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Photoluminescent andPhotocatalytic Properties of TiO2
decorated Bismuth doped
Strontium AluminatesL.A. Daz-Torres1
Carlos R. Garca1, P. Salas2, M. Guzmn1
1.Centro de Investigaciones en ptica A. C. Len Mxico2. Centro de Fsica Aplicada y Tecnologa Avanzada. Universidad
Nacional Autnoma de Mxico.June 2014
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Introduction
Funct ional
materials
OpticalMagnetic
Electrical
Catalytic
Chemical
Luminescence
Photocatalysis
Multifunctional
TiO2 decorated Bi
doped Strontium
aluminates
Phosphorescent materials (PMs)Emergency signaling.Compact fluorescet lamps.
Lasting for hours. 1
1) Materials 2010, 3, 2536-2566.
TiO2is one of the best photocatalyst.
SrAl2O4:Eu2+,Dy3+and Sr4Al14O25:Eu
2+,Dy3+
show long persistence time.
PMs improve the photocatalyc of the TiO2
in composites.2
Bismuth enhance the photocatalytic
activity of some crystalline lattices.3
2) J. Mater Chem A, (2013), 1, 1123-1126.
3) M Sc. and Eng. B (2011) 176, 13821387.
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Introduction
Sr4Al14O25: Eu,Dy can be used without irradiation to assist the Ag3PO4photocatalyst
in water solutions. 6
Persistent materials (PMs) create free carriers (electron or holes) which promote the
photocatalytic process.
Persistent materials have been proposed to help, with exciting light, the
photocatalyst to degrade some contaminants from water and environment.5
5) J. Mater Chem A, (2013), 1, 1123-1126.
6) J. Mol. Cat. A, (2012), 363-364, 129-133.
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Produ ce a decorated TiO2Bi-dop ed stront ium aluminate with a goo d
photo catalyt ic act iv i ty under UV irradiat ion (365 nm ).
That the deco rated TiO2 Bi-dop ed stront ium alum inate could degrade
methylene blue (MB) dye in water solut io ns .
That the Persistence of the stront ium alum inates im proves w ith Bism uth
concentrat ion.
Is it possible to ?
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MotivationDyes in wastewater are the major pollutants.7
Wastewater from
textile industry.
MB as pollutant in
water.
Methylene blue (MB)
contamination dye in a
lake.
7) Int. J. of Env. Sci. (2012),3,3, 940-955.
Object ives:
1 ) Syn thes ize Eu,Dy-s t ron t ium a luminate codoped wi th d i fferen t Bi mola r concent ra tions
betw een 0.0% and 15.0% mo l.
2) Then deco rate i t w i th TiO2at low tem perature.
2) Study the structura l , morp holog ica l and opt ica l proper t ies.
3) Evaluate the pho tocatalyt ic activ i ty of the TiO2decorated samples
in methylene blue degradat ion in so lut ions u nder UV (365 nm) irradiat ion.
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SynthesisWe use the combustion synthesismethod with urea as fuel.
1 2 3 4
Stage 1
Stage 2
1. Dissolved nitrates
in 15 ml of deionised
water.
2. Introduce the beaker
at 600C into the preheated
mufle.
3. Combustion ocurred
lasting 20-30 sec.
4. Green phosphorescent
foaming is obtained.
Sr(NO3)2 ,Al(NO3)3Eu(NO3)3 Dy (NO3)3Bi(NO3)3 .
Powders are pressed
with 2.5 t and disks of
1.0 g are produced.
The disks are annealed
at 1150C for 6h in a carbon
reducing atmosphere
56
(TiO2-SrAlO-Bi)Stage 3
Grind the disks for
Characterization of obtained
powders
7
SrAlO-Bi
Wet mixing in ethanol
1:1 in weight Mixture
TiO2 : SrAlO-Bi
Dry for 24 h and anneal
at 450C for 1h.
Grind and use
as a photocatalyst.
8
9 10
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Photocatalysis
At the beginning After 190 min
1) 0.5 mM solutions of methylene blue and 30 mg ofTiO2-SrAlO-Bi photocatalyst in water strongly
stirred for 1 h in darkness.
2) Then, the UV lamps (365 nm) are turned ON
keeping the stirring. Samples of 0.2 ml are extracted
in regular periods. Samples are centrifuged at 5000 rpm.
3) We measure the absorbance spectrum at regular periods.
Procedure
UV lamps
(365 nm)
Quartz beakerfilled with the solution
magnetic
stirrer plate
Reactor design
Agilent UV-Vis cary 60 spectro photometer
Uti l ised to measure the absorb ance spectra
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Results
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20 30 40 50 60 70
SrAl2O
4JCPDS 34-0379
15.0%
10.0%
5.0%
2.0%
1.0%
2tetha ()
0.0%
Bi, mol.%
Structural analysis by X-ray difraction
of the SrAlO-Bi powders.
For low conc entra tions o f Bi
(x= 0.0%, 1.0%, 2.0% and
5.0 %) the pow ders are
composed
Mainly of the phases: SrAl2O4
and
Sr4Al14O25.
For high concentrat ions of Bi
( x = 10.0 % and 15.0%) the
same stront ium alum inates
phases appear but Bi2O3phase
also appear in theXRD patterns.
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Morphology of the SrA lO-B i powders
0%
2.0%5.0%
10% 15%
1.0%Micrograins of irregular shapes
are observe for all samples afterthe annealed in carbon reduced
atmosphere.
The sample without Bi codoping
show particles with
larger sizes than the othersamples.
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400 450 500 550 600 650
PL
(a.u.)
Wavelength (nm)
0.0%
1.0%
2.0%
5.0%
7.0%
10.0%15.0%
= 380nmexc510 nm
463 nm
Bi mol.%
0.0 2.5 5.0 7.5 10.0 12.5 15.0
PL
Intensity(a.u.)
Bi concentration, mol.%
510 nm band:SrAl2O4:Eu,Dy
0.0 2.5 5.0 7.5 10.0 12.5 15.0
PL
Intensity(a.u.)
Bi concentration, mol.%
463 nm band: Sr4Al
14O
25:Eu,Dy
Photo lum inescence of the SrA lO-B i
powders.
The samp le codop ing w ith the 1.0 % of Bi
show the h ighest luminescence when is
exci ted with 380 nm UV l ight .
As B i concentrat ion increases the
lum inescence intensi ty decreases and
a shi f t to the blue region is ob served.
Tendenc ies of the 510 nm and 463 nm
lumin escence bands as a funct ion of B i
codoping.
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For photocatalysis we select the 0%, 2.0 %, 15.0%and pure TiO2 in order to
evaluate the methylene blue degradation.
These samples were decorated with TiO2 and then the photocatalysis experimentwas made for each sample.
TiO2- decorated SrAlO-B i fo r pho tocatalysis
20 30 40 50 60 70
0
50
100
150
200
250
300
350
counts
2 )
TiO2Anatase phase JCPDS 84-1286
20 30 40 50 60 700
20
40
60
80
100
120
140
**
*
* *
***
*
**
**
**
counts
2
strontium aluminates phasesTiO
2anatase phase
*
XRD pattern of the 2.0 % sample after decorated with TiO2
Pure commercial TiO2 Decorated TiO2-SrAlO-Bi-2.0 %
powder sample
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TiO2- decorated SrAlO-B i fo r pho tocatalysis
Morphology of the pure TiO2and the TiO2-decorated SrAlO-Bi 2.0%
Pure TiO2 TiO2- decorated SrA lO Bi 2.0%
Aparent ly the TiO2nanop art ic les are attached to th e surface of the
large micro grains o f the SrAlO-Bi 2.0 % samp le.
This fact is benef icial for the photo catalyt ic act iv i ty because the su rface
area is enhanc e.
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0 50 100 150 2000
25
50
75
100
%D
egradation
Exposure time (min)
0.0% Bi
2.0% Bi15.0% Bi
Reference Only TiO2
Photocatalyt ic degradat ion of of methylene blue
under UV (365 nm ) ligh t.
The 2.0 % B i TiO2decorated SrAlO sample reach almost a complete
degradat ion after 210 m in o f UV irradiation .
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ConclusionsLong persistent green and grenish blue materials were produced bythe combustion synthesis method followed by annealing in a reducingcarbon atmosphere.
The persistent powders were decorated with TiO2and the photocatalyticactivity was evaluated for the concentrations of x= 0.0%, 2.0%, 15.0%and pure TiO
2.
The decorated TiO2SrAlO 2.0 % Bi-codoping sample show goodphotocatalytic activity, the degradation was 97 % after 210 min underUV (365 nm) irradiation.
The 2.0 % sample show the long lasting persistence time and thePhotocatalytic activity probably due to the Bi levels into the strontiumaluminates lattices which creates electron or holes traps.