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Surface-enhanced Raman scattering (SERS) spectra of Methyl Orange in Ag colloids prepared by electrolysis method
Applied Surface Science 255 (2009) 6007–6010
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Surface-enhanced Raman scattering (SERS) spectra of Methyl Orange in Ag colloids prepared by electrolysis method M.Z. Si a,b,*, Y.P. Kang c, Z.G. Zhang a a
Department of Physics, Harbin Institute of Technology University, Harbin 150080, PR China Department of Physics and Electronic Science, Chuxiong Normal University, Chuxiong 675000, PR China c Department of Physics and Electronic Science, Yunnan Normal University, Kunming 650092, PR China b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 2 February 2008 Received in revised form 14 January 2009 Accepted 20 January 2009 Available online 29 January 2009
Polyvinyl alcohol (PVA)-protected Ag colloids were prepared by an electrolysis method. The surfaceenhanced Raman scattering (SERS) spectra of Methyl Orange (MO), one of the Azo-dye molecules, in Ag colloids were successfully recorded with good concordance comparing to the theoretical results calculated by the Gaussian’98 program. The MO was adsorbed on the surface of Ag nanoparticles by trans-form which plays an important role for the SERS effect. However, the SERS spectra of MO in Ag colloids prepared by chemical reduction method did not appear which may be because of the competition of the borate or citrate ions with the MO. In order to test the applicability of these colloids, the SERS spectra of Sudan red (III) (SR), another of Azo-dye molecules, were measured and the result was good. Crown Copyright ß 2009 Published by Elsevier B.V. All rights reserved.
Keywords: SERS Ag colloids Electrolysis MO
1. Introduction Surface-enhanced Raman scattering (SERS) is a powerful technique for studying the adsorption behavior of molecules on substrate [1,2]. In SERS studies, Ag electrodes, Ag islands, Ag deposited films, and Ag colloids are used as substrates [3–6]. Among them, Ag colloids reduced by borohydride and citrate [7,8] are the most commonly methods used in many researches due to its better enhancement effect and particle stability. Azo-dye molecules, characterized by electron-donating and electron-accepting groups connected by a conjugated p-system, usually show large nonlinear optical responses, which are necessary for optical devices in telecommunications and signal processing applications [9]. Moreover, the Azo-dye molecules have been found with wide applicability in reversible optical data storage [10]. The storage process utilizes the light-induced trans– cis–trans isomerization of the Azo-dye molecules thereby utilizing the local variation of the refractive index of the medium. Methyl Orange (MO) is one of the Azo-dye molecules and was studied by many methods, such as liquid chromatography spectrometry and mass spectrometry [11–15]. However, to our knowledge, no one
* Corresponding author at: Department of Physics and Electronic Science, Chuxiong Normal University, Chuxiong 675000, PR China. Tel.: +86 878 3121785; fax: +86 878 3121785. E-mail address: [email protected] (M.Z. Si).
investigated it with SERS. The main reason was that by using the reduction method to gain the Ag colloids, the borate or citrate ions would be introduced into the colloidal system, which may lead to competition with the MO [16,17]. So one of the key points in wild SERS applications is finding a method of acquiring a highly SERS active substrate [18]. To avoid the chemical competition, Ag colloids were prepared by laser ablation form solid Ag, where ablation had the advantage of generating chemically clean colloidal surfaces [19–21]. However, it was difficult and expensive to gain the Ag colloids using laser ablation method. In this paper, an easy method, electrolysis method, was utilized to obtain chemically clean Ag colloids. The UV–vis spectrum and the transmission electron microscopy (TEM) image were employed to characterize the Ag particles. The SERS spectra of MO in the Ag colloids were investigated and a calculation was performed. The calculated result was compared with the experimental ones. 2. Experimental 2.1. Colloid preparation Two Ag rods (purity 99.5%) were used as anode and cathode, respectively. The diameter of the Ag rods was 0.5 cm. Mixture aqueous solution of polyvinyl alcohol (PVA) and AgNO3 were used as electrolyte. A 7-V direct current was applied on Ag rods for 1 h. Ag colloids with shallow yellow color were obtained as a
0169-4332/$ – see front matter . Crown Copyright ß 2009 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2009.01.055
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M.Z. Si et al. / Applied Surface Science 255 (2009) 6007–6010
homogeneous solution, and they were stable for 2 days at room temperature. The ‘‘Tyndall effect’’ was observed with the resulting solution when any laser was used as a light source which means the Ag particles were in the nanoscale. 2.2. Characterization of Ag colloids The UV–vis spectrum of the prepared Ag colloids was measured by a UV-2401PC. In the measurement, the colloidal sample was filled in clean quartz cell for measurement, and deionized water was used as reference. The recorded spectra region was from 300 to 900 nm. TEM measurements were performed on an H-600 TEM made by the HITACHI Corporation. Sample for TEM studies was prepared by placing a drop of the Ag colloidal solution on a carbon-coated TEM grid. MO aqueous solution (prepared as 5 10 5 M) of 1 ml and SR aqueous solution (saturated solution) of 1 ml were added to the Ag colloids of 1 ml, respectively. The final concentration of MO mixture was of 2.5 10 5 M. Each mixture was transferred into a capillary tube for direct Raman scattering measurement. A confocal microscopy Raman spectrometer (Renishaw 2000 model) was employed to measure the Raman spectra of the samples. Radiation of 514.5 nm from an air-cooled argon ion laser with power of a few mW was used for the SERS excitation. All of the reported spectra represent single scans with 10 s integration time. 3. Computational methods Theoretical calculation of MO was carried out using the Gaussian’98 (Revision A.3) suite of programs. First principle computations were performed by using the hybrid functional B3LYP, Becke’s 3-parameter exchange functional, along with the correlation functional developed by Lee et al. In order to calculate an optimized structure and vibrational spectra of MO, the lanl2dz basis set was employed by using tight convergence criteria. Gauss View (version 3.0) for Windows was used to show all the computed results. An in-house program, VibWidth, was used to artificially apply a 5 cm 1 bandwidth to all peaks in the presented calculated Raman. The calculated wave numbers of all normal modes were scaled down by a factor of 0.9614 to correct systematic errors of the theoretical methodology. 4. Results and discussion 4.1. TEM image and UV–vis spectrum Fig. 1 shows the TEM images and UV–vis spectrum of PVAprotected Ag colloids prepared by electrolysis. From Fig. 1a, it can be seen that the size of the Ag nanoparticles is in a broad size distribution of 30–80 nm. PVA, being a hydrophilic polymer, was adsorbed on the surface of the Ag nanoparticles and thereby stabilized the dispersion. In UV–vis spectrum, a characteristic band at 433 nm of the Ag colloids corresponding to the plasmon surface resonance was observed. It is important to note that such an adsorption band was not observed before electrolysis was applied. In UV–vis spectrum, the peak width of Ag colloids prepared by electrolysis method was much broader than the peak width of the Ag colloids prepared by chemical reduction. This may indicate that the size distribution of Ag nanoparticles prepared by electrolysis method was much broader than that of the Ag nanoparticles prepared by chemical reduction. 4.2. Raman and SERS spectra Fig. 2 presents the structure of MO (Fig. 2a is the 2D structure and Fig. 2b is the structure of MO calculation). The Discrete Fourier
Fig. 1. The UV–vis spectrum and the TEM images of Ag colloids prepared by electrolysis method.
Fig. 2. The structure of MO: (a) the 2D structure and (b) the structure by calculation.
Test (DFT) calculation of MO Raman spectrum matches well with the experimental result (Fig. 3). Although the relative intensities of the peaks of B3LYP/lanl2dz level are not exactly predicted for all Raman, but the peaks’ locations and numbers are similar. So the B3LYP/lanl2dz is a very useful method for the assignment of the normal modes in Raman spectrum. The dominant assignment for MO molecule, including computational and experimental results are given in Table 1. Table 1 Assignment of theoretical wave number values to experimental bands in the normal Raman spectrum of MO. Calculation (freq cm 1128 1154 1179 1302 1337 1362 1389 1430 1557 1571 1597
1
)
Experiment (freq cm 1117 1143 1197 1312 1364 1389 1420 1443 1590
1
)
Assignment
n(Ph–N) d(C–H) d(C–H) n(Ph–N) d(C–H) n(C–C) d(C–H) n(C–N)Me n(C–C) d(C–H) n(N N) n(C–C) d(C–H) n(N N) n(C–C) d(C–H) n(C–C) n(C–C) d(C–C) n(C–C) d(C–C) n(C–C) d(C–C)
M.Z. Si et al. / Applied Surface Science 255 (2009) 6007–6010
6009
Fig. 3. Raman spectra of MO: (a) solid and (b) calculation.
Fig. 4. The SERS spectrum of MO (5 10
Fig. 5. Structure of Sudan red (III).
In order to study the adsorption process of MO on Ag, the SERS spectrum of MO was compared with the normal Raman spectrum of solid MO. Fig. 4 shows the SERS spectrum of MO adsorbed on Ag colloids. 5 10 5 M MO solution was mixed with Ag colloids at the volume ration of 1:1, N N stretching vibration appearing at 1389/1420 cm 1 in the normal Raman spectrum of pure solid
5
M) in Ag colloids.
(Fig. 3a) and at 1392/1419 cm 1 in the SERS spectrum were observed. Also C–C stretching vibration appearing at 1590/1443/ 1312 cm 1 in the normal Raman spectrum of pure solid (Fig. 3a) and at 1606/1558/1444/1312 cm 1 in the SERS spectrum were observed. Ph–N stretching vibration appeared at 1197/ 1117 cm 1 in normal Raman spectrum and at 1197/1113/ 1121 cm 1 in the SERS spectrum. However, the d(C–H) band appeared at 1143 cm 1 both in the normal Raman spectrum and in SERS. The observation of the very strong n(N N) at 1392/ 1419 cm 1 suggests that absorption of the molecule on Ag surface via the N N group. This is further evidenced by the observation of the N/Ag vibration at 237.6 cm 1. So the peak positions and the exhibited similar relative intensities in the SERS spectrum are nearly equivalent to those of the normal Raman spectrum, which suggests the adsorption of the MO on the surface of Ag colloid via trans-form. In order to test the applicability of these colloids, SR (the structure of molecules see Fig. 5) was mixed with it. The SERS spectrum of SR, one of the Azo-dye molecules, can be observed (see Fig. 6). It can be said that the Ag colloids prepared by electrolysis method were useful colloids to gain the SERS spectra of Azo-dye molecules. On the other hand, we cannot measure the SERS spectra of MO and SR from Ag colloids prepared by chemical reduction method, perhaps due to the competition of the borohydride and citrate ions with the MO and SR. The borohydride and citrate ions being adsorbed on the Ag nanoparticles leaving the MO and SR without any chance to be adsorbed. 5. Conclusions
Fig. 6. The SERS spectrum of Sudan red (III) (saturated solution) in Ag colloids.
The SERS spectra of MO and SR in PVA-protected Ag colloids by electrolysis method were obtained. But obtaining SERS spectra of MO and SR in Ag colloids prepared by borate or citrate were not successful. Being the simplest colloids composition of Ag colloids substrate, the process of preparation of the Ag colloids produced no competing species in the aqueous colloids. This provides some advantages in SERS applications. Further study on this is in process.
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M.Z. Si et al. / Applied Surface Science 255 (2009) 6007–6010
Acknowledgement The authors would like to thank Prof. Aroca of Windsor University for providing us the support of the calculation. References [1] [2] [3] [4] [5] [6] [7] [8]
S. Choi, H.G. Park, Appl. Surf. Sci. 243 (2005) 76. S.W. Joo, S.W. Han, K. Kim, J. Colloid Interf. Sci. 265 (2003) 234. M. Fleischman, P.J. Hendra, A.J. McQuillan, Chem. Phys. Lett. 26 (1974) 163. D.L. Jeanmaire, R.P.V. Duyne, J. Electroanal. Chem. 84 (1977) 1. M.G. Albrecht, J.A. Creighton, J. Am. Chem. Soc. 99 (1977) 5215. Y. Saito, J.J. Wang, D.A. Smith, D.N. Batchelder, Langmuir 18 (2002) 2959. P.C. Lee, D.P. Meisel, J. Phys. Chem. 86 (1982) 3391. J.A. Creighton, J. Chem. Soc., Faraday Trans. 75 (1979) 790.
[9] A. Qin, Z. Li, J.W.Y. Lam, B.Z. Tang, Proc. SPIE 6331 (2006) 633105. [10] R.A. Hill, S. Dreher, A. Knoesen, D.R. Yankelevich, Appl. Phys. Lett. 66 (1995) 2156. [11] Y. Niidome, S. Tagawa, S. Yamada, Colloid Surf. A 198–200 (2002) 467. [12] A. Galembeck, S.B.C. Silva, J.P. Silva, J.D. Nero, Opt. Mater. 24 (2004) 637. [13] M. Azuki, K. Morihashi, T. Watanabe, O. Takahashi, O. Kikuchi, J. Mol. Struc.Theochem. 542 (2001) 255. [14] M.S. Masoud, H.H. Hammud, Spectrochim. Acta 57 (2001) 977. [15] A.P. Zhang, Y. Fang, H.B. Shao, J. Colloid Interf. Sci. 298 (2006) 769. [16] C.H. Munro, W.E. Smith, M. Garner, J. Clarkson, P.C. White, Langmuir 11 (1995) 3712. [17] B. Teiten, A. Burneau, J. Colloid Interf. Sci. 206 (1998) 267. [18] H.I.S. Negueria, Spectrochim. Acta A 54 (1998) 1461. [19] T. Tsuji, T. Kakita, M. Tsuji, Appl. Surf. Sci. 206 (2003) 314. [20] R. BrauseH, K. Mo¨ltgen, Kleinermanns, Appl. Phys. B 75 (2002) 711. [21] T. Tsuji, K. Iryo, N. Watanabe, M. Tsuji, Appl. Surf. Sci. 202 (2002) 80.
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Surface-enhanced Raman scattering (SERS) spectra of Methyl Orange in Ag colloids prepared by electrolysis method M.Z. Si a,b,*, Y.P. Kang c, Z.G. Zhang a a
Department of Physics, Harbin Institute of Technology University, Harbin 150080, PR China Department of Physics and Electronic Science, Chuxiong Normal University, Chuxiong 675000, PR China c Department of Physics and Electronic Science, Yunnan Normal University, Kunming 650092, PR China b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 2 February 2008 Received in revised form 14 January 2009 Accepted 20 January 2009 Available online 29 January 2009
Polyvinyl alcohol (PVA)-protected Ag colloids were prepared by an electrolysis method. The surfaceenhanced Raman scattering (SERS) spectra of Methyl Orange (MO), one of the Azo-dye molecules, in Ag colloids were successfully recorded with good concordance comparing to the theoretical results calculated by the Gaussian’98 program. The MO was adsorbed on the surface of Ag nanoparticles by trans-form which plays an important role for the SERS effect. However, the SERS spectra of MO in Ag colloids prepared by chemical reduction method did not appear which may be because of the competition of the borate or citrate ions with the MO. In order to test the applicability of these colloids, the SERS spectra of Sudan red (III) (SR), another of Azo-dye molecules, were measured and the result was good. Crown Copyright ß 2009 Published by Elsevier B.V. All rights reserved.
Keywords: SERS Ag colloids Electrolysis MO
1. Introduction Surface-enhanced Raman scattering (SERS) is a powerful technique for studying the adsorption behavior of molecules on substrate [1,2]. In SERS studies, Ag electrodes, Ag islands, Ag deposited films, and Ag colloids are used as substrates [3–6]. Among them, Ag colloids reduced by borohydride and citrate [7,8] are the most commonly methods used in many researches due to its better enhancement effect and particle stability. Azo-dye molecules, characterized by electron-donating and electron-accepting groups connected by a conjugated p-system, usually show large nonlinear optical responses, which are necessary for optical devices in telecommunications and signal processing applications [9]. Moreover, the Azo-dye molecules have been found with wide applicability in reversible optical data storage [10]. The storage process utilizes the light-induced trans– cis–trans isomerization of the Azo-dye molecules thereby utilizing the local variation of the refractive index of the medium. Methyl Orange (MO) is one of the Azo-dye molecules and was studied by many methods, such as liquid chromatography spectrometry and mass spectrometry [11–15]. However, to our knowledge, no one
* Corresponding author at: Department of Physics and Electronic Science, Chuxiong Normal University, Chuxiong 675000, PR China. Tel.: +86 878 3121785; fax: +86 878 3121785. E-mail address: [email protected] (M.Z. Si).
investigated it with SERS. The main reason was that by using the reduction method to gain the Ag colloids, the borate or citrate ions would be introduced into the colloidal system, which may lead to competition with the MO [16,17]. So one of the key points in wild SERS applications is finding a method of acquiring a highly SERS active substrate [18]. To avoid the chemical competition, Ag colloids were prepared by laser ablation form solid Ag, where ablation had the advantage of generating chemically clean colloidal surfaces [19–21]. However, it was difficult and expensive to gain the Ag colloids using laser ablation method. In this paper, an easy method, electrolysis method, was utilized to obtain chemically clean Ag colloids. The UV–vis spectrum and the transmission electron microscopy (TEM) image were employed to characterize the Ag particles. The SERS spectra of MO in the Ag colloids were investigated and a calculation was performed. The calculated result was compared with the experimental ones. 2. Experimental 2.1. Colloid preparation Two Ag rods (purity 99.5%) were used as anode and cathode, respectively. The diameter of the Ag rods was 0.5 cm. Mixture aqueous solution of polyvinyl alcohol (PVA) and AgNO3 were used as electrolyte. A 7-V direct current was applied on Ag rods for 1 h. Ag colloids with shallow yellow color were obtained as a
0169-4332/$ – see front matter . Crown Copyright ß 2009 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2009.01.055
6008
M.Z. Si et al. / Applied Surface Science 255 (2009) 6007–6010
homogeneous solution, and they were stable for 2 days at room temperature. The ‘‘Tyndall effect’’ was observed with the resulting solution when any laser was used as a light source which means the Ag particles were in the nanoscale. 2.2. Characterization of Ag colloids The UV–vis spectrum of the prepared Ag colloids was measured by a UV-2401PC. In the measurement, the colloidal sample was filled in clean quartz cell for measurement, and deionized water was used as reference. The recorded spectra region was from 300 to 900 nm. TEM measurements were performed on an H-600 TEM made by the HITACHI Corporation. Sample for TEM studies was prepared by placing a drop of the Ag colloidal solution on a carbon-coated TEM grid. MO aqueous solution (prepared as 5 10 5 M) of 1 ml and SR aqueous solution (saturated solution) of 1 ml were added to the Ag colloids of 1 ml, respectively. The final concentration of MO mixture was of 2.5 10 5 M. Each mixture was transferred into a capillary tube for direct Raman scattering measurement. A confocal microscopy Raman spectrometer (Renishaw 2000 model) was employed to measure the Raman spectra of the samples. Radiation of 514.5 nm from an air-cooled argon ion laser with power of a few mW was used for the SERS excitation. All of the reported spectra represent single scans with 10 s integration time. 3. Computational methods Theoretical calculation of MO was carried out using the Gaussian’98 (Revision A.3) suite of programs. First principle computations were performed by using the hybrid functional B3LYP, Becke’s 3-parameter exchange functional, along with the correlation functional developed by Lee et al. In order to calculate an optimized structure and vibrational spectra of MO, the lanl2dz basis set was employed by using tight convergence criteria. Gauss View (version 3.0) for Windows was used to show all the computed results. An in-house program, VibWidth, was used to artificially apply a 5 cm 1 bandwidth to all peaks in the presented calculated Raman. The calculated wave numbers of all normal modes were scaled down by a factor of 0.9614 to correct systematic errors of the theoretical methodology. 4. Results and discussion 4.1. TEM image and UV–vis spectrum Fig. 1 shows the TEM images and UV–vis spectrum of PVAprotected Ag colloids prepared by electrolysis. From Fig. 1a, it can be seen that the size of the Ag nanoparticles is in a broad size distribution of 30–80 nm. PVA, being a hydrophilic polymer, was adsorbed on the surface of the Ag nanoparticles and thereby stabilized the dispersion. In UV–vis spectrum, a characteristic band at 433 nm of the Ag colloids corresponding to the plasmon surface resonance was observed. It is important to note that such an adsorption band was not observed before electrolysis was applied. In UV–vis spectrum, the peak width of Ag colloids prepared by electrolysis method was much broader than the peak width of the Ag colloids prepared by chemical reduction. This may indicate that the size distribution of Ag nanoparticles prepared by electrolysis method was much broader than that of the Ag nanoparticles prepared by chemical reduction. 4.2. Raman and SERS spectra Fig. 2 presents the structure of MO (Fig. 2a is the 2D structure and Fig. 2b is the structure of MO calculation). The Discrete Fourier
Fig. 1. The UV–vis spectrum and the TEM images of Ag colloids prepared by electrolysis method.
Fig. 2. The structure of MO: (a) the 2D structure and (b) the structure by calculation.
Test (DFT) calculation of MO Raman spectrum matches well with the experimental result (Fig. 3). Although the relative intensities of the peaks of B3LYP/lanl2dz level are not exactly predicted for all Raman, but the peaks’ locations and numbers are similar. So the B3LYP/lanl2dz is a very useful method for the assignment of the normal modes in Raman spectrum. The dominant assignment for MO molecule, including computational and experimental results are given in Table 1. Table 1 Assignment of theoretical wave number values to experimental bands in the normal Raman spectrum of MO. Calculation (freq cm 1128 1154 1179 1302 1337 1362 1389 1430 1557 1571 1597
1
)
Experiment (freq cm 1117 1143 1197 1312 1364 1389 1420 1443 1590
1
)
Assignment
n(Ph–N) d(C–H) d(C–H) n(Ph–N) d(C–H) n(C–C) d(C–H) n(C–N)Me n(C–C) d(C–H) n(N N) n(C–C) d(C–H) n(N N) n(C–C) d(C–H) n(C–C) n(C–C) d(C–C) n(C–C) d(C–C) n(C–C) d(C–C)
M.Z. Si et al. / Applied Surface Science 255 (2009) 6007–6010
6009
Fig. 3. Raman spectra of MO: (a) solid and (b) calculation.
Fig. 4. The SERS spectrum of MO (5 10
Fig. 5. Structure of Sudan red (III).
In order to study the adsorption process of MO on Ag, the SERS spectrum of MO was compared with the normal Raman spectrum of solid MO. Fig. 4 shows the SERS spectrum of MO adsorbed on Ag colloids. 5 10 5 M MO solution was mixed with Ag colloids at the volume ration of 1:1, N N stretching vibration appearing at 1389/1420 cm 1 in the normal Raman spectrum of pure solid
5
M) in Ag colloids.
(Fig. 3a) and at 1392/1419 cm 1 in the SERS spectrum were observed. Also C–C stretching vibration appearing at 1590/1443/ 1312 cm 1 in the normal Raman spectrum of pure solid (Fig. 3a) and at 1606/1558/1444/1312 cm 1 in the SERS spectrum were observed. Ph–N stretching vibration appeared at 1197/ 1117 cm 1 in normal Raman spectrum and at 1197/1113/ 1121 cm 1 in the SERS spectrum. However, the d(C–H) band appeared at 1143 cm 1 both in the normal Raman spectrum and in SERS. The observation of the very strong n(N N) at 1392/ 1419 cm 1 suggests that absorption of the molecule on Ag surface via the N N group. This is further evidenced by the observation of the N/Ag vibration at 237.6 cm 1. So the peak positions and the exhibited similar relative intensities in the SERS spectrum are nearly equivalent to those of the normal Raman spectrum, which suggests the adsorption of the MO on the surface of Ag colloid via trans-form. In order to test the applicability of these colloids, SR (the structure of molecules see Fig. 5) was mixed with it. The SERS spectrum of SR, one of the Azo-dye molecules, can be observed (see Fig. 6). It can be said that the Ag colloids prepared by electrolysis method were useful colloids to gain the SERS spectra of Azo-dye molecules. On the other hand, we cannot measure the SERS spectra of MO and SR from Ag colloids prepared by chemical reduction method, perhaps due to the competition of the borohydride and citrate ions with the MO and SR. The borohydride and citrate ions being adsorbed on the Ag nanoparticles leaving the MO and SR without any chance to be adsorbed. 5. Conclusions
Fig. 6. The SERS spectrum of Sudan red (III) (saturated solution) in Ag colloids.
The SERS spectra of MO and SR in PVA-protected Ag colloids by electrolysis method were obtained. But obtaining SERS spectra of MO and SR in Ag colloids prepared by borate or citrate were not successful. Being the simplest colloids composition of Ag colloids substrate, the process of preparation of the Ag colloids produced no competing species in the aqueous colloids. This provides some advantages in SERS applications. Further study on this is in process.
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M.Z. Si et al. / Applied Surface Science 255 (2009) 6007–6010
Acknowledgement The authors would like to thank Prof. Aroca of Windsor University for providing us the support of the calculation. References [1] [2] [3] [4] [5] [6] [7] [8]
S. Choi, H.G. Park, Appl. Surf. Sci. 243 (2005) 76. S.W. Joo, S.W. Han, K. Kim, J. Colloid Interf. Sci. 265 (2003) 234. M. Fleischman, P.J. Hendra, A.J. McQuillan, Chem. Phys. Lett. 26 (1974) 163. D.L. Jeanmaire, R.P.V. Duyne, J. Electroanal. Chem. 84 (1977) 1. M.G. Albrecht, J.A. Creighton, J. Am. Chem. Soc. 99 (1977) 5215. Y. Saito, J.J. Wang, D.A. Smith, D.N. Batchelder, Langmuir 18 (2002) 2959. P.C. Lee, D.P. Meisel, J. Phys. Chem. 86 (1982) 3391. J.A. Creighton, J. Chem. Soc., Faraday Trans. 75 (1979) 790.
[9] A. Qin, Z. Li, J.W.Y. Lam, B.Z. Tang, Proc. SPIE 6331 (2006) 633105. [10] R.A. Hill, S. Dreher, A. Knoesen, D.R. Yankelevich, Appl. Phys. Lett. 66 (1995) 2156. [11] Y. Niidome, S. Tagawa, S. Yamada, Colloid Surf. A 198–200 (2002) 467. [12] A. Galembeck, S.B.C. Silva, J.P. Silva, J.D. Nero, Opt. Mater. 24 (2004) 637. [13] M. Azuki, K. Morihashi, T. Watanabe, O. Takahashi, O. Kikuchi, J. Mol. Struc.Theochem. 542 (2001) 255. [14] M.S. Masoud, H.H. Hammud, Spectrochim. Acta 57 (2001) 977. [15] A.P. Zhang, Y. Fang, H.B. Shao, J. Colloid Interf. Sci. 298 (2006) 769. [16] C.H. Munro, W.E. Smith, M. Garner, J. Clarkson, P.C. White, Langmuir 11 (1995) 3712. [17] B. Teiten, A. Burneau, J. Colloid Interf. Sci. 206 (1998) 267. [18] H.I.S. Negueria, Spectrochim. Acta A 54 (1998) 1461. [19] T. Tsuji, T. Kakita, M. Tsuji, Appl. Surf. Sci. 206 (2003) 314. [20] R. BrauseH, K. Mo¨ltgen, Kleinermanns, Appl. Phys. B 75 (2002) 711. [21] T. Tsuji, K. Iryo, N. Watanabe, M. Tsuji, Appl. Surf. Sci. 202 (2002) 80.