Acute Aquatic Toxicity to Zebrafish and Bioaccumulation in Marine Mussels of Antimony Tin Oxide Nanoparticles.

Antimony tin oxide (Sb2O5/SnO2) is effective in the absorption of infrared radiation for applications, such as skylights. As a nanoparticle (NP), it can be incorporated into films or sheets providing infrared radiation attenuation while allowing for a transparent final product. The acute toxicity exerted by commercial Sb2O5/SnO2 (ATO) NPs was studied in adults and embryos of zebrafish (Danio rerio). Our results suggest that these NPs do not induce an acute toxicity in zebrafish, either adults or embryos. However, some sub-lethal parameters were altered: heart rate and spontaneous movements. Finally, the possible bioaccumulation of these NPs in the aquacultured marine mussel Mytilus sp. was studied. A quantitative analysis was performed using single particle inductively coupled plasma mass spectrometry (sp-ICP-MS). The results indicated that, despite being scarce (2.31 × 106 ± 9.05 × 105 NPs/g), there is some accumulation of the ATO NPs in the mussel. In conclusion, commercial ATO NPs seem to be quite innocuous to aquatic organisms; however, the fact that some of the developmental parameters in zebrafish embryos are altered should be considered for further investigation. More in-depth analysis of these NPs transformations in the digestive tract of humans is needed to assess whether their accumulation in mussels presents an actual risk to humans.

Size Control and Improved Aqueous Colloidal Stability of Surface-Functionalized ZnGa2O4:Cr3+ Bright Persistent Luminescent Nanoparticles.

Near-infrared (NIR)-emitting ZnGa2O4:Cr3+ (ZGO) persistent luminescent nanoparticles (PLNPs) have recently attracted considerable attention for diverse optical applications. The widespread use and promising potential of ZGO material in different applications arise from its prolonged post-excitation emission (several minutes to hours) that eliminates the need for continuous in situ excitation and the possibility of its excitation in different spectral regions (X-rays and UV-vis). However, the lack of precise control over particle size/distribution and its poor water dispersibility and/or limited colloidal stability required for certain biological applications are the major bottlenecks that limit its practical applications. To address these fundamental limitations, herein, we have prepared oleic acid (OA)-stabilized ZGO PLNPs with controlled size (7-12 nm, depending on the type of alcohol used in synthesis) and monodispersity. A further increase in size (8-21 nm), with a concomitant increase in persistent luminescence, could be achieved using a seed-mediated approach, employing the as-prepared ZGO PLNPs from the first synthesis as the seed and growing layers of the same material by adding fresh precursors. To remove their surface oleate groups and make the nanoparticles hydrophilic, two surface modification strategies were evaluated: modification with only poly(acrylic acid) (PAA) as the hydrophilic capping agent and modification with either PAA or cysteamine (Cys) as the hydrophilic capping agent in conjunction with BF4- as the intermediate surface modifier. The latter surface modifications involving BF4- conferred long-term (60 days and longer) colloidal stability to the nanoparticles in aqueous media, which is related to their favorable ζ potential values. The proposed generalized strategy could be used to prepare different kinds of surface-functionalized PLNPs with control of size, hydrophilicity, and colloidal stability and enhanced/prolonged persistent luminescence for diverse potential applications.

Removal of atrazine from aqueous solutions onto a magnetite/chitosan/activated carbon composite in a fixed-bed column system: optimization using response surface methodology.

In this study, a magnetite/chitosan/activated carbon (MCHAC) composite is proposed as an efficient adsorbent for the removal of atrazine from aqueous solutions. The prepared composite was characterized using Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) methods. Response surface methodology (RSM) coupled with composite central design (CCD) were used to optimize the effects of the four independent variables, pH, initial concentration of atrazine (C 0), bed depth (H), and flow rate (Q), which influence the adsorption process. The experimental results modeled using response surface methodology (RSM) coupled with central composite design (CCD) (RSM-CCD) indicated a quadratic relationship with p < 0.0001 for adsorption capacity at saturation (q s) and fraction of bed utilization (FBU). The results of the experiments performed under the optimized conditions, pH = 5.07, C 0 = 137.86 mg L-1, H = 2.99 cm and Q = 1.038 mL min-1, showed a q s value of 62.32 mg g-1 and FBU of 72.26%, with a deviation value of less than 0.05 from the predicted q s and FBU values. The obtained breakthrough curves were fitted with four mathematical models, Thomas, Bohart-Adams, Yan and Yoon-Nelson, in order to determine the limiting step of the mass transfer of the atrazine adsorption onto the composite. A desorption study of the composite revealed the high reuse potential for MCHAC, thus, the prepared material could be used as a low-cost and efficient adsorbent for the decontamination of polluted wastewater.

Optimizing metal-support interphase for efficient fuel cell oxygen reduction reaction catalyst.

The development of cost-effective and highly-efficient electro-catalysts is essential for the advancement of proton exchange membrane fuel cells (PEMFC). We present a novel nitrogen-sulphur co-doped carbon nanotubes-few layer graphene1D-2D hybrid support formed by partially exfoliating multiwall carbon nanotubes (PECNT), to improve interface bonding to catalyst nanoparticles. Detailed Raman spectroscopy and STEM-EDS analyses demonstrate that active sites on the co-doped hybrid support ensure both uniform distribution and improved bonding of the catalyst nanoparticles to the support. Electrochemical studies show that Pt nanoparticles decorated on nitrogen-sulphur co-doped PECNT (Pt/NS-PECNT) have higher electrochemical active surface area and mass activity accompanied by low H2O2 formation and improved positive half-wave potential, as compared to those decorated on co-doped rGO-incorporated PECNT hybrid structure (Pt/NS-(rGO-PECNT)). Fuel cell measurements demonstrate a higher power density for our novel (Pt/NS-PECNT) electro-catalyst when compared to both Pt/NS-(rGO + PECNT), and commercial Pt/C electro-catalyst. We demonstrate in this work that the interconnectivity between Pt-nanoparticles and the dopant or defect sites on the support play a crucial role in enhancing the ORR activity, fuel cell performance, and durability of the catalyst.

Simple and economic elaboration of high purity CaCO3 particles for bone graft applications using a spray pyrolysis technique.

Materials for bone grafting are a major health stake today. The existing synthetic materials only partially answer to the requirements for such uses and do not provide a real alternative solution to the classical way consisting of the reuse of natural osseous materials, known to create other problems. In the present work, we have prepared calcium carbonate powders using spray pyrolysis in the perspective to realize ideal and multi-purposed bricks to form bone graft materials, by bottom-up approaches, using classical techniques. The chemical reactions involved in the synthesis process consist in the thermal decomposition of calcium acetate. This precursor, a classical food additive, is known to be non toxic, easy to use and very cheap. Morphological and chemical characterization was conducted on the obtained materials. Depending on the pyrolysis temperature, we observed partial decomposition of calcium acetate or lime formation. An annealing step is consequently required to finalize the transformation. Finally, it appears that annealed products are pure calcite particles, having a spherical morphology and possessing a low dispersity in the micron size range. These particles exhibit an original internal structure, reinforcing and ensuring the preservation of their morphological characteristics during the sintering process. Furthermore, a porosity value compatible with drug carrier capabilities was measured on the obtained products. All these qualities allow us to consider a multi-purpose use of these particles in almost all types of bone graft materials.

Gadolinium oxysulfide nanoparticles as multimodal imaging agents for T2-weighted MR, X-ray tomography and photoluminescence.

We have synthesized gadolinium oxysulfide nanoparticles (NPs) doped with other lanthanides (Eu(3+), Er(3+), Yb(3+)) via a hydroxycarbonate precursor precipitation route followed by a sulfuration process under a H2S-Ar atmosphere at 750 °C in order to propose new multimodal nanoplatforms for Magnetic Resonance (MR), X-ray and photoluminescence imaging. Gd2O2S:Eu(3+) NPs strongly absorb near UV (≈ 300-400 nm) and re-emit strong red light (624 nm). They can be easily internalized by cancer cells, and imaged by epifluorescence microscopy under excitation in the NUV (365 nm). They are not cytotoxic for living cells up to 100 µg mL(-1). Consequently, they are well adapted for in vitro imaging on cell cultures. Gd2O2S:Eu(3+) NPs also show strong transverse relaxivity and strong X-ray absorption allowing their use as contrast agents for T2-weighted MRI and X-ray tomography. Our study shows that Gd2O2S:Eu(3+) NPs are considerably better than commercial Ferumoxtran-10 NPs as negative contrast agents for MRI. Upconversion emission of Gd2O2S:Er; Yb (1; 8%) NPs under infrared excitation (λ(ex) = 980 nm) shows mainly red emission (≈ 650-680 nm). Consequently, they are more specifically designed for in vivo deep fluorescence imaging, because both excitation and emission are located inside the "transparency window" of biological tissues (650-1200 nm). Magnetic relaxivity and X-ray absorption behaviors of Gd2O2S:Er; Yb NPs are almost similar to Gd2O2S:Eu(3+) NPs.