Search Results (74)

Flexible supercapacitors have emerged as pivotal energy storage components in wearable smart electronic systems, owing to their exceptional electrochemical performance. However, the widespread application of flexible supercapacitors in smart electronic devices is significantly hindered by the developmental bottleneck of high-performance anode materials. In this study, a novel electrode composed of surface-modified Fe₂O₃ nanoneedles uniformly coated with a polypyrrole (PPy) film and anchored on Co-MOF-derived N-C nanoflake arrays (PPy/Fe₂O₃/N-C) is designed. This composite electrode, grown in situ on carbon cloth (CC), demonstrated outstanding specific capacity, rate performance, and mechanical flexibility, attributed to its unique hierarchical 3D arrayed structure and the protective PPy layer. The fabricated PPy/Fe₂O₃/N-C@CC (P-FONC) composite electrode exhibited an excellent specific capacitance of 356.6 mF cm⁻² (143 F g⁻¹) at a current density of 2 mA cm⁻². The current density increased to 20 mA cm⁻², and the composite electrode material preserved a specific capacitance of 278 mF cm⁻² (112 F g⁻¹). Furthermore, the assembled quasi-solid-state Mn/Fe asymmetric supercapacitor, configured with P-FONC as the negative electrode and MnO₂/N-C@CC as the positive electrode, demonstrated robust chemical stability and notable mechanical flexibility. This study sheds fresh light on the creation of three-dimensional composite electrode materials for highly efficient, flexible energy storage systems. Full article

In this study, nanostructured copper oxide-based films with crystallite size below 10 nm were electrochemically synthesized on copper foil and foam electrodes and investigated for their supercapacitive behaviour. The synthesis was carried out via cyclic voltammetry (CV) for up to 1000 cycles in an alkaline electrolyte. By tuning the upper vertex potential (−0.3 V to 0.65 V vs. Ag/AgCl), both phase composition (Cu₂O, Cu(OH)₂, CuO) and morphology (grains, nanoneedles, nanoplatelets) were precisely controlled, demonstrating the versatility of this approach. The kinetics of oxide/hydroxide film formation on foil and foam electrodes were analysed based on EIS data that were interpreted in the frame of equivalent electric circuits and their changes with potential. The capacitive properties of the synthesized films were evaluated using CV in the potential range of 0 V–0.65 V, and the optimized CuO film synthesized on Cu foam exhibited a high specific capacitance of 1380 mF cm⁻². An energy density of 0.061 mWh cm⁻² and power density of 1.28 mW cm⁻² were obtained at 10 mA cm⁻² discharge current. Charge–discharge cycling at 100 mV s⁻¹ for 1000 cycles indicated an initial capacitance increase followed by stable retention, highlighting the structural integrity and electrochemical stability of the films obtained on 3D foam. These findings provide valuable insights into the controlled electrochemical synthesis of copper oxide nanostructures and their potential for high-performance capacitor applications. Full article

In this study, a single zirconium carbide (ZrC) nanoneedle structure oriented in the <100> direction was fabricated by a dual-beam focused ion beam (FIB-SEM) system, and its field emission characteristics and emission current stability were evaluated. Benefiting from controlled fabrication with real-time observation, the ZrC nanoneedle has a smooth surface and a tip with a radius of curvature smaller than 20 nm and a length greater than 2 μm. Due to its low work function and well-controlled morphology, the ZrC nanoneedle emitter, positioned in a high-vacuum chamber, was able to generate a single and collimated electron beam with a current of 1.2 nA at a turn-on voltage of 210 V, and the current increased to 100 nA when the applied voltage reached 325 V. After the treatment of the nanoneedle tip, the field emission exhibited a stable emission for 150 min with a fluctuation of 1.4% and an emission current density as high as 1.4 × 10¹⁰ A m⁻². This work presents an efficient and controllable method for fabricating nanostructures, and this method is applicable to the transition metal compound ZrC as a field emission emitter, demonstrating its potential as an electron source for electron-beam devices. Full article

Current transdermal drug delivery technologies, like patches and ointments, effectively deliver low molecular weight drugs through the skin. However, delivering larger, hydrophilic drugs and macromolecules remains a challenge. In the present study, we developed novel transdermal nanoneedle patches containing levofloxacin-loaded modified chitosan nanoparticles. Chitosan was chemically modified with transcutol in three ratios (1/1, 1/2, 1/3, w/w), and the optimum ratio was used for nanoparticle fabrication via the ionic gelation method. The successful modification was confirmed using ATR-FTIR spectroscopy, while DLS results revealed that only the 1/3 ratio afforded suitably sized particles of 220 nm. After drug encapsulation, the particle size increased to 435 nm, and the final formulations were examined via XRD and an in vitro dissolution test, which suggested that the nanoparticles reach 60% release in a monophasic pattern at 380 h. We then prepared transdermal patches with pyramidal geometry nanoneedles using different poly(lactic acid)/poly(ethylene adipate) (PLA/PEAd) polymer blends of varying ratios, which were characterized in terms of morphology and mechanical compressive strength. The 90/10 blend exhibited the best mechanical properties and was selected for further testing. Ex vivo permeation studies proved that the nanoneedle patches containing drug-loaded nanoparticles achieved the highest levofloxacin permeation (88.1%). Full article

The mimesis of biological mechanisms by artificial devices constitutes the modern, rapidly expanding, multidisciplinary biomimetics sector. In the broader bioinspiration perspective, however, bioarchitectures may perform independent functions without necessarily mimicking their biological generators. In this paper, we explore such Bioarchitectonic notions and demonstrate three-dimensional photonics by the exact replication of insect organs using ultra-porous silica aerogels. The subsequent conformal systolic transformation yields their miniaturized affine ‘clones’ having higher mass density and refractive index. Focusing on the paradigms of ommatidia, the compound eye of the hornet Vespa crabro flavofasciata and the microtrichia of the scarab Protaetia cuprea phoebe, we fabricate their aerogel replicas and derivative clones and investigate their photonic functionalities. Ultralight aerogel microlens arrays are proven to be functional photonic devices having a focal length f ~ 1000 μm and f-number f/30 in the visible spectrum. Stepwise systolic transformation yields denser and affine functional elements, ultimately fused silica clones, exhibiting strong focusing properties due to their very short focal length of f ~ 35 μm and f/3.5. The fabricated transparent aerogel and xerogel replicas of microtrichia demonstrate a remarkable optical waveguiding performance, delivering light to their sub-100 nm nanotips. Dense fused silica conical clones deliver light through sub-50 nm nanotips, enabling nanoscale light–matter interactions. Super-resolution bioarchitectonics offers new and alternative tools and promises novel developments and applications in nanophotonics and other nanotechnology sectors. Full article

Real-time monitoring of physiological indicators inside the body is pivotal for contemporary diagnostics and treatments. Implantable electrodes can not only track specific biomarkers but also facilitate therapeutic interventions. By modifying biometric components, implantable electrodes enable in situ metabolite detection in living tissues, notably beneficial in invasive glucose monitoring, which effectively alleviates the self-blood-glucose-managing burden for patients. However, the development of implantable electrochemical electrodes, especially multi-channel sensing devices, still faces challenges: (1) The complexity of direct preparation hinders functionalized or multi-parameter sensing on a small scale. (2) The fine structure of individual electrodes results in low spatial resolution for sensor functionalization. (3) There is limited conductivity due to simple device structures and weakly conductive electrode materials (such as silicon or polymers). To address these challenges, we developed multiple-channel electrochemical microneedle electrode arrays (MCEMEAs) via a separated functionalization and assembly process. Two-dimensional microneedle (2dMN)-based and one-dimensional microneedle (1dMN)-based electrodes were prepared by laser patterning, which were then modified as sensing electrodes by electrochemical deposition and glucose oxidase decoration to achieve separated functionalization and reduce mutual interference. The electrodes were then assembled into 2dMN- and 1dMN-based multi-channel electrochemical arrays (MCEAs), respectively, to avoid damaging functionalized coatings. In vitro and in vivo results demonstrated that the as-prepared MCEAs exhibit excellent transdermal capability, detection sensitivity, selectivity, and reproducibility, which was capable of real-time, in situ glucose concentration monitoring. Full article

Chemical instability of liquid-repellent surfaces is one of the nontrivial hurdles that hinders their real-world applications. Although much effort has been made to prepare chemically durable liquid-repellent surfaces, little attention has been paid to exploit the instability for versatile use. Herein, we propose to create hydrophilic patterns on a superhydrophobic surface by taking advantage of its chemical instability induced by acid solution treatment. A superhydrophobic Cu(OH)₂ nanoneedle-covered Cu plate that shows poor stability towards HCl solution (1.0 M) is taken as an example. The results show that 2.5 min of HCl solution exposure leads to the etching of Cu(OH)₂ nanoneedles and the partial removal of the self-assembled fluoroalkyl silane molecular layer, resulting in the wettability transition from superhydrophobocity to hydrophilicity, and the water contact angle decreases from ~160° to ~30°. Hydrophilic dimples with different diameters are then created on the superhydrophobic surfaces by depositing HCl droplets with different volumes. Afterwards, the hydrophilic dimple-patterned superhydrophobic surfaces are used for water droplet manipulations, including controlled transfer, merging, and nanoliter droplet deposition. The results thereby verify the feasibility of creating wettability patterns on superhydrophobic surfaces by using their chemical instability towards corrosive solutions, which broadens the fabrication methods and applications of functional liquid-repellent surfaces. Full article

Transition metal phosphides (TMPs) have been widely studied for water decomposition for their monocatalytic property for anodic or cathodic reactions. However, their bifunctional catalytic activity still remains a major challenge. Herein, hexagonal nickel-cobalt bimetallic phosphide nanoneedles with 1–3 μm length and 15–30 nm diameter supported on NF (Ni_xCo_2−xP NDs/NF) with adjusted electron structure have been successfully prepared. The overall alkaline water electrolyzer composed of the optimal anode (Ni_0.67Co_1.33P NDs/NF) and cathode (Ni_1.01Co_0.99P NDs/NF) provide 100 mA cm⁻² at 1.62 V. Gibbs Free Energy for reaction paths proves that the active site in the hydrogen evolution reaction (HER) is Ni and the oxygen evolution reaction (OER) is Co in Ni_xCo_2−xP, respectively. In the HER process, Co-doping can result in an apparent accumulation of charge around Ni active sites in favor of promoting HER activity of Ni sites, and ΔG_H* of 0.19 eV is achieved. In the OER process, the abundant electron transfer around Co-active sites results in the excellent ability to adsorb and desorb *O and *OOH intermediates and an effectively reduced ∆G_RDS of 0.37 eV. This research explains the regulation of electronic structure change on the active sites of bimetallic materials and provides an effective way to design a stable and effective electrocatalytic decomposition of alkaline water. Full article

The aim of this study is to prove that resistive heating enables the synthesis of metal/metal oxide composites in the form of core–shell structures. The thickness and morphology of the oxide layer depends strongly on the nature of the metal, but the influences of parameters such as the time and current profiles and the presence of an external field have also been investigated. The systems chosen for the present study are Zn/ZnO, Ti/TiO₂, and Ni/NiO. The characterization of the samples was performed using techniques based on scanning electron microscopy (SEM). The thicknesses of the oxide layers varied from 10 μm (Zn/ZnO) to 50 μm (Ni/NiO). In the case of Zn- and Ti-based composites, the growth of nanostructures on the oxide layer was observed. Micro- and nanoneedles formed on the ZnO layer while prism-like structures appeared on the TiO₂. In the case of the NiO layer, micro- and nanocrystals were observed. Applying an external electric field seemed to align the ZnO needles, whereas its effect on TiO₂ and NiO was less appreciable, principally affecting the shape of their grain boundaries. The chemical compositions were analysed using X-ray spectroscopy (EDX), which confirmed the existence of an oxide layer. Structural information was obtained by means of X-ray diffraction (XRD) and was later checked using Raman spectroscopy. The oxide layers seemed to be crystalline and, although some non-stoichiometric phases appeared, the stoichiometric phases were predominant; these were wurtzite, rutile, and cubic for Zn, Ti, and Ni oxides, respectively. The photoluminescence technique was used to study the distribution of defects on the shell, and mainly visible bands (2–2.5 eV), attributed to oxygen vacancies, were present. The near-band edges of ZnO and TiO₂ were also observed around 3.2–3.3 eV. Full article

As heterogeneous catalysis is a practical method for activating Oxone, the immobilization of transition metals (e.g., Co, Fe) on carbonaceous supports is a promising platform. Thus, this study attempts to develop a carbon-supported metallic catalyst by growing Co/Fe on carbon foam (CF) via adopting melamine foam as a readily available template which could be transferred to nitrogen-doped CF with marcoporous structures. Specifically, a unique adornment of Co/Fe species on this CF is facilely fabricated through a complexation of Co/Fe with a plant extract, tannic acid, on melamine foam, followed by carbonization to produce nano-needle-like Co/Fe on N-doped CF, forming a magnetic CF (MCF). This resultant MCF exhibits a much higher surface area of 54.6 m²/g than CF (9.5 m²/g), and possesses a much larger specific capacitance of 9.7 F/g, than that of CF as 4.0 F/g. These superior features of MCF enable it to accelerate Oxone activation in order to degrade an emerging contaminant, bis(4-hydroxyphenyl)methanone (BHPM). Furthermore, MCF + Oxone exhibits a lower activation energy as 18.6 kJ/mol for BHPM elimination and retains its effectiveness in eliminating BHPM over multiple rounds. More importantly, the CF is also prepared and directly compared with the MCF to study the composition-structure-property relationship to provide valuable insights for further understanding of catalytic behaviors, surficial characteristics, and application of such a functional carbon material. Full article

In this study, we employed a chemical precipitation method to successfully synthesize nanoparticles of gallium-doped hydroxyapatite (Ga-HAp). The microstructure of Ga-HAp was precisely tailored by modulating the concentration of gallium ions. Our findings unequivocally demonstrate that gallium ions exert a pronounced inhibitory influence on the growth of HAp crystals, and this inhibitory potency exhibits a direct correlation with the concentration of gallium. Furthermore, gallium ions facilitate the metamorphosis of HAp nanoparticles, transitioning them from nanoneedles to nanosheets. It is worth noting, however, that gallium ions exhibit a limited capacity to substitute for calcium ions within the crystal lattice of HAp, with the maximum substitution rate capped at 4.85%. Additionally, gallium plays a pivotal role in constraining the release of ions from HAp, and this behavior remains consistent across samples with varying Ga doping concentrations. Our in vitro experiments confirm that Ga-doped HAp amplifies both the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells. Full article

Nano-needle boron-doped diamond (NNBDD) films increase their performance when used as electrodes in the determination of Pb²⁺. We develop a simple and economical route to produce NNBDD based on the investigation of the diamond growth mode and the ratio of diamond to non-diamond carbon without involving any templates. An enhancement in surface area is achievable for NNBDD film. The NNBDD electrodes are characterized through scanning electron microscopy, Raman spectroscopy, X-ray diffraction, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse anodic stripping voltammetry (DPASV). Furthermore, we use a finite-element numerical method to research the prospects of tip-enhanced electric fields for sensitive detection at low Pb²⁺ concentrations. The NNBDD exhibits significant advantages and great electrical conductivity and is applied to detect trace Pb²⁺ through DPASV. Under pre-deposition accumulation conditions, a wide linear range from 1 to 80 µgL⁻¹ is achieved. A superior detection limit of 0.32 µgL⁻¹ is achieved for Pb²⁺, which indicates great potential for the sensitive detection of heavy metal ions. Full article

Plant fibres are promising candidates to replace synthetic fibres in polymer matrix composites. However, there is still an important issue to overcome: the poor quality of adhesion at the fibre/matrix interface. Many surface treatments of plant fibres have been developed, most of them based on non-environmentally friendly processes. In this paper, a 100% natural treatment is proposed. Hemp yarns are immersed in tap water until the natural growth of limestone beads attached to their surface occurs. The morphology analysis reveals that these calcium carbonate crystals have a nanoneedle architecture, with hemp fibres acting as nucleators for these highly ordered coral-like structures. Tensile tests on ±45° woven hemp/epoxy composites show that the presence of CaCO₃ beads improves the adhesion quality of the fibre/matrix interface and, therefore, increases Young’s modulus value. Full article

The innate immune system is the first line of defense against external threats through the initiation and regulation of inflammation. Macrophage differentiation into functional phenotypes influences the fate of nanomaterials taken up by these immune cells. High-resolution electron microscopy was used to investigate the uptake, distribution, and biotransformation of nanoceria in human and murine M1 and M2 macrophages in unprecedented detail. We found that M1 and M2 macrophages internalize nanoceria differently. M1-type macrophages predominantly sequester nanoceria near the plasma membrane, whereas nanoceria are more uniformly distributed throughout M2 macrophage cytoplasm. In contrast, both macrophage phenotypes show identical nanoceria biotransformation to cerium phosphate nanoneedles and simultaneous nanoceria with ferritin co-precipitation within the cells. Ferritin biomineralization is a direct response to nanoparticle uptake inside both macrophage phenotypes. We also found that the same ferritin biomineralization mechanism occurs after the uptake of Ce-ions into polarized macrophages and into unpolarized human monocytes and murine RAW 264.7 cells. These findings emphasize the need for evaluating ferritin biomineralization in studies that involve the internalization of nano objects, ranging from particles to viruses to biomolecules, to gain greater mechanistic insights into the overall immune responses to nano objects. Full article

Microbial colonization on various surfaces is a serious problem. Biofilms from these microbes pose serious health and economic threats. In addition, the recent global pandemic has also attracted great interest in the latest techniques and technology for antimicrobial surface coatings. Incorporating antimicrobial nanocompounds into materials to prevent microbial adhesion or kill microorganisms has become an increasingly challenging strategy. Recently, many studies have been conducted on the preparation of nanomaterials with antimicrobial properties against diseases caused by pathogens. Despite tremendous efforts to produce antibacterial materials, there is little systematic research on antimicrobial coatings. In this article, we set out to provide a comprehensive overview of nanomaterials-based antimicrobial coatings that can be used to stop the spread of contamination to surfaces. Typically, surfaces can be simple deposits of nanomaterials, embedded nanomaterials, as well as nanotubes, nanowires, nanocolumns, nanofibers, nanoneedles, and bio-inspired structures. Full article