Patterned close-packed nanoparticle arrays are fabricated using lithography and self-assembly. Microcontact printing is used to selectively transfer ordered nanoparticle monolayers, which are self-assembled at the air/water interface, onto relief structures, which are defined lithographically. The morphology and position of the nanoparticle arrays are determined by the relief structures, while the internal order of the arrays is achieved through the self-assembly process and is maintained during the transfer.

We demonstrate a strong photocurrent enhancement in carbon nanotube (CNT) photodetectors by coupling the CNT with a plasmonic nanostructure made of Au nanoparticles. Comparing with the device without coupling to Au nanoparticles, more than 3 times photocurrent enhancement is observed and attributed to the strong local field enhancement on the CNT. The plasmonic near-field coupling with CNTs with different diameters is also investigated and the results suggest that CNTs with larger diameter show stronger enhancement. This work demonstrates the potential to significantly improve the performance of CNT photoelectric devices using metallic nanoparticles that support surface plasmons.

We studied the electronic transport properties of metal nanoparticle arrays, particularly focused on the Coulomb charging energy. By comparison, we confirmed that it is more reasonable to estimate the Coulomb charging energy using the activation energy from the temperature-dependent zero-voltage conductance. Based on this, we systematically and comprehensively investigated the parameters that could be used to tune the Coulomb charging energy in nanoparticle arrays. We found that four parameters, including the particle core size, the inter-particle distance, the nearest neighboring number, and the dielectric constant of ligand molecules, could significantly tune the Coulomb charging energy.

A simple and effective technique has been developed to fabricate patterns of nanoparticle arrays. Lithographically fabricated structures in resists serve as scissors to tailor two-dimensional nanoparticle arrays on a flat poly(dimethylsiloxane) (PDMS) stamp. The desired patterns of nanoparticle arrays remaining on the PDMS stamp after tailoring can be printed onto solid substrates. Various regular nanoparticle patterns, such as squares, triangles, disks, and pentagons, can be easily prepared using this technique. Arbitrary nanoparticle patterns as complex as Chinese characters have been successfully demonstrated. Moreover, nanoparticle stripes with width ranging from micrometers to quasi single nanoparticle diameter have also been achieved. Nanoparticle stripes have been integrated into electronic devices for transport measurements.

A unique positive-to-negative transition of temperature coefficient of conductance (TCC) was observed in self-assembled close-packed Au nanoparticle (AuNP) arrays. The transition of TCC can be interpreted properly with a diffusive hopping model, in which the Coulomb charging energy E a plays a significant role. Two parameters of AuNP arrays, the nearest neighboring number and the particle core size, have been varied to tune E a . Our data show that the positive-to-negative transitions of TCC are relevant to both parameters, which confirms the validity of the diffusive hopping model. V C 2014 AIP Publishing LLC. [http://dx.