Mid-IR spectroscopy of Fe:ZnSe quantum dots

Abstract

We report spectroscopic characterization of Fe:ZnSe quantum dots (for 2% of Zn/Fe molar ratio) fabricated by microemulsion hydrothermal synthesis. Mid-IR photoluminescence of the E↔T transition of Fe ions over 3.5-4.5 μm spectral range was observed in Fe:ZnSe quantum dot samples and kinetics of luminescence have been characterized at temperatures of 30-300 K under direct (2.788 μm) mid-IR excitation and indirect (0.355 μm) photoionization excitation. The radiative lifetime (τ) was estimated from these measurements to be 48 µs while lifetime at room temperature was measured to be 440 ns. This agrees closely with the behavior of bulk material.

Mid-Infrared Emission of Transition Metal Co2+-Doped ZnSe Nanocrystals at Room Temperature via Hydrothermal Preparation

“…Studies − that investigated II–VI nanocrystals with transition metal ions (such as Ni 2+ , Co 2+ , Fe 2+ , and Cr 2+ ) obtained by laser ablation of bulk polycrystalline samples have demonstrated optical characteristics in the mid-IR spectral region, and mid-IR luminescence in the spectral range of 2–6 μm and laser oscillation of Cr 2+ ions , under direct excitation have been achieved. However, laser sputtering methods are unable to avoid problems in the preparations of bulk crystals and have low yield, poor control of particle size distribution, and reagglomeration. , Therefore, in recent years, researchers have attempted to prepare the mid-IR luminescent nanocrystals via chemical synthesis. , In 2011, Zhang et al have obtained the ∼3.5 μm mid-IR emission at 293 K for Co 2+ :ZnSe nanocrystals prepared in aqueous solution by a one-pot method using thioglycolic acid as stabilizer. Furthermore, Myoung et al reported the 3.5–4.5 μm mid-IR emission at 35–200 K for Fe 2+ :ZnSe quantum dots fabricated by microemulsion hydrothermal synthesis.…”

“…However, laser sputtering methods are unable to avoid problems in the preparations of bulk crystals and have low yield, poor control of particle size distribution, and reagglomeration. , Therefore, in recent years, researchers have attempted to prepare the mid-IR luminescent nanocrystals via chemical synthesis. , In 2011, Zhang et al have obtained the ∼3.5 μm mid-IR emission at 293 K for Co 2+ :ZnSe nanocrystals prepared in aqueous solution by a one-pot method using thioglycolic acid as stabilizer. Furthermore, Myoung et al reported the 3.5–4.5 μm mid-IR emission at 35–200 K for Fe 2+ :ZnSe quantum dots fabricated by microemulsion hydrothermal synthesis. The chemical synthesis of ZnSe nanocrystals is easy, environmentally friendly, and inexpensive .…”

“…Moreover, the hydrothermal method can generate nanoscale size grains with narrow size distribution and low aggregation . However, for most previous studies, the transition metal ion-doped II–VI semiconductor nanocrystals have poor optical characteristics in the mid-IR spectral region due to the introduction of the organic phase and the high density of surface defects that severely quench mid-IR fluorescence. , Therefore, reducing the use of organic ligands and improving the surface lattice environment of nanocrystals are effective ways to enhance the mid-IR emission of TM 2+ :ZnSe nanocrystals prepared via chemical methods.…”

“…Nanocrystals have important application prospects in surface enhancement sensing and random lasers . The preparation of highly efficient mid-infrared optical nanocrystals brings new opportunities for available hot-pressed ceramic laser materials and composite fibers …”

Fabrication of Fe2+:ZnSe nanocrystals and application for a passively Q-switched fiber laser

“…In addition, Fe:ZnSe nanocrystals have been reported to be synthesized by chemical routes [17], and the authors paid more attention to the application in visible spectral region. However, to apply in mid-IR spectral region, the existing organic molecule and high density of surface defects in the NCs fabricated via chemical means may result in the quenching of mid-IR luminescence [18,19]. Whereas, femtosecond laser ablation (FLA), a physical process, has been proposed as a green method to synthesize various nanomaterials [20][21][22].…”