?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fd-scholarship-dev.library.pitt.edu%2F36998%2F&rft.title=Peptide-Based+Molecular+Transformations+for+Tuning+the+Structure+and+Properties+of+Chiral+Gold+Nanoparticle+Single+Helices&rft.creator=Punekar%2C+Soumitra+Mokashi&rft.description=Helical+gold+nanoparticle+(AuNP)+superstructures+have+generated+tremendous+research+interest+due+to+wide-ranging+applications+in+metamaterial+optics%2C+chiral+sensing%2C+detection%2C+and+several+other+fields.+These+optical+materials+consist+of+plasmonic+AuNPs+arranged+in+a+helical+topology%2C+giving+rise+to+unique+chiroptical+properties+that+depend+on+the+structural+parameters+of+the+helix.+This+dissertation+describes+advances+in+systematically+modulating+the+structural+features+and+consequently+adjusting+the+chiroptical+properties+of+single-helical+AuNP+superstructures.+The+modifications+to+the+single-helical+nanoscale+architecture+are+achieved+via+small+molecular+transformations+within+a+gold-binding+peptide+assembly+agent%2C+and+in+one+case%2C+addition+of+external+additives.%0D%0ASpecifically%2C+in+Chapter+2%2C+I+present+a+rational+strategy+to+adjust+the+helical+pitch+of+AuNP+single+helices+by+tuning+the+aliphatic+tail+length+within+a+family+of+peptide+conjugate+molecules.+I+demonstrate+that+the+helical+pitch+increases+and+the+chiroptical+signal+intensity+decreases+with+an+increase+in+aliphatic+tail+length.+In+Chapter+3%2C+I+focus+on+the+N-terminus+amino+acid+segment+within+the+peptide+sequence+as+means+of+further+adjusting+assembly+metrics+and+helical+pitch+length.+Via+a+single+amino+acid+mutation+within+a+class+of+peptide+conjugates%2C+I+achieve+an+overall+decrease+in+the+average+helical+pitch+of+single-helical+superstructures.+Chapter+4+describes+the+adjustment+of+particle+size+within+single-helical+superstructures+by+tuning+peptide-NP+interaction+via+C-terminus+peptide+sequence+modification.+Key+amino+acid-NP+interactions+are+identified%2C+via+theoretical+simulations%2C+that+ultimately+affect+the+size+of+component+particles+within+helical+superstructures.+These+molecular+alterations+yield+single+helices+comprising+larger+particles+that+exhibit+intense+chiroptical+signal.+Finally%2C+in+Chapter+5%2C+I+screen+a+series+of+cetyltrimethylammonium+bromide+(CTAB)+analogs+to+control+the+shape+of+constituent+particles+within+helical+superstructures.+I+outline+selection+criteria+(CTAB+tail+length+and+concentration)+necessary+for+the+deliberate+conversion+of+small+particles+within+the+single-helical+superstructures+to+anisotropic+(prisms+and+polygonal)+particles.%0D%0AOverall%2C+the+advances+presented+in+this+dissertation+highlight+multiple+levels+of+control+over+the+nanoscale+architecture+and+properties+of+one+particular+type+of+chiral+superstructures.+This+is+a+significant+step+in+constructing+designed+chiral+NP+assemblies+which+are+essential+for+serving+myriad+potential+applications.&rft.date=2019-09-25&rft.type=University+of+Pittsburgh+ETD&rft.type=PeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=http%3A%2F%2Fd-scholarship-dev.library.pitt.edu%2F36998%2F1%2FPunekar_ETD_Pitt2019.pdf&rft.identifier=++Punekar%2C+Soumitra+Mokashi++(2019)+Peptide-Based+Molecular+Transformations+for+Tuning+the+Structure+and+Properties+of+Chiral+Gold+Nanoparticle+Single+Helices.++Doctoral+Dissertation%2C+University+of+Pittsburgh.++++(Unpublished)++