Photochemical Surface Functionalization Of Single-walled Carbon Nanotubes And Diamond Powder

In the field of nanochemistry, Single-walled carbon nanotubes (SWCNTs) and Diamond are attractive and interesting for researchers due to their verstiles applications in nanotechnology. Due to intermolecular interactions, they are usually present in the form of clusters, which limit their utility in diverse fields of applications. Therefore, chemical functionalization of SWCNTs and Diamond is substantial and useful for easy and efficient chemical processibility. The functionalization inhibits the aggregation of SWCNTs and Diamond, and consequently improves their dispersibility in various organic solvents. The attached functional groups can be used as precursors for the subsequent attachment of a wide variety of other functional groups. Chemical functionalization changes the solution properties of SWCNTs and Diamond and helps to understand the chemistry of these nano materials.Although many studies have addressed the covalent functionalization of SWCNTs and Diamond by using thermal methods, but little attention has been devoted to photochemical methods. There have been few publications focused on the chemical modification techniques of the carbon nanotubes by the introduction of radicals. So, we solely emphasized on photochemical functionalizations of nano materials.In photochemical method, we developed; photoinitiator produces free radicals on photolysis. Commonly, HMPP/HPHMP is used as radical initiator in polymerization reactions, but currently, it is used as a source of functional group to functionalize the SWCNTs. Then, the radicals would functionalize the surface of SWCNTs and Diamond by covalent attachment. Consequently, these functional groups disturb the charge balance around the SWCNTs and Diamond and induce an electronic polarity, leading to an enhanced dispersibility in common organic solvents. Moreover, photochemical modification is direct and selective for the introduction of respective functional groups.Single-walled carbon nanotubes (SWCNTs) and Diamond powder were functionalized by covalent attachment of 2-propanol-2-yl radicals on the surface of SWCNTs, which were generated by the photolysis of 2-hydroxy-2-methyl-l-phenyl-l-propanone (HMPP) and 1-[4-(2-Hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (HPHMP) under ultraviolet (UV) light. Both, Pristine single-walled carbon nanotubes and Diamond powder were first dispersed in solution (tetrahydrofuran/acetone), and then free radicals were attached to the surface of Single-walled carbon nanotubes when mixture was subjected to UV irradiation.In mechanistic approach, the photoelectrons ejected from ultraviolet light played an important role to generate the free radicals and activate the surface of Diamond and Single-walled carbon nanotubes to react each other to form modified products.The functionalization, of Single-walled carbon nanotubes and Diamond powder, was evidenced by UV/Visible Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, Thermal Gravimetric Analysis-Mass Spectrometry (TGA-MS), Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM). Moreover, the dispersibilty of Single-walled carbon nanotubes and Diamond powder (both; pristine and functionalized) was determined in various organic solvents.UV/Visible results indicated the loss of van Hove singularities due to covalent functionalization in case of Single-walled carbon nanotubes. The Functionalization, of Single-walled carbon nanotubes and Diamond, was further proved by FTIR showing a signal around 3420 cm-1 and 1100 cm-1 due to stretching and bending of O-H bond, and others at 2930 and 2839 cm-1 due to stretching of aliphatic C-H bond. In case of Single-walled carbon nanotubes, Raman spectra showed that the intensity ratio of the tangential mode to the disorder mode (IG/ID) decreased for functionalized Single-walled carbon nanotubes. TGA-MS also showed the signal corresponding to m/z 39 at 400℃indicating the presence of 2-propanol-2-yl groups on the surface of functionalized Single-walled carbon nanotubes and Diamond powder. HRTEM and dispersibility data proved that the sidewall functionalization dissociated the bundle structure, improved the dispersibility in common organic solvents and retained the original electronic structure of in case of Single-walled carbon nanotubes without heavy modification, which could damage the Single-walled carbon nanotubes.Similarly, in case of Diamond powder, the SEM and dispersibilty data evidenced that the functionalization detached the clusters of Diamond powder, enhanced the dispersibilty in various organic solvents and did not impair the surface structure of Diamond powder. Functionalization is not hefty in case of Diamond powder even; therefore, Diamond retains its characteristic original robust properties. Functionalized Single-walled carbon nanotubes and Diamond endow both kinds of properties, properties of substrate and properties organic functional groups as well, which made functionalized materials versatile in diverse fields of application.