Graphene nanoribbons grow due to dominolike effect

first_img Explore further Long and narrow, free of defects, and soluble: graphene nanoribbons by bottom-up synthesis (PhysOrg.com) — While many labs are trying to efficiently synthesize large two-dimensional sheets of graphene, a team of researchers from Sweden and the UK is investigating the synthesis of very thin strips of graphene just a few atoms wide. In contrast to graphene, these graphene nanoribbons have a unique electronic structure including a non-zero band gap, which makes them promising candidates for semiconductor applications. But, as with graphene sheets, one of the greatest challenges for now is finding a way to efficiently synthesize these graphene nanoribbons. In their study, researchers Jonas Björk and Sven Stafström from Linköping University in Sweden and Felix Hanke from the University of Liverpool in the UK have used a powerful supercomputer at Linköping University to investigate how graphene nanoribbons grow from an anthracene polymer on a gold substrate. The results of their study are published in a recent issue of the Journal of the American Chemical Society.The scientists discovered that, in the most likely nanoribbon growth process, the gold substrate acts as more than just a support where the reaction can take place. The gold actually catalyzes the reaction by attracting hydrogen atoms from the anthracene polymer (which is made of benzene rings) to bind to the gold surface, initiating the first step of the reaction. In this “dehydrogenation” process, two hydrogen atoms from each unit of the anthracene polymer are transferred to the gold surface, leaving behind a carbon-carbon bond. The carbon-carbon bond forms part of graphene’s honeycomb lattice. Meanwhile, the hydrogen atoms are released from the gold surface through desorption into the vacuum. The supercomputer also revealed that this dehydrogenation reaction repeats due to the effects of positive cooperativity: When a polymer unit has a neighbor that has a carbon-carbon bond, its probability for undergoing the same reaction and gaining its own carbon-carbon bond increases. The result is that the reaction, which starts at one end of the polymer, propagates unit by unit through the entire polymer in a domino-like fashion. After several minutes, the entire polymer is transformed into a well-defined graphene nanoribbon with a width of seven carbon atoms.Figuring out how graphene nanoribbons are synthesized in this way is a complicated molecular-scale process that can only be unraveled in detail by powerful supercomputers. Although there are a few other reaction pathways that the reaction could take, the researchers calculated that this reaction is very highly favored over the others: They estimated that 10,000 reactions proceed along this route than by the second most favorable reaction. Understanding the reaction will allow the researchers to identify the best fabrication method for future experiments and development. “This is a question about how to build materials, either ‘bottom-up’ (synthesis from its constituents) vs. ‘top-down’ (taking something bigger and cutting it to size),” Hanke told PhysOrg.com. “The bottom-up in the graphene nanoribbons approach is very interesting as it allows us to start with the ultimate size limit for a material (an atom, or, say, a small molecule) and then add only those pieces that are really, really needed. Moreover, it also allows us to make graphene nanoribbons that have consistently the same width of, say, seven Angstroms (7×10-10 m), simply by making sure that the ingredients are only polyanthracene and not anything much bigger. This sounds trivial, but it is actually very difficult to achieve in top-down approaches, particularly if atomic precision is desired.”The applications of graphene nanoribbons (and graphene itself) are still in the very early stages, but their properties make the materials look promising. Previous studies have shown that controlling the widths and edge structures of graphene nanoribbons can tune the ribbons’ electronic properties, which could lead to molecular-based electronics such as transistors. By gaining a better understanding of how graphene nanoribbons grow, including the catalytic role of the gold substrate and domino effect of the reaction, scientists have taken another step toward this future technology.“The main hype behind graphene nanoribbons is that you should be able to use them for semiconductor applications, which is due to their highly desirable electronic structure that is different from the electronic structure of graphene,” Hanke said. “The beauty of graphene nanoribbons is that their electronic response is determined simply by their shape. Therefore, being able to understand and build graphene nanoribbons in a controlled manner is a very important process for the continued development of electronics. In particular for anthracene-based nanoribbons, we have a width that is still about 30 times smaller than what is available in current semiconductor-based electronics.” Copyright 2011 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.center_img More information: Jonas Björk, et al. “Zipping Up: Cooperativity Drives the Synthesis of Graphene Nanoribbons.” Journal of the American Chemical Society. DOI:10.1021/ja205857a Citation: Graphene nanoribbons grow due to domino-like effect (2011, September 15) retrieved 18 August 2019 from https://phys.org/news/2011-09-graphene-nanoribbons-due-domino-like-effect.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Computer simulations show that graphene nanoribbons can grow from anthracene polymer on a gold surface in a way that resembles the domino effect. Image credit: Jonas Björk, creator. ©2011 American Chemical Societylast_img read more

Danger on ice Android info thaws in cold boot attack

first_img Samsung launches Galaxy A, its first Android smart phone for Korean market (Phys.org)—Can low temperatures yield access to information in the phone’s memory? Researchers found that a “FROST” attack can unlock an Android’s phone data. Their research findings discuss how hackers can freeze their way into a phone’s sensitive data. Researchers at Erlangen University in Germany showed how their cold boot attack method was able to read information from a Samsung Galaxy Nexus running the latest version of Android. Citation: Danger on ice: Android info thaws in cold boot attack (2013, February 18) retrieved 18 August 2019 from https://phys.org/news/2013-02-danger-ice-android-info-cold.html More information: www1.informatik.uni-erlangen.de/frostwww1.cs.fau.de/filepool/projects/frost/frost.pdf © 2013 Phys.orgcenter_img Explore further They said the hack can be achieved even if the phone is protected by a PIN and with its storage disk encrypted. They said they chose the Galaxy Nexus from Samsung because it was the first device with Android 4.0 and consequently it was the first Android-based smartphone with encryption support. Also, since it is an “official” Google phone, they added, it carries an official Android version from Google unmodified by the phone manufacturer. They said that Google releases are most amenable for in-depth security analysis.In their paper, they wrote, “We present FROST, a tool set that supports the forensic recovery of scrambled telephones. To this end we perform cold boot attacks against Android smartphones and retrieve disk encryption keys from RAM. We show that cold boot attacks against Android phones are generally possible for the first time, and we perform our attacks practically against Galaxy Nexus devices from Samsung.”Authors Tilo Mueller and Michael Spreitzenbarth of the Friedrich-Alexander University of Erlangen-Nuremberg discovered that Android’s boot sequence enabled them to perform cold boot attacks, and they observed how valuable information can be retrieved from RAM. According to the researchers, such cold boot attacks can allow the retrieval of sensitive information such as contact lists, visited web sites, and photos, directly from RAM, even though the bootloader is locked. By chilling the Galaxy Nexus, the researchers could bypass security settings and read from the phone’s memory. The recovery tool FROST stands for Forensic Recovery of Scrambled Telephones. In chilling the phone to freezing temperatures, the information lingered on in memory for five or six seconds, which was long enough to pull data out with a computer.Mueller and Spreitzenbarth found they could read data that included images, e-mails and web browsing history.Their research is not a first in explorations into cold-boot attacks, which were in evidence as early as 2008, shown on PCs. Their research, however, focused on mobile devices. The authors referred to data remanence, where the computer RAM holds residual information briefly even after the computer is shut down. Mueller observed that in cooling the phone the contents are lost in five or six seconds, enough time to reboot the phone and access the memory. Rebooting a phone more often may leave less sensitive data in its memory. On the flip side, their research is not only a warning for Android users but may be helpful for forensic experts who attempt to recover data from a seized phone. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Selfdriving vehicles at the microscale

first_img Play A microvehicle avoids collision with an obstacle. Credit: Li et al. ©2017 American Chemical Society The AI planner, which is at the heart of the smart navigation system, can also detect when the microvehicle drifts from its planned path, which can occur due to the presence of noise. In these cases, the AI planner can simultaneously measure the error and guide the microvehicle back onto the path.One of the main applications of this type of smart microvehicle may be in the biomedical field for tasks such as disease diagnostics, drug delivery, and precision surgery. To demonstrate, the researchers showed that the microvehicle can use the camera to sense and distinguish between cancer cells, red blood cells, and mixed cells, by recognizing differences in their size and shape. The AI planner then regards the cancer cells as the targets and the other cells as the obstacles, and plans a path accordingly. (Phys.org)—In a new study, scientists have developed the microscale version of self-driving vehicles: a 5-μm spherical micromotor that autonomously navigates its way through micro-traffic along a micro-maze to reach its final destination. The researchers expect that these “smart microvehicles” have potential applications in biomedical tasks, such as delivering drugs to tumor cells while avoiding healthy cells. Trajectories of a microvehicle through mazes. The path is planned by an artificial intelligence system and the microvehicle is guided by magnetic fields. Credit: Li et al. ©2017 American Chemical Society Citation: Self-driving vehicles at the microscale (2017, August 28) retrieved 18 August 2019 from https://phys.org/news/2017-08-self-driving-vehicles-microscale.html PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen New algorithm, metrics improve autonomous underwater vehicles’ energy efficiency More information: Tianlong Li et al. “Autonomous Collision-Free Navigation of Microvehicles in Complex and Dynamically Changing Environments.” ACS Nano. DOI: 10.1021/acsnano.7b04525 PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreencenter_img Journal information: ACS Nano The scientists, led by Longqiu Li at the Harbin Institute of Technology in China, and Joseph Wang at the University of California San Diego in the US, have published a paper on the smart microvehicles in a recent issue of ACS Nano.”We have embedded artificial intelligence into a micro/nanorobot,” Li told Phys.org. “We introduce a smart microvehicle for precise autonomous navigation in complicated and dynamically changing environments through optimal path planning. Similar to their large vehicle counterparts, the autonomous navigation of microvehicles entails collision-free movement in dynamic environments.”Until now, micro- and nanomachines have been restricted to navigation that uses a closed-loop control system, in which the machines can only move along a predefined path. The new study marks the first demonstration of micromachines that can autonomously navigate complex, dynamically changing environments, such as those with other moving micromachines.The autonomous navigation process consists of three main steps. A CCD camera attached to a microscope takes pictures and sends them to a feature extraction processor, which identifies obstacles and constructs a map of the environment. The map is then sent as input to an Artificial Intelligence (AI) planner, which uses a path-searching algorithm and fuzzy logic approach to determine the shortest collision-free path among multiple possible paths to the destination. The AI planner then sends these travel directions to a magnetic field generator, which orients a magnetic field in such a way as to steer the microvehicle along the collision-free pathway. © 2017 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Play Microvehicles navigate through mazes. Credit: Li et al. ©2017 American Chemical Society “We want to apply the micro/nanorobotic systems in the field of biomedical operations and nanoscale manipulation,” Li said.In the future, the scientists plan to develop more sophisticated autonomous microvehicles, with features such as autonomous braking, “cruise” control, lane-keeping, and the ability to interact with the environment. Explore furtherlast_img read more

A civil spar with words

first_imgAre you among those who enjoy a really interesting volley of arguments that we call debates in the modern world? Then we would suggest you head for this debate that is being organised in the city by the Debating Society of India (DSOI), in association with the Debating Society of Pakistan. The aim of the debate is noble. Eminent members of the civil societies of both countries would get together and argue. The topic? Engagement between members of civil society is by far the most important factor in promoting a lasting peace between India and Pakistan. The arguments will be moderated by author-politician Shashi Tharoor. Also Read – ‘Playing Jojo was emotionally exhausting’Those representing Pakistan will be — Javed Jabbar, former minister of information and broadcasting; political commentator Najam Sethi; lawyer Salman Raja among others.India will be represented by MP Mani Shankar Aiyar, actor Kabir Bedi, ex-foreign secretary Salman Haidar among others. The debate will provide insights into the role and relative importance of these constituent groups in shaping the India-Pakistan peace dynamic. The format of the debate remains traditional — with speakers on either side of the proposition speaking for a set period, followed by a question and answer interaction with the audience. Also Read – Leslie doing new comedy special with NetflixA most interesting feature of the format for the debate is that it will not be a traditional adversarial India versus Pakistan debate. Instead, the teams supporting either side of the proposition will be made up of two Indians and two Pakistanis. This approach is likely to promote a more holistic approach to the issue under debate. Hear them out.DETAILAt: Taj Palace Hotel, Sardar Patel Marg  When: 10 January Timings: 6.30 pmlast_img read more

Sadhana End of an era of style versatility and panache

first_imgAccredited as one of the most stylish actress of Bollywood in the late 1960s and 1970s, especially known for her “fringe hairstlye”, the reign of Sadhana Shivdesani, popularly known as Sadhana, will remain unmatched and motivational in the Indian entertainment industry.Sadhana passed away on Friday morning in Mumbai after a long battle with cancer, a family friend said. She was 74 and a widow, and is survived by her foster daughter. “Sadhana breathed her last at her home this morning,” said a close friend and BJP city spokesperson Shaina N.C. She joined filmdom as a child artiste in 1955 with a minor appearance in veteran actor-filmmaker Raj Kapoor’s film Shree 420 in which she played a cameo role in the song Mud mud ke na dekh. Also Read – A fresh blend of fameLater on, in 1958, she acted in India’s first Sindhi language film Abaana playing a pivotal role, on a token payment of Re.1. When a promotional image of the movie appeared on the cover of a film magazine, it was noticed by a prominent producer, Sashadhar Mukherjee, and she joined his acting school afterwards. Amongst her highly appreciated works include Parakh, Hum Dono, Ek Musafir, Ek Hasina, Asli Naqli, Mere Mehboob (her first colour movie), Woh Kaun Thi, Rajkumar, Waqt, Aarzoo, Mera Saaya, Gaban, Ek Phool, Do Mali among many others.  Also Read – Martin Freeman confirms ‘Black Panther’ returnSadhana even tried her hands in directions with 1972 film Geeta Mera Naam. She is credited with introducing the famous “fringe” haircut – known as her trademark “Sadhana Cut” – and tight body-hugging churidar-kurtas as a much-copied fashion in Bollywood. Her look was inspired from Hollywood icon Audrey Hepburn. She voluntarily retired from Bollywood in 1994. Amongst her last major public appearances, Sadhana along with her relative and actor Randhir Kapoor walked the ramp at a fashion show in May 2014 to support the cause of cancer and AIDS patients.While her death undoubtedly can be considered as a big loss for the entertainment industry, many Bollywood stars including Lata Mangeshkar, Rishi Kapoor, Anupam Kher, Karan Johar and Anushka Sharma have mourned her tragic demise while sharing their feelings on micro-blogging site Twitter.last_img read more

City to pay tribute to Kathak queen Sitara Devi

first_imgFew of us know that Kathak queen Sitara Devi had a very close connection with Bengal. She was born and brought up in Kolkata. Straddling the world of films and classical dance with equal elan, she also trained Bollywood heroines like Madhubala, Jaya Bhaduri, Kajol and Rani Mukerji during her lifetime. At very tender age, Sitara Devi got a chance to perform in front of Gurudev Rabindranath Tagore in Shantiniketan. After watching her performance, Tagore offered her some gifts while she requested for something which was eternal, his blessings. Finally Tagore blessed her with the title Nrityasamragini – Empress of Dance. Sitara Devi was only 16 years old back then. Also Read – Add new books to your shelfShe was recruited into the film industry early but she quit after a few films as she wanted to pursue her career as a Kathak exponent on stage. She made her film debut with Usha Haran in 1940 and went on appearing in films like Roti, Anjali, Mother India and so on. She performed at the Royal Albert Hall, got the Sangeet Natak Akademi Award, Padma Shree, Kalidas Samman but she refused to take Padma Bhusan as she once said, “Is this government not aware of my contribution to Kathak? I will not accept any award less than Bharat Ratna.” Also Read – Over 2 hours screen time daily will make your kids impulsiveOn the occasion of her death anniversary on December 24, Kalindi Darpan Socio-Cultural Organisation is all set to organise Smaran 2016,  remembering her. “She was very fond of Bengal and spoke Bengali fluently. This is the reason why we are holding the event in Kolkata, though Sitara Devi belonged to the Benaras gharana,” said Kathak exponent Vishal Krishna, her grandson. The event will be held at Dum Dum Rabindra Bhawan. Smaran 2016  will feature exponents from Delhi – Amit Khinchi, disciple of Pt Rajendra Gangani (Kathak legend) and Subhi Johri, student of  Pt Jay Kishan Maharaj. But the main performances will be offered by both  artists who are the grandsons of  Sitara Devi – Vishal Krishna and Kushal Krishna (tabla exponent ) from Benaras. Ace dancer Alokananda Roy will be the chief guest at the event.“It’s an honor for us hosting the prestigious event remembering the legend Sitara Devi where her family members are also involved. This is the only festival which is dedicated to the Kathak legend Sitara Devi. We love to promote the rich tradition of Indian classical dance forms among the youth”, said Soumali Ganguly, Secretary, Darpan socio-cultural organisation.last_img read more

A true expression of creativity

first_imgThere are two directions artists can take in their work. Most establish a distinctive, easily recognizable style, and then remain in that groove. But for Shakti Maira, an artist, sculptor and print maker, things are totally different. His work done over a period of time, when brought together, may look more like a group show. The freedom to strike out in new directions is a true expression of his creativity, which could be described as ‘formed resonance’. His materials and styles move with, and respond to, his life journey. Also Read – Add new books to your shelf ‘Formed resonance’ – an exhibition of sculptures in wood and bronze, by Shakti Maira, is a celebration of art which is an intimate engagement between the artist’s mind and hands. In this exhibition, Shakti will present three-dimensional and two-dimensional works that are created through marks and strokes. There are four groups of drawings in this show .A set of ‘Figure Drawings’ , a small suite of ink drawings and paintings titled ‘Mother India and Her Sons’ that Shakti did when the Ramjanmabhoomi-Babri Masjid tensions were roiling in India, saddened by what India’s sons were doing to a pluralistic nation , a few charcoal drawings that celebrate music and singing, and lastly, a recent group of drawings called ‘The Origin of Form’. It will be inaugurated by Krishen Khanna today.last_img read more