Synthesis of Hybrid Au-In2O3 Nanoparticles Exhibiting Dual

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Synthesis of Hybrid Au-In2O3 Nanoparticles Exhibiting Dual Plasmonic Resonance Thomas R. Gordon, and Raymond E. Schaak Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/cm502396d • Publication Date (Web): 11 Aug 2014 Downloaded from http://pubs.acs.org on August 16, 2014

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Chemistry of Materials

Synthesis of Hybrid Au-In 2 O 3 Nanoparticles Exhibiting Dual Plasmonic Resonance Thomas R. Gordon and Raymond E. Schaak* Department of Chemistry and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States KEYWORDS hybrid nanoparticles, nanoparticle synthesis, indium oxide, gold, semiconductor plasmonics

ABSTRACT: Hybrid nanoparticles composed of multiple material systems provide a platform for studying the coupling between nanoparticles with distinct properties. Here, we describe a non-traditional synthetic pathway to Au-In2O3 hybrid nanoparticles that contain two distinct plasmonic domains: Au, with a localized surface plasmon resonance (LSPR) in the visible, and In2O3, with a LSPR in the mid-infrared. The hybrid nanocrystals are produced by slowly introducing In(III) acetate to Au nanoparticle seeds using a syringe pump. Rather than forming through a traditional heterogeneous seeded-growth process, a series of in-situ and exsitu studies reveal an alternate multi-step pathway. The Au nanoparticles first combine with In to form an alloy of Au and In, which is colloidally stable up to 300 °C in 1-octadecene. The Au-In alloy nanoparticles then transform into intermetallic AuIn2 nanoparticles that are surrounded by a shell of amorphous indium oxide (AuIn2@InOx), followed by the final Au-In2O3 heterodimers upon complete phase segregation.

INTRODUCTION Multiple functionalities can be incorporated into a single colloidal nanoparticle through the design and synthesis of appropriate hybrid systems.1,2 Hybrid nanoparticles with magnetic,3,4 plasmonic,5,6 semiconducting,7 catalytic,8 and photocatalytic9,10 components have been prepared, and these serve as excellent model systems for studying synergistic interactions that may emerge from coupling these materials into a single system. Among the properties most explored in hybrid nanoparticles is the localized surface plasmon resonance (LSPR) of metallic nanocrystals. LSPRs have numerous applications, including in surface enhanced Raman scattering,11 molecular sensing,12 diagnostic imaging,13 and photothermal cancer therapy.14 Several examples of colloidal nanocrystals that contain multiple plasmonic domains have recently been reported.5,6,15,16 The most extensively explored systems are metal-metal heterodimers, in which coupling between the metallic components can result in the formation of charge transfer plasmons.5 In addition, the plasmonic semiconductor Cu2-xSe was recently combined with Au to form Au-Cu2-xSe heterodimers, which exhibited efficacy as contrast agents for photoacoustic therapy.6 Similarly, indium cadmium oxide (ICO) was nucleated and grown on several metals, including gold, and the resulting Au-ICO heterodimers exhibited dual plasmonic resonance.15 Plasmonic semiconductors are formed through heavy (degenerate) doping of a semiconductor nanocrystal and the frequency of the plasmon resonance is tunable with the dopant concentration.17 Such materials have the potential to substitute for the more expensive noble metals while providing similar extinction coefficients and quality factors in certain wavelength ranges.18 In addition, metal-semiconductor heterodimers act

as excellent model systems of charge transfer at the nanoscale, which may be monitored by shifting of the plasmon resonance.19 The interfaces between domains in hybrid nanoparticles can significantly impact their synergistic interactions, and it is therefore important to understand and control how they form. In this report, we investigate the synthesis of Au-In2O3 heterodimers, a dual-plasmonic metal/metal-oxide hybrid nanoparticle system. To carefully control the growth process, an indium(III) stock solution is added to the Au nanoparticle seeds via a syringe pump. During the course of this reaction, we observe and isolate a series of nanoparticle intermediates, including an intermetallic AuIn2@InOx core-shell construct. These nanoparticle intermediates are characterized in-depth by a suite of microscopy, diffraction, and spectroscopic tools. The shifting and broadening of the Au plasmon resonance during the formation of Au-In2O3 provides particularly instructive in-situ optical insights into how the hybrid nanoparticles form; such aspects of this formation pathway would be difficult to assess using other ex-situ techniques. Collectively, these observations reveal that the dual-plasmonic hybrid nanoparticles form not by the expected seeded growth route, but instead by an in-situ alloying and phase segregation pathway. Two plasmonic modes – one in the visible (Au) and one in the near infrared (In2O3) – are observed in the final Au-In2O3 heterodimers.

EXPERIMENTA L SECTION Chemicals and Materials. Hydrogen tetrachloroaurate trihydrate (99.99%, HAuCl4·3H2O), 1-octadecene (1-ODE, tech. 90%), oleylamine (OLAM, tech. 70%), oleic acid (OLAC, tech. 90%), and carbon tetrachloride (CCl4, 99.9%) were pur-

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Figure 1. (Left to right) Schematic, TEM image, HRTEM image, SAED pattern, and EDS spectrum for (a-e) Au nanoparticle seeds and the intermediates and products formed upon heating in a stock solution of In(III) acetate that is delivered via syringe pump: (f-j) Au-In nanoparticles, (k-o) AuIn2@InOx core@shell particles, and (p-t) the final Au-In2O3 heterodimers.

chased from Sigma-Aldrich. Indium (III) acetate (99.99%) was purchased from Alfa Aesar. Ethanol, hexanes, and acetone were purchased from VWR. All chemicals were used as received. All syntheses were carried out under high purity Ar using standard Schlenk techniques, and workup procedures were performed in air. Synthesis of Au Nanoparticle Seeds. OLAM-capped Au nanoparticles were prepared using a method modified from a previous report.20 In the synthesis, 100 mg of HAuCl4·3H2O, 10 mL of 1-ODE, and 10 mL of OLAM were added to a 50mL flask. The solution was purged with flowing Ar for 20 min at room temperature, heated to 120 °C under static Ar atmosphere, and held for 1 h. The product was then cooled to room temperature and isolated by the addition of ethanol followed by centrifugation. The particles were redispersed in hexanes and washed again with ethanol. Finally, the product was collected, redispersed in hexanes at a concentration of 10 mg/mL, and stored for use as the Au nanoparticle stock solution, as described in the following section. Synthesis of Au-In2O3 hybrid nanoparticles. The hybrid nanoparticles were produced by introducing a stock solution of In(III) to the Au nanoparticles using a syringe pump. The In(III) stock solution was prepared by heating 58.4 mg (0.2 mmol) of In(III) acetate, 0.75 mL of OLAC, and 2 mL of 1ODE at 120°C under vacuum for at least 30 min. Next, 6 mL of 1-ODE, 0.75 mL of OLAM, and 5.75 mg of Au nanoparti-

cles (575 μL of the Au nanoparticle stock solution) were combined in a 50 mL flask. After degassing for at least 30 min at 120 °C to remove the hexanes and other volatiles, 0.2 mL of the In(III) stock solution was added to the flask and the reaction was heated quickly (15 °C/min) to 300 °C. Note that the Au nanoparticles agglomerated at such high temperatures when the In(III) stock solution was not added; indium stabilization of Au nanoparticles has been reported previously.21 Once stable at 300 °C, an additional 0.5-2 mL of In(III) stock solution was injected into the flask at a rate of 0.1 mL/min using a syringe pump. After the desired amount of precursor was added, the reaction was quickly cooled to room temperature by removing the heating source and blowing compressed air across the surface of the flask. The nanocrystals were isolated through addition of a mixture of acetone and ethanol (roughly 3:1 acetone:ethanol) and centrifugation at 10,000 rpm, followed by redispersion in hexanes. The particles were washed a second time and redispersed again in hexanes. Due to the presence of some free Au seeds, the yield of nanocrystal heterodimers was improved through size selective precipitation (SSP) from approx. 30% to 92% (determined through analysis of >600 particles by TEM). Acetone was added until the solution turned slightly turbid, and then the solution was centrifuged at 5,000 rpm for 2 min. Characterization. Transmission electron microscopy (TEM) images were obtained from a JEOL 1200 EX II operat-


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ing at 80 kV or a Phillips 420 operating at 120 kV. Highresolution TEM (HRTEM) images, selected area electron diffraction (SAED) patterns, energy-dispersive X-ray spectroscopy (EDS) data, and scanning transmission electron microscopy images coupled with EDS analysis (STEM-EDS) were collected on a JEOL 2010F field emission microscope operating at an accelerating voltage of 200 kV; this instrument is outfitted with an EDAX solid-state X-ray detector. STEM-EDS imaging and analysis were performed using an FEI Titan G2 TEM equipped with a spherical aberration corrector on the probe-forming lens at an accelerating voltage of 200 kV. EDS maps were acquired in the Titan using ChemiSTEM quad detectors at a current of 0.6 nA. Standardless Cliff-Lorimer quantification was performed on the deconvoluted EDS line intensity data using the Bruker Esprit software. ES Vision software (Emispec) was used for EDS data processing. Powder X-ray diffraction (XRD) patterns were collected with samples drop-cast onto a low background Si substrate using a Bruker Advance D8 X-ray diffractometer and Cu Kα radiation at room temperature. Ultraviolet−visible−near-infrared (UV−vis−NIR) measurements were performed on a PerkinElmer Lambda 950 spectrophotometer. FTIR spectra were collected on a Bruker Hyperion 3000. Films were prepared by drop casting a concentrated hexanes solution of nanoparticles (>20 mg/mL) onto a clean glass slide, drying in air, and degassing in a vacuum desiccator. Solution phase data was recorded using a Harrick demountable liquid cell equipped with CaF2 windows.

particles are spherical with an average diameter of 16.6 ± 3.6 nm (Figure 1l). HRTEM images (Figure 1m) confirm the crystallinity of the AuIn2 core and the amorphous nature of the shell. EDS spectra (Figure 1o) confirm an increase in overall In content in the nanocrystals relative to the Au-In alloy particles. Both SAED (Figure 1n) and powder XRD (Figure 2) data indicate that the samples consist primarily of the intermetallic AuIn2 phase. The powder XRD pattern (Figure 2) reveals a small contribution from In2O3, which is attributed to the formation of some heterodimers at this point in the reaction. This is not unexpected, since the reaction continues to progress and it is difficult to capture a pure intermediate under these conditions. A STEM-EDS line scan of a single AuIn2@InOx particle suggests that In is present in both the core and shell, while Au is present only in the core (Figure S1). Interestingly, a similar morphology was observed to result from the ambient oxidation of evaporated and interdiffused Au and In layers on various solid supports, and it was concluded that the In component stabilized Au nanoparticles at high temperatures while retaining catalytic activity for CO oxidation.22 We observe similar stability for both the Au-In alloy and the AuIn2 nanocrystals, which are colloidally stable at 300 °C while in the absence of In under otherwise identical conditions they agglomerate to form large aggregates (Figure S2).

RESULTS AND DISCUSSION Figure 1 shows schematically the particle evolution during the reaction between Au nanocrystals and an In(III) stock solution to ultimately produce Au-In2O3 hybrid nanoparticles, along with the corresponding TEM, HRTEM, SAED, and EDS data. The Au nanocrystal seeds (Figure 1a-e), which are spherical with an average diameter of 11.2 ± 1.3 nm, were synthesized according to a literature protocol.20 Upon heating the Au nanocrystals to 300 °C in the presence of the In(III) stock solution (molar ratio 2:1 Au:In), an alloy of Au and In forms (Figure 1f-j). The Au-In nanoparticles are largely spherical with an average diameter of 11.7 ± 2.0 nm. The powder XRD patterns in Figure 2 show that the peaks corresponding to face centered cubic (fcc) Au broaden and shift to smaller 2θ values (and therefore have a larger lattice constant) while maintaining the fcc crystal structure. Consistent with this behavior, a bulk-phase dilute fcc alloy of In in Au (e.g. Au90In10) has been reported to have a larger lattice parameter (4.11 Å) than pure fcc Au (4.07 Å).21 Similar behavior is observed by SAED (Figure 1d,i). The diffraction data are therefore consistent with the incorporation of In into the Au seeds to form a fcc Au-In alloy. In addition, EDS spectra of the AuIn nanocrystals indicates the presence of both Au and In (Figure 1j). A syringe pump is then utilized to slowly introduce additional In(III) stock solution to the hot reaction mixture, preventing the bulk nucleation of indium oxide nanocrystals. After the addition of 0.5 mL of additional In(III) stock solution at 300 °C, the alloyed nanocrystals transform into core@shell particles containing an intermetallic AuIn2 core and an amorphous indium oxide shell (Figure 1k-o), denoted as AuIn2@InOx. TEM images reveal that the AuIn2@InOx

Figure 2. Powder XRD data for the Au nanoparticle seeds, Au-In alloy and AuIn2@InOx core@shell intermediates, and Au-In2O3 product, along with simulated XRD patterns of Au, AuIn2, and In2O3 for comparison. The asterisks (*) correspond to a small amount of In2O3 in the AuIn2@InOx sample.

Further addition of In(III) acetate (1.5 mL) results in the formation of asymmetric Au@InOx-In2O3 nanocrystal heterodimers (Figure 1p-t), which we refer to hereafter as Au-In2O3. Analysis of TEM images indicates that the In2O3 lobes and the dark Au domains have average diameters of 44.1 ± 2.7 nm and 13.2 ± 1.7 nm, respectively. Powder XRD data confirms the formation of cubic bixbyite-type In2O3, and a small peak at 39 °2θ is consistent with the Au nanocrystal seed (Figure 2).



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Many of the particles shown in Figure 1q could be classified as core-shell particles based on an initial visual inspection, but they are indeed heterodimers; the In2O3 domain is highly faceted, causing the Au-In2O3 particles to preferentially lie with the Au domain facing upward. HRTEM images (Figures 2r,3) confirm the heterodimer morphology, revealing that the Au cores are embedded in a crystalline In2O3 matrix, which surrounds most of the Au particles, as well as a thin amorphous shell on the remainder of the Au. High-resolution STEM-EDS maps allow for identification of the elements in each region of the hybrid nanocrystal (Figure 4). EDS maps of the Au-In2O3 heterodimers confirm the presence of a thin InOx layer on the surface of the Au seed. The data also suggest the segregation of Au and In during the growth of the asymmetric In2O3 domain. The highest concentration of Au is closest to the surface, with increasing In concentration closest to the central In2O3 region (Figure S3).

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Figure 4. (a) HAADF STEM image of a Au-In2O3 heterodimer and the corresponding STEM-EDS element maps for (b) Au, (c) O, and (d) In.

The formation of the Au-In2O3 heterodimers can be tracked by analyzing the change in plasmonic response of the Aubased seed throughout the reaction (Figure 5). Initially, the Au nanoparticle seeds exhibit a LSPR at 520 nm, which is expected for 11 nm oleylamine capped Au nanoparticles in hexanes.23 During the alloying of Au with In, there is significant broadening of the LSPR and a blue-shift to 486 nm. This blue-shift in the plasmonic resonance mirrors recent reports of AuCd alloy nanocrystals,24 and indicates increased electron density in the metallic particles upon alloying. This is also in agreement with X-ray photoelectron spectroscopy (XPS) studies of bulk Au/Cd and Au/In alloys.25 While not the focus of this work, shifting the plasmonic resonance of gold through alloying has been suggested as a method to improve properties for optical metamaterials by reducing loss at certain frequencies.26 Further introduction of In, forming AuIn2@InOx nanocrystals, results in a blue shift of the Au plasmon resonance into the UV. Such behavior is expected, as the plasma frequency of In is 12.8 eV compared with that of Au which is 8.9 eV.27 In the isolated Au-In2O3 nanocrystals, the LSPR of the Au red-shifts back to 528 nm. This red-shift likely results from a combination of the de-alloying of In from the Au during the formation of the In2O3 domain, which would cause the LSPR to shift back toward that of Au, and also from the increase in dielectric constant from having the Au embedded in the indium oxide matrix.

Figure 3. HRTEM image of a Au-In2O3 heterodimer, showing the crystalline cubic lattice of bixbyite-type In2O3 and the amorphous InOx shell surrounding the Au domain.

Figure 5. Optical absorption data for samples taken during the reaction that results in the formation of the Au-In2O3 heterodimers, which includes the Au nanoparticle seeds, the Au-In alloy and AuIn2@InOx core@shell intermediates, and the final AuIn2O3 product. The dashed arrows highlight the progression of samples throughout the course of the reaction.

Indium tin oxide (ITO) nanocrystals exhibiting plasmonic resonance were reported previously, and the LSPR was tunable with dopant concentration from 1618-2200 nm.17 Here, we observe similar resonances in the mid-IR in the absence of aliovalent doping. As shown in Figure 6, Au-In2O3 nanocrystals and In2O3 nanocrystals (prepared identically in the absence


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of Au seeds) dispersed in CCl4 both exhibit a large absorbance in the mid-IR, which we attribute to a plasmonic resonance (Figure 6). Such an observation is not unexpected or unprecedented, since oxygen deficient In2O3 is known to form highly conductive films.28 To further support the assignment of the LSPR mode, films of the nanocrystals were deposited on glass substrates. These In2O3 nanoparticle films exhibited a redshift of the LSPR, which is the expected response for a plasmonic resonance to higher dielectric environments. Similar to the work of Ye et al.,15 coupling between the Au and In2O3 domain is not observed, as expected based on the large energetic separation between the resonances. In Figure 6, the sharp peaks are attributed to residual acetone from the workup procedure, as well as oleic acid.29

ASSOCIATED CONTENT Supporting Information. Additional TEM images and STEMEDS line scans. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author *(R.E.S.) E-mail: [email protected].

Notes The authors declare no competing financial interests.

ACKNOWLEDGMENT This work was supported by the Penn State Materials Research Science and Engineering Center (NSF DMR-0820404). TEM imaging was performed in the Penn State Microscopy and Cytometry Facility (University Park, PA) and at the Materials Characterization Laboratory of the Penn State Materials Research Institute. The authors thank Trevor Clark, Ke Wang, Jennifer Gray, and Josh Stapleton at the Penn State Materials Characterization Laboratory for their assistance in the collection of the TEM images and optical spectra.

REFERENCES

Figure 6. FTIR spectra displaying the LSPR of (left) Au-In2O3 and (right) In2O3 nanoparticles dissolved in CCl4 (red) and deposited onto a glass slide (blue). Note that the sharp peaks in the spectra result from the molecular vibrations of surfactants and residual solvent.

CONCLUSIONS In this work, we have described the synthesis of hybrid nanocrystals based on Au and In2O3. The formation of AuIn2O3 heterodimers proceeds through isolatable intermediates that include an alloy of Au and In and an intermetallic AuIn2@InOx construct. Characterization by XRD, EDS, HRTEM, and UV-vis support the synthetic evolution of the product Au-In2O3 heterodimers and the formation of these intermediate species. This formation pathway is likely facilitated by the slow and continuous addition of the In(III) stock solution and is predicated on the ability to first form an Au-In alloy prior to oxidation. Analysis of the mid-IR absorbance of both In2O3 and Au-In2O3 reveals the presence of a large feature, which is assigned to a plasmonic resonance resulting from a putative oxygen deficient In2O3 domain. Collectively, these results reveal a multi-step synthetic pathway to dual plasmonic hybrid nanoparticles that emerges from a putative seeded-growth synthesis of Au-In2O3 heterodimers from Au nanocrystal seeds, and this is facilitated by introducing In(III) acetate slowly via syringe pump. These synthetic insights may be useful for controllably synthesizing other hybrid nanoparticles, including of complex systems with highly sophisticated and coupled multi-component nanostructures.

1. Costi, R.; Saunders, A. E.; Banin, U. Angew. Chem., Int. Ed. 2010, 49, 4878. 2. Buck, M. R.; Schaak, R. E. Angew. Chem., Int. Ed. 2013, 52, 6154. 3. Shi, W.; Zeng, H.; Sahoo, Y.; Ohulchanskyy, T. Y.; Ding, Y.; Wang, Z. L.; Swihart, M.; Prasad, P. N. Nano Lett. 2006, 6, 875. 4. Lee, K. S.; Anisur, R. M.; Kim, K. W.; Kim, W. S.; Park, T.; Kang, E. J.; Lee, I. S. Chem. Mater. 2012, 24, 682. 5. Sun, Y.; Foley, J. J.; Peng, S.; Li, Z.; Gray, S. K. Nano Lett. 2013, 13, 3958. 6. Liu, X.; Lee, C.; Law, W.; Zhu, D.; Liu, M.; Jeon, M.; Kim, J.; Prasad, P. N.; Kim, C.; Swihart, M. T. Nano Lett. 2013, 13, 4333. 7. Read, C. G.; Biacchi, A. J.; Schaak, R. E. Chem. Mater. 2013, 25, 4304. 8. Wang, C.; Yin, H.; Dai, S.; Sun, S. Chem. Mater. 2010, 22, 3277. 9. Amirav, L.; Alivisatos, A. P. J. Phys. Chem. Lett. 2010, 1, 1051. 10. Acharya, K. P.; Khnayzer, R. S.; O’Connor, T.; Diederich, G.; Kirsanova, M.; Klinkova, A.; Roth, D.; Kinder, E.; Imboden, M.; Zamkov, M. Nano Lett. 2011, 11, 2919. 11. Nie, S.; Emory, S. R. Science 1997, 275, 1102. 12. Willets, K. A.; Van Duyne, R. P. Annu. Rev. Phys. Chem. 2007, 58, 267. 13. Jain, P. K.; Huang, X.; El-Sayed, I. H.; El-Sayed, M. A. Acc. Chem. Res. 2008, 41, 1578. 14. El-Sayed, I. H.; Huang, X.; El-Sayed, M. A. Cancer Lett. 2006, 239, 129. 15. Ye, X.; Reifsnyder Hickey, D.; Fei, J.; Diroll, B. T.; Paik, T.; Chen, J.; Murray, C. B. J. Am. Chem. Soc. 2014, 136, 5106. 16. Feng, Y.; He, J.; Wang, H.; Tay, Y. Y.; Sun, H.; Zhu, L.; Chen, H. J. Am. Chem. Soc. 2012, 134, 2004. 17. Kanehara, M.; Koike, H.; Yoshinaga, T.; Teranishi, T. J. Am. Chem. Soc. 2009, 131, 17736. 18. Gordon, T. R.; Paik, T.; Klein, D. R.; Naik, G. V; Caglayan, H.; Boltasseva, A.; Murray, C. B. Nano Lett. 2013, 13, 2857. 19. Jain, P. K.; Manthiram, K.; Engel, J. H.; White, S. L.; Faucheaux, J. A.; Alivisatos, A. P. Angew. Chem., Int. Ed. 2013, 52, 13671. 20. Motl, N. E.; Bondi, J. F.; Schaak, R. E. Chem. Mater. 2012, 24, 1552. 21. Villars, P.; Calvert, L. D., Eds. Pearson’s Handbook of Crystallographic Data for Intermetallic Phases, 2nd ed.; ASM International: Materials Park, OH, 1991.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

22. Sutter, E. A.; Tong, X.; Jungjohann, K.; Sutter, P. W. Proc. Natl. Acad. Sci. 2013, 110, 10519. 23. Motl, N. E.; Ewusi-Annan, E.; Sines, I. T.; Jensen, L.; Schaak, R. E. J. Phys. Chem. C 2010, 114, 19263. 24. Guardia, P.; Korobchevskaya, K.; Casu, A.; Genovese, A.; Manna, L.; Comin, A. ACS Nano 2013, 7, 1045. 25. Sham, T.; Perlman, M.; Watson, R. Phys. Rev. B 1979, 19, 539.

Page 6 of 7

26. Bobb, D. A.; Zhu, G.; Mayy, M.; Gavrilenko, A. V.; Mead, P.; Gavrilenko, V. I.; Noginov, M. A. Appl. Phys. Lett. 2009, 95, 151102. 27. Zeman, E. J.; Schatz, G. C. J. Phys. Chem. 1987, 91, 634. 28. Tomita, T.; Yamashita, K.; Hayafuji, Y.; Adachi, H. Appl. Phys. Lett. 2005, 87, 051911. 29. Wu, N,; Fu, L.; Su, M.; Aslam, M.; Wong, K. C.; Dravid, V. P. Nano Lett. 2004, 4, 383.


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Synthesis of Hybrid Au-In2O3 Nanoparticles Exhibiting Dual

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