Date of Award
Doctor of Philosophy
Dr. Ekkehard Sinn
Dr. Ramakrishna Guda
Dr. Gellert Mezei
Dr. Sherine Obare
Optical, sensors, heavy metals, fluorescent, detection. sensitive
We designed, synthesised, characterized and investigated optical properties of fluorescent and colorimetric chemosensors based on pyrene, anthracene, rhodamine, fluorescein and coumarine dyes for sensing metal ions, anions, and nerve gas mimics. We focused on fluorescent chemosensors because of their high sensitivity, selectivity, operational simplicity, and rapid response. Such small molecule probes are ideal for developing hand-held detectors.
We developed highly sensitive and selective fluorescent and colorimetric sensors to detect fluoride, copper, chromium, iron and tin ions. The bis-pyrene derivative that we developed for the first time for fluoride sensing is highly selective and sensitive giving rise to a new peak in both absorption and emission spectra. The color change from yellow to pink is highly appealing as it uses low-cost, widely available instrumentation and allows naked eye detection. Such features reduce the background interference and false positives and allow rapid and sensitive detection of fluoride ions. The two pyrene based “turn–on” fluorescent probes that we synthesized are highly selective towards copper (Cu2+) with nanomolar sensitivity. The rhodamine-based sensor that we developed for chromium (Cr3+) allows rapid sensitive and selective detection of Cr3+ at nanomolar levels. This “turn-on” fluorescent sensor shows a very clear color change from colorless to dark pink to dark pink upon Cr3+ binding, which allows naked eye detection of Cr3+. For the first time we developed a rhodamine-based multiphoton sensor for sensitive detection of tin (Sn2+), which is useful for biological imaging.
In summary, we developed fluorescent and colorimetric probes for selective and sensitive detection of metal ions and anions. All these probes can be obtained in 1- or 2-step syntheses using relatively cheap chemicals. Therefore production of these probes is fast, easy and low cost. Almost all of these probes show “turn-on” fluorescence and most of them show a very clear color change upon binding with the analyte. Such features allow sensitive detection of analytes. Nonlinear optical properties, such as ability to absorb two photons, make them useful for fabricating nonlinear optical materials and for bio-imaging. These favorable properties render these probes very promising tools to detect biologically, environmentally and industrially important metal ions and anions.
Restricted to Campus until
Madawala, Rathnayaka M. N. R., "Optical Sensors for the Detection of Metals, Fluoride, and other Toxic Species based on various Dye Molecules" (2015). Dissertations. 533.