Spectrally Resolved Nonlinear Optical Properties of Doped Versus Undoped Quasi-2D Semiconductor Nanocrystals: Copper and Silver Doping Provokes Strong Nonlinearity in Colloidal CdSe Nanoplatelets

Katarzyna C Nawrot,Hilmi Volkan Demir,Bartłomiej Cichy,Marek Samoć,Manoj Sharma,Marcin Nyk,Savas Delikanli,Ashma Sharma

doi:10.1021/acsphotonics.1c01456

Abstract

Nonlinear optical processes are crucial for emerging applications including multiphoton-excited fluorescence microscopy and optical power limiting. Therefore, searching for materials of high multiphoton absorption cross sections is essential for the development of these techniques. We present synthesis of 4.5 monolayer CdSe nanoplatelets (NPLs) doped with silver and copper ions along with the evaluation of their two-photon absorption (TPA) and three-photon absorption (3PA) cross sections. Doping significantly increases the TPA cross section of each NPL sample, which reaches up to 1.33 × 107 GM for the most absorbing copper-doped ones. We also detected 1–2 orders of magnitude-enhanced 3PA cross sections for the doped NPLs in comparison with their undoped counterparts. As TPA and 3PA peaks appear, in the first and the second biological transmission windows, respectively, doped NPLs are promising candidates for multiphoton fluorescence microscopy as bioimaging agents. Moreover, the strong nonlinear response suggests application as active optoelectronic materials in optical sensors.

Highlights

Investigations of nonlinear optical (NLO) properties, and in particular nonlinear absorption of nanomaterials, have become an important issue for the development of numerous NLObased techniques used in different fields, such as multiphotonexcited fluorescence microscopy in medical diagnosis[1,2] or optical power limiting in laser-based technologies.[3]
We used two different doping concentrations both for Ag and Cu dopant ions in the same 4.5 ML CdSe NPL host with the doping concentrations estimated by ICP:MS measurements (Table S1) as 0.4 and 1.2% for Ag dopants and 0.5 and 1.1% for Cu dopants as the probes with average and maximum twophoton absorption (TPA) cross sections, respectively
All the samples exhibit the maximum of nonlinear absorption in the wavelength range of 825−925 nm which we attribute to the TPA effect and an additional peak between

Summary

■ INTRODUCTION

Investigations of nonlinear optical (NLO) properties, and in particular nonlinear absorption of nanomaterials, have become an important issue for the development of numerous NLObased techniques used in different fields, such as multiphotonexcited fluorescence microscopy in medical diagnosis[1,2] or optical power limiting in laser-based technologies.[3]. CdSe QDs were doped with silver ions which increased the efficiency of QD-sensitized photovoltaic cells.[16] we have prepared copper-doped CdSe NPLs with extended quantum yields (QYs) as promising candidates for luminescent solar concentrators[17−19] and developed a light-emitting diode based on the material.[20] Manganese-doped ZnS QDs were investigated in terms of their TPA cross section.[21]. This work contributes to filling this gap in knowledge of NLO properties of nanosystems, presenting TPA and 3PA absorption cross section spectra in a wide range of wavelengths for 4.5 ML CdSe NPLs doped with silver and copper ions. As the temperature reached 130 °C, 120 mg of cadmium acetate dihydrate was added in the powder form and the temperature was increased up to 240 °C where the reaction occurred for 10 min Thereafter, it was terminated by adding 1 mL of OA followed by immediate cooling of the solution with a water bath. The excitation laser system was synchronized with a Hamamatsu C5677 streak camera with a time resolution of 14 ps

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES