| In this thesis, our goal is to obtain functionalized GO composites by modifying on the surface of GO and investigate their properties and applications. There are mainly three parts as follows:1. The aim of our research is to incorporate active sites into low-cost GO materials to prepare functionalized GO composites with higher adsorption capacity using a simple procedure and environmentally benign materials. β-cyclodextrin(β-CD) was first grafted onto poly(acrylic acid)(PAA) by amide reaction, then the β-CD/PAA product was covalently attached to GO nanosheets. The product is called β-CD/PAA/GO. Theβ-CD/PAA/GO product was characterized by scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FTIR), and X-ray diffraction analysis(XRD). The cationic dyes methylene blue(MB)and safranine T(ST) were used as model pollutants. The maximum adsorption capacities of the β-CD/PAA/GO composites were 247.99 mg g–1 for MB and 175.49 mg g–1 for ST. Most strikingly, the composites could easily be regenerated by annealing them under moderate conditions,allowing their reuse with a little loss of adsorption capacity. Their excellent performances demonstrate that β-CD/PAA/GO composites have great potential for application in wastewater treatment.2. Here, we describe a simple and efficient indicator displacement assay(IDA)-based fluorescence method for detecting heparin.Rhodamine B(RB) was first covalently attached to polyethyleneimine(PEI), RB–PEI that was prepared was used as an indicator in this method,and the sensitive detection of heparin is achieved from competition between the GO and heparin to bind with the indicator. Rather weak fluorescence of RB–PEI adsorbed, by electrostatic and π – π attraction,onto the GO surface(RB–PEI/GO) was expected in an aqueous solution.However, in the presence of heparin, cationic RB–PEI will form a stable inter-polyelectrolyte complex with anionic heparin through strongelectrostatic interactions, leading the RB–PEI to desorb from the GO surface and recover the fluorescence signal. The RB–PEI/GO complex could, therefore, be used to detect heparin through the fluorescence turn-on process.3. In this study, β-CD was first grafted onto PEI, then the β-CD-PEI product was covalently attached to GO nanosheets, a novel product have been synthesized and the product is called β-CD-PEI-GO. The free dye rhodamine 6G(R6G) fluoresced strongly and when β-CD-PEI-GO was added, R6 G could enter the inner cavity of β-CD by hydrophobic interaction, and the process of FRET between GO and R6 G might occur and the fluorescence intensity of R6 G could be quenched. However, the process of FRET could be switched off with adding β-carotene, due to its larger hydrophobic association constant with β-CD than that of R6 G,R6G could be replaced from the inner cavity of β-CD host to the outside solution. What’s more, because of the electrostatic repulsion between the positively charged GO and positively charged R6 G, the fluorescence of R6 G could not be quenched again. Therefore, the β-CD-PEI-GO that was first developed could act as a optical sensor and this proposed strategy might provide a simple, rapid, highly sensitivity, good selectivity, and low cost quantitative method for the determination of β-carotene. |
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