letters to nature excitation source(Fig 3c), which shows that a longer primar 14. Peng, x. wickham, 1.& Alivisatos, A P. Kinetics of ll-VI and 11l-V colloidal sen excitation wavelength produces larger particles with in-plane dipole nanocrystal growth "focusing"of size distributions. L Am. Chem. Soc. 120,5343-5344(1998) nanorods. Langmuir 15, 701-709(1999)- with respect to the excitation wavelength( Fig. 3b) 6.Sun, Y G.& Xia, Y N. Shape-controlled synthesis of gold and silver nanoparticles. Science 298. Another feature of using wavelength to control particle size is that 2176-2179(2002) subsequent addition of Ag spherical particles (4.8+ 1.I nm)to the 18. Maillard. M. Giorgio, S& Pileni, M-P Tunin (sce a prism colloid does not lead to enlargement of the nanoprisms synthesis and optical properties. L Phys. Chem. 8 107, 26-2/0/4)a s with similar aspect ratios. Supplementary Information); instead, the particles added 19. Pastoriza-Santos, L. Liz-Marzan, L M Synthesis of silver nanoprisms in DME Nano lett. 2,903-90 photochemically grow into nanoprisms similar in size to the present(202) ones(as determined by the excitation wavelength). This is in 20. Chen, S H- Fan. z X. Carrol D, L Salver nanodiskssynthesis, characterization,and self-assembly ontrast to thermal methods for controlling particle sizes, in 21. Hao, E C. Kelly, K.L. Hupp, IT.& Schat, G C Synthesis of silver nanodisks using polystyrene result of photothermal(or optical burning) effects; such effects 3. ia l t b enp which addition of precursors typically leads to larger particles. mesosphere as templates. L Am. Chem. Soc. 124, 15182-15183(2002) Note that the wavelength control of particle size is not likely to be a 2. Sun. ). have been invoked in other studies involving intense pulse laser (00/ -L Photoinduced conversion of silver nanospheres to nanoprismsScience,1901-1903 irradiation of metal nanostructures(for example, 10W)29.. The 24. Kelly, K.L. Coronado, E, Zhao, L L& Schatz, G C. The optical properties of metal nanoparticles: the light source used to effect nanoprism conversion is very weak(beam influence of size, shape, and dielectric environment. J. Phys. Chen. B 107, 668-677(2003). power≤0.2W). Indeed, according to the equation△T=△H/C and Raman intensities for small particles with arbitrary shapes. J. Chem. Phys. 103, 869-875(1995). (where AH is the absorbed photon energy, and Cp is the heat 26. Draine, B. T. Flatau, P. Discrete-dipole approximation for scattering calculations. L Opt. Sa.Am. capacity of silver,0.235JK-g ) single 550-nm photon absorp- 27. Tang. ZKotow, N.A.& Giersig, M Spontaneous organization of single care nanoparticles into temperature(=0.007 K)(see Supplementary Information). The 28. Penn, RL& Banfield,lE cumulative experimentally determined temperature increase after nanocrystals. Science 281,969-971(1998) 50 h of photolysis(50±20nm) was less than10°C. 29.Link,S, Burda, C, Mohamed, M. B, Nikoobakh, B. El-Sayed. M. A Laser photothermal melting Surface plasmons are typically studied as physical properties of 1165-1170 (19 and fragmentation of gold nanorods: energy and laser pulse-width dependence. L Plrys Chem B 103. metal nanostructures rather than chemical tools that provide 30. KamaL, P. V Photophysical, photochemical and photocatalytic aspects of metal nanoparticles.I.Phys. control over growth and ultimate particle dimensions. The results reported here provide clear evidence for the importance of plasmon excitationintheAgnanoprismgrowthprocessbothfortype1Supplementaryintormationaccompaniesthepaperonwww.naturecom/na colloidal particles to a size that depends on the dipole plasmon Facility at Northwesten t of a Cary 500 spectrometer in the Keck Biophys Northwestern University. CAM and G. CS. thank the AFOSR, ONR, DARPA and NSF dipole plasmon excitation, but is inhibited by quadrupole plasmon Fellowship in Colloid and Surface Chemisty upport of the American Chemical Society Cognis wavelength) and for type 2 particles(whose growth also requires for support of this work RL is grateful for thes xcitation). Although a detailed mechanism for these types of conversions remains to be determined, it is possible that plasmon Competing interests statement The authors declare that they have no competing financial excitation does two things. First, it could redistribute charge on the urfaces of the type I nanoprisms to either facilitate(in the case of Correspondence and requests for materials should be addressed to CAM dipole excitation) or inhibit(in the case of quadrupole excitation) (camirkinechem.northwestern.edu)or G.C.S. (schatz@chem. northwestern. edu) could facilitate ligand dissociation at the particle edges(as ths.? particle-particle fusion. In addition, surface plasmon excitati where the local fields are the most intense ), allowing the type 1 particles to grow through the addition of silver atoms or clusters. Taken together, these results are consistent with a new type of……………………………………… particle size control that is initiated and driven by light, highly Enantiospecific electrodeposition cooperative, and surface-plasmon directed. Received 28 March; accepted 28 August 2003; doi: 10.1038/nature02020 of a chiral catalyst 1. Mirkin, C A, Letsinger, R. L. Mucic, R. C.& Stothoff, L J A DNA-based method for rationally Jay A Switzer, Hiten M. Kothari, Philippe Poizot, Shuji Nakanishi 2. Bruchez, M, Moronne, M, Gin, P, Weiss, S& Alivisatos, A. P Semiconductor nanocrystals as Eric W. Boha fluorescent biological labels. Sciemce 281 of biomolecules. Nature BiotechnoL. 19, 631-635 University of Missouri-Rolla, Rolla, Missouri 65409-1170 USAc 4. Nicewarmer-Pefia, S R et al Submicrometer metallic barcodes. Science 294, 137-141(2001)- Many biomolecules are chiral-they can exist he of two 6. Schmid,G. Large clusters and colloids, Metals in the embryonicstate Chem. Rev. 92, 1709-1727(1992) enantiomeric forms that only differ in that their structures are 7. Wang. LE. Gudiksen, M.S.Duan, XF, Cui,Y& Lieber, C M Highly polarized photoluminescence mirror images of each other. Because only one enantiomer tends and photodetection from single indium phosphide nanowires Scieme 293, 1455-1457(2001 ) to be physiologically active while the other is inactive or even 8. Sun, S. Murray, C. B, Weller, D Folks, L& Moser, A. Monodisperse FePt nanoparticles and ferromagnetic FePt nanocrystal superlattices. Science 287, 1989-1992(2000) toxic, drug compounds are increasingly produced in an enantio- 9. Nirmal, M ct al. Fluorescence intermittency in single cadmium selenide nanocrystals Natere 383, merically pure form using solution-phase homogeneous cata- lysts and enzymes. Chiral surfaces offer the possibility of at can spectrum, controlled growth, and Langmuir15,6738-674(1999) optical developing heterogeneous enantioselective catalysts tha Il Brust. M.& Kiel, C L Some recent advances in more readily be separated from the products and reused. In addition, such surfaces might electrochemical 12. Korgel, B A& Fitzmaurice, D Self-assembly of silver nanocrystals into two-dimensional nanowire chiral molecules. To date, chiral surfaces have been obtained by arrays.Adw. Mater. 10, 661-665(1998). 13. Talapin, D. V et al. Dymamic distribution of growth rates within the ensembles of colloidal ll-Vland adsorbing chiral molecules2-or slicing single crystals so that III-V semiconductor nanocrystals as a factor goverming their hey exhibit high-index faces2-, and some of these surfaces act as Cerm Soc.1245782-5790(2002) enantioselective heterogeneous catalysts.,o. Here we show that e 2003 Nature Publishing Group AtuReiVol4252OctoBer2003www.nature.com/natureexcitation source (Fig. 3c), which shows that a longer primary excitation wavelength produces larger particles with in-plane dipole plasmons (the red-most peak in each spectrum) that are red-shifted with respect to the excitation wavelength (Fig. 3b). Another feature of using wavelength to control particle size is that subsequent addition of Ag spherical particles (4.8 ^ 1.1 nm) to the nanoprism colloid does not lead to enlargement of the nanoprisms (see Supplementary Information); instead, the particles added photochemically grow into nanoprisms similar in size to the present ones (as determined by the excitation wavelength). This is in contrast to thermal methods for controlling particle sizes, in which addition of precursors typically leads to larger particles14. Note that the wavelength control of particle size is not likely to be a result of photothermal (or optical ‘burning’) effects; such effects have been invoked in other studies involving intense pulse laser irradiation of metal nanostructures (for example, 106W)29,30. The light source used to effect nanoprism conversion is very weak (beam power #0.2 W). Indeed, according to the equation DT ¼ DH/Cp (where DH is the absorbed photon energy, and Cp is the heat capacity of silver, 0.235 J K21 g21 ), single 550-nm photon absorp￾tion by a type 1 prism can only lead to a negligible increase in temperature (#0.007 K) (see Supplementary Information). The cumulative experimentally determined temperature increase after 50 h of photolysis (550 ^ 20 nm) was less than 10 8C. Surface plasmons are typically studied as physical properties of metal nanostructures rather than chemical tools that provide control over growth and ultimate particle dimensions. The results reported here provide clear evidence for the importance of plasmon excitation in the Ag nanoprism growth process, both for type 1 particles (which apparently grow from the initially produced colloidal particles to a size that depends on the dipole plasmon wavelength) and for type 2 particles (whose growth also requires dipole plasmon excitation, but is inhibited by quadrupole plasmon excitation). Although a detailed mechanism for these types of conversions remains to be determined, it is possible that plasmon excitation does two things. First, it could redistribute charge on the surfaces of the type 1 nanoprisms to either facilitate (in the case of dipole excitation) or inhibit (in the case of quadrupole excitation) particle–particle fusion. In addition, surface plasmon excitation could facilitate ligand dissociation at the particle edges (as this is where the local fields are the most intense24), allowing the type 1 particles to grow through the addition of silver atoms or clusters. Taken together, these results are consistent with a new type of particle size control that is initiated and driven by light, highly cooperative, and surface-plasmon directed. A Received 28 March; accepted 28 August 2003; doi:10.1038/nature02020. 1. Mirkin, C. A., Letsinger, R. L., Mucic, R. C. & Storhoff, J. J. A DNA-based method for rationally assembling nanoparticles into macroscopic materials. Nature 382, 607–609 (1996). 2. Bruchez, M., Moronne, M., Gin, P., Weiss, S. & Alivisatos, A. P. Semiconductor nanocrystals as fluorescent biological labels. Science 281, 2013–2016 (1998). 3. Han, M., Gao, X., Su, J. Z. & Nie, S. Quantum-dot-tagged microbeads for multiplexed optical coding of biomolecules. Nature Biotechnol. 19, 631–635 (2001). 4. Nicewarner-Pen˜a, S. R. et al. Submicrometer metallic barcodes. Science 294, 137–141 (2001). 5. Cao, Y. C., Jin, R. & Mirkin, C. A. Nanoparticles with Raman spectroscopic fingerprints for DNA and RNA detection. Science 297, 1536–1540 (2002). 6. Schmid, G. Large clusters and colloids. Metals in the embryonic state. Chem. Rev. 92, 1709–1727 (1992). 7. Wang, J. F., Gudiksen, M. S., Duan, X. F., Cui, Y. & Lieber, C. M. Highly polarized photoluminescence and photodetection from single indium phosphide nanowires. Science 293, 1455–1457 (2001). 8. Sun, S., Murray, C. B., Weller, D., Folks, L. & Moser, A. Monodisperse FePt nanoparticles and ferromagnetic FePt nanocrystal superlattices. Science 287, 1989–1992 (2000). 9. Nirmal, M. et al. Fluorescence intermittency in single cadmium selenide nanocrystals. Nature 383, 802–804 (1996). 10. Henglein, A. Radiolytic preparation of ultrafine colloidal gold particles in aqueous solution: optical spectrum, controlled growth, and some chemical reactions. Langmuir 15, 6738–6744 (1999). 11. Brust, M. & Kiely, C. J. Some recent advances in nanostructure preparation from gold and silver particles: a short topical review. Colloid Surf. A 202, 175–186 (2002). 12. Korgel, B. A. & Fitzmaurice, D. Self-assembly of silver nanocrystals into two-dimensional nanowire arrays. Adv. Mater. 10, 661–665 (1998). 13. Talapin, D. V. et al. Dynamic distribution of growth rates within the ensembles of colloidal II–VI and III–V semiconductor nanocrystals as a factor governing their photoluminescence efficiency. J. Am. Chem. Soc. 124, 5782–5790 (2002). 14. Peng, X., Wickham, J. & Alivisatos, A. P. Kinetics of II–VI and III–V colloidal semiconductor nanocrystal growth: “focusing” of size distributions. J. Am. Chem. Soc. 120, 5343–5344 (1998). 15. Chang, S. S., Shih, C. W., Chen, C. D., Lai, W. C. & Wang, C. R. C. The shape transition of gold nanorods. Langmuir 15, 701–709 (1999). 16. Sun, Y. G. & Xia, Y. N. Shape-controlled synthesis of gold and silver nanoparticles. Science 298, 2176–2179 (2002). 17. Maillard, M., Giorgio, S. & Pileni, M. P. Silver nanodisks. Adv. Mater. 14, 1084–1086 (2002). 18. Maillard, M., Giorgio, S. & Pileni, M.-P. Tuning the size of silver nanodisks with similar aspect ratios: synthesis and optical properties. J. Phys. Chem. B 107, 2466–2470 (2003). 19. Pastoriza-Santos, I. & Liz-Marzan, L. M. Synthesis of silver nanoprisms in DMF. Nano Lett. 2, 903–905 (2002). 20. Chen, S. H., Fan, Z. Y. & Carroll, D. L. Silver nanodisks: synthesis, characterization, and self-assembly. J. Phys. Chem. B 106, 10777–10781 (2002). 21. Hao, E. C., Kelly, K. L., Hupp, J. T. & Schatz, G. C. Synthesis of silver nanodisks using polystyrene mesospheres as templates. J. Am. Chem. Soc. 124, 15182–15183 (2002). 22. Sun, Y. & Xia, Y. Triangular nanoplates of silver: synthesis, characterization, and use as sacrificial templates for generating triangular nanorings of gold. Adv. Mater. 15, 695–699 (2003). 23. Jin, R. et al. Photoinduced conversion of silver nanospheres to nanoprisms. Science 294, 1901–1903 (2001). 24. Kelly, K. L., Coronado, E., Zhao, L. L. & Schatz, G. C. The optical properties of metal nanoparticles: the influence of size, shape, and dielectric environment. J. Phys. Chem. B 107, 668–677 (2003). 25. Yang, W. H., Schatz, G. C. & Van Duyne, R. P. Discrete dipole approximation for calculating extinction and Raman intensities for small particles with arbitrary shapes. J. Chem. Phys. 103, 869–875 (1995). 26. Draine, B. T. & Flatau, P. J. Discrete-dipole approximation for scattering calculations. J. Opt. Soc. Am. A 11, 1491–1499 (1994). 27. Tang, Z., Kotov, N. A. & Giersig, M. Spontaneous organization of single CdTe nanoparticles into luminescent nanowires. Science 297, 237–240 (2002). 28. Penn, R. L. & Banfield, J. F. Imperfect oriented attachment: dislocation generation in defect-free nanocrystals. Science 281, 969–971 (1998). 29. Link, S., Burda, C., Mohamed, M. B., Nikoobakht, B. & El-Sayed, M. A. Laser photothermal melting and fragmentation of gold nanorods: energy and laser pulse-width dependence. J. Phys. Chem. B 103, 1165–1170 (1999). 30. Kamat, P. V. Photophysical, photochemical and photocatalytic aspects of metal nanoparticles. J. Phys. Chem. B 106, 7729–7744 (2002). Supplementary Information accompanies the paper on www.nature.com/nature. Acknowledgements We acknowledge the use of a Cary 500 spectrometer in the Keck Biophysics Facility at Northwestern University. C.A.M and G.C.S. thank the AFOSR, ONR, DARPA and NSF for support of this work. R.J. is grateful for the support of the American Chemical Society Cognis Fellowship in Colloid and Surface Chemistry. Competing interests statement The authors declare that they have no competing financial interests. Correspondence and requests for materials should be addressed to C.A.M. (camirkin@chem.northwestern.edu) or G.C.S. (schatz@chem.northwestern.edu). .............................................................. Enantiospecific electrodeposition of a chiral catalyst Jay A. Switzer, Hiten M. Kothari, Philippe Poizot, Shuji Nakanishi & Eric W. Bohannan Department of Chemistry and Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, Missouri 65409-1170, USA ............................................................................................................................................................................. Many biomolecules are chiral—they can exist in one of two enantiomeric forms that only differ in that their structures are mirror images of each other. Because only one enantiomer tends to be physiologically active while the other is inactive or even toxic, drug compounds are increasingly produced in an enantio￾merically pure form1 using solution-phase homogeneous cata￾lysts and enzymes. Chiral surfaces offer the possibility of developing heterogeneous enantioselective catalysts that can more readily be separated from the products and reused. In addition, such surfaces might serve as electrochemical sensors for chiral molecules. To date, chiral surfaces have been obtained by adsorbing chiral molecules2–6 or slicing single crystals so that they exhibit high-index faces7–13, and some of these surfaces act as enantioselective heterogeneous catalysts5,6,10. Here we show that letters to nature 490 © 2003 Nature PublishingGroup NATURE | VOL 425 | 2 OCTOBER 2003 | www.nature.com/nature