Marcos A. Gelesky

Preparation, cation-anion interactions and physicochemical properties of ether-functionalized imidazolium ionic liquids

A set of 1-alkyl ether (and 1-alkyl)-3-methylimidazolium ionic liquids 2-4 ([CxOyMIm]+[Anion]- or [CxMIm]+[Anion]-, where MIm = 3-methylimidazolium; CxOy = 1-alkyl ether, C7O3 = -(CH2)2O(CH2)2O(CH2)2OCH3 (A), C3O1 = -(CH2)2OCH3 (B); Cx = 1-alkyl, C10 = C10H21 (C), C4 = C4H9 (D); and [Anion]- = H3CSO3- (2), BF4- (3) or PF6- (4)) was prepared and characterized. The cation-anion hydrogen bonding strength showed to be mainly anion dependent and decreased in the order H3CSO3- > BF4- > PF6-. All methanesulfonate ionic liquids 2 possessed a strongly deshielded H2 imidazolium ring proton. 1-Alkyl ether functionalized ionic liquids showed higher densities in comparison to their 1-alkyl equivalents. The salts 2a-b, 3a-d and 4a-b are room-temperature ionic liquids. All 1-alkyl ether functionalized ionic liquids (except 4b) are completely amorphous. The widest liquid ranges were obtained with the tetrafluoroborate ionic liquids due to their late solidification and excellent thermal stability. These data provide important information for the understanding of their application scope and the preparation of task-specific 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.

Supported ionic liquid phase rhodium nanoparticle hydrogenation catalysts

Rh(0) nanoparticles (ca. 4 nm) dispersed in an ionic liquid (1-n-butyl-3-methylimidazolium tetrafluoroborate) were immobilized within a silica network, prepared by the sol-gel method. The effect of the sol-gel catalyst (acid or base) on the encapsulated ionic liquid and Rh(0) content, on the silica morphology and texture, and on the catalyst alkene hydrogenation activity was investigated. The Rh(0) content in the resulting xerogels (ca. 0.1 wt% Rh/SiO(2)) was shown to be independent of the sol-gel process. However, acidic conditions afforded higher contents of encapsulated ionic liquid and xerogels with larger pore diameters, which in turn might be responsible for the higher catalyst activity in hydrogenation of the alkenes.

Biochemical responses induced by co-exposition to arsenic and titanium dioxide nanoparticles in the estuarine polychaete Laeonereis acuta.

The production and use of nanoparticles, as titanium dioxide (nanoTiO2) is growing exponentially in the last years and their release into aquatic environment seem be inevitable. Once into environment, this nanomaterial can interact with other contaminant, as arsenic, and to exert toxic effect in living organisms. So, the objective of present study was to evaluate if the co-exposure to nanoTiO2 (1mg/L) can alter the As effect (nominal concentration of 50μg/L) in the estuarine polychaeta Laeonereis acuta after 48h of exposure. Were performed biochemical analyses such ROS production, enzymatic activities (GST, GR and GSTΩ), total antioxidant capacity against peroxyl radicals and damage to macromolecules (lipid and DNA), besides also were determined the accumulation of total arsenic and arsenic speciation in the worms. The results showed that co-exposure induced an increase in the ROS levels, decrease in total antioxidant capacity, increase in GR activity, and damage in lipid and DNA. Also, the co-exposure showed to affect the metabolization capacity of arsenic characterized by increase in dimethylated arsenic forms, a compound moderately toxic. So, these results suggest that the co-exposure to both contaminants is harmful to this species and the use of nanoTiO2 to treatment of contaminated water by arsenic should be considered of a toxicological point of view.

PdCl2 Immobilized in Polyacrylamide: a Low Cost and Eco-Friendly Catalyst for Suzuki-Miyaura Reactions

PdCl2 immobilized in polyacrylamide (PAM), named Pd/PAM, produced at an extremely low cost, was found to be an efficient catalyst for Suzuki-Miyaura cross-coupling reactions. Iodo- and bromoarenes may couple with phenylboronic acid under eco-friendly conditions (i.e., phosphine-free and with ethanol as the solvent) to give excellent product yields. Aryl chlorides, in contrast, were found to be unsuitable reagents in this context, yielding modest results. The recyclability of Pd/PAM is limited because of PdII leaching, which leaves only the base polymer on the surface after six runs. The Pd/PAM catalyst was initially prepared via the formation of a PAM hydrogel using an aqueous PdCl2 solution. After drying, the solid Pd/PAM was characterized by scanning electron microscopy (SEM), electron-dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and inductively coupled plasma optical emission spectrometry (ICP OES).

Predicting the binding properties of single walled carbon nanotubes (SWCNT) with an ADP/ATP mitochondrial carrier using molecular docking, chemoinformatics, and nano-QSBR perturbation theory

Interactions between the single walled carbon nanotube (SWCNT) family and a mitochondrial ADP/ATP carrier (ANT-1) were evaluated using constitutional (functional groups, number of carbon atoms, etc.) and electronic nanodescriptors defined by (n, m)-Hamada indexes (armchair, zig-zag and chiral). The Free Energy of Binding (FEB) was determined by molecular docking simulation and the results showed that FEB was statistically more negative (p SWCNT-OH > SWCNT, suggesting that polar groups favor the anchorage to ANT-1. In this regard, it was showed that key ANT-1 amino acids (Arg 79, Asn 87, Lys 91, Arg 187, Arg 234 and Arg 279) responsible for ADP-transport were conserved in ANT-1 from different species examined to predict SWCNT interactions, including shrimp Litopenaeus vannamei and fish Danio rerio commonly employed in ecotoxicology. The SWCNT-ANT-1 inter-atomic distances for the key ANT-1 amino acids were similar to that with carboxyatractyloside, a classical inhibitor of ANT-1. Significant linear relationships between FEB and n-Hamada index were found for zig-zag SWCNT and SWCNT-COOH (R2 = 0.95 in both cases). A Perturbation Theory-Nano-Quantitative Structure-Binding Relationship (PT-NQSBR) model was fitted that was able to distinguish between strong (FEB < −14.7 kcal mol−1) and weak (FEB ≥ −14.7 kcal mol−1) SWCNT–ANT-1 interactions. A simple ANT-1-inhibition respiratory assay employing mitochondria suspension from L. vannamei, showed good accordance with the predicted model. These results indicate that this methodology can be employed in massive virtual screenings and used for making regulatory decisions in nanotoxicology.

PVP-Stabilized Palladium Nanoparticles in Silica as Effective Catalysts for Hydrogenation Reactions

Palladium nanoparticles stabilized by poly (N-vinyl-2-pyrrolidone) (PVP) can be synthesized by corresponding Pd(acac)2 (acac = acetylacetonate) as precursor in methanol at 80°C for 2 h followed by reduction with NaBH4 and immobilized onto SiO2 prepared by sol-gel process under acidic conditions (HF or HCl). The PVP/Pd molar ratio is set to 6. The effect of the sol-gel catalyst on the silica morphology and texture and on Pd(0) content was investigated. The catalysts prepared (ca. 2% Pd(0)/SiO2/HF and ca. 0,3% Pd(0)/SiO2/HCl) were characterized by TEM, FAAS, and SEM-EDS. Palladium nanoparticles supported in silica with a size 6.6 ± 1.4 nm were obtained. The catalytic activity was tested in hydrogenation of alkenes.

Different crystalline forms of titanium dioxide nanomaterial (rutile and anatase) can influence the toxicity of cooper in golden mussel Limnoperna fortunei

Although some studies have showed the effects of different crystalline structures of nTiO2 (anatase and rutile) and their applicability in several fields, few studies has analyzed the effect of coexposure with other environmental contaminants such as copper. Thus, the objective of this study was to evaluate if the coexposure to nTiO2 (nominal concentration of 1 mg/L; anatase or rutile) can increase the incorporation and toxic effect induced by Cu (nominal concentration of 56 μg/L) in different tissues of Linmoperna fortunei after 120 h of exposure. Our results showed that the coexposure increased the accumulation of Cu in the gills and adductor muscle independently of the crystalline form and can positively or negatively modulate the antioxidant system, depending on the tissue analyzed. However, exposure only to rutile nTiO2 induced damage in the adductor muscle evidenced by the infiltration of hemocytes in this tissue. Additionally, histomorphometric changes based on fractal dimension analysis showed that coexposure to both forms of nTiO2 induced damage in the same tissue. These results suggest that both crystalline forms exhibited toxicity depending on the analyzed tissue and that coexposure of nTiO2 with Cu may be harmful in L. fortunei, indicating that increased attention to the use and release of nTiO2 in the environment is needed to avoid deleterious effects in aquatic biota.

A conservação dos documentos de arquivo: a atuação de autoadesivos nos documentos textuais em suporte papel

Estudos tem contribuido para a definicao de importantes diretrizes acerca da conservacao de documentos de arquivo e, em especial, a conservacao preventiva, fomentando a discussao e a consolidacao de politicas que busquem auxiliar na preservacao dos acervos. Nessa perspectiva, a presente pesquisa, realizada em parceria entre o Instituto de Ciencias Humanas e da Informacao - curso de Arquivologia -, e a Escola de Quimica e Alimentos da Universidade Federal do Rio Grande, tem como objetivo avaliar possiveis acoes de danos provocados pelo uso das folhas autoadesivas nos documentos textuais em suporte papel, visando contribuir com as discussoes e estudos sobre a tematica de conservacao e preservacao dos acervos. A metodologia para o desenvolvimento deste trabalho foi dividida em etapas que consistiram em: selecao da amostragem e pesquisa sobre o surgimento dos blocos autoadesivos, revisao do referencial teorico, analise dos dados coletados traves da tecnica de microscopia eletronica de varredura e posterior divulgacao dos resultados da pesquisa.Palavras-chave: Autoadesivo. Conservacao. Documentos textuais. Microscopia eletronica de varredura. Papel.