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.

Structural Phase- and Degradation-Dependent Thermal Conductivity of CH3NH3PbI3 Perovskite Thin Films

Abstract: Organic–inorganic lead halide perovskites have shown great promise in photovoltaics and optoelectronics. In these applications, device performance and reliability can be strongly influenced by thermal transport in the materials. Through laser pump–probe experiments, different microstructures of CH3NH3PbI3 perovskite thin films are found to give rise to different phonon scattering mechanism. The thermal conductivity in CH3NH3PbI3 neat film decreases with temperature. Even though this agrees with the behavior of its bulk crystalline counterparts, an apparent thermal conductivity change near the structural phase transition temperature of this perovskite (orthorhombic vs tetragonal) has only been observed in the spin-coated films. Analyses suggest that this may be attributed to either an energy landscape change related to organic cation disorder or the thickness change of ferroelectric domain walls formed in the neat perovskite films that affects the phonon scattering at the domain boundaries. In contrast, no...

Photoelectrochemistry in particulate systems. 7. Electron-transfer reactions of indium sulfide semiconductor colloids

Abstract: Small semiconductor colloids of In/sub 2/S/sub 3/ have been prepared in aqueous and nonaqueous media and their absorption properties characterized. A transient photobleaching and formation of S/sup .-/ and S/sub 2/H/sub 2//sup .-/ radicals have been observed upon laser pulse (355 nm) excitation of these colloids. With the aid of transient absorption spectra, the anodic corrosion process in these semiconductor colloids has been elucidated by using laser flash photolysis and pulse radiolysis techniques. With the use of a zwitterionic viologen compound, the interfacial charge-transfer process at the semiconductor surface has been studied. The quantum yield for the reduction of zwitterionic viologen was 0.07, which is similar to the value obtained with other metal chalcogenide semiconductor colloids. The microenvironment of the stabilizer (Nafion) influenced the charge-transfer process between the semiconductor and the redox decay.

Photochemistry of sensitizing dyes: spectroscopic and redox properties of cresyl violet

Abstract: The photosensitizing properties of cresyl violet have been investigated by characterizing singlet and triplet excited states and the reduced and oxidized forms of the dye by picosecond and nanosecond laser flash photolysis. The dye readily forms a charge-transfer complex with amines with complexation constants in the range of 49-3,350 M{sup {minus}1} in methanol. The dye in its singlet and triplet excited states has lifetimes of 2.46 ns and 68 {mu}s, respectively, in acetonitrile. The excited triplet is quenched by ground-state dye molecules with a bimolecular rate constant of 1.45 {times} 10{sup 9} M{sup {minus}1} s{sup {minus}1}. The semioxidized radical of the dye has been generated by oxidation of CV{sup +} with pulse radiolytically generated azide radicals (k = 1.6 {times} 10{sup 10} M{sup {minus}1} s{sup {minus}1}) in aqueous medium. The semireduced dye has been generated by quenching of triplet dye with triphenylamine (k = 1.4 {times} 10{sup 9} M{sup {minus}1} s{sup {minus}1}) in methanol. Photoelectrochemical reduction of cresyl violet in colloidal TiO{sub 2} suspension has also been carried out, with a quantum yield of 0.013.

Disassembly, Reassembly, and Photoelectrochemistry of Etched TiO2 Nanotubes

Abstract: Etched TiO2 nanotubes are removed from the titanium foil substrate by sonication and are reassembled onto new electrodes for photovoltaic applications. CdS nanocrystallites were deposited on the restructured electrodes to compare their performance as quantum dot-sensitized solar cells to aligned nanotube electrodes. The sensitized photoresponses of the photoelectrochemical cell created from reassembled TiO2 nanotubes are very similar to aligned TiO2 nanotube arrays. Transient absorption spectroscopy of dispersed tubes indicates that electron transfer from excited CdS nanocrystallites into TiO2 nanotubes occurs at a rate of 2.0 × 1010 s−1. BET surface area analysis is investigated on etched nanotube powder without the need for weight approximation and was found to be 77.0 ± 2.9 m2/g. The importance of nanotube orientation and porosity on the electrode surface in stabilizing accumulated electrons in TiO2 nanotubes is elucidated from the open circuit voltage decay. Nanotube orientation was also seen to affec...

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.