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Ultrasensitive Detection of MicroRNA with a Bismuthene-enabled Fluorescence Quenching Biosensor
摘要： Bismuthene, a monoelemental two-dimensional material, has shown promise in the biomedicine, electronic, and energy fields due to its high carrier mobility and stability at room temperature. However, its use in biosensing applications is restricted due to the undefined quenching mechanism for dye molecules. Herein, we develop a novel ultrathin bismuthene-based sensing platform for microRNA (miRNA)-specific detection that even discriminates single-base mismatches. The detection limit can reach 60 pM. Excitingly, the fluorescence quenching mechanism of bismuthene, ground state weakly fluorescent charge transfer, is determined via femtosecond pump-probe spectroscopy. This finding provides a proof-of-concept platform to i) fundamentally explore the quenching mechanism of bismuthene and ii) sensitively detect miRNA molecules for early cancer.
关键词： biosensor,Bismuthene,microRNA,charge transfer,fluorescence quenching
更新于2025-09-23 15:21:01
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Valley polarization reversal and spin ferromagnetism and antiferromagnetism in quantum dots of the topological insulator monolayer bismuthene on SiC
摘要： The valley and spin polarizations associated with electronic transport in quantum dots of the large-gap topological insulator (TI) monolayer bismuthene on SiC are investigated in the linear response regime using a minimal tight-binding model that accurately describes the low-energy electronic band structure of this TI. It is found that for zigzag edges the electronic edge states are strongly valley polarized if the Fermi energy lies in the bulk energy band gap. We predict the edge-state valley polarizations to switch between valleys K and K (cid:2) as the Fermi energy varies from the top of the valence band to the bottom of the conduction band or if the direction of electric current through the dot is reversed. If the electrostatic potential in the dot is nonuniform, we predict that the valley polarization of an electron can reverse as it travels through the dot. The valley polarization reversal is due to the zigzag edge-state dispersion crossing the center of the Brillouin zone that separates valleys K and K (cid:2) and is therefore predicted to be a general phenomenon. Although the spin polarization within the edge states is ferromagnetic, as expected for spin Hall devices, our calculations reveal the out-of-plane component of the spin polarization of the bulk valence band scattering states to be antiferromagnetic, and the direction of the out-of-plane component of the Neel vector to depend on whether the electronic accumulation belongs primarily to valley K or K (cid:2).
关键词： quantum dots,ferromagnetism,bismuthene,topological insulator,spin polarization,antiferromagnetism,SiC,tight-binding model,valley polarization
更新于2025-09-23 15:19:57
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Passively Q-switched near-infrared lasers with bismuthene quantum dots as the saturable absorber
摘要： Bismuthene quantum dots (Bi-QDs) were synthesized via the liquid phase exfoliation (LPE) method for the passive Q-switching operation in near-infrared (NIR) region. The nonlinear optical properties of the prepared Bi-QDs were investigated by the open-aperture Z-scan technology. The modulation depths were 18.1% and 5.1% at 1.06 and 1.34 μm, respectively. Based on the Bi-QDs saturable absorber, passively Q-switched Nd:GdVO4 lasers operating at 4F3/2 → 2I11/2 and 4F3/2 → 2I13/2 transitions were demonstrated, showing the wideband optical modulation in NIR regime. For the 4F3/2 → 2I13/2 transition lasing at 1.34 μm, the shortest pulse duration of 155 ns was obtained with a repetition rate of 457 kHz. With respect to the 4F3/2 → 2I11/2 transition at 1.06 μm, the minimum pulse duration was 150 ns with a repetition rate of 424 kHz, leading to a single pulse energy of 261 nJ and a peak power of 1.68 W. In addition, the ground state absorption cross section and the excited state absorption cross section of Bi-QDs were also investigated for the ?rst time. The impact of the excited state lifetime on the output parameters was numerically stimulated by the coupled rate equations. Our work con-?rmed that the trap state in Bi-QDs played an important role in the pulse generation mechanism.
关键词： Saturable absorber,Bismuthene quantum dots,Q-switching,Nonlinear Optical properties,Rate equations
更新于2025-09-23 15:19:57
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Recent progress in ultrafast lasers based on 2D materials as a saturable absorber
摘要： Two-dimensional (2D) materials are crystals with one to a few layers of atoms and are being used in many fields such as optical modulator, photodetector, optical switch, and ultrafast lasers. Their exceptional optoelectronic and nonlinear optical properties make them as a suitable saturable absorber for laser cavities. This review focuses on the recent progress in ultrafast laser use 2D materials as a saturable absorber. 2D materials traditionally include graphene, topological insulators, transition metal dichalcogenides, as well as new materials such as black phosphorus, bismuthene, antimonene, and MXene. Material characteristics, fabrication techniques, and nonlinear properties are also introduced. Finally, future perspectives of ultrafast lasers based on 2D materials are also addressed.
关键词： saturable absorber,MXene,antimonene,bismuthene,graphene,ultrafast lasers,transition metal dichalcogenides,black phosphorus,2D materials,topological insulators
更新于2025-09-19 17:13:59
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Optical Properties of Buckled Bismuthene
摘要： In this paper, the optical properties of buckled bismuthene (a new 2D material) are studied in different strains. Different transitions in bismuthene’s band structure are mentioned and the optical advantages of buckled bismuthene are discussed. It is found that buckled bismuthene is strain independent infrared (IR) reducer and could be used in bio photonics.
关键词： 2D material,optical properties,reflection,group V monolayers,honeycomb lattice,absorption spectra,density functional theory,dielectric function,buckled bismuthene
更新于2025-09-11 14:15:04