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<b><span style="font-size:14.0pt; line-height:200%">PhD Dissertation Defense of Rishabh Jain</span></b></p>
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<b><span style="font-size:12.0pt; line-height:200%">DATE:</span></b><span style="font-size:12.0pt; line-height:200%"> December 6, 2021</span></p>
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<b><span style="font-size:12.0pt; line-height:200%">TIME:</span></b><span style="font-size:12.0pt; line-height:200%"> 12-2pm</span></p>
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<b><span style="font-size:12.0pt; line-height:200%">COMMITTEE CHAIR:</span></b><span style="font-size:12.0pt; line-height:200%"> Prof. Jeffrey Rimer</span></p>
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<b><span style="font-size:12.0pt">LOCATION:</span></b><span style="font-size:12.0pt">
<span style="color:black">Zoom link: </span></span></p>
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(<a href="https://urldefense.com/v3/__https:/uh-edu-cougarnet.zoom.us/j/93170501257?pwd=NWVNZDA4L0ZmWEVJZFRIRU53dUordz09__;!!LkSTlj0I!Sx9f70X5MpQpyxxeoIPU4jbB0jp8A2GhNumg5hjDLXNLOa3GuJxbkqzcps0D-BX8ykz50e4$" target="_blank"><span style="color:#1155CC">https://uh-edu-cougarnet.zoom.us/j/93170501257?pwd=NWVNZDA4L0ZmWEVJZFRIRU53dUordz09</span></a><span style="color:black"></span></p>
<p class="x_MsoTitle" style="margin: 4.05pt 0in 0.0001pt 42pt; font-size: 11pt; font-family: "Times New Roman", serif; font-weight: bold;margin-left:0in; text-align:justify">
<span style="font-size:12.0pt">TITLE: </span><span style="font-size:12.0pt; font-weight:normal">Developing<span style="letter-spacing:-.15pt">
</span>organic-free<span style="letter-spacing:-.15pt"> </span>crystallization<span style="letter-spacing:-.2pt">
</span>pathways<span style="letter-spacing:-.15pt"> </span>for<span style="letter-spacing:-.15pt">
</span>the<span style="letter-spacing:-.15pt"> </span>optimization<span style="letter-spacing:-.3pt">
</span>of<span style="letter-spacing:-.05pt"> </span>zeolite<span style="letter-spacing:-.15pt">
</span>catalysts</span><span style="font-size:12.0pt"></span></p>
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<b><span style="font-size:12.0pt"> </span></b></p>
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<b><span style="font-size:12.5pt"> </span></b></p>
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<span style="font-size:12.0pt">Zeolites are an essential class of crystalline porous materials with a wide range of applications. A<span style="letter-spacing:.05pt">
</span>core<span style="letter-spacing:.05pt"> </span>objective<span style="letter-spacing:.05pt">
</span>of<span style="letter-spacing:.05pt"> </span>optimizing<span style="letter-spacing:.05pt">
</span>zeolites<span style="letter-spacing:.05pt"> </span>is<span style="letter-spacing:.05pt">
</span>to<span style="letter-spacing:.05pt"> </span>produce<span style="letter-spacing:.05pt">
</span>materials<span style="letter-spacing:.05pt"> </span>with<span style="letter-spacing:.05pt">
</span>physicochemical<span style="letter-spacing:.05pt"> </span>properties<span style="letter-spacing:.05pt">
</span>and<span style="letter-spacing:.05pt"> </span>corresponding performances that exceed conventional counterparts. This places an impetus on elucidating<span style="letter-spacing:-2.6pt">
</span>and controlling processes of crystallization where one of the most critical design criteria is the ability to<span style="letter-spacing:.05pt">
</span>prepare zeolite crystals with ultrasmall dimensions to mitigate the deleterious effects of mass transport<span style="letter-spacing:.05pt">
</span><span style="letter-spacing:-.05pt">limitations.</span><span style="letter-spacing:-.65pt">
</span><span style="letter-spacing:-.05pt">Zeolite</span><span style="letter-spacing:-.55pt">
</span><span style="letter-spacing:-.05pt">crystallization</span><span style="letter-spacing:-.55pt">
</span>predominantly<span style="letter-spacing:-.55pt"> </span>occurs<span style="letter-spacing:-.55pt">
</span>by<span style="letter-spacing:-.55pt"> </span>nonclassical<span style="letter-spacing:-.65pt">
</span>pathways<span style="letter-spacing:-.7pt"> </span>involving<span style="letter-spacing:-.55pt">
</span>the<span style="letter-spacing:-.55pt"> </span>attachment<span style="letter-spacing:-2.6pt">
</span>of complex (alumino)silicate precursors to crystal surfaces, yet recurrent images of fully crystalline<span style="letter-spacing:.05pt">
</span>materials with layered surfaces comprised of nanometer-sized steps are evidence that growth also occurs<span style="letter-spacing:.05pt">
</span>by<span style="letter-spacing:-.35pt"> </span>a<span style="letter-spacing:-.4pt">
</span>classical<span style="letter-spacing:-.35pt"> </span>route<span style="letter-spacing:-.45pt">
</span>of<span style="letter-spacing:-.4pt"> </span>molecule<span style="letter-spacing:-.4pt">
</span>(monomer)<span style="letter-spacing:-.45pt"> </span>attachment.<span style="letter-spacing:-.3pt">
</span>Recent<span style="letter-spacing:-.35pt"> </span>studies<span style="letter-spacing:-.35pt">
</span>have<span style="letter-spacing:-.4pt"> </span>shown<span style="letter-spacing:-.3pt">
</span>that<span style="letter-spacing:-.4pt"> </span>a<span style="letter-spacing:-.45pt">
</span>controlled<span style="letter-spacing:-.3pt"> </span>switch<span style="letter-spacing:-2.65pt">
</span>from nonclassical to classical pathways can alter the anisotropic rates of crystallization with concomitant<span style="letter-spacing:.05pt">
</span>impact on material properties that affect their performance in commercial applications; however, few<span style="letter-spacing:.05pt">
</span>studies<span style="letter-spacing:-.15pt"> </span>identify<span style="letter-spacing:-.15pt">
</span>conditions<span style="letter-spacing:-.1pt"> </span>under<span style="letter-spacing:.05pt">
</span>which<span style="letter-spacing:-.15pt"> </span>zeolites<span style="letter-spacing:-.1pt">
</span>grow<span style="letter-spacing:-.2pt"> </span>by a purely classical<span style="letter-spacing:-.15pt">
</span>mechanism.</span></p>
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<span style="font-size:12.0pt">Seed-assisted approaches in zeolite synthesis differ from classical processes in that the seeds tend<span style="letter-spacing:.05pt">
</span>to dissolve, giving rise to an unknown memory of the parent crystal structure that facilitates the nucleation<span style="letter-spacing:-2.65pt">
</span><span style="letter-spacing:-.05pt">of</span><span style="letter-spacing:-.7pt">
</span><span style="letter-spacing:-.05pt">the</span><span style="letter-spacing:-.7pt">
</span><span style="letter-spacing:-.05pt">daughter.</span><span style="letter-spacing:-.6pt">
</span>It<span style="letter-spacing:-.7pt"> </span>has<span style="letter-spacing:-.7pt">
</span>been<span style="letter-spacing:-.75pt"> </span>hypothesized<span style="letter-spacing:-.75pt">
</span>in<span style="letter-spacing:-.75pt"> </span>the<span style="letter-spacing:-.7pt">
</span>literature<span style="letter-spacing:-.6pt"> </span>that<span style="letter-spacing:-.7pt">
</span>a<span style="letter-spacing:-.7pt"> </span>shared<span style="letter-spacing:-.75pt">
</span>structural<span style="letter-spacing:-.7pt"> </span>feature,<span style="letter-spacing:-.6pt">
</span>such<span style="letter-spacing:-.75pt"> </span>as<span style="letter-spacing:-.7pt">
</span>a<span style="letter-spacing:-.6pt"> </span>composite<span style="letter-spacing:-2.65pt">
</span>building unit, between the parent and the crystals produced from a non-seeded growth solution, results in<span style="letter-spacing:.05pt">
</span>identical<span style="letter-spacing:-.15pt"> </span>parent-daughter<span style="letter-spacing:-.1pt">
</span>framework<span style="letter-spacing:-.15pt"> </span>types.</span></p>
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<span style="font-size:12.0pt">This<span style="letter-spacing:.05pt"> </span>Thesis<span style="letter-spacing:.05pt">
</span>focuses<span style="letter-spacing:.05pt"> </span>on<span style="letter-spacing:.05pt">
</span>how<span style="letter-spacing:.05pt"> </span>seed-assisted<span style="letter-spacing:.05pt">
</span>syntheses<span style="letter-spacing:.05pt"> </span>impact<span style="letter-spacing:.05pt">
</span>zeolite<span style="letter-spacing:.05pt"> </span>properties<span style="letter-spacing:.05pt">
</span>such<span style="letter-spacing:.05pt"> </span>as<span style="letter-spacing:.05pt">
</span>size,<span style="letter-spacing:.05pt"> </span>morphology, structure, and defects. We observe that the molar composition of the growth mixture and the<span style="letter-spacing:.05pt">
</span>properties of the seed crystals play a significant role in controlling the kinetics of nucleation and the<span style="letter-spacing:.05pt">
</span>trajectory<span style="letter-spacing:-.6pt"> </span>of<span style="letter-spacing:-.55pt">
</span>interzeolite<span style="letter-spacing:-.5pt"> </span>transformations.<span style="letter-spacing:-.6pt">
</span>Furthermore,<span style="letter-spacing:-.65pt"> </span>we<span style="letter-spacing:-.55pt">
</span>observe<span style="letter-spacing:-.55pt"> </span>that<span style="letter-spacing:-.5pt">
</span>seeds<span style="letter-spacing:-.6pt"> </span>offer<span style="letter-spacing:-.6pt">
</span>unique<span style="letter-spacing:-.7pt"> </span>routes<span style="letter-spacing:-.65pt">
</span>to<span style="letter-spacing:-.6pt"> </span>achieve<span style="letter-spacing:-2.65pt">
</span>small crystal sizes and distinct morphologies in comparison to many conventional syntheses. Advantages<span style="letter-spacing:.05pt">
</span>of seeding include shorter synthesis time and the ability to reduce or eliminate the need for organic<span style="letter-spacing:.05pt">
</span>structure-directing agents, thereby providing a facile and efficient route to design zeolites for various<span style="letter-spacing:.05pt">
</span>industrial applications. The fundamental mechanisms underlying zeolite seed-assisted crystallization are<span style="letter-spacing:.05pt">
</span>complex and elusive; however, our study provides new insight into these processes and highlights the<span style="letter-spacing:.05pt">
</span>important role of<span style="letter-spacing:.05pt"> </span>kinetics<span style="letter-spacing:-.05pt">
</span>in<span style="letter-spacing:-.15pt"> </span>governing<span style="letter-spacing:-.15pt">
</span>parent-daughter<span style="letter-spacing:-.15pt"> </span>(or<span style="letter-spacing:-.1pt">
</span>seed-product)<span style="letter-spacing:-.1pt"> </span>relationships.</span></p>
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<span style="font-size:12.0pt">Furthermore, we use high-temperature atomic force microscopy (AFM) to image zeolite crystal<span style="letter-spacing:.05pt">
</span>surface growth <i>in situ</i>. We report time-resolved images of 2-dimensional growth demonstrating layer<span style="letter-spacing:.05pt">
</span>generation by three distinct mechanisms, including nucleation from the edges of surface defects. Our<span style="letter-spacing:.05pt">
</span>findings reveal that silica nanoparticles in the growth medium incorporate into advancing steps on crystal<span style="letter-spacing:.05pt">
</span>surfaces to generate defects (i.e., amorphous silica occlusions) that largely go undetected in literature.
<i>In<span style="letter-spacing:.05pt"> </span>situ </i>AFM measurements also show the dominance of gel-mediated crystal growth in the case of faujasite<span style="letter-spacing:.05pt">
</span>zeolite<span style="letter-spacing:-.05pt"> </span>syntheses.</span></p>
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