A robust generalized analytical expression for resonance frequencies of plasmonic nanoresonators, which consists of folded rectangular structures, is proposed based on a circuit route. The ...formulation is rigorously derived from the lumped circuit analogue of the plasmon resonance in a rectangular metallic nanorod. Induced by the nonhomogeneous charge distributions in the plasmonic resonators of rectangular end-caps, the electromagnetic forces drive the harmonic oscillations of free electrons in the plasmonic nanoresonators, generating intrinsically nonlinear shape-dependent LC resonance responses. Even for the plasmonic nanoresonators with much larger structure sizes than the skin depths, the significant frequency deviations due to the phase-retardation behavior can still be adequately described by the generalized expression. Moreover, for a large range of plasmonic nanoresonators with various folded rectangular geometries, sizes and materials, the generalized analytical expression gives the underlining physics and provides accurate predictions, which are perfectly verified by a series of numerical simulations. Our studies not only offer quantitative insights of nearly any plasmonic nanoresonators based on folded rectangular geometries, but also reveal potential applications to design complex plasmonic systems, such as periodic arrays with embedded rectangular nanoresonators.
The realization of mid-infrared thermal radiation based on metamaterials insensitive to angle and polarization plays an important role in various thermal photonic applications. However, the ...challenges include the following: most previously designed thermal emitters usually contain metal components with unsatisfied physicochemical stability, accompanied with complex manufacturing technology. The present study proposes a mid-infrared thermal emitter at 3–6 μm wavelength range based on Fibonacci quasi-periodic structure, and a flat one-dimensional structure based on Fibonacci geometry resorting to ITO is designed. The proposed thermal emitter is, theoretically and experimentally, proven to possess good angular and polarization-independent selective thermal emission performance in a relatively wide infrared wavelength range. Furthermore, the good optical and high-temperature thermal stability of the designed thermal emitter is verified in the present experimental research. The thermal emitters proposed have advantages in polarization-independence without scale restraint and low cost but with wide vision. In summary, the present study provides a new tactics for obtaining non-metal spectral selective thermal emitters in a relatively wide wavelength range and thermal photonic applications under harsh conditions.
The electronic structure, elastic and optical properties of the defect quaternary semiconductor CuGaSnSe4 in I4¯ structure are systematically investigated using first-principles calculations. We ...summarize and discuss some of the studies on CuGaSnSe4 in partially ordered chalcopyrite structure and find that there are three atomic arrangements so far, but it is still uncertain which is the most stable. Through detailed simulation and comparison with the corresponding literature, we get three models and predict that M1 model should be the most stable. The band structure and optical properties of compound CuGaSnSe4, including dielectric constant, refractive index and absorption spectrum, are drawn for a more intuitive understanding. The elastic constants are also calculated, which not only prove that CuGaSnSe4 in I4¯ structure is stable naturally but also help solve the problem of no data to accurately predict axial thermal expansion coefficients. The calculated values of the zero frequency dielectric constant and refractive index are comparable to those of the corresponding chalcopyrite structure but slightly larger.
Infrared metasurfaces have exhibited exceptional optical properties that differ from naturally occurring metallic and dielectric nanostructure, enabling non-destructive and label-free sensing in a ...broadband region. However, implementing wavelength multiplexing sensors in broadband infrared has faced significant challenges. These challenges arise from the difficulty in efficiently exciting high
resonances at specific wavelengths and the inability to individually tune each resonance. Herein, we present a dual resonant metasurface that utilizes a metal–dielectric–metal plasmonic grating and a dielectric–metal channel. By adjusting the vertical and horizontal structures of metasurface, we can independently modify the spectrum of the metasurface in the near-infrared and mid-infrared regions. This broadband infrared metasurface exhibits robust spectral regulation, enabling a polarization-dependent strategy for the dual-resonance. It offers a competitive advantage over traditional metallic nanostructure in refractive index sensing at the second near-infrared window and ultrasensitive vibrational spectroscopy in mid-infrared. Specifically, our proposed metasurface achieves protein concentration sensing and dynamic monitoring of protein concentration in the infrared two-zone. Additionally, it enhances the mid-infrared absorption of amide II with a high
resonance. The metasurface which combines wavelength multiplexing and polarization dependent switch for protein recognition and trace detection, presents a novel approach for developing high-performance sensors and Integrated photonics sensors in the broadband infrared region.
Herein, based on the finite‐element calculation method, a high‐sensitivity infrared absorption sensor is designed with ZnSe as the substrate, Mo as the waveguide layer and periodic grating, and Ge as ...the thin film. The absorption performance of the structure is not sensitive to the polarization of the incident light when the transverse‐magnetic light wave is perpendicular to the structure. The thickness of the Ge thin film and the width of the grating column are the main factors for determining its absorption and sensing performance. The optimized structure is sensitive to the refractive index on the grating. Herein, a correspondence between the refractive index change and the position of the peak of the absorbance spectrum is established. When this structure is used as a refractive index sensor, the sensitivity can reach 2300 nm RIU−1 with a high figure of merit of 37.09. In addition, temperature sensing in ethanol shows that the waveguide can quantify the solution temperature by resonance. It is demonstrated in the results that the grating absorber has great potential applications in biomedical sensing.
The polarization‐independent absorber based on a covered micron‐scale metal grating is used for refractive‐index sensing. Its sensitivity is as high as 2300 nm RIU−1 with a figure of merit of 37.09. These results provide a reference for label‐free molecular detection in the mid‐infrared.
The Schiff N‐allylamine‐4‐(ethylenediamine‐5‐methylsalicylidene)‐1,8‐naphthalimide (H2L) and its copper(II) complex, Cu(HL)2·0.5DMF, were synthesized and characterized. The crystal structure of the ...CuII complex reveals a slightly distorted square‐planar arrangement provided by two N and O donors from two deprotonated ligands. In addition, the DNA‐binding properties of the ligand and CuII complex were investigated by fluorescence spectra, electronic absorption, and viscosity measurements. The experimental studies of the DNA‐binding properties indicated that the ligand and CuII complex reacted with DNA via intercalation binding mode, and binding affinity for DNA takes the order: ligand > CuII complex. The antioxidant assay in vitro suggested that both exhibited potential intensely antioxidant properties, and the ligand is more effective than its CuII complex.
Two Ag(I) complexes have been synthesized and characterized systematically. Complexes 1–2 are both a dinuclear metallacycle with 2-fold rotational symmetry. The salient structural feature of 2 is ...that one of two oxygen atoms of carboxylate group of p-coumarate adopts a monodentate bridging mode to connect two Ag(I) ions. Two Ag(I) complexes bind to DNA in an intercalation mode. The complex 2 has a strong potential to be applied as scavengers to eliminate the radicals.
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•Two Ag(I) complexes containing bis-benzimidazole thioether have been reported.•Binuclear metallacycle Ag(I) complex 1–2 show a distorted tetrahedral geometry.•Ag(I) complexes bind to DNA in an intercalation mode.•Complex 2 has the advantage of scavenge hydroxyl and superoxide radical.
Two new binuclear Ag(I) complexes of the types, Ag2(bbt)2(pic)2·2DMF 1 and Ag2(bmbt)2(p-coumarate)2·2CH3OH 2 (bbt = 1,3-bis(2-benzimidazyl)-2-thiapropane; bmbt = 1,3-bis(1-methylbenzimidazol-2-yl)-2-thiapropane; pic = picrate), have been synthesized and characterized by elemental analysis, electrical conductivities, IR, UV–Vis spectral measurements and X-ray single crystal diffraction. Structural analysis show that coordination environment of complexes 1–2 are both a binuclear metallacycle with 2-fold rotational symmetry and can be described as a distorted tetrahedral geometry. In addition, there is strong Ag-Ag interaction in the complex 1. The salient structural feature of 2 is that one of two oxygen atoms of carboxylate group of p-coumarate adopts a monodentate bridging mode to connect two Ag(I) ions. In order to explore the relationship between the structure and biological properties, DNA binding propensity have also been studied. The results suggested that the two ligands and the two Ag(I) complexes bind to DNA via intercalative binding mode, and the order of the binding affinity is 1 > 2 > bbt > bmbt. Moreover, we also discovered that the complex 2 possesses significant antioxidant activity against superoxide and hydroxyl radicals.
A novel copper(I) coordination polymers (CPs) and a binuclear copper(I) complex have been successfully obtained. All Cu(I) ions in complexes 1–2 are tri-coordinated and the geometric structure around ...the central Cu(I) atom can be described as planar trigonal configuration. The photoluminescent transition of Cu(I) complexes 1–2 may be attributed to metal-to-ligand charge-transfer MLCT.
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•Copper(I) coordination polymer 1 and binuclear complex 2 have been reported.•In 1–2, The ligand adopt the μ2-bridging mode to link two Cu(I) atoms, forming two Cu(I) motifs.•There are excellent fluorescence properties of the complexes 1–2 in a solid state.
Reaction of 2,2-(1,4-butanediyl)bis-1,3-benzoxazole (BBO) ligand with Cu(CH3CN)2(PPh3)2X (X=ClO4, PF6) afforded a copper(I) coordination polymer (CP) {Cu(BBO)(PPh3).ClO4}∞ (1) and a binuclear complex Cu2(BBO)(PPh3)4.2PF6.2CH2Cl2 (2) (where PPh3=triphenylphosphine). Two complexes have been characterized. The structural analysis revealed that in complexes 1–2, all Cu(I) ions are tri-coordinated and the geometric structure around the central Cu(I) atom can be described as planar trigonal configuration. Complex 1 exhibits a one-dimensional coordination polymer by two BBO bridging adjacent copper(I) ions and extending along the b axis, forming a single-stranded helix chain structure that extends into 2-D layer frameworks through π…π interactions. Complex 2 shows a binuclear structure and the unit extends to a 2D supramolecular layered framework through C-H…F interactions. Moreover, compared with emissive bands of the free ligand in the solid state, the photoluminescent transition of the Cu(I) complexes 1–2 may be attributed to metal-to-ligand charge-transfer MLCT.
Three mononuclear Cu(I) complexes, namely, Cu(2-PBO)(PPh3)2·ClO4·2CH2Cl2 (1), Cu(3-PBO)(PPh3)2(ClO4)·CH2Cl2 (2) and Cu(PBM)(PPh3)2·ClO4 (3) (2-PBO = 2-(2′-Pyridyl)benzoxazole, ...3-PBO = 2-(3′-Pyridyl)benzoxazole, PBM = 2-(2′-Pyridyl)benzimidazole, PPh3 = triphenylphosphine) have been synthesized and characterized by elemental analyses, IR, 1H NMR, 13C NMR, X-ray single crystal diffraction and thermal analysis. Photoluminescent investigation shows that complexes 1–3 exhibit distinct tunable light green (512 nm)-to-yellow (557 nm) photoluminescence by varying the N-heterocyclic ligands. Three complexes show intense 2-PBO-based yellow, 3-PBO-based light green and intense PBM-based bright green luminescence upon irradiation with a standard UV lamp (λex = 254 nm) at room temperature. Moreover, the electrochemical properties of 1–3 have been investigated by cyclic voltammetry. The results suggest the frontier molecular orbits and the HOMO-LUMO energy gaps of these cuprous complexes are effectively adjusted through the introduction of different N-heterocyclic ligands, thus achieving the selective luminescence of the cuprous complexes.
Three mononuclear Cu(I) complexes have been synthesized and characterized. Photoluminescent investigation shows that complexes 1–3 exhibit distinct tunable light green (512 nm)-to-yellow (557 nm) photoluminescence by varying the N-heterocyclic ligands. Moreover, the electrochemical results suggest the frontier molecular orbits and the HOMO-LUMO energy gaps of these cuprous complexes are effectively adjusted through the introduction of different N-heterocyclic ligands. Display omitted
•Three mononuclear Cu(I) complexes have been synthesized and characterized.•In complexes 1–3, the all Cu(I) are four-coordinated and possessing a slightly distorted trigonal pyramidal geometry.•Complexes 1–3 exhibit distinct tunable photoluminescence by varying the N-heterocyclic ligands.
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