In the present investigation, we have reported the fabrication of a low-cost, magnetically separable, solar light active NiFe 2−x Nd x O 4 photocatalyst with different neodymium contents. The synthesized photocatalyst samples were characterized by a combination of various physicochemical techniques such as PXRD, SEM, EDS, FTIR, and UV−vis spectroscopy. It was observed that Nd substitution can greatly enhance absorption in the whole visible region. With an increase in Nd concentration, NiFe 2−x Nd x O 4 samples show a red shift in absorption. Interestingly, Nd substitution into nickel ferrite results in a dramatic conversion of the inert NiFe 2 O 4 into a highly solar light active photocatalyst for the degradation of organic pollutants and also shows excellent recyclability and durability properties. The significant enhancement in photoactivity under solar light irradiation can be ascribed to the reduction of the nickel ferrite band gap by Nd 3+ substitution. Therefore, these unusual properties of NiFe 2−x Nd x O 4 encourage us to extend photocatalytic degradation to another few organic pollutants. This new photocatalyst system, NiFe 2−x Nd x O 4 , can have other potential environmental and energy applications that only need visible light as energy input.

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In this work, we describe the preparation of a zinc oxide-ethylene glycol nanoparticle ink and the parameters that control the printing using a custom-built direct writer system. The ink (nanoparticle dispersion) was prepared using a two-step wet synthesis method, without using any surfactant. Its viscosity was found to be in the suitable range for printing and straight lines were printed on cleaned glass substrates. The influence of various printing parameters, such as total dispersed volume, number of printed layers, substrate temperature, drying temperature and time, and particle loading, on the morphology of the printed patterns was investigated. In-situ and post-printing drying of the printed pattern, at the same temperature, produced different morphologies, which can be attributed to the direction of heat transfer and solvent removal. Optimization of these printing parameters enabled us to obtain a continuous printed pattern with uniform morphology using a direct writing system, which can be extended to a variety of nanoparticle based inks.

Pure ZnS and ZnS:Y nanoparticles were synthesized by a chemical coprecipitation route using EDTA-ethylenediamine as a stabilizing agent. X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectrometry (FTIR), thermogravimetric-differential scanning calorimetry (TG-DSC), and UV-visible and photoluminescence (PL) spectroscopy were employed to characterize the assynthesized ZnS and ZnS:Y nanoparticles, respectively. XRD and TEM studies show the formation of cubic ZnS:Y particles with an average size of ∼4.5 nm. The doping did not alter the phase of the zinc sulphide, as a result the sample showed cubic zincblende structure. The UV-visible spectra of ZnS and ZnS:Y nanoparticles showed a band gap energy value, 3.85 eV and 3.73 eV, which corresponds to a semiconductor material. A luminescence characteristics such as strong and stable visible-light emissions in the orange region alone with the blue emission peaks were observed for doped ZnS nanoparticles at room temperature. The PL intensity of orange emission peak was found to be increased with an increase in yttrium ions concentration by suppressing blue emission peaks. These results strongly propose that yttrium doped zinc sulphide nanoparticles form a new class of luminescent material.

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