Sub-THz Vibrational Dynamics in Ordered Mesoporous Silica Nanoparticles.

The vibrational dynamics in the sub-THz range of mesoporous silica nanoparticles (MSNs) having ordered cylindrical mesopores was investigated. MCM-41 and SBA-15 particles were synthesized, and their structure was determined using scanning electron microscopy (SEM), low-angle X-ray diffraction (XRD), N2 physisorption analyses, and Raman scattering. Brillouin scattering measurements are reported and enabled determining the stiffness of the silica walls (speed of sound) using finite element calculations for the ordered mesoporous structure. The relevance of this approach is discussed based on the comparison between the numerical and experimental results and previous works reported in the literature.

Manipulating multi-spectral slow photons in bilayer inverse opal TiO2@BiVO4 composites for highly enhanced visible light photocatalysis.

Manipulation of light has been proved to be a promising strategy to increase light harvesting in solar-to-chemical energy conversion, especially in photocatalysis. Inverse opal (IO) photonic structures are highly promising for light manipulation as their periodic dielectric structures enable them to slow down light and localize it within the structure, thereby improving light harvesting and photocatalytic efficiency. However, slow photons are confined to narrow wavelength ranges and hence limit the amount of energy that can be captured through light manipulation. To address this challenge, we synthesized bilayer IO TiO2@BiVO4 structures that manifested two distinct stop band gap (SBG) peaks, arising from different pore sizes in each layer, with slow photons available at either edge of each SBG. In addition, we achieved precise control over the frequencies of these multi-spectral slow photons through pore size and incidence angle variations, that enabled us to tune their wavelengths to the electronic absorption of the photocatalyst for optimal light utilization in aqueous phase visible light photocatalysis. This first proof of concept involving multi-spectral slow photon utilization enabled us to achieve up to 8.5 times and 2.2 times higher photocatalytic efficiencies than the corresponding non-structured and monolayer IO photocatalysts respectively. Through this work, we have successfully and significantly improved light harvesting efficiency in slow photon-assisted photocatalysis, the principles of which can be extended to other light harvesting applications.

Core-shell polygalacturonate magnetic iron oxide nanoparticles: Synthesis, characterization, and functionalities.

This work aims to synthesize polygalacturonate-based magnetic iron oxide nanoparticles (INP-polyGalA). The synthesis consists of the diffusion of both Fe2+ and Fe3+ at a molar ratio of 1:2 through polyGalA solution followed by the addition of an alkaline solution. To form individual nanoparticle materials, the polyGalA concentration needs to be below its overlapping concentration (C*). The synthesized materials (INP-polyGalA) contain about 45% of organic compound (polyGalA), and they have an average particle size ranging from 10 to 50 nm as estimated by several techniques (DLS, TEM and AFM) and their surfaces are negatively charged in pH range 2 to 7. The synthesized NPs showed magnetic characteristics, thanks to the formation of magnetite (Fe3O4) as confirmed by X-ray diffractions (XRD). Moreover, AFM combined with Infra-red mapping allowed us to conclude that polyGalA is located in the core of the nanoparticles but also on their surfaces. More specially, both carboxylate (COO-) and carboxylic (COOH) groups of polyGalA are observed on the NPs surfaces. The presence of such functional groups allowed the synthesized material to (i) bind through the electrostatic interactions methylene blue (MB) which may have a great potential for r pollution control or (ii) to form hydrogel beads (ionotropic gelation) by using calcium as a crosslinking agent which can be used to encapsulate active molecules and target their release by using an external stimulus (magnetic field).

Functionalization of developed bacterial cellulose with magnetite nanoparticles for nanobiotechnology and nanomedicine applications.

This paper deals with the preparation of novel magnetic materials made from tetraaza macrocyclic Schiff base bacterial cellulose ligands with magnetite nanoparticles (Fe3O4NPs) through a multi-step procedure for antimicrobial and cytotoxic activities and chemotherapy in cancer treatment. First, the 2,3-dialdehyde bacterial cellulose (DABC) was chemically modified by ethylenediamine (EDA) and benzil (Bzl) in the presence of ferrous ions. Then, the magnetite nanoparticles (Fe3O4NPs) was produced inside the complex [Fe(DABC-EDA-Bzl)Cl2] through a co-precipitation method. In nanobiotechnology, the magnetic [Fe3O4NP-INS-(DABC-EDA-Bzl)] material was showed moderate antimicrobial and cytotoxic activities against different species and cells, respectively. In particular, the magnetic [Fe3O4NP-INS-(DABC-EDA-Bzl)] material have not any cytotoxic activity towards peripheral blood mononucleocyte (PBMC) cells. Anti-tumor studies demonstrated that the magnetic [Fe3O4NP-INS-(DABC-EDA-Bzl)] material effectively inhibits the growth of the CT26 tumor model in BALB/c mice compared with other resulting materials throughout the experimental period and can be effective drug delivery in nanomedicine.

Comparative studies on the adsorption of metal ions from aqueous solutions using various functionalized graphene oxide sheets as supported adsorbents.

Graphene oxide (GO) was chemically modified by bis(2-pyridylmethyl)amino groups (BPED) through a multistep procedure. For comparison, and to justify the grafting of BPED groups onto the GO sheets, the GO-based material obtained after each step was used as a solid phase adsorbent for removing Cu(II), Ni(II) and Co(II) metal ions from aqueous solutions. The influence of metal ion concentrations, pH, contact time and temperature on their adsorption onto the GO-based adsorbents was investigated and the GO-EDA-CAC-BPED adsorbent showed the highest ability to adsorb Cu(II), Ni(II) and Co(II) with a concentration of 250 mg.L-1 at pH = 7. Additionally, it was demonstrated that the equilibrium adsorption capacities of these metal ions followed the order of Cu(II)>Ni(II)>Co(II) whatever the GO-based adsorbent. Moreover, to examine the underlying mechanism of the adsorption process, pseudo-first order, pseudo-second order, Elovich or Roginsky-Zeldovich and intraparticle diffusion models were fitted to experimental kinetic data. It was shown that the pseudo-second-order model was the most appropriate one to describe the adsorption of heavy metal ions by the GO-based materials. Finally, it was demonstrated that their desorption/regeneration capacities were higher than 10 cycles, opening the path to the removal of metal ions from wastewater solutions.