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Electrocatalytic nitrogen reduction reaction (NRR) has attracted much attention as a sustainable ammonia production technology, but it needs further exploration due to its slow kinetics and the existence of competitive side reactions. In this research, xAu/MIL‐101(Fe) catalysts were obtained by loading gold nanoparticles (Au NPs) onto MIL‐101(Fe) using a one‐step reduction strategy. Herein, MIL‐101(Fe), with high specific surface area and strong N2 adsorption capacity, is used as a support to disperse Au NPs to increase the electrochemical active surface area. Au NPs, with a high NRR activity, is introduced as the active site to promote charge transfer and intermediate formation rates. More importantly, the strong interaction between Au NPs and MIL‐101(Fe) enhances the electron transfer between Au NPs and MIL‐101(Fe), thereby enhancing the activation of N2 and achieving efficient NRR. Among the prepared catalysts, 15 %Au/MIL‐101(Fe) has the highest NH3 yield of 46.37 μg h−1 mg−1cat and a Faraday efficiency of 39.38 % at −0.4 V (vs. RHE). In‐situ FTIR reveals that the NRR mechanism of 15 %Au/MIL‐101(Fe) follows the binding alternating pathway and also indicates that the interaction between Au NPs and MIL‐101(Fe) strengthens the activation of the N≡N bond in the rate‐limiting process, thereby accelerating the NRR process. [ABSTRACT FROM AUTHOR]

Enrofloxacin (ENR) is a commonly used veterinary antibiotic and poses a health risk when present as residues in food. This study describes a dual-mode immunochromatographic test strip (DITS) biosensor for the detection of ENR residues in food. Magnetic graphene oxide nanoparticles (MGO-NPs) are two-dimensional magnetic nanomaterials with a large specific surface area and fine biocompatibility, which can better provide more adsorption points for biological antibodies. Gold nanoparticles (AuNPs) can stimulate the localized surface plasmon resonance effect under laser irradiation, which will increase the temperature to achieve photothermal conversion. The photothermal conversion efficiency of MGO-NPs can be effectively enhanced by combining AuNPs with MGO-NPs to form MGO@Au nanocomposites (MGO@Au-NCs). Then, MGO@Au-NCs were combined with an ENR monoclonal antibody to form the MGO@Au@Ab probe, and the MGO@Au@Ab-DITS biosensor was developed. The biosensor was employed to assess ENR samples spanning concentrations from 0 to 1000 μg/mL. Sample solutions containing ENR were mixed with the MGO@Au@Ab solution, deposited on the test strip's sample pad, and analyzed using both colorimetric and photothermal methods employing an 808 nm infrared laser in a photothermal infrared imaging instrument. The results show that the sensitivity of the photothermal mode sensor is 0.0159°C whereas, the standard deviation (SD) and limit of detection (LOD) is 0.058 and 10.89 μg/mL, respectively with quantification limit (LOQ) of 36.31 μg/mL. In colorimetric mode, the sensitivity of the developed sensor is 5.222 au, with SD, LOD and LOQ of 40.13, 23.05 μg/mL, and76.85 μg/mL, respectively. This innovative MGO@Au@Ab-DITS system has been effectively applied to detect ENR residues in food samples such as juice and milk, laying the groundwork for the detection of other drug residues in food. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) mono-elemental materials (Xenes) show remarkable potential in the fields of fundamental science and technology, have been regarded as a wide range of building blocks for electronic technologies due to their unique chemical, physical, electrical, and optical properties. Here, 2D tellurene/black phosphorus (Te/BP) heterojunctions are successfully fabricated through liquid-phase exfoliation (LPE) method. Their nonlinear optical absorption properties at 1.0, 2.0, and 2.8 μm have been studied by an open-aperture Z-scan method. The results revealed the excellent broadband saturable absorption responses of the prepared BP/Te heterojunctions, which are further confirmed by using them as saturable absorbers (SAs) for passively Q-switched all-solid-state lasers operating at 1.0, 2.0, and 2.8 μm, respectively. In particular, 1.04 μm continuous-wave (CW) mode-locked lasers with a pulse width of 404 fs is realized for the first time, to our best knowledge. Our work indicates that 2D Xenes especially 2D Xenes based heterojunctions have great potential in the fields of pulsed laser generation/modulation and other optoelectronic and photonic devices.

An effective approach to manipulate terahertz (THz) waves involves the utilization of a device structure. In this particular investigation, we have successfully fabricated a SnS2 nanofilm device using femtosecond laser direct ablation. The passive and active polarization‐sensitive characteristics of the SnS2 nanofilm device were examined within the THz frequency range, employing different line spaces of 500, 600, and 700 μm. The combination of the device effect and SnS2 absorption led to an enhanced passive polarization modulation. Moreover, when an external electric field was applied to the SnS2 nanofilm device along the device line, persistent switching and linear modulation of THz wave transmission were observed. These findings indicate that the integration of material properties and device structure in this SnS2 device renders it highly suitable for applications in ultrafast THz switches, filters, and modulation devices. [ABSTRACT FROM AUTHOR]

Ni nanocatalysts based on high surface area carborundum for the decomposition of ammonia to COx-free hydrogen are synthesized using a wet impregnation approach. The catalysts were characterized using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and H2-temperature-programmed reduction (TPR) methods. The Ni/SiC catalyst was found to be extremely active for the decomposition reaction when their activities were assessed in a fixed-bed reactor. Ni content and calcination temperature affect the crystallite size, dispersion, and reducibility of Ni species, thereby impacting the catalytic properties of catalysts. The 30Ni/SiC catalyst demonstrates the highest catalytic activity and long-term stability. At a high space velocity of 30 000 mL gcat–1 h–1, the 30Ni/SiC-700 catalyst converts ammonia by 79.6% at 550 °C, demonstrating that Ni/SiC is an effective ammonia decomposition catalyst. The present study provides a promising avenue for the development of cost-effective and high-performance catalysts for hydrogen production via NH3 decomposition. [ABSTRACT FROM AUTHOR]

Optical fiber sensors based on tapered optical fiber (TOF) structure have attracted a considerable amount of attention from researchers due to the advantages of simple fabrication, high stability, and diverse structures, and have great potential for applications in many fields such as physics, chemistry, and biology. Compared with conventional optical fibers, TOF with their unique structural characteristics significantly improves the sensitivity and response speed of fiber-optic sensors and broadens the application range. This review presents an overview of the latest research status and characteristics of fiber-optic sensors and TOF sensors. Then, the working principle of TOF sensors, fabrication schemes of TOF structures, novel TOF structures in recent years, and the growing emerging application areas are described. Finally, the development trends and challenges of TOF sensors are prospected. The objective of this review is to convey novel perspectives and strategies for the performance optimization and design of TOF sensors based on fiber-optic sensing technologies. [ABSTRACT FROM AUTHOR]

This paper presents the development of taper-in-taper fiber (TITF)–optical fiber-based sensors for chemical and biological detection. TITF structure is a fiber structure formed by fabricating a taper again on the taper region of the traditional taper fiber. The experimental results show that the TITF structure has a lower transmitted intensity than the common taper fiber structure. It is demonstrated that the structure of TITF is more conducive to evanescent waves, thereby making it more sensitive to changes in the refractive index (RI) of the external environment. To confirm this, measurements of ethanol solutions with different water contents are taken using the TITF structure to showcase the chemical sensing, thus verifying its sensitivity to RI changes in the external environment. The sensor can measure ethanol solutions from 0 to 100% with a sensitivity of 4.06 a.u./%. Thereafter, the TITF sensor is modified with ZnO-NPs to enhance its sensitivity for biological sensing (creatinine detection). The transmitted intensity of different concentrations of creatinine solution (0–2000 μM) is measured using the proposed sensor. The sensor showed good linearity and a high sensitivity of 0.11 a.u./μM for creatinine solution. Therefore, it is demonstrated that the TITF sensor with ZnO-NPs can be used for effective biological sensing. [ABSTRACT FROM AUTHOR]

Niobium carbide (Nb2CTx), a type of MXene with high optical transparency, large specific surface area, and good electrical conductivity, is expected to perform as an excellent medium in the field of optical fiber biosensing. Here, we fabricated double S-tapered fiber sensors functionalized with gold nanoparticles/graphene oxide/tyrosinase (AuNPs/GO/tyrosinase) and AuNPs/Nb2CTx/tyrosinase, respectively. The double S-tapered structure can provide more evanescent wave leakage and enhance light–matter interaction. By implementing transmittance experiment, the sensitivity of the two probes were tested to be 17 and 34 pm/μM over 0–300 μM tyramine concentrations. The comparative results demonstrate that Nb2CTx-enhanced localized surface plasmon resonance (LSPR) sensor has more excellent performance due to the existence of surface functional groups and large specific surface area of Nb2CTx. Our work provides a research platform for improving the sensitivity of LSPR sensors. [ABSTRACT FROM AUTHOR]

This article discusses optically active nanomaterials and their optical biosensing applications. In addition to enhancing their sensitivity, these nanomaterials also increase their biocompatibility. For this reason, nanomaterials, particularly those based on their chemical compositions, such as carbon-based nanomaterials, inorganic-based nanomaterials, organic-based nanomaterials, and composite-based nanomaterials for biosensing applications are investigated thoroughly. These nanomaterials are used extensively in the field of fiber optic biosensing to improve response time, detection limit, and nature of specificity. Consequently, this article describes contemporary and application-based research that will be of great use to researchers in the nanomaterial-based optical sensing field. The difficulties encountered during the synthesis, characterization, and application of nanomaterials are also enumerated, and their future prospects are outlined for the reader's benefit. [ABSTRACT FROM AUTHOR]

A novel experimental setup for the generation of arbitrary vector beams is proposed. The system major includes two reflective liquid crystal spatial light modulators (RLC-SLM) and a polarizing beam splitting prism. Moreover, this method is not limited by the wavelength of light wave and the pixel size of SLM. Theoretical analysis shows that when Gaussian beam or a plane beam is illuminated on a computer-generated hologram (CGH) specially designed in this work, the complex amplitudes of the vector field's two orthogonal polarization components may be changed by modifying the encoding parameters, resulting in a vector beam with arbitrary complex amplitude and polarization in the output field. The experimental results also show that the two independent coding channels of the device have good polarization-selective imaging ability, which greatly improves the flexibility of generating arbitrary vector beams. [ABSTRACT FROM AUTHOR]

The barium hexaaluminate (BHA) supported Co 3 O 4 catalysts (XCo/BHA) with varied mass loading of Co (X = 10%, 20%, 30%, 35% and 40%) were prepared by impregnating Co 3 O 4 nanoparticles (NPs) onto BHA support that synthesized through urea combustion method. The catalyst was characterized by high-resolution transmission electron microscope (HRTEM), temperature programmed reduction (TPR), temperature programmed desorption (TPD) and valued the ammonia decomposition performance by fixed-bed reactor. The results showed that Co 3 O 4 NPs were dispersed densely on the BHA surface, with the strong alkaline support that could adjust the binding energy of the active sites and the nitrogen, which was conducive to the ammonia decomposition reaction. Among the synthesized catalysts, 35Co/BHA achieves 87.2% ammonia conversion at 500 °C with a space velocity of 30000 ml g cat −1 h−1, corresponding to a hydrogen production rate of 29.2 mmol H 2 g cat −1 min−1, and also shows excellent catalytic stability. [Display omitted] • BHA supported Co 3 O 4 is highly active toward ammonia decomposition. • 35Co/BHA presents the optimal ammonia conversion rate. • BHA acts as electron donor to promote ammonia decomposition. • Co 3 O 4 NPs are densely dispersed on BHA with increased pore volume. [ABSTRACT FROM AUTHOR]

Glucose, an essential nutrient to the metabolism of organisms, is closely related to human health. Here, a novel serial quadruple tapered structure-based localized surface plasmon resonance (LSPR) sensor is employed to achieve accurate detection of glucose level in the human body. Gold nanoparticles (AuNPs) are immobilized on the serial quadruple taper fiber (SQTF) to induce LSPR. Furthermore, graphene oxide (GO) and multi-wall carbon nanotubes (MWCNTs) are used to increase the binding sites of enzymes to improve the sensing performance of probe. In our work, the SQTF probe surface is functionalized with glucose oxidase (GOx) enzyme to enhance selectivity. The sensitivity and limit of detection (LOD) of functionalized probe structure are 1.04 nm/mM and 0.24 mM over a linear range of 0 mM to10 mM, respectively. In addition, the reusability, reproducibility, stability and selectivity of SQTF probe are assessed to demonstrate the potential in measuring glucose content in the human body. [ABSTRACT FROM AUTHOR]