Abstract Heat transport through nanomaterials such as quantum dots (QDs) is essential for engineering their use in applications such as LEDs and TVs. Vibrational spectroscopy techniques such as Raman spectroscopy can be used to study heat transport in these materials; however, the Raman scattering process is very weak, which limits the signal. One way to solve this issue is to enhance the Raman scattering by the use silver nanoparticles resonant at Raman laser wavelength, through a process called Surface Enhanced Raman Spectroscopy (SERS). In this work, different methods for silver nanoparticles synthesis were explored, and the resulting nanoparticles were used for SERS with crystal violet as a test analyte. As a result, the Raman signal was enhanced significantly, by at least a factor of 90. For future work, we want to extend the use of the Ag NPs for SERS with QDs to study heat transport in these materials. Background Acknowledgements We thank the MIT MSRP program for funding this research. Conclusion References Motivation Future work Methods and Results Synthesis of Silver Nanoparticles with Plasmonic Resonance at 785 nm Thibault Joseph Twahirwa 1 , Jolene Mork 2 , William A. Tisdale 2 1 Department of Physics & Dual-Degree Engineerings, Morehouse College 2 Department of Chemical Engineering, Massachusetts Institute of Technology Why nanoparticles? They have unique optical properties Localized Surface Plasmon resonance ( LSPR) Why silver nanoparticles? Silver has the highest quality factor ( the surface plasmon strength) across the spectrum from 300 to 1200 nm. Silver also exhibits the highest thermal and electrical conductivity of all metals. Silver is relatively cheap Continue SERS optimization to achieve specific sizes and shapes Use Ag NPs to enhance Raman scattering from QDs Reproducible synthesis of silver nanoparticles with defined size. Synthesis of silver nanoparticles of define shapes. Use synthesized Silver nanoparticles to enhance Raman signals( SERS). • Successfully synthesized Ag NPs of different sizes • Achieved triangular (prism) shapes • Best method for synthesis was the no light exposure method by Aherne, et al. • Demonstrated successful surface enhancement of Raman signal 300 400 500 600 700 800 0 0.2 0.4 0.6 0.8 1 5 hours 72 hours 96 hours Wavelength ( nm) Normalized Absorption ( AU) 300 400 500 600 700 800 900 1000 0 0.2 0.4 0.6 0.8 1 24 hours 5 hours 100 hours 124 hours 148 hours Wavelength( nm) Normalized Absorption( AU) -800 -600 -400 -200 0 200 400 600 800 1000 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 Crystal violet Crystal violet + AgNPs( Sphere s) Wavenumber Intensity Synthesis using Silver Nitrate (AgNO 3 ) 1 Reagents • Na 3 C 6 H 5 O 7 (0.3mM) • AgNO 3 (100ml of 0.1mM) • NaBH 4 (1ml of 50mM) • PSSS (Polysodium styrenesulphonate) 5mM/2ml Conditions:light exposure 70hours Synthesis without light exposure 3 Reagents • Na 3 C 6 H 5 O 7 5ml of 2.5mM • AgNO 3 5ml of 0.5mM • NaBH 4 0.3ml of 10mM • PSSS 2.5mM/5ml • Ascorbic Acid 75μl/10mM Synthesis using Silver perchlorate (AgClO 4 ) 2 Reagents • AgClO 4 (1ml/0.01M) at 0 °C • 99 mL of an ice cold solution of 1 mM NaBH 4 and 0.30 mM Na 3 C 6 H 5 O 7 water. • Conditions : light exposure 100hours 1. “Photoinduced Conversion of silver Nanopheres to Nanoprisms” Jin, et al. (Science) 2001. 2. “Optical Properties and Growth Aspects of Silver Nanoprisms Produced by a Highly Reproducible and Rapid Synthesis at Room Temperature. ” Domian Aherne et al. (Advanced functional Materials) 2008. 3. “Spectral Control of Plasmonic Emission Enhancement from Quantum Dots near Single Silver Nanoprisms.” Keiko Munechika et al, 98195-1700.Nano Lett., 2010, 10 (7), pp 2598–2603. 4. “Localized Surface Plasmon Resonance Spectroscopy and Sensing.” Willets and Van Duyne. 300 400 500 600 700 800 900 0 0.2 0.4 0.6 0.8 1 seed 650 μl 500 μl 400μl 120 μl 90 μl 20 μl Wavelength (nm) Normalized Absorption (AU) SERS (Surface-enhanced Raman spectroscopy) A. B. C. UV-Vis spectrum (A) shows little change with illumination time. TEM images (C) show only spherical nanoparticles even after 96 hours. Samples illuminated for 96 hrs. with fluorescent light T = 72 hrs A. B. Seed solutions ( L) and Illuminated solution(R) with fluorescent light UV-Vis spectrum (A) demonstrates changes with illumination time. TEM images (C) show triangle nanoparticles are formed. C. A. B. C. D. E. Silver Nanoparticle synthesis SERS sample preparation Figure – A surface plasmon is characterized as a surface charge density wave at a metal surface. 4 UV-Vis spectrum (A) shows changes with different amount of seeds solution. Set up (B) was used to control the silver amount injected into a seed solution. Image (C) shows color shift as the seed amount decrease. TEM images (D) and (E) show silver nanoprisms synthesized using this method. Crystal violet molecule Raman Signal was enhanced by the factor of >90 using silver nanoprism. T = 148hrs C.