| 1. |
- Albèr, Cathrine, et al.
(författare)
-
Hydration of Hyaluronan : Effects on Structural and Thermodynamic Properties
- 2015
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 119:11, s. 4211-4219
-
Tidskriftsartikel (refereegranskat)abstract
- Hyaluronan (HA) is a frequently occurring biopolymer with a large variety of functions in nature. During the past 60 years, there have been numerous reports on structural and dynamic behavior of HA in water. Nevertheless, studies covering a wider concentration range are still lacking. In this work, we use isothermal scanning sorption calorimetry for the first time to investigate hydration-induced transitions in HA (sodium hyaluronate, 17 kDa). From this method, we obtain the sorption isotherm and the enthalpy and the entropy of hydration. Thermotropic events are evaluated by differential scanning calorimetry (DSC), and structure analysis is performed with X-ray scattering (SWAXS) and light and scanning electron microscopy. During isothermal hydration, HA exhibits a glass transition, followed by crystallization and subsequent dissolution of HA crystals and formation of a one-phase solution. Structural analysis reveals that the crystal may be indexed on an orthorhombic unit cell with space group P212121. Crystallization of HA was found to occur either through endothermic or exothermic processes, depending on the temperature and water content. We propose a mechanism of crystallization that explains this phenomenon based on the interplay between the hydrophobic effect and strengthening of hydrogen bonds during formation of crystals. The combined results were used to construct a binary phase diagram for the HA–water system.
|
|
| 2. |
- Argatov, Ivan, et al.
(författare)
-
A note on artificial neural network modeling of vapor-liquid equilibrium in multicomponent mixtures
- 2019
-
Ingår i: Fluid Phase Equilibria. - : Elsevier. - 0378-3812 .- 1879-0224. ; 502
-
Tidskriftsartikel (refereegranskat)abstract
- Application of artificial neural networks (ANNs) for modeling of vapor-liquid equilibrium in multicomponent mixtures is considered. Two novel ANN-based models are introduced, which can be seen as generalizations of the Wilson model and the NRTL model. A unique feature of the proposed approach is that an ANN approximation for the molar excess Gibbs energy generates approximations for the activity coefficients. A special case of the ternary acetic acid-n-propyl alcohol-water system (at 313.15 K) is used to illustrate the efficiency of the different models, including Wilson's model, Focke's model, and the introduced generalized degree-1 homogeneous neural network model. Also, the latter one-level NN model is compared to the Wilson model on 10 binary systems. The efficiency of the two-level NN model is assessed by a comparison with the NRTL model. (C) 2019 Elsevier B.V. All rights reserved.
|
|
| 3. |
- Argatov, Ivan, et al.
(författare)
-
How to define the storage and loss moduli for a rheologically nonlinear material?
- 2017
-
Ingår i: Continuum Mechanics and Thermodynamics. - : Springer. - 0935-1175 .- 1432-0959. ; 29:6, s. 1375-1387
-
Tidskriftsartikel (refereegranskat)abstract
- A large amplitude oscillatory shear (LAOS) is considered in the strain-controlled regime, and the interrelation between the Fourier transform and the stress decomposition approaches is established. Several definitions of the generalized storage and loss moduli are examined in a unified conceptual scheme based on the Lissajous–Bowditch plots. An illustrative example of evaluating the generalized moduli from a LAOS flow is given.
|
|
| 4. |
- Björklund, Sebastian, et al.
(författare)
-
Alcohols react with MCM-41 at room temperature and chemically modify mesoporous silica
- 2017
-
Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Mesoporous silica has received much attention due to its well-defined structural order, high surface area, and tunable pore diameter. To successfully employ mesoporous silica for nanotechnology applications it is important to consider how it is influenced by solvent molecules due to the fact that most preparation procedures involve treatment in various solvents. In the present work we contribute to this important topic with new results on how MCM-41 is affected by a simple treatment in alcohol at room temperature. The effects of alcohol treatment are characterized by TGA, FTIR, and sorption calorimetry. The results are clear and show that treatment of MCM-41 in methanol, ethanol, propanol, butanol, pentanol, or octanol at room temperature introduces alkoxy groups that are covalently bound to the silica surface. It is shown that alcohol treated MCM-41 becomes more hydrophobic and that this effect is sequentially more prominent going from methanol to octanol. Chemical formation of alkoxy groups onto MCM-41 occurs both for calcined and hydroxylated MCM-41 and the alkoxy groups are hydrolytically unstable and can be replaced by silanol groups after exposure to water. The results are highly relevant for mesoporous silica applications that involve contact or treatment in protic solvents, which is very common.
|
|
| 5. |
- Björklund, Sebastian, et al.
(författare)
-
Humidity scanning quartz crystal microbalance with dissipation monitoring setup for determination of sorption-desorption isotherms and rheological changes
- 2015
-
Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 86:5
-
Tidskriftsartikel (refereegranskat)abstract
- A new method to determine water sorption-desorption isotherms with high resolution in the complete range of water activities (relative humidities) is presented. The method is based on quartz crystal microbalance with dissipation monitoring (QCM-D). The QCM-D is equipped with a humidity module in which the sample film is kept in air with controlled humidity. The experimental setup allows for continuous scanning of the relative humidity from either dry to humid conditions or vice versa. The amount of water sorbed or desorbed from the sample is determined from the resonance frequencies of the coated quartz sensor, via analysis of the overtone dependence. In addition, the method allows for characterization of hydration induced changes of the rheological properties from the dissipation data, which is closely connected to the viscoelasticity of the film. The accuracy of the humidity scanning setup is confirmed in control experiments. Sorption-desorption isotherms of pig gastric mucin and lysozyme, obtained by the new method, show good agreement with previous results. Finally, we show that the deposition technique used to coat the quartz sensor influences the QCM-D data and how this issue can be used to obtain further information on the effect of hydration. In particular, we demonstrate that spin-coating represents an attractive alternative to obtain sorption-desorption isotherms, while drop-coating provides additional information on changes of the rheological properties during hydration.
|
|
| 6. |
- Björklund, Sebastian, et al.
(författare)
-
Hydration-Induced Phase Transitions in Surfactant and Lipid Films
- 2016
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 32:21, s. 5223-5232
-
Tidskriftsartikel (refereegranskat)abstract
- For several surfactant and lipid systems, it is crucial to understand how hydration influences the physical and chemical properties. When humidity changes, it affects the degree of hydration by adding or removing water molecules. In many cases, this process induces transitions between liquid crystalline phases. This phenomenon is of general interest for numerous applications simply because of the fact that humidity variations are ubiquitous. Of particular interest are hydration-induced phase transitions in amphiphilic films, which in many cases appear as the frontier toward a vapor phase with changing humidity. Considering this, it is important to characterize the film thickness needed for the formation of 3D liquid crystalline phases and the lyotropic phase behavior of this kind of film. In this work, we study this issue by employing a recently developed method based on the humidity scanning quartz crystal microbalance with dissipation monitoring (HS QCM-D), which enables continuous scanning of the film hydration. We investigate five surfactants films (DDAO, DTAC, CTAC, SDS, and n-octyl beta-D-glucoside) and one lipid film (monoolein) and show that HS QCM-D enables the fast characterization of hydration-induced phase transitions with small samples. Film thicknesses range from tens to hundreds of nanometers, and clear phase transitions are observed in all cases. It is shown that phase transitions in films occur at the same water activities as for corresponding bulk samples. This allows us to conclude that surfactant and lipid films, with a thickness of as low as 50 nm, are in fact assembled as 3D-structured liquid crystalline phases. Furthermore, liquid crystalline phases of surfactant films show liquidlike behavior, which decreases the accuracy of the absorbed water mass measurement. On the other hand, the monoolein lipid forms more rigid liquid crystalline films, allowing for an accurate determination of the water sorption isotherm, which is also true for the sorption isotherms corresponding to the solid surfactant phases.
|
|
| 7. |
- Björklund, Sebastian, et al.
(författare)
-
Water vapor sorption-desorption hysteresis in glassy surface films of mucins investigated by humidity scanning QCM-D
- 2019
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 545, s. 289-300
-
Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: Investigating the origin of water sorption-desorption hysteresis in glassy biopolymers is important for understanding the properties of biological barriers, such as the mucus epithelium. In general, hysteresis is a result of a complex interplay between diffusion of water and relaxation of the polymer matrix. Our hypothesis is that for thin films, typical for quartz crystal microbalance with dissipation monitoring (QCM-D) experiments performed in gas phase with defined relative humidity, the diffusion limitation is eliminated and hysteresis results only from relaxation of the polymer matrix. Experiments: We use a recently developed humidity scanning (HS) QCM-D method to obtain water sorption-desorption isotherms of mucin films under controlled conditions where water diffusion is not the limiting factor, neither in the vapor phase nor in the glassy mucin film. Findings: We present new results on the water sorption-desorption behavior of glassy mucin films with nanoscale thicknesses. Despite the fact that water diffusion is not the limiting factor, the sorption-desorption branches show clear hysteresis effects that are similar to those typically observed in bulk samples. The hydration-induced glass transition, resolved from monitoring the rheological behavior of the films, is shown to be in excellent agreement with the onset of the sorption-desorption hysteresis. We suggest that the hysteresis effect is related to a difference in dynamical and structural properties of the glassy materials depending on the hydration history of the films.
|
|
| 8. |
- Carlstedt, Jonas, et al.
(författare)
-
Understanding Starch Gelatinization : the Phase Diagram Approach
- 2015
-
Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 129, s. 62-69
-
Tidskriftsartikel (refereegranskat)abstract
- By constructing a detailed phase diagram for the potato starch–water system based on data from optical microscopy, synchrotron X-ray scattering and differential scanning calorimetry, we show that gelatinization can be interpreted in analogy with a eutectic transition. The phase rule explains why the temperature of the gelatinization transition (G) is independent on water content. Furthermore, the melting (M1) endotherm observed in DSC represents a liquidus line; the temperature for this event increases with increasing starch concentration. Both the lamellar spacing and the inter-helix distance were observed to decrease with increasing starch content for starch concentrations between approximately 65 wt% and 75 wt%, while the inter-helix distance continued decreasing upon further dehydration. Understanding starch gelatinization has been a longstanding challenge. The novel approach presented here shows interpretation of this phenomenon from a phase equilibria perspective.
|
|
| 9. |
- Falk, Yana Znamenskaya, et al.
(författare)
-
Effects of Hydration on Structure and Phase Behavior of Pig Gastric Mucin Elucidated by SAXS
- 2018
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 122:30, s. 7539-7546
-
Tidskriftsartikel (refereegranskat)abstract
- In this work small-angle X-ray scattering (SAXS) was used to study hydration and temperature-induced changes of pig gastric mucin (PGM) within the entire concentration range. The scattering is interpreted as originating from PGM fiber-like structures that adopt rod-like bottle-brush conformation in dilute solutions. On the basis of the knowledge about molecular structure of mucins and SAXS data for dilute solutions, we propose a theoretical model for predicting mucin conformation in solution and calculate the corresponding scattering profile. This bottle-brush model comprises a protein backbone with carbohydrate side chains and corresponding structural parameters, such as grafting distance and lengths of the backbone and side chains. It describes the experimental PGM data from dilute solutions in the full q range very well. It furthermore suggests that the carbohydrate side chains are grafted with a regular separation of around 5 nm and a length of 14 nm. The cross-section size with a radius of about 1 nm is also in accordance with the size of the carbohydrate units. Structuring of PGM solutions at higher concentrations was investigated by analyzing semidilute and concentrated PGM samples. Starting at about 20 wt %, Bragg peaks become clearly visible indicating a more ordered mucin system. In very dehydrated and fully dry mucin samples these peaks are not present indicating lack of long-range order. The SAXS data show that the structural change occurring at about 80 wt % mucin and 25 degrees C corresponds to a glass transition in agreement with our previous calorimetric results. Temperature also has an effect on the phase behavior of mucin. At intermediate levels of hydration, a phase transition is observed at about 60-70 degrees C. The main Bragg peak appears to split in two, indicating formation of a different structure at elevated temperatures. These findings are used to improve the PGM water phase diagram.
|
|
| 10. |
- Hering, Kathrin, et al.
(författare)
-
Inkjet printing of surfactants, proteins and enzymes for biomedical applications
- 2016
-
Konferensbidrag (refereegranskat)abstract
- Ink solutions relevant for biomedical applications have been printed using a commercial inkjet printer. Specifically, water-based inks containing surfactant, protein and enzyme have been evaluated. Printability of surfactant ink was theoretically estimated from practically determined surface tension and viscosity of the solution. Quartz crystal microbalance with dissipation monitoring (QCM-D) was used to estimate the mass of inkjet printed surfactant. The effect of printing patterns and hydration on the QCM-D data was evaluated. Finally, horseradish peroxidase ink was printed on skin and an enzymatic reaction on skin was observed. Taken together, the results from this study provide a promising starting point from which inkjet printing of protein-enzyme mixtures on skin can be evaluated.
|
|
| 11. |
- Kocherbitov, Vitaly, et al.
(författare)
-
Effect of Oligomerization of Counterions on Water Activity in Aqueous Cationic Surfactant Systems
- 2016
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 120:28, s. 6961-6968
-
Tidskriftsartikel (refereegranskat)abstract
- A sorption calorimetry study of cationic cetyltrimethyl ammonium surfactants with four different counterions was performed. The counterions were acetate, succinate, citrate, and butyl tetracarboxylate with formal charges ranging from 1 to 4, respectively. The counterions with 2–4 charges can be considered as oligomers. In all the cases, hydration experiments started with dry solid phases that upon water uptake went through solid-state phase transitions and hexagonal to micellar cubic phase transitions. It was found that in liquid-crystalline phases the activity of water increased with the degree of oligomerization or, equivalently, the formal charge of the counterions. The results are discussed in terms of the forces acting between the colloidal aggregates. It is argued that under the conditions investigated, the so-called strong-coupling theory can be used to describe the electrostatic forces between the charged colloidal objects. Therefore, we suggest that the observed dependence of water activity on the degree of polymerization is due to the entropy of mixing of the counterions in the water volume, which we describe using Flory–Huggins theory.
|
|
| 12. |
- Kocherbitov, Vitaly, et al.
(författare)
-
Enthalpy of sorption by glassy polymers
- 2019
-
Ingår i: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 174, s. 33-37
-
Tidskriftsartikel (refereegranskat)abstract
- Thermodynamics and molecular mechanisms of sorption of gases and liquids by glassy polymers and are still not fully understood. In particular, the enthalpy of sorption (or mixing) in the glassy state – a parameter crucial for understanding the thermodynamics of sorption is not properly described by existing approaches. In this work, we propose a thermodynamic theory that describes the effect of the glass transition on the enthalpy of sorption. Firstly, a rigorous thermodynamic expression for the sorption enthalpy is presented, and then equations applicable for practical calculations are derived using certain approximations. The theory presented here is tested on the experimental water sorption data on starch and cellulose. The equations describing the hydration enthalpy are in excellent agreement with experimental data. Remarkably, the glass transition-induced apparent heat capacity change for water in carbohydrate polymers turned out to be negative. Being counterintuitive, this result can however be supported by re-evaluation of the literature data on heat capacities of the starch-water system.
|
|
| 13. |
- Kocherbitov, Vitaly
(författare)
-
Molecular dynamics simulations of liquid crystalline phases of dodecyltrimethylammonium chloride
- 2015
-
Ingår i: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 210:Part A, s. 74-81
-
Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics simulations of four different phases of a cationic surfactant dodecyltrimethylammonium chloride (DTAC) are presented. It is shown that when the topology of the initial configuration matches that of the equilibrium structure, the required equilibration times of MD simulations are only few nanoseconds. The methods of building initial configurations for simulations of the hexagonal and Ia3d bicontinuous cubic phases are described. The simulation results show that locally, the hydrophilic part of the hexagonal phase has a flat bilayer structure. Analysis of radial distribution functions shows that the properties of the hydrophilic layers of the phases are dominated by ion–ion and ion–water interactions. The dynamic properties of the system are dependent on the curvature of the aggregates, and calculated diffusion coefficients are in agreement with experimental NMR data.
|
|
| 14. |
- Kocherbitov, Vitaly
(författare)
-
The nature of nonfreezing water in carbohydrate polymers
- 2016
-
Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 150, s. 353-358
-
Tidskriftsartikel (refereegranskat)abstract
- In an aqueous environment, carbohydrate polymers are surrounded by hydration shells consisting of water molecules that are sometimes called “bound”. When polymer solutions are subjected to low temperatures, a part of water turns into ice, another part remains in the biopolymer phase and is called “nonfreezing water”. Thermodynamic analysis of water freezing shows that the amount of non-freezing water does not reflect the amount of bound water, neither can it be used as a measure of strength of polymer-water interactions. Upon deep cooling, crystallization of water should desiccate polymers more than is observed in experiment. The reason for existence of non-freezing water is an interplay between the crystallization of water and the glass transition in biopolymers that prevents dehydration.
|
|
| 15. |
- Pulyalina, Alexandra, et al.
(författare)
-
Novel approach to determination of sorption in pervaporation process : a case study of isopropanol dehydration by polyamidoimideurea membranes
- 2017
-
Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Development of novel membranes with optimal performance, selectivity, and stability is a key research area in membrane technology. In the present work aromatic polyamidoimideurea (PAIU) is synthesized and tested as promising membrane material for separation of water and alcohol mixtures. The PAIU membrane structure, density, and transport properties are studied. Mass transfer of water and isopropanol through the membrane is estimated by sorption and pervaporation tests to determine equilibrium sorption degree, diffusion coefficients, flux through the membrane, and separation factor. Two techniques of sorption study from liquid and from vapor phases are used as novel approach to experimental study of mass transfer. The vapor sorption calorimetry permits to analyze the behavior of the polymer material in sorption process. In pervaporation of water–isopropanol mixture, almost pure water mainly permeates through PAIU membrane. To improve the performance, a double layer membrane containing a thin PAIU layer on the surface of porous poly(phenylene oxide) support is developed. The double layer membrane is extremely effective in dehydration of isopropanol.
|
|
| 16. |
- Runnsjö, Anna, et al.
(författare)
-
Diffusion through Pig Gastric Mucin : Effect of Relative Humidity
- 2016
-
Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 11:6
-
Tidskriftsartikel (refereegranskat)abstract
- Mucus covers the epithelium found in all intestinal tracts, where it serves as an important protecting barrier, and pharmaceutical drugs administrated by the oral, rectal, vaginal, ocular, or nasal route need to penetrate the mucus in order to reach their targets. Furthermore, the diffusion in mucus as well as the viscosity of mucus in the eyes, nose and throat can change depending on the relative humidity of the surrounding air. In this study we have investigated how diffusion through gels of mucin, the main protein in mucus, is affected by changes in ambient relative humidity (i.e. water activity). Already a small decrease in water activity was found to give rise to a significant decrease in penetration rate through the mucin gel of the antibacterial drug metronidazole. We also show that a decrease in water activity leads to decreased diffusion rate in the mucin gel for the fluorophore fluorescein. This study shows that it is possible to alter transport rates of molecules through mucus by changing the water activity in the gel. It furthermore illustrates the importance of considering effects of the water activity in the mucosa during development of potential pharmaceuticals.
|
|
| 17. |
- Runnsjö, Anna, et al.
(författare)
-
Semifluorinated alkanes and alkanes : a phase study of the perfluorohexyloctane - tetradecane system
- 2017
-
Ingår i: Journal of Chemical Thermodynamics. - : Elsevier. - 0021-9614 .- 1096-3626. ; 105, s. 352-361
-
Tidskriftsartikel (refereegranskat)abstract
- The binary system perfluorohexyloctane (F6H8)–tetradecane (C14) was investigated in order to increase understanding of interactions of semifluorinated alkanes (SFAs) with hydrophobic molecules. The thermal phase behavior for F6H8 and C14 and their mixtures was determined using DSC. The activity coefficients for both components in the mixtures were calculated and Gibbs energy of mixing was determined. Furthermore, enthalpies of mixing were determined with ITC and structural investigations of the solid and the liquid phases were performed with SAXS and SWAXD. It was found that F6H8 displays one solid-solid transition at −42.3 °C (ΔH = 1.1 kJ/mol) and one solid-liquid transition at −5.9 °C (ΔH = 16.6 kJ/mol). Due to the low enthalpy of the solid-liquid transition it is likely that F6H8 is not fully crystallized in the solid phase but partly amorphous. The F6H8–C14 system displays a eutectic phase behavior and the liquid mixtures display a positive deviation from ideal mixing. C14 crystalizes in a triclinic unit cell as shown before, whereas crystallization of F6H8 in a lamellar rippled phase is shown for the first time. This ripple phase comprises a bilayer of tilted alternating heavily interdigitated F6H8 molecules in an oblique subunit cell.
|
|
| 18. |
- Skansberger, Tatyana, et al.
(författare)
-
The Reversible and Irreversible Phenomena in Potato Starch Gelatinization
- 2019
-
Ingår i: Starke (Weinheim). - : John Wiley & Sons. - 0038-9056 .- 1521-379X. ; 71:5-6
-
Tidskriftsartikel (refereegranskat)abstract
- Gelatinization of starch is a complex process and can be considered using two different approaches. In a kinetic approach it is considered as an irreversible process and described using the formalism of chemical kinetics with activation energy as the main parameter. Alternatively, in a thermodynamic approach it can be viewed as a reversible process with van't Hoff enthalpy as the main parameter. The experimental DSC data on gelatinization of native and physically modified potato starches presented in this study support the equilibrium approach. The van't Hoff enthalpy of gelatinization of native potato starch is measured to be 737 ± 13 kJ mol−1, and it is more sensitive to physical modifications of starch than the calorimetric enthalpy. Moreover, van't Hoff enthalpy has a clear correlation with the granule size, while neither gelatinization temperature, nor calorimetric enthalpy are sensitive to the size. To explain the nonequilibrium nature of starch gelatinization, the authors propose a three‐step mechanism, which includes reversible and irreversible steps.
|
|
| 19. |
- Wojtasz, Joanna, et al.
(författare)
-
Hydration and swelling of amorphous cross-linked starch microspheres
- 2016
-
Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 135, s. 225-233
-
Tidskriftsartikel (refereegranskat)abstract
- Hydration of cross-linked starch microspheres, commercially available as a medical device, was investigated using a multi-method approach. We found that the uptake of water is accompanied by substantial swelling and changes of the polymer structure. Sorption calorimetry provided information about thermodynamics of water sorption, revealed presence of isothermal glass transition and absence of hydration-induced crystallization, observed in non-cross linked starch material. The changes in the surface and bulk properties of microspheres at different water–starch concentrations were investigated using synchrotron radiation X-ray scattering and analyzed using concept of fractals. The obtained information, combined with the results of differential scanning calorimetry, was used to construct a phase diagram of the studied material. Finally, hydration induced evolution of polymer structure revealed by the X-ray scattering was linked to the changes observed during swelling with optical microscopy.
|
|
| 20. |
- Znamenskaya, Yana, et al.
(författare)
-
Effect of hydration and dehydration on the properties of SBA-15 layer studied by humidity scanning QCM-D
- 2016
-
Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 230, s. 58-65
-
Tidskriftsartikel (refereegranskat)abstract
- Surface deposited layers of mesoporous silica particles could function as support for bio-sensing or drug release applications. It is crucial to control the surface deposition process and employ relevant techniques to characterize the properties of the particles on the surface. Here, we deposit SBA-15 particles on native silica or cationic surfaces and characterize the hydration and dehydration by employing a novel method based on humidity scanning quartz crystal microbalance with dissipation (HS QCM-D). SBA-15 platelets are deposited with mesopores oriented parallel to the surface normal using drop deposition. SEM shows a monolayer on the surface, which is established as stable. Water sorption-desorption isotherms of the SBA-15 layer from HS QCM-D are compared with isotherms from water sorption calorimetry and nitrogen sorption on bulk material. We demonstrate that HS QCM-D provides results in good agreement with results obtained with the reference methods. The properties of SBA-15 particles are retained during the deposition process and unaffected by the presence of the surface. In addition, HS QCM-D is a fast technique that requires significantly lower amount of material (∼5000 times) compared to experiments on bulk material. HS QCM-D provides complete characterization of the pore size distribution of SBA-15.
|
|
