Nanotechnology Applications for Chemical and Biological Sensors

Recent discoveries indicate that when the materials are brought down to sizes in the range 1–100 nm, theseexhibit unique electrical, optical, magnetic, chemical, and mechanical properties. Methods have now beenestablished to obtain the monodisperse nanocrystals of various metallic and semiconducting materials, single-walled and multi-walled nanotubes of carbon and other metallic and non-metallic materials together withorganic nanomaterials such as supra-molecular nanostructures, dendrimers, hybrid composites with tailoredfunctionalities. The high surface-to-volume ratio with an added element of porosity makes these highly potentialcandidates for chemical and biological sensor applications with higher degree of sensitivity and selectivity ascompared to their bulk counterparts. The paper reviews the recent developments and applications of chemicaland biological sensors based on nanomaterials of various structural forms.Defence Science Journal, 2008, 58(5), pp.636-649, DOI:http://dx.doi.org/10.14429/dsj.58.168

Evaluation of pharmacological and toxicological studies of an ayurvedic medicine Rasaraj Ras on biological system of the male Sprague-Dawley rats

Background: In this study, the pharmacological and toxicological effects along with possible side effects of the classical ayurvedic formulation Rasaraj Ras (RR) which is used as a traditional medicine in the treatment of hemiplegia in the rural population were evaluated.Methods: During this study, various experiments on body growth rate, organ-body weight ratio and tissue hydration indices were performed to evaluate its efficacy and toxicity. To find out the toxicological characteristic of RR, it was administered chronically to the male Sprague-Dawley rats at a dose of 40 mg/kg. After 28 days chronic administration of the RR preparation the following toxicological changes were noted.Results: All throughout the experimental period the RR treated animals were always maintaining negligible changes in body weight, but all throughout the experimental period no statistically significant increase or decrease was noted. There is a statistically significant decrease in the relative percent weight of the male rat heart. There is a statistically highly significant decrease in the absolute weight of the male rat liver. There is a statistically highly significant decrease in the relative percent weight of the male rat liver. There is a statistically significant decrease in the relative percent weight of the male rat kidney. In the tissue hydration index determination, no significant changes were noted in case of any organ.Conclusions: As RR decreases abnormally weight of several organs in body of treated rats, so it should not be administered chronically at a higher dose

Rapid continuous microwave-assisted synthesis of silver nanoparticles to achieve very high productivity and full yield: from mechanistic study to optimal fabrication strategy

Systematic studies of silver nanoparticle synthesis in a continuous-flow single-mode microwave reactor using polyol process were performed, revealing that the synthesis is exceptionally effective to give very small metal particles at full reaction yield and very high productivity. Inlet concentration of silver nitrate or silver acetate, applied as metal precursors, varied between 10 and 50 mM, and flow rates ranged from 0.635 to 2.5 dm3/h, to give 3–24 s reaction time. Owing to its much higher reactivity, silver acetate was shown to be far superior substrate for the synthesis of small (10–20 nm) spherical silver nanoparticles within a few seconds. Its restricted solubility in ethylene glycol, applied as the solvent and reducing agent, appeared to be vital for effective separation of the stage of particle growth from its nucleation to enable rapid synthesis of small particles in a highly loaded system. This was not possible to obtain using silver nitrate. All the observations could perfectly be explained by a classical LaMer–Dinegar model of NPs’ formation, but taking into account also nonisothermal character of the continuous-flow process and acetate dissolution in the reaction system. The performed studies indicate an optimal strategy for the high-yield fabrication of metal particles using polyol method