Properties of Topological Insulating Material: Bi2Te3-PANI

Properties of Topological Insulating Material: Bi2Te3-PANI Synthesis, Characterization and Electrical properties of a Composite of Topological Insulating Material: Bi2Te3-PANI R. R. Urkudea[*], P. T. Patilb, S. B. Kondawarb, U. A. Palikundwara[† ] aX-ray Research Laboratory, Department of Physics, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur 440033, India bPolymer Nanotech Laboratory, Department of Physics, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur 440033, India Abstract In the present work, we carried out a systematic study of structure, UV-Vis Spectra and surface conductivity of pure Bi2Te3, pure Polyaniline (PANI) and Bi2Te3 (5%)-PANI (95%) composite. Bi2Te3 was synthesized by a method similar to solvothermal method, whereas, pure PANI and Bi2Te3-PANI composite were synthesized by a chemical oxidative method. The materials were structurally characterized and the electrical properties were investigated in the temperature range from room temperature to 100 °C. The electrical conductivity of the Bi2Te3-PANI composite is found to be higher than that of its pure constituents at all the temperatures. The enhancement in the surface conductivity may be due to the PANI generated ordered molecular arrangement of Bi2Te3 in the Bi2Te3-PANI composite, as confirmed from powder x-ray diffraction, UV–vis spectral analysis.  © 2015 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the International Conference on Nanomaterials and Technologies (CNT 2014). Keywords: Topological insulators; Bismuth telluride; thermoelectric material; Polyaniline composites; electrical conductivity. 1. Introduction Topological insulators (TIs) are electronic materials that have a bulk band gap like an ordinary insulator but have protected conducting states on their edge or surface (Hasan and Kane, 2010). Most of the current researches are focused on the materials, like Bismuth telluride (Bi2Te3), Antimony telluride (Sb2Te3) and Bismuth selenide (Bi2Se3) due to the topological insulating properties exhibited by them. Bi2Te3 is one of the best TI materials. It is a semiconducting compound with narrow bulk band gap of 0.2 eV. It is also a good material for thermoelectric applications (Das and Soundararajan, 1988). It has shown a drastic change in its thermoelectric properties when it is doped with Polyaniline (PANI) (Li et al., 2011). It has also given added advantages of polymers like inexpensiveness, intrinsically low thermal conductivity, flexibility and good processability etc. (Marjanovic et al., 2013). Various research workers have attempted to synthesize and characterize composites of Bi2Te3 with polyaniline (Zhao et al., 2002; Xu et al., 2005; Hostler et al., 2006; Chatterjee et al., 2009; Toshima et al., 2011). Very recently, mechanical blending method was employed by Li et al. (2011) for the synthesis of Bi2Te3–PANI; they found that the power factor of the composite is less than both of the individual components. However, a report on the synthesis of a Bi2Te3 and PANI hybrid by physical mixing and solution mixing showed a higher power factor in the case of the physical mixture (Toshima et al., 2011). Though there is a vast literature available on the TE properties of Bi2Te3-PANI composites, experimental reports on TI Properties of the composites are not available. Based on this background, in the present work, we carried out a systematic study of structure, UV-Vis Spectra and surface conductivity of Bi2Te3 (5%)-PANI (95%) composite, pure Bi2Te3 and pure PANI. Bi2Te3 was synthesized by a method similar to solvothermal method (Deng et al., 2002), whereas, pure PANI and Bi2Te3-PANI composite were synthesized by a chemical oxidative method (Stejskal and Gilbert, 2002). The materials were structurally characterized and the electrical properties were investigated in the temperature range from room temperature to 100 °C. The electrical conductivity of the Bi2Te3-PANI composite is found to be higher than that of its pure constituents at all the temperatures. The enhancement in the surface conductivity may be due to the construction of highly ordered chain structures of PANI on Bi2Te3, as confirmed from powder x-ray diffraction (XRD), UV–vis spectral analysis. 2. Experimental details 2.1 Materials used Bismuth chloride (BiCl3), Tellurium (Te) metal powder, Potassium hydroxide (KOH), Sodium borohydrate (NaBH4), N-N dimethylformamide (DMF), Hydrochloric acid (HCl), Aniline (C6H5NH2), Acetone [(CH3)2.CO], Methanol (CH3OH) were purchased from Merck Chemicals. Ammonium persulphate [(NH4)2S2O8] was purchased from Hi-media. All the chemicals were of analytical reagent grade and are used without further purification, except aniline which was purified prior to use. 2.2 Preparation of Bi2Te3 A mixture of BiCl3 (10 mmol), Te powder (15 mmol), KOH (80 mmol) and NaBH4 (30 mmol) were put into a beaker of 100 ml capacity. The beaker was then filled with N-N dimethylformamide (DMF) up to 90 ml and was kept into a muffle furnace. Temperature of the furnace was maintained at 100-180 °C for 24 hours and was then slowly cooled to the room temperature. The product was filtered, washed with double distilled water and dried in vacuum oven at 80 °C for 12 hours. 2.3 Preparation of pure PANI and Bi2Te3 PANI Composite PANI was synthesized by using chemical oxidative method (Stejskal and Gilbert, 2002) 0.2 mol Aniline with 0.25 mol Ammonium persulphate was oxidized in acidic aqueous medium. Aniline and Ammonium persulphate were dissolved, separately, in 50 ml solution of 1.0 mol HCl in double distilled water. Both the solutions were kept at room temperature for 1h and were mixed together in a beaker. During the process, the colour of the solution changed from colourless to light blue and then to dark green. The solution was briefly stirred and was left to polymerize for 24 h. The precipitate of PANI was collected on a filter paper, washed with distilled water, then with 20 ml of 0.1M HCl and with Methanol. PANI (emeraldine salt) powder was dried in vacuum oven at 80 °C. A similar procedure was followed for the synthesis of Bi2Te3-PANI composite, but this time Bi2Te3 was introduced in aniline solution. 3. Characterization 3.1 Structural characterization The samples were structurally characterized by XRD and UV–vis spectral analyses. XRD measurements were performed using a Diffractometer (Rigaku Miniflex II x-ray Diffractometer) with Cu KÃŽ ± radiation (ÃŽ » = 1.541838 A °). The UV–vis spectra of the prepared samples were recorded by a spectrophotometer (UV-1800 Shimatzu Spectrophotometer) using samples dissolved in dimethyl formamide in a quartz cuvette. 3.2 Electrical characterization All the prepared samples were pressed at pressure less than 5 tonnes, at room temperature, to form the compacted pellets for measurement of the electrical conductivity. The measurements were carried out, in the temperature range 20-100  °C, by standard four-probe method with constant current source kept at 2 mA. 4. Results and Discussions 4.1 Powder X-ray diffraction Figure 1 shows the XRD patterns of Bi2Te3, pure PANI and Bi2Te3-PANI composite. All the peaks of the pattern for Bi2Te3 can be indexed in rhombohedral structure (JCPDS No: 015-0863) with unit cell parameters: a = 4.358A °; b = 4.358A ° and c = 30.48A °. Broad peaks at 22 ° and 25 ° for pure PANI are observed, which are due to the repeat unit of monomer. Compared with the pure PANI, only one peak is clearly observed at 25 °, the same position, in the XRD pattern of Bi2Te3-PANI composite. The observation of a single peak is related to the monodistribution of the periodicity of the repeat unit of the PANI and ordering of the molecular arrangement of the Bi2Te3 in the PANI matrix (Talwar et al., 2014). This suggests that PANI generate an ordered molecular arrangement of Bi2Te3 in the Bi2Te3-PANI composite. Figure 1 XRD patterns of Pure PANI, Pure Bi2Te3 and Bi2Te3-PANI composite 4.2 UV-vis spectroscopy Figure 2 shows the UV–vis spectra of the samples used to explore the electronic states of Bi2Te3, pure PANI and the Bi2Te3-PANI composite. A characteristic band centred at 697 nm, a shoulder at 478 nm, corresponding to a polaronic transition (polaron- Ï€*) and a band around at 389 nm, assigned to the π–π* electron orbital transition are observed in Bi2Te3-PANI composite. In comparison with UV–vis spectra of the pure PANI: a band around 385 nm, assigned to the π–π* electron orbital transition, shifts to longer wavelength at 389 nm in Bi2Te3-PANI composite. The polaronic transition (polaron- Ï€*) is absent in the pure PANI but is observed in Bi2Te3-PANI composite. These show an interaction between the quinoid ring of PANI and Bi2Te3 (Xia and Wang, 2003). This is a signature of an ordered molecular arrangement in Bi2Te3-PANI composite and it is the purely surface conducting state. Figure 2 UV-vis spectra of Pure PANI, Bi2Te3 and Bi2Te3-PANI composite 4.3 Electrical characterization Figure 3 Variation of the electrical conductivity with temperature of Bi2Te3, PANI and Bi2Te3-PANI composite. The variations of electrical conductivity as a function of temperature of the prepared samples are shown in figure 3. The value of electrical conductivity for Bi2Te3 slightly decreases with the increase in the temperature. However, both PANI and Bi2Te3-PANI composite show increase in the value of electrical conductivity with temperature. The electrical conductivity of the Bi2Te3-PANI composite is higher than that of its pure constituents over a whole temperature range. The enhancement in the surface conductivity indicates the increase in protected states at the surface compared to that of the pure Bi2Te3. This may be due to the large surface provided to the Bi2Te3 by the PANI generated ordered molecular arrangement of Bi2Te3 in the Bi2Te3-PANI composite. 5. Conclusions In conclusion, we carried out a systematic study of structure, UV-Vis Spectra and surface conductivity of Bi2Te3 (5%)-PANI (95%) composite, pure Bi2Te3 and pure PANI. Bi2Te3 was synthesized by a method similar to solvothermal method, whereas, pure PANI and Bi2Te3-PANI composite were synthesized by a chemical oxidative method. The materials were structurally characterized and the electrical properties were investigated in the temperature range from room temperature to 100 °C. The electrical conductivity of the Bi2Te3-PANI composite was found to be higher than that of its pure constituents at all the temperatures. The enhancement in the surface conductivity may be due to the PANI generated ordered molecular arrangement of Bi2Te3 in the Bi2Te3-PANI composite, as confirmed from powder x-ray diffraction (XRD), UV–vis spectral analysis. Acknowledgements It is a pleasure to thank Dr. S. B. Kondawar for helpful discussions. This work was supported by the Department of Science and Technology (DST), India, under women scientist scheme-A (WOS-A), File No. SR/WOS-A/PM-1001/2014. References Chatterjee K., Suresh A., Ganguly S., Kargupta K., Banerjee D., 2009. Bismuth nitrate doped polyaniline – Characterization and properties for thermoelectric application. Mater. Charact. 60, 597–601. Das Damodara V., Soundararajan N., 1988. Size and temperature effects on the thermoelectric power and electrical resistivity of bismuth telluride thin films, Phys. Rev. B 37, 4552-9. Deng Yuan, Xi-song Zhou, Guo-dan Wei, Jing Liu, Ce-Wen Nan, Shu-jing Zhao 2002. Solvothermal preparation and characterization of nanocrystalline Bi2Te3 powder with different morphology, J. of Phy. and chem. of Solids. 63, 2119-2121. Hasan, M., Z., Kane, C., L., 2010. Colloquium: Topological insulators, Reviews of modern physics 82, 3045-23. Hostler S., R., Kaul P., Day K., Qu V., Cullen C., Abramson A., R., 2006. Thermal and electrical characterization of nanocomposites for thermoelectric, IEEE ITHERM 07803295, 24, 1400–5. Li Y., Zhao Q., Wang Y., Bi K., 2011. Synthesis and characterization of Bi2Te3/Polyaniline composites, Mater. Sci. Semicond. Proc. 14, 219-222. Marjanovic, G., C., 2013. Recent advances in polyaniline composites with metals, metalloids and nonmetals, Synthetic Metals 170, 31-56 Stejskal J., Gilbert R.., G., 2002. Polyaniline: Preparation of a Conducting Polymer, Pure Appl. Chem. 74, 857-867. Talwar V., Singh O., Singh R., C., 2014. ZnO assisted polyaniline nanofibers and its application as ammonia gas sensor, Sensors and Actuators: B 191, 276-282. Toshima N., Imai M., Ichikawa S., 2011. Organic–Inorganic Nanohybrids as Novel Thermoelectric Materials: Hybrids of Polyaniline and Bismuth (III) Telluride Nanoparticles, J. Electron. Mater. 40, 898–902. Xia H., Wang Q., 2003. Preparation of Conductive Polyaniline/ Nanosilica particle composites through Ultrasonic Trradiation, J. Appl. Polym. Sci 87, 1811-7. Xu X., Chen L., Wang C., Yao Q., Feng C., J., 2005. Template synthesis of heterostructured polyaniline/Bi2Te3 nanowires, Solid State Chem. 178, 2163-6. Zhao X., B., Hu S., H., Zhao M., J., Zhu T., J., 2002. Thermoelectric properties of Bi0.5Sb1.5 Te3/Polyaniline hybrids prepared by Mechanical blending, Mater. Lett. 52, 147–9. [*]* Corresponding author. Tel.: +91 9921491567; fax: +0-000-000-0000 . E-mail address: [emailprotected] [† ] Corresponding author. Tel.: +91 9890155077; fax: +0-000-000-0000 . E-mail address: [emailprotected] [S1]Elsevier to update with volume and page numbers.

Foodborne Illness Short Answer Questions

Complete answers to questions below: What is the infectious agent (pathogen) that causes this infectious disease? For example, the name of the bacteria, virus, or parasite. The process of infection can be broken down into stages, each of which can be blocked by different defense mechanisms. In the first stage, a new host is exposed to infectious particles shed by an infected individual. The number, route, mode of transmission, and stability of an infectious agent outside the host determines its infectivity.Some pathogens, such as anthrax, are spread by spores that are highly resistant to heat and drying, while others, such as the human immunodeficiency virus (HIV), are spread only by the exchange of bodily fluids or tissues because they are unable to survive as infectious agents outside the body. How is this infectious agent transmitted through food or water? Infectious pathogens include some viruses, bacteria, fungi, protozoa, multicellular parasites, and aberrant proteins known as prions.These pathogens are the cause of disease epidemics, in the sense that without the pathogen, no infectious epidemic occurs. The term infectivity describes the ability of an organism to enter, survive and multiply in the host, while the infectiousness of a disease indicates the comparative ease with which the disease is transmitted to other hosts. Transmission of pathogen can occur in various ways including physical contact, contaminated food, body fluids, objects, airborne inhalation, or through vector organisms What is an example of a real life outbreak of this foodborne illness in the United States?In early October 2012, the Clark County Public Health Department (â€Å"the health department†) received the first reports of a cluster of Salmonella Virchow infections occurring in the county. Additional reports came in rapidly, and by October 9, interviews of ill persons indicated that the source of the developing outbreak was the On the Border restaurant in Vancouver, Wa shington. On October 9, On the Border temporarily ceased operation. Dr. Alan Melnick, Clark County Health Officer, stated that the closure was â€Å"a further precaution to reduce the risk of Salmonella spreading to others. Meanwhile, health department staff continued to interview employees and patrons of the restaurant to learn more about the precise cause of the outbreak. The health department also continued its work with On the Border employees to make sure that standard control measures—e. g. hand-washing and environmental sanitation—were in place and effective, so that when the restaurant resumed operation it would not pose a continuing threat to the health of its patrons.As of the date of the restaurant’s closure on October 9, there were 11 confirmed and five probable cases of Salmonella Virchow infection linked to the consumption of food at the restaurant.  · What are the clinical symptoms, duration of the disease, and treatment if any? Viral hepatitis ; Infectious hepatitis The hepatitis A virus is found mostly in the stools and blood of an infected person about 15 – 45 days before symptoms occur and during the first week of illness.You can catch hepatitis A if: You eat or drink food or water that has been contaminated by stools (feces) containing the hepatitis A virus (fruits, vegetables, shellfish, ice, and water are common sources of the hepatitis A virus You come in contact with the stool or blood of a person who currently has the disease, A person with hepatitis, A does not wash his or her hands properly after going to the bathroom and touches other objects or food, You participate in sexual practices that involve oral-anal contact, About 3,600 cases of hepatitis A are reported each year.Because not everyone has symptoms with hepatitis A infection, many more people are infected than are diagnosed or reported. Risk factors include: International travel, especially to Asia or South or Central America IV drug use, living in a nursing home or rehabilitation center, working in a health care, food, or sewage industry What steps can be taken to prevent further outbreaks? Include individual as well as environmental precautions and methods. Preventing hepatitis A: The virus causing hepatitis A is mostly contracted through food and water.Therefore, proper hygiene is very important in this case. Drink filtered water that is free from any kind of germs and viruses. Make sure that the water which you are getting in your house is filtered properly. If you are travelling, then use only commercially bottled water that is sealed properly. Boiling the water before drinking is also helpful in killing the viruses that cause hepatitis. Wash your hands properly before touching any food items and after using the toilet. Follow proper sanitation in and around your house. Eat food that is cooked well and is fresh.

Decision Analysis The Decision - 1528 Words

Introduction Decision analysis provides powerful techniques to structure complex problems, identify optimal choices, and facilitate communication between the decision analyzer and the person makes the decision. One of the most important values of these techniques is that they enable decision making to be rational rather than intuitive or holistic. They provide a framework for rational decision making in an uncertain environment. As modern decision analysis has been studied for more than five decades, there has been significant improvements in the practices used. These methods have been implemented by companies and organizations and proved to be successful as well as constructive. However, there are also plenty of examples when the recommendation were not implemented or even if they were, they failed to truly support the decision maker(s). Kusnic and Owen found that the implementation rate decreases with the importance of the problem (1992). 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Phrasal Verb Definition and Examples in English

A phrasal verb is a  type of  compound  verb  made up of a verb (usually one of action or movement) and a prepositional adverb—also known as an adverbial particle. Phrasal verbs are sometimes called two-part verbs  (e.g., take off and leave out) or three-part verbs (e.g.,  look up to and look down on). There are hundreds of phrasal verbs in English, many of them (such as tear off, run out [of], and pull through) with multiple meanings. Indeed, as linguist Angela Downing points out, phrasal verbs are one of the most distinctive features of present-day informal English, both in their abundance and in their productivity (English Grammar: A University Course, 2014).  Phrasal verbs often appear in idioms. According to Logan Pearsall Smith in Words and Idioms (1925), the term phrasal verb was introduced by Henry Bradley, senior editor of the Oxford English Dictionary. ​​​Examples and Observations Mignon McLaughlin What you cant get out of, get into wholeheartedly. William Shakespeare Put out the light, and then put out the light. Frank Norris I never truckled; I never took off the hat to Fashion and held it out for pennies. By God, I told them the truth. K.C. Cole Clots of excited children egged each other on, egged on their parents, egged on the blue-haired ladies and the teenage lovers and janitor who put down his mop to play. Joseph Heller Major Major had never played basketball or any other game before, but his great, bobbing height and rapturous enthusiasm helped make up for his innate clumsiness and lack of experience. The Semantic Coherence of Phrasal Verbs Laurel J. Brinton Like compounds, phrasal verbs have semantic coherence, evidenced by the fact that they are sometimes replaceable by single Latinate verbs, as in the following: Furthermore, the meaning of the combination of verb and particle in the phrasal verb may be opaque, that is, not predictable from the meaning of the parts. – The Structure of Modern English: A Linguistic Introduction. John Benjamins, 2000) break out: erupt, escapecount out: excludethink up: imaginetake off: depart, removework out: solveput off: delayegg on: inciteput out: extinguishput off: postpone Phrasal Verbs With Up Ben Zimmer [P]hrasal verbs with up have filled a wide variety of roles in both British and American English. Up gets used for literal upward movement (lift up, stand up) or more figuratively to indicate greater intensity (stir up, fire up) or completion of an act (drink up, burn up). It’s particularly handy for blunt imperatives calling for resolute action: think of wake up!, grow up!, hurry up! and put up or shut up! – On Language: The Meaning of ‘Man Up. The New York Times Magazine, September 5, 2010 Phrasal Verbs and Prepositional Verbs A phrasal verb differs from a sequence of a verb and a preposition (a prepositional verb) in [these] respects. Here call up is a phrasal verb, while call on is only a verb plus a preposition:(R.L. Trask, Dictionary of English Grammar. Penguin, 2000) The particle in a phrasal verb is stressed: They called up the teacher, but not *They called on the teacher.The particle of a phrasal verb can be moved to the end: They called the teacher up, but not *They called the teacher on.The simple verb of a phrasal verb may not be separated from its particle by an adverb: *They called early up the teacher is no good, but They called early on the teacher is fine. Also Known As: compound verb, verb-adverb combination, verb-particle combination, two-part verb, three-part verb