Three luminescent polymorphs based on a new copper(I) complex Cu(2-QBO)(PPh3)PF6 (1, PPh3 = triphenylphosphine, 2-QBO = 2-(2'-quinolyl)benzoxazole) have been synthesized and characterized by FT-IR, UV-vis, elemental analyses, and single-crystal X-ray diffraction analyses. Each polymorph can reversibly convert from one to another through appropriate procedures. Interestingly, such interconversion can be distinguished by their intrinsic crystal morphologies and colors (namely α, dark yellow plate, β, orange block, γ, light yellow needle) as well as photoluminescent (PL) properties. X-ray crystal structure analyses of these three polymorphs show three different supramolecular structures from 1D to 3D, which are expected to be responsible for the formation of three different crystal morphologies such as needle, plate, and block. Combination of the experimental data with DFT calculations on these three polymorphs reveals that the polymorphic interconversion is triggered by the conformation isomerization of the 2-QBO ligand and can be successfully controlled by the polarity of the process solvents (affecting the molecular dipole moment) and thermodynamics (affecting the molecular total energy). It is also found that the different crystal colors of polymorphs and their PL properties are derived from different θ values (dihedral angle between benzoxazolyl and quinolyl group of the 2-QBO ligand) and P-Cu-P angles based on TD-DFT calculations. Moreover, an interesting phase interconversion between γ and β has also been found under different temperature, and this result is consistent with the DFT calculations in which the total energy of β is larger than that of γ. This polymorphism provides a good model to study the relationship between the structure and the physical properties in luminescent copper(I) complexes as well as some profound insights into their PL properties.

Titanium carbide (TiC) has been synthesized by mechanically alloying the elemental powder mixture of titanium and graphite at composition of Ti1−xCx (x=0.35, 0.43, 0.50). Under the employed milling condition, the formation of TiC has been found to undergo an abrupt, exothermic reaction. The final product is TiC for x=0.43 and 0.50, and TiC+Ti (small amount) for x=0.35. It is suggested that this reaction appears to be a self-sustained high-temperature synthesis process. The initial milling stage seems to be an incubation duration for the reaction, and the mechanical impacts to be the ignition of the following abrupt reaction. It is believed that this type of reaction is an important mechanism for mechanical alloying of the highly exothermic alloy systems.

With the development and rising of antimicrobial resistance, rapid and effective killings of bacteria are urgently needed, especially for antibiotic-resistant bacteria and bacterial biofilms that are usually hard to be treated with conventional antibiotics. Here, a rapid and broad-spectrum antibacterial strategy is demonstrated through photothermal ablation with MXene and light. Ti 3 C 2 MXenes, when combined with 808 nm light, show significant antibacterial effects in just 20 min. The antibacterial strategy is effective to 15 bacterial species tested, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE). In addition, the rapid antibacterial strategy works for MRSA biofilms, by damaging the structures as well as killing bacteria in biofilms. Furthermore, the investigation of the antibacterial mechanisms shows that Ti 3 C 2 with light kills bacteria mainly physically through inserting/contact and photothermal effect. This work broadens the potential applications of MXene and provides a way to eradicate bacteria and biofilms physically, without the likelihood of resistance development.

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