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 …

I and i

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%.

Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells

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

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Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

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

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

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.

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Visible-Light Photocatalysis in Nitrogen-Doped Titanium Oxides

Challenges and Opportunities in Designing Perovskite Nanocrystal Heterostructures

ZnS–CuInS2 (ZCIS) alloy nanostructures are becoming increasingly important materials because of their photoluminescence properties. Here we explore the emission properties of ZCIS quantum dots (QDs) capped with dodecanethiol, which exhibit Zn:Cu-dependent emission properties. Absorption and photoluminescence excitation spectra indicate a single, composition-independent light absorbing state. The emission spectra point out the existence of two emissive states with lifetimes of ∼10 ns and ∼100 ns. The photoluminescence and time-resolved emission analysis provide insight into the synergy between the two intraband states and the possibility of modulating the emission through variation in the Zn/Cu ratio. Better understanding of light absorbing and emission mechanisms in alloyed nanostructures is essential for future development of photoelectric and display devices.

Origin of Dual Photoluminescence States in ZnS–CuInS2 Alloy Nanostructures

The role of bis(2,4,6-trihydroxyphenyl)squaraine, Sq, in sensitizing large bandgap semiconductors has been investigated in the present study. The dye in its aggregate form readily interacts with the TiO2 colloids giving rise to a new charge transfer band in the red region. The apparent association constant for the dye aggregate and TiO2 colloid as determined from a Benesi-Hildebrand plot is 1600 M-1. Nanocrystalline semiconductor films prepared from TiO2, ZnO, and SnO2 colloids have been modified with Sq to probe the photosensitization effects. Both dye monomers and aggregates were found to participate in the charge injection process. An incident photon-to-photocurrent efficiency up to 0.7% has been observed.

Interaction of semiconductor colloids with J-aggregates of a squaraine dye and its role in sensitizing nanocrystalline semiconductor films

Photoelectrochemistry in particulate systems. 11. Reduction of phenosafranin dye in colloidal titanium dioxide and cadmium sulfide suspensions

Interfacial charge transfer between a semiconductor nanocrystal and a molecular relay is an important step in nanomaterial photocatalysis. The ferrocene redox couple (Fc+/Fc0, E0 = −4.9 eV vs vacuu...

Prashant V. Kamat

Papers

Challenges and Opportunities in Designing Perovskite Nanocrystal Heterostructures

Origin of Dual Photoluminescence States in ZnS–CuInS2 Alloy Nanostructures

Interaction of semiconductor colloids with J-aggregates of a squaraine dye and its role in sensitizing nanocrystalline semiconductor films

Photoelectrochemistry in particulate systems. 11. Reduction of phenosafranin dye in colloidal titanium dioxide and cadmium sulfide suspensions

Probing Perovskite Photocatalysis. Interfacial Electron Transfer between CsPbBr3 and Ferrocene Redox Couple.