5 research outputs found
Additional file 1: of Cell-bound lipases from Burkholderia sp. ZYB002: gene sequence analysis, expression, enzymatic characterization, and 3D structural model
All PCR conditions and PCR procedures used in this research. (DOC 54 kb
Efficient Oxygen Reduction Electrocatalyst Based on Edge-Nitrogen-Rich Graphene Nanoplatelets: Toward a Large-Scale Synthesis
The
large-scale synthesis of nitrogen doped graphene (N-graphene)
with high oxygen reduction reaction (ORR) performance has received
a lot of attention recently.
In this work, we have developed a facile and economical procedure
for mass production of edge-nitrogen-rich graphene nanoplatelets (ENR-GNPs)
by a combined process of ball milling of graphite powder (GP) in the
presence of melamine and subsequent heat treatment. It is found that
the ball milling process can not only crack and exfoliate pristine
GP into edge-expanded nanoplatelets but also mechanically activate
GP to generate appropriate locations for N-doping. Analysis results
indicate that the doped N atoms mainly locate on the edge of the graphitic
matrix, which contains ca. 3.1 at.% nitrogen content and can be well-dispersed
in aqueous to form multilayer nanoplatelets. The as-prepared ENR-GNPs
electrocatalyst exhibits highly electrocatalytic activity for ORR
due to the synergetic effects of edge-N-doping and nanosized platelets.
Besides, the stability and methanol tolerance of ENR-GNPs are superior
to that of the commercial Pt/C catalyst, which makes the nanoplatelets
a promising candidate for fuel cell cathode catalysts. The present
approach opens up the possibility for simple and mass production of
N-graphene based electrocatalysts in practice
Identifying the Active Site in Nitrogen-Doped Graphene for the VO<sup>2+</sup>/VO<sub>2</sub><sup>+</sup> Redox Reaction
Nitrogen-doped graphene sheets (NGS), synthesized by annealing graphite oxide (GO) with urea at 700–1050 °C, were studied as positive electrodes in a vanadium redox flow battery. The NGS, in particular annealed at 900 °C, exhibited excellent catalytic performance in terms of electron transfer (ET) resistance (4.74 ± 0.51 and 7.27 ± 0.42 Ω for the anodic process and cathodic process, respectively) and reversibility (Δ<i><i>E</i></i> = 100 mV, <i>I</i><sub>pa</sub>/<i>I</i><sub>pc</sub> = 1.38 at a scan rate of 50 mV s<sup>–1</sup>). Detailed research confirms that not the nitrogen doping level but the nitrogen type in the graphene sheets determines the catalytic activity. Among four types of nitrogen species doped into the graphene lattice including pyridinic-N, pyrrolic-N, quaternary nitrogen, and oxidic-N, quaternary nitrogen is verified as a catalytic active center for the [VO]<sup>2+</sup>/[VO<sub>2</sub>]<sup>+</sup> couple reaction. A mechanism is proposed to explain the electrocatalytic performance of NGS for the [VO]<sup>2+</sup>/[VO<sub>2</sub>]<sup>+</sup> couple reaction. The possible formation of a N–V transitional bonding state, which facilitates the ET between the outer electrode and reactant ions, is a key step for its high catalytic activity
Design of Stretchable and Conductive Self-Adhesive Hydrogels as Flexible Sensors by Guar-Gum-Enabled Dynamic Interactions
The limited elasticity and inadequate bonding of hydrogels
made
from guar gum (GG) significantly hinder their widespread implementation
in personalized wearable flexible electronics. In this study, we devise
GG-based self-adhesive hydrogels by creating an interpenetrating network
of GG cross-linked with acrylic, 4-vinylphenylboronic acid, and Ca2+. With the leverage of the dynamic interactions (hydrogen
bonds, borate ester bonds, and coordination bonds) between −OH
in GG and monomers, the hydrogel exhibits a high stretchability of
700%, superior mechanical stress of 110 kPa, and robust adherence
to several substrates. The adhesion strength of 54 kPa on porcine
skin is obtained. Furthermore, the self-adhesive hydrogel possesses
stable conductivity, an elevated gauge factor (GF), and commendable
durability. It can be affixed to the human body as a strain sensor
to obtain precise monitoring of human movement behavior. Our research
offers possibilities for the development of GG-based hydrogels and
applications in wearable electronics and medical monitoring
Syntheses, Crystal Structures, and Properties of Four Metal–Organic Complexes Based on 1,4,5,6,7,7-Hexachlorobicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic Acid
Four metal–organic
complexes [NiÂ(HET)Â(phen)Â(H<sub>2</sub>O)]·(HET)·H<sub>2</sub>O (<b>1</b>), [CuÂ(HET)Â(phen)Â(H<sub>2</sub>O)]·1.5H<sub>2</sub>O (<b>2</b>), [Cu<sub>2</sub>(HET)<sub>2</sub>Â(bipy)<sub>1.5</sub>Â(H<sub>2</sub>O)]Â<b>·</b>15DMF<b>·</b>2H<sub>2</sub>O (<b>3</b>), and [Cd<sub>2</sub>OÂ(HET)<sub>2</sub>Â(bipy)Â(H<sub>2</sub>O)]Â<b>·</b>2H<sub>2</sub>O<b>·</b>EtOH (<b>4</b>) (HET = 1,4,5,6,7,7-hexachlorobicyclo[2.2.1]Âhept-5-ene-2,3-dicarboxylic
acid, phen = 1,10-phenanthroline, bipy = 4,4′-bipyridine) have
been synthesized via hydro- or solvothermal reactions. It was found
that complexes <b>1</b> and <b>2</b> are two-dimensional
(2D) structures built from discrete complexes via the typical intermolecular
interactions, and there was a closed loop built from the lattice water
and carboxylate groups in <b>1</b> through intramolecular hydrogen
bonds. Complex <b>3</b> exhibits three-dimensional (3D) structure
with 5-connected <i><b>bnn</b></i> hexagonal BN topology.
Complex <b>4</b> features a non-interpenetrating <i><b>sql</b></i> 2D coordination network, which is further linked
into a 3D structure by C–H···Cl weak interaction.
The properties of magnetism, fluorescence, and electrochemistry have
also been investigated in this paper