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Crude extracts of Sedum formosanum N.E.Br. obtained from n-butanol partition (BP) and isopropanol salting-out pretreatment (ISP) were analyzed using antioxidation assays. The results indicated that the extract from ISP contained more potent antioxidants and thus exhibited more antioxidant activity in all the assays. The superoxide radical-scavenging activity and inhibition of nitric oxide radicals achieved after ISP were 3.65 and 2.18 times higher than those achieved through BP, respectively. Eight bioactive natural products were isolated and identified according to an analysis of antioxidation activity in different fractions of the ISP crude extract, namely three cyanophoric glycosides 1–3, three flavonoids 4–6 and two phenolic compounds (7 and a new compound 8). Among them, compounds 5 and 6 exhibit the highest antioxidation capability, and the ISP is suitable for obtaining compounds 5 and 6 using HPLC chromatograms. Therefore, ISP is an excellent extraction technology that can be used to extract antioxidant compounds in the nutraceutical and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

The objects of this research are to study the dispersion of CNT (carbon nanotube) in SDS (sodium dodecyl sulfate) aqueous solutions with kinetics approach and to obtain some information about mechanism for this dispersion. Firstly, I measured the UV-visible absorption at 260 nm of CNT in SDS aqueous solutions after different time of dispersion for different concentrations of CNT and SDS. Then, curves of the time-dependent absorbance were analyzed by various mathematical models and were found to fit well with equation of A = A∞ exp(-kobs t), where A∞ is the absorbance at infinite time and kobs is the observed rate constant. The values of A∞, kobs, and, minimum time for dispersion can be obtained. From the effects of concentrations of SDS and CNT on A∞ and kobs, the dissociation constant for CNT-SDS complex and the optimum ratio of [CNT]/[SDS] can be estimated. Finally, the mechanism for this dispersion may be proposed as' $\rm{b-CNT \xrightleftharpoons[\rm{k_{-1} \left[CNT\right]} ]{\rm{k_{1}}} CNT \xrightharpoon[]{\rm{k_{2} \left[SDS\right]}} CNT-SDS}$ where b-CNT, CNT, CNT-SDS, and, ki s are bounded CNT, exfoliated CNT, CNT-SDS complex, and, the rate constants, respectively. In this mechanism, b-CNT is firstly unbounded by supersonic energy to form CNT intermediate with rate constant of k1, which is proportional to the supersonic energy per time. The CNT intermediate then recombines to form b-CNT with rate constant k−1[CNT] or reacts with SDS to form CNT-SDS complex, which has absorbance at 260 nm in UV-visible spectrum, with rate constant of k2 [SDS]. Details of kinetics and mechanism will be discussed in this paper. [ABSTRACT FROM AUTHOR]

Highlights: [•] The supercritical fluid treatment can efficiently reduce the operation current of resistance random access memory. [•] The dangling bonds of Sn:SiO x thin film were cross linking by the hydration–dehydration reaction by supercritical fluid treatment. [•] The current conduction mechanism of low resistance state in post-treated RRAM device was dominated by hopping conduction. [•] The current conduction mechanism of high resistance state in post-treated RRAM device was dominated by Schottky emission. [ABSTRACT FROM AUTHOR]

New organic-inorganic hybrid materials and their anti-electrostatic hybrid membranes are prepared via sol-gel process. The polycondensation of epoxy oligomers and AEAPS/Al2O3 complexes which are organically surface modified submicrometer aluminum trihydroxide inorganic fillers with an active aminoterminal silane coupling agent, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS), are performed. AEAPS enhances the interfacial interactions between the inorganic fillers and epoxy polymers. Meanwhile, this coupling agent maintains well dispersion of fillers in these composites. To improve the mechanical strength and thermal stability, pyromellitic dianhydride (PMDA) is used as curing agent. These hybrid films prepared from this method have excellent physical properties, such as UV-shielding, high transmission in visible resign (> 85%), high hardness (7∼8H) , high adhesive force (7∼8) and low relative surface resistance (9.71 × 1011∼1.26 × 1010 Ω/cm2) with anti-electrostatic characters. For thermal resistance, the best Td value of epoxy/PMDA/AEAPS/Al2O3 is 378.6 °C which is 85.4 °C higher than that of neat epoxy resin. Physical properties of these materials are almost the same as those of the nanocomposites prepared from expensive colloid Al2O3. Evidences from TEM micrograph show that the inorganic additives are dispersed evenly in organic matrix with nanometer scale. [ABSTRACT FROM AUTHOR]

Abstract: Seven flavonoid glycosides (1–7) and one theasaponin (8) were isolated from the defatted Camellia oleifera seeds using the isopropanol salting-out pretreatment (ISP) technique, followed by column chromatography. Among them, compounds 5, 7, and 8 are new compounds. The comparison of oxygen radical absorbance capacity (ORAC) of crude extracts extracted by the n-butanol partition (BP) with those extracted by the ISP showed that the latter method yields eight times greater scavenging capacities than that of the former approach. Besides, ISP exhibited almost twice the extraction efficiency than that of BP. ORAC and Trolox equivalent antioxidant capacity (TEAC) analysis revealed that the most potent antioxidants are compounds 1 and 2, which exhibited 1.78 and 1.41 times higher antioxidant activity than that of Trolox, respectively. These results indicated that the ISP approach improves the extraction efficiency in the isolation of potent antioxidants, making the defatted C. oleifera seeds valuable in the food additive industry. [Copyright &y& Elsevier]

Abstract: The purpose of this research was to investigate a salting-out procedure for isolating four flavonoid glycosides from defatted Camellia oleifera seeds. The procedure included extraction with 80% methanol, methanol removal and addition of an equal amount of hydrophilic isopropanol and salt to separate the isopropanol fraction from the water layer. Using successive column chromatography, kaemferol-3-O-[2-O-β-d-glucopyranosyl-6-O-α-l-rhamnopyranosyl]-β-d-glucopyranoside (compound 1), kaemferol-3-O-[2-O-β-d-xylopyranosyl-6-O-α-l-rhamnopyranosyl]-β-d-glucopyranoside (compound 2), naringenin-7-O-[β-d-xylopyranosyl(1→6)][β-d-glucopyranosyl(1→3)-α-l-rhamnopyranosyl(1→2)]-β-d-glucopyranoside (compound 3) and naringenin-7-O-β-d-xylopyranosyl(1→6)-β-d-glucopyranoside (compound 4) were obtained. The structure of compound 3, a new flavanone glycoside, was analyzed using UV, FT-IR, 1H NMR, 13C NMR and HR-FAB-MS. Quantification using high-performance liquid chromatography (HPLC) demonstrated that defatted C. oleifera seed cake contains 7.92, 17.7, 2.23 and 1.06mg/g of the four compounds. The extraction efficiencies of the four compounds were increased by 23.17%, 7.59%, 48.67% and 47.22% from those obtained with n-butanol partition extraction. This new extraction technique is simpler, faster and less expensive than the traditional extraction method. Accordingly, this salting-out method can potentially replace the existing one. [Copyright &y& Elsevier]

Abstract: LC/(+)ESI/MS3 was used to determine aconitine, mesaconitine, and hypaconitine as target markers in crude methanol extracts of (i) the raw lateral roots of Aconitum carmichaeli, (ii) roots treated by three different refining processes, and (iii) eight generally available traditional Chinese medicine (TCM) preparations containing fuzi (treated lateral roots of A. carmichaeli). The optimal ionization behavior resulted when using electrospray ionization (ESI) in positive-ion mode with 0.005% TFA as an additive in the mobile phase. The consecutive reaction monitoring (CRM) mode provided additional improvements in selectivity, which was exploited to minimize the noise and interference problems. Employing this approach, aconitine and mesaconitine were found to decompose readily during the refining processes, but hypaconitine remains present at the same content, presumably because of its characteristic chemical structure. Thus, treated and untreated fuzi samples can be distinguished by monitoring the ratio of aconitine and mesaconitine to hypaconitine. The limits of detection (LODs) for these three markers were 0.05, 0.08, and 0.03ng/ml. The linearity range for the three marker compounds was 0.1–1000ng/ml. The analysis time was 12min per sample. [Copyright &y& Elsevier]

A series of di-functional benzoxazine (BZ) monomers was synthesized, specifically the double-decker silsesquioxane (DDSQ) cage structure (DDSQ-BZ). Comparative analyses were conducted between DDSQ-BZ monomers and the most commonly utilized bisphenol A-functionalized bifunctional benzoxazine (BPA-BZ) monomer. DDSQ-BZ compounds possess better thermal properties such as high char yield and high thermal decomposition temperature (Td10) after thermal ring-opening polymerization (ROP) because the inorganic DDSQ cage nanostructure features a nano-reinforcement effect. In addition, blending inorganic DDSQ-BZ compounds with epoxy resin was explored to form organic/inorganic hybrids with enhanced thermal and mechanical properties following thermal ROP. The improvement in mechanical properties is primarily attributed to the network structure formed by the cross-linking between DDSQ-BZ and the epoxy resin during thermal ROP, as well as hydrogen bonding interactions formed between the hydroxyl groups generated during thermal ROP and the Si-O-Si bonds in the DDSQ structure. [ABSTRACT FROM AUTHOR]

This research is to develop transparent and UV-shielding Epoxy/SR-494/APTMS/ZnO nanocomposite materials with high heat resistant and anti-static properties. Firstly, the APTMS (3-(acryloxypropyl)trimethoxysilane) performs the silanol intermediates by hydrolysis in pH 4∼5 acid solution. The inorganic anti-static fillers of powder ZnO can be successfully coupled and crosslinked to Epoxy/SR-494 organic matrixes with these silanols of APTMS coupling agents. The remained active -OH functional groups of the APTMS/ZnO complexes can network bonding with epoxy prepolymers. Therefore, the Epoxy/APTMS/ZnO complexes with good anti-static composites will be successfully prepared. Finally, in order to improve the thermal resistant and mechanical properties, the polyfunctionalized SR-494 (pentaery-thritol tetracrylate) acrylate monomers and the Epoxy/APTMS/ZnO composites are chain polymerized to form an excellent cross-linking structure of organic/inorganic nanocomposites. The chemical bonding formation and the best weight contents of reaction components are identified by FT-IR spectra. The thermal resistance, transparence, surface electric resistance, and hardness of these nanocomposites are measured by TGA, DSC, UV-Visible, surface resistant meter, and pencil hardness tester respectively. Experimental results show that these nanocomposites have 90% transmittance and the best Td value is 389.3 °C which is 109.0 °C and 78.6 °C higher than those of pure epoxy resin and pure SR-494 acrylate resin respectively. The glass transition temperature is not detected below 200 °C. The surface electric resistances of Epoxy/SR-494/APTMS/ZnO hybrid thin films are decreased from 3.14 × 1013 to 5.13 × 107 Ω/cm2. The hardness of these nanocomposites is as high as 8H, and those hybrid films have high UV-shielding properties. The morphology structures of the hybrid thin films are estimated by SEM. The results show that the optical thin films are evenly distributed with inorganic colloidal particles and the average particle size of these nanocomposites is 45∼80 nm, while the powder ZnO (particle size: 2∼5 μm) was used as inorganic filler. [ABSTRACT FROM AUTHOR]

In this paper, multi-layer Zn:SiO2/SiO2 structure is introduced to reduce the operation power consumption of resistive random access memory (RRAM) device by modifying the filament formation process. And the configuration of multi-layer Zn:SiO2/SiO2 structure is confirmed and demonstrated by auger electron spectrum. Material analysis together with conduction current fitting is applied to qualitatively evaluate the carrier conduction mechanism on both low resistance state and high resistance state. Finally, single layer and multilayer conduction models are proposed, respectively, to clarify the corresponding conduction characteristics of two types of RRAM devices. [ABSTRACT FROM AUTHOR]

In this study, five flavonoid glycosides were extracted from defatted Camellia oleifera seeds by using a pressurized hot water extraction (PHWE) method. The independent experimental factors (temperature, time and pressure) influencing the PHWE efficiency of the flavonoid glycosides were optimized and quantified using an orthogonal array design and high-performance liquid chromatography – negative mode electron spray ionization/mass spectrometry (HPLC/(−)ESI–MS-MS), respectively. Based on the result of experimental design, the maximum extraction efficiency of flavonoid glycosides were obtained by selecting temperature at 140 °C, pressure at 600 psi, and time for 10 min. The recovery and overall yield of the flavonoid glycosides were greater than those in ultrasonic extraction (UE) (78.5% vs 68.4% and 18.8 mg/g vs 15.91 mg/g). In particularly, compounds 1 and 2, which are kaempferol derivatives, were higher 1.19–1.23 times than those of the compounds obtained through UE (6.63 mg/g vs 5.56 mg/g; 11.89 mg/g vs 9.66 mg/g, respectively). These two compounds have higher polarities and antioxidant capacities than the other three flavonoid glycosides. Thus, PHWE is an excellent alternative method for the extraction of flavonoid glycosides that are highly polar and potent antioxidants. [ABSTRACT FROM AUTHOR]

There is currently a pursuit of synthetic approaches for designing porous carbon materials with selective CO2 capture and/or excellent energy storage performance that significantly impacts the environment and the sustainable development of circular economy. In this study we prepared a new bio-based benzoxazine (AP-BZ) in high yield through Mannich condensation of apigenin, a naturally occurring phenol, with 4-bromoaniline and paraformaldehyde. We then prepared a PA-BZ porous organic polymer (POP) through Sonogashira coupling of AP-BZ with 1,3,6,8-tetraethynylpyrene (P-T) in the presence of Pd(PPh3)4. In situ Fourier transform infrared spectroscopy and differential scanning calorimetry revealed details of the thermal polymerization of the oxazine rings in the AP-BZ monomer and in the PA-BZ POP. Next, we prepared a microporous carbon/metal composite (PCMC) in three steps: Sonogashira coupling of AP-BZ with P-T in the presence of a zeolitic imidazolate framework (ZIF-67) as a directing hard template, affording a PA-BZ POP/ZIF-67 composite; etching in acetic acid; and pyrolysis of the resulting PA-BZ POP/metal composite at 500 °C. Powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller (BET) measurements revealed the properties of the as-prepared PCMC. The PCMC material exhibited outstanding thermal stability (Td10 = 660 °C and char yield = 75 wt%), a high BET surface area (1110 m2 g–1), high CO2 adsorption (5.40 mmol g–1 at 273 K), excellent capacitance (735 F g–1), and a capacitance retention of up to 95% after 2000 galvanostatic charge–discharge (GCD) cycles; these characteristics were excellent when compared with those of the corresponding microporous carbon (MPC) prepared through pyrolysis of the PA-BZ POP precursors with a ZIF-67 template at 500 °C. [ABSTRACT FROM AUTHOR]

A bilayer resistive switching memory device with an inserted porous silicon oxide layer is investigated in this letter. Compared with single Zr:SiOx layer structure, Zr:SiOx/porous SiOx structure outperforms from various aspects, including low operating voltages, tighter distributions of set voltage, higher stability of both low resistance state and high resistance state, and satisfactory endurance characteristics. Electric field simulation by comsolTM Multiphysics is applied, which corroborates that intensive electric field around the pore in porous SiOx layer guides the conduction of electrons. The constraint of conduction path leads to better stabilization and prominent performance of bilayer resistive switching devices. [ABSTRACT FROM AUTHOR]

Abstract: Application of the microwave-enhanced catalytic degradation (MECD) method on the abatement of 4-nitrophenol (4-NP) using nickel oxide was studied. A mix-valenced nickel oxide was prepared from nickel nitrate aqueous solution through a precipitation with sodium hydroxide and an oxidation by sodium hypochlorite with/without microwave-assisted heating. They were characterized by X-ray (XRD), infrared spectroscopy (IR), temperature programmed reduction (TPR), and transmission electron micrographs (TEM). Their catalytic activities towards the degradation of 4-NP were investigated through continuous bubbling of air during the liquid phase and evaluated quantitatively with high pressure liquid chromatography (HPLC). Also, the effect of the kinds of catalyst, temperature, pH, initial concentration, and dosage of catalyst on the efficiency of 4-NP degradation was investigated. The results showed that the 4-NP was completely degraded using the high efficiency MECD method within 15min under [H+]=1.0M, T =40°C, and C =200ppm over nickel oxide. [ABSTRACT FROM AUTHOR]

Two acids, 2( S )-[2( S )-ethylhexyloxy] propionic acid and 2( S )-[2( R )-ethylhexyloxy] propionic acid, were used as the chiral building block for the preparation of four liquid crystals 5, 6, 7 and 8 . The diastereomers of the biphenyl ring system, 5 and 6 , possess the phase sequence I-N * -SmC * -Cr1-Cr2, while the diastereomers of the naphthalene ring system, 7 and 8 , exhibit the sequence I-SmA-SmC * -Cr. The temperature ranges of the SmC * phase for 5 and 6 are wider than those for 7 and 8 ; the phase transition temperatures of the SmC * phase for 7 and 8 are lower than those for 5 and 6 . In the case of the diastereomers of naphthalene ring system, the larger the size of the lateral substituent at the second chiral centre, i.e. ethyl or methyl group, the wider the temperature range of the SmC * phase. [ABSTRACT FROM AUTHOR]

In this study, the electrical conduction mechanism of Zn:SiOx resistance random access memory (RRAM) treated with supercritical CO2 fluid (SCCO2) process was investigated by low temperature measurement. The current of low resistance state for current-voltage curves in SCCO2-treated and untreated Zn:SiOx RRAM were measured and compared under a low temperature range from 100 K to 298 K. The electrical conduction mechanisms of hopping conduction and metal-like behaviors in SCCO2-treated and untreated Zn:SiOx RRAM were discussed, respectively. Finally, the electrical conduction mechanism was analyzed and verified by the chemical composition and bonding intensity of XPS analyses. [ABSTRACT FROM AUTHOR]

This letter investigated the electrical characteristics of resistance random access memory (RRAM) with HfO2/BN bilayer structures. By adopting the high/low permittivity structure, we obtained the excellent device characteristics such as uniform distribution of switching voltage and more stable resistance switching properties of RRAM. The current conduction mechanism of low resistance state in the HfO2/BN device was transferred to space-charge-limited current conduction from Ohmic conduction owing to space electric effect concentrated by the high/low permittivity bilayer structures. The electric field in the bilayer can be verified by comsol simulation software. [ABSTRACT FROM AUTHOR]

In this Letter, the characteristics of set process of hafnium oxide based resistance random access memory are investigated by different set processes with increasing compliance current. Through current fitting, carrier conduction mechanism of low resistance state changes from hopping to surface scattering and finally to ohmic conduction with the increase of setting compliance current. Experimental data of current-voltage measurement under successive increasing temperature confirms the conduction mechanism transition. A model of filament growth is eventually proposed in a way by merging discrete metal precipitates and electrical field simulation by comsol Multiphysics further clarifies the properties of filament growth process. [ABSTRACT FROM AUTHOR]

In this study, the hopping conduction distance variation of Zn:SiO2 resistance random access memory (RRAM) devices with different operating compliance currents was discussed and verified. To investigate and determine the hopping conduction distance dependent activation energy characteristics, the Arrhenius plot of low resistance state of Zn:SiO2 RRAM devices was applied, from which we proposed carrier conduction model. With the increase of current compliance, more metal ions would accumulate to form precipitates with larger diameter, which in turn resulted in the shortening of hopping distance. Because of shorter hopping distance, activation energy for carrier hopping would decrease. [ABSTRACT FROM AUTHOR]