Blue luminescent nanocrystals (NCs) were prepared electrochemically from multiwalled carbon nanotubes (MWCNTs) for the first time. The carbon NCs were characterized by UV−vis, photoluminescence, Raman, XRD spectroscopy, and high-resolution transmission electron microscopy. The structure evolution of the MWCNTs during electrochemical treatments was monitored by SEM ex situ. Since the MWCNTs were formed with scrolled graphene layers, we propose that tetrabutyl ammonium (TBA) cations most probably intercalate into the gaps and the defects during electrochemical cycling and break the tubes near the defects.

Time-resolved x-ray excited optical luminescence (XEOL) and x-ray absorption near edge structures have been employed to study the origin of the multicolor luminescence from SnO2 nanoribbons. The authors find that the yellow-green luminescence has a long lifetime while the blue luminescence a short one. The luminescence is attributed to the radiative decay of trapped electrons in oxygen vacancies just below the conduction band and electrons in the conduction band to intrinsic surface states in the band gap.

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Pure (ZnO) and Eu-doped ZnO (Eu:ZnO) nanostructures have been grown in different morphologies by thermal evaporation. The growth of the structures depends on the temperature and concentration gradient during material deposition as well as on the doping species. X-ray excited optical luminescence (XEOL) from nanostructured ZnO and Eu:ZnO shows a correlation of optical properties with morphology on a nanoscale. In particular, the relative intensity of band gap and defect emission (green light) changes drastically in Eu:ZnO and ZnO nanostructures with different morphology. In this Article, we present experimental results from Eu:ZnO and ZnO nanostructures, using synchrotron radiation-based XEOL, time-gated XEOL, and element specific XANES with partial and total photoluminescence yield (PLY). Our results suggest that the rare earth dopant most likely affects the energy transfer and structural changes by nucleation, rather than direct radiative decay from Eu sites.

We have monitored the changes that occur in the x-ray-excited optical luminescence, absorption, and photoemission spectra as a function of vacuum annealing time and temperature for ZnS nanowires. All measurements were done in situ. Initial heating causes desorption of surface oxides and a concurrent reduction in the intensity of all the luminescence peaks, which we attribute to the creation of surface states that quench the luminescence. Extended annealing causes diffusion of Au from the particle used to nucleate the wire growth, which results in an increase in intensity of its associated luminescent band at 520nm. Changes were also observed in the ZnL- and SK-edge x-ray absorption spectra, which are consistent with this interpretation.

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Confocal Raman microspectroscopy combined with scanning electron microscopy (SEM) was used to characterize morphologies, chemical structures, and optical properties of single tin dioxide nanoribbons under ambient conditions. Raman images, depth profiles, and spectra of the ribbons were analyzed to provide new insights into the structure−property relationship. The Raman images constructed from the normal Raman bands and an additional group of energy bands with very high intensities between 1000 and 1800 cm-1 clearly discriminated the nanoribbons from the luminescent nanostructures grown on ribbon surfaces. The strong luminescent nanostructures have a stoichiometry of SnO x (1 < x < 2), as assessed by energy-dispersive X-ray (EDX) spectroscopy and Raman peaks between 100 and 300 cm-1. The emission can be attributed to the defect state resonant and exciton−phonon coupling luminescence.