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A yellow-emitting cationic iridium(III) complex [(dfppy)2Ir(TBD)]PF6 (TBD: N4,N4′-bis(3-(triethoxysilyl)propyl)-[2,2′-bipyridine]-4,4′-dicarboxamide; dfppy: 2-(2,4-difluorophenyl)pyridine) containing hydrolysable alkoxysilanes was synthesized. Then, a series of silica-based hybrid nanospheres with diameters of around 400 nm was prepared via the hydrolysis of this complex together with tetraethyl orthosilicate (TEOS, a silica source). When the amount of the complex used was 5.0 wt%, hybrid nanospheres showed the best photoluminescence (PL) properties, relative to the PL quantum yield of pure solid [(dfppy)2Ir(TBD)]PF6 (12.7%), that of hybrid nanospheres increased to 26.2%. Moreover, the thermal decomposition temperature (Td) of pure solid [(dfppy)2Ir(TBD)]PF6 was 331 °C, the Td of the complex in hybrid nanospheres increased to 447 °C. However, the yellow light emission was almost unchanged and was still located at 500–750 nm with a maximum wavelength (λem,max) of 577 nm. Under the excitation of blue-emitting chips (λem,max ≈ 455 nm), cold/neutral/warm white light-emitting diodes (WLEDs) with good luminous quality can all be fabricated using these hybrid nanospheres as phosphors in epoxy resin at different blending concentrations. Compared with two or three iridium(III) complexes being contained in silica-based particles as phosphors as described in literatures, in this study, silica-based hybrid nanospheres covalently containing only one yellow-emitting cationic iridium(III) complex as phosphors provide a more effective and simpler method for preparation high-performance WLEDs. [ABSTRACT FROM AUTHOR]

In this work, a series of Cr3+-doped A2NaYF6 (denoted as ANYF:Cr; A = K, Rb, and Cs) fluoroyttrate double-perovskites with broad blue excitation and near-infrared (NIR) emission bands were prepared using a high-temperature solid-state reaction method. The physicochemical and spectroscopic properties of the as-prepared products, including crystal structure, bandgap, morphology, luminescence behaviour and optical performance, were studied in detail. The results show that the Cr3+ activators undergo a decreasing crystal field in ANYF in the direction from K to Cs, yielding a red shift of the emission peak position from 758 to 786 nm, whilst the full-width-at-half-maximum (FWHM) expands from 98 to 104 nm. By virtue of the broadband NIR emission, clear structural images of the tangerine section, mini LED flashlight and circuit board were obtained by merging the optimal RNYF:Cr phosphor on a blue InGaN chip, implying its potential use in light-emitting diodes for non-destructive testing. [ABSTRACT FROM AUTHOR]

Luminescent crystals with high efficiency have huge potential in applications for white light-emitting diodes (LEDs). Herein, organic–inorganic hybrid crystals doped with Mn4+, [N(CH3)4]2XF6:Mn4+ (X = Si, Ge, and Ti), were grown under mild conditions. Their crystal structural evolution was confirmed by single-crystal X-ray diffraction at different temperatures. These crystals exhibit intense red emission with a high external quantum efficiency (73.0% for [N(CH3)4]2TiF6:Mn4+) and good thermal stability. The warm white LEDs were fabricated by combining these red-emitting phosphors with a YAG:Ce3+ ceramic chip. As-grown crystals can significantly optimize the performances of white LEDs (colour rendering index up to 95). Hence, this work provides a new strategy to explore Mn4+-activated organic–inorganic hybrid materials for white LEDs. [ABSTRACT FROM AUTHOR]

A novel cationic iridium(iii) complex [(SRB-DAF)Ir(ppy)2]PF6 (SRB-DAF: 2-((5H-cyclopenta[1,2-b:5,4-b′]dipyridin-5-ylidene)amino)-3′,6′-bis(diethylamino)spiro[isoindoline-1,9′-xanthene]-3-thione and ppy: 2-phenylpyridine) with a thiorhodamine-based auxiliary ligand was designed and synthesized. The spirolactam ring of the thiorhodamine group will be opened with the chelation of Hg2+ ion, and the iridium(iii) complex instantly exhibits remarkable “turn-on” type naked-eye detectable color (λmax,abs = 567 nm) and phosphorescence (λmax,em = 587 nm) changes. Hg2+ can be detected by this iridium(iii) complex with high selectivity and sensitivity in an aqueous solution in the presence of other metal cations (Ag+, Cu2+, Fe2+, Fe3+, Mg2+, Ni2+, Ba2+, Cr3+, Ca2+, Co2+, Na+, Pb2+, Zn2+, Li+, Mn2+, Al3+, K+ and Cd2+) in the pH range 6.9–8.0. As a Hg2+ probe, the iridium(iii) complex exhibited low detection limits of 8.074 × 10−8 M (16 ppb) by luminescence detection and 3.985 × 10−7 M (80 ppb) by absorption detection. [ABSTRACT FROM AUTHOR]

A series of ternary dinuclear europium(iii) complexes [Eu2(2,7-BTFDBC)3−n(DBM)2n(Phen)2] (n = 0, 1, or 2) were synthesized by using 2,7-bis(4′4′4′-trifluoro-1,3-dioxobutyl)-(9-ethyl-9H-carbazole) (2,7-BTFDBC), dibenzoylmethane (DBM), 1,10-phenanthroline (Phen) and europium(iii) ions. All these complexes display a broad excitation band in the blue region and high intensity emission with high colour purity. The intensity of emission significantly increases with the increase of DBM in [Eu2(2,7-BTFDBC)3−n(DBM)2n(Phen)2] (n = 0, 1, or 2). The theoretical predictions of the molecular geometry and electronic absorption spectrum of [Eu2(2,7-BTFDBC)(DBM)4(Phen)2] confirm that the pendant phenyl domains engage in multiple T-shaped and parallel-displaced π-stacking interactions with the coordination sphere of two europium(iii) centers. Using [Eu2(2,7-BTFDBC)(DBM)4(Phen)2] as a red phosphor, a single red LED has been obtained with a ∼460 nm-emitting GaN chip. [ABSTRACT FROM AUTHOR]

A novel red-emitting cationic iridium(iii) complex, [(Lm)2Ir(La)]PF6, (Lm: 2-(9-(2-ethylhexyl)-9H-carbazol-3-yl)benzo[d]thiazole, La: N,N-diphenyl-4-(5-(pyridin-2-yl)-1,3,4-oxadiazol-2-yl)aniline) was synthesized. Its ultraviolet-visible absorption and photoluminescent properties show that the complex can be efficiently excited by a 465 nm-emitting blue GaN chip, its decomposition temperature (Td) is 340 °C, and its relative emission intensity at 100 °C is 88.3% of 25 °C. Perfect red light with a CIE value of (0.65, 0.34) was obtained when it was used as a phosphor at 6.0 wt% blending concentration in epoxy resin in a blue GaN-based LED. A 465 nm-emitting blue GaN-based LED only using yellow-emitting Y3Al5O12:Ce3+ (YAG:Ce) as a phosphor (1.0 wt% in epoxy resin) emitted cold white, and its corresponding color rendering index (CRI) was 74.1, correlated color temperature (CCT) was 6026 K, and luminous efficiency (ηL) was 25.3 lm W−1. It became a neutral white light LED when the iridium(iii) complex was added at 0.5 wt%, the corresponding CRI was 79.5, CCT was 4004 K, and ηL was 32.6 lm W−1. It further became a warm white LED when the complex was blended at 1.0 wt% and 1.5 wt%, the corresponding CRI were 80.0 and 79.6, CCT were 3650 K and 3133 K, ηL were 25.5 lm W−1 and 22.8 lm W−1, and CIE values were (0.40, 0.39) and (0.43, 0.40), respectively. This complex is a promising red phosphor candidate for red LEDs and warm white LEDs. [ABSTRACT FROM AUTHOR]

A yellow-emitting cationic iridium(III) complex [(dfppy) 2 Ir(TBD)]PF 6 (TBD: N 4 , N 4' -bis(3-(triethoxysilyl)propyl)-[2,2'-bipyridine]-4,4'-dicarboxamide; dfppy: 2-(2,4-difluorophenyl)pyridine) containing hydrolysable alkoxysilanes was synthesized. Then, a series of silica-based hybrid nanospheres with diameters of around 400 nm was prepared via the hydrolysis of this complex together with tetraethyl orthosilicate (TEOS, a silica source). When the amount of the complex used was 5.0 wt%, hybrid nanospheres showed the best photoluminescence (PL) properties, relative to the PL quantum yield of pure solid [(dfppy) 2 Ir(TBD)]PF 6 (12.7%), that of hybrid nanospheres increased to 26.2%. Moreover, the thermal decomposition temperature ( T d ) of pure solid [(dfppy) 2 Ir(TBD)]PF 6 was 331 °C, the T d of the complex in hybrid nanospheres increased to 447 °C. However, the yellow light emission was almost unchanged and was still located at 500-750 nm with a maximum wavelength ( λ em,max ) of 577 nm. Under the excitation of blue-emitting chips ( λ em,max ≈ 455 nm), cold/neutral/warm white light-emitting diodes (WLEDs) with good luminous quality can all be fabricated using these hybrid nanospheres as phosphors in epoxy resin at different blending concentrations. Compared with two or three iridium(III) complexes being contained in silica-based particles as phosphors as described in literatures, in this study, silica-based hybrid nanospheres covalently containing only one yellow-emitting cationic iridium(III) complex as phosphors provide a more effective and simpler method for preparation high-performance WLEDs.

Because rare-earth elements are scarce, expensive, and unsustainable, it is of great significance to develop rare-earth-free (even metal-free) luminescent materials as phosphors for LEDs. Here, a graphitic-C 3 N 4 (g-C 3 N 4 ) derivative containing some heptazines merged with phenyls has been synthesized via thermal polymerization of melamine and quinazoline-2,4(1 H ,3 H )-dione at an optimal mole ratio of 18 : 1. In comparison with g-C 3 N 4 synthesized from melamine only, the photoluminescent (PL) emission colour changed from blue to green, the maximum emission wavelength ( λ em,max ) changed from 467 nm to 508 nm, and the PL quantum yield (PLQY) increased from 8.0% to 24.0%. It was further purified via vacuum sublimation, and a product with yellowish green emission ( λ em,max = 517 nm) and PLQY up to 45.5% was obtained. This sublimated product had high thermal stability and low thermal quenching; its thermal decomposition temperature was as high as 527 °C, and its relative PL emission intensity at 100 °C was 90.8% of that at 20 °C. Excited by blue light chips ( λ em,max ≈ 460 nm), cold, neutral and warm white LEDs can be fabricated using the sublimated product and orange-emitting (Sr,Ba) 3 SiO 5 :Eu 2+ as phosphors. The good performances of these white LEDs (for example, the CIE coordinates, color rendering index and correlated color temperature were (0.31, 0.33), 84.4 and 6577 K, respectively) suggest that the low-efficiency blue-emitting g-C 3 N 4 had been successfully converted into a high-efficiency metal-free quasi-green phosphor., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In this work, a series of Cr 3+ -doped A 2 NaYF 6 (denoted as ANYF:Cr; A = K, Rb, and Cs) fluoroyttrate double-perovskites with broad blue excitation and near-infrared (NIR) emission bands were prepared using a high-temperature solid-state reaction method. The physicochemical and spectroscopic properties of the as-prepared products, including crystal structure, bandgap, morphology, luminescence behaviour and optical performance, were studied in detail. The results show that the Cr 3+ activators undergo a decreasing crystal field in ANYF in the direction from K to Cs, yielding a red shift of the emission peak position from 758 to 786 nm, whilst the full-width-at-half-maximum (FWHM) expands from 98 to 104 nm. By virtue of the broadband NIR emission, clear structural images of the tangerine section, mini LED flashlight and circuit board were obtained by merging the optimal RNYF:Cr phosphor on a blue InGaN chip, implying its potential use in light-emitting diodes for non-destructive testing.

A series of ternary dinuclear europium(iii) complexes [Eu2(2,7-BTFDBC)3-n(DBM)2n(Phen)2] (n = 0, 1, or 2) were synthesized by using 2,7-bis(4'4'4'-trifluoro-1,3-dioxobutyl)-(9-ethyl-9H-carbazole) (2,7-BTFDBC), dibenzoylmethane (DBM), 1,10-phenanthroline (Phen) and europium(iii) ions. All these complexes display a broad excitation band in the blue region and high intensity emission with high colour purity. The intensity of emission significantly increases with the increase of DBM in [Eu2(2,7-BTFDBC)3-n(DBM)2n(Phen)2] (n = 0, 1, or 2). The theoretical predictions of the molecular geometry and electronic absorption spectrum of [Eu2(2,7-BTFDBC)(DBM)4(Phen)2] confirm that the pendant phenyl domains engage in multiple T-shaped and parallel-displaced π-stacking interactions with the coordination sphere of two europium(iii) centers. Using [Eu2(2,7-BTFDBC)(DBM)4(Phen)2] as a red phosphor, a single red LED has been obtained with a ∼460 nm-emitting GaN chip.