Single-walled Carbon Nanotubes Research Articles

Guiding the Choice of Carbon Nanotubes Conductive Additives for Silicon Anode Electrode through Microstructure Scale Analysis

Silicon anode electrodes exhibit a large microstructure design space as several carbon additives are considered to improve its conductivity and thus electrochemical performance. Investigating each combination experimentally is time-consuming. In this work, microstructure scale modeling is used to discriminate between different carbon additives to accelerate electrode development [1]. Baseline spherical C45, single wall carbon nano tube (SWCNT, cf. Fig. 1), carbon nano rods (CNR), and mixed SWCNT-CNR are considered and their respective impact on connectivity, effective conductivity, specific surface area, pore size distributions, and effective diffusivity are calculated to provide design recommendations. To do so, microstructures are numerically generated using the NREL open-source Microstructure Analysis Toolbox (MATBOX) available to the battery community* [2].Additionally, the model is used to correlate material utilization and silicon particle size, in agreement with experimental data, to further guide the selection of silicon material.Lastly, the model is used to investigate the porosity specific surface area relationship in the low porosity range, for which the analytical expression 3ε/r (with ε the particle volume fraction and r the particle radius) is no longer valid due to the packing density limit, and revealed a non-monotonic correlation. Such result is very relevant for silicon anode development as one major hindrance to this chemistry is its limited calendar life due to SEI growth, for which the specific surface area is a key parameter. *Nanotube generation new feature will be released after article [1] publication. [1] F. L. E. Usseglio-Viretta, J. H. Kim, J. Preimesberger, N. Neale, P. Weddle, A. Verma, A. M. Colclasure, Guiding the Choice of Carbon Nanotubes Conductive Additives for Silicon Anode Electrode Through Microstructure Scale Analysis, in preparation[2] F. L. E. Usseglio-Viretta, P. Patel, E. Bernhardt, A. Mistry, P. P. Mukherjee, J. Allen, S. J. Cooper, J. Laurencin, K. Smith, MATBOX: An Open-source Microstructure Analysis Toolbox for microstructure generation, segmentation, characterization, visualization, correlation, and meshing, SoftwareX, 17 (2022) 100915. Figure 1

Insights into the Synaptic Properties of Dopamine Release Revealed by Single Walled Carbon Nanotube Biosensors

It is thought that there are two distinct modes of chemical neurotransmission, referred to as fast (synaptic) transmission and slow (volume) transmission. Fast transmission, mediated by ligand-gated ionotropic receptors, operate with millisecond temporal and nanometer spatial precision in excitatory and inhibitory synapses, primarily mediated by glutamate and GABA, respectively. In contrast, slow transmission relies on activation of G-protein coupled receptors (GPCRs) and is mediated by several classes of neuromodulators, including dopamine. Neuromodulators are thought to operate at temporal scales that range from hundreds of milliseconds to minutes, with a spatial specificity that is insufficiently understood but generally described as “diffuse”. In this work, we provide new evidence that shows the spatial precision of dopamine transmission is highly reminiscent of the spatial properties of signaling mediated by the fast acting neurotransmitters.To gain this insight, we used an optical assay named “DopaFilm” that is based on oligonucleotide functionalized single walled carbon nanotube dopamine sensors (nanosensors). Primary dopaminergic neurons were grown on top of glass coverslips functionalized with nanosensors, which enabled visualization of dopamine exocytosis events in single release sites under a continuous 785nm excitation laser. In axonal arbors, DopaFilm can report evoked and spontaneous dopamine release events with high signal to noise ratios of up to 50. Recording on DopaFilm revealed dopamine release is fast, calcium-dependent, and reliant on similar presynaptic protein machinery employed by fast neurotransmitters. These findings challenge the notion that dopamine is a slow transmitter; however it doesn’t preclude the possibility of imprecise spatial signaling, consistent with volume transmission theory. More recent data from our lab now challenges the spatial characteristics of volume transmission model as currently understood in the literature. In this talk, I will discuss new insights gained on dopamine signaling including clear examples of precise spatial arrangements of dopamine release sites, and ultrastructural, biochemical and spatial transcriptomic data that shows that neuromodulatory action can be highly spatially precise in nature.

(Invited) Assembly of Carbon Nanotubes Heterostructures Down to Single-Particle Control

We will present different chemical strategies for the in-solution assembly of single walled carbon nanotube (SWCNT)-based heterostructures, down to single-particle control and resolution. In particular, we interfaced SWCNTs to inorganic semiconducting nanoparticles and nanocrystals, perovskites, as well as metal nanoparticles and nanowires. We developed various approaches towards this end, from the selective and differential functionalisation of CNTs terminal ends with distinct individual nanomoieties , to the use of nanotubes as templates for the growth of nanomaterials on their sidewall or in their cavity. Solution-processed optoelectronic devices were fabricated employing the aforementioned nanohybrids, displaying various sensitivity to a broad range of illumination wavelengths.

(Invited) Electrochemical Tuning of Thermoelectric Performance of Carbon Nanotubes

One-dimensional materials have potential for high performance thermoelectric energy conversion. To experimentally understand how one-dimensional electronic structures can enhance thermoelectric performance, we have investigated the thermoelectric properties of single walled carbon nanotubes (SWCNTs) such as the relationships among electronic structures, the location of Fermi-level, Seebeck coefficients, and Power factor by combining thermoelectric measurements and electrolyte gating techniques. Through the studies, we have revealed unique properties such as violation of thermoelectric trade-off, isotropic Seebeck coefficient, and gigantic power factor [1]. However, in addition to that, it is important to understand how the carrier density also affects the thermal conductivity of the carbon nanotube thin films for correct evaluation of ZT value. Therefore, we have developed a measurement system which can evaluate thermal conductivity by tuning the location of Fermi-level through electrochemical gating techniques. Time-domain thermoreflectance (TDTR) measurement is one of methods which can evaluate the thin film thermal conductivity. In conventional TDTR system, Al is used as metal transducer, but Al is electrochemical reactive, and thus it is very difficult to combine the TDTR measurements with electrochemical techniques. To solve this problem, we developed a TDTR system using Au as a metal transducer [2]. By using Au as a metal transducer, we can evaluate both the electrical and thermal properties at the same time. By using system, we can evaluate thermal properties of thin films during electrolyte gating, and have evaluated how the change of charrier density affects the thermal conductivity of carbon nanotube thin films [3]. By preparing the aligned single-walled carbon nanotube thin film, we evaluated the ZT value in the perpendicular direction to the nanotube axis as a function of carrier density. The ZT value in this direction can be maximized to be 0.1 by tuning the Femi-level around 1st van hove singularity [4].

(Invited) Optimising CNT-FET Biosensor Design: Tuning Biomolecule Interfaces for Aptamer-Biomarker Sensing and Beta-Lactamase Detection

We will present different strategies to control the assembly of single walled carbon nanotube (SWCNT)-biomolecule interfaces towards the fabrication of bioelectronic devices, with a focus on the real-time biosensors with engineered aptamer and protein interfacing. In particular, we will report on the fabrication of nanoscale biosensing devices designed to present biorecognition moieties (aptamers and proteins) in defined orientations; this allowed us to control the local electrostatic surface presented within the Debye length, and thus modulate the conductance gating effect upon binding incoming targets, from biomarkers associated to stress and (neuro) trauma, to classes of enzyme relevant to antimicrobial resistance (beta-lactamases).Our efforts focused in particular on using beta-lactamase binding protein (BLIP2) as receptor due to its potential as a biosensor for the most common antibiotic degrading enzymes, the beta-lactamases (BLs). Attaching BLIP2 at single designed residues positions directly to SCNTs using genetically encoded phenyl azide photochemistry, our devices were able to successfully detect the two different BLs, TEM-1 and KPC-2. The changes in conductance closely matched the predicted electrostatic profile sampled by the CNTs on BL binding.These studies highlight the key role transducer-biomolecule interfaces play in biosensing devices, and the need to control and tune by design the electrostatic gating, for more effective and optimal CNT-FET biosensor construction.

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) Electron Transport in Nanocarbon Networks for Energy Conversion and Storage Applications

Carbon nanostructures have attracted great attention in recent years as novel electrode materials in batteries with increased capacity and conductivity as well as enhanced material stability. In these nanostructures, nanocarbons such as carbon nanotubes and graphene nanoplatelets are interconnected to construct their three-dimensional networks around the host materials for Li deposition. This work focuses on the study of electron transport phenomena in these nanocarbon networks with two model material systems: (1) single-walled carbon nanotube (SWCNT) networks co-embedded with silica microparticles (Fig. (a)), and (2) free-standing three-dimensional graphene (3DG) structures with polymeric surface modifications (Fig. (b)). We characterize the materials for electrical conductivity and thermopower with varying material contents in the composites to reveal several key factors determining their energy-dependent carrier transport characteristics. It is found that in these three-dimensional nanocarbon networks, carrier tunneling at the junctions between nanocarbons along with the network morphology predominantly determines the transport properties. Simultaneous increase in electrical conductivity and thermopower is achieved for SWCNT networks co-embedded with silica microparticles by increasing silica content up to 40 w.t.% at a fixed CNT content. The enhanced electron transport is attributed to the reduced junction distances due to the intimate network formation on the surface of silica particles with a polymer binder. Our transport theory based on the Landauer formalism for junction tunneling reveals that the junction modification with polymer can alter the potential barrier heights for both electrons and holes at the junction to significantly change the transport properties of the composite. Doping of nanocarbons is also investigated for their impacts on the junction transport and the geometric factor of the networks. Finally, we also investigate the use of these carbon nanostructures in solid-state thermoelectric (TE) energy harvesters and ionic TE capacitors to harvest thermal energy from temperature gradients and fluctuations. Figure 1

Single-Walled Carbon Nanotube Based Field-Effect Transistors Functionalized with Odorant Receptors for Biosensing Applications

Bioelectronic detection of volatile organic compounds (VOC) has been demonstrated in a wide range of applications, with early reports focusing on environmental exogenous VOCs due to their adverse effects on human health; bacterial VOC signatures used as disease biomarkers, etc. Carbon nanotube field-effect transistors (CNT-FETs) are considered promising devices for bioelectronic detection due to their sensitivity, robustness and compatibility with microelectronic fabrication technologies. However, implementation of CNT-FETs still faces many challenges. Current VOCs detection approaches rely on separation techniques coupled with mass spectrometry, necessitating expensive equipment, labor-intensive preparation steps and trained personnel, and are not suitable for field use. Overcoming the challenges in the development of bioelectronic CNT-FET sensors holds great promise for high-throughput screening of VOCs.The natural insect odorant receptors (ORs) are highly attractive probes, potentially allowing ultrahigh specificity for VOC biosensing. Insect ORs exhibit remarkable sensitivities and the ability to selectively detect a vast number of VOCs. We have recently developed OR-functionalized carbon nanotube field-effect transistor (FET) devices. These FET devices comprise an isolated single-walled carbon nanotube (SWCNT), serving as the conducting channel material, functionalized with multiple insect ORs. These hybrid devices are capable of transducing ligand binding into an electronic current, without amplification. The insect OR-functionalized CNT FET were applied for the detection of several markers of environmental and clinical importance including Indole, Skatole, Octen-3-ol and Nonyl-aldehyde.We have developed a bioelectronic assay platform that contains a chip with 61 ORs-functionalized CNT-FET devices. Our unique functionalization method is based on directing the attachment of a native ORs-containing nanovesicles (which we have exogenously expressed and functionally characterized) to a generated CNT-FET point defect. Target binding-induced ionic current and conformational changes of ORs affect an electric field that modulates the device conductance.

(Invited) Probing Charge Carrier-Induced Changes in the Complex Dielectric Function in Carbon Nanotube Dispersions

The injection of charge carriers into pi-conjugated semiconductors, whether by electrochemical injection or chemical charge transfer, is a powerful approach to tune their electrical conductivity. Recently, the concept of dielectric catastrophe, where the charge carrier density is sufficiently large to significantly alter the intrinsic dielectric properties, has been demonstrated at high doping levels in organic semiconductor thin films. The observed increase in the dielectric constant leads to reduced coulombic interactions between charge carriers and the associated counterions, promoting enhanced free carrier generation and transport.Here, we employ a combination of steady state optical spectroscopy, quantitative 19F NMR studies, and microwave dielectric loss spectroscopy to probe charge carrier density and transport in doped single-walled carbon nanotube dispersions. We demonstrate that a similar dielectric catastrophe phenomenon can be observed even in isolated single-walled carbon nanotubes dispersed in a low dielectric constant solvent AND, perhaps more surprisingly, at carrier densities less than one carrier per nanotube. The precise details of the observed changes in complex dielectric function are dependent on the chemical structure of the charge-transfer dopant, with a near-instantaneous increase in the dielectric constant and electrical conductivity observed for low carrier densities using bulky benzyloxy-substituted icosahedral dodecaborane cluster dopants, DDBs. We attribute the observations to weak coulombic interactions between the injected charge carrier and the dopant counterion, along with the large polarizability afforded by the unique physicochemical properties of single-walled carbon nanotubes. If time permits, we will show results from recent studies where we extend this approach to the doping of other nanocarbons.

(Invited) Quantum Well Nanotube Emission for Cancer Research and Diagnostics

Quantum well defects (QWDs) on single-walled carbon nanotubes (SWCNTs) enable expanded analyte sensitization and functionalization for biosensing applications. We are using these capabilities to develop new research and diagnostic methods for cancers, infectious disease, and other indications. For instance, we are addressing issues with serum biomarker measurements, which are widely used for diagnostics, but these markers often fail to result in a clear diagnosis of complex disease indications. We developed a method using QWD-modified SWCNTs (QWNTs) to identify a “spectral fingerprint” through the collection of large data sets of molecular binding interactions to an array of QWNTs. We found that a library of QWNTs exhibit differentiated spectral variations in response to an ensemble of molecular binding events in patient serum. Via machine learning algorithms, we built prediction models of nanosensor responses that can reliably identify ovarian cancer, and we have expanded this approach to other indications without known biomarkers, providing a general method to identify clinical indications.

Self-Calibrating Fluorimetric Analysis of Single-Wall Carbon Nanotube Samples for Electronics Applications

Semiconducting single-wall carbon nanotubes (SWCNTs) are a leading candidate to replace or supplement silicon in future generation chip manufacturing. Because they are produced as structural mixtures with varied electronic properties, SWCNTs must first be carefully sorted and purified. This requires new metrology tools that can reliably measure SWCNT sample compositions to guide sorting processes and confirm product purity. We describe here a novel, self-calibrating optical instrument designed for advanced characterization of SWCNT samples. This desktop system will quickly, sensitively, and non-destructively quantify the concentrations of multiple SWCNT (n,m) species. The key advance is adding variance spectroscopy to rapid excitation-emission fluorimetry. Variance spectroscopy is a recently developed method that can determine absolute concentrations of nanoparticles by analyzing statistical variations in the fluorescence signals from small volumes of dilute samples. Measurements are made by a small accessory module linked to a standard NanoSpectralyzer. It will automatically acquire and analyze variance spectra to find the sensitivity calibration factors needed to convert raw fluorescence intensities into actual concentrations of the different SWCNT species. Those measured calibration factors are valid for subsequent samples with similar processing histories, allowing rapid quantitation from quick excitation-emission scans. We expect that this analytical capability will support advances in basic carbon nanotube science and applications.

(Invited) Single-Walled Carbon Nanotube Functionalization Strategies for Monitoring Enzymatic Activity and Inhibition

Semiconducting single-walled carbon nanotubes (SWCNTs) fluoresce in the near-infrared range, which overlaps with the transparency window of biological samples, and they do not photobleach or blink. Moreover, they benefit from biocompatibility and the large surface area available for functionalization. Using tailored surface functionalization, SWCNTs can be rendered optical nanosensors, such that surface binding events or changes in the local proximity of the nanotubes translate to a modulation of the emitted fluorescence. This approach was successfully used to demonstrate the detection of small molecules, volatiles, bacteria, microRNA, proteins, metals, self-assembly processes, and active processes in vivo. We will discuss different strategies for monitoring enzymatic activity and inhibition using SWCNT-based sensors, including the incorporation of the enzyme’s target bond within a synthetic molecular complex used for suspending the SWCNTs, or by the detection of the product of the enzyme hydrolytic activity. We will also highlight recent applications of these techniques in clinically relevant samples. These findings not only showcase the potential of near-infrared fluorescent SWCNT in tracking enzymatic activity but also underscore their promising role in advancing biomedical research and applications.

(Invited) Defect Photoluminescence Generation in Boron Nitride Nanotubes by Chemical Functionalization Approaches

Boron nitride nanotubes (BNNTs) are structural analogues of carbon nanotubes (CNTs). They have nanocylindrical structures composed of rolled-up hexagonal boron nitride (h-BN) sheets. The BN framework consists of alternately connecting boron and nitrogen atoms with sp2 hybridization. Therein, a strong covalent bond with an ionic character is formed due to their electronegativity difference. Accordingly, BNNTs exhibit unique properties such as high mechanical strength, thermal stability, and a wide bandgap semiconducting feature [1]. The large bandgap (ca. 6 eV) is less dependent on tube diameters and chiralities, and optical absorption and emission for pristine tubes occur in deep UV regions (around 200 nm) based on the band edge transition. In typical BNNT samples, however, atomic vacancies in the BN framework are reported to provide longer wavelength photoluminescence (PL) in UV–vis regions [2].To date, chemical functionalization of single-walled CNTs (SWCNTs) have been developed to create luminescent defects emitting red-shifted and bright near-infrared PL [3-6]. In this study, we use the chemical functionalization method to produce luminescent defects in BNNTs [7].A reductive alkylation reaction for BNNTs was conducted using sodium naphthalenide and 1-bromohexane to synthesize hexylated BNNTs (h-BNNTs). In a PL spectrum of h-BNNTs, PL peaks appeared at 334 and 413 nm, which were not observed for unmodified BNNTs. X-ray photoelectron spectroscopy revealed that the hexyl group was covalently attached on the boron site of BNNTs, by which sp3 hybridized boron atoms were partly formed in the BN network as defects. The covalent attachment of the hexyl group was also confirmed by atomic-resolution transmission electron microscope observations. Chemical reaction conditions were found to be a key factor for the emission wavelength variations of the resultant defect PL. Therefore, it is revealed that the luminescent defect formation in BNNTs is achieved based on the chemical functionalization approach. The functionalized BNNTs would be applicable to advanced optical applications such as quantum light sources.[1] D. Golberg et al. ACS Nano,4, 2979 (2010). [2] L. Museur et al. J. Appl. Phys., 118, 084305 (2015). [3] T. Shiraki et al. Acc. Chem. Res., 53, 1846 (2020). [4] B. Gifford et al. Acc. Chem. Res., 53, 1791 (2020). [5] A. H. Brozena et al. Nat. Rev. Chem. 3, 375 (2019). [6] J. Zaumseil. Adv. Opt. Mater. 10, 2101576 (2022). [7] T. Shiraki et al. Chem. Lett. 52, 44 (2023). Figure 1

(Invited) Near-Infrared Optical Probes for the Detection of Electrolytes

Electrolytes play crucial roles in biological functions including but not limited to activating nerve impulses and regulating muscle, heart, and kidney functions. The imbalance of electrolytes in the body can lead to cardiovascular, neurological, ocular, and muscular dysfunctions. Thus, monitoring of electrolytes levels is important for disease diagnosis and monitoring therapies. Photoluminescent single-walled carbon nanotubes (SWCNTs) exhibit outstanding potential in developing molecular probes for optical detection systems. Surface coatings on carbon nanotubes could facilitate effective molecular interactions enabling targeted nanoscale probes. Here, we report development of carbon nanotube-based optical sensors to detect target electrolytes in biological systems. Photoluminescent SWCNTs were encapsulated within synthetic polymers that present electrolyte recognition motifs along the polymer chains. The resulting polymer-SWCNT complexes allowed optical detection of electrolytes at nanomolar range.

(Invited) Sensing the Nanoscale Dynamics and Dimensionality of Brain Tissue By 3D Localization Microscopy of Diffusing Carbon Nanotubes

Elucidating how the nanometric structure of complex environments shapes the mesoscopic motion of the nano-objects within them is a fascinating but still open question. Due to a lack of knowledge of nanoscale details, diffusion properties are often described as anomalous. This applies to many systems, including the brain extracellular space that is the focus of this study. Its structure is indeed heterogeneous and tortuous, and ions, nutrients and signaling molecules diffuse in it for proper function of the brain.In recent years we have developed a strategy based on single-particle localization microscopy using SWIR emitting single-walled carbon nanotubes (SWCNTs) to decypher this brain compartment[1] but also pathological livers[2]. We now show that 3D tracking is essential to link the anomalous diffusion often observed at the macroscale to the local microscopic topologies of the edifices. We will present our recent results for the study of brain extracellular space [3], and other applicable structures including biophysical structures.

Evolution-Based Screening of Fluorescent SWCNT Nanosensors

The functionalization of fluorescent single-walled carbon nanotubes (SWCNTs) has proven to be a versatile platform for the development of biosensors targeting small molecules, proteins, and environmental factors. In this study, we introduce a novel and generic strategy that utilizes random single-stranded DNA (ssDNA) libraries to evolve synthetic molecular recognition on the surface of SWCNTs.Building upon our previous successes, we present the evolution of molecular recognition, specifically targeting the neuromodulator serotonin. This evolution is achieved through a combination of directed evolution and machine learning-based prediction, focusing on the iterative optimization process to enhance the sensitivity and selectivity of ssDNA-SWCNT nanosensors.In addition to neurotransmitter sensing, we extend the application of our evolved random ssDNA-SWCNT complexes to the development of cancer cell-targeting biosensors. Through positive selection, these complexes can be tailored to recognize and bind selectively to cancer cells. Simultaneously, negative selection ensures minimal interaction with normal cells. Those results showcase the broad applicability of our approach, suggesting that the elaborate functionalization of SWCNTs with specific ssDNA sequences can be universally employed for the rapid and convenient fabrication of novel biosensors and artificial antibodies. This research represents a significant step towards the development of highly specific and efficient nanosensors for diverse biomedical applications.

Near-Infrared Fluorescent Carbon Nanotube Sensors for the Plant Hormone Family Gibberellins

Gibberellins (GAs) are a class of phytohormones, important for plant growth, and very difficult to distinguish because of their similarity in chemical structures. Herein, we develop the first nanosensors for GAs by designing and engineering polymer-wrapped single-walled carbon nanotubes (SWNTs) with unique corona phases that selectively bind to bioactive GAs, GA3 and GA4, triggering near-infrared (NIR) fluorescence intensity changes. Using a new coupled Raman/NIR fluorimeter that enables self-referencing of nanosensor NIR fluorescence with its Raman G-band, we demonstrated detection of cellular GA in Arabidopsis, lettuce, and basil roots. The nanosensors reported increased endogenous GA levels in transgenic Arabidopsis mutants that overexpress GA and in emerging lateral roots. Our approach allows rapid spatiotemporal detection of GA across species. The reversible sensor captured the decreasing GA levels in salt-treated lettuce roots, which correlated remarkably with fresh weight changes. This work demonstrates the potential for nanosensors to solve longstanding problems in plant biotechnology.

Near Infrared Nanosensors Enable Optical Imaging of Oxytocin with Selectivity over Vasopressin in Acute Mouse Brain Slices

Oxytocin plays a critical role in regulating social behaviors, yet our understanding of its function in both neurological health and disease remains incomplete. Real-time oxytocin imaging probes with spatiotemporal resolution relevant to its endogenous signaling are required to fully elucidate oxytocin’s role in the brain. Herein, we describe a near-infrared oxytocin nanosensor (nIROXT), a synthetic probe capable of imaging oxytocin in the brain without interference from its structural analogue, vasopressin. nIROXT leverages the inherent tissue-transparent fluorescence of single-walled carbon nanotubes (SWCNT) and the molecular recognition capacity of an oxytocin receptor peptide fragment (OXTp) to selectively and reversibly image oxytocin. We employ these nanosensors to monitor electrically stimulated oxytocin release in brain tissue, revealing oxytocin release sites with a median size of 3 µm in the paraventricular nucleus (PVN) of C57BL/6 mice, which putatively represents the spatial diffusion of oxytocin from its point of release. These data demonstrate that covalent SWCNT constructs, such as nIROXT, are powerful optical tools that can be leveraged to measure neuropeptide release in brain tissue.

Radical-Mediated Creation of Fluorescent Defects in Carbon Nanotubes

The fluorescent defects in carbon nanotubes have been demonstrated to give exceeding optical properties such as room temperature single photon emissions at telecom wavelengths. A handful of methods for creating these defects have been invented in the past 13 years and provides practical guidelines for obtaining desired functional groups. However, most reactions are performed in the aqueous solution, and the transfer of the single-wall carbon nanotubes (SWCNTs) from aqueous to organic solvents are usually challenging. This gives barriers for applications that require SWCNTs to be dissolved in an organic solvent. Here, we introduce controlled creations of three different fluorescent defects in carbon nanotube hosts in organic solvents using a single radical initiator. We achieved selective creations of benzyl, phenyl, and benzoyloxy defects by controlling the reaction conditions such as dissolved oxygen concentration, reaction temperature, solvents, and addition of radical scavengers. It is worth noting that the both radical initiator and solvent can provide functional groups at the defect sites through radical reaction. We believe that this method will serve as a practical platform for designing new fluorescent defects in the organic phase.

Solution Processable Carbon Nanotube-Perovskite Nanohybrids

Carbon nanotubes (CNTs) based nanohybrids have attracted considerable interest for their potential in the design of innovative low-dimensional heterostructures. These nanohybrids can offer unique properties, including enhanced electronic transport and tunability, with a diverse range of optoelectronic applications.Here we present a novel approach for the synthesis of solution-processable nanohybrids made of single-walled carbon nanotubes (SWCNTs) and methylammonium-lead-iodide (MAPI) perovskites, where the CNTs act as templates for the facile and tuneable formation of anisotropic perovskite nanocrystals.We will present the structural characterization and electronic properties of the developed CNT-perovskite nanohybrids and demonstrate their integration (from solution) in field-effect transistor device configurations. By harnessing the synergistic properties of carbon nanotubes and perovskite nanocrystals, we will discuss pathways for the development of photoresponsive devices displaying sensitivity to a broad range of illumination wavelengths.The strategy presented here is of general applicability for the templated synthesis of perovskite nanocrystals toward the fabrication of solution processable in nanoscale optoelectronic devices.