Cu⁺@Sb³⁺-Codoped All-Inorganic Metal Halide of Cs₂ZnCl₄ with Tunable Dual Emission for Fluorescence Anticounterfeiting and Information Encryption

Abstract

In recent years, low-dimensional lead-free metal halides have captured wide interest in the application of fluorescence anticounterfeiting due to their unique optical properties, low toxicity, and excellent environmental stability. Herein, we report an effective multimode photoluminescent material of Cu + @Sb 3+ -codoped Cs 2 ZnCl 4 microcrystals via a facile solution synthesis method. Upon a 365 nm ultraviolet (UV) excitation, Cu + @Sb 3+ -codoped Cs 2 ZnCl 4 shines a highly efficient broad red emission band at 714 nm. Under a 254 nm UV irradiation, this codoped compound exhibits a dual-band emission with an additional high-intensity emission band at 492 nm, enabling a bright sky-blue emission to be observed. The study of the photophysical mechanism reveals that the observed dualemission bands at 492 and 714 nm in this compound stem from the self-trapped exciton emission of [CuCl 4 ] 3− and [SbCl 4 ] − clusters, respectively. In addition, inspired by the obvious excitation-wavelength-dependent emission characteristics and excellent stabilities of Cu + @Sb 3+ -codoped Cs 2 ZnCl 4 , we successfully applied this compound to fluorescent anticounterfeiting and information encryption−decryption applications.

Zero-Dimensional Halides with ns2 Electron (Sb3+) Activation to Generate Broad Photoluminescence

“…Zero-dimensional (0D) metal halides with isolated luminescent centers exhibit PLQY of near unity. In-based OIMHs are considered promising host materials for solid-state lighting. − Doping with various metal cations has been shown to improve the optical properties of OIMHs. Sb-doped OIMHs have been reported to emit blue, orange, or white light, with many applications for near-infrared emission.…”

Mn2+ and Sb3+ Codoped Cs2ZnCl4 Metal Halide with Excitation-Wavelength-Dependent Emission for Fluorescence Anticounterfeiting

“…The fitting results are shown in Figure 4d, S = 19.6, ℏω phonon = 36.4, where the value of S is suitable for STE compared with other values, which were reported. 29,41,34,35 The result also suggests strong electron−phonon coupling in Cs 2 ZnCl 4 :Mn 2+ , Sb 3+ crystals, which means the formation of STE. Moreover, the relationship between the integrated intensity of red emission in Cs 2 ZnCl 4 :Mn 2+ , Sb 3+ crystals and excitation power density was fitted, and it shows a linear relationship with R 2 = 0.999, indicating the red emission derived from the STE, not the permanent defects (Figure S8, Supporting Information).…”

“…These results ensured the successful doping and good repeatability of the samples synthesized by the hydrothermal method, which could further be proven by X-ray photoelectron spectroscopy (XPS) and Raman spectral results. As shown in Figure b, the XPS spectra exhibit the characteristic peaks of Cs 3d, Zn 2p, Cl 2p, Mn 2p, and Sb 3d, and the peaks at 641.4 eV (2p3/2) and 652.6 eV (2p1/2) correspond to the Mn 2+ ions, while the peaks at 539.8 eV (3d3/2) and 530.5 eV (3d5/2) originate from Sb 3+ ions, which can also account for the existence of Mn 2+ and Sb 3+ ions in the host. , The Raman shift spectra (as shown in Figure S2, Supporting Information) also revealed the characteristic signals associated with the vibration of Zn–Cl (110, 125, 137, 285, and 295 cm –1 ), Sb–Cl (97 cm –1 ), and Mn–Cl (136.5, 151.2, and 262.3 cm –1 ), which demonstrates the successful doping of Mn 2+ and Sb 3+ ions into the lattice of Cs 2 ZnCl 4 . − …”

“…As shown in Figure 2b, the XPS spectra exhibit the characteristic peaks of Cs 3d, Zn 2p, Cl 2p, Mn 2p, and Sb 3d, and the peaks at 641.4 eV (2p3/2) and 652.6 eV (2p1/2) correspond to the Mn 2+ ions, while the peaks at 539.8 eV (3d3/2) and 530.5 eV (3d5/2) originate from Sb 3+ ions, which can also account for the existence of Mn 2+ and Sb 3+ ions in the host. 34,35 The Raman shift spectra (as shown in Figure S2, Supporting Information) also revealed the characteristic signals associated with the vibration of Zn−Cl (110, 125, 137, 285, and 295 cm −1 ), Sb−Cl (97 cm −1 ), and Mn−Cl (136.5, 151.2, and 262.3 cm −1 ), which demonstrates the successful doping of Mn 2+ and Sb 3+ ions into the lattice of Cs 2 ZnCl 4 . 37−39 The successful doping effect of Mn 2+ and Sb 3+ ions was further confirmed by the absorption spectra and calculated bandgap (as shown in Figure S3, Supporting Information).…”

“…For example, Ce 3+ doping in Cs 2 ZnCl 4 achieved emission in the ultraviolet region, Cu + doped Cs 2 ZnCl 4 nanocrystals exhibited emission of blue light with a fluorescence quantum yield of 55%, Te 4+ doped Cs 2 ZnCl 4 single crystals produced wide band emission of yellow light, and Sb 3+ doped Cs 2 ZnCl 4 single crystals yielded NIR (745 nm) emission with a fluorescence quantum yield of 69.9%, while Sn 2+ doped Cs 2 ZnCl 4 single crystals led to red emission. − Mn 2+ ions are successfully doped into Cs 2 ZnBr 4 to achieve green emission . Additionally, Mn 2+ and Cu 2+ codoped Cs 2 ZnBr 4 and Cu + and Sb 3+ codoped Cs 2 ZnCl 4 are synthesized and used for multiple anticounterfeiting applications depending on the excitation wavelength. , …”