Browsing by Author "Hedlund, Jenny K."
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Item Application of Visible-Light Photosensitization to Form Alkyl-Radical-Derived Thin Films on GoldQuarels, Rashanique D.; Zhai, Xianglin; Kuruppu, Neepa; Hedlund, Jenny K.; Ellsworth, Ashley A.; Walker, Amy V.; Garno, Jayne C.; Ragains, Justin R.; Hedlund, Jenny K.; Ellsworth, Ashley A.; Walker, Amy V.Visible-light irradiation of phthalimide esters in the presence of the photosensitizer [Ru(bpy)₃]²⁺ and the stoichiometric reducing agent benzyl nicotinamide results in the formation of alkyl radicals under mild conditions. This approach to radical generation has proven useful for the synthesis of small organic molecules. Herein, we demonstrate for the first time the visible-light photosensitized deposition of robust alkyl thin films on Au surfaces using phthalimide esters as the alkyl radical precursors. In particular, we combine visible-light photosensitization with particle lithography to produce nanostructured thin films, the thickness of which can be measured easily using AFM cursor profiles. Analysis with AFM demonstrated that the films are robust and resistant to mechanical force while contact angle goniometry suggests a multilayered and disordered film structure. Analysis with IRRAS, XPS, and TOF SIMS provides further insights.Item Polytype Control of MoS₂ Using Chemical Bath Deposition(American Institute of Physics Inc., 2019-05-01) Hedlund, Jenny K.; Walker, Amy V.; 0000-0003-2114-3644 (Walker, AV); Hedlund, Jenny K.; Walker, Amy V.Molybdenum disulfide (MoS₂) has a wide range of applications from electronics to catalysis. While the properties of single-layer and multilayer MoS₂ films are well understood, controlling the deposited MoS₂ polytype remains a significant challenge. In this work, we employ chemical bath deposition, an aqueous deposition technique, to deposit large area MoS₂ thin films at room temperature. Using Raman spectroscopy and x-ray photoelectron spectroscopy, we show that the deposited MoS₂ polytype can be changed from semiconducting 2H MoS₂ on hydrophobic -CH₃ and -CO₂C₆F₅ terminated self-assembled monolayers (SAMs) to semimetallic 1T MoS₂ on hydrophilic -OH and -COOH terminated SAMs. The data suggest that the deposition of MoS₂ polytypes is controlled by the substrate surface energy. High surface energy substrates stabilize 1T MoS₂ films, while 2H MoS₂ is deposited on lower surface energy substrates. This effect appears to be general enabling the deposition of different MoS₂ polytypes on a wide range of substrates. ©2019 Author(s).