Jingjing Lin

Graphene covered SiC powder as advanced photocatalytic material

Graphene covered SiC powder (GCSP) has been fabricated by well established method of high temperature thermal decomposition of SiC. The structural and photocatalystic characteristics of the prepared GCSP were investigated and compared with that of the pristine SiC powder. Under UV illumination, more than 100% enhancement in photocatalystic activity is achieved in degradation of Rhodamine B (Rh B) by GCSP catalyst than by pristine SiC powder. The possible mechanisms underlining the observed results are discussed. The results suggested that GCSP as a composite of graphene based material has great potential for use as a high performance photocatalyst.

Towards intrinsic magnetism of graphene sheets with irregular zigzag edges

The magnetism of graphene has remained divergent and controversial due to absence of reliable experimental results. Here we show the intrinsic magnetism of graphene edge states revealed based on unidirectional aligned graphene sheets derived from completely carbonized SiC crystals. It is found that ferromagnetism, antiferromagnetism and diamagnetism along with a probable superconductivity exist in the graphene with irregular zigzag edges. A phase diagram is constructed to show the evolution of the magnetism. The ferromagnetic ordering curie-temperature of the fundamental magnetic order unit (FMOU) is 820 ± 80 K. The antiferromagnetic ordering Neel temperature of the FMOUs belonging to different sublattices is about 54 ± 2 K. The diamagnetism is similar to that of graphite and can be well described by the Kotosonovs equation. Our experimental results provide new evidences to clarify the controversial experimental phenomena observed in graphene and contribute to a deeper insight into the nature of magnetism in graphene based system.

Entropy changes due to the first-order phase transition in the Gd5SixGe4−x system

Entropy changes due to magnetostructrual phase transition in Gd5SixGe4−x intermetallics have been studied based on a systematic analysis of experiment data and mean-field theory calculations. It is found that the magnetic and lattice entropy changes have the same sign. Further analysis indicates that the main entropy change (∼60%–∼80%) comes from the field-induced change of the magnetic order, while the rest arise from the entropy difference of the two crystallographic modifications joined by the structural transition, probably due to the variation of the lattice vibration mode. The present work reveals the importance of lattice entropy for a system experiencing a first-order transition.

Magnetic properties of nanostructured Mn oxide particles

Nanostructured Mn oxide particles with an average size of about 7 nm have been prepared by a microemulsion method. X-ray diffraction analysis indicates that the particles possess orthorhombic structure of MnO(OH). The particles are ferromagnetic at low temperature. The Curie temperature is about 35 K and each MnO(OH) molecule generates a magnetic moment of about 0.7 μB. The appearance of the ferromagnetism at low temperature may result from size effect.

Approaching the intrinsic electron field-emission of a graphene film consisting of quasi-freestanding graphene strips.

Knowledge Innovation Engineering of the Chinese Academy of Sciences [KJCX2-YW-W22, YYYJ-0701]; Ministry of Science & Technology of PR China [2007BAE34B00, 2006AA03A146, 2007CB936300, 2006AA03A107]; National Natural Science Foundation of China [50972162, 50702073]; Major State Basic Research Development Program of China (973 Program) [2011CB932700]

Significant enhancement in photocatalytic activity of high quality SiC/graphene core–shell heterojunction with optimal structural parameters

Structure and photocatalytic activity of high quality graphene covered SiC powder (GCSP) composites as metal-free photocatalysts with different sizes and graphene layer numbers are investigated. The results indicate that the GCSP covered with 4–9 layers of graphene reveal outstanding photocatalytic activity enhancement among the other graphene layer numbers. Moreover, it is found that smaller particles have higher activity than the larger ones and more than 730% improvement is achieved by the GCSP derived from 0.5 μm SiC powder relative to the pristine SiC powder, which is more than 6 times of that of photoreduced graphene oxide/SiC composite. Our results demonstrate that it is the high quality graphene and the perfect heterojunction interface between the graphene and SiC particles render the SiC/graphene core–shell heterojunction an outstanding photocatalytic activity, as well as potential for a low cost and metal-free photocatalyst.

Identification of dominant scattering mechanism in epitaxial graphene on SiC

A scheme of identification of scattering mechanisms in epitaxial graphene (EG) on SiC substrate is developed and applied to three EG samples grown on SiC (0001), (11 (2) over bar0), and (10 (1) over bar0) substrates. Hall measurements combined with defect detection technique enable us to evaluate the individual contributions to the carrier scatterings by defects and by substrates. It is found that the dominant scatterings can be due to either substrate or defects, dependent on the substrate orientations. The EG on SiC (11 (2) over bar0) exhibits a better control over the two major scattering mechanisms and achieves the highest mobility even with a high carrier concentration, promising for high performance graphene-based electronic devices. The method developed here will shed light on major aspects in governing carrier transport in EG to harness it effectively