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1.
J Am Chem Soc ; 146(11): 7222-7232, 2024 03 20.
Article in English | MEDLINE | ID: mdl-38469853

ABSTRACT

Defect centers in a nanodiamond (ND) allow the detection of tiny magnetic fields in their direct surroundings, rendering them as an emerging tool for nanoscale sensing applications. Eumelanin, an abundant pigment, plays an important role in biology and material science. Here, for the first time, we evaluate the comproportionation reaction in eumelanin by detecting and quantifying semiquinone radicals through the nitrogen-vacancy color center. A thin layer of eumelanin is polymerized on the surface of nanodiamonds (NDs), and depending on the environmental conditions, such as the local pH value, near-infrared, and ultraviolet light irradiation, the radicals form and react in situ. By combining experiments and theoretical simulations, we quantify the local number and kinetics of free radicals in the eumelanin layer. Next, the ND sensor enters the cells via endosomal vesicles. We quantify the number of radicals formed within the eumelanin layer in these acidic compartments by applying optical relaxometry measurements. In the future, we believe that the ND quantum sensor could provide valuable insights into the chemistry of eumelanin, which could contribute to the understanding and treatment of eumelanin- and melanin-related diseases.


Subject(s)
Melanins , Nanodiamonds , Ultraviolet Rays , Free Radicals
2.
Chem Commun (Camb) ; 55(32): 4615-4618, 2019 Apr 16.
Article in English | MEDLINE | ID: mdl-30860529

ABSTRACT

Gold(ii) species catalyse the cyclisation of N(2-propyn-1-yl)benzamide to 2-phenyl-5-vinylidene-2-oxazoline without halide abstraction while the saturated gold(i) complex is inactive. Redox-switching between gold(ii) and gold(i) turns catalytic turnover on and off.

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