Synthesis and spectral studies on Pb(II) dithiocarbamate complexes containing benzyl and furfuryl groups and their use as precursors for PbS nanoparticles

Article abstract of DOI:10.1016/j.saa.2012.06.052

Nine lead bis(dithiocarbamate) complexes based on benzyl and furfuryl groups have been prepared. The complexes were characterized using IR and NMR spectroscopy. All the complexes showed the expected signals in ¹H and ¹³C NMR spectra associated with the dithiocarbamate ligands. IR and ¹³C NMR spectral studies indicate that the S₂CN double bond character increases with increase in length of alkyl chain bonded to nitrogen atom. Bis(N-benzyl-N-(2-phenylethyl)dithiocarbamato-S,S′)lead(II) (3) and bis(N-furfuryl-N-(2-phenylethyl)dithiocarbamato-S,S′)lead(II) (4) have been used as single source precursors for the synthesis of ethylenediamine capped PbS nanoparticles. Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), FTIR, UV-vis and fluorescence spectroscopy have been used to characterize the as-prepared lead sulfide nanoparticles. The PXRD measurements suggest that PbS nanoparticles are single phase with face-centered-cubic structure.

Full text of DOI:10.1016/j.saa.2012.06.052

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 575–581
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis and spectral studies on Pb(II) dithiocarbamate complexes containing
benzyl and furfuryl groups and their use as precursors for PbS nanoparticles
⇑
Ethiraj Sathiyaraj, Subbiah Thirumaran
Department of Chemistry, Annamalai University, Annamalinagar, 608 002 Tamil Nadu, India
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
"
"
"
"
Lead-dithiocarbamate complexes
based on benzyl and furfuryl groups
were prepared.
En capped PbS nanoparticles were
prepared within 2 min from lead
dithiocarbamate.
PbS particles were characterized by
XRD, SEM, EDAX, UV–vis,
fluorescence and FTIR.
PbS nanoparticles are single phase
with face centered cubic structure.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 April 2012
Received in revised form 14 June 2012
Accepted 25 June 2012
Available online 10 July 2012
Nine lead bis(dithiocarbamate) complexes based on benzyl and furfuryl groups have been prepared. The
complexes were characterized using IR and NMR spectroscopy. All the complexes showed the expected
signals in 1H and 13C NMR spectra associated with the dithiocarbamate ligands. IR and 13C NMR spectral
studies indicate that the S2C'N double bond character increases with increase in length of alkyl chain
bonded to nitrogen atom. Bis(N-benzyl-N-(2-phenylethyl)dithiocarbamato-S,S0)lead(II) (3) and bis(N-fur-
furyl-N-(2-phenylethyl)dithiocarbamato-S,S0)lead(II) (4) have been used as single source precursors for
the synthesis of ethylenediamine capped PbS nanoparticles. Powder X-ray diffraction (PXRD), scanning
electron microscopy (SEM), FTIR, UV–vis and fluorescence spectroscopy have been used to characterize
the as-prepared lead sulfide nanoparticles. The PXRD measurements suggest that PbS nanoparticles are
single phase with face-centered-cubic structure.
Keywords:
Dithiocarbamate
Lead(II)
Spectral
Lead sulfide nanoparticles
Single source precursor
Ó 2012 Elsevier B.V. All rights reserved.
Introduction
ticles [6–8]. The standard method for the determination of lead in
water and food analysis when using atomic absorption spectrome-
Dithiocarbamate complexes of various metal ions are used in
analytical determinations, organic synthesis, medicine, as fungi-
cides, herbicides, lubricants and NO-trapping agents [1–4]. Dithio-
carbamates have also been used as structural motifs in the
supramolecular chemistry due to their robust complexing ability
[5]. Due to their high affinity of a dithiocarbamate ion for metal
ions, these ligands can be used to stabilize silver and gold nanopar-
try is to extract the lead by chelating it with pyrrolidinedithiocar-
bamate [9]. Metal dithiocarbamate complexes have been shown to
be useful precursors for the formation of metal sulfide nanoparti-
cles [10–12]. Lead sulfide is an important IV–VI group semiconduc-
tor, which has attracted considerable attention owing to its special
small direct band gap (0.41 eV) and large excitonic Bohr radius of
18 nm [13,14]. PbS is an important functional material and has
been used in several applications e.g., an IR detector [15] and
Pb2+ ion-selective sensors. For these applications, PbS with differ-
ent particle size is required, particle diameters should vary from
⇑
Corresponding author. Tel.: +91 9842897597.
E-mail address: sthirumaran@yahoo.com (S. Thirumaran).
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.06.052

576
E. Sathiyaraj, S. Thirumaran / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 575–581
a few micrometer for infrared detector applications to several
nanometers for quantum dots. To synthesize metal sulfide nano-
crystals, various methods have been employed, including solvo-
Elemental analysis were performed by a Perkin Elmer series(II)
CHN analyser. FTIR spectra were recorded on a Thermo Nicolet
AVATAR 330 FT-IR spectrophotometer (range 400–4000 cmꢀ1) as
KBr pellets. The NMR spectra were recorded on either Bruker
400 MHz spectrometer or Bruker AVII 500 MHz spectrometer.
UV–vis and fluorescence spectra were recorded on a Perkin Elmer
Lambda 35 UV/vis spectrometer (range 220–500 nm) and Perkin
Elmer L555 spectrofluorimeter, respectively. A JEOL 6360 scanning
electron microscopy fitted with an energy dispersive X-ray spec-
trometer (EDAX) was used to characterize the morphologies and
elemental analysis of the samples. The structure of the prepared
PbS was characterized by SEIFERT JHOD DYE FLEX 2002, diffrac-
thermal route [16,17], the direct reaction route [18], the
c-
irradiation route [19] and so on [20,21]. In this work, we have used
complexes 3 and 4 as a single source precursor and ethylenedia-
mine as a solvent for the preparation of en capped PbS nanoparti-
cles via solvothermal method. This is a simple and versatile
method for the synthesis of PbS nanoparticles in a single pot, low
temperature process.
As a part of our investigation of dithiocarbamate complexes
[22,23], this paper describes the synthesis and spectral studies on
simple homoleptic dithiocarbamate complexes based on benzyl
and furfuryl groups. The solvothermal conversion of the complexes
3 and 4 to PbS nanoparticles and their characterization are also
presented.
tometer with CuK radiation (k = 1.54178 Å).
a
Preparation of complexes
Preparation of amine A–G
Experimental
Benzylamine (0.5 mL, 4.6 mmol) and furfuraldehyde (0.4 mL,
5.1 mmol) were dissolved in methanol (10 mL) and the solution
was stirred for 2 h at room temperature. The solvent was removed
by evaporation. The resulting yellow oil was dissolved in metha-
nol-dichloromethane solvent mixture (1:1, 20 mL) and sodium
borohydride (0.5 g, 13.8 mmol) was added slowly at 5 °C. The mix-
Materials and techniques
All reagents and solvents were commercially available high
grade materials (Merck/Sigma/Spectrochem) and used as received.
Scheme 1. Preparation of complex 1.
Chart 1. Structures of the amines A–I.

E. Sathiyaraj, S. Thirumaran / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 575–581
577
ture was stirred at room temperature for 12 h. After evaporation of
the solvent, the resulting viscous liquid was washed with water
and dichloromethane was added in order to extract the product.
Evaporation of the organic layer gave N-benzyl-N-furfurylamine
(A) as a yellow oil.
The secondary amines C, E and G were prepared by condensation
of benzaldehyde with 2-phenylethylamine, 2-thiophenylethyl-
amine and butylamine respectively to form imine followed by
reduction. The same procedure was used as above to prepare B, D
and F except that furfuraldehyde is used instead of benzaldehyde.
Chart 2. Proposed structures of the complexes 1–9.
Table 1
Elemental analysis and important infrared spectral bands (cmꢀ1).
Compound
Formula
Found (Calcd.) %
C
mC–N
mC–S
H
N
1
2
3
4
5
6
7
8
9
C
C
C
C
C
C
C
C
C
24H24N2O2S4Pb
22H20N2O4S4Pb
32H32N2S4Pb
28H28N2O2S4Pb
28H28N2S5Pb
24H24N2O2S5Pb
24H32N2S4Pb
44H52N4S8Pb2
36H44N4O4S8Pb2
40.16(40.72)
37.02(37.12)
49.10(49.27)
44.12(44.25)
44.09(44.25)
38.74(38.95)
42.01(42.14)
41.01(41.17)
34.14(34.11)
3.35(3.42)
2.77(2.83)
4.04(4.13)
3.74(3.71)
3.60(3.71)
3.19(3.27)
4.59(4.72)
2.18(2.20)
3.43(3.50)
3.87(3.96)
3.82(3.94)
3.48(3.59)
3.60(3.69)
3.59(3.69)
3.71(3.79)
4.01(4.10)
4.38(4.36)
4.34(4.42)
1453
1455
1464
1467
1463
1464
1471
1471
1471
1013
1012
1020
1012
960
954
966
1023
1015

578
E. Sathiyaraj, S. Thirumaran / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 575–581
Preparation of complexes 1–7
reduction. The complexes 1–9 were prepared from a secondary
amine (A–I) in ethanol by the reaction with carbondisulfide and
Amine (A) (0.75 g, 4 mmol) and carbon disulfide (0.3 mL,
4 mmol) were dissolved in ethanol (20 mL) and stirred for
30 min. Pb(NO3)2 (0.70 g, 2 mmol) was dissolved in 100 mL of
water and added to the solution. A pale yellow powder precipitated
that was filtered and dried.
Table 3
13C NMR spectral data of [Pb(dtc)2] complexes.
Compound Chemical shifts in ppm (multiplicity, assignments)
Complexes 2–7 were prepared similarly using respective
amines B–G.
1
47.0 (CH2–C6H5), 54.7 (CH2 furfuryl), 110.3, 110.5, 142.6, 148.9
(C-3, C-4, C-5 and C-2 of furyl ring), 127.9128.1, 128.8, 135.2
(phenyl ring carbons), 206.4 (NCS2)
2
3
47.6 (CH2 furfuryl), 110.3, 110.6, 142.8, 148.9 (C-3, C-4, C-5 and
C-2 of furyl ring), 206.3 (NCS2)
33.2 (N–CH2–CH2–C6H5), 54.0 (N–CH2–CH2–C6H5), 56.3 (CH2–
C6H5), 126.7, 128.0, 128.7, 128.8, 129.0, 135.5, 138.5 (aromatic
carbons), 205.3 (NCS2)
33.1 (N–CH2–CH2–C6H5), 49.2 (N–CH2–CH2–C6H5), 54.3 (CH2
furfuryl), 110.4, 110.7, 142.8, 148.9 (C-3, C-4, C-5 and C-2 of
furyl ring), 126.7, 128.8, 129.0, 138.5 (phenyl ring carbons),
205.1 (NCS2)
27.3 (NCH2–CH2–C4H3S), 53.7 (NCH2–CH2–C4H3S), 56.4 (NCH2–
C6H5), 124.1, 125.7, 127.1, 128.0, 128.8, 135.3, 140.4 (aromatic
carbons), 205.6 (NCS2)
27.2 (NCH2–CH2–C4H3S), 49.2 (NCH2–CH2–C4H3S), 54.1 (NCH2–
C4H3O), 110.3, 110.7, 124.1, 125.7, 127.1, 140.4, 142.7, 148.7
(aromatic carbons), 205.4 (NCS2)
13.8 (NCH2–CH2–CH2–CH3), 20.2 (NCH2–CH2–CH2–CH3), 28.7
(NCH2– CH2–CH2–CH3), 52.1 (NCH2–CH2–CH2–CH3), 55.4
(NCH2–C6H5), 127.7, 128.0, 128.7, 135.6 (phenyl ring carbons),
204.7 (NCS2)
26.1 (N–CH2–CH2–CH2–), 26.4 (N–CH2–CH2–), 51.9 (N–CH2–
CH2–), 55.3 (CH2–C6H5), 127.7, 128.0, 128.8, 129.1, 130.2, 137.1
(aromatic carbons), 206.7 (NCS2)
26.2 (N–CH2–CH2–CH2–), 26.4 (N–CH2–CH2–), 48.3 (N–CH2–
CH2–), 52.2 (CH2 furfuryl), 110.1, 111.1, 143.3, 149.8 (C-3, C-4,
C-5 and C-2 of furyl ring), 205.3 (NCS2)
Preparation of complexes 8 and 9
N,N0-dibenzylhexamethylene-1,6-diamine(H) was obtained
according to the procedure described previously [24]. N,N0-Diben-
zylhexamethylene-1,6-diamine (0.5 g, 1.68 mmol), triethylamine
(0.5 mL, 3.3 mmol) and carbon disulfide (5 mL) were dissolved in
methanol (50 mL) and stirred for 2 h. Pb(NO3)2 (0.55 g, 1.68 mmol)
was dissolved in 20 mL of water and added to the solution. A pale
yellow powder precipitated that was filtered and dried.
Amine (I) and complex 9 were prepared similarly.
4
5
6
7
Preparation of ethylenediamine capped PbS
0.5 g of 3 was dissolved in 15 mL of ethylenediamine in a flask
and then heated to reflux (117 °C) and maintained at this temper-
ature for 2 min. The black precipitate obtained was filtered off and
washed with methanol.
Similar procedure was adopted for the preparation of PbS nano-
particles from 4.
8
9
Results and discussion
Furfuraldehyde was condensed with benzylamine to form the
imine. Sodium borohydride reduction of the imine in methanol-
dichloromethane afforded the N-benzyl-N-furfurylamine (A) as
yellow oil (Scheme 1). The secondary amines B–I were prepared
similarly by condensation of the aldehyde (benzaldehyde and fur-
furaldehyde) with appropriate primary amines (furfurylamine, 2-
phenylethylamine, 2-thiophenylethylamine, butylamine and hex-
amethylenediamine) to give the corresponding imine followed by
Table 2
1H NMR spectral data of [Pb(dtc)2] complexes.
Compound Chemical shifts in ppm (multiplicity, assignments)
1
2
3
4.95 (4H, s, N–CH2–C6H5), 5.13 (4H, s, CH2 furfuryl), 6.33–7.37
(aromatic protons)
5.04 (8H, s, CH2 furfuryl), 6.34 (4H, t, J = 3.2 Hz, H–4 furyl), 6.39
(4H, d, J = 3.2 Hz, H–3 furyl), 7.38 (4H, d, J = 8 Hz, H–5 furyl)
3.01 (4H, t, J = 8 Hz, N–CH2–CH2–C6H5), 3.86 (4H, t, J = 8 Hz, N–
CH2–CH2–C6H5), 4.96 (4H, s, N–CH2–C6H5), 7.13–7.30 (aromatic
protons)
4
5
6
7
2.99 (4H, t, J = 8 Hz, N–CH2–CH2–C6H5), 3.96 (4H, t, J = 8 Hz, N–
CH2–CH2–C6H5), 4.94 (4H, s, CH2 furfuryl), 6.34-7.38 (aromatic
protons)
5.01 (4H, s, NCH2–C6H5), 3.97 (4H, t, J = 7.5 Hz, NCH2–CH2–
C4H3S), 3.31 (4H, t, J = 8 Hz, NCH2–CH2–C4H3S), 6.85–7.38
(aromatic protons)
4.97 (4H, s, NCH2–C4H3O), 4.04 (4H, t, J = 7.5 Hz, NCH2–CH2–
C4H3S), 3.26 (4H, t, J = 8 Hz, NCH2–CH2–C4H3S), 6.38-7.42
(aromatic protons)
5.11 (4H, s, NCH2–C6H5), 3.71 (4H, t, J = 8 Hz, NCH2–CH2–CH2–
CH3), 1.74-1.78 (4H, m, NCH2–CH2–CH2–CH3), 1.31–1.36 (4H, m,
NCH2–CH2–CH2–CH3), 0.93 (6H, t, J = 7.5 Hz, NCH2–CH2–CH2–
CH3), 7.28–7.38 (aromatic protons)
8
9
1.16 (8H, br, N–CH2–CH2–CH2–), 1.60 (8H, br, N–CH2–CH2–),
3.62 (8H, br, N–CH2–CH2–), 5.13 (8H, s, CH2–C6H5), 7.20–7.47
(aromatic protons)
1.21 (8H, br, N–CH2–CH2–CH2–), 1.61 (8H, br, N–CH2–CH2–),
3.69 (8H, br, N–CH2–CH2–), 4.99 (8H, s, CH2 furfuryl), 6.36 [8H,
br, H–4 and H–3 (furyl)], 7.46 [4H, br, H–5 (furyl)]
Fig. 1. XRD patterns of (a) PbS1 and (b) PbS2.

E. Sathiyaraj, S. Thirumaran / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 575–581
579
Pb(NO3)2 in water. Nine amines utilized in this study are shown in
1H NMR spectral studies
Chart 1 and the structures proposed for the complexes 1–9 are gi-
ven in Chart 2.
The methylene protons of benzyl and furfuryl groups appeared
around 5.00 ppm in all the complexes. The methylene protons
(adjacent to nitrogen atom) of alkyl chain are observed around
4.00 ppm for complexes 3–9. The observed deshielding of the
methylene protons adjacent to nitrogen atom in all the cases is
attributed to the release of electrons on the nitrogen of the NR2
groups, forcing high electron density towards the sulfur (or the
metal) via thioureide -system. Although the magnitude of deshiel-
ding decreases with the increase in distance from the metal centre
or the thioureide bond. The other proton signals are also slightly
deshielded on complexation. Interestingly, in the 1H NMR spectra
of 8 and 9, all the methylene protons gave rise to broad signals,
indicating that the complexes are involved in atleast one dynamic
process. Considering the macrocyclic nature of the products (Chart
2), it can be supposed that these exist conformational equilibria in
solution.
FTIR spectral studies
The stretching frequencies associated with the C–N and C–S
bands are listed in Table 1. The infrared spectra of dithiocarbamate
complexes exhibit two characteristic vibrations which are direct
structural significance. The first lies in the region 950–1050 cmꢀ1
(m
C–S) which indicates the coordination mode of (unidentate or
bidentate) of dithiocarbamate ligand [25] while the second lies in
between 1450–1550 cmꢀ1
C–N) and is termed as thioureide band
(m
[26]. In the present study, the mC–S band observed around
1015 cmꢀ1 without any splitting in all the complexes suggesting
the bidentate coordination of the dithiocarbamate moiety. All the
complexes show thioureide mC–N band in the region 1453–
1471 cmꢀ1, which lies between the single and double bond ener-
gies indicating the partial double bond character. This behaviour
may be attributed to the electron releasing ability of the amines,
which forces high electron density towards the sulfur atoms, via
13C NMR spectral studies
The carbon signals for methylene groups adjacent to the nitro-
gen atom appeared in the region 47.0–56.3 ppm. The other meth-
ylene carbon signals are observed in the upfield region of 26.1–
33.2 ppm. A downfield shift of the methylene adjacent to nitrogen
atoms, carbon signals in all the complexes is an indication of the
important consequence of the complexation process, viz., a signif-
icant thioureide Nd+'Cdꢀ contribution to the stability of the com-
plexes and a resultant reduction in the electron density. The most
important 13C NMR signals of the N13CS2 carbons are observed in
the region 204.7–206.7 ppm with very weak intensity characteris-
tic of the quarternary carbon signals.
the thioureide
bond character and shifting the vibration to higher energy
C=N = 1690–1640 cmꢀ1 C–N = 1350–1250 cmꢀ1].
p-system, thus producing the mentioned double
[
m
, m
NMR spectral studies
NMR chemical shifts of the synthesized complexes are summa-
rized in Tables 2 and 3, respectively.
Fig. 2. SEM images of (a) PbS1 and (b) PbS2 and EDAX spectra of (c) PbS1 and (d) PbS2.

580
E. Sathiyaraj, S. Thirumaran / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 575–581
low the reverse order of the above. These indicate that the C'N
double bond character increases with increase in length of alkyl
chain bonded to nitrogen atom. For high C'N -bond order, a high
value for
'
and a low(N13CS2) value are observed earlier [27].
C
N
The presence of phenyl, furyl and thiophenyl groups in dithiocar-
bamates do not show any significant change in thioureide mC–N
bands and N13CS2 chemical shifts of 1–7.
Characterization of ethylenediamine capped PbS nanoparticles
Powder X-ray diffraction studies on PbS
To investigate structure information of samples obtained in the
present experiment, powder X-ray diffraction is carried out. The
PbS nanoparticles prepared from 3 and 4 are represented as PbS1
and PbS2. The powder X-ray diffraction patterns of PbS1 and
PbS2 are shown in Fig. 1. All the diffraction peaks can be indexed
to face-centered-cubic (fcc) PbS, which are in good agreement with
the standard data from the JCPDS card No. 98-1900 (a = 5.929 Å).
The sharp peaks indicate that the products are well crystalline.
The mean crystallite size can be determined from the half-width
of the diffraction peaks using Debye-Scherrer formula [28]. The
mean crystallite sizes are estimated as 66 and 64 nm for PbS1
and PbS2, respectively.
Scanning electron microscopy (SEM) studies
The morphologies of PbS1 and PbS2 are observed by SEM mea-
surement. SEM images of PbS1 and PbS2 are shown in Fig. 2(a and
b). SEM image of PbS1 (Fig. 2a) shows that three types of morphol-
ogy are present; most of the particles are shapeless while the
remainder are square and rectangle shapes. SEM image of PbS2
(Fig. 2b) exhibits that all the particles are shapeless. The average
size of the particles in PbS1 is larger than in PbS2. In both cases,
the average size of the particles is larger than that estimated by
Scherrer formula from the PXRD pattern. Thus we considered that
the particles are composed of smaller crystallites.
Energy dispersive X-ray (EDAX) analysis
Fig. 3. Absorption spectra of (a) PbS1 and (b) PbS2 and Fluorescence spectra of
(kex = 290 nm) (c) PbS1 and (d) PbS2.
The formation of ethylenediamine capped lead sulfide was con-
firmed using the EDAX analysis. EDAX spectra of PbS1 and PbS2 are
shown in Fig. 2(c and d). Energy dispersive X-ray spectra of PbS1
and PbS2 reveal the presence of Pb, S, C, N and O. In both the cases,
The thioureide mC–N bands of complexes 1–7 follow the order:
1 ꢁ 2 < 3 ꢁ 4 ꢁ 5 ꢁ 6 < 7 and the N13CS2 chemical shifts of 1–7 fol-
Fig. 4. IR spectrum of PbS1.

E. Sathiyaraj, S. Thirumaran / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 575–581
581
strong signals are observed for Pb and S. This indicates that the
synthesized products are PbS. The presence of C and N peaks in
the spectra exhibits that the presence of ethylenediamine in the
product. A relatively weak oxygen peak in both the spectra proba-
bly originates from unavoidable surface-adsorption of oxygen to
the lead sulfide particles from exposure to air during sample
processing.
revealed that the C'N double bond character increases with in-
crease in length of alkyl chain bonded to nitrogen atom. In addi-
tion, we reported here a simple and versatile method for the
synthesis of lead sulfide nanoparticles using two complexes 3
and 4 as single source precursors in a single pot low temperature
process. Ethylenediamine has been used as a capping agent. The
nanoparticles showed a blue shift in their absorption band edges.
Optical properties
Appendix A. Supplementary data
UV–vis absorption spectroscopy is a useful technique to moni-
tor optical properties of the quantum-sized particles. Generally,
the wavelength at the maximum exciton absorption (kmax) de-
creases as the size of the nanoparticles decreases, as a consequence
of quantum confinements of the photogenerated electron-hole car-
riers. UV–vis absorption spectra of PbS1 and PbS2 are shown in
Fig. 3(a and b). An absorption shoulder was observed at 275
(4.51 eV) and 271 nm (4.58 eV) for PbS1 and PbS2 nanoparticles,
respectively. The clear appearance of a blue shift of the absorption
peak relative to bulk PbS (310 nm (4.02 eV)) [29] indicates that the
PbS1 and PbS2 nanoparticles are quantum confined.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2012.06.052.
References
[1] K.S. Siqqidi, S.A.A. Nami, L. Chebude, J. Braz. Chem. Soc. 17 (2006) 107–112.
[2] R. Say, E. Birlik, Z. Erdengil, A. Denizli, A. Erzos, J. Hazard. Mater. 150 (2008)
560–564.
[3] Y. Yoshikawa, A. Adachi, H. Sukurai, Life Sci. 80 (2007) 759–766.
[4] S. Ozkirimli, T.I. Apak, M. Kiraz, Yegenoghu, Arch. Pharma. Res. 28 (2005)
1213–1218.
Fluorescence spectra of PbS1 and PbS2 were recorded at excita-
tion wavelength of 290 nm at room temperature and the resulting
spectra are shown in Fig. 3(c and d). Fluorescence spectra of PbS1
and PbS2 show emission peak at 410 (3.02 eV) and 404 nm
(3.07 eV), respectively. This emission is due to the recombination
of electron and hole pair. It was observed that there was a promi-
nent blue shift of the emission band compared with that of the
bulk PbS [30], which might be due to the quantum size effect of
PbS nanoparticles. The difference between absorption and emis-
sion peak wavelength is ca. 135 nm. This indicates the emission
associated with the transition of electrons from trap state to con-
duction band. PbS2 shows blue shift than PbS1, it is well known
that the fluorescence emission shift to lower wavelength with
change in particle size and shape.
[5] L.H. Uppadine, J.M. Weeks, P.D. Beer, J. Chem. Soc. Dalton Trans. 22 (2001)
3367–3372.
[6] M.C. Tony, W. Chen, J. Sun, D. Ghosh, S. Chen, J. Phys. Chem. B 110 (2006)
19238–19242.
[7] L. Guerrini, J.V. Garicia-Ramos, C. Domingo, S. Sanchez-Cortes, Phys. Chem. 11
(2009) 1787–1793.
[8] M.S. Vichers, J. Cooken, P.D. Beer, P.T. Bishop, B. Thiebaut, J. Mater. Chem. 16
(2006) 209–215.
[9] R.W. Daheka, Sci. Total Environ. 89 (1989) 271–277.
[10] N. Srinivasan, S. Thirumaran, Superlattices Microstruct. 51 (2012) 912–920.
[11] P.A. Ajibade, D.C. Onwudiwe, M.J. Moloto, Polyhedron 30 (2011) 246–252.
[12] P.J. Thomas, D. Fan, P. O’Brien, J. Colloid Interface Sci. 354 (2011) 210–218.
[13] J.C. Machol, F.W. Wise, R.C. Patel, D.B. Tanner, Phys. Rev. B 48 (1993) 2819–
2822.
[14] S. Zhou, Y. Fang, C.Z. Sang, J. Mater. Res. 18 (2003) 1188–1191.
[15] D. Arivouli, F.D. Gnanam, P. Ramasamy, J. Mater. Sci. Lett. 7 (1988) 711–713.
[16] Y.D. Li, Y. Ding, Y. Zhang, Y.T. Qian, J. Phys. Chem. Solids 60 (1999) 13–15.
[17] S.H. Yu, M. Yoshimura, Adv. Mater. 14 (2002) 296–300.
[18] A.K. Verma, T.B. Rauch fuss, S.R. Wilson, Inorg. Chem. 34 (1995) 3072–3078.
[19] A.H. Sonici, N. Keghowche, J.A. Delaire, H. Remita, M. Mostafavi, Chem. Phys.
Lett. 422 (2006) 25–29.
Infrared spectral studies on PbS1 and PbS2 nanoparticles
Infrared spectrum of PbS1 is shown in Fig. 4. IR spectra of PbS1
and PbS2 nanoparticles show two characteristic bands around
3430 and 3390 cmꢀ1, which are due to masym and msym vibrations
of –NH2. The bands observed around 2920 and 2850 cmꢀ1 are as-
signed to masym and msym vibrations of –CH2–. IR spectra of both
cases indicate that ethylenediamine is present on the surface of
the PbS nanoparticles and serving as a capping agent for the latter
[20] W. Vogel, P.H. Borse, N. Deshmukh, S.K. Kulkarni, Langmuir 16 (2000) 2032–
2037.
[21] B.L. Cushing, V.L. Kolesnichenko, C.J. O’Connor, Chem. Rev. 104 (2004) 3894–
3946.
[22] N. Srinivasan, P. Valarmathi, S. Thirumaran, S. Ciattini, Transition Met. Chem.
40 (2010) 505–509.
[23] P.V. Subha, P. Valarmathi, N. Srinivasan, S. Thirumaran, K. Saminathan,
Polyhedron 29 (2010) 1078–1082.
[24] R.R. Martinez, R. Mejia-Huicochea, J.A. Guerrero-Alvarez, H. Hopfl, H. Tlahuext,
ARKIVOC 5 (2008) 19–30.
[25] F. Bonati, R. Ugo, J. Organomet. Chem. 110 (1967) 257–264.
[26] J.O. Hill, R.J. Magee, Rev. Inorg. Chem. 3 (1981) 141–197.
[27] H.L.M. Van Gal, J.W. Diesveld, F.W. Pijpers, J.G.M. Van Der Linden, Inorg. Chem.
18 (1979) 3251–3260.
[31]. The shift in masym and msym vibrations of N–H to higher wave-
numbers (ca. 60 cmꢀ1) suggests coordination of ethylenediamine
to the Pb on the surface of the PbS nanoparticles. The lack of bands
due to dithiocarbamate ligands indicates their absence in PbS
nanoparticles.
[28] B.D. Cullity, Elemental X-ray diffraction, second ed., Addison Wesley, Reading
MA, 1978.
[29] T. Trindade, P. O’Brien, X.-M. Zhang, M. Motevalli, J. Mater. Chem. 7 (1997)
1011–1016.
[30] M. Naveneethan, K.D. Nisha, S. Ponnusamy, C. Muthamizhchelvam, Rev. Adv.
Mater. Sci. 21 (2009) 217–224.
Conclusions
Pb(II) dithiocarbamate complexes based on benzyl and furfuryl
groups have been prepared and characterized by elemental analy-
ses and spectroscopic techniques. IR and 13C NMR spectral studies
[31] J.Y. Lee, J. Yang, T.C. Deivaraj, H.P. Too, J. Colloid Interface Sci. 268 (2003) 77–
80.