Enhanced photodegradation of dyes and mixed
dyes by heterogeneous mesoporous Co–Fe/Al
2
O
3
–
MCM-41 nanocomposites: nanoparticles
formation, semiconductor behavior and
mesoporosity†
Amaresh C. Pradhan,
a
Malaya K. Sahoo,
a
Sankeerthana Bellamkonda,
a
K. M. Parida
*
b
and G. Ranga Rao
*
a
In situ loading of mono and bimetallic nanoparticles in the framework of mesoporous Al
2
O
3
–MCM-41 and
its effect on the photo-Fenton degradation of dyes and mixed dyes has been reported in the present study.
The nanocomposites are synthesized by in situ sol–gel cum hydrothermal method where oleic acid has
been used as capping agent for mono and bimetallic nanoparticles. Materials were characterized by high
and low angle XRD, N
2
sorption, and HRTEM to evaluate mesoporosity, morphology and textural
properties. The photoluminescence (PL) study and band gap energy measurement reveals suppression of
e
and h
+
recombination and semiconductor behaviour of bimetallic/Al
2
O
3
–MCM-41 in visible region.
Both the processes of photo-Fenton and photocatalysis takes place over mesoporous Co–Fe/Al
2
O
3
–
MCM-41 nanocomposite, which is found to be an efficient material with 100% efficiency for the
degradation of dyes and mixed dyes (100 mg L
1
) at pH 10 in just 60 minutes. Framework mesoporosity,
nanoparticle morphology of the nanocomposite, semiconductor behavior, lowering of the electron–hole
recombination and the formation of a large number of cOH radicals are the crucial factors for swift
degradation of dyes and mixed dyes by mesoporous Co–Fe/Al
2
O
3
–MCM-41 nanocomposite.
1. Introduction
Mesoporous materials with regular geometry have been recently
paid much attention owing to their great potential in practical
applications such as catalysis, adsorption, separation, sensing,
medical usage, ecology and nanotechnology. These applications
are tailored because of its unique three dimensional structures,
high surface area, tuneable and uniform pore channel and wide
volumes.
1–6
Among the mesoporous material, mesoporous silica
(MCM-41) and metals/metal oxides modied MCM-41 have
been treated as an efficient support and catalyst. The MCM-41
has been engineered by isomorphous substitution of metals
such as Al, Fe, Ti, Cu, Zn, V, Co (ref. 7–9) and extra-framework
modication by mesoporous Al
2
O
3
and mesoporous MnO
2
-
NPs.
10,11
The substitution and extra-framework modication of
metals and metal oxides leads to MCM-41 as an excellent
catalyst. The catalytic activity depends upon the morphology of
the incorporated metals and metal oxides. The best option is
zero dimensional nanoparticles which has large surface-to-
volume ratio and high surface atomic activity.
12
Fabrication of
iron based nanoparticles is an important task. Nanoparticles/
nanostructured Fe
2
O
3
have been synthesized by hydrothermal
method, precipitation method etc.
13–15
But fabrication of Fe
2
O
3
/
Fe nanoparticles by sol–gel method is difficult. Single metal
nanoparticles have small surface area that cause poor photo-
catalytic performances due to insufficient contact with the
reactants.
16
In order to avoid this problem, now researchers are
interested to fabricate metal nanoparticles (MNPs) within the
mesoporous support network. But it is also difficult to fabricate
MNPs within the mesoporous framework in one pot synthesis.
The combination of sol–gel and hydrothermal process in a one
pot method by using suitable template/structure-directing
agent may be helpful to achieve nanoparticles within meso-
porous support strategy. CTAB has been used as a structure
directing agent for synthesis of mesoporous Al
2
O
3
–MCM-41
because creation longer micelle by the formation of NH
4
OH
during synthesis in aqueous medium.
17
Oleic acid has been
treated as a capping agent for the synthesis of metal nano-
particles due to good ability and higher affinity to bind with the
surfaces of the metal precursor forming metal–oleates that in
turn regulate the nucleation and growth of the nanoparticles in
a
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036,
India. E-mail: grrao@iitm.ac.in
b
Centre for Nano Science and Nano Technology, Siksha ‘O’ Anusandhan University,
Bhubaneswar-751030, India. E-mail: paridakulamani@yahoo.com
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c6ra19923b
Cite this: RSC Adv. , 2016, 6, 94263
Received 6th August 2016
Accepted 25th September 2016
DOI: 10.1039/c6ra19923b
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This journal is © The Royal Society of Chemistry 2016 RSC Adv., 2016, 6, 94263–94277 | 94263
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