Rapid microwave-assisted synthesis of saponites and their use as oxidation catalysts

Saponites containing divalent Mg, Ni, or Fe as octahedral cations and trivalent Al and Fe substituting Si in the tetrahedral sheet were synthesized using microwave radiation. Saponite with a high specific surface area was obtained in all the syntheses, although Fe-Al saponite crystallized was impurified by Fe2O3 and analcime. The catalytic activity of the solids for the epoxidation of (Z)-cyclooctene by hydrogen peroxide was tested, the solids obtained being highly active (conversion up to 8.8%, and 100% selectivity to the epoxide

Comparison of antibacterial activity and cytotoxicity of silver nanoparticles and silver-loaded montmorillonite and saponite

Although silver nanoparticles are known for their antibacterial activity, little research has been carried out on what synthesis method provides the most effective particles. In this study, silver nanoparticles were synthesised via chemical reduction by using silver nitrate as the silver precursor, ascorbic acid as the reducing agent and sodium citrate as the stabilising agent. The solutions were adjusted to several pH values employing sodium hydroxide, citric acid or nitric acid. Dynamic light scattering and absorption spectra in the ultraviolet/visible region characterisation revealed that employing nitric acid to adjust the pH produced more varied and larger silver particle sizes. Then, silver nanoparticles were supported on montmorillonite and saponite through wet impregnation or ion exchange methods. Scanning electron microscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy characterisation confirmed that silver nanoparticles were successfully loaded onto the clay minerals. Next, the antibacterial activity of the samples was evaluated against Escherichia coli and Staphylococcus aureus by determining their minimum inhibitory concentrations and minimum bactericidal concentrations. The free silver nanoparticles did not show any antibacterial activity at 125 mg/L. In contrast, the silver-loaded samples obtained by wet impregnation and with a higher silver content displayed the strongest antibacterial effect. Finally, the cytotoxicity of the samples was determined in GM07492-A cell line by using an XTT colorimetric assay. The calculated IC50 values revealed that the supported silver nanoparticles were barely toxic. Thus, the silver-loaded clay minerals obtained here are promising antibacterial materials with a high-grade safety profile

Assessing the danger of self-sustained HIV epidemics in heterosexuals by population based phylogenetic cluster analysis.

Assessing the danger of transition of HIV transmission from a concentrated to a generalized epidemic is of major importance for public health. In this study, we develop a phylogeny-based statistical approach to address this question. As a case study, we use this to investigate the trends and determinants of HIV transmission among Swiss heterosexuals. We extract the corresponding transmission clusters from a phylogenetic tree. To capture the incomplete sampling, the delayed introduction of imported infections to Switzerland, and potential factors associated with basic reproductive number R0, we extend the branching process model to infer transmission parameters. Overall, the R0 is estimated to be 0.44 (95%-confidence interval 0.42-0.46) and it is decreasing by 11% per 10 years (4%-17%). Our findings indicate rather diminishing HIV transmission among Swiss heterosexuals far below the epidemic threshold. Generally, our approach allows to assess the danger of self-sustained epidemics from any viral sequence data

Unravelling HIV-1 Latency, One Cell at a Time.

A single virus is capable of infecting and replicating in a single cell. Recent advances across single-cell omics technologies - genomics, epigenomics, transcriptomics, epitranscriptomics, proteomics, and metabolomics - will offer unprecedented opportunities to gain more insights into the various aspects of the life cycle of viruses and their impact on the host cell. Here, using the human immunodeficiency virus type 1 (HIV-1) as an example, we summarize the current knowledge and the future potential of single-cell omics in the investigation of an important aspect of the life cycle of HIV-1 that represents a major hurdle in achieving viral eradication, HIV-1 latency

Glasses In The Si{single Bond}o{single Bond}c{single Bond}n System Produced By Pyrolysis Of Polycyclic Silazane/siloxane Networks

In this work, polycyclic silazane/siloxane networks bearing Si{single bond}O and Si{single bond}N bonds were synthesized, via hydrosilylation reaction, from cyclotrisilazane, [CH2{double bond, long}CH(CH3)SiNH]3, and cyclotetrasiloxane, [CH3(H)SiO]4, with different Si{single bond}H:Si{single bond}vinyl molar ratios. The resulting polymers were pyrolyzed up to 1000 °C, in N2 atmosphere, producing SiOCN glasses. The polymer-to-ceramic transformation was studied by thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), and chemical analysis. The 1000-1500 °C, high temperature structural evolution was also studied using X-ray diffraction (XRD) and FTIR. The hydrosilylation reaction produced ethylenic bridge crosslinked polymeric precursors with good thermal stability. The SiOCN glasses obtained with ceramic yields higher than 80 wt% showed spectra absorptions of Si{single bond}N, Si{single bond}O, and Si{single bond}C bonds in FTIR. The XRD patterns of the products obtained at 1500 °C displayed diffraction peaks characteristic of β-SiC and a broad halo centered at 22° (2θ), due to the amorphous silica phase. β-SiC diffraction peaks in the XRD patterns were more intense for the precursor richer in polysiloxane units, although absorptions of Si{single bond}N, Si{single bond}C, and Si{single bond}O bonds were also observed in the FTIR spectra. Thus, the final materials were characterized as SiC/SiOCN composites in nano/amorphous phases. © 2007 Elsevier B.V. All rights reserved.35322-2322802288Yajima, S., Omori, M., Hayashi, J., Okamura, K., Matsuzawa, T., Liaw, C.F., (1976) Chem. Lett., p. 551Yajima, S., Shishido, T., Kayano, H., (1976) Nature, 264, p. 237Schiavon, M.A., Yoshida, I.V.P., (2004) J. Mater. Sci., 39, p. 4507Bréquel, H., Parmentier, J., Walter, S., Badheka, R., Trimmel, G., Masse, S., Latournerie, J., Babonneau, F., (2004) Chem. Mater., 16 (13), p. 2585Schmidt, H., Borchardt, G., Muller, A., Bill, J., (2004) J. Non-Cryst. Solids, 341, p. 133Pantano, C.G., Singh, A.K., Zhang, H., (1999) J. Sol-Gel Sci. Technol., 14, p. 7Schiavon, M.A., Radovanovic, E., Yoshida, I.V.P., (2002) Powder Technol., 123, p. 232Kroke, E., Li, Y.-L., Konetschny, C., Lecomte, E., Fasel, C., Riedel, A., (2000) Mater. Sci. Res., R (26), p. 97Schiavon, M.A., Sorarù, G.D., Yoshida, I.V.P., (2002) J. Non-Cryst. Solids, 304, p. 76Breuming, T., (1999) J. Anal. Appl. Pyrol., 49, p. 43Chollon, G., (2000) J. Eur. Ceram. Soc., 20, p. 1959Bao, X., Edirisnghe, M.J., (1999) Compos.: Part A, 30, p. 601Pan, X., Mayer, J., Ruhle, M., Niihara, K., (1996) J. Am. Ceram. Soc., 79, p. 585Rendtel, A., Hubner, H., Hermann, M., Schubert, C., (1998) J. Am. Ceram. Soc., 81, p. 1109Lee, S.Y., (1998) J. Am. Ceram. Soc., 81, p. 1262Iwamoto, Y., Volger, W., Kroke, E., Riedel, R., Saiton, T., Matsunaga, K., (2001) J. Am. Ceram. Soc., 84, p. 2170Hemida, A.T., Birot, M., Pillot, J.P., Dunogues, J., Pailler, R., (1997) J. Mater. Sci., 32, p. 3475Borda, P.P., Legzdins, P., (1980) Anal. Chem., 52, p. 1777Schiavon, M.A., Sorarù, G.D., Yoshida, I.V.P., (2004) J. Non-Cryst. Solids, 348, p. 156Parashar, V.K., Raman, V., Bahl, O.P., (1997) J. Mater. Sci. Lett., 16, p. 1260Lavedrine, A., Bahloul, D., Goursat, P., Coong Kwet Yive, N., Corriu, R., Leclerq, D., Mutin, H., Vioux, A., (1991) J. Eur. Ceram. Soc., 8, p. 221Bahloul, D., Pereira, M., Goursat, P., Choong Kwet Yive, N.S., Corriu, R.J.P., (1993) J. Am. Ceram. Soc., 76, p. 1156Sorarù, G.D., D'Andrea, G., Campostrini, R., Babonneau, F., (1995) J. Mater. Chem., 5 (9), p. 1363Bahloul, D., Pereira, M., Gérardin, C., (1997) J. Mater. Chem., 7, p. 109Gérardin, C., Taulelle, F., Bahloul, D., (1997) J. Mater. Chem., 7, p. 117Schmidt, W.R., Narsavage-Heald, D.M., Jones, D.M., Marchetti, P.S., Raker, D., Maciel, G.E., (1999) Chem. Mater., 11, p. 1455Soraru, G.D., Modena, S., Belotti, P., Das, G., Marrioto, G., Pavesi, L., (2003) Appl. Phys. Lett., 83, p. 749Sorarú, G.D., Suttor, D., (1999) J. Sol-Gel Sci. Technol., 14, p. 69Radovanovic, E., Gozzi, M.F., Gonçalves, M.C., Yoshida, I.V.P., (1999) J. Non-Cryst. Solids, 248, p. 37Duan, R.G., Roebben, G., Vleugels, J., Van der Biest, O., (2005) Acta Mater., 53, p. 2547Wang, C.M., Emoto, H., Mitomo, M., (1998) J. Am. Ceram. Soc., 81, p. 1125Scheffler, M., Pippel, E., Woltersdorf, J., Greil, P., (2003) Mater. Chem. Phys., 80, p. 56

Synthesis Of Manganese Porphyrinosilica Imprinted With Templates Using The Sol-gel Process

The optimized conditions for the preparation of a new manganese porphyrinosilica-template material are reported. The manganese porphyrinosilica-template was prepared by the sol-gel process, by the reaction of -SO2Cl groups present in the phenyl rings of MnTDC(SO2Cl)PPCl with 3-aminopropyltriethoxysilane. The reaction produces a precursor porphyrinopropylsilyl species, which were then polymerized with tetraethoxysilane. The presence of manganese porphyrin on xerogel is confirmed by ultraviolet visible absorption spectroscopy and thermogravimetric analysis (TGA). The prepared materials have surface areas between 19 and 674 m2 g-1. Electron spectroscopy imaging of the materials show that manganese distribution in the xerogel is uniform. Both manganese(III) porphyrinosilica-template and a similar iron(III) porphyrinosilica-template can catalyze the epoxidation of cyclooctene using iodozylbenzene as oxygen donor. The metalloporphyrinosilica-template presents catalytic activity similar to that of metaloporphyrin in solution. © 2000 Elsevier Science B.V. All rights reserved.27301/03/15150158Brinker, C.J., Scherer, G.W., (1990) The Physics and Chemistry of Sol-gel Processing, , Academic Press, San Diego, CaliforniaLan, E.H., Dave, B.C., Fukuto, J.M., Dunn, B., Zink, J.I., Valentine, J.S., (1999) J. Mater. Chem., 9, p. 45Gill, I., Ballesteros, A., (1998) J. Am. Chem. Soc., 120, p. 8587Zhou, H.S., Honma, I., (1998) Chem. Lett., p. 973Das, T.K., Khan, I., Rousseau, D.L., Friedman, J.M., (1998) J. Am. Chem. Soc., 120, p. 10268Dave, B.C., Dunn, B., Valentine, J.S., Zink, J.I., (1994) Anal. Chem., 66, p. 1120Martinez-Lorente, M.A., Battioni, P., Kleemiss, W., Bartoli, J.F., Mansuy, D., (1996) J. Molec. Catal. A, 113, p. 343Dolphin, D., Traylor, T.G., Xie, L.Y., (1997) Acc. Chem. Res., 30, p. 251Meunier, B., (1992) Chem. Rev., 92, p. 1411Iamamoto, Y., Ciuffi, K.J., Sacco, H.C., Prado, C.M.C., Nascimento, O.R., (1994) J. Molec. Catal., 88, p. 167Iamamoto, Y., Ciuffi, K.J., Sacco, H.C., Iwamoto, L.S., Nascimento, O.R., Prado, C.M.C., (1997) J. Molec. Catal., 116, p. 405Battioni, P., Cardin, E., Louloudi, M., Schollhorn, G., Spyroullias, G.A., Mansuy, D., Traylor, T.G., (1996) Chem. Commun., p. 2037Ciuffi, K.J., Sacco, H.C., Valim, J.B., Manso, C.M.C.P., Serra, O.A., Nascimento, O.R., Vidoto, E.A., Iamamoto, Y., (1999) J. Non-Cryst. Solids, 247, p. 146Mark, J.E., Lee, C.Y.-C., Bianconi, P.A., (1995) Hybrid Organic-Inorganic Composites, , American Chemical Society, Washington, DCBystrom, S.E., Borje, A., Akermark, B., (1993) J. Am. Chem. Soc., 115, p. 2081Makote, R., Collinson, M.M., (1998) Chem. Mater., 10, p. 2440Lindsey, J.S., Schreiman, I.C., Hsu, H.C., Kearney, P.C., Marguerettaz, A.M., (1987) J. Org. Chem., 52, p. 827Rocha Gonsalves, A.M.A., Johnstone, R.A.W., Pereira, M.M., Santana, A.M.P., Serra, A.C., Sobral, A.J.F.N., Stocks, P.A., (1996) Heterocyles, 4, p. 43Adler, A.D., Longo, F.R., Kampas, F., Kim, J., (1970) J. Inorg. Nucl. Chem., 32, p. 2443Morrison, R., Boyd, R., (1983) Quimica Orgânica, , Fundação Calouste Gulbenkian, LisbonSharefkin, J.G., Saltzmann, H., (1963) Org. Synth., 43, p. 62Cardoso, A.H., Leite, C.A.P., Galembeck, F., (1998) Langmuir, 14, p. 3189Reimer, L., Zepke, U., Moesch, J., Schulze-Hillert, St., Messemer, M., Probst, W., Weimer, E., (1992) EELS Spectroscopy: A Reference Handbook of Standard Data for Identification and Interpretation of Electron Energy Loss Spectra and for Generation of Electron Spectroscopic Images, , Carl Zeiss, Oberkochen, GermanyBrunauer, S., Emmet, P.H., Teller, E., (1938) J. Am. Chem. Soc., 60, p. 309Sacco, H.C., (1999), PhD thesis, Universidade Estadual Paulista Júlio de Mesquita Filho, Institute de QuímicaCooke, P.R., Lindsay Smith, J.R., (1992) Tetrah. Lett., 33, p. 2737Fleischer, E.B., Fine, D.A., (1978) Inorg. Chim. Acta, 29, p. 267Pouchert, C.J., (1981) The Aldrich Library of Infrared Spectra, , Aldrich Chemical CompanyDhas, N.A., Raj, P., Gedanken, A., (1998) Chem. Mater., 10, p. 3278Sako, S., Kimura, K., (1985) Surf. Sci., 156, p. 511Groves, J.T., Stern, M.K., (1988) J. Am. Chem. Soc., 110, p. 8628Rodgers, K.R., Goff, H.M., (1988) J. Am. Chem. Soc., 110, p. 7049Smegal, J.A., Hill, C.L., (1983) J. Am. Chem. Soc., 105, p. 3515Lippard, S.J., Berg, J.M., (1994) Principles of Bioinorganic Chemistry, , University Science Books, Mill Valley, CaliforniaWilliams, D.H., Fleming, J., (1989) Spectroscopy Methods in Organic Chemistry, 4th Ed., , Mc Graw-Hill, New YorkLindsay Smith, J.R., Sheldon, R.A., (1994) Metalloporphyrins in Catalytic Oxidations, , Marcel Dekker, New York, Chapter 11Gilmartin, C., Lindsay Smith, J.R., (1995) J. Chem. Soc. Perkin Trans., 2, p. 243Cooke, P.R., Gilmartin, C., Gray, G.W., Lindsay Smith, J.R., (1995) J. Chem. Soc. Perkin Trans., 2, p. 1573Thellend, A., Battioni, P., Mansuy, D., (1994) J. Chem. Soc., Chem. Commun., p. 103

Synthesis Of Fluorinated Metalloporphyrinosilica Imprinted With Templates Through Sol-gel Process

We present the synthesis of a hybrid material containing fluorinated iron porphyrins through hydrolysis and polycondensation of iron porphyrin bearing a trifluorosilyl function with tetraethoxysilane in the presence of nitrogen bases acting as template molecules. The presence of metalloporphyrin Soret band is detected in the ultraviolet-visible absorption spectra of all metalloporphyrinosilica-templates. Thermogravimetric analysis and electron paramagnetic resonance of the materials also confirm the presence of metalloporphyrin in a silica network. Electron spectroscopy imaging was that of a non-crystalline microstructure. The iron and silicon distribution are homogeneous for the elements in all particle sites. The iron porphyrinosilicas-template were active as catalysts for cyclooctene epoxidation using iodozylbenzene as oxygen donor. In general, the epoxidation yield is larger for iron porphyrinosilicas-template than for manganese porphyrinosilicas-template. The manganese porphyrinosilicas-template had a smaller activity due to their manganese oxidation state. The largest catalytic yield were obtained with the iron porphyrinosilica-pyridine (85%). © 2000 Elsevier Science B.V. All rights reserved.27301/03/15100108Meunier, B., (1992) Chem. Rev., 92, p. 1411Dolphin, D., Traylor, T.G., Xie, L.Y., (1997) Acc. Chem. Res., 30, p. 251Groves, J.T., (1995) Cytochrome P-450, , Ortiz de Montellani, New YorkMansuy, D., (1993) Coord. Chem. Rev., 125, p. 129Iamamoto, Y., Ciuffi, K.J., Sacco, H.C., Prado, C.M.C., Nascimento, O.R., (1994) J. Molec. Catal., 88, p. 167Iamamoto, Y., Ciuffi, K.J., Sacco, H.C., Iwamoto, L.S., Nascimento, O.R., Prado, C.M.C., (1997) J. Molec. 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Comparison of antibacterial activity and cytotoxicity of silver nanoparticles and silver-loaded montmorillonite and saponite

Although silver nanoparticles are known for their antibacterial activity, little research has been carried out on what synthesis method provides the most effective particles. In this study, silver nanoparticles were synthesised via chemical reduction by using silver nitrate as the silver precursor, ascorbic acid as the reducing agent and sodium citrate as the stabilising agent. The solutions were adjusted to several pH values employing sodium hydroxide, citric acid or nitric acid. Dynamic light scattering and absorption spectra in the ultraviolet/visible region characterisation revealed that employing nitric acid to adjust the pH produced more varied and larger silver particle sizes. Then, silver nanoparticles were supported on montmorillonite and saponite through wet impregnation or ion exchange methods. Scanning electron microscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy characterisation confirmed that silver nanoparticles were successfully loaded onto the clay minerals. Next, the antibacterial activity of the samples was evaluated against Escherichia coli and Staphylococcus aureus by determining their minimum inhibitory concentrations and minimum bactericidal concentrations. The free silver nanoparticles did not show any antibacterial activity at 125 mg/L. In contrast, the silver-loaded samples obtained by wet impregnation and with a higher silver content displayed the strongest antibacterial effect. Finally, the cytotoxicity of the samples was determined in GM07492-A cell line by using an XTT colorimetric assay. The calculated IC50 values revealed that the supported silver nanoparticles were barely toxic. Thus, the silver-loaded clay minerals obtained here are promising antibacterial materials with a high-grade safety profile