Nano

Willow catkins as a kind of seasonal biomass are harmful to human health in terms of causing respiratory ailments and skin anaphylaxis every spring. To explore the high-value utilization of willow catkins, in this study, we attempt to develop a kind of tin-based anode materials with willow catkin derived carbon (WCC) as the matrix. A designed solvent-thermal method involving thiourea as stabilizer and acetone–H₂O mixture as solvent has been employed to fabricate SnO₂–WCC composites, which exhibit uniform deposition of well-dispersed SnO₂ nanoparticles on the surface of WCC. As an anode material for lithium-ion batteries (LIBs), the SnO₂–WCC composite delivered a stable discharge capacity of 565mAh g${}^{-1}$ at 100mA g${}^{-1}$ after 70 cycles and a good rate capability of 349mAh g${}^{-1}$ at 1000mA g${}^{-1}$. The high dispersity of SnO₂ nanoparticles and high conductivity of WCC are both believed to contribute to the excellent electrochemical performances. These results suggest the potential of willow catkins derived carbonaceous materials applied in anode materials of LIBs and shed light on the creation of advanced carbon materials from other biomass materials towards energy storage applications.

Many aspects in the chemical vapor deposition (CVD) growth of graphene remain unclear such as its behavior near the catalyst grain boundaries. Here we investigate the CVD growth mechanism of graphene across the Cu grain boundaries using unidirectional aligned graphene domains, which simplifies the analysis of both graphene and Cu to a large extent. We found that for a graphene domain grown across the Cu grain boundary, the domain orientation is determined by the Cu grain where the domain nucleation center is located, and the Cu grain boundary will not change the growth behavior for this graphene domain. This growth mechanism is consistent with the Cu-step-attached nucleation and edge-attachment-limited growth mechanism for H-terminated graphene domains and will provide more guidance for the synthesis of high-quality graphene with less domain boundaries.

Silver nanoparticles (NPs) and related semiconductors are a family of very important and widely applied photocatalysts. However, the preparation of high stability and activity of this photocatalyst is still a challenge. In this work, we report a stable Ag/AgCl/AgBi(MoO${}_4{)}_2$ heterojunction photocatalyst fabricated via a simple in situ anion-exchange reaction followed by the photoreduction treatment. In the treatment of tetracycline (TC) wastewater under visible light, the AC-0.4 sample (prepared with 0.4mmol KCl) exhibits the significantly improved activity (degradation ratio, DR of 71.3%) compared with the pristine AgBi(MoO${}_4{)}_2$ (30% DR) and Ag/AgCl sample (synthesized by the photoreduction of AgCl) (37% DR) under identical experimental conditions. This activity promotion is from the fast interfacial electron transfer between the heterojunction phases of AgCl/AgBi(MoO${}_4{)}_2$ and the SPR effect of Ag NPs. After five successive recycles, the AC-0.4 sample still maintains good stability and activity for TC degradation, which shows a great potential to be used in practical application. Through the ESR and controlled scavenged experiments, we found the $•$OH and $•$O${}_2^{-}$ are the major reactive intermediate species in the TC photodegradation reaction. Our work provides a new insight into the synthesis of stable and high efficient Ag-based heterojunction photocatalysts for the application of wastewater treatment.

An integrative electroanalytical method was developed for detecting Cd${}^{2+}$ and Pb${}^{2+}$ ions in aqueous solutions. Polysulfide/graphene (RGO-S) nanocomposites were prepared and their performance as electrochemical sensors for Cd${}^{2+}$ and Pb${}^{2+}$ was evaluated. The RGO-S nanocomposite was carefully characterized by scanning electron microscopy with energy-dispersive X-ray spectrometry, transmission electron microscopy, and X-ray photoelectron spectroscopy. The as-prepared RGO-S was incorporated into a pyrolytic graphite electrode (RGO-S/PGE) and used for detecting trace amount of Cd${}^{2+}$ and Pb${}^{2+}$ by differential pulse anodic stripping voltammetry. Under optimal conditions, the stripping peak current of RGO-S/PGE varies linearly with heavy metal ion concentration in the ranges 2.0–300$\mu$g L${}^{-1}$ for Cd${}^{2+}$ and 1.0–300$\mu$g L${}^{-1}$ for Pb${}^{2+}$. The limits of detection for Cd${}^{2+}$ and Pb${}^{2+}$ were estimated to be about 0.67$\mu$g L${}^{-1}$ and 0.17$\mu$g L${}^{-1}$, respectively. The prepared electrochemical heavy-metal-detecting electrode provides good repeatability and reproducibility with high sensitivity, making it a suitable candidate for monitoring Cd${}^{2+}$ and Pb${}^{2+}$ concentrations in aqueous environmental samples.

Hierarchically porous carbons are obtained by a facile process of carbonizing the precursor of diblock copolymer xPS-$b$-polymethylmethacrylate (PMMA). In the diblock copolymer, there is a carbon source of cross-linked polystyrene (xPS) and a sacrificial block of PMMA. The atom transfer radical polymerization was used to synthesize the diblock copolymer with controlled molecular weight and narrow polydispersity in dimethylformamide at 120^∘C. The obtained hierarchically porous carbons (HPCs) exhibit remarkable electrochemical properties, such as higher specific capacitance of 204Fg${}^{-1}$ at the current density of 0.5Ag${}^{-1}$ in 6molL${}^{-1}$ aqueous KOH electrolyte. In addition, it also presents an excellent rate performance of 64% capacitance retention as the current density increases to 10Ag${}^{-1}$ and a superior cycling stability of 98% capacitance retention after 5000 cycles at the current density of 1Ag${}^{-1}$.

The CuInS₂ quantum dots sensitization of TiO₂ nanonails (NNs) array was successfully carried out by a successive ionic layer absorption and reaction (SILAR) method using CuCl₂ ⋅ 2H₂O, InCl₃ ⋅ 4H₂O and Na₂S ⋅ 9H₂O as precursors. The morphology, elemental composition and crystalline structure of the CuInS₂ quantum dots sensitized TiO₂ NNs array heterojunction nanostructures were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and X-ray-photoelectron spectroscopy (XPS). The above characterization results could unanimously reveal that the nanoparticles successfully loaded on the TiO₂ NNs array can be assigned as CuInS₂ quantum dots. UV-Vis absorption measurements indicated that the CuInS₂ quantum dots sensitization extended the visible light absorption. The largest short-circuit photocurrent density of 17.7mA/cm² was obtained, which indicated that the CuInS₂ was a promising material in activating visible light functionalities and enhancing photoelectrochemical performance.

The well-defined NaGdF₄:Yb,Er nanorods (NRs) with various aspect ratios were synthesized using a facile hydrothermal method. The morphology and crystal phase of NRs could be controlled by reaction conditions. NaGdF₄:Yb,Er NRs with various aspect ratios could be synthesized and their upconversion (UC) luminescence was tuned. It is displayed that the NRs with aspect ratios about 5 exhibited the strongest UC luminescence among samples. The growth mechanism and morphology transition of NRs had been deduced by schematic diagram. And UC mechanism had been determined by energy level diagrams. Compared with previous reports, the work provided a facial method for UCNRs with various aspect ratios at lower temperature.

We report engineered iron-based nanoparticles supported on cagelike mesoporous carbon that leaves its most mesopores empty to retain an open pore network and are expected to be efficient catalyst with fast molecular diffusion/transportation. The nano-scale iron-based particle inlayed in mesoporous carbon catalyst was obtained via the introduction of N atoms as an anchor. Results of X-ray diffraction, N₂ sorption and transmission electron microscopy showed that the cagelike mesoporous structure of the carbon matrix was retained during catalyst preparation and iron-based nanoparticles were spatially dispersed on the mesoporous carbon. Importantly, it was found that the obtained iron-based nanoparticles inlayed into mesoporous carbon with a low Fe loading of 1.26wt.% was an appropriate catalyst for the benzene hydroxylation to phenol using H₂O₂ as the oxidant. At a low temperature of 30^∘C, 19.4% conversion to benzene and 14.6% phenol yield were obtained; in addition, the catalyst could be recycled at least four times.

Herein, we report a hierarchical structure formed by wrinkled reduced graphene oxide (rGO) sheets-wrapped carbon fiber via a facile and efficient electrostatic self-assembly method and subsequent annealing treatment. For this material, the Weibull scale parameter is 4.77GPa. After 100 cycles, the rGO@CF retains 91% of its second charge capacity at 50mA ⋅g⁻¹, corresponding to a capacity fading of only 0.09% per cycle. Thus, this structural anode material exhibits enhanced capacity, high initial Coulombic efficiency and high tensile strength. Meanwhile, the carbon fiber and interweaved rGO sheets together form the whole conductive networks to provide multichannel highways for charge transfer (lithium-ion diffusion and electron transport) during discharge–charge processes, promising excellent electrochemical performance of this structural anode material.

How to simply adjust the porosity of carbon materials and largely elevate the capacitive performance of supercapacitors remains interesting but challenging for us. In the present work, we have realized the two purposes by the following steps: firstly, introducing MgO as hard template into potassium hydrogen phthalate can result in the formation of hierarchical pore structures containing micropores and mesopores, whilst individually carbonizing potassium hydrogen phthalate leads to nearly complete micropores; secondly, incorporating rutin as effective redox additive into H₂SO₄ electrolyte can largely improve the capacitances as well as the energy densities by the gain/loss of two electrons and two protons. For example, the capacitances can increase 1.92 fold when carried out in a two-electrode system. Furthermore, adding 0.15mmol L⁻¹ rutin into 1mol L⁻¹ H₂SO₄ can achieve the maximum energy density up to 20.84Wh kg⁻¹ towards the MgO-templated carbon materials. More importantly, it is also inferred that higher porosity of carbon materials indeed benefits for obtaining larger pseudo-capacitive efficiency. Thereby, understanding the matching degree of redox additive’s size and that of pore within carbon matrix will help us facilitate the capacitive increase of supercapacitors.

Fluorescent nitrogen-doped carbon dots (N-CDs) with excellent stability were prepared via single-step hydrothermal carbonization of citric acid (CA) and ethylenediamine (EDA). The as-prepared N-CDs emit blue fluorescence under the excitation of 365nm and have a size distribution of 2.80 ± 0.47nm with benign size effect. The structure and morphology were further characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. It was found that the surface of the N-CDs was successfully functionalized, which presented water solubility and chelation with Fe³⁺. XRD results display a diffraction peak at 23.9°C, which corresponds to the (002) interlayer spacing of a graphitic structure revealing an amorphous carbon phase. Furthermore, due to good sensitivity, N-CDs were used as probes for Fe³⁺ detection. The low limit of detection of 0.6μM as a fluorescence probe was successfully obtained based on the linear relationship between ($F_0-F)∕F_0$ and concentration of Fe³⁺ ions. Besides the satisfactory fluorescence, PVA/N-CDs membranes and fluorescent inks demonstrate potential for anti-counterfeiting applications due to its characteristic flexibility, transparency, removability and invisibility under ambient lighting.

Fluorinated graphene oxide (FGO) was successfully prepared in this paper, and the chemical structure of FGO was characterized. A series of polyimide (PI) composite films with different content of FGO was prepared by in situ polymerization. Because of the homogeneous dispersion of FGO and the strong interfacial interaction between FGO and the PI matrix, the resulting composite films that contained FGO exhibited effects of mechanical properties, thermal properties and dielectric properties that were even better than the pure PI. Furthermore, due to the hydrophobic properties of FGO, the water absorption of the composite films were reduced. The result showed when the 0.6wt.% FGO was filled into the PI, the tensile strength was increased about 66.3%, the decomposition temperature was increased from 540^∘C to 570^∘C, and the dielectric constant (D_k) decreased with the increasing content of FGO, and a D_k value of 2.28 was achieved when the content of FGO was 1.0wt.%.

Development of efficient visible light driven photocatalysts for water splitting has attracted great research interest. Herein, a novel H₂-producing nitrogen-doped graphene quantum dots (NGQDs)-Cu₂O was successfully constructed and synthesized. The as-prepared NGQDs-Cu₂O photocatalysts were benefited for light harvesting and charge separation and showed highly efficient photocatalytic property for hydrogen production by water splitting. Results displayed that the amount of NGQDs exhibited significant influence for H₂ production, and the optimum sample of 3%NGQDs-Cu₂O performed the highest hydrogen-evolution rate of 22.6$\mu$mol h${}^{-1}$ g${}^{-1}$, which was about 2 times higher than that of the pure Cu₂O (10.1$\mu$mol h${}^{-1}$ g${}^{-1}$). By further study, the enhanced photocatalytic performance could be ascribed to the crucial role of NGQDs, which widely improve the separation of photogenerated electron-hole pair’s.