Depletion of intracellular antioxidants is linked to major cytotoxic events and cellular disorders such as oxidative stress and multiple sclerosis. In addition to medical diagnosis, determining the concentration of antioxidants in foodstuffs, food preservatives and cosmetics has proved to be very vital. Gold nanoclusters (Au-NCs) have a core size below 2nm and contain several of metal atoms. They have interesting photophysical properties, are readily functionalized, and are safe to use in various biomedical applications. Herein, a simple and quantitative spectroscopic method based on Au-NCs is developed to detect and image antioxidants such as ascorbic acid (AA). The sensing mechanism is based on the fact that antioxidants can protect the fluorescence of Au-NCs against quenching by highly reactive oxygen species (hROS). Our method shows great accuracy when employed to detect the total antioxidant capacity (TAC) in commercial fruit juice. Moreover, confocal fluorescence microscopy images of HeLa cells show that this approach can be successfully used to image antioxidant levels in living cells. Finally, the potential application of this “light-on” detection method in multiple logic gate fabrication is discussed using Fe2+, H2O2, and AA as inputs, and the fluorescence intensity of Au-NCs as output.