The temperature dependences of the energy and the width of a surface plasmon resonance are studied for copper nanoparticles 17-59 nm in size in the silica host matrix in the temperature interval 293-460 K. An increase of the temperature leads to the red shift and the broadening of the surface plasmon resonance in Cu nanoparticles. The obtained dependences are analyzed within the framework of a theoretical model considering the thermal expansion of a nanoparticle, the electron-phonon scattering in a nanoparticle, and the temperature dependence of the dielectric permittivity of the host matrix. The thermal expansion is shown to be the main mechanism responsible for the temperature-induced red shift of the surface plasmon resonance in copper nanoparticles. The thermal volume expansion coefficient for Cu nanoparticles is found to be size-independent in the studied size range. Meanwhile, the increase of the electron-phonon scattering rate with the temperature is shown to be the dominant mechanism of the surface plasmon resonance broadening in copper nanoparticles.K e y w o r d s: surface plasmon resonance, copper nanoparticles, temperature-induced effects

We study the influence of surface passivating ligands on the optical and structural properties of zinc blende CdSe nanoplatelets. Ligand exchange of native oleic acid with aliphatic thiol or phosphonic acid on the surface of nanoplatelets results in a large shift of exciton transition energy for up to 240 meV. Ligand exchange also leads to structural changes (strain) in the nanoplatelet's core analysed by wide-angle X-ray diffraction. By correlating the experimental data with theoretical calculations we demonstrate that the exciton energy shift is mainly caused by the ligand-induced anisotropic transformation of the crystalline structure altering the well width of the CdSe core. Further the exciton reduced mass in these CdSe quantum wells is determined by a new method and this agrees well with the expected values substantiating that ligand-strain induced changes in the colloidal quantum well thickness are responsible for the observed spectral shifts. Our findings are important for theoretical modeling of other anisotropically strained systems and demonstrate an approach to tune the optical properties of 2D semiconductor nanocrystals over a broad region thus widening the range of possible applications of AB nanoplatelets in optics and optoelectronics.

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The transient induced absorption and bleaching are examined in 10 nm size CuS nanocrystals embedded in polyvinylalcohol film. Partial surface oxidation of CuS nanocrystals produces a new near-IR-absorption band peaked at 1100 nm. The surface oxidized shell is supposed to form a midgap electron acceptor level and the near-IR band relates to the electron transfer from the CuS valence band. The near-IR band is bleached easily by 15 ps pump pulse from YAG:Nd laser (1.08 μm). The bleaching is accompanied by the induced absorption at the red side of CuS fundamental edge. Both signals induced decay quickly with the time constant 65–70 ps. The model is proposed where the electron–hole pair excited by near-IR photon (electron in surface shell and hole inside CuS core) creates strong internal electric field, which induces the Stark red shift of CuS fundamental edge.

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