MgF2:Mn2+: novel material with mechanically-induced luminescence.

Mechanoluminescent (ML) materials can directly convert external mechanical stimulation into light without the need for excitation from other forms of energy, such as light or electricity. This alluring characteristic makes ML materials potentially applicable in a wide range of areas, including dynamic imaging of force, advanced displays, information code, storage, and anti-counterfeiting encryption. However, current reproducible ML materials are restricted to sulfide- and oxide-based materials. In addition, most of the reported ML materials require pre-irradiation with ultraviolet (UV) lamps or other light sources, which seriously hinders their practical applications. Here, we report a novel ML material, MgF2:Mn2+, which emits bright red light under an external dynamic force without the need for pre-charging with UV light. The luminescence properties were systematically studied, and the piezophotonic application was demonstrated. More interestingly, unlike the well-known zinc sulfide ML complexes reported previously, a highly transparent ML film was successfully fabricated by incorporating MgF2:Mn2+ into polydimethylsiloxane (PDMS) matrices. This film is expected to find applications in advanced flexible optoelectronics such as integrated piezophotonics, artificial skin, athletic analytics in sports science, among others.

Near-Infrared Broadband ZnTa2O6:Cr3+ Phosphor for pc-LEDs and Its Application to Nondestructive Testing.

Broadband near-infrared (NIR) phosphors are necessary materials for developing portable NIR light sources. Moreover, exploiting an NIR phosphor with a main peak located beyond a wavelength of 900 nm remains a challenge because this spectral range has great potential in biological nondestructive testing and solution testing. In this study, a range of Cr3+-doped ZnTa2O6 (ZTO) phosphors were completely synthesized by a solid-state method, which show broadband Cr3+ emission centered at 935 nm with a large full width at half maximum (FWHM) of 185 nm due to two distorted octahedral sites. A packaged phosphor-converted light-emitting diode (pc-LED) device is used to penetrate a 5-cm-thick chicken breast and identify diverse solutions based on differences in the measured transmission spectra. The results indicate broad application prospects in the field of biological tissue penetration and solution analysis.

On-Surface Synthesis of [3]Radialenes via [1+1+1] Cycloaddition.

[3]Radialenes are the smallest carbocyclic structures with unusual topologies and cross-conjugated π-electronic structures. Here, we report a novel [1+1+1] cycloaddition reaction for the synthesis of aza[3]radialenes on the Ag(111) surface, where the steric hindrance of the chlorine substituents guides the selective and orientational assembling of the isocyanide precursors. By combining scanning tunneling microscopy, non-contact atomic force microscopy, and time-of-flight secondary ion mass spectrometry, we determined the atomic structure of the produced aza[3]radialenes. Furthermore, two reaction pathways including synergistic and stepwise are proposed based on density functional theory calculations, which reveal the role of the chlorine substituents in the activation of the isocyano groups via electrostatic interaction.

Interlayer Quasi-Bonding Interactions in 2D Layered Materials: A Classification According to the Occupancy of Involved Energy Bands.

Recent studies have revealed that the interlayer interaction in two-dimensional (2D) layered materials is not simply of van der Waals character but could coexist with quasi-bonding character. Herein, we classify the interlayer quasi-bonding interactions into two main categories (I: homo-occupancy interaction; II: hetero-occupancy interaction) according to the occupancy of the involved energy bands near the Fermi level. We then investigate the quasi-bonding-interaction-induced band structure evolution of several representative 2D materials based on density functional theory calculations. Further calculations confirm that this classification is applicable to generic 2D layered materials and provide a unified understanding of the total strength of interlayer interaction, which is a synergetic effect of the van der Waals attraction and the quasi-bonding interaction. The latter is stabilizing in main category II and destabilizing in main category I. Thus, the total interlayer interaction strength is relatively stronger in category II and weaker in category I.

Ladder Phenylenes Synthesized on Au(111) Surface via Selective [2+2] Cycloaddition.

Ladder phenylenes (LPs) composed of alternating fused benzene and cyclobutadiene rings have been synthesized in solution with a maximum length no longer than five units. Longer polymeric LPs have not been obtained so far because of their poor stability and insolubility. Here, we report the synthesis of linear LP chains on the Au(111) surface via dehalogenative [2+2] cycloaddition, in which the steric hindrance of the methyl groups in the 1,2,4,5-tetrabromo-3,6-dimethylbenzene precursor improves the chemoselectivity as well as the orientation orderliness. By combining scanning tunneling microscopy and noncontact atomic force microscopy, we determined the atomic structure and the electronic properties of the LP chains on the metallic substrate and NaCl/Au(111). The tunneling spectroscopy measurements revealed the charged state of chains on the NaCl layer, and this finding is supported by density functional theory calculations, which predict an indirect bandgap and antiferromagnetism in the polymeric LP chains.