JF - Journal of the American Chemical Society
The BODIPY based synthons were prepared by adapting standard synthetic methodologies for the fluorescent dyes. Initial attempts to prepare BODIPY-carboxylic acids 7 and 8 directly from 4-formylbenzoic acid (5) and the appropriate pyrroles failed due to the insolubility of the aldehyde in the typical chlorinated solvents used for BODIPY synthesis. Accordingly, we converted 5 to the tert-butyl ester to improve the solubility of the aldehyde building block. Esterification of 4-formylbenzoic acid (5) with tert-butanol using DCC and DMAP delivered aldehyde 6. Condensation of 6 with either 2,4-dimethylpyrrole or 2,4-dimethyl-3-ethyl pyrrole using TFA as an acid catalyst, followed by oxidation with p-chloranil and addition BF3•OEt2 cleanly generated BODIPY derivatives 7 and 8 in 68% and 50% yield, respectively ().
Synthesis and Chemiluminescence of Luminol - YouTube
Chemiluminescence is the production of light from a chemical reaction. Two chemicals react to form an excited (high-energy) intermediate, which breaks down releasing some of its energy as of light (see glossary for all terms in bold) to reach its ground state (see , below).
BOPEG2 and BOPEG3 display similar spectral profiles that are shifted ~20 – 30 nm to longer wavelengths due to the ethyl groups at the 2- and 6-positions of the BODIPY framework (). Variation of PEG chain length does not attenuate the dye photophysics. All three BOPEG dyes display small Stokes shifts of 12 – 15 nm, and relatively high fluorescence quantum yields, which range from 59 – 82%. Both of these observations are typical of BODIPY derivatives. Interestingly, increasing the length of the PEG chain, is manifest in lower fluorescence quantum yields. The BOPEG photophysics are also largely invariant to solvent polarity, as absorbance and fluorescence spectra with similar profiles to those obtained in CH2Cl2 were also obtained in polar solvents such as MeCN or water ().
Synthesis and chemiluminescence of a protected peroxyoxalate
Chemiluminescence reactions, such as those in glow sticks, are temperature-dependent. The reaction speeds up as the temperature rises – snapping your glow stick in hot water will produce a fantastic glow, but it will not last as long as it would at room temperature. Conversely, the reaction rate slows down at low temperature; this is why keeping your glow stick in the freezer for several hours can allow the stick to glow brightly again when it is removed and warmed up, long after it would otherwise have stopped glowing. The reaction does not stop completely in the freezer, but it does slow down so that the glow is barely detectable.
SYNTHESIS AND CHARACTERIZATION OF LUMINOL …
Because the iron acts as a catalyst, it is only required in trace amounts, therefore only a tiny amount of blood is required to produce a positive result. This means that blood can be detected even when it is not visible to the naked eye.
Regional Centre of Advanced Technologies and Materials
When diphenyl oxalate reacts with hydrogen peroxide (H2O2), it is oxidised to give phenol and a cyclic peroxide. The peroxide reacts with a molecule of dye to give two molecules of carbon dioxide (CO2) and in the process, an electron in the dye molecule is promoted to an excited state. When the excited (high-energy) dye molecule returns to its ground state, a photon of light is released. The reaction is pH-dependent. When the solution is slightly alkaline, the reaction produces a brighter light.
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Forensic scientists use the reaction of luminol to detect blood at crime scenes. A mixture of luminol in a dilute solution of hydrogen peroxide is sprayed onto the area where the forensic scientists suspect that there is blood. The iron present in the haem unit of haemoglobin (see ) in the blood acts as a in the reaction described in . The room must be dark and if blood is present, a blue glow, lasting for about 30 seconds, will be observed. The forensic investigators can record this glow by using photographic film, which can be used as evidence in court for the presence of blood at the scene. (For a teaching activity about forensic science, see .