Photonic crystals in biology - NanoTR-VI

P M.P andP M,Poster Session, Thursday, June 17Theme F686 - N11233D Silver Plasmonic Structure for Surface Enhanced Raman Scattering11Mehmet KahramanPUMustafa ÇulhaUP P*Genetics and Bioengineering Department, Faculty of Engineering and Architecture,Yeditepe University, Kayisdagi, Istanbul, TurkeyAbstract- The construction of highly reproducible and enhancing novel SERS substrate is achieved by controlling the inter-particle distance andaggregate size. In order to control aggregation size and number of nanoparticle in one aggregate, micro-well are prepared with the softlithography. In this method, first, the diluted latex microsphere (1.6 μm) are spread as a thin film using “convective assembly” method on aglass slide, then, polydimethylsiloxane (PDMS) is prepared on the latex thin film. Finally, the PDMS film is removed and latex particles arewashed with an organic solvent. The PDMS stamp with micro-wells is filled with concentrated AgNPs coated with CTAB for further analysisusing SERS. SEM and AFM were used for the characterization of the prepared surfaces. Rhodamine 6G is used as a probe molecule to7-9characterize the substrate. The enhancement factor and limit of the detection of the prepared substrates are found to be 3.7x10P Pand 1.0x10Prespectively.Nanosize metal particles and semiconductors have uniqueoptical, magnetic and electronic properties that do not have intheir bulk form. These properties have been used for manyapplications of science and technology such as; nanoscalechemical sensors, data storage, quantum dots lasers,electronics and SERS substrates [1-4]. The size, shape andtype of the noble metal and aggregate properties ofnanoparticles and inter-particle distance are the criticalparameters influencing SERS activity [5-8] due to theirinfluence on surface plasmons (SPs) that are responsible forthe major enhancement (electromagnetic enhancement)[9] inSERS mechanism. The inter-particle distance stronglyinfluences the enhancement factor and it was reported that theinter-particle distance must be 2-4 nm for the optimal SERSenhancement [10]. Although there is an effort to uselithographic methods to control inter-particle distance, thesemethods generally time consuming, expensive and needskilled personnel.In this study, 3D silver plasmonic structures were preparedwith the concentrated silver nanoparticles. First, thin film(Figure 1 A) of the latex was prepared using “convectiveassembly” method [11]. The experimental parameters such asconcentration of latex spheres, moving stage velocity anddropped volume were studied. Second, PDMS was preparedon the latex thin film by baking at 70 °C for 1 hour. Figure 1 Bshows SEM image of the micro-wells prepared with the 1.6m latex sphere on PDMS. As is seen, the size of the microwellsis slightly smaller (1.4 m) than the size of the latexnanoparticles. This is possibly due to the high viscosity of thepolymer mixture in which latex nanoparticles are completelyburied. Therefore, the size of prepared micro-wells decreasesabout 200 nm. Finally, micro-wells were filled using“convective assembly” method with the concentrated silvernanoparticles containing CTAB, which was used to increase ofthe hydrophobic property of the silver nanoparticles andcontrol inter-particle distance in the aggregates (Figure 1C).The enhancement factor was calculated using IRSERSR/IRBulkR x7CRBulkR/CRSERS Rformula and found as 3.0x10P P. This enhancementfactor is also consistent with 2-4 nm inter-particle distances[12]. The reproducibility of the prepared substrate was testedusing the peak height, area and intensity of the ten peaks at-11512 cmPP. The percent coefficient variance (CV) was foundto be about 10. Limit of the detection (LOD) of the substrate-9was 1.0x10PACFigure 1. A) SEM image of the prepared thin film of the 1600 nmlatex sphere, B) micro-wells of 1600 nm latex sphere, C) micro-wellsfilled with silver nanoparticles.In conclusion we demonstrate that novel SERS substratespossessing high sensitivity, enhancement factor andreproducibility by the controlling of the inter-particle distanceand aggregate size.This work was supported by TÜBTAK and YeditepeUniversity.*Corresponding author: HTmculha@yeditepe.edu.trT[1] A. P. Alivisatos, Science 271, 933 (1996).[2] L. E. Brus, Appl. Phys. A, 53, 465 (1991).[3] Y. Wang and N. Herron, J. Phys. Chem. 95, 525 (1991).[4] P. C. Lee and D. Meisel, J. Phys. Chem. 86, 3391 (1982).[5] S. R. Emory, W. E. Haskins, and S. Nie, J. Am. Chem. Soc. 120,8009. (1998).[6] T. Jensen, L. Kelly, A. Lazarides, and G. C. Schatz, Journal ofCluster Science 10, 295 (1999).[7] E. J. Zeman, and G. C. Schatz, J. Phys. Chem. 91, 634 (1987).[8] J. Jiang, K. Bosnick, M. Maillard, and L. Brus, J. Phys. Chem. B107, 9964 (2003).[9] M. Moskovits, Rev. Mod. Phys. 57, 783 (1985).[10] A. M. Schwartzberg, C. D. Grant, A. Wolcott, C. E. Talley, T. R.Huser, R. Bogomolni, and J. Z. Zhang, J. Phys. Chem. B 108, 19191(2004).[11] P. M. Tessier, O. D. Velev, A. T. Kalambur, J. F. Rabolt, A. M.Lenhoff, and E. W. Kaler, J. Am. Chem. Soc. 122, 9554 (2000).[12] J. Jiang, K. Bosnick, M. Maillard, and L. Brus, J. Phys. Chem. B107, 9964 (2003).B6th Nanoscience and Nanotechnology Conference, zmir, 2010 646