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The widespread use of silver raises concerns about environmental and health risks, necessitating highly sensitive detection methods for trace silver ions (Ag+). Surface plasmon resonance (SPR) sensors offer benefits like label-free detection and rapid response, but their sensitivity for Ag+ detection is limited due to weak ion adsorption. Here, we developed an SPR sensor with MoS42−-intercalated NiAl-layered double hydroxide (LDH) as the adsorption layer of Ag+ to enhance detection sensitivity. Our sensor achieves a sensitivity of 254.75 nm/μg/L and detects Ag+ at a low concentration of 2.8 pM, outperforming various existing sensors. It also shows excellent repeatability, long-term stability, and selectivity, proving effective in real-world environmental samples. This work advances high-performance SPR sensors for heavy metal ion detection. [ABSTRACT FROM AUTHOR]

The hybrid structures of graphene with semiconductor materials based on photogating effect have attracted extensive interest in recent years due to the ultrahigh responsivity. However, the responsivity (or gain) was increased at the expense of response time. In this paper, we devise a mechanism which can obtain an enhanced responsivity and fast response time simultaneously by manipulating the photogating effect (MPE). This concept is demonstrated by using a graphene/silicon-on-insulator (GSOI) hybrid structure. An ultrahigh responsivity of more than 107 A/W and a fast response time of 90 µs were obtained. The specific detectivity D* was measured to be 1.46 ⨯ 1013 Jones at a wavelength of 532 nm. The Silvaco TCAD modeling was carried out to explain the manipulation effect, which was further verified by the GSOI devices with different doping levels of graphene in the experiment. The proposed mechanism provides excellent guidance for modulating carrier distribution and transport, representing a new route to improve the performance of graphene/semiconductor hybrid photodetectors.

A strategy is proposed to achieve wideband tunable perfect plasmonic absorption in graphene nanoribbons by employing attenuated total refraction (ATR) in Otto prism configuration. In this configuration, the Otto prism with a deep-subwavelength dielectric spacer is used to generate tunneling evanescent waves to excite localized plasmons in graphene nanoribbons. The influence of the configuration parameters on the absorption spectra of graphene plasmons is studied systematically, and the key finding is that perfect absorption can be achieved by actively controlling the incident angle of light under ATR conditions, which provides an effective degree of freedom to tune the absorption properties of graphene plasmons. Based on this result, it is further demonstrated that by simultaneously tuning the incident angle and the graphene Fermi energy, the tunable absorption waveband can be significantly enlarged, which is about 3 times wider than the conventional cavity-enhanced configuration. Our proposed strategy to achieve wideband, tunable graphene plasmons could be useful in various infrared plasmonic devices.

Graphene nanowalls (GNWs) exhibit outstanding optoelectronic properties due to their peculiar structure, which makes them a great potential in infrared (IR) detection. Herein, a novel IR detector that is composed of polydimethylsiloxane (PDMS) and designed based on GNWs is demonstrated. Such detector possesses an anomalous temperature coefficient of resistance of 180% K−1 and a relatively high change rate of current (up to 16%) under IR radiation from the human body. It primarily attributes to the ultra-high IR absorption of the GNWs and large coefficient of thermal expansion of PDMS. In addition, the GNW/PDMS device possesses excellent detection performance in the IR region with a responsivity of ~1.15 mA W−1. The calculated detectivity can reach 1.07×108 cm Hz1/2 W−1, which is one or two orders of magnitude larger than that of the traditional carbon-based IR detectors. The significant performance indicates that the GNW/PDMS-based devices reveal a novel design concept and promising applications for the future new-generation IR photodetectors.

Graphene plasmonic modulators can manipulate the mid‐infrared light in transmission mode, which is currently challenging for traditional liquid crystal and digital micromirror devices, opening up a new avenue for infrared scene projection, infrared optical communication, and hyper spectra imaging. Nevertheless, their efficiencies are not high enough due to the single‐layer atomic thickness and low free carrier density of graphene. Here, it is demonstrated that the modulation efficiency can be significantly improved by enhancing the asymmetric light‐plasmon coupling. A general theoretical model is established to describe the modulation behaviors of the modulator, revealing the critical role of the asymmetric coupling rate. By using dielectric environment engineering and graphene structure design experimentally to enhance the asymmetric coupling rate from 0.45×1012 to 7.05×1012 s−1, the modulation efficiency has been improved from 4% to 41% at 1530 cm−1, while maintaining the bandwidth as large as 230 cm−1. The modulator outperforms previous transmission‐type graphene plasmonic modulators in both efficiency and bandwidth, presenting great potential in next‐generation infrared integrated photonics platforms. [ABSTRACT FROM AUTHOR]

Electrical controllable charge density in graphene films has recently attracted considerable research interest for its potential applications in various active devices. In this letter, we demonstrate that graphene acts as an effective tunable loss resource to manipulate the electromagnetic response of a metallic resonant structure at microwave frequency. A transmission-tunable frequency selective surface (FSS) is realized by introducing a graphene sandwich into its near-field region. Remarkable transmission tuning from 81.7% to 25.2% at a resonant frequency of about 6.5 GHz is observed when applying bias voltage from 0 to 3.6 V. The graphene FSS prototype may open up a way for realizing electromagnetic active devices in the microwave range. [ABSTRACT FROM AUTHOR]

Batch production of continuous and uniform graphene films is critical for the application of graphene. Chemical vapor deposition (CVD) has shown great promise for mass producing high-quality graphene films. However, the critical factors affected the uniformity of graphene films during the batch production need to be further studied. Herein, we propose a method for batch production of uniform graphene films by controlling the gaseous carbon source to be uniformly distributed near the substrate surface. By designing the growth space of graphene into a rectangular channel structure, we adjusted the velocity of feedstock gas flow to be uniformly distributed in the channel, which is critical for uniform graphene growth. The monolayer graphene film grown inside the rectangular channel structure shows high uniformity with average sheet resistance of 345 Ω sq−1 without doping. The experimental and simulation results show that the placement of the substrates during batch growth of graphene films will greatly affect the distribution of gas-phase dynamics near the substrate surface and the growth process of graphene. Uniform graphene films with large-scale can be prepared in batches by adjusting the distribution of gas-phase dynamics. [ABSTRACT FROM AUTHOR]