In this paper, a multi-mode surface plasmon resonance absorber based on dart-type single-layer graphene is proposed, which has the advantages of polarization independence, tunability, high ...sensitivity, high figure of merit,
etc.
The device consists of a top layer dart-like patterned single-layer graphene array, a thicker silicon dioxide spacer layer and a metal reflector layer, and has simple structural characteristics. The numerical results show that the device achieves the perfect polarization-independent absorption at the resonance wavelengths of
λ
I
= 3369.55 nm,
λ
II
= 3508.35 nm,
λ
III
= 3689.09 nm and
λ
IV
= 4257.72 nm, with the absorption efficiencies of 99.78%, 99.40%, 99.04% and 99.91%, respectively. The absorption effect of the absorber can be effectively regulated and controlled by adjusting the numerical values such as the geometric parameters and the structural period p of the single-layer graphene array. In addition, by controlling the chemical potential and the relaxation time of the graphene layer, the resonant wavelength and the absorption efficiency of the mode can be dynamically tuned. And can keep high absorption in a wide incident angle range of 0° to 50°. At last, we exposed the structure to different environmental refractive indices, and obtained the corresponding maximum sensitivities in four resonance modes, which are
S
I
= 635.75 nm RIU
−1
,
S
II
= 695.13 nm RIU
−1
,
S
III
= 775.38 nm RIU
−1
and
S
IV
= 839.39 nm RIU
−1
. Maximum figure of merit are 54.03 RIU
−1
, 51.49 RIU
−1
, 43.56 RIU
−1
, and 52.14 RIU
−1
, respectively. Therefore, this study has provided a new inspiration for the design of the graphene-based tunable multi-band perfect metamaterial absorber, which can be applied to the fields such as photodetectors and chemical sensors.
We propose a multi-mode surface plasmon resonance absorber based on dart-type single-layer graphene, it has advantages of polarization independence, tunability and high sensitivity. Four modes of polarization-independent perfect absorption are achieved at 3000-5000 nm.
This paper introduces a novel metamaterial absorber based on surface plasmon resonance (SPR). The absorber is capable of triple-mode perfect absorption, polarization independence, incident angle ...insensitivity, tunability, high sensitivity, and a high figure of merit (FOM). The structure of the absorber consists of a sandwiched stack: a top layer of single-layer graphene array with an open-ended prohibited sign type (OPST) pattern, a middle layer of thicker SiO
, and a bottom layer of the gold metal mirror (Au). The simulation of COMSOL software suggests it achieves perfect absorption at frequencies of
= 4.04 THz,
= 6.76 THz, and
= 9.40 THz, with absorption peaks of 99.404%, 99.353%, and 99.146%, respectively. These three resonant frequencies and corresponding absorption rates can be regulated by controlling the patterned graphene's geometric parameters or just adjusting the Fermi level (
). Additionally, when the incident angle changes between 0~50°, the absorption peaks still reach 99% regardless of the kind of polarization. Finally, to test its refractive index sensing performance, this paper calculates the results of the structure under different environments which demonstrate maximum sensitivities in three modes:
= 0.875 THz/RIU,
= 1.250 THz/RIU, and
= 2.000 THz/RIU. The FOM can reach FOM
= 3.74 RIU
, FOM
= 6.08 RIU
, and FOM
= 9.58 RIU
. In conclusion, we provide a new approach for designing a tunable multi-band SPR metamaterial absorber with potential applications in photodetectors, active optoelectronic devices, and chemical sensors.
At present, solar energy is widely used as a kind of clean energy. The main solar radiation range under AM 1.5 is about 300 ~ 3000 nm. In this paper, we designed an efficient, ultra-broadband perfect ...solar absorber to have as long absorption bands in this range as possible to help alleviate the energy problem. The simulation calculations and experiments of the solar absorber show that the absorption bandwidth with absorption greater than 90% is greater than 2100 nm. It is worth noting that the perfect absorption bandwidth with absorption greater than 99% has more than 1600 nm. The absorption rate over the whole wavelength range (300 nm–3000 nm) (weighted directly around the sun by solar AM 1.5) is more than 90%. We can effectively control the absorption spectrum by adjusting the structural parameters. In addition, the proposed solar absorber is polarization independent, both the transverse electrical (TE) mode and the transverse magnetic (TM) mode, Absorption remains above 80% when the wide incidence angle is as high as 50°. Our propose design has high broadband absorption and great potential for solar thermal energy harvesting, thermoelectrics, and thermal emitters applications.
We propose an ultra-broadband perfect solar energy absorber based on TiN nanodisk and Ti thin film structure. We find that higher solar energy absorption efficiency can be achieved by adjusting the geometric parameters of nanostructures, and the perfect broadband absorption can be achieved in the range of visible light to near infrared. Display omitted
•The solar energy absorber has a perfect broadband absorption in the visible to near-infrared band.•The absorption properties can be changed by the geometric parameters.•The absorber is insensitive to incident angles, regardless of TM or TE polarization.•The absorber has good thermal stability by Ti film and TiN nanodisk.
The paper proposes an ultra-narrow band graphene refractive index sensor, consisting of a patterned graphene layer on the top, a dielectric layer of SiO2 in the middle, and a bottom Au layer. The ...absorption sensor achieves the absorption efficiency of 99.41% and 99.22% at 5.664 THz and 8.062 THz, with the absorption bandwidths 0.0171 THz and 0.0152 THz, respectively. Compared with noble metal absorbers, our graphene absorber can achieve tunability by adjusting the Fermi level and relaxation time of the graphene layer with the geometry of the absorber unchanged, which greatly saves the manufacturing cost. The results show that the sensor has the properties of polarization-independence and large-angle insensitivity due to the symmetric structure. In addition, the practical application of testing the content of hemoglobin biomolecules was conducted, the frequency of first resonance mode shows a shift of 0.017 THz, and the second resonance mode has a shift of 0.016 THz, demonstrating the good frequency sensitivity of our sensor. The S (sensitivities) of the sensor were calculated at 875 GHz/RIU and 775 GHz/RIU, and quality factors FOM (Figure of Merit) are 26.51 and 18.90, respectively; and the minimum limit of detection is 0.04. By comparing with previous similar sensors, our sensor has better sensing performance, which can be applied to photon detection in the terahertz band, biochemical sensing, and other fields.
Solar energy is currently a very popular energy source because it is both clean and renewable. As a result, one of the main areas of research now is the investigation of solar absorbers with broad ...spectrum and high absorption efficiency. In this study, we create an absorber by superimposing three periodic Ti-Al
O
-Ti discs on a W-Ti-Al
O
composite film structure. We evaluated the incident angle, structural components, and electromagnetic field distribution using the finite difference in time domain (FDTD) method in order to investigate the physical process by which the model achieves broadband absorption. We find that distinct wavelengths of tuned or resonant absorption may be produced by the Ti disk array and Al
O
through near-field coupling, cavity-mode coupling, and plasmon resonance, all of which can effectively widen the absorption bandwidth. The findings indicate that the solar absorber's average absorption efficiency can range from 95.8% to 96% over the entire band range of 200 to 3100 nm, with the absorption bandwidth of 2811 nm (244-3055 nm) having the highest absorption rate. Additionally, the absorber only contains tungsten (W), titanium (Ti), and alumina (Al
O
), three materials with high melting points, which offers a strong assurance for the absorber's thermal stability. It also has a very high thermal radiation intensity, reaching a high radiation efficiency of 94.4% at 1000 K, and a weighted average absorption efficiency of 98.3% at AM1.5. Additionally, the incidence angle insensitivity of our suggested solar absorber is good (0-60°) and polarization independence is good (0-90°). These benefits enable a wide range of solar thermal photovoltaic applications for our absorber and offer numerous design options for the ideal absorber.
To efficiently separate photoexcited electron/hole pairs is one of the key points for achieving excellent photocatalysts with high photocatalytic performances. To achieve this aim, here we have ...assembled CaTiO
3
(CTO) nanoparticles onto BiOBr microplates, thus constructing novel Z-scheme CTO@BiOBr heterojunction composite photocatalysts. Observation by scanning/transmission electron microscopy confirms the good decoration of CTO nanoparticles (15–50 nm) on the surface of BiOBr microplates (diameter 0.7–2.2 μm, thickness 70–110 nm). Simulated sunlight was used as the light source, and rhodamine B (RhB) in aqueous solution was used as the model pollutant to assess the photodegradation activity of the samples. It is demonstrated that the CTO@BiOBr composites with an appropriate CTO content exhibit much enhanced photodegradation performances. In particular, the 10%CTO@BiOBr composite with a CTO mass fraction of 10%, which photocatalyzes 99.9% degradation of RhB at 30 min of photocatalysis, has a photocatalytic activity which is about 1.8 and 23.6 times larger than that of bare BiOBr microplates and CTO nanoparticles, respectively. This can be explained as the result of the Z-scheme electron transfer and efficient separation of photoexcited electron/hole pairs, as evidenced by photoluminescence, photocurrent response, and electrochemical impedance spectroscopy investigations.
In this work, we attempted to assemble Au and Ag nanoparticles (NPs) with different sizes onto Bi
4
Ti
3
O
12
(BTO) nanosheets with the aim of synergistically enhancing the photocatalytic ...performance. The as-prepared Au–Ag@BTO composite was systematically characterized by means of TEM, XRD, XPS, FTIR, UV–vis DRS, PL spectroscopy, EIS and photocurrent spectroscopy. The TEM observation demonstrates that larger-sized Au NPs (average size: 20 nm) and smaller-sized Ag NPs (average size: 8 nm) are uniformly decorated on the surface of BTO nanosheets. Compared to bare BTO, the Au–Ag@BTO composite manifests an increased visible light absorption, increased bandgap, increased photocurrent density, decreased charge-transfer resistance and decreased PL intensity. Separately using simulated sunlight, UV light and visible light as the light source, the photocatalytic performance of the composite was evaluated by the degradation of RhB. An enhanced photocatalytic performance of the composite is observed in all the cases. Under UV irradiation, the photocatalytic enhancement is mainly ascribed to the efficient separation of photogenerated electron/hole pairs caused by the smaller-sized Ag NPs, whereas the photocatalytic enhancement under visible light irradiation is dominantly due to the LSPR effects of the larger-sized Au NPs. The synergistic photocatalytic enhancement between Ag and Au NPs is achieved under simulated sunlight irradiation. Active species trapping experiments were carried out, revealing that photogenerated holes and ·O
2
−
radicals play a dominant and secondary role in the photocatalysis, respectively.
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•High-quality carnation flower-like Bi2O2CO3 hierarchical architectures have been synthesized.•Their photoreduction performance for remoing Cr(VI) was evaluated.•Effects of various ...factors on the photoreduction efficiency and involved mechanism were investigated.•Effects of various parameters on the absorbance of the Cr(VI) solution were investigated.
In this study, we have synthesized high-quality carnation flower-like Bi2O2CO3 hierarchical architectures via a hydrothermal route. The as-synthesized Bi2O2CO3 photocatalyst was systematically characterized and analyzed by various techniques. Its photocatalytic activity was investigated by simulated-sunlight driving photoreduction of Cr(VI), revealing that it exhibits excellent photocatalytic removal of Cr(VI). The effects of various factors (H2SO4, NaOH, Cr(VI) concentration, catalyst dosage) on the photoreduction efficiency and involved mechanism were systematically investigated and discussed. In addition, we have also systematically examined the effects of various parameters (H2SO4 concentration, 1,5-diphenylcarbazide (DPC) concentration, Cr(VI) concentration, reaction time t and reaction temperature T) on the absorbance of the Cr(VI) solution, with the aim of correctly determining the Cr(VI) concentration according to UV–vis absorption measurements using DPC as the chromogenic agent.
When surface plasmon resonance (SPR) occurs, the incident light is absorbed by the surface of the SPR structure, thus minimizing the intensity of the reflected light. Therefore, the SPR method is ...adopted in this paper to achieve perfect absorption of the absorbent. In this paper, we first propose a multi-frequency broadband absorber structure based on graphene SPR, which uses the continuous resonance of patterned graphene surface plasmon in the frequency spectrum to form a multi-frequency broadband absorption. In this simulation, a sandwich-stack structure was adopted, whereby the patterned graphene is situated on top of the SiO2 layer and the metal layer. The broad-band absorption bands of the absorber were obtained as 4.14–4.38 THz, 5.78–6.36 THz, and 7.87–8.66 THz through the analog simulation of finite-difference time-domain method (FDTD) solutions. Then, based on the multi-layer resonant unit structure, through the superposition and combination of absorbing units responding to different frequency bands, the perfect absorption of ultra-wideband is achieved. The data results illustrate that the total absorption bandwidth of the absorber is 2.26 THz, and the relative absorption bandwidth Bw is equal to 28.93%. The electric field in X-Y direction of the absorber in the perfect absorption band is analyzed, respectively, and the dynamic tunability of the absorber is studied. Finally, we studied whether the absorbing structure still has efficient absorption characteristics for the two polarization modes when the incident angle is changed from 0° to 70°. The structure model proposed has potential value for application in terahertz photoelectric detection, filtering, and electromagnetic shielding.
Herein, binary CuS/BTO and ternary CuS/Ag/BTO composite photocatalysts have been fabricated by anchoring CuS and Ag nanoparticles onto BaTiO
3
(BTO) polyhedra. The as-prepared composite ...photocatalysts were characterized by means of the techniques of transmission/scanning electron microscopy, x-ray powder diffraction, ultraviolet–visible diffuse reflectance spectroscopy, x-ray photoelectron spectroscopy and photoluminescence spectroscopy. Transient photocurrent and electrochemical impedance spectroscopy measurements suggest that the ternary 5%CuS/(1%Ag/BTO) composite possesses the highest separation efficiency of electron/hole pairs. The photodegradation experiments were conducted by using simulated sunlight as the light source to decompose Rhodamine B in water solution. The 5%CuS/(1%Ag/BTO) and 5%CuS/BTO composites are demonstrated to have the highest and second highest photodegradation activity, respectively. As compared with that of bare BaTiO
3
and CuS, the photoactivity of 5%CuS/(1%Ag/BTO) is increased to 3.3 and 2.0 times, respectively. The electron/hole separation mechanism and the role of localized surface plasmon resonance of Ag nanoparticles in the dye photodegradaton were systematically investigated.
