In conjunction with the depth-dependent pore morphology, severe compositional and chemical bond gradients are revealed (Figure ). The gradient conversion of the precursors, both, from the sensor to the transducer layer as well as within the sensor layer from the core regions to the surfaces, is evident. The global preferential loss of nitrogen during carbonization Within the sensor layer, an abrupt depletion of the local nitrogen content in the shell regions is observed, while the composition of the core regions is rather constant (Figure , N/C maps of sensor layer). Comparing that core composition after laser treatment, i.e., a concentration ratio of nitrogen:carbon around 35:55 (at%), with the composition of the adenine-CNFA (Figure ) indicates a slight preferential loss of nitrogen. Globular regions within the sensor layer with no nitrogen (from glucose-CNFA) were identified as well at higher magnification by STEM but are not further discussed. Substantial concentrations of oxygen of the order of 5 at% are present, both, in the transducer layer as well as the shell of the sensor layer due to the conversion in an oxygen environment (Figure , Figure ).