Probing surface states in C_60 decorated ZnO microwires: detailed photoluminescence and cathodoluminescence investigations



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Rodrigues, Joana and Smazna, Daria and Ben Sedrine, Nabiha and Nogales Díaz, Emilio and Adelung, Rainer and Mishra, Yogendra K and Méndez Martín, Bianchi and Correia, María R. and Monteiro, Teresa (2019) Probing surface states in C_60 decorated ZnO microwires: detailed photoluminescence and cathodoluminescence investigations. Nanoscale advances, 1 (4). pp. 1515-1526. ISSN 2516-0230

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ZnO microwires synthesised by the flame transport method and decorated with C_60 clusters were studied in detail by photoluminescence (PL) and cathodoluminescence (CL) techniques. The optical investigations suggest that the enhanced near band edge recombination observed in the ZnO/ C_60 composites is attributed to the reduction of the ZnO band tail states in the presence of C_60. Well-resolved free and bound excitons recombination, as well as 3.31 eV emission, are observed with increasing amount of C_60 flooding when compared with the ZnO reference sample. Moreover, a shift of the broad visible emission to lower energies occurs with increasing C_60 content. In fact, this band was found to be composed by two optical centres peaked in the green and orange/ red spectral regions, presenting different lifetimes. The orange/ red band exhibits faster lifetime decay, in addition to a more pronounced shift to lower energies, while the peak position of the green emission only shows a slight change. The overall redshift of the broad visible band is further enhanced by the change in the relative intensity of the mentioned optical centres, depending on the excitation intensity and on the C_60 flooding. These results suggest the possibility of controlling/ tuning the visible emission outcome by increasing the C_60 amount on the ZnO surface due to the surface states present in the semiconductor. An adequate control of such phenomena may have quite beneficial implications when sensing applications are envisaged.

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This journal is © The Royal Society of Chemistry 2019
This work was financially supported by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under projects UID/CTM/50025/2019 and POCI-01-0145-FEDER-028755. Kiel authors thank the Deutsche Forschungsgemeinscha. (DFG) for financial support under the scheme SFB 677 (C14). EN and BM thank Spanish MINECO for funding via the project MAT 2015-65274-R-FEDER.

Uncontrolled Keywords:Photocatalytic activity; Green luminescence; Carbon nanotubes; Nanostructures; Emission; Electron; Hybridization; Enhancement; Transitions; Composites
Subjects:Sciences > Physics > Materials
Sciences > Physics > Solid state physics
ID Code:57141
Deposited On:04 Oct 2019 12:24
Last Modified:07 Oct 2019 07:40

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