Preparation Of Functional Material Containing Fluorophore And Its Application In Fluorescent Sensing

Heavy metal ions such as Cd²⁺, Hg²⁺, Pb²⁺are very toxic and remain threats to theenvironment and human health. Cations (K+, Ca²⁺, Fe³⁺, Zn²⁺), anions (I-, F-), some aminoacids and biothiols are essential nutrients for normal human growth. Therefore, it is of greatimportance to realize qualitative and quantitative analysis of these substances.In this paper, we prepared some functional material containing fluophore as fluorescentchemosensors for the rapid, sensitive and selective detection of some substances.A facile strategy was employed to create fluorescence resonance energy transfer(FRET)-based ratiometric sensing systems for ferric ion and mercury ion in all-aqueous mediaby using nano-sized poly(ethylene oxide)-b-polystyrene core/corona micelles as the scaffold.Hydrophobic fluorescent dye nitrobenzoxadiazolyl derivative (NBD), which served as theenergy donor, was incorporated into the micelle core during the micelle formation; aspirolactam-rhodamine derivative (SRhB-OH) was chosen as a sensitive and selective sensorfor Fe³⁺ions and was "adsorbed" into the micelle core/corona interface. A highly efficientring-opening reaction of SRhB-OH induced by Fe³⁺generates the long-wavelength rhodamineB fluorophore which can act as the energy acceptor, thus the micelle nanoparticles can serveas the FRET-based ratiometric detection system for ferric ions. The effects of PS block lengthon the ion sensing performance of the micelles were investigated, and it has been found thatthe micelles formed by the copolymer with moderate block length (PEO₁₁₃-b-PS₁₁₅) waspreferable as the scaffold for the FRET system with the detection limit of1M for Fe³⁺.Using the same way, a hydrophobic fluorescein derivative (FLS-C12) as the energytransfer donor and a spirolactam-rhodamine derivative (RhB-CS) as the probe for mercuryions were incorporated into the PEO₁₁₃-b-PS₁₁₅micelle to construct FRET-based ratiometricdetection system for mercury ions, the detection limit is0.1M in water. This sensor is usableboth in water and in some biological fluids. In addition, the nanosized sensing system canreadily permeate through cell membrane and detect the intracellular Hg²⁺level change.A novel strategy for building polymeric film sensors was reported. First, a florescenceresonance energy transfer (FRET)-based dyad was synthesized, of which aspirolactam-rhodamine derivative (SRhB) was utilized as the ion-recognition element for Fe³⁺, and a ring-opening reaction of SRhB induced by Fe³⁺generates the long-wavelengthrhodamine B fluorophore which can act as the energy acceptor, and dansyl moiety was chosenas the donor. The fluorescent dyad was then covalently linked into the poly(vinyl alcohol)(PVA) matrix, forming a ratiometric fluorescent sensing film usable in aqueous media forFe³⁺. This reusable film can be utilized conveniently to achieve real-time sensing in aqueousmedium just like using a test paper. A wide detection range as well as obvious visualobservation was achieved.Due to the dangerous nature of anthrax, the development of a cost-effective, sensitiveand field-portable sensor for the anthrax biomarker---calcium dipicolinate (CaDPA) is ofexceptional significance. Herein, a flexible polymer-film-based ratiometric sensor fordetecting CaDPA was demonstrated. A reference dye and a probe ligand were covalentlyimmobilized onto the film surface through highly efficient "click chemistry" reaction. Theethylenediaminetetraacetic acid (EDTA)-based ligand binds with Eu(III) and serves as theprobe. The presence of CaDPA induces significantly enhanced emission intensity of the probe,and thereby affording the film a ratiometric sensor for CaDPA. This sensor can selectivelydetect CaDPA in water with the detection limit of100nM. This sensor exhibited stronganti-interfering capability, it can be usable in some biological fluids such as urine and serum.we demonstrated a facile strategy to construct a fluorescent turn-on sensor for iodideanion based on a T-Hg(II)-T complex. A fluorescent anthracene-thymine dyad (An-T) wassynthesized, and mercury ion could bind with this dyad to form a complex(An-T-Hg(II)-T-An) and quench the fluorescent emission of the dyad, affording the dyadAn-T a fluorescent turn-off sensor for mercury ions in aqueous media. More importantly,upon addition of iodide anion, mercury ion was extracted from the complex due to theeven stronger binding between mercury ions and iodide anions, leading to the release ofthe free dyad and the restored fluorescence. This fluorescence quenching and recoveryprocess offers the An-T-Hg(II)-T-An complex a fluorescent turn-on sensor for iodideanion with the detection limit of126nM.A pyrene-thymine compound (PyT) was synthesized, then PyT-Hg(II)-TPy complexwas readily obtained, bring two pyrene moieties into close proximity to constitute thepyrene excimers. In the presence of biothiols, due to the even stronger binding between mercury ions with biothiols, the PyT-Hg(II)-TPy excimers were transformed intomonomers as a result of extraction of the mercury ions from the former. Thisexcimer-monomer transformation induced fluorescence variation and afforded thecomplex PyT-Hg(II)-TPy a ratiometric sensor for biothiols. The detection system is quitesensitive (with the detection limit of69nM for GSH), and can be used in such biologicalfluid as urine.