All articles starting with P

Photoelectrocatalytic reduction

Photoelectrocatalytic reduction drives reactions such as CO2 conversion, nitrate reduction, and hydrogen evolution at a light-activated semiconductor photocathode, with light and applied bias sharing the driving force.

Photoelectrochemical C–H functionalization

Photoelectrochemical C–H functionalization, known as electrophotocatalysis (EPC), is a synthetic method that activates inert carbon–hydrogen bonds using combined light and electric current, avoiding chemical oxidants.

Photoelectrochemical CO2 reduction

Photoelectrochemical CO2 reduction is a catalytic method using light-absorbing semiconductor electrodes, often with an electrical bias, to convert carbon dioxide into fuels and chemicals such as methanol.

Photoelectrochemical detection

Photoelectrochemical detection is an analytical method measuring photocurrent at a photoactive electrode; light excitation and electrical readout keep background low, enabling DNA, immunoassay, and cell biosensing.

Photoelectrochemical sensing

Photoelectrochemical (PEC) sensing is an analytical technique combining optical excitation with electrochemical detection, measuring a target analyte through the photocurrent a photoactive electrode produces under illumination.

Photoelectrochemical water oxidation

Photoelectrochemical water oxidation is the light-driven oxidation of water to oxygen at a semiconductor photoanode, the half-reaction that, paired with hydrogen evolution, converts sunlight and water into hydrogen fuel.

Photoelectrochemical water splitting

Photoelectrochemical water splitting is a method of producing hydrogen from water using sunlight and semiconductor photoelectrodes in a single device, first demonstrated in 1972 and still uncommercialized.

Photoelectron circular dichroism

Photoelectron circular dichroism (PECD) is a chiroptical effect where chiral molecules ionized by circularly polarized light emit electrons with a forward–backward asymmetry, predicted in 1976.

Photoelectron diffraction

Photoelectron diffraction, also called X-ray photoelectron diffraction, is a surface science technique that determines local atomic structure and adsorption geometry from the angular and energy dependence of photoelectron emission.

Photoelectron holography

Photoelectron holography is an imaging technique that reconstructs atomic positions from the interference of direct and scattered photoelectron waves, extended to femtosecond molecular imaging with x-ray free-electron lasers.

Photoelectron spectroscopy

Photoelectron spectroscopy (PES) measures the kinetic energies of electrons ejected from matter by photons, converting them into binding energies, electronic-structure information, and elemental and chemical-state composition. Its main branches include XPS, UPS, and ARPES.

Photoemission electron microscopy

Photoemission electron microscopy (PEEM) images a surface by illuminating it with ultraviolet or X-ray light and forming a magnified image from the ejected electrons, revealing topography, composition, and magnetic domains.

Photoenzymatic C–H functionalization

Photoenzymatic C–H functionalization merges photochemistry with biocatalysis, using light-activated enzymes to convert carbon–hydrogen bonds into carbon–carbon, carbon–oxygen, carbon–nitrogen, or carbon–fluorine bonds with high selectivity under mild conditions.

Photoenzymatic catalysis

Photoenzymatic catalysis, also called photobiocatalysis, combines light-driven photocatalysis with enzymatic catalysis, using photoexcitation to drive radical reactions with the selectivity of a protein active site, enabling new-to-nature chemistry under mild conditions.

Photoenzymatic radical catalysis

Photoenzymatic radical catalysis is a field growing rapidly since 2016 in which visible light excites an enzyme's cofactor to generate radical intermediates, enabling new-to-nature enantioselective reactions.

Photoevaporation

Photoevaporation is the loss of a planet's atmosphere driven by extreme ultraviolet and X-ray radiation from its host star, and one of two leading explanations for the exoplanet radius valley.

Photofermentation

Photofermentation is a light-driven microbial process in which purple non-sulfur bacteria oxidize organic substrates under anaerobic conditions, releasing high-purity hydrogen through the enzyme nitrogenase, studied for bioenergy.

Photofission

Photofission is nuclear fission of a heavy nucleus induced by absorbing a high-energy photon, written (γ, f), with a threshold of about 5 to 6 MeV.

Oct 21, 2026

Photofluorography

Photofluorography (fluorography, mass miniature radiography) photographs the X-ray image on a fluorescent screen onto small 7x7 or 10x10 cm film; used for mass TB chest screening from the 1940s, later replaced by digital radiography.

Photofragment-ion imaging

Photofragment-ion imaging, also called ion imaging, is a chemical dynamics technique introduced in 1987 that images fragment recoil velocities from photodissociation; a 1997 refinement, velocity map imaging, improved its resolution.

Photogating effect

The photogating effect is a photodetection mechanism in which photo-induced charges trapped in or near a semiconductor act as an internal gate, modulating a transistor's channel conductance instead of generating photocurrent directly.

Photogeology

Photogeology is the study and interpretation of aerial photographs, normally vertical, to obtain geologic information and present it as mosaics, geologic maps, and cross sections.

Photografting

Photografting is a surface-modification method in which ultraviolet or visible light drives the covalent attachment of polymer chains or functional groups onto polymers, metals, carbons, and oxides.

Photogram

A photogram is a photograph made without a camera or lens, produced by placing objects on light-sensitive paper and exposing it to light; experiments date to 1802.

Photogrammetry

Photogrammetry builds 3D models, point clouds, and orthophotos from overlapping photographs taken from many positions, and is used in surveying, geology, archaeology, and underwater exploration.

Photograph

Photograph: an image made by light acting on a sensitive surface or electronic sensor; from Greek phos and graphê, coined by Herschel in 1839. Covers film's negative-to-positive chemistry, digital capture, history from Niépce's heliograph, and archival preservation.

Photograph (Ed Sheeran song)

Photograph, Ed Sheeran ballad from the 2014 album x, written with Johnny McDaid, Harrington and Leonard; produced by Jeff Bhasker; peaked at No 10 US, No 15 UK, subject of a settled $20m copyright suit.

Photograph (film)

Photograph (2019) is a Hindi romantic drama written and directed by Ritesh Batra, starring Nawazuddin Siddiqui and Sanya Malhotra. A Mumbai street photographer convinces a shy student to pose as his fiancée; Sundance premiere, Amazon Studios release.

Photograph of Prince Andrew, Virginia Giuffre and Ghislaine Maxwell

Photograph of Prince Andrew, Virginia Giuffre and Ghislaine Maxwell, taken 10 March 2001 at Maxwell's London home by Jeffrey Epstein, published 2011; central evidence in Giuffre's allegations, disputed, later apparently confirmed by a Maxwell email.