Search

In modern medicine, precision diagnosis and treatment using optical materials, such as fluorescence/photoacoustic imaging-guided photodynamic therapy (PDT), are becoming increasingly popular. Photosensitizers (PSs) are the most important component of PDT. Different from conventional PSs with planar molecular structures, which are susceptible to quenching effects caused by aggregation, the distinct advantages of AIE fluorogens open up new avenues for the development of image-guided PDT with improved treatment accuracy and efficacy in practical applications. It is critical that as much of the energy absorbed by optical materials is dissipated into the pathways required to maximize biomedical applications as possible. Intersystem crossing (ISC) represents a key step during the energy conversion process that determines many fundamental optical properties, such as increasing the efficiency of reactive oxygen species (ROS) production from PSs, thus enhancing PDT efficacy. Although some review articles have summarized the accomplishments of various optical materials in imaging and therapeutics, few of them have focused on how to improve the phototherapeutic applications, especially PDT, by adjusting the ISC process of organic optics materials. In this review, we emphasize the latest advances in the reasonable design of AIE-active PSs with type I photochemical mechanism for anticancer or antibacterial applications based on ISC modulation, as well as discuss the future prospects and challenges of them. In order to maximize the anticancer or antibacterial effects of type I AIE PSs, it is the aim of this review to offer advice for their design with the best energy conversion.

The production of alloys with high strength and toughness concurrently is still a difficult challenge. Here, we designed a simple solution-ageing heat treatment system to control the morphology and density of α in Ti-15Mo-3Al-2.7Nb-0.2Si via different heat treatment temperatures. The experimental results show that Ti-15Mo-3Al-2.7Nb-0.2Si exhibits a synergistic combination of tensile strength (1364 MPa), plasticity (7.8% elongation), and fracture toughness (101 MPa·m1/2) through solutions in the α/β biphasic region and duplex ageing. Notably, the strength of the alloy after the second step of the ageing process is increased by 15% compared with that after the first step of the ageing process. However, there is less than a 5% reduction in the fracture toughness. TEM observations show that the matrix continues to precipitate denser secondary α during duplex ageing, which causes the strength to increase significantly and causes the fracture toughness to weaken. Our work may provide a novel method to optimize the mechanical properties of alloys by controlling the precipitates.

The crystal structure has a great influence on mechanical sensitivity and detonation performance of energetic materials. An efficient microfluidic platform was applied for size, morphology, and crystallinity controllable preparation of ultrafine HMX. The microfluidic platform has good mixing performance, quick response, and less reagent consumption. The ultrafine γ-HMX was first prepared at room temperature by microfluidic strategy, and the crystal type can be controlled accurately by adjusting the process parameters. With the increase in flow ratio, the particle size decreases gradually, and the crystal type changed from β-HMX to γ-HMX. Thermal behavior of ultrafine HMX shows that γ→δ is easier than β→δ, and the phase stability of HMX is β > γ > δ. Furthermore, the ultrafine β-HMX has higher thermal stability and energy release efficiency than that of raw HMX. The ultrafine HMX prepared by microfluidic not only has uniform morphology and narrow particle size distribution, but also exhibits high density and low sensitivity. This study provides a safe, facile, and efficient way of controlling particle size, morphology, and crystallinity of ultrafine HMX.

1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) is a type of high energy explosive, its application in weapon systems is limited by its high mechanical sensitivity. At the same time, 1,1-diamino-2,2-dinitroethylene (FOX-7) is a famous insensitive explosive. The preparation of RDX@FOX-7 composites can meet the requirements, high energy and low sensitivity, of the weapon systems. It is difficult for the reactor to achieve uniform quality of composite material, which affects its application performance. Based on the principle of solvent-anti-solvent, the recrystallization process was precisely controlled by microfluidic technology. The RDX@FOX-7 composites with different mass ratios were prepared. At the mass ratio of 10%, the RDX@FOX-7 composites are ellipsoid of about 15 μm with uniform distribution and quality. The advantages of microscale fabrication of composite materials were verified. The results of structure characterization showed that there is no new bond formation in RDX@FOX-7, but the distribution of two components on the surface of the composite was uniform. Based on the structure characterization, we established the structure model of RDX@RDX-7 and speculated the formation process of the composites in microscale. With the increase of FOX-7 mass ratios, the melting temperature of RDX was advanced, the thermal decomposition peak of RDX changed to double peaks, and the activation energy of RDX@FOX-7 composite decreased. These changes were more pronounced between 3 and 10% but not between 10 and 30%. The ignition delay time of RDX@FOX-7 was shorter than that of RDX and FOX-7. RDX@FOX-7 burned more completely than RDX indicating that FOX-7 can assist heat transfer and improve the combustion efficiency of RDX.

This study presents a strategy for the preparation of multiscale α phase by high/low-temperature two-step aging in metastable β titanium alloy, Ti-15Mo-3Al-2.7Nb-0.2Si. The purpose of high-temperature aging is to obtain a number of micro-scale secondary α phases (αS), besides precipitation-free zones (PFZs). After that, in the second stage of low-temperature aging, the nano-scale tertiary α phase (αT) precipitates in the PFZs. The second-step aging temperature and the time at low temperature will have an important effect on αT. On the one hand, with the extension of aging time, the morphology of αT changes from dot-like to needle-like. Secondly, the increase of the second-step aging temperature will promote precipitation of αT in PFZs. The strength increases gradually with the accelerated precipitation of αT, and good plasticity is still maintained. The effect of multiscale α on fracture behavior was investigated by in situ tensile testing. Results show that cracks form a transgranular fracture along the slip line after solution treatment. After first-step aging, the crack easily passes through αS and forms an intergranular fracture. After second-step aging, the formation of multiscale α phase has a stronger effect in hindering the crack growth, which leads to crack propagation mainly by transgranular fracture. Overall, this study demonstrates that the alloy can be heat-treated to achieve an excellent match between strength and ductility, which is expected to meet the application requirements of structural materials of the new generation of aircraft.

Nitrogen-doped carbon-supported metal nano-particles show great promise as high-performance catalysts for novel energies, organic synthesis, environmental protection, and other fields. The synergistic effect between nitrogen-doped carbon and metal nano-particles enhances the catalytic properties. Thus, how to effectively combine nitrogen-doped carbon with metal nano-particles is a crucial factor for the synthesis of novel catalysts. In this paper, we report on a facile method to prepare nitrogen-doped carbon-supported metal nano-particles by using dimethylgly-oxime as ligand. The nano-particles of Pd, Ni, Cu, and Fe were successfully prepared by the pyrolysis of the corresponding clathrate of ions and dimethylglyoxime. The ligand of dimethylglyoxime is adopted as the source for the nitrogen-doped carbon. The nano-structure of the prepared Pd, Ni, Cu, and Fe particles are confirmed by X-ray diffraction, scanning electron microscopy, and trans-mission electron microscopy tests. The catalytic performances of the obtained metal nano-particles for oxygen reduction reaction (ORR) are investigated by cyclic voltammetry, Tafel, linear sweeping voltammetry, rotating disc electrode, rotating ring disc electrode, and other technologies. Results show that the nitrogen-doped carbon-supported metal nano-particles can be highly efficient catalysts for ORR. The results of the paper exhibit a facile methodology to prepare nitrogen-doped carbon-supported metal nano-particles.