Star-Shaped Poly(2-ethyl-2-oxazoline) and Poly(2-isopropyl-2-oxazoline) with Central Thiacalix[4]Arene Fragments: Reduction and Stabilization of Silver Nanoparticles

The interaction of silver nitrate with star-shaped poly(2-ethyl-2-oxazoline) and poly(2-isopropyl-2-oxazoline) containing central thiacalix[4]arene cores, which proceeds under visible light in aqueous solutions at ambient temperature, was studied. It was found that this process led to the formation of stable colloidal solutions of silver nanoparticles. The kinetics of the formation of the nanoparticles was investigated by the observation of a time-dependent increase in the intensity of the plasmon resonance peak that is related to the nanoparticles and appears in the range of 400 to 700 nm. According to the data of electron and X-ray spectroscopy, scanning and transmission electron microscopy, X-ray diffraction analysis, and dynamic light scattering, the radius of the obtained silver nanoparticles is equal to 30 nm. In addition, the flow birefringence experiments showed that solutions of nanoparticles have high optical shear coefficients.

Large-Scale and Low-Cost Fabrication of Silicon Mie Resonators

High index dielectric nanoparticles have been proposed for many different applications. However, widespread utilization in practice also requires large-scale production methods for crystalline silicon nanoparticles, with engineered optical properties in a low-cost manner. Here, we demonstrate a facile, low-cost, and large-scale fabrication method of crystalline silicon colloidal Mie resonators in water, using a blender. The obtained nanoparticles are polydisperse with an almost spherical shape and the diameters controlled in the range 100-200 nm by a centrifugation process. Then the size distribution of silicon nanoparticles enables broad extinction from UV to near-infrared, confirmed by Mie theory when considering the size distribution in the calculations. Thanks to photolithographic and drop-cast deposition techniques to locate the position on a substrate of the colloidal nanoparticles, we experimentally demonstrate that the individual silicon nanoresonators show strong electric and magnetic Mie resonances in the visible range.

Salt-Assisted Ultrasonic Deaggregation of Nanodiamond

We report a new facile, inexpensive, and contaminant-free technique of salt-assisted ultrasonic deaggregation (SAUD) of nanodiamond into single-digit particles stable in aqueous colloidal solution in a wide pH range. The technique utilizes the energy of ultrasound to break apart nanodiamond aggregates in sodium chloride aqueous slurry. In contrast to current deaggregation techniques, which introduce zirconia contaminants into nanodiamond, the single-digit nanodiamond colloids produced by SAUD have no toxic or difficult-to-remove impurities and are therefore well-suited to produce nanodiamonds for numerous applications, including theranostics, composites, and lubrication, etc. Requiring only aqueous slurry of sodium chloride and standard horn sonicator, and yielding highly pure well-dispersed nanodiamond colloids, the technique is an attractive alternative to current nanodiamond deaggregation protocols and can be easily implemented in any laboratory or scaled up for industrial use.

Visible tunable lighting system based on polymer composites embedding ZnO and metallic clusters: from colloids to thin films

The development of phosphor devices free of heavy metal or rare earth elements is an important issue for environmental reasons and energy efficiency. Different mixtures of ZnO nanocrystals with Cs₂Mo₆I₈(OOC₂F₅)₆ cluster compound (CMIF) dispersed into polyvinylpyrrolidone matrix have been prepared by very simple and low cost solution chemistry. The resulting solutions have been used to fabricate highly transparent and luminescent films by dip coating free of heavy metal or rare earth elements. The luminescence properties of solution and dip-coated films were investigated. The luminescence of such a system is strongly dependent on the ratios between ZnO and CMIF amounts, the excitation wavelength and the nature of the system. By varying these two parameters (ratio and wavelength), a large variety of colors, from blue to red as well as white, can be achieved. In addition, differences in the luminescence properties have been observed between solutions and thin films as well as changes of CMIF emission band maximum wavelength. This may suggest some possible interactions between the different luminophore centers, such as energy transfer or ligands exchange on the Mo₆ clusters.