•Three-dimensional graphene foam was synthesized by plasma-enhanced CVD.•The graphene foam exhibited a high electrical conductivity of 125S/cm.•The graphene foam showed a large surface area of ...625.4cm2/g.•The prepared graphene foam/epoxy composites showed a high conductivity.•The derived graphene oxide foam showed an excellent absorption capability.
A three-dimensional (3D), free-standing graphene foam was prepared by plasma-enhanced chemical vapor deposition on nickel-foam. The prepared graphene foam was found to consist of few-layered vertically-aligned graphene sheets with highly graphite structure. Owing to the 3D interconnected porous nanostructures, the graphene foam exhibited a high electrical conductivity of 125S/cm and a large surface area of 625.4cm2/g. For practical application, we prepared the graphene foam/epoxy composites showing a maximum conductivity of 196S/m at 2.5vol.% filler loading, and a rather low percolation threshold of 0.18vol.%. Furthermore, the derived graphene oxide foam exhibited an excellent absorption capability (177.6mg/g for As(V), 399.3mg/g for Pb(II)) and recyclability (above 90% removal efficiency after five cycles) for the removal of heavy metal ions. The present study reveals that the multifunctional graphene foam may broaden the graphene-based materials for the applications in electrically conductive composites and environmental cleanup.
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•Sulfur-doped graphene (SG) was synthesized by a rapid and efficient MAS method.•MAS process involved simultaneous S-doping and GO reduction.•SG showed a high S-doping level and a ...sole thiophene-S bonding configuration.•SG outperformed undoped graphene in electrocatalytic reduction of H2O2.•SG may be a promising electrode material for electrochemical sensor applications.
Heteroatom doping is an effective way to modulate the electronic structure and properties of graphene. Despite a growing interest in sulfur (S)-doped graphene (SG), synthesis of high-quality SG at low cost remains a great challenge. In this study, we developed a rapid, efficient and cost-effective microwave-assisted solvothermal (MAS) method for the preparation of SG. It was found that a short MAS time of 6min could generate few-layer SG (0.5μm in lateral size) having effective oxygen reduction, high level of S-doping, sole thiophene-S bonding configuration, and high electrical conductivity. Furthermore, the resulting SG could serve as an effective electrocatalyst for H2O2 reduction, showing improved electrocatalytic activity over its undoped counterpart and good sensing performances for highly sensitive and selective detection of H2O2, indicating that SG may be a promising candidate for electrochemical sensor applications.
•Ni-rGO hybrids were synthesized by a microwave-assisted method.•NaBH4 was used as a reducing agent to fabricate Ni-rGO hybrids.•Ni-rGO was used as catalyst for the reduction of p-nitrophenol.•Ni-rGO ...showed higher catalytic ability than pure Ni nanoparticles.•Ni-rGO showed good recyclability and stability.
A facile one-pot method was developed to synthesize magnetic nickel nanoparticles (Ni NPs) decorated on reduced graphene oxide (rGO) with NaHB4 as a reductant under microwave irradiation. The morphologies and structures of the Ni-rGO hybrids were investigated by electron microscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy and magnetic measurements. The results showed that Ni-rGO hybrids composed of the well-dispersed Ni NPs with an average diameter of 12nm were successfully prepared. To demonstrate one potential application, the catalytic ability of Ni-rGO was evaluated and it was found that Ni-rGO showed much enhanced catalytic ability, good recyclability and stability toward the catalytic reduction of p-nitrophenol to p-aminophenol. The excellent catalytic activity of Ni-rGO hybrids was due possibly to the synergistic effect of Ni NPs and rGO, including the uniform distribution of Ni NPs onto rGO, enhanced electrons separation and transport, as well as the fast adsorption of p-nitrophenol by rGO.
ZnWO4:Eu3+ and ZnWO4:Eu3+/Li+ phosphors have been synthesized successfully by a microwave-assist hydrothermal process. The phase, morphology and luminescent properties are investigated carefully. The ...XRD and FTIR results indicate that ZnWO4:Eu3+ and ZnWO4:Eu3+/Li+ phosphors have the monoclinic phase. The SEM images indicate that ZnWO4:Eu3+ and ZnWO4:Eu3+/Li+ phosphors are cubes with average particle size about 1 μm. Under the excitation at 395 nm, ZnWO4:Eu3+ and ZnWO4:Eu3+/Li+ phosphors show emission bands originating from the 5D0 → 7Fj (j = 0, 1, 2 and 3) transitions of Eu3+ ions. The Li+ ion acts as charge compensator and results in the enhancement of emission intensity.
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•Synthesis of ZnWO4:Eu3+ and ZnWO4:Eu3+/Li+ cubes with particle size about 1 μm.•Emission bands originating from 5D0 → 7Fj transitions of Eu3+ for phosphors•The low symmetry site for Eu3+ in ZnWO4 host.•Enhancement of luminescent properties by codoping Li+.
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•N, S dual-doped graphene (NS-G) was applied for glucose sensing.•The synergetic effect of N and S atoms improved the electrocatalytic properties.•NS-G provided more active sites for ...oxygen absorption and glucose oxidation.•NS-G outperformed the single-doped N-G for glucose sensing.
This work demonstrated the potential application of the N, S dual-doped graphene (NS-G) as a novel glucose oxidase (GOD) platform for glucose sensing. The NS-G was prepared by a simple two-step solvothermal method using urea as the N precursor and benzyl disulfide as the S precursor. The morphology and structure of as-prepared NS-G were characterized, and its electrochemical properties were examined. In comparison with the single N-doped graphene (N-G) based sensor, the dual-doped NS-G modified sensor showed significantly improved electrochemical sensing performances for glucose detection due to the synergistic effect of the coupling interactions between N and S heteroatoms that were responsible for the superior electrocatalytic properties. This study suggested that dual-doped graphene with two heteroatoms could be an effective way to greatly improve the electrochemical sensing performances of graphene-based GOD glucose biosensor.
•The successful co-doping of Er2+ and Yb3+ ions in BiPO4.•The phase change of BiPO4:Er3+, Yb3+ with the extension of aging time.•The morphology control of BiPO4:Er3+, Yb3+ by varying aging time.•The ...highest UC emission intensity of BiPO4:Er3+, Yb3+ with monoclinic phase.
BiPO4:Er3+, Yb3+ phosphors were synthesized by the solvothermal process. The phase transformation, morphology, and UC luminescent property were characterized by different analytical techniques. The aging time has obvious influence on the phase, morphology, and luminescence of the samples. With the extension of aging time, the phase of BiPO4:Er3+, Yb3+ phosphors changes from hexagon to monocline. The morphology changes from nanorods through nanorugbies to microoctahedra. Under the excitation at 980nm, BiPO4:Er3+, Yb3+ phosphors show green and red UC emissions, which originate from the (2H11/2, 4S3/2)→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ ions. The green and red UC emission intensities increase gradually with the increase of pumping power. On the basis of the luminescent properties, one can conclude that the two-photon process is involved in green and red UC emissions.
Sr sub(3)Bi(PO sub(4)) sub(3):Eu super(2+), Sr sub(3)Bi(PO sub(4)) sub(3):Mn super(2+), and Sr sub(3)Bi(PO sub(4)) sub(3):Eu super(2+), Mn super(2+) phosphors were synthesized by solid state ...reaction. The structure and luminescent characteristics were investigated by X-ray powder diffraction and fluorescent spectrophotometer. All samples have the structural type of eulytine. The excitation and emission spectra of Sr sub(3)Bi(PO sub(4)) sub(3):0.01Eu super(2+) sample show characteristic bands of Eu super(2+) ions. Also, the excitation and emission spectra of Sr sub(3)Bi(PO sub(4)) sub(3):0.06Mn super(2+) sample show characteristic bands of Mn super(2+) ions. The emission color of Sr sub(3)Bi(PO sub(4)) sub(3):Eu super(2+), Mn super(2+) sample could be tuned through tuning the co-dopant concentration of Mn super(2+) ions. The decay times for the Eu super(2+) ions decrease with the increase of Mn super(2+) dopant concentration, but the energy transfer efficiency increases with the increase of Mn super(2+) dopant concentration. On the basis of the luminescent spectra and fluorescence decay curves, we confirm that the energy transfer process from the Eu super(2+) to Mn super(2+) ions takes place in the co-doped Sr sub(3)Bi(PO sub(4)) sub(3) phosphor. Sr sub(3)Bi(PO sub(4)) sub(3):Eu super(2+), Mn super(2+) sample shows the good thermostability. The emission intensity of the sample at 400 K is about 60% of the value at 300 K. These results show Sr sub(3)Bi(PO sub(4)) sub(3):Eu super(2+), Mn super(2+) phosphors could be anticipated for UV-pumped white-light-emitting diodes.
•The successful co-doping of Eu2+ and Mn2+ ions in Sr3Bi(PO4)3.•The tunable emission color of Sr3Bi(PO4)3:Eu2+, Mn2+ phosphors.•Efficient energy transfer from Eu2+ to Mn2+ ions in Sr3Bi(PO4)3.•Good ...thermostability of synthesized Sr3Bi(PO4)3:Eu2+, Mn2+ phosphors.
Sr3Bi(PO4)3:Eu2+, Sr3Bi(PO4)3:Mn2+, and Sr3Bi(PO4)3:Eu2+, Mn2+ phosphors were synthesized by solid state reaction. The structure and luminescent characteristics were investigated by X-ray powder diffraction and fluorescent spectrophotometer. All samples have the structural type of eulytine. The excitation and emission spectra of Sr3Bi(PO4)3:0.01Eu2+ sample show characteristic bands of Eu2+ ions. Also, the excitation and emission spectra of Sr3Bi(PO4)3:0.06Mn2+ sample show characteristic bands of Mn2+ ions. The emission color of Sr3Bi(PO4)3:Eu2+, Mn2+ sample could be tuned through tuning the co-dopant concentration of Mn2+ ions. The decay times for the Eu2+ ions decrease with the increase of Mn2+ dopant concentration, but the energy transfer efficiency increases with the increase of Mn2+ dopant concentration. On the basis of the luminescent spectra and fluorescence decay curves, we confirm that the energy transfer process from the Eu2+ to Mn2+ ions takes place in the co-doped Sr3Bi(PO4)3 phosphor. Sr3Bi(PO4)3:Eu2+, Mn2+ sample shows the good thermostability. The emission intensity of the sample at 400K is about 60% of the value at 300K. These results show Sr3Bi(PO4)3:Eu2+, Mn2+ phosphors could be anticipated for UV-pumped white-light-emitting diodes.
Using fuzzy logic rules, a self-tuning structure for the self-tuning level of a human simulated intelligent controller (HSIC) has been designed. This structure has fuzzy self-tuning abilities in the ...swing-up control of a cart-double pendulum system. It efficiently accomplishes the online self-tuning of the control parameters of a HSIC with hierarchical and multi-mode control structure. The computer simulation and real-time experiments of the swing-up control of a cart-double pendulum system show that the online fuzzy self-tuning of the control parameters markedly enhances the robustness and adaptability of the HSIC.
Vision Transformers (ViTs) have achieved impressive results in large-scale image classification. However, when training from scratch on small datasets, there is still a significant performance gap ...between ViTs and Convolutional Neural Networks (CNNs), which is attributed to the lack of inductive bias. To address this issue, we propose a Graph-based Vision Transformer (GvT) that utilizes graph convolutional projection and graph-pooling. In each block, queries and keys are calculated through graph convolutional projection based on the spatial adjacency matrix, while dot-product attention is used in another graph convolution to generate values. When using more attention heads, the queries and keys become lower-dimensional, making their dot product an uninformative matching function. To overcome this low-rank bottleneck in attention heads, we employ talking-heads technology based on bilinear pooled features and sparse selection of attention tensors. This allows interaction among filtered attention scores and enables each attention mechanism to depend on all queries and keys. Additionally, we apply graph-pooling between two intermediate blocks to reduce the number of tokens and aggregate semantic information more effectively. Our experimental results show that GvT produces comparable or superior outcomes to deep convolutional networks and surpasses vision transformers without pre-training on large datasets. The code for our proposed model is publicly available on the website.
