In this work, we have synthesized BiOCl nanoplates (diameter 140–220 nm, thickness 60–70 nm) via a co-precipitation method, and then created Bi nanoparticles (diameter 35–50 nm) on the surface of ...BiOCl nanoplates via a NaBH4 reduction method. By varying the NaBH4 concentration and reaction time, the evolution of Bi nanoparticles was systematically investigated. It is demonstrated that with increasing the NaBH4 concentration (at a fixing reaction time of 30 min), BiOCl crystals are gradually reduced into Bi nanoparticles, and pure Bi nanoparticles are formed at 120 mM NaBH4 solution treatment. At low-concentration NaBH4 solutions (e.g., 10 and 30 mM), with increasing the reaction time, BiOCl crystals are partially reduced into Bi nanoparticles, and then the Bi nanoparticles return to form BiOCl crystals. At high-concentration NaBH4 solutions (e.g., 120 mM), BiOCl crystals are reduced to Bi nanoparticles completely with a short reaction time, and further prolong the treatment time leads to the transformation of the Bi nanoparticles into a two-phase mixture of BiOCl and Bi2O3 nanowires. The photodegradation performances of the samples were investigated by choosing rhodamine B (RhB) as the model pollutant and using simulated sunlight as the light source. It is demonstrated that an enhanced photodegradation performance can be achieved for the created Bi@BiOCl hybrid composites with appropriate NaBH4 treatment. The underlying photocatalytic mechanism was systematically investigated and discussed.
This paper proposes a tunable sensing detector based on Bulk Dirac semimetals (BDS). The bottom-middle-top structure of the detector is a metal-dielectric-Dirac semimetal. The designed detector is ...simulated in the frequency domain by the finite element method (FEM). And the simulation results indicate that the detector achieves three perfect absorption peaks with absorptivity greater than 99.8% in the range of 2.4-5.2 THz. We analyze the cause of the absorption peak by using random phase approximation theory. The device exhibits good angular insensitivity in different incident angle ranges, and the three absorption peaks can reach 90% absorption rate when the incident angle is in the ranges of 0-60°. And when adjusting the Fermi level of BDS in the ranges of 0.1-0.5 eV, our detector can realize the frequency regulation of the ultra-wide range of 3.90-4.56 THz and realize multi-frequency controllable sensing while maintain the absorption efficiency above 96%. The detector has maximum sensitivity
S
of 238.0 GHz per RIU when the external environment of the refractive index changes from 1.0 to 1.8, and the maximum detection accuracy is 6.5. The device has broad development prospects in the field of space detection and high-sensitivity biosensing detection.
We propose a tunable narrow-band sensing detector with an Au-polyimide-Dirac semimetal structure. Simulations show >99.8% absorptivity at 2.4-5.2 THz. The sensor has active tunability, high refractive index sensitivity, angle insensitivity, and good sensing performance.
In this paper, we demonstrate a dual-band metamaterial perfect absorber based on a Ag-dielectric-Ag multilayer nanostructure. The structure of top metal film covers nanoring grooves array. A ...dielectric layer has a function of confining electromagnetic fields. Theoretical analysis shows that two absorption peaks (1059 nm and 1304 nm) with the absorption of 99.2% and 99.9% have been achieved, respectively. The physical origin of perfect absorption peaks are related to the Fabry-Perot resonance effect and localized surface plasmon resonance (LSPR) of the nanoring grooves. Its perfect absorption and resonance wavelength can be well regulated by adjusting the relevant structural parameters. Additionally, the absorber demonstrates good operation angle-polarization-tolerance at wide incident angles (0–60°). We believe that our design has a promising application in plasmon-enhanced photovoltaic, optical absorption switching, and modulator optical communications in the infrared regime.
Here, we document a D-type double open-loop channel floor plasmon resonance (SPR) photonic crystal fiber (PCF) for temperature sensing. The grooves are designed on the polished surfaces of the ...pinnacle and backside of the PCF and covered with a gold (Au) film, and stomata are distributed around the PCF core in a progressive, periodic arrangement. Two air holes between the Au membrane and the PCF core are designed to shape a leakage window, which no longer solely averts the outward diffusion of Y-polarized (Y-POL) core mode energy, but also sets off its coupling with the Au movie from the leakage window. This SPR-PCF sensor uses the temperature-sensitive property of Polydimethylsiloxane (PDMS) to reap the motive of temperature sensing. Our lookup effects point out that these SPR-PCF sensors have a temperature sensitivity of up to 3757 pm/°C when the temperature varies from 5 °C to 45 °C. In addition, the maximum refractive index sensitivity (RIS) of the SPR-PCF sensor is as excessive as 4847 nm/RIU. These proposed SPR-PCF temperature sensors have an easy nanostructure and proper sensing performance, which now not solely improve the overall sensing performance of small-diameter fiber optic temperature sensors, but also have vast application prospects in geo-logical exploration, biological monitoring, and meteorological prediction due to their remarkable RIS and exclusive nanostructure.
A simple polyacrylamide gel method combined with low temperature sintering technology has been used to synthesize the C–O functional groups grafted MgAl2O4/C3N4/YMnO3 (MAO–CN–YMO) heterojunction ...photocatalysts with enhanced visible‐light‐induced photodegradation toward oxytetracycline hydrochloride (OTC‐HCl). A variety of characterization methods are used to gain insight into the phase purity, crystal structure, microstructure, functional group information, elemental composition, surface defect, light response capability, and photocatalytic activity of the as‐synthesized samples. The influences of the mass ratios of mCN/mYMO, mCN/mMAO, and mMAO/(mCN + mYMO) in CN–YMO, CN–MAO, and MAO–CN–YMO heterojunction photocatalysts on the photocatalytic activity for the degradation of OTC‐HCl was also discussed, and the optimal mass ratio of mMAO/(mCN + mYMO) is identified as 15 wt%. The photocatalytic experiments confirmed that the MAO–CN–YMO heterojunction photocatalysts had high selectivity for the degradation of antibiotics. The prediction of the photocatalytic activity of the MAO–CN–YMO heterojunction photocatalysts for the degradation of OTC‐HCl was made by a variety of intelligent algorithm models. The results of the whale optimization algorithm are highly consistent with the experimental results. Combined with the energy band theory and the characterization results of high‐performance liquid chromatography–tandem mass spectrometry, the free radicals in the reaction solution preferentially attacked the –CH3, –NCH2, and –OH of OTC‐HCl during the degradation of OTC‐HCl by MAO–CN–YMO heterostructure photocatalysts, and then attack –C=O and –C=O–NH2, and finally perform ring‐opening reaction to degrade OTC‐HCl into nontoxic and harmless products of small molecules such as CO2, H2O, and NH4+. This work provides a new idea for the development of novel double p–n junction MAO–CN–YMO heterojunction photocatalysts for antibiotic degradation and the prediction of photocatalytic activity of multiple heterojunction photocatalysts by intelligent algorithms.
By means of critical coupling and impedance matching theory, we have numerically simulated the perfect absorption of monolayer graphene. Through the critical coupling effect and impedance matching, ...we studied a perfect single-band absorption of the monolayer graphene and obtained high quality factor (Q-factor = 664.2) absorption spectrum which has an absorbance close to 100% in the near infrared region. The position of the absorption spectrum can be adjusted by changing the ratio between the radii of the elliptic cylinder air hole and the structural period. The sensitivity of the absorber can be achieved S = 342.7 nm/RIU (RIU is the per refractive index unit) and FOM = 199.2 (FOM is the figure of merit), which has great potential for development on biosensors. We believe that our research will have good application prospects in graphene photonic devices and optoelectronic devices.
•The proposed absorber achieves triple-band absorption.•The proposed absorber has a good working polarization angle tolerance.•The proposed absorber are beneficial to the fabrication of the device.
...In this paper, a triple-band perfect metamaterial absorber based on Cu-dielectric-Cu triple-layer nanostructure is reported. The top metal film structure consists of a ring and four pairs of capacitor plates, which has a frequency selection effect, allowing the absorber to resonate in the near infrared range. Theoretical study shows that the absorption of the three absorption peaks (872.54 nm, 1008.69 nm and 1138.62 nm) are 87.1%, 99.9% and 99.6%, respectively. The average absorption is 95.53%, including two perfect absorption peaks. Changing the structural parameters can affect its absorption peaks and resonant wavelengths. At the same time, due to the high symmetry of the absorber, it is not sensitive to the polarization angle and incident angle. Whether in the TE mode or the TM mode, the absorber at a wide incident angle (0-60°) also exhibits good operating angle polarization tolerance. Therefore, the perfect metamaterial absorber we designed can be widely used in sensing.
We demonstrate an active control of near-field coupling between dark and bright eigenmodes in terahertz metamaterials. The metamaterial unit cell consists of two orthogonally twisted split-ring ...resonators, which are tightly coupled with each other through near field. The monolayer graphene is integrated into the unit cell and the coupling strength of the near field can be actively modulated by the manipulation of graphene conductivity via shifting its Fermi level. This letter presents a unique route toward the realization of ultrafast and active controlled near-field coupled metamaterial devices.
In the study of modern optics, the work of terahertz metamaterial absorbers is mostly multi-band perfect absorbers and ultra-wideband perfect absorbers. In contrast, in practical applications, ...metamaterial absorbers with adjustable resonance frequency or amplitude play an essential role in many forms. Here, we firstly designed an ultra-wideband terahertz metamaterial perfect absorber, achieving over 99% perfect absorption in the 6.6-8.9 THz range. Secondly, based on the absorber, phase change material VO 2 was added to improve the structure, and three tunable terahertz metamaterial absorbers based on VO 2 were designed, respectively realizing broadband movement and conversion between broadband and multi-band. Also, the terahertz absorber with dynamic tuning characteristics can flexibly control the absorption performance, providing an excellent platform for the realization of terahertz filtering, modulation, and so on.
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