Narrow-Bandwidth Spontaneous Luminescence from Oriented Semiconducting Polymer Nanostructures

Abstract

High-resolution fluorescence imaging of isolated nanoparticles of a common semiconducting polymer (poly-[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene, MEH-PPV), produced by ink-jet printing techniques, has revealed highly uniform transition moment orientation perpendicular to the glass substrate. In contrast with the broad emission spectra associated with bulk or single molecules of these species in thin films, we observe narrow photoluminescence emission spectra (10-15 nm fwhm) from individual oriented polymer nanostructures with no evidence of spectral diffusion on time scales of several hundred seconds. The distribution of center frequencies (from several hundred individual nanoparticle measurements) shows clearly defined peaks that can be correlated with excitonic traps of integer multiples of monomer conjugation lengths (8, 9, 10, and 11). The observation of discrete emission characteristics in this important class of materials suggests exciting possibilities in photonics and molecular optoelectronics.

A combined theoretical and experimental study of the polymer inter-chain structure in poly(phenylene vinylene) derivatives

“…This incredible improvement was also reported in our previous articles that describe the details of the experimental measurements and observations [2,34,35]. Similar results have also been found for MEH-PPV but typical quantum yields of z-oriented single molecule nanoparticles of MEH-PPV are <0.5.…”

“…We have used ink-jet printing methods to isolate single conducting polymer chains in microdroplets in various organic solvents (tetrahydrofuran (THF), toluene, etc) typically less than 5 µm initial diameter [34,35]. The droplets evaporate en route to the coverglass substrate thus allowing self-organization of the polymer chain in the absence of host polymer or substrate interactions (see figure 1 for a schematic).…”

“…Together, these measurements provide a picture that suggests stiff-chain organization within individual macromolecules adsorbed on the glass surface. Details of the fluorescence microscopy are given in [34,35]. Fluorescence images were acquired on a Nikon TE 300 inverted microscope with a 1.4 N.A.…”

Conformation and physics of polymer chains: a single-molecule perspective

“…Th e decisive role of structural ordering of the chain in determining the spectral properties of MEH-PPV has been demonstrated in an example of single-MEH-PPV nanoparticles formed by ink-jet printing from dilute solution [50]. Th e particles were oriented on a glass substrate such that the emission dipoles were perpendicular to the substrate surface.…”

Single‐Molecule Characterization of Near‐Infrared‐Emitting Silver Nanoclusters

“…In this case, we focus on the nearinfrared emitters using 633 nm as the excitation wavelength. Although a number of single molecule studies have been performed on AgNC to investigate specifi c photophysical parameters, [ 5,6,8,10,14,25,[27][28][29][30][31][32][33] we simultaneously measure several photophysical properties for each individual cluster, including decay times, emission spectra, and antibunching. This allows us to compare and correlate these photophysical properties within a sample to better understand the photophysical behavior and heterogeneity of these complex as-synthesized AgNC samples.…”