Green synthesis of metal nanoparticles, such as silver or gold nanoparticles, has been attracting increasing attention in recent years. Functionalized magnetite nanoparticles have many uses in various applications, including nanoelectronic devices, molecular recognition, biomedical applications, drug delivery targeting, and optical devices. In this investigation, magnetic cores (Fe3O4) were synthesized using a fabrication method involving coprecipitation ofFe2+andFe3+. In the next step, magnetite-gold composite nanoparticles were synthesized with size ranging from 6–20 nm, using an ethanol extract ofEucalyptus camaldulensisas a natural reducing agent. Transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction spectroscopy, and visible absorption spectroscopy confirmed the fabrication of magnetite-gold composite nanoparticles. In the UV spectra diagram, a red-shift of the surface plasmon of the Au was evidence that contact between gold andFe3O4had occurred. The surface chemistry of the as-prepared magnetite-gold nanoparticles was studied using infrared spectroscopy. The presence of organic compounds with a carboxyl moiety was confirmed on the surface of the magnetite-gold nanoparticles fabricated by this combined chemical and biological reducing process, which we have designated as a semi-biosynthesis method.

The new nanocrystalline composition was synthesized using NiSO 4 and MoO 3 and PPDA (p-phenylenediamine) via the hydrothermal method. The structure, morphology and photoluminescence property of nanocrystal were studied using X-ray diffraction (XRD), Fourier transform infra red (FT-IR) spectroscopy, scanning electron microscopy (SEM), photoluminescence (PL) spectra, thermogravimetric analysis (TGA-DTA) and energy-dispersive X-ray spectroscopy (EDX). The effect of factors such as type and concentration of initial materials, pH values, temperature and reaction duration on the structure and morphology of nanocrystals was investigated in the preparation of composition. The results show that the pH of the initial solution affects the size of the prepared nanocrystals; the size of the crystals is increased and the morphology of the nanostructures is changed with the increment in pH value. According to the obtained results, neutral or low alkaline conditions of pH are more favorable for the formation of the nanocrystals. The obtained nanocrystal shows an intense PL emission at room temperature with a maximum peak at 461 nm and excitation at the wavelength of 300 nm. TGA and DTA analysis display a total weight loss of 13.42%.

Distinct optical diffraction patterns of bacterial colonies in response to SPIONs with various concentrations and surface chemistries are formed.

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