Robust Edge States of Quasi-1D Material Ta2NiSe7 and Applications in Saturable Absorbers.

The helical edge states (ESs) protected by underlying Z2 topology in two-dimensional topological insulators (TIs) arouse upsurges in saturable absorptions thanks to the strong photon-electron coupling in ESs. However, limited TIs demonstrate clear signatures of topological ESs at liquid nitrogen temperatures, hindering the applications of such exotic quantum states. Here, we demonstrate the existence of one-dimensional (1D) ESs at the step edge of the quasi-1D material Ta2NiSe7 at 78 K by scanning tunneling microscopy. Such ESs are rather robust against the irregularity of the edges, suggesting a possible topological origin. The exfoliated Ta2NiSe7 flakes were used as saturable absorbers (SAs) in an Er-doped fiber laser, hosting a mode-locked pulse with a modulation depth of up to 52.6% and a short pulse duration of 225 fs, far outstripping existing TI-based SAs. This work demonstrates the existence of robust 1D ESs and the superior SA performance of Ta2NiSe7.

Epitaxy of Antimonene Thin Films with Screw Dislocations for the Application of Saturable Absorbers.

The exotic optoelectronic properties of antimonene, including strain-induced tunable bandgaps, broad nonlinear refractive response, etc., have evoked profound upsurges for decades. As the screw dislocations break the crystal symmetry and modify interlayer coupling, it is highly desirable to investigate the optical prospects of antimonene with screw dislocations. Herein, controllable epitaxy of spiral ß-antimonene is achieved on Fe3GaTe2 substrates. By fine-tuning growth temperatures, the evolutions of spiral ß-antimonene with non-centrosymmetric stacking are investigated via scanning tunneling microscopy. The effects of interfacial strain and dislocation motion during screw-dislocation-driven growth are also studied. Additionally, a modulation depth of 40.8% and mode locking at 1558 nm with a pulse width of 290 fs are observed in Er-doped pulsed fiber lasers generated with spiral Sb-based saturable absorbers, revealing superior performance that far outstrips reported Sb-based saturable absorbers to date. Our work sheds light on the preparation of Sb films with screw dislocations and demonstrates a promising approach toward fabricating ultrafast optical devices.

Application of femtosecond mode-locked SnTe thin films and generation of bound-state solitons.

In the realm of ultrafast laser technology, the exploration of two-dimensional materials as saturable absorbers (SA) has garnered significant research interest. Our research investigates the characteristics of SnTe thin films, a topological crystalline insulator material, as a potential saturable absorber for ultrafast lasers. Using the molecular beam epitaxy (MBE) technique, we analyze the films' morphology and composition through atomic force microscopy (AFM) and successfully deposit SnTe epilayers on Au(111)/mica substrates. Through the utilization of SnTe-SA, an erbium-doped fiber laser is fabricated, demonstrating a pulse output with a width of 276 fs and a center wavelength of 1560 nm, highlighting the potential of SnTe films in manufacturing ultrafast optical devices. Additionally, tightly bound solitons with a soliton interval of 1.01 ps are observed, contributing to the exploration of soliton nonlinear dynamics.

Advances in bacterial whole-cell biosensors for the detection of bioavailable mercury: A review.

Mercury (Hg) and its organic compounds, especially monomethylmercury (MeHg), cause major damage to the ecosystem and human health. In surface water or sediments, microorganisms play a crucial role in the methylation and demethylation of Hg. Given that Hg transformation processes are intracellular reactions, accurate assessment of the bioavailability of Hg(II)/MeHg in the environment, particularly for microorganisms, is of major importance. Compared with traditional analytical methods, bacterial whole-cell biosensors (BWCBs) provide a more accurate, convenient, and cost-effective strategy to assess the environmental risks of Hg(II)/MeHg. This Review summarizes recent progress in the application of BWCBs in the detection of bioavailable Hg(II)/MeHg, providing insight on current challenges and strategies. The principle and components of BWCBs for Hg(II)/MeHg bioavailability analysis are introduced. Furthermore, the impact of water chemical factors on the bioavailability of Hg is discussed as are future perspectives of BWCBs in bioavailable Hg analysis and optimization of BWCBs.

Simultaneous Cross-type Detection of Water Quality Indexes via a Smartphone-App Integrated Microfluidic Paper-Based Platform.

Water quality guarantee in remote areas necessitates the development of portable, sensitive, fast, cost-effective, and easy-to-use water quality detection methods. The current work reports on a microfluidic paper-based analytical device (µPAD) integrated with a smartphone app for the simultaneous detection of cross-type water quality parameters including pH, Cu(II), Ni(II), Fe(III), and nitrite. The shapes, baking time, amount, and ratios of reaction reagent mixtures of wax µPAD were optimized to improve the color uniformity and intensity effectively. An easy-to-use smartphone app was established for recording, analyzing, and directly reading the colorimetric signals and target concentrations on µPAD. The results showed that under the optimum conditions, the current analytical platform has reached the detection limits of 0.4, 1.9, 2.9, and 1.1 ppm for nitrite, Cu(II), Ni(II), and Fe(III), respectively, and the liner ranges are 2.3-90 ppm (nitrite), 3.8-400 ppm (Cu(II)), 2.9-1000 ppm (Ni(II)), 2.8-500 ppm (Fe(III)), and 5-9 (pH). The proposed portable smartphone-app integrated µPAD detection system was successfully applied to real industrial wastewater and river water quality monitoring. The proposed method has great potential for field water quality detection.