Effect and Mode of Different Concentrations of Citrus Peel Extract Treatment on Browning of Fresh-Cut Sweetpotato.

Browning is one of the main phenomena limiting the production of fresh-cut sweetpotatoes. This study investigated the anti-browning effect of citrus peel extracts and the key components and modes of action associated with browning in fresh-cut sweetpotatoes. Five different concentrations of citrus peel extract (1, 1.5, 2, 2.5 and 3 g/L) were selected to ensure storage quality; and the physical and chemical properties of fresh-cut sweetpotato slices were analysed. A concentration of 2 g/L of citrus peel extract significantly inhibited the browning of fresh-cut sweetpotatoes. The results showed that the browning index and textural characteristics of fresh-cut sweetpotatoes improved significantly after treatment with citrus peel extract; all the citrus peel extract solutions inhibited browning to some extent compared to the control. In addition; LC-IMS-QTOFMS analysis revealed a total of 1366 components in citrus peel extract; the evaluation of citrus peel extract monomeric components that prevent browning in fresh-cut sweetpotato indicated that the components with better anti-browning effects were citrulloside, hesperidin, sage secondary glycosides, isorhamnetin and quercetin. The molecular docking results suggest that citrullosides play a key role in the browning of fresh-cut sweetpotatoes. In this study, the optimum amount of citrus peel extract concentration was found to be 2 g/L.

Surface motif sensitivity of dual emissive gold nanoclusters for robust ratiometric intracellular imaging.

Here, we report novel dual-emissive gold nanoclusters (d-Au NCs) that have two distinctive emissions (420 and 630 nm) under a single wavelength excitation. The two-stage formation mechanism evidences their sensitive response to valine and trivalent chromium ions (Cr3+) in completely different spectral ratiometric modes in living cells with high contrast to successfully avoid signal fluctuations.

Direct Discrimination of Edible Oil Type, Oxidation, and Adulteration by Liquid Interfacial Surface-Enhanced Raman Spectroscopy.

The quality and safety of edible oils is a momentous but formidable challenge, especially regarding identification of oil type, oxidation, and adulteration. Most conventional analytical methods have bottlenecks in sensitivity, specificity, accessibility, or reliability. Surface-enhanced Raman spectroscopy (SERS) is promising as an unlabeled and ultrasensitive technique but limited by modification of inducers or surfactants on metal surfaces for oil analysis. Here, we develop a quantitative SERS analyzer on two-liquid interfacial plasmonic arrays for direct quality classification of edible oils by a portable Raman device. The interfacial plasmonic array is self-assembled through mixing the gold nanoparticle (GNP) sols and oil sample dissolved in chloroform without any surfactants or pretreatments. Different kinds of edible oils dissolved in chloroform directly participate in self-assembly of plasmonic arrays that finally localizes onto a three-dimensional (3D) oil/water interface. The 3D plasmonic array is self-healing, shape adaptive, and can be transferred to any glass containers as a substrate-free SERS analyzer for direct Raman measurements. It produces sensitive responses of SERS on different kinds of edible oils. By virtue of principal component analysis (PCA), this analyzer is able to quickly distinguish six edible oils, oxidized oils, and adulterated oils. Moreover, the solvent chloroform generates unique and stable SERS bands that can utilized as an inherent internal standard (IIS) to calibrate SERS fluctuation and greatly improve quantitation accuracy. Compared to conventional lab methods, this analyzer avoids complex and time-consuming preprocessing and provides significant advantages in cost, speed, and utility. Our study illuminates a facile way to determine edible oil quality and promises great potential in food quality and safety analysis.

Cross-linking structure-induced strong blue emissive gold nanoclusters for intracellular sensing.

Fluorescent gold nanoclusters (Au NCs) are new emerging fluorescent nanomaterials with broad application prospects but limited by the complicated preparation, low quantum yield (QY) and poor biological applications. Here we develop a one pot etching approach for synthesizing fluorescent Au NCs by using the common citrate-capped gold nanoparticles (Au NPs) as the precursor and the poly(amidoamine) (PAMAM) dendrimer as the etching and templating agent. The synthesis conditions are optimized and products are characterized in detail. The results confirm that we have successfully synthesized PAMAM-templated Au NCs (Au-PAMAM NCs) with strong blue emission at 453 nm and a high fluorescence QY of 18%. The optical properties are remarkably superior to that of most other reported fluorescent Au NCs since the formed specific cross-linking structures of Au-PAMAM NCs rigidify the surface Au(i)-ligands and enhance the inner aurophilic interactions. Interestingly, Au-PAMAM NCs display a sensitive and selective fluorescence response toward temperature and Cr2O72- ions, respectively. Quantitative analysis reveals the excellent capacity to distinguish temperature in the range of 15 °C-80 °C and to sense Cr2O72- in a linear range of 0-55 µM with a detection limit of 1.9 µM. Experiments evidence that there is no interference when sensing each of these targets, making Au-PAMAM NCs potential fluorescent probes for these two targets. By means of the small size, excellent water solubility, negligible cytotoxicity, and great cell penetration ability, Au-PAMAM NCs are successfully applied to monitor the dynamic change of temperature and Cr2O72- ions in living cells. This study paves the way for synthesizing high emission and highly biocompatible Au NCs with promising potential in biosensing and imaging in the future.