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Chiral recognition of enantiomers with identical mirror-symmetric molecular structures is important for the analysis of biomolecules, and it conventionally relies on stereoselective interactions in chiral chemical environments. Here, we develop a magneto-electrochemical method for the enhanced detection of chiral amino acids (AAs), that combines the advantages of the high sensitivity of electrochemiluminescent (ECL) biosensors and chirality-induced effects under a magnetic field. The ECL difference between L - and D -enantiomers can be amplified over 35-fold under a field of 3.5 kG, and the chiral discrimination can be achieved in dilute AA solutions down to the nM level. The field-dependent ECL and chronocoulometry measurements suggest that chiral AAs can lock the spins on their radicals and thus enlarge the ECL change under applied magnetic fields (magneto-ECL, MECL), which explains the field-enhanced chiral discrimination of AA enantiomers. Finally, a detailed protocol is demonstrated for the identification of unknown AA solutions, in which the species, chirality and concentration of AAs can be determined simultaneously from the 2D plots of the ECL and MECL results. This work benefits the development of field-assisted detection methods and represents a promising and universal strategy for the comprehensive analysis of chiral biomolecules. [ABSTRACT FROM AUTHOR]

Alumina materials, as one of the cornerstones of the modern chemical industry, possess physical and chemical properties that include excellent mechanical strength and structure stability, which also make them highly suitable as catalyst supports. Alumina-supported Pd-based catalysts with the advantages of exceptional catalytic performance, flexible regulated surface metal/acid sites, and good regeneration ability have been widely used in many traditional chemical industry fields and have also shown great application prospects in emerging fields. This review aims to provide an overview of the recent advances in alumina and its supported Pd-based catalysts. Specifically, the synthesis strategies, morphology transformation mechanisms, and structural properties of alumina with various morphologies are comprehensively summarized and discussed in-depth. Then, the preparation approaches of Pd/Al2O3 catalysts (impregnation, precipitation, and other emerging methods), as well as the metal–support interactions (MSIs), are revisited. Moreover, Some promising applications have been chosen as representative reactions in fine chemicals, environmental purification, and sustainable development fields to highlight the universal functionality of the alumina-supported Pd-based catalysts. The role of the Pd species, alumina support, promoters, and metal–support interactions in the enhancement of catalytic performance are also discussed. Finally, some challenges and upcoming opportunities in the academic and industrial application of the alumina and its supported Pd-based are presented and put forward. [ABSTRACT FROM AUTHOR]

Simultaneously realizing high exciton density and high emission efficiency in light emitting devices is generally challenging because of the competition between exciton accumulation and its radiative recombination. Here, we demonstrate that the hybridized local and charge-transfer (HLCT) excited state in a twisted donor–acceptor molecule can be used to accumulate highly luminescent excitons, leading to both efficient optically pumped lasing and improved electrically injected luminescence. The twisted molecular structure brings the hybridization characteristics of both locally excited (LE) and charge-transfer (CT) states, where the LE component ensures the remarkable quantum yield (>60%) of radiative decay and the CT contribution prolongs the exciton lifetime to a few nanoseconds. By incorporating the HLCT molecule into the polymer semiconductor, optically pumped lasing is achieved from their microspheres, and the threshold is significantly reduced compared with that of the LE molecule. Magneto-photoluminescence measurement reveals that the introduction of CT characteristics is beneficial to the efficient accumulation of bright excitons at high pump intensity. Moreover, the HLCT molecule doped polymer is used as an active layer in organic light emitting diodes, in which the electroluminescence intensity is enhanced by 2 orders of magnitude compared with its LE counterpart especially at high electric current density. The magneto-electroluminescence of the HLCT material decreases at >50 mT fields and is opposite to its magneto-photoluminescence, which reveals the distinct contribution of the CT component in exciton accumulation under optical pump and electrical injection. These findings provide new insights into the design and synthesis of optical gain molecules towards high-performance organic lasers upon optical excitation as well as those under electrical injection conditions. [ABSTRACT FROM AUTHOR]

Singlet fission (SF) is a multiexciton generation process that could potentially offset thermalization losses and boost the efficiency of photovoltaic devices. However, the scope of SF-active materials still remains rather limited due to the specific energetic requirements and complicated modulation of intermolecular interactions. Therefore, there is a high demand for developing new SF-capable compounds targeted at practical application. In the current work, the SF dynamics of thienoquinoid (TQ), which exhibits high extinction coefficient and excellent stability, were studied systematically based on transient absorption spectroscopy and theoretical calculations. Results present a distinctive conformational distortion-harnessed SF process featuring the rapid generation and subsequent annihilation of intramolecular multiexciton (ME) dark state with 21A symmetry. The increased lifetimes could be achieved via the partially constrained conformational distortion and exciton delocalization in solid or aggregate states, yet these SF-populated ME species cannot undergo effective decoupling and dissociate completely into individual triplet excitons instead, recovering to ground state via the triplet–triplet annihilation channel. These findings present a deeper understanding of SF dynamics in the TQ skeleton, which could be conducive to improving the conversion efficiency of SF-based photovoltaic devices and developing new SF compounds. [ABSTRACT FROM AUTHOR]

Triplet accumulation strongly influences the performance of organic lasers and has deleterious effect on the development of the electrically pumped organic lasers. We have designed three strong emissive organic distyryl-framework molecules and obtained tricolor lasers based on their H-aggregate single microcrystals. Such a kind of H-type aggregation minimizes the reabsorption of emissive photons and benefits the buildup of laser. We systematically investigated the relationship between the laser behaviors and triplet population, indicating that the optimized energy level is of crucial importance for the development of organic gain materials. These three molecules possessing both the high gain and potential high carrier transport behaviors can be attractive candidates of organic laser materials for the electrically pumped organic laser and future integrated optoelectronic devices. [ABSTRACT FROM AUTHOR]

We demonstrate a controllable photoluminescence anisotropy amplification in organic luminescent radical-doped microcrystals via exciton funneling. The widely tunable doping ratio resulting from very similar molecular structures between hosts and guests leads to a freely tailorable exciton funneling process, which paves an avenue for the construction of high-performance polarizing optical elements. [ABSTRACT FROM AUTHOR]

Electrochemiluminescence (ECL) of crystalline materials has recently attracted increasing attention due to their unique characteristics and applications, such as crystallization-induced emission, active waveguiding, and biosensing. Tris(2,2′-bipyridine)ruthenium(II), [Ru(bpy)3]2+, a classical metal–organic complex for ECL studies, has been fully investigated in solution as well as its derivatives. However, the dependence of ECL properties on the molecular structure and crystal morphology of these complexes has not been illustrated, partially due to the difficulty in the controlled crystal growth. Here, we adopt a facile molecular engineering strategy to obtain microcrystals of [Ru(bpy)3]2+ derivatives with well-defined morphology (rods, wires, or polyhedrons) and varied phosphorescence emission colors (yellow, orange, and red) by simply changing the position and number of methyl substituents on the bipyridine ligands. The packing modes of molecules influenced by methyl groups play a vital role in crystal growth based on attachment energy analysis. The obtained microcrystals could act as ECL luminophores when modified on glassy carbon electrode surfaces. Those with one-dimensional (1D) morphology generally show superior ECL efficiency and stability to three-dimensional (3D) shaped microcrystals. ECL biosensors made of stable 1D microcrystals show reliable and sensitive responses to hydroxyproline, demonstrating their capacity in recyclable detections. This work demonstrates the great potential of molecular engineering in controlling the morphology, emission colors, and ECL properties of molecular crystals, paving the way for the development of high-performance ECL biosensing and optoelectronic devices. [ABSTRACT FROM AUTHOR]

The invention and development of the laser have revolutionized science, technology, and industry. Metal halide perovskites are an emerging class of semiconductors holding promising potential in further advancing the laser technology. In this Review, we provide a comprehensive overview of metal halide perovskite lasers from the viewpoint of materials chemistry and engineering. After an introduction to the materials chemistry and physics of metal halide perovskites, we present diverse optical cavities for perovskite lasers. We then comprehensively discuss various perovskite lasers with particular functionalities, including tunable lasers, multicolor lasers, continuous-wave lasers, single-mode lasers, subwavelength lasers, random lasers, polariton lasers, and laser arrays. Following this a description of the strategies for improving the stability and reducing the toxicity of metal halide perovskite lasers is provided. Finally, future research directions and challenges toward practical technology applications of perovskite lasers are provided to give an outlook on this emerging field. [ABSTRACT FROM AUTHOR]

Insights into the real catalytic active site(s) of promising oxygen evolution reaction (OER) catalysts is significant for the further development of high-performance catalysts. Spinel cobalt oxide (Co3O4), with both tetrahedral (Co2+) and octahedral (Co3+) sites, has been widely studied as an efficient non-precious OER catalyst. However, controversial results still exist regarding its OER performance in determining the active sites from two different tetrahedral and octahedral sites. Here, we have designed size-controllable Co3O4 hexagonal platelets with (111) exposed surfaces only containing tetrahedral Co2+ sites as model catalysts, and systematically investigated the catalytic properties of the tetrahedral sites on the surface of the (111) plane and the octahedral sites on the surface of the (110)-B plane for the OER using density functional theory (DFT) and various characterization methods. The theoretical and experimental results further reveal that the high catalytic activity is based on the existence of octahedral sites in Co3O4, meaning that the octahedral sites are responsible for the OER reaction and have been identified as the dominant active sites of spinel Co3O4. [ABSTRACT FROM AUTHOR]

Atomization of noble metals enable their electrocatalysis applications with low cost, whereas the isolated mononuclear site after atomization might lead leads to limited performance. Herein, we present a general strategy of atomically confined alloying (ACA) to synthesize an electrocatalyst of single atom iridium-trapping cobalt nanosheets with dual-reactive Ir–Co sites. The atomic Ir@Co nanosheets (1.7 wt% Ir) exhibit excellent oxygen evolution reaction (OER) performance with a small overpotential (273 mV at 10 mA cm−2) and high stability, higher than that of the Ir/C catalyst (290 mV at 10 mA cm−2). More importantly, density functional theory (DFT) calculations combined with experiments demonstrated that water oxidation proceeded on atomic Ir@Co nanosheets via a dinuclear tandem mechanism, in which Ir–Co dual sites cooperatively worked in favour of the sequential transfer from Co–OH* to Ir–O* via a Co–O–Ir intermediate, and stabilization of OOH* species by hydrogen bonding interaction. The cooperative mechanism based on a dinuclear electrocatalyst by ACA is hoped to open up more possibilities of single atom noble metal electrocatalysts for various applications. [ABSTRACT FROM AUTHOR]

A new family of isostructural bimetallic lanthanide metal–organic frameworks of M1−xNdxL2 (M = Eu, Tb, and Dy, 0 ＜ x ＜ 1, L = 2,5-pyridinedicarboxylate) was designed for color-tuning. The controllable color-tuning in the red, green and blue regions has been achieved through energy transfer from visible emitting Ln3+ to near-infrared emitting Ln3+. [ABSTRACT FROM AUTHOR]

Precise control of crystal orientations and macroscopic morphology of a perovskite crystal is crucial for various optoelectronic applications relying on charge carrier transport tuning along exposed crystal facets. Here, taking methylammonium lead bromide (CH3NH3PbBr3) as an example, and employing a novel crystal facet engineering method, we successfully construct two kinds of perovskite crystals with exposed {001} and {110} facets. We find that the free carriers’ photoluminescence lifetime on the {001} facets can be 3 times longer than that on {110} facets. The related mechanisms are investigated via fluorescence lifetime imaging microscopy and in situ transmission electron microscopy. These indicate that the different trap state density of exposed facets and crystal structure changing of CH3NH3PbBr3 under light and electron beam irradiation lead to the differences in carrier transport along different facets. By distinguishing the charge carrier transport on different CH3NH3PbBr3 exposed facets, micro-photodetectors have been constructed. A device fabricated with the {001} exposed facets exhibited two orders of magnitude higher photocurrent and half as much dark current as a {110} facet-based device. Thus, the crystal facet engineering of perovskites can be widely adopted for understanding physical/chemical properties of perovskite crystals and provides great potential for novel perovskite optoelectronic device applications. [ABSTRACT FROM AUTHOR]

As one of the promising cathode materials, NiS2 delivers an ultrahigh theoretical capacity of 870 mA h g−1. However, it suffers from huge capacity fading during multiple cycles because of the close formation enthalpy between NiS2 and other nickel sulphides (Ni3S4, Ni3S2 and NiS) and the large volumetric expansion during charging. To overcome these drawbacks, and being inspired by the morphology of “kiwano”, i.e. the African horned melon, with many protrusions, we design and synthesize a unique “kiwano”-like hollow structure via a facile approach, which is beneficial to shorten the diffusion lengths, buffer the volume expansion and especially control the evolution of intermediate phases. The fabricated electrodes present significantly improved capacity (681 mA h g−1 after 100 cycles at 50 mA g−1), superior cycling stability (580.6 mA h g−1 even after 400 cycles at 0.2C) and fast Li+ storage properties (264 mA h g−1 at 2C). The single intermediate phase Ni3S4, rather than other nickel sulphides, was observed in real time by using in situ transmission electron microscopy (TEM) upon direct lithiation. This was one of the key factors for the outstanding cycling stability. As visualized by in situ TEM, the pores in the kiwano structure can effectively buffer the volume expansion. In addition, Li+ ions prefer to insert into NiS2 through the (111) facet owing to their low activation energy. Density of states (DOS) calculations reveal that NiS2 and the intermediate phase Ni3S4 present extremely high electronic conductivity, thus delivering high rate capacity. These promising findings can provide a new perspective in high-performance lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Cobalt-based layered double hydroxides (Co-based LDHs) are cost-efficient electrocatalysts toward the oxygen evolution reaction (OER) associated with the conversion of clean and renewable energy. Herein we report a facile method for the in situ synthesis of monometallic Co LDH ultrathin nanosheets (UTNSs) through a one-step reaction between cobalt(ii) nitrate and 2-methylimidazole (2MI) in water–methanol solution without the pre-synthesis of zeolitic imidazolate framework-67 (ZIF-67). The as-prepared Co LDH UTNSs possess atomic thickness, abundant oxygen vacancies and three-dimensional (3D) porous features. The best sample exhibits an outstanding OER performance on a glassy carbon electrode (GCE) with an overpotential (η) of 340 mV at 10 mA cm−2, a Tafel slope of 56 mV dec−1 and a turnover frequency (TOF) of 0.801 s−1 at η = 350 mV in 1 M KOH. A two-electrode cell with the Co LDH UTNSs as the anode catalyst and commercial Pt/C as the cathode catalyst achieves a current density of 10 mA cm−2 at the applied voltage of 1.625 V during the long-term electrolysis test. This work demonstrates a novel strategy based on water–methanol solution which is promising for the design and synthesis of ultrathin LDHs as highly active and stable catalysts applied in clean energy production. [ABSTRACT FROM AUTHOR]

Two series of cocrystals with the formula Ln(NO3)5·H2TPPZ (Ln = Eu, Tb, Er and Y, TPPZ = 2,3,5,6-tetra-2-pyridinylpyrazine) have been designed and synthesized. Utilizing single crystal structure parsing, we demonstrate how weak hydrogen bonding interactions between lanthanide nitrates and organic molecules stabilize their cocrystal structures. The lanthanide contraction effect is also proposed to help determine the Ln–O bond regularity, hence rationalizing the stability and structural variation of the cocrystals. Furthermore, the luminescence properties of these cocrystals were analyzed in detail. We found an interesting result of decent red fluorescence of the 1-Eu cocrystal complex. [ABSTRACT FROM AUTHOR]

Integration of multi-color semiconductor nanowire lasers (NWLs) on a silicon substrate is a very challenging task, owing to both the material lattice mismatch and the incompatible growth temperature. Recently, organic–inorganic perovskite (CH3NH3PbX3; X = Cl, Br, I) NWLs have been developed using a surface-initiated solution-growth method, which, however, requires post-synthesis transfer of nanowires from a growth substrate to a silicon wafer for device fabrication. Herein, we report multi-color perovskite nanowire lasers on arbitrary substrates (silicon or quartz substrates) through kinetically controlled growth followed by gas-phase halide exchange. First, we developed an antisolvent–vapor-diffusion induced crystallization method to kinetically direct the growth of CH3NH3PbCl3 towards single-crystal nanowires rather than the crystal habit of plate-like morphology. The ratio of nanowires to square microplates was adjusted to be as high as 97% : 3%. Then we introduced a gas-phase halide-anion-exchange reaction to convert chloride nanowires into bromide and iodide ones upon exposure to the vapor of HX (X = Br, I), while preserving both the high crystallinity and the nanowire morphology. Upon optical excitation, Fabry–Perot lasing around 550 and 785 nm occurs from CH3NH3PbBr3 and CH3NH3PbI3 nanowires with an onset of 9.8 and 9.2 μJ cm−2, respectively, with a maximum quality factor of 1260. [ABSTRACT FROM AUTHOR]

The excited-state intramolecular proton transfer (ESIPT) process provides a real four-level system, which forms the working basis of many laser dyes in solutions but remains largely unexplored in the solid-state gain medium. Herein, we modulated the keto* and enol* emissions by switching the intramolecular hydrogen-bond to the intermolecular hydrogen-bond in the solid-state for tuning the emission colors of ESIPT-microcrystal lasers. Both model compounds of 2′-hydroxychalcone derivatives of M1 and M2 exhibit very similar dual enol* and keto* emissions in the aprotic solvents, typical for ESIPT-active molecules. When aggregated into hexagonal-plate microcrystals (HPMCs), the intramolecular hydrogen-bond ensures the photoinduced proton tautomerization from enol* to keto* tautomers, resulting in intense red fluorescence of M1 HPMCs at 647 nm from the keto* form. In sharp contrast, the introduction of an extra hydroxyl group into M2 leads to the formation of an intermolecular hydrogen bond between two adjacent molecules, which suppresses the ESIPT process in the solid-state and therefore leads to intense green emission of M2 HPMCs at 537 nm from the enol* form. The solid-state photoluminescence efficiencies of HPMCs of M1 and M2 are as high as 42% and 51%, respectively. Moreover, well-faceted HPMCs of both M1 and M2 can function as whispering-gallery mode microresonators, enabling microlasers with very low laser thresholds of 10.8 μJ cm−2 for red-emissive M1-HPMCs and 9.4 μJ cm−2 for green emissive M2-HPMCs. [ABSTRACT FROM AUTHOR]

Utilizing a strong electron acceptor molecule tetracyanoquinodimethane (TCNQ) as probe, we demonstrate how the electronic features and geometric sites determine charge-transfer interactions of noble metal clusters with organic molecules. First-principle calculations by searching local minimum energies suggest that the TCNQ complexes with Ag13, Au12Ag1, Au1Ag12 and Au13 all favor edge-site adsorption, and their structures are highly comparable and possess metal–N–metal bonds. Further analysis on frontier molecular orbitals (FMOs) and natural population analysis (NPA) reveals that it's easier for Ag13/Au1Ag12 clusters to transfer electrons to TCNQ as compared with Au13/Ag1Au12. Spin density isosurfaces indicate that the charge transfer from these 13-atom clusters to TCNQ leads to electronic shell closure of the metal clusters. The difference in the electronegativities of Ag and Au, as well as the significant relativistic effect of gold, results in varying donor–accepter interactions sensitive to the coordination number of the doping atom for both Au12Ag1 and Au1Ag12 clusters. [ABSTRACT FROM AUTHOR]

For the purpose of developing multicolor emissive molecular materials, a U-shaped diplatinum molecular switch 1 with an N,N-dimethylurea bridge was prepared. Three forms of single crystals of 1 with yellow (1A), orange (1B), or red (1C) emission were obtained. X-ray analysis shows that the two constituent [Pt(NCN)] units can have an open (1A and 1C) or closed (1B) conformation with different modes of crystal packing. In particular, intermolecular Pt–Pt interaction is evident for 1C with a short Pt–Pt distance of 3.226 Å. The interconversion among these crystals was triggered by external conditions, with the aid of an additional form of crystal 1D. The deep-red emissive crystal 1C exhibits excellent photophysical properties with λmax,emi of 650 nm, Φ of 36%, and τ of 846 ns. Spectroscopic analysis supports the hypothesis that compound 1 has a dominant open conformation in CHCl3 and a closed conformation in MeOH solution. The conformational switching and the degree of intermolecular interaction with tunable emission colors can be regulated by solvent composition. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) small-molecule semiconducting nanostructures (NSs) have attracted more and more attention due to their unique structures and photoelectric properties. However, the preparation of real ultrafine 1D organic nanocrystals (ONCs), in which the intermolecular charge transfer (CT) is confined to a 1D direction, is still a huge challenge. Here, we report a facile way to controllably synthesize uniform 1D ONCs of μ-oxo dimeric iron(iii) porphyrin [(FeTPP)2O] in a cetyltrimethyl ammonium bromide (CTAB)-assisted wet chemical reaction (WCR). In this work, the shape evolution of the (FeTPP)2O NSs was shown by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Interestingly, the regularity and aspect ratio of the (FeTPP)2O 1D NCs increased with time, while their diameters decreased. Further experiments proved that this was closely associated to the reconstruction of the CTAB micelles. After optimizing the experimental conditions, we not only synthesized uniform 1D ONCs with a width of ∼28 nm and/or an aspect ratio of ∼37, but also obtained 2D ONCs with a thickness of about 10 nm. Here, the finest 1D ONCs that we have seen to date have been prepared. The corresponding UV-vis absorption and photoluminescence (PL) spectra are enhanced with a decrease in the diameter and an increase in the aspect ratio of (FeTPP)2O 1D ONCs with high crystallinity, which clearly shows the first report of the confinement effect of the intermolecular CT state in 1D ONCs. This work paves a new route to prepare 1D ONCs and provides us with a chance to further understand and apply the intermolecular CT in 1D organic photoelectrical devices. [ABSTRACT FROM AUTHOR]

A combined study of electrochemical measurements, intervalence charge transfer analysis, and DFT calculations suggests that the degree of urea-mediated electronic coupling between two cyclometalated ruthenium sites is enhanced by the coordination of urea with Br− or Cl−via hydrogen bonding. In contrast, the redox waves of the diruthenium complex become highly irreversible in the presence of relatively strong basic anions such as H2PO4−, F−, or OAc−. This work demonstrates that the anion–urea interaction can be employed to regulate the electronic coupling and electron transfer between redox-active sites, suggesting the potential applications of the urea-functionalized diruthenium complex in anion sensing and stimuli-responsive molecular electronics. [ABSTRACT FROM AUTHOR]

In the field of organic light-emitting diodes (OLEDs), research interests focus on making the optically dark triplet excitons shine in order to increase the electro-optic conversion efficiency of devices. In this work, two kinds of phenazine compounds, i.e. dibenzo[a,c]phenazine (DBP) and tribenzo[a,c,i]phenazine (TBP), were synthesized and used as model compounds to regulate the emission efficiency of the dark triplet excitons by chemical modification. Charge-transfer induced ultrafast intersystem crossing (CT-ISC) with a time constant of ∼1 ps was observed for these two phenazine derivatives upon photoexcitation with a high triplet yield of 77.1% for DBP and 58.7% for TBP. The triplet excited states of DBP can produce ultra-long phosphorescence with lifetime as long as 318 ms at 77 K. The quantum yield for phosphorescence (ΦP) is determined to be 8.45%. In sharp contrast, the triplet-excited 3TBP* undergoes an efficient reverse intersystem crossing (RISC) process, resulting in bright delayed fluorescence emission with negligible phosphorescence. A controllable luminescence behavior from the triplet states between fluorescence and phosphorescence in phenazine derivatives is demonstrated. Theoretical calculations reveal that the structure-dependent triplet evolution is due to the charge-transfer induced energy level alignment within these compounds. Our results may have potential applications in the design of OLEDs and high triplet yield pure organic materials. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) emission and two-photon excited fluorescence (TPEF) are both desirable features for bioimaging because they offer several advantages, such as deep tissue penetration, high spatial resolution and low background noise. However, incorporation of NIR emission and TPEF into the same labeling dye molecule remains a formidable challenge as it requires three features simultaneously: large two-photon absorption cross-section (δ), high fluorescence quantum yield (Φ) and an appropriate NIR absorption/emission wavelength. Herein, we report a theory-assisted design of novel benzoindolic squaraine (BIS) dye molecules that exhibit a high-performance NIR emission and TPEF properties simultaneously. First, the planarity of the BIS core extended the π-framework, which leads to NIR emission at 682 nm with a quantum yield greater than 40%. Second, we utilized the local electric field effect by the addition of non-conjugated D/A moieties to the BIS core to modulate the two-photon absorption (TPA) cross-section (δ) values. Natural transition orbital calculations suggest that non-conjugated D or A groups do not affect the one-photon photophysical properties of BIS dyes, but can alter the molecular orbitals involved in the Sn← S0 (n≥ 2) TPA process. With this new strategy, we successfully obtained a methoxyl-modified molecule (BIS-1), which presents a TPA window between 780 and 950 nm, with the largest δ value above 12 000 GM. [ABSTRACT FROM AUTHOR]

Three hydrogen-bonded organic–inorganic frameworks (HOIFs) are synthesized. Along with full characterization and a comparison with similarly synthesized deuterated counterparts, we reveal that hydrogen-bond interactions of the HOIFs dominate the thermostability, porosity and selectivity in dye filtration on alumina membranes. [ABSTRACT FROM AUTHOR]

Weak intermolecular interactions in phenylenediamine dimer (pdd) clusters are studied by dispersion-corrected density functional theory (DFT) calculations. Along with the optimization of geometric structures and the calculation of interaction energies, we employ molecular electrostatic potential (MEP) mapping, natural bond orbital (NBO) analysis and quantum theory of atoms in molecule (AIM) to analyze the origin and relative energetic contributions of the weak interactions in these pdd systems. It is revealed that the most stable o-phenylenediamine dimer (opdd) cluster is dominated by N–H…N hydrogen bonds, the p-phenylenediamine dimer (ppdd) cluster is largely stabilized by N–H…π and π…π stacking interactions, while the m-phenylenediamine dimer (mpdd) cluster is mainly held by a combination of n →π*, C–H…π and C–H…N interactions. Energy decomposition analysis (EDA) of the total interaction energies of these clusters further demonstrates that the weak intermolecular interactions are associated with electrostatic and dispersion contributions. Structural spectroscopic analysis is also addressed depicting the coexistence of multiple intermolecular interactions which give rise to the spectral variation in wavenumbers of the infrared and Raman activities. Insights into the weak interactions of pdds help us to understand the molecular mechanisms involved in biochemistry and self-assembly materials. [ABSTRACT FROM AUTHOR]

With respect to the successes from symmetric small molecules, asymmetric ones have recently emerged as an alternative choice. In this paper, we present the synthesis and photovoltaic properties of four asymmetric small molecule donors. The benzo[1,2-b:4,5-b′]dithiophene (BDT) end in the asymmetric push–pull CNR–DPP–BDT (CNR = octyl-2-cyano-3-(thiophen-2-yl)acrylate, DPP = diketopyrrolopyrrole) was tailored from hydrogen (H) to thiophene (T), 2-hexylbithiophene (HTT), and CNR, respectively, obtaining M1, M2, M3, and M4. In this order, the donor–donor interactions are enhanced with an increase of intermolecular forces, such as π–π-stacking and van de Waals forces, which enhances aggregation of the donor molecules. In parallel, the molecular dipolarity (☋μ☋) increases in this order from 5.39 D to 6.26 D, 6.34 D, and 6.92 D, respectively, gradually deviating from the value of PC71BM (5.01 D). The increase in the donor-to-PC71BM doplarity difference acts as another factor for enhancing the donor-to-PC71BM phase-separation. The donor/acceptor domain sizes increase from M1 (10 nm) to M2 (20 nm) and M3 (50 nm), and even formation of island-like mesostructured PC71BM aggregates (200 nm) for M4, corresponding to declined short-circuit current density (Jsc) and fill factor (FF) as well as hole mobility (μh) from M1 to M4. This work reveals that control over the terminal moieties of asymmetric small molecules can be an important factor in tailoring photovoltaic performance. [ABSTRACT FROM AUTHOR]

Organic small molecules with a suitable energy level have usually been considered as photosensitizers rather than catalysts for photocatalytic hydrogen evolution (PHE). Herein, we achieved direct PHE using hydrate zinc tetraphenylporphyrin (ZnP, ZnTPP·H2O) nanostructures synthesized by a liquid-phase chemical reaction as photocatalysts. The shape-dependent photocatalysis revealed that the ZnP nanosheets (ZnP-NS) exhibit higher PHE activity (∼0.16 mmol g−1 h−1) than the ZnP octahedron nanoparticles (ZnP-NPs) (∼0.06 mmol g−1 h−1). After in situ construction of the rubrene/ZnP-NS heterostructure, more efficient PHE of this pure organic nanostructure was obtained due to the occurrence of photoinduced electron transfer and Förster resonance energy transfer (FRET). The optimal PHE rate is ∼0.56 mmol g−1 h−1. Furthermore, with the addition of 3.0 mM methyl viologen (MV) and 3.8 wt% platinum, a PHE rate of ∼9.3 mmol g−1 h−1 can be achieved at pH = 7. This study offers a new route to design organic small molecules as photocatalysts. [ABSTRACT FROM AUTHOR]

Acid-promoted efficient, site- and stereo-selective bicyclization of alkynes to polycyclic compounds (benzobicyclo[3.2.1]octanes) was realized with atom- and step-economy. The reaction proceeded through two C–C bonds formed on remote alkyl C–H bonds via twice long-distance cationic rearrangement. [ABSTRACT FROM AUTHOR]

Interactions between tetracyanoquinodimethane (TCNQ) and two typical silver clusters Ag13 and Ag20 are studied by first-principles DFT calculations. Charge transfer (CT) from silver clusters to TCNQ molecules initiates the Ag–N bond formation at selective sites resulting in the formation of different isomers of Ag13–TCNQ and Ag20–TCNQ complexes. We show here a comprehensive spectroscopic analysis for the two CT complexes on the basis of Raman and infrared activities. Furthermore, frontier molecular orbital (FMO) and natural bond orbital (NBO) analysis of the complexes provides a vivid illustration of electron cloud overlap and interactions. The behavior of TCNQ adsorbed on the tetrahedral Ag20 cluster was even found in good agreement with the experimental measurement of TCNQ molecules on a single-crystal Ag(111) surface. This study not only endeavors to clarify the charge-transfer interactions of TCNQ with silver, but also presents a finding of enhanced charge transfer between Ag13 and TCNQ indicating potential for candidate building blocks of granular materials. [ABSTRACT FROM AUTHOR]

Cryogenic temperature detection plays an irreplaceable role in exploring nature. Developing high sensitivity, accurate, observable and convenient measurements of cryogenic temperature is not only a challenge but also an opportunity for the thermometer field. The small molecule 9-(9,9-dimethyl-9H-fluoren-3yl)-14-phenyl-9,14-dihydrodibenzo[a,c]phenazine (FIPAC) in 2-methyl-tetrahydrofuran (MeTHF) solution is utilized for the detection of cryogenic temperature with a wide range from 138 K to 343 K. This system possesses significantly high sensitivity at low temperature, which reaches as high as 19.4% K−1 at 138 K. The temperature-dependent ratio of the dual emission intensity can be fitted as a single-exponential curve as a function of temperature. This single-exponential curve can be explained by the mechanism that the dual emission feature of FIPAC results from the excited-state configuration transformations upon heating or cooling, which is very different from the previously reported mechanisms. Here, our work gives an overall interpretation for this mechanism. Therefore, application of FIPAC as a cryogenic thermometer is experimentally and theoretically feasible. [ABSTRACT FROM AUTHOR]

A novel palladium catalyzed hydroxylation of unactivated aliphatic C(sp3)–H bonds was successfully developed. Different from conventional methods, water serves as the hydroxyl group source in the reaction. This new reaction demonstrates good reactivity and broad functional group tolerance. The C–H hydroxylated products can be readily transformed into various highly valuable chemicals via known transformations. Based on experimental and theoretical studies, a mechanism involving the Pd(ii)/(iv) pathway is proposed for this hydroxylation reaction. [ABSTRACT FROM AUTHOR]

Photocatalytic water splitting into hydrogen, a renewable and environmentally friendly alternative energy resource, offers a promising way to solve the increasingly urgent energy crisis. We prepare here a series of TiO2–carbon hybrid nanomaterials by heating oleylamine wrapped ultrathin TiO2 nanosheets at different temperatures in an air or inert atmosphere. Photocatalytic experiments show that the activity of these hybrid nanomaterials can be improved and stabilized in comparison to TiO2 nanomaterials without carbon hybridization no matter what shape (ultrathin nanosheets or nanoparticles) and crystalline phase (anatase or rutile) TiO2 presents in the composites. Similar surface species are demonstrated by FTIR and Raman spectroscopy for carbon modified anatase ultrathin nanosheets and nanoparticles, which may result in nearly the same hydrogen production rates of the two photocatalysts. [ABSTRACT FROM AUTHOR]

Nitrogen and oxygen doped hollow carbon spheres (HCSs) have been prepared by pyrolysis of poly(o-phenylenediamine) (PoPD) submicrospheres, which were synthesized by a facile polymerization procedure with an environmental-friendly dopant glycine. Utilizing o-phenylenediamine (oPD) and glycine as the precursors, we are also motivated by the recognition that effective heteroatom doping increases the supercapacitor performance of carbon materials. The as-prepared N- and O- doped HCSs exhibit an enlarged specific surface area (∼355 m2 g−1) and pore volume (∼0.14 cm3 g−1), and they have superior performance in supercapacitors owing to the synergies gained from effective heteroatom doping, their hollow structures, and their good mesoporosity. The reasonable capacitance performance coupled with the facile synthesis procedure suggests supercapacitor applications. [ABSTRACT FROM AUTHOR]

Convenient and economic one-step nitrogenization of oxygen-rich fibril materials, such as absorbent cotton and facial tissue, under gaseous ammonia is used to synthesize various oxygen reduction catalysts. The surface nanoarchitectures of fibrils are remolded by this nitrogenization processing with multi-effects involving the doping of abundant active pyridinic and graphitic N in the carbon skeleton, creating a highly unique mesopore structure with an ultrahigh specific area as well as a high degree of graphitization. The joint optimization of these structure characteristics yields an ideal catalytic nanoarchitecture, which can execute an approximate 4e− oxygen reduction with an activity comparable to that of Pt/C. The durability and methanol tolerance of the catalyst are also essentially superior to that of commercial Pt/C on the basis of this ideal nanoarchitecture. [ABSTRACT FROM AUTHOR]

A host–guest inclusion complexation self-assembly strategy was developed for the synthesis of SHG-active low dimensional supramolecular crystals (LDSCs). p-Nitroaniline guest molecules with high inherent second-order polarizability were introduced into the cavities of the β-cyclodextrin host to form supramolecular inclusion complexes, which were then assembled into microscale crystalline structures with an anti-solvent diffusion combined solvent-evaporation-induced self-assembly method. Two distinct types of LDSCs with controllable dimensions were obtained by altering the polarity of anti-solvents and the concentration of supramolecular monomers. Each type of LDSCs exhibited its characteristic SHG response to the polarized incident signals, which is attributed to the inherent crystal structures. [ABSTRACT FROM AUTHOR]

In this article, we selected BDT–DPP–BDT (DPP = diketopyrrolopyrrole and BDT = 4,8-di-2-(2-ethylhexyl)-thienyl-benzo[1,2-b:4,5-b′]dithiophene) as the model backbone and end-capped it with hydrogen, octyl 2-cyano-3-(thiophen-2-yl)acrylate (CNR), and 2-hexylbithiophene (HTT), respectively, forming three small molecule donors: BDB, CNRBDB and HTTBDB. Introduction of a polar and planar electron-withdrawing unit of CNR to both ends of the BDB backbone enhances the hole mobility from 4.14 × 10−4 to 7.75 × 10−3 cm2 V−1 s−1 and raises the fill factor from 27 to 57% when blended with PC71BM. This is associated with the PC71BM phase size decreasing from 70 to 20 nm. When the electron-donating unit of HTT with poorer planarity is linked to both ends of the BDB backbone, both donor and acceptor phase sizes are decreased to 20 nm. The short-circuit current density is greatly improved from 4.22 to 9.66 mA cm−2, and the fill factor is enhanced to 46%. Overall, this work demonstrates that the end-capped aromatic groups play an important role in tuning the phase size and photovoltaic properties of DPP-based small molecule solar cells. [ABSTRACT FROM AUTHOR]