Recent research and applications in lipid-based food and lipid-incorporated bioink for 3D printing.

Three-dimensional (3D) printing, as an emerging digital production technology, has recently been receiving increasing attention in food processing. It is important to understand the effect of key ingredients of food materials on the printing, which makes it possible to achieve a wider range of structures using few nozzles and to provide tailored nutrition and personalization. This comprehensive review delves into the latest research on 3D-printed lipid-based foods, encompassing a variety of products such as chocolate, processed cheese, as well as meat. It also explores the development and application of food bioinks that incorporate lipids as a pivotal component, including those based on starch, protein, oleogels, bigels, and emulsions, as well as emulsion gels. Moreover, this review identifies the current challenges and presents an outlook on future research directions in the field of 3D food printing, especially the research and application of lipids in food 3D printing.

Incorporation of ascorbic acid in chitosan-based coating combined with plasma-activated water: A technology for quality preservation of red grapes after simulated transportation.

Red grapes possess multiple bioactivities but are highly susceptible to spoilage due to the lack of efficient preservation techniques. Plasma-activated water (PAW) treatment and the incorporation of antioxidants in bio-based coatings are promising methods for preserving produce. In this study, we tested a novel combination by incorporating ascorbic acid (AA) into a chitosan-based edible coating (CH) and combining it with plasma-activated water (PAW) treatment (CA-PAW) before simulating transport vibrations to extend the shelf-life of red grapes. The results from storage at 4 °C for 20 d indicated that the CA-PAW treatment reduced microbial counts by 2.62 log10 CFU/g for bacteria, 1.72 log10 CFU/g for yeasts and molds, and 1.1 log10 CFU/g for coliforms, in comparison to the control group treated with sterile deionized water. Total phenols and total flavonoid content were the highest observed, at 111.2 mg GAE/100 g and 262.67 mg RE/100 g, respectively. This treatment also inhibited water migration and erosion, and reduced damage to cell structure. Microstructural observations revealed that the CH coating on the surface of red grapes diminished the degradation of bioactive components. In conclusion, the CA-PAW treatment effectively inhibited the adverse physiological changes caused by vibration and mechanical damage to red grapes, maintained their nutritional and sensory qualities, and extended the shelf life by at least 8 d.

Enhanced Electrical Transport Properties of Molybdenum Disulfide Field-Effect Transistors by Using Alkali Metal Fluorides as Dielectric Capping Layers.

The electronic properties of 2D materials are highly influenced by the molecular activity at their interfaces. A method was proposed to address this issue by employing passivation techniques using monolayer MoS2 field-effect transistors (FETs) while preserving high performance. Herein, we have used alkali metal fluorides as dielectric capping layers, including lithium fluoride (LiF), sodium fluoride (NaF), and potassium fluoride (KF) dielectric capping layers, to mitigate the environmental impact of oxygen and water exposure. Among them, the LiF dielectric capping layer significantly improved the transistor performance, specifically in terms of enhanced field effect mobility from 74 to 137 cm2/V·s, increased current density from 17 µA/µm to 32.13 µA/µm at a drain voltage of Vd of 1 V, and decreased subthreshold swing to 0.8 V/dec The results have been analytically verified by X-ray photoelectron spectroscopy (XPS) and Raman, and photoluminescence (PL) spectroscopy, and the demonstrated technique can be extended to other transition metal dichalcogenide (TMD)-based FETs, which can become a prospect for cutting-edge electronic applications. These findings highlight certain important trade-offs and provide insight into the significance of interface control and passivation material choice on the electrical stability, performance, and enhancement of the MoS2 FET.

Nonvolatile molecular memory with the multilevel states based on MoS2 nanochannel field effect transistor through tuning gate voltage to control molecular configurations.

A new flexible memory element is crucial for mobile and wearable electronics. A new concept for memory operation and innovative device structure with new materials is certainly required to address the bottleneck of memory applications now and in the future. We report a new nonvolatile molecular memory with a new operating mechanism based on two-dimensional (2D) material nanochannel field-effect transistors (FETs). The smallest channel length for our 2D material nanochannel FETs was approximately 30 nm. The modified molecular configuration for charge induced in the nanochannel of the MoS2 FET can be tuned by applying an up-gate voltage pulse, which can vary the channel conductance to exhibit memory states. Through controlling the amounts of triggered molecules through either different gate voltage pulses or gate duration time, multilevel states were obtained in the molecular memory. These new molecular memory transistors exhibited an erase/program ratio of more than three orders of current magnitude and high sensitivity, of a few picoamperes, at the current level. Reproducible operation and four-level states with stable retention and endurance were achieved. We believe this prototype device has potential for use in future memory devices.

Observation of Wigner crystal phase and ripplon-limited mobility behavior in monolayer CVD MoS2 with grain boundary.

Two-dimensional electron gas (2DEG) is crucial in condensed matter physics and is present on the surface of liquid helium and at the interface of semiconductors. Monolayer MoS2 of 2D materials also contains 2DEG in an atomic layer as a field effect transistor (FET) ultrathin channel. In this study, we synthesized double triangular MoS2 through a chemical vapor deposition method to obtain grain boundaries for forming a ripple structure in the FET channel. When the temperature was higher than approximately 175 K, the temperature dependence of the electron mobility µ was consistent with those in previous experiments and theoretical predictions. When the temperature was lower than approximately 175 K, the mobility behavior decreased with the temperature; this finding was also consistent with that of the previous experiments. We are the first research group to explain the decreasing mobility behavior by using the Wigner crystal phase and to discover the temperature independence of ripplon-limited mobility behavior at lower temperatures. Although these mobility behaviors have been studied on the surface of liquid helium through theories and experiments, they have not been previously analyzed in 2D materials and semiconductors. We are the first research group to report the similar temperature-dependent mobility behavior of the surface of liquid helium and the monolayer MoS2.

High-Current Gain Two-Dimensional MoS2-Base Hot-Electron Transistors.

The vertical transport of nonequilibrium charge carriers through semiconductor heterostructures has led to milestones in electronics with the development of the hot-electron transistor. Recently, significant advances have been made with atomically sharp heterostructures implementing various two-dimensional materials. Although graphene-base hot-electron transistors show great promise for electronic switching at high frequencies, they are limited by their low current gain. Here we show that, by choosing MoS2 and HfO2 for the filter barrier interface and using a noncrystalline semiconductor such as ITO for the collector, we can achieve an unprecedentedly high-current gain (α ∼ 0.95) in our hot-electron transistors operating at room temperature. Furthermore, the current gain can be tuned over 2 orders of magnitude with the collector-base voltage albeit this feature currently presents a drawback in the transistor performance metrics such as poor output resistance and poor intrinsic voltage gain. We anticipate our transistors will pave the way toward the realization of novel flexible 2D material-based high-density, low-energy, and high-frequency hot-carrier electronic applications.

Piezoelectric effect in chemical vapour deposition-grown atomic-monolayer triangular molybdenum disulfide piezotronics.

High-performance piezoelectricity in monolayer semiconducting transition metal dichalcogenides is highly desirable for the development of nanosensors, piezotronics and photo-piezotransistors. Here we report the experimental study of the theoretically predicted piezoelectric effect in triangle monolayer MoS2 devices under isotropic mechanical deformation. The experimental observation indicates that the conductivity of MoS2 devices can be actively modulated by the piezoelectric charge polarization-induced built-in electric field under strain variation. These polarization charges alter the Schottky barrier height on both contacts, resulting in a barrier height increase with increasing compressive strain and decrease with increasing tensile strain. The underlying mechanism of strain-induced in-plane charge polarization is proposed and discussed using energy band diagrams. In addition, a new type of MoS2 strain/force sensor built using a monolayer MoS2 triangle is also demonstrated. Our results provide evidence for strain-gating monolayer MoS2 piezotronics, a promising avenue for achieving augmented functionalities in next-generation electronic and mechanical-electronic nanodevices.

Polymer-free patterning of graphene at sub-10-nm scale by low-energy repetitive electron beam.

A polymer-free technique for generating nanopatterns on both synthesized and exfoliated graphene sheets is proposed and demonstrated. A low-energy (5-30 keV) scanning electron beam with variable repetition rates is used to etch suspended and unsuspended graphene sheets on designed locations. The patterning mechanisms involve a defect-induced knockout process in the initial etching stage and a heat-induced curling process in a later stage. Rough pattern edges appear due to inevitable stochastic knockout of carbon atoms or graphene structure imperfection and can be smoothed by thermal annealing. By using this technique, the minimum feature sizes achieved are about 5 nm for suspended and 7 nm for unsuspended graphene. This study demonstrates a polymer-free direct nanopatterning approach for graphene.

Resonant tunneling through discrete quantum states in stacked atomic-layered MoS2.

Two-dimensional crystals can be assembled into three-dimensional stacks with atomic layer precision, which have already shown plenty of fascinating physical phenomena and been used for prototype vertical-field-effect-transistors.1,2 In this work, interlayer electron tunneling in stacked high-quality crystalline MoS2 films were investigated. A trilayered MoS2 film was sandwiched between top and bottom electrodes with an adjacent bottom gate, and the discrete energy levels in each layer could be tuned by bias and gate voltages. When the discrete energy levels aligned, a resonant tunneling peak appeared in the current-voltage characteristics. The peak position shifts linearly with perpendicular magnetic field, indicating formation of Landau levels. From this linear dependence, the effective mass and Fermi velocity are determined and are confirmed by electronic structure calculations. These fundamental parameters are useful for exploitation of its unique properties.

Direct formation of wafer scale graphene thin layers on insulating substrates by chemical vapor deposition.

Direct formation of high-quality and wafer scale graphene thin layers on insulating gate dielectrics such as SiO(2) is emergent for graphene electronics using Si-wafer compatible fabrication. Here, we report that in a chemical vapor deposition process the carbon species dissociated on Cu surfaces not only result in graphene layers on top of the catalytic Cu thin films but also diffuse through Cu grain boundaries to the interface between Cu and underlying dielectrics. Optimization of the process parameters leads to a continuous and large-area graphene thin layers directly formed on top of the dielectrics. The bottom-gated transistor characteristics for the graphene films have shown quite comparable carrier mobility compared to the top-layer graphene. The proposed method allows us to achieve wafer-sized graphene on versatile insulating substrates without the need of graphene transfer.

Direct observation of electron dephasing due to inelastic scattering from defects in weakly disordered AuPd wires.

To identify and investigate the mechanisms of electron-phonon (e-ph) relaxation in weakly disordered metallic conductors, we measure the electron dephasing rate in a series of suspended and supported 15-nm thick AuPd wires. In a wide temperature range, from ∼8 K to above 20 K, the e-ph interaction dominates in the dephasing processes. The corresponding relaxation rate reveals a quadratic temperature dependence, τ(e-ph)(-1)=A(ep)T2, where A(ep)≈5×10(9) K(-2) s(-1) is essentially the same for all samples studied. Our observations are shown to be in good agreement with the theory which predicts that, even in weakly disordered metallic structures at moderately low temperatures, the major mechanism of the e-ph relaxation is the electron scattering from vibrating defects and impurities.