- Email: [email protected]
Sonochemical synthesis of amorphous long silver sulfide nanowires
Materials Letters 61 (2007) 235 – 238 www.elsevier.com/locate/matlet
Sonochemical synthesis of amorphous long silver sulfide nanowires Ning Du, Hui Zhang, Hongzhi Sun, Deren Yang ⁎ State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310027, People's Republic of China Received 9 November 2005; accepted 6 April 2006 Available online 6 May 2006
Abstract Long silver sulfide nanowires have been prepared via the thioglycolic acid (TGA)-assisted sonochemical method. The transmission electron microscope (TEM) and field emission scanning electron microscope (FESEM) images reveal that the nanowires have uniform width and length. The selected area electron diffraction (SAED) pattern indicates that the Ag2S nanowires are amorphous. Furthermore, the mechanism for the TGAassisted sonochemical synthesis of Ag2S nanowires has been preliminarily presented. © 2006 Elsevier B.V. All rights reserved. Keywords: Silver sulfide; Sonochemical method; Nanowires
1. Introduction In recent years, the synthesis of nanostructures has attracted great interest due to their significant potential applications [1– 3]. While, the research of one-dimensional materials, including nanorods, nanobelts and nanotubes, is the most active area due to their potential applications in nanodevices [4–6]. Lots of approaches have been reported to synthesize one-dimensional materials, such as laser ablation, chemical vapor deposition (CVD), thermal evaporation, hydrothermal process, chemical reaction, and so on [7–12]. Recently, a simple, effective and novel route, i.e. sonochemical method has been developed to prepare nanostructures [13]. Some nanostructures such as Bi2S3 nanorods has been synthesized by ultrasound method [14]. Silver sulfide, as well as other silver chalcogenides, has good photoelectric and thermoelectric properties, which has been widely applied in optical and electronic devices, such as photoconducting cells, photovoltaic cells and so on [15,16]. Therefore, there are many reports about the Ag2S nanostructures due to their potential application in optical and electronic nanodevices [17–20]. However, to our best knowledge, the preparation of Ag2S nanowires by sonochemical method with
⁎ Corresponding author. Tel.: +86 571 87951667; fax: +86 571 87952322. E-mail address: [email protected] (D. Yang). 0167-577X/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2006.04.039
the advantages of simplicity, cost-effectiveness and availability has not yet been reported. Herein, the amorphous long Ag2S nanowires have been prepared by a TGA-assisted sonochemical method. The trick in the sonochemical method presented here is the application of TGA, which directs the preferential growth of Ag2S. 2. Experimental All the chemicals were analytic grade reagents without further purification. Experimental details were as following: 10 ml thioglycolic acid was added into 100 ml 0.02 M AgNO3 aqueous solutions. The solutions were mixed well and irradiated with high-intensity ultrasonic wave at room temperature for 120 min. The black products obtained were washed with distilled water and ethanol and then centrifuged to remove the ions possibly remaining in the final products. Finally the products were dried at 60 °C in air. The field emission scanning electron microscopy (FESEM) images with energy dispersive X-ray (EDAX) was obtained on a FEI SIRION. Transmission electron microscopy (TEM) observation was performed with a JEM 200 CX microscope operated at 160 kV. The optical absorption of Ag2S nanowires was examined by a Perkin-Elmer Lambda 20 UV/Vis Spectrometer. The Fourier transform infrared spectrum (FTIR) of Ag2S nanowires was obtained from Bruker IFS 66 vs-1. The
236
N. Du et al. / Materials Letters 61 (2007) 235–238
Fig. 1. TEM image (a) and (b) of Ag2S nanowires prepared by sonochemical approach. The upper left inset corresponds to the SAED pattern of individual Ag2S nanowire.
KQ5200 ultrasonic cleaning machine with a power of about 60 W was obtained from Kunshan ultrasonic cleaning machine Limited Corporation. 3. Results and discussions Fig. 1 shows the TEM image of the sample obtained by the sonochemical approach. From the Fig. 1a, lots of nanowires with hundreds of micron in length and 100–200 nm in width have been observed. The yield of the amorphous Ag2S is about 85%. The magnified TEM image as shown in Fig. 1b confirms the uniform and regular nanowires morphology. The SAED pattern inserted in Fig. 1b indicates that the nanowires are amorphous. Fig. 2 shows the scenarios for the formation of Ag2S nanowires by sonochemical treatment for different times. The product in the precursor solution treated by sonication for about 5 min displays as a network (see Fig. 2a), which
is supposed to be the complexed Ag2S cluster and is the same as our previous report [21]. After sonicating for 30 min, the porous nanowires are formed due to the attachment of the complexed Ag2S cluster as shown in Fig. 2b. Finally, as the sonication proceeded long enough (about 60 min), as shown in the Fig. 2c, the smooth Ag2S nanowires are formed. Fig. 3 shows the FESEM images of the as-synthesized sample. From the image, large amount of nanowires is obtained with long length, uniform width, and smooth surface. The EDAX analysis performed on many nanowires is shown in Fig. 4. In the EDAX spectrum, the peaks of Ag and S are pronounced and no other peaks are found except for those of Al and O originating from aluminum substrate used to support the Ag2S nanowires, which can be easily oxidized in the air. The molar ratio of silver and sulfur is about 2, which is calculated by EDX software. The room temperature UV–vis absorption of Ag2S nanowires dispersed in ethanol is recorded as shown in Fig. 5. The blue shift to 350 nm can be found compared with the band gap of the characteristic absorption of bulk Ag2S
Fig. 2. TEM image of Ag2S nanowires prepared by sonochemical approach for different times: (a) 5 min; (b) 30 min; (c) 60 min.
N. Du et al. / Materials Letters 61 (2007) 235–238
237
Fig. 5. UV–vis spectrum of Ag2S nanowires prepared by sonochemical approach. influence of H• and OH• from aqueous solution; the other is complexing agent, which controls the nucleation and growth of Ag2S nanowires. The probable reaction process for the formation of nanowires can be summarized as follows:
Fig. 3. FESEM image (a) and (b) of Ag2S nanowires prepared by sonochemical approach.
H2 OÞÞÞÞÞH• þ OH•
ð1Þ
H• þ HSCH2 COOH→CH2 COOH• þ 2Hþ þ S2−
ð2Þ
2Agþ þ S2− →Ag2 S
ð3Þ
mAg2 S þ kHSCH2 COOH þ kAgþ ↔ðAg2 SÞm ðAgSCH2 COOHÞk þ kHþ
ð4Þ
ðAg2 SÞm ðAgSCH2 COOHÞk ↔ðAg2 SÞm ðAgþ Þk þ kSCH2 COOH−
ð5Þ
ðAg2 SÞm ðAgþ Þk þ lS2− ↔ðAg2 SÞn
ð6Þ
probably due to the size effect, chemical modification and amorphous effect, which is identical with the result of the Ag2S nanoparticles in previous report [22]. Regarding the formation of long Ag2S nanowires by TGA-assisted sonochemical process, it is believed that TGA and the ultrasonic condition play the critical roles, which is confirmed by the results without the TGA assistance or ultrasonic condition. As we know, ultrasound, which is intense enough to produce cavitations, can drive chemical reaction [23,24], and during the aqueous sonochemical process, the elevated temperature and pressure inside the collapsing bubble cause water to vaporize and further pyrolyze into H• and OH• radicals [14]. Moreover, it is certain that TGA plays two kinds of function in the sonochemical process. One is sulfur source, which is released under the
In the sonochemical process, the radicals are primarily formed by the ultrasound-initiated dissociation within the collapsing gas bubbles as shown in reaction (1). The in-situ generated H• has great reducing ability and can react with TGA via reaction (2) to release S2− ions, which then combined with Ag+ ions existing in the solution via reaction (3). It is believed that the Ag2S nuclei are formed at this stage. Moreover, the complex clusters i.e. (Ag2S)m (AgSCH2COOH)kd, are formed via the reaction (4), which is similar to the formation of CdS nanorods in our previous report [25]. Reaction (5) illustrates the dissociation of SCH2COOH− from the complexed Ag2S clusters, but we believe that the dissociation of SCH2COOH− occurs at local regions of the complexed Ag2S cluster, where there are Ag+ ions exposed to the S2− ions existing in the solution. Therefore, during the sonochemical process, the
Fig. 4. EDX pattern of Ag2S nanowires prepared by sonochemical approach.
Fig. 6. FTIR spectrum of as-synthesized Ag2S nanowires.
238
N. Du et al. / Materials Letters 61 (2007) 235–238
formation of Ag2S proceeds along the specific directions, dependent on the status of SCH2COOH− dissociation from the complexed Ag2S cluster, Ag2S nanowires, as shown in Fig. 1, will ultimately be formed via reaction (6). The FTIR spectrum of as-synthesized Ag2S nanowires is shown in Fig. 6. From the spectrum, the band at 1390 cm− 1 relation with –COOH symmetrical stretching and the band at 1610 cm− 1 belong to the –COOH anti-symmetrical stretching have been observed, which indicates the action of TGA in the reaction. Moreover, there is no –HS stretching band at about 2546 cm− 1 because the Ag+ replaces H+ in the –HS to form Ag2S nanowires. Frankly, the above explanation for the TGA-assisted sonochemical fabrication of Ag2S nanowires is somewhat conjectural and phenomenological. Intensive investigation is required to derive the exact mechanism for the formation of Ag2S nanowires reported in the present work.
4. Conclusions In summary, a novel sonochemical method for the preparation of very long Ag2S nanowires has been reported for the first time that features simplicity, cost-effectiveness, and environmental friendliness. It is reasonable to believe that the sonochemical method presented here is desirable for fabrication of quasi one-dimensional materials of other chalcogenides. Acknowledgement The authors would like to appreciate the financial supports from the Natural Science Foundation of China (60225010), Key Project of Chinese Ministry of Education and Program for New Century Excellent Talents in Universities. Thanks Prof. Youwen Wang for the TEM and FESEM measurements. References [1] X. Duan, Y. Huang, R. Agarwal, C.M. Lieber, Nature 421 (2003) 241. [2] M.S Fuhrer, J. Nygard, L. Shih, M. Forero, Young-Gui Yoon, M.S.C. Mazzoni, Hyoung Joon Choi, Science 288 (2000) 494.
[3] Z.F. Ren, Z.P. Huang, J.W. Xu, J.H. Wang, P. Bush, M.P. Siegal, P.N. Provencio, Science 282 (1998) 1105. [4] H. Zhang, D. Yang, Y. Ji, X. Ma, J. Xu, D. Que, J. Phys. Chem., B 108 (2004) 3955. [5] Hui Zhang, Deren Yang, Yujie Ji, Xiangyang Ma, Jin Xu, Duanling Que, J. Phys. Chem., B 108 (2004) 1179. [6] Z.W. Pan, Z.R. Dai, Z.L. Wang, Science 291 (2001) 1947. [7] X.F. Duan, C.M. Liber, Adv. Mater. 12 (2000) 298. [8] J. Sha, J.J. Niu, X.Y. Ma, J. Xu, X.B. Zhang, Q. Yang, D.R. Yang, Adv. Mater. 14 (2002) 1219. [9] M.H. Huang, Y.Y. Wu, H. Feick, N. Tran, E. Weber, P.D. Yang, Adv. Mater. 13 (2001) 113. [10] H. Zhang, D. Yang, X. Ma, Y. Ji, J. Xu, D. Que, Nanotechnology 15 (2004) 622. [11] C. Pacholski, A. Kornowski, H. Weller, Angew. Chem., Int. Ed. Engl. 41 (2002) 1188. [12] Jinhua Zhang, Xiaogang Yang, Dunwei Wang, Shengdong Li, Yi Xie, Younan Xia, Yitai Qian, Adv. Mater. 12 (2000) 1348. [13] K.S. Suslick, G.J. Price, Annu. Rev. Mater. Sci. 29 (1999) 295. [14] H. Wang, J.J. Zhu, J.M. Zhu, H.Y. Chen, J. Phys. Chem., B 106 (2002) 3848. [15] J.A. Munoz, C. Gomez, A. Ballester, M.L. Blazquez, F. Gonzalez, M. Figueroa, J. Appl. Electrochem. 28 (1998) 49. [16] M.C. Brelle, J.Z. Zhang, J. Chem. Phys. 108 (1998) 3119. [17] R. Vogel, P. Hoyer, H. Weller, J. Phys. Chem. 98 (1994) 3183. [18] M.M. EI-Nahass, A.A.M. Farag, E.M. Ibrahim, S. Abd-EI-Rahman, Vacuum 72 (2004) 453. [19] R.K. Sharma, S.N. Sharma, A.C. Rastogi, Curr. Appl. Phys. 3 (2003) 257. [20] M.Y. Han, W. Huang, C.H. Chew, L.M. Gan, J. Phys. Chem., B 102 (1998) 1884. [21] Hui Zhang, Deren Yang, Xiangyang Ma, Yujie Ji, Shenzhong Li, Duanling Que, Mater. Chem. Phys. 93 (2005) 65–69. [22] X.F. Qian, J. Yin, J.C. Huang, Y.F. Yang, X.X. Guo, Z.K. Zhu, Mater. Chem. Phys. 68 (2001) 95. [23] K.S. Suslick, Ultrasound: Its Chemical, Physical and Biological Effects, VCH, Weinhein, Germany, 1988. [24] K.S. Suslick, D.A. Hammerton, R.E. Cline, J. Am. Chem. Soc. 108 (1986) 5641. [25] Hui Zhang, Xiangyang Ma, Yujie Ji, Jin Xu, Deren Yang, Chem. Phys. Lett. 377 (2003) 654.
Sonochemical synthesis of amorphous long silver sulfide nanowires Ning Du, Hui Zhang, Hongzhi Sun, Deren Yang ⁎ State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310027, People's Republic of China Received 9 November 2005; accepted 6 April 2006 Available online 6 May 2006
Abstract Long silver sulfide nanowires have been prepared via the thioglycolic acid (TGA)-assisted sonochemical method. The transmission electron microscope (TEM) and field emission scanning electron microscope (FESEM) images reveal that the nanowires have uniform width and length. The selected area electron diffraction (SAED) pattern indicates that the Ag2S nanowires are amorphous. Furthermore, the mechanism for the TGAassisted sonochemical synthesis of Ag2S nanowires has been preliminarily presented. © 2006 Elsevier B.V. All rights reserved. Keywords: Silver sulfide; Sonochemical method; Nanowires
1. Introduction In recent years, the synthesis of nanostructures has attracted great interest due to their significant potential applications [1– 3]. While, the research of one-dimensional materials, including nanorods, nanobelts and nanotubes, is the most active area due to their potential applications in nanodevices [4–6]. Lots of approaches have been reported to synthesize one-dimensional materials, such as laser ablation, chemical vapor deposition (CVD), thermal evaporation, hydrothermal process, chemical reaction, and so on [7–12]. Recently, a simple, effective and novel route, i.e. sonochemical method has been developed to prepare nanostructures [13]. Some nanostructures such as Bi2S3 nanorods has been synthesized by ultrasound method [14]. Silver sulfide, as well as other silver chalcogenides, has good photoelectric and thermoelectric properties, which has been widely applied in optical and electronic devices, such as photoconducting cells, photovoltaic cells and so on [15,16]. Therefore, there are many reports about the Ag2S nanostructures due to their potential application in optical and electronic nanodevices [17–20]. However, to our best knowledge, the preparation of Ag2S nanowires by sonochemical method with
⁎ Corresponding author. Tel.: +86 571 87951667; fax: +86 571 87952322. E-mail address: [email protected] (D. Yang). 0167-577X/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2006.04.039
the advantages of simplicity, cost-effectiveness and availability has not yet been reported. Herein, the amorphous long Ag2S nanowires have been prepared by a TGA-assisted sonochemical method. The trick in the sonochemical method presented here is the application of TGA, which directs the preferential growth of Ag2S. 2. Experimental All the chemicals were analytic grade reagents without further purification. Experimental details were as following: 10 ml thioglycolic acid was added into 100 ml 0.02 M AgNO3 aqueous solutions. The solutions were mixed well and irradiated with high-intensity ultrasonic wave at room temperature for 120 min. The black products obtained were washed with distilled water and ethanol and then centrifuged to remove the ions possibly remaining in the final products. Finally the products were dried at 60 °C in air. The field emission scanning electron microscopy (FESEM) images with energy dispersive X-ray (EDAX) was obtained on a FEI SIRION. Transmission electron microscopy (TEM) observation was performed with a JEM 200 CX microscope operated at 160 kV. The optical absorption of Ag2S nanowires was examined by a Perkin-Elmer Lambda 20 UV/Vis Spectrometer. The Fourier transform infrared spectrum (FTIR) of Ag2S nanowires was obtained from Bruker IFS 66 vs-1. The
236
N. Du et al. / Materials Letters 61 (2007) 235–238
Fig. 1. TEM image (a) and (b) of Ag2S nanowires prepared by sonochemical approach. The upper left inset corresponds to the SAED pattern of individual Ag2S nanowire.
KQ5200 ultrasonic cleaning machine with a power of about 60 W was obtained from Kunshan ultrasonic cleaning machine Limited Corporation. 3. Results and discussions Fig. 1 shows the TEM image of the sample obtained by the sonochemical approach. From the Fig. 1a, lots of nanowires with hundreds of micron in length and 100–200 nm in width have been observed. The yield of the amorphous Ag2S is about 85%. The magnified TEM image as shown in Fig. 1b confirms the uniform and regular nanowires morphology. The SAED pattern inserted in Fig. 1b indicates that the nanowires are amorphous. Fig. 2 shows the scenarios for the formation of Ag2S nanowires by sonochemical treatment for different times. The product in the precursor solution treated by sonication for about 5 min displays as a network (see Fig. 2a), which
is supposed to be the complexed Ag2S cluster and is the same as our previous report [21]. After sonicating for 30 min, the porous nanowires are formed due to the attachment of the complexed Ag2S cluster as shown in Fig. 2b. Finally, as the sonication proceeded long enough (about 60 min), as shown in the Fig. 2c, the smooth Ag2S nanowires are formed. Fig. 3 shows the FESEM images of the as-synthesized sample. From the image, large amount of nanowires is obtained with long length, uniform width, and smooth surface. The EDAX analysis performed on many nanowires is shown in Fig. 4. In the EDAX spectrum, the peaks of Ag and S are pronounced and no other peaks are found except for those of Al and O originating from aluminum substrate used to support the Ag2S nanowires, which can be easily oxidized in the air. The molar ratio of silver and sulfur is about 2, which is calculated by EDX software. The room temperature UV–vis absorption of Ag2S nanowires dispersed in ethanol is recorded as shown in Fig. 5. The blue shift to 350 nm can be found compared with the band gap of the characteristic absorption of bulk Ag2S
Fig. 2. TEM image of Ag2S nanowires prepared by sonochemical approach for different times: (a) 5 min; (b) 30 min; (c) 60 min.
N. Du et al. / Materials Letters 61 (2007) 235–238
237
Fig. 5. UV–vis spectrum of Ag2S nanowires prepared by sonochemical approach. influence of H• and OH• from aqueous solution; the other is complexing agent, which controls the nucleation and growth of Ag2S nanowires. The probable reaction process for the formation of nanowires can be summarized as follows:
Fig. 3. FESEM image (a) and (b) of Ag2S nanowires prepared by sonochemical approach.
H2 OÞÞÞÞÞH• þ OH•
ð1Þ
H• þ HSCH2 COOH→CH2 COOH• þ 2Hþ þ S2−
ð2Þ
2Agþ þ S2− →Ag2 S
ð3Þ
mAg2 S þ kHSCH2 COOH þ kAgþ ↔ðAg2 SÞm ðAgSCH2 COOHÞk þ kHþ
ð4Þ
ðAg2 SÞm ðAgSCH2 COOHÞk ↔ðAg2 SÞm ðAgþ Þk þ kSCH2 COOH−
ð5Þ
ðAg2 SÞm ðAgþ Þk þ lS2− ↔ðAg2 SÞn
ð6Þ
probably due to the size effect, chemical modification and amorphous effect, which is identical with the result of the Ag2S nanoparticles in previous report [22]. Regarding the formation of long Ag2S nanowires by TGA-assisted sonochemical process, it is believed that TGA and the ultrasonic condition play the critical roles, which is confirmed by the results without the TGA assistance or ultrasonic condition. As we know, ultrasound, which is intense enough to produce cavitations, can drive chemical reaction [23,24], and during the aqueous sonochemical process, the elevated temperature and pressure inside the collapsing bubble cause water to vaporize and further pyrolyze into H• and OH• radicals [14]. Moreover, it is certain that TGA plays two kinds of function in the sonochemical process. One is sulfur source, which is released under the
In the sonochemical process, the radicals are primarily formed by the ultrasound-initiated dissociation within the collapsing gas bubbles as shown in reaction (1). The in-situ generated H• has great reducing ability and can react with TGA via reaction (2) to release S2− ions, which then combined with Ag+ ions existing in the solution via reaction (3). It is believed that the Ag2S nuclei are formed at this stage. Moreover, the complex clusters i.e. (Ag2S)m (AgSCH2COOH)kd, are formed via the reaction (4), which is similar to the formation of CdS nanorods in our previous report [25]. Reaction (5) illustrates the dissociation of SCH2COOH− from the complexed Ag2S clusters, but we believe that the dissociation of SCH2COOH− occurs at local regions of the complexed Ag2S cluster, where there are Ag+ ions exposed to the S2− ions existing in the solution. Therefore, during the sonochemical process, the
Fig. 4. EDX pattern of Ag2S nanowires prepared by sonochemical approach.
Fig. 6. FTIR spectrum of as-synthesized Ag2S nanowires.
238
N. Du et al. / Materials Letters 61 (2007) 235–238
formation of Ag2S proceeds along the specific directions, dependent on the status of SCH2COOH− dissociation from the complexed Ag2S cluster, Ag2S nanowires, as shown in Fig. 1, will ultimately be formed via reaction (6). The FTIR spectrum of as-synthesized Ag2S nanowires is shown in Fig. 6. From the spectrum, the band at 1390 cm− 1 relation with –COOH symmetrical stretching and the band at 1610 cm− 1 belong to the –COOH anti-symmetrical stretching have been observed, which indicates the action of TGA in the reaction. Moreover, there is no –HS stretching band at about 2546 cm− 1 because the Ag+ replaces H+ in the –HS to form Ag2S nanowires. Frankly, the above explanation for the TGA-assisted sonochemical fabrication of Ag2S nanowires is somewhat conjectural and phenomenological. Intensive investigation is required to derive the exact mechanism for the formation of Ag2S nanowires reported in the present work.
4. Conclusions In summary, a novel sonochemical method for the preparation of very long Ag2S nanowires has been reported for the first time that features simplicity, cost-effectiveness, and environmental friendliness. It is reasonable to believe that the sonochemical method presented here is desirable for fabrication of quasi one-dimensional materials of other chalcogenides. Acknowledgement The authors would like to appreciate the financial supports from the Natural Science Foundation of China (60225010), Key Project of Chinese Ministry of Education and Program for New Century Excellent Talents in Universities. Thanks Prof. Youwen Wang for the TEM and FESEM measurements. References [1] X. Duan, Y. Huang, R. Agarwal, C.M. Lieber, Nature 421 (2003) 241. [2] M.S Fuhrer, J. Nygard, L. Shih, M. Forero, Young-Gui Yoon, M.S.C. Mazzoni, Hyoung Joon Choi, Science 288 (2000) 494.
[3] Z.F. Ren, Z.P. Huang, J.W. Xu, J.H. Wang, P. Bush, M.P. Siegal, P.N. Provencio, Science 282 (1998) 1105. [4] H. Zhang, D. Yang, Y. Ji, X. Ma, J. Xu, D. Que, J. Phys. Chem., B 108 (2004) 3955. [5] Hui Zhang, Deren Yang, Yujie Ji, Xiangyang Ma, Jin Xu, Duanling Que, J. Phys. Chem., B 108 (2004) 1179. [6] Z.W. Pan, Z.R. Dai, Z.L. Wang, Science 291 (2001) 1947. [7] X.F. Duan, C.M. Liber, Adv. Mater. 12 (2000) 298. [8] J. Sha, J.J. Niu, X.Y. Ma, J. Xu, X.B. Zhang, Q. Yang, D.R. Yang, Adv. Mater. 14 (2002) 1219. [9] M.H. Huang, Y.Y. Wu, H. Feick, N. Tran, E. Weber, P.D. Yang, Adv. Mater. 13 (2001) 113. [10] H. Zhang, D. Yang, X. Ma, Y. Ji, J. Xu, D. Que, Nanotechnology 15 (2004) 622. [11] C. Pacholski, A. Kornowski, H. Weller, Angew. Chem., Int. Ed. Engl. 41 (2002) 1188. [12] Jinhua Zhang, Xiaogang Yang, Dunwei Wang, Shengdong Li, Yi Xie, Younan Xia, Yitai Qian, Adv. Mater. 12 (2000) 1348. [13] K.S. Suslick, G.J. Price, Annu. Rev. Mater. Sci. 29 (1999) 295. [14] H. Wang, J.J. Zhu, J.M. Zhu, H.Y. Chen, J. Phys. Chem., B 106 (2002) 3848. [15] J.A. Munoz, C. Gomez, A. Ballester, M.L. Blazquez, F. Gonzalez, M. Figueroa, J. Appl. Electrochem. 28 (1998) 49. [16] M.C. Brelle, J.Z. Zhang, J. Chem. Phys. 108 (1998) 3119. [17] R. Vogel, P. Hoyer, H. Weller, J. Phys. Chem. 98 (1994) 3183. [18] M.M. EI-Nahass, A.A.M. Farag, E.M. Ibrahim, S. Abd-EI-Rahman, Vacuum 72 (2004) 453. [19] R.K. Sharma, S.N. Sharma, A.C. Rastogi, Curr. Appl. Phys. 3 (2003) 257. [20] M.Y. Han, W. Huang, C.H. Chew, L.M. Gan, J. Phys. Chem., B 102 (1998) 1884. [21] Hui Zhang, Deren Yang, Xiangyang Ma, Yujie Ji, Shenzhong Li, Duanling Que, Mater. Chem. Phys. 93 (2005) 65–69. [22] X.F. Qian, J. Yin, J.C. Huang, Y.F. Yang, X.X. Guo, Z.K. Zhu, Mater. Chem. Phys. 68 (2001) 95. [23] K.S. Suslick, Ultrasound: Its Chemical, Physical and Biological Effects, VCH, Weinhein, Germany, 1988. [24] K.S. Suslick, D.A. Hammerton, R.E. Cline, J. Am. Chem. Soc. 108 (1986) 5641. [25] Hui Zhang, Xiangyang Ma, Yujie Ji, Jin Xu, Deren Yang, Chem. Phys. Lett. 377 (2003) 654.