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A selective blocking method to control the overgrowth of Pt on Au nanorods.

Fennell J, He D, Tanyi AM, Logsdail AJ, Johnston RL, Li ZY, Horswell SL - J. Am. Chem. Soc. (2013)

Bottom Line: A method for the preparation of smooth deposits of Pt on Au nanorods is described, involving sequential deposition steps with selective blocking of surface sites that reduces Pt-on-Pt deposition.The Au-Pt nanorods prepared by this method have higher long-term stability than those prepared by standard Pt deposition.Electrochemical data show that the resulting structure has more extended regions of Pt surface and enhanced activity toward the carbon monoxide oxidation and oxygen reduction reactions.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.

ABSTRACT
A method for the preparation of smooth deposits of Pt on Au nanorods is described, involving sequential deposition steps with selective blocking of surface sites that reduces Pt-on-Pt deposition. The Au-Pt nanorods prepared by this method have higher long-term stability than those prepared by standard Pt deposition. Electrochemical data show that the resulting structure has more extended regions of Pt surface and enhanced activity toward the carbon monoxide oxidation and oxygen reduction reactions.

No MeSH data available.


Related in: MedlinePlus

(a) Schematicrepresentations of Au–Pt NR models: (left)bare Au NR with AR = 3 (length L = 30 nm, width W = 10 nm); (middle) Au NR with added Pt caps (thicknessθ); (right) Au NR with a Pt coating (thickness ϕ). Theangle of the incoming incident radiation relative to the principal(long) axis is 45°. (b) Calculated extinction spectra (Qext) of Au–Pt NRs over the range 400nm > λ > 1100 nm. The spectrum for the bare Au NR (AR= 3) isshown by a black solid line. The spectrum for a Pt-capped Au NR (θ= 5 nm, AR = 4) is plotted as a red dotted line. Spectra for geometricmodels with initial Pt caps (θ1 = 5 nm) and a secondaryPt capping and coating (θ2 = ϕ = 1 or 2 nm,AR = 3.5 or 3.14, respectively) are plotted with blue short-dashedand green long-dashed lines, respectively, illustrating clear quenchingof the spectral features with increasing Pt coating.
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fig4: (a) Schematicrepresentations of Au–Pt NR models: (left)bare Au NR with AR = 3 (length L = 30 nm, width W = 10 nm); (middle) Au NR with added Pt caps (thicknessθ); (right) Au NR with a Pt coating (thickness ϕ). Theangle of the incoming incident radiation relative to the principal(long) axis is 45°. (b) Calculated extinction spectra (Qext) of Au–Pt NRs over the range 400nm > λ > 1100 nm. The spectrum for the bare Au NR (AR= 3) isshown by a black solid line. The spectrum for a Pt-capped Au NR (θ= 5 nm, AR = 4) is plotted as a red dotted line. Spectra for geometricmodels with initial Pt caps (θ1 = 5 nm) and a secondaryPt capping and coating (θ2 = ϕ = 1 or 2 nm,AR = 3.5 or 3.14, respectively) are plotted with blue short-dashedand green long-dashed lines, respectively, illustrating clear quenchingof the spectral features with increasing Pt coating.

Mentions: Calculations of extinction spectra for nonhomogeneousmodels ofNRs are not widely seen in the literature. By adding Pt deposits atthe ends of the Au NR (in a “capping” position; Figure 4a middle) and on the sides of the Au NR (in whatwe have named a “coating” position; Figure 4a right), we were able to calculate the effect ofPt deposition on the optical extinction spectrum. Figure 4b shows the extinction spectra for a bare Au NR(L = 30 nm, W = 10 nm, AR = 3),a Pt-capped Au NR with cap thickness θ = 5 nm (overall AR =4), and Au NRs with initial Pt caps (θ1 = 5 nm) andthen a secondary Pt capping and coating (i.e., a universal covering)with a thickness of 1 or 2 nm (θ2 = ϕ = 1 or2 nm, overall AR = 3.5 or 3.14, respectively), corresponding to theexperimentally observed structures. There are multiple changes tothe extinction spectrum resulting from the additions of Pt, the predominantfactors being the geometric dependence of λmax onthe AR27 and the quenching effects of thePt dielectric medium.12 Our calculations(Figure 4b) show a clear red shift of the LSPRfrom λmax = 627 to 688 nm for the Pt-capped Au NR(AR = 4). The red shift in the LSPR is not as large as that for apure Au NR with AR = 4 (Figure S6).


A selective blocking method to control the overgrowth of Pt on Au nanorods.

Fennell J, He D, Tanyi AM, Logsdail AJ, Johnston RL, Li ZY, Horswell SL - J. Am. Chem. Soc. (2013)

(a) Schematicrepresentations of Au–Pt NR models: (left)bare Au NR with AR = 3 (length L = 30 nm, width W = 10 nm); (middle) Au NR with added Pt caps (thicknessθ); (right) Au NR with a Pt coating (thickness ϕ). Theangle of the incoming incident radiation relative to the principal(long) axis is 45°. (b) Calculated extinction spectra (Qext) of Au–Pt NRs over the range 400nm > λ > 1100 nm. The spectrum for the bare Au NR (AR= 3) isshown by a black solid line. The spectrum for a Pt-capped Au NR (θ= 5 nm, AR = 4) is plotted as a red dotted line. Spectra for geometricmodels with initial Pt caps (θ1 = 5 nm) and a secondaryPt capping and coating (θ2 = ϕ = 1 or 2 nm,AR = 3.5 or 3.14, respectively) are plotted with blue short-dashedand green long-dashed lines, respectively, illustrating clear quenchingof the spectral features with increasing Pt coating.
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fig4: (a) Schematicrepresentations of Au–Pt NR models: (left)bare Au NR with AR = 3 (length L = 30 nm, width W = 10 nm); (middle) Au NR with added Pt caps (thicknessθ); (right) Au NR with a Pt coating (thickness ϕ). Theangle of the incoming incident radiation relative to the principal(long) axis is 45°. (b) Calculated extinction spectra (Qext) of Au–Pt NRs over the range 400nm > λ > 1100 nm. The spectrum for the bare Au NR (AR= 3) isshown by a black solid line. The spectrum for a Pt-capped Au NR (θ= 5 nm, AR = 4) is plotted as a red dotted line. Spectra for geometricmodels with initial Pt caps (θ1 = 5 nm) and a secondaryPt capping and coating (θ2 = ϕ = 1 or 2 nm,AR = 3.5 or 3.14, respectively) are plotted with blue short-dashedand green long-dashed lines, respectively, illustrating clear quenchingof the spectral features with increasing Pt coating.
Mentions: Calculations of extinction spectra for nonhomogeneousmodels ofNRs are not widely seen in the literature. By adding Pt deposits atthe ends of the Au NR (in a “capping” position; Figure 4a middle) and on the sides of the Au NR (in whatwe have named a “coating” position; Figure 4a right), we were able to calculate the effect ofPt deposition on the optical extinction spectrum. Figure 4b shows the extinction spectra for a bare Au NR(L = 30 nm, W = 10 nm, AR = 3),a Pt-capped Au NR with cap thickness θ = 5 nm (overall AR =4), and Au NRs with initial Pt caps (θ1 = 5 nm) andthen a secondary Pt capping and coating (i.e., a universal covering)with a thickness of 1 or 2 nm (θ2 = ϕ = 1 or2 nm, overall AR = 3.5 or 3.14, respectively), corresponding to theexperimentally observed structures. There are multiple changes tothe extinction spectrum resulting from the additions of Pt, the predominantfactors being the geometric dependence of λmax onthe AR27 and the quenching effects of thePt dielectric medium.12 Our calculations(Figure 4b) show a clear red shift of the LSPRfrom λmax = 627 to 688 nm for the Pt-capped Au NR(AR = 4). The red shift in the LSPR is not as large as that for apure Au NR with AR = 4 (Figure S6).

Bottom Line: A method for the preparation of smooth deposits of Pt on Au nanorods is described, involving sequential deposition steps with selective blocking of surface sites that reduces Pt-on-Pt deposition.The Au-Pt nanorods prepared by this method have higher long-term stability than those prepared by standard Pt deposition.Electrochemical data show that the resulting structure has more extended regions of Pt surface and enhanced activity toward the carbon monoxide oxidation and oxygen reduction reactions.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.

ABSTRACT
A method for the preparation of smooth deposits of Pt on Au nanorods is described, involving sequential deposition steps with selective blocking of surface sites that reduces Pt-on-Pt deposition. The Au-Pt nanorods prepared by this method have higher long-term stability than those prepared by standard Pt deposition. Electrochemical data show that the resulting structure has more extended regions of Pt surface and enhanced activity toward the carbon monoxide oxidation and oxygen reduction reactions.

No MeSH data available.


Related in: MedlinePlus