Articles you may be interested inCommunication: Strong excitonic and vibronic effects determine the optical properties of Li2O2High direct energy band gaps determination in In x Al 1−x As coherently grown on InPThe exciton reflection spectra of Cs 3 Bi 2 I 9 layered crystals are investigated in the temperature region 4.2-300 K with light polarization EЌc. It is estimated that the energy gap E g equals 2.857 eV (Tϭ4.2 K) and the exciton binding energy Ry is 279 meV. A nontraditional temperature shift of E g (T) for layered substances is found for the first time. It is learned that this shift is described very well by the Varshni formula. A transition region in the temperature broadening of the half-width H(T) of the exciton band with increase of temperature is registered in the interval between 150 and 220 K. It is shown that this region may be identified as the heterophase structure region where ferroelastic and paraelastic phases coexist. A surge of H(T) at the point of the ferroelastic phase transition (T c ϭ220 K) is also observed.

Poly(ortho-anisidine) (POA)/single-walled carbon nanotubes (SWCNTs) composite films have been prepared by means of oxidative potentiostatic electropolymerization of the monomer (ortho-anisidine) in the presence of purified SWCNTs. The magnetic properties of the obtained films have been investigated by electron spin resonance (ESR) (ν ∼ = 9.4 GHz; temperature range 10-300 K) and compared with those of pure POA films in the same oxidation state. The similarity of the ESR signals and the dependence on temperature of the ESR line features suggest a polaron origin of the paramagnetic states. A strong increase of the ESR integral intensity has been detected for composite samples kept for 72 h in hydrogen atmosphere at room temperature. Under the same conditions, a less pronounced increase in the intensity has been detected in the case of pure polymer films. The kinetics of the hydrogen adsorption-desorption processes in the nanocomposite samples has been investigated and interpreted in the frame of an H-physisorption mechanism. The comparison between the H-induced effects in POA and nanocomposite POA/SWCNTs films has been carried out taking into account the structure of the samples and the presence of defects.can indeed be regarded as unique materials for the possibility they offer in modifying their electrical properties merely by suitable chemical treatments. Unfortunately, the applications of conducting polymers are often limited by poor mechanical features 187 NANO 2008.03:187-194. Downloaded from www.worldscientific.com by NORTHWESTERN UNIVERSITY on 02/06/15. For personal use only. 188 A. A. Konchits et al.

We present a detailed study of the electron magnetic resonance (EMR) properties of Ni nanoparticles (NPs) placed in the bundles of single-walled carbon nanotubes produced by arc discharge with Ni catalyst. The behavior of EMR signals has been investigated in the 10–300K temperature range for the initial powderlike materials and those diluted in a nonmagnetic matrix. The magnetic response evolves between two modes, ferromagnetic and superparamagnetic, depending on both the temperature and distribution of Ni nanoparticles in the sample. The behavior of EMR spectra shows that the initial materials retain the ferromagnetic character of the NP ensemble even at room temperature. This is most likely due to dipole-dipole interactions and macroscopic demagnetizing fields stemming from powderlike composition of the samples. For the diluted materials, the actual superparamagnetic signal is observed at room temperature. As temperature is reduced, the behavior of the EMR parameters reflects a gradual transition from free rotated magnetic moments of NPs to those ordered along the “easy” magnetic axes (blocked state). In the 300–130K temperature range, anomalous temperature dependence of the resonance magnetic field Hres was observed. It is examined in terms of competition between the single-particle anisotropy energy and dipole interactions between the Ni nanoparticles. Finally, a transition to a blocked state occurs at blocking temperature estimated as Tb≈40K. At lower temperatures, both the dense and diluted samples behave identically.