<p>The trace impurities in
pure organic phosphors were always ignored because the ultra-low content
impurities were considered to hardly affect the luminescent properties. Evidences
from corresponding reports and research have shown that impurities may greatly affect
room temperature phosphorescence (RTP) in some crystalline compounds. To date, very
few literatures have clearly study the role of impurities in RTP because of the
difficulty in the separation and structure identification of impurities. Also no
reports have focused on utilizing trace impurities to form new strategies for efficient
RTP.</p>
<p>For the
first time, an impurity was isolated from 1-(4-bromophenyl)-1<i>H</i>-imidazole (1BBI) and
structural identified, which was proved to be the key to RTP in 1BBI crystal. Neither
purified impurity nor 1BBI matrix shown any detectable RTP. The impurity could light
up the unusual ultralong RTP in matrix even at <b>0.01 mol%</b> content. Inspired
by impurity/matrix phosphorescence, a trace-ingredient-mediated bicomponent strategy
was introduced for high phosphorescence quantum yield (QY, up to 74.2%) and extralong
lifetime (up to 430 ms).</p><p><b>Research Highlights of this work are including</b></p><p><b>1. </b><b>The study of impurities in organic luminescent materials, including
phosphorescent materials, is rarely reported due to the great difficulty of
separation, purification</b><b> and structure characterization. This work not only separated, purified
and structure identified the trace impurity in the system but also confirmed
the fact that the impurity engenders the RTP. And the corresponding mechanism
was proposed as well.</b></p><p><b>2. </b><b>Inspired by
the role of impurities in RTP, this work proposed an effective strategy for the
design and preparation of persistent organic RTP based on active ingredient incorporation.
Seven compounds were screened out to conduct the bicomponent RTP system and
achieved bright RTP with high QY (up to 74.2%) and extra-long lifetime (up to
430 ms)) RTP with tunable colors.</b></p><p><b>3. </b><b>Combining
the dual emission of blue fluorescence and yellow phosphorescence, a bicomponent
system achieved a bright white-light emission, which shows its outstanding application
potential.</b></p><p>
The design concept and
strategy of this work supplies an efficient approach to develop RTP by simply
mixing the matrix with a trace amount
of active ingredients. And the trace-ingredient-mediated bicomponent system is preferred
for its high efficiency, color-tunable, low cost and easy to prepare properties,
which will make important sense for facilely developing organic persistent RTP
materials. This work will not only lead to a new understanding of persistent
organic RTP but also develop a facile and effective strategy for RTP afterglow
materials.<br></p>
On the role of the atomic bond types in light emission from Si nanoparticles
