Phase purification of Cu-S system towards Cu1.8S and its catalytic properties for a clock reaction

Article abstract of DOI:10.1039/c5ra17652b

Controlling the composition and crystal phase is an important issue to tune material physical/chemical properties. Herein, it was found that triphenyl phosphine (TPP) can be used as a phase transfer agent to transform CuS, Cu₃₉S₂₈ phases into pure low-sulfur Cu_1.8S phase. When mixed phase copper sulfides were reacted with triphenyl phosphine under suitable temperature, sulfur was extracted to produce the low-sulfur Cu_1.8S phase. It was also demonstrated that the Cu-S product can effectively catalyze a clock reaction between methylene blue and hydrazine in aqueous medium. In addition, the photothermal conversion properties of the Cu-S based products were studied. The results show that the purified Cu_1.8S materials show enhanced or similar properties than the original mixed-phase Cu-S products.

Full text of DOI:10.1039/c5ra17652b

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ARTICLE
Phase Purification of Cu-S System towards Cu S and its
1.8
Catalytic Properties for a Clock Reaction
Received 00th January 2015,
Accepted 00th January 2015
a
b, c, *
b
b
a
a,*
Yuanjun Liu, Guoxing Zhu,
Jing Yang, Chunlin Bao, Jing Wang, Aihua Yuan
Controlling the composition and crystal phase is an important issue to tune material physical/chemical properties. Herein, it
was found that triphenyl phosphine (TPP) can be used as a phase transfer agent to transform CuS, Cu39 28 phases into pure
DOI: 10.1039/x0xx00000x
S
www.rsc.org/
lowꢀsulfur Cu1.8S phase. When mixed phase copper sulfides were reacted with triphenyl phosphine under suitable
temperature, sulfur was extracted to produce the lowꢀsulfur Cu1.8S phase. It was also demonstrated that the CuꢀS product can
effectively catalyze a clock reaction between methylene blue and hydrazine in aqueous medium. In addition, the
photothermal conversion properties of the CuꢀS based products were studied. The results show that the purified Cu1.8
S
materials show enhanced or similar properties than the original mixedꢀphase CuꢀS products.
least nine kinds of different crystal phase with the varied x
2
5
Introduction
2
value in Cu2ꢀxS (x= 0ꢀ1) including Cu S (γꢀ and βꢀchalcocite),
2
6
27, 28
29, 30
Cu1.98S (djurleite), Cu1.8S (digenite),
and CuS (covellite),
Cu1.75S (anilite),
Metal chalcogenide semiconductor materials have been
intensively studied in recent years out of scientific interest and
because of their wide technological application.
3
1, 32
as shown in the Xꢀray diffraction
1
ꢀ3
pattern database. The energy band structure and
physical/chemical properties of Cu2ꢀxS are highly dependent on
the stoichiometric factor, 2-x. However, it is not always
straightforward for synthesizing a copper sulfide product with
targeting phase; usually, mixed phase copper sulfide products
are often obtained through usual synthesis strategies. Up to
date, some methods including phase transformation route have
been devoted for the preparation of copper sulfide products
For example, it was
demonstrated that Cu S and CuS can be obtained from the
With a solidꢀstate
annealing route, CuS also undergoes a reduction to tetragonal
Their
physical and chemical properties can be highly modified by
minute changes in their microscale morphology and size.
Besides morphology and size, chemical composition and crystal
phase are another two basic parameters for tuning their physical
or chemical properties through influencing the bonding
characteristic, vacancies, and so on. For examples, careful
tuning the oxygen stoichiometry in copper oxide materials can
induce the transferring of various superconducting, electronic,
4
ꢀ5
2
6, 33ꢀ35
with pure specific phase.
6
7
4
and magnetic states. FeSe at a very precise composition in
window of 50.6ꢀ51.0% Fe is superconducting, while NiAsꢀtype
FeSe with a nominally 1:1 of Fe to Se (42.0ꢀ50.5%) is not
3
6
freshly formed Cu
9
S
8
nanocrystals.
3
7
7
2
cuprous sulfide Cu S. Recently, Fang et al reported facile
superconducting. Hence, precise controlling and modulating
3
8
synthesis of Cu39
Alivisatos et al has demonstrated the temperatureꢀinduced
structural transꢀformations of Cu S nanorods from a low to a
high chalcocite structure and investigated their size dependent
S28 microcrystals via a solvothermal route.
the composition or crystal phase of metal chalcogenide
materials is of large scientific and technological importance.
The electrical conductivity breadth from metallic to
semiconducting to superconducting and the defect chemistry
owing to nonstoichiometry for copper sulfides render them
2
3
9, 40
phase transformation behaviour.
Zhong et al reported a
phase transformation process from rhombohedral Cu1.8S
8
ꢀ22
attractive for various applications.
Copper sulfides with
4
1
nanocrystals to hexagonal CuS clusters. In spite of these
valuable investigations, relative to highly studied PbS and CdS
microꢀ/nanoscale materials, copper sulfides have not been
extensively studied. In addition, as copper sulfide easily forms
different but close stoichiometric phases, controlling of copper
various Cu/S ratios have demonstrated great potential for wide
applications in fields such as solar cells, photoelectric
transformers,
electrocatalysts and photocatalysts.
nanoꢀswitches,
thermoelectric
materials,
2
3ꢀ24
The CuꢀS system has at
4
2ꢀ44
sulfide crystal phase with simple method is still a challenge.
Among the various Cu2ꢀxS materials, Cu1.8S, which is a
useful ꢀtype semiconductor with indirect bandgap of 1.5ꢀ1.6
eV, has got much attention due to its rich properties and
a.
School of Environmental and Chemical Engineering, Jiangsu University of Science
and Technology, Zhenjiang 212018, China. Email: aihuayuan@just.edu.cn
School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang,
p
b.
c.
2
12013, China, Email: zhuguoxing@ujs.edu.cn
State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing,
10093, China
14, 40, 45, 46
potential applications.
Cu1.8S is known to be used as
2
thermoꢀ or photoelectric transformers and highꢀtemperature
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thermistors. The higher copper deficiency in Cu1.8S material collected by centrifugation, washed with distilled water and
o
makes it show unique localized surface plasmon resonance absolute ethanol, and dried at 45 C under vacuum.
4
0
effect (LSPR). Due to the LSPR effect, Cu1.8S has shown
excellent photothermal conversion effect and would be used as
Phase transformation of copper sulfides to Cu1.8S phase
4
5ꢀ46
o
new type of photothermal agent.
Especially, it was also
Typically, 5 g of TPP was heated to 100 C in a 50 mL of threeꢀ
demonstrated that Cu1.8S with higher ion deficiency can be used
as catalyst inducing the formation of heterostructures.
necked flask and was kept at this temperature for 15 min with
1
4
stirring. 30 mg of copper sulfide sample (mixture of CuS and
o
In this study, a simple and low cost hydrothermal method
was developed for the synthesis of copper sulfide product. The
obtained product contains two kinds of copper sulfides (CuS
and Cu1.8S). Based on this, we described a new chemical
extraction route with triphenyl phosphine (TPP) as extraction
Cu1.8S, or Cu39
S
28) was then added. After reaction at 100 C for
2
h, the product was collected by centrifugation, washed with
o
chloroform and ethanol for several times, and dried at 45 C
under vacuum.
Characterization
agent. This extraction process can transform CuS, Cu39S
28
phases into pure lowꢀsulfur metastable rhombohedral phase
Cu1.8S. This chemistry has at least three important implications.
First, sulfurꢀrich copper sulfides can be chemically transformed
into Cu1.8S phase via TPP extraction of sulfur. This highlights
the possibility of precise Cu1.8S phase targeting with this route.
Secondly, impure samples contain mixtures of multiple copper
XRD patterns were recorded on an Xꢀray diffractometer
(
1
Bruker D8 Advance diffractometer) with Cu Kα radiation (λ =
.5406 Å) at a scanning rate of 5˚ min . Ultravioletꢀvisible
ꢀ1
(
2
UVꢀvis) spectroscopy measurements were performed on a UVꢀ
450 ultravioletꢀvisible spectrophotometer. The morphology
and micostructure analyses were conducted on Hitachi Sꢀ4800
field emission scanning electron microscope (SEM) and a JEMꢀ
sulfides including CuS, Cu1.8S, Cu39S28 can be purified by TPP
extraction of sulfur, with the final product exclusively being
metastable rhombohedral Cu1.8S phase. Third, it seems that the
Cu1.8S product obtained with purification route shows similar
properties to that of Cu1.8S sample obtained with direct
preparation route.
2
010 transmission electron microscope (TEM).
Catalytic properties
ꢀ5
In a typical reaction, 100 µL (~1×10 mol/L, about 17 µg/mL)
of copper sulfide aqueous dispersion was mixed with an 200 µL
of methylene blue (MB) aqueous solution (with concentration
of 5×10 mol/L) in a 1 cm quartz cuvette, and the volume of
the reaction system was added up to 3 mL with deionized
water. 100 µL of 2.5 M aqueous hydrazine hydrate solution was
ꢀ4
Experimental
Materials
CuCl
2 2
·2H O, thiourea, polyvinylpyrrolidone (PVP, K30, Mw = then added to the reaction mixture to induce the reaction. After
58000), ethylene glycol, triphenylphosphine, N, Nꢀdimethylꢀ addition of hydrazine hydrate solution, the blue color of MB
formamide (DMF), chloroform, and ethanol employed in this gradually disappeared. The reaction mixture regained its
research were analytical grade and used without further original blue shade just shaking the mixture in air for several
purification. Deionized water was used in the experiments.
seconds. For detecting the color change of the reaction system,
timeꢀdependent absorption spectra were recorded with a UVꢀ
visible spectrophotometer at room temperature.
Synthesis of mixed-phase copper sulfide products
2 2
In a typical synthesis, 1.36 mmol of CuCl ·2H O, 1.85 mmol of
thiourea, and 0.2 g of PVP (Kꢀ30) were dissolved in 18 mL of
ethylene glycol to obtain a clear solution. The solution was then
Measurement of photothermal conversion effect of the copper
sulfide materials
transferred into a 30 mL of Teflonꢀlined autoclave, sealed and heated For measuring temperature change due to the photothermal
o
at 180 C for 12 h and then cooled down to room temperature conversion effect of copper sulfide materials, 980 nm near
naturally. The final products were collected by centrifugation and infrared (NIR) laser was delivered through a quartz glass
washed with deionized water and absolute ethanol for several times. cuvette containing aqueous dispersion (1 mL with
o
The asꢀobtained products were then dried in a 45 C vacuum oven concentration of 0.03 mg/mL) of copper sulfide samples with
for further characterization. The sample contains mixed phase magnetic stirring. The light source is 0.5 W with a laser beam
copper sulfides, CuS and Cu1.8S.
diameter of 6 mm (Ningbo Ruanming Laser Technology Co.,
Ltd. China). A thermocouple with an accuracy of 0.5 C was
inserted into the aqueous dispersion of the tested samples for
o
Synthesis of Cu39
Cu39
S28 phase copper sulfide
S
28 phase sample was prepared according to a reported recording the change of realꢀtime temperature. The temperature
3
8
3 2 2
method. In a typical synthesis, 2 mmol of Cu(NO ) ·3H
O, 2 was recorded one time per 20 s.
mmol of thiourea, and 2.0 g of PVP were absolutely dissolved
in 20 mL of DMF. The obtained system was then stirred for Results and discussion
about 30 min to obtain a clear green solution, which was then
Synthesis and Characterization
transferred into a 30 mL Teflonꢀlined stainless steel autoclave,
o
In our study, TPP was used as the crystalꢀphase transform
agent. TPP is usually used as nanoparticle capping agent owing
sealed and heated at 120 C for 12 h. After cooling down to
room temperature naturally, the obtained Cu39S28 product was
t
o
2
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Cu
S
.8
No. 65-3561
CuS No. 26-0476
1
1
800
200
d)
1
c)
b)
600
a)
0
20
30
40
50
60
2Theta (degree)
Fig. 1 XRD patterns of a) the synthesized mixed phase sample containing CuS and
o
Cu1.8S and the products after treated by TPP for b) 0.5 h, c) 1 h, and d) 2h at 100 C. The
standard JCPDS XRD patterns for CuS (No. 65ꢀ3561) and Cu1.8S (No. 26ꢀ0476) are also
shown in the bottom.
Fig. 3 a) SEM, b) TEM, c) SAED pattern, and d) HRTEM images of the purified Cu1.8
S
its strong coordination ability of phosphorus atom, phosphorous product.
source for chemical synthesis. Especially, it is also used as a
chemical agent in the form of TPPꢀS complexes. The phase sulfide products during the phase transformation process.
transform process is simple. Direct heating of the copper sulfide Figure 2 shows the SEM and TEM images of the mixture phase
dispersion in TPP will induce the phase transform of copper copper sulfides. It can be seen that the original mixture phase
sulfides. Figure 1 shows the powder Xꢀray diffraction (XRD) copper sulfide product is composed of flowerꢀlike microꢀ
data for the purification process. It is clear that the original Cuꢀ spheres with size of 3ꢀ5 ꢁm (Figure 2a, b). The flowerꢀlike
S
products contain two kinds of copper sulfide phase, microspheres are assembled by sheetꢀlike units. Some irregular
hexagonal covellite CuS (JCPDS No. 65ꢀ3561) and particles are loaded on the flowerꢀlike microstructure,
rhombohedral digenite Cu1.8S (JCPDS No. 26ꢀ0476). After suggesting the mixture phase. TEM image shows similar results
o
treated with TPP at 100 C for 0.5 h, the XRD diffraction peaks (Figure 2c). Inset of Figure 2c shows the selected area electron
corresponding to hexagonal CuS decrease, suggesting the diffraction pattern (SAED). The pattern can be indexed into
transform process of CuS to Cu1.8S is conducted. With 2 h of CuS and Cu1.8S, although they have similar crystal plane
treatment, the obvious enhancement of the peaks at about 2θ = spacing. Two kinds of clear lattice fringes with different
4
2
6.2, 54.8°, and the absolute disappearing of the peak at about spacing in the highꢀresolution TEM indicate the high
θ = 47.9° indicate that pure phase Cu1.8S is obtained after this crystallinity and two different crystal phases involved in it
treatment. This result suggests that TPP can successfully extract (Figure 2d). The lattice fringe with spacing of 0.278 nm would
sulfer from sulfurꢀrich copper sulfide, CuS, forming the be indexed to (10 10) plane of Cu1.8S, while that of 0.198 nm
corresponding lowꢀsulfur compound, Cu1.8S phase.
can be attributed to (008) plane of CuS. After phase purification
We also investigate the morphology change of the copper with TPP, the morphology of the copper sulfide changed. The
assembled flowerꢀlike microspheres are broken, leaving
disorder sheetꢀlike units (Figure 3a, b). The corresponding
SAED pattern and HRTEM shows pure Cu1.8S phase with high
crystallinity (Figure 3c, d). The morphology change indicates
the chemical reaction between copper sulfide and TPP.
It was found that the formation of Cu1.8S phase by TPP
treatment is highly phaseꢀtargeting. Increasing the treatment
o
temperature to 200 C, the obtained product is still Cu1.8
S
phase. Interestingly, other copper sulfide phase, for example
28, can also be transferred into the rhombohedral Cu1.8
phase by this phase transform route. The corresponding results
are shown in Figure 4. Cu39 28 sample was synthesized
Cu39
S
S
S
according to a reported method. Although the XRD patterns are
difficult to distinguish owing to the relatively weak crystalline
and the close XRD patterns between Cu39S28 and Cu1.8S phase,
after TPP treatment, an obvious shift of the strongest peak is
clearly observed, suggesting the crystal phase transformation.
These results suggest that TPP can extract sulfur from
sulfurꢀrich copper sulfide, forming metalꢀrich Cu1.8S phase.
Fig. 2 a, b) SEM, c) TEM, and d) HRTEM images of the mixed phase copper sulfides.
Inset of c) shows the SAED pattern of the product.
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Catalytic properties
1200
It is known that nanoscale copperꢀbased compounds have very
Cu39S28
Cu1.8
51, 52
good catalytic performance.
To investigate the catalytic
S
properties of Cu1.8S products obtained from the purified
procedure, the reaction between methylene blue (MB) and
hydrazine in aqueous medium was conducted. The reaction
shows quite slow reaction rate if no any catalysts were
involved. With suitable catalysts, chemical oscillation
phenomenon between blue color MB and colorless
leucomethylene blue (LMB) can be observed with periodic
shaking. Although it was reported that some copperꢀbased
materials can effectively catalyze this reaction, CuO or Cu
9
6
3
00
00
00
0
b)
a)
2
0
30
40
50
60
2Theta (degree)
5
1, 53
nanoparticles did not show any catalytic effect for it.
Fig. 4 XRD patterns of a) the synthesized Cu39S28 product and b) that after treated by
TPP for 2 h at 100 C. The standard JCPDS XRD patterns for Cu39
Cu1.8S (No. 26ꢀ0476) are shown in the bottom.
o
In the presence of copper sulfide catalyst, hydrazine will
gradually reduce MB at room temperature, forming colorless
LMO (as shown above reaction scheme 1). While, upon further
S28 (No. 36ꢀ0380) and
This extract process is quite different from the previous
reported Cu(I) induced phase transformation route. In that
4
3
H
N
N
case, Cu(I) specie was found to induce Cu1.1S phase to Cu
1.1ꢀ
[
H]
O]
+
NH
+
S phase. It was proposed that a fraction of Cu ions from the
1
.5
S
N
N
S
N
[
solution enters the Cu1.1S lattice, matched by a transfer of
electrons from the solution. In our route, it seems that TPP
extract sulfur from sulfurꢀrich covellite CuS product, causing
the phase transformation. There are reports about crystal
+
Methylene blue ion
Leuco Methylene blue ion
Scheme 1. The chemical oscillation reaction based on methylene blue ions.
4
7ꢀ50
structure of hexagonal covellite CuS.
Studies have shown
shaking reaction system in air, the colorless LMO will be
oxidized again by air forming blue MB. The redox process
demonstrates a simple “clock reaction”, which provides an
engaging illustration of redox phenomena and reaction kinetics.
As shown in Figure 6, the original blue reaction solution
gradually becomes weak with the increasing of duration time.
With duration time of about 20 min, only the liquidꢀair
interface shows blue color, while the solution body becomes
colorless. This is reasonable since oxygen in air will oxidize
LMO. Further prolonging the duration time to 3 h, the air in the
sealed system is possibly exhausted, so the whole solution is
colorless. Once shaking the reaction system in air, blue color
quickly reappears.
that the valence of copper in covellite CuS is monovalent with
+
2ꢀ
ꢀ
+
ꢀ
2ꢀ 43, 47
formalism of (Cu ) (S )(S ) or (Cu ) (S )(S ).
Recent
3
2
3
2
experiments and calculations have put the valence of Cu
5
0
between 1 and 1.5 (1.33 for CuS from calculations). While, all
studies indicate that sulfur in covellite phase exists with various
valence or forms. Figure 5 shows the crystal structure
illustration of covellite CuS phase and digenite Cu1.8S. From
the structural point of view, it is important to note the
similarities of the Cu or S subꢀlattice between covellite and
digenite in the corresponding closeꢀpacked planes, i.e. (001)
and (10ꢀ1), respectively. It would make it easily to transfer
covellite CuS to digenite Cu1.8S under suitable reaction
conditions.
Based on the fact that MB exhibits an intense absorption
band in the region of 500ꢀ700 nm and LMB shows no
In our case, the extract route is possibly driven by the large
formation constant of the TPPꢀS complexes. The bonding of
sulfur and TPP would be stronger, which cause the following
reaction proceed.
CuS + TPP → Cu1.8S + TPPꢀS
In the phase transformation process, solid copper sulfide
reacts with liquid TPP causing the phase transformation. Thus
the reaction rate would be controlled by the solidꢀliquid
interface reaction.
Fig 6. Schematic representation of the “clock reaction” catalyzed by Cu1.8S, that is, blue
Fig. 5 Crystal structure illustration of covellite CuS and digenite Cu1.8S.
color fading and regeneration of MB.
4
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ln(A
t 0
/A ) (at peak of 664 nm) versus time is shown in Figure
8
b. The slope of the straight line gives the rate constant of the
a) 2
.4
ꢀ1
0
2
4
6
8
1
1
1
1
1
min
catalytic reaction, 0.0323 min for pure Cu1.8S. While, mixed
phase copper sulfide sample shows similar and relatively lower
rate constant, 0.0297 min . This indicates that the purified
procedure don’t change the catalytic activity of the copper
sulfide product. In addition, the Cu39S28 product shows the
poorest catalytic activity among the tested three samples. It is
proposed that the tiny composition difference and the different
crystal phase cause their different properties. Copper sulfides
with different phases have different copper and sulfur ions
arrangement in the crystal, which will cause the different
chemical surroundings for the copper or sulfur ions. This finally
induces the different catalytic or related properties.
We then proposed a possible catalytic principle for the
reaction. It is proposed that copper sulfide would promote the
electron transfer process from hydrazine to MB. During the
reaction, hydrazine and MB may be absorbed onto the copper
sulfide surface due to the reasonable affinity. It is believed that
hydrazine supplies electrons to MB via copper sulfide, causing
the generation of colorless LMB. Hydrazine transfers electrons
to Cu(I) to reduce it to Cu(0). Then, MB and dissolved oxygen
in the system oxidizes Cu(0) back to Cu(I). During this
process, MB was reduced forming colorless LMB. The
electronꢀtransfer processes can be supported by the redox
ꢀ1
1.6
0.8
0.0
0
2
4
6
8
28
3
4
5
6
8
8
8
8 min
2
40 320 400 480 560 640 720 800
Wavelength (nm)
b) 2.4
31 s
1
1
0
0
.8
.2
.6
.0
51
20 s
0
s
5
1
2
40 320 400 480 560 640 720 800
Wavelength (nm)
Fig 7. a) Absorption spectra for successive decolorization of MB and b) colour
regeneration catalyzed by Cu1.8S.
+
potential values of φ(N /N H ) = ꢀ1.16 V, φ(Cu /Cu) = 0.52 V,
φ(MB/LMB) = 1.08 V.
2
2
4
5
1, 54
In the reaction system, excess
absorption at this region, we monitored the process of the clock
reaction by a UVꢀvisible spectrophotometer. With the MB blue
color bleaching, a steady decrease of the absorbance of MB was
measured at same intervals, as shown in Figure 7a. It should be
noted that in the absence of copper sulfide catalyst, no such a
decrease in the absorbance of MB was observed in the same
experimental condition. Thus, the important role of the
synthesized copper sulfide product in the “clock reaction” is no
doubt concluded.
hydrazine in turn decreases the dissolved oxygen concentration
in water, which facilitates LMB formation. While, indeed,
detailed catalytic mechanism needs further study.
a)
Cu1.8
S
mixed Cu1.8S and CuS
Cu39S28
2.0
1.5
1.0
It seems that the synthesized Cu1.8S product has a strong
catalytic ability for the reduction of MB by hydrazine at room
temperature. We also investigated the catalytic activities of
mixed phase copper sulfides and Cu39
S
28 product. In contrast,
0.5
0.0
the catalytic activities of them are relatively low (Figure SIꢀ1,
SIꢀ2, see Supporting Information). After complete reduction of
MB, the solution containing colourless LMB can again
regenerate the blue color in the presence of small amount aerial
0
15
30
45
60
75
Time (min)
O
2
on shaking of the reaction mixture openly and so the
b)
Cu1.8
S
characteristic absorption band appears (shown in Figure 7b).
We then investigated the influence of various experimental
parameters on the reaction kinetics. It was found that without
hydrazine, the reaction cannot proceed. More hydrazine is
involved, the reaction rate is quickly. While, it seems that the
catalyst dosage don’t have obvious influence on the reaction
rate in our investigated range. In the presence of copper sulfide
catalysts, the plot of absorption factor as a function of time
0.0
0.5
mixed Cu1.8S and CuS
Cu39S28
-
-1.0
-1.5
-2.0
-2.5
ꢀkt
t 0
(Figure 8a) shows a profile of exponential equation, A = A e ,
0
15
30
45
60
75
which is consistent with a pseudoꢀfirstꢀorder reaction. Thus,
pseudoꢀfirstꢀorder reaction kinetics was applied for the
evaluation of catalytic activity in our case. The relation of
Time (min)
Fig 8. Plots of a) A
copper sulfides, Cu39
t
and b) ln(A
S
t o
/A ) of MB vs reaction time in the presence of mixed
28, and pure Cu1.8S.
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In addition, it is recently reported that CuꢀS system is a new Acknowledgements
promising semiconductor photothermal conversion platforms
The authors are grateful for financial support from National
Natural Science Foundation of China (No. 51203069,
with relatively high photothermal conversion efficiency, good
4
2
photostability, synthetic simplicity, low toxicity and low cost.
5
1102117, 21201010, 21203079), Jiangsu Natural Science
It can effectively induce temperature elevation under NIR
irradiation, which would provide a possible route for cancer
treatment.
Foundation (No. BK2012276), and Cultivating Project of
Young Academic Leader from Jiangsu University.
The NIR photothermal conversion property of the obtained
CuꢀS samples in the aqueous dispersions was then examined at
a fixed concentration of 0.03 mg/mL. The results are shown in
Figure 9. The pure water system was also tested for
comparison. It is obvious that, for the pure water, the NIR
irradiation (980 nm) caused a temperature increase of only
about 4 °C after 8 min. For the aqueous dispersion of CuꢀS
products, the NIR irradiation induced temperature elevation is
much higher than the pure water. For the mixtured sample with
Notes and references
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