[en] Graphical abstract: - Highlights: • Uniform Ag nanoparticle films were synthesized by a modified photocatalytic method on TiO_2 films with Ag seeds for surface-enhanced Raman scattering. • This modified photocatalytic method combine the advantages of the spurting method (high nucleation density) and the traditional photocatalytic method (suitable particle size). • The Raman enhancement of as-prepared Ag NP films was calculated by finite-difference time-domain to validate the experiment data. - Abstract: Uniform Ag nanoparticle (NP) films were synthesized by a modified photocatalytic method on TiO_2 films with Ag seeds for surface-enhanced Raman scattering, which combine the advantages of the spurting method (high nucleation density) and the traditional photocatalytic method (suitable particle size). The Ag seeds were prepared by magnetron sputtering with different time, which would adjust the distribution and transfer of electrons on the surface of TiO_2 film in the process of photocatalytic reduction. The distribution and morphology of Ag NP films can be adjusted by the sputtering time and the UV irradiation time. The Raman enhancement of as-prepared Ag NP films was calculated by finite-difference time-domain to validate the experiment data. It is found that the Ag NP films synthesized on TiO_2 films with suitable pre-deposited Ag seeds exhibit a much higher Raman enhancement activity than the optimum Ag NP film synthesized directly on the TiO_2 film without Ag seeds.

[en] Herein, a scalable method is developed to fabricate carbon nanotube (CNT)/Fe₃O₄(a)C composites, in which the crystallization and morphology of the carbon shell on the surface of Fe₃O₄ nanoparticles can be controlled by manipulating the synthesis conditions of chemical vapor deposition technology. Owing to the synergic dissipation effect of the core-shell structure, as well as the excellent conductive loss induced by the CNT skeleton, the CNT/Fe₃O₄(a)C composite shows a minimum reflection loss of -50.1 dB at 9.7 GHz and an effective bandwidth of 4.6 GHz. This study provides new insight into preparing core-shell-structured microwave absorbers with excellent performance. (author)

[en] A micro/nanoscale strain sensor based on helical gold nanotube films (GNTFs) is proposed, which is prepared by magnetron sputtering using carbon nanocoils (CNCs) as templates. The gauge factor of the sensor reaches 5, while the stretch of it can achieve more than 10% owing to the helical geometries. The resistance increase of GNTFs with temperature decreasing from 300 to 4 K indicates a thermal activation tunneling model for electron transport. With thicknesses increasing from 16 to 32 nm, the GNTFs show a structural transition from discontinuous to quasi-continuous film. In this transition region, the conductive path of GNTFs increases rapidly, resulting in a rapid resistance decrease of CNC–GNTF composite structure. When a helical GNTF is stretched, the resistance is increased. The helical GNTFs in the transition region exhibit the highest response sensitivity, which owes to the special torsion-dominated strains of this helical structure to some extent. The unique helical morphology gives the sensor great stretchability and special electrical response. Choosing appropriate CNCs and GNTFs with suitable thickness, the helical GNTFs can be used as micro/nanostretchable strain sensors, stretchable electrodes or connects, resonators in micro/nanoelectromechanical system.

[en] Highlights: • Oxygen-doped porous carbon was derived from cost-effective biomass material, sodium alginate. • The carbonized aerogel shows 3D interconnected structure with large surface area. • Carbonization temperature and G/M ratio are controlled to adjust the electrochemical properties. • The obtained carbon shows excellent specific capacitance (426.6F/g at 1A/g) and cycling stability. • The results pave a road for the future implication in cost-effective and eco-friendly energy storage devices. -- Abstract: Three-dimensional porous scaffolds doped with the heteroatoms show excellent performances in energy conversion and storage. Herein, we report a green synthesis approach to construct the oxygen-doped porous carbon electrodes by carbonizing the oxygen-rich biomass material, sodium alginate. By precisely controlling the carbonization temperature and increasing the mole ratio of α-L-guluronic acid units/β-D-mannuronic acid units in sodium alginate, the morphology, oxygen content and electrical conductivity of the as-obtained carbonaceous electrode are well balanced. This electrode material delivers capacitance of up to 424.6 F g⁻¹ in 6 M potassium hydroxide (KOH) electrolyte at 1 A g⁻¹, and good cyclic stability with the capacitance retention of >90% after 20,000 charge-discharge cycles. Such excellent electrochemical performance can be attributed to both the unique hierarchical macro-/meso-/microporous structure and the presence of abundant oxygen-containing functional groups in the as-prepared carbonized sodium alginate aerogels. The capacitance of our oxygen-doped porous carbon electrodes is at least twice greater than those of other carbonaceous electrodes produced from biomass precursors reported in literatures. This work provides a facile, effective and environmental-friendly approach for the fabrication of high-performance heteroatom-doped carbon-based electrodes for supercapacitor applications.

[en] Highlights: • We have investigated laser irradiated microbubbles which can be generated at fixed point on surface of an individual carbon nanocoil (CNC) immerged in deionized water. • The microbubble can be operated easily and flexibly. • Based on classical heat and mass transfer theories, the bubble growth data is in good agreement with the simplified model. - Abstract: We have investigated the micro-bubbles generated by laser induction on an individual carbon nanocoil (CNC) immerged in deionized water. The photon energy of the incident focused laser beam is absorbed by CNC and converted to thermal energy, which efficiently vaporizes the surrounding water, and subsequently a micro-bubble is generated at the laser location. The dynamics behavior of bubble generation, including its nucleation, expansion and steady-state, has been studied experimentally and theoretically. We have derived equations to analyze the expansion process of a bubble based on classical heat and mass transfer theories. The conclusion is in good agreement with the experiment. CNC, which acts as a realistic micro-bubble generator, can be operated easily and flexibly

[en] In this paper, we discuss a model of sub-band in resistive switching nonvolatile memories with a structure of silver/aluminum oxide/p-type silicon (Ag/Al_xO_y/p-Si), in which the sub-band is formed by overlapping of wave functions of electron-occupied oxygen vacancies in Al_xO_y layer deposited by atomic layer deposition technology. The switching processes exhibit the characteristics of the bipolarity, discreteness, and no need of forming process, all of which are discussed deeply based on the model of sub-band. The relationships between the SET voltages and distribution of trap levels are analyzed qualitatively. The semiconductor-like behaviors of ON-state resistance affirm the sub-band transport mechanism instead of the metal filament mechanism

[en] Fiber-based flexible thermoelectric (TE) generators are highly desirable due to their capability to convert thermal energy into electricity and their potential applications in wearable electronics. High-performance poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/Tellurium (Te) composite TE fibers have been successfully developed via a continuous wet-spinning approach followed by sulphuric acid treatment. With a simple pre-modification to Te nanowires, the inorganic Te fillers form uniform distribution in PEDOT:PSS. At the optimal condition, the composite fibers exhibit a power factor of 233.5 µW m${}^{-<!--\; ???\; -->1}$ K${}^{-<!--\; ???\; -->2}$ and mechanical strength of 205 MPa, which are among the highest values reported so far for the PEDOT:PSS-based TE fibers. From the viewpoint of TE property enhancement mechanism, understanding the morphology and carrier transport behavior in the 1D organic/inorganic composite fibers remains still challenging. On basis of a series of PEDOT:PSS/Te composite fibers with varying Te fractions, orientations of both the inorganic and organic constituents are quantitatively evaluated. Their electrical conductivities and Seebeck coefficients are also analyzed with modified series-parallel models and energy filtering theory. This work may not only provide a universal approach to produce high-performance organic/inorganic composite TE fibers for various wearable applications, but also help to understand the morphology and charge transport between heterogeneous phases in a 1D composite. (© 2024 Wiley‐VCH GmbH)

[en] Highlights: • We report the facile fabrication of an Au nanostar (NS) monolayer by self-assembly at the water-oil interface. • The prepared Au NS monolayer provides abundant tips and a high density of small nanogaps. • Limit of detection of the Au NS monolayer is determined to be down to 4.2×10⁻¹² M for R6G. • Enhancement factor reaches 1.4 × 10⁶. • The Au NS monolayer can detect multiple molecules. Au Nanostar (NS) monolayer as a surface enhanced Raman scattering (SERS) substrate has been synthesized by self-assembly at a water-oil interface. It is confirmed from the experiment and simulation results that the Au NS monolayer includes lots of “hot spots” at or between the tips of the Au NSs, enhancing the local electromagnetic fields and giving rise to strong SERS signals sequentially. The limit of detection is determined to be down to 4.2 × 10⁻¹² M for rhodamine 6G. Furthermore, the Au NS monolayer can detect multiple molecules, including thiabendazole, methylene blue, 4-mercaptobenzoic acid, and p-amino thiophenol, indicating that the SERS substrate composed of Au NS monolayer has potential applications in analytical chemistry, food safety, and environmental safety.

[en] High fabrication cost, chemical instability, and complex immobilization of enzyme molecules are critical issues of enzyme-based glucose sensors. Designing state-of-the-art, binder-free, and non-enzymatic glucose sensing probes plays an imperative role to cope with the aforementioned issues. 3D carbonaceous nanomaterials coated with transition metal vanadates (TMVs) are a favorable biomimetic platform for glucose quantification. Peculiar hierarchical structure, enhanced conductivity, synergistic interaction, multiple oxidation states, and high catalytic activity would make such composite a potential contender for non-enzymatic glucose sensing. Herein, 3D helical-shaped carbon nanocoils (CNCs) are grown on nickel foam (NF) via chemical vapor deposition method to prepare a robust CNCs/NF scaffold. Then, a hydrothermal route is followed to grow interconnected free-standing Ni${}_3$V${}_2$O${}_8$ nanosheets (NSs) on CNCs/NF scaffold. This novel and binder-free Ni${}_3$V${}_2$O${}_8$ NSs/CNCs/NF hierarchical composite possesses superior electrochemical active area (ECSA) and exceptional electrochemical efficacy. Amperometric analysis exhibits extremely prompt detection time (0.1 s), elevated sensitivity (5214 µA mM${}^{-<!--\; ???\; -->1}$ cm${}^{-<!--\; ???\; -->2}$), and low detection limit (0.04 µM). Developed sensor demonstrates appreciable recoveries (93.3 to 103.3%) regarding glucose concentration in human serum. The appealing analytical results show that deployment of a 3D helical-shaped hierarchical smart scaffold can be an effective strategy for developing efficient and advanced non-enzymatic glucose sensors. (© 2023 Wiley-VCH GmbH)

[en] Highlights: • Direct in-situ hydrothermal growth of CoTe₂ NSs on porous and conductive 3D-Nickel foam scaffold. • Free-standing porous CoTe₂ NSs/NF architecture works as a binder-free electrode for non-enzymatic glucose sensing. • 3D CoTe₂ NSs/NF electrode offers ultra-prompt response time 0.1 s, boosting sensitivity 168000 μA mM⁻¹ cm⁻² and LOD 0.59 μM. • Remarkable anti-interference capability and favorable stability of CoTe₂ NSs array. • Developed NEGS also demonstratesan effective determination of glucose concentration in human blood serum. -- Abstract: The combination of transition-metals with chalcogens provide a platform for developing highly sensitive and stable electro-catalyst materials possessing excellent electrochemical features regarding glucose oxidation. The growth of porous cobalt telluride (CoTe₂) nanosheets (NSs) on a three-dimension (3D) nickel foam (NF) scaffold via anion-exchange transformation is achieved by employing low temperature scalable hydrothermal process. Being an active catalyst material for glucose detection, the CoTe₂ NSs/NF electrode demonstrates an ultra-prompt response time of 0.1 s, boosting sensitivity of 168000 μA mM⁻¹ cm⁻², low limit of detection of 0.59 μM along with excellent anti-interference ability and favorable stability. Besides, the effective electrochemical performance of sensing electrode is recognized with respect to the glucose detection in real human blood serum. Overall, this material guarantees free-standing 3D architecture, interconnected porous NSs morphology, large specific surface area, high conductivity, and appealing electro-catalytic activity. Therefore, the porous CoTe₂ NSs/NF binder-free electrode has a great application prospect as a promising biomimetic catalyst material for highly sensitive and efficient non-enzymatic glucose sensor.