A novel, green, one-pot synthesis of gold nanoparticles (AuNPs) was obtained by the redox reaction between AuCl 4 − and hydroxylatopillar[5]arene (HP5) in aqueous solution with the aid of OH − at room temperature without the need of a traditional harsh reducing agent such as NaBH 4 , N 2 H 4 , etc. Monodisperse AuNPs with a uniform diameter of ∼5.0 nm are fabricated via the proposed one-step colloidal synthesis route by using HP5 as both reducing agent and stabilizer, while AuNPs cannot be effectively protected by noncyclic monomers of HP5. The FTIR, 13 C NMR, and XPS studies demonstrated that the hydroxy groups in HP5 reduce Au 3+ into Au 0 , which leads to nucleation, growth, and formation of AuNPs, and the hydroxy groups themselves are oxidized to carboxyl groups. It is surprising that the HP5 functionalized AuNPs can self-assemble and form multiple well-defined architectures, including vesicles, like nanotubes, and one-/two-dimensional (1D/2D) nanostructures without the need of a guest mediator. The selfassembly mechanism was also studied. Moreover, the prepared HP5@AuNPs could be employed as not only scaffolds but energy acceptors for turn-on fluorescence sensing based on a competitive host−guest interaction. In addition, the AuNPs exhibited very excellent catalytic activity for the reduction of 4-nitrophenol (4-NP). We believe that the versatile HP5@AuNPs could be potentially used in the field of self-assembly, sensing, and catalysis.

Abstract:The structural changes during three-step synthesis of low-molar ratio urea-formaldehyde (UF) resin were tracked by quantitative 13 C nuclear magnetic resonance ( 13 C NMR) analysis and electrospray ionization-mass spectrometry (ESI-MS). Condensations that produced polymers were found to be linked by ether bonds in addition to hydroxymethylation reactions at the first alkaline stage with a formaldehyde to urea ratio of 2:1. Considerable formation of branched methylene linkages, with the highest content among all the condensed structures, was the key feature of the acidic stage. Notable changes were observed for the chemical structures and molecular masses of the resin components after the formaldehyde to urea molar ratio was lowered to 1.2 by adding post-urea at the final alkaline stage. Specifically, most of the branched hydroxymethyl groups on the polymers were cleaved, resulting in a significant decrease in the branching degree of the polymers. The performance degradation of the UF resin was attributed to this debranching effect and the production of components with low molecular masses. Based on the observations, the curing pattern of low molar ratio UF resin was postulated and branched polymeric formaldehyde catcher bearing urea-reactivity was proposed.

The increasingly serious environmental problems make it urgent to develop a new type of sustainable green material which can degrade pollutants and monitor human health. However, the traditional preparation methods are frequently limited by tedious operations, high-energy consumption, and massive pollution. Herein, we present a facile and green method for preparation of MnO2 nanoflakes mediated by macrocyclic molecule calix[8]­arene. The MnO2 nanoflakes in situ grew on the preformed gold nanoparticles, forming an impressive core–shell Au@MnO2 flake-like nanocomposite. The catalytic properties of Au@MnO2 composite for reduction of 4-NP and degradation of MB were 2.4 and 187 times better than commercial Pd/C, respectively. Meanwhile, the as-synthesized Au@MnO2 nanocomposite exhibited specially excellent sensitivity and selectivity for detection of GSH with a limit of detection (LOD) of 0.11 μM. The core–shell nanostructured Au@MnO2 shows great potential value for the sustainable development of the environment and human health.

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The monitoring of nitroaromatic explosives plays a vital role in homeland security and public safety. In this work, by employing allylamine as the source for both carbon and nitrogen, photoluminescent nitrogen-rich carbon nanodots (NC-dots) were prepared via a peaceable and inexpensive hydrothermal route for the first time. The average size of the present synthesized NC-dots is 2.88 ± 0.4 nm. The NC-dots show outstanding blue fluorescence and exhibit a dramatically high fluorescence quantum yield of 15%. The NC-dots were completely characterized using various techniques. The NC-dots could be employed as a fluorescent material for the sensing of TNP with distinguished selectivity. The addition of TNP into the NC-dots resulted in splendid quenching, which was ascribed to the integrative action of fluorescence resonance energy transfer, electron transfer, and the hydrogen-bond interactions between NC-dots and TNP. In parallel, the proposed NC-dots could be applied as a new type of fluorescent ink. In addition, a detailed mechanism for the production of NC-dots via self-polymerization and carbonization was proposed.