Student Project Abstracts 2005 - Pluto - University of Washington

Behavioral Properties of Colloidal Crystals at andAround Thermally Induced Defect SitesMallory DavidsonUniversity of WashingtonAshlee St. John and Dr. L. Andrew LyonLyon Lab, School of Chemistry and BiochemistryGeorgia Institute of TechnologySoft sphere interactions are described for PNIPAm (Poly-N-isopropylAcrylamide) microgel particle assemblies doped with gold nanoparticles as a laser hits a small region of thecrystal. The gold nanoparticles will act as a local heater excited by the laser and will introducea defect into the assembly. The thermoresponsivity of the microgel particles willbe utilized to study the behavioral properties the system. Observation of the assembly as itmelts to form a defect at a particular spot and how the microgel particles will reorder themselvesafter the deswell heat is removed as will be analyzed. Spectrophotometry This will be done for a more fundamental was run tosystem. The particlesthe temperature knowledge increases of colloidal crystals to the with soft sphere determine interactions. In addition, how it many will provide gold alower critical solution better understanding temperatureof the kinetics and thermodynamics nanoparticles of the crystallization were process. needed in theof the polymer; allowing the system assemblies. Enough goldto act more asINTRODUCTIONa fluid. 2nanoparticles were needed toRESULTS AND DISCUSSIONSabsorb photons from the laser, butExperimentThere is a lot of known information on hard sphere interactionswith crystal assemblies, but not a lot about soft sphere in-Gold not Incorporation too many nanoparticles so thatAssemblies of PNIPAm (Poly-NisopropylAcrylamide)microgelsIn order to induce a defect the crystal assemblies needed tothere were no perturbed phaseteraction systems. 1 Colloidal crystals with soft interactions will be be doped with gold nanoparticles. UV VIS Spectrophotometryresearched for fundamental understanding of the kinetics and thermodynamicsbehaviors. At the first noticeablewas run to determine how many gold nanoparticles were neededdoped withof thegoldcrystallizationnanoparticlesprocess. With thewillinformation inpeakthe assemblies.of 520nmEnough gold(thisnanoparticlesis wherewere neededgoldto absorbparticles photons from of the this laser, but size not too absorb) many nanoparticles from sohave provided a through defect this research induced the knowledge by gained can be appliedfor later scientific a frequency applications of optic doubled and sensing Nd: devices. that the there UV were VIS no perturbed read phase out behaviors. determined At the first notice-positioningYAG Namely (Yttrium thermoresponsivity Aluminum of the particles Garnet, will be utilized to study able how peak much of 520nm gold (this is was where put gold particles into of the this size absorb)sample. from the UV It was VIS read found out determined to be how 500L. much gold wasthe =532nm) behavioral properties laser of at the system. a small The particles section deswell as theoftemperaturethe crystal.increases to theAslowerthecriticallasersolutionhitstemperatureaof put See into the figure sample. 1. It was found to be 500μL. See figure 1.the polymer; allowing the system to act more as a fluid.section of the crystalline the gold2nanoparticles will absorb theEXPERIMENT1.6photons from the laser because ofAssembliesUV Vis graphs ofof6.8PNIPAmweight percent of particles(Poly-N-isopropylAcrylamide) microgelsdoped with gold nanoparticles will have a defect inducedParticles with no1.4their high extinction coefficient.The 1.6 energy gained will Particles be without released1.2gold nanoparticlesby positioning a frequency doubled Nd: YAG (Yttrium AluminumGarnet, λ=532nm) laser at a small section of the crystal.in the1.4form of heat. gold This released11.2Particles withParticles with 200heat As the will laser hits warm a section up of the crystalline crystal, the gold and300MicroL of gold1MicroL of Goldnanoparticles0.8can will absorb observe the photons what from the happens laser because of to0.8nanoparticlesoneParticles with 300their highParticles with0.60.6that extinction part coefficient. of the The energy crystal MicroL gained of Gold as will the be released in the500MicroL of gold0.4nanoparticlesdefect form of heat. is This induced. released heat Also will warm one up the can crystal, and one0.40.2Particles with 400observe can 0 what the happens crystal to that MicroLas part of Gold of it the cools crystal as the defect0.2downis induced. 300 400afterAlso 500 one 600 700thecan 800 observe 900laserthe Particlesiscrystal with 500removedas it cools downtoafterMicroL of Gold0the laser is removed Wavelength (nm) to see how the defect reorders a crystal.350 450 550 650 750 850see how the defect reorders into aDifferential interference contrast microscopy was used toWavelength (nmcrystal.look at the microgel particles. Afterwards the images attainedwere analyzed using IDL software. IDL was used to obtain particletrajectories of interference the images. contrastFigure 1. 1. Determination Determination of the amount of gold of nanoparticles theDifferentialamountneeded to dope the crystalline assemblies.microscopy was used to look at theof CMDITR gold Review nanoparticles of Undergraduate Research needed Vol. 2 No. 1 Summer to 2005 29microgel particles. Afterwards thedope the crystalline assemblies.images attained were analyzedAbsorbanceAbsorbance