BEGIN:VCALENDAR VERSION:2.0 X-WR-CALNAME:EventsCalendar PRODID:-//hacksw/handcal//NONSGML v1.0//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:America/New_York LAST-MODIFIED:20240422T053451Z TZURL:https://www.tzurl.org/zoneinfo-outlook/America/New_York X-LIC-LOCATION:America/New_York BEGIN:DAYLIGHT TZNAME:EDT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 DTSTART:19700308T020000 RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU END:DAYLIGHT BEGIN:STANDARD TZNAME:EST TZOFFSETFROM:-0400 TZOFFSETTO:-0500 DTSTART:19701101T020000 RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU END:STANDARD END:VTIMEZONE BEGIN:VEVENT CATEGORIES:College of Arts and Sciences,College of Engineering,Thesis/Disse rtations DESCRIPTION:Abstract:      Chirality plays a fundamental role in biologi cal and chemical systems, and the ability to detect and characterize chira l signals at the nanoscale is of considerable importance for applications ranging from biosensing to enantioselective catalysis. Plasmonic nanostruc tures can strongly enhance chiroptical responses, and these responses depe nd on the geometry, orientation, and coupling between individual particles . Current measurement methods have important limitations in resolving this response. Ensemble circular dichroism (CD) spectroscopy averages the resp onse over many structures, which can hide variations within a sample. Sing le-particle measurements can resolve differences between individual partic les, but they generally treat each particle as a single object and do not provide spatial information within extended structures. This becomes parti cularly challenging for periodic nanostructure arrays and self-assembled s ystems, where the structures can appear as continuous features under a mic roscope and may contain significant local variations in geometry and optic al response. This dissertation addresses this limitation by developing a d ark-field hyperspectral circular differential scattering (CDS) mapping tec hnique that measures chiroptical response with both spatial and spectral r esolution. The first aim develops and validates the instrument itself, usi ng achiral gold nanorods and nanorod dimers spanning a range of inter-part icle separations to confirm that spatial CDS mapping recovers results cons istent with single-particle measurements. The second aim applies the platf orm to periodic helicoid nanoparticle arrays to investigate spatial variat ions in chiroptical response associated with different optical modes, incl uding localized plasmon resonances and collective surface lattice resonanc es. The third aim extends the method to self-assembled gold nanorod-fibril structures, where variations in nanorod packing and orientation arise fro m the assembly process. Spatially resolved CDS measurements will be used t o relate local structure to the resulting chiroptical response. Together, these studies will establish a method for spatially and spectrally resolve d characterization of chiroptical response in complex plasmonic and nanoph otonic systems. The resulting measurements will allow the relationship bet ween local structure, plasmonic coupling, and chiroptical response to be e xamined in systems that are difficult to characterize using conventional e nsemble or single-particle measurements. ADVISOR(s):  Dr. Wei-Shun Chang, Department of Chemistry and Biochemistry (wchang2@umassd.edu) COMMITTEE M EMBERS: Dr. Jongping Hsu, Department of Physics Dr. Maricris L. Mayes, De partment of Chemistry and Biochemistry Dr. Shuowei Cai, Department of Chem istry and Biochemistry NOTE: All EAS Students are ENCOURAGED to attend.\n Event page: https://www.umassd.edu/events/cms/9-10-26-eas-doctoral-proposa l-defense-by-misbah-ul-ain.php X-ALT-DESC;FMTTYPE=text/html:

Abstract:     

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Chira lity plays a fundamental role in biological and chemical systems\, and the ability to detect and characterize chiral signals at the nanoscale is of considerable importance for applications ranging from biosensing to enanti oselective catalysis. Plasmonic nanostructures can strongly enhance chirop tical responses\, and these responses depend on the geometry\, orientation \, and coupling between individual particles. Current measurement methods have important limitations in resolving this response. Ensemble circular d ichroism (CD) spectroscopy averages the response over many structures\, wh ich can hide variations within a sample. Single-particle measurements can resolve differences between individual particles\, but they generally trea t each particle as a single object and do not provide spatial information within extended structures. This becomes particularly challenging for peri odic nanostructure arrays and self-assembled systems\, where the structure s can appear as continuous features under a microscope and may contain sig nificant local variations in geometry and optical response. This dissertat ion addresses this limitation by developing a dark-field hyperspectral cir cular differential scattering (CDS) mapping technique that measures chirop tical response with both spatial and spectral resolution. The first aim de velops and validates the instrument itself\, using achiral gold nanorods a nd nanorod dimers spanning a range of inter-particle separations to confir m that spatial CDS mapping recovers results consistent with single-particl e measurements. The second aim applies the platform to periodic helicoid n anoparticle arrays to investigate spatial variations in chiroptical respon se associated with different optical modes\, including localized plasmon r esonances and collective surface lattice resonances. The third aim extends the method to self-assembled gold nanorod-fibril structures\, where varia tions in nanorod packing and orientation arise from the assembly process. Spatially resolved CDS measurements will be used to relate local structure to the resulting chiroptical response. Together\, these studies will esta blish a method for spatially and spectrally resolved characterization of c hiroptical response in complex plasmonic and nanophotonic systems. The res ulting measurements will allow the relationship between local structure\, plasmonic coupling\, and chiroptical response to be examined in systems th at are difficult to characterize using conventional ensemble or single-par ticle measurements.

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ADVISOR(s):  Dr. Wei-Shun Chang\, Department of Chemistry and Biochemistry (wchang2@umassd.edu)

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COMMITTEE MEMBE RS:

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NO TE: All EAS Students are ENCOURAGED to attend.

Event page: https://www.umassd.edu/events/cms/9-10-26-eas-doctoral -proposal-defense-by-misbah-ul-ain.php

DTSTAMP:20260828T235246 DTSTART;TZID=America/New_York:20260910T100000 DTEND;TZID=America/New_York:20260910T120000 LOCATION:SENG 106 SUMMARY;LANGUAGE=en-us:EAS Doctoral Proposal Defense by Misbah ul Ain UID:0857831e187cdc79bbb32c8b3b63cb4d@www.umassd.edu END:VEVENT END:VCALENDAR