26-Oct-2019: New class of quantum materials for clean energy technology
Researchers from IIT Bombay have discovered special properties in a class of materials called “semi-Dirac metals”. Examples of semi-Dirac metals are systems such as TiO2/V2O3 nanostructures. Through calculations, the researchers have shown that such materials would be transparent to light of a given frequency and polarisation when it is incident along a particular direction. The material would be opaque to the same light when it falls on it from a different direction. There are many known applications for transparent conducting films – the common example being touch screens used in mobiles.
A very high optical conductivity is observed in semi-Dirac materials for electromagnetic waves [light waves] of a specific frequency and specific polarisation. Optical conductivity is a measure of the opacity offered by the material to the passage of light through it.
Dirac metals: Normal metals like gold and silver are good conductors of electricity. A key aspect that decides the quality of conduction is the way energy depends on the momentum of electrons. Dirac metals differ from normal metals in that the energy depends linearly on the momentum. This difference is responsible for their unique properties. Semi-Dirac metals behave like Dirac metals in one direction and like normal metals in the perpendicular directions (since their microscopic structure is different along the two directions).
Within any material, charge carriers, such as electrons, acquire an effective mass which is different from their bare mass depending on the nature of the material. The effective mass and the number of states available for the electron to occupy when it is excited by an electric field, for example, determine the conductivity and other such properties. This is also true of a semi-Dirac metal. In particular, the effective mass becomes zero for conduction along a special direction.
With the advent of man-made 2D materials, such properties have become quite tailorable in what comprises the active field of quantum materials. One such example is that the [energy-momentum] dispersion relation can be linear, leading to large velocities and vanishingly small effective masses. The velocities can be over a 100 times more than normal metals, thus increasing the mobility and currents that can be carried across devices made of these so-called Dirac materials. In the semi-Dirac metals, these properties are direction dependent. The direction-dependence of the microscopical properties gives the material special optical properties.
Alongside, the material should also possess thermoelectric properties. Thermoelectricity is a clean energy technology that uses waste heat to produce electricity typically in low power applications. This technology is used in efficient cars, where it is used to keep lights on and to warm seats. Spacecrafts like Voyager which are too far from the sun to use solar energy can make use of thermoelectricity. The holy grail of thermoelectrics is to increase the heat-to electricity conversion efficiency, for which there has been recent and tremendous interest due to the advent of nanomaterials and quantum materials.
2-Sep-2019: Lignin from agro waste helps make useful nanocomposites
Agricultural waste can find many useful applications. Researchers at the Mohali-based Centre of Innovative and Applied Bioprocessing (CIAB) have developed a lignin-based nanocomposite which could potentially have commercial value. Microbial test results indicate that, in the long run, the lignin-based nanomaterial can act as additive in coating and packaging materials.
Lignin is a complex organic polymer rich in polyphenols with antimicrobial qualities. It is found in almost all dry plants including crop residues and the woody bark of trees. Abundant quantities of lignin are generated as post-harvest agro-biomass and in paper and pulp industries every year, which often go waste.
Burning of post-harvest biomass like straw is common practice among our farmers, which leads to severe environmental pollution. Researchers took up the challenge of converting agro-waste into value-added nanomaterials with antimicrobial properties, thereby not only reducing the pollution but trying to add to farmers’ income.
The team zeroed–in on gold-silver bimetallic nanoparticles to utilise their novel physicochemical properties, and used kraft lignin as the matrix material. Instead of using harsh chemicals and high temperatures to synthesise nanocomposite, researchers applied ‘green’ and reproducible techniques, to derive nanomaterials. The process involved a single-step method utilising lignin as the sole source for reducing, capping and stabilising the nano-agents.
After establishing structural stability and morphology of the nanocomposite, the material was subjected to different microbial assays to evaluate its antimicrobial quality. The results indicated that the lignin-nanocomposite retained antimicrobial and antioxidant qualities of lignin.
The lignin-bimetallic nano complexes were found to exhibit excellent targeting of microbes by the mechanism of reactive oxygen species production and membrane disruption of microbial cells, revealing that nano-complexes were internalised in microbial cells.
20-Aug-2019: Silk protein can help make beauty and skincare products
Silk has fascinated humans for centuries and is a preferred fabric when it comes to making exquisite draping material and sarees. Now Indian scientists have discovered that a protein produced by silkworms can be used to develop a range of beauty and skincare products.
The protein, sericin, is known to possess anti-oxidant and other medicinal properties. These properties depend on amino acid composition and secondary metabolites (polyphenols and flavonoids) of sericin. They vary with source of silkworms and their availability depends on the length of sericin peptides obtained during extraction.
The research group at the Indian Institute of Technology Guwahati (IIT), which has been working on different aspects of sericin, have developed new methods for extraction of sericin isolates and from different varieties of silkworms and have studied properties of resulting sericin. The group has conducted animal studies to investigate properties of the compounds isolated from the protein.
At present sericin from silk varieties such as Muga and Eri is discarded during industrial production of the silk fabric. Processing of one ton fresh cocoons produces about 200 kilograms of sericin.
Sericin was isolated from cocoons of three types of silkworms — Bombyx mori (Mori), Antheraea assamensis (Muga) and Philosamia ricini (Eri) — using five different extraction methods. The protein samples were then studied for their physicochemical properties and antioxidant activity. It emerged that the molecular weight, structures of sericin isolates and total content of metabolites depends on the extraction methods used.
Using alkali-degradation method, researchers extracted sericin from cocoons of three silk varieties and explored their anticancer and protective effects against UV radiation-induced damage in laboratory animals. At higher concentrations, sericin isolates acted as pro-oxidants and increased free radical production in cancer cells, leading to cell death. Treatment with sericin extracted from Muga silkworm showed better protection against UV-induced keratinocytes death than extracts from the other two varieties.
Sericin isolates from Muga silkworms were used in preparation of skincare formulation. Using sericin in these skincare formulations did not affect their flow properties.
Muga sericin-embedded cream could be used for topical skincare application as a potential therapeutic to protect skin against UV radiation-induced inflammation, oxidative damage of epidermal keratinocytes, aging, wrinkling, preventing skin roughness, enhancing the skin elasticity and moisture content.
Overall, sericin compounds isolated from cocoons of North-East varieties have shown better antioxidant, anticancer and protective properties. Muga sericin isolates have been used in cosmetic gel formulation and its properties investigated in animals.
It could be used for protection from oxidative damage, edema, erythema, sunburn, premature aging, wrinkling, and skin cancer. The technology has been patented and currently being explored for commercialization.