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Supported quantum clusters of silver as enhanced catalysts for reduction.

Leelavathi A, Bhaskara Rao TU, Pradeep T - Nanoscale Res Lett (2011)

Bottom Line: We used the conversion of nitro group to amino group as a model reaction to study the catalytic reduction activity of the QCs.The turn-over frequency was 1.87 s-1 per cluster for the reduction of 4-np at 35°C.Among the substrates investigated, the kinetics followed the order, SiO2 > TiO2 > Fe2O3 > Al2O3.

View Article: PubMed Central - HTML - PubMed

Affiliation: DST Unit of Nanoscience (DST UNS), Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India. pradeep@iitm.ac.in.

ABSTRACT
Quantum clusters (QCs) of silver such as Ag7(H2MSA)7, Ag8(H2MSA)8 (H2MSA, mercaptosuccinic acid) were synthesized by the interfacial etching of Ag nanoparticle precursors and were loaded on metal oxide supports to prepare active catalysts. The supported clusters were characterized using high resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and laser desorption ionization mass spectrometry. We used the conversion of nitro group to amino group as a model reaction to study the catalytic reduction activity of the QCs. Various aromatic nitro compounds, namely, 3-nitrophenol (3-np), 4-nitrophenol (4-np), 3-nitroaniline (3-na), and 4-nitroaniline (4-na) were used as substrates. Products were confirmed using UV-visible spectroscopy and electrospray ionization mass spectrometry. The supported QCs remained active and were reused several times after separation. The rate constant suggested that the reaction followed pseudo-first-order kinetics. The turn-over frequency was 1.87 s-1 per cluster for the reduction of 4-np at 35°C. Among the substrates investigated, the kinetics followed the order, SiO2 > TiO2 > Fe2O3 > Al2O3.

No MeSH data available.


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EDAX spectrum of Al2O3@Ag7,8 along with the quantitative data. Insets show the SEM image of the supported QCs (a) and the elemental maps of an aggregate using Ag Lα (b), Al Kα (c), C Kα (d), O Kα (e), and S Kα (f).
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Figure 2: EDAX spectrum of Al2O3@Ag7,8 along with the quantitative data. Insets show the SEM image of the supported QCs (a) and the elemental maps of an aggregate using Ag Lα (b), Al Kα (c), C Kα (d), O Kα (e), and S Kα (f).

Mentions: SEM image and EDAX spectrum of Al2O3@Ag7,8 are shown in Figure 2. Elemental maps using appropriate lines are also shown. The spectrum and images confirmed the presence of silver on alumina. It is clear that silver is uniformly coated on alumina. Elemental mapping confirmed the presence of other elements such as sulphur, oxygen, and carbon quantitatively on the alumina matrix. Nearly, 1:1 ratio of Ag:S is observed in the sample. It is confirmed from the data that Ag QCs are protected with MSA.


Supported quantum clusters of silver as enhanced catalysts for reduction.

Leelavathi A, Bhaskara Rao TU, Pradeep T - Nanoscale Res Lett (2011)

EDAX spectrum of Al2O3@Ag7,8 along with the quantitative data. Insets show the SEM image of the supported QCs (a) and the elemental maps of an aggregate using Ag Lα (b), Al Kα (c), C Kα (d), O Kα (e), and S Kα (f).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211169&req=5

Figure 2: EDAX spectrum of Al2O3@Ag7,8 along with the quantitative data. Insets show the SEM image of the supported QCs (a) and the elemental maps of an aggregate using Ag Lα (b), Al Kα (c), C Kα (d), O Kα (e), and S Kα (f).
Mentions: SEM image and EDAX spectrum of Al2O3@Ag7,8 are shown in Figure 2. Elemental maps using appropriate lines are also shown. The spectrum and images confirmed the presence of silver on alumina. It is clear that silver is uniformly coated on alumina. Elemental mapping confirmed the presence of other elements such as sulphur, oxygen, and carbon quantitatively on the alumina matrix. Nearly, 1:1 ratio of Ag:S is observed in the sample. It is confirmed from the data that Ag QCs are protected with MSA.

Bottom Line: We used the conversion of nitro group to amino group as a model reaction to study the catalytic reduction activity of the QCs.The turn-over frequency was 1.87 s-1 per cluster for the reduction of 4-np at 35°C.Among the substrates investigated, the kinetics followed the order, SiO2 > TiO2 > Fe2O3 > Al2O3.

View Article: PubMed Central - HTML - PubMed

Affiliation: DST Unit of Nanoscience (DST UNS), Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India. pradeep@iitm.ac.in.

ABSTRACT
Quantum clusters (QCs) of silver such as Ag7(H2MSA)7, Ag8(H2MSA)8 (H2MSA, mercaptosuccinic acid) were synthesized by the interfacial etching of Ag nanoparticle precursors and were loaded on metal oxide supports to prepare active catalysts. The supported clusters were characterized using high resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and laser desorption ionization mass spectrometry. We used the conversion of nitro group to amino group as a model reaction to study the catalytic reduction activity of the QCs. Various aromatic nitro compounds, namely, 3-nitrophenol (3-np), 4-nitrophenol (4-np), 3-nitroaniline (3-na), and 4-nitroaniline (4-na) were used as substrates. Products were confirmed using UV-visible spectroscopy and electrospray ionization mass spectrometry. The supported QCs remained active and were reused several times after separation. The rate constant suggested that the reaction followed pseudo-first-order kinetics. The turn-over frequency was 1.87 s-1 per cluster for the reduction of 4-np at 35°C. Among the substrates investigated, the kinetics followed the order, SiO2 > TiO2 > Fe2O3 > Al2O3.

No MeSH data available.


Related in: MedlinePlus