Realizing highly efficient deep-blue organic light-emitting diodes towards Rec.2020 chromaticity by restricting the vibration of the molecular framework.

Deep-blue organic light-emitting diodes (OLEDs) with narrow emission spectra and high efficiency, meeting the Rec.2020 standard, hold significant promise in the realm of 4K/8K ultrahigh-definition displays. However, the development of light-emitting materials exhibiting both narrowband emission and high efficiency, particularly in the realm of deep-blue thermally activated delayed fluorescence (TADF), confronts substantial challenges. Herein, a novel deep-blue TADF emitter, named BOC-PSi, was designed by integrating a rigid B-heterotriangulene acceptor (A) with a rigid phenazasiline donor (D). The replacement of a sp3 carbon atom with a sp3 silicon atom in the D moiety helps to restrict the low-frequency bending vibration throughout the entire D-A molecular backbone, while concurrently accelerating the multi-channel reverse intersystem crossing (RISC) processes. Notably, OLEDs using the BOC-PSi emitter exhibit exceptional performance, with a high maximum external quantum efficiency (EQEmax) approaching 20%, and a superior color purity closely aligning with the Rec.2020 blue standard.

Unveiling the Sources and Transfer of Mercury in Forest Bird Food Chains Using Techniques of Vivo-Nest Video Recording and Stable Isotopes.

Knowledge gaps in mercury (Hg) biomagnification in forest birds, especially in the most species-rich tropical and subtropical forests, limit our understanding of the ecological risks of Hg deposition to forest birds. This study aimed to quantify Hg bioaccumulation and transfer in the food chains of forest birds in a subtropical montane forest using a bird diet recorded by video and stable Hg isotope signals of biological and environmental samples. Results show that inorganic mercury (IHg) does not biomagnify along food chains, whereas methylmercury (MeHg) has trophic magnification factors of 7.4-8.1 for the basal resource-invertebrate-bird food chain. The video observations and MeHg mass balance model suggest that Niltava (Niltava sundara) nestlings ingest 78% of their MeHg from forest floor invertebrates, while Flycatcher (Eumyias thalassinus) nestlings ingest 59% from emergent aquatic invertebrates (which fly onto the canopy) and 40% from canopy invertebrates. The diet of Niltava nestlings contains 40% more MeHg than that of Flycatcher nestlings, resulting in a 60% higher MeHg concentration in their feather. Hg isotopic model shows that atmospheric Hg0 is the main Hg source in the forest bird food chains and contributes >68% in most organisms. However, three categories of canopy invertebrates receive ∼50% Hg from atmospheric Hg2+. Overall, we highlight the ecological risk of MeHg exposure for understory insectivorous birds caused by atmospheric Hg0 deposition and methylation on the forest floor.

A spiroacridine-based thermally activated delayed fluorescence emitter for high-efficiency and narrow-band deep-blue OLEDs.

A novel deep-blue thermally activated delayed fluorescence molecule of SAC-BOC was reported. The SAC-BOC-based device exhibits a narrow full width at half maximum of 57 nm, an impressive maximum external quantum efficiency (EQEmax) of 15.3% and CIE coordinates of (0.144, 0.129).

Isomeric Effect of a π Bridge in an IDT-Based Nonfused Electron Photovoltaic Acceptor.

A pair of isomers, IDT-BOF containing S⋅⋅⋅O/F⋅⋅⋅H noncovalently configurational locks and IDT-BFO containing F⋅⋅⋅H/O⋅⋅⋅H noncovalently configurational locks, with an acceptor-π-donor-π-acceptor (A-π-D-π-A) structure have been designed and synthesized by choosing 4,9-dihydro-s-indaceno[1,2-b : 5,6-b']dithiophene (IDT) as the D unit, an F/n-hexyloxy substituted phenyl ring as π bridge, and 3-(dicyanomethylidene)indan-1-one as the A unit. Owing to the S⋅⋅⋅O/F⋅⋅⋅H or F⋅⋅⋅H/O⋅⋅⋅H noncovalently configurational locks, both IDT-BOF and IDT-BFO have a completely planar structure. IDT-BOF exhibits a similar LUMO to IDT-BFO, but higher HOMO energy levels, leading to a smaller optical bandgap and red-shifted absorption. However, IDT-BOF-based bulk-heterojunction organic solar cells (BHJ-OSCs) coupled with PBDB-T, and PCE-10 as donor materials both exhibited a lower PCE than that of IDT-BFO (PBDB-T: 5.2 vs. 6.1 %; PCE-10: 1.7 vs. 3.2 %). Comprehensively comparing and investigating IDT-BOF : PBDB-T and IDT-BFO : PBDB-T OSCs suggested that the large phase separation and serious charge recombination of IDT-BOF-based OSCs contributed to its lower power conversion efficiency. Importantly, ternary solar cells based on PBDB-T : Y5 as control devices with an additional 10 % IDT-BFO exhibited a 5 % enhancement in the PCE compared to the control device (14.3 vs. 13.46 %).

Ambient Phosphor with High Efficiency and Long Lifetime in Poly(Methyl Methacrylate) Through Charge-Transfer-Mediated Triplet Exciton Formation for Photolithography Applications.

Currently, purely organic compounds showing ambient phosphorescence with high efficiency (ΦP ) and ultra-long lifetime (τP ) are quite rare and often need to be achieved in hydrophilic poly(vinyl alcohol)-based hosts. This severely limits their applications. Here, we provide a solution to this issue by constructing an ortho-linked donor-acceptor (D-A) dyad whose D moiety has not only a long-lived T1 state to achieve a long τP , but also a Tn state that is close to the S1 state of the dyad to trigger effective spin-orbit charge transfer intersystem crossing (SOCT-ISC). The rationality of this strategy was validated by a new phosphor OF-BCz that is able to show a τP of 1.92 s and a ΦP of 30 % even in a less rigid matrix of poly(methyl methacrylate) (PMMA). Excitingly, OF-BCz exhibited its potential as both a photocuring initiator and an in situ quality indicator, allowing for the visual detection of defects in photolithographic patterning.

Acquiring Charge-Transfer-Featured Single-Molecule Ultralong Organic Room Temperature Phosphorescence via Through-Space Electronic Coupling.

Although long-lived triplet charge-transfer (3 CT) state with high energy level has gained significant attention, the development of organic small molecules capable of achieving such states remains a major challenge. Herein, by using the through-space electronic coupling effect, we have developed a compound, namely NIC-DMAC, which has a long-lived 3 CT state at the single-molecule level with a lifetime of 210 ms and a high energy level of up to 2.50 eV. Through a combination of experimental and computational approaches, we have elucidated the photophysical processes of NIC-DMAC, which involve sequential transitions from the first singlet excited state (S1 ) that shows a 1 CT character to the first triplet excited state (T1 ) that exhibits a local excited state feature (3 LE), and then to the second triplet excited state (T2 ) that shows a 3 CT character (i.e., S1 (1 CT)→T1 (3 LE)→T2 (3 CT)). The long lifetime and high energy level of its 3 CT state have enabled NIC-DMAC as an initiator for photocuring in double patterning applications.

A Reusable Fluorescent Molecular Self-Assembly Cage for Simultaneous Detection and Recycling of Silver(I) Ion.

Although molecular self-assembled porous materials capable of ratiometric fluorescence probing and recycling of metal ions are both economically and environmentally attractive, very few current efforts have been devoted. Herein, we demonstrated a three-dimensional pure organic cage, namely 4-cage, which can serve as a fluorescent probe for simultaneous ratiometric detection and recycling of Ag+ ion. Taking advantage of the promising emission behavior of its rigidified tetraphenylethylene scaffolds and the chelating ability of its dynamically reversible imine moieties, on one hand, upon the addition of Ag+ , 4-cage undergoes coordination to form a stable but poorly soluble fluorescent complex, Ag+ @4-cage, accompanied by a fluorescence color change from bluish-green to yellowish-green. This allows us to differentiate Ag+ from other cations with high selectivity. On the other hand, upon the addition of Cl- anion, Ag+ @4-cage can be effectively converted into free 4-cage due to the competitive coordination of Cl- with Ag+ . Through this process, secondary usage of 4-cage and the recycling of Ag+ ion can be achieved.

Combined ICP-OES and XPS analysis to evaluate the [AlO4]0 concentration in quartz: limiting the formation temperature of quartz.

A proposed quartz thermometer is based on the concentration of [AlO4]0 tetrahedra determined by combining inductively coupled plasma optical emission spectrometry (ICP-OES) with X-ray photoelectron spectroscopy (XPS) data. The concentration of [AlO4]0 tetrahedra in the quartz lattice (C[AlO4]0/ppm) and the formation temperatures of quartz (TQ/°C) from agate, gold deposits, and granodiorite are calculated by C[AlO4]0 = CAl total (ppm) × k and TQ (°C) = 3.6 × CAl total (ppm) × k + 33.0, respectively. Where CAl total is the total Al concentration of quartz measured by ICP-OES and k is the relative percentage of [AlO4]0 tetrahedra in the quartz lattice and can be obtained by fitting the Al(2p) XPS spectrum. The obtained formation temperatures of quartz (TQ) agree well with the equilibrium formation temperature (TE) calculated by oxygen isotope data. By comparing the relative positions of the two temperature curves of quartz (TQ and TE), the composition of the mineral-forming fluid can be inferred. The proposed quartz thermometer can be applied to quartz formed under equilibrium conditions and in Al-saturated environments over a wide temperature range (152-566 °C). The use of the quartz thermometer effectively eliminates interference from different fluid compositions and satisfies the requirements of convenience and economy.

The mercury flow through a terrestrial songbird food chain in subtropical pine forest: Elucidated by Bayesian isotope mixing model and stable mercury isotopes.

In order to comprehend the transfer of inorganic mercury (IHg) and methylmercury (MeHg) within food chains in terrestrial pine forests, we collected samples of Great Tit nestlings, common invertebrates, plants, and soil in a subtropical pine forest and used Bayesian isotope mixing model analysis, Hg daily intake, and stable Hg isotopes to elucidate the flow of MeHg and IHg in these food chains. Results indicate that caterpillars and cockroaches are the predominant prey items for nestlings, accounting for a combined contribution of 81.5%. Furthermore, caterpillars, cockroaches, and spiders were found to contribute the most (∼80%) of both IHg and MeHg that dietary accumulated in nestlings. The provisoned invertebrates tend to supply more IHg and diluting the proportion of MeHg as total Hg (MeHg%). Notably, nestling feathers displayed the highest Δ199Hg values but a relatively lower MeHg%, suggesting an imbalanced incorporation of Hg from maternal transfer and dietary accumulation during the nestling stage. This study highlights the efficacy of nestlings as indicators for identifying Hg sources and transfers in avian species and food chains. However, caution must be exercised when using Hg isotope compositions in growing feathers, and the contribution of maternally transferred Hg should not be ignored.

A Low-Cost Test Method for Accurate Detection of Different Excited-State Species with a Lifetime Span over 5 Orders of Magnitude in One Time Window.

Accurate quantification on the quantum yields (φ) of both the prompt fluorescence (PF) and the delayed fluorescence (DF) species is quite essential for the clarification of molecular design rationales for thermally activated delayed fluorescence (TADF) luminogens. Currently, most φPF and φDF data of TADF fluorophores were acquired through time-correlated single-photon counting (TCSPC) lifetime measurement systems. However, because of their equal-time-channel working manner, so far all the commercially available TCSPC systems cannot render accurate measurement on φPF of TADF materials due to the lack of enough valid data points in the faster decay region of the corresponding photoluminescence (PL) decay curves. Although an intensified charge coupled device (ICCD) system equipped with a streak camera or an optical parametric oscillation laser has been proven to be a powerful tool for accurate determination of φPF and φDF of TADF fluorophores, the ultrahigh cost of these ICCD systems makes them inaccessible to most users. Herein, by replacing the timing module of a commercial TCSPC system with a low-cost and versatile time-to-digital converter (TDC) module, we developed a modified TCSPC system that can work in an unequal-time-channel manner. The resultant TDC-TCSPC system can not only concurrently determine the accurate lifetime of PF and DF species whose lifetime span even exceeds 5 orders of magnitude in just one time window but also render accurate measurements on φPF and φDF of TADF fluorophores. The reliability of the TDC-TCSPC method was verified through TCSPC- and ICCD-based comparative experiments on ACMPS, a known TADF fluorophore. Our results not only can provide a low-cost and convenient test method for accurate determination of key experimental data of TADF materials but also will facilitate deeper understanding of the molecular design principles for high-performance TADF materials.

A red ambient afterglow material with lifetime of 0.5 s and efficiency over 12.

γCbPhAP, a D-A dyad with γ-carboline as the D unit and 3-phenylacenaphtho[1,2-b]pyrazine-8,9-dicarbonitrile as the A moiety and phosphorescence core, was designed and synthesized. The doping system of 1 wt% γCbPhAP in PMMA shows red ambient phosphorescence-dominated afterglow with long lifetime of 0.5 s and decent efficiency over 12%.

A water-soluble sensor for distinguishing D2O from H2O by dual-channel absorption/fluorescence ratiometry.

By taking advantage of the slight difference in the acidity of D2O and H2O, we report a novel D2O optical sensor, namely Cy, with integrated great water-solubility, absorption/fluorescence dual-channel ratiometric response and even RGB visual sensing application. This work puts forward a facile method for distinguishing D2O from H2O with high sensitivity and high accuracy.

Ultra-fast triplet-triplet-annihilation-mediated high-lying reverse intersystem crossing triggered by participation of nπ*-featured excited states.

The harvesting of 'hot' triplet excitons through high-lying reverse intersystem crossing mechanism has emerged as a hot research issue in the field of organic light-emitting diodes. However, if high-lying reverse intersystem crossing materials lack the capability to convert 'cold' T1 excitons into singlet ones, the actual maximum exciton utilization efficiency would generally deviate from 100%. Herein, through comparative studies on two naphthalimide-based compounds CzNI and TPANI, we revealed that the 'cold' T1 excitons in high-lying reverse intersystem crossing materials can be utilized effectively through the triplet-triplet annihilation-mediated high-lying reverse intersystem crossing process if they possess certain triplet-triplet upconversion capability. Especially, quite effective triplet-triplet annihilation-mediated high-lying reverse intersystem crossing can be triggered by endowing the high-lying reverse intersystem crossing process with a 3ππ*→1nπ* character. By taking advantage of the permanent orthogonal orbital transition effect of 3ππ*→1nπ*, spin-orbit coupling matrix elements of ca. 10 cm-1 can be acquired, and hence ultra-fast mediated high-lying reverse intersystem crossing process with rate constant over 109 s-1 can be realized.

Mercury Uptake, Accumulation, and Translocation in Roots of Subtropical Forest: Implications of Global Mercury Budget.

Plant roots are responsible for transporting large quantities of nutrients in forest ecosystems and yet are frequently overlooked in global assessments of Hg cycling budgets. In this study, we systematically determined the distribution of total Hg mass and its stable isotopic signatures in a subtropical evergreen forest to elucidate sources of Hg in plant root tissues and the associated translocation mechanisms. Hg stored in roots and its isotopic signatures show significant correlations to those found in surrounding soil at various soil depths. The odd mass-independent fractionation (MIF) of root Hg at a shallow soil depth displays a -0.10‰ to -0.50‰ negative transition compared to the values in aboveground woody biomass. The evidence suggests that root Hg is predominantly derived from surrounding soil, rather than translocation of atmospheric uptake via aboveground tissues. The cortex has a more negative mass-dependent fractionation (MDF) of -0.10‰ to -1.20‰ compared to the soil samples, indicating a preferential uptake of lighter isotopes by roots. The similar MDF and odd-MIF signals found in root components imply limited Hg transport in roots. This work highlights that Hg stored in plant roots is not a significant sink of atmospheric Hg. The heterogeneous distribution of Hg mass in roots of various sizes represents a significant uncertainty of current estimates of Hg pool size in forest ecosystems.

Mineralogical and Geochemical Characteristics of Banded Agates from Placer Deposits: Implications for Agate Genesis.

The phase composition and geochemical characteristics in banded agates with different structural sequences have been investigated in detail. The results reveal that the agate bands have a combination of a pseudo-granular silica → fibrous chalcedony → crystalline quartz (type I) sequence and a newly discovered pseudo-granular silica → crystalline quartz (type II) sequence. The banded agates mainly consist of α-quartz, moganite, and a minor amount of amorphous silica, goethite, hematite, kaolinite, illite, and carbonates. With the evolution of two structural sequences, the content of α-quartz and moganite increases and decreases, respectively. There is no moganite in crystalline quartz. The increased concentration of trace elements like Li, Na, Al, K, Ca, Ti, Mn, and Fe in different bands may correspond to the decrease in the water content in the mineral-forming fluid. The increased trace elements promote the structural transformation process of silica. With the evolution of the type I sequence, the thermal gradients between adjacent bands are 17 and 51 °C, respectively. In contrast, a significantly higher thermal gradient of 53-66 °C is exhibited when pseudo-granular silica transforms directly to crystalline quartz. It is inferred that a slightly increased thermal gradient between adjacent bands promotes the structural transformation process of the type I sequence. The sharply increasing thermal gradient between adjacent bands leads to the formation of the type II sequence from pseudo-granular silica to crystalline quartz. The formation process of different structural sequences in agate may be controlled together by trace element concentrations and thermal gradients.

Visualizing Lysosomal Positioning with a Fluorescent Probe Reveals a New Synergistic Anticancer Effect.

The observation and discovery of lysosome dynamic alterations will greatly contribute to the in-depth understanding of lysosome biology and the development of new cancer therapeutics. To visualize lysosomal dynamics, here we have developed a lysosome-targetable fluorescent probe of NIM-3 showing integrated high selectivity, high photostability, and low cytotoxicity. With the aid of the excellent spatial and temporal imaging capability of NIM-3, three different types of motion of lysosomes were defined, and perinuclear accumulation of lysosomes in response to the pro-inflammatory cytokine stimulus was observed in various cells. More importantly, through lysosomal positioning studies, a new and potential anticancer therapy, i.e., the combination treatment of TNFα (tumor necrosis factor alpha) and chloroquine (CQ, a lysosomal pH elevator), was disclosed. The efficacy of the "CQ + TNFα" treatment was verified by different types of human cancer cells, and the anticancer mechanism may be partially attributed to lysosomal dilation.

Cooperative roles of Sn(IV) and Cu(II) for efficient transformation of biomass-derived acetol towards lactic acid production.

Acetol as one of the major constituent derived from biomass pyrolysis has shown high potential as feedstock to produce chemicals but remains challenging due to the unsatisfied productivity. We here developed a novel technology (Sn(IV)-Cu(II) system), achieving acetol transformation towards lactic acid (LaA) production with an unprecedented yield (91.8 C-mol%), the highest value among the state-of-the-art strategies. The results of experiment and DFT study revealed that [Cu(H2O)4]2+ and [Sn(OH)3(H2O)3]+ were the possible active species, which showed an outstanding synergetic effect. [Cu(H2O)4]2+ exhibited better ability for acetol activation, and gave more contribution to promote the dehydrogenation oxidation in the terminal carbon and hydroxyl of acetol yielding pyruvaldehyde (PRA). Subsequently, the combination of [Sn(OH)3(H2O)3]+ with PRA raised the electrophilicity capacity of terminal C in PRA, thereby facilitating the hydration reaction of PRA so that CH bond energy in the terminal carbon was sharply reduced. This greatly favored the next H-shift from the terminal carbon of hydrated-PRA to adjacent one, allowing LaA synthesis in high productivity. This work might give some important insights for designing new approach to meet the huge demand of LaA in the current market.

Canopy-Level Flux and Vertical Gradients of Hg0 Stable Isotopes in Remote Evergreen Broadleaf Forest Show Year-Around Net Hg0 Deposition.

Vegetation uptake represents the dominant route of Hg input to terrestrial ecosystems. However, this plant-directed sink is poorly constrained due to the challenges in measuring the net Hg0 exchange on the ecosystem scale over a long period. Particularly important is the contribution in the subtropics/tropics, where the bulk (∼70%) of the Hg0 deposition is considered to occur. Using the relaxed eddy accumulation technique, this study presents for the first time a whole ecosystem Hg0 flux record over an evergreen hardwood forest. This tower-based micrometeorological method gauged a cumulated net Hg0 flux of -41.1 µg m-2 over 16 months, suggesting that the subtropical montane forest acts as a large and continuous sink of atmospheric Hg0. The monthly net fluxes were consistently negative (-7.3 to -1.0 µg m-2 month-1) throughout the year, with the smallest absolute values occurring during the mild and dry subseason in spring, which was also the annual lowest in vegetation activity. Colocated measurements of multilevel gradients of Hg0 concentration and its stable isotopic composition support the finding of year-round Hg0 deposition. The stable Hg isotope measurements also show that in-canopy bi-directional Hg0 exchange is prevalent.

Increase of litterfall mercury input and sequestration during decomposition with a montane elevation in Southwest China.

Litterfall mercury (Hg) input has been regarded as the dominant Hg source in montane forest floor. To depict combining effects of vegetation, climate and topography on accumulation of Hg in montane forests, we comprehensively quantified litterfall Hg deposition and decomposition in a serial of subtropical forests along an elevation gradient on both leeward and windward slopes of Mt. Ailao, Southwest China. Results showed that the average litterfall Hg deposition increased from 12.0 ± 4.2 µg m-2 yr-1 in dry-hot valley shrub at 850-1000 m, 14.9 ± 6.8 µg m-2 yr-1 in mixed conifer-broadleaf forest at 1250-2400 m, to 23.1 ± 8.3 µg m-2 yr-1 in evergreen broadleaf forest at 2500-2650 m. Additionally, the windward slope forests had a significantly higher litterfall Hg depositions at the same altitude because the larger precipitation promoted the greater litterfall biomass production. The one-year litter Hg decomposition showed that the Hg mass of litter in dry-hot valley shrub decreased by 29%, while in mixed conifer-broadleaf and evergreen broadleaf forests increased by 22-48%. The dynamics of Hg in decomposing litter was controlled by the temperature mediated litter decomposition rate and the additional adsorption of environmental Hg during decomposition. Overall, our study highlights the litterfall mediated atmospheric mercury inputs and sequestration increase with the montane elevation, thus driving a Hg enhanced accumulation in the high montane forest.

Vivianite and Its Oxidation Products in Mammoth Ivory and Their Implications to the Burial Process.

The phase composition and distribution characteristics have been obtained from two mammoth ivory samples with typical blue and yellowish-brown outer layers. The results reveal that hydroxyapatite, newberyite, organic matter, and quartz exist in all structures of mammoth ivory. Vivianite and santabarbaraite mainly contribute to the blue and yellowish-brown oxide layers of mammoth ivory, respectively. Meanwhile, metavivianite also occurs and partly influences the appearance of oxide layers. Vivianite is a common and complex product that can be formed by the interaction of gradually infiltrated Fe2+ and the original PO4 3- in mammoth ivory. At the later stage, vivianite can be oxidized into metavivianite and santabarbaraite. As a result, mammoth tusks present dark bluish-green and yellowish-brown appearances. The multi-colored oxide layers are formed by different contents of vivianite and its oxidation products, which also provides valuable information on the relative burial intensity and time in different structures. It is inferred that the burial intensity increases in the sequence of yellowish-white dentin → blue outer layer → yellowish-brown outer layer. These observations are hopeful to be widely used in evaluating the changeable burial environment and exploring historical events that occurred on mammoth ivory.