Mechanically Enhanced Nanocrystalline Cellulose/Reduced Graphene Oxide/Polyethylene Glycol Electrically Conductive Composite Film.

Traditional conductive materials do not meet the increasing requirements of electronic products because of such materials' high rigidity, poor flexibility, and slow biodegradation after disposal. Preparing flexible conductive materials with excellent mechanical properties is an active area of research. The key to flexible conductive materials lies in the combination of the polymer matrix and conductive components. This combination can be achieved by making a film of renewable nano-microcrystalline cellulose (NCC) and reduced graphene oxide (rGO) with excellent electrical conductivity-by simple filtration and introducing polyethylene glycol (PEG) to enhance the functionality of the composite film. Graphene imparted conductivity to the composite film, which reached 5.67 S·m-1. A reinforced NCC/rGO/PEG-4 composite film with a thickness of only 21 µm exhibited a tensile strength of 30.56 MPa, which was 83% higher than that of the sample without PEG (16.71 MPa), and toughness of 727.18 kJ·m-3, which was about 132% higher than that of the control sample (NCC/rGO, 313.86 kJ·m-3). This ultra-thin conductive composite film-which can be prepared simply, consists of environmentally sustainable and biodegradable raw materials, and exhibits excellent mechanical properties-has substantial potential for applications in e.g., flexible electronic wearable devices, electrodes, and capacitors.

Ultralight, Mechanically Enhanced, and Thermally Improved Graphene-Cellulose-Polyethyleneimine Aerogels for the Adsorption of Anionic and Cationic Dyes.

Graphene-cellulose-polyethyleneimine aerogels (GA-MCC-PEI) were prepared using a simple, environmentally friendly method to remove anionic and cationic dyes in water. Graphene-cellulose hydrogels were prepared using a hydrothermal method and then immersed in a polyethyleneimine aqueous solution for 48 h to obtain graphene-cellulose-polyethyleneimine hydrogels, which were then freeze-dried. The light and porous composite aerogels had a good compression resistance, and the maximum allowable pressure of the graphene-cellulose-polyethyleneimine aerogel with a cellulose content of 43% was 21.76 kPa, which was 827 times its weight. Adsorption of the anionic dye amaranth and the cationic dye methylene blue by the graphene-cellulose-polyethyleneimine aerogel was satisfactorily modeled using the Langmuir isothermal equation, indicating monolayer adsorption. When the cellulose content was 39%, the equilibrium adsorption capacities of the composite aerogel for amaranth and methylene blue were 369.37 mg/g and 237.33 mg/g, respectively. This graphene-cellulose-polyethyleneimine aerogel can be used to remove dye pollutants in water to maintain ecological balance, thus broadening the application space of aerogel materials, that is, as adsorbents in different environments.

Mechanically Strong, Low Thermal Conductivity and Improved Thermal Stability Polyvinyl Alcohol-Graphene-Nanocellulose Aerogel.

Porous aerogel materials have advantages of a low density, low thermal conductivity and high porosity, and they have broad application prospects in heat insulation and building energy conservation. However, aerogel materials usually exhibit poor mechanical properties. Single-component aerogels are less likely to possess a good thermal stability and mechanical properties. It is necessary to prepare multiple-composite aerogels by reinforcement to meet practical application needs. In this experiment, a simple preparation method for polyvinyl alcohol (PVA)-graphene (GA)-nanocellulose (CNF) ternary composite aerogels was proposed. This is also the first time to prepare ternary composite aerogels by mixing graphene, nanocellulose and polyvinyl alcohol. A GA-CNF hydrogel was prepared by a one-step hydrothermal method, and soaked in PVA solution for 48 h to obtain a PVA-GA-CNF hydrogel. PVA-GA-CNF aerogels were prepared by freeze drying. The ternary composite aerogel has advantages of excellent mechanical properties, a low thermal conductivity and an improved thermal stability, because strong hydrogen bonds form between the PVA, GA and CNF. The composite aerogels were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, Brunauer-Emmett-Teller analysis, dynamic thermal analysis, thermogravimetry and thermal constant analysis to characterize the properties of the ternary composite aerogels. The lightweight, low-density and porous PVA-GA-CNF composite aerogels withstood 628 times their mass. The thermal conductivity of the composite aerogels was 0.044 ± 0.005 W/mK at room temperature and 0.045 ± 0.005 W/mK at 70 °C. This solid, low thermal conductivity and good thermal stability PVA-GA-CNF ternary composite aerogel has potential application in thermal insulation.

Ultralight, High Capacitance, Mechanically Strong Graphene-Cellulose Aerogels.

With increasing energy demand driving the need for eco-friendly and efficient energy storage technology, supercapacitors are becoming increasingly prevalent in wearable devices because of their portability and stability. The performance of these supercapacitors is highly dependent on the choice of electrode material. The high capacitance and mechanical properties needed for these materials can be achieved by combining graphene's stable electrical properties with renewable cellulose's excellent mechanical properties into porous aerogels. In this study, graphene-cellulose hydrogels were prepared by a one-step hydrothermal method, with porous, ultra-light, and mechanically strong graphene-cellulose aerogels then prepared by freeze-drying. These composite aerogels possess excellent mechanical strength and high specific capacitance, capable of bearing about 1095 times the pressure of their own weight. Electrochemical tests show the specific capacitance of these composite aerogels can reach 202 F/g at a scanning rate of 5 mA/cm2. In view of their high surface area and fast charge transport provided by their 3D porous structure, graphene-cellulose aerogels have great potential as sustainable supercapacitor electrodes.

Synthesis, characterization and computational studies of Zn complex based on the 8-hydroxyquinoline group containing benzimidazole.

A novel fluorescent zinc complex with 8-hydroxyquinoline containing benzimidazole ligands has been designed and synthesized. Its emission, IR spectroscopy, thermo-gravimetric analysis as well as electrochemical properties have been studied. The solid-state structures were determined via single crystal X-ray diffraction and powder X-ray diffraction. It was found that the ligands around the Zn atoms are distorted by the constrained coordination environment. Computational studies have also been performed to provide insights into the electronic transitions, excited state origins and electrochemical properties of the complex. Based on the observed luminescence phenomena and the quantum chemical calculated results, it was also investigated that the energy transfer mechanism for the luminescence of the complex, which indicated that the ligand structural distortion could cause the blue shift in the emission profile of the complex.

Adamantane-Based Micro- and Ultra-Microporous Frameworks for Efficient Small Gas and Toxic Organic Vapor Adsorption.

Microporous organic polymers and related porous materials have been applied in a wide range of practical applications such as adsorption, catalysis, adsorption, and sensing fields. However, some limitations, like wide pore size distribution, may limit their further applications, especially for adsorption. Here, micro- and ultra-microporous frameworks (HBPBA-D and TBBPA-D) were designed and synthesized via Sonogashira⁻Hagihara coupling of six/eight-arm bromophenyl adamantane-based "knots" and alkynes-type "rod" monomers. The BET surface area and pore size distribution of these frameworks were in the region of 395⁻488 m² g-1, 0.9⁻1.1 and 0.42 nm, respectively. The as-made prepared frameworks also showed good chemical ability and high thermal stability up to 350 °C, and at 800 °C only 30% mass loss was observed. Their adsorption capacities for small gas molecules such as CO2 and CH4 was 8.9⁻9.0 wt % and 1.43⁻1.63 wt % at 273 K/1 bar, and for the toxic organic vapors n-hexane and benzene, 104⁻172 mg g-1 and 144⁻272 mg g-1 at 298 K/0.8 bar, respectively. These are comparable to many porous polymers with higher BET specific surface areas or after functionalization. These properties make the resulting frameworks efficient absorbent alternatives for small gas or toxic vapor capture, especially in harsh environments.

Synthesis and properties of blue luminescent bipolar materials constructed with carbazole and anthracene units with 4-cyanophenyl substitute at the 9-position of the carbazole unit.

With carbazole and p-cyanobromobenzene as raw materials, 4-(3,6-di (anthracen-9-yl)-9H-carbazol-9-yl)benzonitrile (DACB) and 4-(3,6-bis(anthracene -9-ylethynyl)-9H-carbazol-9-yl)benzonitrile (BACB) were synthesized through the Suzuki coupling reaction and the Sonogashira coupling reaction, respectively. These structures were characterized using 1 H nuclear magnetic resonance (NMR), elemental analysis and mass spectrometry. Their thermal properties, ultraviolet-visible (UV-vis) absorption, fluorescence emission, fluorescence quantum yields and electrochemical properties were also investigated systematically. In addition, a electroluminescence (EL) device was made with BACB as the emitting layer and performance of the EL device was studied. Results showed that: (1) the temperature points with 5% and 10% of DACB weight loss were 443°C and 461°C, respectively, and were 475°C and 506°C with BACB weight loss of 5% and 10%, respectively. When the temperature was 50-300°C, no significantly thermal transition was observed which suggested that they had excellent thermal stability. (2) DACB and BACB had single emission peaks at 415 nm, and 479 nm with fluorescence quantum yields of 0.61 and 0.87, respectively, indicating that both compounds could emit strong blue light. (3) According to electrochemical measurement on BACB and DACB, their gaps were 3.07 eV and 2.76 eV, respectively, which further showed that these two compounds were very stable and acted as efficient blue light materials. (4) The turn-on voltage of the device was 5 V, and the device emitted dark blue light with Commission Internationale de L'Eclairage (CIE) coordinates of (0.157, 0.079).

[Imaging diagnosis of lumbar spinal stenosis].

OBJECTIVE: To investigate value of X-ray, CT and MRI for the diagnosis of lumbar spinal stenosis. METHODS: The data of 130 patients with clinical diagnosis and typical imaging signs of lumbar spinal stenosis were analyzed. The present study included 83 males and 47 females with an average age of 43.5 years (range from 27 to 75 years). CT examination was performed in all patients, routine X-ray examination in 23 patients and routine MRI in 57 patients. RESULTS: The lumbar spinal stenosis showed at L(3,4) plane in 25 patients, L(4,5) in 48 patients and L5S1 in 57 patients. CT showed hyperostosis of lumbar posterior marginal, vertebral lamina, inferior articular process in 46 patients, hypertrophy of superior and inferior articular processsus in 7 patients, calcification or ossification of ligamentum flavum in 13 patients, vertebral body spondylolisthesis in 5 patients, lateral recess stenosis in 24 patients, and intervertebral foramen stenosis in 35 patients. MRI showed intervertebral disk hernia with disc associated with ligamentum flavum hypertrophy in 23 patients, ligamentum flavum symmetrical hypertrophy in 18 patients,extensive multi-segmental ligamentum flavum hypertrophy in 9 patients,and local ligamentum flavum hypertrophy in 7 patients. CONCLUSION: The main cause of secondary lumbar spinal stenosis is degeneration. Traditional X-ray examination has great limitations in diagnosis of lumbar spinal stenosis. CT and MRI have advantages of multi-directional imaging and the high resolution. CT can show well ligament calcification and ossification and other bone change which are showed not well on MRI, so CT is recommended to lumbar spinal stenosis.