<span class='text_page_counter'>(1)</span><div class='page_container' data-page=1>

Original Article

Photoluminescence and photocatalytic properties of novel Bi

₂

O

₃

:Sm

3

ỵ

nanophosphor

S. Ashwini

a,b

, S.C. Prashantha

b,*

, Ramachandra Naik

c,**

, Yashwanth V. Naik

d

,

H. Nagabhushana

d

, K.N. Narasimhamurthy

e

a_{Department of Physics, Channabasaveshwara Institute of Technology, Gubbi 572216, India}

b_{Research Center, Department of Science, East West Institute of Technology, VTU, Bengaluru 560091, India}
c_{Department of Physics, New Horizon College of Engineering, Bengaluru 560103, India}

d_{Prof. CNR Rao Center for Advanced Materials, Tumkur University, Tumkur 572103, India}
e_{Department of Physics, Government First Grade College, Tumkur 572102, India}

a r t i c l e i n f o

Article history:

Received 2 May 2019
Received in revised form
18 August 2019

Accepted 6 September 2019
Available online 14 September 2019
Keywords:

Bi2O3:Sm3ỵ

Photoluminescence
JuddeOfelt
CIE
CCT

a b s t r a c t

The current work involves studies of the synthesis, characterization and photoluminescence for Sm3ỵ(1
e11 mol%) doped Bi2O3nanophosphors (NPs) by a solution combustion method. The average particle size

was determined using powder X-ray diffraction (PXRD) and found to be in the range of 13e30 nm. The
KubelkaeMunk (KeM) function was used to assess the energy gap of Sm3ỵ_{doped Bi}

2O3nanophosphors

which was found to be 2.92e2.96 eV. From the Emission spectra, the JuddeOfelt parameters (U2andU4),

the transition probabilities (AT), the quantum efficiency (h), the luminescence lifetime (tr), the colour

chromaticity coordinates (CIE) and the correlated colour temperature (CCT) values were estimated and
discussed in detail. The CIE chromaticity co-ordinates were close to the NTSC (National Television Standard
Committee) standard value of Orange emission. Using the LangmuireHinshelwood model and Acid Red-88,
the photocatalytic activity results showed that Bi2O3:Sm3ỵNPs are potential materials for the development

of an efcient photocatalyst for environmental remediation. The obtained results prove that the Bi2O3

:-Sm3ỵnanophosphors synthesised by this method can potentially be used in solid state displays and as
a photocatalyst.

© 2019 The Authors. Publishing services by Elsevier B.V. on behalf of Vietnam National University, Hanoi.

This is an open access article under the CC BY license ( />

1. Introduction

Lanthanide ions doped (Ln3ỵ) nanophosphors (NPs) have gained
massive attention owing to their potential applications in various
fields ranging from display[1], solar cells[2], bio-imaging[3], solid
state lasers[4], remote photo activation[5], temperature sensors

[6]and drug release[7].

Furthermore, NPs should possess superior physicochemical
characteristics, such as long lifetimes, large anti-Stokes shifts, high
penetration depth, low toxicity, as well as high resistance to photo
bleaching[8]. Bismuth is the only nontoxic heavy metal that can
easily be purified in large quantities[9].

The semiconductors such as Bi2MoO6, BiOX (X¼ Cl, Br, I), BiVO4

and Bi2O3have a high refractive index and excellent properties for

visible light absorb ion, photoluminescence, dielectric permittivity,
photoconductivity, large oxygen ion conductivity, and, noteworthy,
for photocatalytic activity[10_e12].

At present, the photocatalysis technology has been anticipated to
be a perfect“green” technology by the usage of solar energy in many
fields such as, water-splitting[13], solar cell[14], water and air
pu-rification, organic waste degradation[15], CO2reduction[16]etc. The

decomposition of dye contaminants in contaminated water, as a

branch of photocatalysis, has attracted great attention. To date, with
the exception of intensive research on conventional photocatalysts
such as TiO2, ZnO, ZrO2and other semiconductors with a wide band

gap[17], thefinding out of new photocatalysts with sturdy
degra-dation abilities has become additionally important. Thus, we can
consider Bi2O3as a suitable host material, which is having all these

features.

Bismuth oxide (Bi2O3) is a semiconductor with attractive optical

and electronic properties. Because of these properties, Bi2O3 has
* Corresponding author.

** Corresponding author.

E-mail addresses:(S.C. Prashantha),rcnaikphysics@gmail.
com(R. Naik).

Peer review under responsibility of Vietnam National University, Hanoi.

Contents lists available atScienceDirect

Journal of Science: Advanced Materials and Devices

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j s a m d

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become an important material for several applications such as fuel

cells [18], photocatalysts [19], gas sensors [20], and electronic
components[21]. Another significant characteristic of Bi2O3is its

polymorphism, which results in 5 polymorphic forms (

a

,

b

,

g

,

d

and

u

) with different structures and properties [22], among them
monoclinic

a

which is stable at room temperature and face-centered
cubic

d

that is stable at high temperature. There are various methods
available for the synthesis of Bi2O3 nanophosphors viz.,

sono-chemical, microwave irradiation, hydrothermal, chemical vapour
deposition, micro-emulsion, surfactant thermal strategy, solegel
approach, solution combustion and electro-spinning[23,24].

In this work we report the synthesis of Bi2xO3:Smx(x¼ 0.01 to

0.11) NPs via a simple low temperature solution combustion
method. Compared with the conventional methods adopted for
synthesis, the solution combustion method is advantageous in view
of its low temperature and reduced time consumption which result
in a high degree of crystallinity and homogeneity. The synthesised
nanophosphor is characterized by PXRD and DRS. The effect of
Sm3ỵdoping on the photoluminescence properties were studied in
detail for their possible usage in display applications.

2. Experimental

2.1. Synthesis of Bi2xO3:Smx(x¼ 0.01 to 0.11)

The synthesis of Bi2xO3:Smx (x ¼ 0.01 to 0.11) via solution

combustion method was made using analytical grade Bismuth
ni-trate (Bi(NO3)3$5H2O: 99.99%, Sigma Aldrich Ltd.), Samarium nitrate

(Sm(NO3)3$6H2O: 99.99%, Sigma Aldrich Ltd) as dopant and Urea as

fuel. In a cylindrical Petri dish (300 ml), the aqueous solution
con-taining a stoichiometric quantity of reactants were taken such that
Oxidizer (Bi (NO3)3$5H2O) to Fuel (Urea) ratio is 1 (O/F¼ 1)[25]and

introduced into a pre heated muffle furnace at temperature of
400_{± 10}C. Thermal dehydration of the reaction mixture takes
place and auto-ignites with liberation of gaseous products resulting
in the nano powders. Finally, the so-prepared powders were
calcined at 600 C for 3 h. The theoretical equation, assuming
complete combustion of the redox mixture used for the synthesis of
Bi2O3, can be written as:

2
BiNO3ị3$5H2O


ỵ 5CH4N2O/Bi2O3ỵ 8N2ỵ 5CO2ỵ 20H2O
(1)

2.2. Photocatalytic activity of Bi2O3:Sm3ỵ

At room temperature, the experiment was conducted in a reactor
by utilizing a 125 W mercury vapour lamp as the UV light source
(

l

¼ 254 nm). Using Acid red dye 88 (AR-88) as a model dye, the UV
light photocatalytic activities of Bi2O3:Sm3ỵNPs were evaluated. In

this experiment, 30 mg of synthesized Bi2O3:Sm3ỵNPs was

dis-solved completely into 10 ppm of AR-88 dye solution and stirred
continuously to form a uniform solution. At each 15 min, 5 ml of the
dye solution was inhibited and tested by a UVeVis
spectropho-tometer by means of the typical adsorption band at 510 nm after
centrifugation for the computation of the disintegration of dye[26].

2.3. Characterization

Crystal morphology of the synthesised NPs was determined by
PXRD using X-ray diffractometer (Shimadzu) (V-50 kV, I-20 mA,

l

-1.541 Å, scan rate of 2 _min1_{). Photoluminescence studies are}

made using Horiba (model fluorolog-3, xenon-450 W)
Spectro-flourimeter at Room Temperature. Fluor Essence™ software is used
for spectral analysis. DRS studies of the samples were performed
using Shimadzu UV-2600 in the range 200e800 nm.

3. Results and discussion

3.1. PXRD studies

Fig. 1shows the Powder X-ray diffraction (PXRD) pattern of
undoped and Sm3ỵ(1e11 mol%) doped Bi2O3NPs. All the recorded

peaks were indexed to the Cubic phase of Bi2O3(JCPDS card No.

52-1007, Space Group: Fm-3m (no.225)), suggesting high purity and

crystallinity of the synthesized powders. As the acceptable
per-centage difference Dr(ionic radii)[27]is less than 15% between Bi3ỵ

and Sm3ỵions, Sm3ỵions substitute the Bi3ỵions in the Bi2O3host

DrẳRhCNị  R_R dCNị
hCNị

(2)

For Coordination number CN equal to 6, the radius of the host
cation Rh(CN) is 1.03 Å, and the radius of the doped ion Rd(CN) is

0.958 Å. The calculated Dris found to be 6.99%[28].

The average crystallite size (D) was calculated by using Scherer's
formula[29].

D¼

_b

0:9

l

cos

q

(3)

where

l

represents the wavelength of X-rays (1.54Å),

q

; the
inci-dent angle, and

b

; the full width at half maximum (FWHM) of the
XRD peaks.Table 1 gives the crystallite sizes of the Bi2O3:Sm3ỵ

(1e11 mol%) samples. These are in the range of 13e30 nm which
indicates that, as doping concentration increases, crystallite sizes
decrease.

3.2. Diffuse reflectance spectroscopy studies

To evaluate the energy band gap, the diffuse reectance spectra
(DRS) of Bi2O3:Sm3ỵNPs were carried out and shown inFig. 2. The

spectra mainly exhibit absorption at ~410 nm which is

Fig. 1. PXRD patterns of undoped and Sm3ỵ(1e11 mol%) doped Bi2O3NPs.

Table 1

Crystallite size of Bi2O3:Sm3ỵ.

Sl no. Compound Crystallite size (nm)

1 Bi2O3:Sm3ỵ: 1 mol% 23.535

2 Bi2O3:Sm3ỵ: 3 mol% 22.553

3 Bi2O3:Sm3ỵ: 5 mol% 19.426

4 Bi2O3:Sm3ỵ: 7 mol% 16.640

5 Bi2O3:Sm3ỵ: 9 mol% 13.243

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characteristic for the absorption of Sm3ỵ ions [30]. The
Kubel-kaeMunk relation was adopted to calculate the band gap of the
NPs[31],

FRịh

n

ẳ C
h

n

 Eg

n ₍₄₎

where FRị is the KubelkaeMunk function, h

n

; the photon energy,

C; a constant, Eg ; the optical energy band gap, n; an exponent

which value depends on the nature of the inter band electronic
transition, viz., nẳ ẵ (direct allowed transition), n ¼ 2 (indirect
allowed transition), n¼ 3/2 (direct forbidden transition) and n ¼ 3
(indirect forbidden transition)[24].

Direct or indirect transitions are“allowed” transitions, if the
momentum matrix element characterizing the transition is
different from zero. This means that the transition can hold for sure
if sufficient energy is given to the particle (e.g. electron) involved in
the process.

Direct or indirect transitions are“forbidden” transitions, if the
momentum matrix element characterizing the transition is equal to
zero. The transition cannot hold even if sufficient energy is given.
However, a forbidden transition can sometimes become allowed.
Sometimes a transition can be forbidden in_{first order (first order}
perturbation theory) but it becomes allowed in second order
(second order perturbation theory)[32].

As Bi2O3is a direct band gap material, from the extrapolation of

the lineẵFRịh

n

2to zero (Fig. 3), the Egof the synthesised NPs was

found to be in the range of 2.92e2.96 eV, indicating that the present
material can be a promising photocatalyst since it can absorb UV as
well as the visible region of solar light.

3.3. Photoluminescence studies

Fig. 4shows the excitation spectra of Bi2O3:Sm3ỵNPs for 3, 5 and

7 mol%. The spectra were taken in the range of 360 nme500 nm and

<b>200</b> <b>300</b> <b>400</b> <b>500</b> <b>600</b> <b>700</b> <b>800</b>

<b>0</b>
<b>20</b>
<b>40</b>
<b>60</b>

<b>80</b> <b>Bi₂O₃:Sm3+_{(1-11 mol %)}</b>

<b>)</b>

<b>%(</b>

<b>ec</b>

<b>na</b>

<b>tc</b>

<b>elf</b>

<b>e</b>

<b>R</b>

<b>es</b>

<b>uff</b>

<b>i</b>

<b>D</b>

<b>Wavelength (nm)</b>
<b> 1 mol %</b>

<b> 3 mol %</b>
<b> 5 mol %</b>
<b> 7 mol %</b>
<b> 9 mol %</b>
<b> 11 mol %</b>

Fig. 2. DRS of Sm3ỵ(1e11 mol%) doped Bi2O3NPs.

Fig. 3. Energy gap of Bi2O3:Sm3ỵNPs.

Fig. 5. Emission spectra of Bi2O3:Sm3ỵ(1e11 mol%) (lexcẳ 465 nm).

<b>1</b> <b>3</b> <b>5</b> <b>7</b> <b>9</b> <b>11</b>

<b>4x105</b>

<b>6x105</b>

<b>8x105</b>

<b>1x106</b>

<b>).</b>

<b>u.</b>

<b>a(</b>

<b>yti</b>

<b>s</b>

<b>ne</b>

<b>t</b>

<b>nI</b>

<b>L</b>

<b>P</b>

<b>Sm3+ Concentration (mol%)</b>

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exhibit bands at 365 nm (6H5/2/4D3/2, 5/2), at 395 nm (6H5/2/4F7/
2), at 418 nm (6H5/2/4M19/2), at 448 nm (6H5/2/4G9/2), at 465 nm

(6H5/2/4I13/2) and at 488 nm (6H5/2/4I11/2) which are attributed

to the 4f-4f transition of Sm3ỵ[33]. Among these, the prominent
transition at 465 nm (6H5/2/4I13/2) was taken to explicate the

emission spectra of the NPs.

Fig. 5shows the emission spectra of Bi2xO3:Smx(x¼ 0.01 to 0.11)

calcined at 600C excited under 465 nm. The spectra consist of four
typical transition emission bands centered at 565 nm (yellow),
616 nm (orange), 653 nm (orange red) and 713 nm (red) which are due
to4G5/2/6H5/2,4G5/2/6H7/2,4G5/2/6H9/2and4G5/2/6H11/2

respectively. Actually at excitation, the doped ions are excited to the
higher energy state4H9/2from which they relax non-radiatively to the

metastable state4G5/2through the4F7/2,4G7/2, and4F3/2levels. But4H9/
2 and 4G5/2 correspond to very close and fast non-radiative

re-laxations. So the spectra will have the four transition bands from4G5/2.

Among all the emitted transitions,4_G

5/2/6H7/2(616 nm) is the most

prominent one with strong orange emission which is partly magnetic

dipole and partly electric dipole.4G5/2/6H9/2(653 nm) is purely

electric dipole and in this study the intensity of the electric dipole
transition is less compared to that of the magnetic dipole one,
indi-cating the symmetry behaviour of Sm3ỵions in the host Bi2O3[34,35].

The variation of the PL intensity with respect to the Sm3ỵdopant
concentration is shown inFig. 6. The PL intensity at 616 nm emission
increases up to 5 mol% with the increase of Sm3ỵcontent and,
sub-sequently, it decreases owing to concentration quenching. The energy
of the phosphor is lost due to non-radiative (or also multi
phonon-assisted non-radiative) transitions by the incorporation of Sm3ỵin
the host or Sm3ỵ-Sm3ỵinteraction when excited through vacancies.

3.4. Judd Ofelt (JeO) analysis

Quantum efciency is an important parameter which
de-termines the efficiency of nanophosphors for the applications of
display devices. The electric-dipole (ED) and magnetic-dipole (MD)
transitions are generally used in the investigation of rare earth ions
doped luminescent materials. However, it is challenging to
calcu-late the JeO intensity

U

t(t¼ 2, 4, 6) parameters for powder

ma-terials because the absorption spectra of powder mama-terials can
hardly be recorded.

The radiative transition probabilities (AR) from an excited state

j

0_J0_{to the}_{final state}

_j

_{J are related to forced electric dipole}

transi-tions and they may be written as a function of the JeO intensity

parameters:

AR

j

0_J0_

_j

_J_ẳ 64

p

4w3
3h2J ỵ 1ị

n
n2_{ỵ 2}2

9 Sedỵ n

3_S
md

!

(5)

where, Sedand Smdare the electric and magnetic dipole strengths,

respectively, wJ is the wavenumber of the respective electronic

transition, h is Planck's constant, n is the effective refractive index of
the nanophosphor[36].

The total radiative transition probability (AT) for an excited state

j

0_J0_{is transition}_[37]_{given by formula:}

AT

j

Jị ẳ

X

jJ
AR

j

0_J0_

_j

_J ₍₆₎

The radiative lifetime

t

rị of the excited state

j

0J0 can be

ob-tained by[38].

tr

j

0_J0_ẳ 1
AR

j

Jị

(7)

The luminescence quantum efciency (

h

) can be calculated by
the relation [39] and was found to be ~75% for the present
phosphor:

Table 2

JeO intensity parameters and radiative properties of Sm3ỵ_{doped Bi}
2O3NPs.

Phosphor Bi2O3:Sm3ỵ JeO intensity parameters

(1020cm2₎

Transitions AR(s1) ANR(s1) AT(s1) tr(ms) h(%)

U2 U4

1 mol% 0.41059 0.361985 4_G

5/2/6H5/2
4_G

5/2/6H7/2
4_G

5/2/6H9/2

71.316 24.025 95.341 10.489 74.8

3 mol% 0.401301 0.495693 69.703 23.482 93.185 10.731 74.8

5 mol% 0.351343 0.323457 61.025 20.558 81.584 12.257 74.8

7 mol% 0.386104 0.347901 67.063 22.592 89.656 11.154 74.8

9 mol% 0.354646 0.347472 61.599 20.752 82.351 12.143 74.8

11 mol% 0.392754 0.417446 68.218 22.982 91.199 10.965 74.8

Fig. 7. (a) CIE chromaticity diagram of Bi2O3:Sm3ỵ NPs. (b) CCT diagram of

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h

ẳ AR

ARỵ ANRẳ

AR
AT

(8)
Table 2gives the results of JeO intensity parameters (

U

2and

U

4)

and radiative properties of Bi2O3:Sm3ỵ nanophosphors that are

calculated from the emission spectra. From the results it is clear
that the

U

2and

U

4values are comparatively high due to the fact

that the samples generally possess higher fractions of the rare earth
ions on the surface of the nano crystals compared to the bulk
counterparts[40]. The parameter

U

2is related to the short range

impact in the vicinity of the rare earth Sm3ỵion and

U

4is related to

the long range impact. ARand

t

rwere calculated from the emission

spectra. The quantum efficiency (

h

) is calculated with equation(8)

and found to be equal to 74.8% as shown inTable 2. An increase in
quantum efficiency indicates a better applicability for display
de-vices. It was observed that4G5/2/6H7/2transition of Sm3ỵdoped

Bi2O3 NPs dominates the intensity emitted by the NPs in the

emission spectra. The results infer that the current NPs can be

utilized for display devices[38].

3.5. CIE and CCT analysis

“Commission International de i’Eclairage (CIE) 1931 standards”
were used to calculate the colour coordinates of Bi_2xO3:Smx

(x ¼ 1e11 mol%) from the emission spectra. In the colour space,
coordinates (x, y) are used to specify the colour quality and to
evaluate the phosphors performance. These coordinates are the
most prominent parameters.Fig. 7(a) shows the CIE 1931
chro-maticity diagram for Bi2xO3:Smx(x¼ 1e11 mol%) NPs excited at

365 nm and 465 nm.

The CIE colour coordinates so calculated for Bi2xO3:Smx

(x¼ 1e11 mol%) are summarized inFig. 7(a). It is clear that all the

<b>350</b> <b>400</b> <b>450</b> <b>500</b> <b>550</b> <b>600</b> <b>650</b>

<b>0.00</b>
<b>0.02</b>
<b>0.04</b>
<b>0.06</b>
<b>0.08</b>
<b>0.10</b>

<b>(a) Bi₂O₃: Sm_1mol%</b> <b>0 Min</b>

<b> 15 Min</b>
<b> 30 Min</b>
<b> 45 Min</b>
<b> 60 Min</b>

<b>Absorbance</b>

<b>Wavelength(nm)</b>

<b>350</b> <b>400</b> <b>450</b> <b>500</b> <b>550</b> <b>600</b> <b>650</b>

<b>0.00</b>
<b>0.02</b>
<b>0.04</b>
<b>0.06</b>
<b>0.08</b>

<b>0.10</b> <b>(b) Bi2O3: Sm3 mol%</b> <b>0 Min</b>

<b> 15 Min</b>
<b> 30 Min</b>
<b> 45 Min</b>
<b> 60 Min</b>

<b>Absorbance</b>

<b>Wavelength(nm)</b>

<b>350</b> <b>400</b> <b>450</b> <b>500</b> <b>550</b> <b>600</b> <b>650</b>

<b>0.00</b>
<b>0.02</b>
<b>0.04</b>
<b>0.06</b>
<b>0.08</b>

<b>0.10</b> <b>(c) Bi2O3: Sm5mol%</b> <b>0 Min</b>

<b> 15 Min</b>
<b> 30 Min</b>
<b> 45 Min</b>
<b> 60 Min</b>

<b>Absorbance</b>

<b>Wavelength(nm)</b>

<b>350</b> <b>400</b> <b>450</b> <b>500</b> <b>550</b> <b>600</b> <b>650</b>

<b>0.00</b>
<b>0.02</b>
<b>0.04</b>
<b>0.06</b>
<b>0.08</b>
<b>0.10</b>

<b>(d) Bi₂O₃: Sm7mol%</b> <b>0 Min</b>

<b> 15 Min</b>
<b> 30 Min</b>

<b> 45 Min</b>
<b> 60 Min</b>

<b>Absorbance</b>

<b>Wavelength(nm)</b>

<b>350</b> <b>400</b> <b>450</b> <b>500</b> <b>550</b> <b>600</b> <b>650</b>

<b>0.00</b>
<b>0.05</b>
<b>0.10</b>
<b>0.15</b>

<b>Wavelength(nm)</b>

<b>Absorbance</b>

<b>(e) Bi₂O₃: Sm9 mol%</b> 0 Min

15 Min
30 Min
45 Min
60 Min

<b>350</b> <b>400</b> <b>450</b> <b>500</b> <b>550</b> <b>600</b> <b>650</b>

<b>0.00</b>
<b>0.05</b>
<b>0.10</b>

<b>0.15</b>

<b>(f) Bi₂O₃: Sm_{11 mol%}</b> <b>0 Min</b>

<b> 15 Min</b>
<b> 30 Min</b>
<b> 45 Min</b>
<b> 60 Min</b>

<b>Absorbance</b>

<b>Wavelength(nm)</b>

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samples fall into the scope of orange red light emission.Fig. 7(b)
shows CCT of Bi_2xO3:Smx(x¼ 1e11 mol%) and the average value

was found to be 1758 K[41]. Hence, it is obvious that the NPs can be
used as an Orange red light source to meet the needs of the
illus-trated applications.

3.6. Photocatalytic activity of AR-88 dye

Acid Red-88 (AR-88) is an azo dye. Due to its intense colour,
Ar-88 was used to dye cotton textiles red and used for Photocatalytic
studies. The PCA of Bi2xO3:Smx(x¼ 1e11 mol%) were analysed for

the decolourization of AR-88 in aqueous solution under UV light
irradiation for a time duration of 60 min. The UV visible absorption
spectra of the dye for various concentrations of Bi2xO3:Smx

(x _{¼ 1e11 mol%) are shown in} Fig. 8(a_{ef). To know about the}
response kinetics of AR-88 Dye decolourization, the
LangmuireHinshelwood model was adopted which follows the
equation, ln (C/C0)¼ kt þ a, where, k is the reaction rate constant,

C0the preliminary attention of AR-88, C the attention of AR-88 on

the response time t[22,42].Fig. 9shows the plot of ln (C/C0) photo

decolourization of all catalysts Bi2O3:Sm3ỵunder UV light

irradia-tion. As the doping concentration increases, the photo
decolouri-zation efficiency decreases and after 60 min irradiation it was found
that the photo decolourization efficiency was 98.57% which is the

maximum for 7 mol% (Fig. 10). This might be due to the fact that at
7 mol%, Sm3ỵions on the host Bi2O3behave as electron trapper to

detach the electronehole pairs which is much needed for PCA. At
other molar concentrations, the catalyst may behave as
recombi-nation centres and this leads to less PCA efciency.

4. Conclusion

The present Bi2O3:Sm3ỵ nanophosphors were prepared by a

solution combustion method. The crystallite size was found to be in
the range 13e30 nm. The phosphors upon exciting at comparably
low energy of 465 nm, emit orange colour with all characteristic
transitions of Sm3ỵions. CCT of 1758 K shows that the phosphors

are potential materials for warm white light emitting display
de-vices. Further, it shows an excellent photocatalytic activity which
proofs the multi functionality of the prepared nanophosphors.

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<b>0</b> <b>15</b> <b>30</b> <b>45</b> <b>60</b>

<b>-1.5</b>
<b>-1.0</b>
<b>-0.5</b>

<b>0.0</b>

<b>ln</b>

<b>(</b>

<b>c/c</b>

<b>0</b>

<b>)</b>

<b>Time(min)</b>

<b>Bi₂O₃: Sm_{1 mol %}</b>

<b>Bi₂O₃: Sm_{3 mol %}</b>

<b>Bi₂O₃: Sm_{5 mol %}</b>

<b>Bi₂O₃: Sm_{7 mol %}</b>

<b>Bi2O3: Sm9 mol %</b>

<b>Bi₂O₃: Sm_{11 mol %}</b>

Fig. 9. Plots of ln (C/Co) photo decolourization of all catalysts Bi2O3:Sm3ỵNPs under

UV light irradiation.

<b>0</b> <b>10</b> <b>20</b> <b>30</b> <b>40</b> <b>50</b> <b>60</b>

<b>0</b>
<b>20</b>
<b>40</b>
<b>60</b>
<b>80</b>
<b>100</b>

<b>Bi₂O₃: Sm3+</b>

<b>Time(min)</b>

<b>)</b>

<b>%(</b>

<b>noi</b>

<b>tis</b>

<b>o</b>

<b>p</b>

<b>mo</b>

<b>ce</b>

<b>D</b>

<b> 1 mol%</b>
<b> 3 mol%</b>
<b> 5 mol%</b>
<b> 7 mol%</b>
<b> 9 mol%</b>
<b> 11 mol%</b>

</div>
<span class='text_page_counter'>(7)</span><div class='page_container' data-page=7>

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