Synthesis of nanostructured powders and thin films of iron sulfide from molecular precursors

Article abstract of DOI:10.1039/c8ra04917c

Iron(iii) xanthate single-source precursors [Fe(S₂COR)₃] (R = methyl, ethyl, isopropyl and 1-propyl) were used to deposit iron sulfide thin films and nanostructures by two simple, efficient and low-cost methods (spin coating and solid state deposition). The single-crystal X-ray structures of the iron(iii) n-propyl xanthate and iron(iii) iso-propyl xanthate have been determined. Thermogravimetric analysis (TGA) studies of the complexes shows that decomposition of the complexes produces iron sulfide, pyrite or trolite. The crystallinity of iron sulfide thin films and powder samples was studied using X-ray diffraction (XRD), and their morphology was studied by scanning electron microscopy (SEM).

Full text of DOI:10.1039/c8ra04917c

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PAPER
Synthesis of nanostructured powders and thin films
of iron sulfide from molecular precursors†
Cite this: RSC Adv., 2018, 8, 29096
b
Laila Almanqur,a Inigo Vitorica-yrezabal,a George Whitehead, a David J. Lewis
*
ab
*
and Paul O'Brien
Iron(III) xanthate single-source precursors [Fe(S2COR)3] (R ¼ methyl, ethyl, isopropyl and 1-propyl) were
used to deposit iron sulfide thin films and nanostructures by two simple, efficient and low-cost methods
(spin coating and solid state deposition). The single-crystal X-ray structures of the iron(III) n-propyl
xanthate and iron(III) iso-propyl xanthate have been determined. Thermogravimetric analysis (TGA)
studies of the complexes shows that decomposition of the complexes produces iron sulfide, pyrite or
trolite. The crystallinity of iron sulfide thin films and powder samples was studied using X-ray diffraction
(XRD), and their morphology was studied by scanning electron microscopy (SEM).
Received 8th June 2018
Accepted 5th August 2018
DOI: 10.1039/c8ra04917c
rsc.li/rsc-advances
A variety of methods have been used to prepare iron sulde
nanoparticles including hot injection20–22 and colloidal
methods,23 hydrothermal methods,24 and solvothermal
Introduction
Iron chalcogenides have attracted considerable attention over
the last decade, due to their interesting optical, electrical and
magnetic properties.1,2 Iron sulde is the most earth-abundant
chalcogenide mineral, and is used in several important appli-
cations, including batteries, catalytic processes and biomedical
appliances and is also a potentially useful material for
sustainable and inexpensive photovoltaics applications.3–5 It
has many potential advantages over other materials, including
its low cost, high abundance, negligible toxicity and unique
magnetic, electric and optical properties.6–9 Iron sulde crys-
tallises in many different phases; these include pyrite (cubic
FeS2), marcasite (orthorhombic FeS2), mackinawite (Fe1+xS),
troilite (FeS), pyrrhotite (Fe1ꢀxS), greigite (cubic spinel Fe3S4)
and smythite (Fe3+xS4).10–12 The optical, magnetic and electrical
properties of iron suldes vary according to the stoichiometric
ratio between the iron and sulfur atoms.13 Of these compounds,
cubic pyrite (FeS2) is of interest for its potential use as an
absorber material in photovoltaic and photo-electrochemical
applications because of its suitable band gap (0.80–0.95 eV)
and high absorption coefficient (ꢁ105 Mꢀ1 cmꢀ1) extending
over the visible energy range.14–18 The favoured phases for Li-ion
batteries are suggested to be troilite (FeS) and pyrrhotite
(Fe1ꢀxS). For supercapacitor applications, troilite (FeS) and
greigite (Fe2S3) are potential candidate materials.19
methods.25,26 Nanoscale iron sulde has been synthesized
with various morphologies by the decomposition of several
single source precursors such as iron alkyl dithiocarba-
mates,27,28 iron polysuldes, iron thiobiurets29 iron dieth-
yldithiophosphates,30
FeS
cubane
clusters,31
iron
thiosemicarbazones32 and iron alkyl xanthates.33 In addition,
a great deal of attention has been paid to the deposition and
characterization of iron sulde thin lms. Several deposition
techniques have been employed to deposit iron sulde thin
lms, including chemical bath deposition,34 chemical vapour
deposition,35 chemical bath deposition,36 metal–organic
chemical vapour deposition (MOCVD),37 and aerosol-assisted
chemical vapour deposition (AACVD).38–40
Herein we report the synthesis of tris (O-alkylxanthato)
i
n
iron(III) (alkyl Et, Me, Pr and Pr) complexes. These complexes
have been used for the deposition of iron sulde, troilite (FeS)
and pyrrhotite (Fe1ꢀxS) nanostructured materials, using
a simple, cheap and low temperature synthesis methods – spin
coating and solventless pyrolysis. These provide control over
nanocrystal size and morphologies by variation of temperature
and precursor structure.41,42
Experimental section
aSchool of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL,
UK. E-mail: paul.o'brien@manchester.ac.uk
Materials
Methanol (99.8%), 2-propanol (99.5%), n-propanol (99.9%),
potassium ethyl xanthogenate (96%), carbon disulde (low
benzene 99.9%), chloroform (99.8%), and iron(III) chloride
(99%) were all acquired from Sigma-Aldrich, and used without
further purication.
bSchool of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL,
UK. E-mail: david.lewis-4@manchester.ac.uk
† Electronic supplementary information (ESI) available: Crystal data for CCDC
1846996 and 1846997. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c8ra04917c
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Synthesis of molecular precursors
Synthesis of potassium methyl xanthate. Potassium methyl
xanthate was synthesised according to a method in the litera-
ture.46 In a typical reaction, KOH (5 g, 89.12 mmol) was added to
methanol (excess) and stirred. Thereaer, carbon disulde
(CS2) (6.78 g, 5.38 ml, 89.12 mmol) was added dropwise into the
mixture. A yellow precipitate started to form, which was then
ltered and recrystallised from acetone at room temperature
and dried in the air to give potassium methylxanthate (KS2-
COMe) (12.2 g, 93.5%). Mp: 83–88 ꢂC, elemental analysis for
C2H3KOS2 (%): calc: C, 16.44, H, 2.07, S, 43.77; K, 26.76; found:
C, 16.69; H, 2.01; S, 43.37; K, 27.13 FT-IR (nmax/cmꢀ1): 2989 (w),
2932 (w), 1445 (w), 1428 (s), 1185 (s), 1085 (s), 1038 (s), 944 (w).
1H NMR (400 MHz, D2O): d ppm 1.26 (s, 3H, CH3).
Synthesis of potassium isopropyl xanthate. Potassium iso-
propyl xanthate was synthesised by following the same method,
using isopropanol (80 ml) (13.9 g 89.4%). Mp: 135–140 ꢂC,
elemental analysis for C4H7KOS2 (%): calc: C, 27.59, H, 4.05, S,
36.72; K, 22.45; found: C, 27.61.; H, 3.97; S, 36.53; K, 22.29. FT-
IR (nmax/cmꢀ1): 2969 (m), 1459 (w), 1382 (s), 1181 (s), 1127 (s),
1
1045 (s), 900 (s). H NMR (400 MHz, D2O): d ppm 1.26 (d, 6H,
CH3), 5.45 (m, 1H, CH).
Synthesis of potassium n-propyl xanthate. Potassium n-
propyl xanthate was synthesised by following the same method,
using n-propanol (80 ml) (13.7 g, 88.1%). Mp: 127–130 ꢂC,
elemental analysis for C4H7KOS2 (%): calc: C, 27.59, H, 4.05, S,
36.72; K, 22.45; found: C, 27.73.; H, 4.00; S, 36.73; K, 22.65. FT-
IR (nmax/cmꢀ1, powder): 2968 (s), 2936 (w), 2873 (w), 1452 (s),
Fig. 1 X-ray single crystal structure of (a) [Fe(S2COiPr)3] and (b)
[Fe(S2COnPr)3]. Yellow spheres ¼ sulfur, orange spheres ¼ iron, red
spheres ¼ oxygen, grey spheres ¼ carbon.
1
1377 (w), 1270 (w), 1058 (s), 900 (s). H NMR (400 MHz, D2O):
d ppm 0.90 (t, 3H, CH3), 1.69 (m, 2H, CH2); 1.20 (t, 2H, CH2).
Synthesis of iron(III) methylxanthate, Fe[S2COMe]3 (1). An
aqueous solution of (FeCl3) iron(III) chloride (1.85 g, 11.41
mmol) (20 ml) was slowly added to a solution of ligand KS2-
COMe (5 g, 34.2 mmol) in distilled water (20 ml) while stirring. A
black precipitate formed. The obtained solution was stirred
constantly at room temperature for a further 10 min. The
ltered black precipitate was washed with distilled water twice
and dried under a vacuum overnight. The nal product was
Materials characterisation
Elemental analysis was conducted in the micro-analytical labora-
tory at the University of Manchester with a Carlo Erba EA 1108
elemental analyser. Thermogravimetric analysis (TGA) measure-
ments were recorded from 0 ꢂC to 600 ꢂC at 10 ꢂC minꢀ1 heating
rate under nitrogen, using a Seiko SSC/S200 TGA-DSC. Infrared
spectra (IR) were obtained using a Specac single reectance ATR
instrument (4000–400 cmꢀ1, resolution 4 cmꢀ1). Melting points
were obtained using a Barloworld SMP10 apparatus. Nuclear
magnetic resonance (NMR) was recorded using a 400 MHz Bruker
instrument. Mass spectra were recorded on Shimadzu Axima
Condence MALDI TOF mass spectrometer. Powder X-ray
diffraction (p-XRD) measurements were carried out by using
a Bruker D8 Advance and a Bruker Xpert diffractometer, utilising
ꢂ
˚
Cu-Ka radiation (1.54 A). The samples were scanned between 20
and 80ꢂ, with a step size of 0.02ꢂ 2q. Scanning electronic micros-
copy (SEM) images were obtained using a Philips XL30 FEG SEM.
Inductively coupled plasma optical emission spectroscopy (ICP-
OES) was carried out with a Perkin-Elmer Optima 5300 DV
instrument. Raman spectra were recorded using a Renishaw 1000
microscope system equipped with laser excitation of 514 nm.
Single crystal X-ray diffraction data for compounds were collected
on a dual source Rigaku FR-X rotating anode diffractometer, using
an MoKa wavelength at 150 K, and reduced using a CrysAlisPro
171.39.30c.43 The structure was solved and rened using Shelx-
2016, implemented through Olex2 v1.2.9.44,45
Fig. 2 Thermogravimetric analysis (TGA) profiles of complexes [Fe(S2-
COMe)3] (1), [Fe(S2COEt)3] (2), [Fe(S2COiPr)3] (3), [Fe(S2COnPr)3] (4).
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Synthesis of iron(III) n-propylxanthate, Fe[S2COnPr]3 (4).
Precursor (4) was synthesised by the same method as precursor
(1), using potassium n-propyl xanthate. The nal product was
a shiny black solid precipitateꢂ. The complexes were recrystal-
lized from chloroform at ꢀ20 C. The yield was (4.1 g 92.9%).
Mp: 75–80 ꢂC, elemental analysis calc. C, 31.25; H, 4.59; S, 41.63;
a shiny black solid. Yield: (4.29 g 85.8%). Mp: 252–254 ꢂC,
elemental analysis: found: C, 19.24%; H, 3.07%; S, 50.56%; Fe,
13.56%; calc. C, 19.13%; H, 2.4%; S, 50.0%; Fe, 13.56%. IR (nmax
/
cmꢀ1, powder): 2942 (w), 1436 (s), 1233 (s), 1161 (s), 1026 (s), 927
(s). ES+ (m/z): [M + H]+ 377.8.
Synthesis of iron(III) ethylxanthate, Fe[S2COEt]3 (2).
Precursor (2) was synthesised by the same method of synthesis
a precursor (1) using potassium ethylxanthate. The product
formed was a black solid. Yield: (4.15 g 96.5%). Mp: 108–112 ꢂC,
elemental analysis: found: C, 25.15%; H, 3.54%; S, 44.46%; Fe,
Fe, 12.12; found: C, 31.05; H, 4.52; S, 41.35; Fe, 11.87%. IR (nmax
/
cmꢀ1): 2976 (w), 1340 (s), 1081 (s), 1233 (s), 900 (s). ES+ (m/z):
[M + H]+ 461.9.
Deposition of thin lms by spin coating. The deposition of
iron sulde thin lms was carried out on glass substrates using
precursors (1 to 4) and spin coating (Ossila, 24 V DC, 2.01 A). In
a typical deposition process, 0.125 g of precursor was dissolved
in 0.5 ml of chloroform. Then, 100 mL of precursor solution was
deposited dropwise onto the glass substrate centre by the use of
a micropipette. The rotation speed rate of the spin coater was
set at 1400 rpm for 30 s. Once the process was complete, the
coated substrates were le to dry for a few minutes at room
temperature. Finally, the lms were placed into a tube furnace
and heated at different temperatures for 60 min, under an inert
atmosphere.
13.01%; calc. C, 25.8%; H, 3.6%; S, 45.8%; Fe, 13.3%. IR (nmax
/
cmꢀ1, powder): 2978 (w), 1743 (s), 1442 (w), 1366 (s), 1234 (s),
1107 (s), 997 (s). ES+ (m/z): [M + H]+ 418.8.
Synthesis of iron(III) isopropylxanthate, Fe[S2COiPr]3 (3).
Precursor (3) was synthesised by the same method – of
a precursor (1) using potassium iso-propyl xanthate. The nal
product was a shiny black solid precipitate. The complexes were
ꢂ
recrystallized from chloroform at ꢀ20 C. The yield was (3.8 g
86.1%). Mp: 83–88 ꢂC, elemental analysis: Calc. C, 31.25; H,
4.59; S, 41.63; Fe, 12.12%; found: C, 30; 89; H, 4.54; S, 40.88; Fe,
11.73%. IR (nmax/cmꢀ1, powder): 2976 (w), 1340 (s), 1081 (s),
1233 (s), 900 (s). ES+ (m/z): [M + H]+ 461.9.
Fig. 3 Powder X-ray diffraction (p-XRD) patterns of the iron sulfide thin films obtained by spin coating [Fe(S2COMe)3] (a), [Fe(S2COEt)3] (b),
[Fe(S2COiPr)3] (c) and [Fe(S2COnPr)3] (d) followed by annealing under nitrogen at 400–500 ꢂC for 60 min. The black sticks represent hexagonal
troilite phase (FeS). (ICDD: 01-075-2165).
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toluene. These complexes were stored at ꢀ20 ꢂC to avoid
premature decomposition.
Single-crystal X-ray structure
The single crystal X-ray structure of iron(III) isopropylxanthate,
Fe[S2COiPr]3 (3) and iron(III) n-propylxanthate, Fe[S2COnPr]3 (4)
are shown in Fig. 1. Complexes (3) and (4) crystallised in the
monoclinic system with space group P21/c and P21/n respec-
tively. The iron ion is coordinated to six sulfur atoms from the
three bidentate xanthate ligands in a distorted octahedral
environment.
The Fe–S bond length ranges in complex (3) are 2.29(8)–
˚
2.30(7) A which is slightly longer than those for complex (4)
˚
which is in range of 2.2931–2.3162 A. The Fe–S bond length
obtained from both complexes is considerably closer to the
˚
distance of 2.3083–2.3263 A reported previously for single
crystal X-ray data of tris-(ethylxanthate) iron(III).47 The rene-
ment data is given in ESI Table S1.† Bond lengths and angles are
reported in ESI Table S2 and S3.†
Thermogravimetric analysis (TGA)
ꢂ
Thermal analysis of all complexes was performed up to 600 C
under a nitrogen atmosphere. The thermogram for complexes –
[Fe(S2COEt)3] (2), [Fe(S2COiPr)3] (3) and [Fe(S2COnPr)3] (4) –
show decomposition occurs through two steps, as shown in
Fig. 2. These complexes exhibited approximately similar TGA
proles with a rapid mass loss within the temperature range of
ꢂ
ꢂ
120 to 300 C, and gradual mass loss between 320 to 500 C.
[Fe(S2COMe)3] (1) decomposed in three steps, with the rst step
ꢂ
between 100 to 130 C, and second and nal steps similar to
complexes (2–4). TGA results of the nal residues are compiled
in ESI Table S4.† All four complexes gave nal solid residue
amounts that matched with the calculated value for FeS2 or FeS.
The complexes from (1) to (4) decomposed rstly to give FeS2;
ꢂ
above 350 C FeS is obtained from loss of sulfur.
Deposition of thin lms by spin coating
Iron sulde precursors (1–4) were deposited on glass substrates
by spin coating, using chloroform as solvent. Films of the
precursors were then annealed at different growth tempera-
tures, between 300 to 500 ꢂC, in a furnace tube under N2 for
60 min. The resulting thin lms of iron suldes were uniform
and black in colour and were characterised by p-XRD and SEM.
The p-XRD patterns of thin lms prepared from a chloro-
Fig. 4 SEM images of iron sulfide nanoparticles by spin coating method
from [Fe(S2COMe)3] (1a) at 400 ꢂC and (1b) at 500 ꢂC, [Fe(S2COEt)3] (2a)
at 400 ꢂC and (2b) at 500 ꢂC, Fe(S2COiPr)3] (3a) at 400 ꢂC and (3b) at
500 ꢂC and [Fe(S2COnPr)3] (4a) at 400 ꢂC and (4b) at 500 ꢂC.
Solid state pyrolysis of complexes. The solid precursor 0.4 g form solution of [Fe(S2COMe)3], (1) [Fe(S2COEt)3] (2), [Fe(S2-
was placed in a ceramic boat and annealed in a tube furnace at COiPr)3] (3) and [Fe(S2COnPr)3] (4) and annealed at three
a temperature, based on TGA decomposition data for 1 h under different temperatures (300, 400 and 500 ꢂC) were recorded. The
inert atmosphere.
XRD pattern of iron sulde thin lms annealed at 400 and
500 ꢂC corresponded to hexagonal troilite (FeS, ICDD no: 01-
075-2165) Fig. 3. The diffraction peaks could be assigned to the
(110), (201), (114), (107) and (008) planes. The p-XRD pattern of
Results and discussion
i
The four tris(O-alkylxanthato) iron(III) (alkyl ¼ Me, Et, Pr and thin lm of [Fe(S2COMe)3] (1) annealed at 300 ꢂC exhibited
nPr) complexes, [Fe(S2COMe)3] (1), [Fe(S2COEt)3] (2), [Fe a pure phase hexagonal troilite (FeS) (ESI Fig. S1†) No peaks
(S2COiPr)3] (3) and [Fe(S2COnPr)3] (4) were synthesised by were observed at a growth temperature below 400 ꢂC when
metathesis of iron(III) salts in water. All complexes were soluble precursor [Fe(S2COEt)3] (2) was used. The p-XRD patterns of
in common organic solvents such as chloroform, THF and thin lms deposited at 300 and 350 ꢂC from a chloroform
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Fig. 5 The powder X-ray diffraction (p-XRD) patterns of the iron sulfide nanostructure obtained by pyrolysis method [Fe(S2COMe)3] (a),
[Fe(S2COEt)3] (b), [Fe(S2COiPr)3] (c) and [Fe(S2COnPr)3] (d) at temperature between 400 and 500 ꢂC for 60 min. The black sticks represent
hexagonal pyrrhotite (Fe1ꢀxS) phase (ICDD no: 00-022-1120).
solution of [Fe(S2COiPr)3] (3) [Fe (S2COnPr)3] (4) show a similar spherical crystallites in the size range of 260–300 nm (ESI
trend to that observed from thin lms deposited at 300 ꢂC from Fig. S4†). At 400 and 500 ꢂC clusters of crystallites with an
complex (1) (ESI Fig. S2 and S3†). No crystalline deposition average size of 200–250 nm (Fig. 4(1a) and (1b)) were apparent.
products were observed below 350 ꢂC. It is clear that as The SEM images of iron sulde thin lms from [Fe(S2COEt)3] (2)
annealing temperature increases that the peaks grow sharper as at 400 and 500 ꢂC are shown in Fig. 4(2a) and (2b) respectively.
evidenced by a reduction of the full width at half maximum The morphology of the sample growth at 400 ꢂC exhibited fairly
(FWHM); this generally indicates that the material becomes uniform cluster like crystallites, consisting of spherical nano-
more microcrystalline according to the Scherrer equation.
particles with open pores. At 500 ꢂC, cluster-like crystallites
Energy dispersive X-ray (EDX) spectroscopy of the iron consisting of irregular nanoparticles were obtained. SEM
sulde thin lms showed an approximately 1 : 1 ratio of Fe to S, images of iron sulde thin lms derived from (3) at 300 ꢂC show
consistent with troilite. The results are presented in ESI Table uniform cluster-like crystallites, as in ESI Fig. S5.† In contrast,
S5.†
the lms deposited at 400 ꢂC consist of smaller individual
The surface morphology of iron sulde thin lms derived spherical crystallites with a size range of 140–180 nm, as in
ꢂ
from pyrolysis of precursors (1–4) was studied using SEM. The (Fig. 4(3a)). The lms deposited at 500 C show plate-like crys-
SEM images obtained from an iron sulde thin lm derived tallites with an average size of 250–300 nm Fig. 3(3b). SEM
from precursor (1) and deposited at 300 ꢂC exhibited pseudo images of iron sulde thin lms from (4) displayed the growth
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calculated using the Scherer equation (ESI Table S6†). The
average crystallite size of iron sulde from complex (1) at
growth temperature of 400 ꢂC was 22.3 ꢃ 2.6 nm. Whereas the
crystalline obtained from growth temperature of 500 ꢂC has an
estimated diameter of 28.6 ꢃ 1.6 nm the observed decrement
in crystalline size with temperature indicated the inuence of
temperature. ICP-OES and EDX spectroscopy of iron sulde
samples conrmed the phase obtained from samples at high
temperature of 500 ꢂC is pyrrhotite Fe1ꢀxS summary of results
are shown in (ESI Table S7 and S8†). In addition, Raman
spectroscopy conrmed the formation of pyrrhotite Fe1ꢀx
S
Fig. 6 Raman spectra of hexagonal pyrrhotite phase (Fe1ꢀxS) from
complexes [Fe(S2COMe)3] (a), [Fe(S2COEt)3] (b), [Fe(S2COiPr)3] (c) and
[Fe(S2COnPr)3] (d) at 400 and 500 ꢂC.
of randomly shaped crystallites at 350 ꢂC (ESI Fig. S6†). The lm
growth at 400 ꢂC showed a cluster of densely packed crystallites
Fig. 4(4a), whereas a ower-like cluster were observed when
lms were deposited at 500 ꢂC, as shown in Fig. 4(4b). In
summary, the obtained images of the prepared thin lms
exhibited different sizes and morphologies. The SEM images of
lms deposited from all precursors show that the morphology
of iron sulde thin lms is dependent on the growth
temperature.
Solid state thermolysis of complexes
Solventless pyrolysis was employed for synthesis of iron
sulde crystallites using iron alkyl xanthates complexes (1–4).
The solid complexes were decomposed under a nitrogen
atmosphere in a tube furnace in the temperature range 300–
ꢂ
500 C for 60 min. The p-XRD patterns of the iron sulde ob-
tained from all four precursors [Fe(S2COMe)3] (1), [Fe(S2-
COEt)3] (2), [Fe(S2COiPr)3] (3) and [Fe(S2COnPr)3](4), at 400 and
ꢂ
500 C as shown in Fig. 5(a)–(d). The results show the forma-
tion of a pure hexagonal pyrrhotite (Fe1ꢀxS) phase (ICDD no:
00-022-1120). Reections in the powder pattern corresponding
to the (100), (101), (102), (110) and (201) planes of pyrrhotite
(Fe1ꢀxS) were dominant in the sample obtained from all
precursors. The XRD patterns obtained from the complexes
[Fe(S2COiPr)3] (3) and [Fe(S2COnPr)3] (4) gave a pure pyrrhotite
(Fe1ꢀxS) at all growth temperatures of 300, 400 and 500 ꢂC,
while [Fe(S2COMe)3] (1) and [Fe(S2COEt)3], (2) gave a pure
phase at high temperatures of 400 ꢂC and 500 ꢂC. However, the
XRDꢂ patterns obtained at a growth temperature of 300 and
350 C from the complex [Fe(S2COMe)3] (1) and [Fe(S2COEt)3]
(2), respectively show that some additional peaks corre-
sponded to cubic pyrite (FeS2) (ICDD no: 01-071-0053) (deno-
ted by the symbol*) (ESI Fig. S7 and S8†). The average
crystallites size of iron sulde is affected by growth tempera-
ture. The average crystallite size of iron sulde from precursor
Fig. 7 SEM images of iron sulfide nanoparticles from solventless
pyrolysis of [Fe(S2COMe)3] (1a) at 400 ꢂC and (1b) at 500 ꢂC, [Fe(S2-
COEt)3] (2a) at 400 ꢂC and (2b) at 500. [Fe(S2COiPr)3] (3a) at 400 ꢂC and
(1) to (4) at two different temperatures 400 and 500 ꢂC were (3b) at 500 ꢂC and [Fe(S2COnPr)3] (4a) at 400 ꢂC and (4b) at 500 ꢂC.
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with three vibration mode observed at wavenumbers of 214,
284 cmꢀ1 and 399 cmꢀ1 for all complexes (1–4).
References
Our results are in good agreement with that reported previ-
ously for iron sulde pyrrhotite.48–50 The Raman spectra of
pyrrhotite obtained from the pyrolysis of complexes (1–4) are
presented in Fig. 6 and ESI Fig. S11.†
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ꢂ
SEM images of the iron sulde crystallites growth at 400 C
and 500 ꢂC derived from the thermolysis of complex (1) are
presented in Fig. 7. The morphology of crystallites at growth
temperatures of 300 ꢂC (ESI Fig. S12†) and 400 ꢂC showed
clusters of densely packed crystallites, whilst hexagonal crys-
ꢂ
tallites were observed at a growth temperature of 500 C. SEM
images from the pyrolysis of precursor [Fe(S2COEt)3] (2) at
300 ꢂC (ESI Fig. S13†) and 400 and 500 ꢂC are shown in Fig. 7. At
all growth temperatures of 300–500 ꢂC, regular spherical-like
crystallites were observed. SEM images of iron sulde crystals
grown from the pyrolysis of [Fe(S2COiPr)3] (3) and [Fe(S2-
COnPr)3] (4) exhibited similar morphologies with spherical-like
crystals observed and with considerable variation in particle
size as shown in Fig. 7. The morphology of crystallites obtained
from complexes (1–4) was clearly dependent on the temperature
and the type of precursor.
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Conclusion
In summary, a series of iron alkyl xanthate complexes,
including [Fe(S2COMe)3] (1) [Fe(S2COEt)3] (2) [Fe(S2COiPr)3] (3)
and [Fe(S2COnPr)3] (4) have been successfully synthesised, using
a single-source route. The X-ray crystal structures of [Fe(S2-
COiPr)3] (3) and [Fe(S2COnPr)3] (4) have been determined. These
four complexes were used for the deposition of iron sulde
crystallites. Two simple methods have been described for the
growth of iron sulde nanocrystals which are spin coating and
solventless pyrolysis methods. Different deposition parameters
such as deposition method, deposition temperature and
precursor type were investigated in this study. The deposited
iron sulde phases and the morphology of iron sulde crystal-
lites were signicantly inuenced by the deposition method
used. p-XRD results revealed the formation of troilite when
a spin coat-annealing method was used while iron sulde
pyrrhotite Fe1ꢀxS was mainly formed when the solventless
pyrolysis method was used. Both methods are promising for the
low temperature production of iron sulde materials with
control of the crystalline phase produced.
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