1、Appl Phys A(2011)102:333337DOI 10.1007/s00339-010-5971-yComparative investigation on decorating carbon nanotubeswith different transition metalsJ.Y.Guo C.X.XuReceived:12 November 2009/Accepted:6 April 2010/Published online:31 July 2010 Springer-Verlag 2010Abstract The diffusion dynamics and structur
2、e evolvementof the transition metal(TM=Ni,Cu,Au,and Pt)atomsdecorating carbon nanotubes(CNTs)with differences havebeen systematically studied by Monte Carlo(MC)simula-tion.The studies show that TM atoms can be encapsulatedinside,aggregated and even wrapped on the surface of theCNT,which depend on th
3、e interactions among TMTM andTMC during the spontaneous diffusion process.The deco-rating effect is greatly influenced by the diameters of CNTs,TM atoms tend to be encapsulated inside the tube in the rel-atively large CNTs,while they are inclined to stack on thesurface for the small ones.More intere
4、stingly,Au and Ptatoms would wrap around the smaller CNT,whereas Ni andCu atoms are still clustering outside of the CNTs with theincrease of the number of TM atoms.Simulation results in-dicate that Pt and Au possess a better wetting effect withCNT than Ni and Cu.1 IntroductionDue to their extraordin
5、ary electronic properties,intrinsicstructure,large chemically active surface and stability athigh temperatures,CNTs have been shown promise for re-placing silicon in future generation electronic devices,andhave been used as a support material for encapsulation,dis-persion and stabilization of metal
6、nanoclusters 13.TheseJ.Y.Guo C.X.Xu(?)State Key Laboratory of Bioelectronics,Advanced PhotonicsCenter,Southeast University,Nanjing 210096,P.R.Chinae-mail:J.Y.GuoCollege of Mathematics and Physics,Jiangsu Universityof Science and Technology,Zhenjiang 212001,P.R.Chinahybrid materials have been drawing
7、 a great deal of atten-tion in fundamental research and are widely explored formanyphysical,chemicalandbiologicalapplications,includ-ing nanoscale composite materials,nanoelectronics 46,hydrogen 7 and lithium storage 8,catalysis 9,sen-sors 10,nanoscale pharmaceutical drug delivery devicesetc.11.To g
8、uide fabrication of the materials,it is important tounderstand the formation mechanism of decorating CNTswith metal atoms.Materials composed of CNTs and metalssuch as Ni,Cu,Au,Pt,Pd and Ag 1215 have been stud-ied experimentally by means of surface imaging techniques,such as scanning tunneling micros
9、copy,atomic force mi-croscopy and transmission electron microscopy.Despite theuse of highly developed experimental techniques,the task ofgaining a detailed understanding for the dynamic propertiesof metal atoms,such as diffusion and aggregation,is diffi-cult because imaging techniques only provide t
10、emporal dis-crete images during diffusion processes.On the other hand,atomistic computer simulations have played important rolesin understanding the decorating processes for the propertiesof practicability.In recent years,the molecular dynamicsmethod has been employed to simulate structure 16,so-lid
11、ification of the encapsulated nanoparticles 17,bucklingbehaviors of CNTs filled with metal atoms 18,19 and thediffusion of nanoclusters on CNTs 20.The filling processof Ni atoms into CNTs has been investigated by the MCmethod 21.Other methods,such as the ab initio method,have also been introduced to
12、 show that the metal-decoratedCNTs were good candidates for the hydrogen storage ma-terial only if the metal atom aggregation can be preventedefficiently 22 and the first-principles calculations have ex-plored both the structures and electromagnetic properties ofmetal-filled CNTs 23.334J.Y.Guo,C.X.X
13、uMany theoretical studies have been performed on the dy-namic properties of CNT-supported metal materials,how-ever,few studies on the decorating effects of CNTs with dif-ferent TM atoms at the same conditions have been reported,and systematical investigation is still required.In this work,MC simulat
14、ion is carried out to investigate the decoratingeffects when a certain quantities of different TM atoms dif-fuse to CNTs at the same conditions.The dynamic proper-ties of the spontaneous diffusion and the atomic encapsula-tion,aggregationandwrappedeffectsarediscussedindetail.The interesting structur
15、es in nanoscale are presented,whichare generated by the naked TM atoms diffusing directly toCNTs.The simulation processes provide a simple approachto compare the wetting effects between the TM and CNT.Itis helpful to design some nanocomposite materials and de-vices,such as optimization for catalytic
16、 properties of CNT-supported hybrid nanomaterials or selecting TM which hasthe better wetting effect for TM-based nanoscale intercon-nects with CNTs.2 Models and simulation detailsThe model can essentially be divided into two parts,cover-ing the TMTM and TMC interactions.The effective po-tential of the SuttonChen(SC)potential model is selectedto reliably describe the static and dynamic properties of TM2426 and it has been applied to optimize the structure andsearch for the global minima of TM cl
