Applications of a new type of poly (methyl methacrylate)/TiO 2 nanocomposite as an antibacterial ...

16 Pages·2015·0.8 MB·English

Photochemical &
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Page 1 of 15 Photochemical & Photobiological Sciences
Applicationsof a new type of poly(methyl methacrylate)/TiO nanocompositeas an
2 t
p
antibacterial agent and reducing photocatalyst
i
r
c
s
u
n
Alireza Salabat*, Farid Mirhoseini
a
M
Department of Chemistry, Faculty of Science, Arak University, 38156-8-8349, Arak, Iran
d
e
*Corresponding Author:TEL: [phone];Fax: [phone]; t
p
E-mail address: [email protected] e
c
c
A
Abstract s
e
c
A new type of poly(methyl methacrylate) (PMMA)/TiO nanocomposite film sensitized by ionic
2 n
liquid with low dosage of TiO nanoparticles was prepared based on microemulsion method. The e
2
i
c
photocatalytic activity, via the photoreduction of 4-Nitrophenole (4-NP) to 4-Aminophenole (4-
S
AP) by NaBH and the photocatalytic-based antibacterial activity over Escherichia coli and
4 l
a
Staphylococcus arouse destruction of the prepared nanocomposite film were investigated. The c
i
g
conditions for maximum efficiencyin the present of visible light irradiation have been evaluated.
o
The rate constant of photoreduction of 4-NP to 4-AP was calculated and the maximum rate l
o
constantwas found over the 0.01wt.%of TiO content in photocatalystand solution pH of 7.5.A i
2 b
o
photocatalytic antibacterial maximum activity against gram negative bacterium was also
t
o
obtainedover the 0.01 wt.% of TiO content in photocatalyst. A notable exception of this work is
2 h
that PMMA/TiO nanocomposite films show efficient photocatalyst activity at very low loading P
2
of TiO in contrast of other previousreports. &
2
l
a
c
i
m
e
h
c
o
t
Keywords:TiO ; microemulsion; Photoreduction;4-Nitrophenole; Antibacterial activity
2 o
h
P
1
Photochemical & Photobiological Sciences Page 2 of 15
1. Introduction very low TiO content and to confirm the
2 t
p
necessity of visible light photocatalyst
i
Titanium dioxide (TiO ) as a popular r
2 c
applicability, a very simple process based on
s
photocatalyst has been drawing a lot of
ionic liquid-microemulsion system is u
attention because of its environmental n
conducted in this work to emphasis this global
a
applications in the decomposition of pollutants M
concerns.6 By using the ionic liquid based
and microbial species in water and air.1-3 Since
d
microemulsion system, a polymer-TiO
2
e
the past two decades, much scientific attention
nanocomposite can be deduced which not only t
p
in the field of polymer-based photocatalyst has
is visible light activephotocatalyst without any e
been focused owing to its advantages, such as c
additive, but also improves the recombination c
easy post treatment recovery.2,4 Some of A
of photogenerated holes and electron as the
various research works have additionally been s
major limitation of polymer-TiO2 mediated e
reported in the visible light active TiO c
2
photocatalysis. An important highlight as per
n
photocatalyst. Singh et al.2 presented a
e
our previous literature study is to prepare an
i
remarkable review that this comprehensive c
economical PMMA/ionic liquid sensitized
S
study covers over a hundred published papers.
TiO2 with very low dosage of TiO2. The l
a
Until today, as per other literature survey it
prepared low dosage of PMMA/ TiO can be c
2
appears that the polymer-based TiO was i
2 g
an effective photocatalyst in degradation of
o
fabricated with high loading of TiO and
2
methylene blue dye to overcome the main l
o
sometimes in presence of different sensitizer
drawback of the previous developed i
b
additive such as dye and noble metals.2,5
o
polymer/TiO nanocomposite that published
2 t
It must be noted that the preparation of novel o
by Magalhase et al.7 They prepared low
h
polymer-supported TiO nanocomposite with
2 density polyethylene (LDPE)/ TiO P
2
the above pleasing properties and especially
&
photocatalyst using various TiO contents (32,
2
low TiO contents is a utopia. As the best of
2 l
68, 82 wt.%). In progressing of our previous a
knowledge, we found that still any research c
research work in waste water treatment,6 in
i
papers have been reported on very low m
this study we considered the photodegradation
e
concentration of TiO in polymer composites.
2 of a phenolic compound and also photocatalyst h
This makes a promising research area to be c
antibacterial activity by using a very low TiO2 o
explored and developed further. In order to t
contents (0.008-0.014 wt.%) immobilized in o
providing a novel route for fabrication of a h
PMMA.
P
buoyant polymer-TiO nanocomposite with
2
2
Page 3 of 15 Photochemical & Photobiological Sciences
Phenolic compounds such as 4-Nitrophenol, candidate to use in the health care industry and
t
p
which is one of the organic pollutants listed by environment materials.17,18 Ratova et al.3
i
r
c
EPA in U.S.A, are carcinogenic and harmful produced LDPE/ TiO films by an extrusion
2
s
for the environment. These types of method and tested photocatalytic antibacterial u
n
compounds are extensively used in plastic activity, via the destruction of Escherichia coli
a
M
industries, petrochemical, agrochemical and so at the same time as TiO contents was 5 and 30
2
forth.8 The selective reduction of aromatic wt.%. They also investigated the d
e
nitro compounds to the corresponding photodecomposition of methylene blue dye t
p
aromatic amines which are widely utilized in under UV illumination by the same (LDPE)– e
c
the dyes, photographic, agricultural, and TiO films. Hence, in continuation of our c
2
A
pharmaceutical industries, is one of the research works on microemulsion systems as
s
fundamental transformation with reducing soft template for nanomaterials synthesis19,20, e
c
agents in organic synthesis.9 Photodegradation the chief object of the present examination is
n
e
of p-nitrophenol (PNP) has been investigated to focus on the some environmental
i
c
by Chen at different conditions, in aqueous applications of PMMA/TiO nanocomposite,
2 S
suspension of P25 TiO2 nanoparticles and also prepared by ionic liquid based microemulsion l
a
over immobilized P25 TiO nanoparticles.10 system. An interesting feature of advanced c
2
i
g
They reported pseudo firs-order kinetics that it innovative microemulsion systems is effective
o
respects for all of parent compounds. Indeed, and sustainable synthesis route with very low l
o
we underline to the role of TiO as a concentration of ionic liquid and TiO i
2 2 b
o
photocatalytic antibacterial material that has nanoparticles in composite. In our previous
t
o
considerable beneficial properties such as bio- report, PMMA/TiO /IL nanocomposite as a
2 h
compatibility, high potential for self-cleaning highly efficient visible light photocatalyst was P
and high antibacterial activity11,12 and is now synthesized and characterized.6 In the current &
l
the basis for a number of commercial work, the application of the prepared a
c
antibacterial products.13-16 PMMA/TiO /IL nanocomposite with very low
2 i
m
Surprisingly, there is an increasing interest in dosage of TiO for photoreduction of 4-NP has
2
e
combining photocatalytic activity of TiO and been investigated. The effects of TiO dosage, h
2 2
c
hydrophobic polymer for preparation of pH and light intensity of lamp on the rate o
t
polymer supported TiO in bacteriological constant of photoreduction process have been o
2
h
study.3 So, polymeric materials are a good determined. As a second application the
P
3
Photochemical & Photobiological Sciences Page 4 of 15
antibacterial effect of the nanocomposite was TX-100 (6.56 wt.%) and1-buthnol (2.24 wt.%)
t
p
also tested on the destruction of clinical strain was prepared. Then, different amounts of TiO
2 i
r
c
of Escherichia coli (Gram-negative) and nanoparticles were loaded into this
s
Staphylococcus arouse (Gram-positive) in microemulsion system. Benzoyl peroxide u
n
visible light. (BPO) as an initiator (0.2 wt.% based on the
a
M
weight of MMA) was added to the above
d
2. Experimental stabilized TiO colloidal systems to start
2
e
polymerization process at 60°C. For labeling t
p
Materials
purposes, the resultant transparent nanohybrid e
c
Hydrophilic ionic liquid, ([bmim][BF ]),and films of PMMA/TiO were termed as S1, S2, c
4 2
A
the nonionic surfactant of Triton X-100 were S3, and S4 referring to the amounts of TiO
2
s
purchased from Sigma-Aldrich. The titanium nanoparticles corresponding to 0.008, 0.01, e
c
dioxide TiO nanoparticles used in this study 0.012 and 0.014 wt.%. No apparent visible
2 n
e
was Degussa P25 (ca. 80% anatase, 20% phase separation was observed during
i
c
rutile, with a BET surface area of 50 m2/g and polymerization process for all samples. Pure
S
particle size of less than 15 nm). Methyl PMMA was also prepared under the same l
a
methacrylate (MMA) monomer (AR grade), condition and identically formulated c
i
g
benzoyl peroxide (BPO), 1-butanol, sodium microemulsion without TiO loading. The
2
o
borohydride and 4-nitrophenol as a pollutant nanocomposite films were obtained using an l
o
model were prepared from Merck. All aqueous automatic film applicator (ELCOMETER). i
b
o
solutions were prepared with deionized water The set-up of the automatic film applicator is
t
o
(0.055 µΩ) which was produced in our lab shown in Fig. S1†. All of the produced
h
with PKA (Smart two pure) instrument. transparent films had the uniform thickness P
&
with an average central thickness of 100 μm,
l
as measured by a micrometer. Techniques a
c
Preparation of the modified PMMA/TiO such as UV-Vis diffuse reflectance spectra
2 i
m
nanocomposite (DRS), TEM, FT-IR and TGA were used to
e
characterize the resulting modified h
In order to synthesis modified PMMA/TiO2 c
nanocomposite and reported in our previous o
nanocomposite a microemulsion system
t
paper.6 The UV-Vis transmittance was also o
consisting of hydrophilic ionic liquid
h
P
[bmim][BF ] (2.26 wt.%), MMA (88.94wt.%),
4
4
Page 5 of 15 Photochemical & Photobiological Sciences
used to claim transparency of the fabricated heterogeneously placed into a 20 mL of total
t
p
film. aqueous solution containing 4-nitrophenol
i
r
c
(0.144 mM) and excesses amount of 1.2M
UV-Vis transmittance s
sodium borohydride solution in the presenceof u
n
The UV-Vis transmittance spectrum of the visible light irradiation. During the reduction a
M
prepared nanocomposite for S2 as a typical process the UV−visible spectra of the reaction
d
sample was obtained in air at room mixture was recorded at intervals of 60 min.
e
temperature in the wavelength range of 200– Before analyzing with a double beam UV-vis t
p
600 nm by using a UV/Vis/NIR spectrophotometer (Perkin Elmer lambda 15), e
c
spectrophotometer (JASCO, V-670 (190-2700 the nanocomposite film was removed from all c
A
nm). solutions to stop reaction. The temperature of
s
the reaction solution was kept constant at e
Photocatalytic activitytest
c
25°C. Three following control samples were
n
Photoreactor and Photoreduction of 4-NP employed: blank (1), a solution of 4-NP e
i
c
without the photocatalyst and sodium
S
All the nanocomposites and pure PMMA films
borohydride, blank (2), a solution of 4-NP in l
were initially assessed for the photoreduction a
the presence of the photocatalyst without c
of 4-NP at normal laboratory environmental i
g
sodium borohydride, and blank (3), a solution
conditions. The photoreduction experiment o
of 4-NP with sodium borohydride and without l
was carried out in a glass beaker as the o
the photocatalyst. The removal efficiency was i
b
reaction vessel. The assembled photocatalytic
o
measured by applying the following equations:
activity test system was described elsewhere.6 t
o
In this system there is a sun-light fluorescent h
P
lamp attached vertically at the top. The (cid:2885)(cid:3116)(cid:2879)(cid:2885)(cid:3178)
% Photocatalytic efficiency = (cid:2885)(cid:3116) ×(110)0 &
distance between the light and the reactor was
l
a
fixed at 10 cm. The assembled system was where Ao (at 400 nm) is the initial absorbance c
placed inside a wooden box coloured black so of 4-NP at zero time and At the absorbance of mi
that no stray light can inter the reactor. The 4-NP at ttime. e
h
reduction of 4-nitrophenol to a beneficial c
o
compound, 4-aminophenol, by sodium
Antibacterial activity test (Kirby-Bauer t
o
borohydride was chosen as a model reaction.
h
method)
P
A thin film of the nanocomposite was
5
Photochemical & Photobiological Sciences Page 6 of 15
The photocatalytic-based antibacterial activity
t
p
of each of the produced nanocomposite films
i
3. Results and discussion r
c
and pure PMMA film were evaluated as a
UV-Vis transmittance s
series of photocatalytic experiments. A clinical u
The UV-Vis transmittance spectrum of the n
isolates Escherichia coli bacterium (from
a
prepared PMMA and PMMA/TiO
2 M
Gram-negative) and Staphylococcus arouse
nanocomposite (S2) is illustrated in ESI (Fig.
d
(from Gram-positive) were used for this study.
S2†). As expected, the UV-VIS spectrum of e
Agar well diffusion method21 was used for t
p
PMMA sample exhibit a transmittance of 60%
determination of the degree of photocatalytic e
and higher at or above 260 nm. The UV-Vis c
destruction of Escherichia coli and c
spectrum of PMMA/TiO2 is also revealed an A
Staphylococcus arouse. The pH was fixed at
increase in the transmittance at above 400 nm s
7.3. Briefly, sterile molten Mueller-Hinton e
due to the presence of TiO nanoparticles as
2 c
agar (20 ml) was poured into sterile petri
n
can be seen in Fig. S2†.
e
dishes and allowed to solidify at room
i
c
temperature. Pyre cultures of pathogenic
S
bacteria as 0.5 McFarland (108 CFU/ml) was Effect of TiO2 contents of nanocomposites l
a
swabbed on the Muller-Hinton agar plates. on the4-NP photoreduction c
i
g
Further 5 mm thin film disk of pure PMMA as
In order to study the kinetic of the o
a control sample and all of nanocomposite l
o
photoreduction process by UV-visible method,
films with different dosage of TiO (samples i
2 b
a time-dependent spectra for 4-NP/sodium
o
S1 to S4) were situated onto 5 mm paper disk
borohydride reaction mixture containing t
o
on the inoculated surface of Mueller-Hinton
nanocomposite (S2) was obtained and shown h
agar plates. Inoculated plates were incubated P
in Fig.1. As can be seen, the absorption band
&
for 24 h at 37 °C in a thermostatic light
of the nitrophenolate ions at ca. 400 nm is
l
incubator under visible light irradiation (lamp a
decreased, while the absorption band at ca.
c
60 W). The substrates were kept 20 cm away
i
300 nm increased due to the formation of m
from the light source. The zone of inhibition
aminophenolateions.22 e
was measured and the results were expressed h
c
as mm compared to control pure PMMA. This o
t
procedure was repeated three times. o
h
P
6
Page 7 of 15 Photochemical & Photobiological Sciences
t
p
i
r
c
s
u
n
a
M
d
e
t
p
e
c
c
A
s
e
c
n
e
i
c
Fig 1. Spectral patterns of 4-NP solution during the photocatalytic reduction process in the presence of S2 S
nanocomposite sample, under visible-light irradiation for 6 h. l
a
c
i
g
o
The photocatalytic activity of the prepared electron transfer from donor (BH -) to acceptor
4 l
o
nanocomposites was tested in photoreduction (4-NP). UV−visible spectrophotometric
i
b
of 4-NP by sodium borohydride in aqueous analysis substantiated that the modified o
t
solution. Fig. 2 shows the photoreduction PMMA/TiO served as a photocatalyst for the o
2
h
process of 4-NP at different conditions. The photoreduction reaction.
P
nitrophenolate ion as an intermediate forms in &
(2)
the aqueous solution of sodium borohydride l
(cid:2913)(cid:2911)(cid:2930)(cid:2911)(cid:2922)(cid:2935)(cid:2929)(cid:2930) a
from nitrophenol. The nitrophenolate ion can 4−NP+NaBH(cid:2872)(cid:4657)⎯⎯⎯⎯(cid:4654) 4−AP c
A reduction test on 4-NP as a blank (3)
i
m
be reduced to aminophenolate ion in the
(without photocatalyst) shows that, without
e
presence of desired PMMA/TiO photocatalyst
2 addition of a photocatalyst, the photoreduction h
c
and the reducing agent by equation (2).
of 4-NP by NaBH4 is slow and the o
Actually, visible light active TiO in this new t
2 photoreduction efficiency, which was o
type of nanocomposite is acted to expedite h
calculated by equation (1), is less than 9%
P
7
Photochemical & Photobiological Sciences Page 8 of 15
after 6h of visible light illumination. No absorbance and initial absorbance,
t
p
remarkable change was also observed for respectively. The result of plotting ln(A /A)
0 t i
r
c
blank (1) and (2) solutions. As can be seen versus the reaction time exhibits a good linear
s
from Fig. 2, the concentration of 4-NP correlation. The calculated rate constants of u
n
decreased as a function of irradiation time. photoreduction and the linear regression
a
M
Pure PMMA as S0 sample was also tested in values are reported in Table 1. The rate
d
photoreduction reaction and the obtained result constant toward the S2 sample of the
e
was same as the blank (3). The maximum photocatalyst was calculated as 3.3 × 10−3 t
p
photoreduction efficiency, calculated by min−1, which was the maximum value. As e
c
equation (1), was 78.25 %, belonging to shown in the results of Table 1, the rate c
A
sample S2, after 6 h irradiating. As we constant was increased with the increasing
s
expressed in our previous work,which was the dosage of TiO2 and approaching a limiting e
c
photocatalytic degradation of MB dye, it is value at high loading of nanoparticles. This
n
e
clearly found that the ionic liquid sensitized behaviour may be due to aggregation of
i
c
TiO supported PMMA could be an effective nanoparticles in polymer matrix which causing
2 S
catalyst for the water treatment.6 For this a decrease in the number of surface active l
a
catalyst a noticeable effect of IL on the sites. c
i
g
catalytic activity under visible light was
o
1.2
established and a suitable mechanism was l
o
proposed. 1 i
b
o
Since the sodium borohydride was used in 0.8
t
o
excess, the rate of photoreduction process can 0
A 0.6 h
bedescribed by the following equation22: A/t Blank (1) P
Blank (2)
0.4 Blank (3)
&
S0
(3) S1
0.2 S2 al
(cid:2914)[(cid:2872)(cid:2879)(cid:2898)(cid:2900)] (cid:2961) S3
c
(cid:2914)(cid:2930) = −(cid:1863)[4−NP] S4
where k is the rate constant of the 0 i
m
0 200 400
photoreduction. The concentration of 4-NP time (min) e
h
was calculated based on the absorbance at 400
c
Fig 2. Effect of TiO nanoparticles concentration of
2 o
nm. The rate constant could be determined
PMMA/TiO photocatalyst on 4-NP photoreduction t
2 o
from the slope of the plot of ln(A /A) versus
0 t under visible light irradiation. h
time. A and A are the time-dependent P
t 0
8
Page 9 of 15 Photochemical & Photobiological Sciences
Table 1The calculated pseudo first-order rate constants h++ H O → ·OH + H+ (4)
2 (ads) (ads) t
p
of 4-NP photoreduction and the linear regression values
i
Sample k× 10-3(min-1) R2 This reaction would increase the cr
Blank(1) 0.0900 0.7319 photoreduction of 4-NP by electron and holes s
Blank(2) 0.8000 0.8818 u
mechanismat neutral pH. n
Blank (3) 0.2000 0.9976
a
S0 0.2000 0.9800
M
S1 1.4001 0.9984 100
S2 3.3310 0.9995 on d
S3 1.7000 0.9831 cti e
u 80
S4 1.2011 0.9926 ed t
r p
o
Effect of pH hot 60 e
f p c
y o c
The pH value of the reaction medium during nc 40 A
e
ci
photoreduction reactions plays a very fi s
Ef 20
% e
significant role in the process design and c
0 n
control photocatalysts.6,23 To evaluate the
3 4 5 6 7 8 9 10 11 e
photocatalytic activity at different pH, the S2 pH ci
S
sample was used. The higher efficiencies were
Fig 3.Effect of solution pH on the 4-NP photoreduction
l
a
observed at pH value of about 7.5 (Fig.3). It is
over S2 nanocomposite sample under visible light
c
clear that the change in the solution pH has a irradiation. i
g
o
critical effect on the 4-NP photoreduction,
Effect of light intensity l
o
which directly affects the surface charge
i
b
The kinetics of the 4-NP photoreduction by
properties of the photocatalyst and the
o
adsorption of pollutants.6 As can be seen any (S2) sample, under three various visible light ot
lamps was studied. Table 2 contains a h
further decrease or increase of pH less than 7
P
summary of first order rate constants and
or more than 8, significantly decrease the
&
linear regression values of kinetic data. The
photocatalytic reduction efficiency. Therefore,
l
a
emission spectrum and the total radiation data
we suggest that a pH of 7.5 is optimum for the c
i
reduction of 4-NP with S2 sample of the fluorescence lamps (18, 36 and 60 W), m
nanocomposite.As Islam et al.23expressed the obtained using Avaspec 2048 TEC instrument e
h
effect of pH on degradation of 4-NP against at the same condition of the photocatalysis c
o
test,areshown in Fig.S3† and reported in table
TiO2 at neutral condition, the following t
o
reaction is possible for generation of ·OH: 2. It can be seen that the rate constant value of h
P
4-NP photoreduction under 60 W irradiating
9