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CeO2 nanoparticles possess catalytic activity for hydrolysis of organophosphates such as paraoxon and nerve agents used in chemical warfare. Intoxication with these highly toxic compounds can occur directly through inhalation or dermal contact and lead to rapid and severe consequences including death. It is therefore necessary to have effective means of skin decontamination, and CeO2 nanoparticles are promising. In this study, a wide range of CeO2 nanoparticles were synthesized and their efficiency against paraoxon degradation was evaluated. Nanocubes (NC), nanorods (NR), nano-octahedra (NO), and nanopolyhedra (NPO) were studied along with nanoparticles obtained after calcination (NC*, NR*, NO*, and nanotruncated octahedra NTO*). Results show an influence of calcination, specific surface area, and crystal facets with higher activity for {111} facets compared to {100} facets. pH also impacted POX degradation rates, with higher pH accelerating the degradation. In vitro tests using the Franz cell method demonstrated the skin decontamination efficacy of the CeO2 nanoparticles. NC* exhibited lower efficiency, possibly due to smaller surface area and limited {100} facet degradation. The most efficient nanoparticles were NR* and NO* followed by NTO* consistently with their degradation efficiency and specific surface area. Notably, NR* and NO* performed comparably to FE (Fuller's earth), the standard powder skin decontaminant on battlefield. Unlike FE that can only adsorb paraoxon, CeO2 nanoparticles can neutralize it into safer byproducts. This study highlights the interest of CeO2 nanoparticles and the influence of their physicochemical properties on organophosphorus compound degradation and cutaneous decontamination. [ABSTRACT FROM AUTHOR]

No unified model is available yet to explain the dynamics of laser-induced cavitation bubbles during laser ablation of solid targets in liquids, when an extremely high capillary number is achieved (>100), i.e., when the viscous forces strongly contribute to the friction. By investigating laser-induced bubbles on gold and yttrium-iron-garnet targets as a function of the liquid viscosity, using a nanosecond laser and an ultrafast shadowgraph imaging setup, we give a deeper insight into what determines the bubble dynamics. We find that the competition between the viscous forces and the surface tension (capillary number Ca), on the one hand, and the competition between the viscous forces and inertia (Reynolds number Re), on the other hand, are both key factors. Increasing the viscous forces, and hereby Ca up to 100 has an impact on the bubble shape and results in a very pronounced rim, which separates the bubble in a spherical cap driven by inertia and an interlayer. The temporal evolution of the footprint radius of the interlayer can be addressed in the framework of the inertiocapillary regime. For an intermediate viscosity, the thickness of the interlayer is consistent with a boundary layer equation. Interestingly, our data cannot be interpreted with simplified hydrodynamic (Cox–Voinov) or molecular-kinetic theory models, highlighting the originality of the dynamics reported when extremely high capillary numbers are achieved. Upon bubble collapse, spherical persistent microbubbles are created and partly dispersed in water, whereas the high-viscous polyalphaolefines lead to long-standing oblate persistent bubbles sticking to the target's surface, independent of the ablated target. Overall, liquid's viscosity determines laser ablation-induced cavitation. [ABSTRACT FROM AUTHOR]

By using anhydrous conditions, we report here an optimized synthesis of small but highly emitting upconverting nanoparticles (UCNPs) of LiYF4:Yb3+, Tm3+ without any surface passivation layers of silica or undoped matrix. For this, anhydrous precursors [Li-(TFA)-(monoglyme)] and [Ln-(TFA)3(monoglyme)] (Ln = Y, Gd, Tm, Yb; TFA = trifluoroacetate) were synthesized via a facile one-pot synthetic protocol, which showed excellent thermal decomposition compatibility to afford Ln3+-doped LiLnF4 NPs by simultaneous decomposition in the solution phase. A detailed study of the influence of many key parameters such as the ratio of dopant ions and solvents, concentration of precursors, reaction time, and temperature over crystalline phase, size, shape, morphology, and upconverting properties of the NPs produced followed by a mechanism for the formation of LiYF4-based NPs is presented. The high quality of these NPs is manifested by the fact that their upconversion efficiency is quite comparable to that of a bulk single crystal of the same composition (bulk materials are believed to have far better UC performance due to low surface area and less defects). Successful incorporation of these UCNPs in transparent TiO2 metallogels provided an alternative strategy of highly homogeneous UCNP-TiO2 composites of variable composition (1–10% of NPs) having very high specific surface area (435–580 m2/g). [ABSTRACT FROM AUTHOR]

Rational design and precise engineering are needed to optimize the structural and chemical parameters of functional materials. In this work, we demonstrate how pre-formed binary metal selenides can be an excellent synthetic choice for the synthesis of ternary coinage metal selenide nanoparticles (NPs) with controlled composition. The mild conditions required to obtain these ternary coinage metal selenide NPs offered an easy synthesis of n% CuAgSe–TiO2 (n = 0.01, 0.1, 0.3 and 1.0 mol%) nanocomposites for photocatalytic applications without compromising the structural and morphological characteristics of TiO2 and without having any organic ligands around the NPs. The use of ternary metal selenide nanocomposites CuAgSe–TiO2 results in a clear improvement in their photocatalytic activity for the photodegradation of formic acid as compared to the well-known benchmark for photocatalysis, TiO2 (P25), and its binary metal selenide nanocomposites Cu2−xSe–TiO2. DFT calculations establish semi-metallic behavior of CuAgSe NPs and show that CuAgSe–TiO2 forms a semimetallic-semiconductor heterojunction allowing a better charge separation to enhance its photocatalytic activity. [ABSTRACT FROM AUTHOR]

Exposure to organophosphorus compounds, in military conflicts or terrorist acts, requires an emergency procedure including the availability of efficient decontamination systems. Systems based on nanosized cerium(IV) oxide (CeO2) are highly promising candidates. CeO2 is a heterogeneous catalyst for the degradation of the organophosphorus compounds such as VX agent or sarin. While the synthesis method influences the physicochemical characteristics of the nanoparticle surface and thus their degradation activity, we have compared the degradation activity of nanosized CeO2 powders commercially available, or developed using different synthesis processes, namely hydrothermal process, photochemistry and laser ablation in liquids. The degradation activity was evaluated in vitro by measuring the degradation kinetics of paraoxon organophosphate. A quenching of the degradation activity is observed on the as-produced particles with a surface pollution, especially when organic molecules with carboxylate ion R–COO− are involved in the synthesis process. In contrast, laser-generated nanoparticles in ultra-pure water show the best activity, while the sample presents the lowest specific surface area. After annealing, almost all samples present a clean surface and the degradation activity is mainly driven by the specific surface area. We propose a figure of merit including the particle activity for the degradation of paraoxon, the production costs and the production time. Indeed, the two last parameters are essential to assess the relevance of each method in view of marketing. [ABSTRACT FROM AUTHOR]