Energy Transfer In Nanoparticles Research Articles

Electron to Adsorbate Energy Transfer in Nanoparticles: Adsorption Site, Size, and Support Matter.

Confinement of hot electrons in metal nanoparticles (NPs) is expected to lead to increased reactivity in heterogeneous catalysis. NP size as well as support may influence molecule-NP coupling. Here, we use ultrafast nonlinear vibrational spectroscopy to follow energy transfer from hot electrons generated in Pd NP/MgO/Ag(100) to chemisorbed CO. Photoexcitation and photodesorption occur on an ultrashort time scale and are selective according to adsorption site. When the MgO layer is thick enough, it becomes NP size-dependent. Hot electron confinement within NPs is unfavorable for photodesorption, presumably because its dominant effect is to increase relaxation to phonons. An avenue of research is open where NP size and support thickness, photon energy, and molecular electronic structure will be tuned to obtain either molecular stability or reactivity in response to photon excitation.

Effect of Swelling on Multiple Energy Transfer in Conjugated Polymer Nanoparticles

Many key processes in conjugated polymers are strongly influenced by multiple energy transfer (i.e., exciton diffusion). We investigated the effect of solvent-induced swelling on the kinetics of multiple energy transfer in nanoparticles of the conjugated polymers PFBT and MEH-PPV. Multiple energy transfer between equivalent chromophores results in an increased rate of quenching by defects due to a cascading or funneling effect. The effects of swelling on energy transfer between polymer chromophores and the resulting exciton dynamics were modeled using a random walk on a lattice of chromophores. The simulation results show good agreement with experimental fluorescence quantum yield, and decay kinetics results at low to moderate THF concentrations. We found that the time scale for energy transfer between chromophores (∼5 ps for MEH-PPV nanoparticles and ∼100 ps for PFBT nanoparticles) is highly sensitive to swelling, slowing by an order of magnitude or more for swelled particles. The results support quenchi...

Luminescent nanophotonics and advanced solid state lasers

In this review, authors present their latest findings in luminescence quenching kinetics theory and advanced solid state laser experiments. Luminescence quenching kinetics is a popular and exceptionally useful tool to analyze the nanosized luminophores and laser material nanostructure. Quenching kinetics may be multistage, some stages having a complex, not exponential, form. It is often the case for modern laser materials, which are nanostructurized, and for particular cases of energy transfer (such as cooperative down-conversion). We present compact and easy-to-use analytical expressions and computer simulation for various cases of nonexponential quenching kinetics: migration-accelerated quenching in bulk material; cooperative luminescence quenching in bulk material; and two extreme cases of energy transfer in nanoparticles – static and with superfast migration (both including cooperative case of luminescence quenching in ensembles of acceptors comprised of two-, three-, and more particles). We also review the most perspective laser experiments lately performed in our laboratory, including those on fluoride laser nanoceramics and materials for middle infra-red lasers.

Nonlinear optical properties of Cu nanoparticle composites fabricated by 60 keV negative ion implantation

Steady-state absorption and transient nonlinear response of copper nanoparticle composites in LiNbO 3 were investigated in the visible range. Negative ion implantation at 60 keV was applied to fabricate the Cu nanoparticles in the insulators. The surface plasmon band in steady-state absorption spectra in LiNbO 3 resulted from formation of nanoparticles and showed a broadening and shift to red in comparison with the band in amorphous SiO 2 and MgO · 2.4(Al 2O 3). Transient absorption was measured with the technique of pump–probe femtosecond spectroscopy. The transient bleaching band also shifted with the steady-state plasmon peak and recovered within a picosecond. The transient spectrum of the composites in LiNbO 3, reflects the energy transfer in nanoparticles, overlaps with the optical damage in the matrix. The electron–phonon coupling constant of Cu nanoparticles in LiNbO 3 yielded a value of g=2.4×10 16 W/m 3 K.