Fabrication of stable solid fluorescent starch materials based on Hantzsch reaction.

In this paper, a series of fluorescent starches were prepared simply and effectively by Hantzsch multi-component reaction (MRC). These materials showed bright fluorescence emission. Notably, due to the existence of polysaccharide skeleton, starch molecules can effectively inhibit the common aggregation induced quenching effect caused by the aggregation of conjugated molecules in traditional organic fluorescent materials. Meanwhile, the stability of this material is so excellent that the fluorescence emission of the dried starch derivatives would not destroy after boiling at a high temperature in some common solvents, and even brighter fluorescence can be stimulated in alkaline solution. In addition to fluorescence, starch was also endowed with hydrophobic property by one-pot method connecting long alkyl chains. Compared with native starch, the contact angle of fluorescent hydrophobic starch increased from 29° to 134°. Furthermore, the fluorescent starch can be prepared into film, gel and coating by different processing methods. The preparation of these Hantzsch fluorescent starch materials provide a new way for the functional modification of starch materials and has great application potential in detecting, anti-counterfeiting, security printing and other related fields.

A facile method of functional derivatization based on starch acetoacetate.

In the present work, we constructed a methodology to graft starch with special groups, such as alkyl, phenolic, naphthalimide derivatives (ND) and polymer, by a simple reaction under generally mild conditions without catalysts or UV irradiation, based on precursor starch acetoacetate (SAA). The completeness of these reactions has been proved to be ideal. After grafting, the starch derivatives have some common changes, for instance, their solubility is improved in certain solvents. On the other hand, the introduction of different functional groups will also bring some characteristics to the derivatives (e.g. ND brings fluorescence). In addition, part of the derivatives shows excellent machinability, and their hot-pressed samples exhibit great transparency and mechanical strength. Specially, the alkyl grafted starch displays excellent toughness, properties of deformation and self-recovery. In conclusion, this method has good universality and methodological significance, and offers insights into the larger-scale industrial application of starch.