M. Ashok

Crystallization of hydroxyapatite at physiological temperature

Abstract Well-defined platy crystals of hydroxyapatite (27×2 μm) were crystallized at physiological temperature and pH. The X-ray powder diffraction (XRD) and Proton-Induced X-ray Emission (PIXE) analysis confirmed the crystals to be the pure form of HAP without any contamination from the crystallizing medium. FT-IR studies confirmed the HAP crystals were free from CO inclusion. TGA studies showed the thermal stability of the hydroxyapatite crystals. Texturing of hydroxyapatite crystals was observed on sintering.

Influence of iron and temperature on the crystallization of calcium phosphates at the physiological pH

Abstract The effect of iron and temperature on the crystallization of dicalcium phosphate dihydrate (CaHPO 4 ·2H 2 O, DCPD) in agarose was studied at various temperatures (27, 37 and 47 °C) at the physiological pH (7.4) by the single diffusion method. The spherulitic crystals of hydroxyapatite with a diameter of about 3 mm were observed in the presence of Fe at temperature of 47 °C. The spherulites consisted of thin, elongated needlelike crystals. Quantification of the iron incorporated in the crystals was carried out by elemental analysis. The crystals were characterized by XRD, FTIR and SEM techniques.

Synthesis and characterization of porous shell-like nano hydroxyapatite using cetrimide as template.

Macromolecules of various surfactants and polymers are being used to prepare nano hydroxyapatites (HAp) of varied morphology. Here we report the successful preparation of shell-like nano HAp spheres with fine morphology, uniform size around 200 nm, and stoichiometry ratio 1.7 with 56% nano- (<5 nm) and 44% mesoporosity using the surfactant tetradecyltrimethylammonium bromide (Cetrimide), which was not reported earlier. The critical micelle concentration (CMC) of Cetrimide was calculated as 3.88 mM at room temperature, and based on that, the other parameters of the experiment were determined. The experiment was conducted at ambient temperature and normal pressure without any temperature control, which was considered a crucial parameter in the earlier works. Thus, this method is suitable to bulk production of HAp. All the inspections confirm the successful preparation of shell-like nano HAp spheres that are suitable for biomedical applications.

Energy dispersive X-ray fluorescence analysis of gallstones

The elemental analysis of south Indian gallstones has been carried out using energy dispersive X-ray fluorescence (EDXRF) spectroscopy. A number of important elements including Fe, Cu, Zn, Br, and Pb were estimated from the EDXRF spectra. The results are presented and discussed.

Ultrasonic cavitation induced water in vegetable oil emulsion droplets – A simple and easy technique to synthesize manganese zinc ferrite nanocrystals with improved magnetization

In the present investigation, synthesis of manganese zinc ferrite (Mn(0.5)Zn(0.5)Fe(2)O(4)) nanoparticles with narrow size distribution have been prepared using ultrasound assisted emulsion (consisting of rapeseed oil as an oil phase and aqueous solution of Mn(2+), Zn(2+) and Fe(2+) acetates) and evaporation processes. The as-prepared ferrite was nanocrystalline. In order to remove the small amount of oil present on the surface of the ferrite, it was subjected to heat treatment at 300 °C for 3h. Both the as-prepared and heat treated ferrites have been characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), TGA/DTA, transmission electron microscopy (TEM) and energy dispersion X-ray spectroscopy (EDS) techniques. As-prepared ferrite is of 20 nm, whereas the heat treated ferrite shows the size of 33 nm. In addition, magnetic properties of the as-prepared as well as the heat treated ferrites have also been carried out and the results of which show that the spontaneous magnetization (σ(s)) of the heat treated sample (24.1 emu/g) is significantly higher than that of the as-synthesized sample (1.81 emu/g). The key features of this method are avoiding (a) the cumbersome conditions that exist in the conventional methods; (b) usage of necessary additive components (stabilizers or surfactants, precipitants) and (c) calcination requirements. In addition, rapeseed oil as an oil phase has been used for the first time, replacing the toxic and troublesome organic nonpolar solvents. As a whole, this simple straightforward sonochemical approach results in more phase pure system with improved magnetization.

Observation of cholesterol nucleation in a magnetic field

The in vitro studies on the nucleation, growth and other fundamental aspects of cholesterol crystallization have received considerable attention, as it plays a vital role in the formation of atheroclerotic plaques and gallbladder stones. The cholesterol was crystallized in methanol, ethanol, acetone and isopropanol at the physiological temperature of 37 degrees C in the presence and absence of a low static magnetic field at 0.1 T. The presence of magnetic field was found to have a significant effect on the metastable zone width and induction period of cholesterol.

Trace element analysis of blood samples from mentally challenged children by PIXE

Abstract The accelerator based ion beam analysis method of proton induced X-ray emission (PIXE) has been used for analysing up to 14 elements in the blood serum of patients, collected from rehabilitation centres for the mentally retarded and from Medical College Hospital, Coimbatore, Tamil Nadu, India. The experimental subjects of the different groups displayed significant variations in their levels of certain trace elements such as zinc, iron, copper, phosphorus, chlorine, and rubidium. The results are compared with those of healthy control subjects and are discussed in detail in this paper. Hence, PIXE as a method of trace element analysis can be used to determine trace element content in mentally challenged patients.

BLUE EMISSION AND BANDGAP MODIFICATION IN N:ZnO NANORODS

Nanorods of nitrogen-doped ZnO(N:ZnO) are grown by hydrothermal chemical precipitation method. The average crystallite size, surface morphology, and particle size distribution are estimated and characterized from powder X-ray diffractometer (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), respectively. The characteristic vibration mode of metal-oxide is confirmed from Fourier transform infrared spectroscopy (FT-IR) study. The absorption spectra of N:ZnO in the ultraviolet visible (UV-vis) region and their variations are recorded as a function of dopant concentration. The Tauc plot elucidates that the bandgap of N:ZnO increases up to 6 atomic percent (at.%) of dopant concentration and then decreases for heavy doping. The widening and narrowing in bandgap is interpreted in terms of impurity induced absorption edge shift due to N doping. Photoluminescence (PL) spectra revealed the existence of visible band, arising from impurity related defects.

TRACE ELEMENT ANALYSIS OF SOUTH INDIAN GALLSTONES BY PIXE

Particle Induced X-ray Emission (PIXE) was used to analyse the elemental concentration of gallstones collected from different parts of south India. Cholesterol gallstones are predominant in north India, whereas pigment gallstones are predominant in south India. The black pigment gallstones are common in hemolytic anemia or in presence of infected bile. PIXE has revealed the elemental profile in each sample. The experimental subjects of the different groups displayed significant variation in their levels of certain trace elements such as copper, zinc, and iron. The concentration of copper was found to be predominant in pigment gallstones investigated in the present study.

INVESTIGATION OF THE ELEMENTAL CONCENTRATION OF KIDNEY STONES BY PIXE ANALYSIS

Kidney stones collected from different hospitals in Chennai, south India were analyzed by PIXE with 3MeV protons. The matrix was calcium oxalate and mixture of calcium oxalate and calcium phosphate. Light elements present in minor concentration were P, Cl. Trace elements such as V, Cr, Mn, Fe, Cu, Zn, Sr, Zr & Mo were also present in the stones. Significant amount of Zr was found in one of the samples, Pb and Cd were not present in any of the stones analyzed.