Electronic structure analysis of Bi2WO6 and observation of near infrared emission on Nd3+doping

A simple solid-state reaction method is used to synthesize novel Nd3+doped Bi2WO6 materials and some novel results are reported for the first time. The samples of pristine and Nd3+ doped Bi2WO6, prepared by the precipitation and combustion methods, exhibit poor crystallinity. The pattern remains similar indicating that there is little change in the overall crystal structure after doping. We noticed that luminescence studies on Bi2WO6 are rare. The characteristic line emission with most intense emission at 1071 nm is observed in Nd3+doped Bi2WO6. Most intense excitation can be derived from f-f transitions. The emission can be excited using various wavelengths throughout the visible and NIR region. Transfer among activator ions restricts the luminescence intensity by concentration quenching. There is also a weak excitation band which corresponds to host sensitization. This band in the range 320-440 nm arises from Bi3+-W6+metal-to-metal charge transfer. The calculated critical distance for such transfer is found to be 22.65 angstrom. Thus, intense NIR emission around 1071 nm which can be pumped using various wavelengths throughout the visible and NIR region is observed in Bi2WO6:Nd3+. This can be useful in various applications like telecommunication, bio-imaging with the second biological window (NIR II: 1000-1500 nm), fluorescent cooling, photo morphogenesis etc. The density functional theory (DFT) simulations also support the experimental findings, confirming the electronic properties, nonmagnetic state, and the band gap of pristine and Nd3+doped Bi2WO6 after adding proper electron correlations for W-d states and Nd-f states.