Major losses of fresh horticultural produce transpire during postharvest storage due to prompt senescence and diseases. The traditional postharvest preservation techniques used after harvest are based on cooling and the application of chemical preservation techniques. As a residue-free physical sterilization and preservation method, light-emitting diode (LED) treatment, has recently been applied for postharvest storage of fruits and vegetables by numerous researchers. This paper reviews the recent applications of LEDs in postharvest storage of fresh produce, including its effect on physiological characteristics, secondary metabolism, nutritional attributes, ripening process, senescence, shelf-life improvement, and pathogenic microbial spoilage of fruits and vegetables. LED treatment has promoted the accumulation of different phytochemicals, such as phenolic compounds, vitamins, glucosinolates, chlorophyll, total soluble solids, and carotenoids. Changes in the nutritional content, anthocyanin content, antioxidant capacity, and ripening were also observed after the treatment. Reduction in microbial spoilage and delay senescence were evident after the LED exposure. The influence of LED light depended on the fruit and vegetable variety. Therefore, LED treatment is an efficient and promising strategy for extending the storage life of fruits and vegetables with enhanced nutritional values.

Effect of Light-Emitting Diodes (LEDs) on the Quality of Fruits and Vegetables During Postharvest Period: a Review

As a typical carbon nanomaterial, graphene is frequently used as a modified material due to its excellent optical, electrical, and mechanical properties. Composite materials combining graphene with silicone rubber or silicone resin have significantly improved electrical, thermal, and mechanical properties compared with sole silicone rubber or silicone resin. This paper focused on the influence of graphene on the properties of silicone rubber and silicone resin in recent years. In addition, the application of graphene/silicone rubber composites in sensors and microwave absorption materials was also summarized. This review is expected to provide a systematic and fundamental understanding of the modification effect of graphene on silicone rubber and silicone resin, and look forward to the application of their composite materials in wearable electronic devices and other emerging fields, hope to inspire and perfect the future design of composites and expand their applications.

Effects of graphene on various properties and applications of silicone rubber and silicone resin

In the present study, Eeonomer 200F® was used as a high-performance nanofiller to prepare polyvinyl alcohol (PVA)-based nanocomposite films using a simple and eco-friendly solution casting technique. The prepared PVA/Eeonomer nanocomposite films were further investigated using various techniques including Fourier transform infrared spectroscopy, x-ray diffraction, thermogravimetric analysis, polarized optical microscopy, scanning electron microscopy and mechanical testing. The dielectric behavior of the nanocomposites was examined over a broad frequency range from 50 Hz to 20 MHz and temperatures ranging from 40°C to 150°C. A notable improvement in the thermal stability of the PVA was observed with the incorporation of Eeonomer. The nanocomposites also demonstrated improved mechanical properties due to the fine dispersion of the Eeonomer, and good compatibility and strong interaction between the Eeonomer and the PVA matrix. A significant improvement was observed in the dielectric properties of the PVA upon the addition of Eeonomer. The nanocomposites containing 5 wt.% Eeonomer exhibited a dielectric constant of about 222.65 (50 Hz, 150°C), which was 18 times that of the dielectric constant (12.33) of neat PVA film under the same experimental conditions. These results thus indicate that PVA/Eeonomer nanocomposites can be used as a flexible high-k dielectric material for embedded capacitor applications.

Eeonomer 200F®: A High-Performance Nanofiller for Polymer Reinforcement—Investigation of the Structure, Morphology and Dielectric Properties of Polyvinyl Alcohol/Eeonomer-200F® Nanocomposites for Embedded Capacitor Applications

Preparation and cure kinetics of epoxy with nanodiamond modified with liquid crystalline epoxy

Interest in the development of graphene-based materials for advanced applications is growing, because of the unique features of such nanomaterials and, above all, of their outstanding versatility, which enables several functionalization pathways that lead to materials with extremely tunable properties and architectures. This review is focused on the careful examination of relationships between synthetic approaches currently used to derivatize graphene, main properties achieved, and target applications proposed. Use of functionalized graphene nanomaterials in six engineering areas (materials with enhanced mechanical and thermal performance, energy, sensors, biomedical, water treatment, and catalysis) was critically reviewed, pointing out the latest advances and potential challenges associated with the application of such materials, with a major focus on the effect that the physicochemical features imparted by functionalization routes exert on the achievement of ultimate properties capable of satisfying or even improving the current demand in each field. Finally, current limitations in terms of basic scientific knowledge and nanotechnology were highlighted, along with the potential future directions towards the full exploitation of such fascinating nanomaterials.

An Overview of Functionalized Graphene Nanomaterials for Advanced Applications.

A liquid crystalline molecule, polyurethane-imide (PUI), was used to functionalize graphene nanoplatelets (GNS) via covalent bond and π–π interactions. The PUI functionalized graphene nanoplatelets (PUI–GNS) were characterized by fluorescence spectroscopy, thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman spectroscopy, and then mixed with silicone resin as fillers to fabricate silicon resin nanocomposites. The drastic quenching of the PUI fluorescence elucidated that the biphenyl anchoring unit of liquid crystalline PUI was strongly interacted with the surface of graphene sheets via π–π interactions. FTIR and Raman spectroscopy proved the existence of a covalent interaction between the PUI and GNS. The mechanical properties testing indicated that the tensile strength of silicon resin nanocomposites increased by 521% over that of a neat silicon resin when the mass fraction of PUI–GNS was 1.0%, and the elastic modulus of the silicon resin nanocomposite increased by 902% over that of the neat silicon resin if it came up to 2.0%. The thermal conductivity of the resin filled with the PUI–GNS was improved to be 1.3822 W (m K)−1 at a mass fraction of 10.0%, which was enhanced more than 16.5 times over that of the neat silicon resin. The resulting thermally conductive and mechanically applicable silicon resin nanocomposites could be significant in a wide variety of electronic packaging applications.

Liquid crystal functionalization of graphene nanoplatelets for improved thermal and mechanical properties of silicone resin composites


 Light-emitting diodes (LED) chip scale packages (CSPs) have been promoted as a new light source with many advantages in smaller package size, lower material and process cost, and better heat dissipation effect. However, as it is exposed in harsh environments such as high temperature, high humidity, and high blue light irradiation, silicone material used in LED CSPs always suffers deterioration, which will seriously affect the LED's reliability and working life. Thus, the preparation of high reliable silicone has practical significance to promote the application of LED CSPs in lighting. In this research, titanium was introduced into the molecular chain of phenyl silicone by using the hydrolysis condensation method. A high temperature aging test was then performed to the prepared silicone before and after modification, and their optical, thermomechanical, and dielectric properties were characterized to evaluate their reliabilities. The results show that: (1) the Arrhenius function with the dielectric property as an aging characterization can be used as a temperature accelerated life model to predict the service life of the prepared silicone and (2) the titanium modified silicone can advance the high temperature stability on optical properties, thermomechanical, and dielectric properties and enhance the life expectancy. The major contributions of this study are to support the improvement of the novel LED CSP packaging materials and processes, and also to provide the technical guidance on the fast, accurate, and cost-effective reliability assessment for high-quality LED light sources.

High Temperature Performance Evaluation and Life Prediction for Titanium Modified Silicone Used in Light-Emitting Diodes Chip Scale Packages

In this paper, the polycarbonate (PC) materials were aged using a monochromatic light source of wavelength 185 nm using a model UV-O 3 Clear for a study of light decomposition. The Fourier Transform infrared spectroscopy (FTIR) results showed that intensities of the peak bands corresponding to C=O, C-O, -O-CH- at 1690 cm−1, 1160–1254cm−1, 1050cm−1, decreased with the increase of the aging time, respectively. But the isopropyl at 1380cm−1 didn't show obvious change. In addition, it was found that after the aging test, the thermal decomposition temperatures of the PC samples increased by 21%. Moreover, UV-Visible absorption spectroscopy showed that a band at 290 nm could be contributed to increase of phenolic OH content during aging. Transmittance spectroscopy revealed that the transmittance of the samples decreased with the aging time. And there were not significant changes in the transmittance due to the aging when the samples were exposed to UV radiation for 3 hours above 500 nm.

Si Yu

Papers

Liquid crystal functionalization of graphene nanoplatelets for improved thermal and mechanical properties of silicone resin composites

High Temperature Performance Evaluation and Life Prediction for Titanium Modified Silicone Used in Light-Emitting Diodes Chip Scale Packages

Light decomposition characteristics of UV-irradiated polycarbonate