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.

中文翻译：

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手性感应纯近红外荧光碳纳米管

半导体单壁碳纳米管（SWCNT）在近红外（NIR）中发出荧光，并且发射波长取决于它们的手性（n，m）。与环境的相互作用会影响荧光，可以通过使用生物聚合物（例如DNA）对SWCNT进行功能化来进行定制，这是荧光生物传感器的基础。到目前为止，此类生物传感器主要由具有较大光谱重叠的SWCNT手性混合物构成，这会影响灵敏度和选择性，并会阻止多路传感。获得手性纯传感器的主要挑战是将分离特定SWCNT的方法与通用（生物）功能化方法相结合。这里，我们为重要的分析物（例如神经递质）创建了基于手性的基于SWCNT的纯NIR生物传感器，并研究了SWCNT手性/手性的影响以及长期稳定性和敏感性。为此，我们使用水相两相萃取（ATPE）来获得手性纯的（6,5）-，（7,5）-，（9,4）-和（7,6）-SWCNT（在〜 990、1040、1115和1130 nm）。将表面活性剂脱氧胆酸钠（DOC）交换为特定的单链（ss）DNA序列可得到用于小分析物（多巴胺，核黄素，抗坏血酸，pH）的单手性传感器。分离过程中使用的DOC已完全去除，因为残留物会影响传感。组装的单手性传感器的亮度比未纯化的同类传感器高10倍，并且ssDNA序列影响绝对荧光强度以及胶体（长期）稳定性和对分析物的选择性。（GT）40-（6,5）-SWCNTs显示出对神经递质多巴胺的最大荧光反应（+140％，Kd = 1.9 x10-7 M）和长期稳定性> 14天。此外，特定的ssDNA序列赋予分析物选择性，而与SWCNT的手性和（+/-）（6,5）-SWCNT的手性无关。这些单手性/单色SWCNT能够对多巴胺，核黄素，H2O2和pH进行比例/多重传感。总之，我们证明了用于多种NIR荧光传感应用的单手性（单色）SWCNT的组装，特性和潜力。