Near-infrared Emission Research Articles

Efficient broadband near-infrared emission based on copper-alloyed metal halides

Recently, metal halides have shown broad application prospects due to excellent electronic and optical properties. Although significant developments have been realized, the spectra range of their photoluminescence (PL) emission is mainly limited to the visible region. Near-infrared (NIR) emitting materials are widely used in the fields of night vision, biomedical imaging, non-destructive food inspection, etc. On this occasion, extending the luminescence scope of metal halides to NIR region is of great significance. Generally, NIR-emitted metal halides are realized through rare earth (RE) ions doping. However, RE luminescence usually have narrow-band characteristics, which makes it difficult to realize broadband NIR emission. In this study, we present an efficient broadband NIR-emitted metal halide CsAgBr2 through copper ions alloying, its emission locates at 830 nm with a large FWHM (full width at half maximum) of 332 nm. Theoretical calculations suggest that the incorporation of Cu+ could effectively modulate the density of states and enhance the localized characterization, which is beneficial to boost the PL efficiency. Furthermore, this material displays favorable structure stability under ambient conditions. This study demonstrates the great application potential of Cu+-alloyed CsAgBr2 in the field of NIR optical electronics.

Broadband Near-Infrared Emission from Bi/Cr Co-Doped Aluminosilicate Glasses.

Bismuth-doped aluminosilicate glass has garnered significant attention due to its unique ultra-wide luminescence properties in the near-infrared (NIR) band. Enhancing the NIR luminescence of Bi-doped glass remains challenging. To achieve Bi-doped glass with more excellent luminescent properties, a series of Bi/Cr co-doped glasses were prepared, and the optical and structural properties of the samples were observed. The results indicate that low-concentration Cr doping broadens the luminescence range of Bi/Cr co-doped glass samples. The luminescence peak of Bi in the samples is at 1230 nm, while the peak of Cr is around 804 nm. The addition of an appropriate amount of Bi2O3 can enhance the NIR luminescence of Bi and Cr in the sample, realizing the energy conversion between Bi and Cr. Bi/Cr co-doped is a novel approach for achieving broadband NIR luminescence in glass materials.

NIR-II AIEgens for Infectious Diseases Phototheranostics.

Pathogenic infectious diseases have persistently posed significant threats to public health. Phototheranostics, which combines the functions of diagnostic imaging and therapy, presents an extremely promising solution to block the spread of pathogens as well as the outbreak of epidemics owing to its merits of a wide-spectrum of activity, high controllability, non-invasiveness, and difficult to acquire resistance. Among multifarious phototheranostic agents, second near-infrared (NIR-II, 1000-1700 nm) aggregation-induced emission luminogens (AIEgens) are notable by virtue of their deep penetration depth, excellent biocompatibility, balanced radiative and nonradiative decay and aggregation-enhanced theranostic performance, making them an ideal option for combating pathogens. This minireview provides a systematical summary of the latest advancements in NIR-II AIEgens with emphasis on the molecular design and nanoplatform formulation to fulfill high-efficiency in treating bacterial and viral pathogens, classified by disease models. Then, the current challenges, potential opportunities, and future research directions are presented to facilitate the further progress of this emerging field.

Achieving Near-Infrared Phosphorescence Supramolecular Hydrogel Based on Amphiphilic Bromonaphthalimide Pyridinium Hierarchical Assembly.

Phosphorescent supramolecular hydrogels are currently a prevalent topic for their great promise in various photonic applications. Herein, an efficient near-infrared (NIR) phosphorescence supramolecular hydrogel is reported via the hierarchical assembly strategy in aqueous solution, which is fabricated from amphiphilic bromonaphthalimide pyridinium derivative (G), exfoliated Laponite (LP) nanosheets, and polymeric polyacrylamide (PAAm). Initially, G spontaneously self-aggregates into spherical nanoparticles covered with positively charged pyridinium units and emits single fluorescence at 410nm. Driven by electrostatic interactions with negatively charged nanosheets, the nanoparticles subsequently function as the cross-linked binders and coassemble with LP into supramolecular hydrogels with an engendered red room-temperature phosphorescence (RTP) up to 620nm. Benefiting from hydrogen-bonding interactions-mediated physical cross-linkage, the further introduction of PAAm not only significantly elevates the mechanical strength of the hydrogels showing fast self-healing capability, but also increases phosphorescence lifetime from 2.49to 4.20ms, especially generating phosphorescence at even higher temperature (τ 363 K = 2.46ms). Additionally, efficient RTP energy transfer occurs after doping a small amount of organic dye heptamethine cyanine (IR780) as an acceptor into hydrogels, resulting in a long-lived NIR emission at 823nm with a high donor/acceptor ratio, which is successfully applied for cell labeling in the NIR window.

Strategy to optimize the broadband near-infrared emission based on Eu2+-doped sulfureted garnet phosphors toward emerging spectroscopy applications

Eu2+-doped near-infrared (NIR) emitting phosphors, known for their high efficiency, broadband emission and spectral tunability, have gained much attention. However, achieving efficient NIR emission based on Eu2+ remains a challenge due to the co-existence of Eu3+, especially in materials (i.e. garnets and apatites) containing trivalent lanthanide cations. In this study, a Eu2+ doped sulfureted NIR-emitting garnet phosphor Ca3(Sc, Eu)2Si3(O, S)12: Eu2+ is successfully designed and synthesized. Notably, a strategy for regulating the initial valence state of dopants is proposed by using prepared EuS instead of the conventional Eu2O3 as raw material, enhancing the NIR emission by 135 %. Moreover, a sulfuration strategy is further introduced to enhance the NIR-emitting intensity and internal quantum efficiency by 192 % and 167.8 %, and to improve thermal stability by 154 % at 120 °C. The luminescence origin of the unusual broadband NIR emission is re-examined through chemical unit co-substitution strategy by introducing [Al3+Hf4+] to replace [Sc3+Si4+] ion pairs. Meanwhile, the spectral regulation and the performance optimization mechanism are systematically discussed. Finally, a green light pumped NIR LED device with a photoelectric efficiency of 9.43 %@100 mA and output power of 22.74 mW@100 mA is fabricated, showing remarkable potential in nondestructive testing and biomedical imaging applications.

Fluorescence and photoacoustic (FL/PA) dual-modal probe: Responsive to reactive oxygen species (ROS) for atherosclerotic plaque imaging

Accurate and early detection of atherosclerosis (AS) is imperative for their effective treatment. However, fluorescence probes for efficient diagnosis of AS often encounter insufficient deep tissue penetration, which hinders the reliable assessment of plaque vulnerability. In this work, a reactive oxygen species (ROS) activated near-infrared (NIR) fluorescence and photoacoustic (FL/PA) dual model probe TPA-QO-B is developed by conjugating two chromophores (TPA-QI and O–OH) and ROS-specific group phenylboronic acid ester. The incorporation of ROS-specific group not only induces blue shift in absorbance, but also inhibits the ICT process of TPA-QO-OH, resulting an ignorable initial FL/PA signal. ROS triggers the convertion of TPA-QO-B to TPA-QO-OH, resulting in the concurrent amplification of FL/PA signal. The exceptional selectivity of TPA-QO-B towards ROS makes it effectively distinguish AS mice from the healthy. The NIR emission can achieve a tissue penetration imaging depth of 0.3 cm. Moreover, its PA775 signal possesses the capability to penetrate tissues up to a thickness of 0.8 cm, ensuring deep in vivo imaging of AS model mice in early stage. The ROS-triggered FL/PA dual signal amplification strategy improves the accuracy and addresses the deep tissue penetration problem simultaneously, providing a promising tool for in vivo tracking biomarkers in life science and preclinical applications.

Activator Heavy Solid Solution in Rigid Framework: An Effective Strategy Toward Highly Efficient and Thermally Stable Near‐Infrared Emission for Wireless Communication

AbstractBroadband near‐infrared (NIR) phosphors are crucial components of next‐generation NIR lighting sources. However, the design of high‐efficiency and thermally stable NIR phosphors still poses a significant challenge, whose quantum efficiencies (QEs) are directly limited by their absorption efficiency (AE) toward incident light. Here, an efficient and thermally stable NIR emission with AE up to 64.9% and emission keeping of 91.23% at 423 K is demonstrated via Cr3+ heavy solid solution in rigid framework LiCaGaF6:Cr3+ (LCGFC). Isomorphic LiCaAlF6:Cr3+ also exhibits thermal robustness, while traps in low doping concentration and low QEs. Comparative studies on crystal structure, formation energy, and Helmholtz free energy disclose that Cr3+ substitution on equivalent and equiradius Ga3+ site versus radii differential Al3+ site generates heavier solid solution and sustainable structural rigidity with acquirement of higher AE and better thermal stability. Incorporating LCGFC with a blue InGaN chip, a NIR phosphor‐converted light‐emitting diode is fabricated to realize stable wireless optical communication with good penetrability through biological tissue and some organic products. These findings develop a strategy based on activator heavy solid solutions in a rigid framework to achieve high‐efficiency and thermally stable NIR phosphors but also advance their novel optoelectronic applications.

Imaging of intracellular mitochondrial membrane potential with a highly photostable NIR fluorescent probe

Mitochondrial membrane potential (ΔΨm) participated in important physiological processes such as ATP synthesis, ion exchange, and plays an important role in maintaining normal life activities of cells. Herein, we synthesized a fluorescent probe EDXB (3-ethyl-2-(2-(6-methoxy-2,3-dihydro-1H-xanthen-4-yl) vinyl) benzothiazol-3-ium iodide) with positive charge, which targets mitochondria by electrostatic attraction. The probe has twisted intramolecular charge transfer (TICT) characteristics, resulting in near-infrared fluorescence emission enhanced with the increase of viscosity, when the probe falls off from the mitochondrial membrane to the low-viscosity cytoplasmic aqueous phase, the fluorescence emission intensity is weakened. Therefore, the EDXB exhibited favorable targeting. In addition, EDXB also has good anti-bleaching and pH stability, which enables it to accurately feedback the change of ΔΨm. In the experiment, the intracellular imaging of EDXB certificated mitochondrial depolarization (decrease of ΔΨm) during various cell injury events including cell inflammation, apoptosis and mitophagy. We expect EDXB to be a useful tool for the analysis of ΔΨm changes.

Supramolecular assemblies with aggregation-induced emission for in situ active imaging-guided photodynamic therapy of cancer cells

Photodynamic therapy (PDT) has attracted widespread attention as a novel non-invasive anticancer approach. However, the diminished photosensitivity and limited oxygen exposure caused by the aggregation of traditional photosensitizers greatly impair its overall therapeutic efficacy. Herein, a series of water-soluble aggregation-induced emission luminogens (AIEgens) with triphenylamine as skeleton were synthesized and exhibited bright Near-infrared (NIR) emission and strong reactive oxygen species (ROS) generation. Through host-guest complexation between the multicharged triphenylamine units on AIEgens and cucurbit[10]uril (CB[10]) host molecule, supramolecular nanoassemblies were constructed and exhibited negligible phototoxicity to normal cells due to their limited oxygen contact. In contrast, the efficient release of AIEgens from nanoassemblies through competitive binding of overexpressed peptides in cancer cells with CB[10], enabled the full exploitation of the photosensitivity of AIEgens to produce highly efficient ROS, achieving selective ablation of cancer cells. Moreover, due to the restriction of intramolecular motion (RIM) upon anchored on organelle membranes through electrostatic interactions, the cationic AIEgens with weak fluorescence in physiological environment exhibited intense fluorescence emission, thus realizing imaging-guided PDT. This work may open up an avenue for the development of simple and feasible smart responsive nanomaterials for cancer treatment using supramolecular host-guest complexation strategy.

Interplay of kernel shape and surface structure for NIR luminescence in atomically precise gold nanorods

It is challenging to attain strong near-infrared (NIR) emissive gold nanoclusters. Here we show a rod-shaped cluster with the composition of [Au28(p-MBT)14(Hdppa)3](SO3CF3)2 (1 for short, Hdppa is N,N-bis(diphenylphosphino)amine, p-MBT is 4-methylbenzenethiolate) has been synthesized. Single crystal X-ray structural analysis reveals that it has a rod-like face-centered cubic (fcc) Au22 kernel built from two interpenetrating bicapped cuboctahedral Au15 units. 1 features NIR luminescence with an emission maximum at 920 nm, and the photoluminescence quantum yield (PLQY) is 12%, which is 30-fold of [Au21(m-MBT)12(Hdppa)2]SO3CF3 (2, m-MBT is 3-methylbenzenethiolate) with a similar composition and 60-fold of Au30S(S‑t‑Bu)18 with a similar structure. time-dependent DFT(TDDFT)calculations reveal that the luminescence of 1 is associated with the Au22 kernel. The small Stokes shift of 1 indicates that it has a very small excited state structural distortion, leading to high radiative decay rate (kr) probability. The emission of cluster 1 is a mixture of phosphorescence and thermally activated delayed fluorescence(TADF), and the enhancement of the NIR emission is mainly due to the promotion of kr rather than the inhibition of knr. This work demonstrates that the metal kernel and the surface structure are both very important for cluster-based NIR luminescence materials.

Development of a hybrid rhodamine-hydrazine NIR fluorescent probe for sensitive detection and imaging of peroxynitrite in necrotizing enterocolitis model

This study describes the synthesis and characterization of a novel near-infrared (NIR) fluorescent probe RBNE based on a hybrid rhodamine dye, which shows excellent optical capability for detecting and imaging ONOO− in necrotizing enterocolitis (NEC) mouse model. The probe RBNE undergoes hydrazine redox-process, and subsequently the spirocyclic structure’s opening, resulting in a turn-on fluorescence emission with the presence of ONOO−, which exhibits several excellent features, including a significant Stokes shift of 108 nm, near-infrared emission at 668 nm, a lower detection limit of 56 nM, low cytotoxicity, and excellent imaging ability for ONOO− both in vitro and in vivo. The presented study introduces a novel optical tool that has the potential to significantly advance our understanding of peroxynitrite (ONOO−) behaviors in necrotizing enterocolitis (NEC).

High-Performance Tunable Near-Infrared Emitters of Cr3+-Activated Garnet Phosphor Enabled by Chemical Unit Co-Substitution.

The escalating demand for portable near-infrared (NIR) light sources has posed a formidable challenge to the development of NIR phosphors characterized by high efficiency and exceptional thermal stability. Taking inspiration from the chemical unit co-substitution strategy, high-performance tunable (Lu3- xCax)(Ga5- xGex)O12:6%Cr3+ (x = 0-3) phosphors are designed with an emission center from 704 to 780nm and a broadest full width at half maximum (FWHM) of up to 172nm by introducing Ca2+ and Ge4+ ions into the garnet structure. In particular, Lu3Ga5O12:6%Cr3+ demonstrates an anti-thermal quenching phenomenon (I423K = 113.1%). Compared to Lu3Ga5O12:6%Cr3+, Lu2CaGa4GeO12:6%Cr3+ exhibits significantly improved FWHM and IQE by 108nm and 25.5%, respectively, while maintaining good thermal stability (I423K = 80.4%). Finally, Lu2CaGa4GeO12:6%Cr3+ phosphor is combined with a 465nm blue LED chip to fabricate NIR LED devices, exhibiting a NIR electroluminescence efficiency of 13.31%@100mA and demonstrating successful applications in nocturnal illumination and biomedical imaging technology. This work offers a fresh perspective on the design of highly efficient NIR garnet phosphors.

High-Stability Near-Infrared Luminescent Glass Ceramic and Its Applications.

Near-infrared (NIR) light, valuable for its biological penetration and invisibility to the human eye, is a crucial tool in biomedicine, environmental monitoring, anticounterfeiting, and information encryption, yet traditional NIR luminescent materials are often unstable in humid conditions. Here, a highly stable MgGeO3:Mn2+ glass ceramic (GC) with NIR luminescence was successfully synthesized. As-obtained GC700 boasts exceptional luminescent capabilities and possesses abundant trap structures, enabling data inscription with a 405 nm laser and retrieval via laser/thermal excitation. Moreover, the emission peak of Mn2+ can be manipulated from 630 to 691 nm by increasing the annealing treatment temperature. With the harnessing of the effective NIR emission, stable carrier characteristics, and numerous trap structures, there is potential for application in information encryption. Accordingly, we explored the application of MgGeO3:Mn2+ GC (GC700 and GC800) samples in precious three-dimensional (3D) information storage and NIR mechanoluminescence (ML) for biological tissue imaging. These applications demonstrate the potential and versatility of electron-capturing NIR luminescent materials in a range of cutting-edge fields.

A lipid droplet-targeted NIR fluorescent probe for viscosity detection in Parkinson's disease

Investigating lipid droplets (LDs) is crucial for elucidating their role in biological function and the pathogenesis of related diseases, including Parkinson's disease (PD). Therefore, developing a fluorescent probe to measure LDs viscosity is crucial. To address the challenges of complex biological environments, a chemical toolbox, F-675, was introduced based on the twisted - intramolecular charge transfer mechanism. F-675 featured a large Stokes shift of 158 nm and emitted near-infrared emission at 675 nm, facilitating LDs detection with minimal biological fluorescent background. Additionally, F-675 exhibited excellent selectivity and sensitivity to changes of LDs. Furthermore, F-675 effectively detected LDs changes in PD models, ranging from cells, C. elegans and Parkin null Drosophila. These findings indicate the potential of F-675 as an effective tool for PD diagnosis.

(Invited) Core-Multi-Shell Design: Unlocking Multimodal Capabilities in Lanthanide-Based Nanoparticles

The remarkable optomagnetic properties of the lanthanides (Ln) make Ln-based materials ideal for biomedical applications, including diagnostic (e.g., imaging, nanothermometry) and therapeutic (e.g., drug delivery, photodynamic therapy) approaches. This is due the unique electronic properties of the f-elements allowing for upconversion and near-infrared emission under near-infrared excitation as well as high magnetic moments. Yet, challenges remain, including low emission intensity and efficiency of small nanoparticles (NPs), and reliable, fast synthesis routes. As material chemists, we tackle these challenges with new designs of Ln-NPs by chemically controlled synthesis, application-oriented surface chemistry, and understanding of structure-property-relationships. We developed a straightforward and rapid microwave-assisted synthesis approach towards core-multi-shell Ln-NPs. Careful architecture design and choice of RE3+ dopant ions allow to tune the optical properties of the resultant nanoparticles, i.e., upconversion and near-infrared emission. This presentation will shed light on recent results with respect to microwave-assisted synthesis of Ln-NPs as well as structural and optomagnetic properties, seeking biomedical application.For instance, multimodal bioimaging probes merging optical imaging, magnetic resonance imaging (MRI), and X-ray computed tomography (CT) capabilities have attracted considerable attention due to their potential biomedical applications. This includes nanoparticles that combine upconverting Er3+/Yb3+ and magnetic NaDyF4 for optical/T2-weighted MRI/CT multimodal capabilities. A known drawback of multimodal probes that merge the upconverting Er3+/Yb3+ ion pair with magnetic Dy3+ ions for T2-weighted MRI is the loss of upconversion emission due to Dy3+ poisoning. The synthesis of controlled nanoparticle architectures with tuned inner NaGdF4 shell thicknesses separating Dy3+ and Er3+/Yb3+ allow to shed light on this distance-dependent loss of upconversion due to Yb3+ → Dy3+ energy transfer. As a result, the Ln-NP architecture was tuned to not only restore but enhanced the upconversion emission. In addition to multimodal imaging, Ln-NPs are promising candidates for application in nanothermometry due to the distinct, temperature-induced changes in their spectral features. We seek the development of novel Ln-NP nanothermometers for new opportunities in the near-infrared biological transparency windows (1000 to 2000 nm), by doping RE3+ ions, such as Er3+ and Tm3+ as well as unconventional Pr3+, into core-multi-shell lanthanide-based nanoparticles.

(Invited) Synthesis and Functionalization of Nanographenes with Red to Near-Infrared Emission for Photonic Applications

Nanostructures of graphene demonstrate a wide range of optical, electronic, and magnetic properties depending on their size and chemical structures, which renders them promising as next-generation carbon-based nanomaterials, e.g., for nanoelectronics, spintronics, and photonics. However, it is challenging to accurately control the chemical structures while “cutting” graphene. To this end, large polycyclic aromatic hydrocarbons (PAHs) with nanoscale graphene structures are attracting a renewed attention as atomically precise nanographenes [1]. We have developed the synthesis of dibenzo[hi,st]ovalene (DBOV) as an unprecedented nanographene with high stability, strong red fluorescence, and stimulated emission, demonstrating the potential for organic lasers [2]. The functionalization of DBOV was achieved through regioselective bromination and Suzuki coupling, enabling the introduction of various substituents, for example fluoranthene imide (FAI) groups, inducing the red-shift of the emission to the near-infrared (NIR) region [3]. Different effects on the photophysical properties of the DBOV core have been observed by changing the peripheral functional groups. More recently, we have synthesized hexabenzoperihexacene (HBPH) with zigzag and fjord edges, which displayed high stability and NIR emission with maximum at ~800 nm [4]. Notably, HBPH could be made chiral by introducing bulky tert-butyl groups on the helical fjord edges, allowing the separation of the enantiomers and showing the circular dichroism responses up to 830 nm. These results provide a new insight into the structure-property relationship of such nanographenes and pave the way toward their photonic applications.[1] Paternò, G. M.; Goudappagouda,; Chen, Q.; Lanzani, G.; Scotognella, F; Narita A., Adv. Optical Mater. 2021, 9, 2100508.[2] Paternò, G. M.; Chen, Q.; Wang, X.-Y.; Liu, J.; Motti, S. G.; Petrozza, A.; Feng, X.; Lanzani, G.; Müllen, K.; Narita, A.; Scotognella, F., Angew. Chem. Int. Ed. 2017, 56, 6753–6757.[3] Paternò, G. M.; Chen, Q.; Muñoz-Mármol, R.; Guizzardi, M.; Bonal, V.; Kabe, R.; Barker, A. J.; Boj, P. G.; Chatterjee, S.; Ie, Y.; Villalvilla, J. M.; Quintana, J. A.; Scotognella, F.; Müllen, K.; Díaz-García, M. A.; Narita, A.; Lanzani, G., Mater. Horiz. 2022, 9, 393–402.[4] Xu, X.; Muñoz-Mármol, R.; Vasylevskyi, S.; Villa, A.; Folpini, G.; Scotognella, F.; Paternò, G. M.; Narita, A., Angew. Chem. Int. Ed. 2023, 62, e202218350.

Engineering pH Resilience in Optical Nanotube Sensors for Biomedical Applications

Optical probes enable real-time monitoring of biomarkers in vitro, in vivo, and in cells. Probes based on the fluorescence of semiconducting single-walled carbon nanotubes (SWCNTs) specifically benefit from photostable near-infrared light emissions that are minimally absorbed by biological tissue. SWCNTs are often solubilized by DNA to enable the optical detection of specific bioanalytes. Despite efforts to engineer the selectivity of the DNA sequences towards only specific analytes of interest, these DNA-wrapped sensors are prone to optical perturbations from fluctuations in pH. In this work, we explore the fluorescence effects of DNA-SWCNT in varying pH. We observe a substantial pH effect that varies with the DNA sequence and exploit this pH sensitivity for applications in cancer detection. Using xeno nucleic acids (XNAs), we further engineer optical sensors that show resilience towards fluctuations in pH, enabling the detection of biomarkers in the absence of contributions from varying pH effects.

A New Technology for Industrial Strain Mapping Using Single-Wall Carbon Nanotube Sensors

Measurements of mechanical strain are widely used in heavy industry to design and test new structures and to ensure the safety of installed infrastructure. However, the few practical methods for strain measurement all have serious limitations. To complement these methods, we have developed a new strain technology, called S4 for “strain-sensing smart skin,” which uses single-wall carbon nanotubes (SWCNTs) as microscopic sensors. Nanotubes dilutely embedded in a polymer are applied as a thin film to specimen surfaces of interest. Subsequent strains in the specimen are transmitted by load transfer through the film to the nanotubes, inducing axial compression or extension. Those small structural deformations of the SWCNTs alter the semiconducting band gaps in predictable ways, causing proportional shifts in the peak wavelengths of their near-infrared fluorescence emission. Shifts are quantified by optically exciting the specimen surface and spectrally analyzing the resulting fluorescence to deduce strain values at the probed locations. The S4 method has recently been implemented using hyperspectral imaging. We demonstrate measurements in less than one minute of strain maps containing hundreds of thousands of pixels with 50 microstrain noise levels and 0.2 mm spatial resolution. This technology has promising potential to become a large-scale commercialized application of carbon nanotechnology.

(Invited) An in Vitro Model of Mechanical Strain Enhances Cellular Uptake of Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWCNTs) are ideal optical biosensors due to their intrinsic near-infrared (NIR) emission, which is highly sensitive, easily tunable, and indefinitely photostable. Due to such desirable properties coupled with appropriate functionalization strategies, SWCNTs have been used in numerous in vitro, live-cell, and in vivo applications. Depending on the type of functionalization as well as cell type, SWCNTs can be internalized by live cells via demonstrated energy-dependent endocytosis processes where they are retained within the endosomal pathway or are expelled by the cells. While this uptake and intracellular processing of SWCNTs has been recently examined, these studies are usually performed with standard cell culture techniques in petri dishes or 3D cultures. Unlike these cultures, cells in living organisms are continuously exposed to a wide variety of stimuli, e.g., periodic mechanical strain, during both normal and disease-related conditions. Thus, it is important to investigate how cells under physiological stretching compare to those grown in standard cultures. Herein, using a novel cell stretching platform to mimic physiological conditions, we investigate the uptake of SWCNTs into different human cancer cells.Our results indicate that cells exposed to uniform radial stretching display significantly higher rates of nanoparticle uptake, which can be correlated to their increased level of cellular activity. This approach recognizes the importance of studying cellular responses in environments that more closely resemble the complex conditions found in living organisms. It suggests a potential connection between mechanical stimuli and cellular processes related to SWCNT uptake. This finding has implications for understanding how nanotube uptake differs in different cellular stress environments and how cells respond to their dynamic and ever-changing microenvironment.Investigating how the mechanical strain influences the endocytosis processes and subsequent intracellular fate of SWCNTs can provide valuable insights into the interplay between nanomaterials and living cells under more realistic conditions. Further aiding us in the development of more accurate intracellular biosensors and effective drug delivery platforms using SWCNTs.

(Invited) High Temperature Exciton Properties in Aggregated Single-Walled Carbon Nanotubes

Individual single-walled carbon nanotubes (SWCNTs) at high temperatures have been reported to generate narrow-band thermal radiation in the near-infrared region due to thermally robust excitonic effects [1,2]. This phenomenon potentially offers a new opportunity for utilizing exciton properties in thermal engineering such as thermophotovoltaic energy harvesting requiring excellent wavelength selective near-infrared thermal emitter. However, for its realistic applications in macroscale, it is necessary to make the distinct exciton effect available under high temperature conditions in macroscopic assemblies of SWCNTs. As a first step toward this goal, we have recently determined broadband complex refractive index spectra of single-chirality SWCNT membranes in which SWCNTs are aligned two-dimensionally in a plane [3] and reported their birefringent properties [4]. In the presentation, we will discuss the change in the optical spectra of SWCNT assemblies with increasing temperature, as well as how the aggregation states affect the exciton properties. [1] T. Nishihara, A. Takakura, Y. Miyauchi, and K. Itami, Nat. Commun. 9, 3144 (2018). [2] S. Konabe, T. Nishihara, and Y. Miyauchi, Opt. Lett. 46, 3021 (2021). [3] T. Nishihara, A. Takakura, M. Shimasaki, K. Matsuda, T. Tanaka, H. Kataura, and Y. Miyauchi, Nanophotonics 11, 1011 (2022). [4] H. Wu, T. Nishihara, A. Takakura, K. Matsuda, T. Tanaka, H. Kataura, and Y. Miyauchi, Carbon, in press.