The skyrocketing energy demand and growing urgency to limit anthropogenic strains on our health and environment have created a need for functional materials that can generate energy from clean and renewable sources, capture and detect toxic agents and pollutants, transport charges efficiently in molecular electronic devices, deliver drugs in our bodies, and enable other technological advances. With a long-term goal to meet these demands, we have undertaken a multipronged initiative to develop adaptive materials that can carry out these functions by interacting with various stimuli, such as guest molecules and ions, applied electric field, and light. To this end, we have (1) discovered a novel anion-induced electron transfer phenomenon and defined different modes of electronic interactions between anions and π-acidic receptors that opened the door for discriminating anions on the basis of their electronic properties, (2) constructed dye-sensitized solar cells using self-assembled electron donor–acceptor dyads that convert light into electricity throughout the visible-NIR region, (3) assembled nanoscale vesicles from amphiphilic macrocycles that morph into nanotubes in mild acidic conditions, and (4) constructed new stimuli-responsive metal–organic frameworks (MOFs) that change color and electrical conductivity upon guest encapsulation. The current projects in our lab include:
(1) Reversible Anion and Ion-Pair Recognition under Electronic Control: We are developing novel ion-pair receptors based on π-acidic naphthalenediimide (NDI) units that can not only capture anions and cation simultaneously in a cooperative fashion, but also release them upon electrochemical or photoinduced reduction of the NDI units. We are particularly interested in regulating harmful charge-diffuse anions, such as perchlorate (an explosive), pertechnetate (a nuclear waste), and perrheneate (used in nuclear medicine) ions with these receptors.
(2) Stimuli-Responsive MOFs as Electronic and Photonic Materials: To develop new sensors, semiconductors, light-harvesting, and light-emitting materials, we are constructing stimuli-responsive MOFs using electronically and optically active ligands, integrating them into devices, and investigating how they change their optical and electronic properties in response to guest molecules and ions, applied electric field, and light. The guest-induced color and conductivity changes in MOFs can lead to sensing, while those triggered by electric field and light could expand their utility in electronic devices, batteries, solar cells, and energy efficient lights.
(3) Photocatalytic Water-Splitting for Hydrogen Production: Applying our knowledge and expertise in light to electrical energy conversion with multichromophoric solar cells, we are pursuing photocatalytic water splitting for hydrogen production using self-assembled light-harvesting dyads.
(4) pH-Controlled Drug Delivery Systems: Having developed self-assembled vesicles that morph into nanotubes in acidic media, we are interested in studying their pH-activated delivery capability.
