Carbohydrate Recognition Based On Fluorescence/Phosphorescence Of Aromatic Boronic Acid And Synthesis Of Water-Soluble MWNTs

Chapter 1:In this chapter,first,the structures and properties of carbohydrate and the methods for detection and recognition of them were briefly reviewed. Among these methods,fluorescent probe using aromatic boronic acid for recognition of carbohydrate is one of the most important approaches.On the basis of binding model between carbohydrate and aromatic boronic acid,the approaches to calculate affinity constants of carbohydrate binding with aromatic boronic acid were introduced.Then the principles and current research progress in carbohydrate recognition by aromatic boronic acid probes were summarized in details as different mechanisms including photoinduced electron transfer(PET) and molecular internal charge transfer (ICT).In addition,the researching background in anti-oxygen-quenching room temperature phosphorescence(RTP) and the application of sodium deoxycholate,known as a biological surfactant and used in micelle system for luminescence analysis,were discussed.The recent major progress of our group in this research area was also summarized.Finally,the possibility and advantages to use phosphorescence analytical method for carbohydrate were discussed.Chapter 2:3-Quinoline boronic acid(3-QBA) as a fluorescent probe for recognition of carbohydrates had been developed by using fluorescence spectroscopy.Many factors that affect the fluorescent spectra of 3-QBA were examined including the concentration,ethanol-water ratio,pH value,as well as any common carbohydrates such as D-fructose,D-galactose,D-mannose, and D-glucose.Experiments showed that except of D-glucose,all other carbohydrates can enhance the fluorescence emission of 3-QBA.The binding constants of 3-QBA with different carbohydrates were measured by fitting the fluorescent titration curves of 3-QBA with carbohydrates.They were 7.3×10² L/mol for D-fructose,0.37×10² L/mol for D-galactose,and 0.28×10² L/mol for D-mannose,respectively,indicating a good selectivity for D-fructose.A possible mechanism was briefly discussed.These findings provide a base for further using aromatic boronic acid as a phosphorescent probe for carbohydrate detection.Chapter 3:The RTP properties of 2-Bromoquinoline-3-boronic acid(BrQBA) and its application in carbohydrate recognition were studied.Without deoxygenation,a strong phosphorescence signal of BrQBA was induced in sodium deoxycholate(NaDC) solution.The influences of NaDC concentration,standing time and heating on the RTP intensity of BrQBA were examined.It was found that at 4.0mmol/L of NaDC,the RTP intensity of BrQBA reached maximum because NaDC formed dimer in this concentration,proving a rigid hydrophobic domain for BrQBA by which BrQBA was protected being quenched by oxygen.RTP intensity decay of BrQBA was measured and fitted to a diexponential model with the lifetime of 6.99ms and 1.39 ms as long-lived and short-lived components.The fractional contribution of the long-lived component was 73.5%,suggesting a majority of BrQBA molecules were well-protected by NaDC aggregates.The experiments also showed that RTP intensity and lifetime of BrQBA increased continuously with an increasing standing time and heating would accelerate the interaction between BrQBA and NaDC aggregate.RTP intensities of BrQBA were enhanced upon addition of a variety of carbohydrates.The binding constants of BrQBA with carbohydrate were measured based on RTP method and they are 2.58×10³ L/mol for D-fructose,1.84×10³ L/mol for D-Galactose,1.55×10³ L/mol for D-glucose,and 1.29×10³ L/mol for D-mannose,respectively.The results suggest that BrQBA has a ability to recognize fructose.This was the first time to use phosphorescence spectra of aromatic boronic acid for the recognition of carbohydrates.Chapter 4:The water-soluble hydroxylated multi-walled carbon nanotubes (MWNTols) were synthesized.A L₉(3⁴) orthogonal layout was selected to optimize the experimental factors and TEM,SEM,Raman spectra were used to characterize the products.The solubility of MWNTols in water was 0.72mg/mL.Moreover,polyvinylpyrrolidone(PVP)-wrapped MWNTols were synthesized.The water-solubility of PVP further increases the stability and dispersibility of MWNTols in water(up to 2.34mg/mL).No aggregation or sediment was observed in its saturated solution over 2 month storage at room temperature.The percentage of MWNTols in total MWNTols-PVP is calculated as 41%.