Toward multifunctional wet chemically functionalized graphene-integration of oligomeric, molecular, and particulate building blocks that reveal photoactivity and redox activity.

Many technological applications indispensable in our daily lives rely on carbon. By altering the periodic binding motifs in networks of sp(3), sp(2), and sp-hybridized carbon atoms, researchers have produced a wide palette of carbon allotropes. Over the past two decades, the physicochemical properties of low-dimensional nanocarbons, including fullerenes (0D), carbon nanotubes (1D), and, most recently, graphene (2D), have been explored systematically. An entire area of research has focused on the chemistry of 1D nanocarbons, particularly single-wall carbon nanotubes. These structures exhibit unique electronic, mechanical, and optical properties. These properties are, however, only discernible for single-wall carbon nanotubes that are debundled, individualized, and stabilized, often in solution. Most prominently, they are small band gap, p-type semiconductors or metals with conductances that reach ballistic dimensions. These structures can have poor solubility in many media, and large bundles can originate from attractive interactions such as π-π stacking and London dispersion forces. Therefore, both covalent and noncovalent modifications of single-wall carbon nanotubes have emerged as powerful approaches to overcome some of these problems. Noncovalent functionalization is especially useful in improving the solubility without altering the electronic structure. We expect that many of the strategies that have recently been exploited and established in the context of 1D nanocarbons can be applied to the chemistry of 2D nanocarbons, especially graphene. Two-dimensional nanocarbons are currently attracting extensive attention due to their striking mechanical, optical, and electrical features. Nanocarbons that are a single atom thick are gapless semiconductors and exhibit electron mobilities reaching values of up to 15000 cm(2) V(-1) s(-1) at room temperature. Researchers have made rapid progress in the covalent and/or noncovalent functionalization of graphene with photoactive and or redox active building blocks. In this Account, we summarize our work on the integration of photoactive and/or redox active building blocks, including oligomers, molecules, and particulates, onto graphenoid materials to yield multifunctional electron donor-acceptor conjugates and hybrids. Intriguingly, we produce graphene in the form of single-layer, bilayer, and multilayer graphene through the exfoliation of graphite by surface active agents. The exfoliation occurs through π-π, hydrophobic, van der Waals, electrostatic, and charge transfer interactions, and the surface active agents also serve as versatile anchor groups. We studied the electronic interactions in terms of photoactivity and/or redox activity in depth by steady-state and time-resolved spectroscopy. Finally, we present examples of proof-of-principle solar energy conversion devices.