ZnO@MOF-5 as a Fluorescence “Turn-Off” Sensor for Ultrasensitive Detection as well as Probing of Copper(II) Ions

Abstract

Recently, the synthesis, characterization, and structural evaluation of metal–organic framework (MOF) nanocomposites gain more attention due to the versatility in their applications. In the present work, the fluorescent active ZnO@MOF-5 composite was synthesized by encapsulating ZnO nanoparticles into the zinc terephthalate metal–organic framework (MOF-5). ZnO nanoparticles were prepared by a green method using the leaf extract of Annona muricata . Incorporation of ZnO nanoparticles onto the framework structure (ZnO@MOF-5) was done by a solvothermal method. The new composite material was characterized by Fourier transform infrared spectroscopy, Powder X-ray diffraction, Ultraviolet–visible spectroscopy, Transmission Electron Microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller analysis, Dynamic light scattering, Thermogravimetry-Differential Thermal analysis, and Photoluminescence spectroscopy. The material displayed blue fluorescence with a peak at 402 nm upon excitation at 282.46 nm. ZnO@MOF-5 showed a good fluorescence sensing efficiency toward the detection as well as probing of Cu(II) ions in aqueous solution. Sensing experiments performed revealed that as the concentration of copper ions in the solution increases, the quenching efficiency of the composite also increases. A quenching efficiency of 96.20% was achieved on reaching a concentration of 5 μM. The limit of detection for the sensing of Cu 2+ ions was calculated to be 0.185 μM.

Dual-Functional Manganese-Doped ZnO-MOF Hybrid Material with Enhanced Hydrolytic Stability: A Fluorescent Photoinduced Electron Transfer Sensor for the Ultraselective Detection of Acetic Acid and Chromium (VI)

“…The simulated PXRD pattern shows a slight shift in the 2θ values, by less than one degree when compared with the experimental PXRD, which may be due to the gas phase calculations of the simulated one. However, simulated and experimental values are in good agreement with the CCDC card entries reported earlier . The difference in the intensities seen may be due to the fact that experimental PXRD is done in the solid state, whereas simulated PXRD is in the gaseous state.…”

“…The powder X-ray diffraction (PXRD) patterns of the prepared hybrid composite Mn-doped ZnO@MOF-5 and precursor materials such as MOF-5 and ZnO@MOF-5 are shown in Figure S1. Most of the peaks present in the PXRD pattern of MOF-5 are present in the PXRD patterns of ZnO@MOF-5 reported earlier as well as in Mn-doped ZnO@MOF-5. The possibility of structural collapse of the MOF during the introduction of nanoparticles within the framework is thus discarded beyond doubt.…”

“…However, simulated and experimental values are in good agreement with the CCDC card entries reported earlier. 35 The difference in the intensities seen may be due to the fact that experimental PXRD is done in the solid state, whereas simulated PXRD is in the gaseous state. Due to environmental factors such as exposure to a humid atmosphere, some of the additional peaks are seen in the experimental patterns of MOF-5.…”

“…24 For preparing the MOFnanocomposite, Mn-doped ZnO nanoparticles and MOF-5 were taken in 1:4 ratios and dispersed in 40 mL of dimethyl formamide, as reported in the literature. 35 The mixture was allowed to vortex at room temperature for 30 min for homogeneity using a magnetic stirrer. It was taken in an airtight Teflon-lined autoclave and further heated at 150 °C for 3 h. The pressurized heating inside the autoclave resulted in the effective incorporation of Mn-doped ZnO nanoparticles onto the MOF, which was allowed to cool under ambient conditions.…”

“…The synthesis of MOF-5 was done using a well-known solvothermal method . For preparing the MOF-nanocomposite, Mn-doped ZnO nanoparticles and MOF-5 were taken in 1:4 ratios and dispersed in 40 mL of dimethyl formamide, as reported in the literature . The mixture was allowed to vortex at room temperature for 30 min for homogeneity using a magnetic stirrer.…”