International Journal of Advanced Engineering Research and Technology (IJAERT), ISSN: 23488190 ICRTIET-2014 Conference Proceeding, 30

th -31

st August 2014

59

Divya Jyoti College of Engineering & Technology, Modinagar, Ghaziabad (U.P.), India

Gd2O3 Nanoparticles: Effect on Photoluminescence Studies

Shwet Kumar Rinwa

1, Sahil Chhabra

2

1Department of Chemical Engineering, IIT-BHU, Varanasi, Uttar-Pradesh, India

2Department of Chemistry, IIT-KGP, Kharagpur, West Bengal, India

1. INTRODUCTION

Nanotechnology is almost a household word now-a-

days, or at least some word with Nano in it, such as

nanoscale, nanoparticle, nanophase, nanocrystal, or

nanomachine. Nanoparticles are the simplest form of

structures with sizes in the range of 1-100 nm. These

include fullerens, metalclusters and large molecules

such as proteins.

Rare-earth doped semiconductors are used as

luminescence materials. Usually, efcient energy

transfer from semiconductor host to rare-earth ions

gives the enhancement in luminescence intensity.

Semiconductor hosts such as SnO2, TiO2, and ZnO are

usually used.13 However, such host materials have

limitations because of the large ionic radii mismatch

between metal ion in semiconductor and rare-earth ion

dopant e.g., Sn4+ in SnO2 has r=0.7 and Eu3+ has

r=0.9 .4 In general, rare-earth ions occupy the

surface of semiconductor particles and do not occupy

the lattice of semiconductor. Due to this, only energy

transfer from semiconductor to rare-earth ion takes

place through surface; thereby it could not improve the

luminescence intensity of rare-earth ion. In addition to

this, concentration-quenching effect occurs even for a

few percentages of rare-earth ions. Such limitations

can be avoided if host and rare-earth ions form solid

solutions. Solid solution is possible only when metal

ions of host and rare-earth ions have similar ionic radii.

In this aspect, Y2O3 , Lu2O3, and Gd2O3 are potential

host materials, which can make solid solutions with

rare earth ions even at large concentration with or

without change in crystal structure.

2. RESULT AND DISCUSSION

PHOTOLUMINESCENCE STUDIES

Photoluminescence (PL) spectroscopy is a contactless,

nondestructive method to probe the electronic structure

of materials. The phenomenon of re-emission of

previously absorbed radiation is termed as

luminescence. In photoluminescence, the

molecules/atoms raise to higher energy excited state by

absorption of photons of electromagnetic radiation,

and then return to the ground state with emission of

light. Thus, photoluminescence (PL) spectroscopy is

concerned with the monitoring of light emitted from

molecules/atoms. This technique involves recording of

the excitation and emission spectra of the sample at

particular wavelengths.

It is known from the literature that cubic lattice of

Gd2O3 absorbs at 235nm, while Gd3+

absorbs at 277

and 277 nm due to transition from 8S7/2 to

6I7/2 and

7F0

to 5L6 electronic levels respectively. The principal

emission band occurs at 611nm for the cubic phase.

The transition is due to electric dipole allowed

transition and is strongly affected by the surrounding

environment. Eu3+

also emits at 591nm due to the

magnetic dipole allowed transition which is largely

unaffected by the surrounding environment. The

intensity ratio of the electric dipole allowed transition 5D0

7F2 to that of the magnetic dipole allowed

transition 5D0

7F1 defines the asymmetric ratio and

hence the electronic environment around Eu3+

. We

have produced Eu3+

doped Gd2O3 nanoparticles using

fuel deficient glycine-nitrate-combustion method. The

cubic phase of Gd2O3 is usually stabilized under such

condition. The structure is retained even after doping it

with 4% Eu3+

, as evident from the PL studies, which

indicates of the formation of a single phasic solid

solution of the two (see Fig. 10 (a).

International Journal of Advanced Engineering Research and Technology (IJAERT), ISSN: 23488190 ICRTIET-2014 Conference Proceeding, 30

th -31

st August 2014

60

Divya Jyoti College of Engineering & Technology, Modinagar, Ghaziabad (U.P.), India

Fig. 1: Emission spectra of (a) Gd2-xEuxO3 (x= 0.01,

0.04, 0.06, and 0.08) upon excitation at 275nm, (b) A

typical excitation spectra for emission at ~611nm.

The corresponding excitation profile is typically shown

in the inset (b). The intensity of the emission band at

~610nm, upon excitation at ~275nm, increased linearly

with the increasing concentration of Eu in the sample

(see Fig. 11) say up to 3% but then decreased

indicating concentration induced quenching of

luminescence at higher concentration of Eu.

Fig. 2: Variation of emission intensity with Eu

concentration

3. CONCLUSIONS

1. Phase analysis shows that cubic Gd2O3 was

formed under this condition.

2. The doped samples exhibited a strong emission

band at ~610nm when excited at ~275nm. The

luminescence intensity increased almost linearly

with increasing Eu3+

concentration up to 3% but

then decreased indicating quenching effect at

higher concentration of Eu3+

.

REFERENCES

1. http://cnx.org/content/m38357/latest/?colle

ction=col10699/latest

2. ww.nrel.gov/pv/measurements/photolumin

escence_spectroscopy.html