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1.
Chemosphere ; 248: 125940, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32006828

RESUMO

This study examined the potential of six aliphatic and aromatic amides, commonly found in natural waters or used as chemical aids in water treatment, to act as organic precursors for nine haloacetamides (HAcAms), five haloacetonitriles (HANs), regulated trihalomethanes (THMs) and haloacetic acids (HAAs) upon chlorination and chloramination. The impact of key experimental conditions, representative of drinking water, including pH (7 & 8), retention time (4 & 24 h) and bromide levels (0 & 100 µg/L), on the generation of the target DBPs was investigated. The highest aggregate DBP yields upon chlor(am)ination were reported for the aromatic and hydrophobic hydroxybenzamide; 2.7% ± 0.1% M/M (chlorination) and 1.7% M/M (chloramination). Increased reactivity was observed in aliphatic and hydrophilic compounds, acrylamide (2.5 ± 0.2% M/M) and acetamide (1.3 ± 0.2% M/M), in chlorination and chloramination, respectively. The addition of bromide increased average DBP yields by 50-70%. Relative to chlorination, the application of chloramines reduced DBP formation by 66.5% (without Br-) and by 46.4% (with Br-). However, bromine incorporation in HAAs and HAcAms was enhanced following chloramination, of concern due to the higher toxicological potency of brominated compounds.


Assuntos
Desinfetantes/análise , Poluentes Químicos da Água/análise , Acetamidas , Amidas , Brometos/química , Bromo , Cloraminas/química , Cloro/química , Desinfetantes/química , Desinfecção , Halogenação , Trialometanos/química , Purificação da Água
2.
Chemistry ; 26(5): 1042-1051, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31614042

RESUMO

Following the recent discovery that traditional silver(I) oxide-promoted glycosidations of glycosyl bromides (Koenigs-Knorr reaction) can be greatly accelerated in the presence of catalytic TMSOTf, reported herein is a dedicated study of all major aspects of this reaction. A thorough investigation of numerous silver salts and careful refinement of the reaction conditions led to an improved mechanistic understanding. This, in turn, led to a significant reduction in the amount of silver salt required for these glycosylations. The progress of this reaction can be monitored by naked eye, and the completion of the reaction can be judged by the disappearance of characteristic dark color of Ag2 O. Further evidence on higher reactivity of benzoylated α-bromides in comparison to that of their benzylated counterparts has been acquired.


Assuntos
Ácidos/química , Glicosídeos/química , Brometos/química , Catálise , Glicosilação , Óxidos/química , Compostos de Prata/química
3.
Nat Commun ; 10(1): 3549, 2019 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-31391466

RESUMO

The asymmetric cross-coupling reaction is developed as a straightforward strategy toward 1,1-diaryl alkanes, which are a key skeleton in a series of natural products and bioactive molecules in recent years. Here we report an enantioselective benzylic C(sp3)-H bond arylation via photoredox/nickel dual catalysis. Sterically hindered chiral biimidazoline ligands are designed for this asymmetric cross-coupling reaction. Readily available alkyl benzenes and aryl bromides with various functional groups tolerance can be easily and directly transferred to useful chiral 1,1-diaryl alkanes including pharmaceutical intermediates and bioactive molecules. This reaction proceeds smoothly under mild conditions without the use of external redox reagents.


Assuntos
Alcanos/química , Produtos Biológicos/química , Níquel/química , Processos Fotoquímicos , Brometos/química , Catálise/efeitos da radiação , Elétrons , Luz , Oxirredução , Estereoisomerismo
4.
J Chromatogr A ; 1608: 460413, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31395359

RESUMO

Recent advances in metabolomics have enabled larger proportions of the human metabolome to be analyzed quantitatively. However, this usually requires the use of several chromatographic methods coupled to mass spectrometry to cover the wide range of polarity, acidity/basicity and concentration of metabolites. Chemical derivatization allows in principle a wide coverage in a single method, as it affects both the separation and the detection of metabolites: it increases retention, stabilizes the analytes and improves the sensitivity of the analytes. The majority of quantitative derivatization techniques for LC-MS in metabolomics react with amines, phenols and thiols; however, there are unfortunately very few methods that can target carboxylic acids at the same time, which contribute to a large proportion of the human metabolome. Here, we describe a derivatization technique which simultaneously labels carboxylic acids, thiols and amines using the reagent dimethylaminophenacyl bromide (DmPABr). We further improve the quantitation by employing isotope-coded derivatization (ICD), which uses internal standards derivatized with an isotopically-labelled reagent (DmPABr-D6). We demonstrate the ability to measure and quantify 64 central carbon and energy-related metabolites including amino acids, N-acetylated amino acids, metabolites from the TCA cycle and pyruvate metabolism, acylcarnitines and medium-/long-chain fatty acids. To demonstrate the applicability of the analytical approach, we analyzed urine and SUIT-2 cells utilizing a 15-minute single UPLC-MS/MS method in positive ionization mode. SUIT-2 cells exposed to rotenone showed definitive changes in 28 out of the 64 metabolites, including metabolites from all 7 classes mentioned. By realizing the full potential of DmPABr to derivatize and quantify amines and thiols in addition to carboxylic acids, we extended the coverage of the metabolome, producing a strong platform that can be further applied to a variety of biological studies.


Assuntos
Carbono/química , Carbono/metabolismo , Aminas/química , Aminas/metabolismo , Aminoácidos/análise , Brometos/química , Carbono/urina , Ácidos Carboxílicos/análise , Ácidos Carboxílicos/metabolismo , Linhagem Celular , Cromatografia Líquida/métodos , Humanos , Metaboloma , Metabolômica/métodos , Espectrometria de Massas em Tandem/métodos
5.
ACS Appl Mater Interfaces ; 11(37): 34364-34375, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31442020

RESUMO

In this study, a multifunctional hybrid coating composed of AgBr nanoparticles (AgBrNPs) and two-dimensional molybdenum sulfide (MoS2) nanosheets (AgBr@MoS2) was constructed on Ti implant materials using an in situ growth method for the first time. With 660 nm light and visible light irradiation, the electrons were rapidly excited from the valence band of MoS2 to its conduction band, at the same time, AgBrNPs was used as a photoelectric receiver, which exhibited an enhanced photocatalytic activity due to the rapid transfer of photoelectrons from MoS2 nanosheets to AgBrNPs and the suppression of the recombination of electron-hole pairs. This contributed to the rapid production of reactive oxygen species under 660 nm light irradiation, thus the AgBr@MoS2 system killed bacteria and degraded organic matter quickly and efficiently in a short time. Meanwhile, the AgBr@MoS2 system showed excellent stability due to the strong covalent binding between S and Ag in the system, thus preventing AgBrNPs from being reduced to metal Ag.


Assuntos
Antibacterianos , Bactérias/crescimento & desenvolvimento , Brometos , Desinfecção , Dissulfetos , Luz , Molibdênio , Nanopartículas/química , Compostos de Prata , Animais , Antibacterianos/química , Antibacterianos/farmacologia , Brometos/química , Brometos/farmacologia , Linhagem Celular , Dissulfetos/química , Dissulfetos/farmacologia , Humanos , Camundongos , Viabilidade Microbiana/efeitos dos fármacos , Viabilidade Microbiana/efeitos da radiação , Molibdênio/química , Molibdênio/farmacologia , Ratos , Ratos Sprague-Dawley , Compostos de Prata/química , Compostos de Prata/farmacologia
6.
Analyst ; 144(16): 4880-4886, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31298669

RESUMO

Aflatoxin B1 (AFB1) pollution is one of the most serious problems for food safety. In this paper, a split-type photoelectrochemical (PEC) immunoassay was designed for sensitive detection of AFB1 in foodstuffs by using amorphous TiO2 with all-inorganic perovskite CsPbBr3 nanocrystals (CsPbBr3/a-TiO2). The a-TiO2 layer not only improved the stability of CsPbBr3 nanocrystals, but also facilitated charge transfer, which resulted in the increasing photocurrent of the nanocomposites. Initially, a competitive-type enzyme immunoreaction was executed on a high-binding microplate between the analyte and alkaline phosphatase (ALP)-labeled AFB1-bovine serum albumin (AFB1-BSA) conjugate. Accompanied by the formation of the immunocomplex, the carried ALP triggered enzymatic hydrolysis to generate ascorbic acid (AA, as an electron donor) for increasing the photocurrent of the CsPbBr3/a-TiO2-modified electrode. Coupling with the competitive enzyme immunoassay, the photocurrent of the modified electrode decreased with the increase of target AFB1 concentration in a dynamic working range from 0.01 ng mL-1 to 15 ng mL-1 with a limit of detection (LOD) of 2.8 pg mL-1 under optimum conditions. Furthermore, the photoelectrochemical immunoassay was also utilized to detect AFB1 in peanut and corn samples, giving acceptable accuracy in comparison with the referenced AFB1 enzyme-linked immunosorbent assay (ELISA) method.


Assuntos
Aflatoxina B1/análise , Contaminação de Alimentos/análise , Imunoensaio/métodos , Nanopartículas/química , Aflatoxina B1/imunologia , Fosfatase Alcalina/química , Animais , Anticorpos Imobilizados/imunologia , Arachis/microbiologia , Brometos/química , Bovinos , Césio/química , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Chumbo/química , Limite de Detecção , Nanocompostos/química , Estudo de Prova de Conceito , Soroalbumina Bovina/química , Titânio/química , Zea mays/microbiologia
7.
Anal Sci ; 35(9): 967-972, 2019 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-31080198

RESUMO

Nucleic acid aptamers have been widely used as synthetic probes for bioanalytical applications. Herein, we carried out a detailed study on the immobilization of a series of aptamers ranging from 37 to 88 bases, which are specific to either Escherichia coli (E. coli) or Staphylococcus aureus (S. aureus), on a planar gold substrate via a polyadenine-mediated immobilization method. The resultant surfaces were characterized by both surface plasmon resonance spectroscopy (SPR) and X-ray photoelectron spectroscopy. The results clearly show that the aptamer solution at a lower ionic strength gives rise to a higher lateral density of the aptamer when compared to that at a higher ionic strength. The SPR aptasensors are then employed for detecting their corresponding bacteria (i.e., E. coli and S. aureus, respectively). The data indicate that the SPR aptasensor with a higher density of aptamer exhibits a better capture of target bacteria.


Assuntos
Aptâmeros de Nucleotídeos/química , Escherichia coli/isolamento & purificação , Ouro/química , Poli A/química , Staphylococcus aureus/isolamento & purificação , Ressonância de Plasmônio de Superfície/métodos , Aptâmeros de Nucleotídeos/genética , Aptâmeros de Nucleotídeos/metabolismo , Sequência de Bases , Brometos/química , Escherichia coli/metabolismo , Concentração Osmolar , Compostos de Sódio/química , Staphylococcus aureus/metabolismo
8.
J Environ Radioact ; 205-206: 48-54, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31102905

RESUMO

In the event of a radiological emergency, early and reliable knowledge of radioactivity concentrations is important information for organising countermeasures to protect the general public and emergency workers. This is ensured by all European countries in operating airborne radioactivity and dose rate early warning networks. To increase the provided information, the development of new secondary standards based on scintillation detectors for the measurement of ambient dose rate equivalent was initiated in 2014. This paper shows the state-of-the-art of uncertainties and characteristic limits of low dose rate measurement that can be achieved by scintillation-based detector (CeBr3) and gas-based detectors (a high-pressure ionization chamber, HPIC). The comparison of the devices shows the performance and the metrological potential of the CeBr3 detector: Its uncertainty is already very close to the uncertainty of reference values. Looking at the question how to select a reference instrument, the CeBr3 detector with a special data evaluation is even superior to the HPIC and qualifies therefore as a modern secondary standard: Providing both, dose rate and nuclide information.


Assuntos
Monitoramento de Radiação/métodos , Radiometria , Contagem de Cintilação , Análise Espectral , Brometos/química , Cério/química , Monitoramento de Radiação/instrumentação , Incerteza
9.
Chemosphere ; 228: 735-743, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31071560

RESUMO

This study investigated the oxidative debromination of 2,2-bis(bromomethyl)-1,3-propanediol (BBMP), a widely used brominated flame retardant, and the corresponding formation of brominated by-products by the UV/persulfate process. The debromination of BBMP by the UV/persulfate process was primarily driven by sulfate radicals (SO4-) at pHs 4.0-6.0 and hydroxyl radicals (HO) at pHs 9.0-12.0. The debromination rate increased with increasing pH from 4.0 to 9.0 and remained the same at pHs 9.0 and 12.0. Bromate was formed through the oxidation of bromide released from BBMP mainly by SO4-, with free bromine as a key intermediate. Bromate formation increased with increasing pH from 4.0 to 6.0, while it remarkably decreased with increasing pH from 6.0 to 12.0. This was mainly due to the transformation of SO4- to HO and also the quenching of bromine atoms that were the key intermediate for the formation of free bromine, by hydroxyl ions at the alkaline pH. In addition, the oxidative debromination of BBMP resulted in a significant decrease in the concentrations of total organic bromine, but the formation of brominated acetic acids and unknown brominated organic by-products. The concentrations of brominated organic by-products firstly increased and then decreased with prolonged reaction time. Also, the formation of brominated organic by-products and genotoxicity at pH 9.0 were much lower than that at pH 6.0. In this study, we propose that the UV/persulfate process under mildly alkaline conditions not only debrominates BBMP efficiently but also eliminates the formation of bromate and brominated organic by-products and genotoxicity.


Assuntos
Retardadores de Chama , Propilenoglicóis/química , Poluentes Químicos da Água/química , Bromatos/química , Brometos/química , Bromo/química , Retardadores de Chama/efeitos da radiação , Halogenação , Radical Hidroxila , Oxirredução , Propilenoglicóis/efeitos da radiação , Sulfatos/química , Raios Ultravioleta , Poluentes Químicos da Água/efeitos da radiação
10.
Colloids Surf B Biointerfaces ; 179: 170-179, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-30959229

RESUMO

In this study, novel AgBr-modified g-C3N4 (AgBr/g-C3N4) photocatalysts were prepared by an adsorption-deposition method and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and ultraviolet-visible spectroscopy (UV-vis). Furthermore, the photocatalytic disinfection performance on Escherichia coli (ATCC 15597) was investigated. The as-prepared photocatalysts exhibited well crystalline structures and morphologies with C3N4 and exhibited a stronger bacterial inactivation than that of pristine g-C3N4. The disinfection efficiency reached up to 4.80 log under 150 min of visible light irradiation when AgBr-modified g-C3N4 was prepared at a molar ratio of 1:5 (AgBr: g-C3N4), which was a 4.2 log increase compared with that of pristine g-C3N4 under the same experimental conditions. The enhancement of the photocatalytic activity of AgBr/g-C3N4 was attributed to the effective production and transfer of the photo-induced electrons under visible light irradiation, since the AgBr modification reduced the bandgap energy and boarded the visible light area. Furthermore, h+ was found to be the dominant contributor for bacterial inactivation. The h+ and photo-generated reactive oxygen species (ROSs) damaged the cell membranes and destroyed metabolic processes, resulting in leakage of potassium ions and proteins, lipid peroxidation, degradation of intracellular protein, and a reduction of the ATP levels, which finally lead to bacterial death. These results provide a theoretical basis for the development of low-cost, high-efficiency photocatalysts for green/sustainable water disinfection.


Assuntos
Brometos/química , Desinfecção , Grafite/química , Luz , Nitrilos/química , Compostos de Prata/química , Catálise/efeitos da radiação , Escherichia coli/fisiologia , Escherichia coli/efeitos da radiação , Marcadores de Spin , Difração de Raios X
11.
Molecules ; 24(7)2019 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-30959775

RESUMO

The physicochemical properties of four 1-alkyl-3-methylimidazolium bromide ([CnC1im]Br, n = 5, 6, 7, 8) ionic liquids (ILs) were investigated in this work by using inverse gas chromatography (IGC) from 303.15 K to 343.15 K. Twenty-eight organic solvents were used to obtain the physicochemical properties between each IL and solvent via the IGC method, including the specific retention volume and the Flory⁻Huggins interaction parameter. The Hildebrand solubility parameters of the four [CnC1im]Br ILs were determined by linear extrapolation to be δ 2 ( [ C 5 C 1 im ] Br ) = 25.78 (J·cm-3)0.5, δ 2 ( [ C 6 C 1 im ] Br ) = 25.38 (J·cm-3)0.5, δ 2 ( [ C 7 C 1 im ] Br ) =24.78 (J·cm-3)0.5 and δ 2 ( [ C 8 C 1 im ] Br ) = 24.23 (J·cm-3)0.5 at room temperature (298.15 K). At the same time, the Hansen solubility parameters of the four [CnC1im]Br ILs were simulated by using the Hansen Solubility Parameter in Practice (HSPiP) at room temperature (298.15 K). The results were as follows: δ t ( [ C 5 C 1 im ] Br ) = 25.86 (J·cm-3)0.5, δ t ( [ C 6 C 1 im ] Br ) = 25.39 (J·cm-3)0.5, δ t ( [ C 7 C 1 im ] Br ) = 24.81 (J·cm-3)0.5 and δ t ( [ C 8 C 1 im ] Br ) = 24.33 (J·cm-3)0.5. These values were slightly higher than those obtained by the IGC method, but they only exhibited small errors, covering a range of 0.01 to 0.1 (J·cm-3)0.5. In addition, the miscibility between the IL and the probe was evaluated by IGC, and it exhibited a basic agreement with the HSPiP. This study confirms that the combination of the two methods can accurately calculate solubility parameters and select solvents.


Assuntos
Imidazóis/química , Líquidos Iônicos/química , Solubilidade , Brometos/química , Cromatografia Gasosa , Solventes/química
12.
J Environ Radioact ; 204: 12-20, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30952051

RESUMO

A new medium resolution gamma-ray spectrometer consisting of a cerium bromide (CeBr3) crystal (2˝ x 2˝), is developed and optimized for radioactivity measurements in aquatic environments. This apparatus named GeoMAREA (Gamma-ray spectrometer for in-situ Marine Environmental Applications) is designed to control and prevent radio-contaminants in aquatic environments as well as to estimate the variation of natural radionuclides in marine systems for studying oceanographic processes. The system offers activity concentrations in Bq/m3 for detected gamma-ray emitters in the energy range from 150 to 2600 keV, and can provide sequential continuous monitoring data in a stand-alone mode or it can be integrated in stationary/mobile platforms for (near) real-time applications. The photopeak efficiency values were estimated via the MCNPΧ code. Two experimental points were used to validate the theoretical estimations by deploying the system in a water tank with diluted reference sources such us Caesium-137 (137Cs) and Potassium-40 (40K). The system was subsequently deployed in the field along with a conductivity-temperature (CT) sensor, to measure 40K and radon daughters in a region where submarine groundwater discharges (Anavalos, Kiveri, Greece) are present. The experimental calibration data was utilized to provide a first estimation for the background contribution around the photopeak of 40K, attributed to the Cerium Bromide (CeBr3) intrinsic activity.


Assuntos
Brometos/química , Cério/química , Radioisótopos de Césio/análise , Radioisótopos de Potássio/análise , Monitoramento de Radiação/instrumentação , Espectrometria gama/instrumentação , Poluentes Radioativos da Água/análise , Radioatividade
13.
Int J Hyg Environ Health ; 222(4): 663-669, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-31003882

RESUMO

The mutagenicity of four organic UV filters namely oxybenzone (benzophenone-3), dioxybenzone (benzophenone-8), avobenzone, and octyl methoxycinnamate, in chlorinated bromide-rich water (artificial seawater) was investigated. Mutagenicity was evaluated using Ames test in Salmonella typhimurium TA98 without S9 mix. Chemical analysis using high-resolution mass spectrometry was carried out to elucidate the mutagenic transformation products. Among the studied UV filters, only dioxybenzone exhibited a clear mutagenic activity following chlorination in seawater at ratio 1:10 (UV filter:chlorine). In contrast, no mutagenic activity was detected when chlorine was added at higher doses (ratio 1:1000). High-resolution mass spectrometry analysis showed that mutagenic extracts contained several brominated transformation products of dioxybenzone. Time course analysis of the transformation products at increasing chlorine doses showed that they were unstable and disappeared more quickly at higher chlorine doses. This instability explained the absence of mutagenic activity of dioxybenzone when 1000-fold excess chlorine was added, as no transformation products were detected. Relevance of these findings to the context of swimming pool is discussed. Further investigations taking into consideration the mutagenicity of not only the intermediate transformation products but also the final disinfection byproducts are needed to determine the overall impact of high levels of chlorine on the overall mutagenicity. This study highlights the importance of considering the reactivity of organic UV filters and their transformation products in disinfected recreational waters when sunscreen formulations are prepared.


Assuntos
Benzofenonas , Cloro/química , Desinfetantes/química , Mutagênicos , Protetores Solares , Poluentes Químicos da Água , Benzofenonas/química , Benzofenonas/farmacologia , Brometos/química , Cinamatos/química , Cinamatos/farmacologia , Desinfecção , Halogenação , Testes de Mutagenicidade , Mutagênicos/química , Mutagênicos/farmacologia , Propiofenonas/química , Propiofenonas/farmacologia , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/genética , Água do Mar/química , Protetores Solares/química , Protetores Solares/farmacologia , Poluentes Químicos da Água/química
14.
Ecotoxicol Environ Saf ; 179: 96-103, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31026755

RESUMO

Chloroperoxidase (CPO) is a hybrid of two different families of enzymes, peroxidases and P450s. However, it is poorly understood on CPO's multiple catalytic functions. Herein, phenol was selected as a model substrate to investigate the multiple catalytic roles of CPO. Results showed that phenol was readily transformed into a variety of brominated organic compounds (BOCs) via the CPO-mediated oxidative process. A total of 16 BOCs were identified using gas and liquid chromatography coupled with mass spectrometry. Possible reaction pathways could be attributable to four CPO-mediated processes, including bromination, radical coupling, intramolecular cyclization and debromination. Higher bromide concentrations and lower pH conditions both facilitated the formation of brominated products. While a higher bromination capacity was observed in pH 3.0 solutions, CPO-mediated radical couplings were more favorable at pH 5.0 and 6.0. Although CPO might catalyze chlorination when chloride and bromide coexisted in the solution, BOCs were the dominant products of CPO-mediated phenol oxidation. Results of this study suggest that various catalytic roles of CPO may contribute to the biotic formation of BOCs in the natural environment.


Assuntos
Brometos/química , Cloreto Peroxidase/química , Hidrocarbonetos Bromados/química , Fenol/química , Catálise , Cromatografia Líquida , Halogenação , Estrutura Molecular , Oxirredução , Espectrometria de Massas em Tandem
15.
J Colloid Interface Sci ; 544: 206-216, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30849618

RESUMO

Palladium (Pd)-catalyzed reactions mostly show structure sensitivity: i.e., the selectivity and activity of the reactions are highly dependent on the arrangement of Pd atoms. In this regard, branched Pd nanoparticles show enhanced catalytic performance owing to the presence of low coordinated Pd atoms. In this paper, a novel solution-phase synthesis of flower-like Pd nanodendrites using ribonucleic acid (RNA) as a capping agent and ascorbic acid as a reducing agent was described. On the other hand, the co-use of polyvinylpyrrolidone (PVP) and potassium bromide (KBr) instead of RNA at the same synthesis conditions led to cuboid nanoparticles, while the sole use of ascorbic acid resulted in faceted nanoparticles. The formation of nanodendritic morphology was attributed to the RNA-assisted growth through particle attachment. This scenario was supported by TEM analysis that demonstrated the aggregation of small particles to form larger nanoparticles at the onset of the reaction. The shape and size of the nanoparticles could be readily tuned by the RNA content used. XPS confirmed the formation of metallic Pd nanoparticles. The presence of crystalline planes of {1 1 1}, {2 0 0}, {2 2 0}, {3 1 1} and {2 2 2} was demonstrated by XRD and SAED analyses. The Pd nanodendrites were used for the reduction of p-nitrophenol (PNP) and 2,4,6-trinitrotoluene (TNT), and reduction rate constants (k) were calculated as 1.078 min-1 (normalized rate constant, knor = 59.66 mmol-1 s-1) for PNP and 0.3181 min-1 (knor = 17.6 mmol-1 s-1) for TNT with the corresponding turnover frequencies (TOFs) as 16.06 and 40.80 h-1, respectively.


Assuntos
Dendritos/química , Nanopartículas Metálicas/química , Nanopartículas/química , Paládio/química , Brometos/química , Catálise , Cinética , Nitrofenóis/química , Oxirredução , Tamanho da Partícula , Compostos de Potássio/química , Povidona/química , RNA/química , Propriedades de Superfície , Trinitrotolueno/química
16.
Molecules ; 24(3)2019 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-30759856

RESUMO

The paper analyses influences of the temperature and hydrophilic groups on micellar properties of ionic surfactants with 12-carbonic hydrophobic chains. The aim is to assess the impact of hydrophilic groups and temperature on thermodynamic parameters and micellization. This knowledge is indispensable for the formulation of new dosage forms. The method uses conductometric measurements. The following hydrophilic groups are analyzed: trimethylammonium bromide, trimethylammonium chloride, ethyldimethylammonium bromide, didodecyldimethylammonium bromide, pyridinium chloride, benzyldimethyl-ammonium chloride, methylephedrinium bromide, cis and trans-[(2-benzyloxy)-cyclohexyl-methyl]-N, N-dimethylammonium bromide, sodium sulphate and lithium sulphate. Except for a few cases, there is a good agreement between values of critical micellar concentrations (CMC) and critical vesicle concentration (CVC) obtained here and those which were obtained by other authors and/or by other physicochemical methods. Values of the CMC are compared with respect to the molar masses of hydrophilic groups. It was found that CMC values increased non-linearly with increasing system temperature. The degrees of counterion binding and thermodynamic parameters, like the standard molar Gibbs energy, enthalpy and entropy of micellization are determined and discussed in detail. The results obtained will be incorporated into in silico processes of modeling and design of optimal dosage forms, a current interdisciplinary research focus of the team.


Assuntos
Íons/química , Tensoativos/química , Brometos/química , Simulação por Computador , Interações Hidrofóbicas e Hidrofílicas , Compostos de Lítio/química , Micelas , Modelos Químicos , Compostos de Amônio Quaternário/química , Sulfatos/química , Temperatura , Termodinâmica
17.
Molecules ; 24(4)2019 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-30769954

RESUMO

A facile and sustainable electrochemical umpolung of bromide ion protocol was developed under mild reaction conditions. Transition metal catalysts and exogenous chemical oxidants were obviated for the bromination of C⁻H bond. Notably, graphite rod, which is commercially available at supermarkets and is inexpensive, was employed as the electrode material. This operationally easy and environmentally friendly approach accomplished the synthesis of 3-bromoindole in excellent yield and regioselectivity.


Assuntos
Brometos/química , Técnicas Eletroquímicas , Brometos/análise , Carbono/química , Hidrogênio/química , Indóis/química , Espectroscopia de Ressonância Magnética , Espectrofotometria Infravermelho
18.
Int J Biol Macromol ; 128: 902-910, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30716374

RESUMO

The functionalization of cotton fabric with photoactive TiO2-Ag-AgBr nanostructured layer has been successfully developed using a low temperature non-aqueous sol-gel route and aqueous suspension of AgBr. Evidence for the growth of TiO2 layer and the immobilization of AgBr nanoparticles have been confirmed by Raman, XRD and XPS. GSDR analysis revealed a strong absorption in the visible region brought by surface Plasmon resonance (SPR) of Ag nanocrystals generated at the surface of AgBr. The XPS evidenced the presence of Ag+, Ag0 and bromine, suggesting that Ag0 formed a shell around the deposited AgBr. The immobilized TiO2-Ag-AgBr heterostructured layer imparts a strong photocatalytic activity under visible light for the degradation of dyes in aqueous solution as well as of dimethyl methylphosphonate (DMMP), a chemical warfare agent simulant. These new catalytically active functionalized fabrics, with self-detoxification properties, have great potential for application in chemical protective clothes and might offer new opportunities for the design of functional materials for toxic chemical protection.


Assuntos
Brometos/química , Corantes/química , Fibra de Algodão , Organofosfatos/química , Processos Fotoquímicos , Compostos de Prata/química , Prata/química , Titânio/química , Catálise , Corantes/isolamento & purificação , Nanoestruturas/química , Organofosfatos/isolamento & purificação , Organofosfatos/toxicidade , Temperatura , Água/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água
19.
Bioresour Technol ; 273: 565-572, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30476865

RESUMO

The application of pressure filtration in microalgae harvesting requires chemical pretreatment in order to reduce membrane fouling and to increase water flux. Surfactants have shown potential to enhance microalgae dewaterability by charge neutralization, bridging and releasing extracellular polymeric substances (EPS) and bound water. In this study, the effect of three surfactants including anionic sodium dodecyl sulfate (SDS), non-ionic triton X-100 and cationic cetyl trimethyl ammonium bromide (CTAB) on the dewaterability of Chlamydomonas sp. was investigated. Filtration fluxes and biomass concentrations were used to evaluate the microalgae dewaterability. Based on the results, SDS and Triton X-100 had a negative effect on the dewaterability of microalgae biomass. However, CTAB improved the dewaterability by decreasing the reversible and irreversible fouling resistance. The optimum dosage of CTAB was found to be 1500 mg/L, and resulted in 95.8% and 140% improvement on average water flux and biomass recovery efficiency, respectively.


Assuntos
Biomassa , Brometos/química , Cetrimônio/química , Microalgas/química , Octoxinol/química , Compostos de Amônio Quaternário/química , Dodecilsulfato de Sódio/química , Tensoativos/química , Filtração , Microalgas/metabolismo , Pressão , Água/química
20.
Biomacromolecules ; 20(1): 490-501, 2019 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-30500209

RESUMO

We report a novel method to prepare capsules, beads, or open-cell materials from Pickering emulsions of monomers, stabilized by cellulose nanocrystals (CNCs) grafted with reactive isobutyrate bromide moieties (CNC-Br). CNC-Br particles with different hydrophilic/hydrophobic balance at their surface were prepared and subsequently used to stabilize direct (O/W), inverted (W/O), or double emulsions of styrene or n-BuA. The different emulsions obtained were subsequently polymerized, by initiating an AGET-ATRP polymerization from the brominated particles surrounding the stabilized droplets. The different hybrid polymer materials obtained were subsequently characterized, and the impact of the CNCs functionalization and polymerization conditions was particularly discussed.


Assuntos
Brometos/química , Celulose/análogos & derivados , Nanopartículas/química , Polimerização , Butiratos/química , Emulsões/química , Interações Hidrofóbicas e Hidrofílicas , Estirenos/química , Tensoativos/síntese química
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