Determination of Diffusion Coefficients of Humic Substances by Fluorescence Correlation Spectroscopy:  Role of Solution Conditions

Lead, Jamie R.; Wilkinson, Kevin J.; Starchev, Konstantin; Canonica, Silvio; Buffle, Jacques

doi:10.1021/es9907616

Cited by 125 publications

(96 citation statements)

References 27 publications

(27 reference statements)

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“…It is obvious that each pH of the original HA solution employed had to be different to maintain constant pHs during coagulation and flocculation, and their negative zeta potentials showed a linear decrease from acidic pHs to alkaline pHs as well. This behavior is consistent with the electrostatic and configuration characteristics of HAs that are dependent on pH, specifically, the high intramolecular electrostatic repulsion and stretched configuration at alkaline pHs versus the formation of small aggregates below pH 5.00 [10,39,40] HA solutions, the zeta potentials of PFC-HA micro-flocs decreased from positive to negative as the coagulation pHs increased at all PFC doses, and almost all zeta potentials of PFC-HA micro-flocs were much higher than those of the original HA solutions. A gradual reduction of the above differences was observed, and was accompanied by an increase in coagulation pHs, whereas a gradual enlargement was also observed in Fig.…”

Section: Destabilization Of Ha With Pfcsupporting

confidence: 82%

“…Under these conditions, once PFC was injected into HA solution the remaining alkaline substances after neutralization by hydrogen ions from PFC diluted solution initially reacted with PFC species containing high positive charges and fresh precipitate with low or zero charges were produced, after which the residual PFC polymeric species with positive charges began to neutralize more negative charges of other alkaline substances and HA molecules in these original HA solutions than in the above acidic ones [10,39,40]. Therefore, only a portion of the PFC species with positive charges played a charge neutralization role in HA solutions at neutral and alkaline coagulation pHs.…”

Section: Destabilization Of Ha With Pfcmentioning

confidence: 99%

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Effect of polyferric chloride (PFC) doses and pH on the fractal characteristics of PFC–HA flocs

Wang

Feng

Dentel

et al. 2011

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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a b s t r a c tChanges in the fractal characteristics of PFC-HA flocs with polyferric chloride (PFC) doses and coagulation pHs were investigated in this study. A type of PFC coagulant with a hydrolysis degree (B*) of 0.6027 and a Fe(III) concentration of 0.202 mol/L was employed to coagulate HA solutions at five constant coagulation pHs. Zeta potential tests were employed to reveal the coagulation mechanisms. The physical properties of flocs formed in the coagulation process were analyzed by their CCD image morphology, size distribution, and fractal dimensions. Next, microscopic observations and nitrogen-adsorption-desorption methods were conducted to characterize the pore structure and surface fractal dimensions of powders prepared from these flocs through a cryofixation-vacuum-freeze-drying procedure. The PFC doses and coagulation pHs had an obvious effect on the physical characteristics of PFC-HA flocs and their corresponding powders. Generally, in the low PFC dose range, PFC-HA flocs formed under acidic coagulation pHs and charge neutralization mechanisms were larger, had less irregular boundaries or surfaces (lower D 1 value), a more compact structure (lower D 2 value) and more irregular pore surface or pore size distribution in their dried powder than those formed under neutral and alkaline coagulation pHs and physical enmeshment and/or fresh precipitate adsorption mechanisms involved in the coagulation process. After the PFC doses exceeded this range, a gradual reversal phenomenon occurred. Furthermore, there were different specific PFC dosages that were above the critical reversal point for each property of these flocs or powders, such as the median diameter, one-dimensional fractal dimension, two-dimensional fractal dimension, and pore surface fractal dimension. In addition to these characteristics, the most compact PFC-HA flocs were formed at coagulation pH = 6.00 ± 0.05 and a PFC dosage of 4.04 × 10 −4 mol/L (Fe 3+ ), and the loosest flocs were produced at coagulation pH = 7.00 ± 0.05 and a PFC dose of 1.01 × 10 −4 mol/L (Fe 3+ ).

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Section: Destabilization Of Ha With Pfcsupporting

confidence: 82%

Section: Destabilization Of Ha With Pfcmentioning

confidence: 99%

Effect of polyferric chloride (PFC) doses and pH on the fractal characteristics of PFC–HA flocs

Wang

Feng

Dentel

et al. 2011

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…Similar hydrodynamic diameters of organic molecules have been previously reported by DLS and Fluorescence Correlation Spectroscopy. 22,25 …”

Section: Determination Of Citrate-coated Agnps Aggregation Kinetics Imentioning

confidence: 99%

Citrate-Coated Silver Nanoparticles Interactions with Effluent Organic Matter: Influence of Capping Agent and Solution Conditions

Gutierrez

Aubry²,

Cornejo

et al. 2015

Langmuir

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Just Accepted "Just Accepted" manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides "Just Accepted" as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. "Just Accepted" manuscripts appear in full in PDF format accompanied by an HTML abstract. "Just Accepted" manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). "Just Accepted" is an optional service offered to authors. Therefore, the "Just Accepted" Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the "Just Accepted" Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these "Just Accepted" manuscripts. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 Abstract: Fate and transport studies of silver nanoparticles (AgNPs) discharged from urban wastewaters containing effluent organic matter (EfOM) into natural waters represent a key knowledge gap. In this study, EfOM interfacial interactions with AgNPs and their aggregation kinetics were investigated by atomic force microscopy (AFM) and time-resolved dynamic light scattering (TR-DLS), respectively. Two well-characterized EfOM isolates, i.e., wastewater humic (WW humic) and wastewater colloids (WW colloids, a complex mixture of polysaccharides-proteins-lipids), and a River humic isolate of different characteristics were selected. Citrate-coated AgNPs were selected as representative capped-AgNPs. Citrate-coated AgNPs showed a considerable stability in Na + solutions. However, Ca 2+ ions induced aggregation by cation bridging between carboxyl groups on citrate. Although the presence of River humic increased the stability of citrate-coated AgNPs in Na + solutions due to electrosteric effects, they aggregated in WW humic-containing solutions, indicating the importance of humics characteristics during interactions. Ca 2+ ions increased citrate-coated AgNPs aggregation rates in both humic solutions, suggesting cation bridging between carboxyl groups on their structures as a dominant interacting mechanism. Aggregation of citrate-coated AgNPs in WW colloids solutions was significantly faster than those in both humic solutions. Control experiments in urea solution indicated hydr...

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“…The slow decay component of the ACF was suggested to arise from the 2D diffusion of fluorophores due to their interaction with the surface. 29,34 To quantify the surface contribution, we made this assumption and modeled the measured ACF with equation (3). For a given cover glass, Distance from surface, z (μm) …”

Section: Resultsmentioning

confidence: 99%

“…Fluorescence correlation spectroscopy (FCS) has become the method of choice for investigating various molecular properties such as diffusion, [1][2][3][4][5][6][7] the conformational dynamics of proteins, [8][9][10] and binding and reaction kinetics [10][11][12][13] at the single-molecule level due to the development of excellent laser sources with high beam quality and stability, sophisticated detectors with low noise and high sensitivity, development of objectives with long working distances and high numerical apertures (NAs), and high-quality optics. 14,15 In FCS, signals are recorded as fluctuations in the fluorescence signal from a molecule passing through a detection volume, which is on the order of femtoliters.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the Surface Contribution to Fluorescence Correlation Spectroscopy Measurements

Chowdhury¹,

Manho²

2011

Bulletin of the Korean Chemical Society

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Fluorescence correlation spectroscopy (FCS) is a sophisticated and an accurate analytical technique used to study the diffusion of molecules in a solution at the single-molecule level. FCS is strongly affected by many factors such as the stability of the excitation power, photochemical processes, mismatch between the refractive indices, and variations in the cover glass thickness. We have studied FCS near the surface of a cover glass by using rhodamine 123 as a fluorescent probe and have observed that the surface has a strong influence on the measurements. The temporal autocorrelation of FCS decays with two characteristic times when the confocal detection volume is positioned near the surface of the cover glass. As the position of the detection volume is moved away from the surface, the FCS autocorrelation becomes one-component decaying; the characteristic time of the decay is the same as the faster-decaying component in the FCS autocorrelation near the surface. This observation suggests that the faster component can be attributed to the free diffusion of the probe molecules in the solution, while the slow component has its origin from the interaction between the probe molecules and the surface. We have characterized the surface contribution to the FCS measurements near the surface by changing the position of the detection volume relative to the surface. The influence of the surface on the diffusion of the probe molecules was monitored by changing the chemical properties of the surface. The surface contribution to the temporal autocorrelation of the FCS strongly depends on the chemical nature of the surface. The hydrophobicity of the surface is a major factor determining the surface influence on the free diffusion of the probe molecules near the surface.

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Determination of Diffusion Coefficients of Humic Substances by Fluorescence Correlation Spectroscopy: Role of Solution Conditions

Cited by 125 publications

References 27 publications

Effect of polyferric chloride (PFC) doses and pH on the fractal characteristics of PFC–HA flocs

Effect of polyferric chloride (PFC) doses and pH on the fractal characteristics of PFC–HA flocs

Citrate-Coated Silver Nanoparticles Interactions with Effluent Organic Matter: Influence of Capping Agent and Solution Conditions

Characterization of the Surface Contribution to Fluorescence Correlation Spectroscopy Measurements

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