Ying Wang

P25-Graphene Composite as a High Performance Photocatalyst

Herein we obtained a chemically bonded TiO(2) (P25)-graphene nanocomposite photocatalyst with graphene oxide and P25, using a facile one-step hydrothermal method. During the hydrothermal reaction, both of the reduction of graphene oxide and loading of P25 were achieved. The as-prepared P25-graphene photocatalyst possessed great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties simultaneously, which was rarely reported in other TiO(2)-carbon photocatalysts. Hence, in the photodegradation of methylene blue, a significant enhancement in the reaction rate was observed with P25-graphene, compared to the bare P25 and P25-CNTs with the same carbon content. Overall, this work could provide new insights into the fabrication of a TiO(2)-carbon composite as high performance photocatalysts and facilitate their application in the environmental protection issues.

Nitrogen-Doped Graphene and Its Application in Electrochemical Biosensing

Chemical doping with foreign atoms is an effective method to intrinsically modify the properties of host materials. Among them, nitrogen doping plays a critical role in regulating the electronic properties of carbon materials. Recently, graphene, as a true two-dimensional carbon material, has shown fascinating applications in bioelectronics and biosensors. In this paper, we report a facile strategy to prepare N-doped graphene by using nitrogen plasma treatment of graphene synthesized via a chemical method. Meanwhile, a possible schematic diagram has been proposed to detail the structure of N-doped graphene. By controlling the exposure time, the N percentage in host graphene can be regulated, ranging from 0.11 to 1.35%. Moreover, the as-prepared N-doped graphene has displayed high electrocatalytic activity for reduction of hydrogen peroxide and fast direct electron transfer kinetics for glucose oxidase. The N-doped graphene has further been used for glucose biosensing with concentrations as low as 0.01 mM in the presence of interferences.

Graphene and graphene oxide: biofunctionalization and applications in biotechnology

Graphene is the basic building block of 0D fullerene, 1D carbon nanotubes, and 3D graphite. Graphene has a unique planar structure, as well as novel electronic properties, which have attracted great interests from scientists. This review selectively analyzes current advances in the field of graphene bioapplications. In particular, the biofunctionalization of graphene for biological applications, fluorescence-resonance-energy-transfer-based biosensor development by using graphene or graphene-based nanomaterials, and the investigation of graphene or graphene-based nanomaterials for living cell studies are summarized in more detail. Future perspectives and possible challenges in this rapidly developing area are also discussed.

Aptamer/Graphene Oxide Nanocomplex for In Situ Molecular Probing in Living Cells

Graphene has shown fascinating applications in bionanotechnology, including DNA sensing, protein assays, and drug delivery. However, exploration of graphene with intracellular monitoring and in situ molecular probing is still at an early stage. In this regard, we have designed an aptamer-carboxyfluorescein (FAM)/graphene oxide nanosheet (GO-nS) nanocomplex to investigate its ability for molecular probing in living cells. Results demonstrate that uptake of aptamer-FAM/GO-nS nanocomplex and cellular target monitoring were realized successfully. The dramatic delivery, protection, and sensing capabilities of GO-nS in living cells indicate that graphene oxide could be a robust candidate for many biological fields, such as DNA and protein analysis, gene and drug delivering, and intracellular tracking.

Graphene Fluorescence Resonance Energy Transfer Aptasensor for the Thrombin Detection

Combining nanomaterials and biomolecule recognition units is promising in developing novel clinic diagnostic and protein analysis techniques. In this work, a highly sensitive and specific fluorescence resonance energy transfer (FRET) aptasensor for thrombin detection is developed based on the dye labeled aptamer assembled graphene. Due to the noncovalent assembly between aptamer and graphene, fluorescence quenching of the dye takes place because of FRET. The addition of thrombin leads to the fluorescence recovery due to the formation of quadruplex-thrombin complexes which have weak affinity to graphene and keep the dyes away from graphene surface. Because of the high fluorescence quenching efficiency, unique structure, and electronic properties of graphene, the graphene aptasensor exhibits extraordinarily high sensitivity and excellent specificity in both buffer and blood serum. A detection limit as low as 31.3 pM is obtained based on the graphene FRET aptasensor, which is two orders magnitude lower than those of fluorescent sensors based on carbon nanotubes. The excellent performance of FRET aptasensor based on graphene will also be ascribed to the unique structure and electronic properties of graphene.

Graphene Oxide Amplified Electrogenerated Chemiluminescence of Quantum Dots and Its Selective Sensing for Glutathione from Thiol-Containing Compounds

Here we report a graphene oxide amplified electrogenerated chemiluminescence (ECL) of quantum dots (QDs) platform and its efficient selective sensing for antioxidants. Graphene oxide facilitated the CdTe QDs*+ production and triggered O2*- generation. Then, a high yield of CdTe QDs* was formed due to the combination of CdTe QDs*+ and O2*-, leading to an approximately 5-fold ECL amplification. Glutathione is the most abundant cellular thiol-containing peptide, but its selective sensing is an intractable issue in analytical and biochemical communities because its detection is interfered with by some thiol-containing compounds. This platform showed a detection limit of 8.3 microM (S/N = 3) for glutathione and a selective detection linear dependence from 24 to 214 microM in the presence of 120 muM cysteine and glutathione disulfide. This platform was also successfully used for real sample (eye drug containing glutathione) detection without any pretreatment with a wide linear range from 0.04 to 0.29 microg mL(-1).

Rapid and sensitive detection of protein biomarker using a portable fluorescence biosensor based on quantum dots and a lateral flow test strip.

A portable fluorescence biosensor with rapid and ultrasensitive response for protein biomarker has been built up with quantum dots and a lateral flow test strip. The superior signal brightness and high photostability of quantum dots are combined with the promising advantages of a lateral flow test strip and result in high sensitivity and selectivity and speed for protein detection. Nitrated ceruloplasmin, a significant biomarker for cardiovascular disease, lung cancer, and stress response to smoking, was used as model protein biomarker to demonstrate the good performances of this proposed quantum dot-based lateral flow test strip. Quantitative detection of nitrated ceruloplasmin was realized by recording the fluorescence intensity of quantum dots captured on the test line. Under optimal conditions, this portable fluorescence biosensor displays rapid responses for nitrated ceruloplasmin with the concentration as low as 1 ng/mL. Furthermore, the biosensor was successfully utilized for spiked human plasma sample detection in a wide dynamic range with a detection limit of 8 ng/mL (S/N = 3). The results demonstrate that the quantum dot-based lateral flow test strip is capable of rapid, sensitive, and quantitative detection of nitrated ceruloplasmin and hold a great promise for point-of-care and in field analysis of other protein biomarkers.

Toehold‐initiated Rolling Circle Amplification for Visualizing Individual MicroRNAs In Situ in Single Cells

The ability to quantitate and visualize microRNAs (miRNAs) in situ in single cells would greatly facilitate the elucidation of miRNA-mediated regulatory circuits and their disease associations. A toehold-initiated strand-displacement process was used to initiate rolling circle amplification of specific miRNAs, an approach that achieves both stringent recognition and in situ amplification of the target miRNA. This assay, termed toehold-initiated rolling circle amplification (TIRCA), can be utilized to identify miRNAs at physiological temperature with high specificity and to visualize individual miRNAs in situ in single cells within 3 h. TIRCA is a competitive candidate technique for in situ miRNA imaging and may help us to understand the role of miRNAs in cellular processes and human diseases in more detail.

Self assembly of acetylcholinesterase on a gold nanoparticles–graphene nanosheet hybrid for organophosphate pesticide detection using polyelectrolyte as a linker

A nanohybrid of gold nanoparticles (Au NPs) and chemically reduced graphene oxide nanosheets (cr-Gs) was synthesized by in situgrowth of Au NPs on the surface of graphene nanosheets in the presence of poly(diallyldimethylammonium chloride) (PDDA), which not only improved the dispersion of Au NPs but also stabilized cholinesterase with high activity and loading efficiency. The obtained nanohybrid was characterized by TEM, XRD, XPS, and electrochemistry. Then an enzyme nanoassembly (AChE/Au NPs/cr-Gs) was prepared by self-assembling acetylcholinesterase (AChE) on Au NP/cr-Gs nanohybrid. An electrochemical sensor based on AChE/Au NPs/cr-Gs was further developed for ultrasensitive detection of organophosphate pesticide. The results demonstrate that the developed approach provides a promising strategy to improve the sensitivity and enzyme activity of electrochemical biosensors.

Solvatochromogenic flavone dyes for the detection of water in acetone

Abstract Two flavone dyes, 3-hydroxy-4′-N,N-dimethylaminoflavone (HMAF) and 4′-N,N-dimethylaminoflavone-3-yl methacrylate (DMAFMA), have been investigated as solvatochromogenic fluorophores for the determination of water in acetone. The solvent-dependent absorption and fluorescence spectral characteristics of HMAF and DMAFMA have been studied in a series of organic solvents and water/acetone binary mixtures. Spectral shifts of the compounds were observed in these solvents and their mixtures. DMAFMA exhibits a normal fluorescence emission in various solvents. Besides the normal emission, HMAF shows an abnormal band which is attributed to intramolecular proton transfer occurring across a pre-existing intramolecular hydrogen bond. As a result of the proximity effect, conformation change, and the formation of intra- or intermolecular hydrogen bonds, the emission intensity changes with the change in solvents polarity. A maximum change was observed for HMAF in ethanol, and for DMAFMA in tetrahydrofuran. With incremental addition of small amounts of water to HMAF and DMAFMA acetone solution, spectral red shifts of the compounds were also observed, while the changes in the fluorescence intensity were in a reverse direction for these two compounds. Owing to the formation of solvate complexes involving hydrogen bonding with the increase of water content, the fluorescence intensity of HMAF increases and that of DMAFMA decreases. HMAF fluorescence emission intensity changes as a function of water content in the 0.0–10.0% range, with a detection limit of 0.02%. By using the DMAFMA reagent, a linear range of 0.0–3.0% and a detection limit of 0.005% are achieved. Small amounts of alcohols and aldehydes show no substantial effect on the determination of water in acetone samples with the flavone dyes. The proposed methods were applied to the determination of water in reagent-grade acetone. The results agree well with those obtained by the gas chromatographic method.