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1.
Molecules ; 25(16)2020 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-32785147

RESUMO

A novel biobased monomer for the preparation of thermally reversible networks based on the Diels-Alder reaction was synthesized from jatropha oil. The oil was epoxidized and subsequently reacted with furfurylamine to attach furan groups via an epoxide ring opening reaction. However, furfurylamine also reacted with the ester groups of the triglycerides via aminolysis, thus resulting in short-chain molecules that ultimately yielded brittle thermally reversible polymers upon cross-linking via a Diels-Alder reaction. A full-factorial experimental design was used in finding the optimum conditions to minimize ester aminolysis and to maximize the epoxide ring opening reaction as well as the number of furans attached to the modified oil. The optimum conditions were determined experimentally and were found to be 80 °C, 24 h, 1:1 molar ratio, with 50 mol % of LiBr with respect to the modified oil, resulting in 35% of ester conversion, 99% of epoxide conversion, and an average of 1.32 furans/triglyceride. Ultimately, further optimization by a statistical approach led to an average of 2.19 furans per triglyceride, which eventually yielded a flexible network upon cross-linking via a Diels-Alder reaction instead of the brittle one obtained when the furan-functionalization reaction was not optimized.


Assuntos
Furanos/química , Jatropha/química , Óleos de Plantas/química , Brometos/química , Catálise , Reação de Cicloadição , Compostos de Epóxi/química , Jatropha/metabolismo , Compostos de Lítio/química , Temperatura , Triglicerídeos/química
2.
ACS Nano ; 14(1): 406-414, 2020 01 28.
Artigo em Inglês | MEDLINE | ID: mdl-31860277

RESUMO

Inspired by chasing-escaping behaviors of predator and swarming prey in nature, here we demonstrate a concept to create active micromotor systems from two species of passive microparticles with biomimetic predator-prey interactions. In this concept, the biomimetic predator-prey interactions are established in a binary particle system comprising the diffusiophoretic attractive microparticles (prey particles) and the diffusiophoretic repulsive ones (predator particles). In the absence of additional chemical fuels and external fields, the predator particles are attracted by and constantly chase the swarming prey particles, which, in response, escape from the former and show dynamic group reconfigurations because of the local repulsion. Based on this concept, various synthetic active micromotor systems have been demonstrated, including active ZnO-TiO2, Ag3PO4-TiO2, and ZnO-AgBr micromotor systems. As the predator and prey particles are powered by each other through the biomimetic predator-prey interactions, the concept proposed here provides an advanced method to develop not only a class of single micromotors powered by passive particles or "solid fuels" but also micromotor swarms capable of manipulating "moving cargo". In addition, it also illustrates a proof-of-concept implementation of intelligent micro/nanomotor systems composed of heterogeneous individuals with complementary or cooperative functions.


Assuntos
Materiais Biomiméticos/química , Brometos/química , Fosfatos/química , Compostos de Prata/química , Titânio/química , Óxido de Zinco/química , Tamanho da Partícula , Propriedades de Superfície
3.
Int J Biol Macromol ; 144: 615-623, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31843600

RESUMO

The structural modification of polysaccharides directly affects their physicochemical properties and applications. Dextran, a chained polysaccharide, consists of multiple d-glucose molecules with repetitive structures. In this study, the physicochemical properties of oxidized dextran (DO) at different concentrations of NaClO/NaBr and H2O2 were compared. The results showed that NaClO/NaBr oxidation is more conducive to the formation of carboxyl groups. Oxidized dextran with NaClO/NaBr (DOB) showed good iron (III) chelating ability, and the DOB­iron (III) complex (DOBIC) had an iron content of 28.31%. According to structural analysis, NaClO/NaBr (2 g/100 g of active chlorine) and H2O2 (4 g/100 g), respectively, oxidize the C1 and C2 hydroxyl groups of dextran to carboxyl groups and open the ring when DO and iron have the strongest chelation ability. The complex is indeed a chelate iron complex, and iron core is composed of iron oxyhydroxide or the ß-FeOOH mineral polymorph. These results indicate that DOBIC is expected to be a good iron supplement or food additive to strengthen iron.


Assuntos
Brometos/química , Complexos de Coordenação/química , Dextranos/química , Peróxido de Hidrogênio/química , Quelantes de Ferro/química , Compostos de Sódio/química , Hipoclorito de Sódio/química , Compostos Férricos/química , Concentração de Íons de Hidrogênio , Ferro/química , Cinética , Minerais/química , Peso Molecular , Oxirredução , Relação Estrutura-Atividade
4.
Environ Sci Pollut Res Int ; 26(2): 1584-1594, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30443725

RESUMO

N-nitrosodimethylamine (NDMA), a toxic disinfection byproduct commonly associated with chloramination, has recently been found to form from an anti-yellowing agent (4,4'-hexamethylenebis (1,1-dimethylsemicarbazide) (HDMS)) during ozonation but the mechanisms are unclear. In this paper, the potential roles of molecular ozone (O3) and hydroxyl radical (∙OH) on NDMA formation from HDMS were investigated under various oxidation conditions (ozone dosages, pH) and different components in water (bromide ion (Br-), bicarbonate ion (HCO3-), sulfate ion (SO42-), and humic acid (HA), as well as natural organic matter (NOM) from a lake). Moreover, HDMS transformation pathways by ozonation were determined. The results indicated that the formation of NDMA was enhanced through the combined effect of O3 and ∙OH compared to that by O3 alone (addition of tert-butyl alcohol (tBA) as ∙OH scavenger). ∙OH itself cannot generate NDMA directly; however, it can transform HDMS to intermediates with higher NDMA yield than parent compound. The NDMA generation was affected (small dosages promoted but high dosages inhibited) by HA or Br- no matter with or without tBA. The presence of SO42- and HCO3- ions lowered NDMA formation through ∙OH scavenging effect. Increasing pH not only increased degradation rate constant by enhancing ∙OH generation but also affected HDMS dissociation ratio, reaching the maximum NDMA formation at pH 7-8. Natural constituents in selected water matrix inhibited NDMA formation. Impacts of these influencing factors on NDMA formation by only O3 however were significantly less pronounced over that by the joint roles of O3 and ∙OH. Based on the result of Q-TOF, LC/MS/MS, and GC/MS, the possible transformation pathways of HDMS by ozonation were proposed. The NDMA enhancement mechanism by the combined effect of O3 and ∙OH can be attributed to greater amounts of intermediates with higher NDMA yield (such as unsymmetrical dimethylhydrazine (UDMH)) produced. These findings provide new understanding of NDMA formation upon ozonation of typical amine-based compounds.


Assuntos
Dimetilnitrosamina/química , Água Potável/química , Ozônio/química , Semicarbazidas/química , Bicarbonatos/química , Brometos/química , Cromatografia Gasosa-Espectrometria de Massas , Substâncias Húmicas , Concentração de Íons de Hidrogênio , Radical Hidroxila/química , Sulfatos/química , Espectrometria de Massas em Tandem , Poluentes Químicos da Água/química , Purificação da Água , terc-Butil Álcool/química
5.
Molecules ; 23(12)2018 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-30514001

RESUMO

We have recently discovered that the photodynamic action of many different photosensitizers (PSs) can be dramatically potentiated by addition of a solution containing a range of different inorganic salts. Most of these studies have centered around antimicrobial photodynamic inactivation that kills Gram-negative and Gram-positive bacteria in suspension. Addition of non-toxic water-soluble salts during illumination can kill up to six additional logs of bacterial cells (one million-fold improvement). The PSs investigated range from those that undergo mainly Type I photochemical mechanisms (electron transfer to produce superoxide, hydrogen peroxide, and hydroxyl radicals), such as phenothiazinium dyes, fullerenes, and titanium dioxide, to those that are mainly Type II (energy transfer to produce singlet oxygen), such as porphyrins, and Rose Bengal. At one extreme of the salts is sodium azide, that quenches singlet oxygen but can produce azide radicals (presumed to be highly reactive) via electron transfer from photoexcited phenothiazinium dyes. Potassium iodide is oxidized to molecular iodine by both Type I and Type II PSs, but may also form reactive iodine species. Potassium bromide is oxidized to hypobromite, but only by titanium dioxide photocatalysis (Type I). Potassium thiocyanate appears to require a mixture of Type I and Type II photochemistry to first produce sulfite, that can then form the sulfur trioxide radical anion. Potassium selenocyanate can react with either Type I or Type II (or indeed with other oxidizing agents) to produce the semi-stable selenocyanogen (SCN)2. Finally, sodium nitrite may react with either Type I or Type II PSs to produce peroxynitrate (again, semi-stable) that can kill bacteria and nitrate tyrosine. Many of these salts (except azide) are non-toxic, and may be clinically applicable.


Assuntos
Anti-Infecciosos/farmacologia , Fotoquimioterapia/métodos , Fármacos Fotossensibilizantes/química , Fármacos Fotossensibilizantes/farmacologia , Sais/farmacologia , Anti-Infecciosos/química , Azidas/química , Azidas/farmacologia , Brometos/química , Brometos/farmacologia , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Humanos , Iodetos/química , Iodetos/farmacologia , Testes de Sensibilidade Microbiana , Nitritos/química , Nitritos/farmacologia , Sais/química , Tiocianatos/química , Tiocianatos/farmacologia , Titânio/química , Titânio/farmacologia
6.
Int J Pharm Compd ; 22(3): 240-246, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29878891

RESUMO

The physical, chemical, and microbiological stability of a compounded oral solution with the active ingredients herbal tinctures of valerian and motherwort with sedative action for pediatric treatment was studied. Evaluations for physical, chemical, and microbiological stability were performed initially and throughout the storage period. Physical stability of the oral solution was assessed by coloration, clarity, and pH of the solution. The physical appearance of the oral solution did not change throughout the study period. The chemical stability of the oral solution was evaluated by means of a stability-indicating high-performance thin-layer chromatography analytical technique, identification tests, and assay method of sodium bromide. The microbiological stability of the oral solution was investigated by using the European Pharmacopoeia method using the acceptance criteria for nonsterile aqueous preparations for oral use. It was found that the compounded oral solution was stable for at least 21 days at 25°C ± 2°C/60% RH and 5°C ± 3°C, when protected from light.


Assuntos
Bactérias/isolamento & purificação , Brometos/química , Contaminação de Medicamentos , Fungos/isolamento & purificação , Soluções Farmacêuticas/química , Extratos Vegetais/química , Preparações de Plantas/química , Compostos de Sódio/química , Administração Oral , Cromatografia Líquida de Alta Pressão , Composição de Medicamentos , Estabilidade de Medicamentos , Humanos , Leonurus , Valeriana
7.
Environ Pollut ; 233: 194-200, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29078123

RESUMO

The cleaning-up of viscous oil spilled in ocean is a global challenge, especially in Bohai, due to its slow current movement and poor self-purification capacity. Frequent oil-spill accidents not only cause severe and long-term damages to marine ecosystems, but also lead to a great loss of valuable resources. To eliminate the environmental pollution of oil spills, an efficient and environment-friendly oil-recovery approach is necessary. In this study,1expanded graphite (EG) modified by CTAB-KBr/H3PO4 was synthesized via composite intercalation agents of CTAB-KBr and natural flake graphite, followed by the activation of phosphoric acid at low temperature. The resultant modified expanded graphite (M-EG) obtained an interconnected and continuous open microstructure with lower polarity surface, more and larger pores, and increased surface hydrophobicity. Due to these characteristics, M-EG exhibited a superior adsorption capacity towards marine oil. The saturated adsorption capacities of M-EG were as large as 7.44  g/g for engine oil, 6.12 g/g for crude oil, 5.34 g/g for diesel oil and 4.10 g/g for gasoline oil in 120min, exceeding the capacity of pristine EG. Furthermore, M-EG maintained good removal efficiency under different adsorption conditions, such as temperature, oil types, and sodium salt concentration. In addition, oils sorbed into M-EG could be recovered either by a simple compression or filtration-drying treatment with a recovery ratio of 58-83%. However, filtration-drying treatment shows better performance in preserving microstructures of M-EG, which ensures the adsorbents can be recycled several times. High removal capability, fast adsorption efficiency, excellent stability and good recycling performance make M-EG an ideal candidate for treating marine oil pollution in practical application.


Assuntos
Recuperação e Remediação Ambiental/métodos , Grafite/química , Poluição por Petróleo/análise , Ácidos Fosfóricos/química , Poluentes Químicos da Água/análise , Adsorção , Brometos/química , Cetrimônio , Compostos de Cetrimônio , Gasolina , Interações Hidrofóbicas e Hidrofílicas , Óleos , Petróleo , Compostos de Potássio/química , Regeneração , Temperatura , Poluentes Químicos da Água/química
8.
Sci Rep ; 6: 39490, 2016 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-28000730

RESUMO

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease associated with aggregation of TAR DNA-binding protein-43 (TDP-43) in neuronal cells and manifests as motor neuron dysfunction &muscle atrophy. The carboxyl-terminal prion-like domain of TDP-43 can aggregate in vitro into toxic ß-sheet rich amyloid-like structures. So far, treatment options for ALS are very limited and Riluzole, which targets glutamate receptors, is the only but highly ineffective drug. Therefore, great interest exists in developing molecules for ALS treatment. Here, we have examined certain derivatives of acridine containing same side chains at position 4 &5, for inhibitory potential against TDP-43 aggregation. Among several acridine derivatives examined, AIM4, which contains polar carboxyl groups in the side arms, significantly reduces TDP-43-YFP aggregation in the powerful yeast model cell and also abolishes in vitro amyloid-like aggregation of carboxyl terminal domain of TDP-43, as observed by AFM imaging. Thus, AIM4 can be a lead molecule potentiating further therapeutic research for ALS.


Assuntos
Acridinas/química , Esclerose Lateral Amiotrófica/tratamento farmacológico , Brometos/química , Proteínas de Ligação a DNA/química , Imidazóis/química , Saccharomyces cerevisiae/efeitos dos fármacos , Amiloide/química , Esclerose Lateral Amiotrófica/genética , Dicroísmo Circular , Avaliação Pré-Clínica de Medicamentos , Escherichia coli , Humanos , Microscopia de Força Atômica , Microscopia de Fluorescência , Neurônios Motores/patologia , Atrofia Muscular/patologia , Mutação , Neurônios/metabolismo , Príons/química , Domínios Proteicos , Estrutura Secundária de Proteína , Proteínas Recombinantes/química , Saccharomyces cerevisiae/metabolismo , Raios Ultravioleta
9.
Food Chem ; 197(Pt A): 450-6, 2016 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-26616974

RESUMO

Pineapple peel is generally disposed or used as compost. This study was focused on extracting bromelain from pineapple peel by using reverse micelles. It was found that gemini surfactant C12-8-C12·2Br (octamethylene-α,ω-bis(dimethyldodecylammonium bromide)) showed distinctive advantage over its monomeric counterpart DTAB (dodecyl trimethyl ammonium bromide); under optimized condition, the bromelain extracted with C12-8-C12·2Br reverse micelle had an activity recovery of 163% and a purification fold of 3.3, while when using DTAB reverse micelle, the activity recovery was 95% and the purification fold was 1.7. Therefore, the spacer of gemini surfactant should play a positive role in bromelain extraction and may suggest the potential of gemini surfactant in protein separation since it has been so far rarely used in relative experiments or technologies.


Assuntos
Ananas/química , Bromelaínas/química , Brometos/química , Micelas , Compostos de Amônio Quaternário/química , Tensoativos/química , Extratos Vegetais/química , Relação Estrutura-Atividade
10.
Environ Sci Pollut Res Int ; 23(5): 4778-85, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26538259

RESUMO

This study compared the behaviors of two classic advanced oxidation processes (AOPs), hydroxyl radical-based AOPs ((•)OH-based AOPs) and sulfate radical-based AOPs (SO4 (•-)-based AOPs), represented by UV/ hydrogen peroxide (H2O2) and UV/peroxydisulfate (PDS) systems, respectively, to degrade humic acid (HA) in the presence of halide ions (Cl(-) and Br(-)). The effects of different operational parameters, such as oxidant dosages, halide ions concentration, and pH on HA degradation were investigated in UV/H2O2/Cl(-), UV/PDS/Cl(-), UV/H2O2/Br(-), and UV/PDS/Br(-) processes. It was found that the oxidation capacity of H2O2 and PDS to HA degradation in the presence of halides was nearly in the same order. High dosage of peroxides would lead to an increase in HA removal while excess dosage would slightly inhibit the efficiency. Both Cl(-) and Br(-) would have depressing impact on the two AOPs, but the inhibiting effect of Br(-) was more obvious than that of Cl(-), even the concentration of Cl(-) was far above that of Br(-). The increasing pH would have an adverse effect on HA decomposition in UV/H2O2 system, whereas there was no significant impact of pH in UV/PDS process. Furthermore, infrared spectrometer was used to provide the information of degraded HA in UV/H2O2/Cl(-), UV/PDS/Cl(-), UV/H2O2/Br(-), and UV/PDS/Br(-) processes, and halogenated byproducts were identified in using GC-MS analysis in the four processes. The present research might have significant technical implications on water treatment using advanced oxidation technologies.


Assuntos
Substâncias Húmicas , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Sulfatos/química , Raios Ultravioleta , Purificação da Água , Brometos/química , Cloretos/química , Substâncias Húmicas/efeitos da radiação , Oxirredução , Poluentes Químicos da Água/análise
11.
Nat Prod Commun ; 11(7): 957-961, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30452171

RESUMO

penia-O-Methylquercetin (2) was prepared by permethylation of quercetin (1). Selective demethylation of 2 using either BBr or BCl3/TBAI (tetrabutylammonium iodide) gave five O-methylquercetins (3-6), with satisfactory yields. The reaction can be easily scaled-up. We established an efficient and large-scale preparation of O-methylquercetins.


Assuntos
Quercetina/análogos & derivados , Boranos/química , Compostos de Boro/química , Brometos/química , Cloretos/química , Desmetilação , Estrutura Molecular , Compostos de Amônio Quaternário
12.
J Am Chem Soc ; 137(16): 5292-5, 2015 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-25874950

RESUMO

We report that a regioselective reductive transposition of primary allylic bromides is catalyzed by a biphilic organophosphorus (phosphetane) catalyst. Spectroscopic evidence supports the formation of a pentacoordinate (σ(5)-P) hydridophosphorane as a key reactive intermediate. Kinetics experiments and computational modeling are consistent with a unimolecular decomposition of the σ(5)-P hydridophosphorane via a concerted cyclic transition structure that delivers the observed allylic transposition and completes a novel P(III)/P(V) redox catalytic cycle. These results broaden the growing repertoire of reactions catalyzed within the P(III)/P(V) redox couple and suggest additional opportunities for organophosphorus catalysis in a biphilic mode.


Assuntos
Compostos Alílicos/química , Brometos/química , Compostos Organofosforados/química , Fósforo/química , Catálise , Oxirredução , Estereoisomerismo
13.
Water Res ; 69: 307-317, 2015 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-25497429

RESUMO

Phosphate amendments can be added to U(VI)-contaminated subsurface environments to promote in situ remediation. The primary objective of this study was to evaluate the impacts of phosphate addition on the transport of U(VI) through contaminated sediments. In batch experiments using sediments (<2 mm size fraction) from a site in Rifle, Colorado, U(VI) only weakly adsorbed due to the dominance of the aqueous speciation by Ca-U(VI)-carbonate complexes. Column experiments with these sediments were performed with flow rates that correspond to a groundwater velocity of 1.1 m/day. In the absence of phosphate, the sediments took up 1.68-1.98 µg U/g of sediments when the synthetic groundwater influent contained 4 µM U(VI). When U(VI)-free influents were then introduced with and without phosphate, substantially more uranium was retained within the column when phosphate was present in the influent. Sequential extractions of sediments from the columns revealed that uranium was uniformly distributed along the length of the columns and was primarily in forms that could be extracted by ion exchange and contact with a weak acid. Laser induced fluorescence spectroscopy (LIFS) analysis along with sequential extraction results suggest adsorption as the dominant uranium uptake mechanism. The response of dissolved uranium concentrations to stopped-flow events and the comparison of experimental data with simulations from a simple reactive transport model indicated that uranium adsorption to and desorption from the sediments was not always at local equilibrium.


Assuntos
Sedimentos Geológicos/química , Fosfatos/química , Urânio/química , Adsorção , Técnicas de Cultura Celular por Lotes , Brometos/química , Lasers , Espectrometria de Fluorescência
14.
ChemMedChem ; 9(11): 2509-15, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25196781

RESUMO

Transverse and longitudinal relaxation times (T1ρ and T1) have been widely exploited in NMR to probe the binding of ligands and putative drugs to target proteins. We have shown recently that long-lived states (LLS) can be more sensitive to ligand binding. LLS can be excited if the ligand comprises at least two coupled spins. Herein we broaden the scope of ligand screening by LLS to arbitrary ligands by covalent attachment of a functional group, which comprises a pair of coupled protons that are isolated from neighboring magnetic nuclei. The resulting functionalized ligands have longitudinal relaxation times T1((1)H) that are sufficiently long to allow the powerful combination of LLS with dissolution dynamic nuclear polarization (D-DNP). Hyperpolarized weak "spy ligands" can be displaced by high-affinity competitors. Hyperpolarized LLS allow one to decrease both protein and ligand concentrations to micromolar levels and to significantly increase sample throughput.


Assuntos
Espectroscopia de Ressonância Magnética , Brometos/química , Domínio Catalítico , Avaliação Pré-Clínica de Medicamentos , Ligantes , Proteínas/química , Proteínas/metabolismo , Tiofenos/química
15.
Dalton Trans ; 43(3): 1125-31, 2014 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-24170033

RESUMO

The synthesis of a series of uranyl compounds via oxidation of [Li(THF)4][UX5(THF)] (X = Cl, Br, I) in the presence of Ph3P=O is described. The solid state structures of [Li(O=PPh3)(MeCN)2]2[UO2Cl4], [UO2Br2(O=PPh3)2] and [Li(O=PPh3)4][I3], formed as a by-product from the oxidation of [Li(THF)4][UI5(THF)], is reported. The electronic absorption spectra and photoluminescence spectra of [UO2X2(O=PPh3)2] (X = Cl, Br, I) have been measured and no significant changes in the position of the emission (515-530 nm) or the lifetimes (ca. 1 µs) are observed in this series. However a bathochromic shift is observed in the U-X LMCT band in the electronic absorption spectrum.


Assuntos
Complexos de Coordenação/síntese química , Urânio/química , Brometos/química , Cloretos/química , Complexos de Coordenação/química , Cristalografia por Raios X , Ligação de Hidrogênio , Iodetos/química , Conformação Molecular , Oxirredução
16.
Acc Chem Res ; 47(2): 494-503, 2014 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-24215156

RESUMO

Catalysis by palladium derivatives is now one of the most important tools in organic synthesis. Whether researchers design palladium nanoparticles (NPs) or nanoparticles occur as palladium complexes decompose, these structures can serve as central precatalysts in common carbon-carbon bond formation. Palladium NPs are also valuable alternatives to molecular catalysts because they do not require costly and toxic ligands. In this Account, we review the role of "homeopathic" palladium catalysts in carbon-carbon coupling reactions. Seminal studies from the groups of Beletskaya, Reetz, and de Vries showed that palladium NPs can catalyze Heck and Suzuki-Miyaura reactions with aryl iodides and, in some cases, aryl bromides at part per million levels. As a result, researchers coined the term "homeopathic" palladium catalysis. Industry has developed large-scale applications of these transformations. In addition, chemists have used Crooks' concept of dendrimer encapsulation to set up efficient nanofilters for Suzuki-Miyaura and selective Heck catalysis, although these transformations required high PdNP loading. With arene-centered, ferrocenyl-terminated dendrimers containing triazolyl ligands in the tethers, we designed several generations of dendrimers to compare their catalytic efficiencies, varied the numbers of Pd atoms in the PdNPs, and examined encapsulation vs stabilization. The catalytic efficiencies achieved "homeopathic" (TON = 540 000) behavior no matter the PdNP size and stabilization type. The TON increased with decreasing the Pd/substrate ratio, which suggested a leaching mechanism. Recently, we showed that water-soluble arene-centered dendrimers with tri(ethylene glycol) (TEG) tethers stabilized PdNPs involving supramolecular dendritic assemblies because of the interpenetration of the TEG branches. Such PdNPs are stable and retain their "homeopathic" catalytic activities for Suzuki-Miyaura reactions for months. (TONs can reach 2.7 × 10(6) at 80 °C for aryl bromides and similar values for aryl iodides at 28 °C.) Sonogashira reactions catalyzed by these PdNPs are quantitative with only 0.01% Pd/mol substrate. Kato's group has reported remarkable catalytic efficiencies for mesoporous catalysts formed by polyamidoamine (PAMAM) dendrimer polymerizations. These and other mesoporous structures could allow for catalyst recycling, with efficiencies approaching the "homeopathic" behavior. In recent examples of Suzuki-Miyaura reactions of aryl chlorides, chemists achieved truly "homeopathic" catalysis when a surfactant such as a tetra-n-butylammonium halide or an imidazolium salt was used in stoichiometric quantities with substrate. These results suggest that the reactive halide anion of the salt attacks the neutral Pd species to form a palladate. In the case of aryl chlorides, the reaction may occur through the difficult, rate-limiting oxidative-addition step.


Assuntos
Técnicas de Química Sintética/métodos , Dendrímeros/química , Nanopartículas Metálicas/química , Paládio/química , Brometos/química , Cloretos/química , Ligantes , Estrutura Molecular , Polietilenoglicóis/química
17.
J Hazard Mater ; 263 Pt 2: 562-8, 2013 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-24225581

RESUMO

The cloud point extraction (CPE) of uranyl ions by different kinds of extractants in Triton X-114 (TX-114) micellar solution was investigated upon the addition of ionic liquids (ILs) with various anions, i.e., bromide (Br(-)), tetrafluoroborate (BF4(-)), hexafluorophosphate (PF6(-)) and bis[(trifluoromethyl)sulfonyl]imide (NTf2(-)). A significant increase of the extraction efficiency was found on the addition of NTf2(-) based ILs when using neutral extractant tri-octylphosphine oxide (TOPO), and the extraction efficiency kept high at both nearly neutral and high acidity. However, the CPE with acidic extractants, e.g., bis(2-ethylhexyl) phosphoric acid (HDEHP) and 8-hydroxyquinoline (8-HQ) which are only effective at nearly neutral condition, was not improved by ILs. The results of zeta potential and (19)F NMR measurements indicated that the anion NTf2(-) penetrated into the TX-114 micelles and was enriched in the surfactant-rich phase during the CPE process. Meanwhile, NTf2(-) may act as a counterion in the CPE of UO2(2+) by TOPO. Furthermore, the addition of IL increased the separation factor of UO2(2+) and La(3+), which implied that in the micelle TOPO, NTf2(-) and NO3(-) established a soft template for UO2(2+). Therefore, the combination of CPE and IL provided a supramolecular recognition to concentrate UO2(2+) efficiently and selectively.


Assuntos
Líquidos Iônicos/química , Urânio/química , Boratos/química , Brometos/química , Fracionamento Químico , Desenho de Equipamento , Flúor/química , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Imidas/química , Íons , Isótopos/química , Lantânio/química , Espectroscopia de Ressonância Magnética , Metais/química , Micelas , Octoxinol , Oxiquinolina/química , Fosfatos/química , Polietilenoglicóis/química , Tensoativos , Temperatura , Poluentes Químicos da Água/análise
18.
Artigo em Inglês | MEDLINE | ID: mdl-24110550

RESUMO

The recent rapid growth in demand for aesthetic non-invasive laser treatments such as unwanted skin rejuvenation, removal of age-related vascular blemishes has led to a boom in the medical devices to treat these conditions. Among diverse laser for skin treatment, copper bromide laser is a very effective, safe, and well tolerated treatment for facial telangiectasia at various energy levels and the most important thing of the copper bromide laser device is that the stability of the energy. However there is no evidence about effective copper bromide laser's energy level for the treatment of vascular lesions. We compared energy stability and treatment performance between two energy levels in 2 W and 8 W which commonly use in laser treatment for the vascular lesions. 8 W copper bromide laser was more stable compared than 2 W copper bromide laser. Also, 8 W copper bromide laser was effectively superior to 2 W copper bromide laser in treatment of vascular legion. Consequently, 8 W copper bromide laser treatment for vascular lesion might be more suitable than 2 W copper bromide laser.


Assuntos
Terapia com Luz de Baixa Intensidade/instrumentação , Telangiectasia/radioterapia , Animais , Brometos/química , Cobre/química , Humanos , Coelhos , Pele/irrigação sanguínea , Pele/efeitos da radiação
19.
Chemosphere ; 92(11): 1529-35, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23673364

RESUMO

Water sources are micro-polluted by the increasing range of anthropogenic activities around them. Disinfection byproduct (DBP) precursors in water have gradually expanded from humic acid (HA) and fulvic acid to other important sources of potential organic matter. This study aimed to provide further insights into the effects of microbially derived organic matter as precursors on iodinated trihalomethane (I-THM) speciation and formation during the biological treatment of micro-polluted source water. The occurrence of I-THMs in drinking water treated by biological processes was investigated. The results showed for the first time that CHCl2I and CHBrClI are emerging DBPs in China. Biological pre-treatment and biological activated carbon can increase levels of microbes, which could serve as DBP precursors. Chlorination experiments with bovine serum albumin (BSA), starch, HA, deoxyribonucleic acid (DNA), and fish oil, confirmed the close correlation between the I-THM species identified during the treatment processes and those predicted from the model compounds. The effects of iodide and bromide on the I-THM speciation and formation were related to the biochemical composition of microbially derived organic precursors. Lipids produced up to 16.98µgL(-1) of CHCl2I at an initial iodide concentration of 2mgL(-1). HA and starch produced less CHCl2I at 3.88 and 3.54µgL(-1), respectively, followed by BSA (1.50µgL(-1)) and DNA (1.35µgL(-1)). Only fish oil produced I-THMs when iodide and bromide were both present in solution; the four other model compounds formed brominated species.


Assuntos
Bactérias/metabolismo , Halogenação , Trialometanos/química , Microbiologia da Água , Animais , Brometos/química , Desinfetantes/química , Água Potável/química , Água Potável/microbiologia , Iodetos/química , Trialometanos/análise
20.
Health Phys ; 104(5): 504-10, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23532079

RESUMO

A glass wafer that contains cerium-activated gadolinium-based scintillator has been tested as a nuclear radiation monitor. The detector is prepared by mixing powdered gadolinium and cerium (3+) bromides with alumina, silica, and lithium fluoride, melting the mixture at 1,400°C, and then quenching and annealing the glass. The resulting clear glass matrix emits stimulated blue light that can be collected by a conventional photomultiplier tube. Spectral analysis of radionuclides with this detector shows the energy peaks for alpha particles, the energy continuum for beta particles, the Compton continuum and full-energy peaks for gamma rays, and an energy continuum with specific reaction-product peaks for neutrons. Energy resolution for the 5.5-MeV alpha particle and 0.662-MeV gamma-ray peaks is about 20%. This resolution, although threefold poorer than for single-crystal NaI(Tl) scintillators, contributes to radionuclide identification and quantification. Application of this detector to radiation monitoring is proposed, as well as approaches for improving light collection and energy resolution that will facilitate radionuclide identification and monitoring, especially for alpha particles, beta particles, and low-energy gamma rays.


Assuntos
Brometos/química , Cério/química , Gadolínio/química , Vidro/química , Monitoramento de Radiação , Contagem de Cintilação , Partículas alfa , Óxido de Alumínio/química , Partículas beta , Fluoretos/química , Raios gama , Compostos de Lítio/química , Nêutrons , Dióxido de Silício/química
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