Prashant V. Kamat

Bio: Prashant V. Kamat is an academic researcher from University of Notre Dame. The author has contributed to research in topics: Racism & Excited state. The author has an hindex of 140, co-authored 725 publications receiving 79259 citations. Previous affiliations of Prashant V. Kamat include Indian Institute of Technology Kanpur & Council of Scientific and Industrial Research.

A new photodegradable polyamide containing o-nitrobenzyl chromophore. Steady state and laser flash photolysis studies

Abstract: A new photodegradable and thermally stable polyamide containing a photosensitive o-nitrobenzyl chromophore (4) was prepared by melt condensation of 4-α-methylamino-3-nitro-p-toluoyl chloride (5). On photolysis, 4 undergoes efficient photodegradation and becomes soluble in methanol and aqueous base, whereas the unirradiated polymer is insoluble in both solvents. This solubility difference renders the polymer 4 a potential material for microelectronic applications. The progress of photodegradation can be monitored by measuring the inherent viscosity of the polymer as a function of the irradiation time. The photodegradation pathway of 4 was studied by examining both steady state and laser flash photolysis of a low-molecular-weight model compound, 4-N-benzoyl-α-methylamino- 3-nitro-N′,N′-dimethyl-p-tolumide (6). Steady state irradiation of 6 in methanol gives a mixture of N-methyl-benzamide (10) and an azobenzenedicarboxylic acid 8. The transient species with an absorption maximum around 440 nm, produced from 6 on photolysis using 20 ps flashes of 355 nm laser light or 10 ns flashes of 308 nm laser light, is attributed to the nitronic acid 12. The formation of 12 is suggested to occur through a very fast singlet route and a slower triplet route.

Crown ether derivatives of squaraine: new near-infrared-absorbing, redox-active fluoroionophores for alkali metal recognition

Abstract: Three monoaza crown ether bisphenylsquaraine dyes, 1–3, with excellent solubilities in both polar and non-polar solvents, have been synthesised. The fluorescence yields of these red-sensitive dyes are dependent on the solvent polarity. They are capable of binding quantitatively with alkali metal ions, Li–, Na+, K+, as is seen from their fluorescence quenching and shift in the oxidation potentials. The fluorimetric and electrochemical experiments indicate the potential application of these dyes for cation recognition.

Kinetics of photobleaching recovery in the iron(II)-thionine system

Abstract: A cross-beam illumination kinetic spectrophotometry techniques was used to study the oxidation of leucothionine by Fe(III) in an aqueous medium. The specific rate of oxidation of leucothionine by Fe(III), monitored as photobleaching recovery, was found to follow pseudo-first-order kinetics. This specific rate was found to attain a limiting value with increasing Fe(III). The influence of varying concentrations of Fe(II) and TH/sup +/ was found to be marginal. The observed results supported the approach of complex formation between leucothionine and Fe(III). The activation energy for the oxidation of leucothionine by Fe(III) was 69 kJ mol/sup -1/.

Electron transfer reactions. Reaction of nitrones with potassium

Abstract: Treatment of nitrones (1a–d, 26a,b, 34, 49) with potassium in tetrahydrofuran (THF) gives rise to radical anion (2a–d, 27a,b, 35, 50) and dianion intermediates (3a–d, 28a,b, 36) through electron transfer reactions. These intermediates undergo further transformations to give a variety of products. Thus, the aldehydonitrones (1a–d) give the corresponding aldehydes (10a–c), carboxylic acids (25a–c), and azobenzenes (19a,d), whereas the ketonitrones (26a,b) give deoxygenation products (31a,b). The nitrone 34 gave a mixture of products consisting of benzoic acid (25a), dibenzyl (48), the dimeric product 38, and tetraphenylpyrazine (46), whereas 49 did not give any isolable product. Cyclic voltammetric studies have been employed to measure the reduction potentials for both one-electron and two-electron transfer processes, leading to the radical anions and dianions respectively. These intermediates have been characterized through their electronic spectra and they were quenched by oxygen. Pulse radiolysis of the ...

Hierarchical assembly of porphyrins and fullerenes for solar cells

Abstract: T he rapid consumption of fossil fuels has created unacceptable environmental problems such as greenhouse effects, which may lead to disastrous climatic consequences. Thus, renewable and clean energy such as that obtained by using solar cells is required to maintain the quality of human life as well as the environment. Progress is being made in the development of heterojunction organic solar cells, which possess an active layer of a conjugated donor polymer and an acceptor fullerene.1 In these polymer blends, efficient photoinduced electron transfer occurs at the donor-acceptor interface, and intimate mixing of donor and acceptor is therefore beneficial for efficient charge separation.1,2 For efficient transport of the positive charge carriers through the donor phase and of electrons via the acceptor phase to the electrodes, a phase-segregated network is required.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells

Abstract: Two organolead halide perovskite nanocrystals, CH3NH3PbBr3 and CH3NH3PbI3, were found to efficiently sensitize TiO2 for visible-light conversion in photoelectrochemical cells. When self-assembled on mesoporous TiO2 films, the nanocrystalline perovskites exhibit strong band-gap absorptions as semiconductors. The CH3NH3PbI3-based photocell with spectral sensitivity of up to 800 nm yielded a solar energy conversion efficiency of 3.8%. The CH3NH3PbBr3-based cell showed a high photovoltage of 0.96 V with an external quantum conversion efficiency of 65%.

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

Abstract: Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Visible-Light Photocatalysis in Nitrogen-Doped Titanium Oxides

Abstract: To use solar irradiation or interior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Films and powders of TiO 2- x N x have revealed an improvement over titanium dioxide (TiO 2 ) under visible light (wavelength 2 has proven to be indispensable for band-gap narrowing and photocatalytic activity, as assessed by first-principles calculations and x-ray photoemission spectroscopy.