Linear scaling local correlation approach for solving the coupled cluster equations of large systems

A linear scaling local correlation approach is proposed for approximately solving the coupled cluster doubles (CCD) equations of large systems in a basis of orthogonal localized molecular orbitals (LMOs). By restricting double excitations from spatially close occupied LMOs into their associated virtual LMOs, the number of significant excitation amplitudes scales only linearly with molecular size in large molecules. Significant amplitudes are obtained to a very good approximation by solving the CCD equations of various subsystems, each of which is made up of a cluster associated with the orbital indices of a subset of significant amplitudes and the local environmental domain of the cluster. The combined effect of these two approximations leads to a linear scaling algorithm for large systems. By using typical thresholds, which are designed to target an energy accuracy, our numerical calculations for a wide range of molecules using the 6-31G or 6-31G* basis set demonstrate that the present local correlation approach recovers more than 98.5% of the conventional CCD correlation energy.     

Photogeneration and quenching of reactive oxygen species by urocanic acid

Urocanic acid, UCA, is characterized by two electronic transitions in the UV-B (280-320 nm) which comprise its broad absorption spectrum and give rise to wavelength-dependent isomerization quantum yields. The absorption spectrum of UCA extends into the UV-A (320-400 nm). Given the UV-A component of sunlight is significantly greater than the UV-B component it is hypothesized even weak UV-A photochemistry of UCA could be important for in vivo responses to UV radiation. Degenerate pump-probe experiments performed on t-UCA at several wavelengths in the UV-A reveal an excited-state absorption that undergoes a rapid, approximately 1 ps decay. Photoacoustic experiments performed on both the cis and trans isomers reveal the formation of a long-lived intermediate following UV-A excitation. The efficiency and action spectra for this latter photoactive process are presented and are similar for both isomers of UCA. Cholesterol hydroperoxide assays designed to investigate the nature of the UV-A photoreactivity of t-UCA confirm the production of reactive oxygen species. The bimolecular rate constant for the quenching of singlet oxygen by t-UCA is determined to be 3.5 x 10(6) M(-1) s(-1). Taking into consideration recent theoretical calculations and jet expansion studies of the electronic structure of gas-phase t-UCA, a model is proposed to explain the isomerization and photoreactivity of t-UCA in solution over the UV-A region.     

Recent progress on pure organic room temperature phosphorescence materials based on host-guest interactions

Pure organic room temperature phosphorescence (RTP) has been attracting a lot interest recently. So far, many strategies have succeeded in achieving efficient organic RTP materials by increasing the rate of intersystem crossing (ISC) and suppressing non-radiative transitions. In supramolecular chemistry, the control and regulation of molecular recognition based on the role of the host and guest in supramolecular polymers matrix, has attracted much attention. Recently, researchers have successfully achieved room temperature phosphorescence of pure organic complexes through host-guest interactions. The host molecule specifically includes the phosphorescent guest to reduce non-radiative transitions and enhance room temperature phosphorescence emission. This review aims to describe the developments and achievements of pure organic room temperature phosphorescence systems through the mechanism of host-guest interactions in recent years, and demonstrates the exploration and pursuit of phosphorescent materials of researchers in different fields.     

Highly-efficient photosensitizer based on AIEgen-decorated porphyrin for protein photocleaving

An AIEgen decorated porphyrin(TPETPyP) was easily obtained through a one-step reaction.The bulky TPE in TPETPyP greatly impeded the intermolecular π-π stacking of the porphyrin core,which significantly suppressed aggregation-caused quenching(ACQ) effect of TPETPyP in aqueous solution.The four pyridinium salts formed in TPETPyP also render the whole molecule water solubility,which eliminated its aggregation.TPETPyP exhibited ~1 O_2 quantum yield as high as 0.85 in PBS.Moreover,it also showed high binding affinity to proteins,the major biotarget of ~1 O_2.The high ~1 O_2 quantum yield plus the great binding ability of TPETPyP toward proteins makes it a highly-efficient protein photocleaving agent.Protein electrophoresis experiments demonstrated that TPETPyP can photocleave BSA upon visible light irradiation,indicating that TPETPy P can act as a promising photosensitizer(PS) in PDT.The work here will provide a facile strategy to utilize AIEgens modified traditional PSs for photodynamic therapy(PDT).     

The adsorption of acidic gaseous pollutants on metal and nonmetallic surface studied by first-principles calculation: A review

The acidic gases such as SO₂, NO_x, H₂S and CO₂ are typical harmful pollutants and greenhouse gases in the atmosphere, which are also the main sources of PM_2.5. The most widely used method of treating these gas molecules is to capture them with different adsorption materials, i.e., metal and nonmetallic materials such as MnO₂, MoS₂ and carbon-based materials. And doping transition metal atoms in adsorption materials are beneficial to the gas adsorption process. The first-principles calculation is a powerful tool for studying the adsorption properties of contaminant molecules on different materials at the molecular and atomic levels to understand surface adsorption reactions, adsorption reactivity, and structure-activity relationships which can provide theoretical guidance for laboratory researches and industrial applications. This review introduces the adsorption models and surface properties of these gas molecules on metal and nonmetallic surfaces by first-principles calculation in recent years. The purpose of this review is to provide the theoretical guidance for experimental research and industrial application, and to inspire scientists to benefit from first-principles calculation for applying similar methods in future work.     

Boosting Luminance Energy Transfer Efficiency in Upconversion Nanoparticles with an Energy‐Concentrating Zone

Despite the successful application of upconversion nanoparticles (UCNPs), their low energy transfer efficiency is still a bottleneck to further applications. Here we design UCNPs with a multilayer structure, including an inert NaYF₄:Gd core and an energy‐concentrating zone (ECZ), for efficient energy concentration. The ECZ is composed of an emitting layer of NaYF₄:Yb,Er and an absorption layer of NaYF₄:Nd,Yb with antenna IRDye 800CW to manipulate the energy transfer. The stable and tight packing of 800CW linked originally with a bisphosphonate ligand improves greatly the transfer efficiency. The proximity of the emitting layer to both surface antenna and accepter also decreases energy depletion. Compared to classical UCNPs, the ECZ UCNPs show 3600 times higher luminescence intensity with an energy transfer efficiency near 60 %. In proof‐of‐concept applications, this type of structure was employed for Hg²⁺ detection and for photodynamic therapy under hypoxic conditions.     

Switching on the Photocatalysis of Metal–Organic Frameworks by Engineering Structural Defects

Defect engineering is a versatile approach to modulate band and electronic structures as well as materials performance. Herein, metal–organic frameworks (MOFs) featuring controlled structural defects, namely UiO‐66‐NH₂‐X (X represents the molar equivalents of the modulator, acetic acid, with respect to the linker in synthesis), were synthesized to systematically investigate the effect of structural defects on photocatalytic properties. Remarkably, structural defects in MOFs are able to switch on the photocatalysis. The photocatalytic H₂ production rate presents a volcano‐type trend with increasing structural defects, where Pt@UiO‐66‐NH₂‐100 exhibits the highest activity. Ultrafast transient absorption spectroscopy unveils that UiO‐66‐NH₂‐100 with moderate structural defects possesses the fastest relaxation kinetics and the highest charge separation efficiency, while excessive defects retard the relaxation and reduce charge separation efficiency.     

2D Titania–Carbon Superlattices Vertically Encapsulated in 3D Hollow Carbon Nanospheres Embedded with 0D TiO2 Quantum Dots for Exceptional Sodium‐Ion Storage

Two‐dimensional (2D) superlattices offer promising technological opportunities in tuning the intercalation chemistry of metal ions. Now, well‐ordered 2D superlattices of monolayer titania and carbon with tunable interlayer‐spacing are synthesized by a molecularly mediated thermally induced approach. The 2D superlattices are vertically encapsulated in hollow carbon nanospheres, which are embedded with TiO₂ quantum dots, forming a 0D‐2D‐3D multi‐dimensional architecture. The multi‐dimensional architecture with the 2D superlattices encapsulated inside exhibits a near zero‐strain characteristic and enriched electrochemical reactivity, achieving a highly efficient Na⁺ storage performance with exceptional rate capability and superior long‐term cyclability.     

Manipulating the Stacking of Triplet Chromophores in the Crystal Form for Ultralong Organic Phosphorescence

Provided here is evidence showing that the stacking between triplet chromophores plays a critical role in ultralong organic phosphorescence (UOP) generation within a crystal. By varying the structure of a functional unit, and different on‐off UOP behavior was observed for each structure. Remarkably, 24CPhCz, having the strongest intermolecular interaction between carbazole units exhibited the most impressive UOP with a long lifetime of 1.06 s and a phosphorescence quantum yield of 2.5 %. 34CPhCz showed dual‐emission UOP and thermally activated delayed fluorescence (TADF) with a moderately decreased phosphorescence lifetime of 770 ms, while 35CPhCz only displayed TADF owing to the absence of strong electronic coupling between triplet chromophores. This study provides an explanation for UOP generation in crystal and new guidelines for obtaining UOP materials.     

Effects of different oxygen-containing anions on the structure of water clusters

Using Ni(Im)₆²⁺ (Im = imidazole) as the structural unit, the effects of oxygen-containing anions, such as SO₄^2-, NO₃^? and CO₃^2- on the structure of water clusters were studied. The crystal structures of three compounds [Ni(Im)₆][SO₄(H₂O)₁₁] (1), [Ni(Im)₆][(NO₃)Cl(H₂O)₄] (2), and [Ni(Im)₆][CO₃(H₂O)₅] (3) were obtained. Using Mercury-3.8 software to analyze the above three crystal structures, find different anion of water clusters had a significant effect on the supramolecular structure. At the same time, it also significantly influences the number of water molecules in the crystal structure.