Monolayer Co3O4 Inverse Opals as Multifunctional Sensors for Volatile Organic Compounds

Monolayers of periodic porous Co₃O₄ inverse opal (IO) thin films for gas‐sensor applications were prepared by transferring cobalt‐solution‐dipped polystyrene (PS) monolayers onto sensor substrates and subsequent removal of the PS template by heat treatment. Monolayer Co₃O₄ IO thin films having periodic pores (d≈500 nm) showed a high response of 112.9 to 5 ppm C₂H₅OH at 200 °C with low cross‐responses to other interfering gases. Moreover, the selective detection of xylene and methyl benzenes (xylene+toluene) could be achieved simply by tuning the sensor temperature to 250 and 275 °C, respectively, so that multiple gases can be detected with a single chemiresistor. Unprecedentedly high ethanol response and temperature‐modulated control of selectivity with respect to ethanol, xylene, and methyl benzenes were attributed to the highly chemiresistive IO nanoarchitecture and to the tuned catalytic promotion of different gas‐sensing reactions, respectively. These well‐ordered porous nanostructures could have potential in the field of high‐performance gas sensors based on p‐type oxide semiconductors.     

Novel crystalline supramolecular assemblies of amorphous polypyrrole nanoparticles through surfactant templating

A lamellar-structured crystalline polypyrrole (PPy) supramolecular assembly was prepared by surfactant templating, and the regularly linked amorphous PPy nanoparticles with tunable window sizes could play the role of crystalline lattices in the supramolecular assembly.     

Layered perovskites with giant spontaneous polarizations for nonvolatile memories

A series of titanate-based layered perovskites having large values of the spontaneous polarization P(s) were developed for their applcations to nonvolatile ferroelectric random access memories. Among these, the Nd-modified bismuth titanate [Bi(4-x)Nd(x)Ti(3)O(12) (BNdT)] system exhibited the most remarkable ferroelectric properties. The c-axis oriented BNdT capacitor was characterized by a switchable remanent polarization 2P(r) of over 100 microC/cm(2) and imprinting and fatigue-free behavior. The active Ti site responsible for the giant P(s) was identified with the help of Rietveld analysis, x-ray absorption near-edge structure study, and ab initio quantum computations.     

Dynamic PIV measurement of a high-speed flow issuing from vent-holes of a curtain-type airbag

A curtain-type airbag is a safety device designed to protect passengers from the side collisions of a car. The curtain-type airbag system consists of an inflator, a fill-hose, and a curtain-airbag. The fill-hose is a passageway and distributor of the exploded gases from the inflator to the airbag through vent-holes. Although the design of vent-holes is important for proper deployment of the airbag, it is very difficult to measure the exceedingly high speed flow issuing from the vent-holes by using conventional measurement methods. In this study, we employed a dynamic PIV technique to measure the temporal evolution of instantaneous velocity fields of the flow ejecting from the vent-holes. From the velocity field data measured at a frame rate of 2000 fps, the temporal variation of the volume flux from vent-holes was also evaluated for the diagnosis of airbag performance. The flows ejecting from the vent-holes showed high velocity fluctuations, and the maximum velocity was about 480 m/s. The instantaneous velocity fields in the initial stage showed a swaying motion of a high-speed jet. The accumulated volume flux from the vent-holes was also compared at each vent-hole region.     

Some insight into the structure of the nuclei 19F, 19Ne, 21Ne, 21Na, 23Na and 23Mg through the generator coordinate method and the projected Hartree-Fock method

Structures of two sets of mirror nuclei ¹⁹Ne, ²¹Na, ²³Mg and ¹⁹F, ²¹Ne, ²³Na were studied comparatively by means of the electromagnetic properties of the even-parity states, calculated with the generator coordinate method and with mixing of projected Hartree-Fock determinants. The present results are compared with those of complete diagonalization. In particular, collective features of these nuclei are investigated by comparing the various microscopic results with the predictions of the simple rotational model.     

Release of N(2) from the carbon nanotubes via high-temperature annealing

Nitrogen (N)-doped carbon nanotubes (CNTs) were heated to 1000 degrees C under an ultrahigh vacuum. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) reveal three different N structures; graphitelike, pyridine-like, and molecular N(2). The vibrationally resolved XANES peaks of N(2) were first observed, suggesting the existence of molecular N(2) as intercalated and trapped forms. The annealing process can decrease the average N content from 6.3 at. % to 3.3 at. %, mainly by releasing molecular N(2). Electron energy-loss spectroscopy (EELS) confirms that the annealing releases molecular N(2) from the CNTs.