Table of contents

This study proposes a simple method of Au coating on silver nanowires (Ag NWs) transparent conductive films as the anode of organic light emitting diodes (OLED) to increase the work function of the film and thus enhance hole transport. We carefully engineer the process conditions (pretreatment, solution concentrations, and coating number) of the coating using a diluted HAuCl₄ solution on the Ag NWs film to minimize etching damage on Ag NWs accompanying the galvanic replacement reaction. Ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy show work function increase of Ag NWs upon Au coating. OLED devices based on Au-coated Ag NWs show a lower turn-on voltage and higher luminance, compared with pristine Ag NWs device. Although the Ag NWs device displays poor efficiencies in the low luminance range due to a high leakage, some of the Au-coated Ag NWs devices showed efficiencies higher than those of the ITO device in a high luminance.

The electrochemical performance of supercapacitors might be associated with the homogeneous structure of the electrode materials. However, the relationship between the degree of uniformity for the electrode materials and the electrochemical performance of the supercapacitor is not clear. Herein, we synthesize two types of nickel bicarbonate nanocrystals with different degrees of uniformity to investigate this relationship. As the electroactive material, the nickel bicarbonate nanocrystals with a homogeneous structure could provide a larger space and offer more exposed atoms for the electrochemical reaction than the nanocrystals with a heterogeneous structure. The homogeneous nickel bicarbonate nanocrystals exhibit better electrochemical performance and show excellent specific capacitance (1596 F g⁻¹ at 2 A g⁻¹ and 1260 F g⁻¹ at 30 A g⁻¹), which is approximately twice that of the heterogeneous nickel bicarbonate nanocrystals. The cycling stability for the homogeneity (∼80%) is higher than the inhomogeneity (∼61%) at a high current density of 5 A g⁻¹.

Up to now, the literature on Cu₂S with specific morphology applied to oxygen evolution reaction (OER) in the electrocatalytic field has been limited. In this work, unique peapod-like Cu₂S/C exhibiting superb electrocatalytic performance toward OER is successfully synthesized, by employing Cu(OH)₂ nanorods as the template and nontoxic glucose as the carbon source and then annealing with sublimed sulfur. It can be seen that this work explores a new application area for Cu₂S. More precisely, the novel morphology contributes to increasing the electrochemical active surface area effectively and promoting contact between the Cu₂S nanoparticles and the electrolyte. During electrochemical measurements, the peapod-like Cu₂S/C shows enhanced electrocatalytic activity with a low overpotential of 401 mV at the current density of 10 mA cm⁻² and a Tafel slope of 52 mV dec^–1. More importantly, our material is able to maintain stability for at least 8 h at constant potential and the current loss is negligible after 2000 cycles. Obviously, these striking properties fully demonstrate that the peapod-like Cu₂S/C as an efficient catalyst shows great promise for OER.

Honeycomb-like nickel cobalt sulfide (NiCo₂S₄) nanosheets were directly deposited on fluorine-doped tin oxide substrate by a rapid voltammetric deposition method. The method was also controllable and feasible for preparing NiCo₂S₄ on flexible Ti foil without any heating processes. Compared with Pt, CoS and NiS, NiCo₂S₄ exhibited low charge-transfer resistances and excellent electrocatalytic activity for ${{{\rm{I}}}_{3}}^{-}$ reduction, acting as a counter electrode for a dye-sensitized solar cell. The NiCo₂S₄-based solar cell showed higher power conversion efficiency (7.44%) than that of Pt-based solar cell (7.09%) under simulated illumination (AM 1.5 G, 100 mW cm⁻²). The device based on the flexible NiCo₂S₄/Ti foil achieved a power conversion efficiency of 5.28% under the above illumination conditions. This work can be extended to flexible and wearable technologies due to its facile technique.

Integration of carbon materials with benign iron oxides is blazing a trail in constructing high-performance anodes for lithium-ion batteries (LIBs). In this paper, a unique general, simple, and controllable strategy is developed toward in situ uniform coating of iron oxide nanostructures with graphitized carbon (GrC) layers. The basic synthetic procedure only involves a simple dip-coating process for the loading of Ni-containing seeds and a subsequent Ni-catalyzed chemical vapor deposition (CVD) process for the growth of GrC layers. More importantly, the CVD treatment is conducted at a quite low temperature (450 °C) and with extremely facile liquid carbon sources consisting of ethylene glycol (EG) and ethanol (EA). The GrC content of the resulting hybrids can be controllably regulated by altering the amount of carbon sources. The electrochemical results reveal remarkable performance enhancements of iron oxide@GrC hybrids compared with pristine iron oxides in terms of high specific capacity, excellent rate and cycling performance. This can be attributed to the network-like GrC coating, which can improve not only the electronic conductivity but also the structural integrity of iron oxides. Moreover, the lithium storage performance of samples with different GrC contents is measured, manifesting that optimized electrochemical property can be achieved with appropriate carbon content. Additionally, the superiority of GrC coating is demonstrated by the advanced performance of iron oxide@GrC compared with its corresponding counterpart, i.e., iron oxides with amorphous carbon (AmC) coating. All these results indicate the as-proposed protocol of GrC coating may pave the way for iron oxides to be promising anodes for LIBs.

Herein, we report an efficient and universal strategy for synthesizing a unique triple-shell structured Fe₃O₄@SiO₂@C-Ni hybrid composite. Firstly, the Fe₃O₄ cores were synthesized by hydrothermal reaction, and sequentially coated with SiO₂ and a thin layer of nickel-ion-doped resin-formaldehyde (RF-Ni²⁺) using an extended Stöber method. This was followed by carbonization to produce the Fe₃O₄@SiO₂@C-Ni nanocomposites with metallic nickel nanoparticles embedded in an RF-derived thin graphic carbon layer. Interestingly, the thin SiO₂ spacer layer between RF-Ni²⁺ and Fe₃O₄ plays a critical role on adjusting the size and density of the nickel nanoparticles on the surface of Fe₃O₄@SiO₂ nanospheres. The detailed tailoring mechanism is explicitly discussed, and it is shown that the iron oxide core can react with the nickel nanoparticles without the SiO₂ spacer layer, and the size and density of the nickel nanoparticles can be effectively controlled when the SiO₂ layer exits. The multifunctional composites exhibit a significantly enhanced catalytic performance in the reduction of 4-nitrophenol (4-NP).

Epitaxial growth of graphene on SiC is a scalable procedure that does not require any further transfer step, making this an ideal platform for graphene nanostructure fabrication. Focused ion beam (FIB) is a very promising tool for exploring the reduction of the lateral dimension of graphene on SiC to the nanometre scale. However, exposure of graphene to the Ga⁺ beam causes significant surface damage through amorphisation and contamination, preventing epitaxial graphene growth. In this paper we demonstrate that combining a protective silicon layer with FIB patterning implemented prior to graphene growth can significantly reduce the damage associated with FIB milling. Using this approach, we successfully achieved graphene growth over 3C-SiC/Si FIB patterned nanostructures.

In this work, we report on the production of regular (SiGe/SiO₂)₂₀ multilayer structures by conventional RF-magnetron sputtering, at 350 °C. Transmission electron microscopy, scanning transmission electron microscopy, raman spectroscopy, and x-ray reflectometry measurements revealed that annealing at a temperature of 1000 °C leads to the formation of SiGe nanocrystals between SiO₂ thin layers with good multilayer stability. Reducing the nominal SiGe layer thickness (t_SiGe) from 3.5–2 nm results in a transition from continuous SiGe crystalline layer (t_SiGe ∼ 3.5 nm) to layers consisting of isolated nanocrystals (t_SiGe ∼ 2 nm). Namely, in the latter case, the presence of SiGe nanocrystals ∼3–8 nm in size, is observed. Spectroscopic ellipsometry was applied to determine the evolution of the onset in the effective optical absorption, as well as the dielectric function, in SiGe multilayers as a function of the SiGe thickness. A clear blue-shift in the optical absorption is observed for t_SiGe ∼ 2 nm multilayer, as a consequence of the presence of isolated nanocrystals. Furthermore, the observed near infrared values of n = 2.8 and k = 1.5 are lower than those of bulk SiGe compounds, suggesting the presence of electronic confinement effects in the nanocrystals. The low temperature (70 K) photoluminescence measurements performed on annealed SiGe/SiO₂ nanostructures show an emission band located between 0.7–0.9 eV associated with the development of interface states between the formed nanocrystals and surrounding amorphous matrix.

In this paper, we investigate the impact of vacuum chamber conditions (cleanliness level and vacuum pressure) and imaging parameters (magnification and acceleration voltage) of scanning electron microscopy (SEM) on the contact resistance of two-point in situ nanoprobing of nanomaterials. Using two typical types of conductive nanoprobe, two-point nanoprobing is performed on silicon nanowires, during which changing trends of the nanoprobing contact resistance with the SEM chamber conditions and imaging parameters are quantified. The mechanisms underlying the experimental observations are also explained. Through systematically adjusting the experimental parameters, the probe-sample contact resistance is significantly reduced from the mega-ohm level to the kilo-ohm level. The experimental results can serve as a guideline to evaluate electrical contacts of nanoprobing and instruct how to reduce the contact resistance in SEM-based, two-point nanoprobing.

Single-walled carbon nanotube (SWNT) films are a potential candidate as porous conductive electrodes for energy conversion and storage; tailoring the loading and distribution of active materials grafted on SWNTs is critical for achieving maximum performance. Here, we show that as-synthesized SWNT samples containing residual Fe catalyst can be directly converted to Fe₂O₃/SWNT composite films by thermal annealing in air. The mass loading of Fe₂O₃ nanoparticles is tunable from 63 wt% up to 96 wt%, depending on the annealing temperature (from 450 °C to 600 °C), while maintaining the porous network structure. Interconnected SWNT networks containing high-loading active oxides lead to synergistic effect as an anode material for lithium ion batteries. The performance is improved consistently with increasing Fe₂O₃ loading. As a result, our Fe₂O₃/SWNT composite films exhibit a high reversible capacity (1007.1 mA h g⁻¹ at a current density of 200 mA g⁻¹), excellent rate capability (384.9 mA h g⁻¹ at 5 A g⁻¹) and stable cycling performance with the discharge capacity up to 567.1 mA h g⁻¹ after 600 cycles at 2 A g⁻¹. The high-loading Fe₂O₃/SWNT composite films have potential applications as nanostructured electrodes for various energy devices such as supercapacitors and Li-ion batteries.