Excitation-independent emission carbon nanoribbon polymer as a ratiometric photoluminescent probe for highly selective and sensitive detection of quercetin.

In this study, sulfur-nitrogen co-doped carbon nanoribbon (SNCNR) polymers with stable dual-emission fluorescence were synthesized using a one-step traditional hydrothermal method of 6-mercaptopurine in an aqueous methanol solution. Unexpectedly, the as-prepared SNCNRs with excitation-independent emission, as carbon nanomaterial derivatives, showed stable dispersions of a reticular-like shape and different lengths in the skeleton diameter. Compared with other carbon nanomaterials, the SNCNRs dramatically improved the electronic properties and surface chemical reactivities, and exhibited a sensitive ratiometric response to quercetin (Que) because of the Meisenheimer-like complexes formed through π-π stacking and electrostatic interaction. By using this SNCNR sensor, excellent ratiometric linear relationships (FL345 nm/FL420 nm) existed between the degree of quenching of the SNCNRs and the concentrations of Que in the range of 50.0 nM to 200 µM, and the limit of detection was 21.13 nM (3σ/k). Meanwhile, this sensor shows high selectivity for Que over other biomolecules, most amino acids and metal ions under the same conditions. Finally, this fluorescent probe was successfully applied to the direct analysis of Que in bovine serum and some beverage samples, which showed that it has potential for use in applications in clinical diagnosis and food analysis, and may pave the way for the design of effective fluorescent probes for other biologically related targets and food protection.

Reduced graphene oxide-Hemin-Au nanohybrids: Facile one-pot synthesis and enhanced electrocatalytic activity towards the reduction of hydrogen peroxide.

A facile and effective strategy is demonstrated for the synthesis of ternary reduced graphene oxide-Hemin-Au (rGO-H-Au) nanohybrids. The nanohybrids were synthesized through a one-pot in situ reduction of GO and HAuCl4 under alkaline conditions using GO, Hemin and HAuCl4 as the starting materials. The synthesis process can be finished within 1h in a solution phase, without adding any additional surfactant, stabilizing agent and toxic or harsh chemical reducing agents. The resulting nanohybrids were characterized by UV-vis spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), and so on. Electrochemical measurements showed that the rGO-H-Au nanohybrids exhibited good electrocatalytic activity for the reduction of hydrogen peroxide (H2O2). Based on this property, a simple and highly sensitive amperometric biosensor for H2O2 had been developed. The linear relationships were obtained from 0.1 µM to 40 µM and the detection limit was estimated to be 30 nM. The simple and sensitive sensing platform showed great promising applications in the pharmaceutical, clinical and industrial detection of H2O2.

Direct electrolytic exfoliation of graphite with hemin and single-walled carbon nanotube: Creating functional hybrid nanomaterial for hydrogen peroxide detection.

We present a new, facile and efficient method to prepare functional graphene (GN) hybrid nanomaterials using direct electrolytic exfoliation of graphite robs in hemin (HN) and single-walled carbon nanotube (SWCNT) solution. During the exfoliation process, HN and SWCNT were simultaneously adsorbed on the surface of GN nanosheets through noncovalent π-π interaction, and then 3D GN-HN-SWCNT hybrid nanomaterials were formed. Due to the synergic effect among GN, HN, and SWCNT, these hybrid nanomaterials possessed excellent electrocatalysis properties and were used to construct novel electrochemical biosensor for H2O2 determination. The results displayed a wide linear range of 0.2 µM-0.4 mM and a low detection limit of 0.05 µM. Moreover, the developed sensor was successfully applied for real samples, such as beverages, and showed great promise in routine sensing applications.

An efficient and chemoselective procedure for acylal synthesis.

A novel heterogeneous efficient procedure has been developed for the chemoselective synthesis of acylals (1,1-diacetates) under solvent-free conditions. A novel catalyst prepared by the sulfuric acid catalyzed copolymerization of p-toluenesulfonic acid and paraformaldehyde displays extremely high activities for the title reactions, affording average yields over 90% within several minutes. A comparative study showed that the novel catalyst has much higher activity than other catalysts used for this purpose. Besides, the novel catalyst displays chemoselectivity for the protection of aldehydes in the presence of ketones. In addition the high acidity (4.0 mmol/g), thermal stability (200 ºC) and easy reusability make the novel catalyst one of the best choices for the process.

Surface modification with BSA blocking based on in situ synthesized gold nanoparticles in poly(dimethylsiloxane) microchip.

A stable BSA blocking poly(dimethylsiloxane) (PDMS) microchannel was prepared based on in situ synthesized PDMS-gold nanoparticles composite films. The modified microchip could successfully suppress protein adsorption. The assembly was followed by contact angle, charge-coupled device (CCD) imaging, electroosmotic flow (EOF) measurements and electrophoretic separation methods. Contact angle measurements revealed the coated surface was hydrophilic, water contact angle for coated chips was 45.2 degrees compared to a water contact angle for native PDMS chips of 88.5 degrees. The coated microchips exhibited reproducible and stable EOF behavior. With FITC-labeled myoglobin incubation in the coated channel, no fluorescence was observed with CCD image, and the protein exhibited good electrophoretic effect in the modified microchip.

Direct electrochemistry of horseradish peroxidase on Nafion/[bmim]PF(6)/agarose composite film modified glassy carbon electrode.

A new strategy to construct electrochemical biosensor for direct electrochemistry of horseradish peroxidase (HRP) on glassy carbon electrode (GCE) based on Nafion, agarose hydrogel and hydrophobic room-temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF(6)) composite as sensing platform has been described. [bmim]PF(6) has good conductivity and wide electrochemical windows and agarose can maintain biological activity well. Nafion/[bmim]PF(6)/agarose composite combines the advantages of [bmim]PF(6) and agarose. Electrochemical impedance spectroscopy (EIS), ultraviolet visible spectroscopy (UV-vis), fourier transform infrared (FT-IR) spectroscopy and cyclic voltammetry (CV) were used to characterize the composite film, showing that the composite film could be effectively constructed on the GCE surface and greatly enhance the electron transfer between HRP and electrode. The factors influencing the performance of the resulting biosensor were studied in detail. The biosensor responded to H(2)O(2) in the linear range from 2x10(-6) to 1.6x10(-4)M with a detection limit of 1.2x10(-7)M (based on the S/N=3). The studied biosensor exhibited good accuracy and high sensitivity. Moreover, the proposed method was economical and efficient.

1-Phenyl-4-(triphenyl-phosphanyl-idene)pyrrolidine-2,3,5-trione.

In the title compound, C(28)H(20)NO(3)P, the five-membered maleimide ring is almost planar. The inter-planar angles between the maleimide ring and the three P-bound phenyl rings are 70.6 (2), 60.4 (2) and 54.68 (18)°, while the dihedral angle between the maleimide ring and the N-bound phenyl group is 55.43 (19)°.