T. Pradeep[5] earned a PhD degree in chemical physics working with Professors C. N. R. Rao[6] and M. S. Hegde at the Indian Institute of Science, Bangalore during 1986–91.
[17] For studies of ultrathin surfaces of molecular solids such as ices, he developed unique instrumentation,[18] an important aspect of his research.
These are molecules composed of a few atom cores, protected with ligands, especially thiols which are fundamentally different from their bulk and plasmonic analogues in terms of their optical, electronic, and structural properties.
Such clusters show distinct absorption spectra and well-defined luminescence, mostly in the visible and near-infrared regions, just as molecules.
He introduced several new synthetic approaches to make new clusters (a summary of the methods is presented in reference[19]), showed some of the first examples of chemistry with such materials and developed applications with them.
[27] He created methods to form highly uniform nanotriangles[28] and introduced a new family of materials called mesoflowers.
[29] Combining luminescent atomically precise clusters with mesoflowers and nanofibres, he developed sensors at sub-zeptomole levels[30] which are probably the limits of fast molecular detection.
[31] A number of atomically precise luminescent clusters have been made in proteins and their growth involves inter-protein metal transfer.
[33] Early examples of cluster functionalisation[34] were demonstrated by him and the methods he introduced are shown to impart properties such as fluorescence resonance energy transfer to such systems[35] and these methodologies are now used for applications.
Cluster functionalisation chemistry has recently been extended to make isomers of nanomolecules and these have been isolated in collaboration with Japanese scientists.
Besides the advantage of low internal energy of the ions, which preserves fragile species and intermediates, the methodology helps in miniaturising mass spectrometry.
The chemistry he developed was reductive dehalogenation of halocarbons at noble metal nanoparticle surfaces which when applied to several of the common pesticides present in surface waters of India, resulted in their degradation at room temperature and extremely low concentrations, of the order of parts per billion.
The process when occurs on supported nanoparticles, trace concentrations of halocarbon pesticides can be removed from a flowing water stream.
He developed several new technologies in the recent past to tackle various other contaminants such as arsenic, lead, mercury and organics in water, which are the subject of a few issued and filed patents.
Such capabilities to bring contaminant concentrations under drinking water norms using diverse nanomaterials, feasible synthesis of such materials in quantities, creation of viable processes for their implementation along with the use of efficient sensors would make clean drinking water affordable using nanomaterials.
[45] A critical problem in achieving this goal is the development of advanced and affordable materials with no or reduced environmental impact.
Some of the materials and technologies he has developed over the years have been combined to make affordable all-inclusive point-of-use drinking water purifiers,[16] which are being installed in various parts of the country, both as a community and as domestic units.
His recent discovery of ultrasensitive single-particle sensors with the capacity to detect a few tens of molecules and ions[30][31] may be combined with new materials to make simultaneous sensing and scavenging at ultra-trace levels possible.
The new materials he has developed have been put together to make community purifiers in arsenic affected areas of West Bengal which have been running for seven years.
He created 3D organised structures of nanoparticles called superlattices[48] and used them for surface enhanced Raman imaging[49][50] and specific gas sensing applications.
He showed a transverse electrokinetic effect in metal nanoparticle assemblies which resulted in a potential when a liquid was flown over it.
[53][54] Using spectroscopic and scattering techniques, he showed that long chain monolayers on metal nanoparticle surfaces were rotationally frozen.
Among the various examples, he has shown that the vapour pressures of gases oscillate over melting ice;[57] the study has implications to the fundamental understanding of dynamics of gas phase over condensed systems.
[59] To discover and understand such processes, especially at the very top of ice, he built the very first ultra low energy (1-10 eV) ion scattering spectrometer, a new tool in extremely surface sensitive spectroscopy, working at cryogenic temperatures as in space.
The surfaces are simultaneously characterized by a range of techniques such as reflection-absorption infrared spectroscopy and secondary ion mass spectrometry.
Using this infrastructure the group has shown that methane hydrate can exist in ultrahigh vacuum and at ultra-cold conditions as in interstellar space.
InnoDI (inno-dee-eye) develops and builds Capacitive De-ionization (CDI) based water treatment systems for the Indian and international market and has established manufacturing facilities.
S. K. Das, S. U. S. Choi, W. Yu, T. Pradeep, Nanofluids Science and Technology, John Wiley, New York (2008).
Chapter in, Rasathanthram: Jeevithavum Bhavium (translated as Chemistry: Life and Future), Kerala Sastra Sahitya Parishad, Trissur, 2011.
[44] As scientific understanding of the health effects of contaminants increases, it is likely that their allowed limits will be continuously revised.