Enhanced Aggregation-state Fluorescence Technique For Three-dimensional And Macroscale Visualization Of Materials

Fluorescence visualization technique based on confocal laser scanning microscopy(CLSM)has become an important research tool in the fields of chemistry,material and biology.Three scientists were awarded with the 2014 Nobel prize for chemistry because of their outstanding contributions in developing super-resolution confocal microscopy.This event marked the milestone in the development of fluorescence visualization technique.The quick,non-invasive and high-contrast imaging ability of fluorescence visualization technique make it possible to replace the traditional visualization technique for material characterization in some cases.At present,the most commonly used apparatus for fluorescence visualization technique is confocal laser scanning microscopy(CLSM).The scanning range of CLSM is up to several hundred micrometers,which could be applied to macroscle imaging.In addition,the optical sectioning function and deep penetration depth of laser make it possible to visualize the three-dimensional structure of materials.Besides,the long-term imaging function could realize the in-situ observation of chemical process.In order to meet the demand of visualizing the special properties of materials,we designed and built a series of brand new fluorescence labelling strategies based on cation-? interaction triggered fluorescence and aggregation-induced emission for direct visualization of material structure and reaction process which could not achieved by traditional visualization techniques.These strategies greatly broaden the potential applications of fluorescence visualization technique in material characterizationThe macroscale imaging function of fluorescence visualization technique is applied for visualizing the three-dimensional dispersion of inorganic fillers in polymer matrix.In order to label the non-fluorescent inorganic montmorillonite fillers with fluorescence,polycyclic aromatic hydrocarbons(PAHs)were introduced to the interlayer by co-intercalation with cationic surfactants.Ultraviolet absorption spectra,fluorescence spectra,and fluorescence anisotropy analysis demonstrated the existence of strong cation-? interaction between surfactants and PAHs in the interlayer of montmorillonite.The existence of cation-? interaction avoid the fluorescence quenching of PAHs at aggregation state and contribute to the glaring green fluorescence emission of montmorillonite.After fluorescence visualization of the synthesized montmorillonite-silicone rubber composite,several three-dimensional reconstruction images of montmorillonite dispersion were obtained.Precise quantification of montmorillonite dispersion was realized by designed statistical model.The model was composed of Pearson chi-square test,two-dimensional density comparison and one-dimensional evaluation of numerical characteristics.As a result,the differences between two samples with similar dispersions was successfully distinguished by our quantification method,which is impossible for quantitative methods.This method has the potential to become a standard of dispersion quantification for enterprises involved in organic-inorganic composite.The three-dimensional imaging and video recording functions of fluorescence visualization technique is applied to visualize the flocculation process in algal biodiesel industry.The most efficient flocculation method is surfactant-assisted algal flocculation with a feeding concentration much higher than the critical micelle concentration(CMC).In order to investigate the key factor affecting the flocculation process and efficiency,the synthesized aggregation-induced emission surfactant,tetraphenylethenedodecyltrimethylammonium bromide(TPE-DTAB),was used for the fluorescence visualization of algal flocculation process and structure of flocculation product.Surface tension measurements demonstrated the ultralow CMC of TPE-DTAB.Fluorescence spectra indicated TPE-DTAB could generate strong fluorescence at the aggregation state of micelle.Afterwards,it was observed that the negatively charged algal cells was flocculated by positively charged TPE-DTAB micelles by CLSM.In comparison with conventional surfactant dodecyltrimethylammonium bromide and stearyltrimethylammonium bromide,TPE-DTAB performed a much higher flocculation efficiency.The observation of flocculation process indicated that TPE-DTAB could form much more micelles at same concentration because of the ultralow CMC,leading to a much higher flocculation efficiency.Universal experiment further proved TPE-DTAB has higher flocculation efficiencies towards different kinds of algal cells.Therefore,design and synthesis of surfactant with ultralow CMC is considered to be the best solution for improvement of flocculation efficiency in algal biodiesel industry.Video recording function and intensity quantification function of fluorescence visualization technique can be applied for in-situ observation of adsorption kinetics.In chemical reaction process,visualization of adsorption kinetics has become a long-term problem confusing researchers from different fields.Theoretically,visualization of adsorption kinetics could be obtained by employing fluorescent probe as adsorbate by fluorescence visualization technique.However,conventional fluorescent molecules suffer the decreasing or even quenching of fluorescence at aggregation state during adsorption.Design and synthesis of E-4-formyl-styryl-pyridinium salt(FSPH)with cation-? interaction enhanced fluorescence at aggregation state and application of montmorillonite as adsorbent could visualize the adsorption process.The in-situ fluorescence variation qualitatively visualized the invasion process of FSPH form the edge to the center of montmorillonite.Visualization of kinetics is obtained by quantification of the fluorescence variation along the invasion route.The curves of fluorescence intensity variation were obtained by image analysis software(LAS X)through quantification of several positions from the edge to the center of montmorillonite.Quantification results indicated the whole adsorption process consisted of three steps:Firstly,FSPH aggregated at the edge of montmorillonite;Secondly,more FPSH aggregated at the edge of montmorillonite which resulted in the formation of a block layer;Finally,FSPH in the block layer invaded from the edge to the center.Such adsorption behavior could be applied to montmorillonite with different particle sizes.However,the formation of block layer led to the insufficient utilization of inner space of larger montmorillonite,which means a lower adsorption efficiency.The success of visualizing adsorption kinetics of montmorillonite demonstrated fluorescence visualization technique could be applied to investigation of sophisticated chemical reactions.