Magnetic, Mechanically Interlocked Porphyrin-Carbon Nanotubes for Quantum Computation and Spintronics

Multigram Scale Synthesis of Mechanically-Interlocked Derivatives of SWNT using Mechanochemical Methods

The grinding of chemical reagents enables mixing, promotes molecular collisions, and provides the thermal energy required for chemical reactions, while reducing the need for solvent (often to none) and significantly speeding up reactions. This has made mechanochemistry a powerful alternative to traditional solution chemistry. Here, we show that mechanically interlocked derivatives of single-walled carbon nanotubes (MINTs) can be made via mechanochemistry in a multigram scale. Compared to the previously reported method in suspension, mechanochemistry allows us to reduce the amount of solvent by two orders of magnitude and the reaction time from 72 h to 5 min. The mechanochemical synthesis of MINTs is proven to work both with purified (6,5)-SWNTs and affordable TuballTM SWNTs, enabling the cheap, fast, and environmentally friendly multigram scale synthesis of MINTs. With this new synthetic methodology, we open the door to the real-world applications of MINTs in fields such as polymer composites.

Fabrication of Graphene Polyhedra: Unveiling New Structures, Forms, and Properties

A hybrid nanoporous carbon alloy material is synthesized using a core-shell structure based on metal-organic frameworks, revealing a novel graphene polyhedral form. The presence of carbon and metal as doped cobalt carbides based on morphed graphene within the graphene polyhedra is confirmed through a combination of X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and Raman spectroscopy analyses. These novel graphene polyhedra exhibit magnetoelectric coupling properties at room temperature. The magnetic state control is verified using a magnetic probe; the changes in the magnetic state increased with a higher applied bias, and the poling direction of the magnetic phase is reversed based on the scanning direction of the probe. This discovery holds promise for future applications in ultrafast devices and carbon-based spintronics research.

Triphenylphosphine Oxide: A Versatile Covalent Functionality for Carbon Nanotubes

Broadening the scope of functionalities that can be covalently bound to single-walled carbon nanotubes (SWCNTs) is crucial for enhancing the versatility of this promising nanomaterial class in applied settings. Here we report the covalent linkage of triphenylphosphine oxide [Ph3P(O)] to SWCNTs, a hitherto overlooked surface functionality. We detail the synthesis and structural characterization of a new family of phosphine oxide-functionalized diaryliodonium salts that can facilitate direct Ph3P(O) transfer and afford novel SWCNTs with tunable Ph3P(O) content (SWCNT-P). The molecularly-distributed and robust nature of the covalent Ph3P(O) attachment in SWCNT-P was supported by a combination of characterization methods including Raman, infrared, UV/Vis-NIR and X-ray photoelectron spectroscopies coupled with thermogravimetric analysis. Electron microscopy further revealed the effectiveness of the Ph3P(O) moiety for de-bundling SWCNTs to yield SWCNT-P with superior dispersibility and processability. Finally, electrochemical studies established that SWCNT-P is sensitive to the presence of Li+, Na+ and K+ wherein the Gutmann-Beckett Lewis acidity parameters of the ions were quantitatively transduced by Ph3P(O) to electrochemical responses. This work hence presents a synthetic, structural, spectroscopic and electrochemical foundation for a new phosphorus-enriched responsive nanomaterial platform featuring the Ph3P(O) functionality.

Magnetic dimeric metal-porphyrin rings mechanically bonded around carbon nanotubes: the role of nanotube defects modulating magnetic properties

Carbon nanotubes constitute an excellent option to connect molecular nanomagnets (MNMs) to solid-state devices, allowing the electrical control of the molecule spin state. The main challenge in this area is to obtain stable nanohybrid structures that preserve the magnetic properties and functionality of the molecule. One of the strategies developed to build these structures combining MNMs and carbon nanotubes involves the encapsulation of the nanotube within magnetic organic macrocycle(s), leading to magnetic mechanically interlocked derivatives of carbon nanotubes (mMINTs). Recently, mMINTs with dimeric metal-porphyrin rings containing Cu2+ or Co2+ attached to carbon nanotubes have been synthesized. Different structural and spectroscopic techniques confirm that the metal centers in both mMINTs preserve the coordination sphere and structure of the free macrocycles, with only small deviations from the square planar geometry. However, different magnetic behaviors are observed depending on the metal. The Cu derivative has well-preserved spin geometry, with quantum coherence times on the microsecond scale, as in the free molecule (τ = 25 μs). In contrast, the continuous-wave electron paramagnetic resonance (EPR) spectrum measured on the Co derivative does not show any clear contribution from Co, although EXAFS unambiguously shows the presence of Co2+. In order to understand this different magnetic behavior, we studied mMINTs by means of periodic DFT calculations. The analysis of the optimized geometries, the spin density of the free macrocycles and the mMINTs, the adsorption energies, the extension of the charge transfer between the macrocycle and the nanotube and the density of states reveals a stronger macrocycle-nanotube interaction for the Co-mMINT. Our results point to carbon vacancies in the nanotubes as responsible for the different macrocycle-nanotube interaction and the observed loss of the Co2+ EPR signal in the Co-mMINT.

Integrating Single-Walled Carbon Nanotubes into Supramolecular Assemblies: From Basic Interactions to Emerging Applications

Integrating single-walled carbon nanotubes (SWCNTs) into supramolecular self-assemblies harnesses the distinctive mechanical, optical, and electronic properties of the nanoparticles alongside the structural and chemical properties of the assemblies. Organic molecules capable of forming supramolecular assemblies through hydrophobic, van der Waals, and π-π interactions have been demonstrated to be particularly effective in dispersing and functionalizing SWCNTs, as these same interactions facilitate the binding to the hydrophobic graphene-like surface of the SWCNTs. This review discusses a variety of self-assembling structures that were shown to integrate SWCNTs, ranging from simple micelles and ring structures to complex DNA origami and three-dimensional hydrogels formed by low-molecular-weight gelators. We explore the integration of SWCNTs into various supramolecular assemblies and highlight emerging applications of these composite materials, such as the mechanical enforcement of self-assembling hydrogels and leveraging the near-infrared (NIR) fluorescence properties of SWCNTs for monitoring the molecular self-assembly process. Notably, the distinctive NIR fluorescence of SWCNTs, which overlaps with the biological transparency window, offers significant opportunities for noninvasive sensing applications within the supramolecular platforms. Future research into a deeper understanding of the interactions between SWCNTs and different supramolecular frameworks will expand the potential applications of SWCNT-integrated supramolecular assemblies in fields like biomedical engineering, electronic devices, and environmental sensing.

Simultaneous exfoliation and functionalization of MoS2 with tetrapyridyl porphyrin

Molybdenum disulfide (MoS2) attracts the attention of the scientific community due to its thickness dependent properties. To fully exploit these features, it is necessary to produce the material in mono or few-layers on a large scale. Several methodologies have been developed for this purpose, the most promising one being liquid phase exfoliation (LPE). LPE allows obtaining good quality exfoliated MoS2 in a simple and scalable manner. Herein we report the simultaneous exfoliation and functionalization of MoS2 in chloroform using a specific porphyrin, namely tetrapyridyl porphyrin. We have corroborated that the exfoliation of MoS2 in the volatile solvent increases in the presence of the porphyrin due to the different interactions between them, obtaining dispersions with good concentrations. Additionally, the optical properties of the porphyrin are modified by these interactions. The characterization carried out by several techniques supports the hypothesis that the interactions occur through the pyridyl rings of the porphyrin and the molybdenum atoms of the material.

Simultaneous Inside and Outside Functionalization of Single-Walled Carbon Nanotubes

Functionalizing single-walled carbon nanotubes (SWCNTs) in a robust way that does not affect the sp2 carbon framework is a considerable research challenge. Here we describe how triiodide salts of positively charged macrocycles can be used not only to functionalize SWCNTs from the outside, but simultaneously from the inside. We employed disulfide exchange in aqueous solvent to maximize the solvophobic effect and therefore achieve a high degree of macrocycle immobilization. Characterization by Raman spectroscopy, EDX-STEM and HR-TEM clearly showed that serendipitously this wet-chemical functionalization procedure also led to the encapsulation of polyiodide chains inside the nanotubes. The resulting three-shell composite materials are redox-active and experience an intriguing interplay of electrostatic, solvophobic and mechanical effects that could be of interest for applications in energy storage.

Molecular and Supramolecular Materials: From Light-Harvesting to Quantum Information Science and Technology

The past two decades have witnessed immense advances in quantum information technology (QIT), benefited by advances in physics, chemistry, biology, and materials science and engineering. It is intriguing to consider whether these diverse molecular and supramolecular structures and materials, partially inspired by quantum effects as observed in sophisticated biological systems such as light-harvesting complexes in photosynthesis and the magnetic compass of migratory birds, might play a role in future QIT. If so, how? Herein, we review materials and specify the relationship between structures and quantum properties, and we identify the challenges and limitations that have restricted the intersection of QIT and chemical materials. Examples are broken down into two categories: materials for quantum sensing where nonclassical function is observed on the molecular scale and systems where nonclassical phenomena are present due to intermolecular interactions. We discuss challenges for materials chemistry and make comparisons to related systems found in nature. We conclude that if chemical materials become relevant for QIT, they will enable quite new kinds of properties and functions.

Automated statistical analysis of raman spectra of nanomaterials

Both at the academic and the industrial level, material scientists are exploring routes for mass production and functionalization of graphene, carbon nanotubes (CNT), carbon dots, 2D materials, and heterostructures of these. Proper application of the novel materials requires fast and thorough characterization of the samples. Raman spectroscopy stands out as a standard non-invasive technique capable of giving key information on the structure and electronic properties of nanomaterials, including the presence of defects, degree of functionalization, diameter (in the case of CNT), different polytypes, doping, etc. Here, we present a computational tool to automatically analyze the Raman spectral features of nanomaterials, which we illustrate with the example of CNT and graphene. The algorithm manages hundreds of spectra simultaneously and provides statistical information (distribution of Raman shifts, average values of shifts and relative intensities, standard deviations, correlation between different peaks, etc.) of the main spectral features defining the structure and electronic properties of the samples, as well as publication-ready graphical material.

Mechanical Interlocking to Unlock the Reinforcing Potential of Carbon Nanotubes

Single-walled carbon nanotubes (SWNTs) present extraordinary mechanical properties, with Youngs' modulus>1 TPa and tensile strength>50 GPa; this makes them ideal candidates as fillers for the reinforcement of polymers. However, the performance of SWNTs in this field has fallen behind expectations. This is due to a combination of imperfect individualization of the SWNTs and poor load transfer from the polymer to the SWNTs. Here, we study the reinforcement of polymers of different chemical nature using mechanically interlocked derivatives of single-walled carbon nanotubes (MINTs). We compare the mechanical properties of fibers made of poly (methyl methacrylate) (PMMA) and polysulfone (PSU) and their composites made with pristine SWNTs, MINTs, and the corresponding supramolecular models. With very low loading of MINTs (0.01 % w/w), improvements of more than 100 % on Youngs Modulus and the tensile strength are observed for both the nonpolar aliphatic PMMA and the very polar aromatic PSU polymers, while pristine carbon nanotubes and the supramolecular nanofillers showed smaller reinforcement. These data, together with our previous report on the reinforcement of polystyrene (nonpolar and aromatic), indicate that derivatization of SWNTs as MINTs is a valid general strategy to optimize the interaction between SWNT fillers and the polymer matrix.

Observation of High Magnetic Bistability in Lanthanide (Ln = Gd, Tb and Dy)-Grafted Carbon Nanotube Hybrid Molecular System

There is an immense research interest in molecular hybrid materials posing novel magnetic properties for usage in spintronic devices and quantum technological applications. Although grafting magnetic molecules onto carbon nanotubes (CNTs) is nontrivial, there is a need to explore their single molecule magnetic (SMM) properties post-grafting to a greater degree. Here, we report a one-step chemical approach for lanthanide-EDTA (Ln = GdIII, 1; TbIII, 2 and DyIII, 3) chelate synthesis and their effective grafting onto MWCNT surfaces with high magnetic bistability retention. The magnetic anisotropy of an Ln-CNT hybrid molecular system by replacing the central ions in the hybrid complex was studied and it was found that system 1 exhibited a magnetization reversal from positive to negative values at 70 K with quasi-anti-ferromagnetic ordering, 2 showed diamagnetism to quasi-ferromagnetism and 3 displayed anti-ferromagnetic ordering as the temperature was lowered at an applied field of 200 Oe. A further analysis of magnetization (M) vs. field (H) revealed 1 displaying superparamagnetic behavior, and 2 and 3 displaying smooth hysteresis loops with zero-field slow magnetic relaxation. The present work highlights the importance of the selection of lanthanide ions in designing SMM-CNT hybrid molecular systems with multi-functionalities for building spin valves, molecular transistors, switches, etc.

Single-Walled Carbon Nanotubes Encapsulated within Metallacycles

Mechanically interlocked derivatives of carbon nanotubes (MINTs) are interesting nanotube products since they show high stability without altering the carbon nanotube structure. So far, MINTs have been synthesized using ring-closing metathesis, disulfide exchange reaction, H-bonding or direct threading with macrocycles. Here, we describe the encapsulation of single-walled carbon nanotubes within a palladium-based metallosquare. The formation of MINTs was confirmed by a variety of techniques, including high-resolution transmission electron microscopy. We find the making of these MINTs is remarkably sensitive to structural variations of the metallo-assemblies. When a metallosquare with a cavity of appropriate shape and size is used, the formation of the MINT proceeds successfully by both templated clipping and direct threading. Our studies also show indications on how supramolecular coordination complexes can help expand the potential applications of MINTs.

Mechanical interlocking of SWNTs with N-rich macrocycles for efficient ORR electrocatalysis

Substitutional N-doping of single-walled carbon nanotubes is a common strategy to enhance their electrocatalytic properties in the oxygen-reduction reaction (ORR). Here, we explore the encapsulation of SWNTs within N-rich macrocycles as an alternative strategy to display electroactive sites on the surface of SWNTs. We design and synthesize four types of mechanically interlocked derivatives of SWNTs (MINTs) by combining two types of macrocycles and two types of SWNT samples. Comprehensive electrochemical characterization of these MINTs and their reference SWNTs allows us to establish structure-activity relationships. First, we show that all MINT samples are superior electrocatalysts compared to pristine SWNTs, which serves as general validation of our strategy. Secondly, we show that macrocycles displaying both N atoms and carbonyl groups perform better than those with N atoms only. Finally, we demonstrate that a tighter fit between macrocycles and SWNTs results in enhanced catalytic activity and stability, most likely due to a more effective charge-transfer between the SWNTs and the macrocycles. These results, focusing on the ORR as a testbed, show the possibility of understanding electrocatalytic performance of SWNTs at the molecular level and thus enable the design of more active and more stable catalysts in the future.

Interlocking of Single-Walled Carbon Nanotubes with Metal-Tethered Tetragonal Nanobrackets to Enrich a Few Hundredths of a Nanometer Range in Their Diameters

We have separated carbon nanotubes through host-guest complexation using host molecules named "nanotweezers" and "nanocalipers". In this work, a host molecule named tetragonal "M-nanobrackets", consisting of a pair of dipyrrin nanocalipers corresponding to two brackets "[" and "]" tethered by two metals (M), is designed, synthesized, and employed to separate single-walled carbon nanotubes (SWNTs). A facile three-step process including one-pot Suzuki coupling is developed to synthesize M-nanobrackets in a 37% total yield (M = Cu). Upon extraction of SWNTs with a square nanobracket and Cu(II), in situ formed tetragonal M-nanobrackets are found to interlock SWNTs to disperse them in 2-propanol. The interlocking is confirmed by absorption and Raman spectroscopy as well as transmission electron and atomic force microscopy. Especially, Raman spectroscopy is utilized to prove the interlocking of SWNTs; Cu-nanobrackets are found to show inherent resonance Raman signals and affect the SWNT signals, or a radial breathing vibration, due to the rigid rectangular structure of Cu-nanobrackets. The interlocking is facilely and thoroughly released through demetalation to recover the pristine SWNTs as well as the square nanobracket. Such chemically controlled locking and unlocking for SWNTs are one of the characteristics of our separation process. This enables a precise evaluation by Raman, photoluminescence, and absorption spectroscopy of the diameter selectivity to SWNTs, revealing the diameter enrichment of only three kinds of SWNTs, (7,6), (9,4), and (8,5), in the 0.02 nm diameter range from 0.90 to 0.92 nm among ∼20 kinds of SWNTs from 0.76 to 1.17 nm in their diameter range.

Carbon Nanotube Devices for Quantum Technology

Carbon nanotubes, quintessentially one-dimensional quantum objects, possess a variety of electrical, optical, and mechanical properties that are suited for developing devices that operate on quantum mechanical principles. The states of one-dimensional electrons, excitons, and phonons in carbon nanotubes with exceptionally large quantization energies are promising for high-operating-temperature quantum devices. Here, we discuss recent progress in the development of carbon-nanotube-based devices for quantum technology, i.e., quantum mechanical strategies for revolutionizing computation, sensing, and communication. We cover fundamental properties of carbon nanotubes, their growth and purification methods, and methodologies for assembling them into architectures of ordered nanotubes that manifest macroscopic quantum properties. Most importantly, recent developments and proposals for quantum information processing devices based on individual and assembled nanotubes are reviewed.

Mechanically interlocked derivatives of carbon nanotubes: synthesis and potential applications

An introduction to mechanically interlocked derivatives of single-walled carbon nanotubes: their main structural features, their potential advantages compared to covalent and supramolecular derivatives, how to synthesize them, and their most promising fields for application.