Configurations Of Nanostructures Research Articles

One-Step Dry-Etching Fabrication of Tunable Two-Hierarchical Nanostructures

Two-hierarchical nanostructures, characterized by two distinct configurations along the height direction, exhibit immense potential for applications in various fields due to their significantly enhanced controllable degree compared to single-order structures. However, due to the limitations imposed by planar technology, the realization of two-hierarchical nanostructures encounters huge challenges. In this work, we developed a one-step etching method based on inductively coupled plasma reactive ion etching for two-hierarchical nanostructures. Thanks to the shrinking effect of the Cr mask and the generation of a passivation layer during etching, the target materials experienced two different states from vertical etching to shrink etching. Consequently, the achieved two-hierarchical nanostructure configuration features a cross-section of an upper triangle and a lower rectangle, showing higher controllable degrees compared to the one-order ones. Both the mask pattern and etching parameters play crucial roles, by which two-hierarchical structures with diversiform shapes can be constructed controllably. This method for two-hierarchical nanostructures offers advantages including excellent control over structural properties, high processing efficiency, uniformity across large areas, and universality in materials. This developed strategy not only presents a simple and rapid nanofabrication platform for realizing optoelectronic devices, but also provides innovative ideas for designing the next generation of high-performance devices.

Comparative study of CO adsorption on Au, Cu, MoO2 and MoS2 2D Nanoparticles

This study focuses on a comparative analysis of the electronic properties of triangular, irregular hexagonal, and octagonal 2D nanoparticles containing 10, 12, and 14 motifs, made of Au, Cu, MoO2, and MoS2. The investigation was carried out using density functional theory. The formation energies and vibrational frequencies demonstrate that the 2D nanostructure configurations can exist as stable structures. Edge atoms with lower coordination numbers than central atoms, are the preferred sites for CO adsorption. Using orbital-weighting dual descriptors calculated from Fukui functions enabled the identification of a majority nucleophilic attack sites in Au and Cu nanoparticles, while MoO2 and MoS2-based nanoparticles present almost as many electrophilic sites as nucleophilic sites. The charge transferred between the nanostructures and the CO molecule and the redistribution of the projected density of states were used to assess the strength of interfacial bonds and the nature of the fundamental interaction involved in the bonding.

High-Power Impulse Magnetron Sputter Deposition of Ag on Self-Assembled Au Nanoparticle Arrays at Low-Temperature Dewetting Conditions.

Plasmons have facilitated diverse analytical applications due to the boosting signal detectability by hot spots. In practical applications, it is crucial to fabricate straightforward, large-scale, and reproducible plasmonic substrates. Dewetting treatment, via applying direct thermal annealing of metal films, has been used as a straightforward method in the fabrication of such plasmonic nanostructures. However, tailoring the evolution of the dewetting process of metal films poses considerable experimental complexities, mainly due to nanoscale structure formation. Here, we use grazing-incidence small- and wide-angle X-ray scattering for the in situ investigation of the high-power impulse magnetron sputter deposition of Ag on self-assembled Au nanoparticle arrays at low-temperature dewetting conditions. This approach allows us to examine both the direct formation of binary Au/Ag nanostructure and the consequential impact of the dewetting process on the spatial arrangement of the bimetallic nanoparticles. It is observed that the dewetting at 100 °C is sufficient to favor the establishment of a homogenized structural configuration of bimetallic nanostructures, which is beneficial for localized surface plasmon resonances (LSPRs). The fabricated metal nanostructures show potential application for the surface-enhanced Raman scattering (SERS) detection of rhodamine 6G molecules. As SERS platform, bimetallic nanostructures formed with dewetting conditions turn out to be superior to those without dewetting conditions. The method in this work is envisioned as a facile strategy for the fabrication of plasmonic nanostructures.

Bead-Containing Superhydrophobic Nanofiber Membrane for Membrane Distillation.

This study introduces an innovative approach to enhancing membrane distillation (MD) performance by developing bead-containing superhydrophobic sulfonated polyethersulfone (SPES) nanofibers with S-MWCNTs. By leveraging SPES's inherent hydrophobicity and thermal stability, combined with a nanostructured fibrous configuration, we engineered beads designed to optimize the MD process for water purification applications. Here, oxidized hydrophobic S-MWCNTs were dispersed in a SPES solution at concentrations of 0.5% and 1.0% by weight. These bead membranes are fabricated using a novel electrospinning technique, followed by a post-treatment with the hydrophobic polyfluorinated grafting agent to augment nanofiber membrane surface properties, thereby achieving superhydrophobicity with a water contact angle (WCA) of 145 ± 2° and a higher surface roughness of 512 nm. The enhanced membrane demonstrated a water flux of 87.3 Lm-2 h-1 and achieved nearly 99% salt rejection efficiency at room temperature, using a 3 wt% sodium chloride (NaCl) solution as the feed. The results highlight the potential of superhydrophobic SPES nanofiber beads in revolutionizing MD technology, offering a scalable, efficient, and robust membrane for salt rejection.

Manipulation of Goos–Hänchen shift via hybrid chiral quantum dots system

We present a flexible manipulation and enhancement of the Goos–Hänchen (GH) shifts via surface plasmon polaritons (SPPs) in a hybrid nanostructure configuration composed of metal (Au) and a chiral quantum dots (CQDs) medium. The proposed configuration consists of a hybrid nanostructure where CQDs and metal are organized, leading to the generation of SPPs when exposed to incident light. The interaction between the SPPs and the incident light leads to a significant enhancement in the GH shift of the left-circularly polarized (LCP) and right-circularly polarized (RCP) lights. It is observed that the RCP light induces numerous SPPs at the interface of the metal and CQDs nanostructure, thereby causing a larger GH shift. In contrast, the LCP light does not induce numerous SPPs at the interface of the metal and CQDs nanostructure, leading to a smaller GH shift. It is also studied that the GH shift can be tuned and enhanced by varying the intensity of the control field and electron tunneling strength in the hybrid system. The results have potential applications in the fields of sensing, imaging, nanotechnology, and quantum technology.

Performance improvement of an ultra-thin film CIGS tandem solar cell using new plasmonic cluster nanostructures

This work demonstrates an innovative plasmonic nanostructure configuration to enhance the performance of an ultra-thin film CIGS-based tandem solar cell. Silver nanoparticle clusters with optimized cubic and spherical shapes are incorporated into the bottom CIGS layer to create a light-trapping effect. The optimal nanoparticle dimensions and positioning are determined through analysis of optical and electrical parameters. The plasmonic nanostructures achieve a short-circuit current density of 20.24 mA/cm2 and a power conversion efficiency of 22.9 % - a 12.6 % enhancement over the non-plasmonic case. This improvement is attributed to the near-field enhancement from localized surface plasmon resonance, which significantly boosts the absorption in the critical long-wavelength region. The strategic use of plasmonic nanostructures proves effective in overcoming the light absorption limitations of ultra-thin CIGS tandem solar cells.

Superluminal propagation of surface plasmon polaritons via hybrid chiral quantum dots system

We present a novel methodology for enhancing superluminal surface plasmon polaritons (SPPs) propagations within a hybrid nanostructure configuration consisting of gold (Au) metal and chiral quantum dots (CQDs) medium. The arrangement of CQDs and metal hybrid nanostructures enables the production of SPPs when exposed to incident light. The resonances of SPPs within a hybrid nanostructure are determined through analytical calculations using Maxwell’s equations under specified boundary conditions, while the dynamics of the CQDs system are calculated using the density matrix approach. It is demonstrated that the propagation of SPPs is significantly influenced by both right-circularly polarized (RCP) and left-circularly polarized (LCP) SPPs. Additionally, we investigate the enhancement of superluminal SPPs propagation by varying the electron tunneling strength and the intensity of the control field within the hybrid system. The characteristics of RCP and LCP SPPs have been investigated, indicating a large negative group index and advancement in time. The observation of a large negative group index and advancement in time provides strong evidence for enhanced superluminal SPPs propagation within the proposed hybrid nanostructure. The results have potential applications in the fields of optical information processing, temporal cloaking, quantum communication, and the advancement of computer chip speed.

Impact of aluminum concentration and grading configuration of AlxGa1-xAs nanostructures for solar absorber applications

Impact of aluminum concentration and grading configuration of AlxGa1-xAs nanostructures for solar absorber applications

Growth of thin-film magnetic nanostructures promising for spintronics applications

Multilayered metallic nanostructures are promising for the fabrication of spin valves based on the giant magnetoresistive effect and for studies of the nature of topological magnetism, aimed at the development of new nanoscale data storage and transfer devices, e.g. those based on magnetic skyrmions. It is still an important task to develop methods of synthesis and configuration of thin-film nanostructures and control of spin textures in those nanostructures under electric and spin currents generated as a result of the spin Hall effect in external electric fields. Thin-film polycrystalline ferromagnetic / heavy metal Ru(10nm)/Co(0,8)/Ru(2), Ru(10)/Co(0,8)/Ru(2)/W(4), Pt(5)/Co(0,8)/MgO(2)/Pt(2) and Pt(15)/Co(0,8)/MgO(2)/Pt(2) nanostructures have been synthesized using magnetron sputtering. Electric contacts and Hall structures with different conductive bridge thicknesses have been synthesized on the specimens using electron beam photolithography. Experimental vibration magnetometric data have been utilized to calculate magnetic parameters of the specimens, i.e., saturation magnetization, magnetic anisotropy energy and field and coercive force as functions of ferromagnetic and heavy metal layer types. The domain structure of the specimens has been studied using Kerr microscopy. The electrical resistivity has been simulated and the critical current and current density of the nanostructures have been assessed. We show that all the film specimens exhibit perpendicular magnetic anisotropy and can be used in the studies of current-induced phenomena and spin moment transfer processes in nanostructures.

Ni/Mn electroactive nanohybrids physic-chemical properties for ulterior new generation of supercapacitors

In this paper, highly mesoporous hierarchical mono- and bi- Ni and/or Mn based hydroxide and/or carbonate nanohybrids were synthesized using a facile free template hydrothermal method and investigated as high-performance electroactive nanomaterials for ulterior new generation of supercapacitors. Controlling the Ni/Mn precursors molar ratio and the growth conditions can offer preponderances for performances enhancing via a comparative products physic-chemical properties which were carried out using different techniques like: XRD, FTIR, Raman, XPS, HRTEM/FESEM, EDS, UV–visible and BET. The structural results confirmed the formation of MnCO3, α-3Ni(OH)2·2H2O and Ni(HCO3)2 phases in the synthesized nanomaterials, with different morphologies (nanofibers, nanocubes, porous micro/nanoflowers) depending on the hydrothermal synthesis conditions. Meanwhile, the influence of Ni and Mn transition metal species co-existence on the resulting composition and their optical properties were also discussed. Moreover, their electrochemical measurements were also performed in a 6 M KOH aqueous electrolyte using three electrode system. The results show that 2Ni(HCO3)2/MnCO3 nanohybrid exhibited the highest specific capacitance (capacity) of 2777 F g−1 at 5 mV s−1 (320 mAh.g−1 at 1 A g−1) with high rate capability. This excellent electrochemical kinetics performance is ascribed to the optimized composition of Ni/Mn and its unique nanostructured configuration with intercalated ions, indicating a great potential of this new kind of nanohybrids to deliver both high energy density and high power density in future energy storage devices.

Intercalation chemistry engineering strategy enabled high mass loading and ultrastable electrodes for High-Performance aqueous electrochemical energy storage devices

Aqueous electrochemical energy storage devices (AEESDs) are considered one of the most promising candidates for large-scale energy storage infrastructure due to their high affordability and safety. Developing electrodes with the merits of high energy density and long lifespan remains a challenging issue toward the practical application of AEESDs. Research attempts at electrode materials, nanostructure configuration, and electronic engineering show the limitations due to the inherent contradictions associated with thicker electrodes and ion-accessible kinetics. Herein, we propose an intercalation chemistry engineering strategy to enhance the electrolyte ion (de)intercalation behaviors during the electrochemical charge–discharge. To validate this strategy, the prototypical model of a high-mass-loading MnO2-based electrode is used with controlled intercalation of Na+ and H2O. Theoretical and experimental results reveal that an optimal content of Na+ and H2O on the MnO2-based electrode exhibits superior electrochemical performance. Typically, the resultant electrode exhibits an impressive areal capacitance of 1551 mF/cm2 with a mass loading of 9.7 mg/cm2 (at 1 mA/cm2). Furthermore, the assembled full-cell with obtained MnO2-based electrode delivers a high energy density of 0.12 mWh/cm2 (at 20.02 mW/cm2) and ultra-high cycling stability with a capacitance retention percentage of 89.63 % (345 mF/cm2) even after 100,000 cycles (tested over 72 days).

Ballistic electrolyte ion transport with undisturbed pathways for ultrahigh-rate electrochemical energy storage devices

By controlling the central metal cores of c-MOFs, we obtained a perfect AA-stacking configuration, in which ballistic electrolyte ion transport is theoretically and experimentally demonstrated during the electrochemical charge–discharge process.

An elliptical nanoantenna array plasmonic metasurface for efficient solar energy harvesting.

Plasmonic metasurfaces with subwavelength nanoantenna arrays have attracted much attention for their ability to control and manage optical properties. Solar absorbers are potential candidates for effectively converting photons into heat and electricity. This study introduces a novel ultrathin metasurface solar absorber employing elliptical-shaped nanoantenna arrays. We theoretically and numerically demonstrate a near-perfect broadband absorber with over 90% absorption efficiency in a wide range of wavelengths of 300-2500 nm, using finite element (FEM) and finite-difference time-domain (FDTD) methods. The proposed nanostructure configuration enhances light absorption by exciting localized surface plasmon resonances (LSPRs) between elliptical-shaped nanoantenna gaps at many wavelengths, maintaining stability at wide incident angles and insensitivity to light polarization. Compared to other state-of-the-art absorbers with a thickness of less than 300 nm, the designed nanostructure with 260 nm thickness achieves over 90% optical absorption across a broad range of wavelengths of 300-1116 nm in air (or vacuum) environments and performs effectively under water conditions for solar energy harvesting in a range of wavelengths of 300-1436 nm, and therefore can serve as a solar evaporator. Combining refractory plasmonic titanium nitride (TiN) and semiconductor gallium nitride (GaN) nanostructures holds great potential for efficient optoelectronic and photocatalytic applications, especially in harsh and high-temperature environments like thermophotovoltaic systems. The TiN-based metasurface absorber, with its ultrathin nanostructure and suitable spectral absorption in ultraviolet-visible-infrared spectra, offers scalability and cost-effectiveness. The findings in this work will deepen our understanding of LSPRs and pave a novel path for efficient solar energy conversion.

Size-dependent viscoelasticity in hybrid colloidal gels based on spherical soft nanoparticles and two-dimensional nanosilicates of varying size

HypothesisHetero-aggregation of oppositely charged colloidal particles with controlled architectural and interactional asymmetry allows modifying gel nanostructure and properties. We hypothesize the relative size ratio between cationic nanospheres and varied-size anionic two-dimensional nanoclays will influence the gel formation mechanisms and resulting rheological performance. ExperimentsHybrid colloidal gels formed via hetero-aggregation of cationic gelatin nanospheres (∼400 nm diameter) and five types of nanoclays with similar 1 nm thickness but different lateral sizes ranging from ∼ 30 nm to ∼ 3000 nm. Structure-property relationships were elucidated using a suite of techniques. Microscopy and scattering probed gel nanostructure and particle configuration. Rheology quantified linear and non-linear viscoelastic properties and yielding behavior. Birefringence and polarized imaging assessed size-dependent nanoclay alignment during shear flow. FindingsNanoclay size ratio relative to nanospheres affected the gelation process, network structure, elasticity, yielding, and shear response. Gels with comparably sized components showed maximum elasticity, while yield stress depended on nanoclay rotational mobility. Shear-induced nanoclay alignment was quantified by birefringence, which is more pronounced for larger nanoclay. Varying nanoclay size and interactions with nanospheres controlled dispersion, aggregation, and nematic ordering. These findings indicate that architectural and interactional asymmetry enables more control over gel properties through controlled assembly of anisotropic building blocks.

Electronic transport computation in thermoelectric materials: from ab initio scattering rates to nanostructures

Over the last two decades a plethora of new thermoelectric materials, their alloys, and their nanostructures were synfthesized. The ZT figure of merit, which quantifies the thermoelectric efficiency of these materials increased from values of unity to values consistently beyond two across material families. At the same time, the ability to identify and optimize such materials, has stressed the need for advanced numerical tools for computing electronic transport in materials with arbitrary bandstructure complexity, multiple scattering mechanisms, and a large degree of nanostructuring. Many computational methods have been developed, the majority of which utilize the Boltzmann transport equation (BTE) formalism, spanning from fully ab initio to empirical treatment, with varying degree of computational expense and accuracy. In this paper we describe a suitable computational process that we have recently developed specifically for thermoelectric materials. The method consists of three independent software packages that we have developed and: (1) begins from ab initio calculation of the electron–phonon scattering rates, (2) to then be used within a Boltzmann transport simulator, and (3) calculated quantities from the BTE are then passed on to a Monte Carlo simulator to examine electronic transport in highly nanostructured material configurations. The method we describe is computationally significantly advantageous compared to current fully ab initio and existing Monte Carlo methods, but with a similar degree of accuracy, thus making it truly enabling in understanding and assessing thermoelectric transport in complex band, nanostructured materials.

Advances in Metaphotonics Empowered Single Photon Emission

AbstractSpontaneous photon emission can be drastically modified by placing quantum emitters (QEs) in nanostructured environment, resulting in dramatically enhanced emission rates due to the Purcell effect along with generation of collimated single‐photon beams propagating in design directions and featuring well‐defined polarization states. Recent advances in single‐photon generation engineering demonstrate fascinating possibilities for the directional emission of photons with designed spin and orbital angular momenta, a development that is crucial for exploiting the full potential of QEs within quantum information technologies. Although many different nanostructured configurations are considered for hosting QEs to mold single‐photon beams, collimating of the latter requires relatively large interaction areas to be involved, thus making the use of metasurfaces preferential. Furthermore, optical metasurfaces consisting of planar arrays of resonant nanoscale elements offer complete control over optical fields and thereby design freedom in shaping single‐photon emission. Here, recent advances in exploiting quantum optical metasurfaces for achieving enhanced and directional emission of single photons with specified polarization properties are overviewed. Special attention is paid to hybrid plasmon–QE coupled metasurfaces based on efficient QE coupling to surface plasmon modes that are subsequently outcoupled by designed dielectric nanoarrays into free propagating photon emission. Perspectives for future developments of metasurface empowered QEs are also discussed.

Computationally efficient Monte Carlo electron transport algorithm for nanostructured thermoelectric material configurations

Monte Carlo statistical ray-tracing methods are commonly employed to simulate carrier transport in nanostructured materials. In the case of a large degree of nanostructuring and under linear response (small driving fields), these simulations tend to be computationally overly expensive due to the difficulty in gathering the required flux statistics. Here, we present a novel Monte Carlo ray-tracing algorithm with computational efficiency of at least an order of magnitude compared to existing algorithms. Our new method, which is a hybrid of the analytical Boltzmann transport equation and Monte Carlo used a reduced number of ray-tracing particles, avoids current statistical challenges, such as the subtraction of two opposite going fluxes, the application of a driving force altogether, and the large simulation time required for low-energy carriers. We demonstrate the algorithm’s efficiency and power in accurate simulations in large domain nanostructures with multiple defects. We believe that the new method we present is indeed more robust and user friendly compared to common methods and can enable the efficient study of transport in nanostructured materials under low-field steady-state conditions.

Efficient fabrication of flower-like core-shell nanochip arrays of lanthanum manganate and nickel cobaltate for high-performance supercapacitors.

The low energy density issue raises serious concerns for the large-scale application of supercapacitors. However, the development and utilization of new electrode materials with a high specific capacity to improve the energy density of supercapacitors remain challenging. Herein, an LaMnO3@NiCo2O4/carbon cloth (LMO@NCO/CC) composed of a multilayer flower-like nanochip array is prepared for the first time using an efficient electrodeposition method. This novel structure exploits the high conductivity of LaMnO3/carbon cloth (LMO@CC) to provide an efficient electron transport path for the outer layer of the NiCo2O4/carbon cloth (NCO@CC) nanoarrays, broadening the potential window. Due to the unique nanostructure configuration and the strong synergistic effect of the developed LMO@NCO/CC, the prepared electrodes show excellent supercapacitor performance. At a current density of 1 A g-1, LMO@NCO/CC has a higher specific capacitance value of 942 F g-1. The application value is extended through the fabrication of asymmetric supercapacitors with a maximum energy density of 49 Wh kg-1 and excellent cycle stability (the initial capacitance value remains 106% after 10,000 cycles of charging and discharging at a high current density of 10 A g-1). Our work paves the way for the development of next-generation electrode materials for high-performance supercapacitors.

Low-frequency vibration induced piezoelectric boost to photocatalytic hydrogen evolution through 2D-2D-stacked MoS2-carbon nitride

MoS2-carbon nitride heterostructures which are highly sensitive to low-frequency vibration are demonstrated to be the catalysts for piezo-photocatalytic hydrogen evolution reaction (HER). The configuration of MoS2 nanostructure on carbon nitride plays a crucial role in the piezo-photocatalytic HER activity of MoS2-carbon nitride heterostructure. With the cocatalyst of Pt NPs on the carbon nitride portion, 2D-2D stacked MoS2-carbon nitride catalyst exhibits considerably higher HER rate compared to the pristine carbon nitride and MoS2 nanoflower (NF)-carbon nitride catalysts under illumination coupling with the mechanical energy of vortex-induced shearing force. Experimental and calculation results indicate that the MoS2 nanosheets mainly perform as the piezopotential generator to induce an electric field in the carbon nitride counterpart. With the configuration of 2D-2D stacking, the light harvesting of carbon nitride in the heterostructure remains the same as the pristine one. Nevertheless, the recombination of photogenerated electron-hole pairs in the carbon nitride portion of the MoS2-carbon nitride heterostructure is inhibited due to the electric field induced by MoS2 nanosheet under low-frequency vortex vibration, resulting in the significantly boosted HER rate obtained from the 2D-2D stacked MoS2-carbon nitride heterostructure.

Self-growing nano-liquid-crystal film from dynamic swollen hydrogel substrates.

A hydrogel which spontaneously swells in an aqueous polymer solution was observed to produce a new hydrogel film coated on its swollen surface. Here, inspired by this phenomenon, we theoretically formulate the dynamics of isotropic-to-nematic (I-N) phase transition caused by swelling a hydrogel substrate (HS) in a dilute nanoplatelet suspension, and quantitatively characterize a self-growing nano-liquid-crystal (NLC) film coated on the swollen HS surface. We show that as the HS gets softer, the resulting NLC film can form earlier and achieve greater thickness (up to hundreds of micrometers). Our results and the existing experiments confirm that the growth dynamics of the NLC film or hydrogel film is exclusively regulated by the swelling behaviors of the HS instead of suspension configurations, e.g., I-N phase transition or sol-gel transition, suggesting a universal signature for the solutes ranging from molecules to colloids. However, both the maximum thickness of the NLC film and the corresponding characteristic time rely highly on the inherent elasticity of the HS and nanoplatelet aspect ratio. We demonstrate that the swelling quasiequilibrium state rather than the equilibrium state of the HS is more qualified to formulate a condition which is practically significant in preestimating the moment when the maximum thickness of the NLC film appears. Our theoretical framework serves as a robust paradigm to extensively rationalize (bio)film coatings which self-integrate with diverse nanostructural configurations via swelling-induced phase transition.