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The attachment of well-defined charge-transfer agents to the surface of nanomaterials is an efficient strategy to control their charge density and also to tune their optical, electrical, and physicochemical properties. Particularly interesting are charge-transfer agents that either donate or withdraw electrons depending on the arrangements of their building units and that promise a nondestructive attachment to delicate nanomaterials like sp2compounds. In this work, we rationally synthesize molecular moieties with versatile functionalities. A reactive anchor group allows us to attach them to carbon nanotubes as defined charge-transfer agents while preserving the tubes’ π-conjugation. The charge-transfer agents were synthesized through the stepwise nucleophilic substitution of either one (monosubstituted series) or two (disubstituted series) chlorine atoms of cyanuric chloride by aniline derivatives containing one, two, or three methoxy groups in the para and meta positions. Variation in the number and position of the methoxy group as an electron-transferring group helps us to manipulate the electronic and optical properties of the molecular probes and their charge transfer to the single-walled carbon nanotubes (SWNTs) systematically. The correlation between the optical properties of these molecular probes and their functionality was investigated by experiments and quantum chemical calculations. While the optoelectronic properties of the conjugated charge-transfer agents were dominated by the aniline segments, the triazine warrants the ability to nondestructively attach to the surface of SWNTs. This study is one step ahead toward the production of SWNTs with desired optical and electrical properties by covalent π-preserving functionalization.

Semiconducting single-wall carbon nanotubes possess an intrinsic photoluminescence in the near-infrared region beyond 900 nm, the NIR-II window of biological imaging. Here, we introduce a modular molecule for noncovalent nanotube functionalization which renders carbon nanotubes hydrophilic and fully biocompatible through a one-step process. We demonstrate through electron energy-loss spectroscopy (EELS) spectroscopy that the noncovalent functionalization mechanism relies on tight and extremely robust π–π stacking, which survives an exchange of the solvent as well as drying. Furthermore, the modularity of the molecule design allows for the introduction of functional units into the molecule itself to modify the optical properties of the carbon nanotube, for instance to augment its excitation window through an excitation energy transfer, facilitating the excitation of most carbon nanotube chiralities at one single wavelength.

We study the effects of the proximity of the orthogonal dipole-switching moiety dihydroazulene/vinylheptafulvene (DHA/VHF) to carbon nanotubes (CNTs). The switches are introduced into a micelle surrounding the CNTs, thereby achieving very close proximity between the molecules and the CNTs for the first time. The change of the molecules’ configuration is not hindered by its encapsulation: We report the reversible switching of molecules inside CNT surrounding micelles. The orthogonality of the switch also allows us for the first time to observe the effect of the molecule on the emission spectra of the CNTs and the resulting reversible redshift of the nanotubes’ emission by the change of the molecules’ conformation.

Surfactants are needed to create stable suspensions of carbon nanotubes. Increasingly, these surfactants are given additional functionalities, resulting in bigger and more complex molecules with several subunits. We investigate the effect of assembly of these subunits for a class of perylene-based functional surfactants. The subunits that all surfactants are based on are a perylene core, hydrophilic polyglycerol dendrons, and alkyl chains of different orientations and lengths. The assembly of these subunits affects both the molecules' performance as a surfactant and the efficiency of the energy-transfer complexes formed by the nanotube and surfactant through a π–π stacking mechanism. This results in a best practice guide for designing functional surfactants with π–π stacking cores, and affords more general insights that are applicable to non π–π stacking systems as well.