Effect of ozone treatment on phenylpropanoid metabolism in harvested cantaloupes.

Phenylpropanoid metabolism plays an important role in cantaloupe ripening and senescence, but the mechanism of ozone regulation on phenylpropanoid metabolism remains unclear. This study investigated how ozone treatment modulates the levels of secondary metabolites associated with phenylpropanoid metabolism, the related enzyme activities, and gene expression in cantaloupe. Treating cantaloupes with 15 mg/m3 of ozone after precooling can help maintain postharvest hardness. This treatment also enhances the production and accumulation of secondary metabolites, such as total phenols, flavonoids, and lignin. These metabolites are essential components of the phenylpropanoid metabolic pathway, activating enzymes like phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, 4CL, chalcone synthase, and chalcone isomerase. The results of the transcriptional expression patterns showed that differential gene expression related to phenylpropanoid metabolism in the peel of ozone-treated cantaloupes was primarily observed during the middle and late storage stages. In contrast, the pulp exhibited significant differential gene expression mainly during the early storage stage. Furthermore, it was observed that the level of gene expression in the peel was generally higher than that in the pulp. The correlation between the relative amount of gene changes in cantaloupe, activity of selected enzymes, and concentration of secondary metabolites could be accompanied by positive regulation of the phenylpropanoid metabolic pathway. Therefore, ozone stress induction positively enhances the biosynthesis of flavonoids in cantaloupes, leading to an increased accumulation of secondary metabolites. Additionally, it also improves the postharvest storage quality of cantaloupes.

Millimeter-Sized K2MnF6:Si4+, NH4+ Red-Luminescent Crystals with High Absorption Efficiency (AEmax of 93.5%) and External Quantum Efficiency (EQEmax of 68.9%) Grown by Cooling-Induced Crystallization.

Luminescent bulk crystals exhibit fewer grain boundaries and defects compared with conventional microsized powdery ones. Herein, targeting Mn4+-activated fluoride crystals with a sharp line-type red luminescence spectrum, we propose a new cooling-induced crystallization method to grow the fluoride crystals. By this new method, we successfully grew millimeter-sized K2MnF6:Si4+, NH4+ crystals, featuring an AEmax (absorption efficiency) of 93.5% and an EQEmax (external quantum efficiency) of 68.9%, which are among the best values for Mn4+-activated fluoride red phosphors. The influence of doping Si4+ and/or NH4+ in K2MnF6 on the local coordination structure and luminescence properties was studied. The anomalous thermal quenching behaviors were discussed, the luminescence decay from the excited state was compared, and the origin for the high quantum efficiencies was analyzed.

Highly stable lithium sulfur batteries enhanced by flocculation and solidification of soluble polysulfides in routine ether electrolyte.

Lithium-sulfur batteries (LSBs) are among the most promising next-generation high energy density energy-storage systems. However, practical application has been hindered by fundamental problems, especially shuttling by the higher-order polysulfides (PSs) and slow redox kinetics. Herein, a novel electrolyte-based strategy is proposed by adding an ultrasmall amount of the low-cost and commercially available cationic antistatic agent octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate (SN) into a routine ether electrolyte. Due to the strong cation-anion interaction and bridge-bonding with SN, rapid flocculation of the soluble polysulfide intermediates into solid-state polysulfide-SN sediments is found, which significantly inhibited the adverse shuttling effect. Moreover, a catalytic effect was also demonstrated for conversion of the polysulfide-SN intermediates, which enhanced the redox kinetics of Li-S batteries. Encouragingly, for cells with only 0.1 % added SN, an initial specific capacity of 783.6 mAh/g and a retained specific capacity of 565.7 mAh/g were found at 2C after 200 cycles, which corresponded to an ultralow capacity decay rate of only 0.014 % per cycle. This work may provide a simple and promising regulation strategy for preparing highly stable Li-S batteries.

Application of proteomics to determine the mechanism of ozone on sweet cherries (Prunus avium L.) by time-series analysis.

This research investigated the mechanism of ozone treatment on sweet cherry (Prunus avium L.) by Lable-free quantification proteomics and physiological traits. The results showed that 4557 master proteins were identified in all the samples, and 3149 proteins were common to all groups. Mfuzz analyses revealed 3149 candidate proteins. KEGG annotation and enrichment analysis showed proteins related to carbohydrate and energy metabolism, protein, amino acids, and nucleotide sugar biosynthesis and degradation, and fruit parameters were characterized and quantified. The conclusions were supported by the fact that the qRT-PCR results agreed with the proteomics results. For the first time, this study reveals the mechanism of cherry in response to ozone treatment at a proteome level.

Effects of Atmospheric Cold Plasma Treatment on the Storage Quality and Chlorophyll Metabolism of Postharvest Tomato.

Atmospheric cold plasma (ACP) is a potential green preservation technology, but its preservation mechanism is still unclear, and the effects of different plasma intensities on postharvest tomatoes are little studied. In this study, the effects of different ACP treatments (0 kV, 40 kV, 60 kV, and 80 kV) on the sensory quality, physiological indexes, key enzyme activities, and gene expression related to the chlorophyll metabolism of postharvest tomatoes were investigated during the storage time. The results showed that compared with the control group, the tomatoes in the plasma treatment group had a higher hardness and total soluble solid (TSS) and titratable acid (TA) contents, a lower respiratory intensity and weight loss rate, a higher brightness, and a lower red transformation rate, especially in the 60 kV treatment group. In addition, chlorophyll degradation, carotenoid accumulation, and chlorophyllase and pheophorbide a mono-oxygenase (PAO) enzyme activities in the postharvest tomatoes were inhibited in the 60 kV treatment group, and the expressions of three key genes related to chlorophyll metabolism, chlorophyll (CLH1), pheophytinase (PPH), and red chlorophyll catabolic reductase (RCCR) were down-regulated. The results of the correlation analysis also confirmed that the enzyme activity and gene expression of the chlorophyll metabolism were regulated by the ACP treatment, aiming to maintain the greenness of postharvest tomatoes.

Light-assisted anti-wrinkling on azobenzene-containing polyblend films.

Undesired surface wrinkling is a persistent issue far from being resolved. Here, we report a simple light-assisted strategy to prevent surface wrinkling on azobenzene-containing polyblend films, which is based on the unique photo-responsive behaviors of azobenzene moieties. Upon visible light irradiation, the mechanical strain-induced surface wrinkling of the azo-based polyblend film attached on a pre-strained compliant substrate can be effectively suppressed. The influence of light irradiation conditions and polyblend composition on the wrinkling resistance has been systematically investigated. Notably, empirical scaling laws that can quantify the connection of the critical wrinkling conditions with external and internal factors are derived. This spatiotemporal light-assisted strategy combined with the simple universal blending method would provide a general guideline for the anti-wrinkling purpose in diverse functional material systems/devices.

Polarization-Dependent Ultrasensitive Dynamic Wrinkling on Floating Films Induced by Photo-Orientation of Azopolymer.

Ubiquitous surface wrinkling has been well-studied theoretically and experimentally. How to modulate the stress state of a liquid-supported system for the unexploited wrinkling capabilities remains a challenge. Here we report a simple linearly-polarized-light illumination to spatiotemporally trigger ultrasensitive in situ dynamic wrinkling on a floating azo-film. The smart combination of the liquid substrate with photoresponsive azo-moieties leads to the light-induced ultrafast wrinkling evolution, accompanied by unprecedented sequential wrinkling orientation conversion (from polarization-parallel to polarization-perpendicular). The involved different polarization-dependent sequential photo-orientation for azo side chains and azo-grafted main chains of azopolymers is disclosed experimentally for the first time. Meanwhile, programmable dynamic wrinkling with all-optical switchable surface topographies is available, which has wide application potentials in photoresponsive soft photonics.

Enhanced triethylamine-sensing properties of hierarchical molybdenum trioxide nanostructures derived by oxidizing molybdenum disulfide nanosheets.

A 3D α-MoO3 nanostructure for high-performance triethylamine (TEA) detection was synthesized via the facial oxidation of MoS2 nanoflowers (NFs) obtained by a hydrothermal process. The influence of the time of hydrothermal process in growing MoS2 on the morphologies of the final MoO3 obtained after calcination was investigated. As-obtained MoO3 and their precursors were systematically characterized by various techniques, such as X-ray diffraction, Raman, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 adsorption-desorption isotherms. Results showed that MoO3 with a hierarchical layered nanostructure was successfully obtained. After hydrothermal treatment of the MoS2 precursor for 20 h, the typical MoO3-based sensor (called M20) exhibited a high response of 2.42 at a very low TEA concentration of only 0.1 ppm at 240 °C. The M20 sensor response to 50 ppm TEA was as high as 125 with a fast response/recovery time of 14/22 s. Moreover, the sensor had a high stability and reproducibility as well as a high selectivity against other interfering VOCs or gases. Due to the tendency of TEA to adsorb to active oxygen sites of MoO3, the enhanced sensing properties of MoO3 can be ascribed to the remarkable hierarchical structure and large surface area. MoO3 obtained after calcination of hydrothermally grown MoS2 is thus a promising sensing material for enhanced TEA gas detection.

BaTiF6:Mn4+ Red Phosphor: Synthesis of Single Crystals at Room Temperature and the High Hydrolysis-Resistant Property.

Due to the low solubility of BaF2, the BaTiF6:Mn4+ phosphor for whitelight-emitting diodes application has been generally synthesized by the hydrothermal route, during which process the valence of the manganese dopant is difficult to be controlled as tetravalent. In this paper, a new synthesis method that proceeded at room temperature was reported. This method uses BaTiOF4 as the precursor and allows for the control of the phase transformation rate from BaTiOF4 to BaTiF6 in the K2MnF6/HF acid solution. Benefitting from that, we successfully prepared red-emitting BaTiF6:Mn4+ elongated crystals with a single-crystal nature up to a record-breaking length of 200-300 µm. The effects of the crystallinity of the BaTiOF4 precursor on its phase transformation rate into BaTiF6 and on the optimal Mn4+ doping concentration were studied. The BaTiF6:Mn4+ single-crystal phosphor exhibits relatively excellent hydrolysis-resistant behavior after being immersed in water for 3 h, at which condition the commercial K2SiF6:Mn4+ has become brown. This study may inspire the room-temperature preparation of other hydrolysis-resistant alkali earth fluorotitanate or fluorosilicate phosphors with stable tetravalent manganese doping.

High temperature induced S vacancies in natural molybdenite for robust electrocatalytic nitrogen reduction.

Defect engineering is an important strategy to regulate electronic structure of electrocatalysts for electrochemical N2 fixation, aiming at improving the electron state density and enhancing the adsorption and activation of inert N2. In this paper, a high-temperature strategy to anneal the natural molybdenite under Ar atmosphere was developed, and the as-obtained molybdenite with S vacancies boosted a high activity for N2 reduction reaction. In 0.1 M HCl, the catalyst annealed at 800 °C exhibits a high Faradic efficiency of 17.9% and a NH3 yield of 23.38 µg h-1 mg-1cat. at -0.35 V versus reversible hydrogen electrode, two times higher than that of the pristine molybdenite. The facile one-step annealing method introduces the defects (e.g., S vacancies) in the surface of the natural molybdenite particles to prepare catalysts for generating ammonia by reducing nitrogen at room temperature under ordinary pressure, promoting the development of low-carbon economic prospect.

Microwave-assisted synthesis of hierarchically porous Co3O4/rGO nanocomposite for low-temperature acetone detection.

Acetone sensors with high response and excellent selectivity are of enormous demand for monitoring the diabetes. This paper has reported a novel porous 3D hierarchical Co3O4/rGO nanocomposite synthesized by a microwave-assisted method, by which Co3O4 nanoparticles are rapidly and uniformly anchored on rGO nanosheets. The phase composition, surface morphology of the Co3O4/rGO composites and the effect of rGO on their acetone-sensing performance were systematically investigated. The results show that the sample with an optimized content of rGO (Co3O4/rGO-1) achieves the highest stability and response to acetone (0.5 ~ 200 ppm) at a relatively low temperature (~160 °C). Also, the Co3O4/rGO-1 exhibits a high acetone-sensing selectivity against the gases (or vapors) of H2S, H2, CH4, HCHO, CH3OH, C3H8O and C2H5OH. The enhanced acetone-sensing performance of the Co3O4/rGO composite can be attributed to the Co3O4/rGO p-p heterojunction and the Co3+-C coupling effect between Co3O4 and rGO, improving transport of carriers. In addition, the unique 3D hierarchically porous structure and large surface areas are favorable to adsorption and desorption of gas molecules. This facile microwave-assisted method provides a charming strategy to develop smart rGO-based nanomaterials for real-time detection of harmful gases and rapid medical diagnosis.

Light-Associated Surface Wrinkling-Based Metrology for the Photosoftening Characterization in Azobenzene-Polymer Supramolecular Complexes.

As an intriguing characteristic of azobenzene-containing materials (azo-materials), photoinduced changes in mechanical properties (e.g., photosoftening) have stimulated many efforts both theoretically and experimentally. Here a simple yet powerful tool (i.e., a light-associated surface wrinkling-based method) to study the photosoftening effect in azobenzene-polymer (azo-polymer) supramolecular complexes is reported. The photo-induced modulus decrease of supramolecular complex films is deduced by analyzing the change of critical wrinkle wavelength of strain-induced surface wrinkling, in the case of varying experiment parameters. In particular, thanks to the facile modular tunability of the supramolecular system, the photosoftening effect has been systematically investigated as a function of azo-moiety content and the molecular weight of the host polymer. Notably, a photosoftening coefficient that is related to the chemical composition/structure of azo-polymers is introduced, and a simple formula that can quantify the connection of the photosoftening with external irradiation conditions and internal chemical factors of azo-polymers is derived for the first time. The obtained results are of great importance not only to enhance understanding of the photosoftening mechanism, but also to thoroughly apply it in diverse smart fields.

Microsized Red Luminescent MgAl2O4:Mn4+ Single-Crystal Phosphor Grown in Molten Salt for White LEDs.

A single-crystalline defect-less phosphor is desired for efficient luminescence of the therein doped optical activators. In this paper, microsized MgAl2O4:Mn4+ single-crystal phosphors with bright red luminescence were grown in molten LiCl salt at 950 °C, for application in blue LED pumped white lighting. By comparing the phosphor formation from various Mg2+- and Al3+-bearing sources, both the template-formation and the dissolution-diffusion processes were evidenced to account for the formation of the microsized MgAl2O4:Mn4+ crystallites. Using nano γ-Al2O3 as the Al3+-bearing precursor, the uniform MgAl2O4:Mn4+ microcrystallites with a {111} planes-exposed tetragonal bipyramid morphology were obtained. The photoluminescence property was studied at various temperatures, and Mg ↔ Al anti-site disorder induced luminescence broadening was discussed. The Mn4+ 2Eg → 4A2g transition in MgAl2O4 shows a quite short luminescence wavelength peaking at 651 nm and ultrabroadband emission extending to 850 nm. The luminescence is relatively robust against thermal effect with relatively high thermal quenching temperature of 400 K and activation energy of 0.23 eV. Employing the red-emitting MgAl2O4:Mn4+ crystallites, blue LED pumped white lighting prototypes were fabricated which simulate the solar-like spectrum and show neutral to warm white.

Ultrabroadband red luminescence of Mn4+ in MgAl2O4 peaking at 651 nm.

Blue light pumped red luminescence with broadband and high photon-energy emission is highly desired for phosphor-converted white light-emitting diodes (pc-wLEDs), to achieve a high color rendering index and high luminous efficacy. Mn4+-doped red-emitting phosphors generally exhibit sharp vibronic emissions associated with the parity- and spin-forbidden 2Eg→4A2g transitions. In this paper, two abnormal luminescence behaviors were observed for Mn4+ in the MgAl2O4:Mn4+ spinel phosphor with a short wavelength emission band peaking at 651 nm. Firstly, the Mn4+ 2Eg→4A2g transition exhibits ultrabroadband luminescence in MgAl2O4 and the large full-width at half-maximum (FWHM) is dependent both on the calcination temperature and on the partial substitution of Al3+ with Ga3+. Secondly, the thermal quenching behavior of the Mn4+ 2Eg→4A2g luminescence in MgAl2O4 shows a dependence on its thermal treatment and preparation method. The Rietveld refinement and Raman results demonstrate that the variation in the FWHM of the luminescence spectra is a sum effect of structural ordering (i.e., isotropic displacement decrease of constituent atoms) and the Mg ↔ Al anti-site disorder. A model for the observed varying thermal quenching of luminescence was tentatively proposed. The intrinsic thermal quenching temperature of Mn4+ luminescence in MgAl2O4 was found to be 390-400 K using the samples prepared by the co-precipitation and molten salt methods. The present work gives a novel perspective to understand the luminescence spectra of Mn4+ 2Eg→4A2g transition.

2D/1D V2O5 Nanoplates Anchored Carbon Nanofibers as Efficient Separator Interlayer for Highly Stable Lithium-Sulfur Battery.

Quick capacity loss due to the polysulfide shuttle effects is a critical challenge for high-performance lithium-sulfur (Li-S) batteries. Herein, a novel 2D/1D V2O5 nanoplates anchored carbon nanofiber (V-CF) interlayer coated on standard polypropylene (PP) separator is constructed, and a stabilization mechanism derived from a quasi-confined cushion space (QCCS) that can flexibly accommodate the polysulfide utilization is demonstrated. The incorporation of the V-CF interlayer ensures stable electron and ion pathway, and significantly enhanced long-term cycling performances are obtained. A Li-S battery assembled with the V-CF membrane exhibited a high initial capacity of 1140.8 mAh·g-1 and a reversed capacitance of 1110.2 mAh·g-1 after 100 cycles at 0.2 C. A high reversible capacity of 887.2 mAh·g-1 is also maintained after 500 cycles at 1 C, reaching an ultra-low decay rate of 0.0093% per cycle. The excellent electrochemical properties, especially the long-term cycling stability, can offer a promising designer protocol for developing highly stable Li-S batteries by introducing well-designed fine architectures to the separator.

Effects of ozone concentration on the postharvest quality and microbial diversity of Muscat Hamburg grapes.

Grapevines are widely planted around the world. Although grapes have high nutritional value, they are highly perishable. To explore the effect of ozone concentration on the postharvest quality of Muscat Hamburg grapes, the ethylene production rate, respiratory intensity, soluble solids, titratable acidity, firmness, threshing rate, total yeast and mold counts, and the activities of superoxide dismutase, peroxidase, catalase, polyphenol oxidase and phenylalanine ammonia lyase were determined, and the fungal metagenome on the grape surface was analyzed. Among the ozone treatment groups, 14.98 mg m-3 ozone showed a positive effect on grape preservation. After 80 days of storage, the contents of soluble solids and titratable acidity increased by 3.1% and 0.03%, respectively, compared with the control group. Over the same period, firmness increased by 4.22 N and the threshing rate decreased by 0.5%. During storage, the activity of polyphenol oxidase was inhibited and the activities of superoxide dismutase, peroxidase, catalase, and phenylalanine ammonia lyase were maintained, which delayed the senescence of grapes and maintained freshness. Ozone can reduce the number of fungi on the grape surface, change the colony structure, and reduce the occurrence of diseases. An ozone concentration of 14.98 mg m-3 can delay the senescence of Muscat Hamburg grapes and improve storage quality.

Effects of ozone treatment on the antioxidant capacity of postharvest strawberry.

Strawberries are highly popular around the world because of their juicy flesh and unique taste. However, they are delicate and extremely susceptible to peroxidation of their membrane lipids during storage, which induces water loss and rotting of the fruit. This study investigated the effects of ozone treatment on the physiological traits, active oxygen metabolism, and the antioxidant properties of postharvest strawberry. The results revealed that the weight loss (WL) and respiration rate (RR) of strawberry were inhibited by ozone treatment (OT), while the decline of firmness (FIR) and total soluble solids (TSS) were delayed. Ozone also reduced the generation rate of superoxide radical anions , and the content of hydrogen peroxide (H2O2) enhanced the activity of superoxidase (SOD), catalase (CAT), ascorbate peroxidase (APX), and monodehydroascorbate reductase (MDHAR), as well as promoted the accumulation of ascorbic acid (ASA), glutathione (GSH), and ferric reducing/antioxidant power (FRAP). In addition, a total of 29 antioxidant-related proteins were changed between the OT group and control (CK) group as detected by label-free proteomics during the storage time, and the abundance associated with ASA-GSH cycle was higher in the OT group at the later stage of storage, and the qRT-PCR results were consistent with those of proteomics. The improvement of the antioxidant capacity of postharvest strawberry treated with ozone may be achieved by enhancing the activity of the antioxidant enzymes and increasing the expression of the antioxidant proteins related to the ascorbic acid-glutathione (ASA-GSH) cycle.

Precursor-Engineering Coupled Microwave Molten-Salt Strategy Enhances Photocatalytic Hydrogen Evolution Performance of g-C3 N4 Nanostructures.

A precursor-engineering strategy coupled with a microwave molten-salt process (PE-MWMS) is developed to synthesize graphitic carbon nitride (g-C3 N4 ) with an isotype triazine/heptazine-based g-C3 N4 heterojunction as a photocatalyst for the hydrogen evolution reaction (HER) under visible light illumination. Four hybrid precursor combinations-thiourea/melamine, thiourea/dicyandiamide, urea/melamine, and urea/dicyandiamide-are used to synthesize g-C3 N4 heterojunctions by the PE-MWMS process. Control experiments indicate that the precursor components and microwave treatment have a great effect on the HER performance of the g-C3 N4 samples. Samples synthesized with the optimal molar ratios of thiourea/melamine (2:1), thiourea/dicyandiamide (2:1), urea/melamine (3:1), and urea/dicyandiamide (3:1), exhibit the highest HER rates of 3135, 2519, 2844, and 2565 µmol g-1 h-1 , respectively. The amounts of heptazine and triazine units in the g-C3 N4 samples can be easily adjusted by changing the ratios of the hybrid precursors and play a decisive role in improving the photocatalytic HER activity. Because of the unique composition and microstructure, the efficient separation of electron-hole pairs, the broadened photo-absorption edges, and the narrowed band gaps, the as-obtained triazine/heptazine-based g-C3 N4 nanostructures exhibit promising activity for HER application.

Intense deep-red zero phonon line emission of Mn4+ in double perovskite La4Ti3O12.

Phosphors that emit in the deep-red spectral region are critical for plant cultivation light-emitting diodes. Herein, ultrabroadband deep-red luminescence of Mn4+ in La4Ti3O12 was studied, which showed intense zero phonon line emission. The double-perovskite structural La4Ti3O12 simultaneously contains two Ti4+ sites forming slightly- and highly-distorted TiO6 octahedra, respectively. The influence of octahedral distortion on the Mn4+ emission energy in the two distinct Ti4+ sites was studied both experimentally and theoretically. The spectral measurements indicated that Mn4+ in La4Ti3O12 showed intense zero phonon line emission (ZPL) at deep-red 710-740 nm under excitation of 400 nm charging the O2-→ Mn4+ charge transfer transition. The splitting of the ZPL of the Mn4+ 2Eg→4A2g transition as well as the intensity of ZPL relative to the vibronic phonon sideband emissions were found to be greatly influenced by the degree of octahedral distortion. The crystal-field strength and Racah parameters of Mn4+ in each Ti4+ site were also estimated. The Mn4+ 2Eg→4A2g luminescence exhibited severe thermal quenching, which was explained by the low-lying 4T2g level and charge-transfer state.

Linear-Polyethyleneimine-Templated Synthesis of N-Doped Carbon Nanonet Flakes for High-performance Supercapacitor Electrodes.

Novel N-doped carbon nanonet flakes (NCNFs), consisting of three-dimensional interconnected carbon nanotube and penetrable mesopore channels were synthesized in the assistance of a hybrid catalytic template of silica-coated-linear polyethyleneimine (PEI). Resorcinol-formaldehyde resin and melamine were used as precursors for carbon and nitrogen, respectively, which were spontaneously formed on the silica-coated-PEI template and then annealed at 700 °C in a N2 atmosphere to be transformed into the hierarchical 3D N-doped carbon nanonetworks. The obtained NCNFs possess high surface area (946 m2 g-1), uniform pore size (2-5 nm), and excellent electron and ion conductivity, which were quite beneficial for electrochemical double-layered supercapacitors (EDLSs). The supercapacitor synthesized from NCNFs electrodes exhibited both extremely high capacitance (up to 613 F g-1 at 1 A g-1) and excellent long-term capacitance retention performance (96% capacitive retention after 20,000 cycles), which established the current processing among the most competitive strategies for the synthesis of high performance supercapacitors.