Author Archives: Jessica Darga

Linear and Nonlinear Optical Properties of Monolayer-Protected Gold Nanocluster Films

ACS NANO (2016), 10(1), 562-572


Author(s): Ho-Wu, R. (Ho-Wu, Rosina) ; Yau, S.H. (Yau, Sung Hei) ; Goodson, T. (Goodson, Theodore, III)

Abstract:

Gold nanoclusters have been extensively studied in solution for their unique optical properties. However, many applications of nanoclusters involve the use of the material in the solid state such as films. Au-25(SR)(18) in polymeric hosts was used as the model for studying the optical properties of nanocluster films. Different film-processing conditions as well as types of polymers were explored to produce a good-quality film that is suitable for optical measurements. The best optical film was made using Au-25(C6S)(18) and polystyrene. The formation of nanocluster films drastically reduces the interduster distances to a few nanometers, which were estimated and characterized by optical absorption. The steady-state absorption and emission properties of the nanocluster film maintained their molecular characteristics. The emissions from the nanocluster films are found to be strongly enhanced at 730 nm with a smaller enhancement at 820 nm when the intercluster distance is below 8 nm. The emission enhancement can be attributed to the energy transfer between clusters due to the small interduster distance. Two-photon Z scan revealed that the two-photon absorption cross sections are in the order of 10(6) GM, which is an order of magnitude higher than it is in solution. The two-photon absorption enhancement is correlated with strong dipole coupling. These results show that metal nanoclusters can be made into optical quality films, which increase the interaction between clusters and enhances their linear and nonlinear optical responses.

Synthesis of Ladder-Type Thienoacenes and Their Electronic and Optical Properties

Journal of the American Chemical Scoiety (2016), 138(3), 868-875


Author(s): Zheng, T.Y. (Zheng, Tianyue) ; Cai, Z.X. (Cai, Zhengxu) ; Ho-Wu, R. (Ho-Wu, Rosina) ; Yau, S.H. (Yau, Sung Hei) ; Shaparov, V (Shaparov, Valerii) ; Goodson, T. (Goodson, Theodore, III) ; Yu, L.P. (Yu, Luping)

Abstract:

A series of ladder-type thienoacenes based on benzo[1,2-b:4,5-b’]dithiophene (BDT) have been synthesized and characterized. They were shown to be p-type semiconductors with wide band gaps and able to support multiple stable cationic states. As the conjugation lengthens, these oligomers become more emissive, showing high quantum yields. They were shown to be good two-photon absorbers, exhibiting high two-photon absorption coefficients.