Fig. 8: Transformer response to H2 concentrations down to 0.01% or 100 ppm H2.
From: Neural network enabled nanoplasmonic hydrogen sensors with 100 ppm limit of detection in humid air
a The ISO 26412:2010 hydrogen safety sensor test protocol in synthetic air run at 80 °C with \({{{{{{\boldsymbol{c}}}}}}}_{{{{{{{\boldsymbol{H}}}}}}}_{{{{{{\boldsymbol{2}}}}}}}}\) pulses ranging from 0.01% H2 to 0.2% H2, and measured at RH = 0, 20, 50 and 80%. b Correspondingly obtained λpeak response, characterized by distinct blue-shifts for small \({{{{{{\boldsymbol{c}}}}}}}_{{{{{{{\boldsymbol{H}}}}}}}_{{{{{{\boldsymbol{2}}}}}}}}\) pulses and red-shifts for the largest pulses. c Correspondingly obtained Transformer-based readout, \({{{{{{\boldsymbol{c}}}}}}}_{{{{{{{\boldsymbol{H}}}}}}}_{{{{{{\boldsymbol{2}}}}}}}{{{{{\boldsymbol{,}}}}}}{{{{{\boldsymbol{NN}}}}}}}\), obtained by directly applying the old Transformer model trained in the 0.06 –1.2% H2 concentration range for RH = 0, 20, 50, 80%. d Correspondingly obtained Transformer-based readout from a re-trained model that thus also has seen sensor response to the lowest \({{{{{{\boldsymbol{c}}}}}}}_{{{{{{{\boldsymbol{H}}}}}}}_{{{{{{\boldsymbol{2}}}}}}}}\) pulses during training. Note that now also the lowest 0.01% H2 concentration pulse is predicted with high accuracy. e Sensor LoD as obtained by the standard λpeak readout for the different RH, as defined by signal extrapolation (orange) and the smallest measured H2 pulse which could be discerned within 3 standard deviations (red). f Sensor LoD as obtained by Transformer-based readout, \({{{{{{\boldsymbol{c}}}}}}}_{{{{{{{\boldsymbol{H}}}}}}}_{{{{{{\boldsymbol{2}}}}}}}{{{{{\boldsymbol{,}}}}}}{{{{{\boldsymbol{NN}}}}}}}\). Note again here that while the accuracy of the predictions of the smallest H2 concentrations is lower, the precision remains very high, effectively retaining a low estimated LoD. g Sensor LoD as obtained by the Transformer-based readout after re-training on the given dataset, revealing again an essentially RH-independent LoD that lies significantly below the DoE target of 0.1% and now extends down to 0.01% or 100 ppm as the lowest directly measured H2 concentration. The LoD estimation procedure is described in Supplementary Fig. 16.
