Director's Office

A new class of environmentally benign yellow rare earth pigments as alternatives to lead, cadmium and chromium pigments is presented. These pigments are based on cerium molybdenum oxides corresponding to the structural formulae NaCe0.5(MoO4) and Ce(MoO4)2. The coloring properties of the compositions prepared by varying the Ce:Mo ratio in the presence and absence of phosphates have been evaluated. The reflectance spectra and photoacoustic spectra indicate the absorption in visible and ultraviolet regions under 500 nm, which could originate from the O2p–Ce4f and the O2p–Mo3d double charge transfer transitions, and as a result the pigments show yellow color. In the presence of a phosphate, the products are homogeneous and crystalline at temperatures of 700 °C itself and exist as multiphasic with white colored CePO4 being present in association with cerium molybdenum oxide. Further, the particle size of the cerium molybdenum oxide sample was lower in the presence of phosphate (116 nm).

The interactions between the polysaccharide alginate and iron(III) were investigated. The solution properties were studied through pH-metry, viscometry, zeta potential and particle size measurements. In the presence of alginate, iron(III) was stabilized and no precipitation was observed. Studies indicate that iron(III)–alginate system was more stable than iron(III) or alginate alone. The binding constant is of the order of 104 M−1. A case for ‘site binding model’ for the interaction between alginate and Fe(III) has been made based on the studies using circular dichroism and zeta potential experiments. The number of binding sites per molecule of alginate has been estimated to be 66. This indicates that the alginate can bind more number of Fe(III) ions and thus provide a stable complex which can find wide industrial applications.

Colored pigments with high near infrared reflectance and not based on toxic metal ions like cadmium, lead and cobalt are being sought as cool colorants. Through appropriate doping two pigments Ce–Pr–Mo and Ce–Pr–Fe have been developed to offer a reddish brown and reddish orange color, respectively. These pigments have been characterized and found to be highly crystalline with an average size of 300 nm. A shift in band gap energy from 2.21 to 2.18 eV has been observed when Li2CO3 was used as a mineralizer. Scanning electron microscope-energy dispersive X-ray analysis (SEM–EDAX) measurement indicate a uniform grind shape and distribution of metal ion, with over 65% reflectance in the NIR region, these pigments can well serve as cool colorants.

A new class of environmentally benign brown rare earth colorants as alternatives to toxic inorganic colorants is presented. These colorants are based on mixed rare earth oxides. Unique feature of these colorants is the utilization of mixed rare earth oxides after the removal of radioactive thorium from monazite sand. The utility of mixed rare earth oxides for general exterior coating applications has been evaluated through mass tone/hiding power evaluations and the product has been fine tuned with respect to particle size, combination with hydrophilic agents, binders etc. to achieve good hydrophobicity and covering on porous surfaces like leather. The pigment was compatible with various auxiliaries employed in leather finishing and meets the current requirements for pigments like upgrading of finished leather through excellent covering of surface and improved levelness, no overloading of grain, excellent physical properties, ageing resistance and miscibility with water.

The colour of inorganic colorants is based on metal ions such as cadmium, lead, chromium or cobalt, the majority of which are unfortunately potentially toxic. Thus, there is in a need to introduce alternative metal or metal oxides, which would be environmentally friendly and economically viable as a replacement for potentially toxic inorganic colorants. Rare earth-based colorants offer an additional opportunity for the development of optically pure colours. In this study, a replacement for potentially toxic colorants has been sought through the use of a rare earth metal ion, cerium. Appropriate doping of cerium oxides with molybdenum and iron gives an orange–red colorant. The conditions ideal for optimal colour have been standardised and the resultant colorant characterised through powder X-ray diffraction techniques, particle size measurement, etc. The colorants exhibit good hiding power and tinting strength.

Iron oxide nanoparticles are being viewed with interest owing to the great potential they have in the biomedical applications like MRI contrast enhancement, targeted drug delivery, hyperthermia and recently in magnetic separation of cancer cells from the body. Templated synthesis has been considered ideal for synthesis of iron oxide nanoparticles as particles are attracted magnetically, in addition to usual flocculation through van der Waals attraction. Biological templates are attractive owing to their biocompatibility and the attractive porosity and surface chemistry that nature provides. Polysaccharides like chitosan and alginate have been employed in the synthesis of a polyion complex, which provided the active-binding sites for iron(II) ions in solution to bind. The natural organization of chitosan and alginate into a porous film has been exploited to synthesize spherical iron oxide nanoparticles through careful calcination of the iron(II) conjugate film. Our experiments indicate that the formed nanoparticles are highly crystalline, confirm to the hematite structure and have a superparamagnetic response with a low coercivity of 116 Oe. Particles thus synthesized were highly monodisperse with hydrodynamic diameter of 1.8 nm. The symmetric porosity of the film translates into the synthesis of well-aligned nanoparticles of iron oxide. Compared to synthesis in solution, the film-assisted synthesis offered a greater degree of control over the particle size distribution pattern, with the chitosan–alginate template providing the needed spatial separation to prevent the aggregation due to magnetostatic coupling. Such hematite nanoparticles can either be used directly or converted to paramagnetic magnetite by reduction. Zeta potential measurements indicate highly stable nanoparticles, which can therefore be conjugated to cationic liposomes carrying drugs and magnetically guided to target sites.

Present study deals with the evaluation of biosorptive removal of cadmium by red macro alga Hypnea valentiae. Experiments have been carried out to find the effect of various parameters such as initial cadmium concentration, experimental pH and temperature on the biosorption potential of H. valentiae. Optimum pH for biosorption of cadmium was found to be 6 ± 0.3. A maximum removal of about 17 mg of cadmium per g of micro algae was observed at pH 6.0 for 250 mg L−1 solution of cadmium. Kinetics of cadmium biosorption by H. valentiae biomass is better described by pseudo first order kinetic model. The equilibrium isotherm data are very well represented by Langmuir isotherm equation, which confirmed the monolayer coverage of cadmium onto H. valentiae biomass. Various thermodynamic parameters such as change in enthalpy, free energy and entropy were estimated. It was also clearly observed that the presence of neutral salts and other metal ions affected the cadmium uptake behavior of the biomass considerably.

The use of chromium-containing toxic solid wastes from the leather industry for the removal of dyes from waste-waters has been studied. A batch adsorption model has been employed and the role of various experimental parameters on the efficiency of the process evaluated. The extent of dye removal was studied by varying parameters such as pH, contact time, initial concentration of the dye and amount of adsorbent. The experimental equilibrium data for this system has been analyzed using the linearized forms of Langmuir and Freundlich isotherms. The Langmuir isotherm was found to provide the best theoretical correlation of the experimental data and the adsorption was found to follow pseudo-second-order kinetics. The dye adsorbed solid wastes were used for the preparation of pigments. In essence, this study provides a greener solution for chromium-containing solid wastes, dye containing waste-waters and dye-adsorbed chromium solid wastes. Copyright © 2007 Society of Chemical Industry

Easier, less time consuming, green processes, which yield silver nanoparticles of uniform size, shape and morphology are of interest. Various methods for synthesis, such as conventional temperature assisted process, controlled reaction at elevated temperatures, and microwave assisted process have been evaluated for the kind of silver nanoparticles synthesized. Starch has been employed as a template and reducing agent. Electron microscopy, photon correlation spectroscopy and surface plasmon resonance have been employed to characterize the silver nanoparticles synthesized. Compared to conventional methods, microwave assisted synthesis was faster and provided particles with an average particle size of 12 nm. Further, the starch functions as template, preventing the aggregation of silver nanoparticles.

This paper reports the effect of l-lysine on the conformational, rheological, and thermal properties of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) cross linked collagen and investigates the influence of l-lysine on the self assembly processes of collagen. In the absence of l-lysine, the rheological characterization of collagen cross linked with EDC/NHS showed an increase in shearing stress with shearing speed indicating that the collagen chains become rigid and the molecules are reluctant to flow. On the other hand, the increase in shearing stress with shearing speed is comparatively much less in the presence of l-lysine indicating a greater flexibility of the collagen molecules. The self assembly processes of collagen treated with EDC/NHS in the absence and presence of l-lysine were characterized using powder XRD, FT-IR, polarizing optical microscopy and kinetic studies. XRD studies show an increase in peak intensity and sharpness in the presence of l-lysine indicating the enhancement of crystallinity of collagen nano-fibrils. FT-IR results suggest that the incorporation of l-lysine in the EDC/NHS cross linking favors the molecular stability of collagen. From the present study, it is possible to conclude that the pre-treatment of collagen with l-lysine enhances EDC/NHS cross linking and can be used for biomaterial applications.► EDC/NHS in the presence of l-lysine shows more flexibility. ► Accelerated self assembly process. ► Increased thermal stability. ► Enhanced conformational stability. ► Higher crystalline order.

The process of stabilizing the skin collagen against denaturation under heat, enzymes, stress etc. – popularly described as tanning is carried out either using metal ions (predominantly Cr(III)) or vegetable tannins derived from plant sources rich in polyphenols. Conventional leather processing is carried out in aqueous medium and hence the tannins have been extracted into water, sulfited to increase water solubility and then sold as spray dried extracts. Classical drawbacks include the low resistance of the extracts to bacteria and fungi, copious quantities of water required for extraction and tanning etc. In an attempt to make the leather processing sustainable, taking cue from other economically viable methods for tannin extraction, this paper looks at paradigm shift from water extraction of tannins to solvent based extraction, followed by leather processing in solvent. The results presented with ethanol as the green solvent highlights the significance of the developed method, in...

Regeneration of damaged tissues or organs is one of the significant challenges in tissue engineering and regenerative medicine. Many researchers have fabricated various scaffolds to accelerate the tissue regeneration process. However, most of the scaffolds are limited in clinical trials due to scaffold inconsistency, non-biodegradability, and lack of non-invasive techniques to monitor tissue regeneration after implantation. Recently, carbon dots (CDs) mediated fluorescent scaffolds are widely explored for the application of image-guided tissue engineering due to their controlled architecture, light-emitting ability, higher chemical and photostability, excellent biocompatibility, and biodegradability. In this review, we provide an overview of the recent advancement of CDs in terms of their different synthesis methods, tunable physicochemical, mechanical, and optical properties, and their application in tissue engineering. Finally, this review concludes the further research directions...