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1.
Sci Total Environ ; 834: 155176, 2022 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-35447176

RESUMO

Global climate change increased the frequency of extreme rainfall events, leading to higher flood risk. In addition to the personal and property losses, another important consequence of a flood disaster was release and exposure risks from emerging contaminants, which was usually overlooked. The remobilization and fate of the antibiotics induced by floods remain unclear. We captured antibiotic concentrations around the Chaohu Lake after an unprecedented flood with a range of 5.0-317 ng/L. Higher concentrations in polder waters than their receiving rivers were attributed to the antibiotic release from soil particles and the sharp increase of water: soil ratio by flood storage. Source apportionment analysis of antibiotics implied that diffuse pollution by manure application and aquaculture activity was the predominant sources. Commonalities of spatial variations of antibiotics in polders were related to the condition of waterlogging and pollution source. The total antibiotic storage for all submerged polders was estimated at 27.9 kg. The concentrations and risks from pumping floodwater detained by polders into the lake were much higher than that from discharging flood directly into the lake. The retention-reaction-remobilization process would pose unexpectedly high risks for the lake. This study provided a new sight for constructing ecological wetland flood storage areas.

2.
Chem Commun (Camb) ; 58(24): 3925-3928, 2022 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-35244125

RESUMO

Adjuvants are important components in vaccines to increase the immunogenicity of proteins and induce optimal immunity. In this study, we designed a novel ternary adjuvant system Alum + c-GAMP + poly(I:C) with STING agonist 3,3'-c-GAMP (c-GAMP) and TLR3 agonist poly(I:C) co-adsorbed on the conventional adjuvant aluminum gel (Alum), and further constructed an S1 protein vaccine. Two doses of vaccination with the ternary adjuvant vaccine were sufficient to induce a balanced Th1/Th2 immune response and robust humoral and cellular immunity. Additionally, the ternary adjuvant group had effective neutralizing activity against live virus SARS-CoV-2 and pseudovirus of all variants of concern (alpha, beta, gamma, delta and omicron). These results indicate that the ternary adjuvants have a significant synergistic effect and can rapidly trigger potent immune responses; the combination of the ternary adjuvant system with S1 protein is a promising COVID-19 vaccine candidate.


Assuntos
COVID-19 , SARS-CoV-2 , Adjuvantes Imunológicos/farmacologia , Compostos de Alúmen , Alumínio , Animais , Anticorpos Antivirais , COVID-19/prevenção & controle , Vacinas contra COVID-19/farmacologia , Humanos , Imunidade Celular , Camundongos , Camundongos Endogâmicos BALB C , Poli I
3.
Iran J Immunol ; 19(1): 2, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-35293343

RESUMO

BACKGROUND: Follicular helper T lymphocyte (Tfh) promotes antibody production by B lymphocytes in various diseases, including Pulmonary Tuberculosis (PTB). OBJECTIVE: To explore the potential role of Tfh cells and assess the expression level of PD-1, and IL-21 in PTB. METHODS: 54 newly diagnosed smear-positive PTB, 27 people with latent tuberculosis (LTB) and 27 healthy controls (HC) were enrolled. The PTB group was further divided based on the range of lung field involved (focus number>=3, PTB-X3; <3, PTB-X2). After 6-month therapy, sputum smear (positive, PTB-SP; negative, PTB-SN) or imaging examinations (lesion reduction significant, PTB-os; insignificant, PTB-s) were used to evaluate the conditions of PTB patients. Blood samples were collected from PTB group at month six. CD4+CXCR5+Tfh, and its subsets, CD4+CXCR5+PD-1+Tfh and CD4+CXCR5+ICOS+Tfh in peripheral blood mononuclear cells (PBMCs) were detected. Serum IL-21 concentrations were measured. RESULTS: The frequencies of CD4+CXCR5+Tfh, CD4+CXCR5+ICOS+Tfh and CD4+CXCR5+PD-1+Tfh were higher in PTB group than in HC. IL-21, IL-4 and IFNγ concentrations were significantly higher in PTB group than in HC. The proportion of CD4+CXCR5+Tfh in PTB-X2 was lower than in PTB-X3 group. CD4+CXCR5+PD-1+Tfh proportion in PTB-X2 was lower than that in the PTB-X3. After treatment, CD4+CXCR5+Tfh proportion was significantly lower in the PTB-SN group. CD4+CXCR5+Tfh was lower in the PTB-os group than in the PTB-s group. However, the CD4+CXCR5+PD-1+Tfh and cytokine concentrations of IL-21 were not different. CONCLUSIONS: CD4+CXCR5+Tfh level might predict the sputum results, and lesion decrease rate while CD4+CXCR5+PD-1+Tfh subset and IL-21 were not associated with sputum results or lesion decrease after treatment.


Assuntos
Células T Auxiliares Foliculares , Tuberculose Pulmonar , Humanos , Leucócitos Mononucleares/metabolismo , Receptores CXCR5/metabolismo , Estudos Retrospectivos
4.
Int Immunopharmacol ; 101(Pt B): 108153, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34678689

RESUMO

B7-H3 (CD276 molecule) is an immune checkpoint from the B7 family of molecules that acts more as a co-inhibitory molecule to promote tumor progression. It is abnormally expressed on tumor cells and can be induced to express on antigen-presenting cells (APCs) including dendritic cells (DCs) and macrophages. In the tumor microenvironment (TME), B7-H3 promotes tumor progression by impairing T cell response, promoting the polarization of tumor-associated macrophages (TAMs) to M2, inhibiting the function of DCs, and promoting the migration and invasion of cancer-associated fibroblasts (CAFs). In addition, through non-immunological functions, B7-H3 promotes tumor cell proliferation, invasion, metastasis, resistance, angiogenesis, and metabolism, or in the form of exosomes to promote tumor progression. In this process, microRNAs can regulate the expression of B7-H3. B7-H3 may serve as a potential biomarker for tumor diagnosis and a marker of poor prognosis. Immunotherapy targeting B7-H3 and the combination of B7-H3 and other immune checkpoints have shown certain efficacy. In this review, we summarized the basic characteristics of B7-H3 and its mechanism to promote tumor progression by inducing immunosuppression and non-immunological functions, as well as the potential clinical applications of B7-H3 and immunotherapy based on B7-H3.


Assuntos
Antígenos B7/metabolismo , Regulação da Expressão Gênica/fisiologia , Antígenos B7/genética , Citocinas/genética , Citocinas/metabolismo , Humanos , Macrófagos , Linfócitos T/fisiologia , Distribuição Tecidual
5.
J Environ Manage ; 293: 112953, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34102496

RESUMO

Antibiotics receive many concerns since their negative environmental impacts are being revealed, especially in aqua-agricultural areas. Rainfall events are responsible for transferring excess contaminants to receiving waters. However, the understanding of antibiotics transport and fate responding to rainfall events was constrained by limited event-based data and lacking integrated consideration of dissolved and particulate forms. We developed an intensive monitoring strategy to capture responses of fourteen antibiotics to different types of rainfall events and inter-event low flow periods. Pollutant-rich suspended particles, as high as 1471 ng/g, were found in low flow periods while the very heavy rainfall events and consecutive rainfall events stimulated the release of antibiotics from eroded soil particles to river water. Therefore, these rainfall events drove radical increase of dissolved antibiotic concentration up to 592 ng/L and total flux up to 25.0 g/d. Sulfonamides were particularly sensitive to rainfall events because of their residues in manure-applied agricultural lands. Transport dynamics of most antibiotics were accretion whereas only clarithromycin exhibited a dilution pattern by concentration-discharge relationships. Aquaculture ponds were inferred to significantly contribute tetracycline, oxytetracycline, and clarithromycin. Conventional contaminants were compared to discriminate potential sources of antibiotics and imply effective catchment management. The results provided novel insights into event-based drivers and dynamics of antibiotics and could lead to appropriate management strategy.


Assuntos
Rios , Poluentes Químicos da Água , Agricultura , Antibacterianos/análise , Monitoramento Ambiental , Poluentes Químicos da Água/análise
6.
J Org Chem ; 85(2): 1001-1008, 2020 01 17.
Artigo em Inglês | MEDLINE | ID: mdl-31872767

RESUMO

Here, we report a practical C-H imidation of five-membered heterocycles under metal-free conditions. We also report the first dual C-H bond aminobromination of thiophenes, with benzotriazole, saccharin, 1,2,4-triazole, benzimidazole, pyrazole, 4-bromopyrazole, 5-methyltetrazole, and dibenzenesulfonimides as effective amine sources. Mechanistic studies support the radical pathway of the imidation and aminobromination reactions.

8.
J Environ Manage ; 244: 13-22, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31103730

RESUMO

The occurrence and spatio-temporal patterns of five tetracyclines (TCs) and six of their degradation products were investigated in twenty-eight drinking water sources along the lower Yangtze River (LYR) over dry, normal and flood seasons. Tetracycline (TC), oxytetracycline (OTC) and doxytetracycline (DXC) were the dominant antibiotics detected with the highest occurrence. The maximum concentrations of TC, OTC and DXC were found in dry season as 11.16, 18.98, and 56.09 ng/L, respectively, because of the low dilution, low degradation, and high consumption in this season. Cluster analysis indicated distinct variations in the TCs' compositional profiles in both space and time. OTC and its metabolites contributed 18.5-59.6% of the TC load in dry season, possibly due to the seasonally increased release of pharmaceutical OTCs from sewage effluents, but they were seldom detected in other seasons. Pollution load index analysis showed that tributaries carrying large amounts of veterinary TCs derived from breeding wastewater and untreated rural sewage contributed larger proportions of the TC load for most drinking water sources than sewage outlets. The contribution ratio of the TC load from tributaries (74.5%) was approximately three times higher than that from sewage discharges (25.5%). The study demonstrated that the control of load from tributaries is the key to mitigating TC pollution of the drinking water sources in the LYR. An effective source tracking method for evaluating the contribution of antibiotic load from multiple diffuse pollution origins and identifying the high-risk contamination sources was established for antibiotic management and control.


Assuntos
Água Potável , Poluentes Químicos da Água , Antibacterianos , China , Monitoramento Ambiental , Rios , Tetraciclinas
9.
Org Lett ; 21(7): 2052-2055, 2019 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-30896184

RESUMO

Herein, a practical Cu-catalyzed selenodifluoromethylation protocol was developed, using readily available diselenides as the selenium source under external-oxidant-free conditions. Various structurally diverse 4-seleno-substituted α,α-difluoro-γ-lactams were obtained in moderate to excellent yields. Easy scaleup and the potential for product derivatization make this method attractive for the preparation of other valuable fIuorinated γ-lactams. Mechanistic studies suggest that the catalytic system may involve a radical pathway.

10.
Anat Histol Embryol ; 48(1): 22-32, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30353570

RESUMO

Fish are the most diverse species of all vertebrate groups, and their blood cells have shown variable characteristics in terms of morphology. Cytochemical staining for enzyme activity in blood leukocytes will help assess the immune function of fish. We characterize blood cells from crucian carp (Carassius auratus) and grass carp (Ctenopharyngodon idellus) by using a Diff-Quick stain as well as different cytochemical methods. Blood specimens obtained from crucian carp and grass carp were evaluated after cytochemical staining for acid phosphatase (ACP), alkaline phosphatase (ALP), naphthol AS chloroacetate esterase (AS-DNCE), naphthyl acetate esterase (NAE), α-naphthyl butyrate esterase (NBE), peroxidase (MPO) and periodic acid-Schiff's reaction (PAS) using commercial kits. Blood cell types were evaluated based on their morphological characteristics and the presence or absence of specific chromogen. The expression pattern of enzymes was similar between the two Cyprinidae and was also broadly consistent with other fish species. However, there were some interesting differences detected between crucian carp and grass carp, including naphthol AS chloroacetate esterase activity in monocytes, peroxidase activity and location in thrombocytes. The ACP, ALP and MPO expressions of different leukocytes of the two Cyprinidae were evaluated by Image Pro Plus and were analysed for statistical significant differences. This investigation provides basic haematology and enzyme activity analyses for crucian carp and grass carp and serves as an approach to evaluating the immune response of fish.


Assuntos
Células Sanguíneas/citologia , Carpas/sangue , Carpa Dourada/sangue , Histocitoquímica/veterinária , Fosfatase Ácida/sangue , Fosfatase Alcalina/sangue , Animais , Hidrolases de Éster Carboxílico/sangue , Regulação da Expressão Gênica/genética , Hematologia , Naftol AS D Esterase/sangue , Reação do Ácido Periódico de Schiff , Peroxidase/sangue , Coloração e Rotulagem
11.
Org Biomol Chem ; 16(36): 6655-6658, 2018 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-30183799

RESUMO

An efficient Cu-catalyzed method for direct C-N bond formation on the C-3 position of imidazo[1,2-a]pyridines is reported. The robust copper catalyst tolerated a wide range of functional groups and set the stage for the synthesis of diversely decorated imidazo[1,2-a]pyridines. Preliminary experimental results show that the reaction mechanism is consistent with C-3 radical functionalization.

12.
Environ Pollut ; 220(Pt B): 1301-1310, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27839991

RESUMO

The study investigated the degradation behaviors of swine farm tetracyclines (TCs) at a catchment scale and explored whether multi-pond systems could be beneficial to the interception of TCs so as to reduce the pollution risk to receiving rivers. The occurrence and migration of 12 kinds of tetracycline antibiotics, including their degradation products, were studied in four swine farms of the Meijiang River basin in China. The migration paths of the TCs were examined through sampling and analyzing the soil and/or sediment at different points along the swine wastewater outlet, which included sewer, sewage pond, mixed-canal (stream and sewage), farmland (paddy and upland soil) and finally the river. TC concentrations of all collected samples were obtained by solid phase extraction followed by measurement with high-performance liquid chromatography tandem mass spectrometry. The results showed that sediment TC concentrations varied greatly in different swine farms, from mg·kg-1 to µg·kg-1 levels. TCs had different decay patterns along different migration paths, such that TCs decayed exponentially in paddy soil, while linearly in sewer and mixed canal. The concentrations of TCs and their degradation products decreased in the order: sewer sediment > sewage pond sediment > mixed-canal sediment > paddy soil > upland soil, indicating that TCs tend to be more easily intercepted and accumulated in water-sediment systems such as ponds. Therefore, the multi-pond system could be an effective way to prevent TCs from migrating into rivers. These results provided essential information for contamination control of antibiotics in aquatic environments.


Assuntos
Antibacterianos/análise , Tetraciclinas/análise , Gerenciamento de Resíduos/métodos , Poluentes Químicos da Água/análise , Animais , China , Monitoramento Ambiental , Fazendas , Lagoas , Rios/química , Extração em Fase Sólida , Suínos , Águas Residuárias/química
13.
Chin Med J (Engl) ; 128(2): 159-68, 2015 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-25591556

RESUMO

BACKGROUND: Tuberculosis (TB) is a chronic wasting inflammatory disease characterized by multisystem involvement, which can cause metabolic derangements in afflicted patients. Metabolic signatures have been exploited in the study of several diseases. However, the serum that is successfully used in TB diagnosis on the basis of metabolic profiling is not by much. METHODS: Orthogonal partial least-squares discriminant analysis was capable of distinguishing TB patients from both healthy subjects and patients with conditions other than TB. Therefore, TB-specific metabolic profiling was established. Clusters of potential biomarkers for differentiating TB active from non-TB diseases were identified using Mann-Whitney U-test. Multiple logistic regression analysis of metabolites was calculated to determine the suitable biomarker group that allows the efficient differentiation of patients with TB active from the control subjects. RESULTS: From among 271 participants, 12 metabolites were found to contribute to the distinction between the TB active group and the control groups. These metabolites were mainly involved in the metabolic pathways of the following three biomolecules: Fatty acids, amino acids, and lipids. The receiver operating characteristic curves of 3D, 7D, and 11D-phytanic acid, behenic acid, and threoninyl-γ-glutamate exhibited excellent efficiency with area under the curve (AUC) values of 0.904 (95% confidence interval [CI]: 0863-0.944), 0.93 (95% CI: 0.893-0.966), and 0.964 (95% CI: 00.941-0.988), respectively. The largest and smallest resulting AUCs were 0.964 and 0.720, indicating that these biomarkers may be involved in the disease mechanisms. The combination of lysophosphatidylcholine (18:0), behenic acid, threoninyl-γ-glutamate, and presqualene diphosphate was used to represent the most suitable biomarker group for the differentiation of patients with TB active from the control subjects, with an AUC value of 0.991. CONCLUSION: The metabolic analysis results identified new serum biomarkers that can distinguish TB from non-TB diseases. The metabolomics-based analysis provides specific insights into the biology of TB and may offer new avenues for TB diagnosis.


Assuntos
Biomarcadores/sangue , Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas/métodos , Tuberculose/sangue , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
14.
J Chem Phys ; 141(18): 18C507, 2014 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-25399172

RESUMO

Many experimental and theoretical studies have established the specific anion, as well as cation, effects on the hydrogen-bond structures at the air/water interface of electrolyte solutions. However, the ion effects on the top-most layer of the air/water interface, which is signified by the non-hydrogen-bonded so-called "free OH" group, have not been explicitly discussed or studied. In this report, we present the measurement of changes of the orientational angle of the "free OH" group at the air/water interface of the sodium fluoride (NaF) solutions at different concentrations using the interface selective sum-frequency generation vibrational spectroscopy (SFG-VS) in the ssp and ppp polarizations. The polarization dependent SFG-VS results show that the average tilt angle of the "free OH" changes from about 36.6° ± 0.5° to 44.1° ± 0.6° as the NaF concentration increases from 0 to 0.94 M (nearly saturated). Such tilt angle change is around the axis of the other O-H group of the same water molecule at the top-most layer at the air/water interface that is hydrogen-bonded to the water molecules below the top-most layer. These results provide quantitative molecular details of the ion effects of the NaF salt on the structure of the water molecules at the top-most layer of the air/water interface, even though both the Na(+) cation and the F(-) anion are believed to be among the most excluded ions from the air/water interface.

15.
Environ Sci Pollut Res Int ; 21(12): 7737-45, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24627203

RESUMO

A new method for the degradation of bisphenol A (BPA) in aqueous solution was developed. The oxidative degradation characteristics of BPA in a heterogeneous Fenton reaction catalyzed by Fe3O4/graphite oxide (GO) were studied. Transmission electron microscopic images showed that the Fe3O4 nanoparticles were evenly distributed and were ∼6 nm in diameter. Experimental results suggested that BPA conversion was affected by several factors, such as the loading amount of Fe3O4/GO, pH, and initial H2O2 concentration. In the system with 1.0 g L(-1) of Fe3O4/GO and 20 mmol L(-1) of H2O2, almost 90% of BPA (20 mg L(-1)) was degraded within 6 h at pH 6.0. Based on the degradation products identified by GC-MS, the degradation pathways of BPA were proposed. In addition, the reused catalyst Fe3O4/GO still retained its catalytic activity after three cycles, indicating that Fe3O4/GO had good stability and reusability. These results demonstrated that the heterogeneous Fenton reaction catalyzed by Fe3O4/GO is a promising advanced oxidation technology for the treatment of wastewater containing BPA.


Assuntos
Compostos Benzidrílicos/química , Óxido Ferroso-Férrico/química , Grafite/química , Peróxido de Hidrogênio/química , Ferro/química , Nanocompostos/química , Óxidos/química , Fenóis/química , Águas Residuárias/química , Adsorção , Catálise , Concentração de Íons de Hidrogênio , Oxirredução
16.
J Phys Chem B ; 117(20): 6149-56, 2013 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-23675654

RESUMO

We demonstrate a phase sensitive, vibrationally resonant sum-frequency generation (PSVR-SFG) microscope that combines high resolution, fast image acquisition speed, chemical selectivity, and phase sensitivity. Using the PSVR-SFG microscope, we generate amplitude and phase images of the second-order susceptibility of collagen I fibers in rat tail tendon tissue on resonance with the methylene vibrations of the protein. We find that the phase of the second-order susceptibility shows dependence on the effective polarity of the fibril bundles, revealing fibrous collagen domains of opposite orientations within the tissue. The presence of collagen microdomains in tendon tissue may have implications for the interpretation of the mechanical properties of the tissue.


Assuntos
Microscopia/métodos , Imagem Molecular/métodos , Vibração , Animais , Colágeno Tipo I/metabolismo , Ratos , Tendões/metabolismo
17.
J Colloid Interface Sci ; 357(2): 273-9, 2011 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-21377165

RESUMO

In this work, the surface characteristics of poly(N-vinyl-2-pyrrolidone) (PNVP)-modified nonwoven fabric (NWF) membranes and the effects of the surface characteristics on the membranes antifouling properties were investigated. Effects of grafting time, grafting temperature, and monomer concentration on the grafting degree of PNVP were systematically investigated. The effect of grafting degree on the surface characteristics was also investigated. Scanning electron microscopy (SEM) was used to characterize the structural and morphological changes on the membrane surface. The water contact angles decreased from 113±1.2° to 52±3°, which means that the hydrophilicity of the modified NWF was enhanced with increasing PNVP grafting degree. The surface free energy was calculated, which showed an increase after modification. Static bovine serum albumin (BSA) adsorption experiments were carried out, which showed a decrease of 82.5%. Permeation experiments of water and supernatant solution of active sludge were carried out to determine the antifouling characteristics against the extracellular polymeric substance. Results demonstrated that the modified NWF had higher permeation fluxes and lower flux loss in comparison with the original NWF. Bacterial adhesion on the membrane surface was largely suppressed after the introduction of PNVP.


Assuntos
Incrustação Biológica/prevenção & controle , Membranas Artificiais , Polipropilenos/química , Pirrolidinonas/química , Poluentes Químicos da Água , Animais , Aderência Bacteriana , Bovinos , Interações Hidrofóbicas e Hidrofílicas , Microscopia Eletrônica de Varredura , Estrutura Molecular , Soroalbumina Bovina/química , Propriedades de Superfície
18.
J Phys Chem A ; 115(23): 6015-27, 2011 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-21306145

RESUMO

Substantial progress has been made in the quantitative understanding and interpretation of the hydrogen bonding and ordering structure of the air/water interface since the first sum-frequency generation vibrational spectroscopy (SFG-VS) measurement by Q. Du et al. in 1993 (Phys. Rev. Lett. 1993, 70, 2312-2316). However, there are still disagreements and controversies on the consistency between the different experimental measurements, as well as in the theoretical and computational results. One critical problem lies in the lack of consistency between the SFG-VS intensity measurements and the recently developed SFG-VS phase spectra measurements of the neat air/water interface, which has inspired various theoretical efforts. In this report, the reliability of the SFG-VS intensity spectra of the air/neat water interface is to be quantitatively examined, and possible sources of inaccuracies in the SFG-VS phase spectral measurement are to be discussed based on the nonresonant SHG phase measurements. Solid evidence is shown indicating that the SFG-VS intensity spectra from different laboratories are now quantitatively converging and in agreement with each other. However, the possible inaccuracies and inconsistencies in the SFG-VS phase spectra measurements need to be carefully examined against a properly corrected phase standard to take full advantage of this powerful experimental tool.

19.
J Chem Phys ; 130(13): 134709, 2009 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-19355766

RESUMO

Here we report on the polarization dependent nonresonant second harmonic generation (SHG) measurement of the interfacial water molecules at the aqueous solution of the following salts: NaF, NaCl, NaBr, KF, KCl, and KBr. Through quantitative polarization analysis of the SHG data, the orientational parameter D (D = /) value and the relative surface density of the interfacial water molecules at these aqueous solution surfaces were determined. From these results, we found that addition of each of the six salts caused an increase in the thickness of the interfacial water layer at the surfaces to a certain extent. Noticeably, both the cations and the anions contributed to the changes, and the abilities to increase the thickness of the interfacial water layer were in the following order: KBr > NaBr > KCl > NaCl approximately NaF > KF. Since these changes cannot be factorized into individual anion and cation contributions, there are possible ion pairing or association effects, especially for the NaF case. We also found that the orientational parameter D values of the interfacial water molecules changed to opposite directions for the aqueous solutions of the three sodium salts versus the aqueous solutions of the three potassium salts. These findings clearly indicated unexpected specific Na(+) and K(+) cation effects at the aqueous solution surface. These effects were not anticipated from the recent molecular dynamics simulation results, which concluded that the Na(+) and K(+) cations can be treated as small nonpolarizable hard ions and they are repelled from the aqueous interfaces. These results suggest that the electrolyte aqueous solution surfaces are more complex than the currently prevalent theoretical and experimental understandings.


Assuntos
Ar , Brometos/química , Fluoretos/química , Cloreto de Potássio/química , Compostos de Potássio/química , Cloreto de Sódio/química , Compostos de Sódio/química , Fluoreto de Sódio/química , Água/química
20.
J Chem Phys ; 130(13): 134710, 2009 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-19355767

RESUMO

Sum frequency generation vibrational spectra of the water molecules at the NaF and KF aqueous solution surfaces showed significantly different spectral features and different concentration dependence. This result is the first direct observation of the cation effects of the simple alkali cations, which have been believed to be depleted from the aqueous surface, on the hydrogen bonding structure of the water molecules at the electrolyte solution surfaces. These observations may provide important clues to understand the fundamental phenomenon of ions at the air/water interface.

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