Strongly luminescent CuInS 2 /ZnS core/shell nanocrystals were synthesized from copper iodide, indium acetate, zinc stearate, and dodecanethiol as starting compounds in octadecene solvent. The as-prepared core/shell nanocrystals exhibit a low size distribution (<10%), and present photoluminescence in the range of 550-815 nm with a maximum fluorescence quantum yield (QY) of 60%. Time-resolved fluorescence spectroscopy revealed that the lifetimes of the different spectral components are on the order of hundreds of nanoseconds, indicating that donor-acceptor pair recombinations are at the origin of the observed emission bands. The CuInS 2 /ZnS nanocrystals were subsequently transferred to the aqueous phase via surface ligand exchange with dihydrolipoic acid and used as fluorescent labels for in vivo imaging. After tail vein injection into nude mice, the biodistribution of the quantum dots was monitored during 24 h using fluorescence reflectance imaging.
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Non-destructive Raman spectroscopy has been used to study ancient ceramics. On the basis of spectral features characteristic to the microstructures, the composition and technological processing of ceramics in ancient times could be quantitatively determined. Ceramics are heterogeneous materials composed of grains of different phases, coated by different glazes containing various pigments. The question of reliability and representation of the Raman spectra recorded from the surface of glaze or on a section of shard is discussed. As an illustration, ancient (13-14th centuries) Vietnamese (proto)porcelains made at Ha Lan (Nam Dinh) were studied with particular attention to the analysis of the SiO 4 -based glassy network: Spectral components of the Si-O stretching mode are analysed in terms of isolated (Q 0 ), more or less associated (Q 1 , Q 2 , Q 3 ) or fully-bonded (Q 4 ) SiO 4 tetrahedra. The results show the facility and reliability of Raman spectroscopy as a non-destructive technique suitable for discrimination between ancient ceramics and modern copies.
Different techniques were used to follow the transformation of CdS platelets during grinding and under hydrostatic pressure. X-ray diffraction and transmission electron microscopy revealed that the platelets included zinc blende (cubic) CdS nanodomains dispersed in a wurtzite (hexagonal) single-crystalline matrix. Extended grinding led to a decrease of the grain size and to a progressive transformation of the hexagonal stacking into a cubic one. The same phase transition was observed up to 9 GPa under hydrostatic pressure.Off-resonance Raman spectra collected at different stages of the transition led us to connect band groups that were usually overlooked (in resonance conditions) or considered separately. They all probe the stacking disorder and their intensity can be related to the density of stacking faults. Off-resonance Raman spectroscopy offers a way of probing the optical properties of CdS (and, more generally, layered semiconductors) as a function of the structure and of the confinement of vibrations by structural defects.
The emission mechanism in ZnS-capped 3-nm CuInS
2 nanocrystals was studied by using time-resolved photoluminescence (TRPL). A typical TRPL spectrum demonstrates two broad emission bands. The spectral shifts as functions of the excitation power density and delay times from the excitation moment prove that both emission bands originate from donor-acceptor pair recombinations. Moreover, the temperature-dependent TRPL measurement revealed the importance of trapping sites in the emission mechanism of CuInS
2 nanocrystals.
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