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High catalytic potential of Ag/Pd nanoparticles fromself-regulated reduction method on electroless Ni deposition

Chien-Liang Lee *, Yu-Ching Huang, Li-Chen KuoMaterials and Chemical Research Laboratories, Industrial Technology Research Institutes, Rm. 733, Bldg. 52, 195 Sec. 4, Chung Hsing Road,

310 Chutung, Hsinchu, Taiwan, Republic of China

Received 29 March 2006; received in revised form 7 April 2006; accepted 18 April 2006Available online 19 May 2006

Abstract

Bimetallic Ag/Pd nanoparticles with various the concentration ratios of the additional silver ions to palladium ions ðCþAg=C2þ

Pd Þ havebeen prepared by the self-regulated reduction in the reuxing of sodium n-dodecyl sulfate aqueous solution without additional reducers.The particular size of prepared bimetallic nanoparticles from 6.0 to 2.6 nm is dependent on C þ

Ag=C2þPd . Additionally, surface plasmon

resonance spectra conrm that the prepared bimetallic nanoparticles are Pd shell-riched structures. As supported by the in situ analysisof quartz crystal microgravimetry, the prepared bimetallic nanoparticles can be successfully used as new activators and have the excellentactivity for electroless nickel bath.

2006 Elsevier B.V. All rights reserved.

Keywords: Nanoparticle; Palladium; Electroless copper deposition; Kinetics; Electroless nickel deposition; Bimetallic; Activator; Silver

1. Introduction

Metal nanostructure materials are known to existunique characterization on the optical property of surfaceplasma resonance (SPR) spectrum [1,2], magnetic uids[3], and catalytic reaction [4,5] and electroanalysis [6].Core–shell bimetallic nanoparticles, an interesting studysubject, is found to have excellent activities compared withthat of the pure metal nanoparticles on the catalysis, forinstance Au/Pd [7] and Pd/Pt [8] nanoparticles.

Electroless nickel depositions (END) is an important

surface treatment technology for industries because of itsgood corrosion protection, hardness and wear resistance[9,10]. Although the performance of an electroless processis inuenced by many factors such as composition of thedeposition solution [10,11] and choice of ligands [12], theactivation step is the key factor for controlling the rateand mechanism of electroless deposition [13].

In the early report, we have developed one novel methodfor synthesis of hydrophilic and hydrophobic Pd nanopar-ticles via self-regulated reduction by the reux of sodiumdodecyl sulfate (SDS) solution without additional reduc-tion agents [14]. Pd nanoparticles protected with SDS werefound to exist high activities for catalyzing electroless neu-tral Ni deposition (END) [15]. However, these nanoparti-cles were also measured to have longer induction periodwhich is the time necessary to occur steady-state deposi-tion. Accordingly, the efficient activator for END is stillneeded to be studied. In this paper, we synthesize Ag/Pd

nanoparticles by self-regulated reduction in the reuxedSDS aqueous solution. The particular sizes of bimetallicnanoparticles are controlled by the concentration ratio of the additional silver ions to palladium ions ðCþ

Ag=C2þPd Þ.

As information given by SPR spectrum, the local structuresand feature of these new Ag/Pd nanoparticles are deter-mined to be Pd shell-rich. Subsequently, as for the poten-tial applications, the Ag/Pd nanoparticles prepared fromthe various C þ

Ag=C2þPd values are tried as possible activator

for END. As the analysis support of quartz crystal micro-gravimetry (QCM) and mixed potential theory (MPT), the

1388-2481/$ - see front matter 2006 Elsevier B.V. All rights reserved.

doi:10.1016/j.elecom.2006.04.013

* Corresponding author. Tel.: +886 3 5913919; fax: +886 3 5820001.E-mail address: [email protected] (C.-L. Lee).

www.elsevier.com/locate/elecomElectrochemistry Communications 8 (2006) 1021–1026

mailto:[email protected]

mailto:[email protected]



deposition kinetics and rate catalyzed by Ag/Pd nanoparti-cles are studied. Fair comparison regarding the activity canbe thus made among these bimetallic nanomaterials.

2. Experimental

2.1. Preparation of nanoparticles

The facile synthesis of Ag/Pd (1:1) nanoparticles by self-regulated reduction in sodium dodecyl sulfate (SDS) aque-ous solution is illustrated in the following descriptions.Initially, 0.054 g of palladium acetate (Pd(OAc) 2) and0.0409 g of silver nitrate (AgNO 3) were gradually dissolvedin 50 ml of a neutral aqueous 0.1 M SDS solution. Thesolution was then heated slowly in an oil bath and reuxedat 130 C. After 6 h, the solution turned dark brown andAg/Pd nanoparticles were thus obtained. Based on thesame method, Ag/Pd (10:1) and Ag/Pd (1:10) nanoparticleswere prepared. For preparation of Ag/Pd (10:1) nanoparti-cles, 0.409 g AgNO3 and 0.054 g Pd(OAc) 2 was added inthe reuxing solution. If 0.0409 g AgNO 3 and 0.54 g Pd(OAc)2 is as reactive source, Ag/Pd (1:10) nanoparticleswere formed. In order to compare with the characterizationand activities of prepared bimetallic nanoparticles, pure Pdand Ag nanoparticles were prepared by this synthesismethod. For the formation of Ag and Pd nanoparticles,

0.049 g AgNO3 was added into the SDS solution of reuxed and 0.054 g Pd(OAc)2 is for synthesis of Pdnanoparticles.

2.2. Property measurement of nanoparticles

The characteristic spectra of surface plasma resonance(SPR) for preparing Ag/Pd nanoparticles were monitoredby UV–Vis spectrum (Carry 100, Varian). The size andshape of nanoparticles was measured with a High-Resolu-tion Transmission Electron Microscope (HR-TEM; JEOLJEM-2000EX) and High-Resolution Field Emission Scan-ning Electron Microscope (FE-SEM; Hitachi S-4700I).

2.3. Electrochemical measurement

The synthesized Ag/Pd nanoparticles of C þAg=C2þ

Pd of 1:10, 1:1 and 10:1 were then tried as activator for END.

The bath compositions of the END for electrochemicalquartz crystal microbalance (QCM, SEIKO QCA922)and linear sweep voltammetery (LSV) measurement arelisted in Table 1 , respectively. All electrochemical experi-ments were carried out in the baths controlled at 80 Cand rst bubbled with N 2 gas for 15 min prior to the

measurement.For the QCM experiment, the working electrode inEND measurement was prepared by applying 3 l l nano-particles solution uniformly on a 0.159 cm 2 Au surface of the QCM substrate. The QCM substrate (SEIKO EG&G QA20-A9M-Au) was sputtered with gold on top of 100 A titanium lm from both sides and was connectedto a home-build oscillator. The reference electrode (Hg/Hg 2Cl2) was separated from the main solution compart-ment by a Luggin capillary, which was lled with saturatedKCl solution.

For LSV and mixed-potential theory analysis, the result-ing nanoparticle solution of 3 l l was uniformly droppedonto 0.07 cm 2 glassy carbon electrode (GCE) and heatedat 70 C to evaporate H 2O for 5 min. In order to preventthe catalyst from falling off the electrode, the glass carbonelectrode was rinsed by 3 l l 5 wt% Naon solution andheated at 70 C for 10 min. LSV measurement was carriedout by using a potentiostat (Autolab PGATAT30) incor-porating a rotation disk electrode (RDE). A three-elec-trode cell, consisting of a GCE working electrode, a Ptcounter electrode and a Hg/Hg 2Cl2 reference electrode,was used for the measurement. The LSV experiment wasperformed in anodic or cathodic reaction (see Table 1 ) ata scan rate of 5 mV/s and a rotation speed of working elec-

trode of 3600 rpm.

3. Results and discussion

When synthesizing Ag/Pd nanoparticles, the time isneeded for the solution to turn dark brown, which signalsthe completion of reaction. Figs. 1A–C present FE-SEMimages of Ag/Pd nanoparticles prepared from three differ-ent Cþ

Ag=C2þPd values which are 10:1, 1:1 and 1:10, respec-

tively. It can be seen that Ag/Pd nanoparticles areuniformly distributed on the QCM substrate and the parti-cles size is function of the Cþ

Ag=C2þPd added. The particles

size decreases sequentially from Fig. 1A to C. Actually

Table 1Composition of electroless nickel bath for QCM and LSV analysis

Composition of electroless nickel bath

QCM analysis LSV Anodic bath LSV Cathodic bath

Nickel chloride (NiCl 2) 0.1 mol/dm 3 Sodium hypophosphie(NaH 2PO2 Æ H2O)

0.093 mol/dm 3 Nickel chloride (NiCl 2) 0.1 mol/dm 3

Sodium critrate (HOC(COONa)(CH 2COONa) 2 Æ 2H2O)

0.15 mol/dm 3 Sodium critrate (HOC(COONa)(CH 2COONa) 2 Æ 2H2O)

0.15 mol/dm 3 Sodium critrate (HOC(COONa)(CH 2COONa) 2 Æ 2H2O)

0.15 mol/dm 3

Sodium hypophosphie(NaH 2PO2 Æ H2O)

0.093 mol/dm 3 Triethanolamine (C 6H 15 NO 3) 0.15 mol/dm3 Triethanolamine (C 6H 15 NO 3) 0.15 mol/dm3

Triethanolamine (C 6H 15 NO 3) 0.15 mol/dm3

PH (adjustment with HCl) 8

1022 C.-L. Lee et al. / Electrochemistry Communications 8 (2006) 1021–1026



the diameter of nanoparticles measured by SEM or STM(scanning tunneling microscopy) may include the protec-tion agent surrounding the particle [16]. In addition, theparticles contained in solution dropped on the substrateare easily found to aggregate when they are dried naturally.So, the actual particles’ diameter and morphology havebeen measured by HR-TEM, as shown in the insets of Fig. 1A–C. As a contrast to HR-TEM’s results in the insetpictures of Fig. 1D and E for pure Ag and Pd nanoparticlesprepared by the same method, note that the calculatedmean diameter of the prepared Ag/Pd nanocolloids

decreases theoretically with a decreasing CþAg=C

2þPd , i.e.

Ag/Pd (10:1) (6.0 nm) > Ag/Pd (1:1) (5.7 nm) > Ag:Pd(1:10) (2.56 nm), as summarized and shown in Fig. 2. Itis interesting to be seen that the average diameters andstandard deviations of the prepared Ag/Pd nanoparticlesare function of C þ

Ag=C2þPd . Both the values acutely decrease

with a decrease on the concentration ratio. The preparedbimetallic particle has a narrowest size distribution if theCþ

Ag=C2þPd is 1:10. This means that the particles size can be

controlled via C þAg=C2þ

Pd by this synthesis method.The information for ne structure on the prepared bime-

tallic nanoparticles is provided by surface plasmon reso-

nance (SPR) spectra. For synthesized bimetallic

Fig. 1. The SEM and HR-TEM images of the Ag/Pd nanoparticles prepared from three C þAg=C2þ

Pd ratios, Pd and Ag nanoparticles synthesized by self-regulated reduction of SDS method. (A) Ag/Pd (10:1); (B) Ag/Pd (1:1); (C) Ag/Pd (1:10); (D) Ag; (E) Pd.

C.-L. Lee et al. / Electrochemistry Communications 8 (2006) 1021–1026 1023



nanoparticles, the UV–Vis spectrum is a simple and effec-tive tool to determine that the microstructure is a core-shellor mixed alloy structure. In general, if the outer layer ispure metal and substantial, the characteristic SPR band

presenting the outer metal is more pronounced [17].Fig. 3 shows a comparability of the SPR spectra for theprepared Ag/Pd nanoparticles of C þ

Ag=C2þPd of the three

types, Ag and Pd nanoparticles. Theoretically, accordingto Mie theory [17], the intensity of SPR band for Ag nano-particles can be detected and observed obviously at

428 nm in the UV–Vis spectrum, as shown in Fig. 3.For the Pd nanoparticles solution of black brown,the major SPR band was measured in the UV region. Inthe experimental observation on Ag/Pd nanoparticles, theSPR bands are almost detected to be located at 203 nm,even in the case of Ag/Pd (10:1) nanoparticles of high Agconcentration. The bimetallic nanoparticles’ spectra areconsisting with Pd nanoparticles. As a contrast to theSPR spectrum of physical mixture solution which containsconcentration ratio of 1:1 of the Pd and Ag nanoparticles,the apparent SPR bands for Ag’s characterization is stillobserved. It is plausible that the Pd atoms dominates andenriches the prepared Ag/Pd nanoparticles’ surface.

As for the catalytic potential on electroless nickel depo-sition, the activity of prepared Ag/Pd nanoparticles areremarkable, which have short induction period and addi-

Ag Ag:Pd=10:1 Ag:Pd=1:1 Ag:Pd=1:10 Pd0

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Fig. 2. The statistical calculation in diameter of the prepared Ag/Pd(10:1), Ag/Pd (1:1), Ag/Pd (1:10), Ag and Pd nanoparticles.

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Fig. 3. The surface plasmon spectra of the Ag/Pd (10:1) nanoparticles, Ag/Pd (1:1) nanoparticles and Ag/Pd (1:10) nanoparticles and the contrast spectra

of Ag, Pd nanoparticles and their physical mixture.




tionally increase with a decreasing C þAg=C2þ

Pd of Ag/Pd(1:10) > Ag/Pd (1:1) > Ag/Pd (10:1). Fig. 4A shows theresults of QCM upon in situ measuring the catalytic activ-ity of corresponding bimetallic nanoparticles which aresprayed on the electrodes and thus seen in the SEMimages of Fig. 1A–C in the END bath. The short induc-tion periods, dened as the time necessary for occurringsteady-state deposition, for Ag/Pd (1:10), Ag/Pd (1:1)and Ag/Pd (10:1) were observed. The deposition ratesare recalculated from the electrode frequency changesaccording to the Sauerbrey’s equation [18]. The averagevalue of deposition rate on Ag/Pd (10:1) nanoparticlesis about 1.36 l g/cm 2 s, about 1.48 l g/cm 2 s on Ag/Pd (1:1) nanoparticles and about 1.62 l g/cm 2 s on Ag/Pd (1:10) nanoparticles, as shown in Fig. 4B. Note that

the deposition rate catalyzed by the prepared alloy nano-

particles is higher than Pd and Ag nanoparticles preparedby the same method. This indicates that the prepared Pd/Ag nanoparticles of Pd shell-rich resulted by SPR spec-trum exists excellent activity on END bath.

Theoretically, for electroless metal deposition, the cata-lytic particles play roles as carriers in the path of transfer of electrons from reducing agent to metal ions in the bath.The solid catalysts are thus the import factor for the kinet-ics. The mixed potential theory, which is described by theTafel equation, is often used as an analysis method forthe deposition rate of electroless metal deposition [19,20].Fig. 5 presents the electrochemical current–potential curvesof the Tafel equation of END catalyzed by the preparednanoparticles, which analyzed by using potentiostat.According to the mixed potential theory, the coordinates

of the intersection point of anodic and cathodic curve are

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Fig. 4. The in situ QCM analysis of deposition kinetics of electroless nickel deposition catalyzed with the Ag/Pd nanoparticles prepared from threeCþ

Ag=C2þPd ratios by self-regulated reduction of SDS method, and the contrast deposition kinetics catalyzed with Pd and Ag nanoparticles prepared by the

self-regulated reduction of SDS method. (A) Deposition kinetics. (B) Mean deposition rate.

C.-L. Lee et al. / Electrochemistry Communications 8 (2006) 1021–1026 1025



the deposition current ( I ), at which the deposition reactionsteady-stately occurs. First, it can be seen that the peakcurrent of Ag/Pd (1:10) > Ag/Pd (1:1) > Ag/Pd (10:1) inthe anodic I – E curve are measured and observed. This indi-cates that Ag/Pd (1:10) nanoparticles has the maximum

power toward the catalytic oxidation of reducing agent.The END deposition rate ( Rmp ) by mixed potential theorycan be expressed by Faraday’s law [19] R mp ¼ 1:09 i dep

So, the Rmp on Ag/Pd (1:10), Ag/Pd (1:1), Ag/Pd (10:1), Pdand Ag nanoparticles are about 0.98, 0.77 and

0.39 l g/cm 2 s, respectively, showing the order of Ag/Pd(1:10) > Ag/Pd (1:1) > Ag/Pd (10:1), which is consistingwith the result trend analyzed by QCM data. It stronglyindicates again that the high activity exists in these pre-pared bimetallic nanocatalysts.

4. Conclusion

In conclusion, Ag/Pd nanoparticles of Pd-shell-richedwere successively prepared via simultaneous reduction of the corresponding ions by self-regulated of surfactantmethod. The diameter of prepared bimetallic nanoparticles

can be controlled from 6.0 to 2.6 nm by concentrationratio of Ag to Pd ions added. The SPR characterizationspectra conrm that the prepared bimetallic nanoparticlesare palladium-shell-riched structures. As supported by theanalysis of QCM and LSV, the prepared bimetallic nano-particles can be successfully used as new activators andhave the excellent activity for electroless nickel deposition.

References

[1] W.L. Barnes, A. Dereux, T.W. Ebbesen, Nature 424 (2003) 824.[2] R. Elghanian, J.J. Storhoff, R.C. Mucic, R.L. Letsinger, C.A. Mirkin,

Science 277 (1997) 1078.

[3] M.P. Pileni, Adv. Funct. Mater. 11 (2001) 323.[4] H. Bonnemann, R.M. Richards, Eur. J. Inorg. Chem. (2001) 2455.[5] G.G. Wildgoose, C.E. Banks, R.G. Compton, Small 2 (2006) 182.[6] C.M. Welch, R.G. Compton, Anal. Bioanal. Chem. 384 (2006) 601.[7] Y. Mizukoshi, T. Fujimoto, Y. Nagata, R. Oshima, Y. Maeda, J.

Phys. Chem. B 104 (2000) 6028.[8] N. Toshima, Y. Shirashi, A. Shitsuki, D. Ikenaga, Y. Wang, Eur.

Phys. J. D 16 (2001) 209.[9] J. Colaruotolo, D. Tramontana, in: G.O. Mallory, J.B. Hajdu (Eds.),

Electroless Plating: Fundamentals and Applications, American Elec-troplaters and Surface Finishers Society, Orlando, 1990 (Chapter 8).

[10] R.L. Zeller, Corrosion 50 (1994) 457.[11] M. Bayes, I. Sinitskaya, K. Schell, R. House, Trans. Inst. Met. Finish.

69 (1991) 140.[12] G.F. Cui, N. Li, D.Y. Li, M. Li, J. Electrochem. Soc 152 (2005) C669.

[13] J.F. Hamilton, R.C. Baetzold, Science 205 (1979) 1213.[14] C.L. Lee, C.C. Wan, Y.Y. Wang, Adv. Funct. Mater. 11 (2001) 344.[15] C.J. Lee, Y.C. Huang, C.C. Wan, Y.Y. Wang, Y.J. Ju, L.C. Kuo, J.C.

Oung, J. Electrochem. Soc. 152 (2005) C520.[16] T. Reetz, W. Hwlbig, S.A. Qualser, U. Stimming, N. Breuer, R.

Vogel, Science 267 (1995) 367.[17] P. Mulvaney, Langmuir 12 (1996) 788.[18] A.J. Bard, L.R. Faulkner, Electrochemical Methods: Fundamentals

and Applications, second ed., Wiley, New York, 2001, p. 725.[19] G.O. Mallory, in: G.O. Mallory, J.B. Hajdu (Eds.), Electroless

Plating: Fundamentals and Applications, American Electroplatersand Surface Finishers Society, Orlando, 1990 (Chapter 1).

[20] Y. Sverdlov, V. Bogush, H. Einati, Y. Shacham-Diamand, J.Electrochem. Soc 152 (2005) C631.

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Fig. 5. Cathodic and anodic polarization curves of electroless nickeldeposition catalyzed by Ag/Pd (10:1), Ag/Pd (1:1) and Ag/Pd (1:10)nanoparticles prepared by self-regulated reduction in the absence of eitherNaH 2PO2 or Ni2+ .


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