Synthesis of Organic Semiconductors
During my Ph.D. at Imperial College London (McCulloch group), I designed and synthesized redox-active polymeric organic semiconductors. By attaching functional groups to the redox-active polymers, the polymers were able to interact with water-based electrolytes and could be utilized as optical and electronic sensors. Find out more about material developments in the open-access publications for hole-transporting materials (link 1 and link 2) as well as electron-transporting material (link 3 and link 4).
Pictures of polymeric organic semiconductors I synthesized during my Ph.D.
Electrochemical transistors for bioelectronic applications: Nature uses ions to send signals and information from the brain to various parts of the body - we wanted to tune in and find a way to interfere with the human body to read out signals (e.g. health monitoring). To achieve this, we need electronic devices that are equipped with materials that can interact with water-based electrolytes (e.g. sweat/saliva). I developed polymers that are intentionally designed to interact with aqueous electrolytes and are able to transport ions from the electrolyte into the material, creating a signal that we can detect (measuring a difference in the current flowing through the device). The pictures below show the devices that were developed by collaborators (Prof. Mallaiaras and co-workers) which we equipped with the designed polymers to form high-performing devices.
Operation of an electrochemical transistor with a Ag/AgCl pellet gate electrode.
Microscope pictures of an OECT and illustration from which side charges are injected to operate the device (Picture from Reference 1)
Ion-selective conjugated Polymers
Next to developing materials for electronic devices, I was also motivated to design and synthesize materials that can detect sodium or potassium ions. These ions are responsible for the majority of signal transduction in the human body. The materials I developed undergo a color change when sodium or potassium ions are present, check out the video below to see what happens when ions are added to a polymer solution. Learn more about the work by following the link to the open-access publication [link]
Alexander Giovannitti*, Iuliana P. Maria, David Hanifi, Mary J. Donahue, Daniel Bryant, Katrina J. Barth, Beatrice E. Makdah, Achilleas Savva, Davide Moia, Matyáš Zetek, Piers Barnes, Obadiah G. Reid, Sahika Inal, Garry Rumbles, George G. Malliaras, Jenny Nelson, Jonathan Rivnay,* and Iain McCulloch, The role of the side chain on the performance of n-type conjugated polymers in aqueous electrolytes, Chem. Mater., 2018, 30, 9, 2945–2953 [10.1021/acs.chemmater.8b00321]
Alexander Giovannitti, Dan-Tiberiu Sbircea, Sahika Inal, Christian B. Nielsen, Enrico Bandiello, David A. Hanifi, Michele Sessolo, George G. Malliaras, Iain McCulloch and Jonathan Rivnay*. Controlling the mode of operation of organic transistors through side chain engineering, Proc. Nat. Acad. Sci., 2016, 113, 12017-12022 [10.1073/pnas.1608780113]
Alexander Giovannitti*, Christian B. Nielsen, Dan-Tiberiu Sbircea, Sahika Inal, Mary Donahue, Muhammad R. Niazi, David A. Hanifi, Aram Amassian, George G. Malliaras, Jonathan Rivnay and Iain McCulloch. N-type organic electrochemical transistors with stability in water, Nat. Commun. 2016, 7, 13066-13075. [10.1038/ncomms13066]
Christian B. Nielsen*, Alexander Giovannitti, Dan-Tiberiu Sbircea, Enrico Bandiello, Muhammad R. Niazi, David A. Hanifi, Michele Sessolo, Aram Amassian, George G. Malliaras, Jonathan Rivnay and Iain McCulloch. Molecular Design of Semiconducting Polymers for High-Performance Organic Electrochemical Transistors J. Am. Chem. Soc., 2016, 138, 10252–10259 [10.1021/jacs.6b05280]
Alexander Giovannitti*, Christian B. Nielsen, Jonathan Rivnay, Mindaugas Kirkus, David J. Harkin, Andrew J.P. White, Henning Sirringhaus, George G. Malliaras and Iain McCulloch. Sodium and Potassium Ion Selective Conjugated Polymers for Optical Ion Detection in Solution and Solid State, Adv. Funct. Mater., 2016, 26, 514–523. [10.1002/adfm.201503791]