Cu-Ag particles with different molar ratios have been prepared in the hyperbranched polyester matrix using ascorbic acid as a reducing agent. The third generation hyperbranched polyester has been synthesized by step by step polymerization using the first generation hyperbranched polyester as core molecular and 2, 2-dimethylol propionic acid as branched monomer. The synthesized hyperbranched polyester and Cu-Ag alloy were characterized by FT-IR, 1 H-NMR, UV-vis spectra, X-ray diffraction (XRD), SEM, Energy Dispersive X-ray (EDX), Laser particle size measurement, TEM, etc. The XRD and EDX studies confirm the formation of Cu-Ag alloy. Laser particle size measurement, SEM and TEM studies show that the particles of the Cu-Ag alloy are well-dispersed with average size of 120 nm. The thermal properties of the Cu-Ag alloy have been studied by thermogravimetric Analysis (TGA). The results show that the measurement values are close to the theoretical ones.
The selective photocatalytic conversion of CO2 and H2O to high value-added C2H4 remains a great challenge, mainly attributed to the difficulties in C–C coupling of reaction intermediates and desorption of C2H4* intermediates from the catalyst surface. These two key issues can be simultaneously overcome by alloying Ag with Cu which gives enhanced activity to both reactions. Herein, we developed a facile stepwise photodeposition strategy to load Cu–Ag alloy sub-nanoclusters (ASNCs) on TiO2 for CO2 photoreduction to produce C2H4. The optimized catalyst exhibits a record-high C2H4 formation rate (1110.6 ± 82.5 μmol g−1 h−1) with selectivity of 49.1 ± 1.9%, which is an order-of-magnitude enhancement relative to current work for C2H4 photosynthesis. The in situ FT-IR spectra combined with DFT calculations reveal the synergistic effect of Cu and Ag in Cu–Ag ASNCs, which enable an excellent C–C coupling capability like Ag and promoted C2H4* desorption property like Cu, thus advancing the selective and efficient production of C2H4. The present work provides a deeper understanding on cluster chemistry and C–C coupling mechanism for CO2 reduction on ASNCs and develops a feasible strategy for photoreduction CO2 to C2 fuels or industrial feedstocks.
Lingcan Kong,Xuefeng Chu,Chuanxi Wang,Hong Zhou,Yukang Wu,Wenwei Liu
The aggregation-induced emission (AIE) behavior of metal nanoclusters has attracted much attention owing to their extensive application prospects in bio-imaging and chemical sensors. However, the intrinsic mechanism of metal nanoclusters’ aggregation-induced emission is still not very clear. Herein, Cu nanoclusters S1 and Ag(I)-doped Cu/Ag nanoclusters S2 and S3 coated with D-penicillamine are designed and synthesized by a self-assembly strategy. S1–S3 show strong luminescence properties with luminescence quantum yields as high as 11.4%–14.2%. Moreover, their luminescence peak position shows an obvious hypsochromic shift from 615 (S1) to 570 nm (S3). With the introduction of Ag(I) ions, the assembly morphology also shows clear changes from the irregular assembly structure (S1) to large spherical particles with the average size of 0.18 μm for S2 and 0.47 μm for S3. A detailed investigation of high-resolution transmission electron microscopy (HRTEM) images, X-ray diffraction (XRD) patterns, ESI-TOF-mass spectra, UV-vis absorption spectra, photoluminescence spectra and luminescence lifetimes of Cu/Ag nanoclusters S2 and S3 indicates that Cu/Ag nanoclusters are actually a Cu/Ag alloy nanocluster superstructure and the microscopic arrangement of S2 and S3 is more compact and ordered relative to S1. The more compact and ordered Cu/Ag alloy nanocluster superstructure enhances the metal–metal interaction of inter-nanoclusters and intra-nanoclusters and facilitates the radiative transition of ligand-to-metal charge transfer (LMCT) and/or ligand-to-metal–metal charge transfer (LMMCT), which results in the aggregation-induced emission phenomenon. In addition, an enhanced metal–metal interaction increases the average metal–metal distance of the Cu/Ag nanocluster superstructure, leading to a hypsochromic shift of emission spectra. Furthermore, the Cu/Ag alloy nanoclusters show good stability and reversibility on pH cycling between pH = 3 and 7 and temperature cycling between 5 °C and 48 °C. The Cu/Ag alloy nanoclusters can be used as probes for Ag(I) ion and halide anion detection in real water samples by the ratiometric PL method (I570/I615).
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