Precursor dependent morphological and photo-catalytic behaviour of CdS nanostructures

Article abstract of DOI:10.1016/j.dyepig.2016.10.043

Cadmium complexes based on Xanthate and dithiocarbamate such as [Cd(ethyl xanthate)₂], [Cd(morpholine-4-dithiocarbamate)₂] and [Cd(piperazine1-dithiocarbamate)₂] have been used as efficient single source precursors. The formation of CdS nanostructures have been achieved by solvothermal route of synthesis. Crystallographic and morphological characterization of synthesized nanomaterials has been done by X-ray diffraction (XRD) and electron microscopy [Transmission Electron Microscope (TEM)], respectively. Diffraction and electron microscope studies reveal the formation of wurtzite structured CdS nanostructures of various morphologies (nanorods and nanospheres). UV–vis absorption and Fourier transform infrared (FTIR) spectroscopic studies have been carried for the detailed optical as well as qualitative analyses. It has been reported that the morphology of synthesized nanomaterials strongly depends upon the type of the precursor complexes. Photo-catalytic activity of the synthesized nanostructures has been tested in visible irradiation using methylene blue (MB) dye as a test contaminant in aqueous media. Morphology dependent photo-catalytic activity of the synthesized nanomaterials has been studied in detail to explore the potential of prepared nanostructures to purify polluted water.

Full text of DOI:10.1016/j.dyepig.2016.10.043

Accepted Manuscript
Precursor dependent morphological and photo-catalytic behaviour of CdS
nanostructures
Balwinder Kaur, Karamjit Singh, Ashok Kumar Malik
PII:
S0143-7208(16)31087-7
10.1016/j.dyepig.2016.10.043
DYPI 5559
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 27 June 2016
Revised Date: 17 September 2016
Accepted Date: 29 October 2016
Please cite this article as: Kaur B, Singh K, Malik AK, Precursor dependent morphological and
photo-catalytic behaviour of CdS nanostructures, Dyes and Pigments (2016), doi: 10.1016/
j.dyepig.2016.10.043.
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ACCEPTED MANUSCRIPT
X
N
O
Cd
O
Visible Light
Irradiation
S
S
Diethylenetriamine
S
S
S
S
S
S
Diethylenetriamine
199oC
Cd
199oC
N
X
e- + h+ + H2O
CdS Nanoparticles
Cd(MDTC)2
Cd(PiDTC)2
N
Cd(EX)2
CH3
CH3
S
N
N
Cl
CH3
CH3
MB dye
Degradation Pathway
OH
OH
NH2
CH3
H
SO3H
N
OH
SO3H
N
CH3
CH3
UV absorption profile of MB dye
0
min
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
15 min
30 min
45 min
60 min
75 min
OH
+
CO2 + H2O + SO42- + NH4
Degradation Products
450
500
550
600
650
700
750
Wavelength(nm)

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Precursor Dependent Morphological and Photo-catalytic Behaviour of CdS
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Nanostructures
Balwinder Kaur, Karamjit Singha and Ashok Kumar Malik٭
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Department of Chemistry, Punjabi University Patiala-147 002, Punjab (India)
aDepartment of Physics, Punjabi University Patiala-147 002, Punjab (India)
#Corresponding author e-mail: malik_chem2002@yahoo.co.uk
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Abstract
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Cadmium complexes based on Xanthate and dithiocarbamate such as [Cd(ethyl
xanthate)2], [Cd(morpholine-4-dithiocarbamate)2] and [Cd(piperazine1-dithiocarbamate)2] have
been used as efficient single source precursors. The formation of CdS nanostructures have been
achieved by solvothermal route of synthesis. Crystallographic and morphological
characterization of synthesized nanomaterials has been done by X-ray diffraction (XRD) and
electron microscopy [Transmission Electron Microscope (TEM)], respectively. Diffraction and
electron microscope studies reveal the formation of wurtzite structured CdS nanostructures of
various morphologies (nanorods and nanospheres). UV-vis absorption and Fourier transform
infrared (FTIR) spectroscopic studies have been carried for the detailed optical as well as
qualitative analyses. It has been reported that the morphology of synthesized nanomaterials
strongly depends upon the type of the precursor complexes. Photo-catalytic activity of the
synthesized nanostructures has been tested in visible irradiation using methylene blue (MB) dye
as a test contaminant in aqueous media. Morphology dependent photo-catalytic activity of the
synthesized nanomaterials has been studied in detail to explore the potential of prepared
nanostructures to purify polluted water.
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Keywords:
EthylXanthate(EX);
Morpholine4-dithiocarbamate(MDTC);
Piperazine1-
dithiocarbamate(PiDTC); Cadmium Suphide; Nanostructures; Solvothermal Synthesis; X-ray
diffraction; Electron Microscopy; UV-vis. Absorption Spectroscopy; Infrared Spectroscopy;
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Photo-catalysis.

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Introduction
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Among the various nanomaterials tremendous work has been done on synthesis
and characterization of II-VI metal-chelcogenide semiconductors nanostructures, which posses
attractive properties such as size tunable band gaps, narrow photoluminescence along with broad
and continuous absorption profiles [1-5].The unique size tunable physical and chemical
properties of nanomaterials are unachievable from their bulk counterparts. Crystallography and
morphology of nanomaterials can be controlled via the alteration of various synthesis parameters
such as type of precursors, concentration of reactants, type of capping agents, capping
concentration, reaction temperature and pH of the reaction media [6].
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Cadmium sulfide (CdS) is a II-VI binary metal-chalcogenide semiconductor with
a wide band gap (2.42eV) [7-8]. CdS nanomaterials have enormous potential applications
ranging from microelectronics to non-linear optics, optoelectronics, photo-catalysis, bio-imaging,
sensors and so on [9]. Dithiocarbamates (DTCs) are the class of anionic ligands, which contain
two sulfur donor atoms. These ligands stabilize the positive charge on metal ions towards the
periphery of complex [10]. DTCs of cadmium are the useful precursors for the synthesis of
cadmium sulfide nanoparticles. The metal bis (dithiocarbamate) complexes have been proven to
be prominent single source precursors for the synthesis of metal sulphide nanostructures, since
metal bis (DTCs) are cheaper, harmless and stable in nature at ambient conditions. Variation of
ligands in metal bis (DTC) complexes remarkably effects the crystallography and morphology of
metal-sulphide nanostructures from rods to hemispheres. It has been reported that DETA-assisted
synthesized CdS nanostructures with anisotropic character exhibit excellent photo-catalytic
activity for the degradation of MB dye [11-13]. Similarly, potassium ethyl xanthate ligand is also
useful for the synthesis of CdS nanomaterials [14].
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In the present investigation, solvothermal method has been opted for the
synthesis of various morphologies of CdS nanostructures using Cd(EX)2, Cd( PiDTC)2 and
Cd(MDTC)2 [where EX, MDTC and PiDTC are Ethylxanthate, Morpholine4-dithiocarbamate
and Piperazine1-dithiocarbamate, respectively] as single source precursors. In this research
work, to the best of our knowledge, this is the first attempt to explore the morphology dependent
photo-catalytic activity of CdS nanostructures which are prepared by varying the ligands (EX,
MDTC and PiDTC) in the precursors.

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Experimental
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All the analytical reagent grade chemicals; morpholine (C4H8ON), piperazine (C4H8N2), carbon
disulfide (CS2), sodium hydroxide (NaOH), ethanol (C2H5OH), diethylenetriamine (N3C4H12),
methylene blue dye (C16H18N3SCl), potassium hydroxide (KOH) and diethyl ether (C2H6O)
required for synthesis were procured form S. d. Fine Chemicals Pvt. Ltd and Merck. All the
reagents were used for synthesis without further purification.
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Preparation of Potassium Ethylxanthate
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Potassium hydroxide and ethyl alcohol were refluxed at 70oC for one hour. Then carbon
disulphide was added drop wise to the solution, in an ice bath with continuous shaking followed
by addition of diethyl ether. The resulting potassium ethyl xanthate was filtered and washed with
dry ether. The product was purified by dissolving in the minimum volume of hot acetone
followed by filtration and cooling of the filtrate in an ice bath. Precipitation was observed on
addition of 20 ml of dry ether [15].
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Preparation of [Cd(EX)2]
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Cd(EX)2 was prepared by dissolving 25 ml aqueous solution of the cadmium carbonate
(5mmol) to 25ml of aqueous solution of potassium ethylxanthate (0.01mol). Solid precipitates
were formed immediately and the resulting suspension was stirred for about 45 min. followed by
filtration and through washing with distilled water [16].The schematic synthesis route of
potassium ethylxanthate and [Cd(EX)2] is represented in Fig.1
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Preparation of Piperazine1- dithiocarbamate [PiDTC]
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Piperazine1-dithiocarbamate [PiDTC] was prepared by addition of 0.1mol piperazine in
150 ml diethyl ether in an ice bath maintained at 0˚-5˚C followed by the complete addition of 0.1
mol carbon disulphide. Then a concentrated solution of 0.1mol sodium hydroxide was added
slowly to above solution maintained at same temperature. The resulting mixture was stirred for 4
hours in an ice bath. A pale yellow solid product was separated by filtration and washed with
small amount of ether. Finally, pure [PiDTC] was obtained by recrystallization from acetone[17].
Fig.2 represents the schematic synthesis route of [PiDTC].

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Similar, procedure was opted for the synthesis of Morpholine 4-dithiocarbamate [MDTC][18].
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Preparation of Cadmium Complexes
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Cd(PiDTC)2 was prepared by dissolving 25 ml aqueous solution of 5mmol cadmium carbonate
to 25 ml of aqueous solution of 0.01mol PiDTC. Solid precipitates formed immediately and the
mixture was stirred for about 45min, filtered and rinsed several times with distilled water [19].
Similar, procedure was applied for the preparation of [Cd(MDTC)2][20]. The synthesis protocol
of [PiDTC], [MDTC], [Cd(PiDTC)2] and [Cd(MDTC)2] is represented in Fig.2
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Preparation of CdS Nanoparticles
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Cadmium sulfide nanoparticles were prepared from following single source cadmium precursors:
[Cd(EX)2], [Cd(PiDTC)2] and [Cd(MDTC)2] via solvothermal method. CdS nanostructures were
prepared by refluxing 0.5g of cadmium precursors in 15ml of diethylenetriamine at 1990C for 2
min. The yellowish product was filtered and washed with ethanol [22]. The schematic route of
preparation of CdS nanostructures is shown in Fig.3 and 4
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Characterization of Nanoparticles
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Powder XRD patterns were recorded for the detailed crystallographic characterization of
synthesized nanostructures. The diffraction patterns were recorded in 2θ range of 20˚ - 70˚ using
Rigaku Miniflex-600 Powder X-ray diffractometer by keeping scan speed and step size of 4˚/min
and 0.02˚, respectively. The transmission electron microscope (TEM) measurements were carried
by placing a drop of well dispersed ethanolic solution of nanoparticles on carbon coated copper
grids. The samples were dried at room temperature and analyzed on Hitachi (H-7500) electron
microscope at accelerating voltage of 100 kV. The UV-vis absorption spectra (λ= 300-600nm) of
synthesized CdS nanostructures were recorded using Labtronics spectrophotometer, by
dissolving 1mg nanomaterial in 10ml ethanol at room temperature. The Fourier transform
infrared (FTIR) spectroscopic studies were done using Perkin Elmer FTIR spectrophotometer by
preparing KBr pallets. The vibrational and rotational spectra were recorded in Middle IR (4000-
400 cm-1) and Far IR(700-30cm-1) region, respectively. The photo-catalytic activity potential of
the synthesized nanomaterials under visible light irradiation was tested using MB dye as a test
contaminant in aqueous media. The stock solution of dye was prepared by dissolving 3mg MB
dye in 500ml of water. Before illumination the suspension of dye and CdS (0.01g CdS in 100ml

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dye solution) nanoparticles was stirred in dark for 60 min to ensure adsorption of dye on surface
of CdS nanoparticles. After equilibration of solution, the suspension was illuminated in the
visible light. During irradiation, the aliquots were collected after regular time interval (15 min) to
analyze the photo-degradation of MB dye by UV-vis absorption spectrophotometer.
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Results and Discussion
Mechanism of CdS Nanostructures Formation
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CdS nanorods and nanospheres have been synthesized using diethylenetriamine (DETA) as
template under reflux conditions and chelating solvent .The formation of CdS nanorods and
nanoparticles follow the Solvent Co-ordination Molecular Template (SCMT) mechanism[23],
which has been shown in Fig.3 and 4. Initially, Cd(MDTC)2 complex coordinates with DETA
molecule to form an intermediate as shown in Fig.5. As Cd(MDTC)2-DETA complex is not
thermally stable due to its eight-membered ring structure[24], so augmentation of temperature
diminishes interaction between DETA molecule and Cd(MDTC)2, which results in the formation
of CdS nanorods. Similar, nucleation and growth mechanism will be followed for the synthesis
of CdS nanorods and nanospheres from Cd(EX)2 and Cd(PiDTC)2, respectively, as shown in
Fig.5
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Crystallographic Analyses
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Figs. 6(a-c) show powder x-ray diffraction patterns recorded for synthesized CdS nanostructures
prepared from cadmium complexes. Comparison of recorded diffraction patterns with standard
JCPDS File No.41-1049 confirm the formation of wurzite structured CdS nanocrystallites. It can
be clearly seen from recorded diffraction patterns that the peaks situated at 2θ values 25.3o,
26.6o, 28.6o, 37.0o, 43.7o, 48.0o, 57.0o and 67.0o corresponds to (100), (002), (101), (102), (110),
(103), (112) and (211) planes of CdS prepared from [Cd(ethyl xanthate)2], whereas for CdS
prepared from [Cd(PiDTC)2] and [Cd(MDTC)2], the peak positions slightly shifts to 2θ values
26.8o,27.6o,28.8o,37.0o,43.6o,48.0o, 53.0o and 67.0o and 26.4o,27.5o,28.8o,37.0o,44.0o,47.0o,55.6o
and 68.0o, respectively. Peak broadening observed in recorded diffractograms reveal the
formation of CdS nanocrystallites. The average crystallite size values calculated using Scherer
formula from recorded diffraction pattern of CdS nanoparticles synthesized form precursors
[Cd(EX)2], [Cd(PiDTC)2] and [Cd(MDTC)2] are 10.39 nm, 11.39 nm and 19.00 nm, respectively.
It was observed that X-ray diffraction intensity strongly depends upon the type of ligand. CdS

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nanostructures prepared from [Cd(MDTC)2] show high crystalline texture compared to CdS
nanostructures prepared from other ligands.
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In Fig. 6(a) nanoparticles prepared from [Cd(EX)2] shows a narrow peak at (002) represents that
the nanoparticles are elongated towards the c-axis, which is the characteristic of rod shaped
nanostructures. By the close inspection of Fig.6(a) it can be observed that (002) peak is
somewhat overlapped with (100) plane, whereas this overlapping is diminished in Figs.6(bandc)
indicate that the crystal properties have been greatly affected by varying ligand. No impurity
phase was detected, which reveal the formation of high purity product. Also merging of planes
(100) and (101) observed in CdS synthesized from [Cd(EX)2]. This merging of planes lead to
peak peak broadening. The peak broadening results to lowering of crystallite size.
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Morphological Analyses
The recorded TEM micrographs of CdS nanostructures synthesized via solvothermal method
show that morphology of synthesized nanomaterials varies from heterogeneous nanorods
synthesized from [Cd(EX)2] and [Cd(MDTC)2] to highly monodisperse deformed nanospheres
synthesized from [Cd(PiDTC)2], which suggest that nanostructure morphology strongly depends
upon the type of ligand as shown in case of Fig.7.The aspect ratio of CdS nanorods synthesized
from [Cd(EX)2] and [Cd(MDTC)2] is 6.48 and 4.34, respectively. Average length of the
elongated CdS nanospheres prepared from [Cd(PiDT)2] is ~11.50 nm.
Optical Analyses
UV-vis absorption spectroscopy is a useful technique to monitor the optical properties of nanomaterials.
UV-visible absorption spectra of CdS nanomaterials prepared from [Cd(EX)2], [Cd(PiDTC)2] and
[Cd(MDTC)2] are shown in Figs.8(a,bandc), respectively. It can be clearly seen from the recorded spectra
that the synthesized nanostructure have broad absorption profile in UV-vis region of electromagnetic
spectrum. Fig.8(a) shows CdS nanostructure prepared from [Cd(EX)2],recorded absorption spectra show a
absorption peak in UV-visible region(λ~380nm) along with a shoulder in green region. On the other hand
absorption spectra recorded for the CdS nanostructure prepared from [Cd(PiDTC)2] the absorption peak in
UV region disappears. CdS nanoparticles prepared from [Cd(MDTC)2], absorption edge~ 510 nm
corresponds to CdS band gap,whereas no pronounced absorption edge exist in absorption spectra of capped
with PiDTC ligand. Similar to crystallographic and morphological analyses, studies reveal that the
electronic structure of the CdS nanostructure can be easily tuned with type of ligands.
Infrared Spectral Studies

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Infrared spectra of the ligands and complexes were compared and indexed on careful
comparison. A very broad band exists in the range 3000-3400 cm-1 due to symmetrical and
asymmetrical ν(O–H) vibrations of water molecules in the ethyl xanthate and PiDTC ligand. The
characteristics peaks of C-N bonding present in DTC ligands and Cd(DTC)2 complexes are
present in range 1222-1262 cm-1 as shown in supporting information file (Fig.S1(b),S2,S3(b) and
S4).The presence of peaks in 1380-1480 cm-1 of middle IR spectra confirm the partial double
bond character of C-N bonding in case of DTC ligands and Cd(DTC)2 complexes. The presence
of peaks in the range 900-1001 cm-1 is the evidence of presence of bidentate C-S bonding in
ethyl xanthate and DTC’s and respective complexes as shown in supporting information file
(Fig.S1(a-b),S2,S3(a-b) and S4, respectively). Detailed description of characteristic middle IR
peaks of ligands and complexes are tabulated in Table 1.The IR spectra of CdS nanostructures
prepared from the above mentioned precursors do not show any appreciable peaks of
diethylenetriamine (chelating solvent) as shown in Figs.S5(a-b) andS6.The characteristic peak of
Cd-S bonding in CdS nanoparticles is present in IR region (700-30) cm-1. CdS nanostructures
synthesized from [Cd(EX)2], [Cd(PiDTC)2] and [Cd(MDTC)2] exihibit Cd-S peaks at 435
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cm-1,420 cm-1 and 428 cm-1 respectively, as shown in supporting information file (Figs.S7(a-b)
,
and S8).
Photo-catalytic Degradation of Dye Solution
The photo-catalytic degradation of MB dye in aqueous media by synthesized CdS nanostructures
was carried out under visible light irradiation. The mechanism of the photo-catalytic reaction can
by described as follows:
+
-
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CdS + hν
CdS + h + e
The oxidation of water by holes [H2O ꢀ H+ + OH-]
-
+
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h + OH
OH˚
The transient formation of hydroperoxide redicals:
-
-
O2(g) + e
O˚2
-
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O˚2
+
H+
HO˚2
H2O2
2HO˚2

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-
-
1
H2O2 + e
2OH
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The initial step of MB dye photodegradation can be ascribed to the cleavge of bonds of C-S+=C
functional group in MB dye.
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R-S+=R/ + OH˚
R-S(==O)- R/ + H+
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The sulfoxide group undergo second attack by an OH. Redical producing the sulfone and causing
dissociation of two bezenic rings.
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NH2-C6H3(R)-S(=O)-C6H4-R + OH˚
And/or
NH4-C6H3(R)-SO2+ C6H5-R
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NH2-C6H3(R)-S(=O)-C6H4-R + OH˚
NH4-C6H3(R) +SO2-C6H4-R
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Subsequently can be, sulfone attacked by itself by third OH˚ radical to give sulfonic acid.
SO2-C6H4-R + OH˚ R-C6H4-SO3H
2-
The final release of SO4 ions can be attributed to fourth attack by OH˚.
2-
R-C6H4-SO3H+ OH˚
R-C6H4˚+ SO4 +2H+
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R-C6H4˚ substitution reaction either with OH˚give phenolic compound.Concerning the
mineralization of the three Nitrogen-containing groups in MB dye, two cases have to be
examined. First central imino-group undergo a N=C double bond cleavge induce by cleavge of
double bond of the –S+= group in para position of central aromatic ring to give aniline i.e amino
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group can be substituted by OH˚ Redical to give phenol and release of NH2 which gives
ammonia and ammonium ions as shown below
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R-C6H4-NH2 + OH˚
˚
R-C6H4-OH+ NH2
NH3
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NH2 +H˚
NH3+H+
NH4
+
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The two symmetrical dimethyl phenyl amino groups undergo a progressive degrading oxidation
of one methyl group by attack of OH˚ redical producing an alcohol and then aldehyde which is
oxidized into acid which decarboxylated into CO2 by photo-kolbe reaction.

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-
+
2
1
OH˚+ MB
CO2 +H2O+SO4 +NH4
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So MB can be fully oxidized in a complete mineralization of carbon into CO2, while sulfur
-
2
heteroatoms can be converted into innocous SO4 ions as MB dye contains heyerocyclic ring
containing S and N atoms as shown in Fig.10. This whole reaction scheme can be represented as
+
-
in Fig.9 The mineralization of nitrogen will be more complex, producing NH4 and NO3 [25-26].
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Also there is not reportable data on photobleaching of MB dye under UV-Vis. irrdation.The
residual dye concentration as the function of irradiation time was analyzed by UV-vis absorption
spectrophotometer. The decolorization of dye could be calculated using following formula:
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C(%)= (Ao-A)/Ao x 100
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where C is the decolorization degree, A0 and A are the absorption of dye solution before and after
photo-catalysis, respectively. In supporting information file Figs. S9 (a and b) and S10 show the
UV-vis. absorption spectra of MB dye for different durations of visible light radiation exposure
in the presence of CdS nano-photocatalysts prepared from [Cd(EX)2], [Cd(PiDTC)2] and
[Cd(MDTC)2].It was also observed that pristine dye solution in aqueous media do not show any
photobleaching effect, so the degradation of dye is absolutely caused via the photo-catalytic
activity of nano-photocatalysts. Fig.11 shows the degradation of MB dye vs. time in the presence
of synthesized nano-photocatalysts. It can be clearly seen from the degradation profiles (Fig.11)
that the presence of ligand acts as an efficient photo-catalytic activity modifier. CdS
nanostructures synthesized from [Cd(MDTC)2] show maximum photo-catalytic activity,
observed value of residual dye concentration in the aqueous media after 75 min visible radiation
exposure is 58.14%, whereas the residual dye concentration values for the same duration of
visible irradiation observed in the case of CdS nanostructures prepared from [Cd(PiDTC)2] and
[Cd(EX)2] are 66.63% and 81.60%, respectively. The photo-catalytic efficiency basically
depends upon the generation of photo-excited carriers followed by their surface transfer
dominance over the charge carrier recombination. This is the reason for better photo-catalytic
performance of CdS nanostructures. Although, CdS nanostructures prepared from [Cd(EX)2]
have better visible light absorption profile than CdS nanostructures prepared from [Cd(PiDTC)2],
but CdS nanostructures prepared from [Cd(PiDTC)2] have high surface to volume ratio as well as
huge no. of surface states available for charge carrier trapping to avoid charge carrier
recombination. Thus, nanostructures prepared from [Cd(PiDTC)2] show better photo-catalytic

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activity than the CdS nanostructures prepared from [Cd(EX)2]. On the other hand, CdS
nanostructures prepared from [Cd(MDTC)2] have excellent absorption profile as well as lesser
aspect ratio than nanostructures prepared from [Cd(EX)2], which makes these nanostructures
efficient photo-catalyst. The better photo-catalytic activity could be due to high surface to
volume ratio and presence of significant un-passivated surface states. Moreover, augmentation of
surface to volume ratio with decreasing particle size on nanoscale enhances the contaminant
adsorption cross-section, which increases photo-catalytic efficiency.
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Conclusions
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Solvothermal method is a fast and efficient bottom-up synthesis route, which gives
pure and hightly monodisperse CdS nanostructures, crystallined in wurtzite structure. [Cd(EX)2],
[Cd(MDTC)2] and [Cd(PiDTC)2] are the competent single source precursors for the preparation
of monodisperse CdS nanostructures. Electron microscopic studies reveal that nanostructure
morphology is strongly precursor dependent. Nanorods have been formed in case of [Cd(EX)2]
and [Cd(MDTC)2] precursors, whereas deformed nanorods (elongated nanospheres) are
observed in case of [Cd(PiDTC)2]. CdS nanorods prepared from [Cd(ethyl xanthate)2] and
[Cd(MDTC)2] have aspect ratios 6.48 and 4.48, respectively, whereas the average dimensions of
elongated nanospheres are ~11.50 nm. UV-vis and FTIR spectroscopic reveal the formation of
pristine CdS nanostructures. Synthesized CdS nanostructures have broad absorption profile in
UV-vis region of electromagnetic spectrum. Similar to morphological analyses, spectroscopic
studies infer that electronic structure and surface states of the synthesized CdS nanostructures
can be easily perturbed with alteration in precursor material. Synthesized nanostructures prove to
be efficient heterogeneous nanophoto-catalyst for the degradation of aqueous pollutants. CdS
nanostructures prepared from [Cd(MDTC)2] have higher photo-catalytic efficiency as compare
to nanostructures prepared from other precursors i.e. [Cd(EX)2] and [Cd(PiDTC)2] because these
nanostructures have excellent absorption profile as well as significant number of surface states.
The synthesized nanomaterials seem to be potential candidates for the fabrication of next era
opto-electronic devices.
Acknowledgment
Authors are thankful to Sophisticated Instrument Centre, Punjabi University, Patiala for
providing necessary facilities. Authors are grateful to SAIF, Panjab University,Chandigarh for
TEM and IR analyses.

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Figure Captions:
22 Fig.1 Schematic synthesis route of potassium ethylxanthate and [Cd(EX)2].
23 Fig.2 Schematic synthesis route of [Cd(PiDTC)2] and [Cd(MDTC)2].
24 Fig.3 Schematic synthesis route of CdS nanostructures prepared from [Cd(EX)2].
25
26
Fig.4 Schematic synthesis route of CdS nanostructures prepared from [Cd(PiDTC)2] and
[Cd(MDTC)2].
27 Fig.5 The proposed structures of intermediate complexes.
28 Fig.6 X-ray diffraction patteren of CdS nanoparticles prepared from different complexes;
29
30
31
32
(a)CdS prepared from [Cd(EX)2]; (b) CdS prepared from [Cd(PiDTC)2];
(c) CdS prepared from [Cd(MDTC)2]
Fig.7 TEM micrographs of CdS nanostructures; (a) CdS prepared from [Cd(EX)2];(b) CdS
prepared from [Cd(PiDT)2]; (c) CdS prepared from [Cd(MDTC)2].

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1
2
3
4
Fig.8UV-vis.absorption spectra of CdS nanostructures; (a) CdS nanostructures synthesized from
[Cd(EX)2]; (b)CdS nanostructures synthesized from [Cd(PiDTC)2] (c) UV-vis absorption spectra of
CdS nanostructures synthesized from [Cd(MDTC)2].
Fig.9 Schematic degradation of MB dye/ Ring cleavage.
5
Fig. 10 Methylene Blue.
6
7
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Fig. 11 Photo degradation of MB dye vs. time in the presence of CdS nano-photocatalysts
synthesized from different complexes: (a) Series 1 CdS nanostructures prepared from
[Cd(EX)2] ; (b) Series 2 CdS nanostructures prepared from [Cd(PiDTC)2]; (c) Series 3 CdS
nanostructures prepared from [Cd(MDTC)2]
10
Table Caption:
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Table1 Significant IR Peaks
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Table 1 Significant IR Peaks
ν
(O-H) in cm-1
ν
(C-N) in cm-1
Partial Double
(C-N) in cm-1
ν
(C-S) in cm-1
Sample Name
ν
3430
3431
3390
-
-
901
Potassium
Ethylxanthate
Piperazine1-
dithiocarbamate
Mopholine4-
dithiocarbamte
[Cd(EX)2]
1262
1259
1462
1417
1001
975
3437
3446
-
-
1027
992
1211
1222
1389
1462
[Cd(PiDTC)2]
[Cd(MDTC)2]
980

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DYPI 5559
Figures
S
Refluxing for
1 hour
KOH
+
CS2
Carbon
Disulphide
O
SK
OH
70o C
Ethanol
Potassium
Hydroxide
Potassium ethylxanthate
CdCO3
S
S
S
O
Cd
O
S
Cadmium (EX)2
Fig.1 Schematic synthesis route of potassium ethylxanthate and [Cd(EX)2]
X
X
00-50 C
CS2
NaOH
Stirring
N
N
H
Sodium
Hydroxide
Carbon
Disulphide
S
S
Na
CdCO3
S
S
S
X
N
Cd
N
X
S
X is O in Morpholine 4-Dithiocarbamate
X is N in Piperazine 1-Dithiocarbamate
Fig.2 Schematic synthesis route of [Cd(PiDTC)2] and [Cd(MDTC)2]

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O
O
Cd
O
S
S
S
S
S
S
S
S
Diethylenetriamine
199oC
NH2
NH2
Cd
O
NH
Intermediate Complex
Cadmium (EX)2
CdS Nanostructures
Fig.3 Schematic synthesis route of CdS nanostructures prepared from [Cd(EX)2]
X
X
N
N
NH2
Diethylenetriamine
199oC
S
S
S
S
S
S
S
S
Cd
NH
Cd
NH2
N
X
N
X
Intermediate Complex
CdS Nanostructures
X is N in Piperazine 1-Dithiocarbamate
X is O in Morpholine 4-Dithiocarbamate
Fig.4 Schematic synthesis route of CdS nanostructures prepared from [Cd(PiDTC)2] and
[Cd(MDTC)2]

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X
N
O
NH2
NH2
S
S
S
S
S
S
S
S
NH2
NH2
Cd
NH
Cd
O
NH
N
X
Intermediate Complex
Intermediate Complex
X= O in Morpholine 4-Dithiocarbamate
X= N in Piperazine 1-Dithiocarbamate
Fig.5 The proposed structures of intermediate complexes

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Fig.6 X-ray diffraction patteren of CdS nanoparticles prepared from different complexes;
(a) CdS prepared from [Cd(EX)2]; (b) CdS prepared from [Cd(PiDTC)2];
(c) CdS prepared from [Cd(MDTC)2]

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100 nm
100 nm
100 nm
Fig.7 TEM micrographs of CdS nanostructures; (a) CdS prepared from [Cd(EX)2];(b)
CdS prepared from [Cd(PiDT)2]; (c) CdS prepared from [Cd(MDTC)2]

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0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
(c)
(a)
(b)
300
350
400
450
500
550
600
Wavelength(nm)
Fig. 8 UV-vis absorption spectra of CdS nanostructures synthesized from(a) [Cd(EX)2];(b)
[Cd(PiDT)2] & (c) [Cd(MDTC)2]

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N
CH3
CH3
S
N
N
Cl
CH3
CH3
NH2
CH3
CH3
S
N
N
O
CH3
CH3
NH2
COH
N
SO3H
CH3
OH
OH
NH2
CH3
H
N
OH
SO3H
N
CH3
CH3
OH
SO3H
Fig.9 Schematic degradation of MB dye/ Ring cleavage
N
CH3
CH3
S
N
N
Cl
CH3
CH3
Fig. 10 Methylene Blue

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Fig. 11 Photo degradation of MB dye vs. time in the presence of CdS nano-photocatalysts
synthesized from different complexes: (a) Series 1 CdS nanostructures prepared from
[Cd(EX)2] ; (b) Series 2 CdS nanostructures prepared from [Cd(PiDTC)2]; (c) Series 3
CdS nanostructures prepared from [Cd(MDTC)2]

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Highlights
A facile solvothermal route to prepare CdS nanoparticles of various morphologies.
Simple & eficient way to control morphologies of CdS nanoparticles.
Morphology (nanorods to nanospheres) dependent photocatalytic application.

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X
N
O
Cd
O
Visible Light
Irradiation
S
S
Diethylenetriamine
S
S
S
S
S
S
Diethylenetriamine
199oC
Cd
199oC
N
X
e- + h+ + H2O
CdS Nanoparticles
Cd(MDTC)2
Cd(PiDTC)2
N
Cd(EX)2
CH3
CH3
S
N
N
Cl
CH3
CH3
MB dye
Degradation Pathway
OH
OH
NH2
CH3
H
SO3H
N
OH
SO3H
N
CH3
CH3
UV absorption profile of MB dye
0
min
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
15 min
30 min
45 min
60 min
75 min
OH
+
CO2 + H2O + SO42- + NH4
Degradation Products
450
500
550
600
650
700
750
Wavelength(nm)