Narrow Results

High aspect ratio inorganic structures with at least one dimension between 1 and 100 nm, such as nanotubes, nanowires, and nanorods, have attracted a keen interest both for fundamental research and for advanced applications because of their unique and fascinating properties, largely contributing to the rise of nanoscience as a new discipline of scientific progress worldwide. Although the synthesis of high aspect ratio nanostructures has been achieved through many different strategies, the exact mechanisms that lead to their formation are not clear and need to be elucidated to control the properties and reliability of these nanoscopic “building blocks”. Here I give few examples of growth methods based on chemical and physical processes, and I describe the results of the first characterization of the nanostructures by high-resolution electron microscopy techniques. The analysis of surfaces and interfaces, epitaxial relationships, and defects is expected to advance the understanding of the growth strategies and of the properties at the nanoscale. Far from being a complete review, this report is meant to show the achievements and the difficulties of experimental research in nanoscience, and to introduce the challenges that lay ahead.

Supercapacitors were fabricated by employing nanosized carbon black (NCB) powders and studied in an aqueous electrolyte. The capacitor properties were studied by means of electrochemical techniques such as cyclic voltammetry and constant current charge/discharge. Specific capacitance of these carbon materials, power density and energy density of the supercapacitor were derived from constant current charge/discharge tests. AC impedance technique was employed to deduce the ESR (equivalent series resistance) value and the frequency dependent capacitance. A high specific capacitance of 40 F/g was achieved using the above nanosized carbons in a symmetric electrode configuration.

This paper gives a review of our study of inert gases (helium, argon) in several materials candidate to future fusion reactors. The study is focused on the agglomeration of gas atoms and formation of nanoscale cavities in several materials including stainless steels and silicon carbide under irradiation with ions with energy ranging from 10 keV to 100 MeV.

Amine modified carbon quantum dots was synthesized by the acid oxidation method and hydrothermal route from coal in Barkol coalmine area and amine water. The features and properties of the product were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Photoluminescence Spectra (PL), UV-visible Spectroscopy (UV/vis), Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD). The results indicated that the GQDs have bright aquamarine with high water solubility, good photostability.

To study the formation mechanism of magnesium ammonium phosphate (MAP) stones. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and nanoparticle size analyzer were used to investigate the nanocrystallites in urines of 10 MAP stone patients and 10 healthy persons. Most of the nanocrystallites in healthy urines were uric acid, calcium oxalate dihydrate (COD), β-Ca₃(PO₄)₂ and NH₄MgPO₄. However, there were mainly MAP·6H₂O, calcium oxalate monohydrate (COM), hydroxylapatite, β-Ca₃(PO₄)₂ in the urine of MAP stone patients. The sizes of nanocrystallites were ranged from 22-68 nm in healthy urines and 17-92 nm in lithogenic samples. The stability of nanocrystalline in healthy urines was better than that in lithogenic samples. The nanocrystallites in MAP stone patients have a large size variation and a poor stability, easily aggregated to each other and contained more COM crystals which having a strong adhesion ability to cell membrane. All these factors promote the formation of kidney stones.

Organic monolayer films with carboxyl groups were prepared by a Langmuir-Blodgett (LB) method. When the LB monolayers were soaked in a simulated body fluid (SBF), the nucleation of hydroxyapatite (HAp) took place on them. From infrared spectra analyses, it was found that an interfacial interaction between carboxyl groups and calcium ions was essential for the HAp nucleation. By transmisson electron microscopy, the HAp crystals were found to form plate-like single crystals whose (100) surfaces were wide, parallel to the inorganic/organic interface.

Nanocrystalline MnFe₂O₄ ferrite was prepared using natural binder; egg white was used as an aqueous medium to extend nanoparticle preparation better than any other interesting materials. X-ray diffraction (XRD) and transmission electron microscope (TEM) showed also that the investigated samples revealed the nanosized structure with crystallite size of 39nm. The magnetic susceptibility measurements give a Curie temperature T_C = 613K with effective magnetic moment 23 B. M. The values of magnetic constants as obtained from hysteresis data are, saturation magnetization Ms = 13.71 emu/g, remanent magnetization Mr = 0.1694 emu/g and coercivity Hc = 25.6 Oe.