We will develop, demonstrate, and built a sensor array designed frommathematical models thatare based on the maximum likelihood estimator(MLE), the Cramer- Rao lower bound (CRB), and the density function theory(DFT). The MLE will be used to estimate the concentration of the gases inside a mixture by minimizing the error trough the Cramer-Rao bound.The DFT method will model thephysisorption and chemisorption of gas molecules on the sensor surface of the sensors.The sensor device consists of robust and stable microsensors which will be realized by N5's patented semiconductor-nanophotocatalytic sensing architecture.By designing these sensor arrays with these simulation methods,we will be able to tune optimally the parameter of sensor array, and improve their selectivity levels to the neighborhood of 0.1 ppb, with minimum disturbance to the sensitivity of the sensors .