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Synthesis and Characterization of Gelatin-Based Magnetic Hydrogels.

Helminger M, Wu B, Kollmann T, Benke D, Schwahn D, Pipich V, Faivre D, Zahn D, Cölfen H - Adv Funct Mater (2014)

Bottom Line: The detailed structure of the individual ferrogel components is characterized by small-angle neutron scattering (SANS) using contrast matching.SANS shows an unchanged gelatin structure of average mesh size larger than the nanoparticles with respect to gel concentration while the magnetite nanoparticles size of around 10 nm seems to be limited by the gel mesh size.Overall, the simple and variable synthesis protocol, the cheap and easy accessibility of the components as well as the biocompatibility of the gelatin-based materials suggest them for a number of applications including actuators.

View Article: PubMed Central - PubMed

Affiliation: Physical Chemistry, University of Konstanz Universitätsstrasse 10, D-78457, Konstanz, Germany.

ABSTRACT

A simple preparation of thermoreversible gelatin-based ferrogels in water provides a constant structure defined by the crosslinking degree for gelatin contents between 6 and 18 wt%. The possibility of varying magnetite nanoparticle concentration between 20 and 70 wt% is also reported. Simulation studies hint at the suitability of collagen to bind iron and hydroxide ions, suggesting that collagen acts as a nucleation seed to iron hydroxide aggregation, and thus the intergrowth of collagen and magnetite nanoparticles already at the precursor stage. The detailed structure of the individual ferrogel components is characterized by small-angle neutron scattering (SANS) using contrast matching. The magnetite structure characterization is supplemented by small-angle X-ray scattering and microscopy only visualizing magnetite. SANS shows an unchanged gelatin structure of average mesh size larger than the nanoparticles with respect to gel concentration while the magnetite nanoparticles size of around 10 nm seems to be limited by the gel mesh size. Swelling measurements underline that magnetite acts as additional crosslinker and therefore varying the magnetic and mechanical properties of the ferrogels. Overall, the simple and variable synthesis protocol, the cheap and easy accessibility of the components as well as the biocompatibility of the gelatin-based materials suggest them for a number of applications including actuators.

No MeSH data available.


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Magnetic properties of the synthesized hybrid materials. a) Magnetization curves of a dried ferrogel at 2 K and 293 K. Inset: Enlargement of the low field region showing the different coercive fields for the NPs at 2 and 293 K. b) ZFC-FC curves as a function of temperature.
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fig-7: Magnetic properties of the synthesized hybrid materials. a) Magnetization curves of a dried ferrogel at 2 K and 293 K. Inset: Enlargement of the low field region showing the different coercive fields for the NPs at 2 and 293 K. b) ZFC-FC curves as a function of temperature.

Mentions: The magnetic properties of the composite materials were characterized by using a superconducting quantum interference device (SQUID) magnetometer. Figure 7a shows the magnetization (M) of a representative dried ferrogel sample (10 wt% gelatin in the hydrated gelified state, 60.4 wt.-% mineral content in the dried ferrogel state) as a function of the applied field (H) at 293 K and 2 K. At T = 2 K the magnetization curve shows typical ferrimagnetic hysteresis due to magnetic anisotropy. At 293 K there is no hysteresis observed, which is typical for superparamagnetic materials,55 and consistent with the small size of the nanoparticles. The field-cooled (FC) and zero-field-cooled (ZFC) magnetizations of the magnetite-gelatin composites were also measured (Figure 7b). The maximum of the ZFC curve corresponds to the blocking temperature (TB).56 Values obtained for TB as well as for the saturation magnetization (Ms) at 5000 Oe are listed in Table 1 for several representative samples. The studies show a blocking temperature of around 120 K which also confirms the superparamagnetic behavior of the nanoparticles. The higher TB found for the ferrogel at a lower gelatin concentration (cf. Table 1) might be due to stronger dipolar interactions and dense particle packing in the dry ferrogel state. As can be seen in Table 1 the saturation magnetization (Ms) of the composite materials is lower than that of bulk magnetite (92 emu/g) as well as maghemite (56 emu/g).57 This effect has been observed in many previous studies, and it was proposed that with decreasing particle size, the growing degree of spin disorder at the surface causes the decrease in Ms.58 It has also been reported that defects on the particle surface can influence the magnetic properties.58 The obtained magnetic measurement data show the phenomena of superparamagnetism for the designed composite materials, the same result is also observed for magnetite nanoparticles synthesized by a co-precipitation method in water.57,59–62 From these observations we conclude that the gelatin network has no effect on the magnetic properties of magnetite nanoparticles synthesized inside the gel matrix.


Synthesis and Characterization of Gelatin-Based Magnetic Hydrogels.

Helminger M, Wu B, Kollmann T, Benke D, Schwahn D, Pipich V, Faivre D, Zahn D, Cölfen H - Adv Funct Mater (2014)

Magnetic properties of the synthesized hybrid materials. a) Magnetization curves of a dried ferrogel at 2 K and 293 K. Inset: Enlargement of the low field region showing the different coercive fields for the NPs at 2 and 293 K. b) ZFC-FC curves as a function of temperature.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4379906&req=5

fig-7: Magnetic properties of the synthesized hybrid materials. a) Magnetization curves of a dried ferrogel at 2 K and 293 K. Inset: Enlargement of the low field region showing the different coercive fields for the NPs at 2 and 293 K. b) ZFC-FC curves as a function of temperature.
Mentions: The magnetic properties of the composite materials were characterized by using a superconducting quantum interference device (SQUID) magnetometer. Figure 7a shows the magnetization (M) of a representative dried ferrogel sample (10 wt% gelatin in the hydrated gelified state, 60.4 wt.-% mineral content in the dried ferrogel state) as a function of the applied field (H) at 293 K and 2 K. At T = 2 K the magnetization curve shows typical ferrimagnetic hysteresis due to magnetic anisotropy. At 293 K there is no hysteresis observed, which is typical for superparamagnetic materials,55 and consistent with the small size of the nanoparticles. The field-cooled (FC) and zero-field-cooled (ZFC) magnetizations of the magnetite-gelatin composites were also measured (Figure 7b). The maximum of the ZFC curve corresponds to the blocking temperature (TB).56 Values obtained for TB as well as for the saturation magnetization (Ms) at 5000 Oe are listed in Table 1 for several representative samples. The studies show a blocking temperature of around 120 K which also confirms the superparamagnetic behavior of the nanoparticles. The higher TB found for the ferrogel at a lower gelatin concentration (cf. Table 1) might be due to stronger dipolar interactions and dense particle packing in the dry ferrogel state. As can be seen in Table 1 the saturation magnetization (Ms) of the composite materials is lower than that of bulk magnetite (92 emu/g) as well as maghemite (56 emu/g).57 This effect has been observed in many previous studies, and it was proposed that with decreasing particle size, the growing degree of spin disorder at the surface causes the decrease in Ms.58 It has also been reported that defects on the particle surface can influence the magnetic properties.58 The obtained magnetic measurement data show the phenomena of superparamagnetism for the designed composite materials, the same result is also observed for magnetite nanoparticles synthesized by a co-precipitation method in water.57,59–62 From these observations we conclude that the gelatin network has no effect on the magnetic properties of magnetite nanoparticles synthesized inside the gel matrix.

Bottom Line: The detailed structure of the individual ferrogel components is characterized by small-angle neutron scattering (SANS) using contrast matching.SANS shows an unchanged gelatin structure of average mesh size larger than the nanoparticles with respect to gel concentration while the magnetite nanoparticles size of around 10 nm seems to be limited by the gel mesh size.Overall, the simple and variable synthesis protocol, the cheap and easy accessibility of the components as well as the biocompatibility of the gelatin-based materials suggest them for a number of applications including actuators.

View Article: PubMed Central - PubMed

Affiliation: Physical Chemistry, University of Konstanz Universitätsstrasse 10, D-78457, Konstanz, Germany.

ABSTRACT

A simple preparation of thermoreversible gelatin-based ferrogels in water provides a constant structure defined by the crosslinking degree for gelatin contents between 6 and 18 wt%. The possibility of varying magnetite nanoparticle concentration between 20 and 70 wt% is also reported. Simulation studies hint at the suitability of collagen to bind iron and hydroxide ions, suggesting that collagen acts as a nucleation seed to iron hydroxide aggregation, and thus the intergrowth of collagen and magnetite nanoparticles already at the precursor stage. The detailed structure of the individual ferrogel components is characterized by small-angle neutron scattering (SANS) using contrast matching. The magnetite structure characterization is supplemented by small-angle X-ray scattering and microscopy only visualizing magnetite. SANS shows an unchanged gelatin structure of average mesh size larger than the nanoparticles with respect to gel concentration while the magnetite nanoparticles size of around 10 nm seems to be limited by the gel mesh size. Swelling measurements underline that magnetite acts as additional crosslinker and therefore varying the magnetic and mechanical properties of the ferrogels. Overall, the simple and variable synthesis protocol, the cheap and easy accessibility of the components as well as the biocompatibility of the gelatin-based materials suggest them for a number of applications including actuators.

No MeSH data available.


Related in: MedlinePlus