Fluorescent Crystalloluminescence of N-Isopropylcarbazole

Abstract

We have observed very bright visible luminescence from N-isopropylcarbazole (NIPCz) when the compound crystallizes from the molten state to a crystalline aggregate. The sample crystals were heated on a glass plate to above their melting point (380 K) and cooled gradually under ambient conditions. When their temperature fell below 350 K, sudden rapid crystallization took place, accompanied by bluish-white luminescence. Video imaging of the phenomena revealed that both the crystallization and luminescence occurred in the same time frame of <0.5 ms, demonstrating that the two effects were intimately related to each other, i.e., crystalloluminescence (XTL). Thermal analysis of the sample revealed that the preceding state prior to the crystallization was not a glassy solid, but a supercooled liquid state. The XTL spectrum agreed very well with both photo- and triboluminescence spectra of NIPCz. Moreover, its intensity was considerably higher than the reported values for other crystalloluminescent materials such as NaCl. This is the first demonstration of the fluorescent XTL of an organic material. We discussed the mechanism leading to XTL in detail on the basis of the available models, and we concluded that a valid explanation for XTL could be provided by triboluminescence mechanisms.

Novel ionization processes for use in mass spectrometry: ‘Squeezing’ nonvolatile analyte ions from crystals and droplets

“…At this point, a sublimation‐driven triboluminescence‐like charge separation process still seems to be the best mechanistic explanation for self‐ionizing matrices. A number of self‐ionizing matrices have been found to have triboluminescence properties when a solid, including 3‐NBN, coumarins, carbazoles, frozen water and frozen methanol …”

“…142 Some MAI matrix compounds are also known to exhibit triboluminescence (sometimes called fractoluminescence) when fractured. 118,[190][191][192][193][194][195][196][197][198][199][200] Triboluminescence is common and possibly all the known matrices that produce gas-phase analyte ions at low temperatures undergo a charge separation process when the crystals are fractured. 1 The light observed when these crystals fracture is believed to be caused by opposite charges on adjacent crystal faces producing a discharge between the faces.…”

“…A number of self-ionizing matrices have been found to have triboluminescence properties when a solid, including 3-NBN, coumarins, carbazoles, frozen water and frozen methanol. 118,[190][191][192][193][194][195][196][197][198][199][200] Generally, vacuum ionization produces exceptionally clean mass spectra while inlet ionization, especially using longer inlet tubes and/or increased inlet tube temperature, usually causes additional and more abundant signals in the low-mass range region. In specific cases analyte-Cu adducts were detected when using a heated copper inlet tube.…”

Renaissance of Organic Triboluminescent Materials

“…[28] Avery bright luminescence is observed when NIPC is allowed to crystallize from its molten state (Figure 3). [28] Avery bright luminescence is observed when NIPC is allowed to crystallize from its molten state (Figure 3).…”

Deep ultraviolet and visible crystalloluminescence of sodium chloride

“…1 It can be distinguished from more widely known forms of luminescence, such as chemiluminescence (CL) or triboluminescence (TL), although in many cases the apparent XTL can be linked back to one of these other mechanisms. 2,3 Observations of the phenomenon of XTL dates as far back as 1787, where Pickel reported seeing a bright emission of light during the solidification of fused potassium sulfate. 4 Bandrowski in 1894 was the first to report XTL by precipitation of sodium chloride from solution using hydrochloric acid.…”