Dipanka Dutta

Stabilization of Cu(0)-nanoparticles into the nanopores of modified montmorillonite: An implication on the catalytic approach for “Click” reaction between azides and terminal alkynes

In situ generation of Cu(0)-nanoparticles in the nanopores of modified montmorillonite and their catalytic activity in 1,3-dipolar cycloaddition reactions between azides and terminal alkynes to synthesise 1,2,3-triazoles have been carried out. The modification of montmorillonite was carried out by activation with H2SO4 under controlled conditions for generating nanopores to act as a “host” for the Cu(0)-nanoparticles, which is executed by successful loading of Cu(CH3COO)2 metal precursor through an incipient wetness impregnation technique followed by reduction with NaBH4. A TEM study reveals that Cu(0)-nanoparticles within the size range of 0–10 nm are evenly distributed on the support. The synthesized Cu(0)-nanoparticles exhibit face centered cubic (fcc) lattice geometry and serve as an efficient green catalyst for the “Click” azide–alkyne cycloaddition to afford highly regioselective 1,4-disubstituted 1,2,3-triazoles with excellent yields and selectivity in aqueous medium. The nanocatalysts can be recycled and reused several times without significant loss of their catalytic activity.

Synthesis of Ag–Ag2S Janus nanoparticles supported on an environmentally benign cellulose template and their catalytic applications

Synthesis of Ag–Ag2S Janus nanoparticles (JNP) by a one step co-precipitation technique using a NaOH–thiourea–urea aqueous solution has been reported. The NaOH in cellulose solution acted as the precipitant of Ag–Ag2S nanoparticles and environmentally benign cellulose was used as a template to promote the growth of nanoparticles. The cellulose was extracted from Bambusa tulda, a locally available bamboo species and was carried out by adopting a green approach using a combination of both chemical and biochemical treatment. The synthesized Ag–Ag2S JNP was characterized by UV-Visible spectroscopy, powder XRD, TEM, SEM-EDX and XPS analysis. The TEM study reveals that most of the Ag–Ag2S JNP were spherical in shape and fall in the size range of 10–15 nm. XRD analysis of the Ag–Ag2S JNP shows diffraction peaks for the (111), (200) and (220) planes of a face centered cubic Ag0 crystal along with the characteristic peaks due to Ag2S, which provide evidence for the coexistence of Ag2S and Ag on the cellulose support. The method offers a facile and green pathway for the fabrication of Ag–Ag2S JNP and the synthesized Ag–Ag2S JNP were employed as a heterogeneous catalyst in a model reaction based on the reduction of p-nitrophenol to p-aminophenol. The metal nanocatalysts could be recycled and reused several times without significant loss of their catalytic activities.

Development of a flexible composite from leather industry waste and evaluation of their physico-chemical properties

Worldwide leather industry is known to cause high degree of pollution such as soil and water contamination. Dyed trimming, a leather industry waste, is often dumped near the industrial site and is used for land filling. Recycling of such industrial wastes for making useful products by substituting leather has been investigated and reported here. Flexible composite sheets were made from dyed trimmings only and also in combination with natural fibres in various blend ratios. Wastes from jute and cotton were used as sources of natural fibres. The composite sheets showed maximum tensile strength and breaking loads at 50:50 blend ratios of dyed trimmings and natural fibres. The ultimate tensile strength, elongation, double fold, bursting strength, density and water and oil absorption characteristics of the composite sheets were determined as per American Society for Testing and Materials and Indian Standard methods. The products, i.e. the composite sheets, and the starting materials, i.e. the dyed trimmings and jute and cotton fibres, were also characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Energy-dispersive X-ray analysis of both untreated and treated dyed trimmings was carried out and the presence of chromium 2.54% in untreated samples was recorded but the sample treated with NaOH did not show the presence of chromium. The natural fibre significantly improves the mechanical strength and thermal properties of the blended composite sheets with the increase in flexibility. These flexible sheets possess higher physical strength as compared to leather and may be used as leather substitute for making apparels and goods.Graphical Abstract