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Iron powders and Fe/graphene oxide and Fe/boron nitride composites were synthesized by means of a polyol synthesis method. The effect of NaOH/Fe and ascorbic acid/Fe ratios on the characteristics of synthesized products were evaluated. The samples were characterized by X-ray diffraction, scanning and transmission electron microscopy, low-temperature nitrogen adsorption and Raman-spectroscopy. Ascorbic acid-assisted polyol synthesis resulted in the 10-fold decrease of the iron particles' size and almost 2-fold increase of lead removal efficiency. The deposition of iron on the surface of graphene oxide lead to the formation of small 20-30 nm sized particles as well as bigger 200-300 nm sized particles, while the reduction in presence of boron nitride resulted in the 100-200 nm sized particles. The difference is attributed to the surface state of graphene oxide and boron nitride. Adsorption properties of the obtained materials were studied in the process of Pb 2+ ion removal from wastewater. Nanomaterials 2020, 10, 37 2 of 17 followed precisely. It was reported by H. Chiriac et al. [7] that refluxing of iron sulphate solution in the presence of NaOH in ethylene glycol led to the formation of spherical particles with wide size distribution in a range from 60 to 400 nm.One of the important aspects of iron powders' synthesis by polyol method is the ability to control particles' sizes in various ways. R.J. Joseyphus et al. [8] reported that the choice of polyol affects the size of iron particles. They found that the size decreases in the sequence of ethylene glycol > propylene glycol > trimethylene glycol. However, as a side effect of the decrease of particles' size they observed substantial oxidation of iron particles during the process. Another approach to control the particles' size during polyol process is the utilization of microwave radiation which enhances kinetics of particles' formation. In the works of S. Komarneni et al. [9] and M.N. Nadagouda [10], authors used a microwave-assisted polyol synthesis approach to synthesize rod-shaped submicron iron particles. A successful approach to the synthesis of iron with particles' sizes below 100 nm was proposed by R.J. Joseyphus et al. [11]. They used hexachloroplatinic acid as a nucleating agent for the synthesis of iron under heterogeneous nucleation conditions. Although the concentration of Pt ions was as low as 2 × 10 −7 M, the scaling up of the technology will lead to appreciable cost effects. Thus, other routes to reduce particles' sizes of polyol-synthesized iron should be considered. One such approach constitutes the addition of more powerful reducing agents to the polyol-iron salt system.An ascorbic acid was widely used by different scientific groups for the synthesis of nanosized metal particles. Mostly, the attention was concentrated on the synthesis of noble metals and their alloys. Au [12,13], Ag [14,15], Pt [16,17], Pd [18] and different bimetallic [19,20] nanoparticles were successfully synthesized using ascorbic acid as the reducing agent. It was also ...

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Diamond is attractive for various applications due to its unique mechanical and optical properties. In particular, single crystal diamond needles with high aspect ratios and sharp apexes of nanometer size are demanded for different types of optical sensors including optically sensing tip probes for scanning microscopy. This paper reports on electron microscopy and Raman spectroscopy characterization of the diamond needles having geometrically perfect pyramidal shapes with rectangular atomically flat bases with (001) crystallography orientation, 2-200 nm sharp apexes, and with lengths from about 10-160 μm. The needles were produced by selective oxidation of (001) textured polycrystalline diamond films grown by chemical vapor deposition. Here we study the types and distribution of defects inside and on the surface of the single crystal diamond needles. We show that sp3 type point defects are incorporated into the volume of the diamond crystal during growth, while the surface of the lateral facets is enriched by multiple extended defects. Nitrogen addition to the reaction mixture results in increase of the growth rate on {001} facets correlated with the rise in the concentration of sp3 type defects.

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