A new generation of sensors can be engineered based on the sensing of several markers to satisfy the conditions of the multimodal detection principle. From this point of view, photoacoustic-based sensing approaches are essential. The photoacoustic effect relies on the generation of light-induced deformation (pressure) perturbations in media, which is essential for sensing applications since the photoacoustic response is formed due to a contrast in the optical, thermal, and acoustical properties. It is also particularly important to mention that photoacoustic light-based approaches are flexible enough for the measurement of thermal/elastic parameters. Moreover, the photoacoustic approach can be used for imaging and visualization in material research and biomedical applications. The advantages of photoacoustic devices are their compact sizes and the possibility of on-site measurements, enabling the online monitoring of material parameters. The latter has significance for the development of various sensing applications, including biomedical ones, such as monitoring of the biodistribution of biomolecules. To extend sensing abilities and to find reliable measurement conditions, one needs to clearly understand all the phenomena taking place during energy transformation during photoacoustic signal formation. Therefore, the current paper is devoted to an overview of the main measurement principles used in the photoacoustic setup configurations, with a special focus on the key physical parameters.

Carbon-based nanomaterials are promising for a wide range of biomedical applications, i.e. drug delivery, therapy, and imaging including photoacoustic tomography, where they can serve as contrast agents, biocompatibility and biodistribution of which should be assessed before clinical setting. In this paper, localization of carbon flurooxide nanoparticles, carbon nanodots from β-alanine, carbon nanodots from urea and citric acid and glucose-ethylenediamine nanoparticles (NPs) in organs of Wistar rats were studied by photoacoustic measurements after 24 h of their intravenous injection. 16 ns light pulse from a Q-switched Nd:YAG laser with 1064 nm wavelength was used as an excitation source. The laser-induced photoacoustic signals were recorded with a ring piezoelectric detector. Light absorption by carbon NPs resulted in noticeable enhancement of the photoacoustic amplitude in the tissues where the NPs were accumulated. The NPs were preferably accumulated in liver, kidneys and spleen, and to a lesser extent in heart and gastrocnemius muscles. Together with remarkable fluorescent properties of the studied carbon nanomaterials, their photoacoustic responses allow their application for bi-modal fluorescence-photoacoustic bio-imaging.

The photoacoustic method with piezoelectric detection for the simultaneous evaluation of the thermophysical properties is proposed. The approach is based on the settling of an additional heat sink for redistribution of heat fluxes deposited on the sample surface. First, the approach was tested on the porous silicon with well-defined morphology and well-studied properties. Then, heat capacity and thermal conductivity of silicon nanowire arrays were investigated by recovering the experimental data through numerical simulations. The decrease in heat capacity and effective thermal conductivity of the samples upon increasing thickness and porosity of the sample was observed. Such a behavior could be caused by the increase of the structure heterogeneity. In particular, this can be related to a larger disorder (increased density of broken nanowires and larger porosity) that appears during the etching process of the thick layers.

Mesoparticles with characteristic sizes larger than all known molecules and smaller than usual nanoparticles can easily penetrate inside living cells. Thus, they appear to be especially promising for cancer theranostic application. However, presence of mesoparticles can strongly perturb physico-chemical properties of the biological media in which they are incorporated, it is crucial to know a magnitude of such perturbations. For example, thermal properties of liquid solutions with dispersed mesoparticles are crucial for development of theranostic approaches based on photoacoustic effect. In this paper, thermal transport in nanofluids formed by carbon flurooxide (CFO) mesoparticles is reported. A significant non-linear enhancement of the thermal conductivity of the nanofluids (up to 85%, in comparison with initial basic liquids) depending on volume fraction of the dispersed CFO mesoparticles was found. It was revealed that the thermal conductivity rise can be explained by existence of interfacial layers between the mesoparticles and the hosting liquids.

In this study, we investigated the electrical resistivity and its temperature dependence over the range of 77–293 K in epoxy composites filled with nanosized ferrites (CoFe2O4, CuFe2O4, NiFe2O4) and supplemented with multiwalled carbon nanotubes (MWCNTs) or graphene nanoplatelets (GNPs). The results reveal distinct conduction mechanisms associated with the geometry of the nanocarbon filler. Composites with GNPs exhibit both contact and tunneling conduction, while MWCNTs-filled systems demonstrate tunneling-dominated electron transport across the entire temperature range. The results indicate that careful control of the filler ratio allows tuning of the activation energy and resistivity profile, offering significant potential for applications in temperature sensors, flexible electronics, and self-regulating heating systems.