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A new photocatalyst was synthesized by a combination of the upconversion nanoparticle NaYF4:Yb, Tm, Gd (NYTG) and NH2-MIL-101(Cr) (NMC) to form NYTG/NMC. The heterostructure exhibited great stability and excellent photocatalytic activity through utilization of the wide spectrum from the near-infrared (NIR) to the UV-vis range. Compared with NMC, the photocatalytic performance was increased by 22% for rhodamine B (RhB) with the most suitable amount of Gd3+ ions and the ratio between NYTG and NMC. This could be attributed to the doped Gd3+ ions refining the crystallinity and hexagonal phase of NaYF4 by replacing the Y3+ ions, leading to an enhanced emission intensity along with an increased number of emitted peaks in the UV-vis region. The enhanced photocatalytic performance of NYTG/NMC was also related to the synergistic effects of the individual components, which facilitate the separation of electrons and holes. On the basis of scavenging experiments, the possible mechanism for photocatalytic degradation is proposed to uncover more clues for the further designs of new photocatalysts. This work suggests a pathway to enhance the emission intensity by refining the structure rather than by developing a core–shell structure. [ABSTRACT FROM AUTHOR]

The addition of coadsorbents and the introduction of electron-withdrawing groups in dye sensitizers are considered feasible strategies for improving the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). However, facile and precise predictions of the influence of these two strategies on their photovoltaic properties, including PCE, are challenging. In this contribution, we studied a known D–A–π–A indoline dye WS-2 adsorbed on a TiO2 anode represented by a supercell model. The PCE of this dye was evaluated to be between 9.69% and 13.70%, depending on the supercell representation, compared with an experimental value of 8.55%. The PCE could be increased to 16.39% on a moderate supercell by adding chenodeoxycholic acid (CDCA) as a coadsorbent. Such an enhancement could be ascribed to the intermolecular interaction between WS-2 and CDCA, suppressing excessively high dye coverage and thereby resulting in a remarkable increase in the open-circuit voltage. Based on WS-2, a new molecule WS-2a was rationally designed by substituting the benzothiadiazole moiety of WS-2 with a stronger electron-withdrawing thienyl-diketopyrrolopyrrole group. Consequently, the maximum absorption band showed a large red-shift from 522 to 638 nm, broadening the spectral response into the near-infrared region. A higher PCE of 16.62% was obtained for WS-2a. Moreover, the coadsorption of WS-2a and CDCA onto the TiO2 supercell achieved the best photovoltaic efficiency with a value as high as 24.15%. Therefore, the present study quantitatively reveals the impact of the coadsorbent and electron-withdrawing groups on the optoelectronic properties of dyes, which opens a new avenue to design high-efficiency D–A–π–A-structured organic sensitizers for promising DSSC applications. A discussion on the qualification of these results is given. [ABSTRACT FROM AUTHOR]

Photoelectric conversion efficiency (PCE) is one of the crucial indicators to determine the overall performance of dye-sensitized solar cells (DSSCs), and accurate estimation of PCE is a feasible strategy for developing high-performance DSSC devices. In this contribution, we strategically designed a series of anthracene-based organic dyes 1–4 by introducing different π-bridge or auxiliary acceptor groups. Their photovoltaic properties were explored by first-principles calculations coupled with the normal model and improved normal model. It is found that the introduction of an electron-rich thieno[3,2-b]thiophene-based π-spacer in dye 2 induces a blue-shift of the maximum absorption band with respect to dye 1, while the inclusion of an electron-deficient diketopyrrolopyrrole-based π-bridge in dye 3 and a thieno[3,4-b]pyrazine-based auxiliary acceptor in dye 4 can remarkably extend the optical absorption into the 550–650 nm region. In addition, the open-circuit voltage (VOC), short-circuit photocurrent density (JSC), fill factor (FF) and the corresponding PCE (η) were evaluated by the improved normal model. The estimated results of dye 1 (VOC = 757 mV, JSC = 14.63 mA cm−2, FF = 0.85, and η = 9.41%) reproduce very well the experimentally available data (VOC = 760 mV, JSC = 14.25 mA cm−2, FF = 0.75, and η = 8.08%), suggesting that the improved normal model is an accurate and general method to predict the photoelectric properties of organic dyes. More importantly, dyes 3 and 4 are predicted to exhibit extremely high PCEs of over 32%, both of which are expected to be potential candidates as metal-free organic dyes applied in DSSCs. [ABSTRACT FROM AUTHOR]

Suppressors of cytokine signaling (SOCS) act as negative feedback regulators of the Janus kinase/signal transducer (JAK–STAT) signaling pathway by inhibiting the activity of JAK kinase. The kinase inhibitory region (KIR) of SOCS1 targets the substrate binding groove of JAK with high specificity, as demonstrated by significantly higher IC50 following the mutation of any of residue. To gain a greater understanding of the mechanisms of the inhibition of SOCS1 for JAK1, the binding mode, binding free energy decomposition, and desorption mechanism of JAK–SOCS1 complexes as well as a number of mutant systems were identified by extensive molecular dynamics (MD) simulations and the constant pulling velocity (PCV) method. Electrostatic interactions were identified for their contribution to protein–protein binding, which drove interactions between JAK1 and SOCS1. The polar residues Arg56, Arg59, and Asp105 of SOCS1 and Asp1042 and Asp1040 of JAK1 were key components in the binding, and electrostatic interactions of the side chains were prominent. The binding free energies of the six mutant proteins were lower when compared with those of the control proteins, and the side chain interactions were weakened. The residue Asp1040 played a crucial role in KIR close to the binding groove of JAK1. Moreover, salt bridges contributed significantly to JAK1 and SOCS1 binding and cleavage processes. The study presented herein provides a comprehensive understanding of the thermodynamic and dynamic processes of SOCS1 and JAK1 binding that will contribute meaningfully to the design of future studies related to peptide inhibitors based on SOCS1. [ABSTRACT FROM AUTHOR]

A reliable quantitative description of photoluminescence efficiency is crucial for designing and developing new-type thermally activated delayed fluorescence (TADF) emitters. In this contribution, we computed the conversion and decay rates of a novel TADF-active molecule, 2-(9H-carbazol-9-yl)-thianthrene-5,5,10,10-tetraoxide (CZ-TTR), involving the lowest singlet excited S1 state and triplet excited T1 state. The efficiency of total fluorescence containing prompt fluorescence and delayed fluorescence was obtained correspondingly. The present results reveal that the rate of reverse intersystem crossing from T1 to S1 is calculated to be slightly larger than the radiative and non-radiative decay rates of the S1 state at 300 K temperature, thus resulting in an occurrence of delayed fluorescence. Additionally, the total fluorescence efficiency is estimated to be 54.5%, which agrees very well with the photoluminescence quantum yield of 56.7% observed experimentally. It is also found that the dominant charge transfer characteristics in the S1 and T1 states produce a small energy difference between the two states, and consequently an efficient reverse intersystem crossing process and a high fluorescence efficiency. [ABSTRACT FROM AUTHOR]

Density functional theory and semi-classical Marcus electron transfer theory were employed to investigate the electron transport properties of a sulfur-containing azaacene molecule 10,14-bis(5-(2-ethylhexyl)thiophen-2-yl)dipyrido[3,2-a:20,30-c][1,2,5]thiadiazolo[3,4-i]phenazine (TDTP), which has been proved to have high performance as an electron transport material in inverted perovskite solar cells in a previous experiment. By changing thiophene rings in both side chains to thiazole/benzene rings, two new compounds TDTP-I and TDTP-II were designed. It has been found that both new compounds have lower HOMO and LUMO energy levels and higher electron mobilities than TDTP. In particular, compound TDTP-II has the highest electron mobility among the three. Furthermore, the adsorption properties of TDTP/TDTP-II adsorbed on perovskite (110) surface systems are also studied. It has been shown that TDTP-II has a more negative adsorption energy than TDTP. So our designed compound TDTP-II is expected to be a potential electron transport material in inverted PSCs and changing the side chains could be a feasible way to improve the electron transport properties. [ABSTRACT FROM AUTHOR]

The electronic structures and photophysical properties of three homoleptic iridium(iii) complexes IrL3 with C^N ligands, including 2a (L = 1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole), 5a (L = 1-(2,6-dimethylphenyl)-2-phenyl-1H-imidazole), and 6a (L = 1-(3,5-diisopropylbiphenyl-4-yl)-2-phenyl-1H-imidazole), are investigated by means of the density functional method. Furthermore, seven new complexes are theoretically designed, including 1a (L = 1,2-diphenyl-1H-imidazole), 3a (L = 1-(2,6-dimethoxyphenyl)-2-phenyl-1H-imidazol), 4a (L = 2-(2-phenyl-1H-imidazol-1-yl)isophthalaldehyde), 1b (L = 2-(biphenyl-3-yl)-1H-imidazole), 2b (L = 2-(2′,6′-diisopropylbiphenyl-3-yl)-1H-imidazole), 3b (L = 2-(2′,6′-dimethoxybiphenyl-3-yl)-1H-imidazole), and 4b (L = 3′-(1H-imidazol-2-yl)biphenyl-2,6-dicarbaldehyde), to explore the influence of different substituents and different substituted positions on the electronic structures, phosphorescence properties, and organic light-emitting diode (OLED) performance. The HOMO–LUMO energy gap is greatly decreased by introduction of the –CHO group into the phenyl ring (4a and 4b see SCHEMREFScheme 1/SCHEMREF―sketched structures for all the investigated Ir(iii) complexes). As a result, their absorption and emission spectra present red-shifting leading them to be potential red-emitting phosphors. Other complexes are all blue-emitting materials, indicating that the effect of the substituted position on the emitting color is negligible. However, the addition of the substituent on the para-position of the phenyl ring in the phenylimidazole ligand would increase the quantum yield and electroluminescence (EL) performance compared with that on the imidazole ring. [ABSTRACT FROM AUTHOR]

The geometric and electronic structures, phosphorescence properties and the organic light-emitting diode (OLED) performance of a series of Ir(iii) complexes based on bis[(4,6-di-fluorophenyl)-pyridinato-N,C2′]picolinate (FIrpic) were investigated by using density functional theory/time-dependent density functional theory (DFT/TD-DFT), including Ir(iii)bis[2-(2,4-difluorophenyl)-4-(tert-butyl)pyridinato-N,C2′]picolinate (1a), Ir(iii)bis[2-(2,4-difluorophenyl)-4-(n-heptyl)pyridinato-N,C2′]picolinate (2a), Ir(iii)bis[2-(2,4-difluorophenyl)-4-(3-ethylheptyl)pyridinato-N,C2′]picolinate (3a), Ir(iii)bis[2-(2,4-difluorophenyl)-4-(2,4,6-trimethylphenyl)pyridinato-N,C2′]picolinate (5a), and Ir(iii)bis[2-(2,4-difluoro-3-(2,4,6-trimethylphenyl)phenyl)-pyridinato-N,C2′] picolinate (5b). To explore the influence of the substituted positions on the optical and electronic properties of the Ir(iii) complexes, seven other new complexes were designed by introducing the substituted groups on the difluorophenyl rings or pyridine rings. After introducing the phenyl substituted groups on the pyridine or difluorophenyl rings of cyclometalated ligands, the HOMO–LUMO energy gap is decreased. Thus, the absorption spectra of 4a and 4b undergo a red-shifting, especially for 4a, and have a stronger absorption strength that will be beneficial to improving their quantum yields, which is proved by the further evaluation of the radiative (kr) and non-radiative (knr) rate constants. The combinations of a larger 3MLCT-3MC energy gap, smaller ΔES1–T1, and higher contribution of 3MLCT in the emission process result in the higher quantum yields for complexes 4a and 4b. Besides, the designed complexes 4a and 4b are considered to be potential candidates as blue-emitting materials with better equilibrium between the hole transport (λhole) and electron transport (λelectron). [ABSTRACT FROM AUTHOR]

This work details the synthesis of paramagnetic upconversion nanoparticles doped with Fe 3+ in various morphologies via the thermal decomposition method, followed by comprehensive characterization of their structures, optical properties and magnetism using diverse analytical techniques. Our findings demonstrate that by precisely modulating the ratio of oleic acid to octadecene in the solvent, one can successfully obtain hexagonal nanodiscs with a consistent and well-defined morphology. Further adjustments in the oleic acid to octadecene ratio, coupled with fine-tuning of the Na + /F - ratio, led to the production of small-sized nanorods with uniform morphology. Significantly, all Fe 3+ -doped nanoparticles displayed pronounced paramagnetism, with magnetic susceptibility measurements at 1 T and room temperature of 0.15 emu g -1 and 0.14 emu g -1 for the nanodiscs and nanorods, respectively. To further enhance their magnetic properties, we replaced the Y-matrix with a Gd-matrix, and by fine-tuning the oleic acid/octadecene and Na + /F - ratios, we achieved nanoparticles with uniform morphology. The magnetic susceptibility was 0.82 emu g -1 at 1 T and room temperature. Simultaneously, we could control the nanoparticle size by altering the synthesis temperature. These upconversion nanostructures, characterized by both paramagnetic properties and regular morphology, represent promising dual-mode nanoprobe candidates for optical biological imaging and magnetic resonance imaging., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

The electronic structures and photophysical properties of three homoleptic iridium(iii) complexes IrL3 with C^N ligands, including 2a (L = 1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole), 5a (L = 1-(2,6-dimethylphenyl)-2-phenyl-1H-imidazole), and 6a (L = 1-(3,5-diisopropylbiphenyl-4-yl)-2-phenyl-1H-imidazole), are investigated by means of the density functional method. Furthermore, seven new complexes are theoretically designed, including 1a (L = 1,2-diphenyl-1H-imidazole), 3a (L = 1-(2,6-dimethoxyphenyl)-2-phenyl-1H-imidazol), 4a (L = 2-(2-phenyl-1H-imidazol-1-yl)isophthalaldehyde), 1b (L = 2-(biphenyl-3-yl)-1H-imidazole), 2b (L = 2-(2',6'-diisopropylbiphenyl-3-yl)-1H-imidazole), 3b (L = 2-(2',6'-dimethoxybiphenyl-3-yl)-1H-imidazole), and 4b (L = 3'-(1H-imidazol-2-yl)biphenyl-2,6-dicarbaldehyde), to explore the influence of different substituents and different substituted positions on the electronic structures, phosphorescence properties, and organic light-emitting diode (OLED) performance. The HOMO-LUMO energy gap is greatly decreased by introduction of the -CHO group into the phenyl ring (4a and 4b see -sketched structures for all the investigated Ir(iii) complexes). As a result, their absorption and emission spectra present red-shifting leading them to be potential red-emitting phosphors. Other complexes are all blue-emitting materials, indicating that the effect of the substituted position on the emitting color is negligible. However, the addition of the substituent on the para-position of the phenyl ring in the phenylimidazole ligand would increase the quantum yield and electroluminescence (EL) performance compared with that on the imidazole ring.

The geometric and electronic structures, phosphorescence properties and the organic light-emitting diode (OLED) performance of a series of Ir(III) complexes based on bis[(4,6-di-fluorophenyl)-pyridinato-N,C2']picolinate (FIrpic) were investigated by using density functional theory/time-dependent density functional theory (DFT/TD-DFT), including Ir(III)bis[2-(2,4-difluorophenyl)-4-(tert-butyl)pyridinato-N,C2']picolinate (1a), Ir(III)bis[2-(2,4-difluorophenyl)-4-(n-heptyl)pyridinato-N,C2']picolinate (2a), Ir(III)bis[2-(2,4-difluorophenyl)-4-(3-ethylheptyl)pyridinato-N,C2']picolinate (3a), Ir(III)bis[2-(2,4-difluorophenyl)-4-(2,4,6-trimethylphenyl)pyridinato-N,C2']picolinate (5a), and Ir(III)bis[2-(2,4-difluoro-3-(2,4,6-trimethylphenyl)phenyl)-pyridinato-N,C2'] picolinate (5b). To explore the influence of the substituted positions on the optical and electronic properties of the Ir(III) complexes, seven other new complexes were designed by introducing the substituted groups on the difluorophenyl rings or pyridine rings. After introducing the phenyl substituted groups on the pyridine or difluorophenyl rings of cyclometalated ligands, the HOMO-LUMO energy gap is decreased. Thus, the absorption spectra of 4a and 4b undergo a red-shifting, especially for 4a, and have a stronger absorption strength that will be beneficial to improving their quantum yields, which is proved by the further evaluation of the radiative (k(r)) and non-radiative (k(nr)) rate constants. The combinations of a larger (3)MLCT-(3)MC energy gap, smaller ΔE(S1-T1), and higher contribution of (3)MLCT in the emission process result in the higher quantum yields for complexes 4a and 4b. Besides, the designed complexes 4a and 4b are considered to be potential candidates as blue-emitting materials with better equilibrium between the hole transport (λ(hole)) and electron transport (λ(electron)).

A theoretical investigation into eighteen recently synthesized Pt(ii) complexes [(R1(n)-C^N^C-R2(n))Pt(L)] with doubly deprotonated cyclometalated R1(n)-C^N^C-R2(n) ligands (n = 1-9, R1(n)-C^N^C-R2(n) = 2,6-diphenylpyridine derivatives) and L ligands (L = DMSO, 1-9; L = -C[triple bond, length as m-dash]N-Ar, 1a-9a), which are used as emitters in orange-red emitting diodes, is reported in this paper. Geometric and electronic structures, absorption and emission spectra, phosphorescence quantum yields, and electroluminescence (EL) efficiency were investigated by DFT and TDDFT methods. We focused on the influence of the primary ligand (R1(n)-C^N^C-R2(n)) and auxiliary ligand (L) on the optical and electronic properties of Pt(ii) complexes by introducing carbazole, fluorene, and thiophene group in the primary ligand and/or the replacement of DMSO by -C[triple bond, length as m-dash]N-Ar as an ancillary ligand. The incorporation of carbazole, fluorene, and thiophene into the primary ligand caused the red-shift of absorption and emission spectra. The metal-ligand bond length is contracted where -C[triple bond, length as m-dash]N-Ar was employed as the secondary ligand, which facilitate the metal to ligand charge transfer (MLCT). The larger involvement of MLCT character in emission process is beneficial for improving the quantum yields of 2a-9a. For EL efficiency, all the complexes have a good balance of reorganization energy as potential systems for fabricating effective OLEDs devices except for 1 and 1a. In addition, two new molecules were designed with comparable or better EL efficiency.

DFT and TD-DFT methods have been employed to theoretically investigate the properties of three recently synthesized green-emitting platinum(II) complexes (1-3) bearing tetradentate O^N^C^N ligands (O^C^N^C = 2-(4-(3,5-di-tert-butylphenyl)-6-(3-(pyridin-2-yl)phenyl)-pyridin-2-yl)phenolate and its derivatives) that have been testified to be good emitters in organic light-emitting diodes (OLEDs), especially for complex 3. The effect of the variation of the substituents on the electronic and optical properties is emphatically explored. Our calculation results reveal that the introduction of an electron-releasing group on one phenyl ring of the O^C^N^C ligand (complex 2) does not result in a distinct alteration of the spectra. However, the incorporation of the norbornane group to the O^C^N^C ligand (complex 3) leads to a blue-shift in the absorption and emission spectra as compared with 1. In addition, how the absorption and emission spectra are affected by the solvent polarity is studied. Both the absorption and the emission spectra display red-shifts of various degrees with the decrease of the solvent polarity. The different phosphorescent quantum yields of the three complexes are compared. It is reasonable to believe that the high (3)MLCT (metal-to-ligand charge transfer) contribution and high percentage of the metallic character (M(c), %) in the emission process, as well as the largest vertical transition energy for 3, result in the highest quantum efficiency.