Lanlan Li

Platinum–Copper Nanoframes: One‐Pot Synthesis and Enhanced Electrocatalytic Activity

Platinum-copper nanoframes were produced from copper nanoparticles by a one-pot synthesis method. The growth mechanism was thoroughly studied by experiment and theoretical calculations. Owing to the unique structure, Pt-Cu nanoframes exhibited significantly enhanced catalytic activity toward the electro-oxidation of methanol compared to commercial Pt black.

Synthesis and electro-catalytic activity of Pt-Co nanoflowers

The study of metallic nanoflowers has attracted more and more attention because of their larger surface areas and active sites, which could be applied for surface-sensitive areas. Despite these excellent characteristics, it is still very hard to synthesize noble metal nanoflowers as the flower-like structure is apt to change into some more stable shapes which are covered by lower energy surfaces. In this study, Pt-Co nanoflowers were successfully synthesized by a two-step method via the reaction between Co nanoparticles and Pt precursor. From the transmission electron microscopy (TEM) images, it could be seen clearly that the products possessed a flower-like nanostructure. The morphology of the final products depended on a number of parameters, such as the reaction time and the reaction temperature. Based on the experimental results and theoretical calculation, the formation of nanoflowers could be attributed to the galvanic replacement reaction between Co nanoparticles and Pt precursor. In addition, the electrochemical catalytic activity of Pt-Co nanoflowers toward methanol oxidation was also evaluated in comparison with that of commercial Pt black. Owing to the special structure, the electro-catalytic activity and stability of Pt-Co nanoflowers were much better than those of commercial Pt black.

Facile synthesis of BCNO quantum dots with applications for ion detection, chemosensor and fingerprint identification

Boron carbon oxynitride quantum dots (BCNO QDs) with blue emission were prepared via the template of SBA-15 (a typical mesoporous silica). A modulated photoluminescence sensor was developed based on the different quenching effects of Cu2+ or Hg2+ ions on the luminescence intensity of BCNO QDs. The Cu2+ or Hg2+ ions have an interaction with BCNO QDs due to the electrons transfer between the BCNO and Cu2+ or Hg2+ ions, and the detection limit of Cu2+ or Hg2+ ion concentration can be as less as 10 nM. The BCNO-Cr6+ mixture can be served as a turn-on fluorescent sensor for detecting the ascorbic acid based on the inner filter effect since overlapping of excitation and emission spectra between Cr6+ ions and BCNO QDs. Moreover, the BCNO QDs can also be applied to fingerprint identification and organic fluorescent films under ultraviolet excitation.

Surface states modulation of red emitting carbon dots for white light-emitting diode

Controlling surface states using different functional groups is an effective and facile way to modulate the fluorescence of carbon dots (CDs), but the underlying mechanisms are still unclear and urgent to solve. In this work, we synthesized red emitting CDs and achieved multiple emission states (red, green and blue emission) by tailoring the surface states with different amino groups. In particular, the luminescence mechanism and the role of surface states were studied in detail. It is found that the multiple emission states are related to the speciation of nitrogen (pyridinic N, pyrrolic N, graphitic N and amino N) on the surface of CDs, of which the fluorophore formed by the deformation of p-phenylenediamine contributes to the red emission, pyridinic N is responsible for the green emission state, and pyrrolic N enhances the blue emission. A possible energy level diagram was proposed to disclose the electron transition process and relative levels induced by different surface groups on CDs. In addition, the modulated CDs with multiple emission states can be used as single light converters to fabricate a white light-emitting diode, which has white light color coordinates of (0.31, 0.32), a high color rendering index (CRI) of 85, a luminous efficiency of 8.8 lm W−1 and good stability.

Cu/Ni nanoparticles supported on TiO2(B) nanotubes as hydrogen generation photocatalysts via hydrolysis of ammonia borane

TiO2(B) nanotubes (NTs) were used as carriers to support metal Cu/Ni nanoparticles for the catalytic hydrolysis of ammonia borane (NH3BH3, AB) under visible light. The TiO2 NTs were first prepared by the hydrothermal method and subsequently loaded with Cu/Ni metal nanoparticles by the impregnation reduction method. The structure, morphology, and chemical composition of the as-obtained catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), inductively coupled plasma emission spectroscopy (ICP), and ultraviolet–visible spectroscopy (UV-Vis). The characterization results revealed that the metal nanoparticles were uniformly loaded on the surface of the TiO2 NTs, while the band gap of the catalyst was reduced significantly from 3.22 to 2.68 eV. The catalysts showed an excellent photocatalytic performance towards the hydrolysis of AB for H2 production. Thus, the H2 production rate of Cu0.64Ni0.36-TiO2 NTs reached 5763.86 mL g−1 min−1, with a total turnover frequency (TOF) of 15.90 mol H2 (mol cat)−1 min−1 for a loading volume of metal particles of 5.25 wt%. The results presented herein demonstrate that TiO2(B) can be a potential photocatalyst for effective H2 production, and also provide a cheap and effective approach to improve the light-to-H2 energy conversion.

Removal of Cr(III)/Cr(VI) from wastewater using defective porous boron nitride: a DFT study

Developing highly-efficient adsorbent materials for the removal of Cr(III)/Cr(VI) ions from industrial wastewater is of great importance for environmental pollution control. In this work, density functional theory was used to model the adsorption capacities of Cr(III)/Cr(VI) ions on defective porous boron nitride (p-BN). Our results suggest that both nitrogen (VN) and boron (VB) vacancies contribute to the adsorption of Cr(III)/Cr(VI) ions on p-BN. In the case of a VN defect, the calculated adsorption energy (Eads) values are 3.76 eV and 4.58 eV for single Cr(III) and Cr(VI) ions, respectively, whereas, in the case of a VB defect, the Eads values are 8.55 eV and 10.26 eV for Cr(III) and Cr(VI) ions, respectively. The analysis of the electronic structure reveals that defective levels in the energy gap region strongly affect the adsorption performance of p-BN as an adsorbent. More importantly, we clarify that the strong adsorption of Cr(III)/Cr(VI) ions on defective p-BN is indeed chemical adsorption and not dispersion or electrostatic attraction. High coverage of Cr(III) and Cr(VI) ions and the effect of water solvent molecules were also taken into account. These findings indicate that defective p-BN is an excellent candidate for the removal of Cr(III)/Cr(VI) ions from wastewater.