RSC Advances
Paper
added to the beaker containing the shell samples and heated the dark for 15 min to obtain an adsorption–desorption equi-
ꢁ
with stirring at 60–70 C for 30 minutes. The shell samples were librium between the dyes and TiO2 and MoO –TiO2 nano-
3
ltered off with a strainer and the process was repeated a few composites and chitosan and chitosan-blended MoO –TiO2
3
more times until the ltrate became clear and colorless. The nanocomposite lms. Irradiation was carried out under open-
samples were washed with demineralized water to remove the air conditions. 50 mL of the dye solution with the synthesized
unreacted NaOH. For saving time, the shell samples can be catalysts were constantly aired by a pump to provide oxygen and
soaked in NaOH solution overnight aer the rst NaOH treat- for the thorough mixing of the reaction solution. It was
ment, followed by ltering and washing.
observed that the solvent did not volatilize during the illumi-
(
iii) Demineralization. 7% HCl was slowly added to the nation time. Aer dark adsorption, the rst sample was
shells and the mixture was stirred at room temperature until analyzed. At specic time intervals (15 min), 2–3 mL of the
effervescence ceased. The mixture was ltered-off and washed sample was withdrawn and centrifuged to separate the catalyst.
with excess distilled water. The samples were dried overnight in 1 mL of the sample was properly diluted and its absorbance at
ꢁ
a hot air oven at 60 C to obtain around 100 g of chitin. This step 464 nm was measured immediately to monitor the degradation
is known as demineralization.
iv) Synthesis of chitosan from chitin by partial deacetyla-
of the methyl orange.
(
tion. Chitin was loaded in a RB ask with 50% NaOH. The 2.8. Determination of antibacterial activity
ꢁ
samples were heated at 125 C for 2 h and then allowed to cool
The in vitro antibacterial action of the prepared samples was
examined using Gram negative bacteria (Escherichia coli ATCC
5922) by the well diffusion method. Nutrient agar was
down followed by the addition of 250 mL of water. On the next
day, the sample was ltered-off and the residue was washed
with excess water and dried in a hot air oven at 60 C for 2 h.
2
ꢁ
prepared and poured into sterile Petri dishes and allowed to
solidify. Bacterial cultures (E. coli) grown for 24 h were swabbed
on it. 5 wells (10 mm diameter) were made using a cork borer.
Four different concentrations (250 mg, 500 mg, 750 mg and 1000
mg) of the nanoparticle and one negative control were loaded
2
.4. Casting of the chitosan lm
A chitosan lm was synthesized by a solution cast method. 1 g
of chitosan was dissolved in 100 mL of 1% (v/v) acetic acid
solution and stirred for 24 hours. Subsequently, it was sonicated
for 15 min for efficient dispersion. It was then cast into a Petri-
ꢁ
into the wells. The plates were then incubated at 37 C for 24 h.
Aer incubation, the inhibition diameter was measured. The
percentage of inhibition was calculated using the following
formula (eqn (1))
ꢁ
dish and placed in an oven at 50–60 C for overnight to obtain a
homogeneous lm.
%
of inhibition ¼
2
.5. Casting of chitosan-blended MoO
nanocomposite lm
3 2
g of prepared MoO –TiO composites was added into the
3
–TiO
2
ꢀ
ꢁ
Iðdiameter of the inhibited zoneÞ
ꢂ100 (1)
9
0ðdiameter of the Petri-plate in mmÞ
1
chitosan solution (1 g of chitosan in 100 mL of 1% (v/v) acetic
acid) and the mixture was sonicated for 30 minutes and stirred
2.9. Instrumentation and analysis
continuously for 12 h until a clear solution was obtained. The The following physiochemical techniques have been used to
solution was cast onto Petri plates and dried at room temper- characterize the prepared catalysts. To characterize the phase
ature for 48 h to obtain the composite lm.
structure of the TiO2 and MoO –TiO nanocomposites and
3 2
chitosan and chitosan-blended MoO –TiO nanocomposite
3
2
lms, a Bruker D2 Phaser Desktop X-ray Diffractometer equip-
2
.6. Solar light intensity measurements
˚
ped with Ni-ltered Cu Ka radiation (l ¼ 1.542 A) was used, and
it was operated at an accelerating voltage and emission current
of 30 kV and 10 mA, respectively. Data were acquired over the
Solar light intensity was measured every 30 min and the average
light intensity over the period of each experiment was calcu-
lated. The sensor was always set in the position of maximum
intensity. The intensity of solar light was measured using a New
ꢁ
ꢁ
range of 2q from 0 to 70 with a step size of 0.0017 and a scan
ꢁ
ꢀ1
rate of 7 min . Field emission scanning electron microscopy
FESEM) was performed to examine the surface morphology of
200 000 Lux Digital Meter Light Luxmeter Meter Photometer
(
with a Footcandle FC. The intensity was 1200 ꢂ 100 ꢃ 100 lux
and it was nearly constant throughout the course of the
experiments.
the prepared nanocomposites using a DXS-10 ACKT scanning
electron microscope equipped with EXS, which was used to
study the elemental composition. For Fourier transform
infrared spectroscopy (FT-IR) analysis, the KBr pellets were
2.7. Photocatalytic degradation of methyl orange dye
prepared from the TiO
2
and MoO
3
–TiO
2
nanocomposites and
–TiO nanocomposite
The photocatalytic experiments were carried out under identical the chitosan and chitosan-blended MoO
3
2
conditions on sunny days between 11 a.m. and 2 p.m. In all the lms. FT-IR analysis was performed using a spectrophotometer
experiments, 50 mL of the reaction mixture was irradiated (Perkin Elmer RX1 instrument). Thermogravimetric-differential
under sunlight. An open borosilicate glass tube of 50 mL thermal analysis (TG-DTA) of the nanocomposites was carried
capacity, 40 cm height and 20 mm diameter was used as the out on a WATERS SDT Q 600 TA model instrument. Mechanical
reaction vessel. The suspensions were magnetically stirred in properties (tensile strength and elongation) of the lms were
42508 | RSC Adv., 2015, 5, 42506–42515
This journal is © The Royal Society of Chemistry 2015
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