Nanoparticles offer a larger surface to volume ratio, a higher concentration of undercoordinated surface sites and, due to strong interplay between elastic, geometric and electronic parameters, as well as effects of interaction with support, often improved or unique physical and chemical properties compared to the corresponding bulk material

Untitled.png

Electron microscopy of Cu2O nanocrystals. (a) a monolayer on the TEM grid surface (b) a superlattice, in which the nanoparticles have self-assembled into a close packed structure (c) HRTEM lattice imaging showing single crystal and lattice spacings (d) selected area electron diffraction pattern.

We have produced nanoparticles of a range of metals (e.g. Ag, FePt), semiconductors (e.g. CdSe, CdTe), and metal oxides (e.g. Cu2O, MnO, Fe2O3, TiO2, ZnO, BaTiO3) with highly uniform size distributions. For several material systems, we developed methods that offer tight control over the nanoparticle morphology, crystal structure and stoichiometry. Also oxide nanoparticles (copper oxide shown below ) offer catalytic abilities, which depend on nanoparticle size and differ from the bulk material. Over several years of research we refined methods for the synthesis of semiconductor and transition metal oxides from chemically reactive molecular precursors in which they combine – sometimes in the presence of ligands - to form the desired nanocrystalline product via pyrolysis, decomposition or metal-oxygen framework condensation. Careful consideration of the concentrations, stoichiometry and nature of the addition is required to obtain nanocrystal nucleation that leads to the formation of a narrow size distribution. The size of the nanocrystals (2 - 40 nm) can be controlled by the temperature, time allowed for growth and the subsequent addition of reactants. The nanoparticles are sometimes stabilized in solution by an organic passivating agent, typically long chain alkyl surfactants, including oleic acid or phosphines (semiconductors and metal oxides) and alkyl thiols (metals). Ongoing exploration of novel passivating agents or processes that rely on no stabilizing ligands can yields new products with a broad range of chemical and physical properties. Once fabricated, the particles can be collected by extraction with appropriate organic solvents. For general characterization of the nanoparticles, a large number of techniques are utilized, including absorption spectroscopy, NMR, electron microscopy (SEM, TEM, high and low resolution in both cases), X-ray powder diffraction, scanning probe microscopy, elemental analysis and XPS. With the possibilities in nanoparticle synthesis increasing tremendously with regards to size control, reproducibility and structural complexity, it becomes more and more urgent to define particular directions for the field to follow. To reach this end, our immediate objective is to establish the ground rules that will take us to rational approaches for chemical synthesis of nanomaterials.

Related references

1.     Chen, Z. and O’Brien, S. “Structure Direction of II-IV Semiconductor Quantum Dot Superlattices by Tuning Radius ratio”, ACS Nano, 2008, 2(6), 1219-1229.

2.     Hultman, K. L.; Raffo, A. J.; Grzenda, A. L.; Harris, P. E.; Brown, T. R.; and O’Brien, S “Immunotargeted Superparamagnetic Iron Oxide Nanoparticles” ACS Nano, 2008, 2(3), 477–484.

3.     Lu, C.; Chen, Z. and O’Brien, S. “Optimized Conditions for the Self-Organization of CdSe-Au Binary Nanoparticle Superlattices” Chemistry of Materials, 2008, 20(11), 3594-3600.

4.     Wu, C.-K.; Hultman, K. L.; O'Brien, S.; Koberstein, J. T. “Functional Oligomers for the Control and Fixation of Spatial Organization in Nanoparticle Assemblies.” Journal of the American Chemical Society, 2008, 130(11), 3516-3520.

5.     Zohar, S.; Hultman, K.; O'Brien, S.; Bailey, W. E., “Thin-film superparamagnetic resonance in a gamma-Fe(2)O(3) nanoparticle array” Journal of Applied Physics, 2008, 103.

6.     Chen, Z.; Moore, J.; Radtke, G.; Sirringhaus, H and O’Brien, S “Binary Nanoparticle Superlattices in the Semiconductor-Semiconductor System: CdTe and CdSe” Journal of the American Chemical Society 2007, 129(50); 15702-15709.

7.     Yin, M.; Chen, Z.; Deegan, B.; O'Brien, S. "Wustite Nanocrystals: Synthesis, Structure and Superlattice Formation" Journal of Materials Research 2007, 22(7), 1987-1995.

8.     Willis, A. L.; Chen, Z.; He, J.; Zhu, Y.; Turro, N. J.; O’Brien, S. "Metal acetylacetonates as general precursors for the synthesis of early transition metal oxide nanomaterials" Journal of Nanomaterials, 2007, doi:10.1155/2007/14858.

9.   Zhang, L.; Zhang, J.; Huang, L.; O’Brien, S.; Yu, Z.“ Imaging and Raman Spectroscopy of Individual Single-Wall Carbon Nanotubes on a Large Substrate” Journal of Physical Chemistry C 2007, 111(30);11240-11245.

10.   Funk, S.; Burghaus, U.; White, B.; O'Brien, S.; Turro, N. J. “Adsorption Dynamics of Alkanes on Single-Wall Carbon Nanotubes: A Molecular Beam Scattering Study”, Journal of Physical Chemistry C., 2007, 111(22), 8043-8049.

11.   White, B.; Banerjee, S.; O'Brien, S.; Turro, N. J.; Herman, I. P. "Zeta Potential Measurements of Surfactant-Wrapped Individual Single-Walled Carbon Nanotubes" 2007, 111(37); 13684-13690.

12.   Morales, M. A.; Skomski, R.; Fritz, S.; Shelburne, G.; Shiled, J. E.; Yin, M.; O'Brien, S.; Leslie-Pelecky, D. L. "Surface Anisotropy and Magnetic Freezing of MnO Nanoparticles" Physical Review B 2007, 75, 134423.

13.   Gong, Y.; Andelman, T,; G. F. Neumark, G. F.; O'Brien, S.; Kuskovsky, I. L. “Origin of defect-related green emission from ZnO nanoparticles: effect of surface modification,”  Nanoscale Res. Lett. 2007, 2, 297-302.

14.   Andelman, T.; Gong, Y.; Neumark, G.; O’Brien, S. "Diameter Control and Photoluminescence of ZnO Nanorods from Trialkylamines" Journal of Nanomaterials,  2007, doi:10.1155/2007/73824.

15.   White, B.; Yin, M.; Hall, A.; Le, D.; Stolbov, S.; Rahman, T.; Turro, N.; O'Brien, S. "Complete CO Oxidation over Cu2O Nanoparticles Supported on Silica Gel" Nano Letters 2006, 6, 2095-2098.

16.   Shevchenko, E. V.; Talapin, D. V.; Murray, C. B.; O'Brien, S. "Structural Characterization of Self-Assembled Multifunctional Binary Nanoparticle Superlattices" Journal of the American Chemical Society 2006, 128, 3620-3637.

17.   Shevchenko, E. V.; Talapin, D. V.; Kotov, N. A.; O'Brien, S.; Murray, C. B. "Structural diversity in binary nanoparticle superlattices" Nature 2006, 439, 55-59.

18.   Huang, L.; Chen, Z.; Wilson, J. D.; Banerjee, S.; Robinson, R. D.; Herman, I. P.; Laibowitz, R.; O'Brien, S. "Barium titanate nanocrystals and nanocrystal thin films: synthesis, ferroelectricity and dielectric properties" Journal of Applied Physics 2006, 100, 034316.

19.   Wu, CK; Yin, M; O'Brien, S; Koberstein, J. T. “Quantitative analysis of copper oxide nanoparticle composition and structure by X-ray photoelectron spectroscopy”, Chemistry of Materials, 2006, 18(25), 6054-6058.

20.   Chen, Z.; Huang, L.; He, J.; Zhu, Y.; O’Brien, S. "New nonhydrolytic route to synthesize crystalline BaTiO3 nanocrystals with surface capping ligands" Journal of Materials Research 2006, 21, 3187-3195.

21.   Papaefthymiou, G. C.; Redl, F. X., Black, C. T.; Sandstrom, R. L., Yin, M., Murray, C. B., O'Brien, S. P. “Hybrid magnetic nanoparticles derived from wustite disproportionation reactions at the nanoscale” Hyperfine Interactions, 2005, 165, 7, 239-245.

22.   Zhu, Z. M.; Andelman, T.; Yin, M.; Chen, T. L.; Ehrlich, S. N.; O'Brien, S. P.; Osgood, R. M. "Synchrotron x-ray scattering of ZnO nanorods: Periodic ordering and lattice size" Journal of Materials Research 2005, 20, 1033-1041.

23.   Yin, M.; Wu, C. K.; Lou, Y. B.; Burda, C.; Koberstein, J. T.; Zhu, Y. M.; O'Brien, S. "Copper oxide nanocrystals" Journal of the American Chemical Society 2005, 127, 9506-9511.

24.   Willis, A. L.; Turro, N. J.; O'Brien, S. "Spectroscopic characterization of the Surface of Iron Oxide Nanocrystals" Chemistry of Materials 2005, 17, 5970-5975.

25.   Shevchenko, E. V.; Talapin, D. V.; O'Brien, S.; Murray, C. B. "Polymorphism in AB(13) nanoparticle superlattices: An example of semiconductor-metal metamaterials" Journal of the American Chemical Society 2005, 127, 8741-8747.

26.   Lou, Y.; Yin, M.; O. Brien, S; Burda, C. "Electron-hole pair relaxation dynamics in binary copper-based semiconductor quantum dots" Journal of the Electrochemical Society 2005, 152, G427-G431.

27.   Papaefthymiou, G. C.; Redl, F. X.; Black, C. T.; Sandstrom, R. L.; Yin, M.; Murray, C. B.; O'Brien, S. P., Hybrid magnetic nanoparticles derived from wustite disproportionation reactions at the nanoscale. Hyperfine Interactions 2005, 165, 239-245.

28.   Huang, X. M. H.; Caldwell, R.; Huang, L. M.; Jun, S. C.; Huang, M. Y.; Sfeir, M. Y.; O'Brien, S. P.; Hone, J. "Controlled placement of individual carbon nanotubes" Nano Letters 2005, 5, 1515-1518.

29.   Guo, X. F.; Huang, L. M.; O'Brien, S.; Kim, P.; Nuckolls, C. "Directing and sensing changes in molecular conformation on individual carbon nanotube field effect transistors" Journal of the American Chemical Society 2005, 127, 15045-15047.

30.   Grancharov, S. G.; Zeng, H.; Sun, S. H.; Wang, S. X.; O'Brien, S.; Murray, C. B.; Kirtley, J. R.; Held, G. A. "Bio-functionalization of monodisperse magnetic nanoparticles and their use as biomolecular labels in a magnetic tunnel junction based sensor" Journal of Physical Chemistry B 2005, 109, 13030-13035.

31.   Andelman, T.; Gong, Y. Y.; Polking, M.; Yin, M.; Kuskovsky, I.; Neumark, G.; O'Brien, S. "Morphological control and photoluminescence of zinc oxide nanocrystals" Journal of Physical Chemistry B 2005, 109, 14314-14318.

32.   Yin, M.; Willis, A.; Redl, F.; Turro, N. J.; O'Brien, S. P. "Influence of capping groups on the synthesis of gamma-Fe2O3 nanocrystals" Journal of Materials Research 2004, 19, 1208-1215.

33.   Yin, M.; Gu, Y.; Kuskovsky, I. L.; Andelman, T.; Zhu, Y.; Neumark, G. F.; O'Brien, S. "Zinc oxide quantum rods" Journal of the American Chemical Society 2004, 126, 6206-6207.

34.   Shevchenko, E.; Redl, F.; Yin, M.; Murray, C. B.; O'Brien, S. , Nanoparticle Superlattices, SPIE Proceedings, 2004; p 5554.

35.   Redl, F. X.; Black, C. T.; Papaefthymiou, G. C.; Sandstrom, R. L.; Yin, M.; Zeng, H.; Murray, C. B.; O'Brien, S. P. "Magnetic, electronic, and structural characterization of nonstoichiometric iron oxides at the nanoscale" Journal of the American Chemical Society 2004, 126, 14583-14599.

36.   Gu, Y.; Kuskovsky, I. L.; Yin, M.; O'Brien, S.; Neumark, G. F. "Quantum confinement in ZnO nanorods" Applied Physics Letters 2004, 85, 3833-3835.

37.   Yin, M.; O'Brien, S. "Synthesis of monodisperse nanocrystals of manganese oxides" Journal of the American Chemical Society 2003, 125, 10180-10181.

38.   Redl, F. X.; Cho, K. S.; Murray, C. B.; O'Brien, S. "Three-dimensional binary superlattices of magnetic nanocrystals and semiconductor quantum dots" Nature 2003, 423, 968-971.

39.   Islam, M. A.; Xia, Y. Q.; Steigerwald, M. L.; Yin, M.; Liu, Z.; O'Brien, S.; Levicky, R.; Herman, I. P. "Addition, suppression, and inhibition in the electrophoretic deposition of nanocrystal mixture films for CdSe nanocrystals with gamma-Fe2O3 and Au nanocrystals" Nano Letters 2003, 3, 1603-1606.

40.   Euliss, L. E.; Grancharov, S. G.; O'Brien, S.; Deming, T. J.; Stucky, G. D.; Murray, C. B.; Held, G. A. "Cooperative assembly of magnetic nanoparticles and block copolypeptides in aqueous media" Nano Letters 2003, 3, 1489-1493.

41.   Zhang, C. X.; O'Brien, S.; Balogh, L. "Comparison and stability of CdSe nanocrystals covered with amphiphilic poly(amidoamine) dendrimers" Journal of Physical Chemistry B 2002, 106, 10316-10321.

42.   Turro, N. J.; Lakshminarasimhan, P. H.; Jockusch, S.; O'Brien, S. P.; Grancharov, S. G.; Redl, F. X. "Spectroscopic probe of the surface of iron oxide nanocrystals" Nano Letters 2002, 2, 325-328.

43.   O’Brien, S.; Brus, L.; Murray, C. B.; Held, G. A.; Herman, I. P.; Chiang, V.; Robinson, R.; Lin, J.; Cherniavskaya, O.; Redl, F. X.; Grancharov, S. G.; Yin, M. "The Synthesis, Characterization and Properties of Oxide Nanoparticle and Nanoparticle Composite Systems" ICCE/9 Conference Proceedings 2002, ICCE/9,

44.   Balogh, L.; Zhang, C. X.; O'Brien, S.; Turro, N. J.; Brus, L. "Surface modification of CdSe nanocrystals with organic ligands" Chimica Oggi-Chemistry Today 2002, 20, 45-51.

45.   O'Brien, S.; Brus, L.; Murray, C. B. "Synthesis of monodisperse nanoparticles of barium titanate: Toward a generalized strategy of oxide nanoparticle synthesis" Journal of the American Chemical Society 2001, 123, 12085-12086.