DOI: 10.1002/chem.201100246 Hybrid Gold-Nanoparticle-Cored Conjugated Thiophene Dendrimers: Synthesis, Characterization, and Energy-Transfer Studies Suxiang Deng, TimothyM. Fulghum, Greg Krueger, Derek Patton, Jin-Young Park, and Rigoberto C. Advincula* [a] Introduction As an important class of organic and inorganic hybrid com- posite materials, metal-containing dendrimers are extensive- ly investigated because of their potential applications as nanoscale catalysts, drug delivery agents, chemical sensors, and light-harvesting antenna macromolecules. [1] In general, metal-containing dendrimers can be divided into three cate- gories: 1) dendrimers that encapsulate metal ions; [2] 2) den- drimers with metal ions as an integral part of their struc- ture; [3] examples include dendrimers containing an organo- metallic core and those that use metal ligation to assemble the dendrimer branches, and 3) dendrimers with peripheral groups that can bind metal ions. [4] Metal ions encapsulated inside the interior of dendrimers can be reduced chemically, resulting in the formation of dendrimer-encapsulated metal nanoparticles (DEMNs). Applications of these DEMNs in catalysis have been well demonstrated. [5, 6] Dendrimers of the second category have also been investigated as modified environments for bimolecular-quenching reactions and as light-emitting diodes. [7] Recently, organic chromophores have been attached to the periphery of metal dendrimers to generate novel, light-harvesting, antenna systems. [8] The coupling of energy- and electron-transfer phenomena between inorganic nanoparticles and organic molecules is also of great interest. [9] The difference between the HOMO and LUMO levels between nanoparticles and organic dyes/ conjugated polymers has resulted in either fluorescence en- hancement [10] or quenching. [11] Our group have reported the first synthesis of all-thiophene dendrimers [12] and demon- strated their interesting 2D supramolecular assembly on graphite. Besides their excellent assembly properties on graphite, thiophene dendrimers are also good candidates as light-harvesting antenna macromolecules. Since our groups first report on thiophene-dendrimer synthesis, several new types of thiophene dendrimers for applications, such as light-harvesting, solar-energy conversion, and optoelectron- ics, have been reported. Ma et al. [13] have developed an ef- fective approach to synthesize a series of protected and non- substituted thiophene dendrons and dendrimers up to the fourth generation with 90 thiophene units. The potential ap- plications of these thiophene dendrimers as entangled photon sensors have also been explored. [14] Mitchell et al. [15] have synthesized phenyl-cored thiophene dendrimers and reported a power-conversion efficiency of 1.3 % for organic photovoltaic devices based on these dendrimers. [16] Aso et al. [17] have prepared another series of thiophene dendrim- ers, containing quaterthiophene as repeating conjugated bridges and benzene rings as branching centers. Very recent- ly, Wong et al. reported organic solar cells based on hexa- peri-hexabenzocoronene-cored thiophene dendrimers with a power-conversion efficiency of 2.5 %. [18] Further details Abstract: A series of hybrid Au-nano- particle-dendrimer materials: nanopar- ticle-cored thiophene dendrimers (NCTDs) were synthesized, character- ized, and investigated for their energy- transfer properties. These hybrid nano- particles were obtained by the simulta- neous and in situ reduction of goldACHTUNGTRENNUNG(III) chloride and self-assembly of the thiol- containing thiophene dendritic ligands. The dendron ligands were radially at- tached to the gold nanoparticles and were analyzed by TEM, UV/Vis, 1 H NMR, and FTIR spectroscopies. The solution fluorescence of the at- tached thiophene dendrons are quenched progressively. Both alkyl- chain length and dendron size have sig- nificant influence on the energy-trans- fer efficiency, as well as on core sizes and size distribution of the Au nano- particles. In spite of the phenomenons dependence on nanoparticle size, the energy transfer generally follows the 1/ d 2 distance dependence. Single NCTD nanoparticles were also adsorbed on highly ordered pyrolytic graphite (HOPG) and uniform aggregates were observed on mica flat substrates. Keywords: dendrimers · emission · energy transfer · hybrids · nanopar- ticles [a] Dr. S. Deng, T.M. Fulghum, G. Krueger, D. Patton, J.-Y. Park, Prof. R. C. Advincula University of Houston Department of Chemistry and Department of Chemical and Biomolecular Engineering 4800 Cullen Blvd Houston, TX 77204-5003 (USA) Fax: (+ 1) 713-743-1755 E-mail : radvincula@uh.edu Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201100246. Chem. Eur. J. 2011, 17, 8929 – 8940  2011 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 8929 FULL PAPER