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. 5. Aggregation of bis(2,4-dihydroxyphenyl)squaraine and bis(2,4,6-trihydroxyphenyl)squaraine and their photodissociation in acetonitrile solutions

Abstract: The equilibrium constants and thermodynamic parameters for aggregate formation of bis(2,4-dihydroxyphenyl)- squaraine and bis(2,4,6-trihydroxyphenyl)squaraine have been studied by absorption spectroscopy. The values of the equilibrium constant, K, for the dimerization of SQ1 and SQ2 in acetonitrile at 300 K are (3.1 ± 0.3) × 10 5 M -1 and (2.2 ± 0.1) × 10 5 M -1 , respectively. Iodine enhances the aggregation process. This has been attributed to the formation of charge-transfer complexes between iodine and the dyes and the stronger tendency of these complexes to form aggregates. Excitation of the squaraine dimer with a 532-nm laser pulse leads to the formation of the excited singlet state of monomeric dye as the excited dimer dissociates within the laser pulse duration of 18 ps.

Electron transfer between methyl viologen radicals and graphene oxide: Reduction, electron storage and discharge

Abstract: Photochemically generated methyl viologen radicals undergo electron transfer with graphene oxide (GO) in ethanol suspensions. This charge transfer interaction results in the reduction of GO as well as storage of electrons. The stored electrons can be utilized to reduce Ag + ions and thus anchor silver nanoparticles on reduced graphene oxide (RGO). The spectroscopic experiments that elucidate the quantitative electron transfer and transmission electron microscopy that highlights the potential of designing metal–RGO assemblies are discussed.

Charge Transfer Mediation Through CuxS. The Hole Story of CdSe in Polysulfide

Abstract: Hole transfer to dissolved sulfide species in liquid junction CdSe quantum dot sensitized solar cells is relatively slow when compared to electron transfer from CdSe to TiO2. Controlled exposure of cadmium chalcogenide surfaces to copper ions followed by immersion in sulfide solution promotes development of the interfacial CuxS layer, which mediates hole transfer to polysulfide electrolyte by collection of photogenerated holes from CdSe. In addition, CuxS was also found to interact directly with defect states on the CdSe surface and quench emission characteristic of electron traps resulting from selenide vacancies. Together these effects were found to work in tandem to deliver 6.6% power conversion efficiency using Mn-doped CdS and CdSe cosensitized quantum dot solar cells. Development of an n–p interfacial junction at the photoanode–electrolyte interface in quantum dot solar cells unveils new means for designing high efficiency liquid junction solar cells.

Ruthenium(II) Trisbipyridine Functionalized Gold Nanorods. Morphological Changes and Excited-State Interactions†

Abstract: Gold nanorods synthesized using cetyltrimethylammonium bromide and tetraoctylammonium bromide as stabilizers are functionalized with a thiol derivative of ruthenium(II) trisbipyridyl complex [(Ru(bpy)32+-C5-SH] in dodecanethiol using a place-exchange reaction. The changes in the plasmon absorption bands and transmission electron micrographs indicate significant changes in the gold rod morphology during the place-exchange reaction. The (Ru(bpy)32+-C5-SH in its excited state undergoes quick deactivation when bound to gold nanorods. More than 60% of the emission was quenched when [(Ru(bpy)32+-C5-SH] was bound to gold nanorods. Emission decay analysis indicates that the energy transfer rate constant is greater than 1010 s-1.

Photosensitization Aspects of Pinacyanol H-Aggregates. Charge Injection from Singlet and Triplet Excited States into SnO2 Nanocrystallites

Abstract: The singlet and triplet excited-state behavior of a symmetric carbocyanine dye, 1,1‘-diethyl-2,2‘-carbocyanine (commonly referred as pinacyanol), adsorbed on SiO2 and SnO2 nanocrystallites has been investigated using transient absorption spectroscopy. The adsorption of the dye molecules on the negatively charged SiO2 or SnO2 colloids results in H-type aggregation. When excited with a 532 nm laser pulse we observe a short-lived (τ 5 × 1010 and 7 × 10...

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.