In
this research, highly luminescent silver nanoclusters (Ag NCs)
were prepared by using Na-FAUY zeolite as a scaffold to hinder their
aggregation, and efficient energy transfer from Ag NCs to Tb3+ was realized in Ag+-Tb3+ dual-exchanged Na-FAUY
zeolites and then proved by steady spectral and luminescence lifetime
measurements. Furthermore, the effects of Ag+ loading amount,
thermal treatment, and Tb3+ loading on the luminescence
properties of Ag NCs were studied, and the optimized doping and preparing
conditions were obtained. X-ray photoelectron spectroscopy together
with spectral measurements indicated that the available sites for
Tb3+ and Ag+ are competitive and Tb3+ doping may hinder the effective formation of Ag NCs. It is also
indicated that the loading of Tb3+ may lead to reduced
Si/Al ratios, which greatly influence the luminescence property and
chemical state of Ag NCs, e.g., a high Si/Al ratio leads to blueshift
emission and stronger ionic of Ag NCs. This research may benefit
the design of Ag NCs-involved luminescent zeolites that have potential
applications for photonic devices like LEDs and 3D displays.
Silver
nanoclusters (Ag NCs) are emissive centers that are characteristic
of high quantum yield, tunable emission, and large Stokes shift when
confined inside zeolites, and their luminescence property is closely
related to the cluster size, charge state, local environment, and
extra activation. In this research, we evaluated the luminescence
response of Ag NCs on the extra-framework cations by considering Na-type
FAU-Y (NaY) as the parent zeolite. The extra-framework cations Na+ were partially substituted with Li+ or Ca2+ through the ion-exchange method and analyzed by X-ray diffraction
(XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform
infrared (FT-IR) measurements, based on which a series of MYAg (M
= Na, Li, Ca) zeolites were prepared through subsequent Ag+ exchange and thermal treatment under 600 °C for 2 h. The influence
of extra-framework cations on the lattice parameter of the host zeolite,
the exchange efficiency of Ag+, the formation ability,
and the chemical state and luminescence property of Ag NCs was studied
through the combination of structural and spectral measurements. This
research indicated a flexible pathway for manipulating the luminescence
property of Ag NCs, and the extra-framework cation-dependent luminescence
property enables the FAU-Y zeolite to become a desirable host for
the stabilization of Ag NCs to achieve highly efficient tunable emission.
In this research, the LiY zeolite was firstly synthesized by using NaY as the parent zeolite; thereafter, the LiYAg and NaYAg zeolites created for formaldehyde gas detection were prepared with further Ag+-Li+/Na+ exchange and a mild thermal treatment at 300 °C to promote the formation of luminescent Ag CLs. The spectra experimental results indicated that Ag CLs showed stronger and blue-shifted emissions in LiYAg compared with in NaYAg, and the emission intensity of Ag CLs in both zeolites monotonously decreased when exposed to increasing formaldehyde gas content. Moreover, the linear dependence of the Ag CLs’ emission intensity variation on formaldehyde content indicated a reliable method for fast and sensitive formaldehyde detection. According to the XPS, UV–vis absorption, and N2 adsorption–desorption isotherm studies, the formaldehyde-gas-induced luminescence quenching of Ag CLs is due to the formation of Ag2O and Ag NPs, in which the higher content of Ag+/Ag0 redox couples in LiYAg and larger surface area of NaYAg benefit the precise detection of formaldehyde gas in low- and high-content ranges, respectively. Furthermore, the blue-shifted peak position and widened FWHM of Ag CLs can also be used for the indication of formaldehyde gas and the detection limit of NaYAg and LiYAg, which both meet with the standards of the WHO and OSHA.
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