Passivated Nanoparticles

31 May 2007

Passivated nanoparticles are the building materials for many assemblies. These are nanometer sized colloidal particles and these can be produced from various materials. The nanoparticles are typically terminated by organic monolayer such as alkanethiol molecules and show diverse functional properties. The electronic, optical and catalytic properties of these nanoparticles as reported by many researchers are different from their corresponding bulk material properties. The organic layer act as a binding agent and core by a thiolate bond and consequently prevent the particles from aggregating in either solution or on a surface and thus these nanoparticles retain their functionality as well as uniqueness.

Passivated metal especially gold nanoclusters have been used to form thin films or ordered monolayers. The diameter of nanoparticles especially if it is in the range of 1-10 nm is best suitable for constructing various nanoscale devices. The X ray analysis of super lattice formed by three-dimensional assembly of passivated gold reveals that the macroscopic properties of three-dimensional super lattice are determined by the properties of individual as well as the interaction between nanocrystal due to the ligands attached to the nanoparticles.

Thus the organic molecule or ligand attached to the nanoparticle regulate interparticle bonding and if interparticle spacing is changed, we get change in length of molecular chain and simultaneously we will get the altered values of electronic, optical and transport properties also. Further we can use a variety of organic molecule to passivate the nanoparticle core and therefore we have large number of options to select attachment of individual nanoparticle and to fabricate nanodevices.

It has already been reported self-assembly processes including gold and silver nanowires and nanoparticles in the recent years and a recent study reported successful self-assembly of CdTe nanoparticles to form a crystalline nanowire. Patterning is another area through which nanoparticle assembly can be achieved by modifying surfaces. Nanoparticles thus having selectively passivated or having designed ligands can selectively be self-assembled and a suitable nanodevice can be obtained.

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