X-ray Photoelectron Spectroscopy Investigation of the Nitrogen Species in Photoactive Perfluorophenylazide-Modified Surfaces

Abstract

X-ray Photoelectron Spectroscopy (XPS) was used to characterize the nitrogen species in perfluorophenylazide (PFPA) self-assembled monolayers. PFPA chemistry is a novel immobilization method for tailoring the surface properties of materials. It is a simple route for the efficient immobilization of graphene, proteins, carbohydrates and synthetic polymers onto a variety of surfaces. Upon light irradiation, the azido group in PFPA is converted to a highly reactive singlet nitrene species that readily undergoes CH insertion and C=C addition reactions. Here, the challenge of characterizing the PFPA modified surfaces was addressed by detailed XPS experimental analyses. The three nitrogen peaks detected in the XPS N1s spectra were assigned to amine/amide (400.5 eV) and azide (402.1 and 405.6 eV) species. The observed 2:1 ratio of the areas from the 402.1 eV to 405.6 eV peaks suggests the assignment of the peak at 402.1 eV to the two outer nitrogen atoms in the azido group and assignment of the peak at 405.6 eV to the central nitrogen atom in the azido group. The azide decomposition as the function of x-ray exposure was also determined. Finally, XPS analyses were conducted on patterned graphene to investigate the covalent bond formation between the PFPA and graphene. This study provides strong evidence for the formation of covalent bonds during the PFPA photocoupling process.

Chemical Modification of Poly(Vinyl Alcohol) in Water

“…After click reaction (Figure 4b), the peak at 404.48 eV is reduced and the peak at 400.76 eV is shifted to 400.49 eV, which corresponds to the appearance of the triazole. This modification of the N1s, in good agreement with the literature, indicated the formation of the triazole [22][23][24].…”

Binary Mixed Homopolymer Brushes Tethered to Cellulose Nanocrystals: A Step Towards Compatibilized Polyester Blends

“…According to the results obtained here, PLLA grafting to CNCs produced noticeable increase in C-C and O-C=O character in the carbon 1s spectrum (Figure 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 17 PLLA-g-CNC despite a lack of an azide peak in the XPS data can be explained by decomposition of the azide over time in the XPS due to instability to irradiation 27 All three products have a broad peak around 401 eV, which can be explained as the three closely related nitrogen environments in the 1,2,3-triazole produced by the click reaction. Once the successful grafting of polyesters onto CNCs via a "click" reaction was confirmed, the thermal properties of the homopolymer brushes tethered to nanoparticles were evaluated.…”

Carbohydrate conjugation through microwave-assisted functionalization of single-walled carbon nanotubes using perfluorophenyl azides

“…31 Besides light and heat, PFPAs can also be activated by other energy sources such as electrons and X-rays. 28, 32 …”