## 1 Introduction  
In 1979, Cu\({}^{+}\)(phenanthroline)\({}_{2}\) (the molecular structure of phenanthroline is presented in Figure 1) was discovered to display nuclease activity [1], by cleaving the phosphodies of DNA or RNA. The scission of DNA occurs in the presence of two co-reactants: Cu\({}^{+}\)(phenanthroline)\({}_{2}\) and H\({}_{2}\)O\({}_{2}\)[2, 3]. According to [PERSON] [2], the Cu\({}^{+}\)(phenanthroline)\({}_{2}\) complex coordinates to DNA and the oxidation of this coordinate by H\({}_{2}\)O\({}_{2}\) further generates a cupric hydroxyl radical-like coordinate, responsible for the DNA scission. Hence, copper-phenanthroline coordinates (Cu-Phen) represent the first artificial nucleases studied in biology. Generally, they consist of bis(1,10-phenanthroline)copper(I) complexes [1, 2, 3, 4, 5], although a mono(1,10-phenanthroline)copper  
Figure 1: Molecular structure of 1,10-phenanthroline (Phen). display better nuclease activity [6]. The active synthetic nucleases are commonly described as cuprous complexes. [PERSON] et al. evidenced the intercalative binding of the cupric Cu\({}^{2+}\)(phenanthroline)\({}_{2}\) complex with DNA and attributed the DNA cleavage to this complex. Accordingly, the group of [PERSON] has shown that cupric complexes could cleave DNA in the presence of H\({}_{2}\)O\({}_{2}\) and a reductant, via a mechanism involving coordination of the copper(II) with DNA [7]. Even if it is also proposed that during the reaction several oxidized states of copper, from Cu\({}^{\text{II}}\) to Cu\({}^{\text{III}}\), can be implicated [8], Cu\({}^{\text{II}}\) reduction to Cu\({}^{\text{I}}\) is involved in most cases [9]. The oxidation of lignin derivates with Cu-Phen complexes in the presence of H\({}_{2}\)O\({}_{2}\) has been successfully investigated under alkaline conditions, demonstrating improved oxidative action compared to H\({}_{2}\)O\({}_{2}\) alone [10; 11]. The main application for such a system is in paper pulp bleaching. Under neutral conditions, this H\({}_{2}\)O\({}_{2}\)/Cu-Phen system also displayed activity in the decolorization of colored cellulosic fibers [12], reaching up to 50% color-stripping. However, this activity was accompanied by strong cellulose degradation that can be rationalized based on a radical mechanism via the decomposition of H\({}_{2}\)O\({}_{2}\) into the highly oxidative hydroxyl radical, generated by the presence of Cu-Phen. The present study has been carried out in this context, especially on the color-stripping effect on dyed cellulosic fibers with H\({}_{2}\)O\({}_{2}\)/Cu-Phen at both near-neutral and alkaline pHs. [PERSON] and [PERSON] studied the formation of hydroxyl radicals by a Cu\({}^{\text{I}}\)/H\({}_{2}\)O\({}_{2}\) system [13] using the spin-trapping method based on EPR spectroscopy. This approach indirectly probes the presence of short-lived radical species, such as hydroxyl radicals, that react with a molecule called a spin-trap, to form a stable radical species detectable by EPR spectroscopy. Nitrones including 5,5-dimethyl-1-pyrroline N-oxide (DMPO, see Figure 2) are common spin-traps. In the presence of hydroxyl radicals, DMPO forms the DMPO-OH adduct, which gives a typical four-line signal (Figure 2), with hyperfine splitting constants \(\text{a}_{\text{N}}=\text{a}_{\text{H}}=14.9\) G. [14]  
However, the observation of DMPO-OH does not necessarily mean that HO\({}^{\bullet}\) radicals are formed. Indeed, several phenomena lead to the DMPO-OH adduct, including (i) superoxide radical spin-trapping and decomposition of the corresponding DMPO-OH adduct into DMPO-OH; (ii) the oxidation of DMPO by very strong oxidants (called inverted spin-trapping) [18]; or (iii) the nucleophilic addition of water onto the DMPO spin-trap (Forrester-Hepburn reaction) [19]. Besides, the nucleophilic addition of water is quite usual in aqueous solution and has been proved to be catalyzed by copper ions [13; 15; 20].