Photo-induced self-cleaning functions on 2-anthraquinone carboxylic acid treated cotton fabrics

Article abstract of DOI:10.1039/c1jm12805a

Self-cleaning cotton fabrics were obtained via chemically incorporating photosensitive 2-anthraquinone carboxylic acid (2-AQC) onto the fibers through a mild and efficient esterification reaction. The 2-AQC structures on the treated cotton were confirmed by FTIR characterization. SEM images revealed that the cotton fiber surface became rougher than that of the original cotton fiber after the treatment. TGA analysis confirmed that thermal stability of the treated fibers was almost unchanged. The 2-AQC treated cotton fabrics demonstrated excellent photo-induced self-cleaning properties, including decomposition of 90% aldicarb in 3 hours of UVA exposure and inactivation of over 99% of both E. coli and S. aureus in 1 hour of the light exposure. The self-cleaning functions are a result of formation of reactive oxygen species on the light irradiated and 2-AQC treated cotton. The amount of H₂O₂ formed on the fabrics was determined by a titration method.

Full text of DOI:10.1039/c1jm12805a

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PAPER
Photo-induced self-cleaning functions on 2-anthraquinone carboxylic acid
treated cotton fabrics
*
Ning Liu, Gang Sun and Jing Zhu
Received 18th June 2011, Accepted 27th July 2011
DOI: 10.1039/c1jm12805a
Self-cleaning cotton fabrics were obtained via chemically incorporating photosensitive 2-
anthraquinone carboxylic acid (2-AQC) onto the fibers through a mild and efficient esterification
reaction. The 2-AQC structures on the treated cotton were confirmed by FTIR characterization. SEM
images revealed that the cotton fiber surface became rougher than that of the original cotton fiber after
the treatment. TGA analysis confirmed that thermal stability of the treated fibers was almost
unchanged. The 2-AQC treated cotton fabrics demonstrated excellent photo-induced self-cleaning
properties, including decomposition of 90% aldicarb in 3 hours of UVA exposure and inactivation of
over 99% of both E. coli and S. aureus in 1 hour of the light exposure. The self-cleaning functions are
a result of formation of reactive oxygen species on the light irradiated and 2-AQC treated cotton. The
amount of H2O2 formed on the fabrics was determined by a titration method.
and durable immobilization of the particles onto the fiber
Introduction
surfaces. Therefore, TiO2 nanoparticles are mostly used in
coating materials applied onto the surfaces of fibers.9,10 Thus,
organic soluble photosensitive compounds possessing strong
interactive groups with most polymers and textile fibers are more
appealing for textile applications.11–18 As cotton containing
fabrics are the preferred clothing materials in apparels, it is
necessary to develop self-cleaning cotton fabrics that could
automatically provide detoxification and antibacterial
properties.
Growing exposures to toxic chemicals and infectious pathogens,
as well as threats of biological and chemical attacks from
terrorists have become a major concern to the general public, as
well as to occupational professionals, in recent years.1,2 Various
countermeasures have been developed and undertaken to protect
the public and professionals from these threats, including
wearing barrier protective clothing that can block penetration of
toxins and using functional chemicals that can detoxify the
agents.3,4 More recently, photo-induced oxidative functions of
certain textile colorants under UVA or fluorescent light irradi-
ation have attracted attention.5 The oxidative functions of the
colorants attribute to formation of singlet oxygen, superoxide
radicals, and hydroxyl radicals, so-called reactive oxygen species
(ROS), in the system. The ROS could also form hydrogen
peroxide in water, a known disinfectant widely employed in
inactivating pathogenic microorganisms and degrading other
chemicals.5–7
In order to develop cotton fabrics that can provide photo-
induced chemical detoxification functions, we attempted to use
a facile and efficient process to incorporate photosensitive 2-
anthraquinone carboxylic acid (2-AQC) onto cotton fabrics. In
the presence of N,N0-carbonyldiimidazole (CDI), 2-AQC can
react with hydroxyl groups in cotton cellulose through a mild
esterification reaction.19 The structures of 2-AQC modified
fabrics were confirmed by Fourier transform infrared (FTIR)
spectral data. The fabrics demonstrated antimicrobial functions
against both Gram negative and Gram positive bacteria and
oxidative detoxification functions against aldicarb under UVA
exposures.
Significant research efforts have been made on development of
photo-induced self-cleaning materials in recent years.7–10 As an
example, titanium dioxide (TiO2) nanoparticles can serve as
a photo-active agent on surfaces of materials to generate ROS.
These particles are considered highly efficient and nontoxic, and
as a result are widely used.7,8 But, the TiO2 nanoparticles have
poor affinity and low interactions towards the majority of
organic fibers, which significantly limits the feasibility of direct
Materials
Bleached and desized cotton fabric (#400) was purchased from
Testfabrics, Inc. (West Pittston, PA). 2-Anthraquinone carbox-
ylic acid (2-AQC), anhydrous N,N-dimethylformamide (DMF)
and N,N0-carbonyldiimidazole (CDI) were purchased from
Aldrich Co. (MO, USA). All reagents were used as received
without any further purification.
Fiber and Polymer Science, University of California, Davis, California,
95616, USA. E-mail: gysun@ucdavis.edu; Fax: +1 530-752-7584; Tel:
+1 530-752-0840
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system, equipped with a Waters 2998 photodiode array (PDA)
detector and a Waters Micromass ZQ 2000 (ESI-MS). A reverse
phase C18 column (5 mm particle size, 4.6 by 250 mm) was used.
The flow rate of the mobile phase was set at 0.33 mL minꢂ1, and
the injection volume was 10 mL. The detection wavelength was
set from 190 to 800 nm. Instrument control and data acquisition
were performed by using Micromass MassLynx software
(version 4.1) (Waters Co., Milford, MA, USA). The mobile
phase contains 60% water with 0.1% hydrofluoric acid (HF) and
40% acetonitrile with 0.1% HF.
Functionalization of cellulose by 2-AQC
2-Anthraquinone carboxylic acid was incorporated onto the
cotton fabric by an esterification reaction between the carboxylic
acid and hydroxyl group on cellulose, and the reaction was
catalyzed by CDI (Scheme 1). DMF solutions containing
designated concentrations (0.0125–0.2 M) of 2-AQC and the
equal amount of CDI were shaken at a speed of 100 times per
min for 180 min at 80 ꢀC. Then, the cotton fabrics, cut in sizes of
around 20 cm ꢁ 20 cm, were immersed in the solutions with
different 2-AQC concentrations. The mixtures were continuously
The mass spectrometer conditions were as follows: capillary
voltage, 3.0 kV; cone voltage, 60 eV; source temperature,
ꢀ
shaken for 24 hours at a speed of 100 times per min at 80 C.
Finally the fabrics were washed in hot water for 30 min to remove
any unreacted 2-AQC and other chemicals on the fabric surface.
ꢀ
ꢀ
125 C; desolvation temperature, 350 C; desolvation gas flow,
250 L hꢂ1
.
Characterization
Antibacterial test
The add-on (%) of 2-anthraquinone carboxylic acid on the
treated cellulose was measured by a gravimetric method, in
which the weights of the fabrics before and after treatment were
compared under standard conditions. Fourier transform infrared
(FTIR) spectroscopy was performed on a Nicolet 6700 FTIR
spectrometer (Thermo Electron Co., USA) with 64 scans and
a resolution of 4 cmꢂ1 by using KBr pellets. Thermogravimetric
analysis (TGA) was carried out on a Shimadzu TGA-50 appa-
ratus (Shimadzu science instruments, Inc., USA) at a heating rate
of 10 ꢀC minꢂ1 from 25 ꢀC to 600 ꢀC under nitrogen atmosphere.
The surface morphologies of cotton fabrics were examined by
using a scanning electron microscope (SEM; PhilipsXL30, USA).
Anthraquinone chromophore structures incorporated on the
cotton fibers were observed by a fluorescent microscope Leica
DM2500 (Leica Microsystems, Germany). UVA irradiation was
conducted in a UV crosslinker (Spectrolinker XL-1000, Spec-
troline, USA), with five 8 W lamps at 365 nm (UVA) wavelength.
The distance between the UVA lamps and the material was 12
cm. The light intensity was 1.3–2.0 mW cmꢂ2. The specific color
changes on these exposed fabrics were measured by a colorimeter
(Color-Eye 7000A, GretagMacbath, USA).
Antibacterial properties of the 2-AQC treated cotton fabric were
examined against Staphylococcus aureus (S. aureus) (ATCC
12600, a Gram-positive bacterium) and Escherichia coli (E. coli)
(K-12, a Gram-negative bacterium), according to a modified
AATCC 100 test method. The same cotton fabric without any
treatment was used as a control. Four pieces of 2.5 ꢁ 2.5 cm2
swatches of the control or the treated cotton fabric were placed in
two separate sterilized Petri dishes. A 1.0 mL of an aqueous
suspension containing S. aureus or E. coli was evenly dropped
onto the surfaces of the samples, and then both were illuminated
under UVA irradiation for one hour. After the light exposure,
both samples were placed into separate containers containing
100 mL of sterilized distilled water, respectively. The mixture was
vigorously shaken for 1 min. Then 100 mL of the aqueous solu-
tion was taken out from the container and diluted to 100, 101, 102,
and 103 times in sequence. Finally, 100 mL of the solutions at
different stages of dilutions were placed onto four equal zones of
a nutrient agar plate, and the agar plate was incubated at 37 ꢀC
for 18 h. The reduction of bacteria was calculated according to
the following equation:
B ꢂ A
Liquid chromatography-mass spectrometry (LC-MS) analyses
were performed using a Waters e2695 liquid chromatography
Reduction of bacteriað%Þ ¼
ꢁ100
(1)
B
Scheme 1 Incorporation of 2-anthraquinone carboxylic acid onto cotton fabrics.
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respectively. Then the fabrics immersed in aldicarb aqueous
solutions were irradiated by UVA light for 3 h, and the degra-
dation products were detected by LC-MS.
Detection of H2O2
The iodometric titration method following eqn (2) and (3) was
used to determine the specific amount of H2O2 formed by the
cotton samples. The fabrics with the exact size of 10 ꢁ 10 cm2
were put into 20 mL of deionized water, and then 10 mL of 0.2 M
sulfuric acid and 10 mL of 5% potassium iodide were added to it.
The mixture was exposed to UVA for varied durations. The
mixture was titrated by a 0.001 N sodium thiosulfate solution.
The end point of titration was determined by reading the changes
occurring at a redox electrode. A blank (UV exposed untreated
cotton fabric) titration was also carried out as a control.
Production of H2O2 was then calculated from eqn (4).
Fig. 1 Add-on (%) of 2-AQC on treated cotton fabrics as a function of
2-AQC concentration.
where A and B are the surviving cells (colony forming unit per
mL) on the agar plates corresponding to the 2-AQS treated
cellulose and the control, respectively.
H2O2 + 2KI + H2SO4 / I2 + K2SO4 + 2H2O
I2 + 2Na2S2O3 / Na2S4O6 + 2NaI
(2)
(3)
(4)
Detoxification of aldicarb
To demonstrate pesticide degradation ability, a piece of the
fabric swatch in a size of 5 ꢁ 8.5 cm2 of the control fabric or the
treated cotton fabric was placed in a 50 mL centrifuge tube
containing 5 mL of 0.25 mM aldicarb aqueous solution,
H2O2 (w/w) ¼ 1000 (17) (V2 ꢂ V1)N/(sample weight)
where V2 ¼ titration volume of a sample, V1 ¼ titration volume
of a blank, and N ¼ normality of Na2S2O3.
Fig. 2 FTIR spectra of cotton fabrics: (a) pure cotton, (b) 0.0125 M 2-AQC treated, (c) 0.025 M 2-AQC treated, (d) 0.05 M 2-AQC treated, (e) 0.1 M 2-
AQC treated, and (f) 0.2 M 2-AQC treated.
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Fig. 3 SEM images of cotton fabrics: (a) cotton control, (b) 0.025 M 2-AQC treated and (c) 0.2 M 2-AQC treated.
surface of the treated cotton became rougher. Some particles
appeared on the surfaces, and the amount of the particles
increased with the increase of 2-AQC concentration in the
treatment solutions.
Results and discussions
Preparation of 2-AQC treated cotton fabrics
The esterification of cellulose with 2-anthraquinone carboxylic
acid was conducted in two steps. First, 2-anthraquinone
carboxylic acid reacted with N,N0-carbonyldiimidazole (CDI) in
1 : 1 molar ratio to form carboxylic acid imidazolides in anhy-
drous DMF solutions (Scheme 1). Then, a cotton fabric sample
was added into the solution, and the mixture was vigorously
shaken for 24 hours at 80 ꢀC to ensure the completion of the
reaction. As shown in Fig. 1, after the esterification process, the
add-on percentage of 2-AQC on cotton fabrics increased with
the increase of 2-AQC concentration in the DMF solution. The
plot of the add-on percentage versus 2-AQC concentration dis-
played a linear fit, with the correlation constant greater than
0.98. When the concentration of 2-AQC was increased to 0.2 M,
the add-on percentage of the agent reached more than 7%,
indicating high esterification efficiency of the method.
FTIR results
Fig. 4 Tensile strength of cotton fabrics: (a) control, (b) 0.025 M 2-AQC
treated, (c) 0.05 M 2-AQC treated, (d) 0.1 M 2-AQC treated, and (e) 0.2
M 2-AQC treated.
The chemical structures of 2-AQC treated cotton fabrics with
varied 2-AQC concentrations were evaluated by using FTIR
spectroscopy, which are shown in Fig. 2. All samples exhibited
a characteristic peak at 1318 cmꢂ1 due to a bending vibration
mode of hydrocarbon bond as well as absorption bands at 1370
and 1430 cmꢂ1 due to symmetric stretching of carboxylate groups
from cellulosic molecules.20 On the other hand, the cotton fabrics
treated in five different concentrations of 2-AQC revealed char-
acteristic peaks of the compound and the ester bond in corre-
sponding FTIR spectra. A new peak at 1595 cmꢂ1 is associated to
aromatic C]C stretching from the 2-anthraquinone carboxylic
acid molecule,21 and the peak around 1677 cmꢂ1 is attributed to
carbonyl stretching peak originated from the anthraquinone
group.22 Another new peak at 1727 cmꢂ1 is assigned to the ester
group formed between cellulose and 2-AQC,23 which was
observed in all five 2-AQC treated cotton fabric spectra. The
intensity of the newly appeared peaks is in an ascending order,
same as the increase of the concentration of 2-AQC in finishing
solutions and consistent with the add-on result. It is also noticed
that the carbonyl peak originated from 2-AQC overlaps with the
cellulose characteristic peak at 1600 cmꢂ1 at a lower 2-AQC
concentration.
Fig. 5 TGA curves of cotton fabrics: (a) control cotton, (b) 0.0125 M 2-
AQC treated, (c) 0.025 M 2-AQC treated, (d) 0.05 M 2-AQC treated, (e)
0.1 M 2-AQC treated, and (f) 0.2 M 2-AQC treated.
Fig. 3 shows the surface morphologies of the control and
treated cotton samples. After the esterification reaction, the
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Fig. 6 Fluorescent images of cotton fabrics (magnification: 5ꢁ): (a) cotton control fabric, (b) 0.05 M 2-AQC treated cotton fabric before UVA
exposure, and (c) 0.05 M 2-AQC treated cotton fabric after 1 h of UVA irradiation.
Mechanical and thermal properties
a weak fluorescent effect under white light, compared with the
cotton control sample, confirming the incorporation of 2-AQC
onto cotton fabrics. After the UVA (365 nm) irradiation, the
treated fabric showed a much stronger fluorescent effect, which
could be caused by the photoreaction products of 2-AQC, indi-
cating possible structural changes of 2-AQC on the cellulose after
the irradiation.24–26
Tensile strengths of the control and the 2-AQC treated samples
were measured and are shown in Fig. 4. It was observed that
almost all samples exhibited similar tensile strength values,
demonstrating that the CDI catalyzed esterification reaction
under different 2-AQC concentrations did not dramatically
affect the cellulosic structures. However, the highest 2-AQC
concentration (0.2 M) still caused slight reduction to the tensile
strength.
Antibacterial test
Thermal degradation properties of the 2-AQC treated cotton
fabrics were evaluated by TGA. Fig. 5 demonstrates that thermal
degradation residues (%) of the cotton fabrics increased as more
2-AQC was incorporated onto cellulose because of higher carbon
contents of the 2-AQC on the fabrics. However, the decompo-
sition temperature slightly decreased as more 2-AQC was on the
fabric, possibly due to the newly established weak ester bonds.
However, the overall decrease of degradation temperature and
increased thermal degradation residues were negligible.
Biocidal properties of the 2-AQC treated cotton fabrics were
examined against both E. coli and S. aureus following a modified
AATCC 100 method, and the results are shown in Table 1. Both
the control and the 2-AQC treated samples were inoculated with
1 mL of either E. coli or S. aureus bacterial suspension at
a concentration of 105 to 106 CFU mLꢂ1, and then irradiated
under UVA light (365 nm) for one hour. Viable colony of the
bacteria was barely observed on the 2-AQC treated cotton,
whereas propagated colonies of E. coli and S. aureus were
observed for the control cotton fabric. The 2-AQC treated
fabrics all demonstrated 99.99% reduction rate against E. coli
bacterium even for the cotton treated with the lowest 2-AQC
concentration. The reduction of S. aureus was about 99–99.9%
depending on the concentration of the compound in the finishing
baths. Overall, the test results indicated that the 2-AQC treated
cotton possessed excellent photo-induced biocidal functions.
Fluorescent effect
As a photosensitive anthraquinone compound, 2-AQC may have
photoinduced luminescence phenomenon under continuous light
irradiation.24–26 The UV irradiation may also change the fluo-
rescent effect of 2-AQC if its structure is partially changed.
Fluorescent effects of the cotton control fabric, the 2-AQC
modified cotton fabric (with 1.5% concentration), and the 2-
AQC modified cotton fabric after 1 hour of UVA exposure were
observed by using an optical microscope, as shown in Fig. 6.
After the esterification reaction, the treated sample demonstrated
Detoxification of aldicarb by 2-AQC treated cotton
The treated cotton fabrics also possess photo-induced self-
cleaning functions against certain pesticides. Here, we evaluated
Table 1 Antimicrobial functions of 2-AQC modified cotton fabrics as a function of 2-AQC concentration in finishing baths after 1 h of UVA exposure
E. coli
S. aureus
Dilution times of bacteria
solution after contact time
Dilution ratio of bacteria
solution after contact time
2-AQC concentration/M
102
103
104
105
Bacterial reduction
102
103
104
105
Bacterial reduction
Control
0.0125
0.025
0.05
0.1
0.2
N
1
0
0
2
228
0
0
1
0
28
0
0
0
0
2
0
0
0
0
0
—
197
2
0
1
0
15
1
0
0
0
1
0
0
0
0
0
1
0
0
0
0
0
—
99
99
99
99.9
99.9
99.99
99.99
99.99
99.99
99.99
1
0
0
0
0
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Fig. 7 HPLC results of (a) raw aldicarb solution, (b) original cotton immersed aldicarb solution after 3 h of UVA exposure, and (c) 2-AQC treated
cotton immersed aldicarb solution after 3 h of UVA exposure.
photo-induced detoxification properties of the 2-AQC treated
cotton fabrics against aldicarb, a common pesticide employed in
agricultural productions. An LC-MS system was used to track
the concentration changes of aldicarb and monitor the formation
of degraded compounds in an aldicarb aqueous solution after
exposure to the 2-AQC treated fabric and UVA irradiation.
Fig. 7 demonstrates the LC chromatograms of raw aldicarb
aqueous solution, aldicarb aqueous solution immersed with pure
cotton, aldicarb aqueous solution immersed with 0.05 M 2-AQC
treated cotton fabric, respectively. An aldicarb characteristic
peak appears at around 19.4 min, and the peak was observed in
all chromatograms. However, after irradiated by UVA light for 3
hours, the aldicarb characteristic peak for the solution immersed
with the 2-AQC treated fabric decreased dramatically with an
Table 2 Summary of LC-MS results of aldicarb solutions exposed to 2-AQC treated cotton fabric after UV irradiation according to Fig. 8(a)–(c)
Pesticide and
detoxification products
m/z
(tentative ion)
Mw
Chemical structure
208 ([M + H2O]+)
213 ([M + Na]+)
191 ([M + H]+)
116 ([M–OCONHCH3]+)
Aldicarb
190
224 ([M + H2O]+)
229 ([M + Na]+)
207 ([M + H]+)
132 ([M–OCONHCH3]+)
Aldicarb sulfoxide
206
143 [M + H]+
164 [M–H + Na]+
180 [M–H + Na + OH]+
208 [M + 2H + Na + CH3CN]+
Unidentified compound
142
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area reduction of around 90%, whereas no noticeable changes
were observed from the aldicarb solution containing the control
sample, illustrating the significant degradation effect of the 2-
AQC treated cotton fabrics.
Besides the original peak of aldicarb, small amount of oxidized
products of aldicarb, namely, aldicarb sulfoxide was observed at
around 8.1 min, which showed peaks with [M + H]+ ion at m/z
207, [M + H2O]+ at m/z 224 and [M–OCONHCH3]+ at m/z 132 in
Fig. 8(b). At a retention time of 6.0 min (Fig. 8(c)), another
degradation product was detected and assigned to 2-propenal,2-
methyl-,O-[(methylamino)carbonyl]oxime, which was also
observed in the degradation products of aldicarb solution treated
with nanofiber incorporated with TiO2.27 It demonstrated peaks
with [M + H]+ at m/z 143, [M–H + Na]+ at m/z 164, [M–H + Na +
OH]+ at m/z 180, and [M + 2H + Na + CH3CN]+ at m/z 208.
The chemical detoxification results suggest an oxidative reac-
tion between the treated fabric and aldicarb under light exposure,
similar to what have been reported on other anthraquinone
compounds.15–18
Electrospray ionization mass spectra of aldicarb and degra-
dation products were measured in positive ion mode, and the
results including chemical structures, molecular weight, base
peaks and the most abundant ions are summarized in Table 2. In
the mass spectrum of aldicarb (Fig. 8(a)), three main peaks with
the [M–OCONHCH3]+ ion at m/z 116, [M + H2O]+ at m/z 208
and [M + Na]+ at m/z 223 can be identified, respectively. These
aldicarb characteristic ion peaks were observed in all MS spectra.
Determination of H2O2
Due to the similarity of 2-AQC and another reported photo-
sensitive compounds such as anthraquinone 2-sulfonate, the
photo-induced antibacterial and detoxification functions of the
2-AQC treated cotton were believed as formation of reactive
oxygen species (ROS) on the fabric under light exposure.13–18 The
specific photoreaction pathway of 2-AQC under light exposure is
assumed to follow the same reaction mechanism as anthraqui-
none 2-sulfonate reported in another paper.18 As an indication of
the formation of ROS in this system, amounts of H2O2 formed
on the cotton fabrics treated with three different concentrations
were measured and are shown in Fig. 9. Obviously, cotton
samples containing higher concentrations of 2-AQC produced
more hydrogen peroxide. Even the cotton treated with only
0.025% of 2-AQC still produced more than 100 ppm of hydrogen
peroxide after one hour of UVA exposure. As an effort to prove
the durability and reusability of the photo-active functions, the
same UVA treated samples were exposed to UVA light again
following the sample procedure, less yet more than 60 ppm of
hydrogen peroxide was generated by the three samples.
Accordingly, the UVA treated sample is becoming yellower (Db)
and darker (DL) than before (Table 3) and a tiny new peak
showed up at 3350 cmꢂ1 in the FTIR spectra of the UVA treated
Fig. 8 Mass spectra of aldicarb solution containing the cotton fabrics
treated with 0.05 M 2-AQC after 3 h of UV irradiation: (a) aldicarb at RT
19.4 min, (b) aldicarb sulfoxide at RT 8.1 min and (c) an unidentified
peak at RT 6.0 min.
Fig. 9 Generation of H2O2 by cotton treated with different concentra-
tions of 2-AQC.
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Table 3 Color coordinates of undyed, dyed, and UVA exposed samples
Samples
L
a
b
DL
Da
Db
Standard sample untreated cotton
Cotton with 1.5% 2-AQC before UVA
exposure
Cotton with 1.5% 2-AQC after UVA
exposure
Cotton with 0.5% 2-AQC before UVA
exposure
Cotton with 0.5% 2-AQC after UVA
exposure
Cotton with 0.025% 2-AQC before UVA
exposure
Cotton with 0.025% 2-AQC after UVA
exposure
84.10
83.67
ꢂ0.12
ꢂ2.42
ꢂ0.31
—
ꢂ0.43
—
—
7.15
ꢂ2.30
ꢂ0.90
ꢂ0.94
ꢂ2.20
ꢂ0.51
ꢂ0.68
7.46
18.73
3.06
14.51
1.60
8.57
80.01
84.07
82.20
83.91
82.48
ꢂ1.02
ꢂ1.06
ꢂ2.32
ꢂ0.63
ꢂ0.80
18.42
2.75
ꢂ4.09
ꢂ0.03
ꢂ1.90
ꢂ0.19
ꢂ1.61
14.21
1.29
8.27
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16 D. Wang, N. Liu, W. Xu and G. Sun, J. Phys. Chem., 2011, 115, 6825–
6832.
Conclusions
A photosensitive organic compound, 2-anthraquinone carbox-
ylic acid, was incorporated onto cellulose through an esterifica-
tion reaction. FTIR analysis of the 2-AQS treated cotton fabrics
confirmed the formation of the ester bond between 2-AQC and
cellulosic polymer. The treated cottons basically maintained the
original surface morphology, tensile strength and good thermal
stability, and exhibited photo-induced bactericidal activities
against both S. aureas and E. coli, and oxidative degradation of
a pesticide under UVA irradiation. These photo-induced func-
tions on the treated cotton fabrics are a result of generation of
ROS, which was measured as the formation of H2O2.
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Acknowledgements
This research was financially supported by US National Science
Foundation (CTS 0424716) and the US Defense Threat Reduc-
tion Agency (HDTRA1-08-1-0005). N. Liu is grateful for Jastro
Shields Graduate Research Fellowship provided by the College
of Agricultural and Environmental Sciences of University of
California, Davis.
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This journal is ª The Royal Society of Chemistry 2011