Mesoporous Silica Formation Mechanisms Probed Using Combined Spin–Echo Modulated Small-Angle Neutron Scattering (SEMSANS) and Small-Angle Neutron Scattering (SANS)

Abstract

The initial formation stages of surfactant-templated silica thin films which grow at the air−water interface were studied using combined spin−echo modulated small-angle neutron scattering (SEMSANS) and small-angle neutron scattering (SANS). The films are formed from either a cationic surfactant or nonionic surfactant (C 16 EO 8) in a dilute acidic solution by the addition of tetramethoxysilane. Previous work has suggested a two stage formation mechanism with mesostructured particle formation in the bulk solution driving film formation at the solution surface. From the SEMSANS data, it is possible to pinpoint accurately the time associated with the formation of large particles in solution that go on to form the film and to show their emergence is concomitant with the appearance of Bragg peaks in the SANS pattern, associated with the two-dimensional hexagonal order. The combination of SANS and SEMSANS allows a complete depiction of the steps of the synthesis that occur in the subphase.

Simulations of foil-based spin-echo (modulated) small-angle neutron scattering with a sample using McStas

“…Detection with a grating instead of a high-resolution detector is now also possible. This simulation development will make it possible to investigate more complex data-analysis challenges for combined SANS-SEMSANS measurements at time-of-flight instruments (Plomp et al, 2007), as for example at the instrument Larmor at ISIS (Schmitt et al, 2020). The scattering power and scattering angles are wavelength dependent, which gives interesting effects that require careful data reduction and that can now be simulated.…”

Interfacial Assembly and Applications of Functional Mesoporous Materials

“…Meanwhile, the formed mesostructured materials migrate to the interface and enhance the signal of GISAXS. More importantly, this self-assembly mechanism of mesoporous films is valid for both CTAB and C 16 EO 8 …”

“…In more recent work, Edler and co-workers provided solid proofs of the two-stage formation mechanism which demonstrate that the formed mesostructured particle in the bulk solution drives the formation of mesoporous film on the air− water interface (routes A and B). 251 Combined spin−echo modulated small-angle neutron scattering (SEMSANS) and small-angle neutron scattering (SANS) are used to study the formation kinetics of the mesoporous films. In this case, the combined method allowed the observation of structural evolution in the reaction system within the subphase over a wide range of length scales.…”

“…More importantly, this self-assembly mechanism of mesoporous films is valid for both CTAB and C 16 EO 8 . 251 The key factors for the oriented assembly of functional mesoporous materials on the macroscale liquid−gas interfaces include the evaporating solvent or polyelectrolyte to change the hydrophobic properties of micelles and the precise control over the hydrolysis and condensation of precursors. The framework precursor/surfactant ratio also influences the reaction rate or even disturbs self-assembly behavior.…”

Spin-echo small-angle neutron scattering for multiscale structure analysis of food materials

“…At the spallation source ISIS there are spin-echo components installed at the instrument Larmor, which makes it possible to do SANS measurements, SESANS measurements and both simultaneously (Schmitt et al, 2020). RF-flippers with tilted magnetic interfaces create the precession gradient for a wide wavelength band (Plomp, De Haan, Dalgliesh, Langridge and .…”