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1.
Chemosphere ; 251: 126382, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32443238

RESUMO

A single metal Pd/γ-Al2O3 catalyst and a bimetallic Pd-Ce/γ-Al2O3 catalyst were prepared by the equal-volume impregnation method to investigate the effect of CeO2 loading on the catalytic oxidation of toluene. The specific surface area, surface morphology, and redox performance of the catalyst were characterized by N2 desorption, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), H2-TPR, O2-TPD, and electron paramagnetic resonance (EPR). The results showed that bimetal catalysts loaded CeO2 had smaller nano-PdO particles than those of the Pd/γ-Al2O3 catalyst. Compared with the catalyst of 0.2Pd/γ-Al2O3 (percentage of mass, the same as below), the catalyst doped with 0.3CeO2 had a stronger reduction peak, which was shifted to the low-temperature zone by more than 80 °C. The results of XPS and O2-TPD showed that the introduction of CeO2 provided more surface oxygen vacancy for the catalyst and enhanced its catalytic oxidation ability, and the amount of desorbed O2 increased from 3.55 µmol/g to 8.54 µmol/g. The results of EPR were that the addition of CeO2 increased the content of active oxygen species and oxygen vacancies on the surface of the catalysts, which might be due to the supply of electrons to the O2 and PdO during the Ce3+toCe4+ conversion process. That could have accelerated the catalytic reaction process. Compared with the single precious metal catalyst, the T10 and T90 of the Pd-Ce/γ-Al2O3 catalyst were decreased by 22 °C and 40 °C, respectively.


Assuntos
Tolueno/química , Óxido de Alumínio/química , Catálise , Cério/química , Chumbo/química , Oxirredução , Oxigênio/química , Espectroscopia Fotoeletrônica
2.
Ecotoxicol Environ Saf ; 194: 110456, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32171963

RESUMO

The early stage of aggregation of cerium oxide nanoparticles (CeO2 NPs) in anion solutions was inspected in the absence and presence of extracellular polymeric substance (EPS) with a help of time-resolved dynamic light scattering (DLS). The aggregation kinetics and attachment efficiencies were calculated according to measured hydrodynamic diameter across a range of 1-500 mM NaNO3 and 0.01-100. mM Na2SO4. The aggregation of CeO2 NPs in both NaNO3 and Na2SO4 solution conformed with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. In NaNO3 solution, the critical coagulation concentrations (CCC) of CeO2 NPs was calculated to be about 47 mM; in Na2SO4 solution, CeO2 NPs showed a re-stabilization process and thus there was no CCC value. SO42- had intenser effects on CeO2 NPs aggregation than NO3- might because of the distinction between their polarization, consisting in Hofmeister series. The presence of bound EPS (B-EPS), tightly bound EPS (TB-EPS) and loosely bound EPS (LB-EPS) in NaNO3 solutions all lead to significant decrease in CeO2 NPs aggregation. Steric repulsive force produced by absorbed EPS on CeO2 NPs might take main responsibility in stabilizing CeO2 NPs. Besides, Extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) model successfully predicted the energy barrier between CeO2 NPs with B-EPS, TB-EPS and LB-EPS as a function of NaNO3 concentration. Furthermore, the difference in impeding the CeO2 NPs aggregation with B-EPS, TB-EPS and LB-EPS may be caused by the divergence in molecular weight and component mass fraction especially protein content. These results might subserve the assessment on the fate and transport behaviors of CeO2 NPs released in wastewater treatment plants.


Assuntos
Cério/química , Modelos Químicos , Nanopartículas/química , Matriz Extracelular de Substâncias Poliméricas , Cinética
3.
J Environ Sci (China) ; 90: 110-118, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32081308

RESUMO

This work investigates the effect of cerium substation into strontium cobalt perovskites (CeSrCoO) for the oxidative degradation of Orange II (OII) in dark ambient conditions without the aid of any external stimulants such as light, heating or chemical additives. The OII degradation rate by CeSrCoO reached 65% in the first hour, whilst for the blank sample without cerium (SrCoO) took over 2 hr to reach the same level of OII degradation. Hence, the cerium substitution improved the catalytic activity of the perovskite material, mainly associated with the Ce0.1Sr0.9CoO3 perovskite phase. Upon contacting CeSrCoO, the -NN- azo bonds of the OII molecules broke down resulting in electron donation and the formation of by-products. The electrons are injected into the CeSrCoO and resulted in a redox pair of Co3+/Co2+, establishing a bridge for the electron transfer between OII and the catalysts. Concomitantly, the electrons also formed reactive species (·OH) responsible for OII degradation as evidenced by radical trapping experiment. Reactive species were formed via the reaction between O2 and donated electrons from OII with the aid of cobalt redox pair. As the prepared materials dispensed with the need for light irradiation and additional oxidants, it opens a window of environmental applications for treating contaminated wastewaters.


Assuntos
Compostos de Cálcio/química , Cério/química , Poluentes Ambientais , Óxidos/química , Estrôncio/química , Titânio/química , Catálise , Cobalto
4.
Chemosphere ; 247: 125860, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32069710

RESUMO

Herein, CeO2 catalysts with nanotube, nanobelt, and wire-in-nanotube morphologies were successfully fabricated by a facile single spinneret electrospinning technique. And catalytic activity of these electrospun CeO2 nanomaterials were evaluated by toluene catalytic combustion reaction. Among the three morphologies of CeO2 catalysts, CeO2 nanobelt (CeO2-NB) presented the best toluene catalytic combustion performance (T90% = 230 °C) at WHSV = 60,000 mL g-1 h-1, also exhibited the lowest activation energy (Ea = 80.2 kJ/mol). Based on the characterization by TEM, XRD, BET, SEM, XPS, Raman spectroscopy, H2-TPR, and O2-TPD results, the high catalytic activity of CeO2-NB catalyst was attributed to its porous nanobelt morphology with larger specific surface area and the abundance of surface oxygen vacancies. Furthermore, the CeO2-NB catalysts presented an excellent durability by longtime on-stream test (as well as presence of 5% vol. water vapor), suggesting its great potential for practical air pollution control application.


Assuntos
Cério/química , Nanoestruturas/química , Tolueno/química , Poluição do Ar/prevenção & controle , Catálise , Nanotubos/química , Oxigênio/química , Porosidade , Compostos Orgânicos Voláteis
5.
Chemosphere ; 247: 125863, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31972485

RESUMO

Plasma-catalysis technologies (PCTs) have the potential to control the emissions of volatile organic compounds, although their low-energy efficiency is a bottleneck for their practical applications. A plasma-catalyst reactor filled with a CeO2/γ-Al2O3 catalyst was developed to decompose toluene with a high-energy efficiency enhanced by the elevating reaction temperature. When the reaction temperature was raised from 50 °C to 250 °C, toluene conversion dramatically increased from 45.3% to 95.5% and the energy efficiency increased from 53.5 g/kWh to 113.0 g/kWh. Conversely, the toluene conversion using a thermal catalysis technology (TCT) exhibited a maximum of 16.7%. The activation energy of toluene decomposition using PCTs is 14.0 kJ/mol, which is far lower than those of toluene decomposition using TCTs, which implies that toluene decomposition using PCT differs from that using TCT. The experimental results revealed that the Ce3+/Ce4+ ratio decreased and Oads/Olatt ratio increased after the 40-h evaluation experiment, suggesting that CeO2 promoted the formation of the reactive oxygen species that is beneficial for toluene decomposition.


Assuntos
Poluentes Atmosféricos/análise , Gases em Plasma/química , Tolueno/análise , Compostos Orgânicos Voláteis/análise , Óxido de Alumínio/química , Catálise , Cério/química , Temperatura Alta , Modelos Teóricos , Oxirredução
6.
Chemosphere ; 246: 125762, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31896012

RESUMO

Formaldehyde is a typical indoor air pollutant and its removal is essential to protect human health and meet environmental regulations. Efficient activation of Pd/CeO2 catalyst by non-thermal plasma was investigated to achieve complete oxidation of formaldehyde at room temperature. The catalyst exhibited better activity and stability than conventional thermal reduced sample. Its HCHO conversion to CO2 kept at over 80% during 300 min test at a gas hourly space velocity of 150, 000 mL/g/h and HCHO concentration of 100 ppm. While the conversion dropped from 70% to 50% within 300 min test for the sample reduced at 300 °C. Compared with thermal reduced catalyst, plasma reduced sample exhibited more abundant surface active oxygen species, smaller palladium particle size and narrower particle size distribution. Moreover, palladium particles were partial covered by ceria layer for thermal reduced sample. Although strong interaction between palladium and ceria could be formed, the loss of metallic palladium occurs and hence the oxygen activation and mobility abilities are blocked. In situ DRIFTs results suggested that the intermediates over Pd/CeO2 catalyst were mainly formate, dioxymethylene and polyoxymethylene species, and the formate oxidation into CO2 process was highly promoted in the presence of water.


Assuntos
Poluição do Ar em Ambientes Fechados/análise , Formaldeído/química , Modelos Químicos , Catálise , Cério/química , Humanos , Oxirredução , Paládio/química , Tamanho da Partícula , Temperatura , Água
7.
PLoS One ; 15(1): e0227926, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31951630

RESUMO

Cerium (Ce) oxide nanoparticles (CNP; nanoceria) are reported to have cytotoxic effects on certain cancerous cell lines, while at the same concentration they show no cytotoxicity on normal (healthy) cells. Redox-active CNP exhibit both selective prooxidative as well as antioxidative properties. The former is proposed to be responsible for impairment of tumor growth and invasion and the latter for rescuing normal cells from reactive oxygen species (ROS)-induced damage. Here we address possible underlying mechanisms of prooxidative effects of CNP in a metastatic human melanoma cell line. Malignant melanoma is the most aggressive form of skin cancer, and once it becomes metastatic the prognosis is very poor. We have shown earlier that CNP selectively kill A375 melanoma cells by increasing intracellular ROS levels, whose basic amount is significantly higher than in the normal (healthy) counterpart, the melanocytes. Here we show that CNP initiate a mitochondrial increase of ROS levels accompanied by an increase in mitochondrial thiol oxidation. Furthermore, we observed CNP-induced changes in mitochondrial bioenergetics, dynamics, and cristae morphology demonstrating mitochondrial dysfunction which finally led to tumor cell death. CNP-induced cell death is abolished by administration of PEG-conjugated catalase. Overall, we propose that cerium oxide nanoparticles mediate cell death via hydrogen peroxide production linked to mitochondrial dysfunction.


Assuntos
Cério/farmacologia , Citotoxinas/farmacologia , Melanoma/tratamento farmacológico , Mitocôndrias/efeitos dos fármacos , Antioxidantes/química , Antioxidantes/farmacologia , Catalase/farmacologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Cério/química , Citotoxinas/química , Humanos , Melanoma/metabolismo , Melanoma/patologia , Mitocôndrias/patologia , Nanopartículas/química , Metástase Neoplásica , Compostos de Sulfidrila/metabolismo
8.
Ecotoxicol Environ Saf ; 191: 110228, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31982684

RESUMO

An efficient MnCeOx composite was successfully synthesized for activation of persulfate to degrade acid orange 7 (AO7) and ofloxacin. Pollutants degradation efficiencies with different catalytic systems were investigated. Results showed the performance of MnCeOx was better than MnOx, CeO2 and MnOx + CeO2. Thus, there was a clear synergistic effect (Se) between Mn and Ce in the composite, and the Se was 73.8% for AO7 and 39.6% for ofloxacin. In addition, AO7 removal fitted 1st order reaction while ofloxacin removal fitted 2nd order reaction in MnCeOx/persulfate system. Moreover, MnCeOx/persulfate system showed high efficiency in pH range of 5-9. Mechanism analysis showed that SO4- and OH on the surface of the catalyst were the main active species, and O2- also played an important role in pollutants degradation. Furthermore, MnCeOx showed high activity in actual water. Finally, the possible degradation pathway of ofloxacin was proposed according to the high performance liquid chromatography-mass spectrometry result. Overall, this study provides an efficient and stable catalyst to activate persulfate to degrade refractory pollutants.


Assuntos
Compostos Azo/metabolismo , Benzenossulfonatos/metabolismo , Cério/química , Compostos de Manganês/química , Ofloxacino/metabolismo , Óxidos/química , Sulfatos/química , Poluentes Químicos da Água/metabolismo , Catálise , Oxirredução
9.
Chemosphere ; 243: 125419, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31995875

RESUMO

Cerium titanate catalyst (Ce-TiO2) is competitive as a substitute for the commercial SCR (selective catalytic reduction) catalysts VO5-WO2/TiO2 due to its high SCR activity and excellent redox performance. The reaction mechanisms of Ce-TiO2 at 180 °C, 240 °C, and 300 °C in the presence of SO2 were systematically studied regarding the evolution of the SCR activity, quantitative analysis of sulfate compounds, and comprehensive identification of the fresh and poisoned catalysts. The results demonstrated that NO conversion at 180 °C in the presence of SO2 is highly sensitive to the formation of cerium sulfates/sulfites, limiting the reactivity of NH4+ adsorbed on SO Brønsted acid sites and inhibiting the E-R reaction pathway. At 240 °C, the degradation of NO conversion was commenced by the cumulative influence of cerium sulfates/sulfites. With the increase of the reaction temperature to 300 °C, the NO conversion is gradually immune to the formation of cerium sulfates in spite of the great amount of cerium sulfates deposited on the deeper interior of CeO2. The high SCR activity of the Ce-TiO2 catalyst in the presence of SO2 at a higher reaction temperature might be ascribed to the synergistic catalysis between surface cerium sulfates and bulk CeO2, where surface cerium sulfates act as acid sites for the adsorption of NH3 and the bulk CeO2 acts as the redox sites. The reaction mechanisms of the Ce-TiO2 catalyst in the presence of SO2 at different temperatures are proposed as the two reaction routes.


Assuntos
Amônia/química , Cério/química , Recuperação e Remediação Ambiental/métodos , Dióxido de Enxofre/química , Titânio/química , Adsorção , Catálise , Oxirredução , Sulfatos/química , Temperatura
10.
Environ Pollut ; 257: 113584, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31733953

RESUMO

Parameters such as the settling rate, aggregation rate, and collision frequency in predictive models used to describe the fate of nanoparticles (NPs) are very important for the risk assessment of NPs in the environment. In this study, CeO2 NPs were chosen as the model particles to investigate such parameters through aggregation-settling experiments under environmentally relevant conditions. The results indicate that natural colloids (Ncs) have no effect on the settling of NPs in seawaters, whereas they stabilize the NPs at a low initial particle concentration and promote the heteroaggregation of NPs at a high initial particle concentration in lake waters. In all cases, a suspended sediment absorbs the NPs and Ncs as mixed aggregates, resulting in a rapid settling. Furthermore, the calculation results of the model indicate that the shear force increases the collision frequency of the NPs by 4-5 orders of magnitude higher than that in quiescent waters. However, the break-up effect by the shear force is more obvious, namely, the shear force hinders the aggregation of NPs in natural waters, instead of promoting aggregation. Remarkably, a negative value of the dis-heteroaggregation rate based on the combined von Smoluchowski-Stokes equation can reflect the hindering effect on the aggregation process. The results of this study will provide scientific and accurate guidance for the parameter selection in the existing prediction model and contribute to a prediction of the fate and transport of NPs in the environment.


Assuntos
Cério/química , Nanopartículas/química , Poluentes Químicos da Água/química , Cério/análise , Coloides , Água Doce , Nanopartículas/análise , Poluentes Químicos da Água/análise
11.
Ecotoxicol Environ Saf ; 190: 110062, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31838233

RESUMO

In this work, the shuttle-like CeO2 modified g-C3N4 composite was synthesized and was combined with persulfate (PS) for the efficient photocatalytic degradation of norfloxacin (NOR) under visible light. Scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) emission spectra were used to characterize the structural and optical properties of the as-prepared catalysts. Active species trapping experiments demonstrated that additional sulfate radicals (·SO4-) formed upon the addition of PS which could cooperate with superoxide radicals (O2-), holes (h+) and hydroxyl radicals (OH) to decompose NOR. Singlet oxygen (1O2) was also formed during the reaction and acted as an important active species. The degradation products of NOR were also identified and analyzed by using LC-MS technology, and the possible degradation mechanism and pathways were proposed and discussed. This work indicated that the shuttle-like CeO2 modified g-C3N4 coupled with PS displayed promising applications in the field of pharmaceutical wastewater purification.


Assuntos
Cério/química , Grafite/química , Compostos de Nitrogênio/química , Norfloxacino/metabolismo , Norfloxacino/efeitos da radiação , Poluentes Químicos da Água/metabolismo , Poluentes Químicos da Água/efeitos da radiação , Catálise , Luz , Processos Fotoquímicos , Sulfatos/química , Águas Residuárias , Purificação da Água/métodos , Difração de Raios X
12.
Chemosphere ; 243: 125406, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31783186

RESUMO

The effects of Mn precursors on structure defects and NO catalytic mechanism over Ce0·6Mn0.4Ox catalysts were fully investigated. The Ce0·6Mn0.4Ox-Ac catalyst, synthesized by using MnAc2 as a Mn precursor, showed the best catalytic activity for NO conversion (86.9%) at 250 °C under high space velocity (40,000 mL g-1 h-1). Detailed structure-activity relationship reveals that the abundant oxygen vacancies and the highly migratory oxygen species formed on Ce0·6Mn0.4Ox are the crucial factors that leading to the better NO oxidation activity than that of the other Ce0·6Mn0.4Ox-Y (YNO3, SO4, Cl) catalysts. In situ DRIFTS technique confirms that the differences in formation mode and desorption ability of N-based (nitrates, nitrites, and dimer nitroso) intermediate species are the vital factors for NO high-efficiency catalytic oxidation. The highly reactive surface intermediate species, like monodentate nitrates, were observed particularly on Ce0·6Mn0.4Ox-Ac catalyst, so that the NO oxidation performance on Ce0·6Mn0.4Ox-Ac catalyst was more active comparing with other Ce0·6Mn0.4Ox-Y catalysts. This study can broaden the horizons for understanding NO catalytic oxidation mechanism on serial Ce0·6Mn0.4Ox catalysts and serve as a reference guide in design of structure defects for functional materials by modulating precursor species.


Assuntos
Manganês/química , Óxido Nítrico/química , Catálise , Cério/química , Oxirredução , Oxigênio/química
13.
J Photochem Photobiol B ; 202: 111706, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31775112

RESUMO

The noble metal such as Ag and Au doped CeO2 nanoparticles was successfully prepared by ionic liquid assisted hydrothermal method in the presence of Justicia adhatoda leaves extract and were used as an antibacterial and anticancer agent. The FT-IR and Raman spectrum exhibit the peaks at 460 and 464 cm-1 assigned to CeO stretching vibrations of NPs. The electron microscopic micrographs confirmed the spherical shaped morphology of prepared NPs. The insertion of Ag and Au ions into the CeO2 surface creates lattice defects the leads to reduce the band gap energy of Ag-Au/CeO2 at 3.15 eV. The XRD results suggested the average crystalline size of the silver­gold loaded CeO2 was 28 nm. From the elemental mapping images, we have visualized that existence and uniform distribution of Ag, Au, Ce, and O in the prepared nanomaterials. The antibacterial activity of unloaded and bimetal loaded CeO2 NPs was evaluated with Gram-positive and Gram-negative bacteria using disc diffusion assay. The AgAu loaded CeO2 NPs exhibited the highest zone of inhibition against E. coli and S. aureus strains when compared with pristine CeO2, Ag loaded CeO2, and Au loaded CeO2 NPs. In addition, the 100 µg mL-1 of CeO2, Ag/CeO2, Au/CeO2 and Ag-Au/CeO2 NPs exposed the 50, 51, 52 and 56% of anticancer activity against the HeLa cells respectively. Overall, this study concludes that the ionic liquid functionalized green synthesized bimetal loaded cerium oxide NPs showed potent antibacterial and anticancer activities.


Assuntos
Antibacterianos/química , Antineoplásicos/química , Líquidos Iônicos/química , Adhatoda/química , Nanopartículas Metálicas/química , Antibacterianos/síntese química , Antibacterianos/farmacologia , Antineoplásicos/síntese química , Antineoplásicos/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Cério/química , Testes de Sensibilidade a Antimicrobianos por Disco-Difusão , Ouro/química , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Química Verde , Células HeLa , Humanos , Adhatoda/metabolismo , Nanopartículas Metálicas/toxicidade , Tamanho da Partícula , Extratos Vegetais/química , Folhas de Planta/química , Folhas de Planta/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Prata/química
14.
Environ Pollut ; 257: 113597, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31744685

RESUMO

The ongoing development of nanotechnology has raised concerns regarding the potential risk of nanoparticles (NPs) to the environment, particularly aquatic ecosystems. A relevant aspect that drives NP toxicity is represented by the abiotic and biotic processes occurring in natural matrices that modify NP properties, ultimately affecting their interactions with biological targets. Therefore, the objective of this study was to perform an ecotoxicological evaluation of CeO2NPs with different surface modifications representative of NP bio-interactions with molecules naturally occurring in the water environment, to identify the role of biomolecule coatings on nanoceria toxicity to aquatic organisms. Ad hoc synthesis of CeO2NPs with different coating agents, such as Alginate and Chitosan, was performed. The ecotoxicity of the coated CeO2NPs was assessed on the marine bacteria Aliivibrio fischeri, through the Microtox® assay, and with the freshwater crustacean Daphnia magna. Daphnids at the age of 8 days were exposed for 48 h, and several toxicity endpoints were evaluated, from the molecular level to the entire organism. Specifically, we applied a suite of biomarkers of oxidative stress and neurotoxicity and assessed the effects on behaviour through the evaluation of swimming performance. The different coatings affected the hydrodynamic behaviour and colloidal stability of the CeO2NPs in exposure media. In tap water, NPs coated with Chitosan derivative were more stable, while the coating with Alginate enhanced the aggregation and sedimentation rate. The coatings also significantly influenced the toxic effects of CeO2NPs. Specifically, in D. magna the CeO2NPs coated with Alginate triggered oxidative stress, while behavioural assays showed that CeO2NPs coated with Chitosan induced hyperactivity. Our findings emphasize the role of environmental modification in determining the NP effects on aquatic organisms.


Assuntos
Cério/química , Daphnia/efeitos dos fármacos , Ecotoxicologia , Nanopartículas/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Bioensaio , Ecossistema , Água Doce/química
15.
Chemosphere ; 243: 125309, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31751925

RESUMO

In the present work, a serial of Cu0.02Fe0.2CeyTi1-yOx catalysts are prepared by sol-gel method and applied for NH3-SCR of NO, meanwhile Cu0.02Fe0.2Ce0.2Ti0.8Ox shows good low-temperature NH3-SCR performance with/without water and an outstanding water resistance. The bulk structure, redox ability, surface acidity and surface species of Cu0.02Fe0.2CeyTi1-yOx are measured and discussed by series of characterization in details to illuminate the reasons for the good low-temperature activity and water resistance. The Ce modification can tune the surface acidic distribution, improve the surface oxygen content and surface oxidation reduction cycle (Ce4+ + Fe2+ ↔ Ce3+ + Fe3+), which contribute the good activity. In addition, the effect of water on NH3-SCR performance over Cu0.02Fe0.2TiOx and Cu0.02Fe0·2Ce0·2Ti0.8Ox are investigated emphatically by in situ DRIFTS.


Assuntos
Catálise , Cério/química , Temperatura Baixa , Óxido Nítrico/isolamento & purificação , Amônia/química , Cério/farmacologia , Óxido Nítrico/química , Oxirredução , Titânio/química , Água/química
16.
Mater Sci Eng C Mater Biol Appl ; 107: 110255, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31761203

RESUMO

Multifunctional nanomaterials integrating therapeutic and imaging modalities in one platform have opened a new era in the present therapeutic strategies. In the present study, a multifunctional silk fibroin-based carrier has been designed for the delivery of antioxidant and imaging agents. One-step desolvation method was used to prepare sulforaphane (antioxidant drug) loaded silk fibroin nanoparticles (SFSNPs). These anionic SFSNPs were further coupled with cationic cerium oxide nanoparticles (CeNPs) and PEI passivated carbon dots (CDs) to form self-assembled CeNP-CD@SFSNPs nanocomposites. CDs were synthesized from mulberry leaves (Morus indica) as green source of carbon and bPEI as a passivating agent to get positively charged CDs. The CDs functioned as molecular probes by emitting green fluorescence while the presence of CeNPs augmented the antioxidant potential due to their unique redox property. Time-dependent in vitro release of sulforaphane was fast in acidic pH than under normal physiological conditions. Cytotoxicity studies were performed on L132 normal epithelial lung cell lines and A549 lung cancer cell lines to analyze the toxicity of the nanocomposites. Green fluorescence from the CDs facilitated in fluorescence microscopic imaging and cellular uptake studies. ROS scavenging capability was analyzed by exposing cells to H2O2 stress using flow cytometry and DCFH-DA staining. Overall, the synthesized CeNP-CD@SFSNPs nanocomposites efficiently reduced ROS levels by simultaneously enabling imaging of the cells. Thus, this CeNP-CD@SFSNPs nanocomposite could be a potential candidate for simultaneous imaging and drug delivery against oxidative stress.


Assuntos
Fibroínas/química , Nanocompostos/química , Nanopartículas/química , Estresse Oxidativo/efeitos dos fármacos , Nanomedicina Teranóstica , Células A549 , Antioxidantes/química , Antioxidantes/metabolismo , Antioxidantes/farmacologia , Carbono/química , Sobrevivência Celular/efeitos dos fármacos , Cério/química , Humanos , Peróxido de Hidrogênio/química , Peróxido de Hidrogênio/toxicidade , Concentração de Íons de Hidrogênio , Isotiocianatos/química , Isotiocianatos/metabolismo , Isotiocianatos/farmacologia , Microscopia de Fluorescência , Nanocompostos/toxicidade , Pontos Quânticos/química , Espécies Reativas de Oxigênio/metabolismo
17.
Anal Chim Acta ; 1096: 76-88, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31883594

RESUMO

In this work, we developed cerium oxide/tin oxide (CeO2/SnO2) nanocatalyst with the assistance of urea by a simple sonochemical method and utilized as an efficient electrode material for electrochemical sensing of anti-inflammatory drug 5-aminosalicylic acid (Mesalamine, MES). The CeO2/SnO2 nanoparticles (NPs) were systematically characterized in terms of their crystal structure, morphologies, and physicochemical properties using XRD, Raman, FESEM, HR-TEM, EDX, mapping, and XPS analysis. The characterization results clearly confirmed that the prepared NPs was formed in the phase of CeO2/SnO2 without any other impurities. The electrochemical properties of CeO2/SnO2 NPs were investigated by EIS, CV, and DPV techniques. The CeO2/SnO2 NPs (9.6 µA) modified GCE demonstrated an excellent and improved electrocatalytic activity in terms of higher anodic peak current and lower peak potential when compared to bare GCE (6.7 µA) and CeO2 NPs/GCE (8.2 µA) for the sensing of MES. The CeO2/SnO2 NPs/GCE shows broader linear response range and lower detection limit of 0.02-1572 µM and 0.006 µM, respectively. Moreover, other potentially interfering compounds such as a similar functional group containing biological substances and inorganic species have no interference effect towards MES sensing. In addition, the practicability of the CeO2/SnO2 NPs/GCE was tested by real sample analysis in commercial MES tablet, human urine, and serum samples with the appreciable recovery results.


Assuntos
Anti-Inflamatórios não Esteroides/sangue , Anti-Inflamatórios não Esteroides/urina , Cério/química , Mesalamina/sangue , Mesalamina/urina , Compostos de Estanho/química , Catálise , Monitoramento de Medicamentos/instrumentação , Técnicas Eletroquímicas/instrumentação , Eletrodos , Humanos , Limite de Detecção , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Sonicação
18.
Biosens Bioelectron ; 148: 111791, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31677526

RESUMO

A smartphone-integrated ratiometric fluorescent sensing system (DPA-Ce-GMP-Eu) for visual and point-of-care testing (POCT) of tetracycline with high sensitivity and accuracy was developed. The blue fluorescence of DPA-Ce-GMP was changed into red by doping with Eu3+ duo to the energy transfer from Ce3+ to Eu3+. Upon exposure to tetracycline, coordination between Eu3+ and tetracycline blocks energy transfer from Ce3+ to Eu3+, converting the fluorescent color from red to blue. The tetracycline detection can be realized within a wide concentration range from 0.01 µM to 45 µM. The limit of detection (LOD) reaches as low as 6.6 nM. To realize quantitative point-of-care detection in real samples, a portable device with smartphone as signal reader and analyzer is further designed to integrate with the DPA-Ce-GMP-Eu sensing platform. The Color Picker APP installed in the smartphone can convert the Red, Green and Blue (RGB) channels of the fluorescence images into digital values. With milk as real sample, tetracycline can be on-site detected with LOD of 10.8 nM. This developed platform presents a great promise for POCT in practical application with merits of low cost, easy carry, simple operation, and excellent selectivity and repeatability.


Assuntos
Antibacterianos/análise , Técnicas Biossensoriais/instrumentação , Contaminação de Alimentos/análise , Smartphone/instrumentação , Tetraciclina/análise , Animais , Cério/química , Desenho de Equipamento , Európio/química , Fluorescência , Corantes Fluorescentes/química , Análise de Alimentos/instrumentação , Limite de Detecção , Leite/química , Carne de Porco/análise , Espectrometria de Fluorescência/instrumentação
19.
Talanta ; 207: 120318, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31594597

RESUMO

This study designed a simplistic, efficient, and greener procedure to synthesize CeO2-CNTs. The analysis of structural and morphological characteristics of nano-composites has been done with regard to different procedures (e.g., EDX, XRD, & FESEM). In addition, simultaneous detection of ascorbic acid (AA), dopamine (DA), uric acid (UA) and acetaminophen (AC) has been examined at the modified glassy carbon electrode with CeO2-CNTs nano-composites. The surface area and electron transfer speed of the interplay between neuro-transmitters and electrode may be efficiently enhanced due to the existence of CeO2 nano-particles on CNTs surfaces. Moreover, electro-chemical behavior of electrodes has been dealt with by differential pulse voltammetry (DPV), impedance analysis (EIS), and cyclic voltammetry (CV). Acceptable linear response of AA, DA, UA and AC respectively have been ranged 0.01-900.0 µM, 0.01-700.0 µM, 0.01-900.0 µM, and 0.01-900.0 µM with determination limits (S/N = 3) of 3.1 nM, 2.6 nM, 2.4 nM and 4.4 nM. Ultimately, this procedure was used with successful results for determining AA, DA, UA and AC in real specimens, which suggested probable uses in other sensing studies.


Assuntos
Acetaminofen/análise , Ácido Ascórbico/análise , Cério/química , Dopamina/análise , Micro-Ondas , Nanotubos de Carbono/química , Ácido Úrico/análise , Acetaminofen/química , Ácido Ascórbico/química , Dopamina/química , Eletroquímica , Eletrodos , Química Verde , Concentração de Íons de Hidrogênio , Limite de Detecção , Nanopartículas/química , Nanotecnologia , Propriedades de Superfície , Fatores de Tempo , Ácido Úrico/química
20.
Chemosphere ; 239: 124769, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31526997

RESUMO

In this study, Cerium chloride-induced conformational changes of Bovine Liver Catalase (BLC) has been investigated by molecular docking and further supported by various biophysical techniques. The temporal change of catalytic activity of BLC has also been studied in presence of Ce(III) with different buffer solution in vitro at 25 °C. The differential binding of Ce(III) to BLC observed by simulation study was well supported by the differential regulation of BLC activity in different buffers. After 1 h of incubation with CeCl3, the reduction in activity of BLC was maximum in MOPS, HEPES and Tris buffer, whereas no change in activity was noticed in phosphate buffer. Isothermal Titration Calorimetric (ITC) study also supports the differential binding of Ce(III) to BLC in different buffers. Ce(III)-induced conformational transition in BLC was followed as a function of concentration. Nevertheless, with 24 h incubation of CeCl3 the activity of BLC was highest with higher molar concentration of CeCl3 suggesting the conformational stability of BLC in presence of Ce(III). The compromised activity of BLC in response to Ce(III) is due to the induced conformational change and the degree of change in secondary conformation of BLC was maximum in MOPS, HEPES and Tris and least in phosphate buffer. Therefore, the reduced activity of BLC is controlled by the direct interaction of Ce(III) in the active site of BLC in Tris buffer or indirect interaction of Ce(III) in the non-active site of BLC in MOPS and HEPES buffer.


Assuntos
Catalase/química , Catalase/metabolismo , Cério/química , Fígado/enzimologia , Animais , Tampões (Química) , Calorimetria , Domínio Catalítico , Bovinos , Cério/metabolismo , Cloretos/química , Simulação de Acoplamento Molecular , Conformação Proteica
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