solid BaTiO3:Dy3+ microspheres and their applications in effective detection of latent fingerprints and lip prints

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M. Dhanalakshmi

a,b

, H. Nagabhushana

c,*

, G.P. Darshan

d

, R.B. Basavaraj

c

,

B. Daruka Prasad

e

a_{Department of Physics, Govt. Science College, Bengaluru 560 001, India}

b_{Research and Development Center, Bharathiar University, Coimbatore 641046, India}
c_{Prof. C.N.R. Rao Centre for Advanced Materials, Tumkur University, Tumakuru 572103, India}
d_{Department of Physics, Acharya Institute of Graduate Studies, Bangalore 560 107, India}

e_{Department of Physics, BMS Institute of Technology and Management, VTU, Belagavi-affiliated, Bangalore 560 064, India}

a r t i c l e i n f o

Article history:

Received 19 December 2016
Received in revised form
31 January 2017
Accepted 9 February 2017
Available online 16 February 2017

Keywords:

Sonochemical synthesis
Latentfingerprint
Cheiloscopy
JuddeOfelt analysis

a b s t r a c t

Nanostructured materialsfind potential benefits for surface-based science such as latent fingerprints (LFPs)
and lip print detection on porous and non-porous surfaces. To encounter the drawbacks viz. low sensitivity,
high background hindrance, complicated procedure and high toxicity associated with traditional
fluo-rescent powders were resolved by using hollow/solid BaTiO3:Dy3ỵ(1e5 mol %) microspheres. The

visu-alization of LFPs stained by the optimized BaTiO3:Dy3ỵ(2 mol %) hollow/solid microspheres exhibits

well-defined ridge patterns with high sensitivity, low background hindrance, high efficiency and low toxicity on
various surfaces. The powder X-ray diffraction results revealed the body centered cubic phase of the
pre-pared samples. The emission spectra exhibit intensive peaks at ~480, 575, and 637 nm, which were
attributed to transitions4_F

9/2/6HJ(J¼ 15/2, 13/2, 11/2) of Dy3ỵions, respectively. Surface morphologies

were extensively studied with different sonication times and concentrations of the used barbituric acid.
The Commission International De I-Eclairage (CIE) and Correlated Color Temperature (CCT) analyses
revealed that the present phosphor is highly useful for the fabrication of white light emitting diodes.
© 2017 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

In a crime spot investigation, LFPs are the most important
physical evidence for identification of criminals [1,2]. When a
criminal touches any surface in a spot, skin sweat transferred to the
surface through pores leading to an invisible ridge pattern is well
known as latentfingerprints. In a forensic analysis, LFPs are the most
influential method due to its unique and immutable features[3,4].
Because of invisibility of LFPs, enhancement of LFPs was required for
identification and visualization. Nowadays, several methods have

been used to make LFPs visible. Among them, the powder dusting
method allows for LFPs to be visualized within a short period of time
and without any complicated requirements. The conventional
dusting powders were mainly classified into regular, metallic and

luminescent materials. Regular and metallic powders constituent of
resinous polymers and meshed metals which are hazard to
in-vestigators' health[5]. These conventional powders are not capable
of enhancing LFPs on some complicated surfaces. Luminescent
nanopowders are potential solutions to overtake such limitations,
making LFPs visible. Luminescent nanopowders were explored as
labeling agents for visualization of LFPs and exhibit good contrast,
sensitivity and adhesion efficiency. These factors provide new
possible applications of nano powders in surface science.

In addition, lip prints are form of wrinkles and grooves including
normal lines,fissures and are present in the zone of transition of
human lip between the inner labial mucosa and outer skin[6]. Lip
prints are also a main evidence for identification of an individual in
a forensic dentistry due to its uniqueness, except in monozygotic
twins. The revelation of lip prints was well known as cheiloscopy

[7]. The cheiloscopy plays a major role in forensic science for person
identification in crime investigations, ethnic studies, mass
di-sasters,fire victims, and vehicle accidents.

* Corresponding author.

E-mail address:(H. Nagabhushana).

Peer review under responsibility of Vietnam National University, Hanoi.

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The ultrasonic sonochemical method has received a great
attention for the fabrication of phosphors with unusual and
tailored properties. Further, an ultrasound assisted synthesis route
has great commercial potential advantages with high production
rates, syntheticflexibility on choosing host materials as high
pu-rity nano powders, rapid reaction rate, narrow size distribution,
stable colloidal dispersion, uniform mixing, less synthesis time,
and less energy usage[8]. In this method, the chemical reactions
arise from acoustic cavitations, i.e., formation, growth and
implosive collapse of bubbles in the liquid. The growth of the
bubble happens through the diffusion of solute vapor into the
volume of the bubble, while the collapse of the bubble arises when
the bubble size reaches its maximum value. When the solution was
exposed to ultrasound irradiation, the bubbles were implosively
collapsed by acousticfields in the solution[9]. According to the hot
spot theory, very high temperatures (>5000 K) were achieved
upon the collapse of a bubble. Since this collapse occurs in less
than a nanosecond, very high cooling rates (>1010 K/s) was also
obtained. These extreme environments can drive several chemical
reactions and physical modifications occur as a result, allowing
shape and size of the phosphors to be effectively tuned[10]. There
is a pressing need for synthesis of nano/micro structured materials
at reasonably low temperature for industrial applications.

To the best of our knowledge, there have been no reports on an
ultrasound assisted sonochemical method for fabrication of
BaTiO3:Dy3ỵ (1e5 mol %) powders using Barbituric acid as a

sur-factant. The prepared optimized samples were employed to
visu-alize LFTs and lip prints on various porous and non-porous surfaces.
In addition, the structural and photoluminescent properties were
analyzed, and photometric properties were systematically studied.

2. Experimental

Titanyl nitrate was prepared by taking N-butyl titanate in a petri
dish and a minimum quantity of doubled distilled water was added
to yield titanyl hydroxide. Further, nitric acid was added to this

redox mixture which gave titanyl nitrate. The corresponding
chemical reactions can be given by[11].

TiOC4H9ị4ỵ 3H2O/TiOOHị2ỵ 4C4H9OH (1)

TiOOHị2ỵ 2HNO3/TiONO3ị2ỵ 2H2O (2)

Stoichiometric amount of barium nitrate and titanyl nitrate
were dissolved in 100 ml deionized water and thoroughly mixed
in a magnetic stirrer to get uniform solution. The stoichiometric
amount of dysprosium nitrate (1e5 mol %) was added to the
above resultant solution. Further, different concentrations of
barbituric acid (0.05e0.25% W/V) were added to the resultant
mixture slowly. Ultrasound irradiation was accomplished with a
high-intensity ultrasonic probe (~2.5 cm diameter; Ti horn,
20 kHz, 150 W/cm2) immersed directly in the reaction solution.
Then, the solution mixture was stirred with high-intensity
ul-trasound irradiation under ambient air (the ultrasonic
frequency ~ 20 kHz, the power ~ 150 W) at afixed temperature of

75 C and by varying ultrasonic time (1e6 h). The solution was
kept undisturbed until a white precipitate was formed. The
pre-cipitate was_{filtered and washed several times by using distilled}
water and ethanol to remove any unreacted material. The
ob-tained product was dried at 60 C for 3 h in a vacuum oven.
Finally, the dried precipitate was grinded thoroughly into the
powder form and used for further studies.

2.1. Characterization

The obtained product was well characterized by using Shimadzu
7000 powder X-ray diffractometer using Cuk_a radiation.
Morphology of the product was studied by means of TM 3000,
Hitachi table top Scanning electron microscopy and Hitachi H-8100
Transmission electron microscope. The Perkin Elmer (Lambda-35)
spectrometer was used to study the reflectance of the samples. For

Fig. 1. Fingerprints on the surface of glass stained by (a) TiO2powder (b) BaTiO3:Dy3ỵ2 mol % powder, (c) Fe2O3powder, and (d) BaTiO3:Dy3ỵpowder synthesized by mechanical

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PL measurements Jobin Yvon Spectro_{flourimeter Fluorolog-3}
operational with 450 W Xenon lamp was used.

2.2. Mechanism of visualization of LFPs and lips print using
BaTiO3:Dy3ỵhollow/solid microspheres

FPs collected from healthy volunteers with the age group of ~21
years were deposited on porous and non-porous surfaces namely
microscopic slides, aluminum foils, scratched CDs, leafs, coins,
magazines, pen, colored plastic bag etc. Before deposition,fingers of
volunteers were thoroughly washed with water and dried in air

without touching any surfaces. The optimized BaTiO3:Dy3ỵ(2 mol
%) powder was carefully sprinkled and gentle dusted uniformly on
LFPs using a special“Marabou” feather brush. Further, an UV lamp
(4 W, 254 nm) was illuminated on the stained LFPs and then
pho-tographed using 50 mm f/2.8G ED lens Nikon D3100/AF-S digital
camera. For visualization of latent lip prints, lips were cleaned

thoroughly using smooth tissue paper and then with sterile cotton.
The lips were lightly pressed against a glass slab for ~3e5 s. The
latent lips prints acquired on glass slab were visualized by spraying
the optimized powder with a smooth brushing method and
pho-tographed using a digital camera.

3. Results and discussion

To determine effectiveness and selectivity of the prepared
BaTiO3:Dy3ỵ(2 mol %) powder as afluorescence labeling agent for
the visualization of LFPs on glass slide, conventionally used iron
oxide (Fe2O3) and titanium dioxide (TiO2) powders were used as a
control. It was found that, LFPs developed by Fe2O3, TiO2 and
BaTiO3:Dy3ỵpowders fabricated by mechanical stirring could not
resolve fullngerprint patterns (Fig. 1(a, c& d)). However, LFP
stained by BaTiO3:Dy3ỵ(2 mol %) hollow/solid microspheres under
254 nm UV light revealed well defined friction ridges (Fig. 1b). It is

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evident that the optimized BaTiO3:Dy3ỵpowder can be used as an
effective labeling agent for visualization of LFPs due to their
supe-rior white light emission. Well defined fingerprint images with high
sensitivity were also visualized by BaTiO3:Dy3ỵ(2 mol %) hollow/
solid microspheres on non-porous materials including green leaf,

plastic sheet, plastic pen edge, steel pen edge, TV remote, mobile
screen, coin, and stainless steel (Fig. 2).

In addition, aged (different time periods) LFPs were examined to
exhibit the suitability and robustness of the prepared powder in
advanced forensic detection.Fig. 3(aec) shows the aged LFPs with
different time periods (1 day, 2 week, and 1 month) stained by the
optimized BaTiO3:Dy3ỵ powder. Normally, sensitivity of labeling

powder progressively decreases as aging of the LFPs enhances, due
to evaporation of chemical constituents of the LFPs. In the present
work, even one month aged FP shows defined ridges, indicate the
practicability of the prepared powder. The LFPs on different
textured marbles visualized by optimized BaTiO3:Dy3ỵ(2 mol %)
powder under 254 nm illumination demonstrate the well-defined
ridge patterns withfine contrast and without or less background
hindrance (Fig. 3 (def)). The differently magnified SEM images of
LFP enhanced by prepared BaTiO3:Dy3ỵ(2 mol %) powder were
shown inFig. 4. The prepared powder particles provide uniform
distribution and stronger adhesive ability via each static and
sur-face absorption interactions and it increases the chemical stability,

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permitting the long protection of light and affording affinity with
LFPs.

The above obtained results demonstrated that, the optimized
BaTiO3:Dy3ỵ(2 mol %) powder was explored as an efcient
fluo-rescent labeling agent for visualization of LFPs on various porous
and non-porous surfaces. The prepared optimized powder can
visualize LFPs as a whole, with high sensitivity, efficiency and low

background interference.

Lip prints similar to_{fingerprints have many elevations and}
de-pressions providing evidence in individual identification and
criminal investigation in a forensic dentistry. The study of such lip
prints called as Cheiloscopy. Usually, lip prints can be found where
the surface in contact with the lips[12]. Most commonly in glasses,
cigarettes, straws, food items etc. However, some extra effort has
been required to make lip prints visible. Therefore, we explored
BaTiO3:Dy3ỵ(2 mol %) powder for visualization of lip prints on glass
under UV 254 nm. Fig. 5 shows the lip print stained by the

optimized BaTiO3:Dy3ỵ(2 mol %) powder. From thegure, it was
clearly evident that the whole lip prints with Tsuchihashi's Type V,
Type I, Type I0and Type III grooves (Fig. 5(bee)) were visualized
with high sensitivity and contrast due uniform smaller size and
adhesive nature of the powder.

In the ultrasound assisted sonication method, many
experi-mental parameters namely sonication time, concentration of
sur-factant, pH value and sonication power etc., may affect greatly the
size and morphology of the products. In the present study, the
morphology of the prepared samples was extensively studied with
different sonication times and concentrations of the surfactant.Fig. 6

(aee) shows SEM images of BaTiO3:Dy3ỵ(2 mol %) with different
sonication times (1e5 h) with a 0.25% W/V concentrated barbituric
acid. When the sonication time was ~1 h, several splintered parts
having small lotusflower e like morphology was observed (Fig. 6

(a)). The petals offlowers started blossoming, when the sonication
time was increased to 3 h. Further, increase of the sonication time

Fig. 4. Differently magnied SEM images of ngerprints stained by BaTiO3:Dy3ỵ(2 mol %) powder ((b) is a magnified portion of (a)).

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(4 and 5 h), large number offlowers closed to form a uniform hallow
spherical shaped morphology was obtained (Fig. 6(d& e)). The
obtained spherical morphology preserved even after 5 h sonication
irradiation. Series of trials were conducted to ascertain the impact of
surfactant concentration on theflower morphology and are shown
inFig. 6(fej). When the concentration of barbituric acid was 0.05%
W/V, a yolk-shell shaped structure consisting of many particles was
observed (Fig. 6(f)). A hallow yolk-shell shaped micro structure

appeared, when the concentration of barbituric acid was increased
to 0.10% W/V (Fig. 6(g)). However, with increase of concentration to
0.15% W/V, more hallow was observed and retained even further
extended concentration (0.20% W/V). When the barbituric acid
concentration was increased to 0.25% W/V, significantly condensed
hallow space was observed (Fig. 6(j)).

Fig. 7depicts TEM, HRTEM, SAED patterns, and EDAX images of
the BaTiO3:Dy3ỵ(2 mol %) powder. The TEM image displays layer

Fig. 6. SEM images of BaTiO3:Dy3ỵ(2 mol %) powder with (aee) different sonication times (1e5 h), a barbituric acid concentration of 0.25% W/V, and (fej) different concentrations

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morphology and size ranged from 30 to 50 nm (Fig. 7(a)). The lattice
spacing (d) was estimated from an HRTEM image (Fig. 7(b)) and
found to be ~0.26 nm and the value was well matched with PXRD
values.Fig. 7(c) shows the SAED pattern of the prepared sample and

it confirms the polycrystalline nature of the prepared powder.
Further, elemental compositions such as atomic and molecular
weight were obtained from EDAX, which is shown inFig. 7(d).

Fig. 8(a) shows the PXRD pro_{files of BaTiO}3:Dy3ỵ(1e5 mol %)
powder fabricated with a 6 h sonication time and barbituric acid
(0.25% W/V). The sharp and intense diffraction peaks were in good
agreement with the cubic phase with JCPDS no. 31-0174 [13].
Further, it was observed that small impurity peak of dopant Dy2O3
ions was identied, indicating the successful substitution of Dy3ỵ
ions in the Ba2ỵsites. The intensity of impurity peak increases with
increasing the concentration of dopant ions.

The average crystallite size (D) was estimated using the
Scher-rer's formula[14]and listed inTable 1. It was evident from the table
that, the variation in crystalline size is dependent on dopant Dy3ỵ
concentration. This was due to the increase in strain, leading to the
replacement of Ba2ỵions by smaller radius Dy3ỵions. Generally,
broadening of the PXRD peaks was associated with crystallite sizes
or the strains present within the sample or both. Therefore, the
WilliamsoneHall fitting method (Fig. 8 (b)) [15]was utilized to
estimate the strain induced in the prepared samples and the
ob-tained results were given inTable 1.

Fig. 8(c) displays the diffuse reflectance spectra of the pure and
Dy3ỵdoped BaTiO3powders. The spectra exhibited peaks at ~1071,
887, 796, 381, 364, 348 and 320 nm, which were due to the 4fe4f
transition of the Dy3ỵions[16]. The KubelkaeMunk (KeM) theory
was utilized to estimate optical energy band gap of BaTiO3:Dy3ỵ
(1e5 mol %) powders from the DRS spectra[17]. The optical energy

band gaps (Eg) values of the prepared powders were shown in

Fig. 10(d) and inTable 1. The changes in Egwere mainly ascribed to
degree of order and disorder in the matrix as well as variations in
distribution of energy levels within the band gap[18].

The PL excitation spectrum of BaTiO3:Dy3ỵ (2 mol %) under
480 nm as emission was shown inFig. 9(a). The spectrum exhibited
peaks at ~350, 365, 387 and 435 nm, which were attributed to6H15/
2 / 6P7/2, 6H15/2 / 6P5/2, 6H15/2 / 4I13/2 and 6H15/2 / 4G11/2
respectively.Fig. 9(b) shows the PL emission spectra of BaTiO3:Dy3ỵ
(1e5 mol %) excited at 387 nm at RT. The spectra exhibited distinct
emission peaks at ~480, 574 and 637 nm, which were attributed to
4_F

9/2/6H15/2,4F9/2/6H13/2and4F9/2/6H11/2respectively[19].
From thefigure, it was clear that peak at ~574 nm was more
prom-inent as compared to other two peaks, which was due to a forced
electric dipole transition. The peak at ~480 nm was due to magnetic
dipole transitions and is much less sensitive to the coordination
environment. The yellow emission peak at 574 nm (4F9/2/6H13/2)
was stronger than the blue emission 480 (4_F

9/2/6H15/2), indicating
that Dy3ỵwas located in a more non centro-symmetric position in

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the BaTiO3host[20].Fig. 9(c) shows the partial energy-level diagram
indicating the different excitation and emission mechanism of
BaTiO3:Dy3ỵpowder. Asymmetry ratio (A21) was used to determine
the degree of distortion from the inversion symmetry of the local

environment of the Dy3ỵions in a host matrix[21].

A21¼
H

I2


4_F

9=2/6H13=2


d

l

H

I1


4_F

9=2/6H15=2


d

l

(3)

where I1and I2the intensities of a magnetic dipole transition at
480 nm and the electric dipole transition at 574 nm, respectively.
The variation of A21 with varying Dy3ỵ concentration in
BaTiO3:Dy3ỵ(1e5 mol %) powder was shown inFig. 10(a) and its

estimated values were listed inTable 3.

The effect of doping concentration (Dy3ỵ) on PL emission
in-tensity in the BaTiO3host was shown inFig. 10(a). It was clear from
the figure that, the PL intensity increased with an increase of
concentration of Dy3ỵup to 2 mol % and afterwards it diminished.
The decrease in the PL intensity was due to the well-known
phe-nomenon called as a self-concentration quenching, resulting from
the resonance energy transfer between neighboring Dy3ỵions[22].
From energy match rule, cross-relaxation lines among Dy3ỵions
are responsible for population decrease of4F9/2level as follows:

4_F

9=2ỵ6H15=2/6H9=2
.

6_F

11=2ỵ6F5=2 (4)

4_F

9=2ỵ6H15=2/6H7=2
.

6_F

9=2ỵ6F3=2 (5)

4_F

9=2ỵ6H15=2/6F1=2
.

6_H
9=2

.
6_F

11=2 (6)

In the above process, the excitation energy was transferred from
a Dy3ỵion in a higher excited state to a neighboring Dy3ỵion and
promotes the latter from the ground state to the metastable level.
The Dy3ỵions at4F9/2level undergo de-excitation through a cross
relaxation process while Dy3ỵions in the ground state will allow
the energies from Dy3ỵat6H15/2level simultaneously. Finally, all
the Dy3ỵ ions will go in their ground states and thus the
lumi-nescence related to4F9/2level was quenched[23].

The non radiative energy transfer among Dy3ỵions leads to a
concentration quenching effect. By knowing the critical distance
(Rc) between the neighboring Dy3ỵions, the type of the interaction
mechanism can be explored[24]. The calculated value of Rc was
found to be ~4.47 Å and was almost equal to 5 Å, which leads to the
multipoleemultipole interaction in the BaTiO3host and is the main
cause for concentration quenching of Dy3ỵin the powder. There
were several types of electric multi-polar interactions, which may

be possible, namely, dipoleedipole (ded), dipoleequadrupole
(deq), quadrupoleequadrupole (qeq), etc[25]. Therefore, it was a

Fig. 8. (a) PXRD patterns (b) WeH plots, (c) DR spectra and (d) optical band gap plot of pure and BaTiO3:Dy3ỵ(1e5 mol %) powders prepared with a 5 h sonication time and 0.25%

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necessity to know which type of interaction responsible in the
energy transfer between Dy3ỵions. According to the Dexter and
Schulman theory[26], the ratio emission intensity (I) to
concen-tration of activator ion follows the equation;

I
Xẳ K

h

1ỵ

b

c

ịQ3
i1

(7)

where X; the activator concentration, Q; a constant of multi-polar
interaction and equals 6, 8, or 10 and less than 6 for dipoleedipole;
dipoleequadrupole or quadrupoleequadrupole interactions and
charge transfer mechanism respectively, and K and

b

; constants for
the given host lattice under the same excitation condition.

LogI
X¼ A 

Q

3log X (8)

whereA ẳ log k  log

b

ị.Fig. 10(b) shows thetted linear curve of
log (I/X) vs. log (X) in BaTiO3:Dy3ỵ(1e11 mol %) powder and the
value of the slope to be ~1.205. The calculated value Q was found
to be 6.346 and was almost equal 6. This result indicates that, the
charge transfer mechanism was due to the d_{ed interaction for the}
concentration quenching in the present powder.

The Commission International De I-Eclairage (CIE) chromaticity
co-ordinates of the BaTiO3:Dy3ỵ (1e5 mol %) powders were
calculated and listed inTable 2. It was noticed that, the CIE
co-ordinates for the present powders were located well within the
white region (Fig. 10(c)). The Correlated Color Temperature (CCT)
was estimated by Planckian locus and their values are listed in

Table 2. The quality of the white light in terms of CCT (Fig. 10(d))
was also studied using the McCamy empirical theoretical relation

[27]. And the color purity of the powder was estimated according
to the work[28]and their values are shown inTable 2. These
re-sults clearly show that the present powder may be quite useful for
solid state lighting applications.

The JuddeOfelt (JeO) theory has been widely utilized to study
the radiative transitions of rare-earth ions in several host materials

[29]. Various radiative properties such as J-O intensity parameters
(

U

2&

U

4), emission peak wavelengths (

l

pin nm), radiative

tran-sition probability (AT), calculated radiative (

t

rad) lifetime, branching
ratio (

b

R) and asymmetric ratio (A21) were estimated by using the
PL emission spectra[30]. The relation between radiative emission
rates and the integrated emission intensities were estimated by
using the equation reported elsewhere[31].

A02;4
A01 ¼

I02;4
I01 ¼

h

y

01

h

y

02;4 (9)

Fig. 9. (a) PL excitation spectra of BaTiO3:Dy3ỵ(2 mol %) powder atlemiẳ 480 nm; (b) PL emission spectra of BaTiO3:Dy3ỵ(1e5 mol %) powder atlexc¼ 387 nm; and (c) Energy

levels diagram of Dy3ỵdoped BaTiO3powder.

Table 1

Estimated average crystallite size, strain and energy gap (Eg) values of BaTiO3:Dy3ỵ

(1e5 mol %) powders.
Dy3ỵconc.
(mol %)

Crystallite size
(nm) [DeS approach]

Crystallite
size (nm)
[WeH approach]

Strain

(104₎ Eg(eV)

Pure 30 32 1.4 3.20

1 32 38 1.6 3.23

2 35 36 1.3 3.25

3 38 41 1.9 3.26

4 36 39 1.4 3.28

5 34 35 1.6 3.29

Table 2

Photometric characteristics of doped BaTiO3:Dy3ỵ(1e11 mol %) powders.

BaTiO3:Dy3ỵconc.

(mol %)

CIE CCT CCT (K) CP (%)

X Y U0 V0

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where I0eJand h

n

0eJ; integrated emission intensity and energies
corresponding to transition4F9/2/6HJ(J¼ 15/2, 13/2 and 11/2)
respectively.

The radiative emission rates A0eJ(J ¼ 2, 4) related to forced
electric dipole transitions can be obtained and written as a function
of the J-O intensity parameters:

A_0Jịẳ 64

p

4_w3

J
3h2J ỵ 1ị

nn2_{ỵ 2}2
9

X
lẳ2;4

U

l
D

7_F

9=2Ulị6HJE
2

(10)

where A_ð0JÞ; the coefficient of spontaneous emission, e; the
elec-tronic charge,wJ; the wave number of the corresponding
transi-tion, h; the Planck's constant, Smd; the strength of the magnetic

dipole and n; the RI of the prepared sample.D4_F

9=2Ulị6HJE
2

;
squared reduced matrix element of Dy3ỵions and were 0.2457 and
0.4139 for J¼ 2 and 4 respectively and these values were
inde-pendent of the chemical environment. Thus, by using Eqs.(9) and
(10), the values of

U

2 and

U

4 were calculated and listed in

Table 3. The JeO intensity parameters (

U

2and

U

4) for different host
matrices have been observed[15]and are listed inTable 4.

The total radiative transition probability (ATð

j

JÞ) can be
calcu-lated and expressed as

AT

j

Jị ẳ
X

J0

AJJ0 (11)

The radiative lifetime (

t

_rad

j

J_{ị) of an excited state in terms of}
ATð

j

JÞ is given by

Fig. 10. (a) Effect of concentration of Dy3ỵon the 574 nm emission and the variation of asymmetric ratio in BaTiO3powders, (b) Relation between log(x) and log (I/x), (c) CIE and (d)

CCT diagram of BaTiO3:Dy3ỵ(1e5 mol %) powders.

Table 3

JuddeOfelt intensity parameters (U2,U4), Emission peak wavelengths (lpin nm), radiative transition probability (AT), calculated radiative (trad) lifetime, branching ratio (bR)

and asymmetric ratio (A21) of BaTiO3:Dy3ỵ(1e5 mol %) powder (lexẳ 387 nm).

BaTiO3:Dy3ỵconc.

(mol %)

JuddeOfelt intensity parameters
(1020_cm2₎

Emission peak
wavelengthlpin nm

AT(s1) trad(ms) bR A21

U2 U4

1 5.96 6.56 575.80 287.3 3.48 0.998 1.373

2 6.30 6.51 575.05 303.9 3.29 0.999 1.460

3 6.47 5.95 576.02 312.0 3.20 0.998 1.488

4 7.04 10.51 576.55 339.6 2.94 0.998 1.612

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The branching ratio (

b

ð

j

JÞ) of the resultant emission from an
excited level to its lower levels was given by the relation[32].

b

j

Jị ẳA


j

J;

j

0_J0
AT

j

Jị

(13)

The radiative properties were calculated and are listed in

Table 3. The variation of

U

2 values with Dy3ỵ concentration
in-dicates that it was more sensitive to the ligand environment. The

U

2
parameter value is attributed to the covalency and structural
changes in the vicinity of the Dy3ỵion exhibiting a short range
effect, whereas the

U

4parameter was dependent on the viscosity
and dielectric constant of the host causing a long range effect. The
calculated branching ratio was found to be in the range 0.99 0.50,
which endorses that the prepared powder can emit intense laser
radiation effectively and be suitable for white color displaying
devices.

4. Conclusion

In summary, the BaTiO3:Dy3ỵ(1e5 mol %) powders were
syn-thesized using the ultrasound assisted sonochemical route. The
PXRD profiles indicated that the prepared samples were well
crystalline in nature and a single cubic phase. From DRS, the optical
energy band gaps were estimated to be ~3.20e3.29 eV. LFPs were
visualized using an optimized powder undoubtedly with high
contrast, selectivity and low background interference on various
porous and non-porous surfaces. The PL emission spectra exhibited
intense peaks at ~480, 574, and 637 nm, which were attributed to
4_F

9/2/6H15/2,4F9/2/6H13/2and4F9/2/6H11/2respectively. The
photometric studies (CIE and CCT) suggest that the phosphor is
highly useful for the fabrication of near ultraviolet white light
emitting diodes (NUV-WLEDs).

Acknowledgements

The author Dr. H Nagabhushana thanks VGST, Karnataka for the
sanction of this Project.

References

[1] H.J. Amith Yadav, B. Eraiah, H. Nagabhushana, G.P. Darshan, B. Daruka Prasad,
S.C. Sharma, H.B. Premkumar, K.S. Anantharaju, G.R. Vijayakumar, Facile
ul-trasound route to prepare micro/nano superstructures for multifunctional
applications, ACS Sustain. Chem. Eng. (2017), />acssuschemeng.6b01693.

[2] J. Li, X. Zhu, M. Xue, W. Feng, R. Ma, F. Li, Nd3ỵ-Sensitized upconversion
nanostructure as a dual-channel emitting optical probe for near
infrared-to-near infraredfingerprint imaging, Inorg. Chem. 55 (2016) 10278e10283.

orthosilicate phosphors synthesized by bio-template assisted ultrasound for
solid state lightning and display applications, Ultrason. Sonochem. 34 (2017)
803e820.

[10] K.S. Suslick, The chemical effect of ultrasound, Sci. Am. 260 (1989) 80e86.
[11] A.A. Khort, K.B. Podbolotov, Preparation of BaTiO3nanopowders by the

so-lution combustion method, Ceram. Int. 42 (2016) 15343e15348.

[12] Y. Tsuchihashi, Studies on personal identification by means of lip prints,
Forensic Sci. 3 (1974) 233e248.

[13] M. Xu, Y. Lu, Y. Liu, S. Shi, T. Qian, D. Lu, Sonochemical synthesis of monosized
spherical BaTiO3particles, Powder Tech. 161 (2006) 185e189.

[14] R.B. Basavaraj, H. Nagabhushana, B. Daruka Prasad, S.C. Sharma,
S.C. Prashantha, B.M. Nagabhushana, A single host white light emitting
Zn2SiO4:Re3ỵ(Eu, Dy, Sm) phosphor for LED applications, Optik 126 (2015)

1745e1756.

[15] R.B. Basavaraj, H. Nagabhushana, B. Daruka Prasad, S.C. Sharma,
K.N. Venkatachalaiah, Mimosa pudica mediated praseodymium substituted
calcium silicate nanostructures for white LED application, J. Alloys Compd.
690 (2017) 730e740.

[16] Jing Feng, Liang Zhou, Shu-Yan Song, Zhe-Feng Li, Wei-Qiang Fan, Li-Ning Sun,
Ying-Ning Yu, Hong-Jie Zhang, A study on the near-infrared
luminescent-properties of xerogel materials doped with dysprosium complexes, Dalton
Trans. 39 (2009) 6593e6598.

[17] A.E. Morales, E.S. Mora, U. Pal, Use of diffuse reflectance spectroscopy for
optical characterization of un-supported nanostructures, Rev. Mex. Fis. 53
(2007) 18e22.

[18] R.E. Cohen, H. Krakauer, Electronic structure studies of the differences in
ferroelectric behavior of BaTiO3 and PbTiO3, Ferroelectrics 136 (1992)

65e83.

[19] G. Ramakrishna, Ramachandra Naik, H. Nagabhushana, R.B. Basavaraj,
S.C. Prashantha, S.C. Sharma, K.S. Anantharaju, White light emission and
en-ergy transfer (Dy3ỵ/ Eu3ỵ_{) in combustion synthesized YSO: Dy}3ỵ_{, Eu}3ỵ

nanophosphors, Optik 127 (2016) 2939e2945.

[20] Qingbo Liu, Yufeng Liu, Zhiping Yang, Yue Han, Xu Li, Guangsheng Fu, Multi
wavelength excited white-emitting phosphor Dy3ỵ-activated Ba3Bi(PO4)3,

J. Alloys Compd. 515 (2012) 16e19.

[21] Ramachandra Naik, S.C. Prashantha, H. Nagabhushana, S.C. Sharma,
H.P. Nagaswarupa, K.S. Anantharaju, D.M. Jnaneshwara, K.M. Girish, Tunable
white light emissive Mg2SiO4:Dy3ỵnanophosphor: its photoluminescence,

JuddeOfelt and photocatalytic studies, Dyes Pigm. 127 (2016) 25e36.

[22] J.B. Prasanna Kumar, G. Ramgopal, Y.S. Vidya, K.S. Anantharaju, B. Daruka

Prasad, S.C. Sharma, S.C. Prashantha, H.P. Nagaswarupa, D. Kavyashree,
H. Nagabhushana, Green synthesis of Y2O3:Dy3ỵ nanophosphor with

enhanced photocatalytic activity, Spectrochim. Acta Part A 149 (2015)
687e697.

[23] X.Y. Sun, L.W. Lin, W.F. Wang, J.C. Zhang, White-light emission from Li2Sr13x/
2Dyx SiO4phosphors, Appl. Phys. A 104 (2011) 83e88.

[24] D.V. Sunitha, H. Nagabhushana, S.C. Sharma, B.M. Nagabhushana, B. Daruka
Prasad, R.P.S. Chakradhar, Study on low temperature solution combustion
synthesized Sr2SiO4:Dy3ỵnano phosphor for white LED, Spectrochim. Acta

Part A 127 (2014) 381e387.

[25] H.B. Premkumar, D.V. Sunitha, H. Nagabhushana, S.C. Sharma, B. Daruka
Prasad, B.M. Nagabhushana, C. Shivakumara, J.L. Rao, N.O. Gopal,
K.R. Prabhakara, Shyue-Chu Ke, R.P.S. Chakradhar, Synthesis, structural and
thermoluminescence properties of YAlO3:Dy3ỵ nanophosphors, J. Alloys

Compd. 591 (2014) 337e345.

[26] D.L. Dexter, J.H. Schulman, Theory of concentration quenching in inorganic
phosphors, J. Chem. Phys. 22 (1954) 1063.

[27] C.S. McCamy, Correlated color temperature as an explicit function of
chro-maticity coordinates color, Res. Appl. 17 (1992) 142e144.

</div>
<span class='text_page_counter'>(12)</span><div class='page_container' data-page=12>

[29] B.R. Judd, Optical absorption intensities of rare-earth ions, Phys. Rev. 127
(1962) 750.

[30] G.P. Darshan, H.B. Premkumar, H. Nagabhushana, S.C. Sharma, S.C. Prashantha,
B. Daruka Prasad, Effective fingerprint recognition technique using doped
yttrium aluminate nano phosphor material, J. Colloid Interface Sci. 464 (2016)
206e218.

[31] G.P. Darshan, H.B. Premkumar, H. Nagabhushana, S.C. Sharma, S.C. Prashantha,
H.P. Nagaswarupa, B. Daruka Prasad, Blue light emitting ceramic

nano-pigments of Tm3ỵdoped YAlO3: applications in latentnger print,

anti-counterfeiting and porcelain stoneware, Dyes Pigm. 131 (2016) 268e281.
[32] T. Manohar, S.C. Prashantha, Ramachandra Naik, H. Nagabhushana,

H.P. Nagaswarupa, K.S. Anantharaju, K.M. Girish, H.B. Premkumar, A benign
approach for tailoring the photometric properties and Judd-Ofelt analysis of
LaAlO3:Sm3ỵnanophosphors for thermal sensor and WLED applications, Sens.

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