Graphene has unique physical properties,and a variety of proof-of-concept devices based on graphene have been demonstated.A prerequisite for the application of graphene is its production in a controlled manner because the number of graphene layers and the defects in these layers significantly influence transport properties.In this paper,we briefly review our recent work on the controlled synthesis of graphene and graphene-based composites,the development of methods to characterize graphene layers,and the use of graphene in clean energy applications and for rapid DNA sequencing.For example,we have used Auger electron spectroscopy to characterize the number and structure of graphene layers,produced single-layer graphene over a whole Ni film substrate,synthesized well-dispersed reduced graphene oxide that was uniformly grafted with unique gold nanodots,and fabricated graphene nanoscrolls.We have also explored applications of graphene in organic solar cells and direct,ultrafast DNA sequencing.Finally,we address the challenges that graphene still face in its synthesis and clean energy and biological sensing applications.
One-dimensional crystals of fluorinated perylene diimides were achieved by the self-assembly of them via solvent-nonsolvent exchanging.The π-conjugated fluorinated perylene diimides were assembled into highly-ordered nanostructures of well-defined morphologies in organic solvents due to the π-π interaction between the aromatic cores.It was found that with more introduced F atoms,perylene diimides showed remarkably improved solubility and thus were much easier to grow into crystals,due to the increased polarity induced by the strong electron-withdrawing F group.More importantly,single crystal of N,N＇-diperfluorophenyl-3,4,9,10-perylenetetracarboxylic diimide（DPFPP）was obtained,and the unit cell-dimensions of triclinic structure were determined by the selected area electron diffraction（SAED） pattems to be a=0.712 nm,b=1.072 nm,c=2.914 nm,a=97.0°,β=89.6°,γ=93.4°.Owing to most of the longest c-axis orienting nearly vertically to the long axis of the needle crystal,the molecular planes are expected to be vertical to the needle axis.
HUANG Jiachi LI Hanying MO Xiong SHI Minmin WANG Mang CHEN Hongzheng
Stable aqueous amino-grafted silicon nanoparticles （SiNPs-NH2） were prepared via one-pot solution method. By grafting amino groups on the particle surface, the dispersion of SiNPs in water became very stable and clear aqueous solutions could be obtained. By incorporating SiNPs-NH2 into the hole transport layer of poly（3,4- ethylenedioxythiophene）/polystyrene sulfonic acid （PEDOT＇PSS）, the performance of polymer solar cells composed of poly[2-methoxy,5-（2＇-ethylhexyloxy）-1,4-phenylene vinylene] （MEH-PPV）：[6,6]-phenyl-C61-butyric acid methyl ester （PCBM） as active layer can be improved. SiNPs-NH2 are dispersed uniformly in the PEDOT：PSS solution and help form morphologies with small-sized domains in the PEDOT：PSS film. SiNPs-NH2 serve as screens between conducting polymer PEDOT and ionomer PSS to improve the phase separation and charge transport of the hole transport layer. As a result, the sheet resistance of PEDOT：PSS thin films is decreased from （93 ±5） × 10^5 to （13 ± 3） × 10^5 Ω/□. The power conversion efficiency （PCE） of polymer solar cells was thus improved by 9.8% for devices fabricated with PEDOT＇PSS containing 1 wt% of SiNPs-NH2, compared with the devices fabricated by original PEDOT：PSS.
