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Petroleum Geochemical Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
Certain substances when struck by incident radiation of a shorter wavelength (visible or ultraviolet light) emits light of longer wavelength radiation with fluorescence. The fluorescence is the emission of light from a particular type of material because of incident rays. Fluorescence stops when the incident light is switched off. The emitted light is another kind of electromagnetic radiation having a higher wavelength than the incident light. Fluorescence is exhibited by material having an aromatic structure or chromophore groups with unsaturated chemical bonds. A chromophore is a chemical group responsible for the color of the organic substance. Organic compounds having saturated bonds (paraffin, naphthene) do not exhibit fluorescence.
Laser Spectroscopy in Medical Diagnostics
Published in Barbara W. Henderson, Thomas J. Dougherty, Photodynamic Therapy, 2020
Stefan Andersson-Engels, Roger Berg, Jonas Johansson, Sune Svanberg, Unne Stenram, Katarina Svanberg
Laser-induced fluorescence can be used for spectroscopic characterization of biological tissue, because tissue chromophores are excited to higher energy levels when hit by laser light. The different chromophore molecules absorb light at specific wavelengths. The interaction between the photons and the molecules is determined by the energy levels and the color of the light. In Figure 1, a schematic energy level diagram for a molecule in a solvent is shown. The basic energy structure of a molecule is given by the possible electron excitations. The spacing between different electron energy levels is typically 2–6 eV. Besides electronic energy, the molecules also have vibrational and rotational energy. When a quantum of ultraviolet (UV) light is absorbed by the molecule, it is excited to a higher energy level. The molecule will then very quickly relax nonradiatively to the lowest vibrational level of the higher energy level at which an accumulation occurs. Fluorescence light then follows in the decay to a lower energy level. The fluorescence light is emitted with a rather broad wavelength distribution, with the maximum in the blue-green wavelength region. This broad distribution is the total autofluorescence from several tissue chromophores, such as tryptophan, with its fluorescence peak at about 390 nm when excited at 337 nm; collagen at about 390 nm; elastin at about 410 nm; the coenzyme nicotinamideadenine nucleotide (NADH), with the fluorescence peak at about 470 nm; β-carotene at about 520 nm; and mélanines at about 540 nm.
Diagnostic Test with Targeted Therapy for Cancer: The Theranostic Nanomedicine
Published in Paula V. Messina, Luciano A. Benedini, Damián Placente, Tomorrow’s Healthcare by Nano-sized Approaches, 2020
Paula V. Messina, Luciano A. Benedini, Damián Placente
Chromophores are light-absorbing molecules and they reach states that are more excited by absorption of light. Thus, the excited chromophore returns to the ground (basal) state by the release of energy as fluorescence or heat. When the molecule generates fluorescence, the light released has an equal or longer wavelength than the incident one. However, some chromophores can produce triplet-excited states that are able to transfer the excess of energy to the nearby molecules (or cells). This process has been described as photosensitization (Liu et al. 2014).
Enhancement approaches for photothermal conversion of donor–acceptor conjugated polymer for photothermal therapy: a review
Published in Science and Technology of Advanced Materials, 2022
Thi-Thuy Duong Pham, Le Minh Tu Phan, Sungbo Cho, Juhyun Park
The interaction of a photon impinging on a chromophore can be classified into three processes: transmission, scattering, and absorption (Figure 1(a)). Light transmission occurs when no interaction occurs between photons and molecules. Light scattering (including inelastic or elastic scattering) occurs when incident light is reflected in various directions with different intensities. The remaining process, absorption, depends on complementing (matching) the electromagnetic frequency of light and nature of matter; this transfers the absorbed energy in various energy forms. The electronically and vibrationally excited state transition of a chromophore is derived from the absorption of a photon. It is controlled through a photophysical process following the Jablonski diagram. Therein, the arrangement of vibrational and electronic energy is built along the vertical direction, and the molecular spin multiplicity is managed in horizontal groups. The diagram clarifies the tendency between the radiative and nonradiative decays of a chromophore, enabling the exploration of the fundamental principle for the design of organic phototheranostic agents. As shown in Figure 1(b), radiative transitions are indicated by straight arrows, and nonradiative decays are represented by squiggly arrows.
Restricted substances for textiles
Published in Textile Progress, 2022
Arun Kumar Patra, Siva Rama Kumar Pariti
Many of the application classes of textile dyes have the azo group as their chromophore. In some cases, the same colourant may be classified into more than one application class. For example, disperse dyes can often be applied as solvent dyes and vat dyes sometimes applied as pigments. Like disperse colours, solvent dyes are also non-ionic and sparingly soluble in water, but the molecular weight of solvent dyes is higher. Typically, solvent dyes are used for the colouration of inks, plastics, waxes, fat products and mineral oil products (Ollgaard, Frost, Galster, & Hansen, 1998). Azo pigments are similar to disperse dyes, solvent dyes and mordant dyes in terms of possessing very low solubility in water, their molecular size and hydrophobicity. However, the main differentiator for pigments is their low solubility in organic solvents as well as in water. In another instance, acid dyes and direct dyes are both anionic, water-soluble dyes with similar organic structure but acid dyes usually have lower molecular weight. The following table gives a classification of azo dyes (Table 6).
Derivative UV-Vis spectroscopy of asphaltenes solutions for the determination of the composition
Published in Petroleum Science and Technology, 2020
Ernestina Elizabeth Banda-Cruz, Nohra Violeta Gallardo-Rivas, Reinaldo David Martínez-Orozco, Ulises Páramo-García, Ana María Mendoza-Martínez
Asphaltenes-cyclohexane solutions generate Uv-vis spectrum in the range of 200-450 nm. It is possible to determine first and second derivative of the zero-order spectrum of asphaltenes-cyclohexane solutions by softening the signals and using the Savitzzky-Golay method with second-order polynomial equation. The first derivative of zero-order UV-vis spectrum allowed the identification of five maxima that may be related to composition in asphaltenes solutions ∼ to 225 nm for benzenic compounds, to 259 nm naphthenic compounds, to 295 nm phenanthrene, to 328 nm for linear three-ring aromatic chromophores and by most compact four-ring chromophores and 401 nm for vanadium porphyrins. Thus, optical absorption in the UV can be used to measure the population of small chromophores. The presence of absorption bands of individual chromophores in the UV-vis spectrum provides evidence on the archipelago-type architecture present in the asphaltenes analyzed. The molecules structures of both types of asphaltenes could contain small systems of 2, 3 and 4 fused rings separated by at least one covalent bond.