Sensors - Proceedings of the 2nd National Conference on Sensors, 2014

Nanoporous materials are ideal candidates to fabricate sensors with high sensitivities. Using nanoporous materials both the strength and the type of interactions between analytes and host matrix can be tune at will, and their large surface area permit to achieve ultralow detection limit and to keep high loading capacity and, thus, large dynamic range. Despite these intriguing possibilities their use in sensing technology is still limited because several fundamental aspects are not fully understood. In this article, we show how the strong interaction between the analyte and the optical modes in porous materials increases the net sensitivity of the sensor and we compare our results with state-of-the-art optical sensing using different platforms,. By comparing supported and free standing Porous Silicon membranes we also demonstrate that the sensitivity is easily and heavily overestimated if the sample is not properly washed and the washing is achieved only if mass transport is forced across the membrane itself. , Finally we show that the nonspecific signal may have a linear response with the analyte concentration and it thus extremely difficult to separate from the specific one. The work presented here is of importance in the design of nanoporous materials for sensing application. In fact it demonstrates that the final sensitivity of the device is not defined by its optical quality alone and that several other effects have to be considered to fabricate a reliable sensor.