Yunpeng Zuo

Antiviral Activity of Graphene Oxide: How Sharp Edged Structure and Charge Matter.

Graphene oxide and its derivatives have been widely explored for their antimicrobial properties due to their high surface-to-volume ratios and unique chemical and physical properties. However, little information is available on their effects on viruses. In this study, we report the broad-spectrum antiviral activity of GO against pseudorabies virus (PRV, a DNA virus) and porcine epidemic diarrhea virus (PEDV, an RNA virus). Our results showed that GO significantly suppressed the infection of PRV and PEDV for a 2 log reduction in virus titers at noncytotoxic concentrations. The potent antiviral activity of both GO and rGO can be attributed to the unique single-layer structure and negative charge. First, GO exhibited potent antiviral activity when conjugated with PVP, a nonionic polymer, but not when conjugated with PDDA, a cationic polymer. Additionally, the precursors Gt and GtO showed much weaker antiviral activity than monolayer GO and rGO, suggesting that the nanosheet structure is important for antiviral properties. Furthermore, GO inactivated both viruses by structural destruction prior to viral entry. The overall results suggest the potential of graphene oxide as a novel promising antiviral agent with a broad and potent antiviral activity.

Clean Synthesis of an Economical 3D Nanochain Network of PdCu Alloy with Enhanced Electrocatalytic Performance towards Ethanol Oxidation

A one-pot method for the fast synthesis of a 3D nanochain network (NNC) of PdCu alloy without any surfactants is described. The composition of the as-prepared PdCu alloy catalysts can be precisely controlled by changing the precursor ratio of Pd to Cu. First, the Cu content changes the electronic structure of Pd in the 3D NNC of PdCu alloy. Second, the 3D network structure offers large open pores, high surface areas, and self-supported properties. Third, the surfactant-free strategy results in a relatively clean surface. These factors all contribute to better electrocatalytic activity and durability towards ethanol oxidation. Moreover, the use of copper in the alloy lowers the price of the catalyst by replacing the noble metal palladium with non-noble metal copper. The composition-optimized Pd80 Cu20 alloy in the 3D NNC catalyst shows an increased electrochemically active surface area (80.95 m(2)  g(-1) ) and a 3.62-fold enhancement of mass activity (6.16 A mg(-1) ) over a commercial Pd/C catalyst.

Platinum Dendritic-Flowers Prepared by Tellurium Nanowires Exhibit High Electrocatalytic Activity for Glycerol Oxidation

Dentritic Pt-based nanomaterials with enriched edge and corner atoms have recently attracted considerable attention as electrocatalysts. Meanwhile, Pt(111) facets are generally considered more active for the glycerol oxidation reaction (GOR). Thus, it is significant to construct the rational design and synthesis of dentritic Pt whose surface is mostly enclosed by {111} facets. Reported herein is a unique Pt-branched structure enriched by a large amount of valency unsaturated atoms prepared by the aggravation of the galvanic replacement strategy. The synthesis is developed to generate highly crystallized Pt nanoflowers using Te nanowires as a template. Furthermore, the electrochemical results show that Pt nanoflower is an excellent catalyst with higher mass activity and better structure stability than commercial Pt/C (20% Pt) for glycerol electro-oxidation. Besides, the template-broken approach could provide a novel potential way to synthesize Pt-based or other noble metals/alloys for their advanced functional applications.

Regulating the oxidation degree of nickel foam: a smart strategy to controllably synthesize active Ni3S2 nanorod/nanowire arrays for high-performance supercapacitors

A novel strategy is described in this study to construct three-dimensional (3D) nickel foam (NF) supported active Ni3S2 arrays with varieties of morphologies using a controllable pre-oxidation method followed by a post-hydrothermal treatment. A systematic study of the pre-oxidation effect is presented, and the possible reaction mechanism is discussed. Specifically, through accurately controlling the oxidation degree of the NF precursor, grass-like Ni3S2 nanorod/nanowire arrays grown in situ on the NF network are synthesized. Benefiting from the unique architecture to provide a large interfacial area, effective pathway for charge transport and high electrochemical activity from Ni3S2, the binder-free electrode exhibits remarkable electrochemical performances with a specific areal capacitance of 4.52 F cm−2 at 1.25 mA cm−2, as well as superior cycling stability (108.3% capacitance retention after 2000 cycles). An aqueous asymmetric supercapacitor device composed of such an electrode as the positive electrode and nitrogen-doped porous graphitic carbon (NPGC) as the negative electrode achieves a high energy density of 48.5 W h kg−1 and power density of 4.8 kW kg−1. Further, two such 4 cm2 devices connected in series can successfully illuminate three color-changing LEDs for a long time, demonstrating the great potential for high-performance supercapacitors. The smart strategy described herein could be widely adopted to create other composites with desirable nanostructures.

Highly sensitive enzyme-free immunosorbent assay for porcine circovirus type 2 antibody using Au-Pt/SiO2 nanocomposites as labels

Improving the performance of conventional enzyme-linked immunosorbent assay (ELISA) is of great importance to meet the demand of early clinical diagnosis of various diseases. Herein, we report a feasible enzyme-free immunosorbent assay (EFISA) system using antibody conjugated Au-Pt/SiO2 nanocomposites (APS NCs) as labels. In this system, Au-Pt/SiO2 nanospheres (APS NPs) were first synthesized by wet chemical method and exhibited intrinsic peroxidase and catalase-like activity with excellent water-solubility. Then APS NCs were utilized as labels to replace HRP conjugated antibody, and Fe3O4 magnetic beads (MBs) to entrap the analyte. To discuss the performance of EFISA system, Human IgG was served as a model analyte, and porcine circovirus type 2 (PCV2) serums as real samples. The system boosted the detection limit of HIgG to 75pgmL(-1) with a RSD below 5%, a 264-fold improvement as compared with conventional ELISA. This is the first time that APS NCs have been used and successfully optimized for the sensitive dilution detection of PCV2 antibody (5:10(7)) in ELISA. Besides, APS NCs have advantages related to low cost, easy preparation, good stability and tunable catalytic activity, which make them a potent enzyme mimetic candidate and may find potential applications in bioassays and clinical diagnostics.

Spiny-porous platinum nanotubes with enhanced electrocatalytic activity for methanol oxidation

A facile and general approach is developed to synthesize self-supported spiny-porous Pt nanotubes (SP-PtNTs). The multi-dimensional structure with enriched edge and corner atoms showed 4.3 and 1.53 times higher mass electrocatalytic activity than porous Pt nanotubes (P-PtNTs) and commercial Pt/C (20% Pt), which increased the Pt utilization and decreased the dosage of Pt and the cost of Pt-based catalysts. SP-PtNTs had better stability and dispersibility than P-PtNTs and commercial Pt/C (20% Pt) in the water phase. The brief mechanism for the synthesis of SP-PtNTs could also be extended to synthesize other noble metals, as well as their bimetallic combinations, with excellent catalysis and electrocatalysis. Furthermore, the spiny structure provided extra active sites that might facilitate the application of Pt for use in enzyme-like catalysis or nano-electronic applications.

Self-assembly of Pt-based truncated octahedral crystals into metal-frameworks towards enhanced electrocatalytic activity

Self-assembly of Pt-based truncated octahedral crystals into frameworks has been demonstrated in this paper by suitably adjusting the reactant concentrations and temperature. This approach allows for control of Pt or Pt-based nano-crystals with subnanometer-size as building blocks for metal-frameworks (MFs): sub-micron porous tubes (SMPBs) and mesh (M). Both the Pt-based MFs exhibit enhanced activity and better stability for the oxygen reduction reaction (ORR) and methanol-oxidation reaction (MOR) than PtMFs. The mass activity (MA) of the Pt4Cu-SMPBs (0.619 A mg−1@0.9 V) exhibited 5.12 times enhancement over the commercial Pt/C (0.121 A mg−1@0.9 V) catalyst towards the ORR and the value is well beyond the U.S. Department of Energys 2017 target (0.44 A mgPt−1 @0.9 V). After 8000 cycles of accelerated durability test, the MA of the Pt4Cu-SMPBs (0.411 A mg−1@0.9 V) was still greater than the values of the Pt/C. These metal-framework materials provide a new direction to obtain highly open nanostructures which would readily improve their catalytic properties in both activity and durability while reducing their loading.