Evaluation of metallic and semiconducting single-walled carbon nanotube characteristics

In Situ Raman Spectroscopy-Enabled Microfluidic Gel Chromatography for Revealing Real-Time Separation Dynamics of Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWNTs) exhibit distinct electronic properties, categorized as metallic or semiconducting, determined by their chirality. The precise and selective separation of these electronic types is pivotal for advancing nanotechnology applications. While conventional gel chromatography has been widely employed for large-scale separations, its limitations in addressing microscale dynamics and electronic-type differentiation have persisted. Here, we present a polydimethylsiloxane (PDMS)-based microfluidic gel chromatography platform, coupled with real-time in situ Raman spectroscopy, designed to achieve the high-resolution electronic-type separation of SWNTs. This platform systematically isolates metallic- and semiconducting-enriched fractions (M1-M3 and S1-S3) while quantitatively analyzing separation dynamics through G-band spectral shifts and G-/G+ intensity ratios. By normalizing the SDS concentration and calculating rate constants, we reveal the intrinsic elution kinetics of SWNTs, with metallic fractions exhibiting faster elution dynamics compared to their semiconducting counterparts. Our approach bridges the gap between microscale precision and industrial scalability, emphasizing the critical role of dispersant concentration in fine-tuning separation outcomes. This advancement not only resolves the challenges of electronic-type differentiation but also demonstrates the versatility of PDMS microfluidic systems in delivering real-time insights into nanomaterial purification processes. By integrating continuous dynamic analysis with gel chromatography, this study establishes a transformative framework for scaling nanomaterial separations and unlocking new potential in chirality-specific applications.

Modelling electrical conduction in nanostructure assemblies through complex networks

Carrier transport processes in assemblies of nanostructures rely on morphology-dependent and hierarchical conduction mechanisms, whose complexity cannot be captured by current modelling approaches. Here we apply the concept of complex networks to modelling carrier conduction in such systems. The approach permits assignment of arbitrary connectivity and connection strength between assembly constituents and is thus ideal for nanostructured films, composites and other geometries. Modelling of simplified rod-like nanostructures is consistent with analytical solutions, whereas results for more realistic nanostructure assemblies agree with experimental data and reveal conduction behaviour not captured by previous models. Fitting of ensemble measurements also allows the conduction properties of individual constituents to be extracted, which are subsequently used to guide the realization of transparent electrodes with improved performance. A global optimization process was employed to identify geometries and properties with high potential for transparent conductors. Our intuitive discretization approach, combined with a simple solver tool, allows researchers with little computational experience to carry out realistic simulations.

Reductive dissolution of supergrowth carbon nanotubes for tougher nanocomposites by reactive coagulation spinning

Long single-walled carbon nanotubes, with lengths >10 μm, can be spontaneously dissolved by stirring in a sodium naphthalide N,N-dimethylacetamide solution, yielding solutions of individualised nanotubide ions at concentrations up to 0.74 mg mL^-1. This process was directly compared to ultrasonication and found to be less damaging while maintaining greater intrinsic length, with increased individualisation, yield, and concentration. Nanotubide solutions were spun into fibres using a new reactive coagulation process, which covalently grafts a poly(vinyl chloride) matrix to the nanotubes directly at the point of fibre formation. The grafting process insulated the nanotubes electrically, significantly enhancing the dielectric constant to 340% of the bulk polymer. For comparison, samples were prepared using both Supergrowth nanotubes and conventional shorter commercial single-walled carbon nanotubes. The resulting nanocomposites showed similar, high loadings (ca. 20 wt%), but the fibres formed with Supergrowth nanotubes showed significantly greater failure strain (up to ∼25%), and hence more than double the toughness (30.8 MJ m^-3), compared to composites containing typical ∼1 μm SWCNTs.

Wavelike deformation traveling on a carbon nanotube

The propagation of wavelike ripples on a carbon nanotube (CNT) induced by the radial impact of a C(60) molecule is investigated by molecular dynamics simulations. The ripples start at the impact point and spreads through the tube, accompanied by energy transfer. The ripples would effectively reduce the local energy concentration around the impact point. The propagation of ripples is clearly affected by the diameter but is independent of the chirality of the CNT. Noticeable diffraction occurs when the deformation ripples encounter obstacles or narrow slits, which indicates that the propagation of ripples can be used to detect defects in the CNT. This work provides new and exciting possibilities for CNTs to serve as energy buffers, sensors and new nanoelectromechanical devices.