Non-covalent Methods of Engineering Optical Sensors Based on Single-Walled Carbon Nanotubes

Abstract

Optical sensors based on single-walled carbon nanotubes (SWCNTs) demonstrate tradeoffs that limit their use in in vivo and in vitro environments. Sensor characteristics are primarily governed by the non-covalent wrapping used to suspend the hydrophobic SWCNTs in aqueous solutions, and we herein review the advantages and disadvantages of several of these different wrappings. Sensors based on surfactant wrappings can show enhanced quantum efficiency, high stability, scalability, and diminished selectivity. Conversely, sensors based on synthetic and bio-polymer wrappings tend to show lower quantum efficiency, stability, and scalability, while demonstrating improved selectivity. Major efforts have focused on optimizing sensors based on DNA wrappings, which have intermediate properties that can be improved through synthetic modifications. Although SWCNT sensors have, to date, been mainly engineered using empirical approaches, herein we highlight alternative techniques based on iterative screening that offer a more guided approach to tuning sensor properties. These more rational techniques can yield new combinations that incorporate the advantages of the diverse nanotube wrappings available to create high performance optical sensors.

Fluorescent Single-Walled Carbon Nanotubes for Protein Detection

“…Without surface functionalization, SWCNTs are hydrophobic and tend to bundle due to strong van der Waals attraction forces [48]. In order to form a colloidal suspension of individually dispersed SWCNTs, they are usually non-covalently functionalized with amphiphilic molecules or polymers by sonication [18,[48][49][50][51][52]. Proper surface functionalization can render them biocompatible, and thus, suitable for numerous biomedical applications, including sensing, drug delivery, nanoinjection, phototherapy, imaging, or artificial actuation [13,30,51,.…”

“…Single-walled carbon nanotubes overcome these limitations owing to their inherent non-photobleaching, non-blinking fluorescence, and their sp 2 hybridized all-carbon structure that gives rise to easy surface functionalization and biocompatibility [14,62,172]. Hence, SWCNTs are subjected to intensive research in many emerging applications of optical nanosensors that exploit their nIR fluorescent emission and surface chemistry for target recognition and signal transduction [10,16,30,41,50].…”

Quantendefekte als Werkzeugkasten für die kovalente Funktionalisierung von Kohlenstoffnanoröhren mit Peptiden und Proteinen

“…[5] Folglich fanden SWCNTs bereits Anwendung in verschiedenen Bereichen, die von der In-vivo-NIR-Bildgebung [6][7][8] über die gesteuerte Wirkstofffreisetzung [9,10] bis hin zu optischen NIR-Sensoren reichen. [11][12][13][14][15][16][17][18][19][20] Um ihre gewünschte Funktion in diesen wichtigen Anwendungen erfüllen zu kçnnen, muss die Kohlenstoffnanorçhre z. B. mit der zu transportierenden Fracht oder einer Erkennungseinheit modifiziert werden, die eine Spezifitätfürden zu detektierenden Analyten vermittelt.…”

Carbon Nanohybrids for Advanced Electronic Applications

“…[ 71 ] However, the bundled structure of SWNTs and poor solubility in solvents results in strong π–π interactions, thus restricting their applications. [ 72 ] Covalent chemical functionalization, [ 73–75 ] acid treatment, [ 76–78 ] noncovalent functionalization using hydrophobic interactions, [ 79–81 ] formation of supramolecular complexes in the presence of π electron‐donating compounds including pyrenes, [ 82 ] porphyrins, [ 83 ] and π‐conjugated polymers under ultrasonication are the ways to impart sufficient solubility in SWNTs. [ 72 ] Consequently, the interactions between SWNTs and π electron‐rich compounds can provide moderate solubility to SWNTs.…”