Hexagonal core-shell and alloy Au/Ag nanodisks on ZnO nanorods and their optical enhancement effect
© Zhang et al.; licensee Springer. 2014
Received: 16 February 2014
Accepted: 17 April 2014
Published: 14 May 2014
Au and Ag hybrid hexagonal nanodisks were synthesized on ZnO nanorods' (0002) surface via a new two-step deposition-annealing method. The structural, compositional, as well as optical investigations were carried out systematically to find out the nanodisks' formation mechanism and optical enhancement effect. It was shown that the core-shell Au/Ag nanodisk can be formed under rapid annealing temperature of 500°C, while Au/Ag alloy nanodisks are formed if higher temperatures (>550°C) are applied. The optical effect from these nanodisks was studied through photoluminescence and absorption spectroscopy. It was found that the carrier-plasmon coupling together and carrier transfer between metal and ZnO contribute to the emission enhancement. Furthermore, the results suggest that the composition of nanodisk on the vicinity of metal/ZnO interface plays an important role in terms of the enhancement factors.
KeywordsMetal nanoparticle Nanodisk Zinc oxide Plasmonic
The interest in developing superior nanomaterials has seen tremendous progress in terms of nanofabrication, nanopatterning, and nano-self-assembly [1–3]. These progresses generated a wealth family of novel, engineered structures with desirable shape and electronic and optical properties [4–6]. These not only give researchers the foundation for basic physics phenomena that are not seen in bulk materials but also provided a wide range of application opportunities. A good example is the plasmonic nanostructures; particularly, Au and Ag nanoparticles are the most studied nanomaterials [7–9]. The mature solution-based synthesis techniques for Au and Ag nanostructures have enabled size, shape, and inter-particle spacing controllable solutions or arrays. They have demonstrated strong absorption and scattering resonance in a wide range of wavelength, which is now actively applied in functional devices and systems such as surface plasmon-enhanced Raman spectroscopy , solar cells [11, 12], as well as lasers [13, 14].
The advantages of nanomaterials are not limited to single component but should be extended to the possibilities to combine different nanocomponents into hybrid/composite structures [15, 16]. Hybrid materials feature merits from two or more components and potentially synergistic properties caused by interactions between them. Interactions can be very strong as both the building blocks and separation between them have nanoscale dimensions [17, 18]. For instance, it is well studied that nanoscale emitters benefit from metal nanoparticle or nanofilm surroundings [13, 19, 20]. In the wide bandgap semiconductor ZnO, reports have shown that by placing Au or Ag nanoparticles on ZnO nanorods or films [21, 22], the ZnO's luminescence capability can be enhanced due to the carrier transfer from surface plasmon states to ZnO. More recently, we have developed a facile method to epitaxially grow Au, Ag, Pt, and Pd hexagonal/triangular nanodisks on ZnO nanorods' (0002) surface , in which Au and Ag nanodisks also exhibit very strong photoluminescence (PL) enhancement capability. So, metal/ZnO hybrid nanostructures are good candidate to yield high optical efficiencies in optoelectronic devices, i.e., lasers, LEDs, etc. Hence, further tuning these nanostructure's key parameters, i.e., the composition of Au and Ag inside one nanodisk, may be of substantial interest. On the other hand, since Au and Ag are with very similar lattice parameter and chemical properties, it is therefore possible to form lattice matched Ag/Au multi-layers in nanodisks by an all-solid-state synthesis process, and in this way, some desirable plasmonic structures can be achieved on ZnO nanorods' platform.
In this paper, we focus on the synthesis of Au/Ag core-shell and alloy nanodisks on ZnO nanorods' (0002) surface through a newly developed two-step deposition-annealing method, as well as the systematic characterization of their structural and optical properties. It is found that the annealing temperature determines the structural configuration of the Au/Ag composite nanodisks. Core-shell nanodisks form under the annealing temperature of 500°C, and intermixing Au/Ag alloy nanodisks start to form at the annealing temperature of 550°C. The hybrid structure's PL properties were further studied and analyzed in detail.
The morphology and crystal structures of samples were characterized using field emission scanning electron microscope (SEM) (Carl Zeiss Leo SUPRA 55 system, Oberkochen, Germany) and transmission electron microscope (TEM) (FEI Tecnai G2 F30, E.A. Fischione Instruments, Inc., Export, PA, USA) with electron dispersive spectroscopy (EDS) mapping capability. PL measurements were carried out to characterize the optical properties of ZnO using a 325-nm He-Cd laser with an excitation power of 5 mW. An Oriel Cornerstone 260 1/4 m monochromator and a photomultiplier (Newport Corporation, Irvine, CA, USA) were used in the measurement. The absorption measurement was done by a Lambda 950 UV/VIS/NIR spectrometer (PerkinElmer, Waltham, MA, USA).
Results and discussion
In conclusion, Au and Ag hybrid nanodisk structures were formed on the top end surface of ZnO nanorods. By varying the rapid annealing temperatures, the composite nanodisks' structure changed drastically. The core-shell and alloy Au/Ag nanodisks were achieved and characterized, while their formation mechanisms were discussed. The composite nanodisks' effect on tuning the ZnO nanorods' PL properties was further carried out. It has been found that with higher annealing temperature the PL intensity from ZnO becomes stronger, which is attributed to the shift of resonant wavelength due to composition change in the plasmonic nanodisks.
chemical vapor deposition
electron dispersive spectroscopy
poly (methyl methacrylate)
scanning electron microscope
scanning transmission electron microscopy
transmission electron microscope
The authors thank the financial support from the National Science Foundation of China under the contract number 11204097.
- Mark D, Haeberle S, Roth G, Stetten FV, Zengerle R: Microfluidic lab-on-a-chip platforms: requirements, characteristics and applications. Chem Soc Re 2010, 39: 1153–1182. 10.1039/b820557bView ArticleGoogle Scholar
- Barth JV, Costantini G, Kern K: Engineering atomic and molecular nanostructures at surfaces. Nature 2005, 437: 671–679. 10.1038/nature04166View ArticleGoogle Scholar
- Alivisatos AP: Semiconductor clusters, nanocrystals, and quantum dots. Science 1996, 271: 933–937. 10.1126/science.271.5251.933View ArticleGoogle Scholar
- Yao J, Yan H, Lieber CM: A nanoscale combing technique for the large-scale assembly of highly aligned nanowires. Nature Nanotechnol 2013, 8: 329–335. 10.1038/nnano.2013.55View ArticleGoogle Scholar
- Reed MA, Randall JN, Aggarwal RJ, Matyi RJ, Moore TM, Wetsel AE: Observation of discrete electronic states in a zero-dimensional semiconductor nanostructure. Phys Rev Lett 1988, 60: 535–537. 10.1103/PhysRevLett.60.535View ArticleGoogle Scholar
- Kamat PV: Meeting the clean energy demand: nanostructure architectures for solar energy conversion. J Phys Chem C 2007, 111: 2834–2860. 10.1021/jp066952uView ArticleGoogle Scholar
- Tao AR, Habas S, Yang PD: Shape control of colloidal metal nanocrystals. Small 2008, 4: 310–325. 10.1002/smll.200701295View ArticleGoogle Scholar
- Jain PK, Huang XH, El-Sayed IH, El-Sayed MA: Noble metals on the nanoscale: optical and photothermal properties and some applications in imaging, sensing, biology, and medicine. Accnt Chem Res 2008, 41: 1578–1586. 10.1021/ar7002804View ArticleGoogle Scholar
- Pedersen DB, Wang SL, Duncan EJS, Liang SH: Adsorbate-induced diffusion of Ag and Au atoms out of the cores of Ag@ Au, Au@ Ag, and Ag@ AgI core-shell nanoparticles. J Chem Phys C 2007, 111: 13665–13672. 10.1021/jp073425hView ArticleGoogle Scholar
- Anker JN, Hall WP, Lyandres O, Shah NC, Zha J, Van Duyne RP: Biosensing with plasmonic nanosensors. Nature Mater 2008, 7: 442–453. 10.1038/nmat2162View ArticleGoogle Scholar
- Ferry VE, Verschuuren MA, Li HBT, Verhagen E, Walters RJ, Schropp REI, Atwater HA, Polman A: Light trapping in ultrathin plasmonic solar cells. Opt Express 2010, 18: A237-A245. 10.1364/OE.18.00A237View ArticleGoogle Scholar
- Wu J, Mangham SC, Reddy VR, Manasreh MO, Weaver BD: Surface plasmon enhanced intermediate band based quantum dots solar cell. Solar Energy Mater Solar Cell 2012, 102: 44–49.View ArticleGoogle Scholar
- Oulton RF, Sorger VJ, Zentgraf T, Ma RM, Gladden C, Dai L, Bartal G, Zhang X: Plasmon lasers at deep subwavelength scale. Nature 2009, 461: 629–632. 10.1038/nature08364View ArticleGoogle Scholar
- Wu J, Lee SY, Reddy VR, Manasreh MO, Weaver BD, Yakes MK, Furrow CS, Kunets VP, Benamara M, Salamo GJ: Photoluminescence plasmonic enhancement in InAs quantum dots coupled to gold nanoparticles. Mater Lett 2011, 65: 23–24.Google Scholar
- Wang DH, Choi DW, Li J, Yang ZG, Nie ZM, Kou R, Hu DH, Wang CM, Saraf LV, Zhang JG, Aksay IA, Liu J: Self-assembled TiO2-graphene hybrid nanostructures for enhanced Li-ion. ACS Nano 2009, 3: 907–914. 10.1021/nn900150yView ArticleGoogle Scholar
- Pyun J: Nanocomposite materials from functional polymers and magnetic colloids. Polymer Rev 2007, 47: 231–263. 10.1080/15583720701271294View ArticleGoogle Scholar
- Peng H, Sun X, Cai F, Chen X, Zhu Y, Liao G, Chen D, Li Q, Lu Y, Zhu Y, Jia Q: Electrochromatic carbon nanotube/polydiacetylene nanocomposite fibres. Nat Nanotechnol 2009, 4: 738–741. 10.1038/nnano.2009.264View ArticleGoogle Scholar
- Subramanian V, Wolf E, Kamat PV: Semiconductor–metal composite nanostructures. To what extent do metal nanoparticles improve the photocatalytic activity of TiO2 films? Phys Chem B 2001, 105: 11439–11446. 10.1021/jp011118kView ArticleGoogle Scholar
- Hill MT, Marell M, Leong ESP, Smalbrugge B, Zhu YC, Sun MH, Veldhoven PJ, Geluk EJ, Karouta F, Oei YS, Notzel R, Ning CZ, Smit MK: Lasing in metal-insulator-metal sub-wavelength plasmonic waveguides. Opt Express 2009, 17: 11107–11112. 10.1364/OE.17.011107View ArticleGoogle Scholar
- Achermann M: Exciton − plasmon interactions in metal − semiconductor nanostructures. J Phys Chem Lett 2010, 1: 2837–2843. 10.1021/jz101102eView ArticleGoogle Scholar
- Xiao XH, Ren F, Zhou XD, Peng TC, Wu W, Peng XN, Yu XF, Jiang CZ: Surface plasmon-enhanced light emission using silver nanoparticles embedded in ZnO. Appl Phys Lett 2010, 97: 071909. 10.1063/1.3480417View ArticleGoogle Scholar
- Chen T, Xing GZ, Zhang Z, Chen HY, Wu T: Tailoring the photoluminescence of ZnO nanowires using Au nanoparticles. Nanotechnology 2008, 19: 435711. 10.1088/0957-4484/19/43/435711View ArticleGoogle Scholar
- Chu S, Ren J, Yan D, Huang J, Liu J: Noble metal nanodisks epitaxially formed on ZnO nanorods and their effect on photoluminescence. Appl Phys Lett 2012, 101: 043122. 10.1063/1.4739516View ArticleGoogle Scholar
- Sanchez-Iglesias A, Pastoriza-Santos I, Perez-Juste J, Rodriguez-Gonzalez B, Gacia FJ, Liz-Marzan LM: Synthesis and optical properties of gold nanodecahedra with size control. Adv Mater 2006, 18: 2529–2534. 10.1002/adma.200600475View ArticleGoogle Scholar
- Wandelt K, Niemantsverdriet JW, Dolle P, Markert K: Thermal stability of atomic Ag/Au and Au/Ag interfaces on a Ru (001) substrate. Surf Sci 1989, 213: 612–629. 10.1016/0039-6028(89)90317-8View ArticleGoogle Scholar
- Shore MS, Wang J, Johnston-Peck AC, Oldenburg AL, Tracy JB: Synthesis of Au (core)/Ag (shell) nanoparticles and their conversion to AuAg alloy nanoparticles. Small 2011, 7: 230–234. 10.1002/smll.201001138View ArticleGoogle Scholar
- Shen H, Shan C, Qiao Q, Liu J, Li B, Shen DZ: Stable surface plasmon enhanced ZnO homojunction light-emitting devices. J Mater Chem C 2013, 1: 234–237. 10.1039/c2tc00154cView ArticleGoogle Scholar
- Liu M, Chen R, Adamo G, Macdonald KF, Sie EJ, Sum TC, Zheludev NI, Sun H, Fan HJ: Tuning the influence of metal nanoparticles on ZnO photoluminescence by atomic-layer-deposited dielectric spacer. Nanoplasmonics 2013, 2: 153–160.Google Scholar
- Liu W, Xu HY, Wang CL, Zhang LX, Zhang C, Sun SY, Ma JG, Zhang XT, Wang JN, Liu YC: Selective enhancement of ZnO ultraviolet electroluminescence and improved spatial uniformity of output-light intensity in Ag-nanoparticles-decorated ZnO nanorod array heterojunction light-emitting diodes. Nanoscale 2013, 5: 8634–8639. 10.1039/c3nr02844eView ArticleGoogle Scholar
- Cheng CW, Sie EJ, Liu B, Huan CHA, Sum TC, Sun HD, Fan HJ: Surface plasmon enhanced band edge luminescence of ZnO nanorods by capping Au nanoparticles. Appl Phys Lett 2010, 96: 071107. 10.1063/1.3323091View ArticleGoogle Scholar
- Fang YJ, Sha J, Wang ZL, Wan YT, Xia WW, Wang YW: Behind the change of the photoluminescence property of metal-coated ZnO nanowire arrays. Appl Phys Lett 2011, 98: 033103. 10.1063/1.3543902View ArticleGoogle Scholar
- Kuladeep R, Jyothi L, Shadak Alee K, Deepak KLN, Narayana Rao D: Laser-assisted synthesis of Au-Ag alloy nanoparticles with tunable surface plasmon resonance frequency. Opt Mater Express 2012, 2: 161–172. 10.1364/OME.2.000161View ArticleGoogle Scholar
- Peng Z, Spliethoff B, Tesche B, Walther T, Kleinermanns K: Laser-assisted synthesis of Au-Ag alloy nanoparticles in solution. J Phys Chem B 2006, 110: 2549–2554. 10.1021/jp056677wView ArticleGoogle Scholar
- Davidson ER, Fain SC: Alloy work functions: Extended Hückel calculations for Ag–Au and Cu–Au clusters. J Vac Sci Technol 1976, 13(2):209–213.View ArticleGoogle Scholar
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