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.

Photochemistry of squaraine dyes. 6. Solvent hydrogen bonding effects on the photophysical properties of bis(benzothiazolylidene)squaraines

Abstract: The photophysical properties of two bis(benzothiazolylidene)squaraine dyes have been studied in aromatic hydrocarbon and alcoholic solvents. These dyes exhibit fluorescence quantum yields of 0.06-0.52 and excited singlet lifetimes of 0.48-2.5 ns in these solvents. Although the photophysical properties of the dyes are independent of solvent polarity in the hydrocarbon solvents, in alcoholic solvents a marked hyposchromic shift in the absorption and emission spectra and a reduction in lifetimes of excited state have been observed. These effects have been correlated with the hydrogen bond donating ability of the alcoholic solvents. 17 refs., 6 figs., 2 tabs.

Photochemistry of ruthenium trisbipyridine functionalized on gold nanoparticles.

Abstract: Design of nanohybrid systems possessing several ruthenium trisbipyridine (Ru(bpy)32+) chromophores on the surface of gold nanoparticles, by adopting a place exchange reaction, was reported and their photophysical properties were tuned by varying the density of chromophores. The charge shift between the excited and ground-state Ru(bpy)32+ chromophores was reported for the first time, leading to the formation of Ru(bpy)3+ and Ru(bpy)33+. Electron-transfer products were not observed on decreasing the concentration of Ru(bpy)32+ functionalized on Au nanoparticles or in a saturated solution of unbound chromophores. The close proximity of the chromophores on periphery of the gold core may lead to an electron transfer reaction and the products sustained for several nanoseconds before undergoing recombination, probably due to the stabilizing effect of the polar ethylene glycol moieties embedded between the chromophore groups.

Photochemistry in polymers: photoinduced electron transfer between phenosafranine and triethylamine in perfluorosulfonate membrane

Abstract: Absorption and emission properties of protonated and unprotonated forms of phenosafranine dye are investigated in the perfluorosulfonate ion-exchange membrane (Nafion) and polymer solution. Only the unprotonated form of phenosafranine is photoactive and undergoes electron transfer with triethylamine upon excitation with visible light. The triplet excited state of phenosafranine and the electron-transfer products in the Nafion film are characterized by laser flash photolysis with 532-nm excitation. In a dry evacuated film the triplet lifetime of phenosafranine is greater than 1.5 ms. During the steady-state photolysis, the semireduced dye undergoes disproportionation to accumulate a colorless two-electron-reduction product.

Photoelectrochemistry in colloidal systems. Part 2.—A photogalvanic cell based on TiO2 semiconductor colloid

Abstract: Thiazine and oxazine dyes have been photoelectrochemically reduced in colloidal TiO2 suspensions with bandgap excitation. The one-electron reduction of the dye, which resulted in the production of the semireduced radical ion, with quantum yield up to 0.1, further disproportionated to yield a stable leuco dye. The efficiency of the interfacial electron-transfer process is found to be dependent on the standard reduction potential of the dye. The feasibility of employing a colloidal semiconductor system in the operation of a photogalvanic cell is demonstrated. A photogalvanic power conversion efficiency of 0.002% was achieved with thionine and colloidal TiO2 upon bandgap excitation. The use of TiO2 colloid as a carrier for the deposition of a photoactive or an electroactive species on the electrode surface is also discussed.

Spectral Characterization of the One-Electron Oxidation Product of cis-Bis(isothiocyanato)bis(4,4‘-dicarboxylato-2,2‘-bipyridyl) Ruthenium(II) Complex Using Pulse Radiolysis

Abstract: The spectral characterization of the oxidized form of (ruthenium(II) cis-di(isothiocyanato)bis(4,4‘-dicarboxy-2,2‘-bipyridyl), (commonly known as N3-dye) in aqueous solution is made by reacting the title compound with pulse radiolytically generated radicals N3• and Br2-•. The one-electron oxidized form of Ru(II)-dye initially formed in both these oxidation reactions shows absorption maxima at 320 and 740 nm. Following radiolysis, the one-electron oxidized form of Ru(II)-dye undergoes further transformations to yield a stable product that exhibits a characteristic absorption maximum at 440 nm. Our preliminary results provide the spectral evidence for the formation of two different species that follow the oxidation of Ru(II)-dye.

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.