In the past few decades, massive use of fossil resources has led to the rapid consumption of global oil reserves and soaring oil prices. Therefore, it’s meaningful to research and develop renewable resources. As a kind of plant protein, zein is derived from corn yellow powders [1–3]. There are a large number of hydrophobic amino acids and non-polar amino acid residues in zein, meanwhile zein is lacking of charged acidic, alkaline and polar amino acids [4–6]. Zein owns excellent performances including degradability, self-assembly ability and special solubility [7–9]. Hence, zein has significant potential to replace part of mineral resources which can be applied in medical, packaging, leather, textile fields, etc [10–13].
With the increasing of environmental awareness, consumers’ active lifestyles and green consumption concepts have brought new challenges to daily necessities. For example, clothing is always stained by oils, juices or coffee, which can provide an easeful environment for microbial growth but a bad influence on people’s daily lives and works. Owing to the advantages of high chemical stability and photo-catalytic activity, titanium dioxide (TiO2) has been widely developed to degrade organic contaminants [14–16]. According to researches, TiO2 own four kinds of natural polymorphs (TiO2 (B), brookite, anatase and rutile) and at least five polymorphs that are produced synthetically . Although the crystalline TiO2 has a well defined structure, a large fraction of the atoms located on the surface show structural disorder, leading to them having unique properties different to their bulk crystalline counterparts . This explains why the amorphous TiO2, with their disordered structure can have different properties, for advanced applications, relative to the crystal structures that have well-defined properties [19, 20]. Meanwhile, amorphous TiO2 has also captured a great deal of attention due to the characteristic of the processability at room temperature and the high specific surface area [21, 22]. So, there is a growing interest in studying the performances of amorphous TiO2 which can possess a strong surface activity compared to crystalline TiO2 of the same size [23, 24].
Up to now, the synthesis of functional materials based on TiO2 and zein by combining the photo-catalytic performance of TiO2 and the film-forming property of zein has been reported. Li et al. demonstrated a novel method to prepare composite films by using zein, poly propylene carbonate and anatase TiO2, which indicated TiO2 can endow composite films with photo-catalytic activity . Qu and co-workers reported an effective method to improve the photo-catalytic performance of composite films by adding highly dispersible TiO2 nanoparticles . Sajed et al. created a new nanofibers based on zein and sodium alginate incorporated with TiO2 nanoparticles and betanin by using the electrospinning technique, and the nanofibers were beneficial to improve the shelf life and quality of food as the food packaging . However, there is few reports on the combination of zein and amorphous TiO2, not to mention the design and research of the microstructures of composite materials containing zein and amorphous TiO2.
In our previous researches, the method of interface template synthesis has been used to craft chitosan-coated silica nanocapsules with a double-shelled structure, wich was proved as an effectively method for preparing organic-inorganic double-shell materials . Herein, in this study, amorphous TiO2-coated zein microcapsules (ZTCMs) were also prepared by interface template synthesis to improve the utilization of zein and the specific surface area of amorphous TiO2, and the possible synthesis strategy of ZTCMs was proposed as exhibited in Scheme 1. Firstly, the mixture was obtained after the blending, containing F127, TBOT, THF, was dropwise added into zein ethanol solution. And then, the microcapsules based on zein and F127 gradually formed with the volatilization of ethanol and THF. Meanwhile, the TBOT coated in the micelles was also gradually hydrolyzed. Finally, ZTCMs were obtained after spray drying the microcapsules emulsion.