Glucose Sensing Materials Based on Carbon Nanotubes for Electrochemical Sensing.

There is an urgent need for in situ methods for detecting environmental pollution quickly and accurately. With the development of nanotechnology, a huge potential has been created for the design of highly sensitive sensors with low energy consumption and low costs. If a composite material constructed with carbon nanotubes is used as an electrode in contact with a contaminant, this material undergoes an oxidation-reduction reaction with the contaminant that allows the electrode to function as an electrochemical sensor. This study involved the application of multi-walled carbon nanotubes and modified working electrodes constructed with multi-walled carbon nanotube composites (Ag- and ZnO-multi-walled carbon nanotubes) as electrochemical sensors. These electrodes have good response speed and sensitivity at low concentrations, and they are reusable. To lower the price of these sensors, our goal was to maximize their sensitivity by using the low-cost multiwalled carbon nanotubes in conjunction with silver electroless plating of the multi-walled carbon nanotubes and multi-walled carbon nanotube composites.

Characteristics of Metal-Metal Nano-Area Contact Resistance for Less Than 5 nm Technology Node.

Recently, better understanding of nano-area is required for 5 nm or less technology node. In particular, the high contact resistance generated in a nano-area significantly degrades the device performance. In this study, we propose a direct contact resistance measurement method without a test structure by separate processes to improve the nano-area contact resistance. The nano-area contact resistance of Ti-Ti and Cu-Cu decreased from 6.46 MΩ to 1.08 MΩ and from 3.78 MΩ to 1.48 MΩ, respectively, when the metal line and native layer formed on the surface were removed. In addition, it is confirmed that the contact resistance decreased with an increase in bonding strength in the case of nano-area homo-metal contact. However, the contact resistance is affected by the tunneling effect and bond energy according to the distance between the first layers of atoms in the case of nano-area hetero-metal contact.

PU-Graphene Oxide Composite; Effect of Various Chain Extender on Properties.

High integration of electronic chip not only improved the electronic device's efficiency, but also left the need to stop emitting heat. Thermal interface material (TIM) has been proposed to solve this problem. Traditionally, a large amount of high thermal conductive materials (such as Cu, Al or AlN) was added for better thermal conductivity, which caused undesirable weight-increasing and property-sacrificing. Graphene has great thermal conductivity and mechanical properties. Furthermore, owing to its low density, it is possible to make a lot of TIM even with a small amount. Being composited with PU, it can be an enhanced thermal conductive adhesive. Otherwise, amine compound is considered to be applicable as both a chain extender of PU and a reducing agent of Graphene oxide (GO). In this work, we synthesized PU-GO composite by chemical reaction of NCO and GO. We examined the effects of various amine compounds on chemical and physical properties of GO and PU-GO composite. Adhesion and thermal properties were also studied.

Strain Sensing Characteristics of Rubbery Carbon Nanotube Composite for Flexible Sensors.

In this study, the piezoresistive properties of CNT (Carbon Nanotube)/EPDM composite are characterized for the applications of a flexible sensor. The CNT/EPDM composites were prepared by using a Brabender mixer with MWCNT (Multi-walled Carbon Nanotube) and organoclay. The static and quasi-dynamic voltage output responses of the composite sensor were also experimentally studied and were compared with those of a conventional foil strain gage. The voltage output by using a signal processing system was fairly stable and it shows somehow linear responses at both of loading and unloading cases with hysteresis. The voltage output was distorted under a quasi-dynamic test due to its unsymmetrical piezoresistive characteristics. The CNT/EPDM sensor showed quite tardy response to its settling time test under static deflections and that would be a hurdle for its real time applications. Furthermore, since the CNT/EPDM sensor does not have directional voltage output to tension and compression, it only could be utilized as a mono-directional force sensor such as a compressive touch sensor.

Preparation of Graphene Encapsulated Silicon Nanoball.

Concerning application of graphene, a lot of efforts have been made to improve performance of nanomaterials in many fields, such as electric and electronic devices. Some examples are preparation of 3-dimension structured nanomaterials like nanoballs by CVD process and hybridizing with silicon. These graphene-based materials are proven to be available for secondary battery, EMI and ACF in electronics. Especially, some research has shown that they were very effective to enhance safety and volumetric capacity when they were used as anode materials of secondary battery. Although graphite and its compound with metal have been used as an anode material due to their high stability and reversibility, it still has lower charge capacity. On the contrary, silicon is known as a material which increases the charge capacity up to four times, compared with carbon-based materials, but it has lower stability and reversibility. For that reason, a few researchers just started to improve the charge capacity by hybridization of carbon-based material with silicon. In this paper, we prepared nanocarbon based material which has a new structure of graphene encapsulated silicon nanoball as an anode material which is applicable to high-capacity secondary battery. In order to form a graphene encapsulated silicon nanoballs, the polystyrene encapsulated silicon nanoballs were prepared by emulsion polymerization of styrene monomer with silicon nanoparticles. The resulting nanoballs were immersed in iron chloride solution and then dried. Finally they were treated in high temperature through CVD and etched by hydrogen chloride. Morphology of the graphene encapsulated silicon nanoballs was observed by the field emission scanning electron microscope (FESEM) and the field emission transmission electron microscope (FETEM) to search for core-shell structured nanoball. Spherical structure of graphene encapsulated silicon nanoball was investigated by the Raman, the X-ray Photoelectron Spectroscopy to identify graphene layers on the surface of the inner silicon core.

Electrical impedance properties of carbon nanotube composite electrodes for chemical and biosensor.

Electrical impedance properties of different type of carbon nanotubes based bulk electrodes have been investigated to develop chemical and biosensors. The bulk composite electrodes were fabricated with single-wall and multi-wall carbon nanotubes involving ionic conducting host polymer, Nafion, by using traditional solution-casting techniques. Under the various amounts of buffer solution, resistance and capacitance of the electrodes were measured with LCR meter and their characteristics due to ionic conducting host polymer were investigated by means of electrokinetic analysis. The capacitance values showed drastic change while the resistances only changed within few percent ranges. Electrical impedance measurement provided rapid and simple sensing mechanism to develop chemical sensor and biosensors with bulk nano electrodes.

The Effects of TWEAK, Fn14, and TGF-beta1 on Degeneration of Human Intervertebral Disc.

OBJECTIVE: The purpose of this study is to explain the effect and reciprocal action among tumor necrosis factor (TNF) like weak inducer of apoptosis (TWEAK), fibroblast growth factor-inducible 14 (Fn14), and transforming growth factor-beta1 (TGF-beta1) on degeneration of human intervertebral disc (IVD). METHODS: Human intervertebral disc tissues and cells were cultured with Dulbecco's Modified Eagle's Medium/Nutrient F-12 Ham (DMEM/F-12) media in 37, 5% CO(2) incubator. When IVD tissues were cultured with TWEAK, Fn14 that is an antagonistic receptor for TWEAK and TGF-beta1, the level of sulfated glycosaminoglycan (sGAG) was estimated by dimethyl methyleneblue (DMMB) assay and sex determining region Y (SRY)-box 9 (Sox9) and versican messenger ribonucleic acid (mRNA) levels were estimated by reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: When human IVD tissue was cultured for nine days, the sGAG content was elevated in proportion to culture duration. The sGAG was decreased significantly by TWEAK 100 ng/mL, however, Fn14 500 ng/mL did not change the sGAG production of IVD tissue. The Fn14 increased versican and Sox9 mRNA levels decreased with TWEAK in IVD tissue TGF-beta1 20 ng/mL elevated the sGAG concentration 40% more than control. The sGAG amount decreased with TWEAK was increased with Fn14 or TGF-beta1 but the result was insignificant statistically. TGF-beta1 increased the Sox9 mRNA expression to 180% compared to control group in IVD tissue. Sox9 and versican mRNA levels decreased by TWEAK were increased with TGF-beta1 in primary cultured IVD cells, however, Fn14 did not show increasing effect on Sox9 and versican. CONCLUSION: This study suggests that TWEAK would act a role in intervertebral disc degeneration through decreasing sGAG and the mRNA level of versican and Sox9.

Inhibition of HIV-1 reverse transcriptase and protease by phlorotannins from the brown alga Ecklonia cava.

The bioassay-directed isolation of a marine brown alga, Ecklonia cava, afforded four phlorotannin derivatives, eckol (1), 8,8'-bieckol (2), 8,4"'-dieckol (3), and phlorofucofuroeckol A (4). Among these compounds, 2 and 3 exhibited an inhibitory effect on human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) and protease. Specifically, they inhibited the RT more potently than the protease. The inhibitory activity of compound 2 (IC(50), 0.51 microM) against HIV-1 RT was comparable to that of nevirapine (IC(50), 0.28 microM), a reference compound. An enzyme kinetic assay showed that this compound inhibited the RNA-dependent DNA synthesis activity of HIV-1 RT noncompetitively against dUTP/dTTP with a K(i) value of 0.78 microM. With respect to the homopolymeric template/primer, (rA)n(dT)15, 8,8'-bieckol (2) displayed an uncompetitive type of inhibition (K(i), 0.23 microM).

Inhibition of HIV-1 integrase by galloyl glucoses from Terminalia chebula and flavonol glycoside gallates from Euphorbia pekinensis.

The bioassay-directed isolation of Terminalia chebula fruits afforded four human immunodeficiency virus type 1 (HIV-1) integrase inhibitors, gallic acid ( 1) and three galloyl glucoses ( 2 - 4). In addition, four flavonol glycoside gallates ( 5 - 8) from Euphorbia pekinensis containing the galloyl moiety also showed the inhibitory activity at a level comparable to those of 2 - 4. By comparison with the activities of the compounds not bearing this moiety, it is proposed that the galloyl moiety plays a major role for inhibition against the 3'-processing of HIV-1 integrase of these compounds.