UV Light-Induced Generation of Reactive Oxygen Species and

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UV Light-Induced Generation of Reactive Oxygen Species and Antimicrobial Properties of Cellulose Fabric Modified by 3,3#,4,4#-Benzophenone Tetracarboxylic Acid Aiqin Hou, Guanchen Feng, Jingyuan Zhuo, and Gang Sun ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.5b09993 • Publication Date (Web): 04 Dec 2015 Downloaded from http://pubs.acs.org on December 14, 2015

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ACS Applied Materials & Interfaces

UV Light-Induced Generation of Reactive Oxygen Species and Antimicrobial Properties of Cellulose Fabric Modified by 3,3′,4,4′-Benzophenone Tetracarboxylic Acid Aiqin Hou†‡, Guanchen Feng†, Jingyuan Zhuo‡ and Gang Sun*‡ †

National Engineering Research Center for Dyeing and Finishing of Textiles,

Donghua University, Shanghai 201620, China ‡

Division of Textiles and Clothing, University of California, Davis, California

95616, United States

ABSTRACT: 3,3′,4,4′-Benzophenone tetracarboxylic acid (BPTCA) could directly react with hydroxyl groups on cellulose to form ester bonds. The modified cotton fabrics not only provided good wrinkle-free and ultraviolet (UV) protective functions, but also exhibited important photochemical properties such as producing reactive oxygen species (ROS) including hydroxyl radicals (HO·) and hydrogen peroxide (H2O2) under UV light exposure. The amounts of the produced hydroxyl radical and hydrogen peroxide were measured, and photochemical reactive mechanism of the BPTCA treated cellulose was discussed. The results reveal that the fabrics possess good washing durability in generation of hydroxyl radicals and hydrogen peroxide. The cotton fabrics modified with different concentrations of 3,3′,4,4′-benzophenone tetracarboxylic acid and cured at an elevated temperature demonstrated excellent antimicrobial activities, which provided 99.99% antibacterial activities against both E. coli and S. aureus. The advanced materials have potential applications in medical textiles and biological material fields.

KEYWORDS: Benzophenone tetracarboxylic acid; cellulose materials; modification; reactive oxygen species; antimicrobial property

1. INTRODUCTION Clothing has acted as “second skin” a protective outer layer for humans since 1

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civilization began. With the increasing awareness of infectious diseases caused by various microorganisms, antibacterial textiles have been considered as a tool for prevention of disease transmission through clothing materials. Many novel chemicals and technologies have been developed to incorporate antibacterial functions onto fabrics, including N-halamines,1,2 quaternary ammonium,3−8 heavy metal

9−17

and

photosensitive chemicals such as benzophenone compounds, TiO2 and ZnO nanoparticles18−27. The TiO2 and ZnO nanoparticles18−22 could effectively generate reactive oxygen species (ROS) on polymer surfaces under ultraviolet or day light exposure, which could provide light-induced antimicrobial and self-cleaning functions. However, the nanoparticles on textiles bring in concerns on human safety since the nanoparticles may come off from the surfaces of fibers and penetrate through skin and enter into the human body25. Different photoactive benzophenone derivatives incorporated onto cotton fabrics can also generate reactive oxygen species under ultraviolet (UV) irradiation, providing

the

fabrics

with

antibacterial

activity27.

3,3′,4,4′-benzophenone

tetracarboxylic dianhydride (BPTCD) is a derivative of the benzophenone, which has been proven effective as a light-induced antimicrobial agent on cotton fabrics28. The two anhydride groups in BPTCD can be hydrolyzed to tetracarboxylic acids, making the compound, benzophenone tetracarboxylic acid (BPTCA), soluble in hot water. The aqueous solutions of BPTCA could be directly applied in treatments of cotton fabrics, and the hydrolyzed acid could directly react with hydroxyl groups on cellulose under a catalyst sodium hypophosphite to form ester bonds, crosslinking cellulose and providing wrinkle-free functions to the fabrics. BPTCA, as a derivative of photo-active benzophenone, can absorb UV lights and offer UV protective and photo-sensitive functions on the treated materials29,30. In this study, the photo-active functions of BPTCA treated cotton fabrics and the mechanism of the light induced mechanisms provided by the incorporated benzophenone group were investigated. The generated ROS, including hydroxyl radical and hydrogen peroxide, by the fabrics were measured, and the washing durability of the functions were investigated. Their antimicrobial activities were 2


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evaluated

against

Gram-negative

(Escherichia

coli)

and

Gram-positive

(Staphylococcus aureus) bacteria strains.

2. EXPERIMENTAL METHODS 2.1 Materials. Desized, scoured, and bleached pure cotton plain woven fabric (#400)

was

purchased

3,3′,4,4′-benzophenone

from

TestFabrics,

tetracarboxylic

p-nitrosodimethylaniline (p-NDA),

Inc.

(West

dianhydride

Pittston,

PA).

(BPTCD),

and sodium hypophosphite monohydrate were

purchased from Sigma Aldrich Chemical Co. (Louis, MO, USA). Potassium iodide, ammonium molybdate tetrahydrate and potassium hydrogen phthalate (KHP) were purchased from ACROS (New Jersey, USA). All other chemicals were purchased from Fisher Scientific (Pittsburgh, PA, USA). All reagents were used as received without any further purification. All water used in this study was deionized water. 2.2 Modification of cellulose fabrics with BPTCA. BPTCD was dissolved in deionized water in a certain concentration (10, 30, 50, 70 g/L) at 70-80 oC under agitation to completely hydrolyze to BPTCA. Sodium hypophosphite monohydrate was added as a catalyst to the BPTCA solution based on a molar ratio of catalyst:BPTCD = 1:2. The cotton fabric was first impregnated in the solution containing both BPTCA and the catalyst, then padded through two dips and two nips to reach an average wet pickup of 120%, dried at 90 oC for 3 min, and cured in a curing oven (Roaches International Ltd., Staffordshire, England) at a specified temperature (140, 160, 170, 180 oC) for 3 min. And at last the treated fabrics were washed with water and dried at ambient condition. 2.3 Characterization. Ultraviolet A (UVA), 320~420 nm, exposure of the fabrics was conducted in a UV cross-linker, Spectrolinker XL-1000 (Spectroline, USA), with five 8 w lamps in 365 nm wavelength. The distance between the UV lamps and the samples was 12 cm. The light intensity in the UV cross-linker was 3 mW/cm2. UV-vis absorption spectra were taken with an Evolution 600 UV-visible 3



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spectrophotometer (Thermo Scientific, USA) in a wavelength range of 350-500 nm. An indirect spectrophotometric method31,32 was used to measure the generation of hydroxyl radicals by the BPTCA treated fabrics. According to this method, p-NDA was used as a selective scavenger to measure the formation of hydroxyl radicals, whereas the formation of other reactive oxygen species (ROS) was neglected. Although p-NDA absorbs UVA radiation at 365 nm, according to the literature,32 itself does not generate any ROS. The modified fabric, 8.5×3 cm2, was put inside a 50 mL centrifuge tube. 20 mL p-NDA (20 µmol/L) phosphate buffer (0.01 M, pH 7.4) solution was added into the centrifuge tube, which was exposed under UVA light (365 nm) for a certain time. The concentration of p-NDA left in the solution after different exposure time was measured quantitatively through calibration method with a UV-vis spectroscopy at 440 nm. Hydrogen peroxide generated in the system was quantified with another indirect spectrophotometric method of using the UV-vis spectroscopy according to a Standard Operating Procedure: Procedure for Analyzing Hydrogen Peroxide Concentrations in Water (Procedure No: GSI/SOP/BS/RA/C/7, Issue Date: June 15, 2009). The modified fabric (8.5×3 cm2) was placed in a 50 mL centrifuge tube containing 6 mL deionized water, which was exposed under UVA light (365 nm) for a desired time. After the exposure, 3 mL of each sample solution was taken out from the tube and mixed with 3 mL of a reagent І (water solution of potassium iodide, 66 g/L, sodium hydroxide, 2 g/L, and ammonium molybdate tetrahydrate, 0.2 g/L) and 3 mL of a reagent П (water solution of potassium hydrogen phthalate, 20 g/L). The concentration of H2O2 in the sample solution was measured quantitatively with a prepared calibration curve at 351 nm, and then the quantity of H2O2 generated by the modified cotton fabric was obtained. Washing durability of the ROS generation property of the modified cotton fabrics was evaluated following an AATCC Standard Test Method 61-2009 (2A). The samples were placed in a Launder-O-meter using an accelerated laundering cycle at 49 ± 2 oC in a detergent solution. Then the samples were washed one, two and three times, respectively. Each accelerated washing is equivalent to five home launderings. 4


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The ROS generation property was then evaluated again following the above procedures. The antimicrobial activities of all samples were evaluated against Staphylococcus aureus (S. aureus) (ATCC 12600, a gram-positive bacterium) and Escherichia coli (E. coli) (ATCC K-12, a gram-negative bacterium) according to a modified testing method for antibacterial activity of textiles (AATCC standard test method 100). S. aureus and E. coli were incubated in nutrient broth and tryptic soy broth, respectively, at 37 oC for overnight (18–24 h), and then the cultures of the mid exponential-phase bacterium were diluted with phosphate buffer saline (PBS) to approximately 105 CFU/mL for later use. Two pieces of 3×3 cm2 swatches of the pristine and modified fabrics were placed in separated sterile petri dishes and inoculated with 300 µL diluted bacterial suspension, respectively. All samples were exposed to UVA (365 nm) light for 60 min in the UV-crosslinker, while control samples were covered and stored in dark environment for the same duration. Afterward, the fabrics were soaked in 30 mL of sterilized PBS solution, and then the mixture was shaken vigorously for 1 min. An aliquot of 0.1 mL of the mixture solution was taken out and diluted to 10, 102, 103 and 104 in series, then placed on an agar plate and incubated at 37 oC for 18 h. The same testing procedure was employed for a bacterial solution for no BPTCA modified cotton fabric, serving as an original control. The reduction rate of bacteria was calculated based on the numbers of colony forming units on agar plate according to Eq. (1). Reduction of bacteria (%) = (B–A) / B × 100

(1)

where B is the number of colony forming units of controls (without light exposure) and A is the number of colony forming units of light exposed samples. 3. RESULTS AND DISCUSSION 3.1 Functional modification of cellulose with BPTCA and generation of hydroxyl radical under UVA irradiation The primary goal of this work was to produce multifunctional cotton fabrics with desired

crosslinking

effects,

i.e.

wrinkle-free

functions

and

light-induced 5



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antimicrobial functions, by using the benzophenone group on the modified cotton30. According to the reaction mechanism discussed in the previous paper29, the amount of BPTCA in finishing baths and reaction temperature could significantly affect the formation of ester bonds and the amount of the loaded benzophenone groups on the fabrics. Thus, different concentrations of BPTCA (10, 30, 50, 70 g/L measured in amount of solid BPTCD) were used to treat the fabrics at selected curing temperatures (140, 160, 170, 180 oC). The crosslinking reaction of BPTCA with cellulose is shown in Scheme 1.

O

O

O

O H2O

O O

O BPTCD

O

O

O

HO

OH

HO

OH O

BPTCA

O

Scheme 1. Crosslinking reaction between cellulose and BPTCA Increasing BPTCA concentration in the finishing baths could increase the amount of benzophenone groups incorporated onto the cotton fabrics, which could consequently result in varied light-induced activities. P-NDA was used as a selective scavenger to measure the formation of hydroxyl radicals. Before and after different durations of light exposure, the p-NDA concentration left in the solution was obtained through a calibration curve. In the absence of L-histidine, the bleaching rate of p-NDA can be directly related to the production of hydroxyl radicals. The amounts of produced hydroxyl radicals after different UVA exposure time are calculated by Eqs. 2 and 3. ⊿C= C – Ct

(2)

Bleaching rate of p-NDA= ⊿C/C

(3) 6


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where C is the concentration of p-NDA solution at 0 min exposure time, Ct is the residual concentration of p-NDA solution at t min exposure time. For the cotton fabrics modified with different concentrations of BPTCA, the amounts of produced hydroxyl radicals after different UVA exposure times are compared in Figure 1. According to Figure 1, the amount of hydroxyl radicals formed increased as the UVA exposure time was extended. At the same UVA exposure time, the amount of hydroxyl radicals formed increased with the increase of the concentration of BPTCA in the finishing baths. Although the amount of hydroxyl radicals formed is determined by the amount of the benzophenone groups on the cotton fabrics, the high concentration of 70 g/L brings in concerns on cost and difficulty in dissolving the chemical. Thus, a concentration at 50 g/L was adopted for the explorations of other finishing parameters.

( ( ( (

∆C (P-NDA)/C (P-NDA) (%)

80

L / L L L / / / g g g g

0 0 0 0 1 3 5 7

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


) ) ) )

60

40

20

0

0

20

40

60

80

100

120

UVA exposure time (min)

Figure 1. Generation of hydroxyl radicals by the modified fabrics treated by different concentrations of BPTCA (Fabric treatment condition: Dried at 90 oC for 3 min; Cured at160 oC for 3 min)

Based on the above discussion, the cotton fabrics treated with BPTCA at 50 g/L were employed in a study on the effect of curing temperature. Here the curing temperatures were selected at 140, 160, 170, 180 C, respectively, and the amounts of 7



produced hydroxyl radicals after different times of UVA exposure are shown in Figure 2. The results revealed that the amount of hydroxyl radicals formed also increased as the UVA exposure time was extended. However, it seems that the curing temperature is not an important factor in incorporation of the photo-active groups. At the same UVA exposure time, the cotton fabrics modified at different curing temperatures produced similar amounts of hydroxyl radicals. Such a result is understandable since raising curing temperature probably could increase crosslinking rate of BPTCA with cellulose according to the reaction mechanism between BPTCA and cellulose28. But the photo-active group on the cellulose is determined by the amount of BPTCA groups on the cellulose, which is determined by the first ester bond formation that could occur effectively at lower temperature.

70

C o 0 4 1 C o 0 6 1 C

50

C o 0 8 1

∆C (P-NDA)/C(P-NDA) (%)

60

C o 0 7 1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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40 30 20 10 0

0

20

40

60

80

100

120

Time (min)

Figure 2. Generation of hydroxyl radical of the modified fabrics cured at different temperature. (BPTCD conc: 50g/L)

3.2 Generation of hydrogen peroxide of BPTCA modified cotton fabrics under UVA light irradiation The cotton fabrics modified with varied concentrations of BPTCA could produce H2O2 in addition to hydroxyl radicals. The amounts of the produced H2O2 by the modified cotton fabrics under different UVA exposure times were measured with the H2O2 measurement method and are shown in Figure 3. The results demonstrated that the modified cotton fabrics indeed generated H2O2 under UVA exposure as well. At 8


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the beginning of light exposure, the amounts of the produced H2O2 increased as the UVA exposure time was extended. After 20 min exposure time, the amounts of the produced H2O2 from the BPTCA modified fabrics in concentrations of 10 g/L and 30 g/L showed no significant improvement. The cotton fabrics modified with higher concentrations (50 g/L and 70 g/L) exhibited slightly increased amounts of H2O2 in a similar pattern. In general, the results are consistent with the expectation. 140

10 g/L 30 g/L 50 g/L 70 g/L

120 Hydrogen peroxide (ppm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


100 80 60 40 20 0

0

10

20

30

40

50

60


Figure 3. Generation of H2O2 of the modified fabrics with different amount of BPTCA Similarly, the amounts of H2O2 generated by the BPTCA treated fabrics with a concentration of 50 g/L and under varied curing temperatures were measured following the same method. The amounts of H2O2 produced by the fabrics at different UVA exposure times are shown in Figure 4. It can be seen that the amounts of H2O2 formed increased as the UVA exposure time was prolonged. At the same UVA exposure time, the amount of H2O2 formed by the modified cotton fabrics increased as temperature was raised. Such a result is different from the generated hydroxyl radicals, and was explained in the following section.

9



180

C o 0 4 1 C o 0 6 1

140

C o 0 8 1

Hydrogen peroxide (ppm)

160

C o 0 7 1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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120 100 80 60 40 20 0

0

10

20

30

40

50

60


Figure 4. Generation of H2O2 of the modified fabrics cured at different temperature. 3.3 Photochemical reaction mechanism of benzophenone BPTCA is an aromatic ketone, a derivative of benzophenone, which can be excited into its singlet status (singlet state BZ) after UV light (UVA, 365 nm) or daylight exposure. Going through internal system crossing (ISC), the singlet excited state of the compound can enter its triplet state (triplet state BZ). The benzophenone intermediate in the triplet state can be readily quenched by oxygen or can abstract a hydrogen atom from another molecule, such as a cellulose polymer in cotton fabric, to generate benzophenone radical and cellulose radical (Scheme 2: Eqns. 1-3)33,34. Under continuous light exposure, the benzophenone radical can react with oxygen to produce several reactive oxygen species (ROS) including hydroxyl radicals (·OH), superoxide (·O2-), and hydrogen peroxide (H2O2) (Scheme 2: Eqns. 4-7). Basically, if there are oxygen and hydrogen donors (R'–H) in the system, these benzophenone radicals will abstract hydrogen atoms from these donors and proceed following the reactions 4-7 to produce ROS, under UVA irradiation34. Therefore, the fabrics containing benzophenone chromophore group could be easily excited to the very active radical states and further produce ROS which can not only interact (kill) microorganisms but also react (decompose) toxic compounds, such as pesticides, when they are exposed to UV light27. 10


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(1)

(2)

(3)

(4)

(5)

(6)

(7)

Scheme 2. Photoactive reaction of benzophenone 11



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Page 12 of 21

The above reaction mechanisms of light-active benzophenone derivatives could explain the generations of hydroxyl radicals and hydrogen peroxide on the BPTCA treated fabrics. Hydrogen peroxide is more stable and could accumulate during light exposure, while hydroxyl radical has a very short life time and could be lost if too much is produced without reacting with the scavenger. Thus, the differences of curing temperatures on the generation of hydroxyl radicals and hydrogen peroxide (Figures 2 and 4) might be caused by the measurement methods. 3.4 Washing durability of ROS generation of the modified cotton fabrics. 3.4.1 Washing durability in term of hydroxyl radical generation. The BPTCA modified cotton fabrics were exposed to UVA (365 nm) for 120 min and the amounts of generated hydroxyl radicals were measured initially. Then they were washed following an accelerated laundry method (AATCC Standard Test Method 61-2009 (2A)), dried and exposed to UVA (365 nm) for 120 min again. And the amounts of the generated hydroxyl radical were also measured on the fabrics, respectively. The samples were rewashed, re-exposed to UVA and retested with the hydroxyl radical measurement method for two more times. Each accelerated washing is equivalent to five home launderings. The washing durability results of hydroxyl radical generations from the fabrics treated with different concentrations of BPTCA and cured under different temperatures are shown in Figures 5 and 6, respectively. According to Figures 5 and 6, after the first launder-o-meter washing, the amounts of produced hydroxyl radical of the BPTCA modified cotton fabrics decreased, possibly due to the loss of unbounded or hydrolyzed benzophenone groups. However, the decrease of the produced hydroxyl radical from the modified cotton fabrics was significantly reduced afterward in the following repeated washing.

12


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h s a w e r o f e B

0 8

s e m i t 5 h s a W

0 6 0 5 0 4 0 3 0 2 0 1

∆C (P-NDA) / C (P-NDA) (%)

s e m i t 5 1 h s a W

0 7 0

L / g 0 7

L / g 0 5

L / g 0 3

L / g 0 1

Figure 5. Washing durability of hydroxyl radical generation by BPTCA modified fabrics in different concentrations. h s a w e r o f e B s e m i t 5 h s a W s e m i t 5 1 h s a W

0 7 0 5 0 4 0 3 0 2 0 1 0

∆C (P-NDA) / C (P-NDA) (%)

0 6

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


140 ℃

160 ℃

170 ℃

180 ℃

Figure 6. Washing durability of hydroxyl radical generation by BPTCA modified fabrics cured under different temperatures

3.4.2 Washing durability in term of H2O2 generation. The modified cotton fabrics were exposed to UVA (365 nm) for 60 min and the amounts of generated H2O2 were measured. Following the same laundry procedure, the launder-o-meter washed fabrics were exposed to UVA (365 nm) for 60 min again and the amounts of generated H2O2 were also measured, respectively. The same procedure was repeated for three more 13



times, similar to the durability tests of hydroxyl radical generation. The results of measured H2O2 produced by these fabric samples are shown in Figures 7 and 8, respectively. Similarly, the first laundering resulted in more loses in the generated hydrogen peroxide, and the following washing produced less impact. 0 6 1 h s a w e r o f e B

0 4 1

s e m i t 0 1 h s a W s e m i t 5 1 h s a W

0 0 1 0 8 0 6 0 4 0 2

Hydrogen peroxide (ppm)

s e m i t 5 h s a W

0 2 1 0

L / g 0 7

L / g 0 5

L / g 0 3

L / g 0 1

Figure 7. Washing durability of H2O2 generation of the modified fabrics with different amount of BPTCD.

h s a w e r o f e B

0 8 1

s e m i t 5 h s a W s e m i t 5 1 h s a W

0 4 1 0 2 1 0 0 1 0 8 0 6 0 4 0 2

Hydrogen Peroxide (ppm)

s e m i t 0 1 h s a W

0 6 1 0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 21

140 ℃

160 ℃

170 ℃

180 ℃

Figure 8. Washing durability of H2O2 generation by BPTCA modified fabrics cured at different temperatures 14


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3.5 Antimicrobial activity From the above discussion, the modified cotton fabrics with BPTCA could generate both hydroxyl radicals and hydrogen peroxide in water under UVA light exposure, which could kill microorganisms. In order to evaluate the light-induced antibacterial activity of the BPTCA treated cotton fabrics, all samples were tested against E. coli (Gram-positive) and S. aureus (Gram-negative) according to a modified AATCC standard testing method 100. The pristine and modified cotton fabrics were inoculated with 105 CFU/mL bacterial suspension, and then illuminated under UVA light (365 nm) with a fluence dose of 3 mW/cm2 for 60 min (equivalent to a fluence dose of 10.8 J/cm2). The antibacterial results of the cotton fabrics modified with different concentrations of the chemical and cured under different temperatures are shown in Table 1. All treated fabric samples provided powerful light-induced antibacterial activities against both E. coli and S. aureus under the UVA irradiation. Even the samples modified with low concentration at 10g/L or cured at lower temperature still demonstrated excellent antibacterial activities under UV exposure. The excellent antibacterial results indicate that the photo-active compound, BPTCA, a derivative of benzophenone, retains its photoactive property even after being covalently incorporated to cellulose.

Table 1. Light-induced antimicrobial functions of the cotton fabrics modified with BPTCA Reduction rate of bacterial count (%) Samples

BPTCD

E. coli

S. aureus

(105 CFU/mL)

(105 CFU/mL)

10 g/L

99.99

99.99

30 g/L

99.99

99.99

50 g/L

99.99

99.99

70 g/L

99.99

99.99

140 oC

99.99

99.99 15



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Curing temperature

Page 16 of 21

160 oC

99.99

99.99

170 oC

99.99

99.99

180 oC

99.99

99.99

4. CONCLUSIONS 3,3’4,4’-Benzophenone tetracarboxylic acid is a photoactive compound but also a agent that could directly react with hydroxyl groups on cellulose to form ester bonds, leading to crosslinking cellulose by forming multiple ester bonds. The incorporated photoactive benzophenone groups on cotton fabrics could result in additional functions such as producing reactive oxygen species including hydroxyl radicals and hydrogen peroxide under UVA light exposure. Thus, the treated fabrics are multifunctional. And the light-active functions on the treated fabrics showed good washing durability. The cotton fabrics modified with different concentrations of the acid and cured at an elevated temperature demonstrated excellent antimicrobial activities.

AUTHOR INFORMATION

Corresponding Author *Phone: 530-752-0840. E-mail: [email protected].

ACKNOWLEDGMENTS

Dr. A. Hou is grateful for the financial support from Shanghai Municipal Education Commission for conducting research at University of California, Davis.

REFERENCES

(1) Sun, Y.; Sun, G. Synthesis, Characterization, and Antibacterial Activities of Novel N-Nalamine Polymer Beads Prepared by Suspension Copolymerization. Macromol. 2002, 35, 8909−8912. (2) Cerkez, I.; Kocer, H. B.; Worley, S. D.; Broughton, R. M.; Huang, T. S. N-Halamine Biocidal Coatings via a Layer-by-layer Assembly Technique. Langmuir 2011, 27, 4091−4097. 16


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Anthraquinone Compounds and Their Applications in Wastewater Treatment. Ind. Eng. Chem. Res. 2011, 50, 5326–5333.

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The modified cotton fabrics with 3,3′,4,4′-Benzophenone tetracarboxylic acid could produce reactive oxygen species (ROS), including hydroxyl radicals and hydrogen peroxide, under light exposure. They have excellent antimicrobial activities. 83x35mm (300 x 300 DPI)


UV Light-Induced Generation of Reactive Oxygen Species and

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