Influence of pre- or post-electron beam irradiation on heat-moisture treated maize starch for multiscale structure, physicochemical properties and digestibility.

Electron beam irradiation (EBI) as a green technological method for starch modification can generate starch-based materials with new functions. This study modified maize starch by heat-moisture treatment (HMT) for 1 h and 3 h, and EBI with various intensities (5 kGy and 10 kGy), and their effects of treatment sequence on the multiscale structure, physicochemical properties and in vitro digestibility were investigated. EBI or HMT alone did not change the granule morphology and crystalline type, but reduced the crystallinity and molecular weight and increased the resistant starch content. HMT alone had no significant effect on the solubility of starch, while EBI led to a considerable increase in the solubility of maize starch. The combined treatment of EBI and HMT aggravated apparent viscosity reduction, and the HMT starch pretreated with EBI had a smaller molecular weight and lower viscosity. In contrast, post-EBI samples had higher solubility and RS content. Primarily, it has excellent potential for producing low-viscosity and high-solubility starch foods.

A portable dual-mode colorimetric platform for sensitive detection of Hg2+ based on NiSe2 with Hg2+-Activated oxidase-like activity.

The nanozyme-based colorimetric strategy for heavy metal detection has broad application prospects nowadays. However, the inefficient recognition capabilities of nanozyme sensors for targets hinder its further application. Herein, the authors synthesize bare nickel selenide (NiSe2) via a one-step hydrothermal reaction, in which the Se element possesses a strong binding ability with mercury (Hg). As expected, NiSe2 exhibits oxidase-like activity in the presence of Hg2+, that is, Hg2+ can enhance the oxidase-like activity of NiSe2. The enhanced mechanism is the accelerated electron transfer between NiSe2-Hg2+ and substrate caused by the formation of Hg-Se bonds. Besides, the oxidase-like activity of NiSe2 exhibits excellent selectivity, sensitivity and stability in response to Hg2+, which enables NiSe2-Hg2+ to efficiently oxidize colorless TMB to blue TMB even in harsh environments. Based on this, a dual-mode colorimetric sensor integrating solution reaction and test paper is developed for the detection of Hg2+. In the Hg2+ concentration range of 10-700 nM, the colorimetric platform presents a liner response to Hg2+, which can reach a low LOD of 5.18 nM in solution reaction and 8.42 nM in the test paper. The proposed strategy can also be applied to real water samples with good recovery and excellent self-calibration capability.