for integrated nanoelectronics. To demonstrate this concept, exploited to demonstrate a new approach to multiplexed we have explored multiplexed protein detection using mono- detection of cancer marker proteins with a single nanowire clonal antibody(mAb) functionalized SiNW FETs( Figure The synthesis of structurally and electronically uniform 4a). In previous studies, we have demonstrated multiplexed ultralong SiNWs may open up new opportunities for detection using mAb functionalized devices, but in this case, integrated nanoelectronics and could serve as unique building ch device was from an individual SiNW thus necessitating blocks linking integrated structures from the nanometer well-defined assembly to achieve the FET array Demonstra- through millimeter length scales tion of multiplexed measurements from independently ad- dressable FETs defined on a single ultralong sinw has not Acknowledgment. We thank J. Xiang for helpful discus- been previously achieved using either nanowires or carbon sion. W.L. P acknowledges support from the Korea Research nanotubes. However, this approach could have substantial Foundation Grant funded by the Korean Government(MOE impact on the biosensor area 0a. 3 because it(i) simpl HRD. Basic Research Promotion Fund: KRF-2007-331 DO0194) C. M.L. acknowledges support of this work through the greater device homogeneity for FETs defined on a single a contract from National Institutes of Health, MITRE ultralong SiNW,(ii)opens up the opportunity to assess nsing reproducibility in device arrays where device-to- Supporting Information Available: Two-dimensional device variability should not be the dominating factor Fourier transforms and source-drain current versus gate Conductance versus time data recorded from three distinct voltage curves. This material is available free of charge via FetSdefinedonthesingleultralongSinw,whichwastheInternetathttp://pubs.acs.org functionalized uniformly with the mAb for prostate specific antigen(PSA), showed several key features. First, the devices References exhibited well-defined and reversible conductance increases (1)Morales, A: Lieber, C. M. associated with the binding and unbinding of the specific 2)(a) Lieber, C. M. Wang, Z. L. MRS Bull. 2007. 32. 99.(b) Xia,Y Yang, P. Sun, Y: u. Y: Mayers. B: Gates, B. Yin, Y. Kim. F target PSA. Second, the conductance change was proportional Yan, H. Adu. Mater. 2003. 15. 353. (c) Thelander, C. Agarwal, P to the PSa concentration, as expected for equilibrium bindin Brongersma, S: Eymery, J. Feiner, L. F; Forchel, A Scheffler, M. Riess. W: Ohlsson. B. J: Gosele U: Samuelson, L. Mater. Today response. Third, the concentration-dependent conductance 2006.9,28 change recorded in the distinct FEt elements which were ()Schmidt, V: Gosele, U. Science 2007, 316. 698. separated by >100 um, was similar and testifies to the u,Y; Cui, Y: Huynh, L. Barrelet. C J. Bell, D. C. Lieber, C.M. Nano Lett. 2004. 4. 433 electronic uniformity of the ultralong SiNWs and the uniform (5)Schmidt, V: Senz, S: Gosele, U. Nano Lett. 2005. 5. 931 mAb functionalization Fourth we note that addition bovine(6)(a) Cui, Y ; Zhong, Z. H. Wang, D. L: Wang, w. U. Lieber, C M serum albumin at 1000 times higher concentration showed H: Lieber, C. M. Nature 2006, 441, 489.(c)Ng, H. T: Han,J. no response, demonstrating good selectivity. lAst Yamada, T. Nguyen, P. Chen, Y. P: Meyyappan, M. Nano Lett. reproducible conductance change from each of the addres- 2004. 4. 1247.(d) Park, w.l.: Kim J.S.: Yi, G.-C: Lee, H. J. Adu. sable devices is consistent with the homogeneous device Mater.2005,17,1393 (7)Lu. W: Lieber, C. M. Nat. Mater. 2007, 6, 841 characteristics demonstrated in Figure 3. While the present )(a)Duan, X. Huang, Y: Cui, Y. Wang. J. Lieber, C. M. Natu measurements represent a relatively simple demonstration 2001, 409, 66.(b)Zhong. Z; Qian. F; Wang, D: Lieber. C. M. Nano of multiplex protein detection, they do demonstrate a new Lett. 2003, 3. 343.(c) Huang. Y; Duan. X. Lieber, C. M. Small 2005 1, 142.(d) Qian, F. Li, Y. Gradeeak, S: Barrelet, C. J. Wang. D approach for multiplexing that could be extended in the future Lieber, C. M. Nano Lett. 2004. 4. 1975 to include parallel, real-time measurements from a larger (9)Duan, X. Huang. Y: AgarwaL, R. Lieber, C M Nature 2003, 42/ number of devices functionalized with diverse mAb recep- (10)(a)Cui, Y. Wei, Q: Park, H. Lieber, C M. Science 2001, 293, 1289. (b)Hahm, J; Lieber, C. M. Nano Lett. 2004. 4, 51(c)Shim, M In we have demonstrated the nanocluster- Kam, N. w.S.: Chen. R.J.: Li, Y M. Dai. H.J. Nano Lett. 2002. 2 catalyzed growth of millimeter-long and highly uniform (11) Huang. Y: Duan, X Cui. Y: Lauhon, L J. Kim, K: Lieber, C.M. ngle-crystalline SiNWs with lence2001,294,1313 proximately 100 000. The average Sinw growth rates using (12)Friedman, R. S: McAlpine, M. C; Ricketts, D. S: Ham, D; Lieber C.M. Nature2005,434,1085 Si2H6 reactant were 30-130 times faster than previous rates (13) Zheng, G. Patolsky, F;Cui,Y:Wang. W.U.Lieber, CM.Nat observed using SiHa reactant under similar growth conditions. Biotechnol. 2005. 23. 1294 TEM studies showed that the ultralong SiNWs grow (14)(a)Shi, w.S.; Peng. H. Y. Zheng, Y. F; Wang, N; Shang, N. G Pan, Z. W: Lee, C.S.: Lee, S. T. Adu. Mater. 2000, 12, 1343.(b) preferentially along the(110)direction, independent of Shi. Y: Hu, Q; Araki, H. Suzuki, H: Gao. H: Yang, W: Noda, T. diameter, and suggest that kinetic effects may be used as a Appl. Phys. A: Mater. Sci. Process. 2005, 80, 1733 means for controlling growth directions in NWs produced (15)Kodambaka, S: Tersoff, J Reuter. M. C. Ross, F. M. Phys. ReD. Le.2006.96.09610 by the nanocluster-catalyzed VLs process. In addition, (16) Schmidt, V; Senz, S. Gosele, U. Phys. Reu. B 2007,, 045335 ultralong sinws were used as building blocks to fabricate (17) Patolsky, F; Zheng, G: Lieber, C. M. Nat. Protocols 2006, 1, 1711 one-dimensional FET arrays that exhibit high-degree of (18)Nebol'sin, V. A: Shchetinin, A. A Dolgachev, A. A: Komneeva V Inorg. Mater. 2005, 41, 125 device uniformity over millimeter dimensions and testify to (19) Givargizov, E I J. Cryst. Growth 1975,, 20 the electrical/doping homogeneity of SiNWs produced by Bootsma. G. A; Gassen, H. J.J. Cryst. Growth 1971, 10, 223 (21)Wu, Y: Yang, P J. A. Chem. Soc. 2001. 123, 3165 nanocluster-catalyzed VLS growth. Lastly, the uniform (22)Cui, Y: Lauhon, L.J.; Gudiksen, M.S.: Wang.J: Lieber, C.M.Appl. device properties of nal FET arrays were Phys.Let2001,78,2214 Nano Lett., Vol. 8. No. 9, 2008for integrated nanoelectronics. To demonstrate this concept, we have explored multiplexed protein detection using mono￾clonal antibody (mAb) functionalized SiNW FETs (Figure 4a). In previous studies,13 we have demonstrated multiplexed detection using mAb functionalized devices, but in this case, each device was from an individual SiNW thus necessitating well-defined assembly to achieve the FET array. Demonstra￾tion of multiplexed measurements from independently ad￾dressable FETs defined on a single ultralong SiNW has not been previously achieved using either nanowires or carbon nanotubes. However, this approach could have substantial impact on the biosensor area10a,13 because it (i) simplifies fabrication of multiplexed sensor device arrays and, given the greater device homogeneity for FETs defined on a single ultralong SiNW, (ii) opens up the opportunity to assess sensing reproducibility in device arrays where device-to￾device variability should not be the dominating factor. Conductance versus time data recorded from three distinct FETs defined on the single ultralong SiNW, which was functionalized uniformly with the mAb for prostate specific antigen (PSA), showed several key features. First, the devices exhibited well-defined and reversible conductance increases associated with the binding and unbinding of the specific target PSA. Second, the conductance change was proportional to the PSA concentration, as expected for equilibrium binding response. Third, the concentration-dependent conductance change recorded in the distinct FET elements, which were separated by >100 µm, was similar and testifies to the electronic uniformity of the ultralong SiNWs and the uniform mAb functionalization. Fourth, we note that addition bovine serum albumin at 1000 times higher concentration showed no response, demonstrating good selectivity.13 Last, the reproducible conductance change from each of the addres￾sable devices is consistent with the homogeneous device characteristics demonstrated in Figure 3. While the present measurements represent a relatively simple demonstration of multiplex protein detection, they do demonstrate a new approach for multiplexing that could be extended in the future to include parallel, real-time measurements from a larger number of devices functionalized with diverse mAb recep￾tors. In summary, we have demonstrated the nanocluster￾catalyzed growth of millimeter-long and highly uniform single-crystalline SiNWs with aspect ratios up to ap￾proximately 100 000. The average SiNW growth rates using Si2H6 reactant were 30-130 times faster than previous rates observed using SiH4 reactant under similar growth conditions. TEM studies showed that the ultralong SiNWs grow preferentially along the 〈110〉 direction, independent of diameter, and suggest that kinetic effects may be used as a means for controlling growth directions in NWs produced by the nanocluster-catalyzed VLS process. In addition, ultralong SiNWs were used as building blocks to fabricate one-dimensional FET arrays that exhibit high-degree of device uniformity over millimeter dimensions and testify to the electrical/doping homogeneity of SiNWs produced by nanocluster-catalyzed VLS growth. Lastly, the uniform device properties of one-dimensional FET arrays were exploited to demonstrate a new approach to multiplexed detection of cancer marker proteins with a single nanowire. The synthesis of structurally and electronically uniform ultralong SiNWs may open up new opportunities for integrated nanoelectronics and could serve as unique building blocks linking integrated structures from the nanometer through millimeter length scales. Acknowledgment. We thank J. Xiang for helpful discus￾sion. W.I.P acknowledges support from the Korea Research Foundation Grant funded by the Korean Government (MOE￾HRD, Basic Research Promotion Fund; KRF-2007-331- D00194). C.M.L. acknowledges support of this work through a contract from National Institutes of Health, MITRE Corporation, and Samsung Electronics. Supporting Information Available: Two-dimensional Fourier transforms and source-drain current versus gate voltage curves. This material is available free of charge via the Internet at http://pubs.acs.org. References (1) Morales, A.; Lieber, C. M. Science 1998, 279, 208. (2) (a) Lieber, C. M.; Wang, Z. L. MRS Bull. 2007, 32, 99. (b) Xia, Y.; Yang, P.; Sun, Y.; Wu, Y.; Mayers, B.; Gates, B.; Yin, Y.; Kim, F.; Yan, H. AdV. Mater. 2003, 15, 353. (c) Thelander, C.; Agarwal, P.; Brongersma, S.; Eymery, J.; Feiner, L. F.; Forchel, A.; Scheffler, M.; Riess, W.; Ohlsson, B. J.; Gosele, U.; Samuelson, L. Mater. Today 2006, 9, 28. (3) Schmidt, V.; Go¨sele, U. Science 2007, 316, 698. (4) Wu, Y.; Cui, Y.; Huynh, L.; Barrelet, C. J.; Bell, D. C.; Lieber, C. M. Nano Lett. 2004, 4, 433. (5) Schmidt, V.; Senz, S.; Go¨sele, U. Nano Lett. 2005, 5, 931. (6) (a) Cui, Y.; Zhong, Z. H.; Wang, D. L.; Wang, W. U.; Lieber, C. M. Nano Lett. 2003, 3, 149. (b) Xiang, J.; Lu, W.; Hu, Y.; Wu, Y.; Yan, H.; Lieber, C. M. Nature 2006, 441, 489. (c) Ng, H. T.; Han, J.; Yamada, T.; Nguyen, P.; Chen, Y. P.; Meyyappan, M. Nano Lett. 2004, 4, 1247. (d) Park, W. I.; Kim, J. S.; Yi, G.-C.; Lee, H. J. AdV. Mater. 2005, 17, 1393. (7) Lu, W.; Lieber, C. M. Nat. Mater. 2007, 6, 841. (8) (a) Duan, X.; Huang, Y.; Cui, Y.; Wang, J.; Lieber, C. M. Nature 2001, 409, 66. (b) Zhong, Z.; Qian, F.; Wang, D.; Lieber, C. M. Nano Lett. 2003, 3, 343. (c) Huang, Y.; Duan, X.; Lieber, C. M. Small 2005, 1, 142. (d) Qian, F.; Li, Y.; Gradee`ak, S.; Barrelet, C. J.; Wang, D.; Lieber, C. M. Nano Lett. 2004, 4, 1975. (9) Duan, X.; Huang, Y.; Agarwal, R.; Lieber, C. M. Nature 2003, 421, 241. (10) (a) Cui, Y.; Wei, Q.; Park, H.; Lieber, C. M. Science 2001, 293, 1289. (b) Hahm, J.; Lieber, C. M. Nano Lett. 2004, 4, 51. (c) Shim, M.; Kam, N. W. S.; Chen, R. J.; Li, Y. M.; Dai, H. J. Nano Lett. 2002, 2, 285. (11) Huang, Y.; Duan, X.; Cui, Y.; Lauhon, L. J.; Kim, K.; Lieber, C. M. Science 2001, 294, 1313. (12) Friedman, R. S.; McAlpine, M. C.; Ricketts, D. S.; Ham, D.; Lieber, C. M. Nature 2005, 434, 1085. (13) Zheng, G.; Patolsky, F.; Cui, Y.; Wang, W. U.; Lieber, C. M. Nat. Biotechnol. 2005, 23, 1294. (14) (a) Shi, W. S.; Peng, H. Y.; Zheng, Y. F.; Wang, N.; Shang, N. G.; Pan, Z. W.; Lee, C. S.; Lee, S. T. AdV. Mater. 2000, 12, 1343. (b) Shi, Y.; Hu, Q.; Araki, H.; Suzuki, H.; Gao, H.; Yang, W.; Noda, T. Appl. Phys. A: Mater. Sci. Process. 2005, 80, 1733. (15) Kodambaka, S.; Tersoff, J.; Reuter, M. C.; Ross, F. M. Phys. ReV. Lett. 2006, 96, 096105. (16) Schmidt, V.; Senz, S.; Go¨sele, U. Phys. ReV. B 2007, 75, 045335. (17) Patolsky, F.; Zheng, G.; Lieber, C. M. Nat. Protocols 2006, 1, 1711. (18) Nebol’sin, V. A.; Shchetinin, A. A.; Dolgachev, A. A.; Korneeva, V. V. Inorg. Mater. 2005, 41, 1256. (19) Givargizov, E. I. J. Cryst. Growth 1975, 31, 20. (20) Bootsma, G. A.; Gassen, H. J. J. Cryst. Growth 1971, 10, 223. (21) Wu, Y.; Yang, P. J. Am. Chem. Soc. 2001, 123, 3165. (22) Cui, Y.; Lauhon, L. J.; Gudiksen, M. S.; Wang, J.; Lieber, C. M. Appl. Phys. Lett. 2001, 78, 2214. 3008 Nano Lett., Vol. 8, No. 9, 2008