[en] Undoped ZnO nanoparticles (NPs) with size ∼12 nm were produced using forced hydrolysis methods using diethylene glycol (DEG) [called ZnO-I] or denatured ethanol [called ZnO-II] as the reaction solvent; both using Zn acetate dehydrate as precursor. Both samples showed weak ferromagnetic behavior at 300 K with saturation magnetization M_s = 0.077 ± 0.002 memu/g and 0.088 ± 0.013 memu/g for ZnO-I and ZnO-II samples, respectively. Fourier transform infrared (FTIR) spectra showed that ZnO-I nanocrystals had DEG fragments linked to their surface. Photoluminescence (PL) data showed a broad emission near 500 nm for ZnO-II which is absent in the ZnO-I samples, presumably due to the blocking of surface traps by the capping molecules. Intentional oxygen vacancies created in the ZnO-I NPs by annealing at 450 °C in flowing Ar gas gradually increased M_s up to 90 min and x-ray photoelectron spectra (XPS) suggested that oxygen vacancies may have a key role in the observed changes in M_s. Finally, PL spectra of ZnO showed the appearance of a blue/violet emission, attributed to Zn interstitials, whose intensity changes with annealing time, similar to the trend seen for M_s. The observed variation in the magnetization of ZnO NP with increasing Ar annealing time seems to depend on the changes in the number of Zn interstitials and oxygen vacancies

[en] Many naturally occurring microbiological and synthetic polymer systems have soft interfaces due, e.g., to the presence of polymer brushes at the surfaces. The initial interactions (before contact) in such systems are typically physical rather than chemical in origin, e.g. electrostatic or van der Waals forces. We calculate the form of the summed van der Waals interaction energies U_HS and U_SS between two bulk systems separated by a distance D, when one (U_HS) or both (U_SS) of their surfaces are soft. We find that the summed interactions diverge weakly as D →0, U_HS∼-1/D and U_SS ∼ -ln(1/D), and comment upon the applicability of these results