Room-temperature ferromagnetism has been observed in nanoparticles ͑7 -30 nm diam͒ of nonmagnetic oxides such as CeO 2 , Al 2 O 3 , ZnO, In 2 O 3 , and SnO 2 . The saturated magnetic moments in CeO 2 and Al 2 O 3 nanoparticles are comparable to those observed in transition-metal-doped wideband semiconducting oxides. The other oxide nanoparticles show somewhat lower values of magnetization but with a clear hysteretic behavior. Conversely, the bulk samples obtained by sintering the nanoparticles at high temperatures in air or oxygen became diamagnetic. As there were no magnetic impurities present, we assume that the origin of ferromagnetism may be the exchange interactions between localized electron spin moments resulting from oxygen vacancies at the surfaces of nanoparticles. We suggest that ferromagnetism may be a universal characteristic of nanoparticles of metal oxides.Integration of semiconductor with ferromagnetic functionality of electrons has been the focus of recent research in the area of spintronics because of the difficulties associated with the injection of spins into nonmagnetic semiconductors in conventional spintronic devices. Ferromagnetism in semiconductors and insulators is rare, the well-known ferromagnetic semiconductors being the chalcogenides EuX ͑X =O, S, and Se͒ ͑T C Ͻ 70 K͒ and CdCr 2 X 4 ͑X = S and Se͒ ͑T C Ͻ 142 K͒ with the rocksalt and spinel structure, respectively. 1,2 Following the theoretical prediction of Dietl et al. that Mn-doped ZnO and GaN could exhibit ferromagnetism above room temperature, 3 several studies have focused on films and bulk samples of metal oxides such as TiO 2 , ZnO, In 2 O 3 , SnO 2 , and CeO 2 doped with Mn, Co, and other transition metal ions. [4][5][6][7][8] While the existence of ferromagnetism in transitionmetal-doped semiconducting oxides remains controversial, 9 thin films of the band insulator HfO 2 have been reported to exhibit ferromagnetism at room temperature in the absence of any doping. 10 This is puzzling, since pure HfO 2 does not have any magnetic moment and the bulk sample is diamagnetic. Similar ferromagnetism has been reported in other nonmagnetic materials such as CaB 6 , CaO, and SiC where the origin of ferromagnetism is believed to be due to intrinsic defects. 11-13 It has been suggested that ferromagnetism in thin films of HfO 2 may be related to anion vacancies. 14 It has been reported very recently that thin films of undoped TiO 2 and In 2 O 3 also show ferromagnetism at room temperature, 15 the corresponding bulk forms of these materials being diamagnetic. Thin films of these oxides might have defects or oxygen vacancies that could be responsible for the observed ferromagnetism. Ab initio electronic structure calculations using density functional theory in HfO 2 have shown that isolated halfnium vacancies lead to ferromagnetism. 16 Meanwhile, there is a conflicting report attributing the ferromagnetism in HfO 2 to possible iron contamination while using stainless-steel tweezers in handling thin films. 17 In this Rapid Communication, ...

Thermal and extensive rheological characterization of a nematic liquid crystal gelated with a novel monodisperse dipeptide, also a liquid crystal, has been carried out. For certain concentrations, the calorimetric scans display a two-peak profile across the chiral nematic-isotropic (N*-I) transition, a feature reminiscent of the random-dilution to random-field crossover observed in liquid crystal gels formed with aerosil particles. All samples show shear thinning behavior without a Newtonian plateau region at lower shear rates. Small deformation oscillatory data at lower frequencies exhibit a frequency dependence of the storage (G') and loss (G'') moduli that can be described by a weak power-law, characteristic of soft glassy rheological systems. At higher frequencies, while lower concentration composites have a strong frequency dependence with a trend for possible crossover from viscoelastic solid to viscoelastic liquid behavior, the higher-concentration gels show frequency-independent rheograms of entirely elastic nature G' > G''. The plateau modulus of G' is described by a power-law with an exponent again common to soft materials, such as foams, slurries, etc. Other features which are a hallmark of such materials observed in the present study are: (i) above a critical strain, a strain softening of the moduli with a peak in the loss modulus, (ii) power-law variation of the storage modulus in the nonlinear viscoelastic regime, and (iii) absence of Cox-Merz superposition for the complex viscosity. An attractive feature of these gels is the fast recovery upon removal of large strain and qualitatively different temporal behavior of the recovery between the low and high concentration composites, with the latter indicating the presence of two characteristic time scales.

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We describe the rheological, dielectric and elastic properties of a nematic liquid crystal gel created using an anthrylidene derivative of arjunolic acid, a chiral triterpenoid, obtained from the extracts of the wood of Terminalia arjuna. In this novel gel, having the electron-donor and acceptor components as minority constituents, the gelation and strengthening of charge-transfer complex (CTC) formation are seen to be occurring concomitantly. In addition to being mechanically strong with a large storage modulus, the gel with the maximized CTC exhibits Frank bend elastic constant values that approach nanonewton levels. The highlight of the study is the observation of 4–5 orders of magnitude increase in electrical conductivity for this gel, a value that is higher than even in the CT complexes of 2-d ordered columnar structures. A further important advantage of the present system over the columnar complex is that the high conductivity is seen for ac probing also, and owing to the nematic nature can be switched between its anisotropic limits. Some of these features are ascribed to a specific molecular packing architecture, which reduces the trapping of the charge carriers.

In the present study, an alumina nanoparticle adsorbent is developed using solution combustion synthesis method and is further utilized for the removal of zinc (Zn(II)) and color black G (CBG) from wastewater. The developed adsorbent is characterized using SEM-EDS technique. The effect of various parameters such as the initial concentration, the contact time, the mass of adsorbent and the solution pH are studied for the removal of Zn(II) and CBG. The equilibrium time for both, Zn(II) and CBG is obtained to be approximately 4.5 h. The maximum adsorption of Zn(II) is found at pH value of 7 while the maximum removal of CBG is obtained at pH value of 2. The Langmuir isotherm model is found suitable for explaining the adsorption behavior of Zn(II) (R 2 = 0.976) and CBG (R 2 = 0.974) onto alumina nanoparticles, which supports the monolayer formation of Zn(II) and CBG during the adsorption process. The maximum adsorbent capacity of alumina nanoparticles for the removal of Zn(II) and CBG are obtained as 1,047.83 and 263.16 mg g -1 , respectively. The kinetic data obtained during the experiments are better fitted with the pseudo-first-order model for both, Zn(II) (R 2 = 0.989) and CBG (R 2 = 0.971). A statistical analysis is also carried out to develop the mathematical equation which relates the different independent parameters (initial metal concentration, pH, time and mass of adsorbent) with the dependent parameter (adsorption capacity). The optimum values of independent parameters are estimated using Microsoft Solver.