Han Li

Aqueous two-phase extraction (ATPE) enables the separation of single-chirality and even enantiomeric single-wall carbon nanotubes (SWCNTs) through precise surfactant modulation. We utilize the partition coefficient change condition (PCCC) as a robust metric to describe the response of different (n,m) species to variations in surfactant or co-surfactant composition. This approach allows us to extend sorting capabilities from armchair and non-armchair metallic tubes to cover a broad spectrum of semiconducting diameters. To support these experimental results, we employ molecular simulations of surfactant wrapping and interfacial adsorption, relating observed PCCC shifts to molecular packing rather than relying solely on trial-and-error screening. Furthermore, we integrate this ATPE workflow with CVD-grown, chirality-enriched starting materials. In this synergistic approach, growth provides the coarse selection while ATPE performs the final refinement, significantly increasing overall separation efficiency.

A bifunctional linker for robust and straightforward functionalization of carbon‐based nanomaterials, featuring an azido group at one end and a diazonium group at the other, is synthesized and used to introduce azido groups on the sidewalls of (6,5)‐single‐wall carbon nanotubes. The versatility of the azido groups as reactive handles is demonstrated by further functionalization with 6‐carboxyfluorescein and oligonucleotides through copper‐free strain‐promoted azide—alkyne cycloaddition, ideal for biological applications. UV melting profiles and atomic force microscopy (AFM) images of mixtures of nanotubes functionalized with complementary oligonucleotide strands are consistent with hybridization‐controlled bundling—debundling equilibria.

Accurate determination of enantiomeric purity is essential for advancing chiral materials in nanotechnology, optoelectronics, and quantum information science. Chiroptical spectroscopic techniques provide rapid, non-destructive measurements of enantiomeric excess (ee), but their use for complex systems like single-walled carbon nanotubes (SWCNTs) is limited by the lack of enantiopure references for calibration. Here we demonstrate an absolute approach combining hyperspectral imaging (HSI) with single-nanotube counting statistics and ensemble chiroptical spectroscopy such as electronic circular dichroism (ECD) and Raman optical activity (ROA) to quantify ee without requiring such standards. Analysis of thousands of individual nanotubes reveals sensitivity of HSI and chiroptical responses to synthesis, purification, and SWCNT concentration, highlighting pronounced source-dependent inhomogeneity. Nevertheless, universal calibration curves for ECD and ROA intensities are established from the purest, most uniform enantiomer-sorted samples. This methodology is extendable to other SWCNT chiralities and chiroptical techniques, enabling quantitative enantiomer sorting and systematic investigations of chirality-dependent properties and applications.

Semiconducting single-walled carbon nanotubes (SWCNTs) are versatile near-infrared fluorophores that are engineered to create sensors displaying modulated fluorescence upon interaction with target analytes. SWCNT properties depend on both surface functionalization and underlying lattice structure, defined by the chiral indices ( n , m ), enabling the development of wavelength-tunable nanosensors for biological research and diagnostic applications. While the principles of specific SWCNT surface modification with biomacromolecules have been widely investigated, the impact of surface chemistry and nanotube structure on protein interactions in complex biological fluids remains underexplored. Here, we investigated the role of SWCNT surface coating and chirality in protein corona formation in human blood plasma using mass spectrometry–based proteomics. We systematically compared protein corona formation across single-stranded (ssDNA)- and PEG-phospholipid-coated SWCNTs, as well as across nanotube chiralities ranging from (6,4) to (9,4). Our findings indicate that surface coating identity is the dominant factor governing differential protein adsorption. SWCNTs coated with tight-binding ssDNA sequences exhibited greater protein-corona selectivity, preferentially enriching apolipoproteins and more internally structured proteins, whereas the PEG-phospholipid coating globally reduced, though did not eliminate, protein adsorption. Larger-diameter SWCNTs adsorbed proteins with lower secondary-structure content and greater molecular mass. Protein corona formation was further shaped by protein–protein cooperative binding effects in a SWCNT coating-dependent manner. Finally, molecular dynamics simulations provide mechanistic support for the experimental finding that proteins with higher glycine content display enhanced binding to (GT) ₆ - compared to (TAT) ₄ -coated SWCNTs through distinct glycine-peptide binding modes. These insights provide a framework for the rational design of SWCNT-based sensors for protein-profile recognition in complex biological environments.

Control over the chiroptical properties of low-dimensional semiconductors is a promising route toward next-generation optoelectronics and photonics. With their helical chirality, single-wall carbon nanotubes (SWCNTs) offer a suitable framework for exploring chiral excitonic states. In addition to intrinsic, one-dimensional excitons, the targeted functionalization of SWCNTs with luminescent defects introduces zero-dimensional quantum states that enhance photoluminescence quantum yields and exhibit single-photon emission at room temperature. Here, we demonstrate that these defect states inherit the chirality of the respective SWCNT enantiomer, as evident from near-infrared circular dichroism. This observation is achieved by utilizing photocatalysis for efficient and versatile functionalization of SWCNTs with luminescent oxygen defects. The employed approach, based on anthraquinone derivatives as photocatalysts, is applicable to SWCNTs with different diameters, in aqueous or organic dispersions, with different surfactants, and even enables lateral patterning of defects in SWCNT networks. Low catalyst concentrations and the absence of cytotoxic metals or reactants make this functionalization method highly biocompatible. Introducing luminescent defects with uniform binding configurations in sorted nanotube enantiomers represents a key step toward chirality control of quantum defects in SWCNTs.

Separation of single-chirality single-wall carbon nanotubes (SWCNTs) and their enantiomers holds significant potential for materials science and various applications but challenges in scalability and precision persist. In this study, we introduce a systematic approach to identify separation conditions for metallic SWCNTs in aqueous two-phase extraction (ATPE), precisely identifying improved conditions for isolating multiple armchair and chiral (n,m) species. We quantify these conditions by determining partition coefficient change condition (PCCC) values for both binary and ternary surfactant combinations. This information enables optimization for efficient separation of high-purity armchair nanotubes such as (6,6), (7,7), (8,8) and (9,9), and for isolation of enantiomeric nonarmchair nanotubes, including challenging metallic species such as the (8,5), (7,4), (9,3), (10,4) and (10,7). Lastly, separated single (n,m) populations are reseparated in ATPE at precise steps in both binary and ternary surfactant mixtures to resolve their enantiomers, extracting information on the underlying mechanism of metallic SWCNT ATPE and highlighting the utility of sodium cholate for achieving single enantiomer level separations.

Hyperspectral imaging captures both spectral and spatial information from a sample but is intrinsically slow. The near infrared (NIR, > 800 nm) is advantageous for imaging applications because it falls into the tissue transparency window and also contains vibrational overtone and combination modes useful for molecular fingerprinting. Here, fast hyperspectral NIR imaging is demonstrated using a spectral phasor transformation (HyperNIR). A liquid crystal variable retarder (LCVR) is used for tunable, wavelength‐dependent sine‐ and cosine‐filtering that transforms optical signals into a 2D spectral (phasor) space. Spectral information is thus obtained with just three images. The LCVR can be adjusted to cover a spectral range from 900 to 1600 nm in windows tunable from 50 to 700 nm, which enables distinguishing NIR fluorophores with emission peaks less than 5 nm apart. Furthermore, label‐free hyperspectral NIR reflectance imaging is demonstrated to identify plastic polymers and monitor in vivo plant health. The approach uses the full camera resolution and reaches hyperspectral frame rates of 0.2 s⁻¹, limited only by the switching rate of the LCVR. HyperNIR facilitates straightforward hyperspectral imaging for applications in biomedicine and environmental monitoring.

(6,5) SWCNTs exhibited an adsorption-controlled process, while (6,6) SWCNTs demonstrated a diffusion-controlled process.

Semiconducting single-wall carbon nanotubes (SWCNTs) are a promising material platform for near-infrared in vivo imaging, optical sensing, and single-photon emission at telecommunication wavelengths. The functionalization of SWCNTs with luminescent defects can lead to significantly enhanced photoluminescence (PL) properties due to efficient trapping of highly mobile excitons and red-shifted emission from these trap states. Among the most studied luminescent defect types are oxygen and aryl defects that have largely similar optical properties. So far, no direct comparison between SWCNTs functionalized with oxygen and aryl defects under identical conditions has been performed. Here, we employ a combination of spectroscopic techniques to quantify the number of defects, their distribution along the nanotubes and thus their exciton trapping efficiencies. The different slopes of Raman D/G⁺ ratios versus calculated defect densities from PL quantum yield measurements indicate substantial dissimilarities between oxygen and aryl defects. Supported by statistical analysis of single-nanotube PL spectra at cryogenic temperatures they reveal clustering of oxygen defects. The clustering of 2–3 oxygen defects, which act as a single exciton trap, occurs irrespective of the functionalization method and thus enables the use of simple equations to determine the density of oxygen defects and defect clusters in SWCNTs based on standard Raman spectroscopy. The presented analytical approach is a versatile and sensitive tool to study defect distribution and clustering in SWCNTs and can be applied to any new functionalization method.

The covalent functionalization of single-walled carbon nanotubes (SWNTs) with luminescent oxygen defects increases their brightness and enables their application as optical biosensors or fluorescent probes for in vivo imaging in the second-biological window (NIR-II). However, obtaining luminescent defects with high brightness is challenging with the current functionalization methods due to a restricted window of reaction conditions or the necessity for controlled irradiation with ultraviolet light. Here, we report a method for introducing luminescent oxygen defects via a Fenton-like reaction that uses benign and inexpensive chemicals without light irradiation. (6,5) SWNTs in aqueous dispersion functionalized with this method show bright E₁₁* emission (1105 nm) with 3.2 times higher peak intensities than the pristine E₁₁ emission and a reproducible photoluminescence quantum yield of 3%. The functionalization can be performed within a wide range of reaction parameters and even with unsorted nanotube raw material at high concentrations (100 mg L^-1), giving access to large amounts of brightly luminescent SWNTs. We further find that the introduced oxygen defects rearrange under light irradiation, which gives additional insights into the structure and dynamics of oxygen defects. Finally, the functionalization of ultrashort SWNTs with oxygen defects also enables high photoluminescence quantum yields. Their excellent emission properties are retained after surfactant exchange with biocompatible pegylated phospholipids or single-stranded DNA to make them suitable for in vivo NIR-II imaging and dopamine sensing.