Flexible anode materials for lithium-ion batteries derived from waste biomass-based carbon nanofibers: I. Effect of carbonization temperature

Carbon nanofibers (CNFs) with excellent electrochemical performance represent a novel class of carbon nanostructures for boosting electrochemical applications, especially sustainable electrochemical energy conversion and storage applications. This work builds on an earlier study where the CNFs were prepared from a waste biomass (walnut shells) using a relatively simple procedure of liquefying the biomass, and electrospinning and carbonizing the fibrils. We further improved the mass ratio of the liquefying process and investigated the effects of the high temperature carbonization process at 1000, 1500 and 2000 °C, and comprehensively characterized the morphology, structural properties, and specific surface area of walnut shell-derived CNFs; and their electrochemical performance was also investigated as electrode materials in Li-ion batteries. Results demonstrated that the CNF anode obtained at 1000 °C exhibits a high specific capacity up to 271.7 mA h g⁻¹ at 30 mA g⁻¹, good rate capacity (131.3 and 102.2 mA h g⁻¹ at 1 A g⁻¹ and 2 A g⁻¹, respectively), and excellent cycling performance (above 200 mA h g⁻¹ specific capacity without any capacity decay after 200 cycles at 100 mA g⁻¹). The present work demonstrates the great potential for converting low-cost biomass to high-value carbon materials for applications in energy storage.

Carbon nanofibers (CNFs) with excellent electrochemical performance represent a novel class of carbon nanostructures for boosting electrochemical applications, especially sustainable electrochemical energy conversion and storage applications.     

The effect of metallic Fe(ii) and nonmetallic S codoping on the photocatalytic performance of graphitic carbon nitride

The metallic Fe(ii) ion and nonmetallic S codoped g-C₃N₄ photocatalyst was synthesized through the polymerization of melamine, ferrous chloride and trithiocyanuric acid (TCA) at elevated temperature. The performance of Fe(ii)–S codoped g-C₃N₄ compounds in RhB photocatalytic degradation was found to increase 5 times. This significant enhancement in catalytic activity is probably related to the enhanced visible light adsorption and the mobility of photoinduced electron/hole pairs, attributable to bandgap narrowing and also lowering in the surface electrostatic potential compared to that of the pure g-C₃N₄ nanosheets. XRD and XPS results indicate that the Fe species binds with N-atoms to form Fe–N bonds in the state of Fe(ii) ions. Fe(ii) doping increases the specific surface area, and enhances the photoinduced electron/hole pairs illustrated by PL, EIS spectra and transient photocurrent response measurements. The theoretical results show that divalent Fe(ii) ions coordinating in the pore centre among three triazine units form discrete dopant bands and S dopants substituting the N in triazine skeletons excite much stronger delocalized HOMO and LUMO states, facilitating the migration of photogenerated charge carriers, thus enhancing the visible-light driven photocatalytic performance.

The photoinduced electrons jump more easily to the conduction band of g-C₃N₄ for the Fe impurity band locates above the valence band acting a bridge for electron transfer.     

Bistable electrical switching and nonvolatile memory effects by doping different amounts of GO in poly(9,9-dioctylfluorene-2,7-diyl)

Poly(9,9-dioctylfluorene-2,7-diyl) (PFO) was synthesized under a Suzuki coupling reaction, and its structure was proved by Fourier transform infrared (FT-IR) spectroscopy, and hydrogen and carbon nuclear magnetic resonance (¹H-NMR and ¹³C-NMR). A nonvolatile organic memristor, based on active layers of PFO and PFO:GO composite, was prepared by spin-coating and the influence of GO concentration on the electrical characteristics of the memristor was investigated. The results showed that the device had two kinds of conductance behavior: electric bistable nonvolatile flash memory behavior and conductor behavior. With an increase in GO concentration, the device has an increased ON/OFF current ratio, increasing from 2.1 × 10¹ to 1.9 × 10³, a lower threshold voltage (V_SET), decreasing from −1.1 V to −0.7 V, and better stability. The current remained stable for 3 hours in both the ON state and OFF state, and the ON and OFF state current of the device did not change substantially after 9000 read cycles.

The device shows different conductive behavior: electric bistable nonvolatile flash memory behavior and conductor behavior.     

Biocompatible tumor-targeting nanocomposites based on CuS for tumor imaging and photothermal therapy

Active targeting of tumor receptors is a significant approach for cancer diagnosis. Additionally, development of photothermal agents for photothermal therapy (PTT) has attracted great interest in the field of nanomedicine. In the present study, copper sulfide (CuS) nanoparticles capped with bovine serum albumin (BSA), named CuS@BSA, was synthesized by a convenient method. Then, the near-infrared (NIR) fluorescence probe MBA and the tumor-targeting ligand cyclic RGD were further conjugated on the surface of CuS@BSA, and the obtained nanocomposite was named CuS@BSA-MBA-cRGD. The morphology, optical properties, biotoxicity, tumor-targeting capability and in vitro and in vivo tumor inhibition effect were all characterized comprehensively. This nanocomplex demonstrated enhanced photothermal effects and positive tumor targeting. Thus, the nanocomposite CuS@BSA-MBA-cRGD can used as a promising tumor-targeting PTT agent for simultaneous cancer imaging and photothermal treatment.

This study provides a good platform for diagnosis and treatment, and it is expected to prompt further exploration of the active target efficiency to achieve better tumor treatment.     

High-efficiency and stable piezo-phototronic organic perovskite solar cell

Perovskite materials are regarded as next-generation organic photovoltaic (OPV) materials due to their excellent physical and chemical properties. Recent theoretical and experimental advances also revealed the piezoelectric properties of CH₃NH₃PbI₃ perovskite thin films. In this work, a CH₃NH₃PbI₃ perovskite piezo-phototronic solar cell is studied in theory. The output parameters such as open circuit voltage, current–voltage characteristics, fill factor, power conversion efficiency, and maximum output power with external strains are presented. The coefficient to characterize piezo-phototronic modulation is also calculated for the piezo-phototronic solar cell. With the change of strain, the output performance can be controlled and enhanced. This principle can offer not only a novel and unique approach to produce high-performance, stable perovskite solar cells, but also a principle to design new piezoelectric perovskite optoelectronic devices.

Enhancing the performance of perovskite solar cells with strain based on a piezo-phototronic effect.     

Modified halloysite nanotube filled polyimide composites for film capacitors: high dielectric constant,low dielectric loss and excellent heat resistance

In this work, halloysite nanotubes (HNTs) were chosen as the fillers and high performance polyimide (PI) as the matrix to form a series of dielectric composite materials with high dielectric constant, low dielectric loss and excellent heat resistance. Firstly, KH550 was used to modify the surface of HNTs to make sure of a good dispersion of HNTs into the polymer. The results showed that the addition of KH550 modified HNTs (K-HNTs) can improve the dielectric constant of the composite films while maintaining their excellent dielectric loss properties. To further increase the dielectric constant of the HNTs/PI composites, conductive polyaniline (PANI) was used to coat the surface of HNTs to obtain PANI modified HNTs (PANI-HNTs). Compared with the K-HNTs filled systems, the dielectric constant of the PANI-HNTs/PI nanocomposite films is greatly enhanced. The highest dielectric constant of the PANI-HNTs/PI films can achieve 17.3 (100 Hz) with a low dielectric loss of 0.2 (100 Hz). More importantly, the as-prepared composite films have high breakdown strengths (>110.4 kV mm⁻¹) and low coefficients of thermal expansion, as low as 7 ppm per °C, and a maximum discharge energy density of 0.93 J cm⁻³. Also, such properties are maintained stably up to 300 °C, which is critical for manufacturing heat-resisting film capacitors.

Halloysite nanotubes (HNTs) were chosen as the fillers and polyimide (PI) as the matrix to form a series of composites with excellent dielectric properties and thermostabilities.     

Theoretical study on narrow Fano resonance of nanocrescent for the label-free detection of single molecules and single nanoparticles

This paper reports a narrow Fano resonance of 3D nanocrescent and its application in the label-free detection of single molecules. The Fano resonance depends not only on the gap size but also on the height. The Fano resonance originates from the interference between the quadrupolar mode supported by the horizontal crescent and the dipolar mode along the nanotip. When the height of 3D nanocrescent is 30 nm, the width of Fano resonance is as narrow as 10 nm. The narrow linewidth is caused by the strong narrow resonant absorption coming from the dipolar mode of nanotip overlapping with the quadrupolar mode of nanocrescent, where the absorption spectra are calculated under a horizontal incident light. The narrow Fano resonance is highly sensitive to a single nanoparticle trapped by the nanocrescent. The wavelength shift increases linearly with the refractive index with the relation of Δλ = 22.10n − 28.80, and increases with the size of trapped nanoparticle following a relation of Δλ = 0.826 × r^1.672. These results indicate that if a protein nanoparticle with radius of 2.5 nm is trapped by the nanocrescent, the shift is as large as 4.03 nm.

The narrow Fano resonance caused by the strong narrow resonant absorption is highly sensitive to a trapped nanoparticle.