Phase transfer of TiO2 nanoparticles from water to ionic liquid triggered by phosphonic acid grafting

Controlling the interface between TiO₂ nanocrystals and ionic liquids is of high fundamental and applied interest for energy storage and conversion devices. Phase transfer of nanoparticles from a synthesis medium to a processing or an application medium plays a significant role in nanotechnology. Here we demonstrate that surface modification with phosphonic acids bearing cationic end-groups can trigger the phase transfer of TiO₂ nanoparticles from an aqueous sol to a typical water-immiscible ionic liquid, [Emim][NTf₂]. The transfer involves both the grafting of the phosphonic acid moiety and the exchange of the counter ion of the cationic end-group by NTf₂ anions, as demonstrated by solid-state NMR, elemental analysis and independent grafting and ion exchange experiments. Furthermore, the colloidal stability of the TiO₂ sols in [Emim][NTf₂] strongly depends on the hydrophobic character of the cationic end-groups.

Comment on "Brownian diffusion of a particle at an air/liquid interface: elastic (not viscous) response of the surface"

In a recent article Toro-Mendoza et al. considered an elastic response of an interface in order to explain the enhanced lateral drag of solid particles straddling fluid interfaces we recently measured.

High-resolution ellipsometric studies on fluid interfaces

In this article, highly accurate experimental results reveal the interfacial profile between different macroscopic fluid phases. The deviation from a step profile, quantified by the ellipsometric quantity J(1), shows a strong correlation with the cohesive energy quantified by the Gordon parameter G . Surprisingly, at high values of G , J (1)( < 0) deviates significantly from any predictions. Findings for water and water-like interfaces can be interpreted in terms of the strength of hydrogen bonding at the surface.

Dynamics at the air-water interface revealed by evanescent wave light scattering

A new tool to study surface phenomena by evanescent wave light scattering is employed for an investigation of an aqueous surface through the water phase. When the angle of incidence passes the critical angle of total internal reflection, a high and narrow scattering peak is observed. It is discussed as an enhancement of scattering at critical angle illumination. Peak width and height are affected by the interfacial profile and the focusing of the beam. In addition, the propagation of capillary waves was studied at the surface of pure water and in the presence of latex particles and amphiphilic diblock copolymers. The range of the scattering vectors where propagating surface waves were detected is by far wider than standard surface quasi-elastic light scattering (SQELS) and comparable with those of X-ray photon correlation spectroscopy (XPCS).

Persistence of chromosomal lesions induced in mouse bone marrow cells by mitomycin C, as evaluated by SCE analysis

The frequency of sister-chromatid exchanges (SCE) was evaluated in mouse bone marrow cells at different time intervals (from 19 h to 10 days) after treatment i.p. with mitomycin C (MMC; 1 and 2 mg/kg body weight). Significantly higher frequencies of SCE were found during the first week after treatment, at both doses tested. This result confirms that chromosomal lesions induced by MMC in the mouse may persist in bone marrow cells, in agreement with previous evidence based on chromosomal aberration analysis in the same cell population. In addition, the observation of a unimodal distribution of SCE/cell frequencies at each time tested indicates that the bone marrow cell population on the whole is affected by increased SCE frequency, i.e., that persistent chromosomal lesions may be transmitted along with cell proliferation.

Persistence of chromosomal lesions induced in actively proliferating bone marrow cells of the mouse

The persistence of chromosomal lesions induced in vivo by mitomycin C (MMC) was evaluated by cytogenetic analysis of mouse bone marrow cells. Chromosome aberration (CA) and micronucleus (MN) frequencies were estimated at different times after treatment, up to 42 days. The frequency of CA per cell decreased in the first 3 days after treatment, but a secondary peak appeared on the 4th day, followed by a stabilization around 0.03 CA per cell (significantly different from the control value), which persisted up to 17 days. At the next time intervals tested (28 and 42 days), the CA frequency returned to the control level. In disagreement with these data obtained directly on metaphases, the MN frequency, as evaluated in polychromatic erythrocytes, decreased quickly after treatment, reaching the control value on the 5th day. We attempted to enhance the sensitivity of the MN test by using CREST antibodies and indirect immunofluorescence. However, higher proportions of CREST- MN in treated than in control animals were observed only at short time intervals, confirming the results obtained with the conventional MN assay.

Identification of kinetochore-containing (CREST+) micronuclei in mouse bone marrow erythrocytes

A methodology for the characterization of kinetochore-containing (CREST+) micronuclei (MN), based on the use of antikinetochore antibodies (derived from CREST patients) and indirect immunofluorescence, was applied to mouse bone marrow erythrocytes. The proposed protocol allows us to obtain fluorescent signals of good quality and highly reproducible data. The clastogenic agent mitomycin C (MMC; 1 mg/kg body wt) and the two aneugenic compounds chloral hydrate (CH; 200 mg/kg body wt) and colchicine (COL; 1 mg/kg body wt) were used to verify the sensitivity of this approach to chemicals with different mechanisms of action. These compounds were tested at a 20 h time interval from treatment and all of them were able to significantly increase (P less than 0.001) the frequency of MN in polychromatic erythrocytes. Of the MN observed in preparations from control animals, 45% were CREST+ and this percentage increased significantly (P less than 0.001) after treatment with CH or COL. On the contrary, only 22% CREST+ MN were found after treatment with MMC (statistical comparison with the control value: P less than 0.001). The CREST characterization of MN induced in vivo in mouse bone marrow allows us to infer the origin of MN formation, thus contributing to the identification of aneugenic agents.