Sapra Sameer, Prakash Ankita, Ghangrekar Ajit, Periasamy N, Sarma D D
Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India.
J Phys Chem B. 2005 Feb 10;109(5):1663-8. doi: 10.1021/jp049976e.
We have performed steady-state and time-resolved fluorescence studies on undoped and Mn-doped ZnS nanocrystals with approximately 16 A diameter. While there is no band-edge emission, the intensity of the steady-state blue fluorescence from ZnS surface states decreases upon Mn incorporation, which gives rise to an orange emission. These results show that Mn incorporation competes very effectively with the donor-acceptor surface states for the energy transfer from the electron-hole pair excited across the band gap. In both undoped and doped samples, the time-resolved fluorescence studies establish the presence of a distribution of decay lifetimes possibly due to a number of emission centers in the nanocrystals. A faster short-time decay of the blue emission in the Mn-doped samples compared to that in the undoped sample suggests an additional decay channel for the surface states via an energy transfer from these states to the dopant levels.
我们对直径约为16埃的未掺杂和锰掺杂的硫化锌纳米晶体进行了稳态和时间分辨荧光研究。虽然没有带边发射，但随着锰的掺入，来自硫化锌表面态的稳态蓝色荧光强度降低，这导致了橙色发射。这些结果表明，锰的掺入在从带隙激发的电子-空穴对的能量转移中，与施主-受主表面态非常有效地竞争。在未掺杂和掺杂样品中，时间分辨荧光研究都证实了可能由于纳米晶体中的多个发射中心而存在衰减寿命分布。与未掺杂样品相比，锰掺杂样品中蓝色发射的更快的短时间衰减表明，通过从这些表面态到掺杂剂能级的能量转移，表面态存在额外的衰减通道。
