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A new fluorescent probe (T2) containing pyrene-hydrazone furan moieties was developed and synthesized through a two-step process and then coated onto filter paper to form a paper-based sensor for TNT detection. The T2 sensor uses photoinduced electron transfer (PET) induced fluorescence quenching to detect TNT. The sensor properties were studied using fluorescence spectra, 1H-NMR titration and density functional theory (DFT) calculations. The reaction time of the T2 paper-based sensor for TNT detection was only five minutes. A smartphone was used as an alternative instrument to detect fluorescence signals and a typical image J-processing application was employed to evaluate the grayscale values of the smartphone-captured photographs. The sensor showed a linear concentration range for TNT detection of between 30–500 μM and a detection limit of 30 μM. The T2 paper-based sensor was found to have high selectivity and sensitivity, and it can successfully detect and image TNT in actual samples. This research demonstrates that a T2 paper-based sensor is a promising alternative for TNT detection owing to its short reaction time, high selectivity, sensitivity, and easy applicability. [ABSTRACT FROM AUTHOR]

It is significant to develop low-cost and highly efficient electrocatalysts for the hydrogen evolution reaction (HER) via electrochemical water splitting. Herein, we constructed P-doped NiCo2S4 nanowire arrays on carbon fiber paper (NiCo2S4−xPx/CFP) as a HER electrocatalyst in both acidic and alkaline media. Benefitting from P doping into NiCo2S4, the as-prepared NiCo2S4−xPx/CFP exhibits low HER overpotentials of 80 and 132 mV in acidic and alkaline media at a cathodic current density of 10 mA cm−2, respectively, which are far superior to counterparts of NiCo2S4 nanowire arrays on the carbon fiber paper (NiCo2S4/CFP). Meanwhile, the NiCo2S4−xPx/CFP presents excellent HER stability of 20 hours in acidic and alkaline media. From the results of density functional theory calculations, P doping can not only optimize the hydrogen adsorption energetics on each kind of atomic site of catalysts, but also strengthen the H2O molecule binding ability on the catalyst surface for the alkaline HER and favor kinetics of hydrogen adsorption and H2 formation on the catalyst surface for the acidic HER, eventually improving overall HER performances. The investigation of the HER mechanism modulated by P doping in our work offers novel inspiration to develop highly efficient ternary metal sulfides for the HER. [ABSTRACT FROM AUTHOR]

The strong metal–support interactions (SMSI) between metal and its support have been regarded as a valid approach to enhance the catalytic performance; however, the extent to which exploration of electronic state regulation affects catalytic performance of alcohol oxidation reactions (AOR) has been rarely reported. In this paper, PdAg nanoparticles loaded on a N-doped carbon substrate with controlled nitrogen content (PdAg@NxC, x representing the nitrogen contents) was synthesized through a seeded synthesis strategy for alkaline AOR. Results show that the electronic state of PdAg nanoparticles was significantly modified after nitrogen doping in the carbon support. Experimental and theoretical results indicate that with increasing nitrogen content, the degree of electronic state regulation becomes increasingly significant. Density functional theory (DFT) calculations suggest that the increased degree of SMSI promotes OH* adsorption on the PdAg surface and weakens the binding between catalyst and CO*. As a result, the PdAg@N15.3C with the highest N content exhibits excellent AOR performance, achieving a MA/SA of 10.8 A mgPd−1/13.2 mA cm−2 and 3.8 A mgPd−1/4.7 mA cm−2 on the EOR and MOR, respectively. Moreover, due to the changes in the adsorption energy of key intermediates on PdAg nanoparticles, the onset oxidation potential of PdAg@N15.3C shows a negative shift of 180 mV compared to PdAg@C as revealed by CO stripping analysis, signifying an increase in the CO tolerance. Our study demonstrates the influence of the SMSI effect between the active center and the support on the catalytic performance for AOR and presents a pathway to achieve high AOR performance through SMSI engineering. [ABSTRACT FROM AUTHOR]

We present in this paper the stability of SWCNT hybrid systems with Py molecules. vdW type interactions are therefore the main interaction mechanism between encapsulated molecules and nanotubes, and the simplest model to describe these interactions is the Lennard-Jones potential. We have therefore performed energy minimization calculations on hybrid SWCNTs in a very wide range of diameters and of all chirality using the Lennard-Jones potential. The structure of the carbon nanotube is obtained from the winding of graphene on itself to form a hollow cylinder described by the pair of integers (n, m) entirely determining its structural characteristics, while the optimization of the geometry of the Py molecule is obtained by SIESTA using the exchange–correlation functional LDA. After minimisation, an approach that combines density functional theory, molecular mechanics, bond polarizability model, and spectral moment's method has been used to compute Raman spectra. Two types of vibration modes of SWCNTs attract our attention. Initially, the modifications of the modes of Py after encapsulation will be analyzed. In the following discussion, we examine how the vibrational properties of single-walled carbon nanotubes (SWCNTs) are affected by encapsulation, specifically in relation to the RBM and tangential modes. Our analysis of the Raman active modes supports the notion that the structural integrity of the SWCNTs remains intact and indicates the occurrence of a charge transfer between the Py molecules and SWCNTs. This charge transfer depends on the geometric position of Py in the SWCNT. [ABSTRACT FROM AUTHOR]

The treatment of cancer has always been a challenging problem in the medical community. In this paper, based on density functional theory (DFT), B12N12 nanocage was studied as delivery carriers of sulforaphane (SF) anticancer drug, and the adsorption properties, electronic properties and topological analysis of complexes were calculated. The adsorption energy, solvation energy, electronic and topological properties were calculated by used M06-2X/6-311+G(2d,p), M05-2X/6-31G(p) and B3LYP/6-311G(d,p) theoretical levels, respectively. In addition, the effects of doping and packaging of alkaline earth metal (Be, Mg, Ca) on the related properties were also studied. Doping and packaging metal can improve the transfer characteristics of nanocages by changing the polarity of systems. All calculation results were performed in Gaussian 09 software. The frontier molecular orbital (FMO) and natural bond orbital (NBO) analysis showed that nanocages acting as charge acceptors and drugs as charge donors during the adsorption process. The atoms-in-molecules (AIM) and interaction region indicator (IRI) analysis showed that there were strong polar covalent bonds between drug and nanocages, which enabled drug to be stably adsorbed on nanocages. The solvation effect results showed that acidic conditions were more conducive to drug transport and release. Compared with the original and encapsulated systems, the doping system has better adsorption properties and solvation effect. Moreover, the charge transfer between drug and nanocages in doping system was more frequent and the interaction was stronger. Therefore, our results indicated that the doping nanocages MB11N12 (M = Be, Mg and Ca) were more suitable as the drug carrier system for SF anticancer drug. [ABSTRACT FROM AUTHOR]

The host–guest complexes formed between [9–11]CPPs and C60 were studied extensively due to their excellent photoelectric conversion properties and photochemistry. The drastically increased electron accepting ability of Li+@C60 with respect to C60 may induce strong intermolecular charge transfer interaction with [9–11]CPP. In this paper, a comprehensive computational analysis of the structure, intermolecular interactions, absorption spectra, charge transfer characteristics and nonlinear optical properties of [9–11]CPP⊂C60 and [9–11]CPP⊂Li+@C60 were studied using density functional theory calculations. It was found that the intermolecular binding energies of [10]CPP⊂C60 and [10]CPP⊂Li+@C60 were −47.76 and −60.08 kcal mol−1, which were larger than those of [9, 11]CPP⊂C60 and [9, 11]CPP⊂Li+@C60. Thus, [10]CPP was found to be the most ideal fullerene encapsulator and most suitable for encapsulating C60. In addition, with the increase of the CPP ring size, the second hyperpolarizability (γ) values of [n]CPP⊂C60 increase gradually. In addition, the γ values of [9–11]CPP⊂Li+@C60 were all greater than those of [9–11]CPP⊂C60, indicating that embedding Li+ into fullerene spheres can effectively improve their third-order nonlinear optical responses. [ABSTRACT FROM AUTHOR]

In this paper, the water dissociation abilities of transition metals Cr, Co, Ni, Cu, and surface Cr incorporated into Co, Ni, and Cu matrix were estimated using density functional theory. The calculations indicate that the transition metal matrix can markedly affect the ability of surface Cr to promote H2O dissociation. The barriers of the H2O dissociation step on Cr, Co, Ni, and Cu increase in sequence. After introducing Cr into a transition metal matrix, the H2O dissociation ability of Cr reduces. Compared with pure metals, doping the Co surface with Cr is less favorable for H2O dissociation and introducing Cr onto Ni and Cu surfaces can accelerate the H2O dissociation reaction and Cr–Ni has stronger H2O dissociation ability than Cr–Cu. The electron distribution calculations show that the electron deviation levels from Cr to the metal matrix are a key factor in affecting the H2O dissociation ability of surface Cr, and strong electron deviation is advantageous. The adsorption calculations reveal that the OH-binding energy of catalyst cannot relate to its H2O dissociation ability and follows a rough volcano relationship with its alkaline HER performance. [ABSTRACT FROM AUTHOR]

In this paper, based on density functional theory (DFT), the adsorption and cracking mechanism of CH3OH on the Cu@CnB8 (n = 24, 40, 88) surface is studied. There are three possible paths of C–H, C–O and O–H for the initial cracking of CH3OH on the surface of Cu@CnB8. In this paper, the adsorption energy of CH3OH and intermediates on the Cu@CnB8 surface is calculated, and the related reaction energy and activation energy under the possible cracking path are calculated. The calculation results show that CH3OH is physically adsorbed on the Cu@CnB8 surface. The main path of CH3OH cracking is CH3OH → CH3O → CH2O → CHO → CO. The activity of CH3OH cracking decreases with the increase of Cu@CnB8 size, that is, the small size Cu@CnB8 can be used as an effective catalyst for the cracking of CH3OH. [ABSTRACT FROM AUTHOR]

Calcite is widely used in many fields. The synthesis of calcite is strongly influenced by solvents and additives. In this paper, the adsorption of water and formic acid molecules on the (104) surface of calcite was systematically studied on the atomic scale using the density functional theory (DFT) method. The results show that both molecules can be adsorbed on the calcite surface by occupying the top position of Ca. The results of differential charge density and the projected crystal orbital Hamiltonian population show that the adsorption is controlled by the charge transfer from the oxygen atom to the surface calcium. Formic acid has a carbonyl oxygen and it plays a greater role in stabilizing the surface than water. Moreover, the adsorption of two molecules can be further stabilized by hydrogen bonds formed between the hydrogen atom in the adsorbed molecules and the oxygen in calcite. This work provides a clear understanding of the stabilization of the calcite surface by adsorbing different molecules and also provides the possibility of tuning the synthesis of calcite by choosing a suitable solvent and additives. [ABSTRACT FROM AUTHOR]

This paper reports fluorescein-linked calixarene-based columnar liquid crystals with a broad temperature range of mesophases. The photophysical and density functional theory (DFT) study suggested good electronic behaviour and reactivity of supramesogens. All the synthesized materials (4a–4d) were characterized by FT-IR, 1HNMR, 13C NMR, MALDI-TOF, and elemental analysis and displayed yellow to orange light emission in the solution, thin films, and solid state. Further, all materials showed aggregation-induced emission (AIE) effect with higher quantum yields. The fluorescein-linked supramolecules broadly stabilized the columnar hexagonal phase and formed self-assembly with higher thermal stability. The substituted alkoxy side chains on the terminal position influenced the mesophase temperature range and thermal stability. All the compounds adopted cone conformation, which was confirmed by experimental and computational studies. Further, these fluorescent materials were used to stain model organism nematodes in solution-state aggregation. [ABSTRACT FROM AUTHOR]

Cocatalysts are usually applied in the photocatalytic water splitting process to accelerate the kinetics of the hydrogen evolution reaction (HER). Specifically, the transition metal nitride (Mo2N) featuring a unique local surface plasmon resonance (LSPR) effect has exhibited great potential to function as a HER cocatalyst. However, the low metallicity of Mo2N hampers its ability to improve charge separation. To address this issue, transition metal atom doping (Co and Cu) engineering was used to modulate the electronic structure of Mo2N nanosheets to achieve a higher electrical conductivity and a lower hydrogen adsorption free energy (‖ΔGH*‖), thereby favoring the HER kinetics. Density functional theory (DFT) calculations and experimental results showed that Co-doping and Cu-doping mainly take place at Mo sites in the crystal structure of Mo2N to form stable structures of Co doped Mo2N (Co–Mo2N) and Cu doped Mo2N (Cu–Mo2N). Compared with pristine Mo2N, both Cu–Mo2N and Co–Mo2N demonstrated a much improved cocatalytic effect over g-C3N4 in promoting charge separation, accelerating HER kinetics and enhancing light absorption. The Co–Mo2N with the highest conductivity and lowest ‖ΔGH*‖ illustrated the best cocatalytic effect, and the H2 production performance (367.8 μmol g−1 h−1) of Co–Mo2N/g-C3N4 achieved was 10 and 5 times higher than those of Mo2N/g-C3N4 and Cu–Mo2N/g-C3N4. This paper provides significant guidance in the design and development of efficient cocatalysts for the HER application. [ABSTRACT FROM AUTHOR]

The use of industrial solid waste to produce a cement clinker can not only effectively reduce the consumption of natural resources, but also reduce the pollution of waste. In this paper, the solidification trend of Cr ions in the clinker phases of ordinary Portland cement (OPC) was studied by combining experiments with theoretical simulations. The results from energy dispersive spectrometry, X-ray diffraction, and density functional theory (DFT) simulations suggests that Cr ions will preferentially enter the mineral C4AF by displacing Fe ions. Further analysis of the bond length and bond order, electron density differences and partial density of states suggests that this phenomenon is mainly due to the similar electronic contributions of the host and guest ions. These insights will provide important fundamental guidance for understanding the doping behaviour of chromium ions in an OPC clinker and the utilization of Cr-containing industrial solid waste, thus paving an efficient way for the treatment of Cr-bearing industrial solid waste. [ABSTRACT FROM AUTHOR]

Carbazole-substituted N-heterocyclic carbene (NHC)–gold complexes have exhibited diverse structural features and interesting thermal properties. The role of the remotely linked carbazole group to mesoionic carbene in gold(I)–NHC complexes has been addressed in this paper. Thus, we have synthesized and characterized neutral gold–mesoionic carbene monomers tagged with carbazole groups. The mononuclear gold(I)–carbene complexes [(L1)AuCl] (1) and [(L2)AuCl] (2), where L1.HI = 1-(naphth-1-yl)-3-methyl-4-(carbazolylmethyl)-1,2,3-triazolium iodide and L2.HI = 1-(mesityl)-3-methyl-4-(carbazolylmethyl)-1,2,3-triazolium iodide, were synthesized and characterized. This new class of complexes exhibited interesting gold–hydrogen bonding. In addition, the thermal properties of 1 and 2 were investigated. Density functional theory (DFT) calculations and natural bond orbital (NBO) analysis were carried out on a model system, [(L′)AuCl] (1A), where L′ = 1-phenyl-4-methyl-carbazole-1,2,3-triazol-ylidene, to realize the bonding situations. The calculated metrics agreed reasonably well with the experimental observations. [ABSTRACT FROM AUTHOR]

Sensing nitroaromatic explosives has gained significant attention due to both increased terrorist threats and a need for environmental protection. In this regard, a fluorescent chemosensor, 1-benzyl-3,5-di(thiophen-2-yl)pyrazin-1-ium bromide (BTPyz), was synthesized and characterized via spectroscopic methods. The photophysical properties were investigated using absorption and emission spectral analysis. As a fluorescent chemosensor, BTPyz exhibited a selective response towards 2,4,6-trinitrophenol (TNP) with a detection limit of 11.6 nM and quenching constant (KSV) of 3.8 × 104 M−1. The fluorescence quenching mechanism was attributed to ground-state charge-transfer complex formation and resonance energy transfer, as evident from Uv-visible, fluorescence and NMR spectroscopy, single-crystal XRD studies, and density functional theory calculations. BTPyz was also employed for the contact mode detection of TNP on paper strips. The detection of TNP in real water and soil samples demonstrated BTPyz to be a promising detection tool toward environmental specimens. [ABSTRACT FROM AUTHOR]

The research on inorganic nanozymes remains very active since the first paper on the "Intrinsic peroxidase-like properties of ferromagnetic nanoparticles" was published in Nature Nanotechnology in 2007. However, there is still the question, "What are the inorganic nanozymes?" Inorganic nanomaterials with intrinsic enzyme-like activities were not generated from artificial synthesis processing. The unique architecture of the metal site in inorganic nanomaterials contributes to the specificity and catalytic behavior described by the classic Michaelis–Menten equation, just like an enzyme (protein) or ribozyme (RNA), and as supported by density functional theory calculations. The discovered inorganic nanozymes participate in many key biological catalysis processes, especially related to oxygen. Possibly, they were essential to the emergence of life before RNAs and proteins, and they still play a crucial role in our daily lives, especially from the view of biogeochemistry. These inorganic nanozymes are classified as "inorganic enzymes", in line with the existing classifications of enzymes (proteins) and ribozymes (RNAs) as biocatalysts. By drawing inspiration from the metal architecture in nanomaterials, scientists can design artificial biocatalysts or functionalized nanozymes that are more stable and specific. It is necessary to pursue research to utilize inorganic nanozymes in the current biomedical applications and comprehend how they impact our Earth's environment. [ABSTRACT FROM AUTHOR]

In this paper, a novel Schiff base ligand NaHL (NaHL = sodium (S,E)-2-((4-chloro-2-hydroxybenzylidene) amino) propanoate) was designed and synthesized, and three novel complexes with Zn(II) were obtained by a solvent evaporation technique. Single crystal X-ray diffraction indicated that [Zn(L)(H2O)]n1 and [Zn(L)(H2O)]n2 were one-dimensional coordination polymers (CPs) with a helix structure, while [Zn2(L)2(bipy)] 3 was a two-dimensional CP with the participation of an auxiliary ligand. Fluorescence spectra exhibited that 1 and 2 had good fluorescence properties in both solution and solid states, but 3 was basically quenched due to the addition of ancillary ligands in the solid state. Density functional theory (DFT) calculations have been performed to further reveal the intrinsic fluorescence properties and mechanisms of 1 and 2, which demonstrated the chelate fluorescence enhancement effect (CHEF). Moreover, 1 and 2 show selective recognition of NH4+ and HPO42− accompanied by an efficient fluorescence "turn off" phenomenon, and a series of related experiments demonstrate that 1 and 2 were fully quenched through the removal of Zn2+ from the complex and the protonation of the ligand. [ABSTRACT FROM AUTHOR]

In this paper, eight complexes M-1, M-2, M-3 and M-4 (M = Ir or Rh) in the general formula [M(C^N)2(N^N)] (C^N = cyclometalated ligands and N^N = ancillary ligands) are systematically investigated by density functional theory (DFT) and time-dependent DFT methods. With the aim to study the influence of metal centers for nonlinear optical (NLO) responses, the geometrical and electronic structures, first hyperpolarizabilities (βtot) and UV-Vis absorption spectra are investigated in detail. It is found that the βtot values increase 1.8–3.7 times as the metal atom changes from Rh to Ir. Among all the studied complexes, Ir-3 (C^N = 4-chloro-2-phenylquinoline with N^N = 2,9-dimethyl-1,10-phenanthroline) shows the highest βtot value with an amplitude of 2415.4 a.u. computed at the ωB97XD/6-31G+(d)/SDD level, which can be seen as a promising candidate for second-order NLO materials. In addition, the HOMO energy levels increase upon increasing the size of the metal atom, which contributes to a significant reduction in HOMO–LUMO gaps. The βtot values and HOMO–LUMO gaps are in an inverse relationship. Furthermore, tuning the center metals Ir/Rh can be seen as an effective method to modulate the charge transfer degree. We anticipate that this study may serve as a new strategy for the rational design and synthesis of second-order NLO materials. [ABSTRACT FROM AUTHOR]

In this paper, the mechanism of the deoxygenation of lignite model compounds in the aqueous phase under a CO atmosphere catalyzed by OH− ions was investigated at the M06-2X/6-311++G(d, p) level. The results revealed that for the deoxygenation of phenol, the activity of the H species follows H˙ > H− > H+, and the reaction of CO with OH− ions under aqueous conditions confirmed that H− is the dominating active species. The study of H− attacking carbon atoms at different positions on phenol indicated that deoxygenation via substitution to form benzene is preferred over hydrogenation via addition. The effect of the active species H− on the deoxygenation of the lignite model compounds phenol, benzenediols, and benzenetriols was also examined. This study provides valuable information for future research on lignite deoxygenation. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the electrochromic properties of tricarbonyl rhenium complexes. Using 4,7-diphenylphenanthroline (L1) and 4,7-di(4-substituted)-1,10-phenanthroline (L2–L5) as bidentate ligands, a series of tricarbonyl rhenium complexes, fac-Re(CO)3(Lx)Cl (x = 1–5), were synthesized and characterized by infrared spectroscopy, 1H NMR, 13C NMR, and high resolution mass spectrometry. Their stereochemistry was investigated by single crystal X-ray diffraction. Theoretical highest occupied molecular orbital and lowest unoccupied molecular orbital charge distributions of fac-Re(CO)3(Lx)Cl were calculated by density functional theory calculations. Their electrochemical and electrochromic properties were studied by cyclic voltammetry, UV-vis spectroscopy and chronoamperometry. All fac-Re(CO)3(Lx)Cl complexes underwent a quasi-reversible reduction–oxidation process and an anodic peak at 1.3 V vs. Ag/Ag+. Electrochromic devices based on fac-Re(CO)3(Lx)Cl exhibited good electrochromic performance such as an obvious change in color from bleached yellow state to colored green state (a challenging electrochromic color), rapid response time of less than 3 s, moderate optical contrast and coloration efficiency, and good switching stability (fac-Re(CO)3(L2)Cl retained 95.2% of its initial optical contrast after 2400 electrochromic switching cycles). The fac-Re(CO)3(L2)Cl with an electron-donating group (–OCH3) at its para-position exhibited better performance including good switching stability, a higher optical contrast and a significant change in color than the unsubstituted, –CH3 substituted, –COOCH3 substituted and Br-substituted analogues. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations have been carried out to investigate two synthesized iridium(III) complexes with substituted Phbd (1-phenyl-2-(pyridin-2-yl)-1H-benzo[d]imidazole) and Crbd (9-(4-(2-(pyridin-2-yl)-1H-benzo[d]imidazol-1-yl)phenyl)-9H-carbazole) as ancillary ligands. The aim of this paper is to study the effect of the substituent on the geometrical structures, electronic and second-order nonlinear optical (NLO) properties, and UV-vis absorption spectra. It is found that the first hyperpolarizabilities can be easily modulated by the introduction of Phbd and Crbd units. The complex with Phbd possesses larger first hyperpolarizability values compared to the complex with Crbd as an ancillary ligand. Significantly, the changes in the first hyperpolarizabilities can be qualitatively explained by means of the charge transfer pattern. It is anticipated that the theoretical investigation of these iridium(III) complexes will be helpful for designing high performance and versatile NLO materials. [ABSTRACT FROM AUTHOR]

Nitrile-functionalized anticancer drugs have drawn wide attention. However, the water solubility and side-effects of the drugs reduce their effectiveness in cancer therapy. In this paper, three novel para-, meta- and ortho-linked nitrile-containing water solubility copper(II) porphyrin complexes have been synthesized. Then the relationship between the structure and anticancer performance of the three complexes were investigated. When the complexes have an effect on the cancer cells (A549, H1975, HepG2 and T47D) and normal cell (Hs578 Bst), they demonstrate effective anticancer activity and biocompatibility; the para-nitrile functionalized complex p-CuP can selectively act on H1975 cells, with the lowest IC50 (6.09 μM); the anticancer effect of water-soluble porphyrin ligands (p-L , m-L and o-L) is augmented by coordinate to copper ion(II). Furthermore, DNA binding and flow cytometry methods were applied to research their mechanism, and the results show that these complexes could intercalate DNA and the effect of p-CuP is the best, so there is DNA binding in the anticancer mechanism, also accompanied by mitochondrial dysfunction and arresting cell cycle. In addition, Density Functional Theory (DFT) calculation analyses were carried out for the cationic porphyrin ligands and complexes, using the method with a B3LYP level of theory with the 6-31G(d) and LanL2DZ basis sets, which further proved the biological activities of the target compounds. [ABSTRACT FROM AUTHOR]

Two noncentrosymmetric alkali calcium borates KCa4(BO3)3 and K0.59Rb0.41Ca4(BO3)3 were synthesized by the high temperature solution method. They both crystallize in the polar space group Ama2 (No. 40). According to our investigation, KCa4(BO3)3 is the only potassium calcium borate and K0.59Rb0.41Ca4(BO3)3 is the first potassium rubidium calcium borate. Two borates both exhibit deep-UV cutoff edges (＜200 nm) and moderate second harmonic generation (SHG) responses. In this paper, the detailed summaries of B–O connection styles in the disorder-free alkali- and alkaline-earth-metal borates have been discussed. Relationships between metal cations and boron atoms are studied. In addition, the optical and thermal property characterization of the two borates was systematically studied. To better understand the structure–property relationships, ab initio density functional theory was employed for the calculation of the optical refractive indices, birefringence and SHG coefficients. Additionally, the SHG density method was used to further explore the spatial distribution of the electronic states dominating the NLO activity. [ABSTRACT FROM AUTHOR]

In this paper, the ionic liquid (IL), 1-octyl-3-methylimidazolium hexafluorophosphate ([Omim][PF6]), was employed to synthesize β-cyclodextrin (β-CD)-functionalized carbon nanotubes/TiO2 (IL–CD-CNTs/TiO2) nanocomposite via a one-pot solvothermal process. The as-prepared product was characterized by SEM, TEM, XRD, TG, FT-IR, EIS, and so forth. Coupled with an aspirated in-syringe device, IL–CD-CNTs/TiO2 could yield the rapid removal of water contaminants within 8 min. In addition to the excellent adsorption capacity, this dual-functional photocatalyst also showed enhanced photocatalytic activity under visible light at a degradation rate of 97% within 180 min. The photocatalytic mechanism based on the formation of the inclusion complex, density functional theory, and electronic structure of IL–CD-CNTs/TiO2 was comprehensively discussed. The IL not only served as the reaction medium but also played a crucial role in improving the adsorption capacity and photocatalytic activity. By exhibiting a strong electron-donating character, IL could promote efficient charge transfer, inhibiting the recombination of photogenerated electron–hole pairs. The as-prepared photocatalyst―capable of rapid adsorption and photodegradation―can meet the requirements of practical applications and reveals a promising direction toward wastewater treatment. [ABSTRACT FROM AUTHOR]

A high-performance sulfur dioxide (SO2) sensor based on a platinum (Pt)-loaded titanium dioxide (TiO2)/molybdenum disulfide (MoS2) ternary nanocomposite is synthesized via layer-by-layer self-assembly. Various characterization techniques such as X-ray diffraction, energy dispersive spectrometry, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy show the nanostructure, morphology and composition of the Pt–TiO2/MoS2 nanocomposite. The sensor exhibits a relatively high response value, outstanding selectivity, and good stability toward SO2 gas. Furthermore, Materials Studio is used to establish adsorbent models to calculate the energy, density of states and charge transfer based on density functional theory. This paper indicates that the Pt–TiO2/MoS2 sensor has great potential for the detection of SO2 with outstanding sensing ability. [ABSTRACT FROM AUTHOR]

A comprehensive description on the conformational behaviour of small peptide models is of primary importance to elucidate polypeptide and protein structures and folding pathways. In this paper, an extensive conformational investigation of N-acetyl-N′-methylprolineamide (Ac-Pro-NHMe) in both isolated phase and in solution is reported. The joint use of 1H NMR spectroscopy and DFT calculations allowed to determine the most stable conformers of Ac-Pro-NHMe and to evaluate its conformational preferences in different media. Theoretical calculations at the M06-2X/aug-cc-pVTZ level of theory led to the identification of two and six stable conformers in isolated phase and solution, respectively. These geometries reveal the presence of two isomers, where the –NC(O)Me bond can assume a trans (ϑ = 180°) or cis (ϑ = 0°) orientation in relation to the –(CO)NHMe group of backbone. The theoretical results show that the trans,trans-IId in a down-puckered γ-turn-like structure and ϑ = 180°, is the most populated conformer in isolated phase. In polar solvents, like acetonitrile and DMSO, there is a mixture of both polyproline II and α-helix-like conformers, while in water, the trans,trans-IIu, in an up-puckered polyproline II-like geometry, is the less energetic. Therefore, our results show that conformer populations change upon solvent variation, indicating that the conformational equilibrium of Ac-Pro-NHMe is sensitive to solvent effects. The experimental population values, obtained through the integration of the peaks in the 1H NMR spectrum, confirm the change of conformer populations in different solvents. The results reveal that the theoretical level employed in this study is in good agreement with experimental data. QTAIM and NCI analyses combined with orbital-based NBO calculations reveal that the conformers trans,trans-IId and trans,trans-IIu are stabilized by an intramolecular hydrogen bond (IHB) C=O…HN in isolated phase. However, these geometries are completely destabilized in solution by the weakening of this interaction. Although IHB is essential to the stability of the two conformers in isolated phase, it represents only a secondary factor to the conformational preferences of the compound. The highest stability of trans,trans-IId in isolated phase can be attributed to hyperconjugative interactions. In solution, an interplay of hyperconjugative, steric and electrostatic effects rules the conformational preferences of Ac-Pro-NHMe. [ABSTRACT FROM AUTHOR]

In this paper, we report the novel synthesis of thieno[2,3-c]acridine and furo[2,3-c]acridine derivatives via an intramolecular iodocyclization reaction. The thieno[2,3-c]acridine derivatives exhibited blue fluorescence in hexane. DFT and time-dependent (TD) DFT studies were carried out. This methodology provided a novel pathway to access thieno[2,3-c]acridine and furo[2,3-c]acridine derivatives via a 6-endo iodocyclization reaction. [ABSTRACT FROM AUTHOR]

In this paper, a series of stable Sn-containing heteroaromatic conjugated oligomers, dialkyl dithieno[3,2-b:2′,3′-d]stannole (DTSn) and stannafluorene (SnF) derivatives, were designed and synthesized employing a new synthetic route. The distinctive feature of this route is that terminal groups are linked to the backbone before the stannole cycle closed, which can avoid the cleavage of stannole in the Stille reaction. Three Sn-heteroaromatic small molecules, DTSn-1, SnF-1 and SnF-3, have been obtained and characterized. The density functional theory (DFT) calculations show that the alkyl groups are further displaced from the conjugated backbone due to the larger atomic radius of Sn, which allows a stronger π-stacking interaction to occur. Interestingly, the fluorescence intensity of DTSn-1 is increased in the presence of Al3+ due to interaction between Al3+ and Sn. However, the emissions of the three Sn-containing oligomers can be quenched by Ru3+, which renders these compounds potential candidates as fluorescence detectors for Ru3+. [ABSTRACT FROM AUTHOR]

In this paper, the excited-state proton transfer (ESPT) of 7-hydroxyquinoline (7HQ) in hydrogen-donating methanol (MeOH) was investigated theoretically. The change in the calculated primary bond lengths and the infrared spectra of the 7HQ–(CH3OH)3 configuration from the S0 state to the S1 state testify that the intermolecular hydrogen bonds were strengthened in the S1 state. Therefore, we propose two proton transfer (PT) types in which the ESPT reaction occurs along the hydrogen-bonded bridge O7…H8–O9 (Type-A) or N1…H2–O3 (Type-B). The normal Stokes shift and the large Stokes shift suggest the existence of the enol form 7HQ–(CH3OH)3 and the keto form 7HQ–(CH3OH)3-PT, respectively, and thus that the proton transfer can occur in the excited-state. In order to further study the details of the complicated multiple proton transfer of the 7HQ–(CH3OH)3 cluster, we scanned the potential energy curves for the ground state (S0) and the excited state (S1) of the hydrogen-bonded 7HQ–(CH3OH)3 complex along with the hydrogen-bonding coordinate (distance of the H2–O3 and H8–O9 bonds). The results show the close barrier height between Type-A (5.35 kcal mol−1) and Type-B (6.65 kcal mol−1), which indicates that the two possible PT types may co-exist and have competition between themselves. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis, properties and crystal structure of a new phosphonium-1-indenylide ligand, 4,7-dimethyl-1-C9H4PMePh2, and the syntheses of complexes of rhodium(i) and iridium(i) containing both the parent PHIN ligand, 1-C9H6PMePh2 (I) and 4,7-dimethyl-1-C9H4PMePh2 (II). The complexes [M(η4-COD)(η5-PHIN)]X (M = Rh, Ir; PHIN = I, II; COD = 1,5-cyclooctadiene; X = Cl, BF4) and [Rh(η5-I)(PPh3)2]BF4 have been prepared and characterized by HR-ESM, elemental analyses and NMR spectroscopy. While [Ir(η4-COD)(η5-I)]Cl undergoes one or more chloride-induced exchange processes involving the COD ligand, the analogous complexes of rhodium and iridium with the more weakly coordinating BF4− counter anion exhibit no exchange processes. In contrast, [Rh(η5-I)(PPh3)2]BF4 undergoes an exchange process involving the inequivalent PPh3 phosphorus atoms and which is rationalized using DFT calculations. [ABSTRACT FROM AUTHOR]

The negatively charged polyuronates exhibit a high affinity for binding the bivalent metal cations. This feature is used for the removal of heavy metals from aqueous solutions. The aim of the present paper is to: (i) present the computational strategy, helpful in simulating the metal ion–uronate complexes; (ii) illustrate its applicability to the example of the α-l-guluronate anion (the monomeric unit of alginates) interacting with bivalent metal ions: Zn2+, Cu2+, Cd2+, Mn2+ and Co2+. The study was carried out on the basis of the ‘hybrid’ molecular dynamics simulations in which the selected part of the system (uronate anions and metal cations) is treated with the ab initio level of accuracy, whereas the interactions within the rest of the system are approximated by the classical force fields. The results allowed for determining the basic structural and energetic (for example, the free energy profiles associated with the cation binding–unbinding process) characteristics related to the metal ion–guluronate complexes. Most of the studied ions exhibited the preference for monodentate binding. Bidentate binding can be observed for Mn2+ and Co2+ (dominant binding mode) and Cd2+ (secondary binding mode). The calculated binding free energy order (Cu ＞ Co ＞ Zn ∼ Mn ＞ Cd) follows both the experimentally determined order of transition metal ion–alginate affinities and the metal–uronate interaction energies. The efficiency of the calculations and the general characteristics of the method allow for its potential use in simulations of other uronate–metal ion systems, increasing the range of methods which can be used for studying the metal biosorption processes. [ABSTRACT FROM AUTHOR]