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

Abstract

Accessing fluid infiltration in nanogranular coatings is an outstanding challenge, of relevance for applications ranging from nanomedicine to catalysis. A sensing platform, allowing quantifying the amount of fluid infiltrated in a nanogranular ultrathin coating, with thickness in the 10-40 nm range, is here proposed and theoretically investigated by multiscale modeling. The scheme relies on impulsive photoacoustic excitation of hypersonic mechanical breathing modes in engineered gas-phase-synthesized nanogranular metallic ultrathin films and time-resolved acousto-optical read-out of the breathing modes frequency shift upon liquid infiltration. A superior sensitivity, exceeding 26 × 10 cm/g, is predicted upon equivalent areal mass loading of a few ng/mm. The capability of the present scheme to discriminate among different infiltration patterns is discussed. The platform is an ideal tool to investigate nanofluidics in granular materials and naturally serves as a distributed nanogetter coating, integrating fluid sensing capabilities. The proposed scheme is readily extendable to other nanoscale and mesoscale porous materials.

Time-Domain Investigations of Coherent Phonons in van der Waals Thin Films

“…where R is defined as previously in the impedance mismatch model [246,247] or modified by the interface contact stiffness for an imperfect contact [137]. Remarkably, the damping is independent of the mode frequency, implying that higher Q are expected for higher harmonics, in good agreement with experimental data from [136], which strengthens this interpretation in this recent study.…”

“…The impedance mismatch between the vdW film (of thickness Nd and of impedance Z f ) and the substrate (semi-infinite, of impedance Z s ) drives the interface mechanical behavior. Solving this geometrical configuration in a continuous medium framework, one finds that the complex frequency f of the acoustic oscillation in the thin film is solution of the equation [245][246][247]…”

Antimicrobial Nanostructured Coatings: A Gas Phase Deposition and Magnetron Sputtering Perspective

“…Nanostructured materials (NMs) [1][2][3][4][5] represent an active area of research and a techno-economic sector in continuous expansion in many application domains, as shown by the more than 1400 review papers describing NMs applications that have appeared in the last three years. The technological importance of NMs is due to their tunable physicochemical characteristics, such as optical absorption [6][7][8], electrical conductivity [9,10], photothermal characteristics [11], optical [12,13] and photoacoustic sensing [14,15], surface enhanced Raman scattering effects [16,17], chemical state [18], and bactericidal functionalities [19][20][21]. In particular, the latter research sector has been driven by the interest in understanding the interactions and effects of nanoparticles (NPs) on living organisms [20][21][22][23][24][25][26][27], with prominent attention towards the wet synthesis of NMs and NPs and the study of their effect on cells and bacteria in solution.…”

Ultrafast acoustic vibrations of Au–Ag nanoparticles with varying elongated structures

“…For example, it allows to address the influence of particle size, morphology, interface conditions and mutual mechanical contacts on the nanostructure vibrations, 8 to characterize the coupling with the surrounding environment, 9−12 and to design ultrasensitive mechanical nanobalances that detect frequency shift of vibrational modes when a small mass deposits on the particle surface. [13][14][15][16] Currently, there is a rapidly growing interest in Au-Ag bimetallic nano-objects since they present not only a combination of properties associated with monometallic Au or Ag, but also novel performances due to their synergistic effects. 17−20 However, their acoustic signatures have been little investigated in experiments.…”