Silver Cluster Interactions with Tyrosine: Towards Amino Acid Detection

Tyrosine (Tyr) is involved in the synthesis of neurotransmitters, catecholamines, thyroid hormones, etc. Multiple pathologies are associated with impaired Tyr metabolism. Silver nanoclusters (Ag NCs) can be applied for colorimetric, fluorescent, and surface-enhanced Raman spectroscopy (SERS) detection of Tyr. However, one should understand the theoretical basics of interactions between Tyr and Ag NCs. Thereby, we calculated the binding energy (Eb) between Tyr and Agnq (n = 1–8; q = 0–2) NCs using the density functional theory (DFT) to find the most stable complexes. Since Ag NCs are synthesized on Tyr in an aqueous solution at pH 12.5, we studied Tyr−1, semiquinone (SemiQ−1), and Tyr−2. Ag32+ and Ag5+ had the highest Eb. The absorption spectrum of Tyr−2 significantly red-shifts with the attachment of Ag32+, which is prospective for colorimetric Tyr detection. Ag32+ interacts with all functional groups of SemiQ−1 (phenolate, amino group, and carboxylate), which makes detection of Tyr possible due to band emergence at 1324 cm−1 in the vibrational spectrum. The ground state charge transfer between Ag and carboxylate determines the band emergence at 1661 cm−1 in the Raman spectrum of the SemiQ−1–Ag32+ complex. Thus, the prospects of Tyr detection using silver nanoclusters were demonstrated.

Massively Parallel Selection of NanoCluster Beacons

NanoCluster Beacons (NCBs) are multicolor silver nanocluster probes whose fluorescence can be activated or tuned by a proximal DNA strand called the activator. While a single-nucleotide difference in a pair of activators can lead to drastically different activation outcomes, termed the polar opposite twins (POTs), it is difficult to discover new POT-NCBs using the conventional low-throughput characterization approaches. Here we report a high-throughput selection method that takes advantage of repurposed next-generation-sequencing (NGS) chips to screen the activation fluorescence of ∼40,000 activator sequences. We find the nucleobases at positions 7-12 of the 18-nucleotide-long activator are critical to creating bright NCBs and positions 4-6 and 2-4 are hotspots to generate yellow and red POTs, respectively. Based on these findings, we propose a “zipper bag model” that explains how these hotspots lead to the creation of distinct silver cluster chromophores and contribute to the difference in chromophore chemical yields. Combining high-throughput screening with machine learning algorithms, we establish a pipeline to rationally design bright and multicolor NCBs.

Construction and Properties of Ag-I Polymeric Clusters Attach With Nitrogen Heterocyclic Transition Metal Moiety

Two silver cluster compounds {[Co(1,10′-phen)3]2‧[Ag8I12]} (1) and {[Co(2, 2′-bipy)3]‧[Ag10I11]‧(OH)‧3DMF‧2H2O} (2) (1,10′-phen=1,10′-phenanthroline, 2, 2′-bipy=2,2′-bipyridine) were designed and synthesized by solvent evaporation method. The two silver cluster compounds were characterized by elemental analysis, infrared spectroscopy, ultraviolet spectroscopy, thermogravimetric analysis and X-ray powder diffraction. The crystal structures of compounds 1 and 2 were determined by X-ray crystallography diffraction. Through the electrostatic interaction between the metallic Ag cluster moiety and the metallic Co cluster moiety, form stable interlaced layered super molecular structures. In order to explore functional properties, the catalytic reduction of p-nitrophenol and electrochemical behavior of compounds 1 and 2 were explored. The results show that compounds 1 and 2 can efficiently catalyze the reduction of p-nitrophenol in the aqueous solution, and the reduction and removal rate can reach more than 90%.

Self-Assembly of Silver Clusters into One- and Two-Dimensional Structures as Artificial Intelligent Sensors of Alcohol

Reggeization and response to external stimulus is an important part of artificial intelligence, which would significantly improve the quality of life in the future. The development of new materials for the design of sensitive and responsive sensors has become a crucial component. Here, two silver cluster-based polymers (Ag-CBPs), including one-dimensional (1D) {Ag22(L1)8(CF3CO2)14(CH3OH)2}n chain and two-dimensional (2D) {[Ag12(L2)2(CO2CF3)14(H2O)4(AgCO2CF3)4](HNEt3)2}n film, are designed and used to simulate the human nose - an elegant sensor to smells, to distinguish organic solvents. We study the relationship between the atomic structures of Ag-CBPs determined by X-ray diffraction and electrical properties in the presence of organic solvents (e.g. methanol, ethanol). The ligands, cations and the ligated solvent molecules not only play an important role in the self-assembly process of Ag-CBP materials, but also determine their physiochemical properties. An application of cluster-based polymers is demonstrated in the artificial intelligent sensors.