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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 17, Iss. 8 — Apr. 13, 2009
  • pp: 6239–6244
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Significantly enhanced superbroadband near infrared emission in bismuth/aluminum doped high-silica zeolite derived nanoparticles

Hong-Tao Sun, Takashi Hasegawa, Minoru Fujii, Fumiaki Shimaoka, Zhenhua Bai, Minoru Mizuhata, Shinji Hayashi, and Shigehito Deki  »View Author Affiliations


Optics Express, Vol. 17, Issue 8, pp. 6239-6244 (2009)
http://dx.doi.org/10.1364/OE.17.006239


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Abstract

Significantly enhanced superbroadband near infrared emission has been realized in bismuth/aluminum doped high-silica zeolite derived nanoparticles. The emission intensity can be easily tailored by the introduction of aluminum. The luminescence lifetime can reach up to 695 μs. The results reveal that the existence of charge imbalance environment caused by [A104/2]- units in host materials is requisite to the formation of infrared-active Bi+. The finding presents a feasible route to design high-efficient bismuth activated infrared luminescent nanoparticles. These bismuth doped nanoparticles may find applications as superbroadband near infrared nano optical sources.

© 2009 Optical Society of America

1. Introduction

Zeolites, as smart crystalline materials mainly consisting of [SiO4] and [AlO4] structure units, possess pore structures and these enable them to act as hosts for molecules and ions or as templates for nanostructures synthesis [8

8. P. Li, X. H. Sun, N. B. Wong, C. S. Lee, S. T. Lee, and B. Teo, “Ultrafine and uniform silicon nanowires grown with zeolites,” Chem. Phys. Lett . 365, 22–26 (2002). [CrossRef]

]. Recently, their potential as host materials for rare-earth ions has been evaluated [9

9. M. Ryo, Y. Wada, T. Okubo, T. Nakazawa, Y. Hasegawa, and S. Yanagida, “Spectroscopic study on strongly luminescent Nd(III) exchanged zeolite: TMA+-containing FAU type zeolite as a suitable host for ship-in-bottle synthesis,” J. Mater. Chem . 12, 1748–1753 (2002). [CrossRef]

]. However, the efficiency of the emitters is very small in the NIR region due to the fast relaxation of the excitation energy through nonradiative vibrational deactivation. Moreover, the obtained samples were not air-stable, which were usually kept in vacuum to avoid the adsorption of coordinated water [9

9. M. Ryo, Y. Wada, T. Okubo, T. Nakazawa, Y. Hasegawa, and S. Yanagida, “Spectroscopic study on strongly luminescent Nd(III) exchanged zeolite: TMA+-containing FAU type zeolite as a suitable host for ship-in-bottle synthesis,” J. Mater. Chem . 12, 1748–1753 (2002). [CrossRef]

]. Thus, it is an interesting topic to find a strategy to increase the NIR PL efficiency in active ions doped zeolites.

Very recently, we realized above two purposes by using bismuth doped crystalline nanozeolites [10

10. H. Sun, Y Miwa, F. Shimaoka, M. Fujii, A. Hosokawa, M. Mizuhata, S. Hayashi, and S. Deki, “Superbroadband near infrared nano optical source based on bismuth doped high-silica nanocrystalline zeolites,” Opt. Lett , in press. [PubMed]

]. The emission band covered the range of 930~1620 nm, with a maximum peak at 1146.3 nm, a full width at the half maximum (FWHM) of 152 nm and a lifetime of over 300 μs under the excitation of a 488 nm laser line. In this paper, we studied the effect of aluminum doping on the NIR emission of bismuth doped zeolite derived nanoparticles. NIR emission has been enhanced significantly by the introduction of aluminum in these nanoparticles. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), steady-state and time-resolved PL measurements. Based on these results, the origin and enhancement mechanism of PL were discussed in detail.

2. Experimental

The H form of FAU-type zeolites were purchased from Tosoh Co. Japan (Zeolite Y, grain size: 200 ~ 400 nm). Zeolites was stirred in a 0.01 M aqueous solution of Bi3+ prepared from Bi(NO3)3·5H2O at 80 °C for 72 h to exchange H ions with Bi3+ ions. The products were removed by centrifugation, and dried in air. The Bi3+ embedded zeolites were further stirred in 0.01M Bi3+ and xM Al3+ (x=0.015, 0.025, 0.035) mixed solution at 80 °C for 24 h to dope Al3+ ions. The products were collected by centrifugation, then washed with deionized water, and dried in air at 120 °C. The Bi3+ and Bi3+/Al3+ doped zeolites were calcined at 1150 °C for 20 min in N2 atmospheric condition. All samples were exposed to the laboratory atmosphere prior to measurements. The prepared products were first characterized by X-ray diffractometer (Rigaku-TTR/S2, λ=0.154056 nm). The morphologies of the prepared products were characterized using a FE-SEM (JEOL, JSM-6335F) operating at an accelerating voltage of 15 kV. Bismuth and aluminum concentrations were measured by X-ray fluorescence (XRF) and energy-dispersive X-ray spectroscopy (EDS). The atomic ratios of Bi and Al to (Si+Al+Bi) were summarized in Table 1. Note that the Al content in sample 1 is from zeolites. Luminescence measurements were carried out at room temperature with the excitation of a 488 nm line of an Ar+ laser. The signal was analyzed by a single grating monochromator and detected by a liquid-nitrogen-cooled InGaAs detector. For all the spectra, the spectral response of the detection system was corrected by the reference spectrum of a standard tungsten lamp. Time-resolved luminescence measurements were performed by detecting the modulated luminescence signal with a photomultiplier tube (Hamamatsu, R5509-72), and then analyzing the signal with a photon-counting multichannel scaler. The excitation source for the lifetime measurements was the 488 nm light from an optical parametric oscillator pumped by the third harmonic of a Nd:YAG laser.

Table 1. Determined Bi and Al Ratios of the Samples

table-icon
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3. Results and discussion

Figure 1 shows X-ray diffraction (XRD) patterns of Bi3+ and Bi3+/Al3+ doped zeolites annealed at 1150 °C. The crystalline structure of Bi3+ singly doped sample keeps intact after thermal treatment. However, the amorphization takes place for Bi3+/Al3+ doped samples, although some weak diffraction peaks of zeolite phase can be observed. This indicates that the introduced bismuth and aluminum content existing in zeolite pores strongly affect the eutectic temperature of the samples.

Fig. 1. XRD spectra of Bi3+ and Bi3+/Al3+ doped samples. The peaks denoted by the asterisks are ascribed to the reflections of zeolite phase.

Figure 2(a) displays a typical FE-SEM image of sample 3. The morphology and monodispersity of the annealed zeolites remain almost unchanged. The chemical composition of the above sample was analyzed by EDS as shown in Fig. 2(b), indicating that the particle is composed of Si, Al, O, and Bi. In combination with the corresponding XRD result, it is clear that the product is silica-alumina amorphous nanoparticles.

Fig. 2. (a) FE-SEM image of sample 3. (b) EDS of the above sample.

Figure 3 shows the NIR PL spectra of the samples. All samples show strong NIR emission from 930 to 1620 nm. It is noteworthy that the Bi3+/Al3+ doped samples show much stronger emission than Bi3+ singly doped one; sample 3 displays the strongest emission, which is about eight times stronger than that of sample 1. In Ref. 10

10. H. Sun, Y Miwa, F. Shimaoka, M. Fujii, A. Hosokawa, M. Mizuhata, S. Hayashi, and S. Deki, “Superbroadband near infrared nano optical source based on bismuth doped high-silica nanocrystalline zeolites,” Opt. Lett , in press. [PubMed]

, we proposed that subvalent Bi (Bi+) ions is the NIR PL origin in doped zeolites: Bi+ ions act as charge compensators of [AlO4/2]- units. Thus, the existence of charge imbalance environment in host materials is requisite to the formation of infrared-active Bi+. It was revealed that the homogeneous binary SiO2-Al2O3 glasses with 0.4 to up to 12.0 wt % Al2O3 contain a mixture of 4-, 5-, and 6-fold coordinated Al sites (AlIV, AlV, and AlVI) [11

11. S. Sen and R. E. Youngman, “High-Resolution Multinuclear NMR Structural Study of Binary Aluminosilicate and Other Related Glasses,” J. Phys. Chem. B 108, 7557–7564 (2004). [CrossRef]

]. The relative proportions of these sites are strongly dependent on composition with AlIV being most dominant in glasses with <1wt % Al2O3. It was hypothesized that the tetrahedral [AlO4/2]- units in glasses with <1 wt % Al2O3 are predominantly charge balanced by the formation of oxygen triclusters, and addition of either low field strength alkali ions such as K+ or high field strength rare earth ions such as La3+ to these glasses results in charge balance and stabilization of AlIV sites [11

11. S. Sen and R. E. Youngman, “High-Resolution Multinuclear NMR Structural Study of Binary Aluminosilicate and Other Related Glasses,” J. Phys. Chem. B 108, 7557–7564 (2004). [CrossRef]

]. Therefore, it is reasonable to assume that more [AlO4/2]- units will be formed after annealing when Al content was introduced into the matrix of zeolites, and more Bi+ ions act as charge compensators of [AlO4/2]- units. Owing to the extended nature of 6p orbitals of Bi+, the crystal field plays an important role in the luminescent properties. Thus, the host composition can affect the NIR emission as revealed before [2

2. X. Meng, J. Qiu, M. Peng, D. Chen, Q. Zhao, X. Jiang, and C. Zhu, “Infrared broadband emission of bismuth-doped barium-aluminum-borate glasses,” Opt. Express 13, 1635–1642 (2005), http://www.opticsinfobase.org/abstract.cfm?URI=oe-13-5-1635. [CrossRef] [PubMed]

, 6

6. Q. Qian, Q. Y. Zhang, G. F. Yang, Z. M. Yang, and Z. H. Jiang, “Enhanced broadband near-infrared emission from Bi-doped glasses by codoping with metal oxides,” J. Appl. Phys . 104, 043518-1-3 (2008). [CrossRef]

]. For example, Meng et al. reported the peak position of the broadband infrared emission shifts from 1252 nm to 1300 nm with increasing BaO concentration from 20 mol% to 40 mol% in barium-aluminum-borate glasses. Interestingly, the shape of all spectra shown in Fig. 3 is nearly identical, indicating that Bi+ ions has similar local environments in zeolites and their derived amorphous nanoparticles.

Fig. 3. PL spectra of the samples under the excitation of a 488 nm laser line. All samples were measured under the same condition.

As is known, in the low-excitation regime the luminescence intensity I is proportional to σΦNτ/τrad, where σ is the excitation cross section, Φ the photon flux, N the content of optically active centres, τ the lifetime, and τrad the radiative lifetime. Assuming that τrad and σ of Bi+ ions are same in these samples, the ratios of active Bi+ ions in these samples can be estimated based on the following equation:

NiN1=Ii×τ1I1×τi
(1)

where i is the sample no., Ni the number of Bi+ ions in sample i,I the integrated PL intensity, and τi the measured 1/e lifetime. The calculated result is shown in Fig. 5. The number of Bi+ ions in sample 3 is over twenty times more than that in sample 1. As shown in Table 1, the Al concentration monotonously increases from sample 1 to 4, while Bi concentration decreases. These results reveal that the increase of aluminum content is favorable to the formation of Bi active centres owing to the existence of more [AlO4/2]- units. The number decrease of Bi+ ions in sample 4 arises from the decreased bismuth concentration. These results clearly indicate that some bismuth in the samples is not infrared active, and the creation of a charge imbalance environment in the matrix is requisite to activate bismuth. The above result presents a feasible route to design high-efficient bismuth activated infrared luminescent nanoparticles.

Fig. 4. Fluorescence decay curves of the samples. The detected wavelength is 1146 nm.
Fig. 5. The calculated ratios of active Bi+ ions in these samples.

4. Conclusion

In summary, enhanced superbroadband near infrared emission has been realized in bismuth/aluminum doped high-silica zeolite derived nanoparticles. The emission covers the range of 930 ~ 1620 nm, with a lifetime of as long as 695 μs under the excitation of a 488 nm laser line. The results further reveal that the NIR emission should be from subvalent bismuth infrared active centre, i.e., Bi+, instead of others. The existence of a charge imbalance environment caused by [AlO4/2]- units in host materials is requisite to the formation of infrared-active Bi+, which is the main reason for the enhanced emission in Bi3+/Al3+ doped high-silica zeolite derived nanoparticles. The finding may pave the way for the applications of these NIR luminescent nanoparticles as superbroadband near infrared nano optical sources.

Acknowledgments

This work is supported by the Japan Society of Promotion of Science (JSPS), and the Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (Grant No. 19007322), Japan. H.S thanks the support from JSPS in the form of a fellowship.

References and links

1.

Y. Fujimoto and M. Nakatsuka, “Optical amplification in bismuth-doped silica glass,” Appl. Phys. Lett . 82, 3325–3326 (2003). [CrossRef]

2.

X. Meng, J. Qiu, M. Peng, D. Chen, Q. Zhao, X. Jiang, and C. Zhu, “Infrared broadband emission of bismuth-doped barium-aluminum-borate glasses,” Opt. Express 13, 1635–1642 (2005), http://www.opticsinfobase.org/abstract.cfm?URI=oe-13-5-1635. [CrossRef] [PubMed]

3.

V. V. Dvoyrin, V. M. Mashinsky, L. I. Bulatov, I. A. Bufetov, A. V. Shubin, M. A. Melkumov, E. F. Kustov, E. M. Dianov, A. A. Umnikov, V. F. Khopin, M. V. Yashkov, and A. N. Guryanov, “Bismuth-doped-glass optical fibers-a new active medium for lasers and amplifiers,” Opt. Lett . 31, 2966–2968 (2006). [CrossRef] [PubMed]

4.

Y. Arai, T. Suzuki, Y. Ohishi, S. Morimoto, and S. Khonthon, “Ultrabroadband near-infrared emission from a colorless bismuth-doped glass,” Appl. Phys. Lett . 90, 261110-1-3 (2007). [CrossRef]

5.

V. O. Sokolov, V. G. Plotnichenko, and E. M. Dianov, “Origin of broadband near-infrared luminescence in bismuth-doped glasses,” Opt. Lett . 33, 1488–1490 (2008). [CrossRef] [PubMed]

6.

Q. Qian, Q. Y. Zhang, G. F. Yang, Z. M. Yang, and Z. H. Jiang, “Enhanced broadband near-infrared emission from Bi-doped glasses by codoping with metal oxides,” J. Appl. Phys . 104, 043518-1-3 (2008). [CrossRef]

7.

Okhrimchuk, L. Butvina, E. Dianov, N. Lichkova, V. Zagorodnev, and K. Boldyrev, “Near-infrared luminescence of RbPb2Cl5 : Bi crystals,” Opt. Lett . 33, 2182–2184 (2008). [CrossRef] [PubMed]

8.

P. Li, X. H. Sun, N. B. Wong, C. S. Lee, S. T. Lee, and B. Teo, “Ultrafine and uniform silicon nanowires grown with zeolites,” Chem. Phys. Lett . 365, 22–26 (2002). [CrossRef]

9.

M. Ryo, Y. Wada, T. Okubo, T. Nakazawa, Y. Hasegawa, and S. Yanagida, “Spectroscopic study on strongly luminescent Nd(III) exchanged zeolite: TMA+-containing FAU type zeolite as a suitable host for ship-in-bottle synthesis,” J. Mater. Chem . 12, 1748–1753 (2002). [CrossRef]

10.

H. Sun, Y Miwa, F. Shimaoka, M. Fujii, A. Hosokawa, M. Mizuhata, S. Hayashi, and S. Deki, “Superbroadband near infrared nano optical source based on bismuth doped high-silica nanocrystalline zeolites,” Opt. Lett , in press. [PubMed]

11.

S. Sen and R. E. Youngman, “High-Resolution Multinuclear NMR Structural Study of Binary Aluminosilicate and Other Related Glasses,” J. Phys. Chem. B 108, 7557–7564 (2004). [CrossRef]

OCIS Codes
(160.0160) Materials : Materials
(300.0300) Spectroscopy : Spectroscopy
(300.2140) Spectroscopy : Emission

ToC Category:
Materials

History
Original Manuscript: February 27, 2009
Revised Manuscript: March 25, 2009
Manuscript Accepted: March 26, 2009
Published: April 1, 2009

Citation
Hong-Tao Sun, Takashi Hasegawa, Minoru Fujii, Fumiaki Shimaoka, Zhenhua Bai, Minoru Mizuhata, Shinji Hayashi, and Shigehito Deki, "Significantly enhanced superbroadband near infrared emission in bismuth/aluminum doped high-silica zeolite derived nanoparticles," Opt. Express 17, 6239-6244 (2009)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-8-6239


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References

  1. Y. Fujimoto and M. Nakatsuka, "Optical amplification in bismuth-doped silica glass," Appl. Phys. Lett. 82, 3325-3326 (2003). [CrossRef]
  2. X. Meng, J. Qiu, M. Peng, D. Chen, Q. Zhao, X. Jiang, and C. Zhu, "Infrared broadband emission of bismuth-doped barium-aluminum-borate glasses," Opt. Express 13, 1635-1642 (2005), http://www.opticsinfobase.org/abstract.cfm?URI=oe-13-5-1635. [CrossRef] [PubMed]
  3. V. V. Dvoyrin, V. M. Mashinsky, L. I. Bulatov, I. A. Bufetov, A. V. Shubin, M. A. Melkumov, E. F. Kustov, E. M. Dianov, A. A. Umnikov, V. F. Khopin, M. V. Yashkov, and A. N. Guryanov, "Bismuth-doped-glass optical fibers-a new active medium for lasers and amplifiers," Opt. Lett. 31, 2966-2968 (2006). [CrossRef] [PubMed]
  4. Y. Arai, T. Suzuki, Y. Ohishi, S. Morimoto, and S. Khonthon, "Ultrabroadband near-infrared emission from a colorless bismuth-doped glass," Appl. Phys. Lett. 90, 261110-1-3 (2007). [CrossRef]
  5. V. O. Sokolov, V. G. Plotnichenko, and E. M. Dianov, "Origin of broadband near-infrared luminescence in bismuth-doped glasses," Opt. Lett. 33, 1488-1490 (2008). [CrossRef] [PubMed]
  6. Q. Qian, Q. Y. Zhang, G. F. Yang, Z. M. Yang, and Z. H. Jiang, "Enhanced broadband near-infrared emission from Bi-doped glasses by codoping with metal oxides," J. Appl. Phys. 104, 043518-1-3 (2008). [CrossRef]
  7. Okhrimchuk, L. Butvina, E. Dianov, N. Lichkova, V. Zagorodnev, and K. Boldyrev, "Near-infrared luminescence of RbPb2Cl5 : Bi crystals," Opt. Lett. 33, 2182-2184 (2008). [CrossRef] [PubMed]
  8. P. Li, X. H. Sun, N. B. Wong, C. S. Lee, S. T. Lee, and B. Teo, "Ultrafine and uniform silicon nanowires grown with zeolites," Chem. Phys. Lett. 365, 22-26 (2002). [CrossRef]
  9. M. Ryo, Y. Wada, T. Okubo, T. Nakazawa, Y. Hasegawa, and S. Yanagida, "Spectroscopic study on strongly luminescent Nd(III) exchanged zeolite: TMA+-containing FAU type zeolite as a suitable host for ship-in-bottle synthesis," J. Mater. Chem. 12, 1748-1753 (2002). [CrossRef]
  10. H. Sun, Y. Miwa, F. Shimaoka, M. Fujii, A. Hosokawa, M. Mizuhata, S. Hayashi, and S. Deki, "Superbroadband near infrared nano optical source based on bismuth doped high-silica nanocrystalline zeolites," Opt. Lett.in press. [PubMed]
  11. S. Sen and R. E. Youngman, "High-Resolution Multinuclear NMR Structural Study of Binary Aluminosilicate and Other Related Glasses," J. Phys. Chem. B 108, 7557-7564 (2004). [CrossRef]

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