Comparison study of two aldehyde group finishing agents in surface modification of up-conversion luminescence materials

Surface modification of up-conversion luminescence materials （Na[Y0.57Yb0.39Er0.04]F4 modified by amino groups） by grafting and modifying with aldehyde groups was studied by means of Fourier transform infrared spectroscopy （FTIR）, scanning electron microscopy （SEM）, thermogravimetric analysis （TGA）, and emission spectrum （EM）. The surface modification effect was compared using two different finishhag agents, p-phthalaldehyde and glutaraldehyde. It was found that the surface of up-conversion luminescence materials could be modified by aldehyde groups of the two finishing agents, the systematic dispersibility and the thermostability of the up-conversion luminescence material modified by p-phthalaldehyde were better than those of the material modified by glutaraldehyde, and the luminous intensity of the material modified by p-phthalaldehyde was increased. The AI （the ratio of the suspended segmental quality in the specimen to the total mass of the specimen） of the material modified by p-phthalaldehyde was higher than that of the material modified by glutaraldehyde. It is obviously seen that the embellishment effect of p-phthalaldehyde as a finishing agent was better than that of glutaraldehyde. In addition, the reasons why p-phthalaldehyde is a good finishing agent are also explained.

Anthracene Modified by Aldehyde Groups Exhibiting Aggregation-Induced Emission Properties

In order to get an easy way to achieve the transformation from aggregation-caused quenching luminophores （ACQphores） to aggregation-induced emission luminogens （AIEgens）, we took aldehyde groups as the modifying group to decorate anthracene. The fluorescence performances of 9-anthraldehyde （AnA） and 9,10-anthracenedicarboxaldehyde （AnDA） in solution and aggregated state were studied. We found out that the aldehyde group can transform anthracene with aggregation-caused quenching properties to AIEgen. The single-crystal structures analy- sis of AnA and AnDA showed that their structure characteristics are responsible for the AIE properties of AnA and AnDA. On one hand, the aldehyde group can cause steric effects to lower intermolecular n-π packing style in aggregated state. On the other hand, intermolecular H-bonding interactions can restrict the intramolecular rotation and suppress internal charge transfer. These results may supply a new simple method for the transformation from ACQphores to AIEgens on the point of the molecular design.

Synthesis of 3-Phenyl-6-formyl-3, 4-dihydro-2H-1, 3-benzoxazine

A novel benzoxazine monomer containing aldehyde group, 3-phenyl-6-formyl-3, 4-dihydro-2H-1, 3-benzoxazine （Ald-B）, was synthesized via the Mannich condensation of formaldehyde, p-hydroxybenzaldehyde and aniline. Its structure was characterized by Fourier transform infrared spectroscopy （FTIR）, proton nuclear magnetic resonance （^1HNMR）. The side reaction in the synthesis is discussed.

Preparation of Cellulose Nanofibrils by Multi-Site Regioselective Oxidation

Cellulose nanofibrils(CNFs)are promising sustainable materials that can be applied to nanocomposites,as well as medical and life-sciences devices.However,methods for the preparation of these important materials are energy intensive because heating and mechanical disintegration are required to produce cellulose fibers below 100 nm in size.In this study,CNFs were prepared through the multi-site regioselective oxidation of cellulose with 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO)and periodate at room temperature(20–25°C),without any mechanical-disintegration treatment.Transmission electron microscopy(TEM)revealed that the CNFs had the average widths of 14.1,55.4,and 81.9 nm for three different treatments.Fourier-transform infrared spectroscopy revealed that carboxyl groups were created on the surfaces of the microfibrils,while X-ray diffraction studies showed that the cellulose I structure was maintained after oxidation,and that the cellulose nanofibril crystallinity index exceeded 70%.These results demonstrate that CNFs can be prepared by multi-site regioselective oxidation at room temperature in the absence of mechanical disintegration.In addition,a model was developed to calculate the total content of carboxylate and aldehyde groups of CNFs prepared by the TEMPO mediate oxidation,the periodate oxidation,and the multi-site regioselective oxidation methods based on the particle width determined by TEM.The calculated values of the model were in good agreement with the total content(experimental value)of carboxylate and aldehyde groups of CNFs prepared by the TEMPO-mediated oxidation and the multi-site regioselective oxidation methods.However,the model was not valid for CNFs prepared by the periodate oxidation method.

Synthesis and characterization of a novel series of unsymmetrical porphyrins

A novel series of unsymmetrical porphyrins with aldehyde group at the terminal of the linkage which connected to meso-phenyl through acylamide bond have been synthesized and structurally characterized by IR, (1)H NMR, MS, UV–vis, fluorescence.