Skip to main content
NCBI home page
ACS Omega logoLink to ACS Omega
. 2024 Mar 26;9(14):16496–16507. doi: 10.1021/acsomega.4c00240

Shielding Effects Provide a Dominant Mechanism in J-Aggregation-Induced Photoluminescence Enhancement of Carbon Nanotubes

Hubert Piwoński 1,*, Kacper Szczepski 1, Mariusz Jaremko 1, Łukasz Jaremko 1, Satoshi Habuchi 1,*
PMCID: PMC11007775  PMID: 38617658

Abstract

graphic file with name ao4c00240_0008.jpg

The unique photophysical properties of single-walled carbon nanotubes (SWCNTs) exhibit great potential for bioimaging applications. This led to extensive exploration of photosensitization methods to improve their faint shortwave infrared (SWIR) photoluminescence. Here, we report the mechanisms of SWCNT-assisted J-aggregation of cyanine dyes and the associated photoluminescence enhancement of SWCNTs in the SWIR spectral region. Surprisingly, we found that excitation energy transfer between the cyanine dyes and SWCNTs makes a negligible contribution to the overall photoluminescence enhancement. Instead, the shielding of SWCNTs from the surrounding water molecules through hydrogen bond-assisted macromolecular reorganization of ionic surfactants triggered by counterions and the physisorption of the dye molecules on the side walls of SWCNTs play a primary role in the photoluminescence enhancement of SWCNTs. We observed 2 orders of magnitude photoluminescence enhancement of SWCNTs by optimizing these factors. Our findings suggest that the proper shielding of SWCNTs is the critical factor for their photoluminescence enhancement, which has important implications for their application as imaging agents in biological settings.

Introduction

The composition of sp2-hybridized carbon can be tailored to meet the desired structural performance of nanomaterials of different dimensionalities, including graphene, fullerene, and single-walled carbon nanotubes (SWCNTs). Their exceptional intrinsic properties allowed broad application in diverse areas, including energy storage, chemical processing, quantum photonics, optoelectronics, bioimaging, biotechnology, and medicine.1−3 To harness their unique properties in applications to biological systems, one must convert them from organic- to water-soluble and conquer the tendency to agglomerate into large aggregates or bundles before their implementation to any practical use. Even the least invasive surface modification of carbon nanomaterials can impact the intrinsic properties since their constituent atoms reside entirely on the surface. Consequently, surface chemistry is the most essential part of tailoring their properties. Noncovalent functionalization helps in improving solubility while preserving the intrinsic properties of the system. Thus, noncovalent surface coating by aromatic compounds, amphiphilic molecules, polymers, and DNA has become the most common approach for generating stable and biocompatible aqueous dispersions of different carbon nanomaterials.

Among those nanomaterials, SWCNTs have attracted tremendous attention as unique nanoscale shortwave infrared (SWIR) light emitters of high photostability, making them promising candidates for optoelectronics, deep-tissue imaging,4 and sensing applications.5 Their optical bandgap and distinct electronic properties determined by the quasi-1D structure with a highly delocalized π-electron network result in narrow and diameter-dependent optical bands, allowing for the tuning of absorption and emission by controlling the nanotube diameter and chirality during the synthesis or postsynthetic sorting.6−10 SWCNTs have been successfully utilized as fluorescence probes, including hyperspectral imaging in live mammalian cells,11 probing cell surface receptors,12 subcellular localization in plant cells,13 deep-tissue imaging,14,15 and whole-body small animal imaging.16,17 Although SWCNTs display stable photoluminescence, they typically show low fluorescence quantum yield (QY) in an aqueous suspension (QY varies between 10–4 and 0.01),14,18,19 significantly limiting their single-particle deep-tissue imaging and tracking applications.20 Therefore, developing methods to enhance the photoluminescence brightness of SWCNTs is crucial for improving their sensitivity and detection capabilities.

Various factors contribute to the quenching of the photoluminescence of SWCNTs, including sonication conditions,21 electron-transfer reactions,22 presence of transition-metal ions,23 hole doping,24 and chemically disrupted sp2-hybridized carbon lattice.25−28 Minimizing those effects by attenuating nonradiative relaxation processes leads to QY enhancement,14,29−31 resulting in improved photoluminescence brightness. Mild covalent functionalization,30,32−37 surface coating by ionic surfactants,38−41 ssDNA,42 and defect passivation43,44 have shown significant effects on the photoluminescence enhancement of SWCNTs. In aqueous dispersion, QY as high as QY = 0.08 has been reported for individual SWCNTs (e.g., not an ensemble average).45

Photosensitization (e.g., excitation energy transfer (EET) from photosensitizers to SWCNTs) is an alternative approach to enhance the photoluminescence of SWCNTs. Photosensitizing molecules could be encapsulated in SWCNTs46,47 or attached to the side walls of SWCNTs by either van der Waals, π–π, or charge-transfer interactions.26,48−53 Since the light absorption of the sensitizers and following EET to SWCNTs determine the photoluminescence enhancement, a significant enhancement is, in principle, achieved by depositing a sensitizer with a large absorption cross section at a high density on the surface of SWCNTs. Recently, photoluminescence enhancement of SWCNTs by a molecular aggregate of organic dyes with a slip-stacked arrangement (i.e., J-aggregate) assembled on SWCNTs has been reported.54−56 J-aggregates are unique fluorescent supramolecular assemblies formed by highly ordered organic dyes characterized by a narrow absorption band, large enhanced absorption cross section, and fast and coherent exciton delocalization and migration.57,58 Thus, in principle, J-aggregate-SWCNT complexes could provide highly emissive nanocomposites, allowing imaging experiments under challenging conditions (e.g., single-particle imaging in highly scattering and autofluorescing environments). However, due to their complicated excited-state dynamics and interactions with surrounding environments (e.g., ionic surfactants, counterions, and SWCNTs), the exact mechanisms of photosensitizer-mediated photoluminescence enhancement of SWCNTs, in particular J-aggregates-induced photoluminescence enhancement, remain elusive.

In this study, we investigated detailed mechanisms of SWCNT-assisted J-aggregate formation using two cyanine dyes (S2165 and S0845, Figure 1) with different water solubilities and associated photoluminescence enhancement of SWCNTs. We found that the photoluminescence intensity of SWCNTs was enhanced about a hundredfold under optimized conditions. In addition, narrow absorption bands of the J-aggregates on SWCNTs allowed us to separate the impact of environmental factors and EET on the photoluminescence enhancement of the J-aggregate-SWCNT complexes. Surprisingly, our findings suggest a dominant contribution of the shielding effect of the SWCNTs on the photoluminescence enhancement with a negligible contribution of EET.

Figure 1.

Figure 1

Open in a new tab

(a) Chemical structure of water-soluble S2165 cyanine dye containing sulfobutyl chains. (b) Absorption spectra of S2165 in water-4SDBS (black) and in the presence of 4SDBS-stabilized HiPco SWCNTs (blue). (c) Fluorescence spectra of S2165 in water-4SDBS (black) and in aggregated form in the presence of 4SDBS-stabilized HiPco SWCNTs (blue) upon 530 nm excitation. (d) SWIR fluorescence spectra of 4SDBS-stabilized HiPco SWCNTs in the absence (dashed lines) and presence (solid lines) of S2165 upon 530 nm (blue) and 595 nm (red) excitation. The sharp peaks observed at 1060 nm are the scattering of the excitation light. (e) SWIR photoluminescence spectra of 4SDBS-stabilized HiPco SWCNTs (black) and the same nanotubes in the presence of S2165 (blue) upon 785 nm excitation. (f) Chemical structure of the solvent-insoluble S0845 cyanine dye with propenyl chains. (g) Absorption spectra of S0845 dispersed in water-4SDBS (black) and in the presence of 4SDBS-stabilized HiPco SWCNTs (red). (h) Fluorescence spectra of the S0845 aggregates in water-4SDBS (black) and in the presence of 4SDBS-stabilized HiPco SWCNTs (red) upon 530 nm excitation. (i) SWIR photoluminescence spectra of 4SDBS-stabilized HiPco SWCNTs in the absence (dashed lines) and presence (solid lines) of S0845 recorded upon 530 nm (blue) and 595 nm (red) excitation. (j) SWIR photoluminescence spectra of 4SDBS-stabilized HiPco SWCNTs (black) and the same nanotubes in the presence of S0845 (red) recorded upon excitation at 785 nm.

Results and Discussion

Spectroscopic Properties of Cyanine Dye-SWCNT Complexes

The water-soluble cyanine dye S2165 (Figure 1a) in water-4SDBS solution has a maximum absorption at 583 nm with a corresponding sub-band at 547 nm, showing intense emission spectra peaking at 606 nm (Figure 1b,c). The introduction of S2165 into an aqueous dispersion of HiPco SWCNTs stabilized by a surfactant, sodium 4-dodecylbenzenesulfonate (4SDBS), did not affect the peak absorption of S2165 (Figure 1b). However, this led to spectral broadening (Figure 1b), indicating the interaction between S2165 and the SWCNTs. We observed a significant quenching of S2165 fluorescence upon mixing with the 4SDBS-stabilized HiPco SWCNTs (Figure 1c), also indicating their interaction and associated changes in the excited-state processes of S2165. A weak SWIR photoluminescence of 4SDBS-stabilized HiPco SWCNTs was observed upon excitation at 530 or 595 nm (Figure 1d), whereas the photoluminescence spectra of the S2165-SWCNT complex in the SWIR spectral region excited at 530 or 595 nm were dominated by the tail fluorescence of S2165 (Figure 1d) without any detectable photoluminescence of SWCNTs. The result does not support photosensitization by the adsorbed S2165 dyes. SWIR photoluminescence of the 4SDBS-stabilized HiPco SWCNTs in the water excited at 785 nm (i.e., outside the spectral range of the S2165 absorption) was partially quenched in the spectral range 950–1200 nm upon adding S2165 (Figure 1e). This is accompanied by the concomitant slight fluorescence enhancement in the spectral range of SWCNTs with large diameters (Figure 1e), indicating substantial variations among the different nanotubes.

The solvent-soluble cyanine dye S0845 (Figure 1f) in a water-4SDBS solution exhibited a peak absorption at 553 nm accompanied by a less intense vibronic band at 597 nm (Figure 1g). The change in the absorption spectrum compared with that in an organic solvent (methanol) indicates the formation of S0845 aggregates in the water-4SDBS solution (Figure S1). S0845 in water-4SDBS showed a less bright fluorescence emission upon excitation at 530 nm than S2165, with a maximum located at 632 nm (Figure 1h). We observed a change in the absorption spectra of S0845 upon adding it to an aqueous dispersion of the 4SDBS-stabilized HiPco SWCNTs, including a more intense bathochromic peak at 596 nm and a sub-band at 557 nm (Figure 1g and Figure S2a), which indicates the interaction of S0845 and the SWCNTs. Mixing S0845 and the 4SDBS-stabilized HiPco SWCNTs resulted in almost complete quenching of the S0845 fluorescence upon excitation at 530 nm (Figure 1h and Figure S2b). We also observed an enhancement in the photoluminescence brightness of the 4SDBS-stabilized HiPco SWCNTs excited at 530 or 595 nm in the presence of S0845 (Figure 1d,i). While the result potentially indicates efficient photosensitization through EET from the excited state of S0845 to the SWCNTs, we also found that the photoluminescence of the 4SDBS-stabilized HiPco SWCNTs in water excited at 785 nm was enhanced by a factor of 15 upon adding S0845 (Figure 1j and Figure S2c,d). The result may indicate that the photoluminescence of SWCNTs could be enhanced by surface-adsorbed dye molecules through a mechanism different from photosensitization.

Photoluminescence Enhancement of SWCNTs through J-Aggregate Formation

A previous study on a cyanine dye structurally similar to S2165 showed J-aggregate formation on 4SDBS-stabilized HiPco SWCNTs.54 In our experiment, we did not observe the formation of J-aggregates of S2165 upon mixing with the 4SDBS-stabilized HiPco SWCNTs in water. We thus added cation (Mg2+) to the SWCNT suspension, which promotes the J-aggregate formation of organic dyes in aqueous solution.59,60 We found the appearance of a sharp red-shifted absorption band at 632 nm, a signature of the formation of S2165 J-aggregates, upon mixing the dye with the 4SDBS-stabilized HiPco SWCNT aqueous suspension in the presence of a low concentration of MgCl2 (Figure 2a and Figure S3a). We note that the concentration of MgCl2 required for the formation of the S2165 J-aggregates on the 4SDBS-stabilized HiPco SWCNTs (up to 1.75 × 10–4 M, Figure S3a) is much lower than that required for the S2165 J-aggregate formation in an aqueous solution (up to 1 M, Figure S4). In addition, the peak absorption of the S2165 J-aggregates formed on the 4SDBS-stabilized HiPco SWCNTs (633 nm, Figure 2a and Figure S3a) is much shorter than those formed in water at elevated MgCl2 concentrations (640 nm, Figure S4), demonstrating SWCNT-assisted formation of the J-aggregates (i.e., not salt-induced J-aggregation).

Figure 2.

Figure 2

Open in a new tab

(a) Normalized absorption spectra of the S2165 J-aggregates (red) and S0845 aggregates (blue) on the 4SDBS-stabilized HiPco SWCNTs with the depicted excitation wavelength used in the titration experiment shown in panels (c) and (d). Absorption spectra of 4SDBS-stabilized HiPco SWCNTs dispersed in water were used as a reference to remove the contribution of the absorption bands of SWCNTs. (b) SWIR photoluminescence spectra of the S2165-4SDBS-stabilized HiPco SWCNT complex in the absence (blue) and presence (red) of 35 μM Mg2+ upon 785 nm excitation. (c) Relative SWIR photoluminescence intensities of the S2165-4SDBS-stabilized HiPco SWCNT complex at varied concentrations of MgCl2 upon excitation at 633 nm (J-band, red), 638 nm (outside the J-band, blue), 650 nm (cyan), and 785 nm (magenta). (d) Relative SWIR photoluminescence intensities of the 4SDBS-stabilized HiPco SWCNT complex at varied concentrations of MgCl2 upon excitation at 633 nm (red) and 785 nm (magenta). Each point in panels (c) and (d) represents the integrated photoluminescence of the SWCNT dispersion at a specific titrant concentration divided by the integrated photoluminescence of intact/untreated SWCNT dispersion.

Concomitant with the appearance of the red-shifted sharp absorption band, the fluorescence of S2165 showed progressive intensity reduction with the appearance of a characteristic persistent deep cut in the spectra, which perfectly overlaps with the peak absorption of the newly appearing J-band (Figure S3b). This sharp dip is attributed to the reabsorption of the monomer S2165 fluorescence by the J-aggregates formed on the SWCNTs, with an efficient EET from the excited state of the S2165 J-aggregates to the nanotube scaffold.

We found that the photoluminescence of the S2165-4SDBS-stabilized HiPco SWCNT complex excited at 785 nm (i.e., direct excitation of SWCNTs) enhanced significantly (15-fold) upon adding MgCl2 (Figure 2b, and S3c). The significant photoluminescence enhancement of the 4SDBS-stabilized HiPco SWCNTs by the S2165 J-aggregates (Figure 2b, Figure S3c) upon excitation at 785 nm (i.e., the wavelength with no absorption of the adsorbed dyes) prompted us to perform a more in-depth investigation of the involvement of EET from the S2165 J-aggregates to the SWCNTs in the photoluminescence enhancement of SWCNTs. To that end, we utilized the narrow absorption band of the S2165 J-aggregates in the S2165-SWCNT complex. We excited the complex at four excitation wavelengths: 633 nm for the selective excitation of the S2165 J-aggregates and 638, 660, and 785 nm for the selective excitation of the SWCNTs (Figure 2a). The formation of the S2165 J-aggregates by adding MgCl2 resulted in up to nearly 2 orders of magnitude enhancement in the SWIR emission of the S2165-SWCNT complex when excited at 633 nm (Figure 2c). Importantly, we did not observe any significant difference in the photoluminescence enhancement of the S2165-SWCNT complex between 633 and 638 nm excitation by adding MgCl2 (Figure 2c), although there is a substantial difference in the excitation efficiency of the S2165 J-aggregates in these two wavelengths. This result raises doubts about the involvement of EET (i.e., photosensitization) in the photoluminescence enhancement of SWCNTs by the adsorbed dye molecules, which has been reported by many previous studies.49−52,54

We found that the photoluminescence of the 4SDBS-stabilized HiPco SWCNTs excited at 633 nm was enhanced up to 45 times by adding MgCl2 (Figure 2d). This result strongly suggests that EET from the S2165 J-aggregates to the SWCNTs is not the primary mechanism for the enhancement of the SWCNT photoluminescence, and a different mechanism is dominant in the observed photoluminescence enhancement of the SWCNTs. The photoluminescence enhancement of the S2165-SWCNT complex up to 15-fold was observed at 650 and 785 nm excitation by adding MgCl2 (Figure 2d). A similar photoluminescence enhancement was observed for the 4SDBS-stabilized HiPco SWCNTs excited at 785 nm by the addition of MgCl2 (Figure 2d). Given that there is no light absorption of S2165 at these wavelengths, these results further suggest that the photoluminescence of SWCNTs could be enhanced by a mechanism different from photosensitization.

Interestingly, the adsorption of S0845 to the 4SDBS-stabilized HiPco SWCNTs led to photoluminescence enhancement of SWCNTs similar to that induced by Mg2+, including their wavelength dependence (i.e., 45- and 15-fold enhancement when excited at 595–633 and 785 nm, respectively, Figure S 2d), although their (photo)physical interaction with SWCNTs must be very different. We also found that the J-aggregation of S2165 on the 4SDBS-stabilized HiPco SWCNTs led to the marginal photoluminescence enhancement of SWCNTs compared with S0845 and Mg2+ when excited at 633 nm (Figure 2d and Figure S 2d). In addition, their contributions to the photoluminescence enhancement of SWCNTs excited at 785 nm are nearly identical (Figure 2c,d and Figure S 2d). The fact that S2165 and S0845 interact with SWCNTs differently (i.e., electrostatic interaction and hydrophobic interaction for S2165 and S0845, respectively, see Supporting Text 1) may indicate that a shielding effect (i.e., physical isolation of SWCNTs from the aqueous solution) is dominant in the observed photoluminescence enhancement of SWCNTs. The observed general trend (i.e., wavelength-dependent photoluminescence enhancement of SWCNTs by S2165, S0845, and Mg2+) could also be explained by the diameter (curvature)-dependent coverage of SWCNTs by adsorbed molecules reported previously (see Supporting Text 2).61,62 The excess 4SDBS in the S2165-SWCNT complex suspension led to up to 20-fold enhancement of SWCNT photoluminescence when excited at 785 nm (see Supporting Information, Text 3), further supporting this hypothesis.

Contribution of the Photosensitization on the Photoluminescence Enhancement of SWCNTs

Photosensitization (i.e., EET from adsorbed dyes to SWCNTs) has been reported as a primary origin of the photoluminescence enhancement of dye-coated SWCNTs.48,51,52,54,63,64 However, our results showed that adsorbed dyes, surfactants, and cations affect the photoluminescence behavior of SWCNTs, questioning the contribution of EET to the dye-induced photoluminescence enhancement of SWCNTs. Nearly complete quenching of the S0845 fluorescence upon mixing with the 4SDBS-stabilized HiPco SWCNTs (Figure 1h) may still indicate the existence of EET. Thus, we compared the photoluminescence spectra of the 4SDBS-stabilized HiPco SWCNTs and the 4SDBS-stabilized HiPco SWCNTs mixed with S0845. If EET-induced photoluminescence enhancement occurs, then the (7.5) chirality of SWCNTs that have absorption at a fluorescence wavelength of S0845 would be selectively enhanced. Photoluminescence spectra of 4SDBS-stabilized HiPco SWCNTs mixed with S0845 upon excitation at 595 nm (i.e., the absorption band of S0845) revealed overall 2-fold enhancement as compared to 4SDBS-stabilized HiPco SWCNTs, including the emission peak corresponding to (7.5) chiral nanotubes (Figure 3a), which may be attributed to EET.54 However, photoluminescence spectra of SWCNTs mixed with S0845 recorded upon 633 nm excitation (out of the dye absorption range) revealed a further increase in the (7.5) SWCNT emission peak (Figure 3b), which cannot be explained by the EET mechanism. In addition, we did not observe a significant difference in the (7.5) emission peak in the photoluminescence spectra of 4SDBS-stabilized HiPco SWCNTs and those mixed with S0845 upon 633 nm excitation (Figure 3b). Together, these results suggest that the contribution of EET to the photoluminescence enhancement of the SWCNTs is marginal, although their involvement cannot be entirely excluded.

Figure 3.

Figure 3

Open in a new tab

SWIR photoluminescence spectra of 4SDBS-stabilized HiPco SWCNTs in water (black) and in an aqueous solution containing 10.8 μM S0845 (red) upon excitation at (a) 595 and (b) 633 nm. (c) SWIR photoluminescence spectra of 4SDBS-stabilized HiPco SWCNTs in an aqueous dispersion containing 210 μM Mg2+ (blue) and the S2165-4SDBS-stabilized HiPco SWCNT complex in an aqueous dispersion containing 105 μM Mg2+ (green). The spectra were recorded upon 633 nm excitation. The position of the emission peak corresponding to (7.5) chiral nanotubes has been indicated in all panels.

We also found that the 4SDBS-stabilized HiPco SWCNTs and the 4SDBS-stabilized HiPco SWCNTs mixed with S2165 in the presence of Mg2+ (i.e., S2165 J-aggregates-SWCNT complex) showed very similar photoluminescence spectra (Figure 3c). Although the presence of both S2165 J-aggregates and monomers on SWCNTs makes the quantitative discussion difficult, the observation is consistent with the conclusions derived from the S0845-SWCNT complexes.

Contribution of the Shielding Effect on the Photoluminescence Enhancement of SWCNTs

The shielding effect is a potential alternative mechanism for the photoluminescence enhancement of SWCNTs by the 4SDBS surfactant, Mg2+, and cyanine dyes. It is well-known that surfactant–SWCNT interactions modify the characteristics of SWCNTs. Although the surface coating of SWCNTs by surfactants is primarily for improving its dispersion stability in an aqueous environment and the separation of SWCNTs with different chirality,65,66 the surface coating by surfactants has been reported to contribute to the enhancement of the photoluminescence of SWCNTs.14 Previous studies suggested that 4SDBS adsorbs on SWCNTs in two steps.67−69 The first step occurring at a low concentration is random adsorption of 4SDBS, with their hydrophobic tails parallel to the long axis of SWCNTs.67 At a high concentration, 4SDBS is reorganized into a more ordered adsorption with their aliphatic tails arranged perpendicular to the long axis of SWCNTs.67 The observed 4SDBS concentration-dependent photoluminescence enhancement (Figure S5) indicates that SWCNTs are better protected from the environment when 4SDBS has tightly packed ordered adsorption on SWCNTs.

The addition of cations to surfactant-coated SWCNTs was reported to have an additional protection effect on SWCNTs, leading to the photoluminescence enhancement of SWCNTs,8,40 although the mechanisms of the photoluminescence enhancement have not been fully characterized. Previous studies indicated that cations might penetrate the hydrogen shell of the surfactant head groups and restrict the mobility of water molecules.70 Cations were also reported to trigger the reorganization of the surfactants into a tight and ordered configuration.8,41,71−73 This could contribute to the photoluminescence enhancement of the SWCNTs. To test this hypothesis, we performed a 1D 1H NMR study on 4SDBS-stabilized HiPco SWCNTs dispersions in the absence and presence of Mg2+ and compared them with a 1H NMR spectrum of a free 4SDBS in water. A significant change in 1H NMR spectra of 4SDBS was observed at the 7–8 ppm range, which can be assigned to aromatic protons of the benzenesulfonate group, and at 3.26 ppm, which is not associated with any protons of the 4SDBS molecule structure (Figure 4 and Figure S6). Signals from the aromatic protons of 4SDBS in water appeared in the form of triplet and doublet of doublets around 7.62 and 7.30 ppm, respectively, while lacking any signal at 3.26 ppm (Figure 4b,c). In the presence of SWCNTs, the triplet and doublet of doublets broadened and reduced their intensities (Figure 4b). Simultaneously, a weak signal at 3.26 ppm appeared (Figure 4c). The broadening of the proton signals from the benzenesulfonate group is interpreted by a partially restricted mobility of the protons in the presence of SWCNTs. Upon adding Mg2+, the signals from the aromatic protons merged and further decreased their intensity due to increased restriction of the mobility of protons, reflecting the rearrangement of the benzenesulfonate groups and the formation of the bridged configuration with Mg2+. Simultaneously, the peak at 3.26 ppm increased massively.

Figure 4.

Figure 4

Open in a new tab

(a) 1D 1H NMR spectra of free 4SDBS in water (black) and 4SDBS adsorbed on the surface of HiPco SWCNTs in the absence (red) and presence (blue) of Mg2+. Enlarged views of the spectra are highlighted by (b) cyan rectangle and (c) magenta rectangle in (a).

Computer simulation studies indicated that Mg2+ could enter into the first hydration shell of the head groups of sulfonate surfactants, cause the ordering of water molecules around the head groups, and increase the strength of hydrogen bonds.74,75 These studies also indicated that water molecules in the first hydration shell bind to the sulfonate group either directly or through bridging by introduced Mg2+. Our 1D 1H NMR experiment provides the first direct evidence that a new hydrogen bonding network formed between water molecules and 4SDBS on the surface of SWCNTs is significantly enhanced by Mg2+ (see Supporting Text 4). This finding strongly suggests that the observed Mg2+-induced photoluminescence enhancement of the 4SDBS-stabilized SWCNTs by a factor of up to 45 can be interpreted by the hydrogen bond-assisted isolation of SWCNTs from the bulk water molecules, a well-known fluorescence quencher.76,77

Salt-Induced Reorganization of Cyanine Dyes Interacting with 4SDBS-Stabilized SWCNTs and Its Contribution to the Photoluminescence Enhancement of SWCNTs

The salt-induced J-aggregation of S2165 and its contribution to the photoluminescence enhancement of SWCNTs are also accounted for by the salt-induced reorganization of 4SDBS. The fluorescence of S2165 and the photoluminescence of the 4SDBS-stabilized SWCNTs are both quenched upon their interaction (Figure 1c–e). A similar mutual quenching was reported for a cationic organic dye, methylene blue, which was attributed to a charge-transfer complex with an in-plane orientation of the dyes on the surface of SWCNTs.61,78 This indicates that S2165 interacts with the 4SDBS-stabilized SWCNTs with an in-plane orientation due to the electrostatic attraction between the positively charged chromophore unit and the highly negatively charged SWCNT surface by 4SDBS (Figure 5a). Adding Mg2+ to the suspension led to the significant enhancement of the photoluminescence of SWCNTs (2 orders of magnitude enhancement, Figure 2c). As discussed above, most of the observed enhancement (up to 45-fold) can be attributed to the reorientation of 4SDBS and associated hydrogen bond-assisted bridging of 4SDBS by Mg2+ (see Supporting Text 5).

Figure 5.

Figure 5

Open in a new tab

Proposed model of S2165 dye aggregation on 4SDBS-stabilized HiPco SWCNTs (a) in the absence of Mg2+ and (b) in the presence of Mg2+. (c) Model of the S0845 dye aggregation on the 4SDBS-stabilized HiPco SWCNTs.

This salt-induced surfactant reorganization causes the reorientation of adsorbed S2165 to an out-of-plane orientation through the similar bridging effect between the sulfonic groups of benzenesulfonate and the sulfonyl groups of the sulfobutyl chains of S2165, which is suitable for the formation of J-type aggregates (Figure 5b). In this configuration, the chromophores remain close to the surface of SWCNTs by the electrostatic attraction between the positive charge on the chromophore and the negatively charged surface of SWCNTs. At the same time, the aliphatic chains containing sulfonic groups are exposed to the solution phase and stabilized by Mg2+ bridging with benzenesulfonate groups of 4SDBS. Therefore, the further protection of SWCNTs by the S2165 J-aggregates accounts for the twofold enhancement of the photoluminescence of SWCNTs. The photoluminescence enhancement of 4SDBS-stabilized SWCNTs by the adsorption of S0845 (Figure S 2d) suggests an out-of-plane orientation of S0845 (Figure 5c). In this configuration, S0845 attaches to the surface of the SWCNTs through the aliphatic chains by hydrophobic interactions. The positively charged S0845 chromophore remains exposed to the solution phase and stabilized by interacting with negatively charged benzosulfonic surfactant groups in the chromophore-bridged configuration. The minor enhancement of the photoluminescence of SWCNTs upon adding Mg2+ indicates insignificant reorganization of S0845 and 4SDBS upon adding the salt (Figure S7). The S0845 fluorescence remains quenched on the 4SDBS-stabilized SWCNTs, suggesting an efficient EET to SWCNTs due to its proximity to the SWCNT surface. Together, our findings demonstrate that the photoluminescence enhancement induced by the surface-adsorbed cyanine dyes is predominantly caused by the shielding effect of the SWCNTs from the surrounding bulk water molecules.

Effect of the Surface Curvature

The data presented in this study, as well as those in the previous studies, suggest that 4SDBS on SWCNTs reorganize from the random configuration with their tails parallel to the SWCNT’s long axis into a more ordered configuration with their tails arranged perpendicular to the SWCNT's long axis upon increasing the surfactant concentration or adding electrolytes. Since SWCNTs with smaller curvature (i.e., SWCNTs with larger diameters that emit photoluminescence at longer wavelengths)79 are coated by the surfactant molecules more efficiently,80,81 the surfactant coverage-induced reorganization of 4SDBS to the perpendicular configuration would occur much efficiently at a given 4SDBS concentration. Indeed, we observed chirality-dependent photoluminescence enhancement of SWCNTs with a gradual increase in the 4SDBS concentration in the SWCNTs dispersion (Figure S8).

Similarly, since the salt-bridged perpendicular configuration of 4SDBS is essential for the formation of the Mg2+-induced S2165 J-aggregates on SWCNTs, this Mg2+-induced process would be much more efficient for SWCNTs with a smaller curvature at a given Mg2+ concentration. Indeed, we found selective photoluminescence enhancement of SWCNTs with smaller curvatures in the S2165-SWCNT dispersion exposed to low Mg2+ concentrations (Figure 6a). At higher Mg2+ concentrations, the photoluminescence of SWCNTs with larger curvatures that emit at shorter wavelengths was also enhanced (Figure 6b,c), confirming 4SDBS reorganization and S2165 J-aggregation in the salt-bridged perpendicular configuration. These results demonstrate the curvature-dependent protection of SWCNTs by the surfactant and cyanine dye, which leads to the curvature-dependent enhancement of the photoluminescence of SWCNTs. It is also indicated that the characteristic dimensionality of SWCNTs (i.e., a flat surface along the long axis and a curved surface along the short axis) enables the reorganization of 4SDBS and, therefore, the salt-induced photoluminescence enhancement.

Figure 6.

Figure 6

Open in a new tab

Spectrally resolved curvature-dependent enhancement in the SWIR photoluminescence of 4SDBS-stabilized HiPco SWCNTs mixed with S2165 at varied concentrations of MgCl2. (a) 0–8.75 μM, (b) 8.75–41 μM, and (c) 41 μM–0.35 mM Mg2+. Spectra were recorded upon 633 nm excitation. The absorption spectra of the S2165-SWCNT complex in the absence of Mg2+ are also included in panels (b) and (c) (black lines) as a reference.

In addition, a lack of chiroptical activity of the S2165 J-aggregates-SWCNT complex in the circular dichroism experiment indicates the absence of the torsional arrangement of the S2165 molecules, although such a molecular arrangement cannot be excluded completely due to the racemic nature of SWCNTs (Figure S9). The result may indicate the importance of the flatness along the long axis for the formation of the J-aggregate. We tested this hypothesis by measuring the formation of J-aggregates of S2165 on 4SDBS-stabilized carbon nanomaterials with different dimensionalities, C70 fullerene and graphene (Figure 7a). C70 fullerene has a spherical shape without a flat surface; therefore, the J-aggregation requiring a flat surface would be prevented. Indeed, we did not observe the formation of the S2165 J-aggregates on the surface of the C70 fullerene (Figure 7b). Graphene has a two-dimensional flat shape. While the absence of a curved surface would prevent the efficient formation of the salt-bridged perpendicular configuration of 4SDBS, its flat surface may facilitate the formation of the J-aggregates. As predicted, the S2165 J-aggregates were formed on 4SDBS-stabilized graphene but with relatively low efficiency (Figure 7c). Our results suggest that the curvature and dimensionality play a crucial role in the protection and, thus, the photoluminescence enhancement of SWCNTs by the surfactants, salts, and organic dyes.

Figure 7.

Figure 7

Open in a new tab

Effect of the surface curvature of carbon nanomaterials on the rearrangement of 4SDBS surfactant and associated S2165 J-aggregation. (a) Model of 4SDBS arrangement on C70 fullerene (left) and graphene (right) nanoparticles in the presence of Mg2+. (b) Absorption spectra of the S2165–C70 fullerene composite at varied concentrations of S2165 (0–26 μM) with 175 μM Mg2+. (c) Absorption spectra of the S2165–graphene composite at varied concentrations of S2165 (0–26 μM) with 175 μM Mg2+.

Conclusions

This study investigated the mechanisms responsible for the J-aggregate assembly of cyanine dyes on SWCNTs and associated photoluminescence enhancement. Our findings suggest that surfactant reorganization under the electrolyte perturbation and cation-related bridging arrangement of sulfonic groups of the cyanine dye S2165 and 4SDBS surfactant molecules are responsible for the J-aggregate formation. Importantly, our findings revealed that the excitation energy transfer from the cyanine dyes (i.e., photosensitizer) has a negligible contribution to the photoluminescence enhancement of SWCNTs. Organic molecules are tightly adsorbed on the surfaces of SWCNTs and protect them from water, which accounts for up to a 45-fold enhancement of the photoluminescence of SWCNTs. Similarly, restricting water mobility in the micelle hydration shell by hydrogen bonding with surfactant head groups and the counterions contributes to forming a protective barrier, leading to 45-fold photoluminescence enhancement. Altogether, those mechanisms render almost 2 orders of magnitude photoluminescence enhancement. A more significant protection effect was observed for SWCNTs with smaller diameters, which are the most vulnerable to quenching by water molecules due to the extent of unprotected sidewalls. In addition, this study pointed out that the surface dimensionalities of carbon nanomaterials are crucial for the adsorption and rearrangement of interfacial molecules, including surfactants and small organic dyes. Our findings provide general guidelines for designing and constructing composite nanomaterials based on carbon nanomaterials for imaging applications.

Experimental Section

SWCNTs RAW HiPco and PureWave graphene with a flake size of 150–200 nm composed of thin 4–7-layer graphene nanoplatelets and average thickness of 2.4 nm were purchased from Integris. Fullerene-C60 and [5,6]-fullerene-C70 were purchased from Sigma-Aldrich. Cyanine dyes, S0845 (3-butyl-2-[3-(3-butyl-1,3-dihydro-1,1-dimethyl-2H-benzo[e]indol-2-ylidene)-propenyl]-1-1dimethyl-1H-benzeno[e]indolium iodide) and S2165 (2-[3-[1,1-dimethyl-3-(4-sulfobutyl-1,3-dihydro-1,3-dihydro-benzo[e]indol-2-ylidene]-propenyl]-1,1-dimethyl-3-(4-sulfobutyl)-1H benzo[e]indolium hydroxide, sodium salt), were purchased from FEW Chemicals. 4-Dodecylbenzenesulfonate (4SDBS), sodium chloride, calcium chloride, and magnesium chloride were purchased from Sigma-Aldrich. Lithium acetate dehydrate, silver nitrate, and iron(III) chloride hexahydrate were purchased from Fisher.

SWCNT powder (17 mg) was dispersed in deionized water (50 mL) in the presence of surfactants, e.g., sodium 4-dodecylbenzenesulfonate (4SDBS, 0.4 mM) during 4 h of vigorous sonication using an ultrasonic liquid processor FB705 Sonic Dismembrator (Fisher Scientific) followed by 60 min centrifugation with a 5804 Centrifuge (Eppendorf) at 4200 rpm to remove nondispersed materials (see Supporting Text 6).

Steady-state absorption measurements were performed on a Hitachi U-300 spectrometer (UV-NIR) or a PerkinElmer Lambda-900 spectrometer (UV-SWIR). Steady-state fluorescence measurements were performed on a Horiba FluoroMax-4 spectrofluorometer in the VIS-NIR spectral range or Princeton Instruments IsoPlane spectrograph equipped with PyLoN 1700 InGaAs camera in the SWIR range using either a 785 nm beam of a Ti:saphire laser (Spectra-Physics, MaiTai), Ti:saphire laser (Coherent, Chameleon Ultra) equipped with OPO (Coherent, Chameleon Compact OPO), 632.8 nm line of a HeNe laser (Coherent), or 638 and 660 nm laser diodes (OEM Laser) as excitation sources.82,83 We used 1 cm optical path quartz cells (Hellma) for all measurements. The concentration of nanoparticle dispersions in each experiment was adjusted to obtain an optical density of 0.3 at 400 nm (see Supporting Text 7). Typically, 75 μL of 4SDBS stock dispersion was added to 2.925 mL of Milli-Q water, which provided a suspension containing 8.5 μg/mL SWCNTs and 9.6 μM 4SDBS. Circular dichroism spectra were measured on the JASCO J-1500 spectropolarimeter. The concentration of the cyanine dyes was set to 11 μM unless otherwise stated in the figure legends.

NMR samples were prepared by adding 10% (v/v) D2O to water-soluble SWCNTs/4SDBS. 1H NMR spectra were recorded at 24.85 °C on an 800 MHz Bruker Avance NEO NMR spectrometer equipped with a sensitive triple resonance (H/C/N-D) TCI cryogenic probe. 1H 1D data were collected using the standard Bruker pulse program ZGESP with 64 scans and 32,000 data points. NMR data processing and interpretation were performed using Topspin ver. 4.0.7.

Acknowledgments

We thank Dr. Sergey Laptenok for the fruitful discussions.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.4c00240.

  • (Supporting Text 1) Binding modes of S2165 and S0845 cyanine dyes to the 4SDBS-stabilized SWCNTs; (Supporting Text 2) effect of the curvatures of SWCNTs on the adsorption of surfactant molecules; (Supporting Text 3) effect of the 4SDBS concentration on the photoluminescence enhancement of SWCNTs; (Supporting Text 4) assignment of 3.26 ppm signal in 1HMR spectra to the proton of water; (Supporting Text 5) formation of the Mg2+-mediated hydrogen bonding network between 4SDBS on SWCNTs and surrounding water molecules; (Supporting Text 6) bundles of SWCNTs in the samples; and (Supporting Text 7) concentration of the SWCNT suspension, absorption spectra of S0845, absorption and photoluminescence spectra of S0845-SWCNTs complex, effect of Mg2+ on the absorption and photoluminescence spectra of the S2165-SWCNT complex, effect of Mg2+ on the absorption spectra of S2165, effect of 4SDBS on the absorption and photoluminescence spectra of the S2165-SWCNT complex, 1HMR spectra of free 4SDBS and 4SDBS adsorbed on SWCNTs, S0845 concentration-dependent enhancement of SWIR photoluminescence of S0845-SWCNTs complex, 4SDBS concentration-dependent enhancement of SWIR photoluminescence of SWCNTs, circular dichroism spectra of SWCNTs and S2165-SWCNTs complex, effect of Mg2+ on the absorption and photoluminescence intensity of the S2165-SWCNT complex, effect of the high concentration of Mg2+ on the absorption and photoluminescence spectra of the S2165-SWCNT complex, effect of the concentration and valence of cations on the formation of the S2165 J-aggregates on SWCNTs, absorption spectrum of the S2165-SWCNT complex in D2O, SWIR photoluminescence spectra of SWCNTs in H2O and D2O, and absorption spectrum of 4SDBS-SWCNTs in water (PDF)

Author Contributions

The manuscript was written through the contributions of all authors. All authors have given approval to the final version of the manuscript.

This study was supported by King Abdullah University of Science and Technology (KAUST) and the KAUST Office of Sponsored Research (OSR) under award no. OSR-CRG2020-4390.

The authors declare no competing financial interest.

Supplementary Material

ao4c00240_si_001.pdf (1.9MB, pdf)

References

  1. Jariwala D.; Sangwan V. K.; Lauhon L. J.; Marks T. J.; Hersam M. C. Carbon nanomaterials for electronics, optoelectronics, photovoltaics, and sensing. Chem. Soc. Rev. 2013, 42 (7), 2824–2860. 10.1039/C2CS35335K. [DOI] [PubMed] [Google Scholar]
  2. Hong G.; Diao S.; Antaris A. L.; Dai H. Carbon Nanomaterials for Biological Imaging and Nanomedicinal Therapy. Chem. Rev. 2015, 115 (19), 10816–10906. 10.1021/acs.chemrev.5b00008. [DOI] [PubMed] [Google Scholar]
  3. Maiti D.; Tong X.; Mou X.; Yang K. Carbon-Based Nanomaterials for Biomedical Applications: A Recent Study. Front. Pharmacol. 2019, 9, 1401. 10.3389/fphar.2018.01401. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Kagan B.; Hendler-Neumark A.; Wulf V.; Kamber D.; Ehrlich R.; Bisker G. Super-Resolution Near-Infrared Fluorescence Microscopy of Single-Walled Carbon Nanotubes Using Deep Learning. Advanced Photonics Research 2022, 3 (11), 2200244. 10.1002/adpr.202200244. [DOI] [Google Scholar]
  5. Hofferber E. M.; Stapleton J. A.; Iverson N. M. Review—Single Walled Carbon Nanotubes as Optical Sensors for Biological Applications. J. Electrochem. Soc. 2020, 167 (3), 037530 10.1149/1945-7111/ab64bf. [DOI] [Google Scholar]
  6. Diao S.; Hong G.; Robinson J. T.; Jiao L.; Antaris A. L.; Wu J. Z.; Choi C. L.; Dai H. Chirality Enriched (12,1) and (11,3) Single-Walled Carbon Nanotubes for Biological Imaging. J. Am. Chem. Soc. 2012, 134 (41), 16971–16974. 10.1021/ja307966u. [DOI] [PubMed] [Google Scholar]
  7. Arnold M. S.; Green A. A.; Hulvat J. F.; Stupp S. I.; Hersam M. C. Sorting carbon nanotubes by electronic structure using density differentiation. Nat. Nanotechnol. 2006, 1 (1), 60–65. 10.1038/nnano.2006.52. [DOI] [PubMed] [Google Scholar]
  8. Niyogi S.; Densmore C. G.; Doorn S. K. Electrolyte Tuning of Surfactant Interfacial Behavior for Enhanced Density-Based Separations of Single-Walled Carbon Nanotubes. J. Am. Chem. Soc. 2009, 131 (3), 1144–1153. 10.1021/ja807785e. [DOI] [PubMed] [Google Scholar]
  9. Podlesny B.; Shiraki T.; Janas D. One-step sorting of single-walled carbon nanotubes using aqueous two-phase extraction in the presence of basic salts. Sci. Rep. 2020, 10 (1), 9250. 10.1038/s41598-020-66264-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Podlesny B.; Olszewska B.; Yaari Z.; Jena P. V.; Ghahramani G.; Feiner R.; Heller D. A.; Janas D. En route to single-step, two-phase purification of carbon nanotubes facilitated by high-throughput spectroscopy. Sci. Rep. 2021, 11 (1), 10618. 10.1038/s41598-021-89839-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Roxbury D.; Jena P. V.; Williams R. M.; Enyedi B.; Niethammer P.; Marcet S.; Verhaegen M.; Blais-Ouellette S.; Heller D. A. Hyperspectral Microscopy of Near-Infrared Fluorescence Enables 17-Chirality Carbon Nanotube Imaging. Sci. Rep. 2015, 5 (1), 14167. 10.1038/srep14167. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Welsher K.; Liu Z.; Daranciang D.; Dai H. Selective Probing and Imaging of Cells with Single Walled Carbon Nanotubes as Near-Infrared Fluorescent Molecules. Nano Lett. 2008, 8 (2), 586–590. 10.1021/nl072949q. [DOI] [PubMed] [Google Scholar]
  13. Serag M. F.; Kaji N.; Gaillard C.; Okamoto Y.; Terasaka K.; Jabasini M.; Tokeshi M.; Mizukami H.; Bianco A.; Baba Y. Trafficking and Subcellular Localization of Multiwalled Carbon Nanotubes in Plant Cells. ACS Nano 2011, 5 (1), 493–499. 10.1021/nn102344t. [DOI] [PubMed] [Google Scholar]
  14. Welsher K.; Liu Z.; Sherlock S. P.; Robinson J. T.; Chen Z.; Daranciang D.; Dai H. A route to brightly fluorescent carbon nanotubes for near-infrared imaging in mice. Nat. Nanotechnol. 2009, 4 (11), 773–780. 10.1038/nnano.2009.294. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Welsher K.; Sherlock S. P.; Dai H. Deep-tissue anatomical imaging of mice using carbon nanotube fluorophores in the second near-infrared window. Proc. Natl. Acad. Sci. U. S. A. 2011, 108 (22), 8943–8948. 10.1073/pnas.1014501108. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Bisesi J. H. Jr.; Merten J.; Liu K.; Parks A. N.; Afrooz A. R. M. N.; Glenn J. B.; Klaine S. J.; Kane A. S.; Saleh N. B.; Ferguson P. L.; et al. Tracking and Quantification of Single-Walled Carbon Nanotubes in Fish Using Near Infrared Fluorescence. Environ. Sci. Technol. 2014, 48 (3), 1973–1983. 10.1021/es4046023. [DOI] [PubMed] [Google Scholar]
  17. Leeuw T. K.; Reith R. M.; Simonette R. A.; Harden M. E.; Cherukuri P.; Tsyboulski D. A.; Beckingham K. M.; Weisman R. B. Single-Walled Carbon Nanotubes in the Intact Organism: Near-IR Imaging and Biocompatibility Studies in Drosophila. Nano Lett. 2007, 7 (9), 2650–2654. 10.1021/nl0710452. [DOI] [PubMed] [Google Scholar]
  18. Jones M.; Engtrakul C.; Metzger W. K.; Ellingson R. J.; Nozik A. J.; Heben M. J.; Rumbles G. Analysis of photoluminescence from solubilized single-walled carbon nanotubes. Phys. Rev. B 2005, 71 (11), 115426 10.1103/PhysRevB.71.115426. [DOI] [Google Scholar]
  19. Crochet J.; Clemens M.; Hertel T. Quantum Yield Heterogeneities of Aqueous Single-Wall Carbon Nanotube Suspensions. J. Am. Chem. Soc. 2007, 129 (26), 8058–8059. 10.1021/ja071553d. [DOI] [PubMed] [Google Scholar]
  20. Piwonski H.; Wang Y.; Li W.; Michinobu T.; Habuchi S. Millimeter-Deep Detection of Single Shortwave-Infrared-Emitting Polymer Dots through Turbid Media. Nano Lett. 2020, 20 (12), 8803–8810. 10.1021/acs.nanolett.0c03675. [DOI] [PubMed] [Google Scholar]
  21. Palma M.; Wang W.; Penzo E.; Brathwaite J.; Zheng M.; Hone J.; Nuckolls C.; Wind S. J. Controlled Formation of Carbon Nanotube Junctions via Linker-Induced Assembly in Aqueous Solution. J. Am. Chem. Soc. 2013, 135 (23), 8440–8443. 10.1021/ja4018072. [DOI] [PubMed] [Google Scholar]
  22. O’Connell M. J.; Eibergen E. E.; Doorn S. K. Chiral selectivity in the charge-transfer bleaching of single-walled carbon-nanotube spectra. Nat. Mater. 2005, 4 (5), 412–418. 10.1038/nmat1367. [DOI] [PubMed] [Google Scholar]
  23. Brege J. J.; Gallaway C.; Barron A. R. Fluorescence Quenching of Single-Walled Carbon Nanotubes with Transition-Metal Ions. J. Phys. Chem. C 2009, 113 (11), 4270–4276. 10.1021/jp808667b. [DOI] [Google Scholar]
  24. Cognet L.; Tsyboulski D. A.; Rocha J.-D. R.; Doyle C. D.; Tour J. M.; Weisman R. B. Stepwise Quenching of Exciton Fluorescence in Carbon Nanotubes by Single-Molecule Reactions. Science 2007, 316 (5830), 1465–1468. 10.1126/science.1141316. [DOI] [PubMed] [Google Scholar]
  25. Banerjee S.; Hemraj-Benny T.; Wong S. S. Covalent Surface Chemistry of Single-Walled Carbon Nanotubes. Adv. Mater. 2005, 17 (1), 17–29. 10.1002/adma.200401340. [DOI] [Google Scholar]
  26. Mohanraj J.; Armaroli N. Luminophores and Carbon Nanotubes: An Odd Combination?. J. Phys. Chem. Lett. 2013, 4 (5), 767–778. 10.1021/jz302137d. [DOI] [PubMed] [Google Scholar]
  27. Singh D. K.; Giri P. K.; Iyer P. K. Evidence for Defect-Enhanced Photoluminescence Quenching of Fluorescein by Carbon Nanotubes. J. Phys. Chem. C 2011, 115 (49), 24067–24072. 10.1021/jp207392d. [DOI] [Google Scholar]
  28. Dukovic G.; White B. E.; Zhou Z.; Wang F.; Jockusch S.; Steigerwald M. L.; Heinz T. F.; Friesner R. A.; Turro N. J.; Brus L. E. Reversible Surface Oxidation and Efficient Luminescence Quenching in Semiconductor Single-Wall Carbon Nanotubes. J. Am. Chem. Soc. 2004, 126 (46), 15269–15276. 10.1021/ja046526r. [DOI] [PubMed] [Google Scholar]
  29. Lee A. J.; Wang X.; Carlson L. J.; Smyder J. A.; Loesch B.; Tu X.; Zheng M.; Krauss T. D. Bright Fluorescence from Individual Single-Walled Carbon Nanotubes. Nano Lett. 2011, 11 (4), 1636–1640. 10.1021/nl200077t. [DOI] [PubMed] [Google Scholar]
  30. Setaro A.; Adeli M.; Glaeske M.; Przyrembel D.; Bisswanger T.; Gordeev G.; Maschietto F.; Faghani A.; Paulus B.; Weinelt M.; et al. Preserving π-conjugation in covalently functionalized carbon nanotubes for optoelectronic applications. Nat. Commun. 2017, 8 (1), 14281. 10.1038/ncomms14281. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Maeda Y.; Konno Y.; Nishino A.; Yamada M.; Okudaira S.; Miyauchi Y.; Matsuda K.; Matsui J.; Mitsuishi M.; Suzuki M. Sonochemical reaction to control the near-infrared photoluminescence properties of single-walled carbon nanotubes. Nanoscale 2020, 12 (11), 6263–6270. 10.1039/D0NR00271B. [DOI] [PubMed] [Google Scholar]
  32. Brozena A. H.; Kim M.; Powell L. R.; Wang Y. Controlling the optical properties of carbon nanotubes with organic colour-centre quantum defects. Nature Reviews Chemistry 2019, 3 (6), 375–392. 10.1038/s41570-019-0103-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Onitsuka H.; Fujigaya T.; Nakashima N.; Shiraki T. Control of the Near Infrared Photoluminescence of Locally Functionalized Single-Walled Carbon Nanotubes via Doping by Azacrown-Ether Modification. Chem. – Eur. J. 2018, 24 (37), 9393–9398. 10.1002/chem.201800904. [DOI] [PubMed] [Google Scholar]
  34. Luo H.-B.; Wang P.; Wu X.; Qu H.; Ren X.; Wang Y. One-Pot, Large-Scale Synthesis of Organic Color Center-Tailored Semiconducting Carbon Nanotubes. ACS Nano 2019, 13 (7), 8417–8424. 10.1021/acsnano.9b04087. [DOI] [PubMed] [Google Scholar]
  35. Ghosh S.; Bachilo S. M.; Simonette R. A.; Beckingham K. M.; Weisman R. B. Oxygen Doping Modifies Near-Infrared Band Gaps in Fluorescent Single-Walled Carbon Nanotubes. Science 2010, 330 (6011), 1656–1659. 10.1126/science.1196382. [DOI] [PubMed] [Google Scholar]
  36. Kwon H.; Furmanchuk A. o.; Kim M.; Meany B.; Guo Y.; Schatz G. C.; Wang Y. Molecularly Tunable Fluorescent Quantum Defects. J. Am. Chem. Soc. 2016, 138 (21), 6878–6885. 10.1021/jacs.6b03618. [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Piao Y.; Meany B.; Powell L. R.; Valley N.; Kwon H.; Schatz G. C.; Wang Y. Brightening of carbon nanotube photoluminescence through the incorporation of sp3 defects. Nat. Chem. 2013, 5 (10), 840–845. 10.1038/nchem.1711. [DOI] [PubMed] [Google Scholar]
  38. Duque J. G.; Densmore C. G.; Doorn S. K. Saturation of Surfactant Structure at the Single-Walled Carbon Nanotube Surface. J. Am. Chem. Soc. 2010, 132 (45), 16165–16175. 10.1021/ja106836f. [DOI] [PubMed] [Google Scholar]
  39. Wang R. K.; Chen W.-C.; Campos D. K.; Ziegler K. J. Swelling the Micelle Core Surrounding Single-Walled Carbon Nanotubes with Water-Immiscible Organic Solvents. J. Am. Chem. Soc. 2008, 130 (48), 16330–16337. 10.1021/ja806586v. [DOI] [PubMed] [Google Scholar]
  40. Duque J. G.; Oudjedi L.; Crochet J. J.; Tretiak S.; Lounis B.; Doorn S. K.; Cognet L. Mechanism of Electrolyte-Induced Brightening in Single-Wall Carbon Nanotubes. J. Am. Chem. Soc. 2013, 135 (9), 3379–3382. 10.1021/ja4001757. [DOI] [PubMed] [Google Scholar]
  41. Algoul S. T.; Sengupta S.; Bui T. T.; Velarde L. Tuning the Surface Ordering of Self-Assembled Ionic Surfactants on Semiconducting Single-Walled Carbon Nanotubes: Concentration, Tube Diameter, and Counterions. Langmuir 2018, 34 (31), 9279–9288. 10.1021/acs.langmuir.8b01813. [DOI] [PubMed] [Google Scholar]
  42. Lambert B.; Gillen A. J.; Schuergers N.; Wu S.-J.; Boghossian A. A. Directed evolution of the optoelectronic properties of synthetic nanomaterials. Chem. Commun. 2019, 55 (22), 3239–3242. 10.1039/C8CC08670B. [DOI] [PubMed] [Google Scholar]
  43. Kurnosov N. V.; Karachevtsev M. V.; Leontiev V. S.; Karachevtsev V. A. Tuning the carbon nanotube photoluminescence enhancement at addition of cysteine through the change of external conditions. Mater. Chem. Phys. 2017, 186, 131–137. 10.1016/j.matchemphys.2016.10.038. [DOI] [Google Scholar]
  44. Wang X.; Cao L.; Bunker C. E.; Meziani M. J.; Lu F.; Guliants E. A.; Sun Y.-P. Fluorescence Decoration of Defects in Carbon Nanotubes. J. Phys. Chem. C 2010, 114 (49), 20941–20946. 10.1021/jp1046408. [DOI] [Google Scholar]
  45. Tsyboulski D. A.; Rocha J.-D. R.; Bachilo S. M.; Cognet L.; Weisman R. B. Structure-Dependent Fluorescence Efficiencies of Individual Single-Walled Carbon Nanotubes. Nano Lett. 2007, 7 (10), 3080–3085. 10.1021/nl071561s. [DOI] [PubMed] [Google Scholar]
  46. van Bezouw S.; Arias D. H.; Ihly R.; Cambré S.; Ferguson A. J.; Campo J.; Johnson J. C.; Defillet J.; Wenseleers W.; Blackburn J. L. Diameter-Dependent Optical Absorption and Excitation Energy Transfer from Encapsulated Dye Molecules toward Single-Walled Carbon Nanotubes. ACS Nano 2018, 12 (7), 6881–6894. 10.1021/acsnano.8b02213. [DOI] [PMC free article] [PubMed] [Google Scholar]
  47. Yanagi K.; Iakoubovskii K.; Matsui H.; Matsuzaki H.; Okamoto H.; Miyata Y.; Maniwa Y.; Kazaoui S.; Minami N.; Kataura H. Photosensitive Function of Encapsulated Dye in Carbon Nanotubes. J. Am. Chem. Soc. 2007, 129 (16), 4992–4997. 10.1021/ja067351j. [DOI] [PubMed] [Google Scholar]
  48. Ahmad A.; Kern K.; Balasubramanian K. Selective Enhancement of Carbon Nanotube Photoluminescence by Resonant Energy Transfer. ChemPhysChem 2009, 10 (6), 905–909. 10.1002/cphc.200800796. [DOI] [PubMed] [Google Scholar]
  49. Lutsyk P.; Piryatinski Y.; AlAraimi M.; Arif R.; Shandura M.; Kachkovsky O.; Verbitsky A.; Rozhin A. Emergence of Additional Visible-Range Photoluminescence Due to Aggregation of Cyanine Dye: Astraphloxin on Carbon Nanotubes Dispersed with Anionic Surfactant. J. Phys. Chem. C 2016, 120 (36), 20378–20386. 10.1021/acs.jpcc.6b06272. [DOI] [Google Scholar]
  50. Al Araimi M.; Lutsyk P.; Verbitsky A.; Piryatinski Y.; Shandura M.; Rozhin A. A dioxaborine cyanine dye as a photoluminescence probe for sensing carbon nanotubes. Beilstein Journal of Nanotechnology 2016, 7, 1991–1999. 10.3762/bjnano.7.190. [DOI] [PMC free article] [PubMed] [Google Scholar]
  51. Lutsyk P.; Arif R.; Hruby J.; Bukivskyi A.; Vinijchuk O.; Shandura M.; Yakubovskyi V.; Kovtun Y.; Rance G. A.; Fay M.; et al. A sensing mechanism for the detection of carbon nanotubes using selective photoluminescent probes based on ionic complexes with organic dyes. Light: Science & Applications 2016, 5 (2), e16028–e16028. 10.1038/lsa.2016.28. [DOI] [PMC free article] [PubMed] [Google Scholar]
  52. Nish A.; Hwang J.-Y.; Doig J.; Nicholas R. J. Direct spectroscopic evidence of energy transfer from photo-excited semiconducting polymers to single-walled carbon nanotubes. Nanotechnology 2008, 19 (9), 095603 10.1088/0957-4484/19/9/095603. [DOI] [PubMed] [Google Scholar]
  53. Koyama T.; Miyata Y.; Asada Y.; Shinohara H.; Kataura H.; Nakamura A. Bright Luminescence and Exciton Energy Transfer in Polymer-Wrapped Single-Walled Carbon Nanotube Bundles. J. Phys. Chem. Lett. 2010, 1 (21), 3243–3248. 10.1021/jz101338c. [DOI] [Google Scholar]
  54. Lutsyk P.; Piryatinski Y.; Shandura M.; AlAraimi M.; Tesa M.; Arnaoutakis G. E.; Melvin A. A.; Kachkovsky O.; Verbitsky A.; Rozhin A. Self-Assembly for Two Types of J-Aggregates: cis-Isomers of Dye on the Carbon Nanotube Surface and Free Aggregates of Dye trans-Isomers. J. Phys. Chem. C 2019, 123 (32), 19903–19911. 10.1021/acs.jpcc.9b03341. [DOI] [Google Scholar]
  55. Chen J.; Collier C. P. Noncovalent Functionalization of Single-Walled Carbon Nanotubes with Water-Soluble Porphyrins. J. Phys. Chem. B 2005, 109 (16), 7605–7609. 10.1021/jp050389i. [DOI] [PubMed] [Google Scholar]
  56. Trapani M.; Mazzaglia A.; Piperno A.; Cordaro A.; Zagami R.; Castriciano M. A.; Romeo A.; Monsù Scolaro L. Novel Nanohybrids Based on Supramolecular Assemblies of Meso-tetrakis-(4-sulfonatophenyl) Porphyrin J-aggregates and Amine-Functionalized Carbon Nanotubes. Nanomaterials 2020, 10 (4), 669. 10.3390/nano10040669. [DOI] [PMC free article] [PubMed] [Google Scholar]
  57. Bricks J. L.; Slominskii Y. L.; Panas I. D.; Demchenko A. P. Fluorescent J-aggregates of cyanine dyes: basic research and applications review. Methods and Applications in Fluorescence 2018, 6 (1), 012001 10.1088/2050-6120/aa8d0d. [DOI] [PubMed] [Google Scholar]
  58. Piwoński H.; Nozue S.; Fujita H.; Michinobu T.; Habuchi S. Organic J-Aggregate Nanodots with Enhanced Light Absorption and Near-Unity Fluorescence Quantum Yield. Nano Lett. 2021, 21 (7), 2840–2847. 10.1021/acs.nanolett.0c04928. [DOI] [PMC free article] [PubMed] [Google Scholar]
  59. Slavnova T. D.; Chibisov A. K.; Görner H. Kinetics of Salt-Induced J-aggregation of Cyanine Dyes. J. Phys. Chem. A 2005, 109 (21), 4758–4765. 10.1021/jp058014k. [DOI] [PubMed] [Google Scholar]
  60. Chibisov A. K.; Görner H.; Slavnova T. D. Kinetics of salt-induced J-aggregation of an anionic thiacarbocyanine dye in aqueous solution. Chem. Phys. Lett. 2004, 390 (1), 240–245. 10.1016/j.cplett.2004.03.131. [DOI] [Google Scholar]
  61. Zheng Y.; Alizadehmojarad A. A.; Bachilo S. M.; Kolomeisky A. B.; Weisman R. B. Dye Quenching of Carbon Nanotube Fluorescence Reveals Structure-Selective Coating Coverage. ACS Nano 2020, 14 (9), 12148–12158. 10.1021/acsnano.0c05720. [DOI] [PubMed] [Google Scholar]
  62. Liu H.; Nishide D.; Tanaka T.; Kataura H. Large-scale single-chirality separation of single-wall carbon nanotubes by simple gel chromatography. Nat. Commun. 2011, 2 (1), 309. 10.1038/ncomms1313. [DOI] [PMC free article] [PubMed] [Google Scholar]
  63. Menon A.; Slominskii Y. L.; Joseph J.; Dimitriev O. P.; Guldi D. M. Reversible Charge Transfer with Single-Walled Carbon Nanotubes Upon Harvesting the Low Energy Part of the Solar Spectrum. Small 2020, 16 (8), 1906745. 10.1002/smll.201906745. [DOI] [PubMed] [Google Scholar]
  64. Karachevtsev V. A.; Plokhotnichenko A. M.; Glamazda A. Y.; Leontiev V. S.; Levitsky I. A. Excitonic energy transfer in polymer wrapped carbon nanotubes in gradually grown nanoassemblies. Phys. Chem. Chem. Phys. 2014, 16 (22), 10914–10922. 10.1039/C4CP00776J. [DOI] [PubMed] [Google Scholar]
  65. White B.; Banerjee S.; O’Brien S.; Turro N. J.; Herman I. P. Zeta-Potential Measurements of Surfactant-Wrapped Individual Single-Walled Carbon Nanotubes. J. Phys. Chem. C 2007, 111 (37), 13684–13690. 10.1021/jp070853e. [DOI] [Google Scholar]
  66. Sun Z.; Nicolosi V.; Rickard D.; Bergin S. D.; Aherne D.; Coleman J. N. Quantitative Evaluation of Surfactant-stabilized Single-walled Carbon Nanotubes: Dispersion Quality and Its Correlation with Zeta Potential. J. Phys. Chem. C 2008, 112 (29), 10692–10699. 10.1021/jp8021634. [DOI] [Google Scholar]
  67. Matarredona O.; Rhoads H.; Li Z.; Harwell J. H.; Balzano L.; Resasco D. E. Dispersion of Single-Walled Carbon Nanotubes in Aqueous Solutions of the Anionic Surfactant NaDDBS. J. Phys. Chem. B 2003, 107 (48), 13357–13367. 10.1021/jp0365099. [DOI] [Google Scholar]
  68. Wang X.; Liu Y.; Ma L.; Xu X.; Tian Y. Reclined trend of alkyl chain of sodium dodecylbenzenesulfonate molecules induced by friction. Friction 2022, 10 (9), 1353–1364. 10.1007/s40544-021-0541-1. [DOI] [Google Scholar]
  69. Suttipong M.; Tummala N. R.; Kitiyanan B.; Striolo A. Role of Surfactant Molecular Structure on Self-Assembly: Aqueous SDBS on Carbon Nanotubes. J. Phys. Chem. C 2011, 115 (35), 17286–17296. 10.1021/jp203247r. [DOI] [Google Scholar]
  70. Zhao T.; Xu G.; Yuan S.; Chen Y.; Yan H. Molecular Dynamics Study of Alkyl Benzene Sulfonate at Air/Water Interface: Effect of Inorganic Salts. J. Phys. Chem. B 2010, 114 (15), 5025–5033. 10.1021/jp907438x. [DOI] [PubMed] [Google Scholar]
  71. Lam S.; Zheng M.; Fagan J. A. Characterizing the Effect of Salt and Surfactant Concentration on the Counterion Atmosphere around Surfactant Stabilized SWCNTs Using Analytical Ultracentrifugation. Langmuir 2016, 32 (16), 3926–3936. 10.1021/acs.langmuir.6b00605. [DOI] [PubMed] [Google Scholar]
  72. Tummala N. R.; Striolo A. Role of Counterion Condensation in the Self-Assembly of SDS Surfactants at the Water–Graphite Interface. J. Phys. Chem. B 2008, 112 (7), 1987–2000. 10.1021/jp077678m. [DOI] [PubMed] [Google Scholar]
  73. Xu Z.; Yang X.; Yang Z. A Molecular Simulation Probing of Structure and Interaction for Supramolecular Sodium Dodecyl Sulfate/Single-Wall Carbon Nanotube Assemblies. Nano Lett. 2010, 10 (3), 985–991. 10.1021/nl9041005. [DOI] [PubMed] [Google Scholar]
  74. Yan H.; Yuan S.-L.; Xu G.-Y.; Liu C.-B. Effect of Ca2+ and Mg2+ Ions on Surfactant Solutions Investigated by Molecular Dynamics Simulation. Langmuir 2010, 26 (13), 10448–10459. 10.1021/la100310w. [DOI] [PubMed] [Google Scholar]
  75. Urbic T. Ions increase strength of hydrogen bond in water. Chem. Phys. Lett. 2014, 610–611, 159–162. 10.1016/j.cplett.2014.06.054. [DOI] [PMC free article] [PubMed] [Google Scholar]
  76. Fürstenberg A. Water in Biomolecular Fluorescence Spectroscopy and Imaging: Side Effects and Remedies. Chimia (Aarau) 2017, 71 (1–2), 26–31. 10.2533/chimia.2017.26. [DOI] [PubMed] [Google Scholar]
  77. Maillard J.; Klehs K.; Rumble C.; Vauthey E.; Heilemann M.; Fürstenberg A. Universal quenching of common fluorescent probes by water and alcohols. Chemical Science 2021, 12 (4), 1352–1362. 10.1039/D0SC05431C. [DOI] [PMC free article] [PubMed] [Google Scholar]
  78. Chagovets V. V.; Kosevich M. V.; Stepanian S. G.; Boryak O. A.; Shelkovsky V. S.; Orlov V. V.; Leontiev V. S.; Pokrovskiy V. A.; Adamowicz L.; Karachevtsev V. A. Noncovalent Interaction of Methylene Blue with Carbon Nanotubes: Theoretical and Mass Spectrometry Characterization. J. Phys. Chem. C 2012, 116 (38), 20579–20590. 10.1021/jp306333c. [DOI] [Google Scholar]
  79. Weisman R. B.; Bachilo S. M. Dependence of Optical Transition Energies on Structure for Single-Walled Carbon Nanotubes in Aqueous Suspension: An Empirical Kataura Plot. Nano Lett. 2003, 3 (9), 1235–1238. 10.1021/nl034428i. [DOI] [Google Scholar]
  80. Yomogida Y.; Tanaka T.; Tsuzuki M.; Wei X.; Kataura H. Automatic Sorting of Single-Chirality Single-Wall Carbon Nanotubes Using Hydrophobic Cholates: Implications for Multicolor Near-Infrared Optical Technologies. ACS Applied Nano Materials 2020, 3 (11), 11289–11297. 10.1021/acsanm.0c02389. [DOI] [Google Scholar]
  81. Tummala N. R.; Striolo A. SDS Surfactants on Carbon Nanotubes: Aggregate Morphology. ACS Nano 2009, 3 (3), 595–602. 10.1021/nn8007756. [DOI] [PubMed] [Google Scholar]
  82. Piwonski H.; Li W.; Wang Y.; Michinobu T.; Habuchi S. Improved Fluorescence and Brightness of Near-Infrared and Shortwave Infrared Emitting Polymer Dots for Bioimaging Applications. ACS Appl. Polym. Mater. 2020, 2 (2), 569–577. 10.1021/acsapm.9b00967. [DOI] [Google Scholar]
  83. Piwoński H.; Michinobu T.; Habuchi S. Controlling photophysical properties of ultrasmall conjugated polymer nanoparticles through polymer chain packing. Nat. Commun. 2017, 8 (10), 15256. 10.1038/ncomms15256. [DOI] [PMC free article] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ao4c00240_si_001.pdf (1.9MB, pdf)

Articles from ACS Omega are provided here courtesy of American Chemical Society

RESOURCES