An interactive system and software for processing images of the side looking radar (SLR) was designed. With the help of this system the digital Antarctic map was synthesized from SLR images measured ...by satellite series “Ocean”. A part of this map and values of backscattering cross sections for different Antarctic regions are presented.
Deposition of silica shells onto ZnO nanoparticles (NPs) in dimethyl sulfoxide was found to be an efficient tool for terminating the growth of ZnO NPs during thermal treatment and producing stable ...core–shell ZnO NPs with core sizes of 3.5–5.8 nm. The core–shell ZnO–SiO2 NPs emit two photoluminescence (PL) bands centred at similar370 and similar550 nm originating from the direct radiative electron–hole recombination and defect-mediated electron–hole recombination, respectively. An increase of the ZnO NP size from 3.5 to 5.8 nm is accompanied by a decrease of the intensity of the defect PL band and growth of its radiative life-time from 0.78 to 1.49 μs. FTIR spectroscopy reveals no size dependence of the FTIR-active spectral features of ZnO–SiO2 NPs in the ZnO core size range of 3.5–5.8 nm, while in the Raman spectra a shift of the LO frequency from 577 cm−1 for the 3.5 nm ZnO core to 573 cm−1 for the 5.8 nm core is observed, which can indicate a larger compressive stress in smaller ZnO cores induced by the SiO2 shell. Simultaneous hydrolysis of zinc(II) acetate and tetraethyl orthosilicate also results in the formation of ZnO–SiO2 NPs with the ZnO core size varying from 3.1 to 3.8 nm. However, unlike the case of the SiO2 shell deposition onto the pre-formed ZnO NPs, individual core–shell NPs are not formed but loosely aggregated constellations of ZnO–SiO2 NPs with a size of 20–30 nm are. The variation of the synthetic procedures in the latter method proposed here allows the size of both the ZnO core and SiO2 host particles to be tuned.
Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Deposition of silica shells onto ZnO nanoparticles (NPs) in dimethyl sulfoxide was found to be an efficient tool for terminating the growth of ZnO NPs during thermal treatment and producing stable ...core–shell ZnO NPs with core sizes of 3.5–5.8 nm. The core–shell ZnO–SiO2 NPs emit two photoluminescence (PL) bands centred at similar370 and similar550 nm originating from the direct radiative electron–hole recombination and defect-mediated electron–hole recombination, respectively. An increase of the ZnO NP size from 3.5 to 5.8 nm is accompanied by a decrease of the intensity of the defect PL band and growth of its radiative life-time from 0.78 to 1.49 μs. FTIR spectroscopy reveals no size dependence of the FTIR-active spectral features of ZnO–SiO2 NPs in the ZnO core size range of 3.5–5.8 nm, while in the Raman spectra a shift of the LO frequency from 577 cm−1 for the 3.5 nm ZnO core to 573 cm−1 for the 5.8 nm core is observed, which can indicate a larger compressive stress in smaller ZnO cores induced by the SiO2 shell. Simultaneous hydrolysis of zinc(II) acetate and tetraethyl orthosilicate also results in the formation of ZnO–SiO2 NPs with the ZnO core size varying from 3.1 to 3.8 nm. However, unlike the case of the SiO2 shell deposition onto the pre-formed ZnO NPs, individual core–shell NPs are not formed but loosely aggregated constellations of ZnO–SiO2 NPs with a size of 20–30 nm are. The variation of the synthetic procedures in the latter method proposed here allows the size of both the ZnO core and SiO2 host particles to be tuned.
Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Surface- and tip-enhanced resonant Raman scattering (resonant SERS and TERS) by optical phonons in a monolayer of CdSe quantum dots (QDs) is demonstrated. The SERS enhancement was achieved by ...employing plasmonically active substrates consisting of gold arrays with varying nanocluster diameters prepared by electron-beam lithography. The magnitude of the SERS enhancement depends on the localized surface plasmon resonance (LSPR) energy, which is determined by the structural parameters. The LSPR positions as a function of nanocluster diameter were experimentally determined from spectroscopic micro-ellipsometry, and compared to numerical simulations showing good qualitative agreement. The monolayer of CdSe QDs was deposited by the Langmuir–Blodgett-based technique on the SERS substrates. By tuning the excitation energy close to the band gap of the CdSe QDs and to the LSPR energy, resonant SERS by longitudinal optical (LO) phonons of CdSe QDs was realized. A SERS enhancement factor of 2 × 103 was achieved. This allowed the detection of higher order LO modes of CdSe QDs, evidencing the high crystalline quality of QDs. The dependence of LO phonon mode intensity on the size of Au nanoclusters reveals a resonant character, suggesting that the electromagnetic mechanism of the SERS enhancement is dominant. Finally, the resonant TERS spectrum from CdSe QDs was obtained using electrochemically etched gold tips providing an enhancement on the order of 104. This is an important step towards the detection of the phonon spectrum from a single QD.
Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
Surface- and tip-enhanced resonant Raman scattering (resonant SERS and TERS) by optical phonons in a monolayer of CdSe quantum dots (QDs) is demonstrated. The SERS enhancement was achieved by ...employing plasmonically active substrates consisting of gold arrays with varying nanocluster diameters prepared by electron-beam lithography. The magnitude of the SERS enhancement depends on the localized surface plasmon resonance (LSPR) energy, which is determined by the structural parameters. The LSPR positions as a function of nanocluster diameter were experimentally determined from spectroscopic micro-ellipsometry, and compared to numerical simulations showing good qualitative agreement. The monolayer of CdSe QDs was deposited by the Langmuir–Blodgett-based technique on the SERS substrates. By tuning the excitation energy close to the band gap of the CdSe QDs and to the LSPR energy, resonant SERS by longitudinal optical (LO) phonons of CdSe QDs was realized. A SERS enhancement factor of 2 × 103 was achieved. This allowed the detection of higher order LO modes of CdSe QDs, evidencing the high crystalline quality of QDs. The dependence of LO phonon mode intensity on the size of Au nanoclusters reveals a resonant character, suggesting that the electromagnetic mechanism of the SERS enhancement is dominant. Finally, the resonant TERS spectrum from CdSe QDs was obtained using electrochemically etched gold tips providing an enhancement on the order of 104. This is an important step towards the detection of the phonon spectrum from a single QD.
Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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