Controlling the Nanocontact Nature and the Mechanical Properties of a Silica Nanoparticle Assembly

Abstract

Elaborating advanced nanomaterials based on the assembly of nanoparticles (NPs) is a versatile route for targeting and tuning a wide variety of properties like optical, magnetic, and electrical properties or sensing. This route usually employs a so-called soft chemistry which has the advantage of being quite cheap and transferable to an industrial level. However, getting quantitative information on the quality of the mechanical consolidation of the nanoparticle assembly (ordered or disordered) in a nondestructive manner is not often achieved, although it is crucial for applications and integration of materials in devices. Therefore, we present in this Article a complete method where we evaluate the elasticity of weakly (van der Waals nanocontacts) to strongly (covalent-hydrogen nanocontacts) interacting nanoparticle assemblies. This complete work is realized on a disordered silica nanoparticle network obtained by the sol–gel method. A precise control of the chemical and physical properties of the nanoparticle surface molecular landscape is achieved thanks to infrared, visible, and ultraviolet spectroscopies as well as surface tension measurements and atomic force microscopy, while the nanoparticle assembly elastic stiffness is evaluated by ultrafast nanoacoustics based on an optical pump–probe method.

Robustness of elastic properties in polymer nanocomposite films examined over the full volume fraction range

“…The absence of a significant response to aging proves that for low particle fractions, the polymer nanocomposite system is in quasi-equilibrium. For higher inclusion volumes, the change in behavior is in line with what can be expected if a transition from van-der-Waals to covalently bonded particles takes place, as studied elsewhere 9 , 10 . Finally, we see that robustness to aging effects is achievable by lowering nanoparticle fractions (see insets to Fig.…”

“…Where elastic behavior is concerned, if and how particles form contacts is known to be a determining factor, and fast acoustic techniques have recently been deployed to investigate the problem 9 , 10 . While giving insight into the transition between different chemical bonding regimes (van der Waals, covalent), a simpler and often more practical distinction is that between absence and presence of bonds altogether, depending on inter-particle distance.…”

Photoacoustic Sensing of Trapped Fluids in Nanoporous Thin Films: Device Engineering and Sensing Scheme

“…The sensor working principle relies on ultrafast photoacousics, 42 among the emerging techniques for mechanical nanometrology in a variety of systems ranging from phononic crystals, [43][44][45] ultrathin-films, [46][47][48] to multilayer tube 49 and granular materials. 50 The transduction scheme is as follows: in the excitation step (opto-acoustic transduction) an ultrafast IR laser pump pulse illuminates the device. The energy absorbed by the granular metallic film leads to an impulsive lattice temperature increase of the order of a few Kelvins, avoiding any annealing effect.…”

Longitudinal eigenvibration of multilayer colloidal crystals and the effect of nanoscale contact bridges

“…Similarly, the measurements presented in Reference [3] provided limited information concerning the acoustic modes of the crystal, no characterization of the interparticle contact stiffnesses, and, due to the sintering of the crystal, we expect limited dynamic deformation of the particle contacts was involved. Several studies have also explored the contact-mediated acoustics of 3D colloidal films, however these were either disordered [30,31] , or the spheres were separated by large ligands [32][33][34] or polymer tethers [35] that approach the particle size and result in non-Hertzian contact mechanics.…”