Heterogeneity of Network Structures and Water Dynamics in κ‑Carrageenan Gels Probed by Nanoparticle Diffusometry
Kort, D.W. de; Schuster, Erich ; Hoeben, F.J.M. ; Barnes, R. ; Emondts, Meike ; Janssen, Henk M. ; Lorén, Niklas ; Han, Songi ; As, H. Van; Duynhoven, J.P.M. van - \ 2018
Langmuir 34 (2018). - ISSN 0743-7463 - p. 11110 - 11120.
A set of functionalized nanoparticles (PEGylated dendrimers, d = 2.8−11 nm) was used to probe the structural heterogeneity in Na+/K+ induced κ-carrageenan gels. The self-diffusion behavior of these nanoparticles as observed by 1H pulsed-field gradient NMR, fluorescence recovery after photobleaching, and raster image correlation spectroscopy revealed a fast and a slow component, pointing toward microstructural heterogeneity in the gel network. The self-diffusion behavior of the faster nanoparticles could be modeled with obstruction by a coarse network (average mesh size <100 nm), while the slower-diffusing nanoparticles are trapped in a dense network (lower mesh size limit of 4.6 nm). Overhauser dynamic nuclear polarization-enhanced NMR relaxometry revealed a reduced local solvent water diffusivity near 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-labeled nanoparticles trapped in the dense network, showing that heterogeneity in the physical network is also reflected in heterogeneous self-diffusivity of water. The observed heterogeneity in mesh sizes and in water self-diffusivity is of interest for understanding and modeling of transport through and release of solutes from heterogeneous biopolymer gels.
Complex Coacervate Core Micelles with Spectroscopic Labels for Diffusometric Probing of Biopolymer Networks
Bourouina, Nadia ; Kort, D.W. De; Hoeben, F.J.M. ; Janssen, H.M. ; As, Henk Van; Hohlbein, Johannes ; Duynhoven, J.P.M. Van; Kleijn, J.M. - \ 2015
Langmuir 31 (2015)46. - ISSN 0743-7463 - p. 12635 - 12643.
We present the design, preparation, and characterization of two types of complex coacervate core micelles (C3Ms) with cross-linked cores and spectroscopic labels and demonstrate their use as diffusional probes to investigate the microstructure of percolating biopolymer networks. The first type consists of poly(allylamine hydrochloride) (PAH) and poly(ethylene oxide)-poly(methacrylic acid) (PEO-b-PMAA), labeled with ATTO 488 fluorescent dyes. We show that the size of these probes can be tuned by choosing the length of the PEO-PMAA chains. ATTO 488-labeled PEO113-PMAA15 micelles are very bright with 18 dye molecules incorporated into their cores. The second type is a 19F-labeled micelle, for which we used PAH and a 19F-labeled diblock copolymer tailor-made from poly(ethylene oxide)-poly(acrylic acid) (mPEO79-b-PAA14). These micelles contain approximately 4 wt % of 19F and can be detected by 19F NMR. The 19F labels are placed at the end of a small spacer to allow for the necessary rotational mobility. We used these ATTO- and 19F-labeled micelles to probe the microstructures of a transient gel (xanthan gum) and a cross-linked, heterogeneous gel (κ-carrageenan). For the transient gel, sensitive optical diffusometry methods, including fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, and super-resolution single nanoparticle tracking, allowed us to measure the diffusion coefficient in networks with increasing density. From these measurements, we determined the diameters of the constituent xanthan fibers. In the heterogeneous κ-carrageenan gels, bimodal nanoparticle diffusion was observed, which is a signpost of microstructural heterogeneity of the network.
Scaling Behavior of Dendritic Nanoparticle Mobility in Semidilute Polymer Solutions
Kort, D.W. de; Rombouts, W.H. ; Hoeben, F.J.M. ; Janssen, H.M. ; As, H. van; Duynhoven, J.P.M. van - \ 2015
Macromolecules 48 (2015)20. - ISSN 0024-9297 - p. 7585 - 7591.
In our studies on particle mobility in polymer solutions, we have investigated and determined self-diffusion coefficients of nanoparticles in semidilute solutions of poly(ethylene glycol) (PEG, Mw = 6, 20, 35, and 100 kDa). Specially designed PEGylated dendrimers with well-defined sizes (dh = 3.4–11.0 nm) and with internal 19F moieties allow for background-free 19F NMR diffusion measurements. This way, we were able to assess the self-diffusion coefficients as a function of particle diameter and length scales (correlation length, tube diameter, polymer radius of gyration) with high resolution. Scaling arguments allowed us to visualize a clear crossover between particles probing a lower apparent viscosity to near macroviscosity when the nanoparticle size is comparable to the PEG polymer coil size. The same arguments are shown to correctly predict particle diffusion coefficients as a function of polymer concentration when the particles are smaller than the polymer coils.
19F Labeled polyion micelles as diffusional nanoprobes
Kort, D.W. de; Hoeben, F.J.M. ; Janssen, H.M. ; Bourouina, N. ; Kleijn, J.M. ; Duynhoven, J.P.M. van; As, H. van - \ 2014
In: Magnetic Resonance in Food Science: Defining Food by Magnetic Resonance / Capozzi, F., Laghi, L., Belton, P.S., RSC Publishing - ISBN 9781782622741 - p. 109 - 119.
In modern food manufacturing, there is a strong drive to find alternative formulations in which ingredients are replaced by alternatives derived from a sustainable source. However structure-function relationships remain poorly understood. In order to better understand these relationships, new measurement methods are required to quantify structural properties. At the sub-micron level, powerful microscopy does not allow for reliable quantification of structural features and microscopy methods are invasive and require careful image analysis in order to quantify structural features. For the sub-micron structural characterization of biopolymer hydrogels quantitative nanoprobe diffusometry is emerging as a powerful method to complement knowledge obtained by microscopy. In this study, the authors have used PFG NMR diffusometry to measure diffusion of labeled 19F-C3Ms in a heterogeneous gel model system. In this model system, multi-modal diffusion of dendrimer nanoparticles was observed. They assess the merits of 19F NMR diffusometry for characterization of heterogeneous gels, and compare this to the results obtained by 1H NMR diffusometry.
NMR Nanoparticle Diffusometry in Hydrogels: Enhancing Sensitivity and Selectivity
Kort, D.W. de; Duynhoven, J.P.M. van; Hoeben, F.J.M. ; Janssen, H.M. ; As, H. van - \ 2014
Analytical Chemistry 86 (2014). - ISSN 0003-2700 - p. 9229 - 9235.
fluorescence recovery - laplace inversion - polymer-solutions - field gradient - diffusion - resolution - mobility - gels - spectroscopy - kinetics
From the diffusional behavior of nanoparticles in heterogeneous hydrogels, quantitative information about submicron structural features of the polymer matrix can be derived. Pulsed-gradient spin-echo NMR is often the method of choice because it measures diffusion of the whole ensemble of nanoparticles. However, in 1H diffusion-ordered spectroscopy (DOSY), low-intensity nanoparticle signals have to be separated from a highly protonated background. To circumvent this, we prepared 19F labeled, PEGylated, water-soluble dendritic nanoparticles with a 19F loading of ~7 wt % to enable background free 19F DOSY experiments. 19F nanoparticle diffusometry was benchmarked against 1H diffusion-T2 correlation spectroscopy (DRCOSY), which has a stronger signal separation potential than the commonly used 1H DOSY experiment. We used bootstrap data resampling to estimate confidence intervals and stabilize 2D-Laplace inversion of DRCOSY data with high noise levels and artifacts, allowing quantitative diffusometry even at low magnetic field strengths (30 MHz). The employed methods offer significant advantages in terms of sensitivity and selectivity.
|Groundwater flow and nitrate migration: future developments
Dijksma, R. ; Lanen, H.A.J. van; Klopnowski, M. - \ 2003
In: Monitoring and Modelling Catchment Water Quality and Quantity : 8th ERB Conference, Ghent, Belgium, 27-29 September 2000 / N. Verhoest, J. Hudson, R. Hoeben and F. De Troch Paris : Unesco - p. 23 - 27.
Improvement of TOPLATS-based discharge predictions through assimilation of ERS-based remotely sensed soil moisture values
Pauwels, V.R.N. ; Hoeben, R. ; Verhoest, N.E.C. ; Troch, F.P. De; Troch, P.A. - \ 2002
Hydrological Processes 16 (2002). - ISSN 0885-6087 - p. 995 - 1013.
bodemwater - schatting - remote sensing - afvoer - modellen - soil water - estimation - remote sensing - discharge - models
|Improvement of model-based discharge predictions through assimilation of ERB-based remotely sensed soil moisture values
Pauwels, V. ; Hoeben, R. ; Verhoest, N. ; Troch, F.P. de; Troch, P.A. - \ 2000
In: Book of Abstracts of ERB Conference on Monitoring and modeling catchment water quantity and quality : ERB Conference, Ghent, 27-29 September 2000. - [S.l] : [s.n], 2000 - p. 223 - 227.
Assimilation of active microwave observation data for soil moisture profile estimation
Hoeben, R. ; Troch, P.A. - \ 2000
Water Resources Research 36 (2000)10. - ISSN 0043-1397 - p. 2805 - 2819.
bodemwater - retentie - remote sensing - soil water - retention - remote sensing
This paper discusses the potential of retrieving information about the soil moisture profile from measurements of the surface soil moisture content through active microwave observations of the Earth. Recently, Mancini et al.  have shown through laboratory experiments that the volumetric moisture content of the first few centimeters of a bare soil can be determined within 5 ol accuracy by means of C and L band active microwave observations and inverse modeling. Here we use active microwave observations of the surface soil moisture content in a data assimilation framework to show that this allows the retrieval of the root zone soil moisture profile. The data assimilation procedure developed is based on the Kalman filter technique. Kalman filtering allows reconstruction of the state vector of a system when this system is represented by a dynamic model and when at least part of the state variables are observed regularly. The dynamic model of the system used here is based on the one-dimensional Richards equation. The observation equation is based on the Integral Equation Model [Fung et al., 1992; Fung, 1994] and is used to link the radar observations to surface soil moisture content. It is shown that even in the presence of model and observation noise and infrequent observations, accurate retrieval of the entire moisture profile is possible for a bare soil. ? 2000 American Geophysical Union
|Soil moisture retrieval from ERS and SIR-C measurements at the Zwalm catchment, Belgium
Verhoest, N. ; Hoeben, R. ; Troch, F.P. de; Troch, P.A. - \ 1999
EOS: Transactions, American Geophysical Union 80 (1999)46. - ISSN 0096-3941 - p. F475 - F475.
Multifrequency radar observations of bare surface soil moisture content: A laboratory experiment
Mancini, M. ; Hoeben, R. ; Troch, P.A. - \ 1999
Water Resources Research 35 (1999)6. - ISSN 0043-1397 - p. 1827 - 1838.
bodemwater - meting - remote sensing - soil water - measurement - remote sensing
This paper reports on a laboratory experiment that investigates the use of active microwave observations to estimate volumetric soil moisture content. The experiment, held in 1995, was set up at the European Microwave Signature Laboratory, Joint Research Centre of the European Communities, Ispra (Italy). Full polarimetric radar observations of a 2 m diameter cylindric container filled with a sandy loam soil were performed. During successive wetting and drying cycles, different soil moisture profiles were generated and observed in situ by means of time domain reflectometry probes. The radar data are analyzed based on the Integral Equation Model that simulates radar backscattering given known surface characteristics, such as moisture content and roughness. This allows the evaluation of the predictive power of the simulation model. We find general good agreement between measurements and simulations, but problems occur at high incidence angles. The model is then used to invert soil moisture information from radar measurements. It is shown that, in spite of the complexity of the model involved, it is possible to retrieve under certain circumstances reliable soil moisture estimates with similar accuracies as the in situ measurements. | This paper reports on a laboratory experiment that investigates the use of active microwave observations to estimate volumetric soil moisture content. The experiment, held in 1995, was set up at the European Microwave Signature Laboratory, Joint Research Centre of the European Communities, Ispra (Italy). Full polarimetric radar observations of a 2 m diameter cylindric container filled with a sandy loam soil were performed. During successive wetting and drying cycles, different soil moisture profiles were generated and observed in situ by means of time domain reflectometry probes. The radar data are analyzed based on the Integral Equation Model that simulates radar backscattering given known surface characteristics, such as moisture content and roughness. This allows the evaluation of the predictive power of the simulation model. We find general good agreement between measurements and simulations, but problems occur at high incidence angles. The model is then used to invert soil moisture information from radar measurements. It is shown that, in spite of the complexity of the model involved, it is possible to retrieve under certain circumstances reliable soil moisture estimates with similar accuracies as the in situ measurements.
|An assimilation scheme for soil moisture profiles using active microwave observations
Hoeben, R. ; Troch, P.A. - \ 1999
EOS: Transactions, American Geophysical Union 80 (1999)46. - ISSN 0096-3941 - p. F408 - F408.