Tungsten disulfide (${\mathrm{WS}}_2$), as a representative layered transition metal dichalcogenide (TMDC) material, possesses important potential for applications in highly sensitive sensors. Here, a sensitivity-enhanced surface plasmon resonance (SPR) sensor with a metal film modified by an overlayer of ${\mathrm{WS}}_2$ nanosheets is proposed and demonstrated. The SPR sensitivity is related to the thickness of the ${\mathrm{WS}}_2$ overlayer, which can be tailored by coating a ${\mathrm{WS}}_2$ ethanol suspension with different concentrations or by the number of times of repeated post-coating. Benefitting from its large surface area, high refractive index, and unique optoelectronic properties, the ${\mathrm{WS}}_2$ nanosheet overlayer coated on the gold film significantly improves the sensing sensitivity. The highest sensitivity (up to $2459.3\mathrm{nm}/\mathrm{RIU}$) in the experiment is achieved by coating the ${\mathrm{WS}}_2$ suspension once. Compared to the case without a ${\mathrm{WS}}_2$ overlayer, this result shows a sensitivity enhancement of 26.6%. The influence of the ${\mathrm{WS}}_2$ nanosheet overlayer on the sensing performance improvement is analyzed and discussed. Moreover, the proposed ${\mathrm{WS}}_2$ SPR sensor has a linear correlation coefficient of 99.76% in refractive index range of 1.333 to 1.360. Besides sensitivity enhancement, the ${\mathrm{WS}}_2$ nanosheet overlayer is able to show additional advantages, such as protection of metal film from oxidation, tunability of the resonance wavelength region, biocompatibility, capability of vapor, and gas sensing.

A high-sensitivity vector magnetic field is proposed and demonstrated. The sensor consists of a side-polished-fiber (SPF)-based surface plasmon resonance (SPR) structure integrated with ferrofluid. Because of the high refractive index sensitivity of the SPR scheme and the outstanding magneto optical properties of ferrofluid, the sensor shows a high sensitivity (up to 598.7 pm/Oe) to magnetic field intensity. Moreover, owing to the non-circular-symmetric geometry of the SPF and non-uniform distribution of the ferrofluid around the SPF, the sensor exhibits a sensitivity of $-5.63\mathrm{nm}/\mathrm{deg}$ to the orientation of the magnetic field. The proposed vector magnetic field sensor, integrating over magnetic, plasmonic, and fiber-optic schemes, is highly sensitive to both the intensity and orientation of the magnetic field simultaneously, and holds potential in applications in many fields, such as medicine, industry, and the military.

The fiber geometry, fiber parameters and mode-guiding properties are crucial for realizing high-performance fiber-based sensors. In this work, we propose and demonstrate a few-mode fiber (FMF)–based surface plasmon resonance (SPR) biosensor. The FMF-SPR sensor was fabricated via side-polishing a few-mode fiber and coating a thin layer of gold film, on the basis of the optimization of fiber geometry, thickness of the gold film and mode selection, which were performed with the finite element method. The refractive index (RI) sensing performance of three such sensors with different residual fiber thicknesses were investigated. In the RI range from 1.333 to 1.404, the highest sensitivity up to 4903 nm/RIU and a figure of merit of 46.1 RIU⁻¹ are achieved. For testing the bovine serum albumin (BSA) solution, an averaged BSA RI sensitivity of 6328 nm/RIU and an averaged BSA concentration sensitivity of 1.17 nm/(mg/ml) are realized. Benefiting from only a few modes supported in the FMF, a smaller line-width of the SPR spectrum is obtained, which further results in a higher figure of merit (FOM). Moreover, when combined with the superiority of the mode-multiplexing technology brought by the FMF, the FMF-SPR sensors may find applications in biochemical analysis with high performance and high throughputs.

Metal halide perovskite light-emitting diodes (PeLEDs) have emerged as prospective candidates for high-resolution display and communication applications because of their tunable bandgaps, high photoluminescence quantum yields (PLQYs), and good color purity.^{1 – 5} Since the first report of PeLEDs by Tan et al. in 2014,⁶ external quantum efficiencies (EQEs) exceeding 20% have been achieved at red and near-infrared wavelengths,^{7 – 9} and the state-of-the-art green PeLEDs exhibit outstanding EQEs of over 30%.¹⁰ To date, the EQEs of sky-blue perovskites (480 to 500 nm)-based PeLEDs have exceeded 16%;¹¹ however, as one of primary colors, the efficiency and brightness of pure-blue PeLEDs (460 to 470 nm) are still largely lagging behind. Although the EQE of the pure-blue electroluminescent device is over 11%, its brightness is as low as $1000\mathrm{cd}{\mathrm{m}}^{-2}$, which severely restricts the development for illumination and display applications ($\ge 1000\mathrm{cd}{\mathrm{m}}^{-2}$).¹² Therefore, it is urgent to develop new strategies to further promote the performance of pure-blue PeLEDs.

This paper presents an all-inclusive review of assembly strategies of MNWs, discusses the underlying mechanisms, assesses the developed techniques, and summarizes the representative applications in flexible and stretchable electronics.

A vector magnetometer, composed of a side-polished single-mode-multimode-single-mode fiber structure coated with ferrofluids, is proposed and investigated. The side-polishing of the multimode fiber can expose the evanescent field to the surrounding ferrofluids, whose refractive index in the vicinity of the polished surface can be tuned by both the intensity and direction of the applied magnetic field, thus in turn realizing the magnetic vector sensing. The sensing principles are illustrated in details, and the sensing performances, especially the dependence on the residual thickness (RT) of the side-polished multimode fiber, are well investigated experimentally. It is found that the decrease of the RT can significantly improve the sensitivity to both the magnetic field intensity and the direction, and the highest intensity and direction sensitivities of −0.053 nm/Oe and −5.68 nm/degree have been achieved respectively, when the RT reduces to 50.5 μm. The proposed vector magnetometer, featuring the advantages of simple structure, low cost, and ease of fabrication, can find the potential applications in the fields such as industry, military, and environment.