Yizhong Lu

One-pot synthesis of carbon nanodots for fluorescence turn-on detection of Ag+ based on the Ag+-induced enhancement of fluorescence

Carbon quantum dots (C-dots) are promising fluorescence probes for applications in metal ion detection, biosensing and bioimaging and so on. In this study, water soluble carbon nanodots were synthesized through a simple one-step heat treatment of ethylene glycol solution. In the present preparation, the C-dots may be formed through the hydration, crosslinking and carbonization processes. The synthesized C-dots show a green luminescent emission under ultraviolet excitation, which can be used for the detection of Ag+ ions. Interestingly, in a different way to the usual quenching effects of metal ions on the fluorescence of C-dots, Ag+ exhibited an enhancement effect on the photoluminescence of C-dots, which can be attributed to the reduction of Ag+ to silver nanoclusters (Ag0) on the surface of the C-dots. Based on the linear relationship between fluorescence intensity and concentration of Ag+ ions, the prepared C-dots can be used for sensitive and selective detection of silver ions in environmental water with a limit of detection of 320 nM and a linear range of 0–90 μM.

Novel blue light emitting graphene oxide nanosheets fabricated by surface functionalization

Graphene and graphene oxide (GO) attract increasing attention due to their unique physical and chemical properties and thus the potential applications in optics and electronics. However, the gapless band structure greatly limits their wide applications in opto-electronic devices. Surface functionalization was found to be an effective method to tune the properties of graphene and GO. In the present report, GO hybrid materials with blue-emission were fabricated through the GO surface functionalization with aryl diazonium salts of 2-aminoanthracene. The obtained hybrids were carefully characterized with atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Fourier-transformed infrared spectroscopy (FTIR), Raman spectroscopy and UV-Vis absorption spectroscopy. Significantly different from the cyan emission (∼491 nm) of monomeric 2-aminoanthracene, the as-synthesized GO hybrid composites exhibited strong blue photoluminescence centered at ca. 400 nm. The large blue shift of the luminescence (∼91 nm) obtained from the functionalized GO could be partly ascribed to the rigid chemical environment with anthryl moieties chemically bonded onto GO surface. Such surface-functionalized GO hybrids with unique optical properties render them exciting materials for opto-electronic devices.

Fe, Co, N-functionalized carbon nanotubes in situ grown on 3D porous N-doped carbon foams as a noble metal-free catalyst for oxygen reduction

Designing and manipulating advanced oxygen reduction reaction (ORR) electrocatalysts are of critical importance for the widespread application of fuel cells. In this work, we report a highly versatile and one-pot pyrolysis route for the mass production of a novel three-dimensional N, Fe, Co-functionalized carbon nanotubes rigidly grown on N-doped carbon foams (3D FeCoN–CNTs/NCFs) serving as a noble-metal free catalyst for the oxygen reduction reaction (ORR). Different from the previously reported carbon materials, in the present 3D porous structure, the N, Fe, Co-doped carbon nanotubes are rigidly grown on the skeleton of 3D nitrogen-doped carbon foams (NCFs), showing a high electrochemical stability. Moreover, due to the synergistic effect of the Fe/Co and the N species with the formation of Fe/Co–Nx complexes in the 3D hybrid carbon material and the multiple active sites on the porous structure, the 3D hybrid displayed superior catalytic performance for ORR, high operation stability and strong methanol/CO crossover resistance in alkaline medium. The stable porous structure and the excellent catalytic performance make the 3D FeCoN–CNTs/NCFs a promising non-precious-metal cathodic electrocatalyst for fuel cells.

Sub-nanometer sized Cu6(GSH)3 clusters: one-step synthesis and electrochemical detection of glucose

We report here a one-pot synthesis of sub-nanometer sized copper clusters capped with a water-soluble ligand, L-glutathione (SGH), through a chemical reduction process. The composition of the as-prepared Cu6(SG)3 nanoclusters was confirmed by electrospray ionization mass spectrometry (ESI-MS) and matrix-assisted laser desorption ionization time-of-flight mass spectroscopy (MALDI-TOF MS). The FTIR, 1H NMR and XPS characterization methods showed that with the production of Cu6(SG)3 clusters and the formation of Cu–S bonds, the surface chemical environment of the clusters exhibited a significant change. The produced water-soluble clusters show aggregation-induced fluorescence upon the addition of ethanol into the cluster aqueous solution. By loading on the TiO2 support, the as-prepared copper nanoclusters were successfully applied to the electrochemical detection of glucose. Compared to large Cu nanoparticles, the Cu6(SG)3 nanoclusters exhibited higher sensitivity and a wider linear range for glucose detection.

Hollow Ag@Pd core-shell nanotubes as highly active catalysts for the electro-oxidation of formic acid.

Ag nanowires are prepared as templates by a polyol reduction process. Then Ag nanotubes coated with a thin layer of Pd are synthesized through sequential reduction accompanied with the galvanic displacement reaction. The products show a hollow core-shell nanotubular structure, as demonstrated by detailed characterizations. The Ag@Pd can significantly improve the electrocatalytic activity towards the electro-oxidation of formic acid and enhance the stability of the Pd component. It is proposed that the enhanced electrochemically active surface area and modulated electron structure of Pd by Ag are responsible for the improvement of electrocatalytic activity and durability. The results obtained in this work are different from those previous reports, in which alloy walls with hollow interiors are usually formed. This work provides a new and simple method for synthesizing novel bimetallic core-shell structure with a hollow interior, which can be applied as high-performance catalysts for the electro-oxidation of formic acid.

Colorimetric detection of iron ions (III) based on the highly sensitive plasmonic response of the N-acetyl-l-cysteine-stabilized silver nanoparticles

We report here a facile colorimetric sensor based on the N-acetyl-L-cysteine (NALC)-stabilized Ag nanoparticles (NALC-Ag NPs) for detection of Fe(3+) ions in aqueous solution. The Ag NPs with an average diameter of 6.55±1.0 nm are successfully synthesized through a simple method using sodium borohydride as reducing agent and N-acetyl-L-cysteine as protecting ligand. The synthesized silver nanoparticles show a strong surface plasmon resonance (SPR) around 400 nm and the SPR intensity decreases with the increasing of Fe(3+) concentration in aqueous solution. Based on the linear relationship between SPR intensity and concentration of Fe(3+) ions, the as-synthesized water-soluble silver nanoparticles can be used for the sensitive and selective detection of Fe(3+) ions in water with a linear range from 80 nM to 80 μM and a detection limit of 80 nM. On the basis of the experimental results, a new detection mechanism of oxidation-reduction reaction between Ag NPs and Fe(3+) ions is proposed, which is different from previously reported mechanisms. Moreover, the NALC-Ag NPs could be applied to the detection of Fe(3+) ions in real environmental water samples.