The results on the synthesis and characterization of highly monodisperse Fe-doped ZnO nanocrystals are presented. Stable suspensions of these materials were produced in an ethanol solution at room temperature. To promote crystal growth, the suspensions of nanocrystals were aged in contact with their mother liquors. X-ray diffraction characterization of doped systems at various Fe-atomic fractions x confirmed the exclusive formation of the host ZnO with the wurtzite structure. High resolution transmission electron microscopy analyses of the suspensions revealed the high monodispersity and crystallinity of the 6 -8 nm nanocrystals. Ultraviolet-visible measurements confirmed not only the nanocrystalline nature of the samples but also evidenced the continuous growth of the crystals when aged in their mother liquors. Room-temperature magnetic measurements indicated that the ferromagnetic behavior of doped ZnO was dependent on composition and crystal size of produced nanocrystals. Room-temperature ferromagnetism was established in the nanocrystals synthesized at x = 0.05 and 0.08 aged for 24 and 360 h, respectively. The corresponding room-temperature coercivity values were 45 and 78 Oe.

We present the conditions for room-temperature synthesis of bare, Ni-and Cu-doped ZnO nanocrystals in ethanol and their characterization. The formation of a ZnO host structure was delayed when dopant ions co-existed in the starting solutions. After ageing in mother liquors, well-crystallized doped nanocrystals were produced. Monodispersity of the nanocrystals (5–8 nm) was shown by high resolution transmission electron microscopy (HRTEM). Ultraviolet–visible (UV–vis) and photoluminescence (PL) measurements also confirmed the nanocrystalline nature and the continuous growth of the crystals when aged at room temperature. Room-temperature SQUID measurements showed weak but noticeable ferromagnetism, which was dependent on synthesis conditions.

The present investigation is centered on the study of the growth curves of E. coli and C. xerosis bacteria in the presence of nanosize particles of Zinc Oxide. Previous works demonstrated the sensitivity of the bacteria, when these were reproduced in media that contain nanoparticles of luminescent silicon and Cobalt Ferrite. Doped ZnO nanocrystals were synthesized by conventional precipitation in ethanol solutions as reported by Spanhel and Anderson for bare ZnO. In our case, the syntheses were carried out under room-temperature conditions.The experimental results of E. coli bacteria in contact with a stable suspension of nanoparticles of Zinc Oxide, shows a growth curve without adaptation period. Moreover a short and slowly logarithmic stage has been observed, reaching the stationary stage after approximately four hours compared with one in absence of the nanoparticles (standard curve). During the observations, a change in the lifetime of the bacteria (metabolism) with particulate was noticed,as well as the beginning of the mortality stage. However, different results were recorded for silicon and ferrite. For the case of the bacteria C. xerosis, the curve with particles is above its standard curve, for all times with none of the oscillations which occured in the nanometer silicon. For these bacteria the beginning of the mortality stage is observed when they have particles. For both bacteria with Zinc Oxide nanoparticles this occurs approximately after nine hours.