Polymeric Chemosensors: Synthesis to Application

Abstract

Chapter 2: This research creates a polymeric fluorescent probe (P1) based on difluoroboron dipyrromethene (BODIPY) that can resist very acidic environments. The P1 polymeric probe outperforms small-molecule-based organic pH sensors due to its quick fluorimetric sensitivity to pH changes and excellent water solubility and durability. Protonation of the BODIPY segment's tertiary amine groups prevents photo-induced electron transfer (PET) to the skeleton, causing this drastic pH response. To understand its fluorescence response in acidic pH, E. coli bacteria and in vitro cell imaging are explored. Hypochlorous acid (HOCl) is a vital ROS. Using boron dipyrromethene (BODIPY) and aldoxime units, a polymeric probe (P2) was constructed for colorimetric and fluorometric HOCl detection in pure aquatic conditions. After HOCl treatment, P2 fluoresced with good sensitivity and a low LOD (17 nM). P2 was suitable for field application due to its hydrolytic and photolytic stability and selectivity over other reactive oxygen and nitrogen species. P2, which was non-cytotoxic, imaged HepG2, a human liver cancer cell line. Scientists struggle to identify cyanide (CN¯) in water and cyanogenic foods. Organic probes are water-insoluble, making field use difficult. P3, a novel colorimetric water-soluble polymeric probe for CN¯ detection in pure water, was devised and produced. P3 selectively sensed CN¯ in water at physiological pH by intramolecular charge transfer. CN¯ changed P3's hue from red to yellow (a 57 nm blue shift) at 0.008 mM. Test strips with P3 can be used "in the field" to detect CN¯in aqueous solutions and cyanogenic foods.

Chapter 3: A water-soluble and colorimetrically selective polymeric probe for detecting cyanide ions in pure aqueous media is developed and synthesized. P1 was produced by traditional free-radical polymerization from N,N-dimethylacrylamide, 2-((E)-4-((2-(acryloyloxy)ethyl)(methyl)amino)phenyl)diazenyl) styryl)-1,3,3-trimethyl-3H-indol-1-ium (M1), and N-(4-benzoylphenyl)acrylamide. Spin coating on a quartz slide immobilized P1, which was UV-irradiated. The polymeric film F1 quickly reacted to CN- with a characteristic color shift, increasing its applicability as a cyanide-ion probe beyond the solution phase. Polymer-based thin colorimetric films have garnered a lot of interest as a simple, low-cost option for gas sensing applications. Here, thin polymeric films were developed and employed for the highly sensitive colorimetric detection of a dangerous hydrazine in the vapor phase. To develop a polymeric film for real-time hydrazine vapor tracking, we employed photo cross linkable poly(N,N-dimethylacrylamide-co-azo-dicyano-co-N-(4-benzoylphenyl)acrylamide), abbreviated as P2. Spin-coated P2 on a quartz substrate was irradiated with ultraviolet light to create the heterogeneous film F2. Even at concentrations as low as 10 parts per million (ppm), F2 could detect hydrazine vapor. The system's versatility was demonstrated by the fact that hydrazine could be detected colorimetrically in a range of media, including water and soil types.

Chapter 4: A polymeric chemosensor that detects many physiologically important substances is essential. A cysteine-detectable aldehyde-functionalized azobenzene chain transfer agent, 2-phenylboronic ester methylacrylate (PBA), and N, N'-dimethyl acylamideacrylamide (DMA) were used to synthesize a block copolymer probe (P1). P1 self-assembled micelles in neutral pH water. When cysteine was introduced to the micellar solution, colorimetric detection did not occur because the water-soluble cysteine could not reach the azo-receptor's aldehyde group in the micelles' core. However, glucose swelled the micelles because the PPBA block converted a boronic ester to boronic acid, making it hydrophilic. The azo receptor made cysteine colorimetrically detectable. We detected glucose by titrating P1 solution with glucose at a constant cysteine content. Thus, we provide a new cysteine-glucose detection technology. P2, a poly(ester-amide)-based amphiphilic polymer, is produced for hydrogen sulfide (H2S) detection-triggered burst release of rhodamine from polymeric micelles. The hydrophobic H2S-specific unit (M2) received 6-isocyanohexanoic acid and polyethylene glycol (PEG) dicarboxylic acid by Passerini multicomponent polymerization. P2 self-assembles in water to create polymeric micelles with a hydrophilic PEG shell and a hydrophobic M2 core containing 6-isocyanohexanoic acid. P2 micelles showed selective colorimetric (colorless to yellow) and fluorometric (non-emissive to blue emission) H2S detection in water. 0.09 mM detected. H2S detection caused the polymer backbone to self-destruct, enlarging the micelles and releasing the hydrophobic model drug rhodamine.

Chapter 5: Reliable methods for detecting and separating dangerous heavy metal ions in liquids are essential. In this study, a thermogelling poly(-caprolactone)-poly(ethylene glycol)-poly (PCL-PEG-PCL) triblock copolymer (P1) was synthesized, and a difluoroboron dipyrromethene (BODIPY) fluorophore integrated with thiosemicarbazide units was attached to the chain ends of P1 through consecutive post-polymerization modifications to create P4. P4 used turn-on fluorescence emission to swiftly and selectively detect Hg(II) in 100% aqueous medium at 0.461 µM. A coordination complex between P4 and Hg(II) ions inhibits C=N isomerization and causes turn-on emission. Thermo-controlled sol-gel-dehydrated gel transitions in P4 gels selectively and quantitatively removed Hg(II) from other metal ions. After treating P4 with Na2S in acetone/water at room temperature to form HgS precipitates, it was dried and recycled. Our recyclable thermoresponsive macromolecular probe can detect, separate, and remove Hg(II) from complex aquatic environments.

Chapter 6: Gold (Au) is extremely valuable in a variety of areas; however, its inadequacy increases the desire to recover it from any possible source, such as virgin mines and electronic waste (e-waste). Here we propose a sustainable Au recovery technology from e-waste with high purity and probe recyclability, which is established on selective 1:1 coordination-based colorimetric probes immobilized on the surface of a quartz substrate to form a thin polymeric film (F1). The presence of Au(III) in various e-waste samples was determined via the color changes of F1, and this is used to decide if further Au recovery is lucrative. Thereafter, trace amounts of Au at ultra-high purity (23.97 K) are rapidly recovered (in 10 min) even with approximately 100-fold excess of other metal ions (copper and nickel) commonly found in e-waste without the use of harsh acids, bases, or toxic methods. Au(III)-liberated F1 can be used to further separate Au(III), and this process was repeated for multiple cycles. This study generated and designed fluorescent polymeric hydrogels to trace and recover platinum from spent auto catalysts by selective coordination. These three-dimensional hydrogels were made utilizing a water-soluble polymeric probe [p(DMA-co-M1), P2, where DMA = N,N'-dimethylacrylamide (DMA), M1 = quaternized imidazole with anthracene unit] and N,N'-methylenebisacrylamide as a crosslinker. P2 detected platinum ions at 0.03 mM by fluorescence quenching. P2 hydrogels (HG) detected platinum ions and selectively recovered them from metal ion mixtures because of P2's great sensitivity and selectivity. Used auto catalyst leach liquid hydrogels absorbed 0.2 g platinum/1.0 g hydrogel. Inductively coupled plasma tests showed that the recovered platinum was 95.76% pure and 4.14% palladium. Thiourea regenerated and reused these hydrogels, making them an attractive choice for platinum recovery and circular economy.