Research Highlight: Nanotransfer printing (nTP) set a record low sub-100 nm feature resolution

Researchers at the University of Tennessee (UT) and Oak Ridge National Laboratory (ORNL) developed a new protocol of creating silicon stamps for highly efficient nanotransfer printing (nTP). Current approach mainly relies on in situ formation of a fluoropolymer release layer immediately following anisotropic plasma etching of silicon. The potential of a current nTP approach has been demonstrated by imprinting various functional test structures of low nanometer scale (J. Am. Chem. Soc., DOI: 10.1021/ja201497a).

Deepak Bhandari, graduate student at UT, described the findings as "a technological improvement of nTP feature resolution down to sub-100 nm".

 

A native of Nepal, Deepak obtained both his bachelor and master degree in chemistry from Tribhuvan University, Nepal. After joining UT in Fall 2006, Deepak focused his research on "surface-enhanced Raman Scattering substrates development using both conventional and nanolithographic approaches". Graduating this May 12^th, Deepak joined ORNL as a postdoctoral research associate and plans to pursue career in academia after short postdoctoral experience.

source: http://www.chem.utk.edu/news/SepaniakGroupResearchManuscriptPublishedinJACS.html

More than 1/3rd of Americans and ½ of Germans live within 75 km of a nuclear power plant

Anant Babu Marahatta
Sendai, Japan

Disaster is a disaster. This time, Japan is victimized. No one knows, such catastrophe may happen anytime, anywhere, in the world.　

The current world news is about the crippled Fukushima based Japanese nuclear power plants which was hit by a 9.0-magnitude quake on March 11 of 2011 and then, about 25 minutes later, a devastating tsunami. About 172,000 people lived in the 30-km zone of these plants.

The Japanese government has declared the 20-km evacuation area around the crippled Fukushima No. 1 nuclear power plant a “no-go zone”. It has also urged the residents to abide by the order for their own safety or possibly face fines or detention. Under a special nuclear emergency law, people who enter into the zone will now be subject to fines of up to ¥100,000 and possible detention of up to 30 days.

In order to aware this potential risk of this scenario to the world, a current study released by “Nature” on Friday, 22nd April 2011, shows that about 90 million people worldwide live within 30 kilometers of a nuclear reactor, equivalent to the exclusion zone around Japan's crippled Fukushima plants. The United States alone has nearly 16 million people within this range, followed by more than 9 million each in China, Germany and Pakistan, and 5 to 6 million in India, Taiwan and France.

When the radius is expanded to 75 km, the number of people potentially at risk in case of a nuclear accident jumps to nearly half a billion. More than 110 million are in the U.S., 73 million in China, 57 million in India, 39 million in Germany and 33 million in Japan.

Let’s look at another way; more than 1/3rd of Americans live within 75 km of a nuclear power plant, and nearly half of all Germans.

It does suggest how many people will be at risk if something does go terribly wrong, as happened in Fukushima a month ago and in Chernobyl 25 years ago.

Sources:
‘The Japan Times” daily newspaper.
www.nature.com

A Chemical to capture radioactive substances: "Fukushima-reactors issue"

Anant Babu Marahatta
Tohoku university
Japan

Nuclear energy can be both beneficial and harmful, depending on the way in which it is used. We routinely use X-rays to examine bones for fractures, treat cancer with radiation, and diagnose diseases with the help of radioactive isotopes. Approximately 17% of the electrical energy generated in the world comes from nuclear power plants. 'Nuclear reactors produce electricity so cheaply that it is not necessary to meter it. The users pay a fee and use as much electricity as they want. Atoms provide a safe, clean and dependable source of electricity. '

On the other hand, nuclear hazard which literally means “risk or danger to the human health or to the environment caused by radiation emitted by the radioactive nuclei of a given substance, or the possibility of an uncontrolled explosion originating from a nuclear fusion or fission reaction of atomic nuclei”, that appeared in the Japanese “Fukushima nuclear plants” is the latest example of its negative impact. .

The contamination of the coolant (by radioactive iodine, cesium, and strontium), a mandatory process during nuclear chain reactions, caused by the “Fukushima nuclear reactors leakage” is the current issue of the world. To remove such radioactive substances, recently, a Japanese chemist and a domestic company have jointly developed a powdery chemical that can capture and precipitate radioactive substances in water.

This powder, made of various chemicals and minerals, including zeolite, can remove radioactive substances such as iodine, cesium and strontium, a professor at Kanazawa University said. The powder was able to remove almost 100 percent of cesium when 1.5 grams of the powder were mingled with 100 milliliters of water in which cesium had been dissolved at a density of 1-10 ppm. It has been confirmed to have the ability to remove iodine even at a density of 100 ppm. It is reminded that the densities of radioactive substances seeping into the water at the Fukushima No. 1 nuclear complex are estimated at around 10 ppm. This powder could be used in the ongoing effort to deal with contaminated water at the crippled Fukushima nuclear plant

Regional Chemistry Seminar in Biratnagar on May 7-8, 2011

INVITATION

We are delighted to inform you that Department of Chemistry, Mahendra Morang Adarsh Multiple Campus (Tribhuvan University), Biratnagar with collaboration of Nepal Chemical Society organizing the Regional Chemistry Seminar in Biratnagar, Nepal from May 7- 8, 2011.

We would like to invite you to attend the Seminar and make a grand success.

We look forwards to welcoming you soon in Biratnagar, Nepal

Post Graduate Department of Chemistry
Mahendra Morang Adarsh Multiple Campus, Biratnagar, Nepal

Chemistry Matters: Beauty

From molecules to equations to experiments, learn how and why chemistry is beautiful to Nobel Laureates. This video is one in a series of four, short educational videos capturing 16 Nobel Laureates' opinions on why chemistry matters. 

Chemists Can DANCE!

Potentiometry in Analytical Chemistry

This article was published in SPECTRUM, a science magazine published by ChemSA-Central Department of Chemistry, TU in 2005. I do not know whether this magazine is still being published or not. Since this magazine was published in printed copy only and I had its electronic copy, I want to share it with wide range of readers through NepaChem.-Basant Giri

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Potentiometry is one of the methods used for quantitative analysis in analytical chemistry. Here potential of an electrode in equilibrium with an ion to be determined is measured. There are two ways to quantify the given substance using potentiometry. One is direct Potentiometry and other is potentiometric titration. In direct potentiometry a single measurement of electrode potential is used to determine the concentration of an ionic species in solution.

Potentiometric Titration

In potentiometric titration, the end point is determined by measuring the potential of an indicator electrode as a function of the volume of titrant added. Beherend, in 1893 performed potentiometric titration of chloride, bromide and iodide with mercurous nitrate.

In a simple arrangement for a manual potentiometric titration a reference electrode (e.g. saturated calomel electrode or silver-silver chloride) is coupled with an indicator electrode, which is reversible with one of the ions involved in the titration. The emf of the cell containing the initial solution is determined and emf of the cell after each addition of titrant solution is also measured. Sufficient time should be allowed after each addition for the indicator electrode to reach a reasonably constant potential (~ 1-2 mV) before the next increment is introduced. In this procedure, we are concerned with changes in emf of the cell which is due to the change in concentration of ions reversible to the indicator electrode. Advantages of potentiometric titrations over 'classical' visual indicator methods are:

1. Can be used for coloured, turbid or fluorescent analyte solution.
2.  Can be used if there is no suitable indicator or the colour change is difficult to ascertain.
3. Can be used in the titration of polyprotic acids, mixtures of acids, mixtures of bases or mixtures of halides.

Types of Potentiometric Titration

Depending on the type of the reactions involved to which potential measurement can be applied for end point detection, potentiometric titrations can be classified into followings.

(a) Acid-Base Titration: An electrode, reversible to hydrogen ion (e.g. glass, quinhydron, antimony etc.) is employed in order to follow the progress of acid-base reactions. The potential of such electrode at 25 deg C is given by an equation of the form E = E^o + 0.0591pH., Where E^o is a constant potential depending on the experimental arrangement, the liquid junction potential(s) and reference electrode. Satisfactory results are obtained in all acid-base titrations except (a) where either the acid or the base is weak (K<10^-8) and solutions are very dilute and (b) where either the acid or the base are weak.

(b) Complexometric Titration: Complexometric titration can be followed with an electrode of the metal whose ion is involved in complex formation. For instance a number of ion selective electrodes can be used to monitor the titration of metal ions potentiometrically by EDTA. A silver electrode may be used to follow the titration of cyanide ion with a standard silver solution. The potential of the silver electrode may be expressed at 25 ^oC by E = E^o + 0.0591 log [Ag⁺].

(c) Oxidation-Reduction Titration: Such titrations involve the transfer of electrons from the substance being oxidized to the substance being reduced. Oxidized form + n electrons = reduced form. For such reaction the potential (E) acquired by the indicator electrode at 25^oC is given by E = E^o + (0.0591/n)*log([ox]/[red]).

The potential is controlled by the ratio of these concentrations terms. It is possible to titrate two substances by the same titrant provided the standard potentials of the substances being titrated, and their oxidation or reduction products, differ by about 0.2 V.

(d) Precipitation Titration: In this case, the titration reaction results in the formation of precipitate. A precipitation titration that involves insoluble salts of metals such as mercury, silver, lead and copper may be followed potentiometrically. The indicator electrode may be made of the metal involved in the reaction, a silver electrode for the titration of halides for instance, or may be an electrode whose potential is governed by the concentration of the anion being precipitated.

The potential of the silver electrode used as a cathode with SCE as anode in the titration of potassium iodide with silver nitrate will be governed by following Nernst equation: E_Ag+/Ag = E^o_Ag+/Ag + 0.0591 log [Ag⁺]. The concentration of silver ion is related to the concentration of iodide ion as K_AgI = [Ag⁺][I^-], where K_AgI is the solubility product of silver iodide. Hence, the electrode potential can be expressed in terms of the iodide ion concentration as: E_Ag+/Ag = E^o_Ag+/Ag + 0.0591 logK_AgI - 0.0591log[I^-]

In potentiometric titration the electrode potential over most of the titration range varies gradually, but near the equivalence point the electrode potential changes very abruptly even by the addition of small amount of titrant.

The magnitude of the potential change at the end point depends on the solubility of the substance being precipitated as well as on the concentration of the active ionic species involved. It has been found that potential change of silver electrode for the titration of 0.1M KI with 0.1M AgNO₃ is greater than for the titration of 0.01M KI with 0.01M AgNO₃.

In precipitation based potentiometric titration a number of components differing in solubility product could be analyzed. For example mixture of potassium iodide, potassium bromide and potassium chloride could be titrated with silver nitrate solution using silver electrode and silver-ISE. Among three halides, the solubility product of iodide is least (10^-16) and of chloride is highest (10^-10); silver iodide precipitates first, then silver bromide and at last silver chloride. But due to co-precipitation, adsorption the end points in halide mixture contains error.

Location of the End Point

a) Titration Curve: It is obtained by plotting the successive values of the cell emf on ordinate and corresponding values of volume of titrant added on the abscissa. This gives an S-shaped curve. The central portion of this curve which shows the steeply rising portion corresponds to the volume for the end point of the titration. When there is a small potential change at the end point like in the titration of weak acid with strong base, titration of very dilute solution etc, it is difficult to locate end point by this method. 

Figure 1: Titration method of locating end point 

b) Analytical or Derivative Method: The end point can be more precisely located from the first or second derivative curves. The first derivative curve involves the plot of slope of the titration curve (ΔE/ΔV-ration of change in emf and change in volume added) against the volume of the titrant added. Most frequently ΔE/ΔV is plotted against the average volume of titrant added corresponding to the values of emf taken. Volume on the x- axis corresponding to the peak of the curve is the end point of the titration.

In second derivative curve we plot the slope of first derivative curve (Δ²E/ΔV) against volume. The point on volume axis where the curve cuts through zero on the ordinate gives the end point. This point corresponds to the largest steepest point on titration curve and maximum slope of the ΔE/ΔV curve. 

Figure 2: First derivative Curve 

Above mentioned methods need values of potential corresponding to very small change in volume of titrant added near the end point for good result. In the immediate vicinity of the end point the concentration of the original reactant becomes very small, and it usually becomes impossible for the ions to control the indicator electrode potential. The cell emf becomes unstable and indefinite because the indicator electrode is not longer bathed with sufficient quantities of each electroactive species. Therefore the above methods may not give satisfactory results. Again also, results obtained by above methods may be in error if the reaction is not symmetrical e.g. in titration of silver ions with chromate ions.

Figure 3: Second derivative curve

c) Gran Plot: This is a new method of end point location in potentiometric titration developed by G. Gran in 1952 and modified by others. This method does the numerical manipulation of titration curves into linear straight lines intersecting at the equivalence point.During the potentiometric titration of KI with AgNO₃ following reaction occurs: KI(aq) + AgNO₃(aq) → AgI(s) + KNO₃(aq). The cell for the titration is SCE//KI,AgI/Ag and the emf of the cell is given by E_cell = E^o_cell - 2.303*(RT/F)*log(I^-) . The emf of the cell increases during potentiometric titration of KI with AgNO₃. By manipulating above equation one can derive the following equation for locating the end point by Gran's method.

Where V₀ = Initial volume of KI taken, V = Volume of AgNO₃ solution added, V_e = Volume of AgNO₃ solution at end point, C_Ag+ = Concentration of AgNO₃ solution added, F = Faraday's constant, R = Gas constant, T = Temperature, γ = Activity coefficient.

In above equation the term  

is called Gran's function. When Gran's function is  plotted against volume of AgNO₃ added 'V', a straight line will be obtained. Such a plot is called Gran Plot.

Above equation best fits for the data points taken only before the equivalence point. The end point can also be obtained from the data points after the end point by plotting 

against the volume of titrant added.

Figure 4: Gran Plot of Locating End Point

Thus the end point from Gran Plot can be obtained either taking the points before the end point or taking the points after the end point. It is obvious that the results obtained from linear curves would be more accurate than from the non-linear ones. The linear straight lines can be extrapolated to the volume axis to locate the end point. By the development of calculator, later on computer and using ion selective electrode, use of Gran Plot is increasing.

The advantages of using Gran's method of locating end point are: Simplicity of measurement, Simplicity of Calculation, Versatility and Precision.

This author had reported (see my MSc thesis) the titration errors and uncertainty in locating the end point using Gran method is reduced when a large portion (nearly 60%) of the titration curve is represented either before or after the equivalence point. One could use data points near equivalence points, neglecting the points at beginning for best result. It has been found that accurate end point from Gran plot can be obtained by using last 40% of data points near the end point.

Conclusion

Two ways of end point location in potnetiometric titration are mainly in practice in our lab. First is the titration curve and second is the first derivative curve. In these methods greater weightage is given to the data points near the end point and for better and accurate result large number of data points corresponding to very small change ion volume of titrant added near the end point must be used. But near the end point influence due to chemistry of reaction is high. In Gran's method of locating end point in potentiometric titration, the above errors can be removed because in this method greater weightage should not be given to readings near the end point. At last following points can be said on behalf of Gran method:

It is superior method than others. Removes all difficulties associated with classical methods, can be used to unsymmetrical reactions.

• Gran's method does not need values of emf near the end point. Therefore this method is more precise and accurate.
• Extrapolations of linear straight lines are used to locate the end point. Data points only before the end point can be used to locate the end point.
• Small numbers of data points give accurate end point.
• End point from Gran plot can be obtained even with last 40% of data points from near to the equivalence point with best result.

References

1. Vogel's textbook of "Quantitative Chemical Analysis" sixth edition.
2. Kolthoff, Sandell, Mechan, Bruclcenstin "Quantitative Chemical Analysis" forth edition.
3. Wilson, C.L.; Wilson, D. W.; "Comprehensive Analytical Chemistry" 2^nd A, Electrical Methods, Elsevier Publishing Company, 1964.
4. Day, R.A.; Underwood, R.L.; "Quantitative Analysis" sixth edition Prentice Hall of India, 1993.
5. Williard, H.H.; Merritt, L.L.; Dean, J.A.; Settle, F.A.; "Instrumental Methods of Analysis", sixth edition, Van Nostrand, 1981.
6. Gran, G.; Analyst (London), 1952, 77, 661.
7. Dick, J.G.; Analytical Chemistry, International Student Edition, McGraw - Hill Kogakusha, Ltd. 1973.
8. Gran, G.; Acta. Chem. Scand., 1950, 4, 559.
9. Sorenson, P.; Kem Maanedsbl.; 1951, 32, 73.
10. Burden, S.L. and Euler, D.E.; Proc. Indiana Acad. Sci.; 1973, 82, 167.
11. Burden, S.L. and Euler, D. E.; Analytical Chemistry, 1975, 47, 793.
12. Giri, B.; M. Sc. Dissertation, Central Department of Chemistry, T.U. 2004. 

Polychar 19 Successfully Held in Kathmandu, Nepal

Polychar 19 was held in Kathmandu, Nepal on 20-24 ^th March 2011.

The conference was inaugurated by Nepali Prime Minister Jhal Nath Khanal on Sunday of 20^th March 2011.Prof. Witold Brostow, President of Polychar, University of North Texas, USA, Dr. Rameshwar Adhikari, Polychar 19, Convener, Tribhuvan University, Nepal

I found the Polychar 19 International Conference was the Biggest Scientific Gathering for Nepal. The gathering made a history for Nepal. Renowned Scientists from 50 Countries discussed the recent trends and new avenues of Advanced Materials during the meeting. The technical Program was 162 oral presentations including 6 plenary lectures and 180 posters.

Technical Session was divided in four groups as under Invited lectures, Special lectures, Oral and Poster sessions including following topics:

1.                  Predictive methods, characterization and structure-property relationships

2.                  Synthesis of polymers, nanomaterials and smart materials

3.                  Mechanical properties and performance, dielectric and electrical properties

4.                  Surfaces, interfaces and tribology, rheology, solutions and processing

5.                  Biomaterials and tissue engineering, natural and Green Polymers and recycling

 The following Awards were distributed during the closing ceremony.

·                     The Paul J. Flory Polymer Research Prize

·                     The International Materials Science Prize

·                     Bruce Hartmann Award for a Young Scientist

·                     Other awards for non-students up to the age of 32

·                     Carl Klason Prize for the Best Student Paper

More than 50 volunteers were the students of Tribhuvan University and Trichandra Campus of Master Degree in Chemistry. They not only attended the conference but also interacted with more than 300 scientists from 50 countries.

On 20^th March 2011 from 08.00 am to 16.00 pm, Short Course on Polymer Characterization was held. It was so effective that programme almost covered the course of M.Sc. first year of Physical Chemistry “Surface Characterization”. At the same day, the conference was inaugurated by Nepali Prime Minister Jhal Nath Khanal.

The Schedule was as follows:

March 20, 2011, Sunday: Short Course on Polymer Characterization and Opening Ceremony

Short Course - Polymer Characterization

Venue: Durbar Hall, Park Village Resort Hotel

 Chairmen: Dr. Valerio Causin (Padova) and Dr. Sven Henning (Halle)

0800 – 0805	Welcome Prof. Mukunda P. Gajurel, Dean of Institute of Science and Technology, Tribhuvan University, Kathmandu
0805 – 0850	Prof. Witold Brostow, University of North Texas, Denton, TX, USA Polymer Tribology
0850 – 0935	Prof. Jean-Michel Guenet, Institut Charles Sadron, Strasbourg, France Polymer Characterization by Scattering Techniques
0935 – 1020	Prof. Michael Hess, University of Siegen , Siegen, Germany Dynamic Mechanical and Calorimetrical Analysis of Polymers
1020 – 1045	Tea/Coffee Break
1045 – 1130	Prof. Helmut Münstedt, University of Erlangen-Nürnberg, Germany Fundamentals of Polymer Rheology
1130 – 1215	Prof. Dusan Berek, Slovak Academy of Sciences, Bratislava, Slovakia Chromatographic Characterization of Polymers
1215 – 1300	Lunch Break
1300 – 1345	Prof. Goerg H. Michler, Martin Luther University, Halle, Germany Electron Microscopy of Polymers
1345 – 1430	Dr. Christopher J. Plummer, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland Mechanical Properties and Deformation Micromechanisms in Polymers
1430 – 1515	Prof. Anatolii D. Pomogailo, Russian Academy of Sciences, Moscow, Russia Trends in Chemistry of Nanocomposites
1515 – 1600	Prof. Jean Marc Saiter, University of Rouen, Rouen, France Routes to New Green Composite Materials
16:30-	Inauguration Ceremony and Reception Venue: Open Theatre of Park Village Resort Hotel

On 21^th March  2011, there were two plenary lectures from 08:30 to 09:50, tea break was from 09:50 to 10:20. There were three technical sessions in three Halls from 10:20 to 17:25. But there was Lunch break from 12:05 to 13:00 and poster session with tea break was from 14:45 to 16:00.

On 22^nd  March  2011, there were two plenary lectures from 08:30 to 09:50, tea break was from 09:50 to 10:20. There were three technical sessions in three Halls from 10:20 to 17:25. But there was Lunch break from 12:05 to 13:00 and poster session with tea break was from 14:45 to 16:00.

On 23^rd   March  2011, there were two plenary lectures from 08:30 to 09:50, tea break was from 09:50 to 10:20. There were three technical sessions in three Halls from 10:20 to 15:05. The lunch break and Polychar Prize Committee Meeting was from 12:05 to 13:25. Closing ceremony including Prize distribution followed by dinner was held from 16:30 to 21:00.

  

On 24^th    March  2011, Sight seeing was arranged for the Guest Scientists.

Here are some pictures from the event.

The very young female chemist of France presented the research work in the Polychar 19

The very young male chemist of Japan presented the research work on Polychar 19

Bidur Rijal, the chemist of Nepal doing Ph.D in France, presented the research work on Poster in Polychar 19

The Nepalese Chemists were enjoying Polychar 19, the International conference World Forum on Advanced Materials. From the left, Sabita Gautam Dahal,Biratnagar;  Rameshwar Adhikari, Kathmandu; Ajaya Bhattarai, Biratngar, Nepal

The very old male chemist of Russia presented the research work as Special lecture in Polychar 19, the International conference World Forum on Advanced Materials at Kathmandu, Nepal

By Dr. Ajaya Bhattarai