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Author requested closed access (OA after 2yrs) in Vireo ETD system Limited application/pdf http://hdl.handle.net/2142/109619 en © 2020 VARUN MOHAN Photocatalysis Light-Matter interactions Natural Gas Upgradation Nanoparticles Tracking the evolution of photoexcitations in strongly light absorbing systems text Thesis Jain, Prashant K Shim, Moonsub Braun, Paul V Chen, Qian Mohan, Varun 2021-03-05T21:47:26Z 2021-03-05T21:47:26Z 2023-03-05T21:47:41Z 2020-12-04 2020-12 This dissertation consists of the work done towards a Ph.D. degree in the research group of Professor Prashant K. Jain at the University of Illinois at Urbana-Champaign. Here, I describe the study of the conversion of light energy using hybrid perovskite and noble metal-based semiconductor nanoparticles. The large surface-area-to-volume ratios and superlative ability to absorb visible light make these materials worthy candidates for solar energy harvesting. The primary questions I have asked in my research are: what is the fate of photoexcitation in a nanostructured material and how can we channel such photo-excitations in an efficient and selective manner? Chapter 1 of this dissertation introduces some of the theoretical backdrops to my studies of strongly light-absorbing plasmonic nanoparticulate systems. This chapter elucidates what follows and introduces the concepts and terms used. Chapter 2 presents my investigation of hybrid organic-inorganic perovskite materials for potential uses towards light trapping and emission. We discovered that commonly observed luminescence from microcrystals of these materials showed a spectrum that varied with sample morphology and location on the sample. The origin of this spectral heterogeneity was then traced to the phenomenon of luminescence self-absorption, which is prevalent due to the overlapping absorption and emission, i.e., small Stokes-shift, in these materials. Then we explored light-to-chemical-energy conversion in perovskite materials, but they proved to be photochemically unstable; so, we turned our attention to noble metal nanoparticles, which have strong plasmon resonance absorption and high photostability. Chapter 3 describes the investigation of light-to-chemical energy conversion in colloidal gold (Au) nanoparticles In particular, we studied the effect of visible-light excitation of Au nanoparticles in the presence of an electron acceptor (HAuCl4) and a hole acceptor (short-chain alcohol). This led to the discovery of a hitherto unknown photoreaction, which involves the splitting and chlorination of the alcohol generating a chloroalkane and an aldehyde. This reaction was found to take place with several alcohols, which led us to a general reaction mechanism that is catalyzed synergistically by the photoexcited nanoparticle and the Lewis acidic HAuCl4. In the specific case of 2-butanol as the hole acceptor, we found a substantial difference between the product distributions of the light-driven reaction as compared to a thermal reaction. This finding represents an example of light-driven-control of catalytic selectivity. Finally, as presented in Chapter 4, the insights gained from the study described in Chapter 3 led me to a new, simple chemical process for low-temperature chlorination of methane in a non-corrosive aqueous environment. The kinetics and mechanism of this reaction were studied. Methane chlorination is at the heart of natural-gas upgradation, so this new finding represents an ideal culmination of my dissertation. An outlook and potential future directions are presented in Chapter 5. Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-12-01 The student, Varun Mohan, accepted the attached license on 2020-12-01 at 18:31. The student, Varun Mohan, submitted this Dissertation for approval on 2020-12-01 at 18:50. This Dissertation was approved for publication on 2020-12-04 at 10:01. DSpace SAF Submission Ingestion Package generated from Vireo submission #16022 on 2021-03-04 at 16:33:11 Made available in DSpace on 2021-03-05T21:47:26Z (GMT). No. of bitstreams: 8 MOHAN-DISSERTATION-2020.pdf: 6485299 bytes, checksum: 37964bef8b0bcdb3b302810970072847 (MD5) LICENSE.txt: 4208 bytes, checksum: 037a5657378106ff7ce5db0466464d09 (MD5) RightsLink Printable License.pdf: 206034 bytes, checksum: b7b7c85eeee51326f95c886eadb92ee7 (MD5) RightsLink Printable License_1.pdf: 206016 bytes, checksum: 71706239f2ccde924ba9fad18b6bc886 (MD5) RightsLink Printable License_2.pdf: 205185 bytes, checksum: 641a730a7778c15eeda4fa30dc945a2d (MD5) Rightslink? by Copyright Clearance Center.pdf: 131604 bytes, checksum: 6af5f1671576f584d94196732a29a468 (MD5) Rightslink? by Copyright Clearance Center_1.pdf: 131430 bytes, checksum: b75581a55391d1af31b0c6282aacd998 (MD5) Rightslink? by Copyright Clearance Center_2.pdf: 130197 bytes, checksum: 0b2c8deaa6e679e4d866bdf87adbf3d0 (MD5) Previous issue date: 2020-12-04 Embargo set by: Seth Robbins for item 117325 Lift date: 2023-03-05T21:47:41Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Dissertation Materials Science & Engineerng Materials Science & Engr University of Illinois at Urbana-Champaign Ph.D.