ESI ZnAL EU

Gold nanosphere enhanced green and red fluorescence in ZnO:Al,Eu3+
Swati Bishnoi, Rupali Das, and Santa Chawla*
Luminescent Materials Group, CSIR-National Physical Laboratory, Dr.K.S.Krishnan Road, New Delhi-110012,
India
Electronic Supplementary information
Synthesis of Au NPs
Au nanoparticles (Au NP) were synthesized by optimizing the method developed by Turkevish1. The Au NPs were
synthesized by the wet colloidal synthesis method using HAuCl4, DI and Tri-sodium citrate (TSC). The desired
shape and size of the nanoparticles were achieved using optimized concentrations of TSC. The synthesized Au NP
solution was deep red coloured. The morphology was studied by TEM which revealed that the synthesized Au
nanoparticles are spherical in morphology. The TEM micrographs of the Au NP are shown in Fig (S1(c)).
Synthesis of ZnO:Al,Eu phosphor
For the synthesis of Al,Eu3+ co doped ZnO nanopowders, analytical grade commercial zinc oxide ZnO(99.99%
Pure), aluminium oxide Al2O3 and Eu2O3 have been used. Doped ZnO nanostructures are synthesized by controlled
solid state reaction, For preparation of ZnO:Al,Eu powder, (5 mole%) Eu2O3, (94%) ZnO powder and (1%) Al2O3,
were taken according to stoichiometric formula with Aluminium and Europium ions as substitutional dopant in
Zinc position. All the powder precursors were taken according to their calculated weight and mixed thoroughly in
pestle-mortar and were finally packed in recrystallized alumina boat. The precursor material was fired at 1200oC for
2 hours in air atmosphere. The resulting white material was allowed to cool slowly at room temperature and cooled
material was crushed in mortar and pestle to obtain a fine white powder.
Instrument detail
Phase characterization was done by powder X-ray diffraction using a Rigaku miniflex X-ray diffractometer.
Transmission electron microscopes (FEI TECNAI F 30 TWIN, TECNAI TEM, JEOL JEM-1011) has been used for
studying morphology of nanoparticles. The absorption spectrum of the Ag NP solution was measured with Avantes
UV-Visible spectrometer. Fluorescence spectroscopy was performed by using Edinburgh instruments luminescence
spectrometer (FLSP920). Confocal fluorescence microscope (WITec alpha 300M+) was employed for fluorescence
mapping of the hybrid thin film material system with 100x objective lens with N.A 0.9 and UV diode laser
(λ~375nm, output power 10mW, Toptica) as exciting source. Time resolved photoluminescence (PL) decay was
measured using Edinburgh Instruments Time resolved Spectrometer (FLSP920] using a pulsed Xe lamp as
excitation source and employing time correlated single photon counting (TCSPC) technique.
Structure and morphology
The XRD pattern of the synthesized ZnO:Al,Eu3+ phosphor material exhibited “wurtzite hexagonal” phase of ZnO
(JCPDS Card No. 36-1451) as shown in Fig.S1(a). SEM image of ZnO:Al,Eu3+ reveal particles with irregular
morphology exhibiting hexagonal faces (Fig S1(b)). For TEM study of synthesized Au colloidal solution, the
solution was deposited on carbon coated TEM grid and examined in HRTEM that reveal mostly spherical
morphology with diameter around 30nm as shown in Fig. S1(c).
Fig. S1(a) XRD Spectra of ZnO:Al,Eu (b) SEM image of ZnO:Al,Eu (c) TEM image of Au nanospheres
FDTD Simulation parameters
The FDTD simulations on Au nanospheres (30nm) were performed by importing real TEM micrograph for
calculating generated near field and extinction spectra. The mesh size for simulation was set to 0.5nm2 and
Conformal Variant 1 meshing attribute was employed 2 to eliminate stair casing effects. The optical dielectric
function of gold is modeled using the Johnson and Christy dispersion model. The background refractive index was
considered as 1.33 for water. A cubic Yee cell was considered with PML boundaries. Single particle absorption,
scattering and extinction spectra have also been simulated using FDTD method.
Fig S2: The real and imaginary part of dielectric function of Au NP (i)&(ii) from Johnson and Christy and the
corresponding FDTD model fit.
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J. Kimling, M. Maier, B. Okenve, V. Kotaidis, H. Ballot, and A. Plech, J. Phys. Chem. B 2006, 110, 1570015707
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F.K.Guedje, M.Giloan, M. Potara, M.N.Hounkonnou and S.Astilean , Phys Scr. 86, 055702 (2012).
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Lumerical FDTD Solutions 8.7.1, FDTD Solutions Getting Started, Release 8.7.1.