To address the instability issue of the single-protected probe P2, we hypothesized that double substitution of the -OH groups of 1,4-NQH2 by boronates could make the probe more stable. Therefore, the probe P3 was synthesized and then tested for its long-term stability in the Tris buffer. The data in Figure show the absorbance of a dilute P3 solution (recorded at 262 nm, for an overview of the full spectrum see Figure ), which after a rapid decrease during the first few minutes (ensuing from the hydrolysis of pinacols), stabilizes at 0.17 over several hours. This result clearly demonstrates the high chemical stability of P3, which once hydrolyzed into diboronic acid does no longer decomposes into 1,4-NQ, therefore validating our initial hypothesis. This much higher chemical stability also correlates with a slower protodeboronation rate since the kinetic trace recorded at 290 nm (specific to the probe absorbance) is also very stable over several hours (see Figure ). Adding one equivalent of H2O2 to the solution results in a fast absorbance increase at 262 nm, rising to a maximal value in less than 5 min (red plot in Figure ). It thus attests to an efficient H2O2-mediated deprotection of P3 into 1,4-NQ and so to a high responsiveness of the doubly protected probe to H2O2. In order to determine the deprotection rate of P3, we repeated the experiment at different H2O2 concentrations (Figure ). As expected, the kinetics show a faster increase in absorbance as the H2O2 concentration is higher. However, unlike P2 the maximal absorbance change scales with the stoichiometry of H2O2 (see SI and Figure for details), which means that for each substoichiometric H2O2 concentration added to the solution of P3, only the corresponding substoichiometric equivalent in [1,4-NQ] can be recovered. This distinct behavior of P3 can be explained from the need to provide two equivalents of H2O2 for a full deprotection of one equivalent, but also from the ability to regenerate an additional equivalent of H2O2 from each released molecule of 1,4-NQH2. This also points out that the autoxidation of 1,4-NQH2 is an efficient process for producing H2O2 at a yield close to 100% (a result which agrees with what was previously reported for the autoxidation of 1,4-NQ ). The experimental kinetics reported in Figure should therefore fulfil the mechanism presented by reactions S5 to S9 in SI, wherein P3 is first converted into the monoprotected intermediate P2 and then into 1,4-NQ according to the same H2O2-mediated catalytic transformation described above for P2. This reaction scheme is therefore characterized by two deprotection rate constants, namely k . In fact, much better fits were obtained by artificially considering the second deprotection rate fast enough (e.g.,