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)

Plants use secondary metabolites such as polyphenols for chemical defense against pathogens and herbivores. Despite their importance in plant pathogen interactions and tolerance to diseases,i tr emains challenging to detect polyphenols in complex plant tissues.H ere,w ec reate molecular sensors for plant polyphenol imaging that are based on nearinfrared (NIR) fluorescent single-wall carbon nanotubes (SWCNTs). We identified polyethylene glycol-phospholipids that render (6,5)-SWCNTs sensitive (K d = 90 nM) to plant polyphenols (tannins,f lavonoids,… ), whichr ed-shift (up to 20 nm) and quenchtheir emission (ca. 1000 nm). These sensors report changes in total polyphenol level after herbivore or pathogen challenge in crop plant systems (Soybean Glycine max) and leaf tissue extracts (Tococa spp.). We furthermore demonstrate remote chemical imaging of pathogen-induced polyphenol release from roots of soybean seedlings over the time course of 24 h. This approach allows in situ visualization and understanding of the chemical plant defense in real time and paves the way for plant phenotyping for optimized polyphenol secretion.

Both photo-and biocatalysis are well-established and intensively studied. The combination of these two approaches is also an emerging research field, commonly referred to as semi-artificial photosynthesis. Semi-artificial photosynthesis aims at combining highly efficient synthetic light harvesters with the self-healing and potent catalytic properties of biocatalysis. In this study, a semi-artificial photocatalytic system featuring Escherichia coli bacteria, which heterologously express the [FeFe] hydrogenase enzyme HydA1 from green algae, is employed as a hydrogen gas production catalyst. To probe the influence of photochemistry on overall system performance, the E. coli whole-cell catalyst is combined with two different photosensitizers and redox mediators. The addition of a redox mediator greatly improves the rates and longevity of the photocatalytic system, as reflected in increases of both the turn-over number (0.777 vs 10.9 μmol H 2 mL −1 OD 600 −1) and the turn-over frequency (175 vs 334 μmol H 2 mL −1 h −1 OD 600 −1). The redox mediator is found to both protect from photobleaching and enable electron transport to the hydrogenase from an extracellular photosensitizer. However, E. coli cells are strongly affected by the photocatalytic system, leading to a decrease in cell integrity and cell viability, possibly due to toxic decomposition products formed during the photocatalytic process. We furthermore employed steady-state and transient absorption spectroscopy to investigate solution potentials and the kinetics of electron transfer processes between the sacrificial electron donor, photosensitizer, redox mediator, and the [FeFe] hydrogenase as the final electron acceptor. These results allowed us to rationalize the different activities observed in photocatalytic assays and offer a better understanding of the factors that influence the photocatalytic performance of E. coli-based whole-cell systems.

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.

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