The red macroalgae Porphyra, commonly known as Nori, is widely used as food around the world due to its high nutrient content, including the significant abundance of colored phycobiliproteins (PBPs). Among these, R-phycocyanin (R-PC) stands out for its vibrant purple color and numerous bioactive properties, making it a valuable protein for the food industry. However, R-PC\'s limited thermal stability necessitates alternative processing methods to preserve its color and bioactive properties. Our study aimed to investigate the in-situ stability of oligomeric R-PC under high pressure (HP) conditions (up to 4000 bar) using a combination of absorption, fluorescence, and small-angle X-ray scattering (SAXS) techniques. The unfolding of R-PC is a multiphase process. Initially, low pressure induces conformational changes in the R-PC oligomeric form (trimers). As pressure increases above 1600 bar, these trimers dissociate into monomers, and at pressures above 3000 bar, the subunits begin to unfold. When returned to atmospheric pressure, R-PC partially refolds, retaining 50% of its original color absorbance. In contrast, heat treatment causes irreversible and detrimental effects on R-PC color, highlighting the advantages of HP treatment in preserving both the color and bioactive properties of R-PC compared to heat treatment.

Simultaneous enhancement of free excitons (FEs) emission and self-trapped excitons (STEs) emission remains greatly challenging because of the radiative pathway competition. Here, a significant fluorescence improvement, associated with the radiative recombination of both FEs and STEs is firstly achieved in an unconventional ACI-type hybrid perovskite, (ACA)(MA)PbI4 (ACA=acetamidinium) crystals with {PbI6} octahedron units, through hydrostatic pressure processing. Note that (ACA)(MA)PbI4 exhibits a 91.5-fold emission enhancement and considerable piezochromism from green to red in a mild pressure interval of 1 atm to 2.5 GPa. The substantial distortion of both individual halide octahedron and the Pb-I-Pb angles between two halide octahedra under high pressure indeed determines the pressure-tuning localized excitons behavior. Upon higher pressure, photocurrent enhancement is also observed, which is attributed to the promoted electronic connectivity in (ACA)(MA)PbI4. The anisotropic compaction reduces the distance between neighboring organic molecules and {PbI6} octahedra, leading to the enhancement of hydrogen bonding interactions. This work not only offers a deep understanding of the structure-optical relationships of ACI-type perovskites, but also presents insights into breaking the limits of luminescent efficiency by pressure-suppressed nonradiative recombination.

We have developed a HPLC system where phase-separation multiphase flow works in the separation column as an eluent. We call the novel separation mechanism a phase-separation mode. The ternary mixed solution of water/acetonitrile/ethyl acetate, which is one of the two-phase-separation mixed solutions, caused the phase-separation multiphase flow via phase change from homogeneous to heterogeneous with the temperature effect (from 20 to 0 °C). In this study, we tried to perform phase-separation multiphase flow with the pressure effect instead of the temperature one. The fused-silica capillary tube (50 cm length and 50 µm inner diameter) was allied to the downstream of the column to apply the pressure of 5.5 MPa to the system. Model analytes of 2,6-naphthalenedisulfonic acid (2,6-NDS) and 1-naphthol (1-NA) were examined. For example, solutions (the volume% of water/acetonitrile/ethyl acetate; 20:55:25, organic-rich) and (60:30:10, water-rich) were used as eluent. The model analytes were not separated with both solutions at the pressure of 1.5 MPa and 20 °C. But with the organic-rich solution, 1-NA and 2,6-NDS were separated in this order and with the water-rich solution, they were separated in the reverse order at the pressure of 5.5 MPa and 20 °C. The phase-separation mode could be performed at the high pressure even at the room temperature.

The study of Na-carbonates stability and their transformations in aqueous carbonate fluid under high P-T conditions is relevant from the point of view of the understanding geochemical processes of the Na-assisted carbon circulation in the Earth\'s crust and subduction zones. In situ Raman study of Na-bearing carbonate-water-Fe-metal system in diamond anvil cell (DAC) at high P-T conditions revealed that carbonates decompose with abiogenic formation of formates and other organic compounds that differs from behavior of carbonates in dry system. XRD and FTIR methods have been used additionally to determine the phase composition. Na-bearing carbonates (nahcolite NaHCO3, shortite Na2Ca2(CO3)3 and cancrinite Na7Ca[(CO3)1.5Al6Si6O24]⋅2H2O) in aqueous fluid decompose to form simple carbonates and formates (as dominant organic molecules) at moderate P-T parameters (above ∼0.2 GPa, 200 °C). Our experimental results directly confirm the hypothesis of Horita and Berndt (Science, 1999) about possible yield of organic formates in the carbonate-water-metal system. Nahcolite NaHCO3 in aqueous fluid in the presence of Fe metal decomposes into anhydrous phases: natrite γ-Na2CO3, siderite, magnetite (due to dissolution of Fe steel gasket), Na-formate and likely organic molecular crystalline solvate of Na-formate and methyl formate. Shortite decays into anhydrous phases: aragonite CaCO3, Na-Ca-formates and an amorphous phase. Cancrinite decomposes to unidentified carbonate-alumonosilicate phases, Na-Ca-formates and unknown organic molecular crystal. Magnetite is also formed in this system due to dissolution of Fe steel gasket used in DAC. The present study provides a new insight in processes of abiogenic formation of organic matter from carbonates in the crust and upper mantle.

Achieving superconductivity at room temperature (RT) is a holy grail in physics. Recent discoveries on high-Tc superconductivity in binary hydrides H3S and LaH10 at high pressure have directed the search for RT superconductors to compress hydrides with conventional electron-phonon mechanisms. Here, an exceptional family of superhydrides is predicated under high pressures, MH12 (M = Mg, Sc, Zr, Hf, Lu), all exhibiting RT superconductivity with calculated Tcs ranging from 313 to 398 K. In contrast to H3S and LaH10, the hydrogen sublattice in MH12 is arranged as quasi-atomic H2 units. This unique configuration is closely associated with high Tc, attributed to the high electronic density of states derived from H2 antibonding states at the Fermi level and the strong electron-phonon coupling related to the bending vibration of H2 and H-M-H. Notably, MgH12 and ScH12 remain dynamically stable even at pressure below 100 GPa. The findings offer crucial insights into achieving RT superconductivity and pave the way for innovative directions in experimental research.

Transition metal dichalcogenide TiSe2 exhibits a superconducting dome within a low pressure range of 2-4 GPa, which peaks with the maximal transition temperature Tc of ≈1.8 K. Here it is reported that applying high pressure induces a new superconducting state in TiSe2, which starts at ≈16 GPa with a substantially higher Tc that reaches 5.6 K at ≈21.5 GPa with no sign of decline. Combining high-throughput first-principles structure search, X-ray diffraction, and Raman spectroscopy measurements up to 30 GPa, It is found that TiSe2 undergoes a first-order structural transition from the 1T phase under ambient pressure to a new 4O phase under high pressure. Comparative ab initio calculations reveal that while the conventional phonon-mediated pairing mechanism may account for the superconductivity observed in 1T-TiSe2 under low pressure, the electron-phonon coupling of 4O-TiSe2 is too weak to induce a superconducting state whose transition temperature is as high as 5.6 K under high pressure. The new superconducting state found in pressurized TiSe2 requires further study on its underlying mechanism.

PdSe2 is a puckered transition metal dichalcogenide that has been reported to undergo a two-dimensional to three-dimensional structural transition under pressure. Here, we investigated the electronic and phononic evolution of PdSe2 under high pressure using pump-probe spectroscopy. We observed the electronic intraband and interband transitions occurring in the d orbitals of Pd, revealing the disappearance of the Jahn-Teller effect under high pressure. Furthermore, we found that the decay rates of interband recombination and intraband relaxation lifetimes change at 3 and 7 GPa, respectively. First-principles calculations suggest that the bandgap closure slows the decay rate of interband recombination after 3 GPa, while the saturation of phonon-phonon scattering is the main reason for the relatively constant intraband relaxation lifetime. Our work provides a novel perspective for understanding the evolution of the electron and modulation of the carrier dynamics by phonons under pressure.

The crystal structure of lithium xanthinate hydrate was studied by single crystal X-ray diffraction and Raman spectroscopy on cooling to 100 K and under compression to 5.3 GPa. A phase transition at ∼4 GPa is observed. No phase transitions occur on cooling. Anisotropy of lattice strain and changes in intermolecular interactions are compared.

High pressure is both an environmental challenge to which deep sea biology has to adapt, and a highly sensitive thermodynamic tool that can be used to trigger structural changes in biological molecules and assemblies. Lipid membranes are amongst the most pressure sensitive biological assemblies and pressure can have a large influence on their structure and properties. In this chapter, we will explore the use of high pressure small angle X-ray diffraction and high pressure microscopy to measure and quantify changes in the lateral structure of lipid membranes under both equilibrium high pressure conditions and in response to pressure jumps.

2D van der Waals (vdW) magnets have recently emerged as a promising material system for spintronic device innovations due to their intriguing phenomena in the reduced dimension and simple integration of magnetic heterostructures without the restriction of lattice matching. However, it is still challenging to realize Curie temperature far above room temperature and controllable magnetic anisotropy for spintronics application in 2D vdW magnetic materials. In this work, the pressure-tuned dome-like ferromagnetic-paramagnetic phase diagram in an iron-based 2D layered ferromagnet Fe3GaTe2 is reported. Continuously tunable magnetic anisotropy from out-of-plane to in-plane direction is achieved via the application of pressure. Such behavior is attributed to the competition between intralayer and interlayer exchange interactions and enhanced DOS near the Fermi level. The study presents the prominent properties of pressure-engineered 2D ferromagnetic materials, which can be used in the next-generation spintronic devices.