Highly Efficient Deep Blue Fluorescent Organic Light-Emitting Diodes Boosted by Thermally Activated Delayed Fluorescence Sensitization

Highly efficient deep blue fluorescent material and various thermally activated delayed fluorescent (TADF) blue sensitization materials were synthesized for fluorescent deep blue organic light-emitting diodes (OLEDs). These materials were designed and selected by considering efficient energy transfer conditions (i.e., spectral overlap and quantum efficiency) between sensitizer and acceptor. Energy transfer process from TADF host sensitizers to deep blue fluorescent emitter has been investigated by measuring the energy transfer rate. Measured energy transfer rate was to be 1.24 × 10¹⁰ s^–1 (mol/dm³)⁻¹ for a prompt decay of fluorescence and 2.61 × 10⁸ s^–1 (mol/dm³)⁻¹ for delayed fluorescence, which demonstrated the efficient energy transfer. Indeed, highly efficient deep blue fluorescent OLEDs boosted by the TADF host-sensitization process were successfully fabricated. The maximum external quantum efficiency was 19.0% with color coordinates of (0.14, 0.15) and 15.5% with color coordinates of (0.15, 0.11) in the different host system. The efficiency roll-off characteristic and device operating lifetime were also improved by this efficient sensitization process

Maintenance of <i>^s.tGlmS⁺p</i> in <i>S. typhimurium</i> proliferating in tumor tissue.

<p>(A) GlmS⁻ mutant (SKS1002, A) and parental <i>Salmonellae</i> (SHJ2037, B) carrying <i>^s.tGlmS⁺p</i> were injected into CT26 tumor-bearing mice through the tail vein (3×10⁷ CFU). Tumor tissues were sampled on the indicated days, homogenized, and spread on GlcNAc-supplemented LB plates containing kanamycin and chloramphenicol for the enumeration of total number of bacteria and ampicillin for the determination of plasmid-carrying bacteria.</p

Plasmid maintenance in <i>E. coli</i> using the <i>glmS</i> system.

<p>GlmS⁻ mutant bacteria (CKS1001) or the parental strain (CH1436) carrying <i>^E.cGlmS⁺p</i> were subcultured (1/1000) in minimal media every 12 hrs. The fraction of bacteria carrying <i>^E.cGlmS⁺p</i> at the indicated time was determined on GlcNAc-supplemented LB plates containing ampicillin (50 mg/ml).</p

Maintenance of <i>pLux</i> in <i>E. coli</i> proliferating in tumor tissue.

<p>(A) GlmS⁻ mutant bacteria (CKS1001) and parental wild type <i>E. coli</i> (CH1436) carrying <i>^E.cGlmS⁺ pLux</i> were injected into CT26 tumor-bearing mice through the tail vein (1×10⁸ CFU). Bioluminescent signals from <i>pLux</i> were monitored at the indicated times using an <i>in vivo</i> imaging system. (B) The photon intensity of the tumor region was plotted as a function of time for GlmS⁻ mutant and wild-type <i>E. coli</i>. The region of interest (ROI) was selected manually over the tumor region and the area was kept constant. Photon intensity was recorded as the maximum intensity (photons s⁻¹ cm⁻² sr⁻¹) within the ROI. Data represent the means and SEM of three independent experiments. (C) Tumor tissues were sampled on the indicated days. The total number of bacteria and the number of bacteria carrying <i>^E.cGlmS⁺ pLux</i> was assessed by CFU determination.</p

Maintenance of <i>^S.tGlmS⁺p</i> in <i>S. typhimurium</i> proliferating in tumor tissues.

<p><i>SMR2130</i> (GlmS⁻) and <i>SKS1002</i> (WT) strains carrying <i>^S.tGlmS⁺pLux</i> (3×10⁷ CFU), were injected intravenously into mouse bearing 4T-1 (mouse breast cancer) or ASPC-1 (human pancreatic cancer). Tumor tissue were sampled at 7 days after the injection, homogenized, spread on LB plates containing kanamycin and chloramphenicol and/or amphicilin, and enumerated total number of bacteria (Km^R Cm^R) and those carrying plasmid(Amp^R).</p

Phenotype of GlmS⁻ mutant <i>E. coli</i>.

<p>(A) Growth of GlmS⁻ mutant <i>E. coli</i> under various media conditions. GlmS⁻ mutant <i>E. coli</i> (CKS1001, open circles) and GlmS⁻ mutant <i>E. coli</i> carrying <i>^E.cGlmS⁺p</i> (closed circles) grown overnight in LB supplemented with 0.2% GlcNAc were diluted 50-fold in minimal media or media supplemented with 0.2% GlcNAc (open triangles) and grown for 24 hrs. Wild-type parental <i>E. coli</i> (CH1436, closed triangles) were grown in the same way in minimal media. Samples were taken at the indicated times for CFU determination on supplemented LB plates. (B) GlmS⁻ mutant (CKS1001) or parental wild-type <i>E. coli</i> (CH1436) carrying ϕ<i>hdeAB</i>p:<i>lacZYA</i> grown overnight in LB supplemented with 0.2% GlcNAc were diluted 50-fold in minimal media and grown for 5 hrs. β-galactosidase activity (A₄₂₀/min/ml) in the supernatants and lysed pellets was determined. (C) GlmS⁻ mutant bacteria (CKS1001) carrying <i>^E.cGlmS⁺pGFP</i> or <i>pGFP</i> grown overnight in LB supplemented with 0.2% GlcNAc were diluted 50-fold in minimal media and cultured for the indicated times. Wild-type parental <i>E. coli</i> (CH1436) carrying <i>pGFP</i> was grown the same way in minimal media. Samples were taken at the indicated times, the supernatant (<i>s</i>) and pellet (<i>p</i>) fractions were isolated, and the fractions were separated by 12% SDS-PAGE for determination of GFP by Western blotting.</p

Growth of WT (CH1018, A) and GlmS⁻ (CKS1001, B) mutant <i>E. coli</i> in the minimal media with supplementations.

<p>∼5×10⁵ CFU/ml of bacteria were inoculated in the M9 media containing indicated supplementations, grown for 24 hrs at 37°C, and total numbers of bacteria were enumerated on minimal media plates containing 500 mM GlcNAc. Final concentrations of each organ extracts were 0.2 mg/ml.</p

Bacterial strains and plasmids used in this study.

<p>Bacterial strains and plasmids used in this study.</p

Intracellular growth of GlmS⁻ mutant <i>S. typhimurium</i>.

<p>(A) 5×10⁵ CFU of GlmS⁻ mutant (SKS1001) and wild-type (SCH2005) <i>Salmonellae</i> grown in LB supplemented with 0.2% GlcNAc was mixed with HeLa cells. Gentamycin-resistant intracellular <i>Salmonellae</i> were enumerated by determining the number of CFU at the indicated times. (B) The intracellular GlmS⁻ mutant bacteria, GlmS⁻ mutant bacteria carrying <i>^S.tGlmS⁺p</i>, and wild-type bacteria were enumerated at 0 and 24 hrs in HeLa cells (B) and peritoneal macrophages (C).</p

Phenotype of GlmS⁻ mutant <i>S. typhimurium</i>.

<p>(A) Growth of GlmS⁻ mutant <i>Salmonellae</i> under various media conditions. GlmS⁻ mutant <i>Salmonella</i> (SKS1001,open circles) and the GlmS⁻ mutant <i>Salmonella</i> carrying <i>^S.tGlmS⁺p</i> (closed circles) grown overnight in LB supplemented with 0.2% GlcNAc were diluted 50-fold in minimal media or media supplemented with 0.2% GlcNAc (open triangles) and grown for 24 hrs. Wild-type parental <i>Salmonella</i> (SCH2005, closed triangles) were grown in the same way in minimal media. Samples were taken at the indicated times for CFU determination on supplemented LB plates.</p