Qiliang Cui

The crystal stacking order plays a crucial role in determining the structure and physical properties of 2D layered materials. A variation in the stacking sequence of adjacent 2D building blocks causes drastic changes in their functionalities. In this work, the structural variation of belloite (Cu(OH)Cl), as a function of pressure, is presented. Through in situ synchrotron X-ray diffraction and Raman scattering studies, in combination with first-principles theoretical simulations, a structural transformation from the initial monoclinic phase into an orthorhombic one has been established at 18.7 GPa, featuring variations in the stacking sequence of the tectonic monolayers. In the monoclinic phase, they are arranged in an AAAA sequence. While in the orthorhombic phase, the monolayers are stacked in an ABAB sequence. Such phenomena are similar to those observed in van der Waals 2D materials, with pressure-induced changes in the stacking order between layers. In addition, an isostructural phase transition within the initial monoclinic phase is also observed to occur at 12.9–16 GPa, which is associated with layer-sliding and a change in hydrogen bond configuration. These results show that Cu(OH)Cl, as well as other hydrogen-bonded 2D layered materials, can provide a convenient platform for studying the effects of the crystal stacking order.

Ag/TiO₂ wood-based nanocomposites were prepared by the methods of ultrasound impregnation and vacuum impregnation. The as-prepared samples were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), mercury intrusion porosimetry (MIP), and water contact angles (WCAs). The anti-mold properties of the Ag/TiO₂ wood-based nanocomposites were improved by 14 times compared to those of the original wood. The nano-Ag/TiO₂, which was impregnated in the tracheid and attached to the cell walls, was able to form a two-stage rough structure and reduce the number of hydroxyl functional groups on the wood surfaces. The resulting decline of wood hydrophobic and equilibrium moisture content (EMC) destroyed the moisture environment necessary for mold survival. Ag/TiO₂ was deposited in the wood pores, which reduced the number and volume of pores and blocked the path of mold infection. Thus, the anti-mold properties of the Ag/TiO₂ wood-based nanocomposite were improved by cutting off the water source and blocking the mold infection path. This study reveals the anti-mold mechanism of Ag/TiO₂ wood-based nanocomposites and provides a feasible pathway for wood-based nanocomposites with anti-mold functions.

The high-pressure Raman and IR measurements of NaN₃ were performed at room temperature with pressure up to 35.0 and 26.0 GPa, respectively. Three phase transitions of β-NaN₃ → α-NaN₃ → γ-NaN₃ → δ-NaN₃ were revealed at 0.5, 14.0, and 27.6 GPa. All fundamental vibrational modes were analyzed based on experimental and theoretical methods. The phase transition from β-NaN₃ to α-NaN₃ is attributed to the shearing distortion of unit cell and the rotation of the azide ions with increasing pressure. The abnormal symmetric evolution of bending modes observed in IR measurements reveals the rotational behavior of azide groups upon compression. Moreover, the azide ions might evolve into an energetically favorable arrangement under a higher pressure.

This study presents a systematic investigation of AlN:Co nanowires synthesis by a DC arc discharge plasma method that is catalyst- and template-free. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) have been used to characterize the structure, components, morphology and size of the nanowires. Raman spectroscopy revealed very symmetric and strong phonon modes, indicating very good crystal quality of the AlN:Co nanowires. Comparison of the Raman spectra of AlN and AlN:Co nanowires showed that the Co doping influenced the lattice structure, producing impurities and defects. The photoluminescence emission spectrum (PL) confirmed that the Co²⁺ ions existed in the AlN:Co nanowires and enhanced the optical light range and intensity of the material. A magnetic study suggested that ferromagnetism in the AlN:Co nanowires may be due to the Co ion clusters, accompanied by Al vacancies. In brief, 1D-AlN:Co nanowires were fabricated with high aspect ratio and high crystal quality and possessed excellent optical and magnetic properties. These features are very valuable for scaling up manufacturing opportunities of AlN-based DMSs and will be beneficial to manipulate and integrate these for nanodevice fabrication in spintronics.