Density Functional Theory Investigation of Temperature-Dependent Properties of Cu-Nitrogen-Doped Graphene as a Cathode Material in Fuel Cell Applications.

In this study, density functional theory (DFT) was used to investigate the influence of temperature on the performance of a novel Cu-nitrogen-doped graphene Cu-N/Gr nanocomposite as a catalyst for the oxygen reduction reaction (ORR) in fuel cell applications. Our DFT calculations, conducted using Gaussian 09w with the 3-21G/B3LYP basis set, focus on the Cu-nitrogen-doped graphene nanocomposite cathode catalyst, exploring its behavior at three distinct temperatures: 298.15 K, 353.

Influence of metal salts (Al, Ca, and Mg) on the work function and hole extraction at carbon counter electrodes in perovskite solar cells.

Hole transport material-free carbon-based perovskite solar cells (HTM-free -PSCs) are recognized as a cost-effective and stable alternative to conventional perovskite solar cells. However, the significant energy level misalignment between the perovskite layer and the carbon counter electrode (CE) results in ineffective hole extraction and unfavorable charge recombination, which decreases the power conversion efficiency (PCE). Here, we report the introduction of metal salts (Al, Ca, and Mg) into graphite/carbon black (Gr/CB) CEs to modify the work function and enhance the hole selectivity of the CE.

Cu - Nitrogen doped graphene (Cu-N/Gr) nanocomposite as cathode catalyst in fuel cells - DFT study.

Novel Cu-nitrogen doped graphene nanocomposite catalysts are developed to investigate the Cu-nitrogen doped fuel cell cathode catalyst. Density functional theory calculations are performed using Gaussian 09w software to study the oxygen reduction reaction (ORR) on Cu-nitrogen doped graphene nanocomposite cathode catalyst in low-temperature fuel cells. Three different nanocomposite structures Cu-N/Gr, Cu-N/Gr and Cu-N/Gr were considered in the acidic medium under standard conditions (298.

Visible-Range Multiple-Channel Metal-Shell Rod-Shaped Narrowband Plasmonic Metamaterial Absorber for Refractive Index and Temperature Sensing.

Multiple resonance modes in an optical absorber are necessary for nanophotonic devices and encounter a challenge in the visible range. This article designs a multiple-channel plasmonic metamaterial absorber (PMA) that comprises a hexagonal arrangement of metal-shell nanorods in a unit cell over a continuous thin metal layer, operating in the visible range of the sensitive refractive index (RI) and temperature applications. Finite element method simulations are utilized to investigate the physical natures, such as the absorptance spectrum, magnetic flux and surface charge densities, electric field intensity, and electromagnetic power loss density.

Graphite/Carbon Black Counter Electrode Deposition Methods to Improve the Efficiency and Stability of Hole-Transport-Layer-Free Perovskite Solar Cells.

The interfacial compatibility between the graphite/carbon black composite counter electrode (Gr/CB CE) and the perovskite layer is a crucial determinant of the performance of the hole-transport-layer-free carbon-based perovskite solar cells, and judicious selection of the Gr/CB CE application method is essential for achieving an optimum contact. In this work, three different types of Gr/CB CEs application methods are investigated: (1) deposition of Gr/CB on the fluorine-doped tin oxide (FTO) substrate, followed by clamping to the perovskite layer, (2) direct deposition of Gr/CB onto the perovskite layer, and (3) deposition of Gr/CB onto the PbI precursor layer, followed by immersion in methylammonium iodide solution for the conversion of PbI to perovskite. The results revealed that Method 3 produced superior Gr/CB-perovskite contacts, resulting in up to 8.

Enhanced photoluminescence and shortened lifetime of DCJTB by photoinduced metal deposition on a ferroelectric lithography substrate.

The photodeposition of metallic nanostructures onto ferroelectric surfaces could enable new applications based on the assembly of molecules and patterning local surface reactivity by enhancing surface field intensity. DCJTB (4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran) is an excellent fluorescent dye and dopant material with a high quantum efficiency used for OLED displays on the market. However, how to raise the photoluminescence (PL) and reduce the lifetime of DCJTB in a substrate remain extraordinary challenges for its application.

Theoretical Study of CO Adsorption Interactions with Cr-Doped Tungsten Oxide/Graphene Composites for Gas Sensor Application.

The present study explores the CO adsorption properties with graphene, tungsten oxide/graphene composite, and Cr-doped tungsten oxide/graphene composite using density functional theory (DFT) calculations. The results of the study reveal the Cr-doped tungsten oxide/graphene composites, g-CrW O ( = 2 to 4), to have a lowered highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap, high surface reactivity, and a strong cluster-graphene binding energy, hence exhibiting a strong adsorption interaction with CO. The CO adsorption interaction shows physisorption properties by having a greater tendency for Mulliken and natural bond orbital (NBO) charge transfer supported by a strong physisorption interaction toward the g-CrW O ( = 2 to 4) composite with HOMO-LUMO energy gaps of -0.

Ultrahigh Sensitivity of a Plasmonic Pressure Sensor with a Compact Size.

This study proposes a compact plasmonic metal-insulator-metal pressure sensor comprising a bus waveguide and a resonator, including one horizontal slot and several stubs. We calculate the transmittance spectrum and the electromagnetic field distribution using the finite element method. When the resonator's top layer undergoes pressure, the resonance wavelength redshifts with increasing deformation, and their relation is nearly linear.

Significantly enhanced coupling effect and gap plasmon resonance in a MIM-cavity based sensing structure.

Herein, we design a high sensitivity with a multi-mode plasmonic sensor based on the square ring-shaped resonators containing silver nanorods together with a metal-insulator-metal bus waveguide. The finite element method can analyze the structure's transmittance properties and electromagnetic field distributions in detail. Results show that the coupling effect between the bus waveguide and the side-coupled resonator can enhance by generating gap plasmon resonance among the silver nanorods, increasing the cavity plasmon mode in the resonator.

Improved Refractive Index-Sensing Performance of Multimode Fano-Resonance-Based Metal-Insulator-Metal Nanostructures.

This work proposed a multiple mode Fano resonance-based refractive index sensor with high sensitivity that is a rarely investigated structure. The designed device consists of a metal-insulator-metal (MIM) waveguide with two rectangular stubs side-coupled with an elliptical resonator embedded with an air path in the resonator and several metal defects set in the bus waveguide. We systematically studied three types of sensor structures employing the finite element method.

Ultrawide Bandgap and High Sensitivity of a Plasmonic Metal-Insulator-Metal Waveguide Filter with Cavity and Baffles.

A plasmonic metal-insulator-metal waveguide filter consisting of one rectangular cavity and three silver baffles is numerically investigated using the finite element method and theoretically described by the cavity resonance mode theory. The proposed structure shows a simple shape with a small number of structural parameters that can function as a plasmonic sensor with a filter property, high sensitivity and figure of merit, and wide bandgap. Simulation results demonstrate that a cavity with three silver baffles could significantly affect the resonance condition and remarkably enhance the sensor performance compared to its counterpart without baffles.

Highly Sensitive and Tunable Plasmonic Sensor Based on a Nanoring Resonator with Silver Nanorods.

We numerically and theoretically investigate a highly sensitive and tunable plasmonic refractive index sensor that is composed of a metal-insulator-metal waveguide with a side-coupled nanoring, containing silver nanorods using the finite element method. Results reveal that the presence of silver nanorods in the nanoring has a significant impact on sensitivity and tunability performance. It gives a flexible way to tune the system response in the proposed structure.

Perfect Dual-Band Absorber Based on Plasmonic Effect with the Cross-Hair/Nanorod Combination.

Plasmonic effect using a cross-hair can convey strongly localized surface plasmon modes among the separated composite nanostructures. Compared to its counterpart without the cross-hair, this characteristic has the remarkable merit of enhancing absorptance at resonance and can make the structure carry out a dual-band plasmonic perfect absorber (PPA). In this paper, we propose and design a novel dual-band PPA with a gathering of four metal-shell nanorods using a cross-hair operating at visible and near-infrared regions.

Fabrication and Characterization of a Metallic-Dielectric Nanorod Array by Nanosphere Lithography for Plasmonic Sensing Application.

In this paper, a periodic metallic-dielectric nanorod array which consists of Si nanorods coated with 30 nm Ag thin film set in a hexagonal configuration is fabricated and characterized. The fabrication procedure is performed by using nanosphere lithography with reactive ion etching, followed by Ag thin-film deposition. The mechanism of the surface and gap plasmon modes supported by the fabricated structure is numerically demonstrated by the three-dimensional finite element method.

Ultra-High Refractive Index Sensing Structure Based on a Metal-Insulator-Metal Waveguide-Coupled T-Shape Cavity with Metal Nanorod Defects.

An ultra-high plasmonic refractive index sensing structure composed of a metal-insulator-metal (MIM) waveguide coupled to a T-shape cavity and several metal nanorod defects is proposed and investigated by using finite element method. The designed plasmonic MIM waveguide can constitute a cavity resonance zone and the metal nanorod defects can effectively trap the light in the T-shape cavity. The results reveal that both the size of defects in wider rectangular cavity and the length of narrower rectangular cavity are primary factors increasing the sensitivity performance.

Depolying Tunable Metal-Shell/Dielectric Core Nanorod Arrays as the Virtually Perfect Absorber in the Near-Infrared Regime.

In this paper, the coupled Ag-shell/dielectric-core nanorod for sensor application is investigated and the different dielectric core plasmonic metamaterial is adopted in our design. The operational principle is based on the concept of combining the lattice resonance, localized surface plasmon resonance (SPR), and cavity plasmon resonance modes within the nanostructure. The underlying mechanisms are investigated numerically by using the three-dimensional finite element method and the numerical results of coupled solid Ag nanorods are included for comparison.

Enhanced Carbon monoxide-sensing properties of Chromium-doped ZnO nanostructures.

Low power consumption, fast response and quick recovery times are important parameters for gas sensors performance. Herein, we report the experimental and theoretical studies of ZnO and Cr doped ZnO nanostructures used in low temperature (50 °C) sensors for the detection of CO. The synthesized films were characterized by XRD, UV-Vis, FE-SEM and EDX.

Simultaneous realization of high sensing sensitivity and tunability in plasmonic nanostructures arrays.

A plasmonic nanostructure (PNS) which integrates metallic and dielectric media within a single structure has been shown to exhibit specific plasmonic properties which are considered useful in refractive index (RI) sensor applications. In this paper, the simultaneous realization of sensitivity and tunability of the optical properties of PNSs consisting of alternative Ag and dielectric of nanosphere/nanorod array have been proposed and compared by using three-dimensional finite element method. The proposed system can support plasmonic hybrid modes and the localized surface plasmonic resonances and cavity plasmonic resonances within the individual PNS can be excited by the incident light.

Tunable Optical Performances on a Periodic Array of Plasmonic Bowtie Nanoantennas with Hollow Cavities.

We propose a design method to tune the near-field intensities and absorption spectra of a periodic array of plasmonic bowtie nanoantennas (PBNAs) by introducing the hollow cavities inside the metal nanostructures. The numerical method is performed by finite element method that demonstrates the engineered hollow PBNAs can tune the optical spectrum in the range of 400-3000 nm. Simulation results show the hollow number is a key factor for enhancing the cavity plasmon resonance with respect to the hotspot region in PBNAs.

Synthesis of nanostructured β-Ni(OH)2 by electrochemical dissolution-precipitation and its application as a water oxidation catalyst.

A straightforward electrochemical dissolution-precipitation approach has been developed to synthesize nanostructured β-Ni(OH)2 powders (particle size 10-100 nm, specific surface area ∼100 m(2) g(-1)) from Ni metal anodes. The approach differs from existing electrochemical synthesis methods in that it predominantly results in bulk precipitation of nanoparticles, without significant film growth on either of the electrodes. Heat treatment of the as-synthesized β-Ni(OH)2 afforded NiO with mostly preserved nanostructure and very high specific surface area (≤100 m(2) g(-1), depending on calcination temperature).

Potential natural sensitizers extracted from the skin of Canarium odontophyllum fruits for dye-sensitized solar cells.

Possibility of use of dye extract from skin samples of a seasonal, indigenous fruit from Borneo, namely Canarium odontophyllum, in dye sensitized solar cells (DSSCs) are explored. Three main groups of flavonoid pigments are detected and these pigments exhibit different UV-vis absorption properties, and hence showing different light harvesting capabilities. When applied in DSSCs.