Photochemical Tailoring of Single-Wall Carbon Nanotubes by Photoexcited Sodium Hypochlorite

Single-wall carbon nanotubes (SWCNTs) are intriguing 1D nanomaterials whose unusual electronic properties are of interest for a wide array of applications. More specifically, semiconducting SWCNTs have structure-specific electronic transitions that allow for discrete near-infrared fluorescence spectra. These optical properties offer the potential for bioimaging applications because the wavelengths of semiconducting SWCNT emission fall within the biological window and are nearly free of autofluorescence background. An approach to optimize the emissive properties of semiconducting SWCNTs is to develop methods that allow for spectral tailoring and enhancement of fluorescence intensities. One way to accomplish this is through the covalent functionalization of SWCNTs. Since the first SWCNT covalent functionalization that maintained NIR SWCNT emissions was reported in 2010, active research has continued on new approaches to obtain more efficient and controlled functionalization. In this thesis project, the role of photodissociated sodium hypochlorite to obtain covalently functionalized SWCNTs was studied. New fluorescence emission features were found and assigned to additional addend sites. The effect on functionalization of varying sodium hypochlorite concentrations, irradiation intensities, and irradiation durations for photodissociation was studied. The suppression of functionalization by dissolved oxygen was also investigated and successfully mitigated through argon purging of SWCNT solutions. Beyond understanding the parameters necessary to promote SWCNT functionalization through sodium hypochlorite photolysis, the fluorescence quantum yield of the new photoproducts was also studied and quantified. Due to the complexity and heterogeneity of SWCNT samples, comprehensive characterization of dopant sites is a challenging but valuable task for optimal control of their emissive properties. This thesis thoroughly explored likely reaction channels of photodissociated sodium hypochlorite in acidic and basic conditions and highlights how dissociation pathways impact the resulting SWCNT adducts. These findings show that, contrary to previously published conclusions, the addends on the SWCNTs in this system arise from radicals produced through reactions of the primary photodissociation products of sodium hypochlorite. Since the reaction channels are different depending on the pH of the system, these investigations account for differences in addend identity. This study brings new clarity to SWCNT doping by photoexcited sodium hypochlorite, a functionalization method that spectrally tailors the emissions of small diameter SWCNTs and can be useful in sensing applications.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Natural Sciences

Grantor

Rice University

Year dc:date.issued

2022

Author dc:creator

• Espinoza, Vanessa Briana

Advisor dc:contributor.advisor

• Weisman, R. Bruce

• single-wall carbon nanotubes
• hypochlorite ion
• SWCNTs
• covalent functionalization
• radical addition
• exciton traps
• near-IR fluorescence
• photochemical tailoring

Statement dc:rights

• Copyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1911/113278

OAI identifier oai:identifier

oai:repository.rice.edu:1911/113278