Highly Luminescent Copper Nanoclusters Stabilized by Ascorbic Acid for the Quantitative Detection of 4-Aminoazobenzene

As one of the widely studied metal nanoclusters, the preparation of copper nanoclusters (Cu NCs) by a facile method with high fluorescence performance has been the interest of researchers. In this paper, a simple, green, clean, and time-saving chemical etching method was used to synthesize water-soluble Cu NCs using ascorbic acid (AA) as the reducing agent. The as-prepared Cu NCs showed strong green fluorescence (with a quantum yield as high as 33.6%) and high ion stability, and good antioxidant activity as well. The resultant Cu NCs were used for the detection of 4-aminoazobenzene (one of 24 kinds of prohibited textile compounds) in water with a minimum detection limit of 1.44 μM, which has good potential for fabric safety monitoring.

Carboranes: the strongest Brønsted acids in alcohol dehydration

Alcohol dehydration mechanisms identified through the slopes of activation energies vs. carbenium ion stability of alcohols.

Physical and chemical model of ion stability and movement within the dynamic and voltage-gated STM tip–surface tunneling junction

The interaction and mobility of ions in complex systems are fundamental to processes throughout chemistry, biology, and physics. However, nanoscale characterization of ion stability and migration remains poorly understood. Here, we examine ion movements to and from physisorbed molecular receptors at solution–graphite interfaces by developing a theoretical model alongside experimental scanning tunneling microscopy (STM) results. The model includes van der Waals forces and electrostatic interactions originating from the surface, tip, and physisorbed receptors, as well as a tip–surface electric field arising from the STM bias voltage (Vb). Our model reveals how both the electric field and tip–surface distance, dtip, can influence anion stability at the receptor binding sites on the surface or at the STM tip, as well as the size of the barrier for anion transitions between those locations. These predictions agree well with prior and new STM results from the interactions of anions with aryl-triazole receptors that order into functional monolayers on graphite. Scanning produces clear resolution at large magnitude negative surface biases (−0.8 V) while resolution degrades at small negative surface biases (−0.4 V). The loss in resolution arises from frequent tip retractions assigned to anion migration within the tip–surface tunneling region. This experimental evidence in combination with support from the model demonstrates a local voltage gating of anions with the STM tip inside physisorbed receptors. This generalized model and experimental evidence may help to provide a basis to understand the nanoscale details of related chemical transformations and their underlying thermodynamic and kinetic preferences.

Preparation and characterisation of novel cross-linked poly (IBOMA-BA-DFMA) latex

Purpose – The purpose of this research was to synthesize a novel cross-linked latex copolymerised by butyl acrylate (BA), isobornyl methacrylate (IBOMA), hydroxy propyl methacrylate (HPMA) and dodecafluoroheptyl methacrylate (DFMA). IBOMA is a very useful functional monomer. Its molecular structure not only contains bornyl acetate alkoxy but also includes a double bond, which can be copolymerised with other unsaturated monomers via free radical polymerization. The large nonpolar bicyclic alkyl in bornyl acetate alkoxy offers the polymer chain strong space steric protection, which endows the polymer with some special properties. Design/methodology/approach – The semi-continuous seeded emulsion polymerisation technology was adopted to copolymerise BA, IBOMA, HPMA and DFMA in the water phase, which was initiated with potassium persulfate (KPS) and emulsified with the mixed surfactants of sodium dodecyl sulphate (SDS) and OP-10. Findings – The particle size of the latex decreases with an increase in the amount of IBOMA. All the latexes have good mechanical stability and calcium ion stability. The latex has good film-forming property when the IBOMA amount is controlled moderately. The optimal IBOMA amount is 10.00 g. The thermal stability and water resistance of the film are improved. Practical implications – The latexes can be applied as a binder of coatings and adhesions. Originality/value – The effect of the amount of IBOMA and BA on the properties of the resultant latex and its film were investigated in detail. In comparison with the latexes copolymerised without IBOMA, the novel latex has better thermal stability and water resistance.

Stability and Mechanical Properties of Hard/Soft Latex Blends

In this contribution, hard/soft latex blends were prepared by mixing proportionable non-crosslinkable hard and self-crosslinkable soft latices. The stability and mechanical properties of latex blends were comparatively studied with the neat latex with high glass transition temperature (Tg). It was found that the calcium ion stability of the latex blends is better than neat hard latex. In addition, the stress at break decreased with the increasing of φs (mass fraction of soft particle in latex blends) and the break elongation increased when φs below 0.8. Meanwhile, the value of tensile stress and break elongation of the hard latex film with coalescing agent, DPnB, additive is between that of the latex blends film with 60% and 70% soft particle. The study on viscoelasticity of the latex films demonstrated that this composite latex can be considered as phase separation blend involving a soft phase filled with hard spheres. The results indicate that the soft latex can serve as the substitution of coalescing agents in water-based ink industry to obtain low or zero VOC ink, without compromise on properties.