The Characteristics of ZnO/SnO₂ Sensing Materials by Ultrasonic and Hydrothermal Treatments to Volatile Organic Compounds

pISSN 1225-5475/eISSN 2093-7563

 Ωƒ ◊ ˆ≠≥Æ˝° «—

ZnO/SnO

˙Ûμ

VOC

ØÿŒ1 ^• μ¬Δ1 ^• ظ‚2 ^• „ıˆ1,+

The Characteristics of ZnO/SnO₂Sensing Materials by

Ultrasonic and Hydrothermal Treatments to Volatile Organic Compounds

Joon-Boo Yu¹, Seung-Hoon Do¹, Hyung-Gi Byun², and Jeung-Soo Huh^1,+

Abstract

The important factors in sensors are sensitivity, selectivity, and response time. Oxide semiconductors are high sensitivity, fast response and the advantage of miniaturization. Zn-doped SnO₂materials have been synthesized in order to improve the selectivity of the sensor.

ZnO/ SnO₂crystals were prepared by a simple hydrothermal process and ultrasound pretreated hydrothermal process. ZnO/ SnO₂urchins were fabricated in the precursor solution with [Zn²⁺]:[Sn⁴⁺] ratio of 1:5 and rod structures were fabricated ratio of 1:1 and 1:3. Surface area ratio was increased by increasing the ratio of [Sn⁴⁺]. The sensitivity of sensors were highest at the [Zn²⁺]:[Sn⁴⁺] ratio of 1:5 in ethanol, acetaldehyde, toluene, and nitric oxide .

Keywords : ZnO-SnO₂, Hydrothermal, Ultrasonic, VOC

1. ≠ –

›μºƒ °∫æ≠¬ ºÛÕ›μº •È° °∫° ¢Àflª ß œÓ™¬ ¸‚¸μμ« Ø≠¶ ÃÎœÁ, ÎŒ– ̬°≠ »§—

›” Í≠∞à ¿ßø» ¨∏«Ó ‘Ÿ. ›μºƒ °∫æ≠° ¨∏

° ˝fl«Ó ÷¬ Ãج ˆ”μ° ¸£Ì ʶ˚ÃÁ, ^{˚Á— ∑}

°¶¶ ÁÎœÈ Ø§°∫° Η ±√∫ª Ùœ ˆ ÷¬ ° ßÆ ÃŸ[1-5].

°∫æ≠Œ πà ÃÎ«Ì ÷¬ Á·¬SnO₂^{¶ Ò‘œ©} ZnO, TiO₂, In₂O₃, WO₃Óà ¨∏«Ó ¿Ì ÷Ÿ. ^ؘZnO^ÕSnO₂^¬

ŸÁ— Ø∂∫ ◊ °¨∫ °∫ˆ° πà ÁÎ«Ì ÷Ÿ[6, 7]. ^°

∫æ≠« ˆ…¬ª ‚Û√∞¬ Ê˝∏Œ °∫Õ« ¢ÀÈ˚ª ı

°√∞‚ ßÿ ˆ∞˙« ©‚¶ ™Î ©‚Œ ŸÃ¬ Õ˙ ø√°

™ÎŒÂ, ^™ÎÕÃÓ, ^™Î∏, ™Îμ Ó« ∏∂° ˚Û ˆμ‚

ª Ì¡œ© ’∫Ê˝° Η ŸÁ— ¨∏° ¯‡«Ì ÷Ÿ[8-11].

ˆ∞˙« ’∫ª ß— Ê˝∏Œ ߸˝, ^π-^{÷ ’∫˝}, ^ˆ≠≥Æ

˝ Ó« £‹— ’∫ Ê˝Ã ˚Ϋ˙∏Á, ’∫∞˙°  Ωƒ¶ ÷

‚˚∏Œ ¯fiœ©  Ωƒ¶ fi∫ ∞˙« π“Œß∏ ° ˆ¶ fi Δ ˙¬ Û¬°≠ ≠— ≠–›¿ª œ∏∞¬  Ωƒ ≥Æ Ê˝Ã ÷ Ÿ[12-14].

ª ÌÆ°≠¬ ˆ≠≥Æ« ›¿∫ª ı°√— ’∫ ∞˙« ™Î

≠ ◊ ∏∂ ≥±∏Œ °∫μ¶ ‚Û√∞Ì⁄ œ¥Ÿ. ZnO/SnO₂

° Η ’∫∏Œ ˆ≠≥Æ˝˙  Ωƒ ¸≥Æ ƒ ˆ≠≥Æ˝ª Á Îœ¥∏Á, ˆ∞˙« °∫° ›¿∫ ÷fl∫ Ø‚≠’∞(volatile organic compounds)^{Œ °∫√}, ^ÁÁ£, ^{ΔºÆ À•˜ÂÕ}NO^°

Η ÀˆØ∫ª ¨∏œ¥Ÿ.

2. «Ë Ê˝

2.1 ^{ˆ∞˙« ’∫}

ˆ∞˙ŒZn/SnO₂« ’∫∫ ˆ≠≥Æ˝(HDP)^{˙  Ωƒ ¸≥}

1ʜΖ≥ ›”≈“Á¯–˙(Dept. of Materials Science and Metallurgical Engineering)

80 Daehakro, Bukgu, Daegu 702-701, Korea

2≠¯Î–≥ ¸⁄§∏Î≈¯–Œ(Department of Electronic, Information & Communication Engineering)

Joongangro, Samcheok, Kangwon, 245-711, Korea

+Corresponding author : [email protected]

(Received : Oct. 12, 2012, Revised : Nov. 9, 2012, Accepted : Nov. 19, 2012)

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/licenses/by- nc/3.0)which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Æ ƒ ˆ≠≥Æ˝(UHDP)^{Œ ¯‡œ¥Ÿ}. ÃÈ ’∫ª ß— ∞˙∫

Tin chloride(SnCl₄^§5H₂O, 98%, Aldrich, USA)^ÕZinc acetate dehydrate ((C₂H₃O₂)₂Zn^§2H₂O, 99.999%, Aldrich, USA)^ÃÁ,

ˆÍ≠™Æ˝(NaOH)^{˙ °∫√}(40 ml)/^ªÃ¬ˆ(40 ml)^°Tin chloride^ÕZinc acetate dehydrate^¶1:1 Ò≤Œ ∑°œ© fl Ï

©Zn^˙Snà Îÿ» Î◊ª ∏È˙Ÿ. à Î◊∫ ˆ≠≥ƶ ßÿ

180^…°≠15√£ ø» ˆ≠≥ƶ œ¥Ÿ. «— ∞∫ Î◊∫  Ω ƒ –‚‚¶ ÁÎœ©20 KHz, 500 W ^{« ∂«°≠}1 h ^{ø» ¸≥}

Æ ƒ°180^…°≠15√£ ø» ˆ≠≥Æ œ¥Ÿ. ^{ˆ≠≥Æ ƒ “¯}

∞ ◊ ™Æ˝ ì, ∞“ ì Óª ¶≈œ‚ ßœ© ¯…–Æ‚Œ º¥œ© ÚÓ¯ ߸∞∫90^…°≠10√£ ø» «∂œ© ˆ–ª

¶≈— ⁄ Ȉ« –ªª Ú˙Ÿ. ^{–ª∫ ∑°«¬}[Zn²⁺]:[Sn⁴⁺]^«

Ù ‘ÆÒ¶ ¶Óœ¥∏Á, ^{◊ Ò≤∫}1:1, 1:3, 1:5, 1:7^{Œ œ¥Ÿ}. 2.2 æ≠« ¶¤ ◊ ¯§

æ≠ ¶¤ª ßÿ «Æ‹ ˛Ã¤¶MEMS^{¯§≥Æœ©} Fig. 2

Õ ∞à ‚«ª ∏È˙∏Á, æ≠ ø¤ª ß— ˜ÕÕ ˆ∞˙ª ß— ¸ÿ∏Œ ∏∫«Ó ÷Ÿ. ^{‚«« ©‚¬}1.8 mm ^ø1.8 mm

ÃÁ, ˆ∞˙« ı¯ Œ–∫ fl”°0.9 mm ^ø0.9 mm^{Œ ∏∫}

«Ó ÷Ÿ.

ˆ∞˙∫ ·-◊«Óª ÁÎœ© ΩØÆŒ ∏ÈÓ ¸ÿ ß° √

¡100^…°≠1√£ ø» «∂— ƒ°600^…°≠1^{√£ ø» “∫}

œ¥Ÿ. æ≠« ¿‰∫ Δ° ƒ(1)^{ª ÁÎœ¥Ÿ}.

3. ·˙ ◊ Ì˚

3.1 ^{ˆ∞˙« –Æ}

ˆ≠≥Æ˝∏Œ ’∫—ZnO/SnO₂^«FE-SEM^ÃȬ Fig. 3

˙ ∞à ™∏μŸ. [Zn²⁺]:[Sn⁴⁺]^{« Ò≤Ã}1:1^°≠flake^{« Á∏}

Œ ™∏™Ì, 1:3°≠¬ ŒÂÕ ÀªÃ ¸¬° ™∏μŸ. Zn^{∫ Œ}

ÂŒ ’∫«˙ÌSn∫ ∏¸∏Œ ™∏™Ì ÷∏Á, Sn^{« Áà ı°}

‘° ˚Û ∏¸° ŒÂ° ŸÓ ÷¬nano-urchin ^{∏∂Œ ™∏μ}

Ÿ. ^«—[Zn²⁺]:[Sn⁴⁺]« Ò≤° ˚• Ò•È˚∫1:1^°≠¬12.715 m²/g^{Œ ™∏μ∏Á}, 1:5^{°≠ °Â ´}21.457^{à «˙Ì}1:7, 1:9^Œ

Ø“ˆœ Ò•È˚∫19.8, 18.17^{Œ “œ¥Ÿ}.

 Ωƒ ¸≥ƃ ˆ≠≥ƶ «‡œ© Ú∫ ZnO/SnO₂^«FE- SEM^{« ÃȬ}Fig. 4^{Õ ∞à ™∏μ∏Á}, ^{ˆ≠≥Æ°≠Õ ∞Ã} Zn^˙Sn^{« Ò≤Ã}1:3^˙1:5^{° ≠ ™ÎŒÂÕ}nano-urchin^∏∂

Œ ™∏μŸ.  Ωƒ ¸≥Æ— ÊÏZn^˙Sn« Ò≤° ˚Û Ò • È˚∫1:3^°≠58.9^ÃÌ1:5^°≠194.2Œ ˆ≠≥Æ∏ ˆ‡— ÊÏ

∏Ÿ ‡10^{Ë° ı°œ¥Ÿ}. Fig. 3^˙Fig. 4°≠ ™∏≠ Õ˙ ∞Ã

SnO₂^°ZnÃ μŒ «Ó≠ ’∫∞« Áà ؜Á, [Zn²⁺]:[Sn⁴⁺]

Ù ‘ÆÒ° ´ 삪 fi¬ Õª À ˆ ÷Ÿ[15]. ^«—,  ^{Ωƒ ≥Æ}

¶ — ƒ° ˆ≠≥Æ Ê˝ª ˚Îœ‘ «È øœ—[Zn²⁺]:[Sn⁴⁺]

Ù ‘ÆÒ°≠ Ò•È˚à ı°œ¬ ∏∂¶ ∏È ˆ ÷Ì ÃÕ∫ ı Fig. . 2. MEMS substrate for sensor.

S (%) = Rair R- Rairgas ^ø100 (1)

Fig. 1. The preparation process of Zn/SnO2.

Fig. 3. FE-SEM image of Zn/SnO2by HDP : The ratio [Zn²⁺]:

[Sn⁴⁺] of (a) 1:1, (b)1:3, (c) 1:5, (d) 1:7.

–∫ Ò•È˚ª °ˆ‘ «Ó ‹Œ°∫Èà ̯“ ˆ ÷¬ ÁÃÆ Èà ı°œ¥Ÿ.

3.2 ^{°∫ Àˆ Ø∫}

ˆ≠≥Æ˝˙  Ωƒ ¸≥ƃ ˆ≠≥Æ˝° ˚Û ’∫» –ª Œ ¶¤— æ≠«VOCs °∫° Η ÀˆØ∫ª ¯§œ¥Ÿ. ^Àˆ

°∫¬ °∫√, ^ÁÁ£, ^{ΔºÆÀ•˜Â}, œÍ≠˙“« °∫Œ ø

¤ ¬μ¬300^{…°≠ ¯§œ¥Ÿ}.

ˆ≠≥Æ˝∏Œ ’∫—Zn/SnO₂Œ ∏Á æ≠« ¿‰∫Fig. 5

° ™∏¬∏Á, °∫√ °∫° Η ›¿ª ¯§— ·˙ß. ^¿‰

Ó±∫[Zn²⁺]:[Sn⁴⁺]« Ò≤° ˚Û ˜Ã° ÷∏Á, 1:7^{°≠ °Â}

Ù∫ μ¶ ™∏ªÌ1:1°≠ °Â ∑∫ μ° ™∏μŸ. ^æ≠«

μ¬ °∫Õ ›¿œ¬ Ò•È˚« 삪 fi¬ Õª À ˆ ÷Ÿ.

Fig. 6°≠ ÁÁ£ °∫° Η ˆ≠≥ÆÕ  Ωƒ ¸≥Æ — æ

≠¶ ø√° ¯§— ·˙ß.  Ωƒ ¸≥ƃ ˆ≠≥Æ » æ≠«

μ° Ù‘ ™∏™Ì ÷∏Á, ÃÕ∫ Ò•È˚à ı°— μ‚∏Œ

«‹»Ÿ. [Zn²⁺]:[Sn⁴⁺]^{« «— Ò≤Ã}1:3 ^∏Ÿ¬1:5^{° ∂› Ù‘}

™∏™Ì ÷Ÿ.

Fig. 7∫ ΔºÆÀ•˜Â °∫0.05 ppm^ŒÕ1 ppm^{Óˆ ¯§}

·˙ß.  Ωƒ ¸≥Æ» æ≠°≠[Zn²⁺]:[Sn⁴⁺]^{« Ù ‘ÆÒ°}

1:5 ¶¤» æ≠∏à ˆØ∫ª ∏¥Ÿ. ^«—Fig. 8^{∫ œÍ≠˙“}

Fig. 4. FE-SEM image of Zn/SnO₂UHDP ; The ratio[Zn²⁺]:

[Sn⁴⁺] of (a) 1:3, (b) 1:5.

Fig. 5. The Response of Zn/SnO₂sensors to ethanol ; (a) hydro- thermal process, (b) Ultrasonic and hydrothermal process.

Fig. 6. The response of Zn/SnO2sensors to toluene.

Fig. 7. The response of Zn/SnO₂sensors to acetaldehyde.

Fig. 8. The response of Zn/SnO₂sensors to NO.

(b) (a)

°∫° Η ¯§ ·˙Œ0.2, 2, 4 ppm^{ª ¯§œ¥∏Á}, ^ΔºÆÀ

•˜ÂÕ ∞à  Ωƒ ¸≥ƃ ˆ≠≥Æ » æ≠ fl°≠

[Zn²⁺]:[Sn⁴⁺]^{« Ù ‘ÆÒ°}1:5 ¶¤» æ≠°≠ ›¿Ã ÷˙Ÿ.

ÃÈ °∫° ›¿— æ≠¬ Ò•È˚Ã190 m²/g ^ÃÛÃ˙Ÿ.

4. ·–

ª ¨∏°≠Zn/SnO₂∞˙ª ’∫œ‚ ßœ© ˆ≠≥Æ˝˙  

Ωƒ ¸≥Æ ƒ ˆ≠≥ƶ «√œ© æ≠¶ ¶¤œ© ¯§œ¥Ÿ.

ˆ∞˙« ∏∂Õ Ò•È˚∫[Zn²⁺]:[Sn⁴⁺]« Ù ‘ÆÒ° ˚Û ŒÂ «¬urchin^{∏∂Œ ™∏μŸ}. Zn/SnO₂^°≠Zn^{™ÎŒÂŒ ∫}

Âœ¬• ÒÿSnO₂¬ ‘⁄ ¸¬Œ ÷∏«ŒSnO₂^{« Áà ˚Óˆ}

È[Zn²⁺]^{∫ ŒÂŒ ¸∫«Á}[Sn⁴⁺]∫ ŒÂ« fl…° ıì Á

«urchin∏∂¶ Æfl‘ «Ó Ò•È˚∫ ı°œ¥Ÿ.  ^{Ωƒ ¸≥}

Ƭ[Zn²⁺], [Sn⁴⁺]« ‘⁄¶ ¤‘ –‚œ© ˆ≠≥Æ “ ß ›¿

à fl œÓØ ˆ ÷˙Ÿ. ˚Û≠  Ωƒ ¸≥Ƭ Ò•È˚∫ Ù ‘ ÆÒ° ˚Û3~9^{Ë ı°œ¥Ÿ}.

ˆ≠≥Æ˝ª Îÿ ’∫»Zn/SnO₂∞˙° Òœ©  Ωƒ ¸≥

ƃ ˆ≠≥Æ˝ª ÁÎœ© ’∫»Zn/SnO₂^{¬ ÁÁ£}, ^°∫√°

∫° Îœ© Ù∫ μ Ø∫ª ∏¥Ÿ. ^œÍ≠˙“, ^{ΔºÆÀ•˜Â}

°∫° Η ˙Ûμ« ¯§œ‚ ß— ˆ∞˙« Ò•È˚« μ‚

ª ÆŒœŸ.

Á« ¤

à ÌÆ∫2009‚μ ʜΖ≥ ¨∏‚ ≥ˆ ¨∏Ò° «œ©

¨∏«˙Ω.

REFERENCES

[1] D. D. Lee, W. Y. Chung, and B. K. Sohn, “High sensitivity and selectivity methane gas sensors doped with Rh as a catalyst”, Sens. Actuators B, Vol. 13, pp.

252-255, 1993.

[2] F. H. Ribeiro, M. Chow, and R. A. D Betta, “Kinetics of the complete oxidation of methane over supported palladium catalysts”, J. of Catal., Vol. 146, p. 533, 1994.

[3] R. Burch, F. J. Urbaro, and P. K. Loader, “Methane combustion over palladium catalysts”, Appl. Catal.

A, Vol. 123, pp. 173-184, 1995

[4] G. Korotcenkov, “Metal oxides for solid-state gas

sensors: what determines our choice?”, Mater. Sci Eng. B, Vol. 139, pp. 1-23, 2007.

[5] N. Yamazoe, “Toward innovation of gas sensor technology”, Sens. Actuators B, Vol. 108, pp. 2-14, 2005.

[6] N. Yamazoe, “New approaches for improving semi- condutor gas sensors”, Sens. Actuators B, Vol. 5, pp.

7-19, 1991.

[7] D. D. Lee, “Chemical sensors technology”, J. Sensor Sci. & Tech., Vol. 18, No. 1, pp. 1-21, 2009.

[8] E. Oh and H. Choi, “High performance NO₂gas sensor based on ZnO nanorod grown by ultra sonic irradiation”, Sens. Actuators B, Vol. 141, pp. 239- 243, 2009.

[9] M.W. Ahn, K.S. Park, J.H. Heo, J.G. Park, D.W.

Kim, K. J. Choi, J.H. Lee, and S.H. Hong, “Gas properties of defect-controlled ZnO-nanowire gas sensor”, J. Appl. Phys. Lett., Vol. 93, p. 263103, 2008.

[10] S. L. Zhang, B. H. Cho, J. B. Yu, J. O. Lim, H. G.

Byun, and J. S. Huh, “Preparation, characterization and sensing properties of ZnO nanotubes”, Sens.

Lett., Vol. 9, pp. 374-378, 2011.

[11] S. L. Zhang, B. H. Cho, J. B. Yu, J. O. Lim, H. G.

Byun, D.D. Lee, and J. S. Huh, “Volatile organic compounds gas sensing properties of ZnO nanorings”, Sens. Lett., Vol. 9, pp. 845–849, 2011.

[12] P. M. Aneesh, K. A. Vanaja, and M. K. Jayaraj,

“Synthsis of ZnO nanoparticle's by hydrothermal method”, Proc. of SPIE, Vol. 6639, 66390J, Cali- fonia, USA, 2007.

[13] S. H. Jung, E. Oh, K. H. Lee, W. Park, and S. H.

Jeong, “A sonochemical method for fabricating aligned ZnO nanorods”, Adv. Mater. Vol. 19, pp.

749-753, 2007.

[14] K. H. Kim, J. G. Kim, and K. C. Park, “The CO sensing properties of thick film gas sensor using Co₃O₄powders prepared by hydrothermal reaction method”, J. Sensor Sci. & Tech., Vol. 19, No. 5, pp.

385-390, 2010.

[15] X. Ding, D. Zeng, and C. Xie, “Controlled growth of SnO2 nanorods clusters via Zndoping and its influence on gas-sensing properties”, Sens.

Actuators B, Vol. 149, pp. 336-344, 2010.

Ø ÿ Œ(Joon Boo Yu)

U1992‚ ¸øΖ≥ ¸⁄¯–˙(^¯–Á)

U1996‚ ¸øΖ≥ ¸⁄¯–˙(^¯–Æ

Á)

U2010‚ ʜΖ≥ ›”≈“Á¯–˙(^¯

–⁄Á)

U÷¸…–fl: æ≠ Á· ◊ æ≠√∫¤,

≠–æ≠« «·–fl ¿Î

μ ¬ Δ(Seoung-Hun Do)

U2009‚ ʜΖ≥ ›”≈“Á¯–˙

(^¯–Á)

U2011‚ ʜΖ≥ ™Î˙–‚˙˙(^¯–

ÆÁ)

U÷¸…–fl: ^{æ≠ Á·}

Ø ¸ ‚(Hyung Gi Byun)

U1994^{‚ «º∫ÕΖ≥}(^¯–⁄Á)

U1996 ~ ˆÁ ≠¯Î–≥ ¸⁄§∏Î≈¯

–Œ ≥ˆ

U÷¸…–fl: E-nose, ^–œŒƒ

„ ı ˆ(Jeung-Soo Huh)

U1994^‚MIT (^¯–⁄Á)

U1995 ~ ˆÁ ʜΖ≥ ›”≈“Á¯–

˙ ≥ˆ

U÷¸…–fl: E-Nose, Chemical/Bio sensor