Qiuyu Zeng,Yifan Wang,Ansar Javeed,Fengyun Chen,Jiaxing Li,Yating Guan,Baiyu Chen,Bingnan Han
To address the issue of food spoilage causing health and economic loss, we developed a pH/NH 3 dual sensitive hydrogel based on polyvinyl alcohol/chitosan (PVA/CS) containing chitosan-phenol red (CP). The CP was synthesized via Mannich reaction and immobilized it in PVA/CS hydrogel through freezing/thawing method to prepare the final PVA/CS/CP hydrogel. The synthesis of CP was confirmed by 1 H NMR, FT–IR, XRD, UV–vis, and XPS. The characteristics of hydrogel were evaluated by FT–IR, XRD, SEM, mechanical properties, thermal stability, leaching, and color stability tests. The PVA/CS/CP hydrogel showed distinctly different color at various pH and NH 3 vapor levels (yellow to purple). The hydrogel exhibited obvious color changes (ΔE = 46.95) in response to shrimp spoilage, stored at 4 °C. It showed positive and strong correlation between the ΔE values of the indicator hydrogel and total volatile basic nitrogen (TVB-N) as (R 2 = 0.9573) and with pH as (R 2 = 0.8686), respectively. These results clearly show that the PVA/CS/CP hydrogel could be applied for naked-eye real-time monitoring of seafood freshness in intelligent packaging.
Kai Jia,Jiahua Ye,Guoxin Zhuang,Zanyong Zhuang,Yan Yu
Fabrication of low-dimensional nano-MOFs as well as nanoparticles/metal-organic frameworks (MOFs) hybrids has sparked new scientific interests but remains a challenging task. Taking Cu 3 (BTC) 2 as a proof of concept, it is demonstrated thats NH 3 ⋅H 2 O solution of a confined pH value can readily shape the bulk Cu 3 (BTC) 2 into nanoscale Cu 3 (BTC) 2 , beyond the need to control the crystal growth kinetics of MOFs. Adjusting the pH of NH 3 ⋅H 2 O within a much small range (10–11) allows fine tuning over the size and shape of nanoscale Cu 3 (BTC) 2 . Particularly at pH = 11, NH 3 ⋅H 2 O exhibits weak reducibility that triggers a reduction of part of Cu 3 (BTC) 2 into Cu 2 O, while shaping the other into Cu 3 (BTC) 2 nanowires. Benefiting from the coincidence of reduction and etching effects, the newly generated Cu 2 O dots can in situ anchor onto adjacent Cu 3 (BTC) 2 nanowires at highly dispersive state, forming a well-defined sponge-like architecture built of Cu 2 O dots and nano-Cu 3 (BTC) 2 . The CuO x derived from annealing of the Cu 2 O dots/nano-Cu 3 (BTC) 2 hybrid preserves the sophisticated sponge architecture and high porosity, and exhibits promising applications in phenol scavenging, with efficiency outperforming its counterparts and many other Cu-based catalysts reported in literature. It is anticipated that the findings here pave the way for the rational design of intricate nano-MOFs in a more efficient way.
Shiqi Li,Ling Liu,Silong Yang,Xingnan Wang,Yahong Yuan,Tianli Yue,Rui Cai,Zhouli Wang
In this study, a double-layer intelligent packaging, which is designed by a layer-by-layer casting strategy, is employed for efficient food preservation and high contrast monitoring. Specifically, novel zein/tannic acid (TA) composite colloidal particles (ZTs) were prepared by manipulating the non-covalent interaction between zein and TA using an easy antisolvent method. The stable oregano essential oil (OEO) Pickering emulsion (ZTOEO) with varying concentrations of ZTs (0.1%–1.0%) was successfully prepared. The optimized ZTOEO, containing 0.8% ZTs, was then integrated into the emulsified hydrophobic layer of the konjac glucomannan (Kgm) matrix. Finally, the carrageenan (Car) matrix containing alizarine (Al) as an indicator was added to construct the bilayer structure. The outer Car/Al layer serves as an acid/base responsive indicator layer, while the inner Kgm/ZTOEO layer functions as a high-barrier bacteriostatic layer. The double-layer Kgm/ZTOEO-Car/Al is integrated through intermolecular hydrogen bonding and dehydration condensation. Kgm/ZTOEO-Car/Al exhibits excellent slow-release antibacterial and antioxidant activity, with a sensitive, repeatable and accurate visual response to pH/NH 3 . The composite film demonstrates good mechanical strength, thermal stability, light blocking, and water vapor and oxygen permeability. The individual inner Kgm/ZTOEO film effectively prolonged the shelf-life and quality of fruits, which the double-layer Kgm/ZTOEO-Car/Al film showed minimal changes in TVB-N (16.65 mg/100 g) even after monitoring and maintaining the shrimp freshness for 48 h. It can be easily processed on a large scale into packaging bags and indicator labels. This packaging is expected to be an eco-friendly, low-cost, bacteriostatic, suitable for applications requiring real-time monitoring and maintenance of fruit/seafood freshness.
危险品化学品经营许可证（带存储）