Tag: news

Dielectica traverses through the literature on this topic – and summarizes as they appear.

Key Words: SERS, Gallbladder, Gold Nanostructure, Nickel foam

Human body is believed to be a well developed machine that can perform complex operations. Gallbladder is a very important part of human organ system. It accumulates particular fluid called ‘bile’ which can break down the fat present in the consumed food and thus helps digestion process. However, any problem in the Gallbladder system can create several health problems such as severe abdominal pain, jaundice, gallstones. In extreme cases when the growth of stones is dominant, patients are left with the option of surgery to get rid of the stones or the removal of entire gallbladder in worst condition. Thus proper diagnosis of Gallbladder related diseases is very much essential to lead a healthy life.

Most of the disease diagnosis methods are based on spectroscopy i.e. the interaction between matter and electromagnetic radiation. In this context, Surface-enhanced Raman scattering (SERS) is believed to be a potential spectroscopic tool, named after the pioneering Indian scientist Sir. C. V. Raman. Recently, Prof. H. Chung and co-workers have reported an advanced SERS-based technique capable of direct measurement of raw bile juice to identify any Gallbladder related disease in the upcoming issue of the journal Sensors & Actuators, B:  Chemical [1]. Over other known techniques the reported method is believed to be advantageous as it doesn’t require any pre-treatment process and thus becomes a handy analytical route for fast screening. The group has developed a paper strip based system where specially designed gold nanostructure (of dendrite shape) has been encaged over nickel foam (a cage like morphology of nickel). In this study, Gold nanostructure has been chosen owing to its high SERS efficiency. With such experimental designing, the team has studied the discrimination of various samples of raw bile juice collected from Gallbladder stone and Gallbladder polyp patients. According to the authors, although the reported method is very promising, future activities on accuracy, sampling range etc. are to be performed for making the technique applicable for clinical analysis.

Sources:
[1] T. D. Vu et. al. Sens. Actuators B Chem., 329,129238 (2021).
https://www.sciencedirect.com/science/article/abs/pii/S0925400520315781

The 2020 Meet with Science and Technology in Portugal (encontro CIÊNCIA’20) is now on progress (3^rd and 4^th of November). Current edition of the annual meeting of Portuguese researchers aims to promote a wide debate on the main topics and challenges of the scientific agenda beyond the world of scientific investigation. The main objective is to encourage not only the participation from diverse fields/sectors, but also to create and enhance the interaction among researchers, the business sector and the general public. Hence, there lies the main attraction of this event to various levels of society as this is a platform to connect science and technology together with the general public in a very popular way. Also, Nobel laureates take part to expand their experiences to the common people.

This Science Meet is promoted by the Foundation for Science and Technology (FCT) in collaboration with Ciência Viva – National Agency for Scientific and Technological Culture and the Parliamentary Education and Science Commission, and has the institutional support of the Government through the Minister of Science , Technology and Higher Education. “The main motto of the Science 2020 Meeting will be the importance and challenges of science, research and innovation in the recovery of Portugal in times of pandemic, making this country and Europe more resilient, more digital, greener, more social and more global” [1].

Many scientific and technological demonstrations are going on in which several eminent groups from research and industry fields are participating. Among many others, the group of Elvira Fortunato and Rodrigo Martins from ‘Institute of Nanostructures, Nanomodeling and Nanofabrication, Faculty of Science and Technology, Universidade Nova de Lisboa’ (CENIMAT-i3N) is no doubt a very famous and well-recognised one in their field (Materials Science) from Portugal. They have presented their contribution on ´´Systems for converting mechanical to electrical energy for autonomous low-consumption devices´´ [2]. In this demonstration, several prototypes which are developed at CENIMAT-i3N (FCT UNL) during different international and national research projects are presented, to show the conversion of the mechanical energy of movements to electrical energy. This kind of energy harvesters are now an emerging field of research and application as they reuse the wasted energy in daily body movements/dynamical motions by converting them into the electrical energy that can be further utilized to power up several portable devices and applications. To demonstrate in a simple way to the general public, the development processes of these devices with planar or linear configurations are also exhibited, as well as their application when connecting simple electrical devices such as an analog clock and LEDs. In the video link [2], it is quite interesting to find the details about how different kind of biocompatible polymers and substrates like carbon and textile fibers have been coated with several energy harvesting materials (piezoelectric or tribo-electric or mechano-electrical) and then designed to develop the device prototypes [3-6]. This new kind of mechanical energy harvesters can have immense impact in reaching the sustainable development goals, as well to extend a new stream for renewable energy applications for a better, greener and cleaner environment.

References:
[1] https://www.encontrociencia.pt/index.php
[2] https://www.youtube.com/watch?v=cIiRqn7rqZs
[3] G. Ferreira, S. Goswami, S. Nandy, L. Pereira, R. Martins, E. Fortunato, Advanced Functional Materials 2020, 30, 1908994
[4] S. Goswami, A. dos Santos, S. Nandy, R. Igreja, P. Barquinha, R. Martins, E. Fortunato, Nano Energy 2019, 60, 794
[5] A. Rovisco, A. dos Santos, T. Cramer, J. Martins, R. Branquinho, H. Águas, B. Fraboni, E. Fortunato, R. Martins, R. Igreja, P. Barquinha, ACS Applied Materials & Interfaces 2020, 12, 18421-18430
[6] A. dos Santos, N. Pinela, P. Alves, R. Santos, E. Fortunato, R. Martins, H. Águas, R. Igreja, Advanced Electronic Materials 2018, 4, 1800182.

Dielectica traverses through the literature on this topic – and summarizes as they appear.

Correspondence prepared by: Debdatta Panigrahi, National Institute for Materials Science, Japan, email: debdattapanigrahi123@gmail.com (21:10:2020, 10:30)

Key Words: Logic Gate, Transistor, Antiambipolar, Inverter   

Tokyo: An inverter is a logic gate (termed as “NOT” gate) that is used to invert the applied input signal. Conventional binary inverters can handle two logic states, “1” and “0”. If the applied input is low (“0”) the inverter output becomes high (“1”) and vice versa. Since the early days of digital electronics, binary inverters have been one of the key components of integrated circuits and become the basic building blocks of every sophisticated electronic device that we use in our daily lives today-smartphones, laptops, tablets and many others.

Of late, we are witnessing another significant technological revolution that could possibly have even more positive impact on modern information technology, the emergence of organic semiconductor based ternary inverters which can exhibit three distinct logic states; “1”, ‘1/2” and “0”. With the approaching end of Moore’s Law (which states that the number of transistors on a microchip doubles every two years), the logic data density in binary integrated circuits can hardly be further improved due to the physical limitation. In this aspect, ternary logic can be a promising substitute to the binary logic owing to their capacity of handling higher density of information and their compatibility with low-power, high speed and less complex digital logic design technology. Ternary logic systems can drastically reduce the number of connections between devices inside the chip by transmitting more information, thereby simplifying the integrated circuit design and implementation [1].

Recently, a new genre of pn-junction transistors (termed as “antiambipolar transistors”) have been exploited for the realization of ternary inverters owing to their negative differential resistance characteristics. So far, several materials have been employed for the implementation of high performance antiambipolar transistors and low voltage operable, well balanced ternary inverters [2-4]. In particular, ternary logic circuits fabricated with organic semiconductors have several advantages compared to their inorganic counterparts [5-6]. First of all, organic semiconductors provide the advantages of easy and low-cost deposition and patterning processes. Another important advantage of this class of semiconductors is their intrinsic mechanical flexibility, which offers the scope of flexible and wearable electronics. They are capable of withstanding mechanical stresses, giving compatibility with the flexible substrates. Therefore, simultaneous attainment of mechanical flexibility and high data processability is possible in organic ternary inverters. Moreover, the strong optical absorption of the organic semiconductors enables the fine-tuning of their electronic properties, which can open up the possibility of new optoelectronic interconnection devices for next generation information technology.

Sources:

[1] S. L. Hurst, IEEE T. Comput. 12, 1160 (1984).
https://www.computer.org/csdl/journal/tc/1984/12/01676392/13rRUIIVljg

[2] Y. Wakayama, R. Hayakawa, Adv. Funct. Mater. 30, 1903724 (2019).
https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201903724

[3] M.Huang et. al. Nat. Nanotechnol. 12, 1148 (2017).
https://www.nature.com/articles/nnano.2017.208

[4] J. Shim et. al. ACS Nano 11, 6319, (2017).
https://pubs.acs.org/doi/abs/10.1021/acsnano.7b02635

[5] K. Kobashi et. al. Nano lett. 18, 43559 (2018).
https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.8b01357

[6] H.Yoo et. al. J. Adv. Mat. 31, 1808265 (2019). https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.201808265

Dielectica traverses through the literature on this topic – and summarizes as they appear.

Correspondence prepared by: Sayan Bayan¹ and Suman Chakraborty², ¹S. N. Bose National Centre for Basic Sciences, Kolkata, India, email: sayan.bayan@gmail.com, ²Physical Research Laboratory, Gujrat, India, email: suman.chakrabarty37@gmail.com (16:10:2020 and 14:00)

Key Words: Black holes, Event horizon, General Theory of Relativity, Singularity

India: The Nobel Prize in Physics for the year 2020has been awarded in one half to Roger Penrose“for the discovery that black hole formation is a robust prediction of the general theory of relativity” and the other half jointly to Reinhard Genzel and Andrea Ghez “for the discovery of a supermassive compact object at the centre of our galaxy”. Henceforth, the three scientists shared this prize for their outstanding discoveries about the ‘black hole’ which is considered as one of the most mysterious themes in Physics. To give a thought on their discovery, one needs to understand what are black holes and why are they so mysterious?

A black hole can be defined as a region in space where gravity is so strong that even light cannot escape through it. The black hole is enclosed by a boundary called ‘event horizon’ which defines the region where the velocity required to escape exceeds the speed of light [1]. Such strong gravity originates from the fact that matter gets squeezed into a very tiny space. Such a situation can be realized during the death of a star having mass more than three times the mass of the Sun. Since light cannot get out of black holes, it is conventionally invisible in naked eyes. However, a black hole can be realized by the virtue of its gravitational pull on other stars around it. The strong gravitational force of a black hole will pull matter from other stars. During this process, the compression and heat generation (in millions of degrees) will lead to the production of X-rays that radiate in space. Thus the outward region of the black hole can be realized by the emission of X-rays. In many occasions, the spreading of radio waves has also been witnessed [2].

Now back to the past, theoretically, the existence of black holes has been traced from Einstein’s general theory of relativity, although Einstein himself denied the concept of black holes. According to this theory, the force of gravity arises from the warping of spacetime (fusion of three dimensional space and one dimensional time) around a body. The core of this theory is some nonlinear equations known as Einstein field equations. Soon after the appearance of this theory, Karl Schwarzschild found the non-trivial solution of the Einstein field equations which led to the concept of gravitational collapse and the condition of singularity [3]. A singularity is a location where the gravitational field becomes infinite. However, the concept of singularity was debated a lot as many scientists attempted to prove that singularities don’t appear in generic solutions. In 1955, A. K. Raychadhuri’s work remarkably transformed the field of general theory of relativity as the equations laid by him formed the basis of all singularity theorems [3]. The defining moment came with the singularity theorem in 1965 where Penrose sparked the idea of incompleteness to describe singular spacetime and for the first time he introduced the concept of a closed trapped surface. The concept of a closed trapped surface reveals the inner region of an event horizon and can be assumed as the surface from which light is not moving away. Thus Penrose established that singularities appear generically and concluded with his Nobel winning discovery. Penrose’s singularity theorem was ample and straightaway and led to the development of modern singularity theorems [3].      

Penrose established the existence of black holes theoretically, while teams led by Ghez and Genzel’s demonstrated experimental evidence of such celestial giants at the heart of our Galaxy. Since a long time physicists suspected that most galaxies include a supermassive black hole at the centre. The bright Sagittarius A* (Sgr A*) – a radio source situated at the centre of Milky Way, was suspected as a black hole. In the 1980s, Genzel and Charles Townes (another Nobel laureate) exploited InfraRed (IR) spectroscopy to track gas clouds orbiting at the centre of the Milky Way. Although they could infer the presence of a massive, compact source of gravitation, the evidence was not ultimate.

The prime challenge was to detect the emission from the stars amidst the gas and dust obstacles. However in 1990, teams led by Ghez and Genzel came out to address this issue with the world’s biggest telescopes which work in the near-IR region suitable for sensing the light that can escape the dusty region of the galactic centre.  Ghez and her team used the Keck Observatory, Hawaii, while Genzel and his co-workers used the Very Large Telescope on Cerro Paranal, Chile. With a series of developments in imaging techniques, they could improve the resolution and sensitivity to the faint light from the celestial world.

The two teams tracked and plotted the tracks of several stars near the centre of the galaxy for a decade, particularly the star called S0-2 by Ghez’s group or S2 by Genzel’s team.  This led to the understanding that the motion and pattern of the stars are influenced by the presence of an invisible source of four million solar masses and which is certainly a supermassive black hole [4]. This was not only the strongest evidence of the presence of the giant black hole at the galaxy’s core, but also stimulates research on the immense gravitational effects on its stellar neighbours.

Sources:
[1] https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-a-black-hole-k4.html
[2] https://science.nasa.gov/astrophysics/focus-areas/black-holes
[3] J. M. M. Senovilla, D. Garfinkle, Class. Quantum Grav., 32, 124008 (2015).
https://iopscience.iop.org/article/10.1088/0264-9381/32/12/124008
[4] www.timesonline.co.uk/tol/news/uk/science/article5316001.ece

Dielectica traverses through the literature on this topic – and summarizes as they appear.

Correspondence prepared by: Dr. Md Palashuddin Sk, Assistant Professor of Aligarh Muslim University, Uttar Pradesh, India, email: palashuddin.ch@amu.ac.in (12:10:2020, 17:30)

Key Words: Haemoglobin, Carbogenic Dots, luminescence, nanocrystals

Aligarh: Haemoglobin (Hb) is an essential iron-containing protein, which exists in the red blood corpuscles. Hb consists of four iron-porphyrin units (heme) together with the globular protein moiety. Atomic iron encaged into the heme moiety plays a crucial role in transporting molecular oxygen (O₂) from the respiratory organs to the different parts of our body through blood and carrying the major portion of carbon dioxide from these parts to the lungs at the same time. The Hb level in blood to the well-functioning of the organism in the human body is 13.0-18.0 g/dL and 12.0- 16.0 g/dL for male and female, respectively [1]. On the contrary, Hb amount below this level solely causes several blood disorder diseases (even fatality) such as thalassemia, anaemia, and leukaemia. Approximately, two billion people (mainly women and children), worldwide suffer from particular anaemia due to the lower level of Hb in blood. The lower level of Hb thus becomes a major issue and hence is of substantial significance for clinical diagnosis purposes. In this regard, the sensitive detection and determination of Hb in clinical diagnostics is essential to assess the extent of blood disorder diseases and to evaluate various intervention programs aimed at control of the same.

There are quite a few analytical methods like electrochemical, colorimetric, and various spectroscopic techniques are generally employed for the detection of Hb in the blood. Unfortunately, most of these techniques require harsh, expensive chemicals, tedious and complicated probe preparation and of low sensitivity detection ability as well.  In this scenario, the luminescent carbogenic dots (Cdots) are paid great attention due to their higher water solubility, biocompatibility, high quantum yield, and excellent optical (stability towards the chemical/physical environment changes such as pH, ionic strength, etc.) and well enough chemical stability.

Following this trend, our Research Group at Aligarh Muslim University, India, has recently developed a Hb sensor from the reaction by-product, which is accidentally isolated during the synthesis of tin oxide (SnO₂) nanocrystals [1]. The purified by-product is confirmed as luminescent carbogenic dots which is again produced due to the polymerization and consequent carbonization of the excess of 4,7,10-trioxa-1,13-tridecanediamine (TTDDA). Yet, TTDDA is a hazardous reagent, it is used as a stabilizing agent in metal nanocrystals synthesis [1]. The advantage of such synthesis lies in the fact that the obtained product SnO₂ nanocrystals and the reaction side product are environmentally friendly and are produced through the sustainable way. Our Research Group has actually employed the principle of luminescence turn-off property of Cdots with the interaction of Hb to develop a diagnostic method for qualitative and quantitative detection of Hb in the blood. The observed luminescence property of the Cdots remains highly selective towards the detection of a trace amount of Hb. Efficient ground state complexation between Cdots and Hb is solely responsible for the unprecedented selectivity of Cdots towards Hb detection. Keeping in mind the issues of accuracy in the visual detection, economic factors and the portability, we have further developed a fluorescent test strip-based sensing method. The rapid sensing experiment by using the fluorescent test strip has also been studied with the voluntary collection of blood samples, and various interfering chemical substances, proteins, amino acids, metal ions, anions, etc at pH ~7.4 in order to realize the selectivity as well. Upon addition of Hb, the emission intensity of Cdots is drastically reduced; while, in the case of other analytes addition, hardly any reasonable change in the intensity observed, validating the accuracy of the test strip. Test strip-based luminescence turn-off property of Cdots in the presence of Hb further defines their applicability in fabricating portable and inexpensive sensing devices. Even the trace amount of blood present in the human urine is also possible to be detected by this paper-based method, the author stated. The present paper strips based detection technique has advantages over conventional methods (absorption-based spectroscopic methods) because of the portability, cost-effectiveness, time-saving, high sensitivity, ease to measuring Hb, requiring minimum instrumentation and so forth. The user-friendly nature of this technique is quite desirable and beneficial mainly in the remote areas or primary health care centres to monitor the Hb level of patients.

Sources:
[1] F. Arshad et. al., New J. Chem., 44, 6213 (2020)
https://pubs.rsc.org/en/content/articlelanding/2020/nj/d0nj00401d#!divAbstract

By Dr. Amaresh Kumar Sahoo, Assistant Professor,Department of Applied Sciences, IIIT Allahabad, India; Email:asahoo@iiita.ac.in

The 2020 Nobel Prize in Physiology or Medicine is awarded to Prof.Harvey J. Alter, Prof.Michael Houghton and Prof.Charles M. Rice “for the discovery of Hepatitis C virus“. This is a blood-borne disease that has been the reason for more than a million deaths and caused a major health problem around the globe. The viral infection is the leading cause of different types of Hepatitis, with some of its forms that remained dormant for years until developed life-threatening symptoms. Much appreciation to Prof. Harvey J. Alter, Prof.Michael Houghton and Prof.Charles M. Rice for their groundbreaking discoveries that led to the identification of causative agent of this blood-borne disease, a novel virus, Hepatitis C Virus. The committee members of the Nobel Assembly at Karolinsky Institute in Stockholm, Sweden issued several statements regarding the revolutionary impact of this pioneering discovery in understanding the causes and cure for chronic Hepatitis. They added, “for the first time in the history, the disease can now be cured and it also raises hope of eradicating the disease caused by Hepatitis C virus from the world population”.

Infection sources of liver dysfunction and other health issues like fatigue and vomiting. This also causes jaundice characterized by yellow pigmentation of eyes and skin. Moreover, it may cause acute and chronic infections to lead to serious health complications like liver cancer or Cirrhosis. The cases of Hepatitis were seen upsurge rapidly since 1960 due to the increased number of surgeries and multiple blood transfusions. In World Health Organization (WHO) report around 1.34 million deaths mainly due to Hepatitis C virus infections were reported in 2015, which is approximately 63% increase in cases since 1990. Originally only Hepatitis Type A and Hepatitis Type B were known. The discovery of a vaccine for Hepatitis type B partially reduced the risk but chronic liver damage and liver cancer persisted. In the 1970s, Harvey Alter, a senior investigator for the National Institutes of Health in Maryland discovered a new type of Hepatitis Virus while studying the blood transfusion among the patients at the U.S. National Institutes of Health. Later, Michael Houghton, a British Scientist while working for a pharmaceutical firm Chiron then, dedicatedly put the strenuous effort in isolating the genetic sequence of the virus and given a name to this unknown virus as Hepatitis C Virus in 1989. Subsequently, Professor Charles M. Rice consistently worked at the Center for the Study of Hepatitis C as Scientific and Executive Director from 2001 to 2018 at Rockefeller University at New York and provided the final pieces of evidence stating that Hepatitis C Virus alone could cause Hepatitis. This is a RNA virus, which is having envelope glycoproteins such as E1 and E2 on the outside of the viral surface. The hepatitis C virus (HCV) causes hepatitis C, which is contagious in nature, and an infected person may transmit it to a non-infected person via blood contact. Therefore, the transfusions of unscreened blood and blood products or unsterilized medical setups have been found to be the major route of the transmission of HCV infections. It would be mentioned here that different genetic variations (genotypes) are present in the case of HCV strains. Thus, the prescription of the medicines is done based on the genotype of infection of HCV.  Use of combination therapy of recombinant interferon (IFNα) and the nucleoside analogue ribavirin was being recommended initially. However, several side effects and risks factors limit their widespread usages. In this line of interest, the development of drugs was proposed by specifically targeting the viral RNA-dependent RNA polymerase or other vital proteins.

The work of these three Nobel Laureates distinctively characterizes this form of Hepatitis from other clinical entity and found to be caused by an RNA virus of the Flavivirus family, termed as Hepatitis B virus. It is a milestone achievement that paved the way for the introduction of a new screening technique and an effective antiviral drug in medicine that could dramatically reduce the risk of Hepatitis C infection. 

Ref : https://www.nobelprize.org/prizes/medicine/2020/summary/#main-navigation-js

Dielectica traverses through the literature on this topic– and summarizes as they appear.

Correspondence prepared by: Suman Chakraborty, Physical Research Laboratory, Ahmadabad, Gujrat, India, email: suman.chakrabarty37@gmail.com (05:10:2020, 18:30 IST)

Key Words: Magnetosphere, Radiation belts, Space environment, Radiation Belt Storm Probes

Ahmedabad, India: Any planet that has a magnetic field is capable of deflecting charged particles travelling towards it and forms a protective cavity around itself called the magnetosphere. Besides shielding the planet from charged particles, the magnetosphere is also capable of trapping charged particles along magnetic field lines, forming a region called the radiation belts. The Earth’s radiation belts were discovered in 1958 by James Van Allen, a physicist at the University of Iowa using a simple cosmic ray experiment consisting of a Geiger counter and a tape recorder on the first US satellite, Explorer 1. During the flight, radiation levels seemed to increase and then suddenly drop to zero and then again to increase followed by a further sudden drop to zero. What the team soon realized was that regions appearing as zero were really off the scale! These high-radiation regions were mapped and identified as the radiation belts which are now often dubbed as the “Van Allen Radiation Belts” after the name of James Van Allen [1].

So, what are the radiation belts?
The Earth’s radiation belts are two giant donut-shaped regions of magnetically trapped, highly energetic charged particles with the Earth sitting at the center of the “donut hole”. It comprises of an inner belt and an outer belt with a “slot region” separating the two belts [1,2].

The figure shows the Van Allen Radiation Belts with the Earth at its center. We can clearly see a two-belt structure with a region of depleted charged particles in between the two belts. Although numerous studies have been conducted for the past several decades, the most prominent outcomes came since the launch of the Van Allen Probes in 2012. The Van Allen Probes (VAP; 2012 – 2019), initially known as the Radiation Belt Storm Probes (RBSP), were two identical spacecrafts that were deployed to study the Van Allen Radiation Belts. NASA conducted the VAP mission as part of the “Living with a Star” program. It was initially planned for 2 years, but eventually operated for 7 years. The probes showed that the radiation belts are even more complex than previously imagined and the shape of the belts depends on what particles are being studied. Such observations are more important today as our society now relies on more than 800 satellites operating in the radiation belts for communication and navigation. Dr. David Sibeck, VAP mission scientist at NASA’s Goddard Space Flight Center in Maryland, in a 2018 statement said, “Our current technology is ever more susceptible to these accelerated particles because even a single hit from a particle can upset our even smaller instruments and electronics. As technology advances, it’s actually becoming even more pressing to understand and predict our space environment“[1].

Part of interest to study the radiation belts came from its location. It is known that the radiation belts can expand and contract depending on solar activity. During intense solar activity, the belt can expand and even extend over the orbit of the International Space Station (ISS; Orbit height: 408 km). The ISS has been permanently inhabited since 2000, with typical astronauts staying there for six months at a time. In 2015 – 2016, NASA astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko remained there for almost a year. As astronauts stay in orbit for longer duration, their radiation exposure may also increase, leading to concerns about long-term habitation for astronauts in space. The knowledge of space environment is also necessary to design future spacecrafts in order to prevent them from short out due to an electrical overload that may lead to disruption of communication. All these aspects make the radiation belts a hot topic of research for the space science community. In an August 2016 NASA statement, Dr. Sibeck said, “We study radiation belts because they pose a hazard to spacecraft and astronauts. If you knew how bad the radiation could get, you would build a better spacecraft to accommodate that” [1].

Sources:
[1] https://www.space.com/33948-van-allen-radiation-belts.html
[2] https://www.nasa.gov/mission_pages/rbsp/mission/fun-facts.html

Dielectica traverses through the literature on this device – and summarizes as they appear.

Correspondence prepared by: Priyanka Bhadra and Chandra Kishore, email: himimimi2006@gmail.com (28^th September, 2020 10:20 JST)

Dielectica traverses through the literature on this device – and summarizes as they appear.

Correspondence prepared by: Sourabh Pal, Indian Institute of Technology, Kharagpur, India. Email id: sourabhelt92@gmail.com (24^th September, 2020 08:30 IST)

KOLKATA: Portable electronic devices have now become an indispensable part of our life. The conventional electronic systems pervade in every aspect of human life, whether it is mobile phones, televisions, computers, or medical instruments, and many more. Most of electronic devices has been conquered by optoelectronics which can offer the purposes that are not possible with simple electronics. They can transmit information to a much longer distance at a significantly higher rate. Optoelectronic devices engage those electronic devices that engender light, control light, and convert optical signals into electrical ones. Optoelectronics has become the subject matter of extensive research in recent years, leading to the development of various commercial products, such as light emitting diodes (LEDs) for home lightning and display panel in television, semiconductor lasers as emitters, and photodiodes as detectors for application in communication, medical and defense and solar cells as a renewable energy source for electricity production.

While many of these optoelectronic devices are very well developed and industrially feasible, more fundamental research is required to improve their efficiency and reduce the cost. In the past few decades, inorganic materials such as silicon and III-V compound semiconductors are widely used in manufacturing the aforementioned optoelectronic devices. However, complex manufacturing processes of such devices lead to a higher production cost. Additionally, the high temperature fabrication steps required in the manufacturing process of inorganic devices creates several difficulties for industrializations. Hence, as a savior of current research society, the researchers have discovered a new class of semiconducting materials: the hybrid organic inorganic metal halide perovskites which have been extensively explored for application in optoelectronic devices owing to the extraordinary electrical and optical properties. These materials are expected to benefit from the striking features of both inorganic and organic materials, such as high charge carrier mobility and low temperature processing possibility. The research on perovskite based devices has experienced rapid growth since the last decade.

The perovskite (CaTiO₃) is a kind of mineral, which was first identified by Russian mineralogist Gustav Rose in 1839 while performing mineralogical studies at Ural mountains. The mineral was named “perovskite” in the honor of Russian mineralogist Count Lev Aleksevich Von Perovski (1792–1856)[1]. Thereafter, the materials with the crystallographic structure similar to the CaTiO₃, like ABX₃ are referred to as perovskite. Here ‘A’ denote positively charged large atomic or molecular cations situated at the center of the cube, ‘B’ atoms also of positive charges located at the corners of the cube, and X is an anion (negatively charged) smaller in size, placed at the faces of the cube. The fascinating properties such as ambipolar charge transport, high charge mobility, large absorption coefficients, band-gap tunability, lower exciton binding energy, large diffusion length resulted in the incredible attention in perovskites and their promising applications, ranging from solar cell, novel lasers, photo detectors to field effect transistors among others. During the past few years, it has been observed that the conventional perovskite based materials exhibit excellent photoluminescence quantum yields with tunable light emission property over the entire visible spectral range. Utilizing these exciting luminescence properties, Prof. Zheng and his group from Nanjing University of Science and Technology, China fabricated highly efficient LED devices in 2015, from which the new era of quantum LEDs (QLED) has been commenced [2]. The gradual increment of the efficiency of electricity-driven LEDs has been updated every year, which makes the practical application much more feasible. Prof. Wang and a research team of Penn State researchers made the discovery while synthesizing perovskite materials for use in next generation solar cells [3]. Perovskites with a crystal structure good at absorbing visible light are an area of focus in developing both rigid and flexible solar cells that can compete commercially with traditional cells made with silicon. These 2D perovskite materials are cheaper to fabricate than silicon and can be equally efficient at absorbing sunlight. The material offers power conversion efficiencies similar to silicon solar cells but can also be used to develop flexible semi-transparent and light-weight cells appropriate for applications in buildings and a variety of urban spaces. In 2019, a group of Steve Albrecht from Helmholtz Young Investigator Group (YIG) at HZB (Helmholtz-Zentrum Berlin) and Bernd Stannowski from the HZB Institute PVcomB (Competence Centre Photovoltaics Berlin) have developed a tandem solar cell made of the semiconductors perovskite and silicon that converts 29.15 per cent of the incident light into electrical energy [4]. These are the highest recorded values reported for scalable perovskite solar cells. Recently, NASA stated that a quick way to secure a reliable supply of electricity for an extended stay on the Moon or Mars would use an ink-jet-like printer to make super-thin solar cells from perovskites [5]. This can undoubtedly open up a new pathway towards science and technology. Hence, the remarkable potential demonstrated by the perovskites could lead to a breakthrough in optoelectronics technology. Innovative research on perovskite based devices would further contribute towards the development of a sustainable and accessible electronic world.

Sources:

1. “Perovskite: Name Puzzle and German-Russian Odyssey of Discovery” by Eugene A. Katz; DOI: 10.1002/hlca.202000061.
2. “Quantum Dot Light-Emitting Diodes Based on Inorganic Perovskite Cesium Lead Halides (CsPbX3 )”, Adv. Mater. 2015, 27, 7162–7167; DOI: 10.1002/adma.201502567.
3. “Distinct conducting layer edge states in two-dimensional (2D) halide perovskite”, Science Advances, 2019; 5 (7); DOI: 10.1126/sciadv.aau324.
4. “Highly efficient monolithic perovskite silicon tandem solar cells: analyzing the influence of current mismatch on device performance”, Sustainable Energy & Fuels, 2019, 3, 1995–2005; DOI: 10.1039/c9se00120d.
5. “Building Solar Panels in Space Might be as Easy as Clicking Print”, NASA; Website: www.nasa.gov/feature/glenn/2019/building-solar-panels-in-space-might-be-as-easy-as-clicking-print.

Dielectica traverses through the literature on this device – and summarizes as they appear.

Correspondence prepared by: Aakash Hossain, School of Materials Sciences and Nanotechnology, Jadavpur University (23^rd September, 2020 08:30 IST)

KOLKATA: The advent of nuclear science and production of atomic energy was started in India under the initiative of a group of scientists led by physicist Dr. Homi Jehangir Bhabha (often referred as “The Indian Oppenheimer”) shortly after the independence of India on 15th August’ 1947. This led to the formation of the Atomic Energy Act in 1948, which created the Indian Atomic Energy Commission, whose purpose was to develop and control the atomic energy to fulfil the necessities connected with it. During that time, the Prime Minister of India, Jawaharlal Nehru believed that India’s nuclear program primarily to be focussed on peaceful applications and not for the creation of any weapons [1]. Although, he later opened the doorway for using nuclear energy to create weapons, for which the nation was compelled to do so. India also opposed the Baruch Plan of the United States [2], which proposed an American monopoly on the control of nuclear energy, on the grounds that such a plan restricted national research and development of atomic energy.

In 1954, the construction of the Bhabha Atomic Research Centre (BARC) at Trombay led to the serious development of India as a nuclear power and eventually BARC became the primary research centre for India’s nuclear energy program. In 1955, Canada collaborated with India by providing a nuclear reactor based on the National Research Experimental Reactor (NRX) at Chalk river, Ontario[3]. The Canada-India Reactor Utility Services (CIRUS) was established thereafter, which completed the project in July 1960. However, most of the plutonium grade weapons, which were produced by CIRUS, were used for India’s first nuclear test. A further agreement was signed at that time with the United States government for providing 21 tons of heavy water for the reactor under the “Atoms for Peace” program ^[4]. Later on, India designed a pool type reactor in 1955, for which United Kingdom Atomic Energy Authority used to supply uranium fuel elements ^[5]. The reactor named as Apsara, was inaugurated by Jawaharlal Nehru in 20^th January 1957 ^[6]. Finally, in 1958, a third reactor was designed in Trombay, named as ZERLINA (Zero Energy Reactor for Lattice Investigation and New Assemblies) which was commissioned in 1961^[7].

In February 1965, Dr. Bhabha visited Washington DC seeking for an American collaboration through the project Plowshare program, in which India could initiate peaceful nuclear explosions to test her nuclear weapons. But at the end, America went against this nuclear co-operation with India. In the year 1966, physicist Dr. Raja Ramanna took charge as the head of BARC after Dr. Bhabha’s death in a plane crash and became the principal designer behind India’s first nuclear device. India wanted to eliminate the western interference in her journey towards being a nuclear power. In the year 1968, India refused to sign the Nuclear Non-Proliferation Treaty (NPT) which could not differentiate between military and peaceful nuclear explosion and it only recognised the United States, Britain and Soviet Union as nuclear weapon states. In September 1972, under the leadership of Dr. Raja Ramanna and with the approval of Prime Minister, Indira Gandhi, India got the approval for testing her first nuclear device. Finally, on 18th May 1974, BARC tested the first nuclear explosive device weighing 3000 pounds and creating an energy surge equivalent to 8 kilotons of TNT. A team of 75 scientists were involved in the designing of the plutonium device. The test, officially known as Pokhran I, was very often referred as the “Smiling Buddha” ^[8]. After this test, India lost her support from Canada and the United States of America, who considered it as a violation of the “Atoms for Peace” program. After 1974, India had to face difficulties in procuring nuclear materials from a suddenly hostile international market. Almost two decades went by for preparing a nuclear arsenal which was capable of military deployment. The BARC leadership, after facing all the challenges, constructed its largest nuclear plant till date which is the Dhruva reactor in 1977 at Trombay which reached its full potential by 1988. Consequently, the Defence Research and Development Lab (DRDL) designed short range (Prithvi) and long range (Agni) missiles both of which were equipped with nuclear warheads. During the regime of Prime Minister Atal Behari Vajpayee, India officially became a nuclear state. Five nuclear devices were tested on May 11th 1998 under the Pokhran II series during the period of physicist Dr. Rajagopala Chidambaram as head of BARC. Although not all of them detonated, the energy surge created was equivalent to 45 kilotons of TNT (16 kilotons according to independent sources). After this massive success, India established the National Security Advisory Board, where a no first-use-policy was devised for Indian nuclear weapons. But it was later amended that if any biological or chemical attack initiated against India, these nuclear weapons can be used. In 2005, India signed a civil nuclear agreement with the United States of America, by which India got an access to buy nuclear materials through international suppliers in exchange of which India has to protect the civilian nuclear facilities, which also includes inspection by the International Atomic Energy Agency [9]. To this day, the prime minister of India, Narendra Damodar Modi chairs the Nuclear Command Authority to call for a nuclear strike. The estimated nuclear warheads possessed by India at present are 135. Henceforth, for every Indian it is a matter of pride that India has achieved and still continues to achieve milestones in nuclear research, which not only makes Indian military strong but is also playing an important role in the daily lives of ordinary civilians.

References- 

1. International nuclear programs- Indian Nuclear program. Atomic Heritage Foundation
2. The Baruch Plan by Bernard Baruch (June 1946). Atomic Heritage Foundation
3. 50 year old Research N-Reactor shut down. Outlookindia.com/newswire
4. Eisenhower’s Atoms for Peace program-Nuclear Power Today. Atomic Heritage Foundation
5. “India’s First atomic reactor- Science Notes and News” . Current science. August 1956. Retrieved 3rd September 2017
6. “Apsara Nuclear Reactor”- NTI Nuclear Security Index. Retrieved 12th April 2015. Archived 19th April 2015
7. “Atomic Research for Asian Welfare”- Press Information Bureau of India. Archived from the original from August 8th 2017 
8. “Bhabha’s quest for the bomb” by George Perkovich- Bulletin of the Atomic Scientists. Vol. 56 No. 3. Pages 54-63 
9. U.S.- India: Civil Nuclear Cooperation. Archive of the U.S. Department of State.