The Synthesis And Property Of Fluorescent Silica Cross-linked Micellar Nanoparticles

Photochemistry has developed rapidly. These days, many researchers inphotochemistry field have shifted research focus from single molecular tomuticomponent nanostructures. Muticomponent nanostructures can be used asfunctional materials, which enable complex process (energy transfer, electron transfer,etc.) to occur in this system. Among most of nanostructures, silica cross-linkedmicellar nanoparticles worked as idea scaffolds for constructing multicomponentfunctional nanomaterials due to its unique features, such as ultrasmall nanosize, highwater solubility, nontoxity and good biocompatibility. Silica cross-linked micellarnanoparticles have been used as scaffolds to encapsulate π-conjugated organic dyesfor water-soluble fluorescence materials design. The main achievements in my Ph.D.thesis are shown as follows.The first part demonstrated that water-soluble fluorescent hybrid materials can besuccessfully synthesized by using silica cross-linked micellar nanoparticles (SCMNPs)as scaffolds to encapsulate fluorescent conjugated dyes for pH sensing, porphyrinsensing and tunable colour emission. Three dyes were separately encapsulated insideSCMNPs (dye-SCMNPs). Each of the dye-SCMNPs indicated longer lifetime inwater than that of free dye dissolved in organic solvent. The7-(hexadecyloxy) coumarin-3-ethylformate (HCE) encapsulated inside SCMNPs (HCE-SCMNPs)exhibited fluorescence quenching by pH change in aqueous media. Furthermore, itwas confirmed that the radiative and non-radiative energy transfer processes bothoccurred between HCE-SCMNPs and tetraphenyl-porphyrin (TPP), which were usedto synthesize the water-soluble TPP sensor. Significantly, HCE-SCMNPs doped with5,12-dicotyl-quinacridone (8CQA) and TPP showed water soluble white lightemission (CIE (0.29,0.34)) upon singlet excitation of376nm due to colouradjustment of8CQA and energy transfer from HCE (donor) to TPP (acceptor).The second part demonstrated that luminescent chemosensor based on silicacross-linked micellar nanoparticles (SCMNPs) was design by encapsulating a schiffbase (4E)-4-((10-dodecyl-10H-phenothiazin-7-yl) methyleneamino)-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one (EDDP) for the selective detection of Fe3+. Inthe mixture of acetonitrile and water, the addition of Fe3+/Fe2+to EDDP induced adecrease and a red-shift in fluorescence emission which results from the hydrolysis ofSchiff base. While in aqueous media, EDDP encapsulated inside SCMNPs(EDDP-SCMNPs) shows a high selectively fluorescence quenching by Fe3+. InEDDP-SCMNPs system, the electron transferred from EDDP in the core to Fe3+onthe shell. However, EDDP-SCMNPs showed no sensing ability of Fe2+due to theweak electron-accepting of Fe2+. A strong electron-accepting ability of Fe3+inEDDP-SCMNPs system was verified using UV-absorption, fluorescence emission and3D fluorescence spectra. Significantly, because of the ultrasmall size, nontoxity, highwater solubility and biocompatibility of EDDP-SCMNPs, which can protect theemitting of EDDP in aqueous media, this material exerts promising features inbiological system.In the third part, we first use (4E)-4-(4-(diphenylamino) benzylideneamino)-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one (DBDDP) as a fluorescence turn-on sensor for Fe3+detection in organic solvent. To achieve Fe3+system sensing inaqueous media, DBDDP doped SCMNPs (DBDDP-SCMNPs) and functionalizedSCMNPs (DBDDP-NH2-SCMNPs and DBDDP-SO3H-SCMNPs) are synthesizedusing encapsulation method via electron transfer process. Surface charge ofnanoparticles is used to tune Fe3+fluorescence sensing ability. The sensing abilitiesare following in this order: DBDDP-SO3H-SCMNPs> DBDDP-SCMNPs>DBDDP-NH2-SCMNPs. Electron transfer processes of three nanoparticles areverified by fluorescence emission quenching. The linear correlation betweenquenching intensity and lower concentration of Fe3+was accord to Stern–Volmerequation.Thus, silica cross-linked micellar nanoparticles have been used to encapsulatefluorescent organic dyes for water-soluble sensing. The sensing ability can be adjustedby functionalized SCMNPs. The encapsulating process is easy to build promisingbiocompatibility materials, which can be used in intracellular system.