Search Results (30)

The expansion of the Internet of Things (IoT) has rendered wireless passive, highly stable, and room-temperature gas sensors indispensable for sensor applications. In this work, a room-temperature surface acoustic wave (SAW) H₂S sensor based on a thin film of nano-mesh woven with Bi₂S₃ nanoribbons was successfully designed and prepared. The impact of varying inorganic salts solution ligand substitution of long-chain organic ligands of Bi₂S₃ films on performance was assessed. Notably, the responses of the sensors following ligand substitution exhibited improvement to varying degrees. In particular, the Cu(NO₃)₂-treated sensor to 10 ppm H₂S was 203% of that of the untreated sensor. Furthermore, the impact of visible light activation on sensor performance was assessed. The results show the sensor has a high sensitivity to H₂S molecules under yellow light activation at room temperature, with excellent selectivity, fast response speed and low detection limit. The sensor exhibited a response to 10 ppm H₂S under yellow light activation that was approximately equal ~ two times greater than the response observed in a dark environment. This work provides a novel approach to enhance the performance of room-temperature SAW H₂S sensors. Full article

Advanced oxidation catalyzed by metal oxides is a promising approach for degrading organic pollutants in wastewater. A critical strategy to enhance the performance of these catalysts is optimizing the dispersion of their active components through innovative synthesis methods. In this study, we report a one-pot synthesis of g-C₃N₄ nanomeshes supported with highly dispersed VO₂ catalysts (V-g-C₃N₄) for the advanced oxidation of methylene blue (MB). The characterization results reveal that the involvement of VCl₃ in the pyrolysis of melamine facilitates the formation of g-C₃N₄ nanomeshes with abundant amino groups (NH/NH₂). The strong interaction between vanadia species and amino groups prevents VO₂ particles from agglomerating, resulting in a significantly higher vanadia dispersion than V-g-C₃N₄-im synthesized via the traditional impregnation method. V-g-C₃N₄ exhibits a sophisticated microstructure and surface structure, which leads to a rate constant 2.3-fold higher than V-g-C₃N₄-im in the catalytic degradation of methylene blue using H₂O₂ as the oxidant. X-ray photoelectron spectroscopy, trapping experiments, and electron paramagnetic resonance measurements reveal that the rapid adsorption and fast diffusion of MB over g-C₃N₄ nanomeshes, together with the efficient H₂O₂ activation into ·OH radicals via the V⁴⁺/V⁵⁺ redox cycle, synergistically contribute to the superior MB removal efficiency of V-g-C₃N₄. Moreover, V-g-C₃N₄ demonstrates no significant decrease in activity even after the fourth cycle, indicating its excellent stability during the pollutant removal process. Full article

Ultraviolet (UV) photodetectors (PDs) are characterized by wide wavelength selectivity and strong anti-interference capability. The focus of research is not only limited to the adjustment of the structure composition, but it also delves deeper into its working mechanism and performance optimization. In this study, a heterojunction self-powered photodetector with a unique honeycomb structure was successfully constructed by combining the advantages of two semiconductor materials, zinc oxide (ZnO) and nickel oxide (NiO), using magnetron sputtering and hydrothermal synthesis. The detector has high responsivity, high detectivity and favorable spectral selectivity under UV irradiation. The nearly 10-fold increase in responsivity and detectivity of the detector with the introduction of the honeycomb structure under zero-bias conditions is attributed to the macroporous structure of the ZnO honeycomb nano-mesh, which increases the surface active sites and facilitates the enhancement of light trapping. This study provides significant value to the field of UV detection by improving detector performance through structural optimization. Full article

In this paper, we investigate various graphene monolayer nanomesh structures (diodes) formed only by nanoholes, with a diameter of just 20 nm and etched from the graphene layer in different shapes (such as rhombus, bow tie, rectangle, trapezoid, and triangle), and their electrical properties targeting electromagnetic energy harvesting applications. In this respect, the main parameters characterizing any nonlinear device for energy harvesting are extracted from tens of measurements performed on a single chip containing the fabricated diodes. The best nano-perforated graphene structure is the triangle nanomesh structure, which exhibits remarkable performance in terms of its characteristic parameters, e.g., a 420 Ω differential resistance for optimal impedance matching to an antenna, a high responsivity greater than 10³ V/W, and a low noise equivalent power of 847 pW/√Hz at 0 V. Full article

Touch serves as an important medium for human–environment interaction. The piezoresistive tactile sensor has attracted much attention due to its convenient technology, simple principle, and convenient signal acquisition and analysis. In this paper, conductive beads-on-string polyvinyl alcohol (PVA)/polyaniline doped with dodecyl benzene sulfonic acid (PANI-DBSA) nanofibers were fabricated via the electrospinning technique. Due to the special nanostructure of PVA-coated PANI-DBSA, the tactile sensor presented a wide measuring range of 12 Pa–121 kPa and appreciable sensitivity of 8.576 kPa⁻¹ at 12 Pa~484 Pa. In addition, the response time and recovery time of the sensor were approximately 500 ms, demonstrating promising prospects in the field of tactile sensing for active upper limb prostheses. Full article

A two-dimensional porous silica nanomesh (VMT-SiO₂) was used as a carrier to prepare MgO-CuO-based catalysts and tested for one-step ethanol conversion to 1,3-butadiene. The effects of catalyst composition and different calcination temperatures on the reaction performances of the catalysts were mainly investigated. Combining various characterization techniques, such as HRTEM, XRD, FT-IR, and TPD, it was found that the dispersion state of MgO and CuO on the catalyst surface was related to the calcination temperature, which further induced changes in the acid–base properties. A small number of acidic centers and a proper proportion of medium–strong alkaline centers maintained a subtle balance, affecting catalytic performance. A lower total acid/base ratio is more conducive to ethanol conversion and 1,3-butadiene formation. At the same time, the synergistic effect of CuO and MgO promotes the transformation of the intermediate acetaldehyde product, which is the key to ensuring the subsequent aldol condensation and then 1,3-butadiene formation. Among the investigated samples, the CuO/MgO-VMT-SiO₂ catalyst calcined at 500 °C exhibited the best catalytic performance, with an impressive ethanol conversion of 47.8% and 1,3-butadiene formation (42.6% selectivity and a space-time yield of 182.0 g_C4H6·kg_cat⁻¹·h⁻¹). Full article

We demonstrate two distinct experimental processes involving the large-area growth of ordered and disordered silicon nanowire arrays (SiNWs) on a p-type silicon substrate using the metal-assisted chemical etching method. The two processes are based on the etching of monocrystalline silicon wafers by randomly distributed Ag films and ultra-thin Au films with ordered nano-mesh arrays, respectively, wherein the growth of SiNWs is implemented using a specific proportion of a HF-containing solution at room temperature. In this study, the microstructural change mechanisms for the two morphologically different arrays before and after annealing were investigated using Raman spectra. The effects of various mechanisms on the observed Raman scattering peak’s deviation from symmetry, redshift and broadening were analyzed. The evolution of the unstable amorphous structures of nanoscale materials during the high-temperature annealing process was observed via high-resolution scanning electron microscope (SEM) observations. The scattering peak parameters determined from the Raman spectra led to conclusions concerning the various mechanisms by which high-temperature annealing influences the microstructures of the two morphologically different SiNWs fabricated on the p-type silicon substrate. Therefore, the deviation of SiNWs from the monocrystalline silicon scattering peak at 520.05 cm⁻¹ when changing the diameter of the nanowire columns was calculated to further analyze the effect of thermal annealing on Raman characteristics. Full article

Photocatalytic technology based on silver phosphate (Ag₃PO₄) has excellent potential in removing antibiotic pollutants, but the low separation rate of photogenerated hole-electron pairs restricts the application of the photocatalyst. In this study, it was found that the combination of nitrogen-doped carbon (NDC) with carbon defects and Ag₃PO₄ can significantly enhance the photocatalytic ability of Ag₃PO₄. After it was exposed to visible light for 5 min, the photocatalytic degradation efficiency of oxytetracycline (OTC) by the composite photocatalyst Ag₃PO₄@NDC could reach 100%. In addition, the structure of NDC, Ag₃PO_4, and Ag₃PO₄@NDC was systematically characterized by SEM, TEM, XRD, Raman, and EPR. The XPS results revealed intense interface interaction between Ag₃PO₄ and NDC, and electrons would transfer from Ag₃PO₄ to the NDC surface. A possible mechanism for enhancing the photocatalytic reaction of the Ag₃PO₄@NDC composite catalyst was proposed. This study provides a highly efficient visible light catalytic material, which can be a valuable reference for designing and developing a new highly efficient visible light catalyst. Full article

The physicochemical nature of the amino group NH₂’s landing on the basal plane of the graphene and on the edge atoms of the graphene nanomesh was revealed. The mechanism of covalent binding between the NH₂ groups and the carbon atoms of the graphene and the GNM was discovered in silico by the SCC DFTB method. The maximum amount ratio of the amino groups to carbon atoms equaled 4.8% for GNM and 4.6% for the basal plane. The established values of the concentration and the trend of change in the work function of electrons are experimentally confirmed. Full article

As a promising topological insulator, two-dimensional (2D) bismuth selenide (Bi₂Se₃) attracts extensive research interest. Controllable surface doping of layered Bi₂Se₃ becomes a crucial issue for the relevant applications. Here, we propose an efficient method for the chemical thinning and surface doping of layered Bi₂Se₃, forming Se/Bi₂Se₃ heterostructures with tunable thickness ranging from a few nanometers to hundreds of nanometers. The thickness can be regulated by varying the reaction time and large-size few-layer Bi₂Se₃ sheets can be obtained. Different from previous liquid-exfoliation methods that require complex reaction process, in-situ and thickness-controllable exfoliation of large-size layered Bi₂Se₃ can be realized via the developed method. Additionally, the formation of Se nanomeshes coated on the Bi₂Se₃ sheets remarkably enhance the intensity of Raman vibration peaks, indicating that this method can be used for surface-enhanced Raman scattering. The proposed chemical thinning and surface-doping method is expected to be extended to other bulk-layered materials for high-efficient preparation of 2D heterostructures. Full article

Terahertz (THz) electromagnetic waves are attractive for use in nondestructive and biocompatible sensing applications. Thermal sensors are widely used for THz detection owing to the small photon energies of THz radiation, where this requires materials with low thermal conductivity and a small heat capacity to ensure the sensitive and fast operation of the sensors. In this study, we investigated the thermal and optical properties of porous nanomesh structures for sensitive THz bolometric detection. Nanometer (nm)-scale hole array structures were formed on gallium arsenide (GaAs) microelectromechanical system (MEMS) beams to improve their thermal properties. The thermal conductance of the porous MEMS beams was obtained by measuring their thermal bandwidths; it was found to decrease by as much as ~90% when the porosity (P) of the porous nanostructure was increased to ~0.69. We also measured the THz absorptance of the porous hole array structure. The results show that although the porous nanostructure has a much smaller area than the bulk material, it maintained a high coefficient of THz absorptance because the featured size was much smaller than the THz wavelength. The measured absorptance agreed well with that calculated by using the Drude model. These results demonstrate that the porous nanomesh structure is promising for developing highly sensitive THz thermal sensors. Full article

In order to improve the photocatalytic activity of TiO₂, we successfully loaded nano-CuO on the TiO₂ nanomeshes as CuO-TiO₂ nanocomposites through a facile electrodeposition method. The optimized calcined temperature after Cu electrodeposition is confirmed as 450 °C, which could furthest assist the crystallization of anatase TiO₂ and guarantee the high photocatalytic activity of CuO-TiO₂ nanocomposites. Comparing with pure TiO₂ nanomeshes, CuO-TiO₂ nanocomposites showed better degradability of methylene blue, and the degradation efficiency reached to 35% after 120 min irradiation. Additionally, CuO-TiO₂ nanocomposites exhibit much stronger absorption intensity within the visible light scope, more than two times than that of pure TiO₂ nanomeshes, which indicates that the loading of nano-CuO could promote photocatalytic efficiency by the strong visible light absorption. Additionally, CuO-TiO₂ nanocomposites show faster photocurrent response and lower charge transfer resistance than that of pure TiO₂ nanomeshes, which implies that the recombination rate of photogenerated electron-hole pairs was reduced after nano-CuO loading. Full article

Graphene nanomesh (GNM) is one of the most intensively studied materials today. Chemical activity of atoms near GNM’s nanoholes provides favorable adsorption of different atoms and molecules, besides that, GNM is a prospect material for growing carbon nanotubes (CNTs) on its surface. This study calculates the dependence of CNT’s growing parameters on the geometrical form of a nanohole. It was determined by the original methodic that the CNT’s growing from circle nanoholes was the most energetically favorable. Another attractive property of GNM is a tunable gap in its band structure that depends on GNM’s topology. It is found by quantum chemical methods that the passivation of dangling bonds near the hole of hydrogen atoms decreases the conductance of the structure by 2–3.5 times. Controlling the GNM’s conductance may be an important tool for its application in nanoelectronics. Full article

Nanoarchitectonics of two-dimensional materials from zero-dimensional fullerenes is mainly introduced in this short review. Fullerenes are simple objects with mono-elemental (carbon) composition and zero-dimensional structure. However, fullerenes and their derivatives can create various types of two-dimensional materials. The exemplified approaches demonstrated fabrications of various two-dimensional materials including size-tunable hexagonal fullerene nanosheet, two-dimensional fullerene nano-mesh, van der Waals two-dimensional fullerene solid, fullerene/ferrocene hybrid hexagonal nanosheet, fullerene/cobalt porphyrin hybrid nanosheet, two-dimensional fullerene array in the supramolecular template, two-dimensional van der Waals supramolecular framework, supramolecular fullerene liquid crystal, frustrated layered self-assembly from two-dimensional nanosheet, and hierarchical zero-to-one-to-two dimensional fullerene assembly for cell culture. Full article

Junction networks made of longitudinally connected metal oxide nanowires (MOx NWs) have been widely utilized in resistive-type gas sensors because the potential barrier at the NW junctions leads to improved gas sensing performances. However, conventional MOx–NW-based gas sensors exhibit limited gas access to the sensing sites and reduced utilization of the entire NW surfaces because the NW networks are grown on the substrate. This study presents a novel gas sensor platform facilitating the formation of ZnO NW junction networks in a suspended architecture by growing ZnO NWs radially on a suspended carbon mesh backbone consisting of sub-micrometer-sized wires. NW networks were densely formed in the lateral and longitudinal directions of the ZnO NWs, forming additional longitudinally connected junctions in the voids of the carbon mesh. Therefore, target gases could efficiently access the sensing sites, including the junctions and the entire surface of the ZnO NWs. Thus, the present sensor, based on a suspended network of longitudinally connected NW junctions, exhibited enhanced gas response, sensitivity, and lower limit of detection compared to sensors consisting of only laterally connected NWs. In addition, complete sensor structures consisting of a suspended carbon mesh backbone and ZnO NWs could be prepared using only batch fabrication processes such as carbon microelectromechanical systems and hydrothermal synthesis, allowing cost-effective sensor fabrication. Full article