DFT calculations. The calculated trends closely followed those determined experimentally.
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- Date Issued: 2018
Donor-acceptor effects on the optical limiting properties of BODIPY dyes
- Authors: Hlatshwayo, Zweli Thabiso
- Date: 2018
- Subjects: Dyes and dyeing -- Chemistry , Photosensitizing compounds -- Therapeutic use , Cancer -- Photochemotherapy , Upconversion nanoparticles (UCNPs)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63368 , vital:28397
- Description: The main objectives of the research described in this thesis were firstly to synthesize and characterize a series of structurally related BODIPY dyes that are potentially suitable for use in applications, secondly to conjugate a carboxylic acid substituted BODIPY dye to amine-functionalized upconversion nanoparticles (UCNPs) through an amide bond to enable singlet oxygen production upon irradiation at 978 nm in the biological window for tissue penetration for biomedical applications, and thirdly to compare the nonlinear optical (NLO) properties of various BODIPY dyes to determine whether push-pull effects enhance their utility for optical limiting (OL) applications. Halogenated BODIPY cores with high singlet oxygen quantum yields were prepared, which absorb in the green portion of the visible region and making it difficult to treat deeper skin tumors in the context of photodynamic therapy (PDT) applications. UCNPs generally absorb in the near-infrared (NIR) region (978 nm), and this is advantageous because, this is where absorption by water, cells and tissues is minimized. NaYF4: Yb/Er/Gd UCNPs were synthesized, amine functionalized and successfully conjugated to a halogenated carboxylic acid functionalized BODIPY. This allowed for favorable Förster resonance energy transfer (FRET) since one of the emission wavelengths of the NaYF4: Yb/Er/Gd UCNPs overlaps with the main absorption band of the BODIPY at 540 nm. The conjugate was irradiated at 978 nm, but instability of the BODIPY dye was observed, which made singlet oxygen quantum yield determination impossible. An enhanced singlet oxygen quantum yield value was observed upon irradiation of the conjugate at 540 nm, suggesting that further studies of this system are warranted. The OL properties of BODIPY cores and dyes, which are π-extended at the 3,5-positions with styryl groups, were studied in a series of different organic solvents at 532 nm by using the z-scan technique on a nanosecond timescale. Many of the dyes were used to compare the effects of introducing electron donor and acceptor groups on the OL properties of the dyes. The dipole moments of these dyes were found to correlate with the OL response. The OL results indicate that BODIPY dyes with push-pull properties, which are π-extended at the 3,5-positions with styryl groups, can be considered as viable candidates for use in OL applications. The studies sought to establish the effect of ESA in the triplet manifold as compared to the singlet manifold in as far as the OL response is concerned. The most promising dyes were embedded in polystyrene thin films, and this was found to significantly enhance their OL properties.
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- Date Issued: 2018