Beyond metals: theoretical discovery of semiconducting MAX phases and their potential application in thermoelectrics.

MAX phase is a family of ceramic compounds, typically known for their metallic properties. However, we show here that some of them may be narrow bandgap semiconductors. Using a series of first-principles calculations, we have investigated the electronic structures of 861 dynamically stable MAX phases. Notably, Sc2SC, Y2SC, Y2SeC, Sc3AuC2, and Y3AuC2 have been identified as semiconductors with band gaps ranging from 0.2 to 0.5 eV. Furthermore, we have assessed the thermodynamic stability of these systems by generating ternary phase diagrams utilizing evolutionary algorithm techniques. Their dynamic stabilities are confirmed by phonon calculations. Additionally, we have explored the potential thermoelectric efficiencies of these materials by combining Boltzmann transport theory with first-principles calculations. The relaxation times are estimated using scattering theory. The zT coefficients for the aforementioned systems fall within the range of 0.5 to 2.5 at temperatures spanning from 300 to 700 K, indicating their suitability for high-temperature thermoelectric applications.

Energy harvesting from mechanical vibrations: self-rectification effect.

The use of environmental vibrations as an energy source for stimulating small-scale energy harvesting (EH) devices has received significant attention in recent years. The conversion of alternating currents (AC) to direct currents (DC) is essential to powering electronic devices effectively. This study proposes a method where hexagonal boron nitride nanoribbons and nanotubes harvest energy and rectify the output voltage simultaneously with no need for an external rectifying circuit. This is a step to eliminate the necessity of batteries for EH devices, which require a constant power supply to generate electrical energy while maintaining their nanoscale dimensions. A molecular dynamics approach was used to simulate the response of boron nitride structures to mechanical vibrations. The polarization and voltage generated under tensile and compressing strain fields were calculated, and it was demonstrated that the buckling of the nano-mechanical structures could be engineered to rectify the generated voltage. This paves the way for the design of more efficient and scalable energy harvesting devices.

Asymmetric effects of amphipathic molecules on mechanosensitive channels.

Mechanosensitive (MS) ion channels are primary transducers of mechanical force into electrical and/or chemical intracellular signals. Many diverse MS channel families have been shown to respond to membrane forces. As a result of this intimate relationship with the membrane and proximal lipids, amphipathic compounds exert significant effects on the gating of MS channels. Here, we performed all-atom molecular dynamics (MD) simulations and employed patch-clamp recording to investigate the effect of two amphipaths, Fluorouracil (5-FU) a chemotherapy agent, and the anaesthetic trifluoroethanol (TFE) on structurally distinct mechanosensitive channels. We show that these amphipaths have a profound effect on the bilayer order parameter as well as transbilayer pressure profile. We used bacterial mechanosensitive channels (MscL/MscS) and a eukaryotic mechanosensitive channel (TREK-1) as force-from-lipids reporters and showed that these amphipaths have differential effects on these channels depending on the amphipaths' size and shape as well as which leaflet of the bilayer they incorporate into. 5-FU is more asymmetric in shape and size than TFE and does not penetrate as deep within the bilayer as TFE. Thereby, 5-FU has a more profound effect on the bilayer and channel activity than TFE at much lower concentrations. We postulate that asymmetric effects of amphipathic molecules on mechanosensitive membrane proteins through the bilayer represents a general regulatory mechanism for these proteins.