Quantitative analysis of thiolated ligand exchange on gold nanoparticles monitored by 1H NMR spectroscopy.

We use nuclear magnetic resonance spectroscopy methods to quantify the extent of ligand exchange between different types of thiolated molecules on the surface of gold nanoparticles. Specifically, we determine ligand density values for single-moiety ligand shells and then use these data to describe ligand exchange behavior with a second, thiolated molecule. Using these techniques, we identify trends in gold nanoparticle functionalization efficiency with respect to ligand type, concentration, and reaction time as well as distinguish between functionalization pathways where the new ligand may either replace the existing ligand shell (exchange) or add to it ("backfilling").

Evolution of the electron mobility in polymer solar cells with different fullerene acceptors.

We investigate the evolution of the electron mobility of two different acceptors, [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) and indene-C60 bisadduct (ICBA), in a poly(3-hexylthiophene) blend solar cell during a prolonged thermal aging process. High electron mobility does not correlate with the best device performance in our study of the P3HT:PC71BM and P3HT:ICBA systems. Very little changes are observed in the polymer crystallinity as a function of time.

An Apparent Size-Exclusion Quantification Limit Reveals a Molecular Weight Limit in the Synthesis of Externally Initiated Polythiophenes.

We report the linear and nonlinear regions of the relationship between number average molecular weight determined by gel permeation chromatography (GPC) and H NMR end-group analysis for a series of -tolyl-initiated poly(3-hexylthiophene)s (P3HTs). For conjugated polymers with chains that are 39-138 repeat units in length (6.5-23 kDa), GPC systematically overestimates the number average molecular weight () by a factor of 1.