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Mechanical and Opto-mechanical Prope...

Raja, Shilpa Naresh.

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Mechanical and Opto-mechanical Properties of Branched Semiconductor Nanocrystal Stress Sensors.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Mechanical and Opto-mechanical Properties of Branched Semiconductor Nanocrystal Stress Sensors./
Author:	Raja, Shilpa Naresh.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2016,
Description:	67 p.
Notes:	Source: Dissertation Abstracts International, Volume: 78-07(E), Section: B.
Contained By:	Dissertation Abstracts International78-07B(E).
Subject:	Materials science. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10191688
ISBN:	9781369558593

Mechanical and Opto-mechanical Properties of Branched Semiconductor Nanocrystal Stress Sensors.
Raja, Shilpa Naresh.

Mechanical and Opto-mechanical Properties of Branched Semiconductor Nanocrystal Stress Sensors. - Ann Arbor : ProQuest Dissertations & Theses, 2016 - 67 p.

Source: Dissertation Abstracts International, Volume: 78-07(E), Section: B.

Thesis (Ph.D.)--University of California, Berkeley, 2016.

This dissertation highlights advances in using semiconductor tetrapod quantum dots (tQDs) as stress sensors in structural polymer nanocomposites. Semiconductor nanocrystals have undergone many developments in terms of synthetic control of shape and size since their inception, and one example is the ability to create branched nanocrystals such as tQDs. tQDs are core/shell tetrahedrally symmetric, branched nanocrystals. In this thesis, studies will utilize tQDs consisting of a ~4 nm cadmium selenide (CdSe) core and ~25 nm long cadmium sulfide (CdS) arms. Their type I band alignment and the modulus difference between their core and shell, along with their branching, makes them sensitive to applied mechanical environmental stresses. The CdS arms receive stress from a host matrix in which the tQDs are embedded and transmit it to the CdSe core. The tQD's photoluminescence emission spectral maximum undergoes a monotonic red-shift, or decrease in energy, with increasing tensile stress, due to widening bond distances in the core. The tQD's property of nanoscale stress-sensing is of relevance to fields such as polymer dynamics, sensing of premature fracture in service, and biomechanical stress sensing.

ISBN: 9781369558593Subjects--Topical Terms:

543314
Materials science.

Mechanical and Opto-mechanical Properties of Branched Semiconductor Nanocrystal Stress Sensors.
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100 1 $a Raja, Shilpa Naresh. $3 3284507
245 1 0 $a Mechanical and Opto-mechanical Properties of Branched Semiconductor Nanocrystal Stress Sensors.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2016
300 $a 67 p.
500 $a Source: Dissertation Abstracts International, Volume: 78-07(E), Section: B.
500 $a Adviser: Armand Paul Alivisatos.
502 $a Thesis (Ph.D.)--University of California, Berkeley, 2016.
520 $a This dissertation highlights advances in using semiconductor tetrapod quantum dots (tQDs) as stress sensors in structural polymer nanocomposites. Semiconductor nanocrystals have undergone many developments in terms of synthetic control of shape and size since their inception, and one example is the ability to create branched nanocrystals such as tQDs. tQDs are core/shell tetrahedrally symmetric, branched nanocrystals. In this thesis, studies will utilize tQDs consisting of a ~4 nm cadmium selenide (CdSe) core and ~25 nm long cadmium sulfide (CdS) arms. Their type I band alignment and the modulus difference between their core and shell, along with their branching, makes them sensitive to applied mechanical environmental stresses. The CdS arms receive stress from a host matrix in which the tQDs are embedded and transmit it to the CdSe core. The tQD's photoluminescence emission spectral maximum undergoes a monotonic red-shift, or decrease in energy, with increasing tensile stress, due to widening bond distances in the core. The tQD's property of nanoscale stress-sensing is of relevance to fields such as polymer dynamics, sensing of premature fracture in service, and biomechanical stress sensing.
520 $a We have fabricated and characterized the structure and opto-mechanical sensing ability of a wide variety of tQD-polymer nanocomposites. We demonstrate tQD sensing of tension and compression as well as more complex stress responses, such as stress relaxation and hysteresis. We perform optical and mechanical tests simultaneously, discovering a new sensing modality, and orders of magnitude of stress amplification in the tQD core. We also discover tQD sensing of dispersion including a switch in optomechanical response characteristic when tQDs are in direct contact.
520 $a In addition to demonstrating and analyzing these new phenomena, we theoretically explore, with micromechanical finite element simulations and atomistic density functional theory, the origins of the tQD stress response. We further examine, experimentally and theoretically, the ability of tQDs to serve as mechanical fillers, finding that they have greater potential to improve the Young's modulus of structural polymers than linear nanorods and nano-spheres due to their branched shape. The results in this dissertation contribute to the understanding of the structural, mechanical, and optical sensing properties of nanocomposites of polymers and semiconductor tQD nanocrystals.
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650 4 $a Nanoscience. $3 587832
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773 0 $t Dissertation Abstracts International $g 78-07B(E).
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