Structure And Properties Of Oxidized Cellulose Nanofibrilfilm Modified By Zn(Ⅱ) Terpyridine Complex

TEMPO-oxidized cellulose nanofibril（tCNF）is a kind of nanocellulose prepared by oxidation pretreatment combined with mechanical method.tCNF is made from the most abundant,renewable and biodegradable material in nature.It is a kind of uniform and transparent gel when in the dispersed state.Because of a considerable portion hydroxyl is oxidized to carboxylic group,the tCNF is easier to disperse.A transparent nanopaper（film）can be obtained after removal of dispersed system.This transparent nanopaper has potential application value in the field of optics owing to its high transmittance and transparency.Due to the existence ofπ-πconjugated system inside the molecule,the terpyridine ligand and its metal complex have abundant photophysical properties.Therefore,loading Zn-tpy onto the tCNF film through the coordination bond to combine its excellent optical properties with the tCNF film can not only expand the application range of the Zn-tpy but also get the most out of tCNF film excellent properties.Two kinds of terpyridine ligands with different terminal groups were synthesized from p-dimethylaminobenzaldehyde,2-acetylpyridine and 3,4,5-trimethoxybenzaldehyde.N,N-dimethyl-4-[2,2’:6’,2"-terridinyl]-4’-phenylaniline and 3,4,5-trimethoxyphenyl-4-[2,2’:6’,2"-triple pyridine]-4’-phenylaniline（N-tpy and O-tpy）.The two ligands are further reacted with ZnCl₂to obtain two kinds of Zn（Ⅱ）terpyridine complexes,which were Zn（Ⅱ）N,N-Dimethyl-4-[2,2’:6’,2"-teridinyl]-4’-phenylaniline and Zn（Ⅱ）3,4,5-trimethoxyphenyl-4-[2,2’:6’,2"-teridinyl]-4’-phenylaniline（abbreviated as Zn-N-tpy and Zn-O-tpy）.The coordination bond modification of tCNF with Zn-N-tpy and Zn-O-tpy respectively gave two kinds of Zn（Ⅱ）terpyridine complexes modified tCNF film with fluorescence effect and solvation coloring performance（Zn-N-nanopaper and Zn-O-nanopaper）.Further,Zn-O-nanopaper was treated with a different alcohol solvent,and its optical haze were adjustable.The conclusions obtained are as follows:1.According to research,N-tpy,O-tpy,Zn-N-tpy and Zn-O-tpy have good fluorescence properties.The absorption peaks in the UV-Vis absorption spectra of the N-tpy and O-tpy（two kinds terpyridine ligands）were 311 nm and 331 nm,and their fluorescence emission peaks were 546 nm and 410 nm.Due to the coordination of Zn²⁺,there were metal-ligands charge transfer inside the Zn-tpy molecules,so the UV-visible absorption spectra and fluorescence emission spectra of the two Zn-tpy have different degrees of red shift.Among them,Zn-N-tpy was red-shifted to 349 nm and 577 nm,and Zn-O-tpy was red-shifted to 400 nm and514 nm.2.The emission peak of Zn-N-nanopaper was 643 nm.After treatment with different solvents,the molecular dipole moment changed,and the fluorescence emission peak of Zn-N-nanopaper shifted.Different solvents have different effects on the molecular dipole moment,so the fluorescence emission peaks of the Zn-N-nanopaper varies in the range of 622-687 nm.The emission peak of Zn-O-nanopaper was 555 nm.After treatment with different solvents,the variation of the molecular dipole moment was different,so the positions of the fluorescence emission peaks have different displacements.The emission peak position of benzyl alcohol-treated Zn-O-nanopaper was the largest blue shift.The red shift of Zn-O-nanopaper treated with triethylamine was the most.It can be seen that Zn-N-nanopaper and Zn-O-nanopaper have good application prospects in the fields of solvent detection and fluorescence sensing.3.The Zn-O-nanopaper was further treated with alcohol solvents,and its optical haze were adjustable.Due to the different thicknesses of Zn-O-nanopaper have different surface stresses,the stimulations of alcohol solvents have different effect on the thickness and optical haze of Zn-O-nanopaper.The stimulations of alcohol solvents have little effect on the thinner Zn-O-nanopaper（0.018 mm）.As the thickness of Zn-O-nanopaper increases（0.028-0.039 mm）,the effect was gradually increased.Therefore,it was the lateral expansion for the thinner Zn-O-nanopaper,with the increase of the thickness,its role gradually became longitudinal expansion.The Zn-O-nanopaper treated with alcohol solvents have good absorption capacity in the ultraviolet region（250-420 nm）,and after 150minutes of UV irradiation at 365 nm,the absorption hardly changes,indicating that it has good light stability and strong ultraviolet blocking ability.Therefore,it has great potential applications in the field of fluorescent lamps,flexible displays and glass curtain walls.