Лаборатория нейтронной физики им. И.М. Франка

Общелабораторный семинар

Руководитель – Швецов В.Н.

Дата и время: вторник, 25 декабря 2018 г., в 11:00

Место: Конференц-зал, Лаборатория нейтронной физики им. И.М. Франка

1. Тема семинара: «Молекулы ДНК на неорганических поверхностях»

   Докладчик: Д-р Субрата Маджумдер (Национальный технологический институт, Патна, Индия)

   Аннотация:
   
   In a eukaryotic cell a long genomic DNA molecule is packed in chromatin within micrometer scale nucleic space. In the chromatin the DNA wraps around an octamer of core histone protein. Thus, the DNA is compacted in a large scale while the genes are remaining accessible. Also, in an aqueous solution due to the electrostatic repulsion the DNA molecules remain in an elongated coil state. In the field of biosensors, biotechnology, optical bioimaging etc these interaction and controlled adsorption/compaction on oxide surfaces is extremely important to understand also plays crucial role in maintaining the vital segment of device miniaturization.
   The compaction or adsorption of DNA molecule has been widely studied for different cations, surfactants etc. The compaction of long, single chain, double stranded DNA molecules by Silicon nanoparticles (NPs) has been shown due to the interaction process between the negatively charged DNA backbones and the positively charged NPs. Similarly, the adsorption properties of DNA molecules on ZrO2, TiO2, SiO2, and ZnO surfaces are also studied extensively and will be discussed. A suitable theoretical model will also be discussed in understanding these phenomena.
   
   

2. Тема семинара: «2D материалы: синтез, характеризация и применения»

   Докладчик: Д-р Санхита Маджумдар (Центр передовых технологий в области экологически чистой энергии и сенсорных систем, Индийский институт инженерных наук и технологий (IIEST), Шибпур, Индия)

   Аннотация:
   
   For about a decade, 2D (two-dimensional) materials have represented one of the hottest directions in solid-state research. Although, the existence of 2D materials was a highly debated issue up to the second decades of the 20th century as, according to the classical physics, 2D materials are thermodynamically instable at any finite temperature due to thermal lattice fluctuations. However, theorists and philosophers had assumed the existence of free standing 2D materials before the real time fabrication of this type of material and they have also illustrated their possible properties. Materials science had a major scientific breakthrough in 2004 when Novoselov and Geim isolated the first single layer 2D material, graphene, through the Scotch tape exfoliation of graphite. The importance of this achievement was sealed in 2010, when the Nobel price was awarded to both researchers.
   It is easy to understand that 2D materials are typically quite strong within each layer (via strong ionic and covalent intra-layer forces). Such materials have found applications in many arenas such as, photovoltaics, sensors, electrodes, water purification etc. due to their extraordinary properties that can be tailored by assembling them together and these properties are much different from their 3D counterparts. Moreover, their properties also depend on their inter-layer thickness and symmetry. Thickness-dependent properties are responsible for generating different band-gap, even, it has been changed from direct bandgap to indirect bandgap materials. Changes in symmetry are responsible for altering their polarizations. 2D materials are mainly arranged in honeycomb geometry and is very thin, hard, strong, light, transparent, bendable, stretchable in nature and is very good conductor for light, heat and magnetism. Graphene is an atomically-thin sp2 carbon layered material with a honeycomb lattice that has almost the same crystal energy as diamond. As each graphene carbon has only three bonds instead of four for diamond, the graphene C–C bonds are about 25% stronger. Thus, it is the most stable material known to date.
   Like graphene, some other 2D materials are also known, like silicene (allotrope of silicon), borophene (crystalline atomic monolayer of boron), germanene (two-dimensional allotrope of germanium), phosphorene (allotrope of phosphorus), bismuthene (allotrope of bismuth) etc. as well as some compounds like, zirconium diboride (ZrB2), zirconium carbide (ZrC), molybdenum disulphide (MoS2) etc. In our work, we want to synthesize some 2D materials through simple technique of preparation to develop tailored made structures with tuneable thickness and alterable band-gap. Different dopant/catalysts can also be incorporated as per application requirement specially keep in mind for their use in the field of energy harvesting as well as the major material for different kind of sensors like, gas sensor, optical Sensor, bio-sensor etc.