Jianhui Deng

Electrochemical Synthesis of Carbon Nanodots Directly from Alcohols

Carbon nanodots (C-dots) show great potential as an important material for biochemical sensing, energy conversion, photocatalysis, and optoelectronics because of their water solubility, chemical inertness, low toxicity, and photo- and electronic properties. Numerous methods have been proposed for the preparation of C-dots. However, complex procedures and strong acid treatments are often required, and the as-prepared C-dots tend to be of low quality, and in particular, have a low efficiency for photoluminescence. Herein, a facile and general strategy involving the electrochemical carbonization of low-molecular-weight alcohols is proposed. As precursors, the alcohols transited into carbon-containing particles after electrochemical carbonization under basic conditions. The resultant C-dots exhibit excellent excitation- and size-dependent fluorescence without the need for complicated purification and passivation procedures. The sizes of the as-prepared C-dots can be adjusted by varying the applied potential. High-quality C-dots are prepared successfully from different small molecular alcohols, suggesting that this research provides a new, highly universal method for the preparation of fluorescent C-dots. In addition, luminescence microscopy of the C-dots is demonstrated in human cancer cells. The results indicate that the as-prepared C-dots have low toxicity and can be used in imaging applications.

A new turn-on fluorescent probe for selective detection of glutathione and cysteine in living cells.

A fluorescent probe (N-(4-methyl-2-oxo-2H-chromen-7-yl)-2,4-dinitrobenzenesulfonamide), which exhibits high selectivity to glutathione and cysteine among amino acids including sulphur-containing methionine and metal ions, was synthesized. The experiments demonstrate that the fluorescent probe is a reliable and specific probe for glutathione and cysteine in living cells.

One-pot electrochemical synthesis of functionalized fluorescent carbon dots and their selective sensing for mercury ion

We propose a simple, economical, and one-pot method to synthesize water-soluble functionalized fluorescent carbon dots (C-Dots) through electrochemical carbonization of sodium citrate and urea. The as-prepared C-Dots have good photostability and exhibit a high quantum yield of 11.9%. The sizes of the C-Dots are mainly distributed in the range of 1.0-3.5 nm with an average size of 2.4 nm. It has been further used as a novel label-free sensing probe for selective detection of Hg(2+) ions with detection limit as low as 3.3 nM. The detection linear range is 0.01-10 μM. The as-prepared C-Dots are also successfully applied for the determination of Hg(2+) in real water samples.

Fluorescence resonance energy transfer aptasensor for platelet-derived growth factor detection based on upconversion nanoparticles in 30% blood serum

Au nanoparticles (AuNPs) have good absorption properties in the visible region, while upconversion nanoparticles (UCNPs) have an emission at 547 nm upon excitation with a 980 nm laser, which could avoid most interfering signals of biomolecules in serum. In this paper, we developed an aptasensor for platelet-derived growth factor (PDGF–BB) detection in 30% blood serum based on fluorescence resonance energy transfer between AuNPs and UCNPs. With the proposed aptasensor, PDGF–BB in 30% blood serum was detected. Two consecutive linear ranges allow a wide determination of PDGF–BB concentrations with a low detection limit of 10 nM (S/N = 3). Importantly, the fluorescence biosensor can directly detect PDGF–BB in blood serum of lymphoma patient. This detection approach can also exhibit good stability and selectivity.

Large scale preparation of graphene quantum dots from graphite oxide in pure water via one-step electrochemical tailoring

A novel electrochemical synthesis for graphene quantum dots (GQD) with a large scale from graphite oxide (GO) in pure water has been proposed. GQDs with different sizes and different emission colors were obtained with a yield of 65.5% in weight, which exhibited intrinsic peroxidase-like activity in glucose detection.

Label-free silicon quantum dots as fluorescent probe for selective and sensitive detection of copper ions.

In this work, label-free silicon quantum dots (SiQDs) were used as a novel fluorescence probe for the sensitive and selective detection of Cu(2+). The fluorescence of the SiQDs was effectively quenched by H2O2 from the reaction of ascorbic acid with O2, and hydroxyl radicals from Fenton reaction between H2O2 and Cu(+). The fluorescence intensity of SiQDs was quenched about 25% in 15 min after the addition of H2O2 (1mM). While the SiQDs was incubated with AA (1mM) and Cu(2+) (1 µM) under the same conditions, the fluorescence intensity of SiQDs decreased about 55%. Obviously, the recycling of Cu(2+) in the test system may lead to a dramatical decrease in the fluorescence of SiQDs. Under the optimized experimental conditions, the rate of fluorescence quenching of SiQDs was linearly dependent on the Cu(2+) concentration ranging from 25 to 600 nM with the limit of detection as low as 8 nM, which was much lower than that of existing methods. Moreover, the probe was successfully applied to the determination of Cu(2+) in different environmental water samples and human hair.

Self-assembled oligo(phenylene ethynylene)s/graphene nanocomposite with improved electrochemical performances for dopamine determination

In this work, a novel 1,4-bis (4- aminophenylethynyl)benzene (OPE-NH2, a symmetric linear conjugated oligo(phenylene ethynylene)s derive) and chemically-reduced graphene oxide (rGO) nanocomposite (OPE-NH2/rGO) was synthesized by a simple self-assembly method. The OPE-NH2/rGO nanocomposite was stable and water soluble. The formation of OPE-NH2/rGO nanocomposite was ascribed to the π-π stacking interaction between the conjugated structure of OPE-NH2 and rGO as well as the electrostatic force between the amino group of OPE-NH2 and the carboxyl group on rGO, which was characterized by FT-IR, UV-vis spectra and fluorescence spectra. The OPE-NH2/rGO nanocomposite exhibited significantly improved electrocatalytic activity to the oxidization of dopamine (DA) than that of rGO or OPE-NH2. The electrochemical performances of OPE-NH2/rGO were dependent on the OPE-NH2 contents, and OPE-NH2 content of 5wt% exhibited the highest activity. Compared with that of rGO, the nanocomposite presented superior high sensitivity with detection limit of 5nM, excellent selectivity, wide linear range (0.01-60μM) and good stability on the determination of DA. The practical application of the developed OPE-NH2/rGO nanocomposite modified electrode was successfully demonstrated for DA determination in human serum samples.

Fabrication of New GH-CS/Fc-NH2/Cytc Modified Electrode and Its Application in Detection of Nitrite

Abstract Highly conjugated linear molecular wires are one of the basic elements for constructing molecular electronic devices. Among these conjugated compounds, ferrocene-terminated compounds as well as their derivatives were widely studied because of their ideal electrochemical activity. Based on these, a new ferrocene-terminated phenylethynyaniline (Fc-NH 2 ) was synthesized by Sonogashira cross coupling reaction. The structure of the target compound was identified by infrared (IR), nuclear magnetic resonance (NMR), mass spectra (MS) and cyclic voltammetry (CV). By combining the graphene-chitosan (GH-CS) and Fc-NH 2 , a new composite of GH-CS/Fc-NH 2 was prepared and then used for immobilization of Cytc to prepare the GH-CS/Fc-NH 2 /cytochrome c (Cytc)/GCE. It was found from the CV result that a pair of peaks near −0.2 V was appeared, which could be attributed to Cytc. The GH-CS/Fc-NH 2 /Cytc modified GCE shows good catalysis towards NaNO 2 , and good linear relationship was found in the range of 1.0 × 10 −7 −1.5 × 10 −4 M with the detection limit bellow 4.0 × 10 −8 M. Therefore, Cytc could be immobilized on the GH-CS/Fc-NH 2 and the direct electron transfer was realized between the electrode and solution, and showed good prospect for detection of NaNO 2 .