Multifunctional layered magnetic composites

A fabrication method of a multifunctional hybrid material is achieved by using the insoluble organic nacre matrix of the Haliotis laevigata shell infiltrated with gelatin as a confined reaction environment. Inside this organic scaffold magnetite nanoparticles (MNPs) are synthesized. The amount of MNPs can be controlled through the synthesis protocol therefore mineral loadings starting from 15 wt % up to 65 wt % can be realized. The demineralized organic nacre matrix is characterized by small-angle and very-small-angle neutron scattering (SANS and VSANS) showing an unchanged organic matrix structure after demineralization compared to the original mineralized nacre reference. Light microscopy and confocal laser scanning microscopy studies of stained samples show the presence of insoluble proteins at the chitin surface but not between the chitin layers. Successful and homogeneous gelatin infiltration in between the chitin layers can be shown. The hybrid material is characterized by TEM and shows a layered structure filled with MNPs with a size of around 10 nm. Magnetic analysis of the material demonstrates superparamagnetic behavior as characteristic for the particle size. Simulation studies show the potential of collagen and chitin to act as nucleators, where there is a slight preference of chitin over collagen as a nucleator for magnetite. Colloidal-probe AFM measurements demonstrate that introduction of a ferrogel into the chitin matrix leads to a certain increase in the stiffness of the composite material.


Small-Angle Neutron Scattering (SANS and VSANS):
As described in [1], SANS and VSANS experiments were carried out at the KWS1 and KWS 3 diffractometers correction and calibration were performed using the software described in [3]. Some of the SANS data were measured at SANS II at Paul Scherrer Institute (PSI) in Villigen, Switzerland. The sample-to-detector distances were 1 and 5 m, the corresponding collimation lengths 4 and 5 m, and the wavelength 0.52 nm. These settings allowed us to cover a Q-range from 0.1 to 3.5 nm −1 .
In order to become sensitive to larger length scales of the order of micrometers, i.e., S4

The Beaucage expression
The Beaucage expression is given according to representing a combination of Guinier's and Porod's laws describing the scattering at low and large Q, respectively. More quantitatively both approximations are valid for the parameter u = R g Q smaller or larger than 1, with u representing the product of radius of gyration R g and scattering vector Q (defined below). Guinier's law has the shape of a Gaussian function whereas for Q larger than 1/R g (u > 1) a power law according to is often observed, which in case of  = 4 represents the famous Porod law of compact particles with a sharp surface [4].

The correlation model:
In the above equation, the first term describes Porod scattering from clusters (exponent = n) and the second term is a Lorentzian function describing scattering from polymer chains (exponent = m). This second term characterizes the polymer/solvent interactions and therefore the thermodynamics. The parameter (ξ) is a correlation length for the polymer chains. This correlation length represents a weighted-average inter distance between the hydrogen/deuterium-containing groups.
The multiplicative factors of the Porod and Lorentzian terms (A and C, respectively), the Q independent incoherent background scattering (BKG), and the lower-Q and higher-Q scattering exponents (n and m, respectively) were obtained by a nonlinear, least squares fit of the data.

Gelatin
Gelatin is derived from partial hydrolysis of native collagen and can be considered as a polydisperse copolymer with a broad molar mass distribution. At temperatures above the gelation temperature (T gel ) gelatin and below the overlap concentration of about 0.5 wt % (in H 2 O) native collagen forms a homogeneous solution in water. This is seen from the SAXS data in Figure S2. It is seen that the biopolymer of 0.

Mechanical characterization
The Hertz model is one of the fundamental theories to describe the elastic deformation of two bodies in contact [7]. It assumes homogeneous, isotropic and linear elastic bodies with negligible adhesion or friction during deformation. For normal loading and small deformations (10 % of film thickness or particle diameter) the applied force F scales with deformation d like: Here, E is the relative Young's modulus and R is the radius of a sphere (in our case the colloidal probe). The relative modulus is composed of the moduli E i and Poisson's ratio ν i of the two bodies in contact:   Figure S6 with linear fit indicating a slope of 1.47, close to the predicted 1.5 from Hertzian theory. Inset: statistic evaluation of log-log slopes (19 curves), mean value = 1.49 ± 0.08. S10