Nanocrystals Incorporated with Mordenite Zeolite Composites with Enhanced Upconversion Emission for Cu²⁺ Detection

In this research, upconversion nanocrystals incorporated with MOR zeolite composites were synthesized using the desilicated MOR zeolite as a host for the in situ growth of NaREF₄ (RE = Y, Gd) Yb/Er nanocrystals. The structure and morphology of the composites were studied with XRD, XPS, and TEM measurements, and the spectral studies indicated that the subsequent thermal treatment can effectively improve the upconversion emission intensity of Er³⁺. By using the NaYF₄:Yb/Er@DSi1.0MOR-HT composite that holds the strongest upconversion emission, a probe of UCNC@DSiMOR/BPEI was constructed with the modification of branched poly ethylenimine for the detection of Cu²⁺. It was indicated that the integrated emission intensity of Er³⁺ shows a linear dependence with the logarithm value of the Cu²⁺ concentration ranging from 0.1 to 10 μM. This study offered a feasible method for the construction of UCNC@zeolite composites with enhanced upconversion emission, which may have a potential application as fluorescent probes for the detection of various metal ions by adjusting the doping luminescent center.