Development of Small Molecule and Responsive Polymer Based Colorimetric and Fluorometric Chemosensors

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In recent years, the design and development of optical molecular probes for detection of toxic
metal ions, anions, reactive species and gases have great interest in the field of chemistry and
biology because of their impact on health and the environment. For instance, the over doses of
toxic metals and anions result dangerous effects to human as well as eco-environment systems
due to their indispensable roles in viral (or physiological) processes. Especially, mercury, iron
and copper most toxic elements consequences most of the horrible diseases. Similarly, low
concentrations toxic anions like fluoride and cyanide ions causes severe effects to human
including the symptoms of dental and skeletal fluorosis, osteosarcoma, convulsion, vomiting and
loss of consciousness. Furthermore, the detection of so called greenhouse gas carbon dioxide has
gain wide interest due to effects to environment such as global warming. Thus, it is very
important to design small molecule/stimuli responsive polymers based probes for selective and
efficient detection of cations, anions and gases. In this thesis, we have developed both small
molecules and responsive polymers based molecular probes for the detection of toxic metal ions,
anions, chemical warfare agents and picric acid by colorimetric /fluorometric detection approach.
Furthermore, it was also investigated tunable sensitivity of responsive polymer probes towards
metal ions, nerve gases and picric acid by operating the external stimuli. The literature reports on
design strategies of small molecular and polymeric probes for the detection of the various
analytes including toxic cations, anions, gases, chemical warfare agents etc. and their detection
methods are widely explained in the introduction chapter 1|Chapter 2 demonstrated the development of azoaniline based small molecular probes for dual
sensing of copper, chemical warfare agents and fluoride ions with two distinct modes of
detection. Two new bifunctional probes were designed, which contain Cu2+-sensitive o-
(phenylazo)aniline, F--sensitive silyl groups and free amine group to provide the reaction site for
the detection of nerve agent mimics (DCP). Absorption and emission studies were conducted to
examine the dual sensing abilities of these probes with the sequential addition of F- followed by
Cu2+ or the sequential addition of DCP followed by Cu2+ and vice-versa. Moreover, it was
investigated that the detection time towards DCP could also be controlled by the cyclization
extent through a changing of the amount of Cu2+ ions that is added.|Chapter 3 emphasized the synthesis and development of pyrene based turn-on fluorescent
polymeric probe for the tunable detection of nerve agent mimics. The newly synthesized
polymeric probe P2 has shown selective turn-on fluorescence response towards detect diethyl
cyanophosphate (DCNP), a nerve agent mimic in both the solution and vapor phase with a
detection limit of 0.1 mM due to DCNP promoted intramolecular N-alkylation. Moreover, the
detection of DCNP was successfully controlled by altering the purging of CO2/N2 gases or tuning
the pH of the solution. P2 showed an efficient ON/OFF reversible fluorescence response towards
CO2 and N2 gases, further helping tunable ON/OFF sensing of DCNP. The CO2-tunable detection
of DCNP was further correlated to the pH-dependent control of detection sensitivity. Thus, these
CO2/pH controllable detection properties can offer new insights into the design of new stimuliresponsive polymeric probes with fluorescence turn-on detection of nerve agent mimics|Chapter 4 included a pyrene based polymeric probe for detection of picric acid in film state as
well as in 100% aqueous media. Interestingly, the polymeric film showed a turn-off fluorescence
signal with the addition of picric acid. A drastic quenching was observed in the emission spectra
of the probe towards increasing the concentration of picric acid due to PET process through
strong electrostatic interaction between picrate anions and quaternary ammonium cations. It is
also important to note that, the detection sensitivity of the film towards picric acid was found in
attogram and also used film could be recycled just by washing out the analyte with water. The
pH- dependent sensing studies revealed that the sensitivity of polymer towards picric acid could
be tuned by changing the pH in both solution and film state.|Chapter 5 contained an azo aniline-based colorimetric polymeric probe for the detection of Fe
(III) metal ions and cyanide ions. After the incremental addition of Fe (III) ions, the probe
showed a blue shift by changing its color from brick red to yellow color, whereas, in presence of
cyanide ions it underwent a bathochromic shift with the color change from brick red to purple.
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울산대학교 일반대학원 화학과
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