Search Results (134)

The interest in macromolecular alkoxysilyl-functionalized hybrids (self-assembling or nanostructured), which could be used as precursors in biomimetic silica precipitation and for the synthesis of hollow spherical silica particles, is growing. Nevertheless, reports on all-organosilicon systems for bioinspired silica precipitation are scarce. Therefore, a new kind of polyalkoxysilane macromonomer–linear polysilsesquioxane (LPSQ) of ladder-like backbone, functionalized in side chains with trimethoxysilyl groups (LPSQ-R-Si(OMe)₃), was designed following this approach. It was obtained by photoinitiated thiol-ene addition of 3-mercaptopropyltrimethoxysilane to the vinyl-functionalized polysilsesquioxane precursor, carried out in situ in tetraethoxysilane (TEOS). The mixture of LPSQ-R-Si(OMe)₃ and TEOS (co-monomers) was used in a sol–gel process conducted under acidic conditions (0.5 M HCl/NaCl) in the presence of Pluronic^® F-127 triblock copolymer as a template. LPSQ-R-Si(OMe)₃ played a key role for the formation of microparticles of a spherical shape that were formed under the applied conditions, while their size (as low as 3–4 µm) was controlled by the stirring rate. The hybrid materials were hydrophobic and showed good thermal and oxidative stability. Introduction of zinc acetate (Zn(OAc)₂) as an additive in the sol–gel process influenced the pH of the reaction medium, which resulted in structural reinforcement of the hybrid microparticles owing to more effective condensation of silanol groups and a relative increase of the content of SiO₂. The proposed method shows directions in designing the properties of hybrid materials and can be translated to other silicon–organic polymers and oligomers that could be used to produce hollow silica particles. The established role of various factors (macromonomer structure, pH, and stirring rate) allows for the modulation of particle morphology. Full article

To address mass transport limitations in carbon nanofiber membrane electrodes for overall water splitting, a self-supporting nitrogen-doped hollow carbon nanofiber membrane embedded with Co/Co₂P heterojunctions (Co/Co₂P-NCNFs-H) was fabricated via continuous coaxial electrospinning. The architecture features uniform hollow channels (200–250 nm diameter, 30–50 nm wall thickness) and a high specific surface area (254 m² g⁻¹), as confirmed by SEM, TEM, and BET analysis. The Co/Co₂P heterojunction was uniformly dispersed on nitrogen-doped hollow carbon nanofibers through electrospinning, leverages interfacial electronic synergy to accelerate charge transfer and optimize the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Electrochemical tests demonstrated exceptional catalytic activity, achieving current densities of 100 mA cm⁻² at ultralow overpotentials of 405.6 mV (OER) and 247.9 mV (HER) in 1.0 M KOH—surpassing most reported transition metal catalysts for both half-reactions. Moreover, the electrode exhibited robust long-term stability, maintaining performance for nearly 20 h at 0.6 V (vs. Ag/AgCl) (OER) and over 250 h at −1.5 V (vs. Ag/AgCl) (HER), attributed to the mechanical integrity of the hollow architecture and strong metal–carbon interactions. This work demonstrates that integrating hollow nanostructures (enhanced mass transport) and heterojunction engineering (optimized electronic configurations) creates a scalable strategy for designing efficient bifunctional catalysts, offering significant promise for sustainable hydrogen production via water electrolysis. Full article

The rapid development of energy storage technologies has led to an increasing demand for high-performance electrode materials that can enhance both the energy density and the cycling stability of batteries. In this study, polypyrrole (PPy) nanorods with partial hollow features are utilized as a conductive and flexible framework for the in situ growth of VO₂ nanospheres via a simple hydrothermal method, forming a well-defined core–shell PPy/VO₂ nanocomposite. This hierarchical nanostructure combines the excellent electrical conductivity and mechanical flexibility of PPy with the high theoretical capacity of VO₂, creating a synergistic effect that significantly enhances the electrochemical performance. The well-integrated interface between PPy and VO₂ reduces interfacial resistance, promotes efficient electron and ion transport, and improves the overall energy conversion efficiency. Electrochemical testing reveals that the PPy/VO₂ nanocomposite delivers a high specific capacity of 413 mAh g⁻¹ at 100 mA g⁻¹ and retains 87.2% of its initial capacity after 1200 cycles, demonstrating exceptional rate capability and long-term cycling stability. This work provides a versatile strategy for designing high-performance cathode materials and highlights the promising potential of PPy/VO₂ nanocomposites for next-generation high-energy-density aqueous zinc-ion batteries. Full article

Recent advancements in photonics have intensified the performance requirements for optical systems and present significant challenges for optical coating technologies. Conventional interference coating systems often prove to be insufficient, especially in applications requiring large angles of light incidence or a wide wavelength range. Nanostructures, which consist of an air material mixture, offer promising alternatives. In this work, silica nanostructures are manufactured by the AR-plas2 method, in which first an organic layer is evaporated onto a substrate. This organic layer forms self-organizing nanostructures by a plasma etching step, which are subsequently coated with silica. Finally, the organic residues are removed by additional plasma etching and heat treatment steps, which results in hollow silica structures. The work examines the optical and functional properties of these structures designed for 355 nm to demonstrate their use as anti-reflective coatings for advanced optical systems. Full article

Developing sustainable and efficient electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing energy storage technologies. This study explored the dual role of phosphorus as a dopant in carbon matrices and a key component in nickel phosphides (Ni₂P and Ni₁₂P₅), synthesized using dopamine (PDA) and ammonium phosphate as eco-friendly precursors. The phase formation of nickel phosphides was found to be highly dependent on the P/PDA ratio (0.15, 0.3, 0.6, and 0.9), allowing for the selective synthesis of Ni₂P or Ni₁₂P₅. Operando Raman spectroscopy revealed that both phases undergo surface transformation into nickel (oxy)hydroxide species under OER conditions, yet Ni₂P-based catalysts demonstrated superior activity and long-term stability. This enhancement is attributed to efficient electron transfer at the dynamic Ni₂P/NiOOH interface. Additionally, hollow nanostructures formed at intermediate P/PDA ratios (≤0.3) via the Kirkendall effect and Ostwald ripening contributed to an increased specific surface area and micropore volume, further improving the catalytic performance. Electrochemical impedance spectroscopy confirmed reduced interfacial resistance and enhanced charge transport. These findings offer new insights into the rational design of high-performance electrocatalysts and propose a green, tunable synthesis approach for advanced energy conversion applications. Full article

Hollow flower-like multi-metallic nanocrystals have attracted significant research attention due to their exceptional catalytic properties, which stem from their high surface area-to-volume ratio and abundant active sites. Nevertheless, conventional synthesis methods for noble metal nanocrystals typically involve complex procedures or require harsh reaction conditions. In this work, we developed a facile and environmentally benign strategy for fabricating hollow flower-shaped trimetallic nanocrystals at ambient temperature. Our approach employs AgCl nanocubes, derived from AgNO₃ and HAuCl₄, as self-sacrificing templates. Through ascorbic acid-mediated reduction of metal precursors, we successfully synthesized three distinct types of hollow flower-like nanocrystals: AuAgCu, AuAgPt, and AuAgPd. Comprehensive characterization confirmed the well-defined morphology and precise composition control of the as-prepared nanocrystals. The catalytic performance was systematically evaluated through in situ UV–vis spectroscopy monitoring of 4-nitrophenylthiophenol reduction, revealing the following activity trend: AuAgCu > AuAgPt > AuAgPd. This study not only provides a versatile platform for constructing sophisticated multi-metallic nanostructures but also offers valuable insights into the structure–activity relationship of complex catalysts. Full article

This study investigated the morphological dependence of ZnO nanostructures, specifically nanotube- and nanorod-based electrodes, on their electrochemical performance for the detection of lead ions (Pb²⁺) in aqueous solutions. The results demonstrate that ZnO nanotubes exhibit significantly enhanced sensitivity compared to nanorods during CV measurements. During SWV measurements, the sensitivity (116.79 mA·mM⁻¹) and a lower limit of detection of 0.0437 μM were determined. The hollow, high-aspect-ratio structure of nanotubes provides a larger active surface area and facilitates better ion accessibility, resulting in superior electron transfer efficiency and catalytic activity. These results underscore the critical role of morphology in optimizing ZnO-based sensors. Analysis of real water samples from various natural reservoirs revealed no detectable lead, while lead was identified exclusively in artificially prepared samples containing water exposed to lead hunting shot. Over a 30-day period, the sensor retained over 95% of its initial performance when stored under vacuum conditions, demonstrating minimal signal degradation. Under ambient conditions, stability loss was attributed to moisture adsorption on the porous nanostructure. The sensor also displayed outstanding reproducibility, with current response variations across multiple probes remaining within 4%. The cost-effective and simple fabrication process of ZnO nanostructures further highlights their potential for scalable production, environmental monitoring, and integration into portable sensing devices. Full article

Background: Phytocarriers are advanced drug delivery systems that use biocompatible and biodegradable materials to enhance the efficacy, stability, and bioavailability of natural products. The sea buckthorn (Hippophae rhamnoides L.) berry extract is rich in essential fatty acids and antioxidants, including vitamin C, vitamin E, and anthocyanins, which contribute to its wide-ranging health benefits. In this study, we assessed the morphology, intracellular delivery, and anti-inflammatory effect of sodium cholate (NaC) and sodium deoxycholate (NaDC)-based phytocarriers loaded with ethanolic extract from sea buckthorn berries (sea buckthorn carrier nanostructures, further defined as phytocarriers). Methods: Negative and electron cryo-microscopy were used to analyze hollow and loaded nanocarriers. The cyto-compatibility of nanocarriers was assessed by endpoint (LDH and MTS) and real-time cell assays, on both human fibroblasts (HS27) and human normal monocytes (SC). The anti-inflammatory effect of hollow and loaded nanocarriers was tested by multiplexing. Results: The negative and electron cryo-microscopy analyses showed that NaC-based phytocarriers were spherical, whilst NaDC-based phytocarriers were predominantly polymorphic. Moreover, the NaDC-based phytocarriers frequently formed large lipid networks or “plaques”. Although 24 h cytotoxicity testing showed both types of nanocarriers are biocompatible with human fibroblasts and monocytes, based on a long-term real-time assay, NaDC delayed fibroblast proliferation. NaC sea buckthorn phytocarriers did not impair fibroblast proliferation in the long term and they were uptaken by cells, as shown by hyperspectral microscopy. NaC nanocarriers and NaC sea buckthorn phytocarriers induced an anti-inflammatory effect, lowering IL-8 cytokine production in normal human monocytes as soon as 4 h of treatment lapsed. Conclusions: NaC-derived phytocarriers loaded with sea buckthorn alcoholic extract are a cell-compatible delivery system with anti-inflammatory properties. Full article

In recent years, metal surface plasmon resonance sensors and dielectric guided-mode resonance sensors have attracted the attention of researchers. Metal sensors are sensitive to environmental disturbances but have high optical losses, while dielectric sensors have low losses but limited sensitivity. To overcome these limitations, hybrid resonance sensors that combine the advantages of metal and dielectric were proposed to achieve a high sensitivity and a high Q factor at the same time. In this paper, a hybrid hollow cylindrical tetramer array was designed, and the effects of the hole radius, external radius, height, period, incidence angle, and polarization angle of the hollow cylindrical tetramer array on the refractive index sensing properties were quantitatively analyzed using the finite difference time domain method. It is found that the position of the resonance peaks can be freely tuned in the visible and near-infrared regions, and a sensitivity of up to 542.8 nm/RIU can be achieved, with a Q factor of 1495.1 and a figure of merit of 1103.3 RIU⁻¹. The hybrid metal–dielectric nanostructured array provides a possibility for the realization of high-performance sensing devices. Full article

Pollution of freshwater by synthetic organic dyes is a major concern due to their high toxicity and mutagenicity. In this study, the degradation of Congo red (CR) and malachite green (MG) dyes was investigated using nanostructured Gd₂O₃. It was prepared using the coprecipitation method, using gadolinium nitrate and concentrated formic acid, with subsequent calcination at 600 °C. Its morphology corresponds to hollow porous microspheres with a size between 0.5 and 7.5 μm. The optical bandgap energy was determined by using the Tauc method, giving 4.8 eV. The degradation of the dyes was evaluated by UV-vis spectroscopy, which revealed that dissociative adsorption (in the dark) played a key role. It is explained by the cleavage and fragmentation of the organic molecules by hydroxyl radicals (^•OH), superoxide radicals (^•${\mathrm{O}}_2^{-}$) and other reactive oxygen species (ROS) produced on the surface of Gd₂O₃. For CR, the degradation percentage was ~56%, through dissociative adsorption, while UV light photocatalysis increased it to ~65%. For MG, these values were ~78% and ~91%, respectively. The difference in degradation percentages is explained in terms of the isoelectric point of solid (IEPS) of Gd₂O₃ and the electrical charge of the dyes. FTIR and XPS spectra provided evidence of the role of ROS in dye degradation. Full article

Fabricating photoanodes with a strong light-scattering effect can improve the photoconversion efficiency of dye-sensitized solar cells (DSSCs). In this work, a facile microwave hydrothermal process was developed to prepare Au@TiO₂ core–shell nanostructures, and then the Au core was removed by etching, resulting in hollow TiO₂. Morphological characterizations such as field emission scanning and transmission electron microscopy measurements have been used for the successful formation of core–shell and hollow TiO₂ nanostructures. Next, we attempted to deposit the different-sized hollow TiO₂-based microspheres simultaneously on the surface of small-sized TiO₂ nanoparticles-based compact film as light-scattering layers via electrophoretic deposition. The deposited hollow TiO₂ microspheres constitute bi- and tri-layers that not only improve the light-harvesting properties but also speed up the photogenerated charge transfer. Compared to commercial TiO₂ compact film (4.75%), the resulting bi-layer and tri-layered films-based DSSCs displayed power conversion efficiencies of 6.33% and 8.08%, respectively. It is revealed that the deposited bi- and tri-layered films can enhance the light absorption ability via multiple photon reflection. This work validates a novel and controllable strategy to develop light-scattering layers with increased light-harvesting properties for highly efficient dye-sensitized solar cells. Full article

Sodium hydroxide (NaOH) is increasingly drawing attention as a highly selective etchant for femtosecond laser-modified fused silica. Unprecedented etching contrasts between the irradiated and pristine areas have enabled the fabrication of hollow, high-aspect-ratio structures in the bulk of the material, overcoming the micrometer threshold as the minimum feature size. In this work, we systematically study the effect of NaOH solutions under different etching conditions (etchant concentration, temperature, and etching time) on the tracks created by tightly focused femtosecond laser pulses to assess the best practices for the fabrication of hollow nanostructures in bulk fused silica. Full article

Pure tin oxide (SnO₂) as a typical conductometric hydrogen sulfide (H₂S) gas-sensing material always suffers from limited sensitivity, elevated operation temperature, and poor selectivity. To overcome these hindrances, in this work, hollow CuO-SnO₂ nanotubes were successfully electrospun for room-temperature (25 °C) trace H₂S detection under blue light activation. Among all SnO₂-based candidates, a pure SnO₂ sensor showed no signal, even toward 10 ppm, while the 1% CuO-SnO₂ sensor achieved a limit of detection (LoD) value of 2.5 ppm, a large response of 4.7, and a short response/recovery time of 21/61 s toward 10 ppm H₂S, as well as nice repeatability, long-term stability, and selectivity. This excellent performance could be ascribed to the one-dimensional (1D) hollow nanostructure, abundant p-n heterojunctions, and the photoelectric effect of the CuO-SnO₂ nanotubes. The proposed design strategies cater to the demanding requirements of high sensitivity and low power consumption in future application scenarios such as Internet of Things and smart optoelectronic systems. Full article

Anisotropic plasmonic nanoparticles usually generate SERS enhancement factors that are significantly larger than those generated by spherical plasmonic nanostructures, so the former are usually preferred as substrates for SERS measurements. Gold nanorods are one of the most commonly used anisotropic nanomaterials for SERS experiments. Unfortunately, even a slight contamination of the surfactant used in the process of the synthesis of gold nanorods has a significant impact on the geometry of the resulting nanostructures. In this work, using easily formed silver nanorods as templates, hollow AuAg nanorods are formed by means of a silver–gold galvanic exchange reaction (in this process, nanostructures with a cavity inside form because one gold atom replaces three silver atoms). Hollow AuAg nanorods are highly active during SERS measurements—for shorter wavelengths of the excitation radiation, they display greater SERS activity than Au nanorods. To our knowledge, this is the first example of the use of hollow plasmonic nanorods for SERS measurements. Elemental mapping of the rods showed that the silver, some of which remained after the galvanic replacement, is mainly located close to the internal cavity that was formed, whereas the gold is mainly located at the outermost regions of the nanostructure. This explains the high chemical stability of these nanostructures. Full article

The utilization of sheet structure composites as a viable conductive filler has been implemented in polymer-based electromagnetic shielding materials. However, the development of an innovative sheet structure to enhance electromagnetic shielding performance remains a significant challenge. Herein, we propose a novel design incorporating silver-modified nanosheet self-assembled hollow spheres to optimize their performance. The unique microporous structure of the hollow composite, combined with the self-assembled surface nanosheets, facilitates multiple reflections of electromagnetic waves, thereby enhancing the dissipation of electromagnetic energy. The contribution of absorbing and reflecting electromagnetic waves in hollow nanostructures could be attributed to both the inner and outer surfaces. When multiple reflection attenuation is implemented, the self-assembled stack structure of nanosheets outside the composite material significantly enhances the occurrence of multiple reflections, thereby effectively improving its shielding performance. The structure also facilitates multiple reflections of incoming electromagnetic waves at the internal and external interfaces of the material, thereby enhancing the shielding efficiency. Simultaneously, the incorporation of silver particles can enhance conductivity and further augment the shielding properties. Finally, the optimized Ag/NiSi-Ni nanocomposites can demonstrate superior initial permeability (2.1 × 10⁻⁶ H m⁻¹), saturation magnetization (13.2 emu g⁻¹), and conductivity (1.2 × 10⁻³ Ω•m). This work could offer insights for structural design of conductive fillers with improved electromagnetic shielding performance. Full article