Li Ruiyi

Nickel–cobalt double hydroxides microspheres with hollow interior and hedgehog-like exterior structures for supercapacitors

Nickel–cobalt double hydroxide microspheres (Ni–Co-DHM) have been synthesized by a facile and cost-effective in situ method. The obtained Ni–Co-DHM displays a three-dimensional architecture with hollow interior and hedgehog-like exterior structures. The unique architecture greatly improves the faradaic redox reaction and mass transfer. The Ni–Co-DHM electrode offers an excellent pseudocapacitance performance, including high specific capacitance and rate capability, good charge–discharge stability and long-term cycling life. Its maximum specific capacitance was found to be 2275.5 F g−1 at current density of 1 A g−1, which is more than 3-fold that of common nickel–cobalt double hydroxides and 2-fold that of the mechanical mixture of Co(OH)2 and Ni(OH)2 microspheres. The specific capacitance can remain at 1007.8 F g−1 when the current density increases to 25 A g−1. The capacitance can keep at least 92.9% at current density of 10 A g−1 after 5000 cycles. Therefore, this work provides a promising approach for the design and synthesis of structure tunable materials with largely enhanced supercapacitor behavior, which can be potentially applied in energy storage/conversion devices.

Electrochemical immunosensor for ultrasensitive detection of microcystin-LR based on graphene-gold nanocomposite/functional conducting polymer/gold nanoparticle/ionic liquid composite film with electrodeposition.

The study developed an electrochemical immunosensor for ultrasensitive detection of microcystin-LR in water. Graphene oxide and chloroauric acid were alternately electrodeposited on the surface of glassy carbon electrode for 20 cycles to fabricate graphene-gold nanocomposite. The composite was characterized and its apparent heterogeneous electron transfer rate constant (37.28±0.16 cm s (-1)) was estimated by Lavirons model. To immobilize microcystin-LR antibody and improve the electrical conductivity, 2,5-di-(2-thienyl)-1-pyrrole-1-(p-benzoic acid) and chloroauric acid were electrodeposited on the modified electrode in sequence. The ionic liquid was then dropped on the electrode surface and finally microcystin-LR antibody was covalently connected to the conducting polymer film. Experiment showed the electrochemical technique offers control over reaction parameters and excellent repeatability. The graphene-gold nanocomposite and gold nanoparticles enhance electron transfer of Fe(CN)6(3-/4-) to the electrode. The ionic liquid, 1-isobutyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide, improves stability of the antibody. The sensor displays good repeatability (RSD=1.2%), sensitive electrochemical response to microcystin-LR in the range of 1.0×10(-16)-8.0×10(-15)M and detection limit of 3.7×10(-17)M (S/N=3). The peak current change of the sensor after and before incubation with 2.0×10(-15)M of microcystin-LR can retain 95% over a 20-weeks storage period. Proposed method presents remarkable improvement of sensitivity, repeatability and stability when compared to present microcystin-LR sensors. It has been successfully applied to the microcystin-LR determination in water samples with a spiked recovery in the range of 96.3-105.8%.

Ultrafast synthesis of gold/proline-functionalized graphene quantum dots and its use for ultrasensitive electrochemical detection of p-acetamidophenol

Gold/proline-functionalized graphene quantum dots were first reported. The growth of gold nanoparticles can complete within one minute. The resulting nanohybrid was used as a novel sensing material for electrochemical detection of p-acetamidophenol. Significant synergy between graphene quantum dots and gold nanoparticles was achieved, and the sensor offers ultrahigh sensitivity.

Resonance light scattering method for the detection of peanut allergen-Ara h 1 using gold nanorods prepared by improved synthesis through the use of a sodium dodecyl benzene sulfonate additive

Peanut allergen is a growing food safety problem because peanut seeds are increasingly used in the food industry. Here we report a resonance light scattering (RLS) method for the detection of peanut allergen-Araxa0hxa01 with gold nanorods (GNRs) prepared by an improved synthesis through the use of an anionic surfactant sodium dodecyl benzene sulfonate (SDBS) additive. The study demonstrated that the use of SDBS allows the reduction of hexadecyltrimethylammonium bromide to 0.05 M as opposed to 0.1 M in well-established protocols, and improves the monodispersity and stability of the GNRs. Moreover, a probe DNA modified with a thiol at its 5′ end and a biotin at its 3′ end was attached to the surface of the as-synthesized GNRs to form a stem–loop structure by self-assembly through facile gold–thiol affinity. The stem–loop probe was “closed” when the target DNA was absent; however, the hybridization of the target DNA with the probe DNA induces the conformational change to “open”, along with the biotin at its 3′ end moving away from the GNR surface, which results in an increase of the RLS intensity of the GNRs. The detection limit was found to be 0.06 pM with the linear response ranging from 0.0002 to 50 nM. The present method offers the improvement of rapidity, sensitivity and selectivity compared with other reported methods. It has been successfully applied for the determination of peanut allergen-Araxa0hxa01 in peanut milk beverage.