Thermal decomposition synthesis of nanorods bismuth sulphide from bismuth N-ethyl cyclohexyl dithiocarbamate complex

Article abstract of DOI:10.1016/j.tca.2016.03.001

Nanorods of bismuth sulphide were prepared by thermal decomposition of bismuth N-ethyl cyclohexyl dithiocarbamate at different calcination duration. X-ray diffraction (XRD) analysis shows that at 400°C, the precursor was fully decomposed to orthorhombic b

Full text of DOI:10.1016/j.tca.2016.03.001

Accepted Manuscript
Title: Thermal Decomposition Synthesis of Nanorods Bismuth
Sulphide from Bismuth N-ethyl Cyclohexyl Dithiocarbamate
Complex
Author: Nurul Hidayah Abdullah Zulkarnain Zainal Sidik
Silong Mohamed Ibrahim Mohamed Tahir Kar-Ban Tan
Sook-Keng Chang
PII:
S0040-6031(16)30023-5
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.tca.2016.03.001
TCA 77448
To appear in:
Thermochimica Acta
Received date:
Revised date:
Accepted date:
30-9-2015
28-2-2016
4-3-2016
Please cite this article as: Nurul Hidayah Abdullah, Zulkarnain Zainal,
Sidik Silong, Mohamed Ibrahim Mohamed Tahir, Kar-Ban Tan, Sook-Keng
Chang, Thermal Decomposition Synthesis of Nanorods Bismuth Sulphide from
Bismuth N-ethyl Cyclohexyl Dithiocarbamate Complex, Thermochimica Acta
http://dx.doi.org/10.1016/j.tca.2016.03.001
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Thermal Decomposition Synthesis of Nanorods Bismuth Sulphide from Bismuth N-ethyl
Cyclohexyl Dithiocarbamate Complex
a,b
a,b*
c
Nurul Hidayah Abdullah , Zulkarnain Zainal zulkar@upm.edu.my, Sidik Silong ,
a
a
b
Mohamed Ibrahim Mohamed Tahir , Kar-Ban Tan , Sook-Keng Chang
a
Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM
Serdang, Selangor, Malaysia
b
Materials Synthesis and Characterization Laboratory, Institute of Advanced Technology,
Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
UiTM Negeri Sembilan, Kampus Kuala Pilah, Pekan Parit Tinggi, 72000 Kuala Pilah,
c
Negeri Sembilan, Malaysia
Tel.: +6 03 89464209; fax: +6 03 89464232
1

Highlights
Bismuth N-ethyl cyclohexyl dithiocarbamate was used as single source precursor.
No surfactant was used in the preparation of Bi S nanorods.
2
3
Pure phase orthorhombic Bi S is obtained.
2
3
Bismuth sulphide with an average atomic ratio of Bi:S close to 2:3 is obtained.
Abstract
Nanorods of bismuth sulphide were prepared by thermal decomposition of bismuth N-
ethyl cyclohexyl dithiocarbamate at different calcination duration. X-ray diffraction (XRD)
analysis shows that at 400 °C, the precursor was fully decomposed to orthorhombic bismuth
sulphide after 2 hours of calcination. Besides, calcination duration does not affect the
existence of Bi S phase. Field emission scanning electron microscopy (FESEM) and
2
3
transmission electron microscopy (TEM) analyses reveal that Bi S nanorods with an average
2
3
width ranging from 29-36 nm were obtained. Energy dispersive X-ray (EDX) analysis
confirmed the atomic ratio of Bi and S close to 2:3, giving a possible composition of Bi S .
2
3
Direct band gap energy of Bi S decreases from 1.83 eV to 1.54 eV as calcination time
2
3
increases.
Keywords: Semiconductors; Heat treatment; Nanostructures; Electron microscopy (TEM and
SEM)
2

1
. Introduction
The fabrication of semiconductor based devices have gained much attention since the
invention of the transistor in 1947 by American physicists and the development of the
integrated silicon chip in the 70s which have been of great use in our daily lives. Advanced
technological devices have been rapidly develop for man’s insatiable need ranging from MP3
players, computers, mobile phones, and nowadays, flat screen televisions such as liquid
crystal display (LCD) and light emitting diode (LED). The escalating interest in both
academic and industrial fields in semiconductor technology has led to the increase of studies
on binary and ternary semiconductor compounds for their potential applications in electronic
and photovoltaic devices respectively [1,2].
The development of nanostructured materials has grown rapidly owing to the
dramatic changes in properties (electrical, thermal, mechanical, electronic, optical) in
nanoscale dimension through control of matter at the 1–100 nm scale which make them
different from their bulk [2,3]. The remarkable concern in nanotechnology has led to the
development of semiconducting metal sulphide nanomaterials which possess novel
spectroscopic and electronic properties that offer great potential for broad range of
applications especially in photovoltaics [4], optoelectronic [5], electrochemical sensors [6],
and energy conversion and storage [7]. Nanostructures from inorganic, organic and
composite materials can be classified into zero dimensional (0D), one dimensional (1D), two-
dimensional (2D) and three-dimensional (3D) with sizes down to the nanometer [2,3,7,8].
Several metal sulphides with different shapes and sizes including nanotubes [9], nanorods
[
10], nanoparticles [11], nanoflakes [12], and nanobelts [13] have been synthesized for the
development of diverse electronic nanodevices.
3

Researchers have demonstrated the synthesis of nanostructured metal sulphides such
as NiS, Bi S CoS, ZnS, Sb S , CuS, CdS, and In S by various methods [14-21]. Among the
2
3,
2
3
2 3
remarkable reported semiconductor material, Bi S has been given considerable attention in
2
3
the field of research due to its potential applications in hydrogen storage [22], high-energy
batteries [23], catalytic fields [24], optoelectronic nanodevices [25] photodegradation of dyes
[
26, 27], solar cell [28] and nanomedicine [29]. For instance, Bi S nanowires with band gap
2 3
5
2
energy of ~1.33 eV and current density of about 10 A/cm has been reported to be a potential
candidate for application in field-emission electronic devices [30]. Furthermore, high quality
nanorods and nanowires of Bi S have been highlighted to be suitable materials for solar
2
3
energy, optoelectronic and photoelectronic applications [25,31]. Besides, there is a report
about the synthesis of orthorhombic Bi S nanoparticles as a photocatalyst for removal of
2
3
methylene blue dye [32]. Bao et al. [25] studied on photoswitchable conductivity of Bi2S3
nanowires. From the findings, it was found that the nanowire Bi S exhibit nonlinear current-
2
3
voltage (I-V) characteristics and excellent photoresponse which could be used in
optoelectronic nanodevices. In addition, Bi S nanorods also have been reported as an ideal
2
3
agent for in vivo photothermal ablation of tumors and effective tumor metastasis inhibition
29].Furthermore, Bi S nanorods incorporated with poly(3-hexylthiophene) (P3HT) have
[
2
3
been investigated as new candidate for the fabrication of low-cost and environmentally
friendly polymer/inorganic hybrid solar cells [28]. Besides, the incorporation of Bi2S3
nanoparticles with TiO has been highlight to have crucial roles in improving the
2
photocatalytic activity for the degradation of methyl orange under visible irradiation [26]. In
addition, Bi S nanostructures also have been reported to have high efficiency in the
2
3
photodegradation of rhodamine B (RhB) [27].
Various methods have been employed for the preparation of bismuth sulphides such
as refluxing method [33], solvothermal [16,34,35], hydrothermal [17,26], molten salt solvent
4

strategy [36], sonochemical [37], single diffusion method [38], ionic liquid-assisted
templating route [39], hot injection technique [27], chemical precipitation [40], in
situ thermal sulfuration method [41], microwave irradiation [42,20], solventless synthesis
[
43,44] and thermal decomposition of single source precursor [45,46]. Among these methods,
thermal decomposition of single source precursor is one of the most anticipating techniques
to be explored due to the simplicity and different types of precursor have different features
which can be exploited for synthesis of nanomaterials with different properties than
their bulk counterparts. Wang et al. [44] also reported about the influence of the length of the
alkyl group of the precursor on the size of the nanoproduct. They emphasized that precursor
with shorter alkyl group yields larger rods of Bi S .
2
3
Metal dithiocarbamate has been widely studied as single source precursor for the
preparation of metal sulphide [47,48,49]. Thermal decomposition (thermolysis or pyrolysis)
of single source precursors are proven to provide easier and simpler control of the shapes and
sizes, and growth of high quality nanoparticles in large scale production [11,14,48]. The
preparation of metal dithiocarbamates has been extensively reported by facile reaction
between metal salt with carbon disulphide and secondary amine in ethanol or methanol
solution [50-54]. Thermal decomposition of organometallic precursors can be done by simply
heating the precursors at high temperature in sealed furnace or in high boiling point of
solvent to break down the compound into metal sulphide [11,55]. The utilization of single
source precursors for preparation of metal sulphides offer several advantages owing to the
synthesis process can be conducted under anaerobic condition which is important due to
some groups of II-VI and III-V are air sensitive [56]. Furthermore, the use of volatile, toxic
and/or pyrophoric precursors also can be avoided. Besides, the utilization of one volatile
precursor may cause the purification process to be handled easily than that of two or more
volatile precursors that most likely to contribute to the existence of impurities in the
5

nanoparticles. In addition, low temperature deposition routes are also possible for the
production of semiconductor nanoparticles. Hence, these factors can affect the optical
properties of the compound relative to the predicting optical properties owing to the
difference in sizes and shapes of the particles [56].
Herein, bismuth N-ethyl cyclohexyl dithiocarbamate was used as single-source
precursor for the preparation of bismuth sulphide via thermal decomposition method at 400
°
C. The synthesized bismuth dithiocarbamate was subjected to different calcination duration
and the obtained bismuth sulphide will be investigated on its structural, morphological,
compositional and band gap properties.
2
. Experimental Methods
2
.1
Preparation and Characterization of Bismuth Dithiocarbamate
Preparation of Bi(III) complex of N-ethyl cyclohexyl dithiocarbamate was achieved
by in-situ reaction of corresponding metal salt with carbon disulphide and potassium
hydroxide in cold ethanolic solution of secondary amine. Stoichiometric mol ratio of metal to
ligand 1:3 was prepared. Carbon disulphide (0.063 mol) and N-ethylcyclohexylamine (0.063
mol) were added sequentially into ethanolic solution of potassium hydroxide (0.063 mol) and
stirred for an hour at 0−4 °C. After an hour of stirring, bismuth(III) chloride (0.021 mol) was
added and stirred for another two hours. Dark yellowish orange precipitates was formed and
then filtrated and washed thoroughly with distilled water and cold ethanol followed by
drying. Recrystallization in chloroform and ethanol solutions yielded pure crystalline material
of C H N S Bi.
2
7
48
3 6
The infrared spectrum of sample was recorded by Universal Attenuated Total
Reflection (UATR) technique on a Perkin Elmer 100 Series FT-IR Spectrometer. The
-1
spectrum was analyzed in the range of 280-4000 cm using liquid nitrogen as carrier gas at
6

room temperature to verify the presence of functional groups in the synthesized compound.
Elemental analysis (C, H, N and S) was carried out on a LECO CHNS-932 instrument. The
percentage of bismuth content was determined by Optima 7300 DV Optical Emission
Spectrometer (OES). Mass spectrum was recorded using Shimadzu Gas Chromatograph-
Mass Spectrometer (GCMS-QP5050A) using direct injection (DI-MS) technique to verify the
purity and molecular weight of the compound. Thermogravimetric analysis/ differential
gravimetric (TGA/DTG) analyses were carried out using Mettler Toledo Thermal
Gravimetric Analyzer (TGA/SDTA 851e). The sample was analyzed from ambient to 600 ºC
-1
in nitrogen atmosphere with the heating rate of 10 ºC min to determine decomposition
temperature and weight loss of the material. Differential scanning calorimetry (DSC)
spectrum was recorded using DSC 7 (Perkin Elmer) equipped with liquid nitrogen cooling
system. The sample was analyzed from 0 ºC to 450 ºC in nitrogen atmosphere with the
-1
heating rate of 10 ºC min to determine the thermodynamic events such as melting point and
decomposition temperature.
2
.2
Preparation and Characterization of Bismuth Sulphide
Bismuth dithiocarbamate was placed in porcelain crucible in the sealed tubular
furnace. The furnace was purged for 15 minutes with nitrogen gas to remove oxygen. Then,
the sample was heated at temperature 400 ºC and different calcination duration of 2, 4 and 6
-1
hours in nitrogen atmosphere. The rate of heating was set to 5 ºC min . The sample was
cooled down before it was taken out from the furnace to prevent the oxidation of the
compound. The products were characterized by powder XRD, FESEM, EDX, TEM, and UV-
VIS-NIR.
7

The phase and structure analysis were carried out using the Shidmazu Model XRD-
6
000 Diffractometer with CuK (λ = 1.5418Å) radiation, employing sampling width of 0.02°
α
in the range from 10 to 80°. The accelerating voltage and current were 30 kV and 30 mA
respectively. The morphologies of the samples were studied by JSM-7600F JEOL FESEM
attached with energy dispersive X-ray (EDX) analyzer. The chemical compositions were
determined by EDX analysis. A Hitachi H-7100 TEM was used to examine the morphology
and the particle sizes of the prepared sample. The diffuse reflectance spectra of the as
synthesized powders were recorded at room temperature using the Shimadzu UV-3600
Ultraviolet-visible-near infrared (UV-VIS-NIR) spectrophotometer.
3
. Results and Discussion
.1 Synthesis of Bismuth Dithiocarbamate
The reaction of CS with secondary N-ethyl cyclohexylamine in the presence of
3
2
aqueous KOH leads to the formation of potassium N-ethyl cyclohexyl dithiocarbamate.
Bismuth dithiocarbamate (Bi-DTC) was obtained by the reaction of the ligand and bismuth
chloride with mol ratio of 3:1. A general reaction scheme for the above preparation is given
in Fig. 1.
The C, H, N, S and Bi elemental analyses data show good agreement between the
experimental and theoretical percentage based on the suggested molecular formula (Table 1).
The synthesized Bi-DTC displays metal:ligand ratio of 1:3 (metal:ligand). High percentage
yield of 96% indicates that the in situ chemical reaction is suitable for the preparation of this
compound. The physical data and elemental analysis of Bi-DTC is listed in Table 1.
3
.2
Fourier Transform Infrared Spectroscopy Analysis
8

Analysis by infrared spectroscopy was performed to gather the information on the
presence of the functional groups. Fig. 2 shows the spectrum of Bi-DTC obtained in the range
-1
of 4000-280 cm . The three main regions of interest in dithiocarbamate compounds are
-
−1
primarily correlated to ν(C—N) of NCS that appears in the range of 1580–1450 cm ; the
2
−
1
1
2
060–940 cm region which is associated with asymmetric ν(C—S) of CSS; and the 420–
−
1
50 cm region that assigned to ν(M—S) bond [57-60]. All the main regions that correlated
to dithiocarbamate compounds are observed from the spectrum at wavelength 1469, 1007,
−
1
3
60 cm for ν(C—N), ν(—CSS) and ν(M—S) respectively. The energy of the the ν(C—N)
band obtained by bismuth complex can be correlated with the intermediate between the
−
1
−1
stretching frequencies of single (1250–1360 cm ) and doubly (1640–1690 cm ) bonded
carbon and nitrogen, suggesting the partial double bond character of the prepared compound
−
1
[
61]. From IR spectrum, the two bands observed at 1007 and 987 cm indicate the
−
1
monodentate character of Bi-DTC. The presence of only one band in the 1000±70 cm
region is attributed to bidentate character; meanwhile the splitting of the same band in the
same region is attributed to monodentate character [58,62]. According to Sarwar et al. [63] a
-
1
split band indicates an asymmetrically bonded bidentate ligand (Δν<20 cm ) or a
-1
monodentate bound ligand (Δν>20 cm ). The splitting peaks of bismuth complexes in this
region also have been reported before [50,64]. The appearance of absorption band at 2928
-1
cm was attributed to the ν(C-H) stretching for the methyl group [58].
3
.3
Mass Spectral Analysis of Bismuth Dithiocarbamate
Mass spectral analysis was performed to determine the molecular weight and
fragmentation patterns of Bi-DTC. Fig. 3 shows the mass spectrum of Bi-DTC. Molecular ion
+
•
that is related to the molecular weight of the proposed molecular formula, [BiC H N S ] is
2
7
48
3 6
not found. This can be resulted from either pyrolytic decomposition because of the relatively
9

high temperature is used or due to the fragmentation of the molecular ion in the ionization
chamber [65]. Similar observation also has been reported from another mass spectral analysis
of bismuth dithiocarbamates with different types of ligands .They also found the
+
fragmentation of [Bi(S CNR ) ] as the parent ion in their mass spectra with no observation
2
2 2
+
of [Bi(S CNR ) ] [46,66] . Based on the mass spectrum analysis, peak corresponds to higher
2
2 3
value of 613 m/z can be denoted as direct fragments of the molecular ions with the formula of
+
[
Bi(S CNC H ) ] attributed to the loss of one attached ligand from the proposed molecular
2
8
16 2
formula, [Bi(S CNC H ) ]. The observed molecular ion peak is corresponded to the
2
8
16 3
formation of polynuclear compounds from the pyrolytic decomposition of the complexes,
during which condensation reactions took place [65]. The base peak observed in the mass
spectra is varied depending on the temperature of the ionization chamber and the type of an
amine group of the dithiocarbamate ligand. The base peak may correspond either to the
+
+
[
R NCS] or to the [CS ] ion [65]. Bi-DTC shows mass spectrum with molecular ion peak at
2 2
+
+
+
1
70, 88, and 55 m/z that attribute to the cleavage of [C H NCS] , [C H NS] and [C H ]
8 16 3 6 4 7
+
respectively. The fragment ion mass at 411 m/z was due to the cleavage of [BiS CNC H ] .
2
8
16
This analysis can provide useful information to support the proposed molecular formula as
obtained by elemental composition analysis. Table 2 summarizes the value of molecular ion
peaks for selected mass spectral fragments of bismuth dithiocarbamate.
3
.4
Thermal Analysis of Bismuth Dithiocarbamate
Thermal behaviour of metal complexes was studied by TGA, DTG and DSC in the
presence of nitrogen gas. The summary of thermal analysis results are presented in Table 3.
TGA and DTG were investigated by heating the Bi-DTC from ambient to 600 ºC with the
-1
heating rate of 10 ºC min . The first stage (76-192 °C) is a consecutive step that maximized
at 122 °C and 142 °C as shown in the DTG curve (Fig. 4), which could be attributed to the
1
0

removal of three ethyl groups with weight loss of 11.69 % (calculated 10.67 %) (Table 3).
The decomposition of the remaining organic part of Bi-DTC with weight loss of 56.69%
(calculated 57.80%) was observed at the temperature of 211-346 °C with DTG peak of 307
°
C. The formation of Bi S as residue was observed after heat treatment with percentage of
2
3
residue found is 31.62 % (calculated 31.53 %). No further change is apparent until 600 °C
and this indicates the stability of bismuth sulphide up to this temperature without further
change to metal oxide. This result is in agreement with the other finding that highlights on the
formation of Bi S as residue after undergoing thermal treatment of metal complex under
2
3
nitrogen flow [67]. DSC thermogram (Fig. 5) shows the existence of two endothermic peaks
at 127 °C and 157 °C, which could be assigned to the consecutive release of ethyl groups.
The sharp endothermic peak was observed at 178 °C attribute to the phase transition. Broad
endothermic hump between 292-304 °C was observed due to the decomposition of remaining
part of organic moiety to give Bi S as residue which is consistent with the TGA analysis.
2
3
3
.5
Structural Study of Bismuth Sulphide
The crystalline structures of the bismuth sulphides were examined by X-ray
diffraction analysis. By changing the calcination duration from 2 to 6 hours at 400 °C, no
significant change on the sample phases can be observed. The XRD pattern remains similar
except for a slight change in the peak intensity. Sharp diffraction line displays in Fig. 6
reveals the crystalline form of Bi S . Besides, all the diffraction peaks can be indexed as
2
3
orthorhombic phase of Bi S (ICDD File no. 017-0320; a = 11.1490 Å, b =11.3040 Å, c =
2
3
3
.9810Å, α = β = γ = 90°). The XRD pattern of the Bi S nanoparticles exhibits prominent
2 3
peaks at scattering angles (2θ) of around 25, 28.5 and 32 which could be indexed to (130),
211), and (211) planes respectively. Therefore, it is proven that pure orthorhombic Bi S can
(
2
3
be obtained via thermal decomposition of Bi-DTC at 400 °C. There is no existence of Bi O
2
3
or impurities in the prepared samples. Based on the Debye Scherrer equation [68], the
1
1

crystallite size is found to increase from approximate 21 nm to 26 nm as calcination duration
increases from 2 to 6 hours (Table 4).
3
.6
Morphological and Compositional Studies
Bismuth sulphides prepared by thermal decomposition of Bi-DTC at 400 °C were
analyzed by FESEM and TEM. FESEM images display the formation of Bi S nanorods. Fig.
2
3
7
shows a mixture of short and long nanorods of Bi S obtained after calcination from 2 to 6
2 3
hours. Different calcination duration does not affect the morphology of the sample except for
a slight change in the particle size. The particle size distribution (Figure 8) show that the
average width of Bi S between 29-36 nm. From table 4, the difference between the average
2
3
crystallite sizes and particle width are shown. Different sizes of Bi S are observed due to the
2
3
non uniform formation of Bi S and overlapping of particles caused by the agglomeration.
2
3
Besides, the particle may compose of two or more individual crystallites. Moreover, the
estimation of crystallite sizes by Debye Scherer Equation is generally consistent with TEM
analysis for determination of nearly spherical particles rather than nanorod shapes. From
this study increased in calcination duration results to the formation of large sizes of Bi2S3
nanorods. Other study also highlight the formation of large size of Bi S nanostructures with
2
3
increased in reaction time [46]. Chen et al. [69] have reported on the formation of well
crystallized Bi S nanorods with particle size ranging from 15-90 nm prepared from bismuth
2
3
citrate by reflux reaction in dimethylformamide (DMF) at 160 °C in the presence of
cetyltrimethylammonium bromide (CTAB) as a capping agent. In contrast to their results,
Bi S nanorods are obtained without using capping agent and DMF in this work. Energy
2
3
dispersive X-Ray (EDX) analysis was performed for the quantitative analysis of Bi S as
2
3
shown in Fig. 9. The typical EDX spectrum depicts the average atomic ratio of Bi:S close to
:3, indicating of good stoichiometric sample. Wang et al. [44] have discussed about the
2
1
2

formation of Bi S nanorod. Based on the study, they find that (001) planes have the fastest
2
3
growth velocity due to highest surface energy. During the ripening process, big Bi2S3
particles preferred to grow into rods along [001] direction by consuming small particles.
Furthermore the Bi S nanorods grown along the c axis are rather stable thermodynamically
2
3
or kinetically. This explains well why the Bi S nanorods prefer to grow along the c axis
2
3
instead of the b or a axes. Furthermore there is also a report about when unstable nanodots
assembled in a line, and with prolonged heating time, the attachment and recrystallization
occurred, resulting in the formation of nanorods [46].
3
.7 Band Gap Analysis
Band gap values of the prepared samples were determined by diffuse reflectance
spectra. Fig. 10 displays Kubelka–Munk transformed reflectance spectra of bismuth
2
sulphides. The band gap of the materials were determined from the plotted of (F(R)hν) vs hν.
2
F(R) is Kubelka-Munk function where, F(R)=(1-R) /2R, R is experimentally observed
2
reflectance [70,71]. The energy intercept of a plot of (F(R)hν) versus hν gives direct band
gap value when the linear region is extrapolated to the zero ordinate [71]. The band gap
energy of Bi S decreases as longer calcination duration was set from 2 to 6 hours. The
2
3
obtained band gap values are around 1.83, 1.56 and 1.54 eV for 2, 4 and 6 hours of
calcination duration respectively. These values are slightly higher than that of the reported
band gap of Bi S (1.3 eV) [44,72]. Wang et al. [44] have reported on the direct band gap of
2
3
1
.5 eV for Bi S nanorods. The blue shift might be ascribed to the quantum size effect due to
2 3
the high aspect ratio of the nanorods relative to the bulk orthorhombic Bi S [44]. It can be
2
3
concluded that shorter calcination duration of 2 hours results to the formation of nanorods
Bi S with smaller particle sizes and higher band gap energy.
2
3
1
3

Conclusion
Bismuth sulphide nanorods were successfully synthesized via thermal decomposition of
bismuth N-ethyl cyclohexyl dithiocarbamate complex under nitrogen gas flow. Thermal
decomposition of Bi-DTC at different calcination duration of 2, 4 and 6 hours at 400 °C
yielded high purity orthorhombic Bi S . The XRD analysis also supported that the calcination
2
3
of Bi-DTC from 2 to 6 hours may lead to the formation of orthorhombic Bi S . Different
2
3
calcination duration did not provide significant effect on the sample phases except for a slight
change in the peak intensities and particle sizes. The observed band gap were in the range of
1
.54 to 1.83 eV and this indicates blue shift if compared to the bulk sample (1.3 eV). Longer
calcination duration resulted in decrement of band gap energy. Besides, EDX analysis
confirmed the presence of Bi to S close to ratio 2 : 3 which correspond to the formation of
Bi S . This study shows that thermal decomposition of Bi-DTC at calcination duration from 2
2
3
to 6 hours able to generate nanosized bismuth sulphides, suggesting promising applications in
electronic and solar cell devices.
Acknowledgements
Financial support from the Research University Grant Scheme of UPM (RUGS 05-01-09-
0
814RU) is highly appreciated.
1
4

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Figure Captions
Fig. 1. General reaction of bismuth dithiocarbamate.
Fig. 2. FTIR spectrum of bismuth dithiocarbamate.
Fig. 3. Mass spectrum of bismuth dithiocarbamate.
Fig. 4. TGA and DTG thermograms of bismuth dithiocarbamate.
Fig. 5. DSC thermogram of bismuth dithiocarbamate.
Fig. 6. XRD patterns of Bi S powder prepared at 400 °C and different calcination duration:
2
3
(a) 2 h (b) 4 h (c) 6 h.
Fig.7. Electron microscopy images of bismuth sulphide prepared at 400 °C and different
calcination duration: (a) 2 h (FESEM), (b) 4 h (FESEM), (c) 6 h (FESEM), (d) 2 h (TEM),
(e) 4 h (TEM) and (f) 6 h (TEM).
Fig. 8. Images of particle size distribution of bismuth sulphide prepared at 400 °C and
different calcination duration: (a) 2 h (TEM), (b) 4 h (TEM), (c) 6 h (TEM).
Fig. 9. EDX spectra of bismuth sulphide prepared at 400 °C and different calcination
duration: (a) 2 h (b) 4 h (c) 6 h.
Fig. 10. Kubelka–Munk transformed reflectance spectra of bismuth sulphides prepared at 400
°
C and different calcination duration: (a) 2 h (b) 4 h (c) 6 h.
2
4

Table 1 Physical and elemental analysis of bismuth dithiocarbamate
Compound
Formula Weight)
Yield
(%)
Colour
Elemental Analysis
%Found
(
(g/mol)
(Calc.)
C
H
N
S
Bi
C H N S Bi
96
Yellowish
Orange
38.48
5.48
5.13
24.28
25.61
27
48
3 6
(815)
(39.74) (5.93) (5.15) (23.58) (25.99)
2
5

Table 2 Selected mass spectral fragments for bismuth dithiocarbamate
Probable ion
Value of molecular ion
peak, m/z
+
•
[
[
[
[
[
[
Bi(S CNC H ) ]
2 8 16 3
....
+
Bi(S CNC H ) ]
613
2
8
16 2
+
BiS CNC H ]
411
170
88
2
8
16
+
C H NCS]
8
16
+
C H NS]
3
6
+
C H ]
55
4
7
2
6

Table 3 Thermal analysis of bismuth dithiocarbamate
Compound DSC DTG Decomposition Percentage
Percentage
residue
(%)
Residue
expected
peak Max
°C) value
°C)
Temperature
(°C)
weight loss
(%)
(
(
Found
Found
(Calc.)
(Calc.)
C H N S Bi 127
122
307
76-192
211-346
11.69(10.67) 31.62(31.53)
56.69(57.80)
Bi2S3
27
48
3 6
1
1
2
3
57
78
92
04
2
7

Table 4 Crystallite and mean particle sizes of bismuth sulphide
Sample
Duration of
calcination (hour)
Average
Crystallite sizes,
t (nm)
Mean
Particle
width (nm)
Bi S (2 h)
2
4
6
21.03
23.79
25.58
29.35
29.76
35.95
2
3
Bi S (4 h)
2
3
Bi S (6 h)
2
3
2
8

Figure 1