Using UV Absorption Spectroscopy to Analyze ssDNA-Coated CNTs

Single-stranded DNA (ssDNA) shows remarkable selectivity when coated onto single-walled carbon nanotubes. Although many previous reports have focused on the applications of these structures, very few reports have analyzed their structure and composition.

Using UV Absorption Spectroscopy to Analyze ssDNA-Coated CNTs

Study: Compositional Analysis of ssDNA-Coated Single-Wall Carbon Nanotubes through UV Absorption Spectroscopy. Image Credit Oselote/Shutterstock.com 

An article published in  Nano Letters analyzed ssDNA-coated single-walled carbon nanotubes via ultraviolet (UV) absorption and measured the total carbon content.

The results revealed average concentrations of ssDNA and single-walled carbon nanotubes in the samples that helped deduce the average mid-UV absorptivity of single-wall carbon nanotubes for three different samples of small-diameter carbon nanotubes produced via the CoMoCAT and HiPco growth processes.

The measured absorptivity values quantified the ssDNA-to-single-walled carbon nanotube mass ratio, suggesting the average number of carbon atoms (of carbon nanotubes) suspended on single ssDNA strands of T30G or T15GT15 oligos.

Furthermore, spectrophotometry was employed to measure the absolute concentrations of similar single-walled carbon nanotube samples in aqueous sodium dodecyl sulfate (SDS), a typical surfactant that is transparent in the mid-UV. 

Replica exchange molecular dynamics (REMD) simulations of one ssDNA strand were compared with the experimental parameters. Results revealed a concurrence between the computed and experimentally measured single-walled carbon nanotube carbon atoms per strand of ssDNA.

What Are Single-Walled Carbon Nanotubes?

Single-walled carbon nanotubes are one-dimensional (1D) carbon materials where graphene sheets roll up to form hollow tubes with atomic-thickness walls. Owing to its chemical structure and dimensional constraints, this material exhibits exceptional mechanical, electrical, thermal, and optical properties.

The electrical properties of carbon nanotubes depend on their lattice orientation which is given by two parameters (n,m). The disaggregation of single-walled carbon nanotubes is a vital step in engineering and scientific applications. Hence, raw single-walled carbon nanotubes are coated with polymers (for example, ssDNA) and surfactants and dispersed into liquid suspensions for their facile disaggregation.

Solute concentration plays a critical role when working with a solution or suspension. However, determining this concentration is difficult for most samples of single-walled carbon nanotubes owing to their inhomogeneous compositions. Although optical absorption measurements are inexpensive, quick, and non-destructive techniques for determining the solute concentration, knowledge of the absolute absorptivity values is required.

The (n,m)-specific values for near-infrared transitions are available for a wide range of semiconducting species. These values cannot be used to determine the concentration of single-walled carbon nanotubes because of the difficulty in estimating the metallic single-walled carbon nanotubes, the incomplete collection of known semiconducting absorptivity, and crowded near-infrared absorption spectra.

As all (n,m) species exhibit robust absorption in the UV range, UV spectroscopy may provide a more suitable spectral area for calculating the overall concentration of single-walled carbon nanotubes.

Analysis of ssDNA-Coated Single-Wall Carbon Nanotubes

The present study demonstrated a convenient method to measure UV extinction coefficients for single-walled carbon nanotube samples with small diameters grown via CoMoCAT and HiPco growth processes. The overall carbon concentration of single-walled carbon nanotubes and ssDNA in the dialyzed sample was measured by employing a total carbon analyzer.

Moreover, adding SDS to the sample enabled the removal of ssDNA from the single-walled carbon nanotube and facilitated the measurement of pure ssDNA concentration via UV absorption spectroscopy, which resulted in an unperturbed ssDNA spectrum.

Furthermore, the difference in total carbon concentration and ssDNA helped compute the absolute concentration of single-walled carbon nanotubes, which could be applied to determine the UV extinction coefficients of single-walled carbon nanotubes.

A spectrophotometric assay of single-walled carbon nanotubes was conducted based on the obtained UV extinction coefficients, which could be useful in various applications. Additionally, the mass ratio quantification of surface-adsorbed ssDNA to single-walled carbon nanotubes indicated the number of carbon atoms covered by one ssDNA strand.

The experimental validation of the REMD simulations of ssDNA structures on single-walled carbon nanotubes depended on the total carbon content. Thus, the experimental results supported the simulations and provided a deeper understanding of the structures of ssDNA oligos covering single-walled carbon nanotubes.

Conclusion

In conclusion, the composition of single-walled carbon nanotubes distributed in ssDNA oligos was quantified by combining measurements of total carbon content and UV absorption spectroscopy. The analysis provided the absolute UV extinction coefficient values for three separate single-walled carbon nanotube sample batches.

The resulting coefficient values can be used to perform UV absorption experiments to determine the absolute concentrations of single-walled carbon nanotubes in aqueous SDS solutions. The present study also provided the relative masses of single-walled carbon nanotubes and ssDNA in samples that had free ssDNA removed.

Comparing the observed ratios with REMD predictions revealed the average number of carbon atoms per ssDNA strand, which helped determine the typical number of nanotube carbon atoms suspended per strand.

Reference

Alizadehmojarad, A. A., Bachilo, S. M., Weisman, R. B. (2022). Compositional Analysis of ssDNA-Coated Single-Wall Carbon Nanotubes through UV Absorption Spectroscopy. Nano Letters. Available at: https://pubs.acs.org/doi/10.1021/acs.nanolett.2c02850

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

Bhavna Kaveti

Written by

Bhavna Kaveti

Bhavna Kaveti is a science writer based in Hyderabad, India. She has a Masters in Pharmaceutical Chemistry from Vellore Institute of Technology, India, and a Ph.D. in Organic and Medicinal Chemistry from Universidad de Guanajuato, Mexico. Her research work involved designing and synthesizing heterocycle-based bioactive molecules, where she had exposure to both multistep and multicomponent synthesis. During her doctoral studies, she worked on synthesizing various linked and fused heterocycle-based peptidomimetic molecules that are anticipated to have a bioactive potential for further functionalization. While working on her thesis and research papers, she explored her passion for scientific writing and communications.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Kaveti, Bhavna. (2022, October 17). Using UV Absorption Spectroscopy to Analyze ssDNA-Coated CNTs. AZoNano. Retrieved on June 25, 2024 from https://www.azonano.com/news.aspx?newsID=39807.

  • MLA

    Kaveti, Bhavna. "Using UV Absorption Spectroscopy to Analyze ssDNA-Coated CNTs". AZoNano. 25 June 2024. <https://www.azonano.com/news.aspx?newsID=39807>.

  • Chicago

    Kaveti, Bhavna. "Using UV Absorption Spectroscopy to Analyze ssDNA-Coated CNTs". AZoNano. https://www.azonano.com/news.aspx?newsID=39807. (accessed June 25, 2024).

  • Harvard

    Kaveti, Bhavna. 2022. Using UV Absorption Spectroscopy to Analyze ssDNA-Coated CNTs. AZoNano, viewed 25 June 2024, https://www.azonano.com/news.aspx?newsID=39807.

Tell Us What You Think

Do you have a review, update or anything you would like to add to this news story?

Leave your feedback
Your comment type
Submit

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.