MXene quantum dots (MQDs) have recently attracted increasing attention as zero-dimensional derivatives of MXenes with enhanced quantum confinement effects, tunable surface chemistry, and broadband nonlinear optical responses. This review provides a focused and critical synthesis of recent advances in Ti3C2Tx and V2C MQDs for ultrafast laser photonics. The current literature on synthesis strategies - including electrochemical exfoliation, HF-free solvothermal routes, and laser ablation - is systematically examined in relation to size control, surface termination engineering, and defect regulation. Reported nonlinear optical mechanisms, such as saturable absorption (SA), reverse saturable absorption (RSA), and two-photon absorption (TPA), are comparatively analyzed with emphasis on their impact on pulse duration, modulation depth, saturation intensity, and operational stability in fiber and solid-state laser systems. Broadband compatibility across the 1.0-1.55 mu m spectral region and device-level integration strategies are discussed to clarify structure - property - performance relationships. By consolidating dispersed findings and identifying material and device-level challenges, this review outlines key design principles and future directions for engineering MQDs as stable and high-performance saturable absorbers in next-generation ultrafast photonic systems. [GRAPHICS] .
The supersonic particle-laden turbulent mixing layer is considered a promising method to enhance supersonic combustion in scramjet engine design. The injection of particles into the mixing flow is one way to improve fuel-oxidizer mixing and enhance the energy density of the fuel. In this paper, we continue our numerical study of the high-speed hydrogen and air mixing layer with solid particles using the Eulerian-Lagrangian approach. The quasi two-dimensional Navier-Stokes equations with the third-order essentially nonoscillatory (ENO) scheme are carried out. Ordinary differential equations of particles are solved with the explicit second-order Euler method. The basic purpose is to study the influence of gas temperatures on the flow and particle behavior. The result of particles heating around formed vortices in a mixing layer is presented for two options of the variation of temperatures at the entrance. In the first one, the upper hydrogen flow temperature is taken to be the same, while the temperature of the bottom airflow is changed. And, in the second case, on the contrary, the upper hydrogen flow temperature is varied. It is revealed that a decrease in the temperature in the vortex core due to the rapid turnover of a high-speed flow leads to a significant discrepancy in the distribution of maximum and minimum temperatures between the vortex core and its braid. This is what causes the wave-like shape of the particle temperatures in the mixing layer. In addition, particles are moved in the high-temperature airflow (on the periphery of the mixture layer) and are heated up very quickly.
