PbTe nanostructures were prepared by a hydrothermal method on presence of different surfactant. Results show that in constant condition by changing the capping agent the morphology of as-obtained PbTe were revolutionize PbTe nanostructures show a strong photoluminescence peak at 402 nm at room temperature, also optical absorption spectrum of PbTe nanostructures exhibit an extreme blue-shift, which is attributed to the quantum confinement of charge carriers in the nanostructures. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, photoluminescence spectroscopy, and Fourier transformed infrared spectroscopy were used to characterize the as-produced PbTe nanostructures

Gholamrezaei, S.

Salavati-Niasari, M.

English

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 3 No 2, 02NNPT01(3pp) (2014) 
 
 
2304-1862/2014/3(2)02NNPT01(3) 02NNPT01-1  2014 Sumy State University 
Investigation of Presence Different Surfactant on Morphologies of PbTe Nanostructures 
 
S. Gholamrezaei, M. Salavati-Niasari* 
 
Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P. O. Box. 87317–51167, I.R. Iran. 
 
(Received 05 January 2014; published online 29 August 2014) 
 
PbTe nanostructures were prepared by a hydrothermal method on presence of different surfactant. Re-
sults show that in constant condition by changing the capping agent the morphology of as-obtained PbTe 
were revolutionize PbTe nanostructures show a strong photoluminescence peak at 402 nm at room tem-
perature, also optical absorption spectrum of PbTe nanostructures exhibit an extreme blue-shift, which is 
attributed to the quantum confinement of charge carriers in the nanostructures. X-ray diffraction, scan-
ning electron microscopy, transmission electron microscopy, photoluminescence spectroscopy, and Fourier 
transformed infrared spectroscopy were used to characterize the as-produced PbTe nanostructures. 
 
Keywords: Nanostructures, Hydrothermal method, PbTe. 
 
 PACS numbers: 68.37.Hk, 75.75.Cd 
 
 
                                                 
* salavati@kashanu.ac.ir 
1. INTRODUCTION 
 
Thermoelectric (TE) technology is one of the energy 
exchange technologies that substitute heat and 
electricity, theoretical predictions and experimental 
results demonstrate that decreasing the size of the 
building blocks of TE materials is an efficient technique 
to improve TE properties [1-4]. PbTe with a large Bohr 
excitation radius (46 nm) in contrast with other 
semiconductors can exhibit excellent electrical transport 
properties. [5]. Because of these properties, it is an 
perfect applicant for investigating novel properties and 
behavior under quantum confinement conditions [6]. 
Therefore, adapting the size and morphology of PbTe is 
very important, to make novel behavior and properties. 
The fabrication different morphology of PbTe in a simple 
method have attracted much interest. Various structures 
of PbTe have been synthesized by different methods 
including magnetron sputtering, laser fragmentation 
liquid medium, chemical bath, solvothermal, microwave 
and sonochemical method [7-10]. Perceptibly 
hydrothermal is a only one of its kind method for prepa-
ration nanostructures with controllable morphologies. 
Principal morphology in other methods like sol-gel, 
microwave, sonochemical and etc is nanoparticle. 
Hydrothermal method because of some conditions; e.g., 
high temperature and pressure provides preferred 
orientation morphology [11]. In this paper different 
morphologies of PbTe such as nanoparticles, nanorods, 
nanocubes and nanosheets of PbTe were synthesized 
using of Pb(NO3)2, TeCl4 and N2H4.H2O in presence of 
different surfactants. 
 
2. EXPRIMENTAL 
 
2.1 Materials and Methods 
 
All of the material such as Pb(NO3)2, TeCl4, N2H4 
H2O were purchased from Merck Company. All of the 
chemicals were used as received without additional 
purification. XRD patterns were recorded via a Philips, 
X-ray diffractometer by Ni-filtered Cu Kα radiation. 
FT-IR spectra were recorded on Galaxy series 
FTIR5000 spectrophotometer. Room temperature pho-
toluminescence was deliberate by a Perkin Elmer fluo-
rescence instrument. SEM images were gained using a 
LEO instrument model 1455VP. Prior to taking images, 
the samples were coated by a very thin layer of Pt to 
make the sample surface conductor and avert charge 
accretion, and obtaining an improved contrast.  
 
2.2 Synthesis Method 
 
In a typical synthesis, an aqueous solution of 
Pb(NO3)2, at presence of different surfactants, such as 
cetyltrimethyl ammonium bromide (CTAB), sodium 
dodecyl sulfonate (SDS), polyethylene glycol (PEG), and 
polyvinyl pyrrolidone (PVP) was mixed with TeCl4. 
After taht  N2H4 H2O was added drop-wise. Then, the 
reactants were put into a 250 ml capacity Teflon-lined 
autoclave. The autoclave was maintained at 160 °C for 
6 h and then cooled naturally to room temperature. The 
product was centrifuged, washed with alcohol and 
distilled water for several times, and dried in oven at 
60 °C for 8 h. 
 
3. RESULT AND DISCUSSION 
 
One of the XRD pattern of these materials are 
shown in Fig. 1, as an example, which reveals the 
nanocrystalline nature of the as-prepared products 
because of the widening of the diffraction peaks. In 
presence of all of the surfactant PbTe were produced. 
These patterns are also indexed as a pure cubic phase 
(space group: Fm-3m) that have appropriate accordance 
with the literature value (JCPDS No. 78-1905). The 
crystallite size measurements were calculated by 
Scherrer equation and the estimated crystallite size of 
sample in presence of CTAB, SDS, PEG600, PVP25000 
are 51, 25, 38 and 21 nm respectively. 
SEM images of as product PbTe in presence of 
CTAB are shown in Fig. 2a, the morphology of products 
is nanorods, Fig. 2b shows SEM images of as 
synthesized PbTe nanostructures in presence of SDS. 
 S. GHOLAMREZAEI, M. SALAVATI-NIASARI PROC. NAP 3, 02NNPT01 (2014) 
 
 
02NNPT01-2 
 
 
Fig. 1 – XRD pattern of PbTe 
 
 
 
Fig. 2 – SEM images of PbTe in presence of (a) CTAB (b) SDS 
(c) PVP25000 
 
The morphology of product is nanocube. Fig. 2c 
illustrate SEM images of PbTe that synthesized in the 
presence of polymeric surfactants. In presence of PVP 
nanoparticles are synthesized (Fig. 2c). there for by  
 
 
Fig. 3 – Probably mechanism for preparation of PbTe 
 
 
 
Fig. 4 – TEM and SAED of PbTe nanoparticles 
 
 
 
 INVESTIGATION OF PRESENCE DIFFERENT SURFACTANT… PROC. NAP 3, 02NNPT01 (2014) 
 
 
02NNPT01-3 
changing of capping agent in constant other conditions 
the morphology of product were deformed. 
Fig. 3 demonstrate probably orientation of surfac-
tant for preparation of suitable micelles that formed 
the PbTe nanostructures schematically. 
Fig. 4 show TEM image of PbTe nanoparticles in 
presence of PVP with average diameter of 5 nm. The 
noticeable grain boundaries among a little amorphous 
region in this figure prove the poly-crystallinity. 
Selected area electron diffraction of PbTe nanoparticles 
also is shown in Fig. 6g which supports poly 
crystallinity of the product. Diffused halo ring and 
several sharp spots in the SAED pattern indicate that 
the sample is composed of an amorphous structure with 
many crystallines embedded within. The halo ring were 
originated from (511) and (331) crystalline plates. 
The optical absorption spectrum of PbTe 
nanostructures is shown in Fig. 5. It illustrates tree 
excitonic absorption peaks at 234, 335 and 390 nm, and 
the value of band gap energy is ~ 2.9 eV [12]. These 
values for optical absorption exhibit an extreme blue-
shift in comparison with bulk PbTe. (Bulk PbTe has a 
band gap in 3859 nm (0.31 eV)), which is caused to the 
quantum confinement of charge carriers in the 
nanostructures [13]. 
 
 
 
Fig. 5 – Optical absorption spectrum of PbTe 
 
Fig. 6 shown photoluminescence (PL) measurement 
of PbTe with excitation wavelength 250 nm at room 
temperature. The PL spectrum shows a strong peak at 
400 nm that can be related to a high level transition in 
PbTe semiconductor crystallites. Therefore this reports, 
the kind of band edge luminescence results from the 
recombination of excitons and / or shallowly trapped 
electron-hole pairs [12]. An extra weak peak is 
recognizable at 664.5 nm that appears to be related to 
structural defects or light scattering of solvent. The 
band gap energy for these nanostructures were 
calculated to be 3.0 eV that larger than the band gap 
energy of bulk PbTe structures and has appropriate 
conformity to the value of band gap appriseded based 
on UV-vis. 
 
 
 
Fig. 6 – PL spectrum of the PbTe sample 
 
4. CONCLUSIONS 
 
PbTe nanostructures were prepared via a simple 
hydrothermal method. Nanostructures were 
characterized using XRD, SEM, PL and UV-vis 
techniques. The effects of presence various surfactants 
such as cationic, anionic, and polymeric surfactant on 
the morphology and purity of the products were 
investigated. According to these results by changing 
the capping agent achieved different morphologies. It 
was found that at room temperature the as-obtained 
PbTe nanostructures show a strong PL peak at 400 nm. 
 
ACKNOWLEDGMENT 
 
Authors are grateful to the council of University of 
Kashan for supporting this work. 
 
 
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Investigation of presence different surfactant on morphologies of PbTe nanostructures

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Investigation of presence different surfactant on morphologies of PbTe nanostructures

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