Microbial synthesis of gold nanoparticles: Current status and future prospects

Gold nanoparticles have been employed in biomedicine since the last decade because of their unique optical, electrical and photothermal properties. Present review discusses the microbial synthesis, properties and biomedical applications of gold nanoparticles. Different microbial synthesis strategies used so far for obtaining better yield and stability have been described. It also includes different methods used for the characterization and analysis of gold nanoparticles, viz. UV–visible spectroscopy, Fourier transform infrared spectroscopy, X ray diffraction spectroscopy, scanning electron microscopy, ransmission electron microscopy, atomic force microscopy, electron dispersive X ray, X ray photoelectron spectroscopy and cyclic voltametry. The different mechanisms involved in microbial synthesis of gold nanoparticles have been discussed. The information related to applications of microbially synthesized gold nanoparticles and patents on microbial synthesis of gold nanoparticles has been summarized.     

Studies on the iodine complexes of pyridine picolines and aminopyridine by constant activity method

The iodine complexes of pyridine, -, β-, γ- picolines, 2-aminopyridine and 2,2′-bipyridine in cyclohexane were studied by the constant activity method, their spectral characteristics and thermodynamic parameters were determined. The equilibrium constants, molar extinction coefficients of the charge-transfer band maxima, _CT, at 25°C and heats of complexation, ΔH°, are respectively as follows:

1. (a) pyridine-iodine, 107 dm³mol⁻¹ 24200 dm³mol⁻¹m⁻¹ and 31 KJ/mol;

2. (b) -picoline-iodine, 172 dm³mol⁻¹m⁻¹, 49700 dm³mol⁻¹m⁻¹ and 33 KJ/mol;

3. (c) β-picoline-iodine, 243 dm³mol⁻¹, 50300 dm³mol⁻¹m⁻¹ and 35 KJ/mol;

4. (d) γ-picoline-iodine, 342 dm³mol⁻¹, 55900 dm³mol⁻¹m⁻¹ and 41 KJ/m;

5. (e) 2-aminopyridine-iodine, 427 dm³mol⁻¹, 60800 dm³mol⁻¹m⁻¹ and 47 KJ/mol;

6. (f) 2,2′-bipyridine-iodine, 6.0 dm³mol⁻¹,−, 21 KJ/mol.

The values of the blue shifted iodine band maxima of the above mentioned donors and their molar extinction coefficients are, 420 nm (1450 dm³mol⁻¹m⁻¹), 419 nm (1470 dm³mol⁻¹m⁻¹), 418 nm (1640 dm³mol⁻¹m⁻¹), 417 nm (1570 dm³mol⁻¹m⁻¹), 410 nm (1574 dm³mol⁻¹m⁻¹) and 452 nm (1370 dm³mol⁻¹m⁻¹) respectively. The oscillator strengths and transition dipole moments of the blue-shifted iodine bands are characterised.     

Ultrasonic bath with longitudinal vibrations: a novel configuration for efficient wastewater treatment

Efficacy of a novel configuration for large-scale wastewater treatment applications has been investigated using formic acid degradation as a model reaction. The reactor is first characterized using energy efficiency measurements and the optimum operating volume for maximum transfer of supplied energy and hence maximum cavitational effects has been established. Effect of initial concentration of the pollutant on the rates of degradation has been investigated. Comparison has been also made with the conventional ultrasonic horn in terms of energy efficiency and cavitational yield for the model reaction. With an aim of possible reduction in the total treatment time, some intensification studies have been undertaken considering hydrogen peroxide as an additional source of free radicals.     

Ecofriendly and facile Nano ZnO catalyzed solvent-free enamination of 1,3-dicarbonyls

Nano zinc oxide (Nano-ZnO) was explored as a reusable catalyst for the enamination of 1,3-dicarbonyls using diverse amines. To make the process environmentally viable, the reaction was carried out under solvent-free conditions and found to give good yield of desired products. The catalyst was characterized by various analytical techniques such as UV-spectroscopy, XRD, and TEM. The catalyst was found to be reusable up to four catalytic cycles without any appreciable loss in activity.