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ProfesseurMail : albert.nguyen-van-nhien@u-picardie.fr
Tel : 03 22 82 75 69
Fax : 03 22 82 75 60
Les travaux concernent l'étude de la réaction d'aminocyanation en série saccharidique et son implication dans l'élaboration de glycoaminoacides, de nucléosides modifiés et de façon plus large, à des composés hétérocycliques spiraniques.
De façon similaire l'utilisation des glyco-cyanomésylates obtenus à partir des différents cyanhydrines permet d'obtenir comme intermédiaire réactionnel des glyco-carbénoïdes et d'étudier leur application pour la préparation de composés polycycliques issus des réaction d'insertion de type C,H ou O,Si.
Ces deux types de composés sont également utilisés dans des réactions de type Staudinger-aza wittig afin d'obtenir des dérivés de type aminopyrrolidines.
Straightforward extraction and selective bioconversion of high purity chitin from Bombyx eri larva: Toward an integrated insect biorefinery |
Synthesis of high molecular weight chitosan from chitin by mechanochemistry and aging |
Effect of standard light illumination on electrolyte’s stability of lithium-ion batteries based on ethylene and di-methyl carbonates |
Preparation of nucleoside derivative carrying an isothiazole or oxathiole cycle with an antiproliferative activity |
The influence of chloride and hydrogen sulfate anions in two polymerised ionic liquids based on the poly(1-(hydroxyethyl)-3-vinylimidazolium cation, synthesis, thermal and vibrational studies |
XRD and ATR/FTIR investigations of various montmorillonite clays modified by monocationic and dicationic imidazolium ionic liquids |
New iodide-based amino acid molecules for more sustainable electrolytes in dye-sensitized solar cells |
The effect of room temperature ionic liquids on the selective biocatalytic hydrolysis of chitin via sequential or simultaneous strategies |
Imidazolium-based titanium substrates against bacterial colonization |
Towards Renewable Iodide Sources for Electrolytes in Dye-Sensitized Solar Cells |
Consequences of Solid Electrolyte Interphase (SEI) Formation upon Aging on Charge-Transfer Processes in Dye-Sensitized Solar Cells |
SiO2/Ionic Liquid Hybrid Nanoparticles for Solid-State Lithium Ion Conduction |
Interface stability of a TiO(2)/3-methoxypropionitrile-based electrolyte: first evidence for solid electrolyte interphase formation and implications |
Chitins of different purity grades (45%, 89.7% and 93.3%) were efficiently extracted from Bombyx eri larva and fully physico-chemically characterized. Compared to commercially available and extracted α-chitin from shrimp shell, the collected data showed that insect chitins had similar characteristics in terms of crystallographic structures (α-chitin), thermal stability and degree of acetylation (>87%). The major differences lay in the crystallinity indexes (66% vs 75% for shrimp chitin) and in the morphological structures. Furthermore, low ash contents were determined for the insect chitins (1.90% vs 21.73% for shrimp chitin), making this chitin extraction and purification easier, which is highly valuable for an industrial application. Indeed, after only one step (deproteinization), the obtained chitin from Bombyx eri showed higher purity grade than the one extracted from shrimp shells under the same conditions. Insect chitins were then subjected to room temperature ionic liquid (RTIL) pretreatment prior to enzymatic degradation and presented a higher enzymatic digestibility compared to commercial one whatever their purity grade and would be thus a more relevant source for the selective production of N-acetyl-D-glucosamine (899.2 mg/g of chitin-2 steps vs 760 mg/g of chitin com). Moreover, for the first time, the fermentescibility of chitin hydrolysates was demonstrated with Scheffersomyces stipitis used as ethanologenic microorganism.
Chitosan can be obtained from the deacetylation of chitin. This process is however difficult and usually accompanied by depolymerization, affording low molecular weight chitosan. We report a novel path, relying on the combination of mechanochemistry and aging, to yield high molecular weight chitosan with minimal use of energy and solvent. This method is versatile and applicable to a number of chitin sources, including crude crustacean and insect shells, yielding deacetylation up to 98% and remarkably high molecular weights. Chitin deacetylation was studied by magic angle spinning nuclear magnetic resonance and molecular weight was estimated by viscometry. This process affords chitosan in a safer fashion and with less materials and energy usage compared to the classic hydrothermal one.
The chemical reaction of 2-chloroethanol with 1-vinylimidazol as precursor led to the corresponding compound 1-hydroxyethyl-3-vinylimidazolium chloride [EtOHVIM+] [Cl−]. In the next step, treatment of [EtOHVIM+][Cl−] with 2,2-azobisisobutyronitril (AIBN) afforded the poly1-(hydroxyethyl)-3-vinylimidazolium chloride (poly[EtOHVIM+][Cl−]), Finally, the reaction of (poly[EtOHVIM+][Cl−]) and sulfuric acid led to poly 1-(hydroxyethyl)-3-vinylimidazolium hydrogen sulfate (poly[EtOHVIM+][HSO4−]) by replacing the [Cl−] halide by an [HSO4−] anion. The structure of these compounds was identified by 1H NMR, 13C NMR as preliminary spectroscopic characterization. To obtain information on the structure and vibrational behavior in these compounds, vibrational spectroscopy measurements were investigated by Fourier Transform-Infrared-Attenuated Total Reflectance and Fourier Transform Raman spectroscopy in the spectral range 600–4000 cm−1 and 4000–500 cm−1, respectively. The Polymerization of IL gave rise to specific marks in the Raman and IR spectra and enhanced its vibrational property. Also, in order to understand the thermal stability in these compounds, the results concerning the melting point, glass transition and decomposition were determined by thermogravimetric analysis (TGA), differential thermal (DTG), and differential scanning calorimetry (DSC). The results indicated that the poly [EtOHVIM+][HSO4−] compound showed interesting thermal properties like high temperature of degradation and low temperature of glass transition compared to poly[EtOHVIM+][Cl−].
Three different montmorillonites (Mts) labeled K10, KSF and SWy-3 were analyzed by X-ray diffraction and ATR/FTIR spectroscopy. The XRD results enabled validation of the purification process of the studied clays. In the spectral regions 3800–2600 and 1800-1300 cm-1, the study of different intensity ratios of peaks assigned to the OH bending and stretching modes displayed the specific vibrational behavior of SWy-3 which is certainly influenced by a greater proportion of Na+ in its structure. Before analyzing the clays modified by ionic liquids, we characterized two imidazolium based ionic liquids (ILs) with anion I-: [EMIM+] [I−] monocationic ionic liquid and [M(CH₂) IM2+] [2I−] dicationic ionic liquid. The passage from [EMIM+] [I−] to [M(CH₂) IM2+] [2I−] reveals significant vibrational changes through various modes: ν(NH), rings ν(CC), rings ν(CN), ν(CH2(N)), ν(CH3(N)) in addition to anion interaction modes. When purified, these ionic liquids modify clays, the XRD analysis shows that the studied modified clays exhibited higher d-value increase with respect to the purified Mts, and the reflection peaks 2θ (°) of plane (001) were displaced towards lower values as a consequence of the ionic liquid intercalation process. ATR/FTIR spectra recorded in the spectral zone 4000-600 cm-1 indicated the appearance of new peaks and a significant intensity variation between clays in relation to the type of chosen ionic liquid. These vibrational changes are directly connected to the presence of ionic liquids in clays. XRD and ATR/FTIR investigations show a stronger effect of the [M(CH2) IM2+] [2I−] dicationic ionic liquid on the Mts than the monocationic ionic liquid and the SWy-3 Mt is more sensitive to monocationic and dicationic ionic liquids than K10 and KSF Mts.
The electrolyte is the second key component governing at once power conversion performances and stability of dye-sensitized solar cells. Towards the integration of more sustainable materials, we focused in the replacement of the major constituent of the electrolyte, namely the 1,3 di-alkyl imidazolium iodide. We synthesized two new iodide molecules derived from natural amino acid family (L-proline): (S)-2-(methoxycarbonyl)-1,1-dimethylpyrrolidinium iodide (PMeI) and (S)-2-(ethoxycarbonyl)-1,1-ethylpyrrolidinium iodide (PEtI). In combination with the C106 polypyridyl ruthenium(+II) sensitizer, power conversion efficiencies of 7.1% for PMeI and 6.5% for PEtI were obtained under standard Air Mass 1.5G conditions in conjunction with low-volatile 3-methoxypropionitrile-based solvent. The relationship between these new iodide molecules, the power conversion efficiency and interfacial charge transfer processes is herein discussed and systematically compared to the best standard 1,3 di-methylimidazolium iodide.
An efficient conversion of chitin, the second most abundant renewable polymer on the Earth, into N-acetylglucosamine and N,N[prime or minute]-diacetylchitobiose, using room temperature ionic liquids (RTILs) and commercially available chitinases is described for the first time. The sequential strategy consists of the use of RTILs to pretreat chitin under mild conditions as a first step before enzymatic hydrolysis. [C2mim][OAc] (1-ethyl-3-methyl imidazolium) pretreatment provides an efficient production of N-acetylglucosamine (185.0 +/- 4.0 mg per g chitin) or N,N[prime or minute]-diacetylchitobiose (667.60 +/- 20.71 mg per g chitin) catalyzed by chitinase from Trichoderma viride or Streptomyces griseus, respectively. A thorough investigation of the structural changes of chitin induced by RTIL pretreatment suggested an increase in enzymes' accessibility to the chitin substrate. Alternatively, a one-pot enzymatic hydrolysis of chitin in [C2mim][OAc]-aqueous medium constitutes a promising simultaneous route to selectively generate N-acetylglucosamine or N,N[prime or minute]-diacetylchitobiose by decreasing the required [C2mim][OAc] amount and the number of steps. Finally, the combination of the two chitinases from T. viride and S. griseus was shown to be very relevant to considerably increase the production of N-acetylglucosamine up to 760.0 +/- 0.1 mg per g chitin.
Nosocomial infections are often induced by the presence of pathogenic organisms on the surface of medical devices or hospital equipment. Chemical modifications of the surface are recognized as efficient strategies to prevent bacterial adhesion but they may have a negative impact on the material's interaction with living tissues. Here we have developed a photoactivated method for the modification of titanium substrates. A photoinduced technique employing a grafting-onto process has been successfully performed to covalently anchor an imidazolium-derivative siloxane onto titanium surfaces. Imidazolium surfaces showed higher bacteria-repellency performances than native titanium substrates, achieving more than 98% anti-adhesion efficiency against Escherichia coli after 24 h of incubation. In addition, these surfaces allowed for the adhesion and viability of osteoblasts cells without evidence of cytotoxicity.
Solid electrolyte interphase (SEI) layers form on sensitized-TiO2 photoanodes and platinum counter electrodes when dye-sensitized solar cells (DSSCs) are subjected to an accelerated aging protocol (e.g., heating at 85 °C in the dark for 500 h). To understand how this impacts device operation, we conducted an electrochemical impedance spectroscopy study and found that the SEI induces an additional electron-transfer process from the TiO2 to the electrolyte. This is materialized by the onset of a new charge-transfer semicircle at higher frequencies, predominantly visible under bias voltages similar to and greater than the open-circuit voltage. Our results emphasize the detrimental role of SEI formation on device performance and lifetime. Additionally, nanosecond transient absorption spectroscopy showed that SEI formation reduced the rate of oxidized dye regeneration. We also found that a proportion of the photogenerated holes on the dyes were transferred to the SEI itself. A prolonged aging duration led to the electrode’s mesoporosity network being entirely clogged by the SEI, thus impeding efficient transport of the electrolyte redox couple and being responsible for a further decline in photovoltaic performances.
We report the physical and electrical characterization of a series of substituted imidazolium-based ionic liquids grafted on Stöber-type SiO2. This hybrid architecture affords an increase of the lithium transference to 0.56 by hindering TFSI? (bis(trifluoromethane)sulfonimide) mobility to the total ionic conductivity. When doped with 16 wt % wt LiTFSI, the resulting hybrid organic/inorganic solid material exhibits a lithium diffusion coefficient of 2 ? 10?12 m2/s at 87 °C and a conductivity of ca. 10?6 S/cm at room temperature and 10?4 S/cm at 65 °C with an activation energy barrier of 0.89 eV.