Cellulose nanocrystals conjugated with metallophthalocyanines: Applications in visible-light driven photocatalysts and memory devices

  • Author / Creator
    Chaulagain, Narendra
  • Cellulose is the most abundantly available renewable polymers on the planet, which have received scientific attention from numerous research communities. Cellulose nanocrystals (CNCs) are crystalline nanorods obtained through the acid hydrolysis of cellulosic materials such as wood pulp, cotton fibers, carded hemp, etc. Nontoxicity, formidable colloidal solidity, outstanding biocompatibility and biodegradability, and transparency are fundamental properties of CNCs and motivation for the construction of CNC-based blends and polymer nanocomposites improved properties. The optical properties of the host polymers such as absorption and fluorescence can be enhanced by blending with CNCs, as the needle-shaped morphology of CNCs can provide a spindle for the wrapping and untwisting of polymer chains, thus reducing concentration quenching while increasing the conjugation length. Recently, highly photoluminescent metallophthalocyanine conjugated with cellulose nanocrystals exhibited potential applications in organic electronic devices. The purpose of this project is to study the as-synthesized metallophthalocyanine conjugated CNC materials for electronic device applications.
    The first study involves the formation of a thin films of zinc phthalocyanine covalently conjugated with cellulose nanocrystals (ZnPc@CNC). ZnPc@CNC thin films formed on FTO (bottom contact) using the drop-casting technique followed by metal top-contact deposition exhibit a significant hysteresis in their current-voltage plots indicating electrical bistability. The memory devices use hysteresis by associating the conductive state at zero voltage with a Boolean 1 and 0, which shapes the premise for most logic circuits in use. It was seen that the device based on bare ZnPc results in zero current at zero voltage and conjugation of CNC is responsible for the improvement in electrical properties of the organic material. This research provides a new and facile strategy to fabricate memory devices.
    The second study involves the assessment of as-synthesized cobalt phthalocyanine (CoPc) and its CNC conjugate (CoPc@CNC) for rhodamine B (RhB) photodegradation application. The superior photocatalytic performance of the conjugate as compared to the bare CoPc has been rationalized by experimental observations. Although CoPc is regularly utilized to sensitize other active photocatalysts to enhance the RhB dye degradation, photocatalytic dye degradation of stand-alone CoPc without the addition of any oxidants has not been reported yet. In this work, we have systematically investigated the photocatalytic dye degradation potential of octacarboxylated CoPc and CoPc@CNC systems without any added oxidant under visible light. In the first 30 minutes of the dark cycle, it was noticed that bare CoPc adsorbed ~80% of the RhB dye; however, no photocatalytic activity was observed under AM1.5G one sun-simulated light. On the other hand, the same amount of CoPc@CNC conjugate adsorbed ~25% of the RhB dye in the dark cycle and demonstrated good photocatalytic activity with almost 80% of dye degradation. In addition, the latter has also exhibited the enhanced electronic properties of active materials due to the existence of electrically insulating and naturally occurring polymers (i.e., CNCs).

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
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