Doped oxides of cerium as inorganic colorants

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.     

Colored cool colorants based on rare earth metal ions

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.     

Natural rubber latex/potato starch nanocrystal nanocomposites: Correlation morphology/electrical properties

This paper discusses the preparation and characterization of nanocomposites obtained with potato starch nanocrystals, and their use as fillers in order to realize nanocomposites with a natural rubber latex matrix. The preparation of potato starch nanocrystals was done by hydrolysis of potato starch powder using sulfuric acid. The synthesized potato starch nanocrystal suspensions were mixed with natural rubber latex by latex stage mixing process using a magnetic stirrer. In this way, composites containing up to 20% w/w of fillers have been obtained. Morphological studies indicated a relatively uniform dispersion of starch nanocrystals in the nanocomposites until 15% w/w filler loading. Dielectric measurements confirm the existence of a threshold at a composition close to 15% w/w of filler at which the fillers become agglomerated.     

Influence of functionalized nanoparticles on conformational stability of type I collagen for possible biomedical applications

Collagen–nanoparticle interactions are vital for many biomedical applications including drug delivery and tissue engineering applications. Iron oxide nanoparticles synthesized using starch template according to our earlier reported procedures were functionalized by treating them with Gum Arabic (GA), a biocompatible polysaccharide, so as to enhance the interaction between nanoparticle surfaces and collagen. Viscosity, circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) techniques have been used to study the collagen–nanoparticle interactions. The relative viscosity for collagen–nanoparticle conjugate was found to increase with increase in concentration of the nanoparticle within the concentration range investigated, which is due to the aggregation of protein onto the surface of nanoparticle. The CD spectra for the collagen–nanoparticle at different concentration ratios do not have much variation in the Rpn values (ratio of positive peak intensity over negative peak intensity) after functionalization with GA. The variation of molar ellipticity values for collagen–nanoparticle is due to the glycoprotein present in GA. The collagen triple helical structure is maintained after interaction with nanoparticles. The FTIR spectra of native collagen, Coll–Fs (nanoparticle without functionalization) and Coll–FsG (nanoparticle functionalized with GA) show clearly the amide I, II, III bands, with respect to collagen. The ability of polysaccharide stabilized/functionalized nanoparticles to maintain the collagen properties would help in its biomedical applications.     

Carbon Dots-Mediated Fluorescent Scaffolds: Recent Trends in Image-Guided Tissue Engineering Applications

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 that can be explored to apply CDs in tissue engineering.     

Green route for the utilization of chrome shavings (chromium-containing solid waste) in tanning industry

Chromium-containing wastes from various industrial sectors are under critical review. Leather processing is one such industrial activity that generates chromium-bearing wastes in different forms. One of them is chrome shavings, and this contributes to an extent of 10% of the quantum of raw skins/hides processed, amounting to 0.8 million ton globally. In this study, the high protein content of chrome shavings has been utilized for reduction of chromium(VI) in the preparation of chrome tanning agent. This approach has been exploited for the development of two products: one with chrome shavings alone as reducing agent and the other with equal proportion of chrome shavings and molasses. The developed products exhibit more masking due to the formation of intermediate organic oligopeptides. This has been corroborated through the spectral, hydrolysis, and species-wise distribution studies. The formation of these organic masking agents helps in chrome tanning by shifting the precipitation point of chromium to relatively higher pH levels. Hence, the developed products find use as chrome tanning agents for leather processing, thus providing a means for better utilization of chrome shaving wastes.     

The use of toxic solid waste for the adsorption of dyes from waste streams

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