Silica-dendrimer core-shell microspheres with encapsulated ultrasmall palladium nanoparticles: Efficient and easily recyclable heterogeneous nanocatalysts

Ankush V. Biradar, Archana A. Biradar, Tewodros Asefa

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

We report the synthesis, characterization, and catalytic properties of novel monodisperse SiO 2@Pd-PAMAM core-shell microspheres containing SiO 2 microsphere cores and PAMAM dendrimer-encapsulated Pd nanoparticle (Pd-PAMAM) shells. First, SiO 2 microspheres, which were prepared by the Stöber method, were functionalized with vinyl groups by grafting their surfaces with vinyltriethoxysilane (VTS). The vinyl groups were then converted into epoxides by using m-chloroperoxybenzoic acid. Upon treatment with amine-terminated G4 poly(amidoamine) (PAMAM) dendrimers, the SiO 2-supported epoxides underwent ring-opening and gave SiO 2@PAMAM core-shell microspheres. Pd nanoparticles within the cores of the SiO 2-supported PAMAM dendrimers were synthesized by letting Pd(II) ions complex with the amine groups in the cores of the dendrimers and then reducing them into Pd(0) with NaBH 4. This produced the SiO 2@Pd-PAMAM core-shell microspheres. The presence of the different functional groups on the materials was monitored by following the changes in FTIR spectra, elemental analyses, and weight losses on thermogravimetric traces. Transmission electron microscopy (TEM) images showed the presence of Pd nanoparticles with average size of 1.56 ± 0.67 nm on the surface of the monodisperse SiO 2@Pd-PAMAM core-shell microspheres. The SiO 2@Pd-PAMAM core-shell microspheres were successfully used as an easily recyclable catalyst for hydrogenation of various olefins, alkynes, keto, and nitro groups, giving ∼100% conversion and high turnover numbers (TONs) under 10 bar H 2 pressure, at room temperature and in times ranging from 10 min to 3 h. In addition, the SiO 2@Pd-PAMAM core-shell microspheres were proven to be recyclable catalysts up to five times with barely any leaching of palladium into the reaction mixture.

Original languageEnglish (US)
Pages (from-to)14408-14418
Number of pages11
JournalLangmuir
Volume27
Issue number23
DOIs
StatePublished - Dec 6 2011

Fingerprint

Dendrimers
dendrimers
Palladium
Microspheres
Silicon Dioxide
palladium
Silica
Nanoparticles
silicon dioxide
nanoparticles
Epoxy Compounds
epoxy compounds
Amines
amines
Catalysts
Alkynes
catalysts
Alkenes
alkynes
leaching

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Cite this

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title = "Silica-dendrimer core-shell microspheres with encapsulated ultrasmall palladium nanoparticles: Efficient and easily recyclable heterogeneous nanocatalysts",
abstract = "We report the synthesis, characterization, and catalytic properties of novel monodisperse SiO 2@Pd-PAMAM core-shell microspheres containing SiO 2 microsphere cores and PAMAM dendrimer-encapsulated Pd nanoparticle (Pd-PAMAM) shells. First, SiO 2 microspheres, which were prepared by the St{\"o}ber method, were functionalized with vinyl groups by grafting their surfaces with vinyltriethoxysilane (VTS). The vinyl groups were then converted into epoxides by using m-chloroperoxybenzoic acid. Upon treatment with amine-terminated G4 poly(amidoamine) (PAMAM) dendrimers, the SiO 2-supported epoxides underwent ring-opening and gave SiO 2@PAMAM core-shell microspheres. Pd nanoparticles within the cores of the SiO 2-supported PAMAM dendrimers were synthesized by letting Pd(II) ions complex with the amine groups in the cores of the dendrimers and then reducing them into Pd(0) with NaBH 4. This produced the SiO 2@Pd-PAMAM core-shell microspheres. The presence of the different functional groups on the materials was monitored by following the changes in FTIR spectra, elemental analyses, and weight losses on thermogravimetric traces. Transmission electron microscopy (TEM) images showed the presence of Pd nanoparticles with average size of 1.56 ± 0.67 nm on the surface of the monodisperse SiO 2@Pd-PAMAM core-shell microspheres. The SiO 2@Pd-PAMAM core-shell microspheres were successfully used as an easily recyclable catalyst for hydrogenation of various olefins, alkynes, keto, and nitro groups, giving ∼100{\%} conversion and high turnover numbers (TONs) under 10 bar H 2 pressure, at room temperature and in times ranging from 10 min to 3 h. In addition, the SiO 2@Pd-PAMAM core-shell microspheres were proven to be recyclable catalysts up to five times with barely any leaching of palladium into the reaction mixture.",
author = "Biradar, {Ankush V.} and Biradar, {Archana A.} and Tewodros Asefa",
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Silica-dendrimer core-shell microspheres with encapsulated ultrasmall palladium nanoparticles : Efficient and easily recyclable heterogeneous nanocatalysts. / Biradar, Ankush V.; Biradar, Archana A.; Asefa, Tewodros.

In: Langmuir, Vol. 27, No. 23, 06.12.2011, p. 14408-14418.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Silica-dendrimer core-shell microspheres with encapsulated ultrasmall palladium nanoparticles

T2 - Efficient and easily recyclable heterogeneous nanocatalysts

AU - Biradar, Ankush V.

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N2 - We report the synthesis, characterization, and catalytic properties of novel monodisperse SiO 2@Pd-PAMAM core-shell microspheres containing SiO 2 microsphere cores and PAMAM dendrimer-encapsulated Pd nanoparticle (Pd-PAMAM) shells. First, SiO 2 microspheres, which were prepared by the Stöber method, were functionalized with vinyl groups by grafting their surfaces with vinyltriethoxysilane (VTS). The vinyl groups were then converted into epoxides by using m-chloroperoxybenzoic acid. Upon treatment with amine-terminated G4 poly(amidoamine) (PAMAM) dendrimers, the SiO 2-supported epoxides underwent ring-opening and gave SiO 2@PAMAM core-shell microspheres. Pd nanoparticles within the cores of the SiO 2-supported PAMAM dendrimers were synthesized by letting Pd(II) ions complex with the amine groups in the cores of the dendrimers and then reducing them into Pd(0) with NaBH 4. This produced the SiO 2@Pd-PAMAM core-shell microspheres. The presence of the different functional groups on the materials was monitored by following the changes in FTIR spectra, elemental analyses, and weight losses on thermogravimetric traces. Transmission electron microscopy (TEM) images showed the presence of Pd nanoparticles with average size of 1.56 ± 0.67 nm on the surface of the monodisperse SiO 2@Pd-PAMAM core-shell microspheres. The SiO 2@Pd-PAMAM core-shell microspheres were successfully used as an easily recyclable catalyst for hydrogenation of various olefins, alkynes, keto, and nitro groups, giving ∼100% conversion and high turnover numbers (TONs) under 10 bar H 2 pressure, at room temperature and in times ranging from 10 min to 3 h. In addition, the SiO 2@Pd-PAMAM core-shell microspheres were proven to be recyclable catalysts up to five times with barely any leaching of palladium into the reaction mixture.

AB - We report the synthesis, characterization, and catalytic properties of novel monodisperse SiO 2@Pd-PAMAM core-shell microspheres containing SiO 2 microsphere cores and PAMAM dendrimer-encapsulated Pd nanoparticle (Pd-PAMAM) shells. First, SiO 2 microspheres, which were prepared by the Stöber method, were functionalized with vinyl groups by grafting their surfaces with vinyltriethoxysilane (VTS). The vinyl groups were then converted into epoxides by using m-chloroperoxybenzoic acid. Upon treatment with amine-terminated G4 poly(amidoamine) (PAMAM) dendrimers, the SiO 2-supported epoxides underwent ring-opening and gave SiO 2@PAMAM core-shell microspheres. Pd nanoparticles within the cores of the SiO 2-supported PAMAM dendrimers were synthesized by letting Pd(II) ions complex with the amine groups in the cores of the dendrimers and then reducing them into Pd(0) with NaBH 4. This produced the SiO 2@Pd-PAMAM core-shell microspheres. The presence of the different functional groups on the materials was monitored by following the changes in FTIR spectra, elemental analyses, and weight losses on thermogravimetric traces. Transmission electron microscopy (TEM) images showed the presence of Pd nanoparticles with average size of 1.56 ± 0.67 nm on the surface of the monodisperse SiO 2@Pd-PAMAM core-shell microspheres. The SiO 2@Pd-PAMAM core-shell microspheres were successfully used as an easily recyclable catalyst for hydrogenation of various olefins, alkynes, keto, and nitro groups, giving ∼100% conversion and high turnover numbers (TONs) under 10 bar H 2 pressure, at room temperature and in times ranging from 10 min to 3 h. In addition, the SiO 2@Pd-PAMAM core-shell microspheres were proven to be recyclable catalysts up to five times with barely any leaching of palladium into the reaction mixture.

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