On-site detection of phosgene agents by surface-enhanced Raman spectroscopy coupled with a chemical transformation approach

Article abstract of DOI:10.1002/jrs.4780

Phosgene and its analogs are greatly harmful to the public health, environmental safety and homeland security as widely used industrial substances with extremely high toxicity. In order to rapidly evaluate the emergency risk caused by these chemicals, a new highly sensitive method based on surface-enhanced Raman spectroscopy (SERS) technique for measurement of phosgene agents was developed for the first time. Coupled with a chemical transformation approach, the highly toxic phosgene was conveniently converted to a SERS-sensitive probe, i.e. iodine (I₂), with low toxicity or non-toxicity. The characteristic SERS peak in 459 cm^-1 was used for quantitation and was presumed as a formation of triiodide anion (I₃^-), which was induced in an iodide (I^-)-aggregation Au NPs system. The total measurement can be completed in ~20 min with the limits of detection of ~60 μg/l (phosgene) and ~30 μg/l (diphosgene), respectively, on a portable Raman spectrometer. This work is the first report of SERS measurement on phosgene and diphosgene in a quantitative level. This method is expected to meet the requirements of on-site detection of phosgene agents, promote emergency responses and raise more opportunities for the portable SERS applications. A sensitive surface-enhanced Raman spectroscopy method for measurement of phosgene agents with a chemical transformation approach was reported for the first time. With the transformed product iodine, a more stable triiodide anion was formed in an iodide-aggregated Au nanoparticles system appeared as a characteristic ultraviolet-visible absorption peak at 352 nm and a surface-enhanced Raman spectroscopy peak of 459 cm^-1. Three phosgene agents exhibit different reaction rates.

Full text of DOI:10.1002/jrs.4780

Research article
Received: 7 March 2015
Revised: 30 July 2015
Accepted: 31 July 2015
Published online in Wiley Online Library: 20 September 2015
(wileyonlinelibrary.com) DOI 10.1002/jrs.4780
On-site detection of phosgene agents by
surface-enhanced Raman spectroscopy coupled
with a chemical transformation approach
Haiyue Gao, Jianfeng Wu, Yingjie Zhu, Lei Guo* and Jianwei Xie*
Phosgene and its analogs are greatly harmful to the public health, environmental safety and homeland security as widely used
industrial substances with extremely high toxicity. In order to rapidly evaluate the emergency risk caused by these chemicals, a
new highly sensitive method based on surface-enhanced Raman spectroscopy (SERS) technique for measurement of phosgene
agents was developed for the first time. Coupled with a chemical transformation approach, the highly toxic phosgene was conve-
niently converted to a SERS-sensitive probe, i.e. iodine (I
2
), with low toxicity or non-toxicity. The characteristic SERS peak in
À1
À
4
59 cm was used for quantitation and was presumed as a formation of triiodide anion (I
3
), which was induced in an iodide
À
(I )-aggregation Au NPs system. The total measurement can be completed in ~20min with the limits of detection of ~60μg/l
(phosgene) and ~30μg/l (diphosgene), respectively, on a portable Raman spectrometer. This work is the first report of SERS mea-
surement on phosgene and diphosgene in a quantitative level. This method is expected to meet the requirements of on-site de-
tection of phosgene agents, promote emergency responses and raise more opportunities for the portable SERS applications.
Copyright © 2015 John Wiley & Sons, Ltd.
Additional supporting information may be found in the online version of this article at the publisher’s web site.
Keywords: phosgene; SERS; chemical transformation approach; iodine; triiodide
formed hydrolyzed products triggered the second damages, e.g.
the acidosis induced by hydrochloric acids. Up to now, no antidote
Introduction
Phosgene (carbonyl chloride, COCl
substance employed in large quantities as a highly reactive halo-
genation and acylation agent in industry synthesis. Diphosgene
2
) is an important industrial
was discovered against the damage of phosgene. Therefore, on-site
detection and rapid measurement of phosgene agents should
arouse first and vital attention to ensure the prompt and accurate
emergency response.
2 3 2 2 4
(trichloromethyl chloroformate, ClCO CCl , C O Cl ) has a similar
chemical property but is more suitable for main uses in the labo-
ratory. These two industrial substances are ultrahigh toxic and
have been classified as the choking chemical warfare agents sev-
Over the past decades, several on-site detection methods for
phosgene agents have been established, including mobile gas
[
7,8]
[9,10]
chromatography,
ion mobility spectrometry,
fluorescence
[1]
eral decades before. Triphosgene (bis(trichloromethyl) carbon-
ate, CO(OCCl ) , C O Cl ), another compound related to
spectroscopy, especially fluorescence resonance energy transfer
[
3,11,12]
[13,14]
3
2
3
3
6
(FRET),
and electrochemical methods.
Although these
phosgene, which is used as a substitute of phosgene due to its
methods are simple, sensitive and easy-to-use, they still have some
disadvantages or inconvenience. For example, ion mobility spec-
trometry and FRET methods sometimes offered false-positive
[
2,3]
good stability and phosgene-alike reactivity,
also has a poten-
tial risk when it decomposes into phosgene under some certain
conditions. The chemical structures of all three phosgene agents
are shown in Fig. 1. Misuses or leakages of phosgene agents have
attracted much attention from the industry and the whole
[
2]
responses. The sensitivity and efficiency of FRET methods are of-
ten limited by the interference from the overlap between the donor
[
3]
emission and its acceptor.
[4]
society. In 2004, a serious triphosgene leakage accident oc-
curred in Fuzhou City (Fujian province, China). The injury symp-
toms appeared 4 h after the inhalation exposure, and then one
death and 260 injuries were caused within 1 h. (Figure 1)
Surface-enhanced Raman spectroscopy can implement trace de-
tection in aqueous solutions and provide the characteristic molecu-
lar vibration rotation fingerprint information. With a portable
Phosgene agents are severe lung irritants, they can cause pulmo-
nary edema, following asphyxia, and even death. The permissible
exposure limit dose of phosgene is 0.1mg/l, and the immediate
*
Correspondence to: Jianwei Xie and Lei Guo, State Key Laboratory of Toxicology
and Medical Countermeasures and Laboratory of Toxicant Analysis, Beijing
Institute of Pharmacology and Toxicology, Academy of Military Medical
Sciences, Beijing 100850, China.
[
5]
danger to health and life limit dose is 2 mg/l. In general, the hu-
man lung can be damaged with more than 30 mg/l phosgene ex-
posure, and a fatal lung edema appeared with a dose higher than
E-mail: xiejw@bmi.ac.cn; guolei@bmi.ac.cn
[6]
3
00 mg/l. A common lung injury hypothesis is believed that the
State Key Laboratory of Toxicology and Medical Countermeasures and
Laboratory of Toxicant Analysis, Beijing Institute of Pharmacology and
Toxicology, Academy of Military Medical Sciences, Beijing 100850, China
acylation reaction rapidly occurred between phosgene and
amino-, thiol- and hydroxyl- groups in the lung tissues, and the
J. Raman Spectrosc. 2016, 47, 233–239
Copyright © 2015 John Wiley & Sons, Ltd.

H. Gao et al.
Preparation of gold nanoparticles-based SERS substrate
The gold nanoparticles (Au NPs) were synthesized according to a
[
15]
typical citrate reaction method. An aliquot of 100 ml chloroauric
acid solution at 100 mg/l was added to a 250 ml round-bottom
flask, which connected with a reflux condensation. The solution
was heated in oil bath with continuous stirring at 1500 r/min until
stable reflux occurred. An aliquot of 850 μl sodium citrate at
Figure 1. The chemical structures of all three phosgene agents.
Raman spectrometer, the surface-enhanced Raman spectroscopy
1% (w/v) ratio was then rapidly added into the chloroauric acid so-
(
SERS) method can be evolved as a useful on-site analytical
[15,16]
lution. After a few minutes, the color of solution was turned from
dark red into violet color or blue. A continued heating and stirring
was held for 40min, then the solution was cooled to room temper-
ature, and the Au NPs were generated. The shapes of Au NPs are
round, with an average diameter from 50 to 52nm, which is calcu-
tool.
However, because phosgene can be easily decomposed
in the aqueous solution and no strong Raman scattering formed
due to its simple molecular structure even in the case of adsorption
onto the surface of nanoparticles, it is impossible to directly mea-
sure phosgene itself. It may be one reason that there is no SERS re-
port on phosgene so far. In order to address the previous issues and
meet the needs of on-site measurement, here we developed a
novel but indirect strategy for phosgene detection, in which we
use potassium iodide (KI) to promote more Raman ‘hot spots’ and
apply a chemical transformation to converse the highly toxic phos-
[
16]
lated from a published equation according to the UV–Vis absor-
bance band at 530–532 nm and confirmed with transmission
electric microscopy measurement.
To obtain the Au NPs-based SERS substrate, the Au NPs solution
of 2 ml was centrifuged at 5000 r/min for 5 min, then re-dissolved in
ultrapure water of 200μl; different kinds of potassium salt of 40 μl
at 50 mmol/l was then added as an aggregating agent, and the
color of the whole solution was shown as middle violet. The aggre-
gated Au NPs as a SERS substrate can be applied to the direct detec-
gene into the SERS-sensitive Raman probe (iodine, I
icity or non-toxicity. The whole processes can be completed in
20 min. The method is simple and practical, providing a new
2
) with low tox-
~
way for the detection of important threatened chemical substances
that cannot be directly measured by SERS, and thus is promising for
the practical countermeasures in potential public health threat, en-
vironmental pollution or terrorist attacks.
2
tion of converted product, I .
Chemical transformation of phosgene or diphosgene to iodine
For the measurement of phosgene and diphosgene, a chemical
transformation approach was employed. According to the
equations 1 and 2 in Fig. 2, phosgene and diphosgene can be
quantitatively transformed to iodine according to a strict stoichio-
metric ratio at room temperature.
Experimental
Material and instrument
Phosgene was made in-house under safe and strict protection. Di-
phosgene was obtained from the Research Institute of Chemical De-
fense (Beijing, China). Triphosgene was purchased from Alfa Aesar
(
MA, USA). I was obtained from Beijing Chemical Reagent Company
2
(Beijing, China) and was re-crystallized before use. Sodium iodide
(
NaI), potassium iodide (KI) and other chemicals were purchased
from Sinopharm Chemical Reagent Co. Ltd. (Beijing, China). All
chemicals were of analytical grade or better. Unless noted, all solu-
tions were prepared in ultrapure water, which was generated from
a Milli-Q A10 water purification system (Millipore, MA, USA).
Figure 2. The reaction equations of phosgene and diphosgene with
sodium iodide.
To obtain a stock solution of I at 16 mg/l, phosgene of 16 mg/l or
2
The SERS spectra were collected on a portable Raman spectrom-
eter (i-Raman, B&W TEK Inc., DE, USA) equipped with a video micro-
scope sampling system (BAC151A, B&W TEK Inc.). The laser
excitation wavelength was 785 nm, and the accumulation time of
Raman spectra was 10s with the averaged data for three scans.
The laser power was set at 180 mW unless otherwise noted.
Ultraviolet-visible absorption (UV–Vis) spectrometric measure-
ments were performed on a Cary 300 double-beam UV–Vis spec-
trometer (Varian Inc., CA, USA). The zeta potential and particles
diameter were obtained by a Zetasizer μV light scatter detector
diphosgene of 8 mg/l was injected into an acetone solution of NaI
with the concentration of 16 or 32 mg/l, respectively, and reacted
at room temperature. It should be noted that the concentration of
NaI can be set at slightly excess than theoretical concentration to
ensure a complete chemical conversion. UV–Vis spectrometric moni-
toring results showed that both phosgene agents were turned into I2
with an ~100% yield in 15 min (Fig. S1). Later, a solution of I at
2
1
.6 mg/l was prepared by direct dilution with acetone. Then, aliquot
of 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 and 8.0 μl of such a I solution was
injected into 240 μl Au NPs, respectively, in which the concentrations
of I were 8, 12, 16, 20, 24, 28, 32 and 64 μg/l, respectively. For a more
dense solution of I , aliquot of 1.2, 1.4 and 2.0 μl of I stock solution
at 16 mg/l was injected into 240 μl Au NPs, respectively, in which
the concentrations of I were 96, 112 and 160 μg/l, respectively.
2
(Malvern Instrument Ltd., UK). Transmission electric microscope
2
images were obtained from a Hitachi H-7650 instrument (Hitachi
Technologies Co., Tokyo, Japan).
2
2
2
Preparation of phosgene
Because of the high toxicity of phosgene, all procedures must be
performed in a ventilation cabinet. Triphosgene of 0.43 g was dis-
solved in hexane of 2.15g in ice–salt bath, then a certain amount
of dimethylformamide was slowly added until no bubble produced;
the generated gas was phosgene, which was directly adsorbed in
an acetone solution.
Determination of diphosgene in air
Different concentrations of diphosgene in air were tested as the
real samples. First of all, the gaseous diphosgene of 5.6, 11.2 and
16.8 μl was injected into a flask full of air, respectively, then 10 ml
NaI acetone solution was added into the flask to fully adsorb the
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On-site detection of phosgene agents by surface-enhanced Raman spectroscopy
diluted diphosgene. The reaction was kept for 20 min at room tem-
4
perature and was diluted for 10 -fold. Then, 1 μl diluted solution
was added into 240μl aggregated Au NPs for SERS measurement.
The concentrations of I were 12, 25 and 30 μg/l, respectively. Each
2
sample was measured in triplicates.
Result and discussion
Pretreatment of SERS sample and the chemical methods
Phosgene has a relatively simple structure, and the available Raman
spectroscopy of phosgene can be only found as simulation data until
[17]
now. Anantharishnan et al. has reported that the computational
simulation Raman shifts of phosgene are 302, 442, 573, 832 and
À1
À1
1
803 cm , in which 573 and 1803 cm are the primary valence
À1
À1
oscillations, 302 cm is a deformation oscillation, 832 cm is a
valence type and 442cm is one of the deformation oscillation at
À1
depolarized status. Direct and sensitive SERS measurement of
phosgene is so difficult that no successful report can be followed.
In our experiment, the SERS spectra of phosgene cannot be directly
detected even at a 25 mg/l level in a portable Raman spectrometer
with Au NPs (52 nm) or other common nanoparticle substrates.
To address the sensitivity issue, we proposed a chemical transfor-
mation approach inspired by the high reactivity of phosgene. At
room temperature, phosgene or diphosgene can quantitatively re-
Figure 3. The normalized surface-enhanced Raman spectroscopy (SERS)
intensity of I (10 mg/l) on Au nanoparticles aggregated by different kind
of potassium salt. All intensities were normalized to the intensity of KI-
added case.
2
relatively low or no SERS enhancement effects. We then introduced
KI as the aggregation agent for the SERS measurement of phosgene
in the coming research (Scheme 1).
À
act with NaI in a rapid, direct and specific manner, and then I
generated as the product. This reaction was rapid and can be com-
pleted in 15 min. The product I was thus measured as the specific
2
was
To further illustrate the enhancement effect of X anion in this
aggregation while I is coexisted, we have prepared nine kinds of
2
2
Au NPs by simple chemical adsorption approaches and compared
analyte in SERS instead of phosgene agents. This chemical transfor-
mation approach avoids the phosgene hydroxylation, can be con-
veniently performed in aqueous or wet atmosphere and converts
the highly toxic reactant to the low or non-toxic substances, which
meets the on-site demand quite well.
the UV–Vis absorption spectra, the diameters and zeta potentials
À
À
À
À
of bare Au NPs, Au NPs@F , Au NPs@Cl , Au NPs@Br , Au NPs@I ,
À
À
À
À
Au NPs@F @I , Au NPs@Cl @I , Au NPs@Br @I , Au NPs@I @I and
2
2
2
2
Au NPs@I . The results were shown in Fig. 4 and Table 1.
2
As shown in Fig. 4A, Au NPs exhibit a maximum Vis absorption
À
peak at 532 nm. With the addition of X anions, the intensity of this
absorption peak is decreased. Furthermore, as shown in Fig. 4B,
with the addition of iodine, a new peak of 352 nm appears in the
Aggregation in the SERS measurement
À
À
formed Au NPs@I @I
peak position previously reported, which indicates that molecu-
2
particle system. It is consistent with the I
3
[
27]
Toward the practical and high-sensitivity aspect of SERS measure-
ment, the structure of nanoparticles and thus induced ‘hot spot’
are always the important factors to be considered. ‘Hot spots’ is
the gap region of a pair of strongly coupled nanoparticles, and
the highest Raman response of above 10 usually occurs at the
lar polarization occurred as a product of the charge transition from
À
I
anion to I
2
. It is also proved that in our chemical derivatization
[
18]
À
system of phosgene, I
261 nm in Fig. 4B is corresponding to I
3
was actually generated. The peak of
6
[27]
2
molecules.
were mixed with
À
inter-particle ‘hot spot’ in which the electromagnetic optical fields
As shown in Table 1, when the X anions or I
2
[
19,20]
are highly concentrated.
The assembly of nanoparticles to ag-
the Au NPs solution, the hydrodynamic diameters of such nanopar-
gregation is a very efficient way to obtain the ‘hot spot’, and various
ways have been reported, among them the inorganic salt induc-
ticles have increased ~3–4 nm, while there is no obvious relation-
[
21]
ship between the thickness of the layer and the species of the
[
22,23]
À
tion way is the most convenient.
salts, including KF, KCl, KBr, KI, KNO
PO , were used to induce the Au NPs particles aggregation.
The results of aggregation efficiency in Fig. 3 showed that KI was
the best reagent to generate highest SERS response for 10 mg/l I
Here, ten kinds of potassium
anion or I
2
. When I
2
was further added into the Au NPs@X solution,
3
, KHCO , K CO , K SO and
3
2
3
2
4
the corresponding hydrodynamic diameters were increased an-
other 5 to 22nm. This increase is so notable that some reunion
could be formed, in which an aggregation state must be generated
[
24]
K
3
4
À
2
from the mono-disperse solution. When the Au NPs@X were cov-
À
and the other three halogen (X) salts, KF, KCl and KBr, provided con-
ered by a layer of X , the highly negative charge of zeta potential
À
siderable enhancement. We assumed that X could not only afford
from À29.0 to À36.6 mV were observed. When I
2
was further
an one-atom-thick monolayer onto the surface of Au NPs and in-
added, all the zeta potentials were increased at an extent of
À
duced effective aggregation but also protect the existence of I
10–13mV. The Au NPs@I @I exhibit the largest zeta potential,
2
2
À
[25]
À
by forming triiodide ions (X I ) anion and thus tethered I into
À15.9mV, which supports that the I is tethered to the former
2
2
À
the ‘hot spots’ with an appearance of Raman sharp peak. The de-
duction was supported by further zeta potential and UV–Vis exper-
added I , and I is thus formed as well as its zeta potential is in-
2
3
À
creased a lot. The molecules of I3 in the ‘hot spots’ provide the
largest response of SERS response, which leads to the successful
detection of phosgene by an indirect method.
iments. The salts of KNO3 and K SO4 also offered comparable
2
enhancement with KCl or KBr; the possible reason relies on the
good affinity of Au–N or Au–S, which is benefit for the aggregation
However, only in a suitable ratio that the KI can induce more
SERS ‘hot spots’ to provide stronger SERS response. Our results
[26]
of Au NPs. The salts of K CO , KHCO and K PO only provided
2
3
3
3
4
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H. Gao et al.
Scheme 1. The chemical transformation approach of phosgene agents in surface-enhanced Raman spectroscopy (SERS) measurement. NPs, nanoparticles.
À
À
À
À
À
À
Figure 4. The UV–Vis absorption spectra of Au NPs, Au NPs@F , Au NPs@Cl , Au NPs@Br and Au NPs@I (A) and the Au NPs@F @I
NPs@Br @I , Au NPs@I @I and Au NPs@I (B).
2 2 2
2
, Au NPs@Cl @I
2
, Au
À
À
Table 1. The hydrodynamic diameter, zeta potential and Vis absorption data of different Au NPs particles
Kind of NPs
Au NPs
Au NPs
Au NPs
À
Au NPs
À
Au NPs
@I
Au NPs
Au NPs
Au NPs
Au NPs
Au NPs
@I
À
À
À
À
À
@F
@Cl
@Br
@F @I
2
@Cl @I
2
@Br @I
2
@I @I
2
2
Hydrodynamic
diameter (nm)
Potential (mV)
Ab of 532 nm
55.9
58.9
59.0
59.0
58.9
81.5
67.9
64.0
81.2
60.6
À35.7
À29.0
À36.0
À33.5
À36.6
À19.9
À16.4
À20.8
À15.9
À24.9
1.82
1.66
1.65
1.63
1.58
1.54
1.28
0.54
0.86
1.60
NPs, nanoparticles.
All data were triplicated.
showed that the best molecular ratio of salt to Au NPs was
The pH of the solution also influences the aggregation of nano-
particles. We investigated the pH value from 3.0 to 11.0 in the case
of KI as the aggregation agent (data not shown). The results
showed that the best aggregation occurred in the neutral pH.
7
2
× 10 , i.e. when we kept the Au NPs at a concentration of 500
pmol/l, the correspondingly potassium salt was prepared at a
concentration of 10 mmol/l. We further observed that the addi-
tion of excess ratio of salt destroyed the structures of the ‘hot
spots’ and apparently produced a coagulation of the Au NPs,
and then all the solution SERS signals deteriorated. The curve
of SERS intensity versus the concentration of added KI is shown
in Fig. S2.
À1
Characteristic Raman shift of 459 cm
À1
To confirm that the Raman shift of 459 cm was exactly induced
by I , but not by the other substances adsorbed onto the surfaces
2
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On-site detection of phosgene agents by surface-enhanced Raman spectroscopy
2
Figure 5. The surface-enhanced Raman spectroscopy (SERS) spectra of spiked or formed I at 1 mg/l (A) and the time-dependent curve (B).
of Au NPs, we investigated the SERS response of blanks, i.e. the
blank substrate (the KI-aggregated Au NPs) and the blank sample
(
the acetone solution without I
2
). As shown in Fig. S3, the results
À1
showed that only a Raman shift of 113 cm for Au–I bond ap-
peared in the blank substrate, which was consistent with Xu’s
paper.
characteristic Raman shift at 800 cm of acetone was observed
in the blank sample. We also confirmed that the production of I2
was the dominant factor contributed to the band of 459 cm by
[28]
When the concentration of acetone is large enough, a
À1
À1
standard spiking method. The addition of pure standard I2 of
1
4
mg/l into the KI-aggregated Au NPs also induce the same
À1
59 cm shift, as shown in Fig. 5A. This consistency proves that
À1
À
the Raman shift of 459cm is indeed the shift of the product I3
and can be used as the characteristic shift in our chemical transfor-
mation method.
A time-dependent tendency occurred toward the I2 product
either obtained from the chemical transformation method or as a
standard added into the KI-aggregated Au NPs. The SERS intensity
is gradually increased with the elapsed time, reaches the maximum
at 5 min and can be kept at least 1 h without obvious decrease
2
Figure 6. The surface-enhanced Raman spectroscopy spectra I at 5 μg/l in
three kinds of organic solvent–water mixed systems and in aqueous
solution. Dimethyl sulfoxide (DMSO).
(Fig. 5B). Thus, all samples were measured in 5 min after the addi-
tion of the analyte. Because I
activity, it is believed that the formation of I
2
is not so stable due to its medium re-
À
3
is largely helpful to
maintain the stability of SERS signal in the case of KI-aggregated
Au NPs. This continued signal is very convenient for us to perform
the on-site measurement.
À
The Raman shifts of I
3
in aqueous solution are reported at be-
À1 [29]
low 150 cm
.
However, as noted by Ref. [30], the kind of solvent
affected the Raman shift of triiodide anions a lot. We compared
three kinds of organic solvent–water mixed systems with aqueous
À1
solution and found that the Raman peak of 459 cm appear in
three organic solvent–water mixed systems but disappear in aque-
ous solution, in which the acetone–water mixed system contributes
À1
the largest intensity (Fig. 6). Here, we suppose that the 459cm in
our SERS case is belonging to the red shift of which commonly
À1
observed below 150 cm in aqueous solution in Raman spectros-
À1
Figure 7. The surface-enhanced Raman spectroscopy spectra at 459 cm
versus the concentrations of I
copy, and the large red shift might due to the ultra stability of
triiodide in mixed acetone–water system and the surface-enhanced
Raman shift effect.
2
from 8 to 160 μg/l (A); the inserted figure (B)
shows the linear curve of I from 8 to 32 μg/l.
2
determination in SERS. As shown in Fig. 7, it has a good SERS re-
Quantitative measurement of phosgene and diphosgene, and
the reaction behaviors of three kinds of phosgene agents
sponse from 8 to 160 μg/l I , with the linearity from 8 to 32 μg/l
2
2
(
r = 0.973), and a limit of detection (LOD) is as low as ~3 μg/l. When
À
À1
The SERS band of I3 has a distinct single peak at 459 cm , which
is more conductive for semi-determination or quantitative
the concentration of I was beyond 160 μg/l, its SERS intensity
2
reached a platform, which means that the I2 was saturated at
J. Raman Spectrosc. 2016, 47, 233–239
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H. Gao et al.
À
Figure 8. The UV–Vis time-dependent absorbance curves at 365 nm (A) and the time-dependent surface-enhanced Raman spectroscopy intensity (B) of I
product, which was generated by phosgene, diphosgene and partially decomposed triphosgene.
3
the surfaces of the KI-aggregated Au NPs. Toward diphosgene and
phosgene in our chemical transformation method, the LOD were
triphosgene, can be indirectly measured with LODs as low as
dozens of micrograms per liter. This chemical transformation is
proved to be quite feasible in the determination of contaminated
air samples. We believe that this SERS method has potential to be
employed in the emergency responses toward public health, envi-
ronmental safety and homeland security.
30 and 60μg/l, respectively.
In our experiment, the LOD of I was ~3 μg/l, which was much
2
[31]
lower than the results of UV–Vis spectrometry,
starch
[32]
[33]
colorization and FRET
as their LODs were at milligrams per
liter level. This method affords a great potential to achieve more
sensitivity. Another aspect should be noted, phosgene agents are
prone to be hydrolyzed in aqueous solution, but through this
chemical transformation approach in a mixed water–acetone solu-
tion, the hydroxylation could be ignored.
Acknowledgements
This research was supported by the National Major Instrument
Project of the Ministry of Science and Technology of China (no.
In this chemical transformation approach, phosgene and di-
phosgene can be easily reacted with NaI in acetone solution at
2011YQ03012411) and the National Foundation of Natural Science
(no. 81302473).
room temperature, and the products include I , sodium chloride
2
[
34]
(NaCl) and carbon monoxide (CO).
Because triphosgene can
be readily decomposed into phosgene, we expect that
triphosgene also can be monitored by this method. Considering
References
[
1] S. L. Hoenig, Compendium of Chemical Warfare Agents, Springer
Science, New York, 2007.
2] D. Feng, Y. Y. Zhang, W. Shi, X. H. Li, H. M. Ma, Chem. Commun. 2010, 46,
203.
[3] X. J. Wu, Z. S. Wu, Y. H. Yang, S. F. Han, Chem. Commun. 2012, 48, 1895.
4] U. P. Kodavanti, D. L. Costa, S. N. Giri, B. Starcher, G. E. Hatch, Fundam.
that the same concentration of I product at 50 mg/l, phosgene
2
of 50 mg/l and diphosgene of 25 mg/l were used in this chemi-
cal transformation method according to the stoichiometric ratio;
we also prepared triphosgene of 17 mg/l based on that one
triphosgene molecule can be totally decomposed to three phos-
[
9
[
Appl. Toxicol. 1997, 37, 54.
[5] S. Virji, R. Kojima, J. D. Fowler, J. G. Villanueva, R. B. Keaner, B. H. Weiller,
Nano Res. 2009, 2, 135.
gene in the most ideal condition. The UV–Vis absorbance data
À
and SERS intensity of the produced I
3
over time are shown
in Fig. 8. Triphosgene with the lowest reaction rate in compari-
son with phosgene and diphosgene were also detected using
this chemical transformation approach; the main reason is due
to its partial decomposition fate.
[6] G. G. Esposito, D. Lillian, G. E. Podolak, R. M. Tuggle, Anal. Chem. 1977,
49, 1774.
[
7] W. S. Wu, V. S. Gaind, Analyst 1993, 118, 1285.
8] A. Kuessner, J. Chromatogr. 1981, 204, 159.
9] B. Muir, D. B. Cooper, W. A. Carrick, C. M. Timperley, B. J. Slater, S. Quick,
[
[
J. Chormatogr. A. 2005, 1098, 156.
[
10] Y. Juillet, C. Dubois, F. Bintein, J. Dissard, A. Boss, Anal. Bioanal. Chem.
Determination of phosgene and diphosgene in air sample
2
014, 406, 5137.
[
[
[
11] M. Burnworth, S. J. Rowan, C. Weder, Chem. Eur. J. 2007, 13, 7828.
12] H. X. Zhang, D. M. Rudkevich, Chem. Commun. 2007, 12, 1238.
13] N. Nakano, A. Yamamoto, Y. Kobayashi, K. Nagashima, Talanta 1995, 42,
641.
To validate our method, we also constructed the contaminated
air samples by mixing the gaseous diphosgene into the air as
an example. We obtained the recovery from 85% to 109% for di-
phosgene (Table S1), indicating that our method is very conve-
nient and reliable for on-site measurement of phosgene or
diphosgene.
[
14] T. A. Ryan, C. Ryan, E. A. Sedon, K. R. Seddon Ryan, Phosgene and Related
Carbonyl Halides Amsterdam, Elsevier, Amsterdam, 1996.
15] G. Frens, Nature Phys. Sci. 1973, 241, 20.
[
[
16] W. Haiss, N. T. K. Thanh, J. Aveyard, D. G. Fernig, Anal. Chem. 2007, 79,
4215.
[
17] R. Anantharishnan, Department of Physics, Indian Institute of Science,
Bangalore, 1981.
Conclusion
[
[
18] W. Y. Li, P. H. C. Camargo, X. M. Lu, Y. N. Xia, Nano Lett. 2009, 9, 485.
19] P. L. Stiles, J. A. Dieringer, N. C. Shah, R. P. Van Duyne, Rev. Anal. Chem.
We firstly developed a simple, sensitive and rapid chemical transfor-
mation method for the quantitative measurement of phosgene and
diphosgene using SERS technique. The iodide salt was discovered
as the efficient aggregation agent to achieve high sensitivity for de-
2
008, 1, 601.
20] J. P. Camden, J. A. Dieringer, J. Zhao, R. P. VanDuyne, Acc. Chem. Res.
008, 41, 1653.
[
[
2
21] S. L. Kleinman, R. R. Frontiera, A. Henry, J. A. Dieringer, R. P. Van Duyne,
tection of the product I . Phosgene and diphosgene, even
Phys. Chem. Chem. Phys. 2013, 15, 21.
2
wileyonlinelibrary.com/journal/jrs
Copyright © 2015 John Wiley & Sons, Ltd.
J. Raman Spectrosc. 2016, 47, 233–239

On-site detection of phosgene agents by surface-enhanced Raman spectroscopy
[
[
22] R. Gao, N. Choi, S. I. Chang, S. H. Kang, J. M. Song, S. I. Cho, D. W. Lim,
J. Choo, Anal. Chim. Acta 2010, 681, 87.
23] A. J. Hobro, S. Jabeen, B. Z. Chowdhry, E. W. Blanch, J. Phys. Chem. C
[31] B. Xu, I. S. Park, Y. Li, D. J. Chen, Y. Y. J. Tong, J. Electroanal. Chem. 2011,
662, 52.
[32] J. Abraham, A. D. Emmanuel, K. Joachim, Talanta 2009, 80, 231.
[33] M. Davydova, A. Kromka, P. Exnar, M. Stuchlik, K. Hruska, M. Vanecek,
M. Kalbac, Phys. Status Solidi A 2009, 206, 2070.
2
010, 114, 7314.
[24] J. Wang, Y. F. Li, C. Z. Huang, Anal. Chem. Acta. 2008, 626, 37.
[25] A. E. Burgess, J. C. Davidson, J. Chem. Educ. 2014, 91, 300.
[26] L. Jiang, J. Qian, F. H. Cai, S. L. He, Anal. Bioanal. Chem. 2011, 400,
[34] S. Franke, Lehrbuch der Militärchemie, Wiley-VCH Verlag GmbH & Co.
KGaA, Weinheim, Berlin, 1969.
2793.
[
[
27] S. H. Jung, J. W. Yeon, Y. Kang, K. Song, Asian J. Chem. 2014, 26, 4084.
28] L. J. Xu, C. Zong, X. S. Zheng, P. Hu, J. M. Feng, B. Ren, Anal. Chem. 2014,
Supporting information
8
6, 2238.
[
[
29] A. E. Johnson, A. B. Myers, J. Phys. Chem. 1996, 100, 7778.
30] H. Naorem, S. D. Devi, Spectrochim. Acta A Mol. Biomol. Spectrosc. 2013,
Additional supporting information may be found in the online ver-
101, 67.
sion of this article at the publisher’s web site.
J. Raman Spectrosc. 2016, 47, 233–239
Copyright © 2015 John Wiley & Sons, Ltd.
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