The Structure And Energy Transfer Study Of Color-tunable Cellulose Derivatives/Terbium And Europium Nanocomplex

Carboxymethyl cellulose?CMC?and hydroxypropyl carboxymethyl cellulose?HPCMC?are cellulose derivatives containing carboxyl groups.Both cellulose derivatives are characterized by eco-friendly environment property,good water solubility and high polymer stability.Rare earth metals are valuable strategic resources with a wide range of application in many fields.In this thesis,we have adopt CMC and HPCMC as polymer ligands to chemically react with Tb³⁺ and Eu³⁺,to synthesize the binuclear nanocomplexes with good luminescent and and tunable color property,meeting the demand of modern green chemistry and practical application.In this experiment,by controlling the experimental conditions,the morphology and crystalline structure were analyzed by SEM,EDX,TEM and XRD;the chemical bonding state are investigated by FTIR and XPS and with it,combined with UV-vis,PL and LT,the antenna effect,fluorescence property and the energy transfer between Tb³⁺ and Eu³⁺ in complexes are discussed in detail.Finally,we use CIE to analyze the color tunable property of complexes with different molar ratio of Tb³⁺ and Eu³⁺.Main conclusions of this thesis were summarized as follows:?1?Tb³⁺ and Eu³⁺ can coordinate with O atoms in –OH,-COO-and COC of CMC and HPCMC ligands,synthesizing CMC-Tb/Eu and HPCMC-Tb/Eu nanoparticles in waterbath or under microwave.Compared with waterbath heating mode,the microwave heating mode can lower the complexes particles size and make the crystalline smaller.?2?Antenna effect: Ligand CMC and HPCMC can serve as main acceptor to absorb ultraviolet light and transfer the energy to Tb³⁺ and Eu³⁺ via Tb?III?-O and Eu?III?-O.?3?Under 350 nm excitation,CMC-Tb/Eu and HPCMC-Tb/Eu nanocomplexes can emit mixed color with the characteristic fluorescence of Tb³⁺ and Eu³⁺.The color emitted by nanocomplexes vary according to the molar ratio of Tb³⁺ and Eu³⁺,achieving the aim of tunable color.In the process of lighting,there is Tb³⁺?Eu³⁺ energy transfer process in CMC-Tb/Eu and HPCMC-Tb/Eu nanocomplexes.?4?In this experiment,for CMC-Tb/Eu and HPCMC-Tb/Eu nanocomplexes,the degreeof crystalline and the conjugation degree are the main factors affecting the intensity of fluorescence.Generally,lower crystalline makes intensity of fluorescence decline and the enhanced conjugation promotes intensity of fluorescence.For CMC-Tb/Eu nanocomplexes,the effect of lower crystalline is less than the one of higher conjugation on fluorescence,enhancing the intensity of fluorescence.However,for HPCMC-Tb/Eu nanocomplexes,the effect of lower crystalline is stronger than the one of higher conjugation on fluorescence,so the intensity of fluorescence declines.