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Photosensitizer
Photosensitizers are light absorbers that alter the course of a photochemical reaction. They usually are catalysts. They can function by many mechanisms; sometimes they abstract an electron from the substrate, and sometimes they abstract a hydrogen atom from the substrate. At the end of this process, the photosensitizer returns to its ground state, where it remains chemically intact, poised to absorb more light. One branch of chemistry which frequently utilizes photosensitizers is polymer chemistry, using photosensitizers in reactions such as photopolymerization, photocrosslinking, and photodegradation. Photosensitizers are also used to generate prolonged excited electronic states in organic molecules with uses in photocatalysis, photon upconversion and photodynamic therapy. Generally, photosensitizers absorb electromagnetic radiation consisting of Infrared, infrared radiation, Light, visible light radiation, and Ultraviolet, ultraviolet radiation and transfer absorbed energy into ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photodynamic Therapy (red)
Photodynamic therapy (PDT) is a form of phototherapy involving light and a photosensitizing chemical substance used in conjunction with molecular oxygen to elicit cell death (phototoxicity). PDT is used in treating acne, macular degeneration#Wet AMD, wet age-related macular degeneration, psoriasis, and Herpes simplex, herpes. It is used to treat malignant cancers, including head and neck, lung, bladder and skin. Advantages lessen the need for delicate surgery and lengthy recuperation and minimal formation of scar tissue and disfigurement. A side effect is the associated photosensitisation of skin tissue. Basics PDT applications involve three components: a photosensitizer, a light source and tissue oxygen. The wavelength of the light source needs to be appropriate for exciting the photosensitizer to produce radicals and/or reactive oxygen species. These are Radical (chemistry), free radicals (Type I) generated through electron abstraction or transfer from a substrate molecul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photodynamic Therapy
Photodynamic therapy (PDT) is a form of phototherapy involving light and a photosensitizing chemical substance used in conjunction with molecular oxygen to elicit cell death ( phototoxicity). PDT is used in treating acne, wet age-related macular degeneration, psoriasis, and herpes. It is used to treat malignant cancers, including head and neck, lung, bladder and skin. Advantages lessen the need for delicate surgery and lengthy recuperation and minimal formation of scar tissue and disfigurement. A side effect is the associated photosensitisation of skin tissue. Basics PDT applications involve three components: a photosensitizer, a light source and tissue oxygen. The wavelength of the light source needs to be appropriate for exciting the photosensitizer to produce radicals and/or reactive oxygen species. These are free radicals (Type I) generated through electron abstraction or transfer from a substrate molecule and highly reactive state of oxygen known as singlet oxygen ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photocatalysis
In chemistry, photocatalysis is the acceleration of a photoreaction in the presence of a photocatalyst, the excited state of which "repeatedly interacts with the reaction partners forming reaction intermediates and regenerates itself after each cycle of such interactions." In many cases, the catalyst is a solid that upon irradiation with UV- or visible light generates electron–hole pairs that generate free radicals. Photocatalysts belong to three main groups; heterogeneous, homogeneous, and plasmonic antenna-reactor catalysts. The use of each catalysts depends on the preferred application and required catalysis reaction. History Early mentions (1911–1938) The earliest mention came in 1911, when German chemist Dr. Alexander Eibner integrated the concept in his research of the illumination of zinc oxide (ZnO) on the bleaching of the dark blue pigment, Prussian blue. Around this time, Bruner and Kozak published an article discussing the deterioration of oxalic acid in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photochemistry
Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 Nanometre, nm), visible light, visible (400–750 nm), or infrared radiation (750–2500 nm). In nature, photochemistry is of immense importance as it is the basis of photosynthesis, vision, and the formation of vitamin D with sunlight. It is also responsible for the appearance of DNA mutations leading to skin cancers. Photochemical reactions proceed differently than temperature-driven reactions. Photochemical paths access high-energy intermediates that cannot be generated thermally, thereby overcoming large Activation energy, activation barriers in a short period of time, and allowing reactions otherwise inaccessible by thermal processes. Photochemistry can also be destructive, as illustrated by the photodegradation of plastics. Concept Grotthuss–Dra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photocatalysis
In chemistry, photocatalysis is the acceleration of a photoreaction in the presence of a photocatalyst, the excited state of which "repeatedly interacts with the reaction partners forming reaction intermediates and regenerates itself after each cycle of such interactions." In many cases, the catalyst is a solid that upon irradiation with UV- or visible light generates electron–hole pairs that generate free radicals. Photocatalysts belong to three main groups; heterogeneous, homogeneous, and plasmonic antenna-reactor catalysts. The use of each catalysts depends on the preferred application and required catalysis reaction. History Early mentions (1911–1938) The earliest mention came in 1911, when German chemist Dr. Alexander Eibner integrated the concept in his research of the illumination of zinc oxide (ZnO) on the bleaching of the dark blue pigment, Prussian blue. Around this time, Bruner and Kozak published an article discussing the deterioration of oxalic acid in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photon Upconversion
Photon upconversion (UC) is a process in which the sequential Absorption (electromagnetic radiation), absorption of two or more photons leads to the Emission spectrum, emission of light at shorter wavelength than the excitation wavelength. It is an Stokes shift, anti-Stokes type emission. An example is the conversion of infrared light to visible light. Upconversion can take place in both organic and inorganic materials, through a number of different mechanisms. Organic molecules that can achieve photon upconversion through triplet-triplet annihilation are typically Polycyclic aromatic hydrocarbon, polycyclic aromatic hydrocarbons (PAHs). Inorganic materials capable of photon upconversion often contain ions of d-block or f-block elements. Examples of these ions are lanthanides, Ln3+, titanium, Ti2+, nickel, Ni2+, molybdenum, Mo3+, rhenium, Re4+, osmium, Os4+, and so on. Physical mechanisms There are three basic mechanisms for photon upconversion in inorganic materials and at leas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoacid
Photoacids are molecules that become more acidic upon absorption of light. Either the light causes a photodissociation to produce a strong acid, or the light causes photoassociation (such as a ring forming reaction) that leads to an increased acidity and dissociation of a proton. There are two main types of molecules that release protons upon illumination: photoacid generators (PAGs) and photoacids (PAHs). PAGs undergo proton photodissociation irreversibly, while PAHs are molecules that undergo proton photodissociation and thermal reassociation. In this latter case, the excited state is strongly acidic, but reversible. Photoacid generators An example due to photodissociation is triphenylsulfonium triflate. This colourless salt consists of a sulfonium cation and the triflate anion. Many related salts are known including those with other noncoordinating anions and those with diverse substituents on the phenyl rings. The triphenylsulfonium salts absorb at a wavelength of 233&nb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoinitiator
In chemistry, a photoinitiator is a molecule that creates reactive species (free radicals, cations or anions) when exposed to radiation (Ultraviolet, UV or Visible spectrum, visible). Synthetic photoinitiators are key components in photopolymers (for example, photo-curable coatings, adhesives and dental restoratives). Some small molecules in the Atmosphere of Earth, atmosphere can also act as photoinitiators by decomposing to give free radicals (in photochemical smog). For instance, nitrogen dioxide () is produced in large quantities by gasoline-burning internal combustion engines. in the troposphere gives smog its brown coloration and Catalysis, catalyzes production of toxic ground-level ozone (). Molecular oxygen () also serves as a photoinitiator in the stratosphere, breaking down into atomic oxygen and combining with in order to form the ozone in the ozone layer. Reactions Photoinitators can create reactive species by different pathways including photodissociation and elec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simplified Schematic For A Photosensitizer Affecting A Substrate
Simplification, Simplify, or Simplified may refer to: Mathematics Simplification is the process of replacing a expression (mathematics), mathematical expression by an equivalent one that is simpler (usually shorter), according to a well-founded ordering. Examples include: * Computer algebra#Simplification, Simplification of algebraic expressions, in computer algebra * Simplification of boolean expressions i.e. logic optimization * Simplification by conjunction elimination in inference in logic yields a simpler, but generally non-equivalent formula * Fraction#Simplification, Simplification of fractions Science * Approximations simplify a more detailed or difficult to use process or model Linguistics * Simplification of Chinese characters * Simplified English (other) * Text simplification Music * ''Simplify'', a 1999 album by Ryan Shupe & the RubberBand * Simplified (band), a 2002 rock band from Charlotte, North Carolina * Simplified (album), ''Simplified'' (album), a 2005 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radical (chemistry)
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron. With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spontaneously dimerize. Most organic radicals have short lifetimes. A notable example of a radical is the hydroxyl radical (HO·), a molecule that has one unpaired electron on the oxygen atom. Two other examples are triplet oxygen and triplet carbene (꞉) which have two unpaired electrons. Radicals may be generated in a number of ways, but typical methods involve redox reactions. Ionizing radiation, heat, electrical discharges, and electrolysis are known to produce radicals. Radicals are intermediates in many chemical reactions, more so than is apparent from the balanced equations. Radicals are important in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes. A majority ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoinitiator
In chemistry, a photoinitiator is a molecule that creates reactive species (free radicals, cations or anions) when exposed to radiation (Ultraviolet, UV or Visible spectrum, visible). Synthetic photoinitiators are key components in photopolymers (for example, photo-curable coatings, adhesives and dental restoratives). Some small molecules in the Atmosphere of Earth, atmosphere can also act as photoinitiators by decomposing to give free radicals (in photochemical smog). For instance, nitrogen dioxide () is produced in large quantities by gasoline-burning internal combustion engines. in the troposphere gives smog its brown coloration and Catalysis, catalyzes production of toxic ground-level ozone (). Molecular oxygen () also serves as a photoinitiator in the stratosphere, breaking down into atomic oxygen and combining with in order to form the ozone in the ozone layer. Reactions Photoinitators can create reactive species by different pathways including photodissociation and elec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoacid
Photoacids are molecules that become more acidic upon absorption of light. Either the light causes a photodissociation to produce a strong acid, or the light causes photoassociation (such as a ring forming reaction) that leads to an increased acidity and dissociation of a proton. There are two main types of molecules that release protons upon illumination: photoacid generators (PAGs) and photoacids (PAHs). PAGs undergo proton photodissociation irreversibly, while PAHs are molecules that undergo proton photodissociation and thermal reassociation. In this latter case, the excited state is strongly acidic, but reversible. Photoacid generators An example due to photodissociation is triphenylsulfonium triflate. This colourless salt consists of a sulfonium cation and the triflate anion. Many related salts are known including those with other noncoordinating anions and those with diverse substituents on the phenyl rings. The triphenylsulfonium salts absorb at a wavelength of 233&nb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
