Student Project Abstracts 2005 - Pluto - University of Washington

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SYNTHESIS AND ANALYSIS OF THIOL-STABILIZED NANOPARTICLES(a)(b)Figure 2. Absorption spectra of silver nanoparticles in polystyrene thin films. The particles were coated with octanethiol to dodecanethiol ratios of (a) 1:1 and (b) 3:1Nanocomposite FilmsThe silver nanoparticles were dissolved in a polystyrenematrix and made into thin films to study their optical properties.The first method used to make these films was spin coating. Thenanoparticles and polystyrene were first dissolved in a solventsuch as toluene and placed in a small vial. A small amount ofsolution was then drawn from the vial with a syringe. A glasssubstrate was placed onto the spin coater and the solution wasfiltered and dispensed onto the substrate evenly. The substratewas allowed to spin for two minutes at 1000 rpm. UV-vis absorptionspectra were measured for these films with varying ligandratios and nanoparticle concentrations. Films made in thismanner, however, were too thin to be used for x-ray diffractionstudies, so a different method, (solvent-evaporation method), wasemployed. The glass substrates also had to be modified with anadhesion promoter to keep the polymer from peeling off of theglass slides.Three drops of the adhesion promoter solution were put ontothe slide and the slide was then rotated at 3000 rpm for 3 secondson the spin coater. The slide was then heated at 90°C on ahot plate for 30 seconds. This process was repeated 3 times. Initially,to make the nanocomposite films, a microscope slide wascovered with the nanoparticle/polymer solution and placed in anevaporation chamber overnight to allow the solvent to slowlyevaporate. The films obtained were thick enough for x-ray diffractionmeasurements, but the particles were not very well dispersedthroughout the film. This was likely due to the particlesaggregating overnight as the solvent evaporated.To try and prevent the aggregation of particles the solutionswere filtered in the same way but the films were prepared at ahigher temperature. The temperature had to be lower than theboiling point of the solvent to keep the film from bubbling, soa solvent with a high boiling point was used (dichlorobenzene).The modified slides were placed on a hot plate and first heatedto 120°C. The nanocomposite solution was then filtered onto theslides and allowed to sit for 1 hour.RESULTSAbsorption spectra were obtained for the nanocompositefilms made by spin coating (Fig. 2). The nanoparticles were synthesizedwith octanethiol to dodecanethiol ligand ratios of 1:1 and3:1. The concentration of nanoparticles for each successive filmin each graph was decreased by one-half. The absorption spectrafor the 1:1 films exhibit a shoulder at about 400 nm, which as ofnow cannot be fully explained. The absorption peaks of the 1:1films are narrower than those of the 3:1 films, which may correlatewith a change in the shape and distribution of silver nanoparticleswithin the polymer matrix. A blue shift in the position of theplasmon resonance band is observed when the concentration ofnanoparticles in the film decreases.58 CMDITR Review of Undergraduate Research Vol. 2 No. 1 Summer 2005
CONCLUSIONSChanging the thiol ligands bonded to the silver nanoparticleshas shown to alter the optical properties of the nanocomposites.This is likely due to the fact that different ligands or differentligand ratios in the case of mixed coatings, can affect the interactionbetween nanoparticles or between the nanoparticles and thepolymer, and the arrangement in the solid matrices. For weakbinding, as the concentration of nanoparticles decreases, thespace between individual particles increases, and the interactionsbetween them could become weaker. More studies are needed todetermine why this causes a blue shift in the absorption peaks.FUTURE WORKIn the future, properties of chromophore thiol-coated metalnanoparticles will be investigated to determine how differentligands affect nonlinear optical properties of the nanoparticlechromophoresystem. By using solvent evaporation methods, thefilms can be made with a thickness that is sufficient for use inx-ray diffraction studies. X-ray diffraction will be used to furtherstudy the spatial arrangements of the silver nanoparticles in polymermatrices.ACKNOWLEDGEMENTSDr. Joe Perry, Faculty Advisor, Georgia Institute of TechnologyWojtek Haske, Graduate Student, Georgia Institute of TechnologyPerry Group, Georgia Institute of TechnologyDr. Carl Bonner, Faculty Advisor, Norfolk State UniversityCenter for Materials Research, Norfolk State UniversityREFERENCES1. Stellacci, F.; et al. J. Am. Chem. Soc. 2003, 125, 328HOWELLCMDITR Review of Undergraduate Research Vol. 2 No. 1 Summer 2005 59
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TABLE OF CONTENTSSynthesis of Dendr
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Page 8 and 9: SYNTHESIS OF DENDRIMER BUILDING BLO
Page 10 and 11: throughout the work period. Five su
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Page 14 and 15: BARIUM TITANATE DOPED SOL-GEL FOR E
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Page 18 and 19: SYNTHESIS OF NORBORNENE MONOMER OF
Page 20: 20 CMDITR Review of Undergraduate R
Page 23 and 24: using different reaction conditions
Page 25 and 26: Synthesis of Nonlinear Optical-Acti
Page 27 and 28: quality of the XRD structures wasca
Page 29 and 30: Behavioral Properties of Colloidal
Page 32 and 33: Transmission electron microscopy ha
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Page 38 and 39: Fabry-Perot modulators with electro
Page 42 and 43: QUANTIZED HAMILTON DYNAMICS APPLIED
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Page 48 and 49: Dr. Robert NorwoodChris DeRoseAmir
Page 50 and 51: SYNTHESIS OF TPD-BASED COMPOUNDS FO
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Page 54 and 55: OPTIMIZING HYBRID WAVEGUIDESpropaga
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Page 62 and 63: QUINOXALINE-CONTAINING POLYFLUORENE
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Page 68 and 69: SYNTHESIS OF DENDRON-FUNCTIONALIZED
Page 72 and 73: BUILDING AN OPTICAL OXIMETER TO MEA
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Page 88 and 89: 1,1-DIPHENYL-2,3,4,5-TETRAKIS(9,9-D
Page 90 and 91: EFFECTS OF SURFACE CHEMISTRY ON CAD
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Page 96 and 97: SYNTHESIS OF A POLYENE EO CHROMOPHO
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OPTIMIZATION OF SEMICONDUCTOR NANOP
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OPTIMIZATION OF SEMICONDUCTOR NANOP
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CHARACTERIZATION OF THE PHOTODECOMP
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ELECTROLUMINESCENT PROPERTIES OF OR
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DETERMINATION OF MOLECULAR ORIENTAT
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DETERMINATION OF MOLECULAR ORIENTAT
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HYDROGEL MATERIALS FOR TWO-PHOTON M
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HYDROGEL MATERIALS FOR TWO-PHOTON M
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THE DESIGN OF A FLUID DELIVERY SYST
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THE DESIGN OF A FLUID DELIVERY SYST
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Student Project Abstracts 2005 - Pluto - University of Washington

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