Pure Boric Acid Does Not Show Room‐Temperature Phosphorescence (RTP)

Abstract

Boric acid (BA) has been used as a transparent glass matrix for optical materials for over 100 years. However, recently, apparent room‐temperature phosphorescence (RTP) from BA (crystalline and powder states) was reported (Zheng et al., Angew. Chem. Int. Ed. 2021, 60, 9500) when irradiated at 280 nm under ambient conditions. We suspected that RTP from their BA sample was induced by an unidentified impurity. Our experimental results show that pure BA synthesized from B(OMe)3 does not luminesce in the solid state when irradiated at 250–400 nm, while commercial BA indeed (faintly) luminesces. Our theoretical calculations show that neither individual BA molecules nor aggregates would absorb light at >175 nm, and we observe no absorption of solid pure BA experimentally at >200 nm. Therefore, it is not possible for pure BA to be excited at >250 nm even in the solid state. Thus, pure BA does not display RTP, whereas trace impurities can induce RTP.

Ultralong Organic Phosphorescence Modulation of Aromatic Carbonyls and Multi‐Component Systems

“…This nanocrystal with the bright persistent red RTP, is directly applied for imaging of breast cancer cells. Despite excellent RTP performance, the RTP of some carbazole derivatives has been reported to originate from impurities, [ 59 ] similar phenomena have been reported for other substances, [ 60 ] which emphasized the necessity of purifying the luminophore.…”

“…New phosphors with color‐tunable [ 118‐119 ] emission bands are also desirable. Unique oxygen consumption mechanism of the polymethyl methacrylate doping system, [ 120 ] mechanoluminescence [ 96,107,12 ] and impurity induced phosphorescence [ 60 ] are also required for further study to elaborate their mechanism profoundly. In terms of application areas, more types of matrixes and crystals should be explored to adapt to different applications, especially the biological field.…”

Dibenzyl Isophthalates as Versatile Hosts in Room Temperature Phosphorescence Host-Guest Systems

“…[30][31][32][33][34][35][36][37][38][39] In an increasing number of cases, the RTP emission of a compound was found to arise from incorporated trace impurities, making them in reality host-guest RTP systems. [40][41][42][43][44] Identifying these impurities, or even just proving their existence, can be very challenging as RTP may arise even already at ppb levels of contamination. 45 Therefore, host-guest systems steadily gain in importance among purely-organic RTP materials.…”