One-dimensional Heterostructures Research Articles

Strong coupling of multiple optical interface modes with ultra-narrow linewidth in one-dimensional topological photonic heterostructures.

Coherent coupling of optical modes with a high Q-factor underpins realization of efficient light-matter interaction with multi-channels in resonant nanostructures. Here we theoretically studied the strong longitudinal coupling of three topological photonic states (TPSs) in a one-dimensional topological photonic crystal heterostructure embedded with a graphene monolayer in the visible frequencies. It is found that the three TPSs can strongly interplay with one another in the longitudinal direction, enabling a large Rabi splitting (∼ 48 meV) in spectral response. The triple-band perfect absorption and selective longitudinal field confinement have been demonstrated, where the linewidth of hybrid modes can reach 0.2 nm with Q-factor up to 2.6 × 103. Mode hybridization of dual- and triple-TPSs were investigated by calculation of the field profiles and Hopfield coefficients of the hybrid modes. Moreover, simulation results further show that resonant frequencies of the three hybrid TPSs can be actively controlled by simply changing the incident angle or structural parameters, which are nearly polarization independent in this strong coupling system. With the multichannel, narrow-band light trapping and selectively strong field localization in this simple multilayer regime, one can envision new possibilities for developing the practical topological photonic devices for on-chip optical detection, sensing, filtering, and light-emitting.

One-dimensional heterostructures of polyoxometalate-encapsulated carbon nanotubes for enhanced capacitive energy storage

One-dimensional heterostructures of polyoxometalate-encapsulated carbon nanotubes for enhanced capacitive energy storage

Transition Metal Dichalcogenides Heterostructures Nanoribbons

The integration of two-dimensional van der Waals (vdW) heterostructures breaks through the constraints of lattice matching and symmetry, offering substantial opportunities in the development of advanced materials. After the width is reduced, one-dimensional vdW heterostructures show rich band structures and strong spin–orbit coupling behaviors, widening the applications in optoelectronics and spintronics. However, the synthesis of one-dimensional vdW heterostructure nanoribbons has rarely been reported yet. Herein, we report a general approach to realizing transition metal dichalcogenide (TMD) heterostructure nanoribbons for the first time by unzipping self-assembled TMD heterostructure nanoscrolls. As demonstrated by MoS2/WS2 nanoribbons, the obtained TMD heterostructure nanoribbons with alternating stacked layers possess flat edge structures and high quality. Meanwhile, this strategy can be extended to create diverse vdW TMD nanoribbons, demonstrating its versatility. Our work thus shows great potential to prepare TMD heterostructure nanoribbons with various compositions and stacking modes, and new structures can be customized with targeted properties.

Rabi splitting and unidirectional reflectionless propagation in one-dimensional topological plasmonic crystal

In this paper, we study the strong coupling between the topological edge state and Fabry–Perot cavity state in a one-dimensional plasmonic crystal heterostructure. Finite element method simulations show that a significant plasmonic Rabi splitting is achieved in the near-infrared region and Rabi energy can reach up to 45.5 meV. A dual-band near-perfect absorption phenomenon can be observed, and a coupled oscillator model is proposed to explain the origin of Rabi splitting. In addition, the dual-band unidirectional reflectionless plasmonic propagation in the Rabi splitting region is investigated, and the non-Hermitian scattering matrix is used to verify the existence of double exceptional points. The study may find applications in plasmonic switchers, on-chip sensors, diode-like devices, and filters.

Topologically protected multiple resonant modes in a one-dimensional photonic crystal heterostructure

This paper proposed and theoretically examined a double-interfaced one-dimensional photonic crystal heterostructure for strong localization of topologically protected resonant modes. It is challenging to achieve these modes for a range of wavelengths using a single photonic crystal. The design proposed in this study is a heterostructure of photonic crystals 1 (PC1) and 2 (PC2), and it provides distributed localized modes from the infrared to ultraviolet wavelength ranges. In addition, multiple resonant modes occur at certain photonic bandgaps due to the addition of the third photonic crystal (PC3), which is analytically modeled with the heterostructure of PC1 and PC2. The enhancement in the number of resonant modes depends on the PC2 number of unit-cells and the reflection phase of the proposed heterostructure. The reflection phase is abruptly changing from 0 to π for several wavelengths inside the bandgap. These resonance modes are also dependent on the topological behavior of each connected photonic crystal and are immune to small disorder and back-scattering within the crystal. The high-quality factor (Q-factor ∼107) shows strong light–matter interaction of these multiple resonant modes. The characterization was done in terms of the Zak phase, sign of the reflection phase, and bandgap overlapping. Consequently, this heterostructure may pave the way for new topological photonics and new applications in optoelectronics, frequency up-conversion, photonic devices, rainbow trapping, multiwavelength optical filters, and so on.

Perfect light absorber with a PT phase transition via coupled topological interface states

Recently, the concepts of parity–time (PT) symmetry and band topology have inspired many novel ideas for light manipulation in their respective directions. Here we propose and demonstrate a perfect light absorber with a PT phase transition via coupled topological interface states (TISs), which combines the two concepts in a one-dimensional photonic crystal heterostructure. By fine tuning the coupling between TISs, the PT phase transition is revealed by the evolution of absorption spectra in both ideal and non-ideal PT symmetry cases. Especially, in the ideal case, a perfect light absorber at an exceptional point with unidirectional invisibility is numerically obtained. In the non-ideal case, a perfect light absorber in a broken phase is experimentally realized, which verifies the possibility of tailoring non-Hermiticity by engineering the coupling. Our work paves the way for novel effects and functional devices from the exceptional point of coupled TISs, such as a unidirectional light absorber and exceptional-point sensor.

Tunable Fano resonance in coupled topological one-dimensional photonic crystal heterostructure and defective photonic crystal

In this paper, we theoretically investigate the transmission properties of a structure composed of a topological one-dimensional photonic crystal (1D PhC) heterostructure and a conventional 1D PhC containing indium-antimonide (InSb) as a defect layer using the transfer matrix method. The phenomenon of Fano resonance can be achieved by coupling the defect mode with the topological edge state mode, which is supported by the topological PhC. The numerical results show that a narrow Fano resonance is observed in the transmission spectrum of the structure in the presence of the external magnetic field applied to the InSb defect layer. The optical properties of the InSb defect layer, and, therefore, the Fano resonance, can be dynamically controlled by changing the applied external magnetic field. The results obtained with the proposed structure reveal that the magnetic field has the greatest influence on controlling the optical properties of the Fano resonance. These findings could be beneficial for optical devices such as optical filters, sensors, and optical switches.

WO3 Nanowire-Attached Reduced Graphene Oxide-Based 1D-2D Heterostructures for Near-Infrared Light-Driven Synergistic Photocatalytic and Photothermal Inactivation of Multidrug-Resistant Superbugs.

The rapid emergence of superbugs which are resistant to existing antibiotics is becoming a huge global threat to public health, which demands the discovery of next-generation antibacterial agents for combating superbugs. Herein, we report the design of a two-dimensional (2D) reduced graphene oxide (r-GO) and one-dimensional (1D) WO3 nanowire-based photothermal-photocatalytic heterostructure for combating multiantibiotic-resistant Salmonella DT104, carbapenem-resistant Enterobacteriaceae Escherichia coli, and methicillin-resistant Staphylococcus aureus superbugs. In the presence of near-infrared (NIR) light, due to the generation of electrons and holes, the WO3-based heterostructure generates reactive oxygen species by photocatalytic reaction from water and oxygen, which kills superbugs. To enhance the photocatalytic superbug killing efficiency, r-GO has been used for suppressing the recombination of the photoinduced electron-hole pairs. Reported data show that NIR light-driven synergistic photocatalytic-photothermal processes can be used for 100% degradation of methylene blue using a heterostructure-based catalyst, and the photodegradation rate for the heterostructure is much better than the literature data for different types of WO3/GO-based nanocomposites. Experimentally, time-dependent antibacterial efficiency data reveals that the heterostructure can destroy 100% superbugs within 30 min of light exposure via a synergistic photothermal and photocatalytic mechanism, whereas the WO3 nanowire can kill around 35% superbugs only via photocatalytic action only and r-GO can kill 25% superbugs via photothermal action even after 30 min of exposure to light. Systematic time-dependent microscopy and spectroscopy studies reveal that the excellent antisuperbug activities for heterostructures are due to membrane damage, ATP, and DNA/RNA breakage. For possible real-life applications, sun light-based superbug inactivation shows 100% inactivation possible within 250 min of light exposure using 12 mg/mL heterostructures. The reported sun light-driven killing of superbugs provides a simple and versatile platform to combat drug-resistant superbugs.

One dimensional nickel phosphide polymorphic heterostructure as carbon-free functional support loading single-atom iridium for promoted electrocatalytic water oxidation

Although conducting materials such as carbon nanotube and carbon fiber paper (CFP) have been extensively employed as support of electrocatalytic active sites, most of them are of poor catalytic functionality by themselves and undesirable stability during strong acid/alkaline environments or oxidation process. Here we report a novel one-dimensional (1D) nickel phosphide polymorphic heterostructure (denoted as NPPH) to work as one effective carbon-free functional support for loading of single-atom Ir water oxidation electrocatalyst. Specifically, the NPPH composed of both Ni12P5 and Ni2P phases is not only active for robust alkaline water oxidation but also is of good stability and hydrophilicity for favorable loading of single-atom dispersed iridium. The NPPH supported single-atom Ir electrocatalyst (Ir/NPPH) is found to exhibit remarkably superior water oxidation activity with respect to the NPPH itself or CFP supported single-atom Ir catalyst (Ir/CFP), demonstrating the synergetic promotion effect between NPPH and single-atom Ir catalyst. Furthermore, the NPPH supported single-atom Ir catalyst can bear alkaline water oxidation for over 120 h at current density of 50 mA cm−2. The NPPH developed here is expected as functional support to composite with other water oxidation catalysts, as may be an alternative strategy of developing highly efficient carbon-free electrocatalysts.

Mechanical and thermal properties of graphyne-coated carbon nanotubes: a molecular dynamics simulation on one-dimensional all-carbon van der Waals heterostructures.

The mechanical and thermal properties of a hybrid nanotube consisting of a coaxial carbon nanotube (CNT) inside a graphyne nanotube (GNT), i.e., CNT@GNT, are investigated in this paper by using molecular dynamics simulations. The results show that the mechanical properties of CNT@GNT under uniaxial tension depend on the nanotube chirality of its components. Specifically, the Young's modulus of the CNT@GNT structure with an inner zigzag CNT is larger than that of its counterpart with an armchair CNT, while CNT@GNT with an armchair CNT and a zigzag GNT is found to possess the largest tensile strength and fracture strain. In addition, a unique fracture behavior of the successive rupture of its two components is observed in CNT@GNT. The thermal conductivity of CNT@GNT is found to be almost independent of the nanotube chirality of its components but increases as the length and diameter of the CNT@GNT increase. Moreover, strain engineering is shown as an effective avenue to modulate the thermal conductivity of CNT@GNT, which can be enhanced by tension but reduced by compression. The analysis of the phonon spectrum and spectral energy density demonstrates that this strain effect originates from changes of the phonon group velocity and phonon scattering in the strained CNT@GNT.

Transient thermal rectification effect of one-dimensional heterostructure

Like an electric diode, thermal diode transmits heat in a specific direction, and thermal rectification is also a fundamental phenomenon for active heat flow control. However, in practical applications, thermal rectification needs to be operated under transient conditions. In this study, transient thermal rectification ratio of a one-dimensional heterostructure is numerically investigated by using the finite element method. The effects of interface thermal resistance, interface initial gap, periodic boundary condition and geometric and material parameters on the transient thermal resistance ratio are obtained. Research indicates that the interface thermal resistance can enhance the thermal rectification effect of the system, and the introduction of the initial interface gap improves the transient thermal rectification ratio by an order of magnitude. The ability to engineer the thermal diffusivity of materials allows us to control the heat flux and improve transient thermal rectification ratio. Since interface thermal resistance can enlarge the difference in heat transfer capability between forward case and reverse case, it is reasonable to suggest that adjusting the interface thermal resistance may also enhance the thermal rectification effect, but excessive interface thermal resistance will reduce it. Under the periodic temperature boundary conditions, the larger the temperature difference in boundary fluctuation, the larger the fluctuation amplitude of the transient thermal rectification ratio is. The fluctuation frequency of thermal rectification changes with the periodic boundary frequency, which also affects the amplitude of the fluctuation. Furthermore, by adjusting the initial interface gap, the gap is closed during heat transfer and the interface thermal resistance is reduced in the forward case, while the interface gap is kept open in the reverse case, thereby improving the overall thermal rectification ratio by an order of magnitude. For different transient stages, the equivalent thermal conductivity can be changed by adjusting the material and geometrical properties to improve the thermal rectification ratio.Therefore, the proposed numerical approach and results can guide the optimal design of the transient thermal rectifier.

Iridium-incorporated cobalt nanofibers as efficient and robust bifunctional catalysts for high-performance water electrolysis

Iridium (Ir)-incorporated cobalt (Co) nanofibers (Co-Ir-600) are fabricated via an electrospinning-calcination-in situ H2 reduction-galvanic replacement process. Benefitting from the unique one-dimensional nanofibrous heterostructure that allows rapid electron/mass transfer as well as the synergy between Ir and Co components, the Co-Ir catalyst shows a remarkable electrocatalytic activity for oxygen evolution reaction (OER) with an extremely low overpotential of 169 mV at 10 mA cm−2 in an alkaline electrolyte. Furthermore, the catalyst also presents a high hydrogen evolution reaction (HER) performance. Therefore, an alkaline electrolyzer is constructed with the Co-Ir-600 nanofibrous catalyst as both the anode and cathode electrodes, and only a small cell voltage of 1.51 V is needed to achieve 10 mA cm−2 with outstanding durability. This performance is superior to that of benchmark Pt/C∥IrO2 electrodes and many other reported water electrolysis cells. This study supplies a general and efficient way to prepare cost-effective and high-performance metal-based overall water splitting electrocatalysts.

Formation of One-Dimensional van der Waals Heterostructures via Self-Assembly of Blue Phosphorene Nanoribbons to Carbon Nanotubes

Van der Waals heterostructures composed of low-dimensional atomic layers host rich physics for new device applications, such as magic-angle twisted bilayer graphene and coaxial multi-walled hetero-nanotubes. Aside from exploring their abnormal physical behavior, fabrication of such structures also presents a great challenge to this area, owing to the subtle and sensitive interactions among neighboring layers. Here we show by molecular dynamics simulations that narrow blue phosphorene nanoribbons can be encapsulated into carbon nanotubes driven by van der Waals interactions and form one-dimensional heterostructures. It shows that by varying carbon nanotube diameters and nanoribbon width, the nanoribbons can either retain their original straight structures or twist into tubular structures. Wrapping phases are also observed for large-sized blue phosphorus. It is found that the underlying mechanism originates from the competition between van der Waals energy and bending energy induced by tube curvature. A phase diagram of the resultant 1D structure is thus obtained based on a simple analysis of energetics. The results are expected to stimulate further experimental efforts in fabricating one-dimensional van der Waals heterostructues with desired functionality.

One-dimensional heterostructure: The selective decoration of single-walled carbon nanotube tips with metallic nanoparticles

One-dimensional heterostructure: The selective decoration of single-walled carbon nanotube tips with metallic nanoparticles

Carrier localization in zero-dimensional and one-dimensional CdSe-CdS heterostructures.

Mobile charge carriers in heterostructured nanoparticles are relevant for applications requiring charge separation and extraction. We investigate the benchmark systems CdSe-CdS core-shell quantum dots and quantum dots in quantum rods by optical and THz pump-probe spectroscopy. We relate photoconductivity and carrier location and observe that only shell-located electrons in quantum rods contribute to an observable photoconductivity. Despite the shallow electron confinement in the quasi-type II heterostructures, core-located carriers are bound into immobile excitons that respond on external electrical fields by polarization.

Robust type-I band alignment in ZnS nanowire/MoTe2 nanotube van der Waals heterostructures

This work utilizes the density functional theory approach to evaluate the electronic structures of ZnS nanowire/MoTe2 nanotube (ZnSNW/MoTeNT) one-dimensional (1D) van der Waals heterostructures (vdWhs) under axial strain. It is demonstrated that the ZnSNW/MoTeNT 1D vdWhs with different diameters have robust type-Ⅰ band alignment (BA). Furthermore, it is discovered that type-Ⅰ BA is robust under axial strain ranging from −5% to 5%. Besides, the axial strain of 3% leads to the ZnSNW/MoTeNT 1D vdWhs transitions from indirect bandgap semiconductor to direct bandgap semiconductor. According to the mentioned findings, the ZnSNW/MoTeNT 1D vdWhs have robust type-Ⅰ BA even under axial strain.

Graphene-based dual-band near-perfect absorption in Rabi splitting between topological edge and Fabry–Perot cavity modes

We propose a graphene embedded one-dimensional (1D) topological photonic crystal heterostructure, where the coupling occurs between the topological edge mode (TEM) and the Fabry–Perot cavity mode (CM). It is shown that the coupling leads to the hybridization between TEM and CM, with a Rabi splitting. Based on finite element method, a dual-band near-perfect absorption is found in the Rabi splitting region in near-infrared range. The resonant wavelengths of the two absorption peaks are 1537 and 1579 nm, respectively. And the two absorption peaks can be modulated by the thickness of the defect layer, the coupling distance between TEM and CM, Fermi energy of graphene, and incident angle of light (under TE and TM polarization). In particular, when the Fermi energy of graphene slightly increases over 0.4 eV, the imaginary part of permittivity of graphene is near 0, so does the dual-band absorption. Theoretically, the TEM-CM coupling can be analyzed by the classic oscillator model. The controllable two absorption bands may achieve potential applications in active optoelectronic devices at communication wavelengths, such as optical switches, sensors and modulators.

Catalyzed Growth for Atomic-Precision Colloidal Chalcogenide Nanowires and Heterostructures: Progress and Perspective.

One-dimensional colloidal semiconductor nanowires are of wide interest in nanoscale electronics and photonics. As compared to the zero-dimensional counterparts, their geometrical anisotropy offers an additional degree of freedom to tailor the electronic and optical properties and enables customized heterostructures with increased complexity. The colloidal synthetic chemistry developed over past decades has fueled the emergence of diverse one-dimensional nanocrystals and heterostructures, whereas the synthetic pursuit for compositionally and structurally defining them at the atomic-level precision remains yet a giant challenge. Catalyzed growth, wherein nanowires grow at the catalyst-nanowire interfaces in a layer-by-layer manner, offers a promising path toward such an ultimate goal. In this Perspective, we will take a close look at how catalyzed growth would enable the on-demand, atomic-precision control of colloidal nanowires and their heterostructures. We then further highlight their potentials for constructing higher-order heteroarchitectures with new and/or enhanced performances. Finally, we conclude with a forward-looking perspective on future challenges.

Molecular Dynamics Investigation on Thermal Stability and Shape Evolution of Pd-Au Heterostructured Nanorods: Implications for Catalysis

Heterogeneous nanostructures have attracted tremendous interest because of their exceptional properties and promising applications in extensive fields. In this work, we employed molecular dynamics (MD) simulations to investigate thermally driven structural and shape evolutions of Pd-Au heterostructured nanorods consisting of hexagonal close-packed (hcp) Pd-core/Au-shell structures in the middle and face-centered cubic (fcc) Au terminated at both ends (referred to as fcc-2H-fcc Pd@Au nanorods). Our results reveal that these nanorods exhibit a two-stage melting mode, that is, melting initiates at both ends of the nanorods and extends to the middle with increasing temperature. Moreover, specific thermodynamic behaviors are associated with the core size. With the lowering core size, the difference in the melting points between the core and the shell in the nanorods decreases accordingly, and the two-stage melting characteristic tends to be obscure. During heating, these nanorods experience a significant shrinkage after the melting of Au at both ends, forming a liquid-like shell/solid-core structure prior to the overall melting. However, two-stage melting is absent in fcc-2H-fcc Au nanorods. These results extend the fundamental understanding of the thermal stability of metallic heterostructured nanorods and provide a theoretical reference for the design and application of one-dimensional metallic heterostructures.

One-dimensional van der Waals heterostructures: Growth mechanism and handedness correlation revealed by nondestructive TEM

We recently synthesized one-dimensional (1D) van der Waals heterostructures in which different atomic layers (e.g., boron nitride or molybdenum disulfide) seamlessly wrap around a single-walled carbon nanotube (SWCNT) and form a coaxial, crystalized heteronanotube. The growth process of 1D heterostructure is unconventional-different crystals need to nucleate on a highly curved surface and extend nanotubes shell by shell-so understanding the formation mechanism is of fundamental research interest. In this work, we perform a follow-up and comprehensive study on the structural details and formation mechanism of chemical vapor deposition (CVD)-synthesized 1D heterostructures. Edge structures, nucleation sites, and crystal epitaxial relationships are clearly revealed using transmission electron microscopy (TEM). This is achieved by the direct synthesis of heteronanotubes on a CVD-compatible Si/SiO2 TEM grid, which enabled a transfer-free and nondestructive access to many intrinsic structural details. In particular, we have distinguished different-shaped boron nitride nanotube (BNNT) edges, which are confirmed by electron diffraction at the same location to be strictly associated with its own chiral angle and polarity. We also demonstrate the importance of surface cleanness and isolation for the formation of perfect 1D heterostructures. Furthermore, we elucidate the handedness correlation between the SWCNT template and BNNT crystals. This work not only provides an in-depth understanding of this 1D heterostructure material group but also, in a more general perspective, serves as an interesting investigation on crystal growth on highly curved (radius of a couple of nanometers) atomic substrates.