mouni roy - Academia.edu (original) (raw)

Papers by mouni roy

Mesoporous cube shaped hematite (a-Fe 2 O 3) particles were prepared using FeCl 3 as an Fe 3+ pre... more Mesoporous cube shaped hematite (a-Fe 2 O 3) particles were prepared using FeCl 3 as an Fe 3+ precursor and 1-butyl-3-methylimidazolium bromide (ionic liquid) as a soft template in the presence of different alkali metal (lithium, sodium and potassium) acetates, under hydrothermal conditions at 150 1C/4 h followed by calcination at 350 1C. The formation of the a-Fe 2 O 3 phase in the synthesized samples was confirmed by XRD, FTIR and Raman spectroscopy. Unlike K + ions, intercalation of Li + and Na + ions occurred in a-Fe 2 O 3 crystal layers as evidenced by XRD and Raman spectroscopy. Electron microscopy (FESEM and TEM) images showed the formation of cube-like particles of different sizes in the presence of Li + , Na + and K + ions. The mesoporosity of the products was confirmed by N 2 adsorption–desorption studies, while their optical properties were analyzed by UV-DRS. Na + ion intercalated a-Fe 2 O 3 micro-cubes showed improved coercivity (5.7 kOe) due to increased strain in crystals, and shape and magnetocrystalline anisotropy. Temperature dependent magnetization of the samples confirmed the existence of Morin temperature in the range of 199–260 K. Catalytic degradation of methylene blue (MB), a toxic water pollutant, was studied using the synthesized products via a heterogeneous photo-Fenton process. The degradation products were traced by electrospray ionization-mass spectrometry (ESI-MS). The a-Fe 2 O 3 microcubes obtained in the presence of Na + ions exhibited a more efficient degradation of MB to non-toxic open chain products.

A simple soft bi-templating process was used for the synthesis of mesoporous manganese oxide nano... more A simple soft bi-templating process was used for the synthesis of mesoporous manganese oxide nanostructures using KMnO 4 as a precursor and polyethylene glycol and cetyltrimethylammonium bromide as templates in the presence of benzaldehyde as an organic additive in alkaline media, followed by calcination at 400 1C. X-ray diffraction and Raman spectroscopic analysis of the calcined products confirmed the existence of stoichiometric (MnO 2 and Mn 5 O 8) and non-stoichiometric mixed phases (MnO 2 + Mn 5 O 8) of Mn oxides obtained by tuning the concentration of the additive and the synthesis time. The surface properties of the prepared Mn oxides were determined by X-ray photoelectron spectroscopy. The mesoporosity of the samples was confirmed by N 2 adsorption–desorption. Different synthetic conditions resulted in the formation of different morphologies of the Mn oxides (a-MnO 2 , Mn 5 O 8 , and a-MnO 2 + Mn 5 O 8), such as nanoparticles, nanorods, and nanowires. The synthesized mesoporous Mn oxide nanostructures were used for the catalytic oxidation of the harmful air pollutant carbon monoxide. The Mn 5 O 8 nanoparticles with the highest Brunauer–Emmett–Teller surface area and the non-stoichiometric manganese oxide (a-MnO 2 + Mn 5 O 8) nanorods with a higher Mn 3+ concentration had the best catalytic efficiency.

Cr2O3 nanocubes with porous structure were synthesized by solvothermal method at 150 C/24 h usin... more Cr2O3 nanocubes with porous structure were synthesized by solvothermal method at 150 C/24 h using
potassium dichromate (K2Cr2O7), N, N-dimethyl formamide (DMF) and water. Crystallization of Cr2O3
was noticed at 400 C. The vibration bands at 564 cm1 and 629 cm1 signified to CreO stretching of
Cr2O3, and the intense Raman peak at 532 cm1 was assigned to A1g symmetry of Cr2O3. The XPS results
show the binding energy of 576.8 eV, and 586.4 eV corresponding to Cr 2p3/2 and Cr 2p1/2, respectively of
Cr 2p of Cr2O3 phase. The absorption peaks at 455 nm and 600 nm reflect the d3 electronic transition of
Cr3þ ion attributing to 4A2g/4T1g and 4A2g/4T2g, respectively. The size of the nanocubes was about 50
e200 nm. The BET surface area and total pore volume of 400C- treated sample were found to be
23 m2 g1 and 0.18 cm3 g1, respectively.

Mesoporous self-assembled cobalt oxide (Co3O4) of different shapes was synthesized by a facile so... more Mesoporous self-assembled cobalt oxide (Co3O4) of different shapes was synthesized by a facile
soft-chemical process using cobalt nitrate, oxalic acid and phosphoric acid in the presence of cationic
templates, cetyltrimethylammonium bromide, 1-butyl-3-methylimidazolium bromide, and pyridinium
bromide at 75 1C/2 h followed by calcination at 300 1C. The effect of cationic templates of the samples
on the physico-chemical properties, and the photocatalytic efficiency for the degradation of Chicago
Sky Blue 6B was studied. Pyridinium bromide and 1-butyl-3-methylimidazolium bromide facilitated
formation of particles with different shaped morphology compared to cetyltrimethylammonium
bromide. The rod-like particles having higher surface area exhibited higher photocatalytic performance.

Porous cobalt oxide (Co3O4) nanorod (50–100 nm) and nanosheet-like (70–100 nm) particles were syn... more Porous cobalt oxide (Co3O4) nanorod (50–100 nm) and nanosheet-like (70–100 nm) particles were synthesized
by a facile hydrothermal method at 150 °C for 2–5 h and 12–24 h, respectively, using aqueousbased
precursors like cobalt nitrate, urea and water in the absence of any templating agents followed by
their calcination at 300 °C. Morphology and textural properties were tuned by changing the synthesis
time at 150 °C. A 3D architecture of Co3O4 was formed by the self-assembly of nanostructured (nanorod
and nanosheet) particles. The BET surface area, pore volume and pore diameter of the sample prepared
at 150 °C for 5 h were 112 m2 g−1, 0.5 cm3 g−1 and 7.4 nm, respectively, and it exhibited the highest catalytic
performance with a rate constant of 56.8 × 10−3 min−1 for the degradation of Chicago Sky Blue 6B, a
carcinogenic azo dye used in the textile, paper and food industries. Rod-like particles with a mesoporous
structure rendered a better catalytic efficiency than sheet-like particles having both microporous and
mesoporous structures. An interrelationship amongst the morphology, textural properties and the catalytic
efficiency of Co3O4 was established.

Mesoporous cube-shaped CuO with a multishell microcarpet-like patterned interior was synthesized ... more Mesoporous cube-shaped CuO with a multishell microcarpet-like
patterned interior was synthesized via a facile aqueous-based process using copper
nitrate, oxalic acid, and phosphoric acid in the presence of triblock copolymers
(TBCs), L64, P123, and F68 at 80 °C/2 h followed by calcination at 300−500 °C.
The obtained products were characterized by differential thermal analysis,
thermogravimetry, Fourier transform infrared spectroscopy, Raman spectroscopy,
X-ray diffraction, N2 adsorption−desorption, field emission scanning electron
microscopy, and transmission electron microscopy. A possible mechanism for the
formation of microcarpet-like patterned interiors in the presence of TBCs as
surfactants was illustrated.

Silver nanoparticles (AgNPs) dispersible in water were synthesized at room temperature in the pre... more Silver nanoparticles (AgNPs) dispersible in
water were synthesized at room temperature in the presence
of carambola fruit extract at different pH. The
UV–Vis absorption revealed that with increase in pH of the
solution, the intensity of the peaks became higher and
narrower along with blue shift signifying decrease in particle
size. Crystallinity of Ag in the synthesized product
was determined by X-ray diffraction. Fourier transform
infrared spectroscopy confirmed the presence of polyols,
aldehydes, amines and organic acids in the fruit extract
which became useful as capping and reducing agent for the
synthesis of AgNPs. Transmission electron microscopy
showed the average particle size of Ag as 16, 13 and 12 nm
for pH 4, pH 7 and pH 10, respectively, while the corresponding
sizes determined by DLS method were found to
be 169, 134 and 80 nm. The high negative zeta potential
values indicated dispersion stability of AgNPs. The present
method is important in terms of green, energy-efficient and
environmentally friendly process.

Dumbbell-shaped CuO particles were synthesized by a rapid hydrothermal process at 150 1C/2 h via ... more Dumbbell-shaped CuO particles were synthesized by a rapid hydrothermal process at 150 1C/2 h via
template-free route. Powder X-ray diffraction (PXRD) showed the crystallization of Cu2(OH)2CO3 in the
as-prepared samples, and monoclinic CuO phase for 300 1C-treated samples. The BET surface area, total
pore volume and average pore diameter of the samples were found to be 67.4 m2 g
1
, 0.39 cm3 g
1
, and
23 nm, respectively. Microstructural analysis indicated dumbbell-shaped morphology comprising of selfassembled
microrod-like particles (length 2–10 μm, dia 200–300 nm). Single-crystalline nature of the
particles was confirmed by selected area electron diffraction (SAED) and high resolution transmission
electron microscopy (HRTEM) images. A tentative formation mechanism was illustrated.

The synthesis of solvent-adoptable monometallic Ni and NiCo alloy nanochains by a one-pot solutio... more The synthesis of solvent-adoptable monometallic Ni
and NiCo alloy nanochains by a one-pot solution phase reduction
method in the presence of poly(4-vinylphenol) (PVPh) is
demonstrated. The elemental compositions of the as-prepared alloys
are determined by inductively coupled plasma optical emission
spectroscopy (ICP-OES) and energy-dispersive X-ray spectroscopy
(EDS), which are matching well with the target compositions. The
morphology analysis by TEM and FESEM confirms that the
nanochains are made up of organized spherical monometallic Ni or
bimetallic NiCo alloy nanoparticles (NPs). However, there is no
nanochain formation when the alloy is prepared without the polymer
PVPh. A possible mechanism for the formation of such NiCo alloy
nanochains is discussed. The X-ray diffraction and selected area
electron diffraction patterns reveal that the Ni/NiCo alloys are polycrystalline with fcc structure. The obtained Ni or NiCo alloy
nanostructures are ferromagnetic with very high coercivity. The polymer Ni/NiCo alloy nanochains are dispersible in both water
and organic media that makes them versatile enough to use as catalysts in the reactions carried out in both types of media. The
catalytic activities of these Ni/NiCo alloy nanochains are extremely high in the borohydride reduction of p-nitrophenol in water.
In organic solvents, these nanochains can act as efficient catalysts, under ligand-free condition, for the C−S cross-coupling
reactions of various aryl iodides and aryl thiols for obtaining the corresponding cross-coupled products in good to excellent yield
up to 96%. The NiCo nanochain also successfully catalyzes the C−O cross-coupling reaction in organic medium. A possible
mechanism for NiCo alloy nanochain-catalyzed cross-coupling reaction is proposed.

We describe a gelation study of a series of different fatty acid–amino acid conjugated amphiphile... more We describe a gelation study of a series of different fatty acid–amino acid conjugated amphiphiles in
various mixed solvent systems with water. Field emission scanning electron microscopy (FESEM),
polarized optical microscopy (POM) and X-ray diffraction (XRD) study reveals that the self-organization
of the amphiphile molecules in the mixed solvent leads to the formation of crystalline fibers, which
form the opaque white gel. This amino acid amphiphile-based gel acts as a catalyst as well as a
template for the hydrolysis/condensation of tetraethoxysilane (TEOS) to silica and forms a composite
gel. The methanol extraction of the opaque white as-prepared composite gel results in the formation of
a transparent nanostructured silica gel. The recovered amphiphilic gelator, after a methanol wash, can
be reused for preparing a gel, which can subsequently be used as a catalyst to prepare a nanostructured
silica gel again. The FESEM study confirms that the formed nanostructured silica gel is made up of
spherical silica nanoparticles. We also extend this gel-based catalysis strategy to prepare silica–zirconia
mixed oxide nanostructures. TEM examination reveals the formation of spherical silica–zirconia
nanoparticle of high surface area as confirmed through BET surface area measurement. Finally, the
photocatalytic activity of silica–zirconia mixed oxide is investigated towards methylene blue
degradation. The mixed oxide shows higher photocatalytic efficiency than neat zirconia nanostructures.

Mesoporous cube shaped hematite (a-Fe 2 O 3) particles were prepared using FeCl 3 as an Fe 3+ pre... more Mesoporous cube shaped hematite (a-Fe 2 O 3) particles were prepared using FeCl 3 as an Fe 3+ precursor and 1-butyl-3-methylimidazolium bromide (ionic liquid) as a soft template in the presence of different alkali metal (lithium, sodium and potassium) acetates, under hydrothermal conditions at 150 1C/4 h followed by calcination at 350 1C. The formation of the a-Fe 2 O 3 phase in the synthesized samples was confirmed by XRD, FTIR and Raman spectroscopy. Unlike K + ions, intercalation of Li + and Na + ions occurred in a-Fe 2 O 3 crystal layers as evidenced by XRD and Raman spectroscopy. Electron microscopy (FESEM and TEM) images showed the formation of cube-like particles of different sizes in the presence of Li + , Na + and K + ions. The mesoporosity of the products was confirmed by N 2 adsorption–desorption studies, while their optical properties were analyzed by UV-DRS. Na + ion intercalated a-Fe 2 O 3 micro-cubes showed improved coercivity (5.7 kOe) due to increased strain in crystals, and shape and magnetocrystalline anisotropy. Temperature dependent magnetization of the samples confirmed the existence of Morin temperature in the range of 199–260 K. Catalytic degradation of methylene blue (MB), a toxic water pollutant, was studied using the synthesized products via a heterogeneous photo-Fenton process. The degradation products were traced by electrospray ionization-mass spectrometry (ESI-MS). The a-Fe 2 O 3 microcubes obtained in the presence of Na + ions exhibited a more efficient degradation of MB to non-toxic open chain products.

A simple soft bi-templating process was used for the synthesis of mesoporous manganese oxide nano... more A simple soft bi-templating process was used for the synthesis of mesoporous manganese oxide nanostructures using KMnO 4 as a precursor and polyethylene glycol and cetyltrimethylammonium bromide as templates in the presence of benzaldehyde as an organic additive in alkaline media, followed by calcination at 400 1C. X-ray diffraction and Raman spectroscopic analysis of the calcined products confirmed the existence of stoichiometric (MnO 2 and Mn 5 O 8) and non-stoichiometric mixed phases (MnO 2 + Mn 5 O 8) of Mn oxides obtained by tuning the concentration of the additive and the synthesis time. The surface properties of the prepared Mn oxides were determined by X-ray photoelectron spectroscopy. The mesoporosity of the samples was confirmed by N 2 adsorption–desorption. Different synthetic conditions resulted in the formation of different morphologies of the Mn oxides (a-MnO 2 , Mn 5 O 8 , and a-MnO 2 + Mn 5 O 8), such as nanoparticles, nanorods, and nanowires. The synthesized mesoporous Mn oxide nanostructures were used for the catalytic oxidation of the harmful air pollutant carbon monoxide. The Mn 5 O 8 nanoparticles with the highest Brunauer–Emmett–Teller surface area and the non-stoichiometric manganese oxide (a-MnO 2 + Mn 5 O 8) nanorods with a higher Mn 3+ concentration had the best catalytic efficiency.

Cr2O3 nanocubes with porous structure were synthesized by solvothermal method at 150 C/24 h usin... more Cr2O3 nanocubes with porous structure were synthesized by solvothermal method at 150 C/24 h using
potassium dichromate (K2Cr2O7), N, N-dimethyl formamide (DMF) and water. Crystallization of Cr2O3
was noticed at 400 C. The vibration bands at 564 cm1 and 629 cm1 signified to CreO stretching of
Cr2O3, and the intense Raman peak at 532 cm1 was assigned to A1g symmetry of Cr2O3. The XPS results
show the binding energy of 576.8 eV, and 586.4 eV corresponding to Cr 2p3/2 and Cr 2p1/2, respectively of
Cr 2p of Cr2O3 phase. The absorption peaks at 455 nm and 600 nm reflect the d3 electronic transition of
Cr3þ ion attributing to 4A2g/4T1g and 4A2g/4T2g, respectively. The size of the nanocubes was about 50
e200 nm. The BET surface area and total pore volume of 400C- treated sample were found to be
23 m2 g1 and 0.18 cm3 g1, respectively.

Mesoporous self-assembled cobalt oxide (Co3O4) of different shapes was synthesized by a facile so... more Mesoporous self-assembled cobalt oxide (Co3O4) of different shapes was synthesized by a facile
soft-chemical process using cobalt nitrate, oxalic acid and phosphoric acid in the presence of cationic
templates, cetyltrimethylammonium bromide, 1-butyl-3-methylimidazolium bromide, and pyridinium
bromide at 75 1C/2 h followed by calcination at 300 1C. The effect of cationic templates of the samples
on the physico-chemical properties, and the photocatalytic efficiency for the degradation of Chicago
Sky Blue 6B was studied. Pyridinium bromide and 1-butyl-3-methylimidazolium bromide facilitated
formation of particles with different shaped morphology compared to cetyltrimethylammonium
bromide. The rod-like particles having higher surface area exhibited higher photocatalytic performance.

Porous cobalt oxide (Co3O4) nanorod (50–100 nm) and nanosheet-like (70–100 nm) particles were syn... more Porous cobalt oxide (Co3O4) nanorod (50–100 nm) and nanosheet-like (70–100 nm) particles were synthesized
by a facile hydrothermal method at 150 °C for 2–5 h and 12–24 h, respectively, using aqueousbased
precursors like cobalt nitrate, urea and water in the absence of any templating agents followed by
their calcination at 300 °C. Morphology and textural properties were tuned by changing the synthesis
time at 150 °C. A 3D architecture of Co3O4 was formed by the self-assembly of nanostructured (nanorod
and nanosheet) particles. The BET surface area, pore volume and pore diameter of the sample prepared
at 150 °C for 5 h were 112 m2 g−1, 0.5 cm3 g−1 and 7.4 nm, respectively, and it exhibited the highest catalytic
performance with a rate constant of 56.8 × 10−3 min−1 for the degradation of Chicago Sky Blue 6B, a
carcinogenic azo dye used in the textile, paper and food industries. Rod-like particles with a mesoporous
structure rendered a better catalytic efficiency than sheet-like particles having both microporous and
mesoporous structures. An interrelationship amongst the morphology, textural properties and the catalytic
efficiency of Co3O4 was established.

Mesoporous cube-shaped CuO with a multishell microcarpet-like patterned interior was synthesized ... more Mesoporous cube-shaped CuO with a multishell microcarpet-like
patterned interior was synthesized via a facile aqueous-based process using copper
nitrate, oxalic acid, and phosphoric acid in the presence of triblock copolymers
(TBCs), L64, P123, and F68 at 80 °C/2 h followed by calcination at 300−500 °C.
The obtained products were characterized by differential thermal analysis,
thermogravimetry, Fourier transform infrared spectroscopy, Raman spectroscopy,
X-ray diffraction, N2 adsorption−desorption, field emission scanning electron
microscopy, and transmission electron microscopy. A possible mechanism for the
formation of microcarpet-like patterned interiors in the presence of TBCs as
surfactants was illustrated.

Silver nanoparticles (AgNPs) dispersible in water were synthesized at room temperature in the pre... more Silver nanoparticles (AgNPs) dispersible in
water were synthesized at room temperature in the presence
of carambola fruit extract at different pH. The
UV–Vis absorption revealed that with increase in pH of the
solution, the intensity of the peaks became higher and
narrower along with blue shift signifying decrease in particle
size. Crystallinity of Ag in the synthesized product
was determined by X-ray diffraction. Fourier transform
infrared spectroscopy confirmed the presence of polyols,
aldehydes, amines and organic acids in the fruit extract
which became useful as capping and reducing agent for the
synthesis of AgNPs. Transmission electron microscopy
showed the average particle size of Ag as 16, 13 and 12 nm
for pH 4, pH 7 and pH 10, respectively, while the corresponding
sizes determined by DLS method were found to
be 169, 134 and 80 nm. The high negative zeta potential
values indicated dispersion stability of AgNPs. The present
method is important in terms of green, energy-efficient and
environmentally friendly process.

Dumbbell-shaped CuO particles were synthesized by a rapid hydrothermal process at 150 1C/2 h via ... more Dumbbell-shaped CuO particles were synthesized by a rapid hydrothermal process at 150 1C/2 h via
template-free route. Powder X-ray diffraction (PXRD) showed the crystallization of Cu2(OH)2CO3 in the
as-prepared samples, and monoclinic CuO phase for 300 1C-treated samples. The BET surface area, total
pore volume and average pore diameter of the samples were found to be 67.4 m2 g
1
, 0.39 cm3 g
1
, and
23 nm, respectively. Microstructural analysis indicated dumbbell-shaped morphology comprising of selfassembled
microrod-like particles (length 2–10 μm, dia 200–300 nm). Single-crystalline nature of the
particles was confirmed by selected area electron diffraction (SAED) and high resolution transmission
electron microscopy (HRTEM) images. A tentative formation mechanism was illustrated.

The synthesis of solvent-adoptable monometallic Ni and NiCo alloy nanochains by a one-pot solutio... more The synthesis of solvent-adoptable monometallic Ni
and NiCo alloy nanochains by a one-pot solution phase reduction
method in the presence of poly(4-vinylphenol) (PVPh) is
demonstrated. The elemental compositions of the as-prepared alloys
are determined by inductively coupled plasma optical emission
spectroscopy (ICP-OES) and energy-dispersive X-ray spectroscopy
(EDS), which are matching well with the target compositions. The
morphology analysis by TEM and FESEM confirms that the
nanochains are made up of organized spherical monometallic Ni or
bimetallic NiCo alloy nanoparticles (NPs). However, there is no
nanochain formation when the alloy is prepared without the polymer
PVPh. A possible mechanism for the formation of such NiCo alloy
nanochains is discussed. The X-ray diffraction and selected area
electron diffraction patterns reveal that the Ni/NiCo alloys are polycrystalline with fcc structure. The obtained Ni or NiCo alloy
nanostructures are ferromagnetic with very high coercivity. The polymer Ni/NiCo alloy nanochains are dispersible in both water
and organic media that makes them versatile enough to use as catalysts in the reactions carried out in both types of media. The
catalytic activities of these Ni/NiCo alloy nanochains are extremely high in the borohydride reduction of p-nitrophenol in water.
In organic solvents, these nanochains can act as efficient catalysts, under ligand-free condition, for the C−S cross-coupling
reactions of various aryl iodides and aryl thiols for obtaining the corresponding cross-coupled products in good to excellent yield
up to 96%. The NiCo nanochain also successfully catalyzes the C−O cross-coupling reaction in organic medium. A possible
mechanism for NiCo alloy nanochain-catalyzed cross-coupling reaction is proposed.

We describe a gelation study of a series of different fatty acid–amino acid conjugated amphiphile... more We describe a gelation study of a series of different fatty acid–amino acid conjugated amphiphiles in
various mixed solvent systems with water. Field emission scanning electron microscopy (FESEM),
polarized optical microscopy (POM) and X-ray diffraction (XRD) study reveals that the self-organization
of the amphiphile molecules in the mixed solvent leads to the formation of crystalline fibers, which
form the opaque white gel. This amino acid amphiphile-based gel acts as a catalyst as well as a
template for the hydrolysis/condensation of tetraethoxysilane (TEOS) to silica and forms a composite
gel. The methanol extraction of the opaque white as-prepared composite gel results in the formation of
a transparent nanostructured silica gel. The recovered amphiphilic gelator, after a methanol wash, can
be reused for preparing a gel, which can subsequently be used as a catalyst to prepare a nanostructured
silica gel again. The FESEM study confirms that the formed nanostructured silica gel is made up of
spherical silica nanoparticles. We also extend this gel-based catalysis strategy to prepare silica–zirconia
mixed oxide nanostructures. TEM examination reveals the formation of spherical silica–zirconia
nanoparticle of high surface area as confirmed through BET surface area measurement. Finally, the
photocatalytic activity of silica–zirconia mixed oxide is investigated towards methylene blue
degradation. The mixed oxide shows higher photocatalytic efficiency than neat zirconia nanostructures.