Antimicrobial membrane cellulose acetate containing ionic liquid and metal nanoparticles.

Stable metallic Au(0), Ag(0) and Pt(0) nanoparticle-containing membrane films (20 microm thickness) were obtained by combining irregularly shaped nanoparticles of monomodal size distributions (11 +/- 1.5 nm Au(0), 8.9 +/- 2.1 nm Ag(0) and 2.8 +/- 0.4 nm Pt(0)) in the ionic liquid (IL) 1-n-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (BMI x (NTf)2) with a syrup of cellulose acetate (CA) in acetone. The presence of small and stable Au(0), Ag(0) or Pt(0) nanoparticles induced an augmentation in the CA/IL film surface areas. The addition of the IL to the membrane resulted in an increase of its elasticity and a decrease in its tenacity and toughness, whereas its stress at break was not influenced. High antimicrobial activity was observed in membranes containing Au(0), Ag(0) and Pt(0) metal concentrations as low as 1 mg of metal per 5 g of CA. The CA/IL/nanoparticle combination enhanced the activity and durability of the metal nanoparticles and provided greater antimicrobial activity against E. coli and S. aureus bacteria.

Chitosan Microspheres from Shrimp Waste Supporting Pd Nanoparticles in Ionic Liquids: An Efficient and Eco-Friendly Catalyst for Hydrogenation Reactions.

Palladium nanoparticles (Pd NPs) (ca. 4.8 nm) were synthesized from Palladium acetylacetonate [Pd(acac)2] using ionic liquids 1-n-butyl-3-methylimidazolium hexafluorophosphate [BMI.PF6] or 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMI.N(Tf)2] as stabilizing agents. The catalyst named Pd NPs/IL/Chitosan, was characterized and analyzed by the different techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), infrared (IR) and Brunauer-Emmett-Teller (BET) method (BET), to evaluate the composition of the material as well as the texture, size, distribution, homogeneity, structure and surface area. The catalyst Pd NPs/IL/Chitosan exhibited high catalytic activity in the hydrogenation reactions, when compared to Pd NPs not supported; this fact is related possibly to the large surface area and the durability and stability provided by the support of the biopolymer in combination with ionic liquids.

Metal nanoparticle/ionic liquid/cellulose: new catalytically active membrane materials for hydrogenation reactions.

Transition metal-containing membrane films of 10, 20, and 40 µm thickness were obtained by the combination of irregularly shaped nanoparticles with monomodal size distributions of 4.8 ± 1.1 nm (Rh(0)) and 3.0 ± 0.4 nm (Pt(0)) dispersed in the ionic liquid (IL) 1-n-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (BMI·(NTf)(2)) with a syrup of cellulose acetate (CA) in acetone. The Rh(0) and Pt(0) metal concentration increased proportionally with increases in film thickness up to 20 µm, and then the material became metal saturated. The presence of small and stable Rh(0) or Pt(0) nanoparticles induced an augmentation in the CA/IL film surface areas. The augmentation of the IL content resulted in an increase of elasticity and decrease in tenacity and toughness, whereas the stress at break was not influenced. The introduction of IL probably causes an increase in the separation between the cellulose macromolecules that results in a higher flexibility, lower viscosity, and better formability of the cellulose material. The nanoparticle/IL/CA combinations exhibit an excellent synergistic effect that enhances the activity and durability of the catalyst for the hydrogenation of cyclohexene. The nanoparticle/IL/cellulose acetate film membranes display higher catalytic activity (up to 7353 h(-1) for the 20 µm film of CA/IL/Pt(0)) and stability than the nanoparticles dispersed only in the IL.

Synthesis and characterization of Pt0 nanoparticles in imidazolium ionic liquids.

The controlled decomposition of Pt2(dba)3 (dba = dibenzylideneacetone) dispersed in 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4) and hexafluorophosphate (BMI.PF6) ionic liquids in the presence of cyclohexene by molecular hydrogen produces Pt0 nanoparticles. The formation of these nanoparticles follows the two-step [A --> B, A + B --> 2B (k1, k2)] autocatalytic mechanism. The catalytic activity in the hydrogenation of cyclohexene is influenced by the nature of the anion rather than the mean-diameter of the nanoparticles. Thus, higher catalytic activity was obtained with Pt0 dispersed in BMI.BF4 containing the less coordinating anion although these nanoparticles possess a larger mean diameter (3.4 nm) than those obtained in BMI.PF6 (2.3 nm). Similar mean diameter values were estimated from in situ XRD and SAXS. XPS analyses clearly show the interactions of the ionic liquid with the metal surface demonstrating the formation of an ionic liquid protective layer surrounding the platinum nanoparticles. SAXS analysis indicated the formation of a semi-organized ionic liquid layer surrounding the metal particles with an extended molecular length of around 2.8 nm in BMI.BF4 and 3.3 nm in BMI.PF6.

A novel support for laccase immobilization: cellulose acetate modified with ionic liquid and application in biosensor for methyldopa detection.

A material based on cellulose acetate (CA) and the room temperature ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI·N(Tf)(2)) was developed and characterized by scanning electron microscopy, electron dispersive spectroscopy and infrared analysis. Laccase (Lac) from Aspergillus oryzae was immobilized in this material to investigate the behavior of methyldopa by square-wave voltammetry. Under optimized conditions, the Lac biosensor based on CA/BMI·N(Tf)(2) exhibited an excellent electrocatalytic performance: the analytical curve showed good linear range for methyldopa concentrations from 34.8 to 370.3 µM with a detection limit of 5.5 µM. This sensor demonstrated acceptable stability (ca. 60 days; at least 350 determinations), good repeatability and reproducibility (relative standard deviations of 1.5 and 4.3%, respectively). The recovery study of methyldopa in pharmaceutical formulations ranged from 94.1 to 105.9%. The determination of this substance using the biosensor compared favorably with that using a spectrophotometry procedure at the 95% confidence level, and indicated potential application to methyldopa determination in pharmaceutical samples.

Biosensor for chlorogenic acid based on an ionic liquid containing iridium nanoparticles and polyphenol oxidase.

A biosensor based on the ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate containing dispersed iridium nanoparticles (Ir-BMI.PF(6)) and polyphenol oxidase was constructed. This enzyme was obtained from the sugar apple (Annona squamosa), immobilized in chitosan ionically crosslinked with oxalate. The biosensor was used for determination of chlorogenic acid by square wave voltammetry. The polyphenol oxidase catalyzes the oxidation of chlorogenic acid to the corresponding o-quinone, which is electrochemically reduced back to this substance at +0.25V vs. Ag/AgCl. Under optimized operational conditions the chlorogenic acid concentration was linear in the range of 3.48x10(-6) to 4.95x10(-5)mol L(-1) with a detection limit of 9.15x10(-7)mol L(-1). The biosensor was applied in the determination of chlorogenic acid in organic and decaffeinated coffee and the results compared with those obtained using the capillary electrophoresis method. The recovery study for chlorogenic acid in these samples gave values of 93.2-105.7%.

Comparison of advanced processes on the oxidation of acid orange 7 dye.

The degradation of acid orange 7 dye (AO7) was studied using a 1 L semi-batch tank stirred glass reactor for performing three different photochemical processes (photoperoxidation, Fenton, photo-Fenton). A commercial low pressure lamp was used for irradiation of samples. The advancement of degradation was monitored by measurement of color reduction, UV-spectra, HPLC-UV and COD. The obtained results showed that the photo-Fenton treatment was the most effective for the degradation of AO7.

Nanoscale Pt(0) particles prepared in imidazolium room temperature ionic liquids: synthesis from an organometallic precursor, characterization, and catalytic properties in hydrogenation reactions.

The reaction of Pt(2)(dba)(3) (dba = bis-dibenzylidene acetone) dispersed in room temperature 1-n-butyl-3-methylimidazolium (BMI) hexafluorophosphate ionic liquid with molecular hydrogen (4 atm) at 75 degrees C leads to stable and isolable nanometric Pt(0) particles. The X-ray diffraction analysis (XRD) of the material indicated that it is constituted of Pt(0). Transmission electron microscopy (TEM) analysis of the particles dispersed in the ionic liquid shows the formation of [Pt(0)](n) nanoparticles of 2.0-2.5 nm in diameter. A detailed examination of the nanoparticles imbibed in the ionic liquid and their environment shows an interaction of the BMI.PF(6) ionic liquid with the Pt(0) nanoparticles. The isolated [Pt(0)](n) nanoparticles can be redispersed in the ionic liquid or in acetone or used in solventless conditions for liquid-liquid biphasic, homogeneous, or heterogeneous hydrogenation of alkenes and arenes under mild reaction conditions (75 degrees C and 4 atm). The recovered platinum nanoparticles can be reused as a solid or redispersed in the ionic liquid several times without any significant loss in catalytic activity.