Design, Synthesis and Technology Development of Polymer Sensors for the Efficient Heavy Metal and Anion Sensing

Samanta, Tapendu (2021) Design, Synthesis and Technology Development of Polymer Sensors for the Efficient Heavy Metal and Anion Sensing. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Tapendu Samanta (14RS072)) 14RS072.pdf - Submitted Version Restricted to Repository staff only Download (8MB)

Abstract

Development of norbornene based polymeric materials for sensing heavy metals and anions is the goal of my research work. The advantages of polymeric probes over monomeric sensors in terms of detection limit, response time, and water solubility have been discussed with proper experimental evidence. The effect of pollution originated from heavy metals such as Hg²⁺, As(III), Fe³⁺, and anions like F⁻ has been discussed in detail in Chapter 1. Also, monitoring systems for the mentioned ions along with different strategies adopted by the scientific community have been listed. In Chapter 2, we targeted F- ion for detection and developed NDNP (monomer) and Poly-NDNP (polymer) using 2,4-dinitrophenyl as the chromogenic moiety. Both these sensors can detect F- ion in the nM range via color change which is beneficial for monitoring the analyte in naked-eye. Excellent selectivity over other competitive ions and sensitivity even in environmental samples suggested the uniqueness of both the monomer and polymer towards the sensing application of F⁻ ion. In chapter 3, we have protected one norbornene based aldehyde system with 1,2- ethanedithiol to produce 1,3-dithiolane moiety which is reactive towards Hg²⁺ as well as CH₃Hg⁺ ions by activating excited-state intramolecular proton transfer (ESIPT) process and showed cyan-green emission. Sensing behavior towards Hg²⁺ and CH₃Hg+ of 1,3-dithiolane based monomer NT has been studied thoroughly to establish the applicability of the probe in DMSO/Water medium. This solubility issue has been solved by introducing pegylated norbornene block with NT and copolymerizes these using rings opening metathesis polymerization (ROMP) technique to synthesize Poly-PEG-NT. Poly-PEG-NT can detect Hg²⁺ in pure water medium with a very low limit of detection (LOD) value. Both NT and Poly-PEG-NT have the capability of monitoring Hg²⁺ in an environmental water sample as well as in living cells also. In chapter 4, we demonstrated a xanthene-based polynorbornene probe, Poly-Nor-FT for exclusive detection of As(III) ion (AsO₂⁻) in water samples using both UV-Vis and fluorescence spectroscopy techniques. Spirolactam ring is the main feature of Poly-Nor-FT for the colorimetric and fluorimetric detection of As(III) ion. Excellent selectivity and sub ppb level detection capability of Poly-Nor-FT encouraged us to explore all possible applications for 'in-field' naked-eye detection of As(III) using polymer-coated paper strips. Also, we have proposed one waveguided plasmonic crystal based metadevice for sensitive detection of As(III) with the help of fano resonance. Similarly, in chapter 4, rhodamine B has been used as the signaling unit and combined with norbornene moiety to synthesis monomer NR. NR has been further polymerized using Grubbs‘ 2nd generation catalyst to produce homopolymer PNR. Both NR and PNR have been established as potential colorimetric and fluorimetric sensory systems for highly selective detection of Fe³⁺ ion in CH₃CN/water medium with very low detection limit compared to permissible protocols. Interestingly, the superiority of PNR in terms of response time has been explored over the monomer NR.

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