Nanoprism Arrays Research Articles

Versailles Santa Barbara-5 derived bifunctional one-dimensional electrocatalysts of hierarchical Ni3S2 nanoprism@nanosheets arrays for self-supporting and binder-free efficient supercapacitor and methanol oxidation reaction

We herein present a structure consisting of two-dimensional (2D) single-crystal Ni3S2 nanosheets designed on one-dimensional (1D) Ni3S2 nanoprism arrays (also known as Ni3S2 nanoprism@nanosheets). These arrays are directly synthesized over nickel foam, which is referred to as Ni3S2/NF. These structures can be used as binderless, self-supporting electrodes for bifunctional methanol oxidation reaction (MOR) applications and high energy density hybrid supercapacitors (HSC). Ni3S2/NF is synthesized through the two steps of hydrothermal processes. In step I, 1D hexagonal Versailles Santa Barbara-5 (VSB-5) nanorod arrays have been prepared onto the surface of NF (denoted as VSB-5/NF). The precursor for step II was 1D VSB-5 nanorod arrays, which were transformed into Ni3S2 using Na2S as a sulfur source via the Kirkendall effect. Electrochemical examination results show that as-synthesized Ni3S2/NF electrode exhibited a high specific capacitance (Cs) of 145.0 mA h g−1 at 5 A g−1, low series resistance (0.18 Ω) and charge-transfer resistance (0.05 Ω), small relaxation time constant (τ0 = 8 ms) and high frequency response at 125.8 Hz. Ni3S2/NF has a superior specific capacity of 145.0 mA h g−1 at 5 A g−1 as a SC electrode. The Ni3S2/NF//CNTs/NF HSC can be operated up to 1.6 V in a 3 M KOH electrolyte, delivering an impressive energy density of 256.35 W h kg−1 at a power density of 6400 W kg−1. The as-assembled Ni3S2/NF//CNTs/NF HSC device exhibited an impressive stability of 81 % even after undergoing 10,000 charge-discharge cycles. When compared to previously reported catalysts, Ni3S2/NF was proved to be an excellent electrocatalyst for MOR due to its ability to generate a current density of 215.0 mA cm−2 at 0.5 VSCE, while maintaining a superior and stable current density of 619.2 mA cm−2 at 0.8 VSCE.

Low-defect and stress-free AlN(0001) nanoprisms and microrods selectively grown on micro-patterned c-sapphire substrate by plasma-assisted molecular beam epitaxy

This paper describes different growth modes of AlN layers on micro-cone patterned c-sapphire substrates (μ-PSSs) using plasma-assisted molecular beam epitaxy. Ordered arrays of AlN nanoprisms and microrods were selectively grown on the tips of μ-PSS's microcones according to a bottom-up formation mechanism using sequential migration enhanced and metal-modulated epitaxy (MME) under metal-rich growth conditions at 820 °C. Transmission electron microscopy revealed structurally perfect AlN regions above the tips of the μ-PSSs, which initiate as inverted nanopyramids with {1011¯} side faces, evolving into hexagonal nanoprisms with orientations of {11¯00} and (0001) for side and top surfaces, respectively. The diameter and height of these ordered hexagonal nanoprisms, which have a 60% probability of nucleating, were about 1 μm. Long-term MME growth of these nanoprisms in both vertical and lateral directions led to the formation of AlN(0001) microrods with a maximum possible diameter of two micrometers and a height of up to 6 μm. Atomic force microscopy revealed a mixed step-flow and 2D nucleation growth mechanism for the flat tops of these AlN nanoprisms and microrods with an average surface roughness of 1–2 monolayers. Micro-Raman spectroscopy demonstrated narrow E2 (high) linewidths of 3.8 and 4.2 cm−1 for essentially stress-free AlN nanoprisms and microrods, respectively.

One-step surfactant-free photoreduction synthesis of single-crystal silver triangular nanoprisms by surface modified chemically patterned ferroelectric crystals for SERS application

Anisotropic metal nanoparticles with plasmonic and photocatalytic action exhibit significant applications for SERS detection and green transformation. Current synthetic approaches using multiple chemicals cause substantial resource consumption and surface chemical residues that hinder analyte adsorption and thus prevent efficient action. Herein, we present a green production process using surface modified ferroelectric templates to grow triangular Ag nanoprisms for surface enhanced Raman spectroscopy (SERS). Surface modification of ferroelectric templates with positively charged ions suppresses the Ag nucleation on template surface and enables the reaction-controlled process to promote anisotropic photoreduction for the growth of Ag nanoprisms. Under optimal experimental conditions, numerous Ag nanoprisms with the (111) plane can be photoreduced with sharp tips and edges and greatly strengthen the excited electric field for Raman signal enhancement. The synthesized Ag nanoprism array presents superior SERS performance, including enhancement factor of 3.78 × 108, limit of detection as low as 4.95 × 10-9 M, and Raman signal enhancement by 8.63 times. The practical application of Ag nanoprisms is effectively demonstrated by the SERS detection of antibiotics. The reaction control by utilization of surface-modified ferroelectric templates provides a promising prospect for the green synthesis of anisotropic metal nanomaterials and the technical development of green applications.

Zinc and fluorine ions dual-modulated NiCoP nanoprism array electrocatalysts for efficient water splitting

Designing efficient, stable, and low-cost bifunctional catalysts for overall water splitting is significant but challenging. In this work, Zn and F ions co-doped NiCoP nanoprism arrays grown directly on nickel foam (Zn/F-NiCoP/NF) was synthesized via hydrothermal method followed by phosphorization treatment. The resultant Zn/F-NiCoP/NF exhibits high electrocatalytic activity towards hydrogen evolution reaction (HER, η10 = 59 mV) and oxygen evolution reaction (OER, η50 = 285 mV). An alkaline electrolyzer using Zn/F-NiCoP/NF as both cathode and anode requires a low cell voltage of 1.568 V at a current density of 10 mA cm−2 with a high long-term stability of up to 40 h, which outperforms many reported Ni,Co-based catalysts. Density functional theory (DFT) calculations proof that simultaneous doping of NiCoP with Zn and F ions provides flexibility to regulate the electronic configuration and downshifts the transition metal d-band center, thereby optimizing adsorption energy between reactants and intermediates, which enhances the HER and OER catalytic activities. This work highlights that cation–anion co-doping strategy is an effective way to develop highly active transition metal phosphides electrocatalyst for water splitting.

Rapid and ultralow level SERS detection of ethylparaben using silver nanoprisms functionalized sea urchin-like Zinc oxide nanorod arrays for food safety analysis

Surface enhanced Raman spectroscopy (SERS) offers a tremendous opportunity to sense food additives in a fast, flexible and ultrasensitive mode. In the present study, we have designed silver nanoprism (AgNPr) functionalized Zinc Oxide (ZnO) hetero architectures for SERS sensing of food preservatives such as ethylparaben (EP). ZnO nanorods (NRs) were found to be formed which organized into sea urchin-like morphology via a facile hydrothermal process. While varying the growth time from 3 to 72 h, the nanorod length was found to be enhanced from 500 to 1900 nm range. The effect of morphology of as-fabricated substrates was well correlated with absorption and vibrational modes. Moreover, silver nanoprisms with peculiar triangular morphology with a size range of 20–80 nm were synthesized for functionalizing ZnO arrays; whose incorporation was further confirmed by EDS and XPS analysis. SERS studies demonstrated that AgNPr/ZnO NRs assembly exhibited synergistic Raman signal enhancement, which was modulated by the length of the nanorods. The highest SERS activity was exhibited by substrates with ∼1500 nm nanorod length. The reproducibility and reusability of optimized AgNPr/ZnO NRs substrates were demonstrated as well. The developed sensor exhibited highly specific real-time sensing of EP with sensitivity down to pico-molar levels; could be considered a good candidate for rapid, in situ identification of food preservatives for food safety applications. • Hierarchical zinc oxide-silver nanoprism arrays were designed as SERS sensors. • Morphological properties of sensor was well correlated with SERS performance. • Nanorod lengths of ∼1500 nm demonstrated highest signal enhancement. • Food additive like ethylparaben (EP) was detected down to pico-molar levels. • The optical sensing of EP was evidenced with high sensitivity and reusability.

A numerical study of plasmon-induced enhancement of dipole emission by arrays of silver nanospheres and nanoprisms

Plasmon-induced enhancement of the photoluminescence (PL) intensity of quantum emitters by plasmon nanoparticles (PNPs) is a promising approach for the design and fabrication of PL hybrid materials with improved properties for biosensing and optoelectronics applications. This enhancement can be achieved through careful selection of such parameters as the PNP’s shape, material, size, the type of the medium around them, as well as the excitation and emission wavelengths of the emitter. Here, we simulated the nano-hybrid materials based on arrays of silver nanospheres, nanoprisms, and their combinations, located on polymer films with embedded dipole emitters. For these systems, the Purcell effect, as well as the excitation enhancement, transmittance, and absorption were evaluated. The results show the way to improve the PL properties of thin hybrid films by careful design of their composition using developed models.

Nanoplasmonic Biosensing Approach for Endotoxin Detection in Pharmaceutical Field

The outer membrane of Gram-negative bacteria contains bacterial endotoxins known as Lipopolysaccharides (LPS). Owing to the strong immune responses induced in humans and animals, these large molecules have a strong toxic effect that can cause severe fever, hypotension, shock, and death. Endotoxins are often present in the environment and medical implants and represent undesirable contaminations of pharmaceutical preparations and medical devices. To overcome the limitations of the standard technique, novel methods for early and sensitive detection of LPS will be of crucial importance. In this work, an interesting approach for the sensitive detection of LPS has been realized by exploiting optical features of nanoplasmonic transducers supporting Localized Surface Plasmon Resonances (LSPRs). Ordered arrays of gold nano-prisms and nano-disks have been realized by nanospheres lithography. The realized transducers have been integrated into a simple and miniaturized lab-on-a-chip (LOC) platform and functionalized with specific antibodies as sensing elements for the detection of LPS. Interactions of specific antibodies anchored on protein A-modified sensor chips with the investigated analyte resulted in a spectral shift in the plasmonic resonance peak of the transducers. A good linear relationship between peak shifts and the LPS concentration has been demonstrated for the fabricated nano-structures with a detection limit down to 5 ng/mL. Integration with a proper microfluidic platform demonstrates the possibility of yielding a prototypal compact device to be used as an analytical test for quality determination of pharmaceutical products.

CoP nanoprism arrays: Pseudocapacitive behavior on the electrode-electrolyte interface and electrochemical application as an anode material for supercapacitors

The self-supported transition metal phosphide with specific morphology and architecture has been investigated extensively due to excellent conductivity, stability, and morphologic diversity. In the work, cobalt phosphide with special nanoprism arrays in-situ grown on the nickel foam skeleton forms a typical three-dimensional open structure. It exhibits notable electrochemical performance when employed as an anode in a single electrode system, which owns a high mass specific capacitance (1349 F g−1 at the current density of 1 A g−1, which is the highest compared with that in the extant literature), good rate capacity and cycle stability. Besides, pseudocapacitive contribution to the entire capacity is up to about 77%, revealing the nature of high mass specific capacitance of the as-prepared CoP@NF as the working electrode. Furthermore, an asymmetrical supercapacitor device has been fabricated using CoP@NF as an anode and CMK-3@NF as a cathode. It can deliver a high power density of 325 W kg−1 at the energy density of 24 Wh kg−1 and the specific capacitance retention of about 93% after 5000 cycles. The results demonstrate that CoP@NF with special nanoprism arrays is a promising potential candidate as the electrode material of supercapacitors and other energy-storing applications.

Low-crystalline FeOx@PPy hybridized with (Ni0.25Mn0.75)3O4@PPy to constructed high-voltage aqueous hybrid capacitor with 2.4 V

The operating voltage of aqueous hybrid capacitors are generally limited to 2 V due to the decomposition of water, which significantly impede the progress of energy density. Herein, the porous low-crystalline FeOx nanorod array on carbon cloth is prepared by the novel electrochemical Li+ pre-insertion method, and a 2.4 V high-voltage aqueous hybrid capacitor device is successfully obtained after matching with the nickel doped (Ni0.25Mn0.75)3O4@PPy nanoprisms array. The low-crystalline structure of FeOx preserved during the first Li+ insertion and space created via the elimination of low-crystalline Li2O dramatically provides sufficient electronic and ionic transfer channels. In addition, surface polypyrrole (PPy) stabilization is employed to further enhance electron conductivity and electrode stabilization. Benefitting from increasing active sites, fast ion diffusion and electron transfer the obtained low-crystalline FeOx@PPy electrode exhibits improved electrochemical performance, especially for capacitance and stability. Moreover, the aqueous hybrid capacitors (Ni0.25Mn0.75)3O4@PPy//FeOx@PPy device delivers a high energy density of 72.4 Wh kg−1 with the ultra-high voltage, and admirable cycling stability (94.7% retention after 4000 cycles). Our work highlights the novel electrochemical Li+ pre-insertion method to achieve superior low-crystalline electrodes materials and designs the high-voltage aqueous hybrid energy storage devices.

Plasmon-enhanced nonlinear nanofocusing of gold nanoprisms driven via an ultrafast azimuthal vector beam.

We present the plasmon-enhanced nonlinear nanofocusing of a gold (Au) nanoprism array substrate (ANAS) driven via an ultrafast azimuthal vector beam (AVB). Theoretical calculations show that the electric-field intensity of the ANAS vertically excited via the femtosecond AVB is higher than that of LPB excitation. In this experiment, the second-order surface nonlinear optical response of the ANAS is adopted to examine the nonlinear plasmonic nanofocusing of the ANAS, and it was observed that the second harmonic (SH) intensity of the ANAS excited via the femtosecond AVB is ∼3.8 times higher than that of LPB excitation, revealing that the ANAS under AVB excitation has a better nonlinear plasmonic nanofocusing characteristic than that under LPB excitation. Furthermore, the GaSe nanosheets are transferred on the ANAS to examine the nonlinear plasmonic nanofocusing of the ANAS. The SH intensity of the GaSe nanosheets deposited on the ANAS via the femtosecond AVB excitation has been enhanced ∼4.7 times than that of LPB excitation, indicating that the ANAS via AVB excitation has better nonlinear plasmonic nanofocusing than that of LPB excitation. This method may be used as a nonlinear nanofocusing light source to increase the light-matter nonlinear interaction.

Oxygen vacancies confined in nickel oxide nanoprism arrays for promoted electrocatalytic water splitting

Experimental and DFT calculation results show that the presence of oxygen vacancies can decrease the adsorption energy of intermediates at active sites and facilitate the adsorption of intermediates, thus improving the catalytic properties.

Broadband tunable nonlinear optical response in plasmonic metamaterials -INVITED

Nanostructured materials with tunable nonlinear optical response are of great interest for different applications in nanophotonics. In this work we report the results of a comprehensive study on the nonlinear optical properties of two kinds of plasmonic metamaterials, i.e., honeycomb nanoprism arrays and multilayer hyperbolic metamaterials, which proved to have a very rich spectrum of parameters (as metamaterials morphology and composition, wavelength and polarization of an input beam) to exploit for controlling their nonlinear response over a broad spectral range.

Azimuthal vector beam exciting silver triangular nanoprisms for increasing the performance of surface-enhanced Raman spectroscopy

Surface-enhanced Raman spectroscopy (SERS) with high-sensitivity performance is a very necessary detection technology. Here, we present a method for increasing the performance of SERS based on silver triangular nanoprism arrays (ATNAs) vertically excited via a focused azimuthal vector beam (AVB). The ATNA substrates with different structural parameters are prepared based on the traditional self-assembled and modified film lift-off technique. Based on a theoretical model established adopting the structural parameters of the ATNA substrates, theoretical simulation results show that AVB excitation can achieve greater electric-field enhancement than linearly polarized beam (LPB) excitation. Experimental result indicates that SERS sensitivity obtained via AVB excitation is 10−13 M (1 M = 1 mol/L) using rhodamine 6G (R6G) as the target analyte, which is 2 orders of magnitude lower than that of LPB excitation (10−11 M). Meanwhile, the uniformity and reproducibility of the ATNA substrates are examined using Raman mapping and batch-to-batch measurement, respectively, and the Raman enhancement factor is calculated to be ∼3.3×107. This method of vector light field excitation may be used to improve the SERS performance of the substrates in fields of ultra-sensitive Raman detection.

Plasmon-enhanced exciton emissions and Raman scattering of CVD-grown monolayer WS2 on Ag nanoprism arrays

Monolayer transition metal dichalcogenides (TMDs) usually have weak optical emission due to the poor light absorption as being atomically thin. Enhancing their optical properties by surface plasmon resonance is attractive for applying atomically thin TMDs in optoelectronic and photonic devices. Here, Ag/WS2 hybrid structure was fabricated by transferring monolayer WS2 grown via chemical vapor deposition (CVD) onto optimized periodic Ag nanoprism array with well-matched resonance by controlling the mask geometry and etching time of polystyrene (PS) nanospheres. Significant enhanced photoluminescence (PL) emission and Raman scattering were successfully achieved. Especially, the higher enhancement is realized for neutral excitons of monolayer WS2. Theoretical calculations reveal that the plasmonic enhancement mainly results from the highly enhanced local electric field and the charge transfer. This work explores the feasibility of exciton emission and Raman scattering enhancement for TMDs with plasmonic nanostructures fabricated by low-cost and easily-manipulated nanosphere lithography (NSL), which paves a way towards the applications of plasmon-enhanced TMD sensors, emitters, and photodetectors.

Polarization dependence of second harmonic generation from plasmonic nanoprism arrays

The second order nonlinear optical response of gold nanoprisms arrays is investigated by means of second harmonic generation (SHG) experiments and simulations. The polarization dependence of the nonlinear response exhibits a 6-fold symmetry, attributed to the local field enhancement through the excitation of the surface plasmon resonances in bow-tie nanoantennas forming the arrays. Experiments show that for polarization of the input light producing excitation of the plasmonic resonances in the bow-tie nanoantennas, the SHG signal is enhanced; this despite the fact that the linear absorption spectrum is not dependent on polarization. The results are confirmed by electrodynamic simulations which demonstrate that SHG is also determined by the local field distribution in the nanoarrays. Moreover, the maximum of SHG intensity is observed at slightly off-resonance excitation, as implemented in the experiments, showing a close relation between the polarization dependence and the structure of the material, additionally revealing the importance of the presence of non-normal electric field components as under focused beam and oblique illumination.

Resonant light absorption and plasmon tunability of lateral triangular Au nanoprisms array

Optical characteristics and electric field distribution of triangular Au nanoprism in a unit and units array under polarized light irradiation were systematically studied by numerical simulation with finite difference time domain method. It is found that the plasmonic properties of the triangular nanoprism are dominated by the electric polarization rather than the wave propagation. The triangular nanoprism presents similar optical response with a strong dipole band under different wave propagations if the electric polarization vectors are parallel to the triangular cross section. The lateral triangular Au nanoprisms array possesses a large tunability of the plasmonic properties contributed from the combined influence of inter-particle distance, particles size, polarization angle and even environmental medium. From the plasmon band shift versus the refractive index, ultra-high local surface plasmon resonance sensitivity (509.96 nm/RIU, figure of merit=5.55) is reached at ∼850nm, making this array promising for biochemical sensing applications.

High rate-performance supercapacitor based on nitrogen-doped hollow hexagonal carbon nanoprism arrays with ultrathin wall thickness in situ fabricated on carbon cloth

Free-standing carbon materials are promising supercapacitor electrode materials due to their outstanding properties, such as simple assemble process, high rate performance and good stability etc. We present here the fabrication of novel nitrogen-doped hollow hexagonal carbon nanoprism arrays on carbon fiber cloth for supercapacitor via chemical vapor deposition with ZnO as the sacrifice template. The hexagonal nanoprism structure of ZnO template can be well duplicated by ultrathin nitrogen-doped carbon layer through an in situ carbon deposition process. In this method, the template-removing step is not necessary attributed to the carbothermal reduction reaction between ZnO and carbon during the chemical vapor deposition process. The carbon fibers serve as highways for rapid electron transfer. Meanwhile, the in situ growth of nanoprism arrays on carbon fiber results in intact interface and low interface resistance. The open channel structure of the carbon arrays can shorten the ions diffusion path and facilitate the fast electrolyte transport. All these structural advantages contribute to the excellent rate performance of the fabricated carbon composite with scan rate and current density reaching up to 20 V s−1 and 300 mA cm−2, respectively. The present work paves a new way for designing high-rate and highly stable carbon electrode materials for supercapacitors.

Tuning the linear and nonlinear optical properties of ordered plasmonic nanoarrays by morphological control with thermal annealing

The capability to tune the linear and nonlinear optical response of plasmonic nanoarrays is of great interest for the realization of solid-state plasmonic nanodevices with application in many different fields in nanophotonics. In the present work we demonstrated the possibility to tailor, in a controlled way, the morphological properties of gold nanoprism arrays fabricated by nanosphere lithography, by performing thermal annealing treatments in air, preserving their bidimensional ordered arrangement. This allows to engineer the linear optical properties of the samples, finely tuning the spectral position and amplitude of their surface plasmon resonance peak. Moreover, we demonstrated that the fine control of the nanostructures' morphology provides a way to get the continuous modulation of the nonlinear optical parameters (nonlinear refractive index and nonlinear absorption coefficient) of the nanoarray. The experimental findings have been supported by finite elements method electrodynamic simulations, which provided a very good agreement.

Buffer-layer-assisted morphological manipulation of metal nanoparticle arrays by laser irradiation

We evaluate the performance of an adhesion buffer layer between ordered metal nanoparticle arrays and dielectric substrates on the particles' morphological manipulation by pulsed laser irradiation. The experiments are performed irradiating with only one nanosecond pulse at 355 nm, triangular nanoprism arrays fabricated by nanosphere lithography (polystyrene spheres with 1030 nm in diameter), followed by film deposition by magnetron sputtering. The reshaping of the nanoprisms into spheres as result of laser-induced melting is investigated for three different materials: prisms made of Cr, Au and Au with a buffer layer made of Cr (Au/Cr). These elements are chosen because their interfacial interaction with the substrates (soda-lime glass and fused silica) is quite different. Our results show that single pulse irradiation at fluences above the metal melting threshold allows the formation of disorder spheres for the case of Au, but ordered spheres for the cases of Cr and Cr/Au. Therefore, the function of the buffer layer is to improve the adhesion between the prisms and the substrate, thus allowing their reshaping by laser-induced melting but preserving their position. The strong interaction between Cr and the substrate is also exploited for the nanostructuration of the substrate by the formation of ordered holes with sub-micrometer dimensions. These findings reboot laser postprocessing of ordered structures fabricated by nanosphere lithography exploit to explore new capacities of nanostructuration.

Polarization-Controllable Plasmonic Enhancement on the Optical Response of Two-Dimensional GaSe Layers.

Resonant plasmonic coupling has been considered as a promising strategy to enhance the optical response and manipulate the polarization of two-dimensional (2D) layer materials toward the practical applications. Here, a hybrid structure with periodic Ag nanoprism arrays was designed and fabricated on 2D GaSe layers to enhance these optical properties. By using the optimized hybrid structure with well-matched resonance, significant enhanced Raman scattering and band edge emission were successfully realized, and it is also interestingly found that the higher enhancement would be achieved while decreasing the thickness of GaSe layers. Theoretical simulation indicated that the strongly enhanced local field and the modified charge densities are the main reasons. By further introducing the patterned gratings on the plasmonic hybrid structure, selective excitation with controllable polarization was readily realized, besides the strongly enhanced photoluminescence intensity. This work provides a strategy for the plasmonic engineering of polarization controllable 2D optoelectronic devices.