Room-Temperature Phosphorescence Sensing Of Doped Quantum Dots And Halogen Bond Supramolecular Self-Assembly

Various nanomaterials have been applied in the field of analytical chemistry for achieving the corresponding purposes. The present paper is reported under the research background. We developed novel nanoluminescent and magnetic materials to sense and enrich explosives in environment. At the same time, halogen bond supramolecular architecture was investigated to understand halogen bond interaction mechanism and application to pharmaceuticals analysis.This work combines the synthesis of nanomaterials, the separation and analysis techniques, and self-assembling techniques. The purposes are applying the functional materials in chemical sensors. The major contents are described as follows:1. Room-temperature phosphorescence (RTP) chemosensor and Rayleigh scattering (RS) chemodosimeter dual-recognition probe based on Mn-doped ZnS quantum dotsIn this chapter, combining advantages of quantum dots (QDs) including the chemical modification of functional groups and the installation of recognition receptors at their surfaces with those of phosphorescence such as the avoidance of auto-fluorescence and scattering light, L-Cysteine (L-Cys) capped Mn-doped ZnS QDs have been synthesized and used for RTP to sense and for RS chemodosimetry to image ultratrace2,4,6-trinitrotoluene (TNT) in water. It was found that the L-cys capped Mn-doped ZnS QDs interdots aggregate with TNT species induced by the formation of Meisenheimer complexes (MHCs) through acid-base pairing interaction between L-cys and TNT, hydrogen bonding and electrostatic interaction between L-cys intermolecules. Although the resultant MHCs may quench the fluorescence at430nm, interdots aggregation can greatly influence the light scattering property of the aqueous QDs system, and therefore, dominant RS enhancement at defect-related emission wavelength is observed under the excitation of violet light of Mn-doped ZnS QDs, which is applied in chemodosimetry to image TNT in water. Meanwhile, Mn-doped ZnS QDs also exhibit a highly selective response to the quenching of4T1-6A1transition emission and show a very good linearity in the range of0.0025-0.45uM TNT with detection limit down to0.8nM and RSD of2.3%(n=5).2. Synthesis in aqueous solution and characterisation of a new cobalt-doped ZnS quantum dots as a hybrid ratiometric chemoensorIn this chapter, cobalt (Co2+)-doped (CoD) ZnS QDs are synthesisea in aqueous solution and characterised for the first time. L-Cys ligands on the surface of CoD ZnS QDs can bind TNT to form MHCs mainly through acid-base pairing interaction between TNT and L-cys and the assistance of hydrogen bonding and electrostatic co-interactions among L-cys intermolecules. The aggregation of interdots induced by MHCs greatly influences the light scattering property of the QDs in aqueous solution, and RS enhancement at the defect-related emission wavelengths as well as its left side is observed with the excitation of CoD ZnS QDs by violet light. RS enhancement, combining with the quenching of the orange transition emission induced by TNT anions, results in a change in the ratiometric visualisation of the system being investigated. A novel CoD ZnS QD-based hybrid ratiometric chemosensor has therefore been developed for simple and sensitive analysis of TNT in water. This ratiometric probe can assay down to25nM TNT in solution without interference from a matrix of real water sample and other nitroaromatic compounds.3. Chemosensor and photo-driven enzyme mimetics based on magnetic-room temperature phosphorescent multifunctional nanocompositesIn this chapter, combining magnetic response property of Fe3O4nanoparticles with chemosensory that of QDs, Fe3O4magnetic nanoparticles (MNPs) and Mn-doped ZnS QDs nanocomposites (MNPs/QDs NCs) have been synthesized and used for RTP sensing and for magnetic separation of captured ultratrace TNT in water. Significantly, magnetic-RTP MNPs/QDs NCs can be found as photo-driven enzyme mimetics for degradation of TNT through Haber-Weiss cycle reactions for the first time. Meanwhile, MNPs/QDs NCs exhibit a highly selective response for TNT with detection limit down to4.6nM through the quenching of the4T1-6A1transition emission. By in situ monitoring EPR signals, production of hydroxy radical (OH*) is attributed fundamentally to catalytic reactions occurring at metal ions at the surface of Fe3O4nanoparticles rather than those released from the MNPs into a solution. Importantly, the proposed methods, as well as suitable for detecting the ultratrace TNT, could be used as one of the most promising approaches for developing highly efficient degradation of orangics contaminated waters to generate treated waters which could be easily reused or released into the environment without any harmful effects.4. Mechanism and application of halogen bond in solution indueed fluorescence enhancement and catalyzed I-I cleavageIn this chapter, the strongest XB donor (iodine) and photoinduced electron transfer (PET) molecule (ciprofloxacin, Cip) are selected as objectives to investigate XB in solution under weakly alkaline medium. New UV-vis absorption peaks and fluorescence enhancement are observed with the injection of iodine into ethanol solution of Cip, suggesting the disruption of PET charge separation process through XB interaction. The2:1stoichiometry of XB complex is testified using a modified Benesi-Hildebrand method.1H NMR spectra reveals that iodine molecule can interact with three nitrogen atoms of Cip to form triple XBs when concentration of iodine is far higher than that of Cip, leading to all protons of Cip shift to low field. FT-IR spectra demonstrate that nitrogen atom of imino group is the preferential interaction site of XB. However, the mass spectrometry (MS) information about the complex of Cip and iodine ([Cip+I]) is not caught using electrospray ionization MS (ESI-MS) and even cold-spray ionization (CSI) sources. Theoretical calculation results indicate that the formation of IN XB can not only disrupt the PET charge separation process of Cip to enhance fluorescence but also catalyze the cleavage of iodine molecule (Ⅰ-Ⅰ) to come into being Ⅰ3-XB, which satisfactorily explains the triiodine anion (I3-) observed in crystal, UV-vis titration spectra and MS, and how the four iodine atoms involved in XB self-assembly stably exist.