Synthesis of photoactivated highly fluorescent Mn2+-doped ZnSe quantum dots as effective lead sensor in drinking water

In this work, manganese doped zinc selenide (Mn@ZnSe) quantum dots (QDs) were prepared via a direct aqueous route. The X-ray diffraction pattern reveals the crystalline cubic zinc blende structure of QDs. With Mn²⁺ doping, a new high-intensity orange photoluminescence (PL) band centered at around 580 nm obtained owing to ⁴T₁ → ⁶A₁ of Mn²⁺ ion transitions (for orange QLEDs). The freshly prepared water-dispersible QDs were treated under the UV-radiation for the photoactivation process, which enhanced the PL quantum efficiency from 5 % to 17.3 %. The response of QDs towards different metals was recorded in terms of absorption, PL and PL-lifetime. Among the numerous metals, Pb²⁺ shows strong PL quenching and the corresponding Stern-Volmer plot showed linearity with the detection limits of 29.8 × 10⁻⁶ M in ultrapure water. The developed Mn@ZnSe QDs could act as a non-toxic sensor to sense hazardous lead in drinking water.