Dehydration of Alginic Acid Cryogel by TiCl4 vapor : Direct Access to Mesoporous TiO2@C Nanocomposites and Their Performance in Lithium-Ion Batteries

A new strategy for the synthesis of mesoporous TiO2@C nanocomposites through the direct mineralization of seaweed-derived alginic acid cryogel by TiCl4 through a solid/vapor reaction pathway is presented. In this synthesis, alginic acid cryogel can have multiple roles; i) mesoporous template, ii) carbon source, and iii) oxygen source for the TiO2 precursor, TiCl4. The resulting TiO2@alginic acid composite was transformed either into pure mesoporous TiO2 by calcination or into mesoporous TiO2@C nanocomposites by pyrolysis. By comparing with a nonporous TiO2@C composite, the importance of the mesopores on the performance of electrodes for lithium-ion batteries based on mesoporous TiO2@C composite was clearly evidenced. In addition, the carbon matrix in the mesoporous TiO2@C nanocomposite also showed electrochemical activity versus lithium ions, providing twice the capacity of pure mesoporous TiO2 or alginic acid-derived mesoporous carbon (A600). Given the simplicity and environmental friendliness of the process, the mesoporous TiO2@C nanocomposite could satisfy the main prerequisites of green and sustainable chemistry while showing improved electrochemical performance as a negative electrode for lithium-ion batteries

Alginic acid-derived mesoporous carbonaceous materials (Starbon®) as negative electrodes for lithium ion batteries : Importance of porosity and electronic conductivity

Alginic acid-derived mesoporous carbonaceous materials (Starbon® A800 series) were investigated as negative electrodes for lithium ion batteries. To this extent, a set of mesoporous carbons with different pore volume and electronic conductivity was tested. The best electrochemical performance was obtained for A800 with High Pore Volume (A800HPV), which displays both the highest pore volume (0.9 cm3 g−1) and the highest electronic conductivity (84 S m−1) of the tested materials. When compared to a commercial mesoporous carbon, A800HPV was found to exhibit both better long-term stability, and a markedly improved rate capability. The presence of a hierarchical interconnected pore network in A800HPV, accounting for a high electrolyte accessibility, could lay at the origin of the good electrochemical performance. Overall, the electronic conductivity and the mesopore size appear to be the most important parameters, much more than the specific surface area. Finally, A800HPV electrodes display similar electrochemical performance when formulated with or without added conductive additive, which could make for a simpler and more eco-friendly electrode processing

Mechanisms and Kinetics for Sorption of CO2 on Bicontinuous Mesoporous Silica Modified with n-Propylamine

We studied equilibrium adsorption and uptake kinetics and identified molecular species that formed during sorption of carbon dioxide on amine-modified silica. Bicontinuous silicas (AMS-6 and MCM-48) were postsynthetically modified with (3-aminopropyl)triethoxysilane or (3-aminopropyl)methyldiethoxysilane, and amine-modified AMS-6 adsorbed more CO(2) than did amine-modified MCM-48. By in situ FTIR spectroscopy, we showed that the amine groups reacted with CO(2) and formed ammonium carbamate ion pairs as well as carbamic acids under both dry and moist conditions. The carbamic acid was stabilized by hydrogen bonds, and ammonium carbamate ion pairs formed preferably on sorbents with high densities of amine groups. Under dry conditions, silylpropylcarbamate formed, slowly, by condensing carbamic acid and silanol groups. The ratio of ammonium carbamate ion pairs to silylpropylcarbamate was higher for samples with high amine contents than samples with low amine contents. Bicarbonates or carbonates did not form under dry or moist conditions. The uptake of CO(2) was enhanced in the presence of water, which was rationalized by the observed release of additional amine groups under these conditions and related formation of ammonium carbamate ion pairs. Distinct evidence for a fourth and irreversibly formed moiety was observed under sorption of CO(2) under dry conditions. Significant amounts of physisorbed, linear CO(2) were detected at relatively high partial pressures of CO(2), such that they could adsorb only after the reactive amine groups were consumed.authorCount :7</p

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

International audienceControlling 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

Core–shell Au@(TiO2, SiO2) nanoparticles with tunable morphology

International audienc

The Effect of Surface Modification of Aligned Poly-L-Lactic Acid Electrospun Fibers on Fiber Degradation and Neurite Extension.

The surface of aligned, electrospun poly-L-lactic acid (PLLA) fibers was chemically modified to determine if surface chemistry and hydrophilicity could improve neurite extension from chick dorsal root ganglia. Specifically, diethylenetriamine (DTA, for amine functionalization), 2-(2-aminoethoxy)ethanol (AEO, for alcohol functionalization), or GRGDS (cell adhesion peptide) were covalently attached to the surface of electrospun fibers. Water contact angle measurements revealed that surface modification of electrospun fibers significantly improved fiber hydrophilicity compared to unmodified fibers (p < 0.05). Scanning electron microscopy (SEM) of fibers revealed that surface modification changed fiber topography modestly, with DTA modified fibers displaying the roughest surface structure. Degradation of chemically modified fibers revealed no change in fiber diameter in any group over a period of seven days. Unexpectedly, neurites from chick DRG were longest on fibers without surface modification (1651 ± 488 μm) and fibers containing GRGDS (1560 ± 107 μm). Fibers modified with oxygen plasma (1240 ± 143 μm) or DTA (1118 ± 82 μm) produced shorter neurites than the GRGDS or unmodified fibers, but were not statistically shorter than unmodified and GRGDS modified fibers. Fibers modified with AEO (844 ± 151 μm) were significantly shorter than unmodified and GRGDS modified fibers (p<0.05). Based on these results, we conclude that fiber hydrophilic enhancement alone on electrospun PLLA fibers does not enhance neurite outgrowth. Further work must be conducted to better understand why neurite extension was not improved on more hydrophilic fibers, but the results presented here do not recommend hydrophilic surface modification for the purpose of improving neurite extension unless a bioactive ligand is used

Surface morphology of electrospun fibers before chemical modification (Untreated row) or after different chemical modifications to the fibers.

<p>Fibers were imaged by SEM before degradation (Day 0) or after 1, 2.5, or 7 days in PBS. Untreated fibers were smooth, but plasma treated fibers or fibers modified with GRGDS or AEO showed a rougher surface. DTA fibers appeared even rougher, and contained pits in the surface of the fibers. No trends in fiber surface morphology were observed at any time point, suggesting differences in surface roughness were a result of the different chemical modifications. All images were captured at the same magnification, the scale bar (top right image) is 1 <b>μ</b>m.</p

Neurite extension from chick DRG on electrospun PLLA fibers (A) and after plasma treatment (B) or after modification with DTA (C), AEO (D), or GRGDS (E).

<p>Measurement of maximum neurite extension (F, n = 3) revealed that the maximum neurite extension occurred on untreated fibers and fibers modified with GRGDS, and the untreated fibers and fibers modified with GRGDS were statistically significant from the fibers modified with AEO (†, p < 0.05). This data suggests no advantage to improving electrospun fiber hydrophilicity since all groups are more hydrophilic than the untreated control, but maximum neurite extension does not improve on any group compared to the control. All scale bars are 400 <b>μ</b>m.</p

XPS of electrospun scaffolds to determine the presence of specific surface chemistries over time.

<p>First, the C1s region of the XPS data was evaluated to determine the change in surface chemistry before and after oxygen plasma treatment (A). The three peaks in (A) correspond to C-C and C-H bonds (283.4 and 284.8 eV), C-O bonds (286.8eV), and C = O bonds (289eV). Next, the nitrogen region of each scaffold was used to determine the presence of DTA (B), AEO (C), or GRGDS (D). The decrease in the nitrogen signal for DTA and AEO suggest surface erosion may be removing the surface chemistry. No decrease in signal is observed for the GRGDS peptide, suggesting GRGDS remains bound to the surface of the fibers throughout seven days of degradation.</p