R & D Overview
A stable magnetic nanocomposite of collagen and superparamagnetic iron oxide nanoparticles (SPIONs) is prepared by a simple process utilizing protein wastes from leather industry. Molecular interaction between helical collagen fibers and spherical SPIONs is proven through calorimetric, microscopic and spectroscopic techniques. This nanocomposite exhibited selective oil absorption and magnetic tracking ability, allowing it to be used in oil removal applications. The environmental sustainability of the oil adsorbed nanobiocomposite is also demonstrated here through its conversion into a bi-functional graphitic nanocarbon material via heat treatment.
Self-doped carbon nanomaterials
We reported the synthesis of multifunctional carbon nanostructures from pristine collagen wastes by a simple high temperature treatment. Our studies reveal that the nanocarbons derived from the bio-waste have a partially graphitized structure with onion-like morphology and are naturally doped with N and O. The nanocarbons here have multifunctional properties due to the rich chemical functionalities attached to the graphitic carbons in the lattice. We also demonstrated that it can be potentially used as electrodes in a Li-ion battery with high capacity.
Chromium-carbon core-shell nanomaterials
Chromium-complexed collagen is generated as waste during processing of skin into leather. We reported a simple heat treatment process to convert this hazardous industrial waste into core-shell chromium-carbon nanomaterials having a chromium-based nanoparticle core encapsulated by partially graphitized nanocarbon layers that are self-doped with O and N functionalities. We demonstrate that these core-shell nanomaterials can be potentially utilized in electromagnetic interference (EMI) shielding application or as a catalyst in aza-Michael addition reaction.
A simple method is reported for the preparation of multifunctional biocomposite films by using collagen waste trimmed from goatskins. The waste was cleaned and carbonized to synthesize conducting and magnetic graphitic nanocarbon (GrC). Collagen was extracted from the trimmed waste and combined with chitosan and GrC to form flexible, semi-transparent, conductive and magnetic biocomposite films (GrC/Col–Ch) of micron-thickness. The small ferromagnetic property of the synthesized biocomposite films has been potentially used for magnetic tracking and actuation.
In another method, we reported large-scale biosynthesis of copper nanoparticles using extract of henna leaves as reductant. Owing to the substantial electrical conductivity of the calcined copper nanoparticles, we used them to prepare conductive nanobiocomposites utilizing collagen wastes. We demonstrated that the nanobiocomposites, when inserted between batteries, illuminate a light emitting diode lamp.
Biocompatible hybrid collagen-based scaffolds
Collagen (C) was extracted from skin waste using acetic acid and blended with starch (ST)/soy protein (SP)/2-hydroxy ethyl cellulose/ modified guar gum/ locust bean gum to prepare hybrid films/scaffolds. The prepared hybrid films/scaffolds were examined for biocompatibility, physical and chemical properties. The equilibrium swelling, in vitro biodegradation and in vitro cytotoxicity studies show good biostability and biocompatibility for the hybrid films/scaffolds. In-vivo wound healing studies using Wistar albino rats demonstrate the potential of the developed scaffolds for tissue engineering applications. Therefore, it is envisaged that the promising properties of the developed hybrid films/scaffolds suggest a beneficial role for the biomedical applications.
Flexible composite sheets
We proposed a method to reuse these wastes to form smart composite sheets using eco-benign and cost effective polymers. The waste chrome shavings were shredded into finer pieces and partially hydrolyzed using dilute acids. Eco-friendly polymers based on 2-hydroxyethylcellulose (HEC) and polydimethylsiloxane (PDMS) have been employed to fabricate sheets of desirable size. In general, the formed composite sheets show satisfactory improvement in their properties as the composition of the polymer increases. In particular, cellulose incorporated sheets were found to have increased thermal and mechanical properties when compared to that of siloxane incorporated composite sheets. Both types of sheets exhibit an inverse relationship between softness and tensile stress. Unlike cellulose based sheets, siloxane incorporated sheets behave irrationally with concentration. Specifically, tensile and thermal properties tend to increase gradually upon increase in siloxane concentration upto 20 wt.% followed by an abrupt decrease when the concentration increased further up to 40 wt.%. Thus, the developed smart composite sheets demonstrate potential for numerous applications in footwear, clothing and related industries, besides finding a new way for the reuse of different forms of unwanted leather wastes.
Leather is a unique consumer material possessing a variety of properties such as strength, viscoelasticity, flexibility, and longevity. However, the use of leather for smart product applications is a challenge since it is an electrically insulating material. Here, we report a simple method to produce conducting leathers using an in situ polymerization of pyrrole/aniline. The concentrations of pyrrole/anilne, dopant, and oxidant and the number of polymerization were optimized to produce maximum conductivity in the treated leathers. Highly conducting leathers were prepared using 0.3 M of pyrrole, a dopant concentration of 10 wt % of pyrrole, oxidant concentration of 0.8 M (2.67 ferric chloride to pyrrole molar ratio) and double in situ polymerization at 5°C. We also show that the treated leathers are black or green depending on whether pyrrole or aniline was used, respectively through reflectance measurements, thereby suggesting that the use of toxic and expensive dyes can be avoided for coloration process. We further demonstrate that the treated leathers, with a maximum conductivity of 7.4 S/cm, can be used for making conductive gloves for operating touch-screen devices apart from other smart product applications.
Leather, a stable chromium–collagen matrix, is insensitive to magnets although it is paramagnetic. Here we show that the coating of the leather surface with iron oxide nanoparticles can provide magnetic leathers showing significant responses to permanent magnets. Iron oxide nanoparticles, synthesized using a simple co-precipitation technique, predominantly comprised magnetite (Fe3O4) with a particle size around 16 nm as revealed through X-ray diffraction and scanning electron microscopic analyses. Ethanol dispersed nanoparticles were mixed with commercial leather finishing dispersion and coated on the leather surface. Vibrating sample magnetometric measurements show that the resulting ferromagnetic effect is comparable to the leathers coated with commercial magnetic pigments. Surface coating of leathers with magnetic nanoparticles did not affect any of the physical properties of the leather. We further demonstrate that the prepared magnetic leathers have potential for advanced applications including adhesive-free wall tiling and energy harvesting from human motions