Dramatic Increase In Electrical Conductivity Research Articles

Selective detection of sulfur trioxide in the presence of environmental gases by AlN nanotube

The adsorption of N2, O2, H2O, and SO3 gases was explored onto an AlN nanotube (AlNNT) by means of density functional theory computations. When N2 and O2, and H2O approached the AlNNT, the electronic characteristics of the AlNNT did not change dramatically. As SO3 approached the AlNNT, its adsorption released 21.8 kcal/mol of energy. As the electronic analysis demonstrated, there was an approximately −30.3% reduction in the HOMO–LUMO gap of the nano-tube (from 4.09 to 2.85 eV) after SO3 adsorption and there was a dramatic increase in electrical conductivity. Therefore, the AlNNT was capable of generating electrical noise as the SO3 molecules approached, showing that the AlNNT can be used as a promising sensor. It was found that this nanotube could selectively detect SO3 gas among the above-mentioned molecules. The recovery time (RT) for the AlNNT was 7.7 s for SO3 desorption, demonstrating a short RT.

Impact of non-stoichiometry in the thermoelectric performance of polyol method prepared Cu1+xIn1−xS2 (x = −0.3, −0.2, −0.1, 0, 0.1, 0.2) nanowires

A significantly enhanced thermoelectric power factor at 320 K in a facile polyol method prepared non-stoichiometric Cu1+xIn1−xS2 (x = −0.3, −0.2, −0.1, 0, 0.1, 0.2) nanowires with traces of Cu2S has been demonstrated here. Rietveld refinement of powder XRD and Raman analysis confirm these. Field effect scanning electron microscopy (FESEM) study shows micron size CuInS2 spherical particles made up from 8.8 nm diameter with about 35 nm length nanowires. The dramatic increase in electrical conductivity and hence thermoelectric performance with increasing x is attributed to the formation of defects, Cu2S, and increase in carrier concentrations. The power factor reaches a high of 0.8 μW m−1 K−2 at 320 K and an electrical conductivity of 2800 S/m, which is about 35 and 250 times higher, respectively, than that of pure CuInS2 and hot-pressed Bi2S3 nanorods respectively at this temperature. These results expect high-power factor improvement for power production in the future.

Dielectric Property Measurement of Breast—Tumor Phantom Model Under Pulsed Electric Field Treatment

Pulsed electric field (PEF) is an emerging bioelectrical technology. This paper includes one such application in the medical field. Realistic phantoms serve as an innovative tool for exploring the feasibility of new technologies, reducing the number of human and animal trials in medical research for optimizing the design concepts that can be useful for treating the diseases. This paper includes modeling of the breast (homogeneous and heterogeneous) and cancerous tumor equivalent semisolid phantoms by using tissue-mimicking materials, such as agar, gelatin, oil, etc., and the effect of the PEF on these models was observed. Field analysis of the phantoms was simulated using finite element analysis. Dielectric properties of the modeled phantom were measured before and after PEF, using impedance analyzer over a frequency range of 50 Hz to 50 MHz and obtained values were validated by using Debye model. Tumor phantoms are embedded in breast phantoms and are exposed to ten number of pulses for 2 and 4 kV/cm with rising and fall time of 1.2/ $50~\mu \text{s}$ using needle electrode configuration. Application of PEF on tumor model alters the membrane resulting in a dramatic increase in electrical conductivity indicating the pore formation as in other electroporation-based-therapies and the permittivity of the tissue decreased considerably at higher applied fields. The measurement of dielectric properties and its changes due to electric fields can be used as a tool for effective PEF treatment for cancer.

Highly stable Al-doped ZnO by ligand-free synthesis as general thickness-insensitive interlayers for organic solar cells

Highly conductive and dispersible Al-doped ZnO (AZO) nanoparticles (NPs) have been successfully prepared by ligand-free colloidal synthesis at low temperature and stabilization by surfactant-aid including ethanolamine (EA), ethylenediamine (EDA), diethylenetriamine (DETA) and triethylenetetramine (TETA). Due to the strong intermolecular hydrogen-bonding interactions between AZO NPs and the amino groups from surfactants, the inevitable aggregation was suppressed and the surface defect sites were passivated obviously. The existence of electron transfer from the nitrogen of the amino groups to the zinc of AZO, led to a dramatic increase in electrical conductivity. A homogeneous current intensity value up to ~2200 pA for AZO tread by DETA was characterized by conductive atomic force microscopy (C-AFM), which was more superior than that of the reported sol-gel synthesized AZO with the assistance of EA surfactant (refer to 170.7 pA). Furthermore, non-fullerenes solar cells based on PBDB-T:ITIC with AZO-DETA (80 nm) yielded a best device efficiency of 10.7% and kept up prominent PCE exceeding 10% even with more thicker interlayer (95 nm).

Dramatic increase in electrical conductivity in epoxy composites with uni-directionally oriented laminae of carbon nanotubes

Carbon nanotubes (CNTs) felts of aligned lamellar structure were prepared by ice templating and then infiltrated by liquid epoxy resin by vacuum pressure impregnation (INCNT/EP). Conventional physical blending method was also used to prepare carbon nanotube/epoxy composite as a comparison (PHCNT/EP). Microstructal observations of INCNT/EP fracture surfaces revealed the formation of a three-dimensional (3D) framework composed of unidirectionally oriented CNTs lamellae, which lead to a dramatic increase in electrical conductivity of the composite, by 15 orders of magnitude compared to pure epoxy and by 3 orders of magnitude compared to PHCNT/EP composite. Electrical conductivity of the INCNT/EP composite reached to 0.158S/cm at CNT loading of 1.31wt%. Meanwhile, improvements in Young’s modulus (up to 25.5%) and yield strength (up to 12.2%) of the INCNT/EP composite under compressive loadings compared to pure epoxy were obtained. It is also observed that INCNT/EP composites show stable compressive behaviour and can effectively resist the sudden decrease of stress due to its skeleton structure of CNTs lamellae after the strain of ca. 50%.

High Performance Natural Rubber Composites with Well-Organized Interconnected Graphene Networks for Strain-Sensing Application

High-concentration reduced graphene oxide (RGO) solution was produced using gelatin (Gel) as the stabilizer and subreductant and hydrazine hydrate (HHA) as the main reductant. The Gel-HHA-RGO nanosheets exhibited excellent colloidal dispersibility and stability in alkaline condition. The Gel-HHA-RGO filled natural rubber (NR) composites were prepared by water-based solution casting. Well-organized interconnected RGO networks were constructed throughout the NR matrix, which played an important role in determining the properties of composites. The tensile modulus and dynamic storage modulus were improved by several orders of magnitude with increasing RGO content. Meanwhile, a dramatic increase in electrical conductivity with a low percolation threshold of 0.21 vol % was perceived. Strain-sensing tests revealed that the RGO/NR composites exhibited outstanding strain sensitivity and repeatability, which could be used to detect the cyclic movements of human joints. The results are promising in the rubber indus...

Synthesis of acid-soluble graphene and its use in producing a reduced graphene oxide–poly(benzobisoxazole) composite

A new chemically modified graphene was prepared using carboxylated graphene oxide (GO) and fluorinated poly(hydroxyamide) (6FPHA), the latter is the precursor of fluorinated poly(benzobisoxazole) (6FPBO). The results showed that, unlike common GO, which can only be dispersed in water under neutral or basic conditions, the RGO–6FPBO (reduced graphene oxide–6FPBO) could be stably dispersed in Lewis acids. The RGO–6FPBO–poly(benzobisoxazole) (PBO) composite was achieved by simple solution blending of RGO–6FPBO and PBO in methanesulfonic acid. The obtained RGO–6FPBO–PBO composite films exhibited a dramatic increase in electrical conductivity, by 8 orders of magnitude at the RGO–6FPBO content of 4 wt%, without significantly sacrificing optical transparency. When the content of RGO–6FPBO was higher than 4 wt%, the dielectric constant of the composite film also increased remarkably. The mechanical properties and thermal stability of the composite were also improved by the incorporation of RGO–6FPBO.

Sol–gel route to carbon nanotube borosilicate glass composites

Dense borosilicate glass matrix composites containing up to 3 wt% of multiwalled carbon nanotubes were produced by a sol–gel process. The three different silicate precursors employed (tetramethylsilane (TMOS), methyltriethoxysilane (MTES) and methyltrimethoxysilane (MTMS)) yielded transparent xerogels which were subsequently crushed and densified by hot pressing at 800 °C. The dispersion of the carbon nanotubes was aided by using an organic–inorganic binder (3-aminopropyl triethoxysilane) which limited flocculation of the CNTs in the silica sol. After densification, the borosilicate glass composites containing up to 2 wt% CNTs showed significant improvements in hardness and compression strength, as well as thermal conductivity, whilst percolation effects lead to a dramatic increase in electrical conductivity above 1 wt%. This simple approach to disperse CNTs into a technical silicate glass matrix via the sol–gel process focusses specifically on the borosilicate system, but the procedure can be applied to produce other inorganic matrix composites containing CNTs.

Hydrogen in bulk and nanoscale ZnO

Zinc oxide (ZnO) is a wide-band gap semiconductor that has attracted resurgent interest as an electronic material for a range of applications. In our work, we have focused on the properties of hydrogen donors in ZnO. In bulk, single-crystal ZnO doped with hydrogen or deuterium, infrared (IR) absorption peaks corresponding to O–H and O–D stretch modes were observed at 3326.3 and 2470.3 cm −1, respectively, at liquid-helium temperatures. IR spectroscopy using polarized light showed that the O–H dipoles are aligned along an angle 111° to the c-axis. The slight negative shift of the O–H mode as a function of hydrostatic pressure suggests that the hydrogen resides in an anti-bonding orientation. The O–H complexes are unstable, perhaps due to the formation of “hidden” H 2 molecules. As dimensions approach the nanoscale, the vastly increased surface-to-volume ratio leads to interesting phenomena. At moderate annealing temperatures (350 °C), hydrogen interacts with the nanoparticles, resulting in a dramatic increase in electrical conductivity, free-carrier absorption, and IR reflectivity.