1. A light emitting diode (LED) sensor comprising:a first LED junction constructed to emit a radiation;
a second LED junction constructed to receive a radiation and provide a detectable electronic response responsive to the received radiation;
a package encapsulating the first LED junction and the second LED junction, wherein the package defines a contoured envelope having a contoured surface; and
a material located adjacently to the contoured surface, wherein the material is constructed to include a property, wherein the property includes reflecting or absorbing and re-emitting the emitted radiation to the second LED, wherein the property includes reflecting an external radiation and preventing the external radiation from being received by the second LED, wherein the material includes a layer that includes a palladium alloy constructed to change optical reflectivity due to hydrogen absorption, and wherein the LED sensor is configured to detect the presence of hydrogen.