Mengmeng Fan

Recent progress in 2D or 3D N-doped graphene synthesis and the characterizations, properties, and modulations of N species

Nitrogen (N)-doped graphene (N-substituted or nitrogenated graphene) (NG) has become a new class of graphene material due to its modified properties such as the tunable work function, n-type semiconductivity, increasing biocompatibility, and, in particular, the synergistic function with various functional materials. However, the preparation of NG by a simple and effective method is still lacking. The modification of NG mainly depends on the N species and the N content. Thus, we focus on the recent progress in preparing methods of 2D NG and the respective key modulating parameters to modulate the N species and the N content. Furthermore, many effective charactering techniques are covered to accurately analyze the properties of N species, and the distribution and topography of N atoms. Also, we review the effect of N species on graphene, especially, the optical and electronic properties. Since constructing 3D structure is considered a promising strategy to prevent the restacking of 2D NG, the summary for preparing 3D NG is made on the basis of methodology of 2D NG. In a word, this review provides a reference for preparing 2D or 3D NG, modulating and characterizing N species, which are greatly contributed to the NG application.

Novel Cu@SiO2/bacterial cellulose nanofibers: Preparation and excellent performance in antibacterial activity.

The antibacterial composite based on bacterial cellulose (BC) was successfully prepared by in-situ synthesis of SiO2 coated Cu nanoparticles (Cu@SiO2/BC) and its properties were characterized. Its chemical structures and morphologies were evaluated by Fourier transformation infrared spectrum (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the SiO2 coated Cu particles were well homogeneously precipitated on the surface of BC. The Cu@SiO2/BC was more resistant to oxidation than the Cu nanoparticles impregnated into BC (Cu/BC) and then Cu@SiO2/BC could prolong the antimicrobial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli).

Modified PEDOT by benign preparing N-doped reduced graphene oxide as potential bio-electrode coating material

We have successfully prepared poly (3,4-ethylenedioxythiophene) (PEDOT)/N-doped reduced graphene oxide (N-rGO) by electrodeposition, post-reduction, and doping N atoms with a microorganism (as a green reagent) to modify PEDOT and resolve the exfoliation and fragmentation problems of pristine PEDOT. This modification greatly improves the electrochemical properties of PEDOT, showing great potential for a bio-electrode coating material, which should have excellent electrochemical properties, stability and biocompatibility. The as-prepared PEDOT/N-rGO shows lower impedance, and higher capacitive performance and cyclical stability than pristine PEDOT due to the doping of N-rGO. An MTT assay demonstrates this modified PEDOT has good adhesion, cell viability and proliferation, similar to pristine PEDOT. This indicates that the modification process does not restrain the good biocompatibility of pristine PEDOT, which results from the doping of highly biocompatible N-rGO by this green method. The wrinkled structure, residual oxygen containing functional groups and dopant N atoms of N-rGO lead to the formation of a fluctuating surface and an increase in the hydrophilicity of PEDOT, which increase the specific surface area and cell adhesion in cell culture, respectively. Consequently, this modified PEDOT improves the electrochemical properties, and resolves the exfoliation and fragmentation problems of pristine PEDOT, while still retaining the high biocompatibility of pristine PEDOT, which is promising for a bio-electrode coating material.

Biosynthesis approach to nitrogen doped graphene by denitrifying bacteria CFMI-1

Here we present a novel approach to prepare N-doped graphene under ambient conditions by denitrifying bacteria CFMI-1. The N element can be effectively introduced into graphene and 8.2% (atom %) N doping level can be achieved. N-doped graphene possesses a size around 300–600 nm and an average thickness of 1–2 nm.

Microbial oxidation of graphite by Acidithiobacillus ferrooxidans CFMI-1

Graphite oxide was prepared by a simple and environmentally-friendly bio-oxidation strategy using Acidithiobacillus ferrooxidans CFMI-1 bacteria. The obtained graphite oxide nanosheets have a few layers with 1.5–1.7 nm (about 3–4 layers of sheets) height and 150–900 nm size.

N‐Doped Carbon Nanofibrous Network Derived from Bacterial Cellulose for the Loading of Pt Nanoparticles for Methanol Oxidation Reaction

The large-scale, low-cost preparation of Pt-based catalysts with high activity and durability for the methanol oxidation reaction is still challenging. The key to achieving this aim is finding suitable supporting materials. In this paper, N-doped carbon nanofibrous networks are prepared by annealing a gel containing two inexpensive and ecofriendly precursors, that is, bacterial cellulose and urea, for the loading of Pt nanoparticles. An undoped analogue is also prepared for comparison. Meanwhile, the effect of the annealing temperature on the performance of the catalysts is evaluated. The results show that the N doping and higher annealing temperature can improve the electron conductivity of the catalyst and provide more active sites for the loading of ultrafine Pt nanoparticles with a narrow size distribution. The best catalyst exhibits a remarkably high electrocatalytic activity (627 mA mg-1 ), excellent poison tolerance, and high durability. This work demonstrates an ideal Pt supporting material for the methanol oxidation reaction.

Preparation of bacterial cellulose based nitrogen-doped carbon nanofibers and their applications in the oxygen reduction reaction and sodium–ion battery

It is of great practical importance to design low-cost materials as catalysts for the oxygen reduction reaction (ORR) and as an anode for sodium–ion batteries (SIBs). In this paper, we report a class of nitrogen-doped carbon materials with a three-dimensional nanofibrous network derived from inexpensive biomass bacterial cellulose (BC) for both ORR and SIB applications. The samples were prepared by treating the BC aerogels with various amounts of pyrrole to ensure a uniform coating on the surface of the BC nanofibers, followed by a carbonization process under different temperatures. The products were essentially carbon nanofibers coated by a nitrogen-doped carbon layer and retained the initial structure of BC. The optimum amount of pyrrole was 0.05 mL and the optimum carbonization temperature was 900 °C. Our best catalyst exhibited good electrocatalytic performance and durability in ORR, without the presence of noble metals. An electrode made from the same material has also demonstrated a stable cycling performance and superior rate capability in SIB application. Our work has demonstrated a rational design of electroactive carbon materials from a low-cost precursor.