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${\rm Au}_{25}\lpar {{\rm C}_6{\rm H}_{14}{\rm S}} \rpar_{18}{}^-$ icosahedron and [Au 25 (PPh) 10 (C 6 H 14 S) 5 Cl 2 ] 2+ bi-icosahedron clusters were synthesized. Ligand exchange reactions were carried out with a new coumarin-derived fluorophore (Cou-SH) to label both clusters. Labeled and unlabeled Au 25 were compared and the changes in the electronic structure were determined. The labeled clusters showed marked changes in electronic states, as evidenced by the quenching in the UV region and enhancement in the near infrared. The quantum yield from Cou-SH decreased and the quantum yield from the labeled Au 25 increased. Second, the authors observed changes in the electrochemical band gap. 

Signal detection limit (SDL), limit of detection (LOD), and limit of quantitation of a portable Raman spectrometer were measured for smokeless gunpowder stabilizers, diphenylamine (DPA) and ethyl centralite (EC), in acetone, acetonitrile, ethanol, and methanol. Acetone yielded the lowest LOD for three of four DPA peaks, and acetonitrile yielded the lowest LOD for two of three EC peaks and the remaining DPA peak. When gold nanoparticles were added to the DPA solutions in acetone and acetonitrile, statistically significant changes were observed (DPA peak position, full width at half maximum, and/or total area) and SDL was improved for the majority of all peaks in both solvents. 

ABSTRACT Graphene oxide serves as a precursor to various technologies, which include batteries, biosensors, solar cells, and supercapacitors. Gold nanoparticles exhibit excellent electrochemical and photophysical properties, allowing for electronic absorption and the ability to absorb light energy at the plasmonic wavelength. Palladium nanoparticles are highly sensitive and functional in room temperature, making it an ideal metal for catalytic applications. We report the synthesis of functional graphene oxide from graphite flakes followed by the insertion of gold and palladium nanoparticles through an oleylamine ligand. In this report, the fermi level of graphene oxide (GOx), gold-graphene oxide (Au-GOx), and palladium-graphene oxide (Pd-GOx) was shown to be effectively controlled. Additionally, each system showed complete solubility in ethanol and in the case of Au-GOx, enhanced solubility was seen in tetrahydrofuran as well.