Tuning optical properties of poly(3-hexylthiophene) nanoparticles through hydrothermal processing.

Poly(3-hexylthiophene) (P3HT) nanoparticles (NPs) were prepared by a reprecipitation method. Hydrothermal processing applied external pressure to the pristine P3HT NPs at temperatures ranging from 60 to 150 °C. Optical absorption and photoluminescence (PL) spectra for the hydrothermally treated P3HT NPs varied markedly with the processing temperature. With increasing treatment temperature, the absorption peak broadened and the peak position shifted from 510 to 623 nm; moreover, the intensity ratio of the 0-1 to 0-0 emission varied. These changes were caused by interactions between the P3HT main chains and alkyl side groups and conformational modifications induced by the high pressure during the hydrothermal process. The evolution of the optical absorption spectra of the P3HT NPs during the hydrothermal processing was strongly correlated with the variation of PL excitation spectra and with the PL emission spectra of a single NP.

Photoluminescence characteristics for hybrid nanotubes of light emitting poly(3-methylthiophene) coated with copper: fluorescence effect.

The enhanced nanometer-scale photoluminescence (PL) and quantum yield of hybrid double layered nanotubes (HDLNTs) consisting of a light-emitting poly(3-methylthiophene) (P3MT) nanotube coated with nanometer-scale copper (Cu) metal were observed and presented. The HDLNTs of the Cu coated P3MT (P3MT/Cu) were synthesized through a sequential electrochemical synthetic method in an anodic alumina oxide (Al2O3) nanoporous template. We confirmed that the Cu nanotubes were covered outside the light emitting P3MT nanotubes based a high resolution transmission electron microscope image. From laser confocal microscope (LCM) PL experiments of an isolated single strand of the P3MT nanotubes and of their HDLNTs, we observed a -100 times enhancement of the PL peak intensity for the HDLNTs of P3MT/Cu compared to that of the P3MT single nanotube, which was qualitatively confirmed through the measurement of the quantum yield. The energy and/or charge transfer effects in surface plasmon resonance contributed to the larger enhancement of the PL efficiency of the hybrid P3MT/Cu nanotubes. The PL decay life-time of the excitons of the P3MT nanotubes using a time resolved PL was not changed after the formation of the HDLNTs, implying that the PL enhancement of the hybrid nanotubes might have originated from fluorescence, not phosphorescence.

Photoluminescence and optical waveguiding characteristics of bisalkoxy tin(IV) porphyrin microcrystals.

Guide me: Laser confocal microscope photoluminescence (LCM-PL) and optical waveguiding characteristics for tin(IV) porphyrin-based microcrystalline rods and plates were investigated. The efficiency of optical waveguiding for the rods (0.04 µm(-1)) was five times better than for the plate, due to stronger π-π interaction and a short layer distance (3.035 vs. 3.328 Å).

Tuning photoluminescence of organic rubrene nanoparticles through a hydrothermal process.

Light-emitting 5,6,11,12-tetraphenylnaphthacene (rubrene) nanoparticles (NPs) prepared by a reprecipitation method were treated hydrothermally. The diameters of hydrothermally treated rubrene NPs were changed from 100 nm to 2 µm, depending on hydrothermal temperature. Photoluminescence (PL) characteristics of rubrene NPs varied with hydrothermal temperatures. Luminescence of pristine rubrene NPs was yellow-orange, and it changed to blue as the hydrothermal temperature increased to 180°C. The light-emitting color distribution of the NPs was confirmed using confocal laser spectrum microscope. As the hydrothermal temperature increased from 110°C to 160°C, the blue light emission at 464 to approximately 516 nm from filtered-down NPs was enhanced by H-type aggregation. Filtered-up rubrene NPs treated at 170°C and 180°C exhibited blue luminescence due to the decrease of intermolecular excimer densities with the rapid increase in size. Variations in PL of hydrothermally treated rubrene NPs resulted from different size distributions of the NPs.

Light-emitting color barcode nanowires using polymers: nanoscale optical characteristics.

We report on the light-emitting color barcode nanowires (LECB-NWs), which were fabricated by alternating the electrochemical polymerization of light-emitting polymers with various luminescence colors and efficiencies. The nanoscale photoluminescence characteristics of LECB-NWs were investigated using a laser confocal microscope with a high spatial resolution. The alternating light emissions of the LECB-NWs showed orange-yellow, red, and green colors due to the serial combination of poly(3-butylthiophene), poly(3-methylthiophene), and poly(3,4-ethylenedioxythiophene), respectively, with distinct luminescence intensities. The optical detection sensitivity and stability of LECB-NWs have been enhanced through a nanoscale Cu metal coating onto the NWs, based on surface plasmon resonance coupling and protection against oxidation. The flexibility of the LECB-NWs has been investigated through the folding and unfolding of the NWs by an applied nanotip impetus. The flexible LECB-NWs can be used as highly sensitive optical identification nanosystems for nanoscale or microscale products with complex physical shapes.

Complex nanoparticle of light-emitting MEH-PPV with Au: enhanced luminescence.

Complex nanoparticles (NPs) of poly(2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV) NP adsorbed with Au NPs (MEH-PPV/Au NPs) were fabricated through a reprecipitation method. The formation of MEH-PPV/Au NP complexes was confirmed through high-resolution transmission electron microscopy and Fourier transform infrared experiments. The laser confocal microscope photoluminescence (PL) efficiency of the complex MEH-PPV/Au single NP dramatically increased compared with that of the MEH-PPV single NP without Au NPs, which was directly confirmed through color charge-coupled device images. The enhanced PL efficiency of the MEH-PPV/Au NP complex might have originated from the energy transfer effect in a surface plasmon resonance coupling between a MEH-PPV NP and Au NPs. The strong local field enhancement due to nanogaps between Au NPs in the background of a light-emitting MEH-PPV NP might be another origin of the PL enhancement of the NP complex, as supported by finite difference time domain calculations. We also observed the blue shift of the PL peaks of the single MEH-PPV and MEH-PPV/Au NP, compared with the solution PL peaks of those NPs.