Sensing with Chirality-Pure Near-Infrared Fluorescent Carbon Nanotubes

Abstract

Semiconducting single wall carbon nanotubes (SWCNTs) fluoresce in the near infrared (NIR) and the emission wavelength depends on their chirality (n,m). Interactions with the environment affect the fluorescence and can be tailored by functionalizing SWCNTs with biopolymers such as DNA, which is the basis for fluorescent biosensors. So far, such biosensors were mainly assembled from mixtures of SWCNT chiralities with large spectral overlap, which affects sensitivity as well as selectivity and prevents multiplexed sensing. The main challenge to gain chirality pure sensors has been to combine approaches to isolate specific SWCNTs and generic (bio)functionalization approaches. Here, we created chirality pure SWCNT-based NIR biosensors for important analytes such as neurotransmitters and investigated the impact of SWCNT chirality/handedness as well as long-term stability and sensitivity. For this purpose, we used aqueous two-phase extraction (ATPE) to gain chirality pure (6,5)-, (7,5)-, (9,4)-and (7,6)-SWCNTs (emission at ~ 990, 1040, 1115 and 1130 nm). Exchange of the surfactant sodium deoxycholate (DOC) to specific singlestranded (ss)DNA sequences yielded monochiral sensors for small analytes (dopamine, riboflavin, ascorbic acid, pH). DOC used in the separation process was completely removed because residues impaired sensing. The assembled monochiral sensors were up to 10 times brighter than their non-purified counterparts and the ssDNA sequence affected absolute fluorescence intensity as well as colloidal (long-term) stability and selectivity for the analytes. (GT)40-(6,5)-SWCNTs displayed the maximum fluorescence response to the neurotransmitter dopamine (+140 %, Kd = 1.9 x10-7 M) and a long-term stability > 14 days. Furthermore, the specific ssDNA sequences imparted selectivity to the analytes independent of SWCNT chirality and handedness of (+/-) (6,5)-SWCNTs. These monochiral/single-color SWCNTs enabled ratiometric/multiplexed sensing of dopamine, riboflavin, H2O2 and pH. In summary, we demonstrated the assembly, characteristics and potential of monochiral (single-color) SWCNTs for multiple NIR fluorescent sensing applications.File list (2) download file view on ChemRxiv Chirality pure sensing_MS.pdf (1.87 MiB) download file view on ChemRxiv Chirality pure sensing_SI.pdf (3.43 MiB)

Quantum Defects in Fluorescent Carbon Nanotubes for Sensing and Mechanistic Studies

“…For most experiments, (GT) 10 -functionalized pristine CoMoCat-(6,5)-SWCNTs (from now on referred to as pSWCNTs) were used. Further purification 48 was used for experiments in which spectral congestion by other chiralities could cause a bias (see materials and methods 49 ). Defects (NO 2 -Aryl) were incorporated into (6,5)-SWCNTs by a reaction with diazonium salts (see materials and methods for details).…”

“…We used it to establish ratiometric sensing at two different wavelengths (Figure 6). Such approaches are desired in biosensing because they are more robust and promise higher signal/noise ratios 48 . The dopamine response almost equals the average of the expected dopamine responses for two independent pSWCNT and dSWCNT samples, which further underlines that the presence of NO 2 -Aryl-units does not interfere with the overall DNA structure on the SWCNTs.…”

Detection and Imaging of the Plant Pathogen Response by Near‐Infrared Fluorescent Polyphenol Sensors

“…[30] Fors uch an approach, (n,m) chirality-pure or even enantiomer-pure SWCNTs are necessary. [62] We prepared chirality-pure (6,5)-SWCNTs with PEG-PL to act as polyphenol-responsive sensor,w hile monochiral (7,6)-SWCNTs coated with (AT) 15 -ssDNAserved as reference that does not react to polyphenols (Figure 4h,S upplementary Figure S1, S15). Inside agar,t hey allowed ratiometric imaging using appropriate emission filters (PEG-PL-(6,5)-SWCNTs:9 00-1100 nm and (AT) 15 -(7,6)-SWCNTs: > 1100 nm).…”

Detektion und Visualisierung der Pflanzen‐Pathogen‐Response durch Nah‐Infrarot‐fluoreszente Polyphenolsensoren

“…Als Nächstes wurde untersucht, ob chemisches Sensing mit monochiralen SWCNTs und somit einer wohldefinierten Sensitivitätund Selektivitätder Sensoren. [62] Experimente mit multichiralen (HiPco) PEG-PL-SWCNTs zeigten jedoch deutliche Unterschiede,die auf ein Polyphenolprofil und eine chiralitätsabhängige Reaktion hindeuten (ergänzende Abbildung S4). Um die Sensoren ferner in komplexeren Umgebungen zu testen, verwendeten wir Pflanzengewebeextrakt und Kulturmedium.…”