The use of upconverting nanoparticles to drive organic photoreactions

One of the primary disadvantages of organic photochemistry is the need for high-energy UV light, light that has many detrimental qualities. A viable solution to this problem is the use of upconverting nanoparticles (UCNP) that can locally convert near infrared (NIR) laser light into UV light or visible light of sufficient energy to drive organic photoreactions. In an initial study (Chapter 3), the use of UCNPs to drive both UV and visible light dependent photoreactions with NIR light was demonstrated using 1,2-dithienylethene (DTE) molecular switches functioning as probes. In this study the concept of NIR-to-visible ‘remote-control’ photorelease was also introduced. In a second study (Chapter 4), two multicolour UCNPs were developed. It was demonstrated that by only altering the power-density of the one wavelength NIR excitation source, the photochemistry of two DTE molecular switches could be selectively and bi-directionally driven along its two reaction pathways. In a third study (Chapter 5), fluorescence modulation bioimaging was demonstrated in vivo in C. elegans nematodes. The fluorescence modulation in aqueous medium was achieved by decorating the surface of an UCNP with polyethylene glycol functionalized DTE molecular switches by ‘click’ chemistry. In a fourth study (Chapter 6), multimodal fluorescence modulation of a multicolour UCNP by two DTE molecular switches decorated on the surface of the UCNP was demonstrated. Apart from a greater degree of control in this more advanced system, it is also capable of NIR-to-UV ‘remote-control’ photoswitching. In a fifth study (Chapter 8), the surface of an UCNP was decorated with 3’,5’-dialkoxybenzoin photocages and the concept of NIR-to-UV ‘remote-control’ photorelease for potential use in drug-delivery was demonstrated. In a sixth study (Chapter 9), a fully water dispersible drug-delivery system was synthesized. Unfortunately the system proved impractical due to the choice of both photorelease system and therapeutic payload. In a seventh study (Chapter 10), a donor-acceptor 4-dimethylamino-3’,5’-dimethoxybenzoin photocage with both red-shifted absorbance and a significantly enhanced molar absorbance coefficient was synthesized and its initial and unique photochemistry was studied.