Pentiptycene Polymer/Single-Walled Carbon Nanotube Complexes: Applications in Benzene, Toluene, and o-Xylene Detection

We report the dispersion of single-walled carbon nanotubes (SWCNTs) using pentiptycene polymers and their use in chemiresistance-based and QCM-D sensors. Poly(p-phenylene ethynylene)s (PPEs) incorporating pentiptycene moieties present a concave surface that promotes π-π interactions and van der Waals interactions with SWCNTs. In contrast to more common polymer-dispersing mechanisms that involve the wrapping of polymers around the SWCNTs, we conclude that the H-shape of pentiptycene groups and the linear rigid-rod structure creates a slot for nanotube binding. UV-vis-NIR, Raman, and fluorescence spectra and TEM images of polymer/SWCNTs support this dispersion model, which shows size selectivity to SWCNTs with diameters of 0.8-0.9 nm. Steric bulk on the channels is problematic, and tert-butylated pentiptycenes do not form stable dispersions with SWCNTs. This result, along with the diameter preference, supports the model in which the SWCNTs are bound to the concave clefts of the pentiptycenes. The binding model suggests that the polymer/SWCNTs complex creates galleries, and we have demonstrated the binding of benzene, toluene, and o-xylene (BTX) vapors as the basis for a robust, sensitive, and selective sensing platform for BTX detection. The utility of our sensors is demonstrated by the detection of benzene at the OSHA short-term exposure limit of 5 ppm in air.

π-Concave Hosts for Curved Carbon Nanomaterials

Carbon nanomaterials have been at the forefront of nanotechnology since its inception. At the heart of this research are the curved carbon nanomaterial families: fullerenes and carbon nanotubes. While both have incredible properties that have been capitalized upon in a wide variety of applications, there is an aspect that is not commonly exploited by nanoscientists and organic chemists alike: the interaction of curved carbon nanomaterials with curved organic small molecules. By taking advantage of these interactions, new avenues are opened for the use of fullerenes and carbon nanotubes.

Nanoparticles and DNA - a powerful and growing functional combination in bionanotechnology

Functionally integrating DNA and other nucleic acids with nanoparticles in all their different physicochemical forms has produced a rich variety of composite nanomaterials which, in many cases, display unique or augmented properties due to the synergistic activity of both components. These capabilities, in turn, are attracting greater attention from various research communities in search of new nanoscale tools for diverse applications that include (bio)sensing, labeling, targeted imaging, cellular delivery, diagnostics, therapeutics, theranostics, bioelectronics, and biocomputing to name just a few amongst many others. Here, we review this vibrant and growing research area from the perspective of the materials themselves and their unique capabilities. Inorganic nanocrystals such as quantum dots or those made from gold or other (noble) metals along with metal oxides and carbon allotropes are desired as participants in these hybrid materials since they can provide distinctive optical, physical, magnetic, and electrochemical properties. Beyond this, synthetic polymer-based and proteinaceous or viral nanoparticulate materials are also useful in the same role since they can provide a predefined and biocompatible cargo-carrying and targeting capability. The DNA component typically provides sequence-based addressability for probes along with, more recently, unique architectural properties that directly originate from the burgeoning structural DNA field. Additionally, DNA aptamers can also provide specific recognition capabilities against many diverse non-nucleic acid targets across a range of size scales from ions to full protein and cells. In addition to appending DNA to inorganic or polymeric nanoparticles, purely DNA-based nanoparticles have recently surfaced as an excellent assembly platform and have started finding application in areas like sensing, imaging and immunotherapy. We focus on selected and representative nanoparticle-DNA materials and highlight their myriad applications using examples from the literature. Overall, it is clear that this unique functional combination of nanomaterials has far more to offer than what we have seen to date and as new capabilities for each of these materials are developed, so, too, will new applications emerge.

Enzymatic formation of carbohydrate rings catalyzed by single-walled carbon nanotubes

Macrocyclic carbohydrate rings were formed via enzymatic reactions around single-walled carbon nanotubes (SWNTs) as a catalyst. Cyclodextrin glucanotransferase, starch substrate and SWNTs were reacted in buffer solution to yield cyclodextrin (CD) rings wrapped around individual SWNTs. Atomic force microscopy showed the resulting complexes to be rings of 12-50 nm in diameter, which were highly soluble and dispersed in aqueous solution. They were further characterized by Raman and Fourier transform infrared spectroscopy and molecular simulation using density functional theory calculation. In the absence of SWNT, hydrogen bonding between glucose units determines the structure of maltose (the precursor of CD) and produces the curvature along the glucose chain. Wrapping SWNT along the short axis was preferred with curvature in the presence of SWNTs and with the hydrophobic interactions between the SWNTs and CD molecules. This synthetic approach may be useful for the functionalization of carbon nanotubes for development of nanostructures.

Sugar-functionalized triptycenes used for dispersion of single-walled carbon nanotubes in aqueous solution by supramolecular interaction

Two water-soluble sugar-functionalized triptycene derivatives were synthesized and used for dispersion of SWCNTs in aqueous solution via supramolecular interaction.

Nano- and microstructuration of supramolecular materials driven by H-bonded uracil·2,6-diamidopyridine complexes

In the last few decades, multiple H-bonded arrays have been shown to be versatile tools to prepare functional supramolecular materials. Supramolecular complexes formed by uracil (Ur) and 2,6-diamidopyridine (DAP) developed by Lehn are the first examples of multiple H-bonded systems governing the formation of supramolecular polymers in solution. Although a large variety of complementary multiple H-bonded complexes has been prepared, the use of the heteromolecular Ur·DAP complex still remains very promising due to its ease of preparation and its intermediate association strength that ensures a dynamical character to the self-assembly and self-organisation processes. In this feature article, we report a detailed account on the results that our group has obtained in this field by designing and engineering a novel library of shape persistent molecular modules able to transfer their geometrical information to the final supramolecular architectures through the formation of Ur·DAP complexes both at the nanoscopic and microscopic levels.

Effects of β-cyclodextrin on the intestinal absorption of berberine hydrochloride, a P-glycoprotein substrate

The major objective of this work is to investigate the enhancing effect of β-cyclodextrin on the intestinal absorption of berberine hydrochloride, a P-glycoprotein (Pgp) substrate. The inclusion complexation behavior of BBH with β-CD was investigated by phase-solubility diagram, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray powder diffractometry, NMR spectroscopy, and molecular modeling studies. Results indicated that the 1,3-benzodioxole of BBH was included into the cavity of β-CD to form an inclusion complex which exhibited higher dissolution rate than BBH in vitro. The intestinal absorption of the inclusion complex in rats was significantly higher than the free drug due to its solubilizing effect and Pgp modulatory activity. The mechanisms of β-CD on Pgp modulation were demonstrated by modifying the Pgp ATPase activity, the Pgp mRNA level and the Pgp expression.