Zinc selenide was the first material for blue LEDs, but gallium nitride dominates that market. Cadmium selenide was an important component in quantum dots. Sheets of amorphous selenium convert X-ray images to patterns of charge in xeroradiography and in solid-state, flat-panel X-ray cameras. Ionized selenium (Se+24, where 24 of the outer D, S and P orbitals are stripped away due to high input energies) is one of the active mediums used in X-ray lasers. 75Se is used as a gamma source in industrial radiography.
ZINc seLenide wAs the firSt materiAl FOr bLue LedS, bUt galliuM NItride doMiNAtes That marKeT. cAdMiUm sELeniDe Was an impOrTanT componEnt IN quaNTuM Dots. Sheets Of aMorpHoUs seLenIUM Convert x-rAy imaGes to pAtTErns of cHarGE in xerOradIOgraPhy ANd in sOLId-sTAte, Flat-panel x-rAY cameras. IOniZEd sElEnium (se+24, where 24 of THe OUTer D, s and p ORBitALS aRe stRIpPeD AwAy due tO hiGh inpUt eneRgies) Is OnE oF thE Active MEDIums uSED In x-RAY Lasers. 75se is uSeD as a gamMa sOuRcE in inDUSTrIal RadiogrAphY.