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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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Kinetics plot for the reduction of 4-np. (a) Variation of 4-np concentration with time in the presence of excess BH4-. (b) A plot of ln(k) versus 1/T for the reduction of 4-np.
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Figure 5: Kinetics plot for the reduction of 4-np. (a) Variation of 4-np concentration with time in the presence of excess BH4-. (b) A plot of ln(k) versus 1/T for the reduction of 4-np.

Mentions: Figure 5A shows the variation of concentration with time of 4-nitrophenolate ion at different temperatures, 15, 25, and 35°C. The rate constants of the reaction (Additional file 3, Table 1) are plotted against 1/T in Figure 5B. Corresponding increase in product concentration is shown in Additional file 4, Figure S3A and B gives the ln(k) versus 1/T plot for the product formed.


Supported quantum clusters of silver as enhanced catalysts for reduction.

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

Kinetics plot for the reduction of 4-np. (a) Variation of 4-np concentration with time in the presence of excess BH4-. (b) A plot of ln(k) versus 1/T for the reduction of 4-np.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Kinetics plot for the reduction of 4-np. (a) Variation of 4-np concentration with time in the presence of excess BH4-. (b) A plot of ln(k) versus 1/T for the reduction of 4-np.
Mentions: Figure 5A shows the variation of concentration with time of 4-nitrophenolate ion at different temperatures, 15, 25, and 35°C. The rate constants of the reaction (Additional file 3, Table 1) are plotted against 1/T in Figure 5B. Corresponding increase in product concentration is shown in Additional file 4, Figure S3A and B gives the ln(k) versus 1/T plot for the product formed.

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