In the past decade, there have also been reports of covalent modification of SWCNTs. Fluorescent SWCNTs with a red-shifted NIR emission feature are generated by introducing sp 'quantum defects' into the sp 2 lattice of the SWCNTs . Such quantum defects have been even used to conjugate nanobodies or even grow peptides on the SWCNT surface . Furthermore, pH sensitive moieties and boronic acid motifs to bind alcohols have been demonstrated. SWCNTs modified with quantum defects can also serve as sensors but the fluorescence change was inverted to similar SWCNTs without the quantum defects . More recently, Zheng et al. demonstrated covalent SWCNT modification with ssDNA. Here, the dye rose Bengal (RB) is used to create singlet oxygen upon irradiation with green light. Singlet oxygen selectively reacts with guanine bases in DNA to create a guanine endo peroxide. The activated guanine attacks the sidewall of the SWCNTs and forms a covalent bond. Therefore, the dose of singlet oxygen and the guanine content of the ssDNA sequence determine the number of guanines bound to the SWCNT surface.