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1.
Luminescence ; 36(6): 1469-1475, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34022100

RESUMO

Fifty-four Eucommia ulmoides leaves were subjected to a hydrothermal technique to synthesize carbon dots (CDs) of 3.55 ± 1.45 nm size. The nanomaterial possessed excellent stability and strong fluorescence emission (φf 42.3%). In a neutral buffer solution, the fluorescence signals of CDs solution were enhanced by aluminium ion without interference from other ions. Degree of enhancement correlated linearly with the Al3+ content in the range 0.01-2.5 mM. Response of this method was fast and sensitive (detection limit was 23 nM). The CDs performed successfully as a sensitive sensor for trace Al3+ determination in water samples, and satisfactory results were obtained.


Assuntos
Carbono , Pontos Quânticos , Corantes Fluorescentes , Espectrometria de Fluorescência , Água
2.
Anal Methods ; 12(43): 5195-5201, 2020 11 21.
Artigo em Inglês | MEDLINE | ID: mdl-33090130

RESUMO

N-Doped carbon dots (CDs) had been simply produced by a one-pot synthesis process using amygdalic acid and threonine. The resulting product was water-soluble and exhibited strong luminescence emission with a fluorescence quantum yield of 19.25%. The emission of CDs was obviously and selectively decreased upon adding 2,4,6-trinitrophenol (TNP). It was proved that the fluorescence resonance energy transfer was the main mechanism for quenching. An efficient fluorescence probe with satisfied sensitivity for TNP determination was found. The range of the linear response for TNP detection was 0.5-40.0 µmol L-1, and the limit of detection was 20 nmol L-1. The content of trace TNP in water samples was successfully detected with this method. The CDs were also applied in HepG2 cell imaging and the fabrication of fluorescent films by dispersing the solid freeze-drying CD (SCD) powder into PMMA, which exhibited some application value in biology and photovoltaics.

3.
Crit Care Med ; 48(11): e1004-e1011, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32897668

RESUMO

OBJECTIVES: To evaluate and compare the efficacy of National Early Warning Score, National Early Warning Score 2, Rapid Emergency Medicine Score, Confusion, Respiratory rate, Blood pressure, Age 65 score, and quick Sepsis-related Organ Failure Assessment on predicting in-hospital death in patients with coronavirus disease 2019. DESIGN: A retrospective, observational study. SETTING: Single center, West Campus of Wuhan Union hospital-a temporary center to manage critically ill patients with coronavirus disease 2019. PATIENTS: A total of 673 consecutive adult patients with coronavirus disease 2019 between January 30, 2020, and March 14, 2020. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Data on demography, comorbidities, vital signs, mental status, oxygen saturation, and use of supplemental oxygen at admission to the ward were collected from medical records and used to score National Early Warning Score, National Early Warning Score 2, Rapid Emergency Medicine Score, Confusion, Respiratory rate, Blood pressure, Age 65 score, and quick Sepsis-related Organ Failure Assessment. Total number of patients was 673 (51% male) and median (interquartile range) age was 61 years (50-69 yr). One-hundred twenty-one patients died (18%). For predicting in-hospital death, the area under the receiver operating characteristics (95% CI) for National Early Warning Score, National Early Warning Score 2, Rapid Emergency Medicine Score, Confusion, Respiratory rate, Blood pressure, Age 65 score, and quick Sepsis-related Organ Failure Assessment were 0.882 (0.847-0.916), 0.880 (0.845-0.914), 0.839 (0.800-0.879), 0.766 (0.718-0.814), and 0.694 (0.641-0.746), respectively. Among the parameters of National Early Warning Score, the oxygen saturation score was found to be the most significant predictor of in-hospital death. The area under the receiver operating characteristic (95% CI) for oxygen saturation score was 0.875 (0.834-0.916). CONCLUSIONS: In this single-center study, the discrimination of National Early Warning Score/National Early Warning Score 2 for predicting mortality in patients with coronavirus disease 2019 admitted to the ward was found to be superior to Rapid Emergency Medicine Score, Confusion, Respiratory rate, Blood pressure, Age 65 score, and quick Sepsis-related Organ Failure Assessment. Peripheral oxygen saturation could independently predict in-hospital death in these patients. Further validation of our finding in multiple settings is needed to determine its applicability for coronavirus disease 2019.


Assuntos
Betacoronavirus , Infecções por Coronavirus/diagnóstico , Infecções por Coronavirus/mortalidade , Estado Terminal/mortalidade , Escore de Alerta Precoce , Pneumonia Viral/diagnóstico , Pneumonia Viral/mortalidade , Idoso , Pressão Sanguínea , COVID-19 , Feminino , Mortalidade Hospitalar , Humanos , Unidades de Terapia Intensiva , Masculino , Pessoa de Meia-Idade , Escores de Disfunção Orgânica , Pandemias , Prognóstico , Estudos Retrospectivos , Medição de Risco , SARS-CoV-2
4.
Talanta ; 202: 375-383, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31171198

RESUMO

Two kinds of carbon dots (CDs) with different solubility, aqueous soluble CDs (ACDs) and organic soluble CDs (OCDs), were produced at the same time by one step hydrothermal synthesis method using sorbic acid and proline as carbon precursor and nitrogen dopant, respectively. The synthesized CDs were characterized by means of UV, fluorescence, TEM, elemental analysis, IR and XPS et al. Based on the effective and proportional fluorescence quenching by Cr(VI), ACDs were successfully used as a high sensitive and selective probe for Cr(VI) detection. Internal filtration effect (IFE) played an important role in the quenching process. Under the optimal conditions, linear response for Cr(Ⅵ) was observed in the range of 0.5-100 µmol/L, and the calculated detection limit was 34 nmol/L. The method has been satisfactorily applied to detect Cr(VI) ions in real water samples of our campus. Then, the ACDs were further applied for cell imaging in B16F10 cells. Furthermore, OCDs were well dispersed into PMMA to fabricate OCDs/PMMA composites as fluorescent films.

5.
Chem Soc Rev ; 48(3): 885-907, 2019 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-30601526

RESUMO

Aluminosilicate zeolites with controllable morphology have attracted considerable attention due to their potential applications in catalysis, adsorption, and separation technologies, as well as the biomedical field. However, the rational design and preparation of zeolites with the required morphology have not been achieved because the zeolite crystallization mechanism has not been fully understood, and therefore, the nucleation and crystal growth processes cannot be oriented. This paper reviews the progresses achieved in zeolite morphology control. The chemical compositions of the synthesis gel, including template (or the structure-directing agent) and framework heteroatoms, silica and alumina sources, alkali metal cations and mineralization ions, crystallization conditions, and synthesis methods have a considerable impact on the crystal morphology. The oriented assembly of zeolite crystals into special morphologies, such as hierarchical porous structures, zeolite membranes, hollow zeolite spheres, and core@shell-structured zeolites, can be realized by using soft and/or hard template methods and adjusting the synthesis and crystallization conditions. In addition, zeolite crystallization and crystal assembly mechanisms are investigated for providing an overall insight into the regulation of zeolite crystal morphology.

6.
Chemphyschem ; 19(4): 496-503, 2018 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-29334171

RESUMO

Although dienes or trienes have been shown to be possible precursors for cyclization, direct cyclization of alkenes or alkoxides has not been systematically studied yet. Thus, the reaction mechanism of cyclization of linear alkenes over H-ITQ-13 was investigated here by density functional theory considering dispersive interactions (DFT-D). The similar free energy of different linear alkoxides of the same carbon number suggests that they can co-exist in the H-ITQ-13 intersection at 673.15 K during the methanol to olefins (MTO) process. The formation of linear alkenes by olefins methylation with methoxyl groups (ZOCH3 ), trimethyloxonium ions (TMO+ ), and methanol are kinetically more favorable than by dimerization of olefins. Linear alkoxides or alkenes prefer direct cyclization to cycloalkanes rather than hydride transfer to diene. This study provides new insight into the alkene cyclization and aromatization mechanisms in MTO process.

7.
J Phys Chem A ; 118(39): 8901-10, 2014 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-24559413

RESUMO

The mechanism of olefin elimination in the process of methanol-to-olefins (MTO) over a series of zeolites like HZSM-5, HMOR, HBEA, and HMCM-22 was investigated by DFT-D calculations, which is a crucial step that controls the MTO product distribution. The results demonstrate that the manners of olefin elimination are related to the pore structure of zeolite catalyst and the interaction between proton transfer reagent (water or methanol) and zeolite acidic framework. The indirect spiro mechanism is preferable to the direct mechanism over HMOR, HBEA, and HMCM-22 zeolites with large pores, as suggested by the energy barrier of rate-determining step and the potential energy surface (PES), but is unfavorable over HZSM-5 with medium-sized pores due to the steric hindrance of spiro intermediates. Over various zeolites, water and methanol perform differently in proton transfer to form the spiro intermediates; over HMOR and HBEA with strong acidity, water is superior to methanol in promoting propene elimination, whereas over HMCM-22 with relatively weaker acidity, methanol is more favorable as a proton transfer reagent.

8.
Artigo em Inglês | MEDLINE | ID: mdl-24036307

RESUMO

In this work, the interaction of jatrorrhizine with human serum albumin (HSA) was studied by means of UV-vis and fluorescence spectra. The intrinsic fluorescence of HSA was quenched by jatrorrhizine, which was rationalized in terms of the static quenching mechanism. The results show that jatrorrhizine can obviously bind to HSA molecules. According to fluorescence quenching calculations, the bimolecular quenching constant (kq), apparent quenching constant (KSV) at different temperatures were obtained. The binding constants K are 4059 L mol(-1) and 1438 L mol(-1) at 299 K and 304 K respectively, and the number of binding sites n is almost 1. The thermodynamic parameters determined by the Van't Hoff analysis of the binding constants (ΔH -12.25 kJ mol(-1) and ΔS 28.17 J mol(-1) K(-1)) clearly indicate that the electrostatic force plays a major role in the process. The efficiency of energy transfer and the distance between the donor (HSA) and the acceptor (jatrorrhizine) were calculated as 22.2% and 3.19 nm according to Föster's non-radiative energy transfer theory. In addition, synchronous fluorescence spectroscopy reveals that jatrorrhizine can influence HSA's microstructure. That is, jatrorrhizine is more vicinal to tryptophane (Trp) residue than to tyrosine (Tyr) residue and the damage site is also mainly at Trp residue. Molecular modeling result shows that jatrorrhizine-HSA complex formed not only on the basis of electrostatic forces, but also on the basis of π-π staking and hydrogen bond. The research results will offer a reference for the studies on the biological effects and action mechanism of small molecule with protein.


Assuntos
Berberina/análogos & derivados , Modelos Moleculares , Albumina Sérica/química , Albumina Sérica/metabolismo , Berberina/química , Berberina/metabolismo , Sítios de Ligação , Transferência de Energia , Humanos , Cinética , Soluções , Espectrometria de Fluorescência , Temperatura
9.
Artigo em Inglês | MEDLINE | ID: mdl-23220665

RESUMO

A series of oxazole derivatives, 5-methyl-2-(p-methylphenyl)-4-acetyl oxazole (MMPAO), 5-methyl-2-(p-methoxyphenyl)-4-acetyl oxazole (MOPAO), 5-methyl-2-(p-N,N'-dimethylamino-phenyl)-4-acetyl oxazole (MDMAPAO) and 5-methyl-2-(p-N,N'-diphenylaminophenyl)-4-acetyl oxazole (MDPAPAO) have been synthesized and studied to compare their photophysical properties. The UV-visible absorption spectra of MDMAPAO and MDPAPAO are bathochromatically shifted as compared to that of MMPAO and MOPAO. The fluorescence emission of MDPAPAO is very sensitive to the polarity of solvents. The magnitude of change in the dipole moment was calculated using the Lippert-Mataga equation. MDPAPAO shows the highest change in the dipole moment (Δu=13.3D) than that of the other three oxazole derivatives. The spectral properties including fluorescence quantum yield and lifetime were determined in solvents with different polarities. MDPAPAO displays the highest fluorescence quantum yield and lifetime, following a bi-exponential fluorescent decay fashion. Our result demonstrates that the excited state of MDPAPAO possesses the property of intramolecular charge transfer.


Assuntos
Elétrons , Oxazóis/química , Derivados de Benzeno/síntese química , Derivados de Benzeno/química , Oxazóis/síntese química , Solventes/química , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta
10.
Luminescence ; 28(3): 412-8, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-22753316

RESUMO

A carbazole-based compound with intramolecular charge transfer (ICT) characteristics, 3,6-bis-((N-ethylcarbazole-3-)-propene-1-keto)-N-ethylcarbazole (BCzPCz) was synthesized by N-alkylation, acetylation and aldol condensation. BCzPCz was further confirmed by IR and (1)H NMR. The central N-ethylcarbazole was connected with two N-ethylcarbazole units through the propenone group in BCzPCz. N-ethylcarbazole and carbonyl groups were electron donors (D) and acceptors (A), respectively. The UV-vis absorption and fluorescence characteristics of BCzPCz were also investigated in different solvents. Solvatochromism was attributed to ICT complex formation in singlet excited state. Magnitude of the change in the dipole moment was 24.78 D according to Lippert-Mataga equation. Fluorescence of BCzPCz was significantly affected by pH and was quenched in acidic medium. Fluorescence quantum yield of BCzPCz was 0.516 in ethanol. Experimental results showed its potential use as a fluorescence probe and as two-photon absorption material.


Assuntos
Carbazóis/química , Corantes Fluorescentes/química , Fluorescência , Espectroscopia de Ressonância Magnética , Estrutura Molecular
11.
ChemSusChem ; 5(7): 1274-9, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22696279

RESUMO

A hierarchical microporous carbon material with a Brunauer-Emmett-Teller surface area of 1348 m(2) g(-1) and a pore volume of 0.67 cm(3) g(-1) was prepared from yeast through chemical activation with potassium hydroxide. This type of material contains large numbers of nitrogen-containing groups (nitrogen content >5.3 wt%), and, consequently, basic sites. As a result, this material shows a faster adsorption rate and a higher adsorption capacity of CO(2) than the material obtained by directly carbonizing yeast under the same conditions. The difference is more pronounced in the presence of N(2) or H(2)O, showing that chemical activation of discarded yeast with potassium hydroxide could afford high-performance microporous carbon materials for the capture of CO(2).


Assuntos
Dióxido de Carbono/química , Dióxido de Carbono/isolamento & purificação , Carbono/química , Saccharomyces cerevisiae/química , Adsorção , Hidróxidos/química , Nitrogênio/química , Porosidade , Compostos de Potássio/química
12.
Artigo em Inglês | MEDLINE | ID: mdl-22613127

RESUMO

The binding mode and mechanism of the interactions between two planar cationic alkaloids chelerythrine (Che) and sanguinarine (San) with calf thymus DNA (ctDNA) were systematically investigated at pH 5.40 using UV-vis absorption spectroscopy, fluorescence spectroscopy and cyclic voltammetry. Che and San show strong fluorescence at 570 and 589 nm, respectively. Che displays fluorescence enhancement with ctDNA whereas the fluorescence of San is quenched on interaction with ctDNA. In addition, UV-vis spectra of both alkaloids show apparent hypochromicity and are bathochromic shifted, indicating that they could intercalate into ctDNA bases. The fluorescence polarization of Che and San increases in the presence of ctDNA, again implying the intercalation of two alkaloids with ctDNA. This conclusion was also supported by the results obtained from anion quenching and cyclic voltammetry. The binding constants of both alkaloids with ctDNA were calculated in the order of 10(5)L/mol. San binds with ctDNA 3-fold stronger than Che. The stoichiometric bindings are five nucleotides per Che or San. Electrostatic binding also exists between the alkaloids and DNA helix. Finally, theoretical calculations show that only certain parts of Che and San molecules intercalate into the DNA helix.


Assuntos
Alcaloides/metabolismo , Benzofenantridinas/metabolismo , DNA/metabolismo , Isoquinolinas/metabolismo , Luminescência , Absorção , Técnicas Eletroquímicas , Polarização de Fluorescência , Cinética , Cloreto de Sódio/química , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta
13.
Spectrochim Acta A Mol Biomol Spectrosc ; 73(2): 221-5, 2009 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-19303807

RESUMO

A novel pyrazoline derivative, named 1-phenyl-3-biphenyl-5-(N-ethylcarbazole-3-yl)-2-pyrazoline, was synthesized, and its structure was confirmed by means of IR, (1)H NMR, and elementary analysis. The compound emits strong yellow fluorescence. Decrease of fluorescence intensity of the pyrazoline derivative in the presence of calf thymus DNA (ct DNA) is observed, and the quenching obey Stern-Volmer equation. There is a single quenching mechanism for the complex, which belongs to static quenching. KI quenching study shows that the magnitude of K(SV) of the bound pyrazoline is lower than that of the free one. It is also found that ionic strength could affect the interaction. Binding constants for pyrazoline with ct DNA and salmon sperm DNA (ss DNA) are in the same order of 10(4) molL(-1), and binding site size are about 1 per base pairs. Experimental results indicate that the new compound might insert into DNA base pairs by intercalative binding mode.


Assuntos
Sondas de DNA/síntese química , Corantes Fluorescentes , Pirazinas , Animais , Bovinos , Sondas de DNA/química , Corantes Fluorescentes/síntese química , Corantes Fluorescentes/química , Concentração de Íons de Hidrogênio , Estrutura Molecular , Pirazinas/síntese química , Pirazinas/química , Espectrometria de Fluorescência
14.
Talanta ; 77(5): 1707-14, 2009 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-19159787

RESUMO

The synthesis and absorption/fluorescence properties of two novel intramolecular charge transfer (ICT) compounds of (fluorene-2-yl)-(9-ethylcarbazole-3-yl) ketene and 1-phenyl-3-(fluorenone-2-yl)-5-(9-ethylcarbazole-3-yl)-2-pyrazoline were reported. The primary structure of the target compounds was characterized by IR and (1)H NMR. The systems contained a fluorenone or a propenon group as an electron acceptor (A) and an N-ethylcarbazole and a pyrazoline group as electron donors (D). From the emissive properties it was concluded that the electronic coupling between D and A was sufficient to allow charge transfer in these molecules. The ICT maximal emission displayed a large wavelength shift and Stokes shifts increased in response to the increase of the solvent polarity. The highly solvatochromic properties made the two compounds of great interest as new classes of fluorescent probes, electroluminescent and electrofax materials.


Assuntos
Corantes Fluorescentes/síntese química , Análise Espectral/métodos , Elétrons , Etilenos , Corantes Fluorescentes/química , Cetonas , Pirazóis , Solventes , Espectrometria de Fluorescência
15.
Talanta ; 77(3): 1043-9, 2009 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-19064089

RESUMO

The spectroscopic characterizations of solid substrate room temperature phosphorescence (SS-RTP) of palmatine (Pal) have been studied. Strong RTP signal at 615nm can be induced on filter paper in the presence of TIAc. The interaction between calf thymus DNA (ctDNA) and Pal has been investigated at pH 6.90 using fluorescence, UV-vis, SS-RTP and cyclic voltammogram spectroscopy. Strong binding affinity of Pal with DNA is revealed from the absorption and fluorescence studies in the liquid state. With the addition of ctDNA, the fluorescence intensity of Pal is enhanced greatly and UV-vis spectra show no apparent hypochromicity and red shift, which indicates that Pal intercalates into ctDNA bases. However, this conclusion could not explain the phenomena from fluorescence polarization and denatured DNA measurements, which indicate that groove binding is at least the main binding mode. Binding constant and binding site size have been calculated to be 2.57x10(4)L/mol and 0.16 based on Scatchard plot from fluorescence titration data. Groove binding has also been supported by phosphorescence lifetime and anion quenching experiments. Above studies demonstrate that there should exist intercalative binding and groove binding in the interaction of Pal and DNA. Furthermore, cyclic voltammogram study suggests that electrostatic binding exists at the same time exactly. Taken together, the binding model obtained in this study is mixed-mode.


Assuntos
Alcaloides de Berberina/análise , Alcaloides de Berberina/química , DNA/análise , DNA/química , Espectrometria de Fluorescência/métodos , Animais , Bovinos , Filtração , Concentração de Íons de Hidrogênio , Compostos Inorgânicos/química , Medições Luminescentes , Estrutura Molecular , Espectrofotometria , Especificidade por Substrato
16.
Artigo em Inglês | MEDLINE | ID: mdl-15036084

RESUMO

A comparative study on the spectroscopic behavior of cryptotanshinone (CTan), tanshinone IIA (Tan IIA), and tanshinone I (Tan I) has been investigated, including UV-Vis absorption, low temperature phosphorescence (LTP), low temperature fluorescence (LTF), paper substrate-room temperature phosphorescence (PS-RTP), paper substrate-room temperature fluorescence (PS-RTF) and fluorescence in liquid (LF). The effect of pH on the luminescence intensity is discussed. Lifetime and polarization of the LTP and RTP have been examined with phosphorescence lifetime in the range of 0.6-0.9s and polarization in the range of 0.10-0.27. Analytical characteristics of LF, PS-RTF and PS-RTP of CTan, Tan IIA, and Tan I have been studied.


Assuntos
Fenantrenos/análise , Espectrometria de Fluorescência/métodos , Espectrofotometria/métodos , Abietanos , Concentração de Íons de Hidrogênio , Modelos Químicos , Temperatura , Fatores de Tempo , Raios Ultravioleta
18.
Spectrochim Acta A Mol Biomol Spectrosc ; 59(12): 2759-66, 2003 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-14499836

RESUMO

The inclusion complexes of beta-cyclodextrin (beta-CD) and HP-beta-cyclodextrin (HP-beta-CD) with a kind of tanshinone, cryptotanshinone (CTan) were investigated by using spectrophotometry. Stable inclusion complexes were established in solution and in solid state and were characterized by UV, IR and 1H NMR spectra, respectively. The optimum pH for inclusion is about 7.5. Stoichiometry of the inclusion complex is 1:1. The stabilities of beta-CD and HP-beta-CD to CTan were in the order: beta-CD

Assuntos
Ciclodextrinas/química , Fenantrenos/química , beta-Ciclodextrinas , 2-Hidroxipropil-beta-Ciclodextrina , Ciclodextrinas/metabolismo , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Fenantrenos/metabolismo , Espectrofotometria Infravermelho , Espectrofotometria Ultravioleta , Termodinâmica
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