Oxide Template Research Articles

Versatile photocatalytic activities of indenoquinoxalines for dye reduction, single-crystal nucleation, and MNP formation with iron scrap under sunlight.

In this work, 11H-indeno[1,2-b]quinoxalin-11-one (IQ), 7-nitro-11H-indeno[1,2-b]quinoxalin-11-one (NIQ), and 7-chloro-11H-indeno[1,2-b]quinoxalin-11-one (CIQ) as indenoquinoxalines (IQPs) and 7-nitro-2'-(4-nitrophenyl)-5',6',7',7a'-tetrahydrospiro[indeno[1,2-b]quinoxaline-11,3'-pyrrolizine]-1',1'(2'H)-dicarbonitrile (SIQPNO2) spiroheterocyclics were synthesized. These molecules photocatalytically reduced methylene blue (MB), methyl orange (MO), brilliant blue R (BBR), and Rhodamine B (RhB) in aqueous acetonitrile (aq-ACN) under sunlight (SL) for the first time. The IQPs and SIQPNO2 with a lanthanide graphene oxide template (LGT) of lanthanide sulfide nanorods (Ln2S3, Ce2S3, Tb2S3, and Ho2S3) photocatalytically reduced the dyes. IQ alone reduced MB in ∼2 min, while with LaGT, CeGT, TbGT, and HoGT in 7, 10, 11, and 13 min, respectively. NIQ and CIQ alone photocatalytically reduced MB in 18 and 32 min, while with LaGT, CeGT, TbGT, and HoGT in 18, 31, 23, and 28 min and 33, 55, 45, and 51 min, respectively. IQ with CO2 photocatalytically reduced MB and QHIn in 90 s and 17 min unlike 2 and 24 min without CO2, respectively. SIQPNO2 alone reduced MB in 190 min, while with CeGT, TbGT, HoGT, and LaGT in 242, 225, 197, and 88 min, respectively. IQ with LaGT photocatalytically reduced MB in 7 min, while SIQPNO2 with LaGT in 88 min. IQ received maximum photon (hv) producing robust redox cycles (ROCs) compared to SIQPNO2. SIQPI, SIQPII, SIQPIII, and SIQPNO2 (SIQPs) individually reduced MB in 95, 43, 54, and 190 min, while SIQPs with NIQ in 63, 35, 47, and 64 min, respectively. IQ with Fe scrap in ACN developed a single crystal in 2 weeks, while in 2 : 8, 3 : 7, 5 : 5, 7 : 3, and 8 : 2 aq-ACN media, the magnetic nanoparticles (MNPs) developed at normal temperature and pressure (NTP).

Hybrid Particle Size Template Method for Controllable Synthesis of Nitrogen-Doped Multilevel Porous Carbon as High-Rate Zn-Ion Hybrid Supercapacitor Cathode Materials.

Achieving high rate performance without compromising energy density has always been a critical objective for zinc-ion hybrid supercapacitors (ZHSCs). The pore structure and surface properties of carbon cathode materials play a crucial role. We propose utilizing a hybrid particle size (20 and 40 nm) magnesium oxide templates to regulate the pore structure of nitrogen-doped porous carbon derived from the soybean isolate. The multilevel pore structure enhanced ion transport efficiency while also improving the utilization of micropores. Nitrogen doping and oxygen-containing functional groups enhanced the wettability of carbon materials with aqueous electrolytes and facilitated the chemisorption of Zn2+ on the carbon material surface. The nitrogen-doped multilevel porous carbon material (HT-NMPC-1/1) prepared with a 1 : 1 mass ratio of the two templates exhibited a specific capacity of 146.65 mAh g-1 at 0.2 A g-1. Moreover, the Swagelok cells assembled with HT-NMPC-1/1 and Zn foil achieved a high energy density of 121.5 W h kg-1, high power output of 166 W kg-1, and 93.09 % capacity retention after 8000 cycles at 2 A g-1. Therefore, HT-NMPC-1/1 is a highly promising candidate for ZHSCs cathode materials. Furthermore, the novel pore regulation strategy and straightforward preparation method offer valuable reference points for other porous carbon-based functional materials.

High Quality-Factor All-Dielectric Metacavity for Label-Free Biosensing.

High sensitivity and high quality-factor are crucial for achieving outstanding sensing performance in photonic biosensors. However, strong optical field confinement and high light-biomolecule interactions on photonic surfaces are usually contradictory and challenging to satisfy simultaneously. Here, a distinctive configuration for addressing this issue is reported: embedding a nanophotonic metasurface inside a micro vertical cavity as a meta-channel (metacavity) biosensor. The analyte solution serves as the cavity medium, thereby maximizing the light-analyte interaction. Simulation validation is conducted to optimize the metacavity with high structural robustness and remarkable optical and sensing properties. Large-scale low-cost metacavity biosensors are realized by combining anodic aluminum oxide template technique and wafer bonding. Experimentally, the metacavity biosensor demonstrates a notable quality-factor (maximum 4140) and high bulk refractometric sensitivity (450nmRIU-1), resulting in an unprecedented figure-of-merit (1670 RIU-1). Moreover, the metacavity biosensor achieves high surface sensitivity, together with a detection-limit of 119 viral copies mL-1 for label-free severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pseudovirus sensing, revealing remarkable performance in both bulk and surface sensing.

Aluminium surface work hardening enables multi-scale 3D lithography.

Multi-scale structures are ubiquitous in biological systems. However, manufacturing man-made structures with controllable features spanning multiple length scales, particularly down to nanoscale features, is very challenging, which seriously impacts their collective properties. Here we introduce an aluminium-based three-dimensional lithography that combines sequential nano-micro-macro-imprinting and anodization of multi-scale anodic aluminium oxide templates to manufacture well-defined multi-scale structures, using various materials. The high-fidelity nano-patterns and micro-patterns were facilitated by the surface work hardening phenomenon, where the nano-patterns can be further fine-tailored by anodization to have high-aspect-ratio and tunable nano-holes. Based on the aluminium-based three-dimensional lithography, multi-scale materials across length scales of at least 107 orders of magnitude were precisely fabricated, including carbon, semiconductors and metals. We integrated pressure sensors and biosensors with superior and customizable performances by tailoring the multi-scale carbon networks on different length scales from nanofibres and micropyramids to macrodome arrays. This work provides a versatile technique for prototyping on-demand multi-scale structures and materials to explore desirable mechanical and physical properties.

Integration of highly ordered plasmonic nanocavity array structure with the electrostatic driving force for dynamic control of SERS signals and label-free detection of λ-DNA.

With the rapid development of nanoscience and nanotechnology, surface-enhanced Raman spectroscopy (SERS) is widely used for the detection of analyte molecules and biomolecules in liquids. However, due to the plasmonic near-field effect, the key challenge of SERS detection in liquids is to attract target molecules in solutions into the plasmonic "hot spots". In this work, the SERS-active substrates (Ag@AAO) with excellent signal sensitivity and uniformity were successfully prepared by sputtering Ag films on anodized aluminum oxide (AAO) templates. Subsequently, integrating the substrate into a liquid chamber, the movement of target molecules in the liquid was effectively controlled by the electrostatic driving force, and the enrichment, separation and detection of R6 G molecules on the plasmonic "hot spots" were realized in a single device. The integrated system can dynamically control the SERS signal of low-concentration R6 G solution (10-10 M and 10-11 M). Moreover, the label-free direct detection capability of the integrated system for 30 ng/µL λ-DNA (dsDNA) is expected to greatly expand the application potential of SERS technology in biomolecular sensing and genetic engineering.

Comparative study in magnetic properties of FeCo alloy nanowires and a first-order reversal curve analysis

FeCo alloy nanowires have potential applications in data storage, magnetic sensors and spintronic devices. In this paper, FeCo alloy nanowires with varying diameters were fabricated within an anodic aluminum oxide (AAO) template using electrodeposition method at a constant potential. Characterization of the morphology and structure revealed that the polycrystalline body-center-cubic(bcc) FeCo alloy nanowires were obtained. The influence of diameter of FeCo alloy nanowires on magnetic interaction, domain state and magnetic mechanism was investigated through a first-order reversal curve (FORC) analysis. The findings showed that with an increase in the diameter of FeCo alloy nanowires from 20 nm to 60 nm and 100 nm, the interaction force between the FeCo alloy nanowires increased, the domain state of FeCo alloy nanowires changed from Single Domain (SD) to Multi-Domain (MD), the magnetic reversal mode changed from coherent reversal mode to curling reversal mode.

Dielectric study of low-cost porous anodic aluminum oxide (AAO) template and AAO template-copper nanowires (Cu/AAO) nanocomposites as a capacitor for energy storage

In this work, we explore the effect of increasing electrodeposition time on the dielectric properties of Cu/AAO nanocomposites. Cu nanowires are electrodeposited within the AAO template pores fabricated using a two-step anodization process. The morphology, composition, and crystalline structure are characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The dielectric properties, including the real part and the imaginary part of the effective complex relative permittivity and the effective AC conductivity of the AAO template and Cu/AAO nanocomposites, are subsequently analyzed. The results demonstrate a clear improvement in effective permittivity and effective AC conductivity of Cu/AAO nanocomposites with increasing electrodeposition time, indicating the potential for tailoring the dielectric properties of AAO templates through the incorporation of metal nanowires for advanced capacitor applications.

(Invited) Architectural Refinement in Core-Shell Ni/Ni(OH)2 Nanowires Array for Enhanced Supercapacitor Performance - A Comprehensive Electrochemical and Finite Element Study

We investigated the electrochemical performance and effect of different aspect ratios of core-shell Ni/Ni(OH)2 nanowires arrayed in an asymmetric supercapacitor with graphene flakes. We created thenanowires with diameters of 35 nm, 100 nm, 150 nm and different height using electrodeposition with help of Anodic Alumina Oxide template, allowing us to regulate their dimensions accurately. We identified an intriguing trend: supercapacitor performance first rises with nanowire height, but then steadily drops when a critical threshold is reached. We used Finite Element Analysis (FEA) to corroborate our experimental results and uncover the underlying electrochemical processes in order to better explain and comprehend this phenomenon. According to the FEA simulations, the nanowire length effects the distribution and accessibility of ionic species surrounding the nanowire array, which influences the charge storage and transfer processes. Figure 1

(Invited) The Influence of Magnetic Fields on the Oxygen Evolution Reaction Catalyzed By Cobalt-Iron Oxide Nanowire Arrays

To mitigate climate change through the establishment of a renewable energy infrastructure, advancements in energy storage technologies are imperative. Electrochemical water splitting via electrolyzers enables the conversion of electrical energy into chemical energy. However, the performance of these devices, particularly that of the oxygen evolution reaction (OER) occurring at the anode, still needs to be improved. Previous studies have demonstrated that magnetic fields can induce convective flow to the electrode through Lorentz and Kelvin force effects, thereby improving the mass transport.[1] In contrast to the Lorentz force, the Kelvin force can be substantially increased by introducing magnetic nanostructures to create high magnetic field gradients in the vicinity of the electrode surface.[2] Given the magnetic properties inherent to many earth-abundant metal-based and nanostructured electrocatalysts promising for the OER, there is potential for intelligently designing electrodes to leverage magnetic field effects in the future. However, a comprehensive understanding of these magnetic field effects is currently lacking. In the scope of this work, we aimed to systematically investigate the influence of magnetic fields on the oxygen evolution reaction. Considering the substantial magnetic field gradients generated by magnetic nanowires, we fabricated arrays of freestanding cobalt-iron oxide nanowires to explore the influence of magnetic fields on the oxygen evolution reaction catalyzed by these nanostructured electrocatalysts. Templated electrodeposition of cobalt-iron alloy into the pores of anodic aluminum oxide membranes enabled a straightforward control over nanowire diameter and length. Subsequent removal of the aluminum oxide template in alkaline solution yielded cobalt-iron oxide nanowires composed to 60% of Fe and 40% of Co standing freely on an electrochemically stable gold substrate. Superimposing a magnetic field during water oxidation on the so-prepared nanowire arrays resulted in an increase in the measured oxidation current (see Figure). To deconvolute the contributions of the Lorentz and Kelvin force, experiments were conducted in two different magnetic field orientations: either parallel or perpendicular to the electrode surface. In the parallel orientation, a linear correlation between the increase in current and the strength of the applied magnetic field was observed. In contrast, when the magnetic field was aligned perpendicular to the electrode surface, a plateau in the current enhancement manifested at higher magnetic field strengths, indicating different dominant effects in the two configurations.[1] K. Ngamchuea, K. Tschulik, R. G. Compton, Magnetic control: Switchable ultrahigh magnetic gradients at Fe3O4 nanoparticles to enhance solution-phase mass transport, Nano Res. 2015, 8, 3293–3306.[2] L. M. Monzon, J. Coey, Magnetic fields in electrochemistry: The Kelvin force. A mini-review, Electrochem. commun. 2014, 42, 42–45. Figure 1

Light-Assisted Fabrication of Hierarchical Azopolymer Structures Using the Breath Figure Method and AAO Templates.

Hierarchical polymer structures have garnered widespread application across various fields owing to their distinct surface properties and expansive surface areas. Conventional hierarchical polymer structures, however, often lack postfabrication scalability and spatial selectivity. In this study, we propose a novel strategy to prepare light-assisted hierarchical polymer structures using azopolymers (PAzo), the breath figure method, and anodic aluminum oxide (AAO) templates. Initially, the breath figure PAzo films are prepared by dripping a PAzo chloroform solution onto glass substrates in a high-humidity environment. The AAO templates are then placed on the breath figure PAzo film. Upon ultraviolet (UV) light exposure, the azobenzene groups in the azopolymers undergo trans-cis photoisomerization. This process causes the glass transition temperature (Tg) of the PAzo to become lower than room temperature, allowing the azopolymer to enter the nanopores of the AAO templates. The hierarchical azopolymer structures are then formed by using a sodium hydroxide solution to remove the templates. Furthermore, exploring the effects of PAzo concentration and UV light exposure duration on the film morphology reveals optimized conditions for hierarchical structure formation. Additionally, the water contact angles of these polymer structures are measured. The hierarchical PAzo structures exhibit higher hydrophobicity compared with the flat PAzo films and the PAzo breath figure films. Finally, patterned breath figure films can be prepared using designed photomasks, demonstrating the method's capability for spatial selectivity.

Random lasers with controlled emission modes by colloidal semiconductor quantum dots coupled to plasmonic nanorod arrays

Random lasers based on scattering for light amplification have gained extensive attention due to their simple structures. Colloidal semiconductor quantum dots (CSQDs) are excellent candidates as active media for random lasing. However, achieving CSQDs-based random lasers is challenging because the non-radiative Auger recombination produces a remarkable carrier loss. Here, we report random lasers with low thresholds based on the CSQDs coupled to the plasmonic nanorod arrays. The random lasers result from the enhancing excitation and emission rates of the CSQDs through plasmon resonance energy transfer induced by the spectral overlap between the resonant cavity modes of the plasmonic nanorod arrays and the excitons of the CSQDs, which reduces the carrier loss and establishes the optical gain in the CSQDs. Moreover, the incoherent and coherent emission modes can be controlled by varying the filling configurations (i.e., full-filling and partial-filling) of the plasmonic nanorods embedded in anodic aluminum oxide templates. Consequently, the incoherent random laser with a threshold of 19.3 μJ/mm2 and coherent random lasers with a threshold of 13.5 μJ/mm2 are performed, respectively. The proposed system provides a feasible method for low-threshold CSQDs-based random lasers with controlled emission modes, showing a promising avenue for potential applications.

High Density 3D Carbon Tube Nanoarray Electrode Boosting the Capacitance of Filter Capacitor

HighlightsA novel method is developed for precise control over the structure of 3D anodic aluminum oxide templates, enabling fine-tuning of both the vertical pore diameter and interspace within the templates.3D carbon tube nanoarrays featuring significantly thinner and denser tubes are constructed as high-quality electrodes for miniaturized filter capacitors.The 3D compactly arranged carbon tube-based capacitor achieves a remarkable specific areal capacitance of 3.23 mF cm−2 with a phase angle of − 80.2° at 120 Hz.

Plasmonic Bound States in the Continuum Metasurface-Semiconductor-Metal Architecture Enables Efficient Hot-Electron-Based Photodetector.

Plasmonic hot-electron-based photodetectors (HEB-PDs) have received widespread attention for their ability to realize effective carrier collection under sub-bandgap illumination. However, due to the low hot electron emission probability, most of the existing HEB-PDs exhibit poor responsivity, which significantly restricts their practical applications. Here, by employing the binary-pore anodic alumina oxide template technique, we proposed a compact plasmonic bound state in continuum metasurface-semiconductor-metal-based (BIC M-S-M) HEB-PD. The symmetry-protected BIC can manipulate a strong gap surface plasmon in the stacked M-S-M structure, which effectively enhances light-matter interactions and improves the photoresponse of the integrated device. Notably, the optimal M-S-M HEB-PD with near-unit absorption (∼90%) around 800 nm delivers a responsivity of 5.18 A/W and an IPCE of 824.23% under 780 nm normal incidence (1 V external bias). Moreover, the ultrathin feature of BIC M-S-M (∼150 nm) on the flexible substrate demonstrates excellent stability under a wide range of illumination angles from -40° to 40° and at the curvature surface from 0.05 to 0.13 mm-1. The proposed plasmonic BIC strategy is very promising for many other hot-electron-related fields, such as photocatalysis, biosensing, imaging, and so on.

Dispersion and stability of gold nanorods prepared by anodized aluminum oxide (AAO) templates in alkaline solution

Dispersion and stability of gold nanorods prepared by anodized aluminum oxide (AAO) templates in alkaline solution

Temperature dependent structural and magnetic properties of permalloy (Ni80Fe20) nanotubes

One dimensional Permalloy (Ni80Fe20) nanotubes (NTs) were successfully fabricated using Anodic Aluminum Oxide (AAO) templates with 100 nm diameter by employing a low-cost electrodeposition route at room temperature. As prepared Ni80Fe20 NTs morphology, elemental analysis and structural details have been investigated by using field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and X-Ray diffraction (XRD) respectively. The structure of prepared Permalloy nanostructures has face centered cubic (FCC) phase with polycrystalline in nature. The Ni80Fe20 NTs were annealed at 200 °C, 400 °C and 600 °C. The vibrating sample magnetometer (VSM) measurements showed that all the samples exhibit ferromagnetic nature. Furthermore, VSM has been employed to study the saturation magnetization (MS), Squareness (SQ) and Coercivity (HC) as the function of annealing temperature. A comparative study of magnetization reversal mechanism has also been conducted. The easy axis lies in the direction perpendicular to the NTS axis due to the dominance in shape anisotropy. Annealing temperature improved the magnetic properties of Permalloy (PA) NTs. This work will provide significant applications in the field of spintronics and high-density data storage devices.

Metal Organic Framework Derived Spinel Nickel‐Ferrites Employing Reduced Graphene Oxide Template for Supercapacitor and Photocatalytic Dye Degradation

AbstractSpinel oxides from transition metals are the most crucial components for producing supercapacitive electrodes and photocatalytic semiconductor materials. However poor electrical conductivity and restricted specific energy of these materials are two main drawbacks for energy storage applications. This investigation used reduced graphene oxide templated spinel nickel ferrites nanoparticles (RGO@SNFs), synthesized using Fe2Ni MIL‐88 MOF via hydrothermal conditions followed by a pyrolysis process. The structural properties and morphology of the hybrid are characterized through several methods, including XRD, FTIR, BET‐PSD, and FESEM. Superconducting electrochemical studies such as Galvano static charge‐discharge, impedance spectroscopy and cyclic voltammetry are carried out on a hybrid electrode to examine the impact of the RGO template on SNF nanoparticles. This electrode may be an alluring choice for supercapacitor applications because of its capacitance 115 F/g and retention rate of approximately 95 % following 2000 cycles. Additionally, a model dye degradation process utilizing Rhodamine B (RhB) was used to examine the photodegradation action of these materials. The designed catalyst also represents excellent photo‐degradation activity toward RhB, and seventy‐five minutes of sun light were enough to destroy about 99 % of the dye.

Three-dimensional anodic aluminum templates via a single-step pulsed potential method

Recent advances in the fabrication of three-dimensional Anodic Aluminum Oxide templates have opened novel opportunities in the generation of photonic structures and material nanostructuration. So far these structures have been produced from the standard two-step pulsed potential anodization and modulated current density anodization approaches. However, their fabrication is slow, with the two-step approach relying on intermediate oxide removal steps that often use toxic etchants. In this work, we report the fabrication of 3D Anodic Aluminum Oxide templates from a single-step pulsed potential method, completely removing the need for intermediate etching steps, and decreasing total fabrication times to less than 24 hours. Structural coloration was also successfully demonstrated and analyzed in these templates, for 99.999% and 99.5% Al precursors, presenting the same morphology and optical functionality as templates produced from two-step processes.

Oxide Solid–Solution Catalysts with Good Redox Properties for Liquid–Phase Aerobic Additive–Free Oxidation: A Review

AbstractIn this review, we discuss liquid–phase redox reactions using oxide solid–solution catalysts. These oxide solid solutions are readily prepared by introducing various elements into the foundational metal oxide template. Doping with metal species leads to the formation of [MOx] clusters with unique coordination structures, which is a remarkable feature that deserves attention. Consequently, oxide solid solutions exhibit catalytic capabilities that extend beyond those of conventional metal–oxide catalysts. Notably, these [MOx] clusters occasionally exhibit exceptional redox activities that can be used to catalyze liquid–phase redox reactions. Hence, we conjecture that a connection exists between catalyst structure and activity. This review delves into oxide solid–solution catalysts through the lenses of organic chemistry, solid catalysts, and computational chemistry, thereby collectively shaping our understanding and prospects in this field.

Efficient concentration of trace analyte with ordered hotspot construction for a robust and sensitive SERS platform

Surface-enhanced Raman scattering (SERS) platform, which enables trace analyte detection, has important application prospects. By structuring/modifying the surface of the SERS substrate, analyte in highly diluted solutions can be concentrated into localized active areas for highly sensitive detection. However, subject to the difficulty of the fabrication process, it remains challenging to balance hot-spot construction and the concentration capacity of analyte simultaneously. Therefore, preparing SERS substrates with densely ordered hot spots and efficient concentration capacity is of great significance for highly sensitive detection. Herein, we propose an Ag and fluoroalkyl-modified hierarchical armour substrate (Ag/F-HA), which has a double-layer stacking design to combine analyte concentration with hotspot construction. The microarmour structure is fabricated by femtosecond-laser processing to serve as a superhydrophobic and low-adhesive surface to concentrate analyte, while the anodic aluminium oxide (AAO) template creates a nanopillar array serving as dense and ordered hot spots. Under the synergistic action of hot spots and analyte concentration, Ag/F-HA achieves a detection limit down to 10−7 M doxorubicin (DOX) molecules with a RSD of 7.69%. Additionally, Ag/F-HA exhibits excellent robustness to resist external disturbances such as liquid splash or abrasion. Based on our strategy, SERS substrates with directional analyte concentrations are further explored by patterning microcone arrays with defects. This work opens a way to the realistic implementation of SERS in diverse scenarios.

ReS2-MoS2 heterojunction nanotube FET with superlattice structures for ultrasensitive detection of miRNA

Ultrasensitive detection of cancer biomarkers holds immense importance in facilitating the early diagnosis and treatment of cancer. Compared to conventional detection techniques, field-effect transistor (FET) biosensors have demonstrated substantial potential in achieving sensitive detection of cancer biomarkers. However, the ultrasensitive FET still remains great challenges due to the limited electron transport capacity and sensitivity of channel materials. Herein, we employed rhenium disulfide-molybdenum disulfide nanotube (ReS2-MoS2 NT) featuring superlattice structures as channel materials in FET biosensors for the highly sensitive detection of cancer biomarker miRNA-21. More concretely, ReS2-MoS2 NT featuring superlattice structures was synthesized using the anodic aluminum oxide (AAO) template sacrifice method and atomic layer deposition (ALD) method. The electrical properties of single ReS2-MoS2 NT FET were regulated by adjusting the total layers and number of heterojunction interfaces, and the optimal number of heterojunction interfaces of 7 was obtained. Finally, FET biosensors utilizing the network ReS2-MoS2 NT as the channel materials were fabricated and exhibited remarkable sensitivity in detecting miRNA-21 under an external light source. The linear range for detection spanned from 10 aM to 1 nM, with an exceptionally low detection limit of 2.1 aM. This study holds promise for replacing current channel materials and surpassing the detection threshold of cancer biomarkers in the future.