Visible-light-induced photocatalytic reduction of aromatic nitrobenzenes to the corresponding anilinesat room temperature using reduced graphene oxide (rGO) immobilized iron(II) bipyridine complex asphotocatalyst is described. The rGO-immobilized iron catalyst exhibited superior catalytic activity thanhomogeneous iron(II) bipyridine complex and much higher than metal free rGO photocatalysts. Theheterogeneous photocatalyst was found to be robust and could easily be recovered and reused for severalruns without any significant loss in photocatalytic activity.
Graphene oxide grafted with iridium complex as a superior heterogeneous catal...Pawan Kumar
A novel graphene oxide (GO)-immobilized heteroleptic iridium complex was synthesized and demonstrated
as a first heterogenized homogeneous catalyst for the production of dimethylformamide (DMF)
from carbon dioxide, hydrogen, and dimethylamine. The synthesized hybrid catalyst showed comparable
activity as homogeneous heteroleptic iridium complex with additional benefits such as facile recovery
and recycling of the catalyst. After completion of the reaction, the heterogeneous catalyst was easily
recovered by filtration, and reused for subsequent recycling processes without any significant change in
the catalytic efficiency.
Graphene oxide grafted with iridium complex as a superior heterogeneous catal...Pawan Kumar
A novel graphene oxide (GO)-immobilized heteroleptic iridium complex was synthesized and demonstrated
as a first heterogenized homogeneous catalyst for the production of dimethylformamide (DMF)
from carbon dioxide, hydrogen, and dimethylamine. The synthesized hybrid catalyst showed comparable
activity as homogeneous heteroleptic iridium complex with additional benefits such as facile recovery
and recycling of the catalyst. After completion of the reaction, the heterogeneous catalyst was easily
recovered by filtration, and reused for subsequent recycling processes without any significant change in
the catalytic efficiency.
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Reduced graphene oxide–CuO nanocomposites for photocatalyticconversion of CO2...Pawan Kumar
tReduced graphene oxide (rGO)–copper oxide nanocomposites are prepared by covalent grafting of CuOnanorods on the rGO skeleton. Chemical and structural features of rGO–CuO nanocomposites are probedby FTIR, XPS, XRD and HRTEM analyses. Photocatalytic potential of rGO–CuO nanocomposites is exploredfor reduction of CO2into the methanol under the visible light irradiation. The breadth of CuO nanorods andthe oxidation state of Cu in the rGO–CuO/Cu2O nanocomposites are systematically varied to investigatetheir photocatalytic activities. The pristine CuO nanorods exhibited very low photocatalytic activity owingto fast recombination of charge carriers and yielded 175 mol g−1methanol, whereas rGO–Cu2O andrGO–CuO exhibited significantly improved photocatalytic activities and yielded five (862 mol g−1) andseven (1228 mol g−1) folds methanol, respectively. The superior photocatalytic activity of CuO in therGO–CuO nanocomposites was attributed to slow recombination of charge carriers and efficient transferof photo-generated electrons through the rGO skeleton. This study further excludes the use of scavengingdonor.
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Nickel Decorated on Phosphorous-Doped Carbon Nitride as an Efficient Photocat...Pawan Kumar
Nickel nanoparticle-decorated phosphorous-doped graphitic carbon nitride (Ni@g-PC3N4)
was synthesized and used as an efficient photoactive catalyst for the reduction of various
nitrobenzenes under visible light irradiation. Hydrazine monohydrate was used as the source
of protons and electrons for the intended reaction. The developed photocatalyst was found to be
highly active and afforded excellent product yields under mild experimental conditions. In addition,
the photocatalyst could easily be recovered and reused for several runs without any detectable
leaching during the reaction.
Graphene oxide grafted with iridium complex as a superior heterogeneous catal...Pawan Kumar
A novel graphene oxide (GO)-immobilized heteroleptic iridium complex was synthesized and demonstrated
as a first heterogenized homogeneous catalyst for the production of dimethylformamide (DMF)
from carbon dioxide, hydrogen, and dimethylamine. The synthesized hybrid catalyst showed comparable
activity as homogeneous heteroleptic iridium complex with additional benefits such as facile recovery
and recycling of the catalyst. After completion of the reaction, the heterogeneous catalyst was easily
recovered by filtration, and reused for subsequent recycling processes without any significant change in
the catalytic efficiency.
Graphene oxide grafted with iridium complex as a superior heterogeneous catal...Pawan Kumar
A novel graphene oxide (GO)-immobilized heteroleptic iridium complex was synthesized and demonstrated
as a first heterogenized homogeneous catalyst for the production of dimethylformamide (DMF)
from carbon dioxide, hydrogen, and dimethylamine. The synthesized hybrid catalyst showed comparable
activity as homogeneous heteroleptic iridium complex with additional benefits such as facile recovery
and recycling of the catalyst. After completion of the reaction, the heterogeneous catalyst was easily
recovered by filtration, and reused for subsequent recycling processes without any significant change in
the catalytic efficiency.
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Reduced graphene oxide–CuO nanocomposites for photocatalyticconversion of CO2...Pawan Kumar
tReduced graphene oxide (rGO)–copper oxide nanocomposites are prepared by covalent grafting of CuOnanorods on the rGO skeleton. Chemical and structural features of rGO–CuO nanocomposites are probedby FTIR, XPS, XRD and HRTEM analyses. Photocatalytic potential of rGO–CuO nanocomposites is exploredfor reduction of CO2into the methanol under the visible light irradiation. The breadth of CuO nanorods andthe oxidation state of Cu in the rGO–CuO/Cu2O nanocomposites are systematically varied to investigatetheir photocatalytic activities. The pristine CuO nanorods exhibited very low photocatalytic activity owingto fast recombination of charge carriers and yielded 175 mol g−1methanol, whereas rGO–Cu2O andrGO–CuO exhibited significantly improved photocatalytic activities and yielded five (862 mol g−1) andseven (1228 mol g−1) folds methanol, respectively. The superior photocatalytic activity of CuO in therGO–CuO nanocomposites was attributed to slow recombination of charge carriers and efficient transferof photo-generated electrons through the rGO skeleton. This study further excludes the use of scavengingdonor.
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Nickel Decorated on Phosphorous-Doped Carbon Nitride as an Efficient Photocat...Pawan Kumar
Nickel nanoparticle-decorated phosphorous-doped graphitic carbon nitride (Ni@g-PC3N4)
was synthesized and used as an efficient photoactive catalyst for the reduction of various
nitrobenzenes under visible light irradiation. Hydrazine monohydrate was used as the source
of protons and electrons for the intended reaction. The developed photocatalyst was found to be
highly active and afforded excellent product yields under mild experimental conditions. In addition,
the photocatalyst could easily be recovered and reused for several runs without any detectable
leaching during the reaction.
Visible Light Photocatalytic Degradation of Methylene Blue and Malachite Gree...IJEAB
A facile solid state metathesis synthesis of barium tungstate (BaWO4) followed by ball milling and subsequent preparation of barium tungstate-graphene oxide (BaWO4–GO) nano composite using a colloidal blending process and its application as a visible light photocatalyst for the degradation of Malachite green and Methylene blue dyes. The morphology and composition of barium tungstate (BaWO4) nano composite have been characterized using X-Ray Diffraction (XRD), UV–Visible Diffuse Reflectance Spectra (UV-DRS), Raman Spectra, Field Emission Scanning Electron Microscopy (FESEM) – EDAX and UV Visible Spectroscopy. This composite material is found to be a wide band gap semiconductor with band gap of 4.3 eV. The sample shows poor transmittance in ultraviolet region while it has maximum transmittance in visible-near infrared regions. It shows an increase in range and intensity of light absorption and the reduction of electron–hole pair recombination in BaWO4 with the introducing of GO on to it.
Carbon Dioxide to Chemicals and Fuels Course Material.
National Centre for Catalysis Research (NCCR, IIT Madras), considered for the first on-line course the topic of Carbon dioxide to Chemicals and Fuels. NCCR has learnt many such lessons which are necessary for the researchers to understand and also have a complete comprehension of the limitations.
REDUCTION AND REDUCING AGENTS. in this presentation we explain the
Definition
Identification
Position in periodic table
Examples etc
of reduction and reducing agents.
Photocatalytic Properties of GO-(Cd0.8-Zn0.2)S Nanocomposites Prepared by Che...IJLT EMAS
Graphene oxide - (Cd0.8-Zn0.2)S nanocomposite
material was synthesized by the simple and economically viable
chemical precipitation method at different temperatures and its
photocatalytic properties were investigated. Measurement of
photocatalytic degradation of Rhodamine B dye was carried out
under visible light. The photocatalytic efficiency of the
synthesized nanocomposites was calculated and the effect of bath
temperature on the photocatalytic efficiency was studied. The
studies suggest that the prepared nanocomposites exhibit
reasonably good photocatalytic properties. Better photocatalysis
is observed at lower bath temperatures for preparation of the
nanocomposites. Photocatalytic efficiency close to 70% has been
obtained for the synthesised GO-(Cd0.8-Zn0.2) S nanocomposites
which can be further improved by optimizing the preparative
conditions
Abstract— 2, 4-dinitrophenol and 2, 4, 6- trinitrophenol were successfully photodegraded using visible light active monoclinic BiVO4 as photocatalyst. 10ppm of dinitrophenol is photodegraded using 50mg BiVO4 under irradiation for 3h. 10ppm trinitrophenol is photodegraded using 100mg BiVO4 under irradiation for 3h. Ease of photodegradation of DNP and TNP varied in the order DNP > TNP for the same amount of photocatalyst. Photoluminescence studies confirmed the formation of •OH free radicals due to irradiation. Synergetic effect is noticed between BiVO4 and H2O2.
PEGylated magnetic nanoparticles (PEG@Fe3O4) as cost effectivealternative for...Pawan Kumar
An efficient, cost effective and environmental friendly PEGylated magnetic nanoparticle catalyzed oxida-tive cyanation via CH activation of tertiary amines to corresponding -aminonitriles using hydrogenperoxide as oxidant and sodium cyanide as cyanide source is described. The synthesized nanocatalyst waseasily recovered with the help of external magnet and was successfully reused for several runs withoutany significant loss in catalytic activity.
PEGylated magnetic nanoparticles (PEG@Fe3O4) as cost effectivealternative for...Pawan Kumar
tAn efficient, cost effective and environmental friendly PEGylated magnetic nanoparticle catalyzed oxida-tive cyanation via CH activation of tertiary amines to corresponding -aminonitriles using hydrogenperoxide as oxidant and sodium cyanide as cyanide source is described. The synthesized nanocatalyst waseasily recovered with the help of external magnet and was successfully reused for several runs withoutany significant loss in catalytic activity.
Reduced graphene oxide–CuO nanocomposites for photocatalyticconversion of CO2...Pawan Kumar
Reduced graphene oxide (rGO)–copper oxide nanocomposites are prepared by covalent grafting of CuOnanorods on the rGO skeleton. Chemical and structural features of rGO–CuO nanocomposites are probedby FTIR, XPS, XRD and HRTEM analyses. Photocatalytic potential of rGO–CuO nanocomposites is exploredfor reduction of CO2into the methanol under the visible light irradiation. The breadth of CuO nanorods andthe oxidation state of Cu in the rGO–CuO/Cu2O nanocomposites are systematically varied to investigatetheir photocatalytic activities. The pristine CuO nanorods exhibited very low photocatalytic activity owingto fast recombination of charge carriers and yielded 175 mol g−1methanol, whereas rGO–Cu2O andrGO–CuO exhibited significantly improved photocatalytic activities and yielded five (862 mol g−1) andseven (1228 mol g−1) folds methanol, respectively. The superior photocatalytic activity of CuO in therGO–CuO nanocomposites was attributed to slow recombination of charge carriers and efficient transferof photo-generated electrons through the rGO skeleton. This study further excludes the use of scavengingdonor.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after 24 h irradiation was 9934 μmol g−1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride 145 μmol g−1cat under identical conditions. The presence of triethylamine was found to be vital for the higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Visible Light Photocatalytic Degradation of Methylene Blue and Malachite Gree...IJEAB
A facile solid state metathesis synthesis of barium tungstate (BaWO4) followed by ball milling and subsequent preparation of barium tungstate-graphene oxide (BaWO4–GO) nano composite using a colloidal blending process and its application as a visible light photocatalyst for the degradation of Malachite green and Methylene blue dyes. The morphology and composition of barium tungstate (BaWO4) nano composite have been characterized using X-Ray Diffraction (XRD), UV–Visible Diffuse Reflectance Spectra (UV-DRS), Raman Spectra, Field Emission Scanning Electron Microscopy (FESEM) – EDAX and UV Visible Spectroscopy. This composite material is found to be a wide band gap semiconductor with band gap of 4.3 eV. The sample shows poor transmittance in ultraviolet region while it has maximum transmittance in visible-near infrared regions. It shows an increase in range and intensity of light absorption and the reduction of electron–hole pair recombination in BaWO4 with the introducing of GO on to it.
Carbon Dioxide to Chemicals and Fuels Course Material.
National Centre for Catalysis Research (NCCR, IIT Madras), considered for the first on-line course the topic of Carbon dioxide to Chemicals and Fuels. NCCR has learnt many such lessons which are necessary for the researchers to understand and also have a complete comprehension of the limitations.
REDUCTION AND REDUCING AGENTS. in this presentation we explain the
Definition
Identification
Position in periodic table
Examples etc
of reduction and reducing agents.
Photocatalytic Properties of GO-(Cd0.8-Zn0.2)S Nanocomposites Prepared by Che...IJLT EMAS
Graphene oxide - (Cd0.8-Zn0.2)S nanocomposite
material was synthesized by the simple and economically viable
chemical precipitation method at different temperatures and its
photocatalytic properties were investigated. Measurement of
photocatalytic degradation of Rhodamine B dye was carried out
under visible light. The photocatalytic efficiency of the
synthesized nanocomposites was calculated and the effect of bath
temperature on the photocatalytic efficiency was studied. The
studies suggest that the prepared nanocomposites exhibit
reasonably good photocatalytic properties. Better photocatalysis
is observed at lower bath temperatures for preparation of the
nanocomposites. Photocatalytic efficiency close to 70% has been
obtained for the synthesised GO-(Cd0.8-Zn0.2) S nanocomposites
which can be further improved by optimizing the preparative
conditions
Abstract— 2, 4-dinitrophenol and 2, 4, 6- trinitrophenol were successfully photodegraded using visible light active monoclinic BiVO4 as photocatalyst. 10ppm of dinitrophenol is photodegraded using 50mg BiVO4 under irradiation for 3h. 10ppm trinitrophenol is photodegraded using 100mg BiVO4 under irradiation for 3h. Ease of photodegradation of DNP and TNP varied in the order DNP > TNP for the same amount of photocatalyst. Photoluminescence studies confirmed the formation of •OH free radicals due to irradiation. Synergetic effect is noticed between BiVO4 and H2O2.
PEGylated magnetic nanoparticles (PEG@Fe3O4) as cost effectivealternative for...Pawan Kumar
An efficient, cost effective and environmental friendly PEGylated magnetic nanoparticle catalyzed oxida-tive cyanation via CH activation of tertiary amines to corresponding -aminonitriles using hydrogenperoxide as oxidant and sodium cyanide as cyanide source is described. The synthesized nanocatalyst waseasily recovered with the help of external magnet and was successfully reused for several runs withoutany significant loss in catalytic activity.
PEGylated magnetic nanoparticles (PEG@Fe3O4) as cost effectivealternative for...Pawan Kumar
tAn efficient, cost effective and environmental friendly PEGylated magnetic nanoparticle catalyzed oxida-tive cyanation via CH activation of tertiary amines to corresponding -aminonitriles using hydrogenperoxide as oxidant and sodium cyanide as cyanide source is described. The synthesized nanocatalyst waseasily recovered with the help of external magnet and was successfully reused for several runs withoutany significant loss in catalytic activity.
Reduced graphene oxide–CuO nanocomposites for photocatalyticconversion of CO2...Pawan Kumar
Reduced graphene oxide (rGO)–copper oxide nanocomposites are prepared by covalent grafting of CuOnanorods on the rGO skeleton. Chemical and structural features of rGO–CuO nanocomposites are probedby FTIR, XPS, XRD and HRTEM analyses. Photocatalytic potential of rGO–CuO nanocomposites is exploredfor reduction of CO2into the methanol under the visible light irradiation. The breadth of CuO nanorods andthe oxidation state of Cu in the rGO–CuO/Cu2O nanocomposites are systematically varied to investigatetheir photocatalytic activities. The pristine CuO nanorods exhibited very low photocatalytic activity owingto fast recombination of charge carriers and yielded 175 mol g−1methanol, whereas rGO–Cu2O andrGO–CuO exhibited significantly improved photocatalytic activities and yielded five (862 mol g−1) andseven (1228 mol g−1) folds methanol, respectively. The superior photocatalytic activity of CuO in therGO–CuO nanocomposites was attributed to slow recombination of charge carriers and efficient transferof photo-generated electrons through the rGO skeleton. This study further excludes the use of scavengingdonor.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after 24 h irradiation was 9934 μmol g−1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride 145 μmol g−1cat under identical conditions. The presence of triethylamine was found to be vital for the higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Metal-organic hybrid: Photoreduction of CO2 using graphitic carbon nitride su...Pawan Kumar
A novel heteroleptic iridium complex supported on graphitic carbon nitride was synthesized and used
for photoreduction of carbon dioxide under visible light irradiation. The methanol yield obtained after
24 h irradiation was 9934 mmol g1cat (TON 1241 with respect to Ir) by using triethylamine (TEA) as a
sacrificial donor, which was significantly higher as compared to the semiconductor carbon nitride
145 mmol g1cat under identical conditions. The presence of triethylamine was found to be vital for the
higher methanol yield. After the reaction, the photocatalyst could easily be recovered and reused for
subsequent six runs without significant loss in photo activity.
Octahedral rhenium K4[Re6S8(CN)6] and Cu(OH)2cluster modifiedTiO2for the phot...Pawan Kumar
tOctahedral hexacyano rhenium K4[Re6S8(CN)6] cluster complexes were grafted onto photoactive Cu(OH)2cluster modified TiO2{Cu(OH)2/TiO2} support. The rhenium and copper cluster modified TiO2photocata-lyst combines the advantages of heterogeneous catalyst (facile recovery, recycling ability of the catalyst)with the reactivity, selectivity of the soluble molecular catalyst. The synthesized heterogeneous cata-lyst was found to be highly efficient photoredox catalyst for the reduction of CO2under visible lightirradiation. Methanol was found to be the major liquid product with the formation of hydrogen as a byproduct as determined with GC-FID and GC-TCD, respectively. The methanol yield after 24 h irradiationwas found to be 149 mol/0.1 g cat. for Re-cluster@Cu(OH)2/TiO2photocatalyst that is much higher than35 mol/0.1 g cat. for Cu(OH)2/TiO2and 75 mol/0.1 g cat. for equimolar rhenium cluster in the presenceof triethanolamine (TEOA) as a sacrificial donor. The quantum yields (MeOH) of Re-cluster@Cu(OH)2/TiO2and Cu(OH)2/TiO2were found to be 0.018 and 0.004 mol einstein−1, respectively. These values are muchhigher than those reported for other heterogeneous catalysts for six electron transfer reaction
Graphene oxide grafted with iridium complex as a superior heterogeneous catal...Pawan Kumar
A novel graphene oxide (GO)-immobilized heteroleptic iridium complex was synthesized and demonstrated
as a first heterogenized homogeneous catalyst for the production of dimethylformamide (DMF)
from carbon dioxide, hydrogen, and dimethylamine. The synthesized hybrid catalyst showed comparable
activity as homogeneous heteroleptic iridium complex with additional benefits such as facile recovery
and recycling of the catalyst. After completion of the reaction, the heterogeneous catalyst was easily
recovered by filtration, and reused for subsequent recycling processes without any significant change in
the catalytic efficiency
tA highly efficient, recyclable and magnetically separable core-shell structured CuZnO@Fe3O4microspherewrapped with reduced graphene oxide (rGO@CuZnO@Fe3O4) photocatalyst has been developed and usedfor the photoreduction of carbon dioxide with water to produce methanol under visible light irradiation.Owing to the synergistic effect of the components and to the presence of a thin Fe2O3layer on Fe3O4,rGO@CuZnO@Fe3O44 exhibited higher catalytic activity as compared to the other possible combinationssuch as CuZnO@Fe3O42 and GO@CuZnO@Fe3O43 microspheres. The yield of methanol in case of using2 and 3 as photocatalyst was found to be 858 and 1749 mol g−1cat, respectively. However, the yieldwas increased to 2656 mol g−1cat when rGO@CuZnO@Fe3O44 was used as photocatalyst under sim-ilar experimental conditions. This superior photocatalytic activity of 4 was assumed to be due to therestoration of the sp2hybridized aromatic system in rGO, which facilitated the movement of electronsand resulted in better charge separation. The synthesized heterogeneous photocatalyst could readily berecovered by external magnet and successfully reused for six subsequent cycles without significant loss in the product yield.
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized
using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized
catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without
using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
Magnetic Fe3O4@MgAl–LDH composite grafted with cobalt phthalocyanine as an ef...Pawan Kumar
Magnetically separable layered double hydroxide MgAl–LDH@Fe3O4 composite supported cobalt
phthalocyanine catalyst was synthesized and used for the aerobic oxidation of mercaptans to corresponding
disulfides under alkali free conditions. The catalyst exhibited excellent activity for the oxidation of
mercaptans using molecular oxygen as an oxidant which can be effectively recovered by using an external
magnetic field. In addition, the covalent immobilization of cobalt phthalocyanine to MgAl–LDH@Fe3O4
support prevents the leaching of the catalyst and improves its activity and stability
Biological and Medical Applications of Graphene NanoparticlesAI Publications
Graphene which is one of the latest additions to nanocarbon family has peculiar band structure, extraordinary thermal and electronic conductance and room temperature quantum Hall effect. It is used in for various applications in diverse fields ranging from catalysis to electronics. In addition to being components in electronic devices, GO have been used in nanocomposite materials, polymer composite materials, energy storage, biomedical applications, catalysis and as a surfactant with some overlaps between these fields Graphene oxide is a unique material that can be viewed as a single monomolecular layer of graphite with various oxygen containing functionalities such as epoxide, carbonyl, carboxyl and hydroxyl groups.
Synthesis and Characterization of Polyaniline Doped with Cu Salts and Cu Comp...ijtsrd
In this work, we have synthesized polyaniline doped with Cu II salts and coordination complexes in presence of Aniline was polymerized in presence ammonium persulphate APS . We varied the concentration of APS and also that of Cu II salts and complexes to see the effect of these on the properties of polyaniline. We investigated the effect of the dopant and ligand around Cu II ion on the morphology, crystallinity and conductivity of the resultant polyaniline. The products were characterized by UV Vis, FT IR spectroscopy, while the morphology and crystallinity were investigated by scanning electron microscopy, and X ray diffraction studies respectively. Results show that the morphology, crystallinity and conductivity of the doped polyanilines are found to be influenced by nature of ligand. Madhab Upadhyaya | Dilip K Kakati "Synthesis and Characterization of Polyaniline Doped with Cu-Salts and Cu-Complexes" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-6 | Issue-7 , December 2022, URL: https://www.ijtsrd.com/papers/ijtsrd52609.pdf Paper URL: https://www.ijtsrd.com/chemistry/other/52609/synthesis-and-characterization-of-polyaniline-doped-with-cusalts-and-cucomplexes/madhab-upadhyaya
Carbon Nitride Grafted Cobalt Complex (Co@npg-C3N4) for Visible LightAssiste...Pawan Kumar
Azide containing bipyridine complex of cobalt was grafted to
the propargylated nanoporous graphitic carbon nitride (npg-C3
N4) via click reaction to obtain heterogenized photocatalyst
which could efficiently provide direct esterification of aldehydes
under visible light irradiation at room temperature. The use of
click reaction as grafting strategy provided covalent attachment
of the cobalt complex to support which not only provided
higher loading but also precluded the leaching. Furthermore,
the presence of carbon nitride support exhibited synergistic
effect to enhance the reaction rate. In addition, the milder basic
nature of nitrogen containing graphitic support provided
efficient ester synthesis without the need for an external base.
The synthesized photocatalyst was found to be quite robust
which could easily be recovered and reused several times
without significantly losing activity.
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized
using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized
catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without
using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...Pawan Kumar
Many industrial processes such transesterification of fatty acid for biodiesel production, soap manufacturing and biosynthesis of ethanol generate glycerol as a major by-product that can be used to produce commodity chemicals. Photocatalytic transformation of glycerol is an enticing approach that can exclude the need of harsh oxidants and extraneous thermal energy. However, the product yield and selectivity remain poor due to low absorption and unsymmetrical site distribution on the catalyst surface. Herein, tellurium (Te) nanorods/nanosheets (TeNRs/NSs) wrapped potassium-doped carbon nitride (KCN) van der Waal (vdW) heterojunction (TeKCN) is designed to enhance charge separation and visible-NIR absorption. The iridium (Ir) single atom sites decoration on the TeKCN core-shell structure (TeKCNIr) promotes selective oxidation of glycerol to glyceraldehyde with a conversion of 45.6% and selectivity of 61.6% under AM1.5G irradiation. The catalytic selectivity can reach up to 88% under 450 nm monochromatic light. X-ray absorption spectroscopy (XAS) demonstrates the presence of undercoordinated IrN2O2 sites which improved catalytic selectivity for glycol oxidation. Band energies and computational calculations reveal faile charge transfer in the TeKCNIr heterostructure. EPR and scavenger tests discern that superoxide (O2•−) and hydroxyl (•OH) radicals are prime components driving glycerol oxidation.
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...Pawan Kumar
Many industrial processes such transesterification of fatty acid for biodiesel production, soap manufacturing and biosynthesis of ethanol generate glycerol as a major by-product that can be used to produce commodity chemicals. Photocatalytic transformation of glycerol is an enticing approach that can exclude the need of harsh oxidants and extraneous thermal energy. However, the product yield and selectivity remain poor due to low absorption and unsymmetrical site distribution on the catalyst surface. Herein, tellurium (Te) nanorods/nanosheets (TeNRs/NSs) wrapped potassium-doped carbon nitride (KCN) van der Waal (vdW) heterojunction (TeKCN) is designed to enhance charge separation and visible-NIR absorption. The iridium (Ir) single atom sites decoration on the TeKCN core-shell structure (TeKCNIr) promotes selective oxidation of glycerol to glyceraldehyde with a conversion of 45.6% and selectivity of 61.6% under AM1.5G irradiation. The catalytic selectivity can reach up to 88% under 450 nm monochromatic light. X-ray absorption spectroscopy (XAS) demonstrates the presence of undercoordinated IrN2O2 sites which improved catalytic selectivity for glycol oxidation. Band energies and computational calculations reveal faile charge transfer in the TeKCNIr heterostructure. EPR and scavenger tests discern that superoxide (O2•−) and hydroxyl (•OH) radicals are prime components driving glycerol oxidation.
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...Pawan Kumar
Many industrial processes such transesterification of fatty acid for biodiesel production, soap manufacturing and biosynthesis of ethanol generate glycerol as a major by-product that can be used to produce commodity chemicals. Photocatalytic transformation of glycerol is an enticing approach that can exclude the need of harsh oxidants and extraneous thermal energy. However, the product yield and selectivity remain poor due to low absorption and unsymmetrical site distribution on the catalyst surface. Herein, tellurium (Te) nanorods/nanosheets (TeNRs/NSs) wrapped potassium-doped carbon nitride (KCN) van der Waal (vdW) heterojunction (TeKCN) is designed to enhance charge separation and visible-NIR absorption. The iridium (Ir) single atom sites decoration on the TeKCN core-shell structure (TeKCNIr) promotes selective oxidation of glycerol to glyceraldehyde with a conversion of 45.6% and selectivity of 61.6% under AM1.5G irradiation. The catalytic selectivity can reach up to 88% under 450 nm monochromatic light. X-ray absorption spectroscopy (XAS) demonstrates the presence of undercoordinated IrN2O2 sites which improved catalytic selectivity for glycol oxidation. Band energies and computational calculations reveal faile charge transfer in the TeKCNIr heterostructure. EPR and scavenger tests discern that superoxide (O2•−) and hydroxyl (•OH) radicals are prime components driving glycerol oxidation.
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...Pawan Kumar
Biomass photorefining is a promising strategy to address the energy crisis and transition toward carbon carbon-neutral society. Here, we demonstrate the feasibility of direct cellulose photorefining into arabinose by a rationally designed oxygen-doped polymeric carbon nitride, which generates favorable oxidative species (e.g., O2–, •OH) for selective oxidative reactions at neutral conditions. In addition, we also illustrate the mechanism of the photocatalytic cellulose to arabinose conversion by density functional theory calculations. The oxygen insertion derived from oxidative radicals at the C1 position of glucose within cellulose leads to oxidative cleavage of β-1,4 glycosidic linkages, resulting in the subsequent gluconic acid formation. The following decarboxylation process of gluconic acid via C1–C2 α-scissions, triggered by surface oxygen-doped active sites, generates arabinose and formic acid, respectively. This work not only offers a mechanistic understanding of cellulose photorefining to arabinose but also sets up an example for illuminating the path toward direct cellulose photorefining into value-added bioproducts under mild conditions.
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...Pawan Kumar
Biomass photorefining is a promising strategy to address the energy crisis and transition toward carbon carbon-neutral society. Here, we demonstrate the feasibility of direct cellulose photorefining into arabinose by a rationally designed oxygen-doped polymeric carbon nitride, which generates favorable oxidative species (e.g., O2–, •OH) for selective oxidative reactions at neutral conditions. In addition, we also illustrate the mechanism of the photocatalytic cellulose to arabinose conversion by density functional theory calculations. The oxygen insertion derived from oxidative radicals at the C1 position of glucose within cellulose leads to oxidative cleavage of β-1,4 glycosidic linkages, resulting in the subsequent gluconic acid formation. The following decarboxylation process of gluconic acid via C1–C2 α-scissions, triggered by surface oxygen-doped active sites, generates arabinose and formic acid, respectively. This work not only offers a mechanistic understanding of cellulose photorefining to arabinose but also sets up an example for illuminating the path toward direct cellulose photorefining into value-added bioproducts under mild conditions.
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...Pawan Kumar
Biomass photorefining is a promising strategy to address the energy crisis and transition toward carbon carbon-neutral society. Here, we demonstrate the feasibility of direct cellulose photorefining into arabinose by a rationally designed oxygen-doped polymeric carbon nitride, which generates favorable oxidative species (e.g., O2–, •OH) for selective oxidative reactions at neutral conditions. In addition, we also illustrate the mechanism of the photocatalytic cellulose to arabinose conversion by density functional theory calculations. The oxygen insertion derived from oxidative radicals at the C1 position of glucose within cellulose leads to oxidative cleavage of β-1,4 glycosidic linkages, resulting in the subsequent gluconic acid formation. The following decarboxylation process of gluconic acid via C1–C2 α-scissions, triggered by surface oxygen-doped active sites, generates arabinose and formic acid, respectively. This work not only offers a mechanistic understanding of cellulose photorefining to arabinose but also sets up an example for illuminating the path toward direct cellulose photorefining into value-added bioproducts under mild conditions.
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...Pawan Kumar
Direct selective transformation of greenhouse methane (CH4) to liquid oxygenates (methanol) can substitute energy-intensive two-step (reforming/Fischer–Tropsch) synthesis while creating environmental benefits. The development of inexpensive, selective, and robust catalysts that enable room temperature conversion will decide the future of this technology. Single-atom catalysts (SACs) with isolated active centers embedded in support have displayed significant promises in catalysis to drive challenging reactions. Herein, high-density Ni single atoms are developed and stabilized on carbon nitride (NiCN) via thermal condensation of preorganized Ni-coordinated melem units. The physicochemical characterization of NiCN with various analytical techniques including HAADF-STEM and X-ray absorption fine structure (XAFS) validate the successful formation of Ni single atoms coordinated to the heptazine-constituted CN network. The presence of uniform catalytic sites improved visible absorption and carrier separation in densely populated NiCN SAC resulting in 100% selective photoconversion of (CH4) to methanol using H2O2 as an oxidant. The superior catalytic activity can be attributed to the generation of high oxidation (NiIII═O) sites and selective C─H bond cleavage to generate •CH3 radicals on Ni centers, which can combine with •OH radicals to generate CH3OH.
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...Pawan Kumar
Direct selective transformation of greenhouse methane (CH4) to liquid oxygenates (methanol) can substitute energy-intensive two-step (reforming/Fischer–Tropsch) synthesis while creating environmental benefits. The development of inexpensive, selective, and robust catalysts that enable room temperature conversion will decide the future of this technology. Single-atom catalysts (SACs) with isolated active centers embedded in support have displayed significant promises in catalysis to drive challenging reactions. Herein, high-density Ni single atoms are developed and stabilized on carbon nitride (NiCN) via thermal condensation of preorganized Ni-coordinated melem units. The physicochemical characterization of NiCN with various analytical techniques including HAADF-STEM and X-ray absorption fine structure (XAFS) validate the successful formation of Ni single atoms coordinated to the heptazine-constituted CN network. The presence of uniform catalytic sites improved visible absorption and carrier separation in densely populated NiCN SAC resulting in 100% selective photoconversion of (CH4) to methanol using H2O2 as an oxidant. The superior catalytic activity can be attributed to the generation of high oxidation (NiIII═O) sites and selective C─H bond cleavage to generate •CH3 radicals on Ni centers, which can combine with •OH radicals to generate CH3OH.
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...Pawan Kumar
Here, we demonstrate the selective cellobiose (building block of cellulose) photoreforming for gluconic acid and syngas co-production in acidic conditions by rationally designing a bifunctional polymeric carbon nitride (CN) with potassium/sulfur co-dopant. This heteroatomic doped CN photocatalyst possesses enhanced visible light absorption, higher charge separation efficiency than pristine CN. Under acidic conditions, cellobiose is not only more efficiently hydrolyzed into glucose but also promotes the syngas and gluconic acid production. Density functional theory (DFT) calculations reveal the favorable generation of •O2− during the photocatalytic reaction, which is essential for gluconic acid production. Consequently, the fine-designed photocatalyst presents excellent cellobiose conversion (>80%) and gluconic acid selectivity (>70%) together with the co-production of syngas (~56 μmol g-1 h-1) under light illumination. The current work demonstrates the feasibility of biomass photoreforming with value-added chemicals and syngas co-production under mild condition.
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...Pawan Kumar
Here, we demonstrate the selective cellobiose (building block of cellulose) photoreforming for gluconic acid and syngas co-production in acidic conditions by rationally designing a bifunctional polymeric carbon nitride (CN) with potassium/sulfur co-dopant. This heteroatomic doped CN photocatalyst possesses enhanced visible light absorption, higher charge separation efficiency than pristine CN. Under acidic conditions, cellobiose is not only more efficiently hydrolyzed into glucose but also promotes the syngas and gluconic acid production. Density functional theory (DFT) calculations reveal the favorable generation of •O2− during the photocatalytic reaction, which is essential for gluconic acid production. Consequently, the fine-designed photocatalyst presents excellent cellobiose conversion (>80%) and gluconic acid selectivity (>70%) together with the co-production of syngas (~56 μmol g-1 h-1) under light illumination. The current work demonstrates the feasibility of biomass photoreforming with value-added chemicals and syngas co-production under mild condition.
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...Pawan Kumar
Here, we demonstrate the selective cellobiose (building block of cellulose) photoreforming for gluconic acid and syngas co-production in acidic conditions by rationally designing a bifunctional polymeric carbon nitride (CN) with potassium/sulfur co-dopant. This heteroatomic doped CN photocatalyst possesses enhanced visible light absorption, higher charge separation efficiency than pristine CN. Under acidic conditions, cellobiose is not only more efficiently hydrolyzed into glucose but also promotes the syngas and gluconic acid production. Density functional theory (DFT) calculations reveal the favorable generation of •O2− during the photocatalytic reaction, which is essential for gluconic acid production. Consequently, the fine-designed photocatalyst presents excellent cellobiose conversion (>80%) and gluconic acid selectivity (>70%) together with the co-production of syngas (~56 μmol g-1 h-1) under light illumination. The current work demonstrates the feasibility of biomass photoreforming with value-added chemicals and syngas co-production under mild condition.
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...Pawan Kumar
Direct selective transformation of greenhouse methane (CH4) to liquid oxygenates (methanol) can substitute energy-intensive two-step (reforming/Fischer–Tropsch) synthesis while creating environmental benefits. The development of inexpensive, selective, and robust catalysts that enable room temperature conversion will decide the future of this technology. Single-atom catalysts (SACs) with isolated active centers embedded in support have displayed significant promises in catalysis to drive challenging reactions. Herein, high-density Ni single atoms are developed and stabilized on carbon nitride (NiCN) via thermal condensation of preorganized Ni-coordinated melem units. The physicochemical characterization of NiCN with various analytical techniques including HAADF-STEM and X-ray absorption fine structure (XAFS) validate the successful formation of Ni single atoms coordinated to the heptazine-constituted CN network. The presence of uniform catalytic sites improved visible absorption and carrier separation in densely populated NiCN SAC resulting in 100% selective photoconversion of (CH4) to methanol using H2O2 as an oxidant. The superior catalytic activity can be attributed to the generation of high oxidation (NiIII═O) sites and selective C─H bond cleavage to generate •CH3 radicals on Ni centers, which can combine with •OH radicals to generate CH3OH.
Recent advancements in tuning the electronic structures of transitional metal...Pawan Kumar
The smooth transition from finite non-renewables to renewable energy conversion technologies will require efficient electrocatalysts which can harness intermittent energies to store in the form of chemical bonds. The oxygen evolution reaction (OER) impedes the widespread usage of water electrolyzers to convert H2O into H2 and persists as a bottleneck, including other energy conversion devices with sluggish four H+/e− kinetics. In this context, designing highly active and stable catalysts capable of driving a lower overpotential in the OER to produce continuous hydrogen (H2) is a primary demanded. This chapter discussed the mechanism of the OER in conventional adsorbate oxygen and lattice oxygen participation in transition metal oxides (TMOs). Further, the influences of surface engineering, doping, and defects in the TMOs and understanding the electronic structure to screen electrodes towards the structure–activity relationship are highlighted. Specifically, the adsorption strength of O 2p is understood in detail as its binding ability over the surface of TMOs can be correlated directly to the OER activity. The iterative development of TMOs in terms of understanding electronic structural attributes is essential for the commercial deployment of energy conversion technologies. The comprehensive outlook of this chapter investigates thoroughly how TMOs can be used as significant materials for the OER in the near future.
Hole transport materials (HTMs) have a significant impact on the effectiveness of organic electronic devices; therefore, we present a molecular architecture of pyrazino[2,3-g]quinoxaline (PQ10)-based room-temperature organic liquid crystalline semiconductor (OLCS) as an alternative HTM. The PQ10 compound exhibits three different rectangular columnar (Colr) phases offering an impressive hole mobility of 8.8 × 10−3 cm2V−1s−1 which is found to be dexterous than most of existing polymeric hole transport materials. The charge transport mechanism is governed by the hole polarons hopping through H-aggregates of the PQ10 molecules and the hole mobility remains nearly constant throughout the mesophase range, but it decreases with increasing applied electric field. The current-voltage characteristics of the PQ10 have also been investigated in all three Colr phases and explained via the Poole-Frenkel conduction mechanism. The dielectric spectroscopy has been eventually carried out to understand the nature of dielectric permittivity and conductivity as a function of temperature and a correlation is established between the molecular architecture of the Colr phases and aforementioned physical properties. Solar cell simulation has been additionally performed to demonstrate that the PQ10 material can be a better choice as HTM for organic electronics and photovoltaic applications.
Multifunctional carbon nitride nanoarchitectures for catalysisPawan Kumar
Catalysis is at the heart of modern-day chemical and pharmaceutical industries, and there is an urgent demand to develop metal-free, high surface area, and efficient catalysts in a scalable, reproducible and economic manner. Amongst the ever-expanding two-dimensional materials family, carbon nitride (CN) has emerged as the most researched material for catalytic applications due to its unique molecular structure with tunable visible range band gap, surface defects, basic sites, and nitrogen functionalities. These properties also endow it with anchoring capability with a large number of catalytically active sites and provide opportunities for doping, hybridization, sensitization, etc. To make considerable progress in the use of CN as a highly effective catalyst for various applications, it is critical to have an in-depth understanding of its synthesis, structure and surface sites. The present review provides an overview of the recent advances in synthetic approaches of CN, its physicochemical properties, and band gap engineering, with a focus on its exclusive usage in a variety of catalytic reactions, including hydrogen evolution reactions, overall water splitting, water oxidation, CO2 reduction, nitrogen reduction reactions, pollutant degradation, and organocatalysis. While the structural design and band gap engineering of catalysts are elaborated, the surface chemistry is dealt with in detail to demonstrate efficient catalytic performances. Burning challenges in catalytic design and future outlook are elucidated.
Production of Renewable Fuels by the Photocatalytic Reduction of CO2 using Ma...Pawan Kumar
The photo-reductive performance of natural ilmenite was boosted and the production of renewable fuels from the reduction of CO2 was enhanced by doping the natural mineral with magnesium. The doping was achieved by high energy ball milling in the presence of MgO and Mg(NO3)2. The photo-reduction of CO2 in aqueous solution led to the evolution of H2, CH4, C2H4, and C2H6, and the insertion of Mg in the structure of ilmenite enabled increases of up to 1245% in the fuel production yield, reaching total production of 210.9 µmol h-1 gcat-1. Displacements of the conduction band to more negative potentials were evidenced for the samples doped with magnesium. Indirect effects such as increases in the valence band maximum, and the introduction of intermediate energy levels were also evidenced through the measurement of the crystallite size and the determination of the band structure of the materials. Mott-Schottky analyses of the samples showed the n-type nature of the semiconductor materials and enabled the estimation of the density of charge carriers, which strongly influenced the photocatalytic performance. The strong potential of the application of natural ilmenite in gas phase artificial photosynthesis was proved by the evaluation of CO2 reduction in gas conditions, which allowed the enhancement in the selectivity and significantly increased the production of CH4 as compared to aqueous solution, reaching an important yield of CH4 of 16.1 µmol h-1 gcat-1.
Nanoengineered Au-Carbon Nitride Interfaces Enhance PhotoCatalytic Pure Water...Pawan Kumar
Photocatalytic pure water splitting using solar energy is one of the promising routes to produce sustainable green hydrogen (H2). Tuning the interfacial active site density at catalytic heterojunctions and better light management are imperative to steer the structure-activity correlations to enhance the photo-efficiency of nanocomposite photocatalysts. Herein, we report the decoration of nitrogen defects-rich carbon nitride CN(T) with metallic Au nanostructures of different morphologies and sizes to investigate their influence on the photocatalytic hydrogen evolution reactions (HER). The CN(T)-7-NP nano-heterostructure comprises Au nanoparticles (NPs) of ~7 nm and thiourea-derived defective CN exhibits an excellent H2 production rate of 76.8 µmol g–1 h–1 from pure water under simulated AM 1.5 solar irradiation. In contrast to large-size Au nanorods, the high activity of CN(T)-7-NP was attributed to their strong localized surface plasmon resonance (LSPR) mediated visible absorption and interfacial charge separation. The surface ligands used to control Au nanostructures morphology were found to play a major role in the stabilization of NPs and improve interfacial charge transport between Au NPs and CN(T). First-principles calculations revealed that defects in CN and Au-CN interfacial sites in these nanocomposites facilitate the separation of e-/h+ pairs after light excitation and provide lower energy barrier pathways for H2 production by photocatalytic water splitting.
Nanoengineered Au-Carbon Nitride Interfaces Enhance Photo-Catalytic Pure Wate...Pawan Kumar
Photocatalytic pure water splitting using solar energy is one of the promising routes to produce sustainable green hydrogen (H2). Tuning the interfacial active site density at catalytic heterojunctions and better light management are imperative to steer the structure-activity correlations to enhance the photo-efficiency of nanocomposite photocatalysts. Herein, we report the decoration of nitrogen defects-rich carbon nitride CN(T) with metallic Au nanostructures of different morphologies and sizes to investigate their influence on the photocatalytic hydrogen evolution reactions (HER). The CN(T)-7-NP nano-heterostructure comprises Au nanoparticles (NPs) of ~7 nm and thiourea-derived defective CN exhibits an excellent H2 production rate of 76.8 µmol g–1 h–1 from pure water under simulated AM 1.5 solar irradiation. In contrast to large-size Au nanorods, the high activity of CN(T)-7-NP was attributed to their strong localized surface plasmon resonance (LSPR) mediated visible absorption and interfacial charge separation. The surface ligands used to control Au nanostructures morphology were found to play a major role in the stabilization of NPs and improve interfacial charge transport between Au NPs and CN(T). First-principles calculations revealed that defects in CN and Au-CN interfacial sites in these nanocomposites facilitate the separation of e-/h+ pairs after light excitation and provide lower energy barrier pathways for H2 production by photocatalytic water splitting.
Cooperative Copper Single Atom Catalyst in Two-dimensional Carbon Nitride for...Pawan Kumar
Renewable electricity powered carbon dioxide (CO2) reduction (eCO2R) to high-value fuels like methane (CH4) holds the potential to close the carbon cycle at meaningful scales. However, this kinetically staggered 8-electron multistep reduction still suffers from inadequate catalytic efficiency and current density. Atomic Cu-structures can boost eCO2R-to-CH4 selectivity due to enhanced intermediate binding energies (BEs) resulting from favorably shifted d-band centers. Herein, we exploit two-dimensional carbon nitride (CN) matrices, viz. Na-polyheptazine (PHI) and Li-polytriazine imides (PTI), to host Cu-N2 type single atom sites with high density (∼1.5 at%), via a facile metal ion exchange process. Optimized Cu loading in nanocrystalline Cu-PTI maximizes eCO2R-to-CH4 performance with Faradaic efficiency (FECH4) of ≈68% and a high partial current density of 348 mA cm−2 at a low potential of -0.84 V versus RHE, surpassing the state-of-the-art catalysts. Multi-Cu substituted N-appended nanopores in the CN frameworks yield thermodynamically stable quasi-dual/triple sites with large interatomic distances dictated by the pore dimensions. First-principles calculations elucidate the relative Cu-CN cooperative effects between the two matrices and how the Cu-Cu distance and local environment dictate the adsorbate BEs, density of states, and CO2-to-CH4 energy profile landscape. The 9N pores in Cu-PTI yield cooperative Cu-Cu sites that synergistically enhance the kinetics of the rate-limiting steps in the eCO2R-to-CH4 pathway.
Bioinspired multimetal electrocatalyst for selective methane oxidationPawan Kumar
Selective partial electrooxidation of methane (CH4) to liquid oxygenates has been a long-sought goal. However, the high activation energy of C–H bonds and competing oxygen evolution reaction limit product selectivity and reaction rates. Inspired by iron (IV)-oxo containing metalloenzymes’ functionality to activate the C–H bond, here we report on the design of a copper-iron-nickel catalyst for selective oxidation of CH4 to formate via a peroxide-assisted pathway. Each catalyst serves a specific role which is confirmed via electrochemical, in situ, and theoretical studies. A combination of electrochemical and in situ spectroelectrochemical studies revealed that H2O2 oxidation on nickel led to the formation of active oxygen species which trigger the formation of iron (IV) at low voltages. Density functional theory analysis helped reveal the role of iron (IV)-oxo species in reducing the activation energy barrier for CH4 deprotonation and the critical role of copper to suppress overoxidation. Our multimetal catalyst exhibits a formate faradaic efficiency of 42% at an applied potential of 0.9 V versus a reversible hydrogen electrode.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
ANAMOLOUS SECONDARY GROWTH IN DICOT ROOTS.pptxRASHMI M G
Abnormal or anomalous secondary growth in plants. It defines secondary growth as an increase in plant girth due to vascular cambium or cork cambium. Anomalous secondary growth does not follow the normal pattern of a single vascular cambium producing xylem internally and phloem externally.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
The use of Nauplii and metanauplii artemia in aquaculture (brine shrimp).pptxMAGOTI ERNEST
Although Artemia has been known to man for centuries, its use as a food for the culture of larval organisms apparently began only in the 1930s, when several investigators found that it made an excellent food for newly hatched fish larvae (Litvinenko et al., 2023). As aquaculture developed in the 1960s and ‘70s, the use of Artemia also became more widespread, due both to its convenience and to its nutritional value for larval organisms (Arenas-Pardo et al., 2024). The fact that Artemia dormant cysts can be stored for long periods in cans, and then used as an off-the-shelf food requiring only 24 h of incubation makes them the most convenient, least labor-intensive, live food available for aquaculture (Sorgeloos & Roubach, 2021). The nutritional value of Artemia, especially for marine organisms, is not constant, but varies both geographically and temporally. During the last decade, however, both the causes of Artemia nutritional variability and methods to improve poorquality Artemia have been identified (Loufi et al., 2024).
Brine shrimp (Artemia spp.) are used in marine aquaculture worldwide. Annually, more than 2,000 metric tons of dry cysts are used for cultivation of fish, crustacean, and shellfish larva. Brine shrimp are important to aquaculture because newly hatched brine shrimp nauplii (larvae) provide a food source for many fish fry (Mozanzadeh et al., 2021). Culture and harvesting of brine shrimp eggs represents another aspect of the aquaculture industry. Nauplii and metanauplii of Artemia, commonly known as brine shrimp, play a crucial role in aquaculture due to their nutritional value and suitability as live feed for many aquatic species, particularly in larval stages (Sorgeloos & Roubach, 2021).
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
2. 104 A. Kumar et al. / Applied Surface Science 386 (2016) 103–114
Scheme 1. Visible light assisted photoreduction of nitrobenzenes.
with its high specific surface area have made graphene an attractive
photocatalyst as well as ideal support for constructing new type of
graphene-based photocatalysts for photocatalytic reactions [23].
In this regard, extensive research work has done on the develop-
ment of novel graphene-based semiconductor photocatalysts for
photocatalytic hydrogen generation and CO2 reduction [24,25]. For
example Xiang et al., recently published a review on semiconductor
graphene based photocatalysts for solar fuel production including
hydrogen generation and CO2 reduction [26]. Putri et al., reviewed
the applications of heteroatom doped graphene in photocatalysis
[27]. Min et al., reported dye-cosensitized graphene/Pt photocata-
lyst for high efficient visible light hydrogen evolution [28]. Kong
et al., reported novel Pt–Sn alloy decorated graphene nanohy-
brid [29] and amorphous CoSnxOy decorated graphene nanohybrid
photocatalyst for highly efficient photocatalytic hydrogen evolu-
tion [30]. In another report they described dye-Sensitized NiSx
catalyst decorated on graphene for highly efficient reduction of
water to hydrogen under visible light irradiation [31]. Similarly
a number of reports are known on photocatalytic CO2 reduction
using graphene based photocatalysts [32]. In this regard, we have
recently reported graphene oxide immobilized cobalt phthalocya-
nine [33] and ruthenium trinuclear polyazine complex [34] for the
photo-reduction carbon dioxide to methanol under visible light
irradiation.
In the present paper we have synthesized a low cost, easily avail-
able and environmentally benign iron bipyridne [Fe(II)(bpy)3]2+
complex which subsequently grafted to rGO support to make
it recoverable and recyclable. The synthesized heterogeneous
(Fe(bpy)3@rGO 3) catalyst was used for the photoreduction of
nitrobenzenes to corresponding anilines using hydrazine hydrate
at room temperature under visible light irradiation (Scheme 1).
2. Experimental section
2.1. Materials
Iron(II) chloride (98%), 2,2 -bipyridine (99%), graphite flakes,
ammonium hexafluoro phosphate (99.9%) was purchased from
Aldrich were of analytical grade and used without further purifi-
cation. All other chemicals were of A.R. grade and used without
further purification.
2.2. Synthesis of [Fe(II)(bpy)3](PF6)2 complex [35]
In a typical synthesis, 0.80 mmol iron(II) chloride (0.1 g) was
dissolved in a minimum amount of water and in another solution
2.56 mmol bipyridine (0.4 g) was dissolved in a minimum amount
of ethanol. Both solutions were mixed together under stirring and
then an aqueous solution of ammonium hexafluorophosphate was
added to obtain a deep red color precipitate. The obtained precip-
itate was collected by filtration and washed with cold water and
ethanol. Yield: 75%, UV–vis (max) = 285 nm, and 523 nm.
2.3. Synthesis of graphene oxide [36]
Exfoliated graphene oxide was synthesized by oxidation of
graphite with KMnO4 and H2SO4 according to the literature pro-
cedure. Briefly, in a round bottom flask immersed in a ice bath, 2 g
graphite flakes were taken and then 68 mL H2SO4, 1.50 g sodium
nitrate was added; the resulting suspension was stirred for 5 min.
Then 9.0 g KMnO4 was added slowly to this mixture and the result-
ing mixture was stirred for additional 5 days. Next to this 5% diluted
H2SO4 (100 mL) was added and heated at 90 ◦C for 2 h with continu-
ous stirring. To this mixture 30 wt% H2O2 solution (approximately
5.4 mL) was added and stirred for 2 h at room temperature. The
raw GO was isolated by centrifugation (6000 rpm) and washed with
H2SO4 (3 wt%), H2O2 (0.5 wt%) and HCl (3 wt%). Final washing was
done with distilled water until pH of filtrate became neutral to get
exfoliated graphene oxide.
2.4. Synthesis of reduced graphene oxide [37]
Reduced graphene oxide was synthesized by hydrothermal
method by using water and ethanol as a solvent. GO (400 mg)
was dispersed in water/ethanol (60 mL/30 mL) mixture and soni-
cated for 2 h. The obtained suspension was transferred to a 100 mL
teflon-sealed autoclave and maintained at 120 ◦C for 24 h. This
hydrothermal treatment reduces oxygen carrying functionalities of
graphene oxide. The resulting reduced graphene oxide (rGO) was
recovered by filtration, washed by water, and dried at 60 ◦C for 24 h.
2.5. Synthesis of iron(II) bipyridine and reduced graphene oxide
nanocomposite
For the synthesis of Fe(bpy)3@rGO nanocomposite 0.25 g of
[Fe(bpy)3]PF6 and 1.0 g reduced graphene oxide was added in
250 mL acetonitrile/water (1/1) mixture. This mixture was soni-
cated for 30 min to dispersing the reduced graphene oxide. Then
obtained mixture was stirred for 24 h at room temperature. The
obtained catalyst was filtered with PTFE filter and washed with ace-
tonitrile and water. Fe content of synthesized catalyst was found
to be 1.1 wt% (0.197 mmol/g) as determined by ICP-AES analysis.
Thus the calculated value of loading of Fe(bpy)3(PF6)2 complex in
composite should be 16 wt%.
2.6. Photocatalytic reduction of nitrobenzene
The photocatalytic activity of synthesized catalyst was checked
under visible light by using 20 W LED (Model No. HP-FL-20W-F-
Hope LED Opto-Electric Co., Ltd., >400 nm). In a borosil round
bottom flask 25 mg of Fe(bpy)3@rGO catalyst was taken and 25 mL
of acetonitrile/DCM(dichloromethane)/methanol was added. The
resulting mixture was sonicated for 10 min to disperse the cata-
lyst. Next to this 0.1 mmol aromatic nitro compound and 1 mmol
hydrazine monohydrate was added to round bottomed flask and
sealed with a rubber septum. The reaction mixture was irradiated
in visible light with the collection of samples at regular intervals.
The collected samples were analyzed by TLC and GC to monitor
the progress of reaction. After completion of reaction solvent was
removed under reduced pressure and the crude product was puri-
fied by column chromatography. The identification of product was
done by GC–MS and 1H NMR.
2.7. Chemical and structural characterizations
The rough structure of materials was determined with the help
of scanning electron microscopy (SEM) image collected on FE-SEM
(Jeol Model JSM-6340F). To get fine morphologies of the synthe-
sized materials, high resolution transmission electron microscopy
was performed by using FEI-TecnaiG2 TwinTEM operating at an
acceleration voltage of 200 kV. The samples for HR-TEM were
obtained by dispersing them into a minimum amount of water
and deposited carbon coated copper grid. Vibrational spectra of
samples for executing various functional groups was collected by
using Fourier transform infrared spectroscopy and recorded on
3. A. Kumar et al. / Applied Surface Science 386 (2016) 103–114 105
Scheme 2. Synthetic procedure of Fe(bpy)3
+2
/rGO catalyst 3.
PerkinElmer spectrum RX-1 IR spectrophotometer having potas-
sium bromide window. The phase and crystalline structure phase
was determined with powder X-ray diffraction pattern recorded on
Bruker D8 Advance diffractometer at 40 kV and 40 mA with Cu K␣
radiation ( = 0.15418 nm). Raman spectra of materials were col-
lected at room temperature using a Raman microprobe (HR-800
Jobin-Yvon) with 532 nm Nd-YAG excitation source. XPS measure-
ments were obtained on a KRATOS-AXIS 165 instrument equipped
with dual aluminum–magnesium anodes by using MgK␣ radiation
(h = 1253.6 eV) operated at 5 kV and 15 mA with pass energy 80 eV
and an increment of 0.1 eV. To overcome the charging problem, a
charge neutralizer of 2 eV was applied and the binding energy of C1s
core level (BE ≈ 284.6 eV) of adventitious hydrocarbon was used as
a standard. The XPS spectra were recorded by using a nonlinear
square method with the convolution of Lorentzian and Gaussian
functions, after subtracting a polynomial background from the raw
spectra. Absorption profile of iron(II) bipyridine complex in ace-
tonitrile and solid UV of other samples was collected on Perkin
Elmer lambda-19 UV–vis-NIR spectrophotometer using a 10 mm
quartz cell, using BaSO4 as reference. The BET surface area(SBET),
BJH porosity, mean pore diameter and other surface properties of
materials were examined by N2 adsorption-desorption isotherm
at 77 K by using VP; Micromeritics ASAP2010. Thermo gravimetric
analysis for calculating the thermal degradation pattern material
and various functionalities present was carried out using a thermal
analyzer TA-SDT Q-600. Analysis was carried out in the temper-
ature range of 40–800 ◦C under nitrogen flow with heating rate
10 ◦C/min. Proton (1H) and carbon (13C) NMR of the iron complex
was taken at 500 MHz by using Bruker Advance-II 500 MHz instru-
ment. The iron content of catalyst was determined by inductively
coupled plasma atomic emission spectrometer (ICP-AES, DRE, PS-
3000 UV, Leeman Labs Inc., USA). The photoreduction products
were analyzed and quantified with GC–MS.
3. Results and discussion
3.1. Synthesis and characterization of Fe(bpy)3@rGO
nanocomposite 3
During the present study, exfoliated graphene oxide was syn-
thesized from graphite by following the modified Hummer method
[36]. The harsh oxidation of graphite with KMnO4 and H2SO4 gen-
erates lot of oxygen containing functionalities at the surface of
graphene oxide that facilitate the separation of sheets due to the
repulsion between oxygen atoms. The synthesized graphene oxide
was subjected to hydrothermal treatment with ethanol and water
to convert it into reduced graphene oxide (rGO) 1 [37]. The larger
surface area and high electron mobility of electrons due to the
conjugated structure make reduced graphene oxide a better pho-
toactive support for anchoring of homogeneous metal complex
[38]. The iron(II) bipyridine complex 2 as synthesized by follow-
ing the literature procedure [34] was grafted to rGO surface by the
- interaction between bipyridine and graphite sheets as shown
in Scheme 2.
The surface morphology of synthesized GO, rGO and 3 was deter-
mined with the scanning electron microscopy as shown in Fig. 1.
The SEM image of GO (Fig. 1a) shows crumpled, twisted structure
due to the folding of exfoliated sheets. After reduction of GO to
rGO the wrinkles and folds were found to be increased without
having any significant change in surface morphology (Fig. 1b). The
non-covalent attachment of 2 to rGO nanosheets generate some
erupted structures as shown in Fig. 1c which are probably due to the
– interaction between iron(II) bipyridine complex and graphene
sheets. The EDX pattern of Fe(bpy)3@rGO 3 clearly indicates the
presence of iron in the synthesized material (Fig. 1d).
The overlapped, transparent sheets in the HR-TEM image of GO
suggested few layer thickness of sheets due to the better oxidation
of graphite nanosheets (Fig. 2a). After the reduction of graphene
oxide to rGO no major change in the structure was observed
(Fig. 2b). Similarly, immobilization of Fe(bpy)3
+2 complex units
on the rGO support did not make any significant change in the
morphology of catalyst (Fig. 2c). Selected area electron diffraction
pattern of the synthesized composite 3 indicated that the material
was amorphous in nature (Fig. 2d). Furthermore, the number of
only few rings in the SAED pattern confirms that most of the sheets
were single layered.
FT-IR spectra of the samples are shown in Fig. 3. Graphite exhibit
a very less intense peak at 3432 cm−1 due to the presence of inter-
calated water in the form of moisture Fig. 3a [39]. Graphene oxide
shows a characteristic peak at 3430 cm−1 corresponding to the
combined vibration of OH groups located on the edge of sheets
and OH of COOH groups. The peaks at 1727 cm−1 is due to the
stretching vibration of C O of carboxylic groups and the peaks
at 1267 and 1052 cm−1 are attributed to the epoxide groups and
C O C bonds respectively. The peak at 1614 cm−1 is attributed to
C C of aromatic skeleton vibrations as shown in Fig. 3b [40]. For
reduced graphene oxide the peak at 1577 cm−1 is corresponding to
the C C of aromatic skeleton vibrations of graphene sheets and a
4. 106 A. Kumar et al. / Applied Surface Science 386 (2016) 103–114
Fig. 1. FE-SEM images of: (a) GO; (b) rGO; (c) Fe(bpy)3@rGO 3; and (d) EDX pattern of 3.
small peak at 1724 cm−1 is attributed to the C O vibration of resid-
ual COOH as shown in Fig. 3c. The significant reduction of OH
peak at 3430 cm−1 clearly indicates that most of the oxygen carry-
ing groups were reduced during the hydrothermal treatment [41].
The FTIR spectrum of 3 as shown in Fig. 3d is found to be almost
similar to the rGO, which is probably due to the low loading of the
complex on the rGO surface.
The Raman spectra of pristine graphite, GO, rGO, and
Fe(bpy)3@rGO are shown in Fig. 4. Graphite shows its character-
istic G band at 1590 cm−1 as shown in Fig. 4a. In case of graphene
oxide, the characteristic D (1353 cm−1) and G bands (1591 cm−1) of
nearly equal intensity are obtained (Fig. 4b). Due to the presence of
several defects in GO in the form of sp3 carbons D band is observed.
The ratio of D and G band intensity (ID/IG) is found to be nearly 1.00,
suggesting that large number of defects is presented in the form of
epoxide and other oxygen containing functionalities on GO sheet
[42]. In case of reduced graphene oxide the intensity of D band is
decreased mainly due to the partial removal of oxygen contain-
ing groups during the hydrothermal treatment (Fig. 4c) [43]. This
was a clear indication of restoration of conjugated system. The
non covalent attachment of [Fe(bpy)3]+2 complex on rGO did not
change the position or intensity of D and G bands in Fe(bpy)3
+2/rGO
catalyst 3 (Fig. 4d).
XRD diffractogram of graphite gave a sharp peak at 2 value
26.6◦ due to 002 plane reflections with 0.34 nm interlayer spacing
(Fig. 5a). GO gave a characteristics peak at 2 value 10.2◦ corre-
sponding to the 001 plane with the 0.87 nm interlayer distance
(Fig. 5b) [44]. After the reduction of graphene oxide the peak at
10.2◦ was disappeared due to the significant reduction of oxygen
carrying functionalities and a very small peak at 2 value 24.8◦ was
observed, probably due to some degree of sheets stacking at some
points [45]. After the functionalization of rGO with iron complex
moieties, the XRD pattern remained almost unchanged which is
mainly due to the lower loading of the complex.
In order to confirm the presence of iron complex 2 in the catalyst
3 and to investigate the surface chemical properties, XPS analysis
was performed (Fig. 6). The wide survey scan of catalyst 3 confirmed
the presence of C1s, N1s, O1 s and Fe2p in the catalyst (Fig. 6a). High
resolution XPS of Fe(bpy)3@rGO 3 in Fe 2p region gave two charac-
teristic peaks due to Fe2p3/2 and Fe2p1/2 at binding energy 710.7 eV
and 724.1 eV, respectively [46]. The high-resolution C1 s spectrum
for GO exhibited four peak components at 284.7, 286.4, 287.9 and
288.9 eV, which were specific to C C, C O, C O, and COOH groups
respectively (Fig. 6c) [47]. While in the C1 s spectrum of catalyst 3
the significant reduction in the peak intensity of oxygen contain-
ing function groups confirmed the successful removal of oxygen
functionalities during the reduction of GO to rGO (Fig. 6d).
Nitrogen adsorption desorption isotherm was used for deter-
mining the surface properties of the synthesized materials. The
Type (IV) loop of isotherm for GO, rGO, and 3 confirmed
the mesoporous nature of the material [48]. BET surface area
(SBET), total pore volume (VP) and mean pore diameter (rp)
5. A. Kumar et al. / Applied Surface Science 386 (2016) 103–114 107
Fig. 2. TEM images of: (a) GO; (b) rGO; (c) 3, and (d) SAED pattern of 3.
Fig. 3. FTIR Spectra of: (a) Graphite; (b) GO; (c) rGO and (d) catalyst 3.
6. 108 A. Kumar et al. / Applied Surface Science 386 (2016) 103–114
Fig. 4. Raman spectra of: (a) graphite; (b) GO; (c) rGO and (d) 3.
was found to be 87.247 m2 g−1, 0.1212 cm3 g−1 and 5.5566 nm
for GO, 32.72 m2 g−1, 0.074 cm3 g−1 and 9.046 nm for rGO and
13.16 m2 g−1, 0.070 cm3 g−1 and 21.308 nm for 3 respectively. The
Fig. 5. XRD Pattern of: (a) graphite; (b) GO; (c) rGO and (d) 3.
changes observed in the surface properties clearly depicted the suc-
cessful intercalation of iron complex units 2 between the layers of
rGO sheets (Fig. S1).
Fig. 6. XPS spectra: (a) survey scan of 3; (b) high resolution Fe 2p spectrum of 3; (c) C1 s spectrum of GO; (d) C1 s spectrum of 3.
7. A. Kumar et al. / Applied Surface Science 386 (2016) 103–114 109
Fig. 7. UV–vis absorption spectra of: (a) 2; (b) GO; (c) rGO; (d) 3.
The UV–vis spectra of synthesized materials are shown in Fig. 7.
The electronic UV–vis spectra of Fe(bpy)3](PF6)2 in acetonitrile
gave a intense peak at 284 nm due to inter ligand → * (LLCT)
transition. The weak peak at 523 nm was attributed to the metal
d() → ligand(*) (MLCT) transition (Fig. 7a). UV–vis spectra of GO
(Fig. 7b) shows its characteristics intense absorption band near to
230 nm due to → * transition of aromatic ring electrons and a
small hump near to 300 nm was due to n → * of carbonyl group
[49]. Reduced graphene oxide shows a sharp intense peak at 315 nm
due to the restoration of conjugated aromatic system (Fig. 7c).
The disappearance of peaks at 230 and 300 nm of GO and appear-
ance of a new peak at 315 nm was in well concordance with the
literature and suggested the significant deoxygenating of GO dur-
ing the reduction process. As shown in Fig. 7c, reduced graphene
oxide gave strong absorption in the visible region which is mainly
attributed to the black body effect of the graphene sheets having
conjugated sp2 carbon–carbon structure with lower oxygen to car-
bon atomic ratio [50]. However, graphene oxide (GO) has higher
oxygen to carbon atomic ratio due to the presence of a number of
sp3 carbons bonded with various oxygen functional groups. Owing
to the presence of sp3 carbons, graphene oxide possesses less con-
jugated structure than rGO and therefore shows poor absorption in
visible light (Fig. 7b). The UV–vis spectra of iron complex function-
alized rGO 3 was found to be similar to rGO, which indicates the
lower loading of Fe(bpy)3](PF6)2 2 in composite and therefore the
peak due to MLCT transition of iron complex is suppressed by the
absorption of rGO (Fig. 7d).
Tauc’s plots of synthesized materials were obtained to confirm
the visible light activity of the photocatalysts (Fig. 8). It can be seen
from Tauc’s plot (Fig. 8a) that iron complex 2 exhibited three band
gap values i.e at 2.02 eV, 3.60 eV due to MLCT and 3.99 eV due to
LLCT which suggested that the complex 2 can absorb well in the
visible region. For graphene oxide the band gap was found to be
at 2.2 eV due to –* transition and 3.6 eV due to n–* transition,
which clearly indicated that the visible light mediated transitions
were not possible (Fig. 8b). While for rGO due to residual oxy-
genated zone on sheets the value of band gap was found to be
1.3 eV and 2.8 eV, suggesting the visible light activity (Fig. 8c). After
the attachment of iron complex 2 to rGO, the band gap value of 3
remained almost nearly same probably due to low loading of the
iron complex to the support (Fig. 8d).
Thermal stability of the synthesized materials was determined
by thermogravimetric (TG) analysis as shown in Fig. 9. Thermogram
of graphite (Fig. 9a) indicated the stability of the material up to
700 ◦C and then a sharp decomposition due to the formation of CO
and CO2. In case of GO three major weight losses were observed, the
first weight loss at 100 ◦C was due to the loss of water, the second
major weight loss from 150 to 250 ◦C was due to the loss of oxy-
gen containing functionalities. Subsequently a linear weight loss
pattern was obtained due to the degradation of carbon of aromatic
sheets (Fig. 9b) [51]. The thermogram of rGO shows a small weight
loss in the region between 200 and 475 ◦C which is attributed to
the removal of most of the oxygen containing functionalities dur-
ing reduction. After 475 ◦C, there is a sharp and steady weight loss
because of the degradation of carbon containing sheets (Fig. 9c)
[52]. The almost similar degradation behaviour of rGO and graphite
clearly indicates the successful synthesis of reduced graphene oxide
after reduction process. The catalyst 3 also exhibited similar degra-
dation pattern as rGO because of low loading of iron complex.
3.2. Photo-catalytic activity
After the successful synthesis and characterization, the rGO
immobilized iron catalyst 3 was tested for the photocatalytic reduc-
tion of nitrobenzene as the representative substrate under the
visible light irradiation using hydrazine hydrate as a source of pro-
ton. For the comparison purpose, the same reaction was performed
using graphene oxide, reduced graphene oxide and homogeneous
iron(II) bipyridine complex 2 as photocatalysts under identical
experimental conditions. A time vs. product yield graph for all cat-
alyst components is shown in Fig. 10. Furthermore, the results of
these experiments are summarized in Table 1. As shown in Fig. 10
and Table 1, the catalyst 3 was found to be more active in compari-
son to the homogeneous iron complex 2 as catalyst. The less activity
of homogeneous complex 2 in comparison to rGO immobilized cat-
alyst 3 may be due to the short lived excited state of iron complex
which makes it difficult to transfer electrons efficiently to nitroben-
zene due to faster recombination of charge. However, after the
8. 110 A. Kumar et al. / Applied Surface Science 386 (2016) 103–114
Fig. 8. Tauc plots of: (a) 2; (b) GO; (c) rGO; (d) 3.
Table 1
Effect of conditions on reduction of nitrobenzene to anilinea
.
Entry Reaction condition Time/h Catalyst Yield (%)b
1 Dark 12 2 0.6c
GO 0
rGO 0
3 1.6
2 Visible light, DCM as
solvent
12 2 6.4c
GO 4.2
rGO 0
3 18.5
3 Visible light, methanol
as solvent
12 2 12.8c
GO 5.8
rGO 3.2
3 47.0
4 Visible light,
Acetonitrile as solvent
12 2 23.0c
GO 7
rGO 9
3 88.0
rGO + 2 29.0d
a
Reaction conditions; nitrobenzene (0.1 mmol); catalyst, 25 mg; hydrazine
monohydrate (1 mmol); Irradiation, White cold LED > 400 nm, Power at reaction
vessel 70 W/m2
.
b
determind by GCMS; DCM = dichloromethane.
c
equivalent amount as presented in catalyst 3.
d
Physical mixtuture of rGO + 2, Fe(bpy)2(PF6)2 = 0.197 mmol/g cat.
immobilization of complex to rGO, the higher conductive surface
of rGO provide better mobility of electrons and therefore led to the
better charge separation on the surface. These photogenerated elec-
trons can be used for the reduction of nitrobenzene to aniline. The
reduction of nitrobenzene did not occur while using GO and rGO as
catalysts under described reaction conditions. The absence of any
reaction product by using rGO as catalyst suggested that the iron is
the real catalyst and rGO is mainly improving the catalytic activity
of complex 2 via providing better charge separation. Similarly, in
dark the reduction of nitrobenzene using catalyst 3 afforded negli-
gible yield of aniline, which confirms the visible light driven nature
of reaction (Table 1, entry 1). Furthermore, in an additional reaction
by using a physical mixture of rGO and 2 in equimolar ratio as in cat-
alyst 3, the comparable product yield as homogeneous catalyst was
achieved. This finding clearly depicted that the immobilization of
complex 2 on rGO support provides better transportation of charge
on rGO’s surface and therefore gives significant enhancement in
the activity (Table 1, entry 4). To evaluate the effect of solvent, the
reduction of nitrobenzene was performed in different solvents such
as dichloromethane, methanol and acetonitrile (Table 1, entry 2–4).
Among the various solvents studied, acetonitrile was found to be
most suitable solvent for this reaction.
However the maximum loading of Fe(bpy)3(PF6)2 complex on
reduced graphene oxide that can be achieved without leaching was
16 wt% having 1.1 wt% iron content as determined by ICP-AES anal-
ysis. However to explore the effect of amount of Fe(bpy)3(PF6)2
on the product yield, a number of Fe(bpy)3/rGO composites with
variable iron content as 0.1, 1.0, 1.5, 2.0 and 3.0 wt% were synthe-
sized and tested under identical reaction conditions. It has been
observed that the yield of aniline is increased with increasing the
iron content of Fe(bpy)3/rGO composite from 0.5 to 2.0 wt%. How-
ever further increase in the amount to 3.0 wt% does not increase
9. A. Kumar et al. / Applied Surface Science 386 (2016) 103–114 111
Fig. 9. TGA thermogram of: (a) graphite; (b) GO; (c) rGO and (d) 3.
Fig. 10. Time vs product yield for reduction of nitrobenezene using different pho-
tocatalysts.
the yield, indicating that the saturation point is reached where fur-
ther transfer of electrons from complex to reduced graphene oxide
sheets is not possible (Fig. 11).
After completion of these optimization studies, the reaction was
generalized to various substituted nitrobenzenes and the results of
these experiments are summarized in Table 2. The developed cata-
lyst 3 afforded moderate to excellent yield of the corresponding
anilines under visible light irradiation. Among the various sub-
stituents, the substrates containing electron donating groups were
Fig. 11. Product yield vs Fe(bpy)3(PF6)2 amount in catalyst after 6 h of irradiation.
found to be more reactive and provided higher yield of the corre-
sponding anilines (Table 2, entry 2–6).
Further we have carried out the recycling experiments to check
the stability and reusability of the photocatalyst 3. The catalyst
was separated from reaction mixture by centrifugation and washed
with ethanol and dried at 50 ◦C. The loss of the catalyst during cen-
trifugation was considered during the addition of fresh reactant in
recycling run. The recovered catalyst was used for subsequent six
runs under described experimental conditions (Fig. 12). As shown
in Fig. 12, the catalytic activity of the photocatalyst remained nearly
same even after the six runs without any significant change in the
10. 112 A. Kumar et al. / Applied Surface Science 386 (2016) 103–114
Table 2
Photocatalytic reduction of nitro compoundsa
.
Entry Reactant Product Time/h Conv (%)b
Yield (%)c
TOF (h−1
)
1 8 90 88 11
2 8 93 90 11.25
3 8 92 89 11.12
4 8 94 92 11.50
5 8 95 92 11.5
6 8 97 96 12
7 10 86 83 8.3
8 12 80 75 6.25
9 12 82 78 6.50
10 12 76 72 6.00
a
Reaction conditions; nitro compound, 0.1 mmol; catalyst, 25 mg; hydrazine monohydrate, 1 mmol; Irradiation, White cold 20 W LED > 400 nm, Power at reaction vessel
70 W/m2
.
b
Conv. (%) =
(n◦
x
−nx,
)
n◦
x
x 100.
c
Yield (%) =
mole of product
mole of substrate
x 100 .
where nx
◦
is the number of moles of substrate before the reaction and nx’ is the number of moles of substrate after the reaction.
Fig. 12. Recycling experiments.
yield of the desired product. Furthermore, the recovered catalyst as
obtained after six runs was analyzed by ICP AES and the iron con-
tent of catalyst was found to be 1.0 wt% in comparison to 1.1 wt%
for freshly synthesized catalyst.
It is well documented that reduction of nitrobenzene to aniline
can proceed by two possible reaction pathways [53]. The first direct
route include nitrosobenzene and N-phenylhydroxyl amine inter-
mediates while second condensation route include condensation
of nitrosobenzene and N-phenylhydroxylamine to give azoxyben-
zene, azobenzene and hydazobenzene intermediates (Scheme 3). In
order to confirm that reduction of nitrobenzene to aniline proceed
via direct route we have carried out photoreduction of azobenzene
under similar reaction conditions. After the reaction only hydra-
zobenzene can be isolated and no aniline was detected, confirms
that reduction of nitrobezene proceeds through direct route.
Although the exact mechanism of the reaction is not clear at this
stage, however a single electron transfer initiated plausible mech-
anism was proposed on the basis of existing reports (Scheme 4)
[54,55]. Reduction of graphene oxide transform sp3 carbons into
sp2 carbons and changes semiconductor sheet of graphene oxide
to conductive reduced graphene oxide [56–58]. Reduced graphene
oxide (rGO) due to presence of extensive network of conjugated sp2
carbons provides excellent mobility of electrons. After the absorp-
tion of visible light iron(II) complex on the surface of rGO gets
excited from singlet to triplate state via MLCT transition. The exited
triplet state transfer electrons to nitrobenzene and oxidized to Fe3+
state. Reduced graphene oxide due to conductive surface provides
high mobility to photogenerated electrons which prevent charge
recombination [59,60]. The oxidized Fe3+ complex receive elec-
trons from hydrazine through reductive quenching to convert back
into Fe2+ state. Hydrazine works as sacrificial electron and proton
11. A. Kumar et al. / Applied Surface Science 386 (2016) 103–114 113
Scheme 3. Reaction pathways for reduction of nitrobenzene to anilines.
Scheme 4. Plausible reaction mechanism of reduction of nitro compounds using photocatalyst 3.
donor which finally after donating six protons and six electrons get
converted to its oxidation product “nitrogen”.
3/2NH2NH2 → 3N2 + 6e−
+ 6H+
As the electron transfer from Fe(II) complex is a single elec-
tron process, the reduction of nitrobenzene to aniline occurs in a
step-wise manner through the formation of nitrosobenzene and
N-phenylhydroxylamine as intermediates by using six electrons
and six protons. Thus, reduced graphene oxide increases catalytic
activity of the iron complex through facilitating electron transfer to
reactant molecule along with the extensive sites for the attachment
[61].
4. Conclusions
The present paper describes a first successful example of hetero-
genized homogeneous photocatalyst for the reduction of aromatic
nitro compounds to corresponding amines under visible light irra-
diation at room temperature. Iron complex because of its good
visible light absorbance and rGO due to better charge transporta-
tion on its surface exhibited synergistic effect to boost the reduction
of nitrobenzenes to corresponding anilines. The rGO-immobilized
iron catalyst exhibited higher catalytic activity in comparison to
homogeneous iron(II) bipyridine and much higher than metal free
rGO photocatalysts. The heterogenized photocatalyst was found to
be highly stable and could easily be recovered and reused for several
runs without any significant loss in photocatalytic activity.
Acknowledgements
We kindly acknowledge Director, CSIR-IIP for his permission to
publish these results. AK and PK are thankful to UGC and CSIR, New
Delhi, respectively for research fellowship. Authors also thanks to
analytical sciences division of CSIR-IIP, Dehradun for providing sup-
port in analysis.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.apsusc.2016.05.
139.
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