•Four new bionic photocatalysts (1–4) with [2Fe2S] model complexes were reported.•H2 evolution of 1–4 was evaluated, the max H2 yield reached 52.9 ± 1.6 TON (vs. 4).•Inactivity of system was mainly due to photo-degradation of EBS2− and catalyst (1–4).•Reduced FeIFe0 species could be formed by ET from 1*EBS2− to FeIFeI.•The effect of [2Fe2S] complexes’ structure on H2 production mechanism was discussed.Four novel [2Fe2S] model complexes (1–4) had been synthesized and characterized by IR, 1H NMR, elemental analysis and single crystal X-ray crystallography (for 2). The key parameters affecting H2 evolution of title compounds (1–4) were optimized by constructing homogeneous photo-catalytic system consisting of title compounds (1–4) as catalyst, erythrosin B sodium salt (EBS2−) as photo-sensitizer (PS) and triethylamine (TEA) as sacrificial reagent in CH3CN/H2O solution under the irradiation of visible light. The maximum H2 evolution was separately 211.4 ± 6.5 μmol (52.9 ± 1.6 TON vs. 4), 199.4 ± 13.5 μmol (49.9 ± 3.4 TON vs. 1), 124.8 ± 7.6 μmol (31.2 ± 1.9 TON vs. 3) and 34.9 ± 6.9 μmol (8.7 ± 1.7 TON vs. 2) under the optimal conditions with catalyst of 2 × 10−4 mol·L−1, EBS2− of 4 × 10−4 mol·L−1, TEA of 10% (v/v) and pH 12 in CH3CN/H2O (1/1, v/v) solution. Furthermore, the structural effect and mechanism of electron transfer in the present system was carefully discussed by fluorescence spectra and cyclic voltammetry (CV) measurements.We have constructed a homogeneous photo-catalytic system using [2Fe2S] model complexes 1–4 as biomimetic photo-catalysts, EBS2− as PS and TEA as sacrificial reagent in CH3CN/H2O (v/v, 1/1) solution under the visible light irradiation. The H2 evolution performance and mechanism of target complexes 1–4 were evaluated. The result suggested that the different structures of [2Fe2S] simulate complexes affect on H2 evolution performance and mechanism, the maximum H2 evolution was 211.4 ± 6.5 μmol (52.9 ± 1.6 TON vs. 4). The H2 generation mechanism might be able to firstly form an intermediate Fe0FeI by electron transferring from 1*EBS2− to [2Fe2S] center, and then underwent an ECEC (for 1, 2 and 4) or EECC (for 3) process to form the important H2–Fe2S2 (η2-H2–FeIIFeI) species of H2 production. The result indicated the target complexes are potential candidates as photo-catalysts for H2 generation.

Easily prepared and stable solution-processed carbon dots (CDs) have been used and systematically investigated as the electron transport layers (ETLs) for both small-molecule and polymer-based solar cells. Significantly enhanced device performance and lifetime are observed. The enhanced performance is mainly driven by the improvements of the short circuit current (Jsc) and the fill factor (FF), caused by decreasing the work function of Al electrodes and series resistance, increasing shunt resistances, and balancing electrons and hole mobility. Therefore, the devices with CDs as the ETLs have higher charge transport and collection efficiency. In addition, lifetimes of the devices with CDs as the ETLs are also significantly improved, due to the much better air-stability of CD materials compared to LiF as the ETLs. And another reason is that it can efficiently prevent the formation of an unstable cathode contact for the diffusion of Al ions at the interface. These results indicate that CDs, relatively cheap and stable materials, have great potential to be promising ETL materials for industrial-scale manufacture of organic solar cells.

Two series of new lanthanide coordination polymers have been obtained by solvothermal reaction of Ln(NO3)3 and pamoic acid under different pH values. Both series of compounds show three-dimensional porous frameworks composed of dinuclear Ln(III) subunits. Series B demonstrates fascinating solvent-induced dynamic behaviors in an SCSC (single crystal to single crystal) manner. The capability of activated series B to absorb liquid acetone was investigated by means of 1H NMR spectroscopy, demonstrating the potential of Ln-MOFs as highly efficient and reusable liquid acetone sorbents. In addition, photoluminescence properties of Nd (3), Eu (5) and Yb (10) were measured and discussed. Lanthanide contraction effect also played a crucial role in the formation of each series of complexes. Analysis of the relations between the ionic radius (Ln3+) and the number of f electrons in these complexes indicates that lanthanide contraction effect in both series can be well described by the Raymond model.

Two novel Dy-based MOFs, namely, {[Dy2(PA)3(H2O)3(DMF)]·(DMF)2·(H2O)}n (1) and [Dy2(PA)3(H2O)2(DMF)2]·(DMF)3·(H2O)}n (2) (H2PA = pamoic acid), were solvothermally synthesized from the reaction of Dy(NO3)3 and H2PA at different pH values. Interestingly, both complexes can be obtained simultaneously within the pH range of 5.0–6.2, while higher pH values (6.2–7.0) promote the formation of compound 1 and lower pH values (2.0–5.0) tend to produce pure complex 2. Single-crystal X-ray diffraction studies indicate that 1 and 2 are both three-dimensional frameworks composed of dinuclear Dy(III) subunits featuring pcu networks with the point symbol of {412·63}. Significantly, their slight structure difference results in these two compounds showing completely different magnetic properties. Variable temperature magnetization measurements (χMT–T) demonstrate ferromagnetic interactions in compound 1, while possible antiferromagnetic interactions were observed in compound 2. Alternating current (ac) susceptibility measurements indicate that both the in-phase (χ′) and out-of-phase (χ′′) components showed frequency dependence in compound 1, suggesting that there is a slow relaxation behavior of the magnetization, which is typical of single-molecule magnets (SMMs), while no out-of-phase ac signal was noticed for 2. Furthermore, both 1 and 2 exhibit the characteristic luminescence of Dy3+ upon excitation at 365 nm, but with different intensities. The reasons for such magnetic and luminescence differences are discussed in detail.

•A luminescent Eu-MOF with free phenanthroline N sites was synthesized.•Its high stability in water is very important for the practical application.•It exhibits highly sensitive and selective sensing of Cu2 + ion in aqueous solution.•The mechanism of the sensing properties was studied in detail.A luminescent europium metal–organic framework [Eu(HL)(L)(H2O)2]·2H2O (1) (H2L = (2,3-f)-pyrazino(1,10)phenanthroline-2,3-dicarboxylic acid) with uncoordinated phenanthroline nitrogen sites was hydrothermally synthesized. It exhibits highly sensitive and selective sensing of Cu2 + in aqueous solution. To the best of our knowledge, complex 1 is the first luminescent Eu-MOF with uncoordinated phenanthroline nitrogen sites for selective sensing of Cu2 + in aqueous solution. The probable sensing mechanism was discussed in detail.A luminescent Eu-MOF with uncoordinated phenanthroline nitrogen sites was hydrothermally synthesized. It exhibits highly sensitive and selective sensing of Cu2 + in aqueous solution.

The (ppy)-based Pt(II) complex (Pt-1) with deprotonated 2-(diphenylphosphino)benzoic acid as an anionic ligand displays phosphorescence of monomers with a remarkably higher quantum yield than that of the corresponding iridium complex (Ir-1). A prototype OLED using Pt-1 exhibits high performance with an external quantum efficiency of 4.93%.

Five new metal–organic frameworks, namely [Cd(PA)(H2O)(DMF)2]n (1), {[Co(PA)(4,4′-bipy)(H2O) (CH3OH)]·DMF}n (2), {[Cd2(PA)2(4,4′-bipy)1.5(H2O)3]·2DMF·2H2O}n (3), {[Ni(PA)(bpp)(H2O)2]·DMF}n (4) and {[Cd(PA)(bpp)(CH3OH)]·CH3OH}n (5), (H2PA = pamoic acid, 4,4′-bipy = 4,4′-bipyridine, bpp = 1,3-bi(4-pyridyl) propane), have been solvothermally synthesized and characterized by elemental analysis, IR and X-ray diffraction. Complex 1 displays a zigzag chain structure, while both 2 and 4 are 2D layered polymers. In complex 3, two crystallographically independent Cd2+ ions are bridged by PA2− anions alternately to form an infinite (Cd–PA2−)n chain, which extends into a 2D network through 4,4′-bipy linkers. Complex 5 possesses a 3D framework with the point symbol of (83·102·12). Various weak interactions may play a key role in stabilizing the observed structures. Their luminescent properties and thermal stabilities have also been investigated. Complex 5 displays strong green luminescence with an emission maximum at 548 nm.Graphical abstractFive new metal–organic frameworks exhibiting structural diversity, from infinite chain to 3D framework, have been synthesized from reactions with pamoic acid (H2PA) under solvothermal conditions. The compound {[Cd(PA)(bpp)(CH3OH)]·CH3OH}n displays strong green luminescence with an emission maximum at 548 nm.

A highly pure red luminescent heterobimetallic complex [EuZnL(tta)2(μ-tfa)] (L = N,N′-bis(salicylidene)-2,3-propanediamine, tta = 2-thenoyltrifluoroacetonate, tfa = trifluoroacetate) was synthesized. The EL device with this complex exhibits an inspiring current efficiency of 3.7 cd A−1 at a brightness of 300 cd m−2 and gives a maximum Eu(III)-based pure red emitting luminance of 1982.5 cd m−2 at 13.8 V.

The reaction of 2-hydroxybenzophenone derivatives with europium ions has afforded a new family of luminescent nonanuclear Eu(III) clusters. Crystal structure analysis of the clusters reveals that the metal core comprises two vertex-sharing square pyramidal units. Most of these complexes show emissions typical of Eu3+ ion under visible light excitation (400–420 nm) at room temperature. Photophysical characterization and DFT study reveal a correlation between luminescent efficiencies of Eu(III) complexes and the electronic features of the ligands, which can be tuned by the nature of substituents in the 4-position of the ligands. The ligands with a fluorine substituent possess more suitable triplet energy levels, resulting in more intensive luminescence.

A series of lanthanide coordination polymers, {[Ln(L)(OX)0.5(H2O)2]·3H2O}n (Ln = La 1, and Ce 2), [Ln2(L)2(OX)(H2O)3]n (Ln = Pr 3, Nd 4, Sm 5, Eu 6, Gd 7, Tb 8, Dy 9, Er 10, and Yb 11) (H2L = (3-(4-hydroxypyridinium-1-yl) phthalic acid, H2OX = oxalic acid), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. The title compounds are crystallized in the same triclinic space group P but display different 2D layer structures with different dinuclear secondary building units (SBUs) due to the effect of lanthanide contraction. Furthermore, X-ray diffraction and thermogravimetric analysis of 1–11 are also studied, which demonstrate their high purities and good thermal stabilities. Luminescent measurements indicate that the Eu (6), Tb (8), and Dy (9) compounds exhibit ligand (L2−) sensitized emissions in red, green, and yellow light regions, respectively.

Reactions of [Zn(L)(H2O)] precursor and EuCl3 with the aid of CO32− ions derived from atmospheric CO2 affording an unusual heteropolynuclear cluster [Zn4L4Eu4(CO3)6]·EtOH. In the core of the cluster, four hetero-binuclear [ZnLEu] units linked by six CO32− anions forms a well defined [Zn4Eu4] skeleton with good planarity, which plays an important role in stabilizing the cluster.

A series of coordination polymers with various helical subunits, namely, [Cd(L)(CH3OH)(H2O)]n (2), {[Cd(L)(1,4-bbi)]·(H2O)}n (3), {[Cd(L)(m-bix)(H2O)]·(H2O)2}n (4), [Zn(L)(4,4′-bpy)0.5]n (5), and [Zn(L)(bpp)]n (6) (H2L = 3-(4-hydroxypyridinium-1-yl) phthalic acid; PA = phthalic acid, a part of 3-(4-hydroxypyridinium-1-yl) phthalic acid)), have been hydro(solvo)thermally synthesized through the reaction of 3-(4-hydroxypyridinium-1-yl) phthalic acid with divalent zinc and cadmium salts in the presence or absence of N-donor ancillary coligands (1,4-bbi = 1,1′-(1,4-butanediyl)bis(imidazole), m-bix = 1,3-bis(imidazol-1-ylmethyl)benzene, 4,4′-bpy = 4,4′-bipyridine, bpp = 1,3-bi(4-pyridyl)propane). As a result of various coordination modes of the versatile 3-(4-hydroxypyridinium-1-yl) phthalic acid and different coligands, these compounds exhibit structural diversity. Compound 2 displays a layered structure containing two kinds of (Cd–L)n and (Cd–PA)n helical chains. Compound 3 features a 3D supramolecular framework embodying a type of supramolecular helical chain. Compound 4 exhibits a metal–organic ribbon structure with two kinds of helical chains. Compound 5 features a 3D architecture in which a 1D lemniscate shape pseudo meso-helix chain is observed. Compound 6 exhibits a 2D achiral layer in which the 1D (Zn–bpp)n helical chains are alternately arranged in a right- and left-handed sequence. These compounds have been characterized by powder X-ray diffractions (PXRD) and thermal gravimetric analyses (TGA). In addition, their photochemical properties have also been investigated.

Solvothermal reactions of Pb(Ac)2 with a new flexible 1,3-bis(4-pyridyl-3-cyano)propane (1, BPCP) ligand under different synthesis conditions via an in situ ligand transformation reaction produced three true coordination polymorphs, namely, [PbL2–]n (for 2 and 3) and [Pb3L2–3]n (4), as well as their polymorphic framework [(Pb2L2–)·2H2O]n (5) (H2L = 1,3-bis(4-pyridyl-3-carboxyl)propane). These compounds were characterized by elemental analysis, IR, TG, PXRD, and single-crystal X-ray diffraction. In these compounds, the L2–ligand exhibits different coordination conformations and modes tuned by different synthesis conditions, including reaction temperature, cooling rate, and additive, and constructs various architectures by bridging a variety of building units. Polymorphs 2 and 3 display a 3D framework with 1D channels built up from dinuclear ringlike [Pb2L2–2] units and dinuclear semi-ring-like [Pb2L2–] units, respectively. Polymorph 4 also features a 3D architecture constructed from dinuclear ringlike [Pb2L2–2] units interlinked by the L2– ligand. Interestingly, the framework of 4 is big enough to allow the other net to penetrate to form a 2-fold interpenetrating framework with a trinodal (3,6,10)-connected topology with a point symbol of (43)(44·610·8)(48·624·89·104). For 5, there exists two kinds of dinuclear ringlike [Pb2L2–2] units. These [Pb2L2–2] units are interconnected by Pb atoms to afford a 2D undulant network that is further connected by the hydrogen-bonding interactions and weak interactions to afford a 3D supramolecular network. In addition, the photoluminescence properties of 1–5 and the H2L ligand in the solid state at room temperature were also investigated.

Hydrothermal in-situ reactions of 4,4′-bis(3,3′-dicyano)pyridine (pydcy) with Cd(NO3)2·6H2O under the similar reaction condition but different solvent media result in two new compounds [C48H32Cd2N8O18](1) and [C17H13CdN3O5](2). Compound 1 features a new dimeric carboxylate bridged structure, while compound 2 gives a 3D framework with large hexagon channels embodied with water molecules. Topology analysis of 2 defines a type of {83} etb topology. TGA and XRPD analysis indicated that the guest water molecules in 2 can be removed to result in a nanoporous network. Both compounds exhibit intense fluorescence at room temperature, which may originate from the ligand-to-metal charge transfer (LMCT) state.Two novel Cd(II) coordination compounds based on this ligand under similar conditions but different solvent media were conveniently synthesized and characterized by X-ray crystallography.Highlights► Two new Cd(II) compounds are obtained by the in-situ hydrothermal reactions. ► The frameworks of the complexes are profoundly influenced by the solvent media. ► Water molecules in compound 2 can be removed to result in a nanoporous network. ► Both compounds exhibit intense fluorescence at room temperature.

A simplified triple-layered pure red organic light-emitting diode with high efficiency and a slow efficiency roll-off was fabricated by using Eu(DBM)3(sbf) (DBM = dibenzoylmethane, sbf = 4,5-diaza-9,9′-spirobifluorene) as emitter. In particular, an impressive current efficiency of 3.31 cd A−1 and an external quantum efficiency of 1.8% were maintained at a high luminance of 100 cd m−2.

A new complex of Ir(pi)2(acac) (L = 2-(4-bromophenyl)-1-ethyl-1H-phenanthro[9,10-d]imidazole) was designed and synthesized. Its molecular structure was determined by a single-crystal X-ray diffraction analysis. The Ir(III) complex showed characteristic phosphorescence with an emission of 570 nm and a high quantum efficiency of 28%. A high performance yellow OLEDs was successfully fabricated by using this Ir(III) complex as dopant.A new iridium(III) complex of Ir(pi)2(acac) (pi = 2-(4-bromophenyl)-1-ethyl-1H-phenanthro[9,10-d]imidazole) with efficient photo- and electro-luminescent properties was conveniently synthesized and characterized by X-ray crystallography.Research highlights► Syntheses of iridium complex Ir(pi)2(acac) with the 2-(4-bromophenyl)-1-ethyl-1H-phenanthro[9,10-d]imidazole ligand. ► Crystallographic characterization of the Ir(pi)2(acac) was studied. ► Ir(pi)2(acac) is a promising phosphorescent material for OLEDs.

The coordination polymer {[Cu3(hbpdc)(OH)2(H2O)]·2H2O}n (1, hbpdc = 3,3′-dihydroxy-2,2′-bipyridine-6,6′-dicarboxylic anion) was prepared under hydrothermal conditions. Single-crystal X-ray diffraction revealed that complex 1 features a highly ordered 3D nanoporous structure encapsulating a zigzag water chain. Variable-temperature magnetic studies indicated the presence of strong antiferromagnetic coupling.

With N-(5-phenyl-1,3,4-oxadiazol-2-yl)-benzamide (HL1) as the first ligand, three new luminescent europium complexes Eu2Na2(L1)6(OH)2·2C2H5OH·2CHCl3 (1), Eu(L1)3(phen) (phen = 1,10-phenanthroline) (2) and Eu2Na2(L1)6(L2)2(OH)2·8CHCl3 [L2 = 2,5-bis(2-pyridyl)-1,3,4-oxadiazole] (3) have been prepared and structurally characterized. Each ligand L1 coordinates with a Eu3+ ion through a carbonyl oxygen atom and oxadiazol nitrogen atom, the coordination geometry at europium is a distorted square antiprism. Complexes 1 and 3 have centrosymmetric dimeric structural features with OH− as the bridging ligand, while 2 is mononuclear with phen as the neutral ligand. All these complexes show efficient red emissions typical of Eu3+ ions at room temperature, the overall quantum yields of complexes 1, 2 and 3 were 0.15, 0.37 and 0.23, respectively. Using Eu(L1)3(phen) as the emitting material, an electroluminescent device with the structure ITO/TPD (30 nm)/Eu(L1)3(phen): TPD (1 : 3, 50 nm)/AlQ (30 nm)/Mg0.9Ag0.1/Ag was fabricated. The device emits sharp red light originating from europium complex, demonstrating that Eu(L1)3(phen) is a promising red emitter with good electron-transporting property.

The assembly of Zn(II) and Cd(II) centers with different counter anions and XIL ligand (XIL = N,N-bis(pyridin-3-yl)-2,6-pyridinedicarboxamide) gave rise to three new coordination complexes, Zn(XIL)Cl2·DMF (1), [Zn(XIL)2(SCN)2·2H2O]n (2) and [Cd(XIL)2(SCN)2·2H2O]n (3). Complex 1 exists as a centrosymmetric dimer with XIL as exo-bidentate ligand bridging two ZnCl2 units. The dimer forms a 3D supermolecular structure through the hydrogen bonding and strong π–π stacking interactions. Complexes 2 and 3 are iso-structural with a 1D double-chain configuration with XIL as bridging ligand and SCN− as terminal ligand. Among the three complexes, complex 1 exhibits the strongest photoluminescence.

A novel template-activation method was used to create nanoporous carbon materials derived from core–shells@rGO sheets. The carbon materials were prepared through an acid etching and thermal activation procedure with three-dimensional Fe3O4@C@rGO composites as precursors and Fe3O4 nanoparticles as the structural template. The activation at different temperatures could provide materials with different specific surface areas. The unique nanoporous structures with large surface areas are ideal adsorbents. The nanoporous carbon materials were used as adsorbents for the removal of rhodamine B (Rh-B). C@rGO-650 illustrated better adsorption performance than the other synthesized adsorbents. It displayed good recyclability, and its highest adsorption capacity reached up to 14.8 L·g–1. The remarkable adsorption properties make nanoporous carbon a useful candidate for wastewater treatment. This template-activation method can also broaden the potential applications of core–shells@sheet structures for the construction of nanoporous carbon, which helps to resolve the related energy and environmental issues.Topics: Adsorption; Core-shell materials; Crystal structure; Distribution function; Heat treatment; Nanocomposites; Nanoparticles; Nanoporous materials; Surface reaction; Surface structure;

With N-(5-phenyl-1,3,4-oxadiazol-2-yl)-benzamide (HL1) as the first ligand, three new luminescent europium complexes Eu2Na2(L1)6(OH)2·2C2H5OH·2CHCl3 (1), Eu(L1)3(phen) (phen = 1,10-phenanthroline) (2) and Eu2Na2(L1)6(L2)2(OH)2·8CHCl3 [L2 = 2,5-bis(2-pyridyl)-1,3,4-oxadiazole] (3) have been prepared and structurally characterized. Each ligand L1 coordinates with a Eu3+ ion through a carbonyl oxygen atom and oxadiazol nitrogen atom, the coordination geometry at europium is a distorted square antiprism. Complexes 1 and 3 have centrosymmetric dimeric structural features with OH− as the bridging ligand, while 2 is mononuclear with phen as the neutral ligand. All these complexes show efficient red emissions typical of Eu3+ ions at room temperature, the overall quantum yields of complexes 1, 2 and 3 were 0.15, 0.37 and 0.23, respectively. Using Eu(L1)3(phen) as the emitting material, an electroluminescent device with the structure ITO/TPD (30 nm)/Eu(L1)3(phen): TPD (1 : 3, 50 nm)/AlQ (30 nm)/Mg0.9Ag0.1/Ag was fabricated. The device emits sharp red light originating from europium complex, demonstrating that Eu(L1)3(phen) is a promising red emitter with good electron-transporting property.

Easily prepared and stable solution-processed carbon dots (CDs) have been used and systematically investigated as the electron transport layers (ETLs) for both small-molecule and polymer-based solar cells. Significantly enhanced device performance and lifetime are observed. The enhanced performance is mainly driven by the improvements of the short circuit current (Jsc) and the fill factor (FF), caused by decreasing the work function of Al electrodes and series resistance, increasing shunt resistances, and balancing electrons and hole mobility. Therefore, the devices with CDs as the ETLs have higher charge transport and collection efficiency. In addition, lifetimes of the devices with CDs as the ETLs are also significantly improved, due to the much better air-stability of CD materials compared to LiF as the ETLs. And another reason is that it can efficiently prevent the formation of an unstable cathode contact for the diffusion of Al ions at the interface. These results indicate that CDs, relatively cheap and stable materials, have great potential to be promising ETL materials for industrial-scale manufacture of organic solar cells.

A highly pure red luminescent heterobimetallic complex [EuZnL(tta)2(μ-tfa)] (L = N,N′-bis(salicylidene)-2,3-propanediamine, tta = 2-thenoyltrifluoroacetonate, tfa = trifluoroacetate) was synthesized. The EL device with this complex exhibits an inspiring current efficiency of 3.7 cd A−1 at a brightness of 300 cd m−2 and gives a maximum Eu(III)-based pure red emitting luminance of 1982.5 cd m−2 at 13.8 V.

The (ppy)-based Pt(II) complex (Pt-1) with deprotonated 2-(diphenylphosphino)benzoic acid as an anionic ligand displays phosphorescence of monomers with a remarkably higher quantum yield than that of the corresponding iridium complex (Ir-1). A prototype OLED using Pt-1 exhibits high performance with an external quantum efficiency of 4.93%.

Reactions of [Zn(L)(H2O)] precursor and EuCl3 with the aid of CO32− ions derived from atmospheric CO2 affording an unusual heteropolynuclear cluster [Zn4L4Eu4(CO3)6]·EtOH. In the core of the cluster, four hetero-binuclear [ZnLEu] units linked by six CO32− anions forms a well defined [Zn4Eu4] skeleton with good planarity, which plays an important role in stabilizing the cluster.

A simplified triple-layered pure red organic light-emitting diode with high efficiency and a slow efficiency roll-off was fabricated by using Eu(DBM)3(sbf) (DBM = dibenzoylmethane, sbf = 4,5-diaza-9,9′-spirobifluorene) as emitter. In particular, an impressive current efficiency of 3.31 cd A−1 and an external quantum efficiency of 1.8% were maintained at a high luminance of 100 cd m−2.