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Chem. Mater. 2001, 13, 648-654
Synthesis and Characterization of Nanosized ZnS Confined in Ordered Mesoporous Silica Wen-Hua Zhang,* Jian-Lin Shi, Hang-Rong Chen, Zi-Le Hua, and Dong-Sheng Yan State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050, People’s Republic of China Received July 26, 2000. Revised Manuscript Received December 5, 2000
Nanosized ZnS has been prepared inside MCM-41 hosts by two related schemes, both of which are derived from surface modification methods. The ZnS-containing MCM-41 samples with and without the functional groups (ethylenediamine groups in this case) were designated as ZnS-ED-MCM-41 and ZnS-MCM-41(cal), respectively. The ZnS-MCM-41 composites were characterized by powder X-ray diffraction patterns, transmission electron microscopy, energy disperse spectra, N2 adsorption-desorption isotherms, UV-vis diffuse reflectance spectra, and photoluminescence (PL) spectra. The ZnS was mainly formed and retained in the channels of the MCM-41 host, and its growth was controlled by the channels. In contrast, the amount of ZnS on the external surface is much smaller. The existence of ZnS inside the MCM-41 hosts resulted in a considerable decrease in surface area, pore diameter, and pore volume, and a massive blue shift in the UV-vis spectra was observed. In comparison with the ZnS-MCM-41(cal) sample, a dramatic increase in PL emission for the ZnS-ED-MCM41 sample was observed, which was suggested to arise from a strong interaction between the ZnS clusters and the organic component. The nature of the PL spectra has been tentatively attributed to the sulfur vacancies in the present experiment. Finally, the synthesis of other sulfides, such as CdS and CuS clusters, has also been explored inside the channels of the MCM-41 host.
Introduction In the past 2 decades, great efforts have been dedicated to the study of nanosized materials, which possess many novel properties that differ considerably from those of the bulk.1 Because of the size quantization effects and potential applications in optoelectronics, lowdimensional semiconductor materials, including zerodimensional quantum dots and one-dimensional quantum wires, have attracted special attention. Great advancement has been made in preparing nanostructured semiconductor materials in recent years;2 for example, such materials have been prepared in colloids,3 polymer matrixes,4 self-assembled monolayers,5 and zeolites.6 Among these, to use porous materials as hosts for limiting the growth of clusters inside their pores is a relatively promising scheme. Several methods have * Present corresponding address: State Key Lab of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China. (1) (a) Henglein, A. Chem. Rev. 1989, 89, 1861. (b) Ronsencher, E.; Fiore, A.; Vinter, B.; Berger, V.; Bois, P.; Nagle, J. Science 1996, 271, 168. (c) Yanagida, S.; Yooshiya, M.; Shiragami, T.; Pac, C.; Mori, H.; Fujita, H. J. Phys. Chem. 1990, 94, 3104. (2) A special section of Science 1990, 254, 1300. (3) (a) Spanhel, L.; Anderson, M. A. J. Am. Chem. Soc. 1991, 113, 2826. (b) Kamat, P. V.; Patrick, B. J. Phys. Chem. 1992, 96, 6829. (c) Henglein, A.; Giersig, M. J. Phys. Chem. B 1999, 103, 9533. (d) Wilcoxon, J. P.; Provencio, P. P. J. Phys. Chem. B 1999, 103, 9808. (4) (a) Kane, R. S.; Cohen, R. E.; Silbey, R. Chem. Mater. 1996, 8, 1919. (b) Verelst, M.; Ely, T. O.; Amiens, C.; Snoeck, E.; Lecante, P.; Mosset, A.; Respaud, M.; Broto, J. M.; Chaudret, B. Chem. Mater. 1999, 11, 2702.
been explored to fabricate such nanoclusters in the pores of zeolites, such as cation exchange7 followed by in situ post-treatment and by the MOCVD method.8 Copper nanoparticles and microsized fibers have been synthesized by using carbon nanotubes as the template.9 In2O310 and silver11 nanoparticles inside irregular mesoporous materials have also been prepared through incipient wetness impregnation of In2(SO4)3 and AgNO3, followed by thermal treatment. Since the discovery of the novel mesoporous molecular sieves M41S in 1992,12 much effort has been dedicated (5) (a) Colvin, V. L.; Goldstein, A. N.; Alivisatos, A. P. J. Am. Chem. Soc. 1992, 114, 5221. (b) Rizza, R.; Fitzmaurice, D.; Hearne, S.; Hughes, G.; Spoto, G.; Ciliberto, E.; Kerp, H.; Schropp, R. Chem. Mater. 1997, 9, 2969. (c) Hu, K.; Brust, M.; Bard, A. Chem. Mater. 1998, 10, 1160. (d) Sarathy, K. V.; Thomas, P. J.; Kulkarni, G. U.; Rao, C. N. R. J. Phys. Chem. B 1999, 103, 399. (6) (a) Wang, Y.; Herron, N. J. Phys. Chem. 1987, 91, 257. (b) Herron, N.; Wang, Y.; Eddy, E. E.; Stucky, G. D.; Cox, G. D.; Moller, K.; Bein, T. J. Am. Chem. Soc. 1989, 111, 530. (c) Moller, K.; Eddy, M. M.; Stucky, G. D.; Herron, N.; Bein, T. J. Am. Chem. Soc. 1989, 111, 2561. (7) (a) Uchida, H.; Ogata, T.; Yoneyama, H. Chem. Phys. Lett. 1990, 173, 103. (b) Liu, X.; Iu, K.-K.; Thomas, J. K. Chem. Phys. Lett. 1992, 195, 163. (8) (a) MacDougall, J. E.; Eckert, H.; Stucky, G. D.; Herron, N.; Wang, Y.; Moller, K.; Bein, T.; Cox, D. J. Am. Chem. Soc. 1989, 111, 8007. (b) Steele, M. R.; MacDonald, P. M.; Ozin, G. A.; J. Am. Chem. Soc. 1993, 115, 7285. (c) Ozin, G. A.; Steele, M. R. Adv. Mater. 1994, 6, 300. (9) Chen, P.; Wu, X.; Lin, J.; Tan, K. L. J. Phys. Chem. B 1999, 103, 4559. (10) Zhou, H.; Cai, W.; Zhang, L. Mater. Res. Bull. 1999, 34, 845. (11) Cai, W.; Tan, M.; Wang, G.; Zhang, L. Appl. Phys. Lett. 1996, 69, 2980.
10.1021/cm000621r CCC: $20.00 © 2001 American Chemical Society Published on Web 01/20/2001
Nanosized ZnS Confined in Ordered Mesoporous Silica
to exploiting their formation mechanism,13 surface modification,14 and inclusion chemistry.15,16 MCM-41 is a very attractive member in the M41S series due to its one-dimensional and hexagonal arrays of mesopores that can be adjusted within the range of 1.5-30 nm. The MCM-41 materials loaded with nanoclusters within their channels have received considerable attention in the past several years, and many nanoclusters have been encapsulated into their channels, such as Ge,17 Fe2O3,18 GaAs,19 InP,20 ruthenium carbonyls,21 Ru-Ag bimetallic nanoparticles,22 and GaN.23 Very recently, we also succeeded in the synthesis of nanosized ZnO24 in the channels MCM-41 materials by means of a surface modification scheme. The size of the ZnO clusters was found to be
