T. Pradeep
Encyclopedia
Thalappil Pradeep is a professor in Department of Chemistry at Indian Institute of Technology Madras.
s and ice surfaces. His group studied the dynamics of monolayers in monolayer
protected nanoparticles and has shown that monolayers are rotationally frozen on nanoparticle surfaces and do not exist in a ‘rotator phase’ as believed earlier. His group found a ‘transverse electrokinetic effect’ in which a potential is generated on nanoparticle assemblies anchored on surfaces, when a liquid flows over them. He showed that the equilibrium constant of the prototypical proton transfer reaction, NH3 + HCl → NH4Cl, is orders of magnitude lower on ice. Most recently he found that diffusion
of chemically similar molecules through ultra thin ice films exhibits several surprises. A new structural transition on the top-most layers of ice surfaces has been discovered at low temperatures.
, irrespective of whether it is metallic or semiconducting. This is primarily attributed to the increase in the number of defects introduced by nanoparticle binding, which leads to the complete loss of metallicity
of the tubes. While the visible light fluorescence
has shown large potential in sensing, many novel applications are likely to be discovered through the loss of metallic nature of SWNTs.
His recent research is mostly concerned with anisotropic nanostructures and luminescent noble metal clusters. He found that noble metal nanoparticles can completely degrade halocarbon
s into amorphous carbon and metal halides. There are many important aspects of this novel discovery: complete degradation of halocarbons, extension of the study to toxic pesticide
s as many of them are halocarbons, eco-friendly nature as the end-products are harmless, efficient removal mechanism of pesticide residues in drinking water
and simple visual color based detection system for pesticide detection. Due to zero electricity usage, this technology is likely to be of use to rural population affected by pesticide contamination. The technology has been commercialized and a nanoparticle-based water filter has been introduced in the market in partnership with Eureka Forbes Limited. Incidentally it is the very first nanoparticle based water filter.
Pradeep discovered an unusual proton transfer phenomenon on ice surfaces and showed that metastable species can be stabilized at ice surfaces. In a very recent study he has shown that while the diffusion of CCl4 is blocked by a three to four monolayers of ice, hundreds of monolayers are needed to block the transport of CHCl3 and CH2Cl2. The oscillation
of vapor pressure of CO2 over melting ice is another discovery. Several studies have confirmed that this is a general phenomenon concerning the dynamics of the gas phase above a condensed system during its phase transition
. The bond specific processes at the top layers of ice are studied through in-house developed ultrahigh vacuum instrument working at 10−11. Such studies are important for the understanding of reactions involving ice particles in the atmosphere.
It is also important to re-iterate that the issue of nano-toxicity is still not demystified. During this process of improving scientific understanding, we should make all efforts not to create a new problem while solving an older problem. A classic example of which is DDT
and other pesticides, which helped in bringing an agricultural revolution
but also led to dramatic increase in the concentration of toxic contaminants in the environment.
Research summary
Pradeep’s work is in the area of molecular materials and surfaces. In his formative years, he measured the very first vibrationally resolved photoelectron spectrum of Ar2 and discovered a novel transition metal ion, NiH2+. These days most of his work is on nanoparticleNanoparticle
In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size : in terms of diameter, coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are sized...
s and ice surfaces. His group studied the dynamics of monolayers in monolayer
Monolayer
- Chemistry :A Langmuir monolayer or insoluble monolayer is a one-molecule thick layer of an insoluble organic material spread onto an aqueous subphase. Traditional compounds used to prepare Langmuir monolayers are amphiphilic materials that possess a hydrophilic headgroup and a hydrophobic tail...
protected nanoparticles and has shown that monolayers are rotationally frozen on nanoparticle surfaces and do not exist in a ‘rotator phase’ as believed earlier. His group found a ‘transverse electrokinetic effect’ in which a potential is generated on nanoparticle assemblies anchored on surfaces, when a liquid flows over them. He showed that the equilibrium constant of the prototypical proton transfer reaction, NH3 + HCl → NH4Cl, is orders of magnitude lower on ice. Most recently he found that diffusion
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...
of chemically similar molecules through ultra thin ice films exhibits several surprises. A new structural transition on the top-most layers of ice surfaces has been discovered at low temperatures.
Key results in the recent past
Pradeep discovered that in the presence of metal nanoparticles, single walled carbon nanotube (SWNT) bundles emit light in the visible region of the electromagnetic spectrumElectromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....
, irrespective of whether it is metallic or semiconducting. This is primarily attributed to the increase in the number of defects introduced by nanoparticle binding, which leads to the complete loss of metallicity
Metallicity
In astronomy and physical cosmology, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium...
of the tubes. While the visible light fluorescence
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
has shown large potential in sensing, many novel applications are likely to be discovered through the loss of metallic nature of SWNTs.
His recent research is mostly concerned with anisotropic nanostructures and luminescent noble metal clusters. He found that noble metal nanoparticles can completely degrade halocarbon
Halocarbon
Halocarbon compounds are chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms resulting in the formation of organofluorine compounds, organochlorine compounds, organobromine compounds, and organoiodine compounds...
s into amorphous carbon and metal halides. There are many important aspects of this novel discovery: complete degradation of halocarbons, extension of the study to toxic pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
s as many of them are halocarbons, eco-friendly nature as the end-products are harmless, efficient removal mechanism of pesticide residues in drinking water
Drinking water
Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...
and simple visual color based detection system for pesticide detection. Due to zero electricity usage, this technology is likely to be of use to rural population affected by pesticide contamination. The technology has been commercialized and a nanoparticle-based water filter has been introduced in the market in partnership with Eureka Forbes Limited. Incidentally it is the very first nanoparticle based water filter.
Pradeep discovered an unusual proton transfer phenomenon on ice surfaces and showed that metastable species can be stabilized at ice surfaces. In a very recent study he has shown that while the diffusion of CCl4 is blocked by a three to four monolayers of ice, hundreds of monolayers are needed to block the transport of CHCl3 and CH2Cl2. The oscillation
Oscillation
Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...
of vapor pressure of CO2 over melting ice is another discovery. Several studies have confirmed that this is a general phenomenon concerning the dynamics of the gas phase above a condensed system during its phase transition
Phase transition
A phase transition is the transformation of a thermodynamic system from one phase or state of matter to another.A phase of a thermodynamic system and the states of matter have uniform physical properties....
. The bond specific processes at the top layers of ice are studied through in-house developed ultrahigh vacuum instrument working at 10−11. Such studies are important for the understanding of reactions involving ice particles in the atmosphere.
Views on nanotechnology
Pradeep has been advocating the use of noble metal based nanotechnology for purifying the environment. As scientific understanding of the health effects of contaminants increases, it is likely that their allowed limits will be continuously revised. The contaminants levels are expected to reach molecular limits in the years to come. This implies that the technologies we use have to become molecule-specific and nanotechnology becomes the obvious choice.It is also important to re-iterate that the issue of nano-toxicity is still not demystified. During this process of improving scientific understanding, we should make all efforts not to create a new problem while solving an older problem. A classic example of which is DDT
DDT
DDT is one of the most well-known synthetic insecticides. It is a chemical with a long, unique, and controversial history....
and other pesticides, which helped in bringing an agricultural revolution
Agricultural revolution
Agricultural Revolution or Agrarian Revolution may refer to:*The Neolithic Revolution , the initial transition from hunting and gathering to settled agriculture in prehistory...
but also led to dramatic increase in the concentration of toxic contaminants in the environment.
Education
Pradeep earned a PhD degree in chemical physics working with Professors C. N. R. Rao and M. S. Hegde at the Indian Institute of Science, Bangalore. Subsequently, he spent about 2 years as a post-doctoral fellow at the University of California, Berkeley and Purdue University, Indiana. Since then, he has been working in the Indian Institute of Technology Madras, where he is a full professor now. He also held visiting positions at Purdue University, USA; Leiden University, Netherlands; EPFL, Switzerland; Institute of Chemistry, Taiwan; Pohang University of Science and Technology, South Korea and University of Hyogo, Japan.Books - Technology
- T. Pradeep (Ed.), Advances in Physical Chemistry, New Delhi, 1999
- T. Pradeep, Nano: The Essentials Understanding Nanoscience and Nanotechnology, New Delhi, 2007, reprinted 2008, 2009 & 2010, McGraw Hill Education, New Delhi 2008
- S. K. Das, S. U. S. Choi, W. Yu, T. Pradeep, Nanofluids Science and Technology, New York, 2008