Au Nanorods andPd Nanoparticles

Department of Chemical and Biomolecular EngineeringRice University, Houston, TX

Sriram ChandrasekharProf. Michael S. Wong

Experiments Summary

Expt # AimSynthesis Method

Characterization

TCE HDC, k Success Problem

1 Au Nrod A - - n Need fresh NaBH4, Ascorbic Acid

2 Au Nrod A UV-Vis - Y Sample with 0.15 ml AgNO3 did not work

3 Pd Nbar B,C DLS 0 n No catalytic activity - reason unknown

4 Pd Ncube D,E DLS - n DLS unsuccessful - Pd salt remained unreduced

5 Pd Ncube F - 0.0068 Y Low catalytic activity

6 Pd icosahedra C - 0.0016 Y Low catalytic activity

Method

A Nikoobakht & El-Sayed. Chem. Mater., Vol. 15, No. 10, 2003

B Xia et al; Adv. Funct. Mater. 2009, Vol 19, pg 189-200

C Xia et al; Adv. Funct. Mater. 2009, Vol 19, pg 189-200; PARR

D Xia et al; J. Am. Chem. Soc. 2007, Vol.129, pg 3665-3675, using DEG; PARR

E Xia et al; J. Am. Chem. Soc. 2007, Vol.129, pg 3665-3675, using DEG

F Xia et al; J. Am. Chem. Soc. 2007, Vol.129, pg 3665-3675, using DEG; PARR, 3 hrs

Au Nanorods Synthesis

Method: Nikoobakht & El-Sayed. Chem. Mater., Vol. 15, No. 10, 2003

Seed Solution

CTAB: 5.0 ml, 0.20M

HAuCl4: 5.0 ml, 0.0005M

NaBH4: 0.6 ml, 0.01M (iced)

Rigorous Stirring

Growth Solution

CTAB: 5.0 ml, 0.20M

AgNO3: [0.05-0.25] ml, 0.004M

HAuCl4: 5.0 ml, 0.001M

Ascorbic Acid: 70ul, 0.0788M

Product

Seed Solution: 12 ul

Add to Growth Solution

Wait 10-20 min

0.05ml

AgNO3

0.10ml

AgNO3

0.15ml

AgNO3

0.20ml

AgNO3

0.25ml

AgNO3

Seed Solution Growth SolutionProducts after 20 mins

Product Pictures

0.05ml

AgNO3

0.10ml

AgNO3

0.15ml

AgNO3

0.20ml

AgNO3

0.25ml

AgNO3

Products after 20 minsProducts after 10 mins

0.05ml

AgNO3

0.10ml

AgNO3

0.15ml

AgNO3

0.20ml

AgNO3

0.25ml

AgNO3

Au Nanorods Characterization

Absorption v Wavelength for different AgNO3 volumes (ml)

0

0.2

0.4

0.6

0.8

1

1.2

300 400 500 600 700 800 900

Wavelength

Ab

sorp

tio

n

0.05

0.1

0.15

0.2

0.25

UV-Vis Spectra of synthesized Au NRs UV-Vis Spectra of Au NRs from Paper

The two spectra compare favorably with peaks at similar wavelengths indicating a successful synthesis of Au NRs of different lengths. The sample with 0.15 ml of AgNO3 did not grow to the expected length, but this is likely due to human error in preparation.

Pd Nanocubes Synthesis

Na2PdCl4 + KBr

In 3ml DEG

PVP + 8ml DEG

11 mL DEG

15.0 mM Na2PdCl4458 mM KBr

67 mM PVP

Parr: oven100 ºC, 3h

Product

Expected length: 12nm

(Dark Brown)

Method: Xia et al; J. Am. Chem. Soc., Vol 129, No. 12, 2007

DEG = diethylene glycol

Pd Icosahedra Synthesis

Na2PdCl4

In water

Citric Acid + PVP

In water

11 mL solution

5.8 mM Na2PdCl428 mM Citric Acid

29 mM PVP

Parr: oven90 ºC, 26h

Product

Expected edge lengths: 25nm

(Grey)

Method: Xia et al; Adv. Funct. Mater. Vol 19, pg 189-200, 2009

DEG = diethylene glycol

Motivation for DEG NCube Synthesis

Pd Cuboctahedrathermodynamically favorable shape; 4nm edge length

Gives the highest catalytic activity among Pd-only NPs.

Cuboctahedra have 6 {100} and 8 {111} facets

Paper determines that slow reduction of Pd salt leads to Ncubes; DEG is a weak reducing agent

Result of DEG reduction in paper:NCubes with edge length: 8nmFacets: All {100} facets

TCE HDC Reaction

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 5 10 15 20 25 30 35

Time (min)

Pd Icosahedra

Pd Nanocubes

The Pd nanocubes showed better catalytic activity

Rate constants were calculated using the formula: kt = ln(1/(1-X)) where X is conversion. Thus k is the slope from a plot of ln(1/(1-X)) vs. t

Nor

mal

ized

Mas

s E

than

e/P

enta

ne

Icosahedra Nanocube

k 0.0016 0.0068

Au@Pd Core/Shell Nbars

Au NR Synthesis: same procedure as described above

Required chemicals are available