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Simultaneous detection of multiple amino acids (AAs) instead of individual AAs is inherently worthwhile for improving diagnostic accuracy in clinical applications. Here, a facile and reliable colorimetric microfluidic paper-based analytical device (μPAD) using carbon dots doped with transition metals (Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, and Zn2+) has been provided to detect and discriminate 20 natural amino acids. To make the colourless metal-doped carbon dots suitable for colorimetric assays, they were mixed with ninhydrin to form a charge transfer complex. This optical tongue system, which was constructed by dropping mixtures of ninhydrin with a series of metal-doped carbon dots on a paper substrate in an array format, represented obvious but different colorimetric signatures for every examined amino acid. Since bovine serum albumin was used as a chiral selector reagent for synthesizing the CDs, the sensor device represented excellent selectivity to identify enantiomeric species of AAs. This is the first optical array device that can simultaneously discriminate AAs and several of their enantiomers. We employed various statistical and chemometric methods to analyze the digital data library collected by Image J software, including principal component analysis (PCA), linear discriminant analysis (LDA), and hierarchical cluster analysis (HCA). Twenty AAs could be well distinguished at various concentrations (10.00, 5.00, 2.50, and 1.25 mM). The colorimetric patterns were highly repeatable and were characteristic of individual AAs. Besides qualitative analysis, the designed μPAD-based optical tongue represented quantitative analysis ability, e.g., for lysine in the concentration ranges of 0.005–20.0 mM with a detection limit of 1.0 × 10−6 M and for arginine in the concentration range of 0.12–20.00 mM with a detection limit of 80.0 × 10−6 M. In addition, the binary, ternary, and quaternary mixtures of AAs could also be well recognized with this sensor. [ABSTRACT FROM AUTHOR]

Cu–Pd bimetallic catalysts were fabricated on carbon paper (CP) by the electrodeposition method via a dynamic hydrogen bubble template approach. At a potential of −1.2 V vs. RHE, the Faradaic efficiency (FE) of C2H4 could reach 45.2% with a current density of 17.4 mA cm−2 in an H-type electrolytic cell. Detailed studies suggest that the enhanced performance of Cu–Pd/CP was attributed mainly to the synergistic effect, low interfacial charge transfer resistance, and the 3D architecture of the catalysts. [ABSTRACT FROM AUTHOR]

The rate performance of LiFePO4 batteries is improved by inserting a carbon interlayer, which is synthesized by a simple and cheap pyrolysis of the filter paper commonly used in the laboratories. The specific capacity of the LiFePO4 batteries at low current density is only slightly improved after the introduction of the carbon interlayer, while the specific capacity at high current density is greatly enhanced with a specific capacity of 90 mA h g−1 and 76 mA h g−1 at 10 C and 20 C, respectively, compared to a specific capacity of 17 mA h g−1 and 8 mA h g−1 of LiFePO4 batteries without a carbon interlayer. The improved electrochemical performance is attributed to the porous architecture of the carbon interlayer, serving as a conductive skeleton, largely reducing the charge transfer resistance. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (gCN) has shown great potential in photocatalysis. Developing suitable cocatalysts is a critical way to enhance gCN's photocatalytic performance. In this paper cobalt–nickel bimetallic phosphide (CoNiP) was used as a cocatalyst to modify gCN. A gCN/CoNiP composite was successfully prepared by a simple hydrothermal method. XRD, XPS, SEM, UV-vis DRS, and PL characterization studies showed that a Schottky junction-like structure was constructed between gCN and CoNiP, which intensified the visible light response, enhanced the charge transfer rate and prohibited the recombination of photogenerated carriers, thus significantly improving gCN photocatalytic activity. Under simulated sunlight, the removal efficiency of methylene blue (10 mg L−1) was 97.8% by 120 min of irradiation, 44.6% higher than that of gCN. The quenching experiment showed that ˙O2−, ˙OH and h+ were the main active species. Based on the above points, the possible mechanism of photocatalysis was deduced. [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 pyrolysis of metal–organic frameworks (MOFs) has emerged as a promising route to synthesize carbon/metal oxide-based materials with diverse phase compositions, morphologies, sizes and surface areas. In this paper, 1,3,5-benzoic acid (BTC) and 2,4,6-tri(4-pyridinyl)-1-pyridine (TPP) were used as ligands to prepare a novel cobalt-based MOF (Co-MOF) which was used as a precursor to obtain five carbon-based materials at different temperatures (Co-C200/400/600/800/1000). Furthermore, five dyes were used as degradation targets to investigate the photocatalytic degradation performance of the title materials under UV light irradiation. Co-C1000 exhibited the best photocatalytic degradation performance for methyl orange (MO), and the degradation rate could reach 99.21%. The enhanced photocatalytic activity was attributed to narrower band-gaps and a synergistic effect originating from the well-aligned straddling band structures between Co/CoO/Co3O4 and C, also resulting in a faster interfacial charge transfer during the photocatalytic reaction. This study will aid in the development of photocatalysts generated from carbon-based materials via the pyrolysis transformation of MOFs, therefore greatly enhancing the photocatalytic performance. [ABSTRACT FROM AUTHOR]

The commercialization of lithium–sulfur batteries is facing great challenges, such as the "shuttle effect" and the poor conductivity of sulfur and Li2S2/Li2S, so it is extremely important to design new separator-modified materials with fast charge transfer capability and effective immobilization of polysulfides (LiPSs) to facilitate their conversion to address these challenges. In this paper, we propose a simple way to synthesize NiCo2O4 nanospheres containing oxygen vacancies (OV-NiCo2O4 NSs) and thus modify the separator. The synthesized OV-NiCo2O4 NSs accelerated the conversion of LiPSs through strong chemical interactions. In addition, the introduction of oxygen vacancies provided more active sites for LiPSs, which improved the electron conduction rate and accelerated the ion transport. Based on the above advantages, the battery with an OV-NiCo2O4 modified separator showed excellent electrochemical performance (the initial capacity of the battery was 801 mA h g−1 at 0.5 C, the specific capacity of discharge was maintained at 695 mA h g−1 after 500 cycles, and the capacity retention rate was as high as 87%). [ABSTRACT FROM AUTHOR]

Semiconductor photocatalysis is a potential solution to meet energy needs with green and inexhaustible solar energy. However, designing efficient and stable photocatalysts is a challenging task due to the limited ability to effectively separate electrons and holes. In this paper, by using a straightforward ethanol dispersion technique, we were able to combine ultrathin layered Cu-TCPP MOFs with g-C3N4 nanosheets, resulting in the creation of an extremely effective nano-composite photocatalyst with exceptional UV-vis activity. CT/CN heterojunctions displayed remarkable photocatalytic efficacy for the production of H2, with 3CT/CN showcasing a five-fold enhancement in photoactivity as compared to the unadorned g-C3N4. Based on the results of photoluminescence spectroscopy, electrochemical impedance spectroscopy, and electrochemical reduction, the considerably improved charge transfer and separation, together with the possible catalytic capability of uniformly distributed metal nodes in Cu-TCPP, are believed to be the underlying reason for the observed exceptional photoactivity. After thorough analysis, a potential process for charge transfer and segregation between g-C3N4 and Cu-TCPP has been suggested. [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]

This paper reports a theoretical study on the structures and electronic and optical properties of M2B240/− (M = Li, Na, and K) clusters using the particle swarm optimization (CALYPSO) searching method and density functional theory (DFT) calculations. The lowest energy structures of M2B24 (M = Li, Na, and K) clusters with high symmetry are composed of three stacked ring forms, and two M atoms are located on the axis of the tubular structures. The lowest energy structure of the Li2B24− cluster exhibits an open bowl-shaped structure, while the lowest energy structures of Na2B24− and K2B24− clusters have a double-ring tubular shape. Based on these structures, some electronic properties including charge transfer, bonding character, dipole moment, polarizability, and thermodynamic properties were investigated systematically. In addition, to provide a theoretical basis for the identification and confirmation of studied clusters, the PES, IR, Raman, and UV-visible spectra with different and meaningful characteristic peaks were simulated, which can be considered as the reference for future experimental studies. [ABSTRACT FROM AUTHOR]

Constructing a suitable heterojunction structure while maintaining a tight interface to promote the separation of photogenerated electrons is of great significance for improving the photocatalytic activity. In this paper, a new PANI/NH2-MIL-101(Fe) II-scheme heterojunction was prepared by a hydrothermal method. PANI with a porous structure was firstly obtained by the template method, and then PANI fragments were loaded on the surface of NH2-MIL-101(Fe) crystals under hydrothermal conditions to obtain a PANI/NH2-MIL-101(Fe) photocatalyst. The photocatalytic degradation of TC under simulated sunlight can reach 90% within an hour, and the maximum hydrogen evolution rate is 7040 μmol g−1 h−1 under visible light. The enhanced catalytic performance of PANI/NH2-MIL-101(Fe) was attributed to the appropriate matching of the VB and CB of PANI and NH2-MIL-101(Fe), and secondly, the coordination bonds formed between PANI and NH2-MIL-101(Fe) provided a channel for charge separation and transfer. Finally, a possible mechanism of the photocatalytic system was proposed through a free radical capture experiment and characterization analysis. More importantly, the experiment proved that the heterojunction formed by PANI and NH2-MIL-101(Fe) can achieve the effect of complementing each other, which provides a feasible idea and method for the design of efficient heterojunction photocatalysts. [ABSTRACT FROM AUTHOR]

Designing counter electrodes (CEs) with high efficiency and understanding the mechanism of dye-sensitized solar cells (DSSCs) are still challenges. In this paper, we synthesized K-doped molybdenum disulfide (K-MoS2) with few layers and it has a great enhancement effect on the electrocatalytic activity compared to pure MoS2 CE and reference Pt CE. A dual electron-path model is proposed to explain the mechanism, which is supported by first-principles calculations. When an electron in MoS2 is transferred to the triiodide, the K atoms can act as an electron reservoir to provide another electron in a short time to improve the catalytic activity. So the proposed dual-electron effect in this paper is helpful to understand the charge transfer mechanism on the interfaces of these CEs and may be crucial for obtaining high photoelectric efficiencies in DSSCs. [ABSTRACT FROM AUTHOR]

The impact of substituents at the 4- and 7-positions of 1,10-phenanthroline-2,9-dicarboxamides on the photophysical properties of the ligands and their coordination compounds with the lanthanide triad--europium, gadolinium, and terbium--was analyzed. This study demonstrates how modification of the electronic nature of ligands through the incorporation of diverse functional groups affects the luminescence properties of their complexes. The introduction of various substituents leads to the appearance of intra-ligand or ligand-to-ligand charge transfer (CT) states. The highest luminescence efficiency was observed for LH·Eu(NO3)3 (Qin = 54.1% and QL = 9.6%), suggesting strong luminescence quenching of the CT state. It was found that a relatively low ΔE (-3000 cm-1) supports direct energy transfer from S1 to T1 bypassing the CT state, even though it is outside Reinhoudt's optimal range. The introduction of fluorines leads to the strongest luminescence quenching among all the substituents. [ABSTRACT FROM AUTHOR]

The employment of catalysts to split water to create hydrogen is viewed as an effective solution to the energy crisis problem. In this work, type II heterojunction CdIn2S4/g-C3N4 nanocomposites with different mass ratios were successfully synthesised using a simple sonication technique. The results show that the constructed CdIn2S4/g-C3N4 heterojunctions exhibit better catalytic performance in the photoelectrocatalytic water splitting reaction, and the photocurrent density of the composite with a composite ratio of 15% reaches 0.35 mA cm−2 at 1.23 V (vs. RHE), which is a 2.33-fold enhancement relative to g-C3N4. The constructed heterojunction facilitates the photogenerated charge transfer between CdIn2S4 and g-C3N4, effectively accelerating the separation of photogenerated electrons and holes. This work provides theoretical guidance for efficient PEC water splitting technology. [ABSTRACT FROM AUTHOR]

The photoinduced decarboxylative radical cascade alkylation/cyclization strategy of diverse benzimidazoles containing unactivated alkene moieties towards the synthesis of polycyclic benzimidazoles via ligand-to-metal-charge-transfer (LMCT) has been developed. Specifically, the reaction initiates the decarboxylation of alkyl carboxylic acids through light-induced charge transfer from the ligand to iron, resulting in the formation of alkyl radical centers. Moreover, the protocol has prominent features, such as a broad substrate scope, high regioselectivity, mild reaction conditions, operational simplicity and readily available air acting as the sole oxidant. [ABSTRACT FROM AUTHOR]

Metal oxide composites with graphene/graphene oxide have increasingly gained popularity in enhancing the photocatalytic degradation of several existing harmful dyes. Moreover, identifying the role of carbon networks and their interactions in composite formation would assist in the design and development of photocatalysts. In the present study, we investigated the role of carbon networks in improving photocatalytic properties. Electronic structure analysis of cobalt oxide–graphene (C2)/graphene oxide (C3) nanocomposites using XAS suggested possible charge transfer from cobalt oxide nanoparticles to the carbon network during composite formation. The photocatalytic degradation of C3 towards phenol dye (1 × 10−3 M) was >50% and improved the degradation rate with k = 0.231 h−1.In the quest to understand the mechanism unfolding on its surface, in situ XAS under UV–visible irradiation was performed, which shed light on delayed excitonic recombination in the synthesized nanocomposites. This enabled hydroxy radicals (˙OH) to play a preeminent role in the cleavage of the phenol ring and its intermediaries. Based on these observations, a detailed mechanism for charge transfer occurring during nanocomposite formation and the mechanism involved in the enhanced photocatalytic activity of the nanocomposite photocatalyst towards phenol degradation under the influence of UV–visible irradiation are discussed. [ABSTRACT FROM AUTHOR]

Novel macrocycle co-crystals (MCCs) consisting of electron-rich phenanthrene[2]arene (P2) and electro-deficient 1,2,4,5-tetracyanobenzene (TCNB) have been prepared. The formed MCCs exhibited a specific selective vapochromic response to benzene among five aromatic hydrocarbon volatile organic compounds. Single-crystal structures and PXRD analyses confirmed that this specific selective vapochromic behavior was mainly attributed to the excellent benzene adsorption capacity of P2, leading to dissociation of P2@TCNB co-crystals and CT interactions which affect its optical features. [ABSTRACT FROM AUTHOR]

Due to the high oxidation potential of arenes and alkenes, previous methods of benzylic and allylic C–H oxidation necessitated the use of strong oxidizing agents, metal catalysts, or free radical initiators (such as photocatalysts or hydrogen atom transfer reagents) to be effective. Herein, we employ oxygen to generate a triple-spin charge transfer state with π-conjugated compounds effectively accessing the triplet excited states of arenes, followed by energy transfer to form singlet oxygen facilitating C–H bond oxidation. Distinct from previous oxidations, it is the first time that a series of natural products and drug molecules (27 examples) are selectively oxidized without any catalysts or additives. The transformation can be implemented under sunlight to produce valuable unsaturated (aromatic) ketones and only water as waste, which meets every one of the 12 principles of green chemistry. [ABSTRACT FROM AUTHOR]

We present photophysical studies on homoleptic zinc-dipyrrin complexes representing intramolecular donor–acceptor systems. Intramolecular charge transfer depends on ligand variation and intermolecular environmental influences. In particular, we focus on steady-state and transient absorption methods to compare the response of the ligand dynamics with that of the complexes after photoexcitation. For the first time, we successfully tested zinc bis(dipyrrinato) complexes as photocatalysts in two different aerobic photooxidation reactions. Early-time dynamics after 100 fs in dichloromethane and in ethanol can be assigned to charge transfer states, while the subsequent response constitutes broad-band excited state dynamics, most likely of overlapping singlet and triplet states when probed in a relatively wide spectral window from 350 to 1400 nm and up to a delay time of 1.6 ns. In addition, a strong correlation between steady-state and time-resolved experiments makes this experimental approach a versatile tool for future investigations of this class of molecules, especially with respect to photocatalysis. The results of this study underpin the need for further development for quantifying amplitudes of the excited state population of electronically excited singlet and triplet states. [ABSTRACT FROM AUTHOR]

Photochromic 1,3,3-trimethylindolino-β-naphthopyrylospiran (TMI–NPS) and 1,3,3-trimethylindolinonaphthospirooxazine (TMI–NSO) spiropyrans transform into the open merocyanine (MC) form, which exhibits a red-violet color upon reacting with one equivalent of anhydrous FeIIICl3 or FeIIIBr3 in o-dichlorobenzene. Slow mixing with n-hexane precipitates black crystals of the coordination complexes: (TMI–NPS)·FeIIICl3 (1), (TMI–NPS)·FeIIIBr3·2C6H4Cl2 (2) and (TMI–NSO)·FeX3·0.5C6H4Cl2 (where X = Cl for 3 and Br for 4). The oxygen atoms of the MC form of spiropyrans coordinate to FeIII forming short Fe–O bonds of 1.841(2) for 1, 1.839(2) for 2, and 1.888(2) Å length for 4. Complexes manifest intense absorption bands in the visible range, and the spectra are different for the two spiropyrans. Iron(III) ions have high (S = 5/2) spin states in 1 and 2, and complexes 2–4 manifest broad isotropic EPR signals with g = 2.05–2.11. An asymmetric EPR signal with the main component at g = 3.44 (4.2 K) is observed for 1. According to DFT, strong charge transfer from ligands to electron accepting FeIII ions and large dipole moments are evaluated in the complexes. The intense color of the (TMI–NSO)·FeIIIBr3 complex disappears when it reacts with 5,6,11,12,17,18-hexaazatrinaphthylene (HATNA). This decoloration indicates the formation of a colorless closed form of TMI–NPS and (HATNA)·FeIIIX3. Slow mixing with n-hexane precipitates crystals of (C22H19N2O+)(FeIIIBr4−) (5) salt containing nearly planar C22H19N2O+ cations (1,3,3-trimethyl-2-(naphtho[1,2-d]oxazol-2yl-3H-indol-1-ium cations) obtained as a result of the oxidative rearrangement and deprotonation of TMI–NSO. These cations manifest intense bands at 471 and 497 nm. They are diamagnetic and only an isotropic EPR signal with g = 2.15–2.16 is observed from the FeIIIBr4− anions. The properties of the complexes and possible routes to the formation of 5 are discussed based on DFT calculations. [ABSTRACT FROM AUTHOR]

The development of electrocatalysts that can maintain high reactivity and stability over a wide pH range during electrolysis reactions is essential for the realization of a clean hydrogen energy society. Herein, we report the synthesis of AuIr alloy nanoparticles (NPs) with an excellent oxygen evolution reaction (OER) performance over a wide pH range. The NPs were synthesized via an antisolvent crystallization-based method and maintained their small sizes regardless of adjustments in the ratio of the Au/Ir precursor. AuIr/C exhibited low overpotential and good long-term stability under acidic and alkaline conditions compared with the Ir/C and commercial RuO2. The enhanced OER performance of AuIr/C was attributed to efficient charge transfer, resulting in an optimal synergistic effect of electrons. [ABSTRACT FROM AUTHOR]

There remains considerable debate over the adsorption mechanism of acetylene in transformer fault gas detection. Herein, a graphene-based gas sensor with distinct decorated N, B configuration was constructed and evaluated via DFT. The adsorption and activation of C2H2 can be better facilitated over B-decorated pyridinic N sites than that on graphitic N and pyrrolic N configurations, presenting the adsorption energies of −0.22, −0.17 and 0.16 eV, respectively. Electron localization function (ELF) configurations and Bader charge analysis indicate that the electronic interaction between the graphitic substrates and C2H2 maybe responsible for tuning C2H2 adsorption behavior since the electron acceptor C2H2 transfers 0.497, 0.459 and 0.206 e from B-decorated pyridinic N, graphitic N and pyrrolic N configurations, respectively. Compared with pyridinic-N/G, the modification by B destroys the π electron pair of graphene, which is not conducive to the activation of the graphene surface. Additionally, in the DOS analysis, there is a clear overlap between B and N atoms, confirming the favorable contribution of B atoms to the adsorption performance. Compared with the other two co-doping structures, the pyridinic N–B/G structure has a higher p-band center, ensuring superior adsorption and activation capabilities for C2H2 during the reaction process. Significant contributions have been made by this research to the application of non-metal-doped graphene materials in gas sensor devices and the synthesis of highly efficient catalysts. [ABSTRACT FROM AUTHOR]

The construction of heterostructures in nanostructured anodes has been testified to be a feasible strategy to promote the comprehensive sodium storage properties of sodium-ion batteries, which benefit from the unique synergistic effects and interfacial interactions between different constituents. However, it remains a big challenge to develop simple and cost-effective synthesis methods for rationally building heterostructures within electrode materials. In this study, a facile and cost-effective approach using a hydrothermal method and a subsequent annealing process has been developed to engineer flower-like MoO2/MoS2 heterostructures encapsulated in nitrogen-doped carbon (MoO2/MoS2@NC) as anodes for sodium-ion batteries. The nitrogen-doped carbon enhances the electrical conductivity and mitigates the huge volume expansion of the electrode materials during the sodiation/desodiation process via the confinement effect. The heterostructure endows the MoO2/MoS2@NC anode with rapid Na+ diffusion and charge transfer within the electrode, contributing to a fast electrochemical reaction kinetics. Benefiting from the good synergistic effects of different components and unique merits of the heterostructures, the MoO2/MoS2@NC anode exhibits favorable sodium storage properties, including high capacity and good rate properties as well as excellent cycling stability. [ABSTRACT FROM AUTHOR]

Full-colour emitting materials have been widely studied driven by their promising potential application in fluorescence imaging and optoelectronic devices. In this paper, the synthesis and charactization of four asymmetric D–A type pyrene-based luminogens 2 is presented. The experimental results revealed that this type of pyrene derivative possesses tunable optical properties by introducing D/A groups at the 1-, 3-positions and K-region (5-position) of the pyrene core. Wide emission bands from deep blue (429 nm) to yellow (567 nm) were obtained in different solutions or states. Combined with the theoretical calculations, this work provides an efficient strategy to develop pyrene-based full-colour photoelectric materials. [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 glow discharge (GD) plasma, the excitation/ionization of sputtered, analytically interesting atoms can occur by collisional interaction of the ground state of sputtered atoms M(g) with the plasma particles (such as electrons and excited atoms/ions of plasma gas). Similarly, the excitation/ionization of sputtered atoms can also occur by collisional interaction of the metastable states of sputtered atoms M(m) and plasma particles. Thus, the M(m) can provide an alternative imperative route of excitation/ionization for sputtered atoms of elements in the plasma. The excitation/ionization via M(m) can be particularly important for selective plasma processes, such as asymmetric charge transfer and Penning excitation. Extensive work has been done in analytical GDs regarding metastable states of plasma gases I(m). However, so far, very modest effort has been extended in the direction of the M(m). Knowledge of the cross-sections and rate constants of various collisional processes en-route of the M(m) are valuable to provide broad physical data as input for theoretical calculations of ionization rates and accurate prediction of relative sensitive factors in mass spectrometry. All of these factors make it extremely important that detailed information about the metastable states of the analyte atoms is available. In this tutorial review paper, the metastable states of analyte atoms, types of metastability, populating/depopulating collisional and radiative processes, and their stringent role in the gas-phase collisional processes are reported and critically discussed in detail. [ABSTRACT FROM AUTHOR]

The development of semiconductor heterojunctions is a promising and yet challenging strategy to boost the performance in photoelectrochemical (PEC) water splitting. This paper describes the fabrication of a heterojunction photoanode by coupling α-Fe2O3 and g-C3N4via aerosol-assisted chemical vapour deposition (AACVD) followed by spin coating and air annealing. Enhanced PEC performance and stability are observed for the α-Fe2O3/g-C3N4 heterojunction photoanode in comparison to pristine α-Fe2O3 and the reason is systematically discussed in this paper. Most importantly, the fabricated α-Fe2O3/g-C3N4 film shows impressive stability, retaining more than 90% of the initial current over 12 h operating time. The excellent stability of the heterojunction photoanode is achieved due to the unique nanoflake structure of α-Fe2O3 induced by AACVD. This nanostructure promotes good adhesion with the g-C3N4 particles, as the particles tend to be trapped within the α-Fe2O3 valleys and eventually create strong and large interfacial contacts. This leads to improved separation of charge carriers at the α-Fe2O3/g-C3N4 interface and suppression of charge recombination in the photoanode, which are confirmed by the transient decay time, charge transfer efficiency and electrochemical impedance analysis. Our findings demonstrate the importance of nanostructure engineering for developing heterojunction structures with efficient charge transfer dynamics. [ABSTRACT FROM AUTHOR]

Due to the slow reaction kinetics of the oxygen evolution reaction (OER), the electrolysis rate of water is greatly limited. Therefore, it is of great significance to study stable and efficient non-noble metal based electrocatalysts. In this paper, three-dimensional (3D) spherical V-NiFe LDH@Ni3S2 was developed by exquisitely decorating ultra-thin V-doped NiFe layered dihydroxide (NiFe-LDH) on Ni3S2 nanosheets supported by nickel foam (NF). It is worth mentioning that V-NiFe LDH@Ni3S2 exhibits an excellent electrocatalytic performance and only 178 mV overpotential is required in 1 M KOH to achieve a current density of 10 mA cm−2. Long-term chronoamperometry manifests its superior electrochemical stability. The combination of NiFe LDH and conductive substrate coupling can drastically afford abundant active sites and accelerate charge transfer, and V doping can markedly regulate the electronic structure. Therefore, the activity and durability of the electrocatalysts are greatly improved. This study may provide a new strategy for the preparation of efficient OER electrocatalysts. [ABSTRACT FROM AUTHOR]

Semiconductor–metal heterostructures are attractive surface-enhanced Raman scattering (SERS)-active materials, which can boost the performance effectively because of the synergistic contribution of the electromagnetic (EM) and charge transfer (CT) enhancement effects. In this paper, a photo-responsive Si/TiO2/Ag heterostructure is prepared and its SERS is explored. The interfacial energy level alignment promotes its CT, resulting in charge separation and favors the measurement of adsorbed molecules on the Ag domains, leading to the increase of SERS activity. The enhancement factor (EF) of the Si/TiO2/Ag heterostructure with rhodamine 6G (R6G) as a probe molecule is estimated to be 1.23 × 1012, possessing excellent repeatability, and the relative standard deviation (RSD) is about 2.09%. Moreover, it can be used to detect glyphosate (Gly) very easily at concentrations as low as 0.1 ppb, which is far lower than the national maximum pesticide residue limit in food. Notably, the Si/TiO2/Ag SERS substrate possesses UV cleaning performance and can serve as a promising recyclable SERS-active substrate in practical trace detection applications at very low cost. [ABSTRACT FROM AUTHOR]

We previously reported that phenyl- and vinyl-silsesquioxanes (SQs), [RSiO1.5]8,10,12 (R = Ph or vinyl) functionalized with three or more conjugated moieties show red-shifted absorption- and emission features suggesting 3-D conjugation via a cage centered LUMOs. Corner missing [PhSiO1.5]7(OSiMe3)3 and edge opened, end capped [PhSiO1.5]8(OSiMe2)2 (double decker, DD) analogs also offer red shifted spectra again indicating 3-D conjugation and a cage centered LUMO. Copolymerization of DD [PhSiO1.5]8(OSiMevinyl)2 with multiple R–Ar–Br gives copolymers with emission red-shifts that change with degree of polymerization (DP), exhibit charge transfer to F4TNCQ and terpolymer averaged red-shifts suggesting through chain conjugation even with two (O–Si–O) end caps possibly via a cage centered LUMO. Surprisingly, ladder (LL) SQ, (vinylMeSiO2)[PhSiO1.5]4(O2SiMevinyl) copolymers offer emission red-shifts even greater for analogous copolymers requiring a different explanation. Here we assess the photophysical behavior of copolymers of a more extreme SQ form: the half cage [PhSiO1.5]4(OSiMe2Vinyl)4, Vy4HC SQs. We again see small red-shifted absorptions coupled with significant red-shifted emissions, even with just a half cage, thus further supporting the existence of pπ–dπ and/or σ*–π* conjugation through Si–O–Si bonds and contrary to most traditional views of Si–O–Si linked polymers. These same copolymers donate an electron to F4TCNQ generating the radical anion, F4TCNQ−. as further proof of conjugation. Column chromatographic separation of short from longer chain oligomers reveals a direct correlation between DP and emission λmax red-shifts as another indication of conjugation. Further, one- and two-photon absorption and emission spectroscopy reveals multiple excited fluorescence-emitting states in a violation of Kasha's rule wherein emission occurs only from the lowest excited state. Traditional modeling studies again find HOMO LUMO energy levels residing only on the aromatic co-monomers rather than through Si–O–Si bonds as recently found in related polymers. [ABSTRACT FROM AUTHOR]

PDY-132 and its blends with different concentrations of poly(9,9-dioctylfluorenyl-co-3 bithiophene) F8T2 were employed as an emissive matrix for organic light-emitting devices (OLEDs). The Urbach energy lies well below 50 meV, which reflects the reduced energetic disorder, signifying the efficient charge transfer in the polymer blends. The photoluminescence time constants vary proportionally from 0.89–0.35 ns as a function of the acceptor concentration in the FRET pairs, reflecting 2.5× faster charge transfer in the blends than in PDY-132. The Förster radius of 57 Å, decay time of 0.89 ns, quenching constant of 0.12 μM−1, quenching rate constant of 1.4 × 108 μM−1 s−1, charge transfer lifetime of 6.21 ns to 2.38 ns, and non-radiative transfer rate of 4.0 × 108 s−1 exhibit the excellent parameters for efficient charge transfer within the blend, resulting in lowering of the turn on voltage by 67% from 6.5 V to 2 V. The current density of 3 mA cm−2 increases to 25 mA cm−2, an increase of 8× with increasing concentration of F8T2. [ABSTRACT FROM AUTHOR]

Crystal engineering is emerging as an important approach to design functional materials. In this work, we explore the scope of a sulfonate–pyridinium supramolecular synthon to design the organic salt [(TPT-H)2+(NDSA-H)2−·4H2O] (1), based on 1,5-naphthalenedisulfonic acid (NDSA-2H) and 2,4,6-tris(2-pyridyl)-s-triazine (TPT). Structural studies of 1 establish proton transfer between crystal formers and their aggregation through the water-masked sulfonate–pyridinium synthon to form one-dimensional hydrogen bonded tapes, which further aggregate through weak π–π and C–H⋯O interactions to form a three-dimensional layered solid. The greenish solid 1 exhibits mild charge transfer interactions in the solid-state, as indicated by the red-shift of the absorption beyond 400 cm−1 in the diffuse reflectance spectrum. Interestingly, 1 exhibit mild brownish emission (λmax = 550 nm), which undergoes remarkable blue-shifting on exposure to ammonia fumes (λmax = 450 nm), heat (λmax = 494.8 nm), and grinding (λmax = 542.9 nm). This multi-stimuli responsive behavior of 1 has been investigated in detail, with the help of diffuse reflectance, fluorescence, thermal, spectroscopic, and diffraction studies, and a plausible commentary of the behavior in light of its structure is provided. The intriguing multi-stimuli response behavior of 1 indicates the potential scope of sulfonate–pyridinium based organic salts in applications as sensors and intelligent materials. [ABSTRACT FROM AUTHOR]

Formamidinium lead bromide (FAPbBr3) perovskite nanocrystals (NCs) are promising materials due to their narrow band emission and high photoluminescence (PL) quantum yield. In the present work, oleyl amine functionalized FAPbBr3 NCs were synthesized. These NCs were then attached to 4-(phenylazo)benzoic acid (PABA) to form a fluorescent photodeactivatable FAPbBr3 NCs-PABA dyad. Ultraviolet (UV) irradiation caused trans–cis isomerization of PABA that reverted to the trans-isomer upon storage in the dark after 40 min. Upon UV irradiation of the FAPbBr3 NCs-PABA dyad, PABA was converted from the trans isomer to the cis isomer. Strong PL quenching of FAPbBr3 NCs was observed due to photoexcited charge transfer from the conduction band of NCs to the LUMO of the cis-isomer of PABA. The decrease in the PL intensity of NCs also manifested as a decrease in the PL lifetime. The positions of band edges, estimated by cyclic voltammetry, suggested that the electron transfer from photoexcited FAPbBr3 NCs to the cis-isomer of PABA was responsible for the PL quenching of FAPbBr3 NCs. The photoinduced reversible trans–cis isomerization of PABA accompanied by the strong PL quenching of FAPbBr3 NCs in the FAPbBr3 NCs-PABA dyad, due to photoexcited electron transfer from NCs to PABA in the dyad, could help in the design of photo-driven fluorescent probes with high-contrast due to the narrow emission band of FAPbBr3 NCs. [ABSTRACT FROM AUTHOR]

The construction of Z-scheme heterojunctions is still a challenge. Structure tailoring and energy band engineering of metal–organic frameworks (MOFs) permit the rational design and fabrication of Z-scheme MOF/graphene oxide (GO) heterojunctions to enhance photocatalytic performance. Herein, a novel Z-scheme Zn-MOF/GO heterojunction as an environmentally friendly, reusable, and highly efficient visible-light-induced photocatalyst for methylene blue (Mb) decoloration and/or Cr(VI) reduction was synthesized. The Zn-MOF/GO composite displayed much higher photodegradation performance than pure Zn-MOF. Besides, the photocatalytic performance of composites is related to the amounts of GO, and Zn-MOF/GO(15%) showed the best activity. Specifically, Zn-MOF/GO(15%) presented 92.6% Mb decoloration, 98.8% Cr(VI) reduction, and the simultaneous removal of Mb (87.9%) and Cr(VI) (99.8%) with good stability. The improved performance for Zn-MOF/GO(15%) can be due to the formation of the Z-scheme heterojunction and built-in electric field, which can not only promote the photogenerated electron–hole separation and transfer, but also broaden the spectrum of light absorption. Furthermore, the improved plausible photodegradation mechanism of Zn-MOF/GO(15%) was provided, and e−, h+ and ·OH were the primary reactive species during the photodegradation reactions. [ABSTRACT FROM AUTHOR]

Achieving ultra-simple and high-efficiency monochrome and white organic light-emitting diodes (OLEDs) is still a long-running challenge in the fields of display and solid-state lighting sources. In recent years, researchers have focused on hybridized local and charge transfer (HLCT) materials due to theoretically complete exciton utilization, low-efficiency roll-off, and doping-free preparation process and have successfully developed a series of blue HLCT materials with excellent electroluminescence (EL) performance. However, all HLCT emitter-based white OLEDs have not been reported to date. Recently, our group reported two complementary HLCT materials, 9-(4-(10-(naphthalen-2-yl)anthracen-9-yl)phenyl)-9H-carbazole (pCzAnN) (blue) and 4-(7-(10-(naphthalen-2-yl)anthracene-9-yl)benzo[c][1,2,5]thiadiazol-4-yl)-N,N-diphenylaniline (TBAN) (yellow), which simultaneously exhibit just opposite carrier transport properties. Herein, by carrier balance strategy, the fabricated pCzAnN-based non-doped deep-blue OLED achieves the maximum external quantum efficiency (EQE) of 9.36%, which is among the highest values reported to date for HLCT-based non-doped blue OLEDs. At the same time, the efficient non-doped yellow OLED with TBAN emitter was demonstrated with maximum luminance and EQE reaching 76 600 cd m−2 and 6.19%, respectively. On the basis of the above, the first all HLCT emitter-based white OLED was proposed by inserting a carrier regulation layer between non-doped complementary light-emitting layers (pCzAnN and TBAN). The resulting white OLEDs realize the maximum EQE exceeding the theoretical limit of 5% for traditional fluorescent OELDs, and the EL spectra can be easily tuned by simply changing the thickness of the exciton regulation layer to obtain a balanced white light emission with the maximum color rendering index of 84. This work opens up a new way for the development of ultra-simple and high-performance white OLEDs. [ABSTRACT FROM AUTHOR]

The preparation of a cocrystal is one of the effective strategies to tune the luminescence properties of organic crystals. In this work, four charge transfer cocrystals were constructed with isomeric substances of amino substituted dimethyl phthalates as the donors and 1,2,4,5-tetracyanobenzene as the acceptor. The emission range of the individual electron donors is from 400 nm to 505 nm, while all cocrystals have their emission redshift exceeding 100 nm. The tunable emission range of the charge transfer cocrystals is from 573 nm to 640 nm. All the obtained four cocrystals contain π–π stacking structures with the presence of π–π and C–H⋯π interactions. Fourier transform infrared spectroscopy and UV-vis spectroscopy demonstrated the presence of charge transfer interactions in the cocrystals. The tuning of the luminescence properties of the cocrystals was explained by the analysis of the crystal packing structure and the intermolecular interaction, and the distribution of frontier orbitals was obtained by DFT calculation. We believe our work is helpful to understand the relationship between the crystal structure and luminescence properties in the charge transfer cocrystals and provide guidance for the modulation of the luminescence properties. [ABSTRACT FROM AUTHOR]

To develop hydrogen energy production and address the issues of global warming, inexpensive, effective, and long-lasting transition metal-based electrocatalysts for the synthesis of hydrogen are crucial. Herein, a porous electrocatalyst NiMo/Ni/NF was successfully constructed by a two-step electrodeposition process, and was used in the hydrogen evolution reaction (HER) of electrocatalytic water decomposition. NiMo nanoparticles were coated on porous Ni/NF grown on nickel foam (NF), leading to a resilient porous structure with enhanced conductivity for efficient charge transfer, as well as distinctive threedimensional channels for quick electrolyte diffusion and gas release. Notably, the low overpotential (42 mV) and fast kinetics (Tafel slope of 44 mV dec-1) at a current density of 10 mA cm-2 in 1.0 M KOH solution demonstrate the excellent HER activity of the electrode, which was superior to that of recently reported non-noble metal-based catalysts. Additionally, NiMo/Ni/NF showed extraordinary catalytic durability in stability tests at a current density of 10 mA cm-2 for 70 h. The porous structure catalyst and the electrodeposition-electrocatalysis technique examined in this study offer new approaches for the advancement of the electrocatalysis field because of these benefits. [ABSTRACT FROM AUTHOR]

The reaction of Pd(OAc)2 with (Z)-5-arylidene-4-(4H)-imidazolones (2a-e) and (Z)-4-arylidene-5(4H)- thiazolones (3a-e) in trifluoroacetic acid results in the corresponding orthopalladated dinuclear complexes (4a-e, imidazolones; 11a-d, thiazolones) with trifluoroacetate bridges through regioselective C-H activation at the ortho position of the 4-arylidene group. Compound 4e, which contains an imidazolone substituted at 2- and 4-positions of the arylidene ring with methoxide groups and exhibits strong push-pull charge transfer, is an excellent precursor for the synthesis of fluorescent complexes with green yellowish emission and remarkable quantum yields. Breaking the bridging system with pyridine yields the mononuclear complex 5e (ΦF = 5%), while metathesis of trifluoroacetate ligands with chloride leads to the dinuclear complex 6e, also a precursor of fluorescent complexes by breaking the chloride bridging system with pyridine (7e, ΦF = 7%), or by substitution of chloride ligands with pyridine (8e, ΦF = 15%) or acetylacetonate (9e, ΦF = 2%). In addition to notable photophysical properties, dinuclear complexes 4 and 11 also exhibit significant photochemical reactivity. Thus, irradiation of orthopalladates 4a-c and 11a-c in CH2Cl2 with blue light (465 nm) proceeds via [2 + 2] photocycloaddition of the CvC double bonds of imidazolone and thiazolone ligands, yielding the corresponding cyclobutane-bridging diaminotruxillic derivatives 10a-c and 12a-c, respectively. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) stands out as a highly promising conducting polymer with potential for advanced utilization in high-performance pseudocapacitors. Therefore, there exists a pressing need to bolster the structural durability of PANI, achievable by developing composite materials that can enhance its viability for supercapacitor applications. In this particular study, a pioneering approach was undertaken to produce a novel NiMn2O4/PANI supercapacitor electrode material. A comprehensive array of analytical techniques was employed to ascertain the structural configuration, morphology, oxidation states of elements, composition, and surface characteristics of the electrode material. The electrochemical evaluation of the NiMn2O4/PANI composite shows a specific capacitance (Cs) of 1530 ± 2 F g−1 at 1 A g−1. Significantly, the composite material displays an outstanding 93.61% retention of its capacity after an extensive 10 000 cycles, signifying remarkable cycling stability, while the 2-electrode configuration reveals a Cs value of 764 F g−1 at 5 mV s−1 and 826 F g−1 at 1 A g−1 with a smaller charge transfer resistance (Rct) value of 0.67 Ω. Chronoamperometric tests showed excellent stability of the fabricated material up to 50 h. This significant advancement bears immense promise for its potential implementation in high-efficiency energy storage systems and heralds a new phase in the development of supercapacitor technology with improved stability and performance metrics. [ABSTRACT FROM AUTHOR]

The preparation of two tri-iodide salts, C7H11N2+·I3−·0.5H2O (1) and (C2H5)4N+·I3− (2), synthesized by the slow diffusion method in solution, is reported. Their structures have been characterized by means of single-crystal X-ray diffraction. They consist of two different arrangements of tri-iodide ions, organized in a one-dimensional linear chain for 1 and in two-dimensional T-shaped sheets for 2, stabilized by 4-dimethylaminopyridinium and tetraethylammonium ligands. An asymmetry of the tri-iodide anions is observed in both structures, and is associated to the I⋯I halogen and hydrogen bonding interactions. The generation of the resulting supramolecular networks for these compounds was found to be driven by hydrogen-bond assisted self-assembly. The crystal structures of the two compounds were found to be supported essentially by H⋯I interactions between organic molecules and tri-iodide anions. For compound 2, an additionally stabilization by O⋯H/H⋯O interactions due to the presence of water molecules occurs. The dominant intermolecular interactions and their directionality have been examined by Hirshfeld surfaces and fingerprint analysis. Both compounds were characterized further by FT-IR and Raman spectroscopy, TGA/DTG and UV-visible absorption by means of thin film methods. The target compounds were also studied computationally using density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches to explore their potential performances and to rationalize the experimental results. An electronic transition from 3σg to has been proven to dominate intramolecular charge transfer occurring for both 1 and 2. This electronic communication leads to an HOMO–LUMO energy gap of 4.208 eV for 1 and 4.255 eV for 2. [ABSTRACT FROM AUTHOR]

A series of novel Eu3+-activated Ba2Gd2/3TeO6 (BGT) phosphors were successfully synthesised via a high temperature solid state reaction method. The crystal structure analysis showed that Eu3+-doped Ba2Gd2/3TeO6 double perovskite phosphors possess monoclinic symmetry with space group P21/n. The as-prepared phosphors can be efficiently excited by far-ultraviolet light to generate reddish orange luminescence of around 593 nm corresponding to the 5D0 → 7F1 transitions of Eu3+ ions. Gd3+ acts as a sensitizer for luminescence enhancement. The highest luminescence intensity corresponded to x = 0.11 Eu3+ concentration, and the critical distance was calculated to be 9.61 Å, indicating that multipolar interaction is behind the concentration quenching mechanism. Besides, the optimum concentration Eu3+-activated Ba2Gd2/3TeO6 phosphor exhibited color co-ordinates of (0.63, 0.36), a high color purity of 94.21% and a quantum efficiency of 18%. JO intensity parameters reveal the slight distortion of the crystal field around the activator ion. Notably, the maximum relative sensitivities of the BGT:0.11Eu3+ phosphor were found to be 0.19% K−1 within the temperature range of 300–500 K and 2.07% K−1 within 80–300 K, and it can potentially be used as a promising thermometer in high and low temperature regions, respectively. The luminescent labels based on fluorescent ink and PL chalk demonstrate the potential application of synthesized phosphors in anti-counterfeiting and security labeling. [ABSTRACT FROM AUTHOR]

The substantial expense associated with catalysts significantly hampers the progress of electrolytic water-based hydrogen production technology. There is an urgent need to find non-precious metal catalysts that are both cost-effective and highly efficient. Here, the porous Ni2P–FePx nanomaterials were successfully prepared by hydrothermal method, nickel foam as the base, iron nitrate solution as the caustic agent and iron source, and finally phosphating at low temperature. The obtained porous Ni2P–FePx nanosheets showed excellent catalytic activity under alkaline PH = 14, and an overpotential of merely 241 mV was required to achieve a current density of 50 mA cm−2. The morphology of the nanosheet can still be flawlessly presented on the screen after 50 h of working at high current density. [ABSTRACT FROM AUTHOR]

In the process of handling and storage of radioactive actinides it is essential to selectively sequester the minor actinides, such as Am and Cm, through a competitive complexation process. Herein we computationally designed two core modified ligands (L21− and L3) through systematic oxygen substitution at the NH sites of dipyriamethyrin (L1_2H), a hexadentate expanded porphyrin, and studied their competitive complexation towards trivalent actinides (An = Am/Cm) from their trichlorides using density functional theory (DFT). We observed shorter An–N bonds and longer An–O bonds in complexes based on core modified ligands (L21− and L3). The An–Cl bond length increases with increasing axial coordination number (i.e., from L12− to L3) to accommodate the ligands. All the bonds were identified to be electrostatic in nature. L12− exhibits shorter bonds and larger bond orders on complexing with Am than with Cm. On moving from complexes of L21− to L3, the An–N bond lengths are shortened, while An–O bond lengths become larger. Between the complexes of Am and Cm, there is marginal difference in their bond distances with L21− and L3. Charge analysis shows ligand to metal charge transfer during coordination, with back-donation from An to N/O and Cl. The calculated spin-density analysis indicates that An remains in its trivalent oxidation state on complexation, while orbital occupation analysis shows that the 5f and 6d orbitals are involved in bonding; this was confirmed by molecular orbital (MO) analysis that shows the complexes of L21− and L3 to exhibit higher degeneracy in their overlapping MOs. Further, the energy decomposition analysis (EDA) confirms that all ionic bonds are primarily due to electrostatic contributions, where the orbital contributions increase from L12− to L3 complexes and maximum covalency was observed in Cm complexes due to the energy matching between the 5f orbitals of Cm and the 2p orbitals of N and Cl, compared to Am. To confirm the competitiveness in the complexation of the ligand towards Am vs. Cm, the thermodynamic parameters were analysed for the ligand and metal substitution reactions. L12− shows more affinity towards Am than Cm, while L21− and L3 prefer Cm. [ABSTRACT FROM AUTHOR]

Achieving high photoelectrochemical conversion efficiency requires the logical layout of a composite photocatalyst with optimal charge separation and transfer with ideal light harvesting capabilities to enhance the photocatalytic performance and the degradation rate towards organic pollutants. Herein, a novel In2O3/WO3@Ti4N3Tx S-scheme heterojunction was successfully synthesized and confirmed through valence band VB-XPS and Mott Schottky combined analysis. The formed MXene-doped In2O3/WO3@Ti4N3Tx S-scheme significantly enhances the charge flow and spatial separation with an improved oxidation and reduction ability. An in-built interfacial electric field at the WO3–In2O3 boundary enhanced the light-harvesting capacity, whereas Ti4N3Tx MXene offers a unique electron trapping effect which effectively lowers high charge carrier recombination rate-related photocatalytic deficit. It preserves the exceptional redox potency of the photocatalyst by providing a directed acceleration and effective separation of the photogenerated charges. A high carrier density (ND = 7.83 × 1021 cm−3) with a lower negative flat band (VFB = −0.064 V vs. Ag/AgCl) was obtained by Mott–Schottky analysis for 3 wt% In2O3/WO3@Ti4N3Tx, an indicator that a low overpotential is needed to activate photocatalytic reactions. This study, therefore, provides a novel thought for the design and fabrication of an S-scheme heterojunction for photocatalytic reactions for mineralization of organic pollutants in water and clean energy production. [ABSTRACT FROM AUTHOR]

A V2C MXene has a high theoretical capacity and low diffusion barrier, showing tremendous potential in lithium-ion batteries. However, most reports on V2C focus on a multilayered structure that is stacked, which diminishes the ionic accessibility and results in unsatisfactory cycling stability. Therefore, we synthesized a few-layer V2C (f-V2C) material and added multi-walled carbon nanotubes (MWCNTs). The formed f-V2C/MWCNT provides abundant pores, which enhance ionic accessibility, so that Li+ can easily enter the layer space. The introduction of MWCNTs can further separate the f-V2C, expand the specific surface area, reduce the charge transfer resistance, and heighten the structural stability. The experiments reveal that f-V2C/MWCNT has a high specific capacity of 531 mA h g−1 at 0.1 A g−1 after 100 cycles. Even at a high current density of 5.0 A g−1, the specific capacity can still reach 166 mA h g−1. Moreover, the f-V2C/MWCNT structure shows good cycling stability with a capacity retention rate of 95% after 1000 cycles at 5.0 A g−1. The above findings indicate that f-V2C/MWCNT has great application potential in the field of Li+ storage. [ABSTRACT FROM AUTHOR]

In this study, we focus on the theoretical calculation of global and local chemical reactivity descriptors for chiral carbon dots derived from pyrene and amino acids through ADPT (auxiliary density perturbation theory) linear response implemented in deMon2k software. We assessed the presence of hydroxyl, hydrosulfide groups, and nitrogen heteroatoms in the graphitic system of carbon dots. After optimizing the geometries, global chemical reactivity descriptors were computed using both traditional and analytical approaches. It has been observed that the presence of nitrogen heteroatoms increases the overall nucleophilic character of CDs, reduces the HOMO–LUMO gap and generates more nucleophilic and electrophilic reactive sites throughout the aromatic system. The position of nitrogen atoms was found to influence the planarity of the graphitic system, potentially compromising properties related to intramolecular electron transfer. Thiol groups at the edges of the CDs were identified to enhance the nucleophilic character of the pyrene fragment, exhibiting a more positive charge compared to the oxygen of the alcohol group. Amino acid fragments exhibit stereoselective reactivity, however, in the model systems examined here, their reactivity is surpassed by the pyrene fragment, which is highly reactive due to its planar conjugate system. These findings could contribute significantly to the structural design and understanding of properties for carbon dots developed for various technological applications. [ABSTRACT FROM AUTHOR]

A series of charge transfer cocrystals with fluorescence properties involving 1,2,4,5-tetracyanobenzene (TCNB, C10H2N4) as acceptor, fluorene (FR, C13H10) and its bromide 2-bromofluorene (2-BrFR, C13H9Br), carbazole (CZ, C12H9N) and its bromide 2-bromocarbazole (2-BrCZ, C12H8BrN) as donor were synthesized via cocrystal design strategies. The formation mechanism of the crystal structure was explored by density functional theory at the molecular level. The stacking structure of the cocrystal was formed by the combination of charge transfer interactions, π–π interactions and hydrogen bonding. The N atom of donors in TCNB–CZ and TCNB–2-BrCZ could enhance the charge transfer, appearing as a red shift of the fluorescence emission wavelength. Conversely, the Br atom in TCNB–2-BrFR and TCNB–2-BrCZ weakens the charge transfer, giving a blue shift in the fluorescence emission spectrum. The four new cocrystals exhibit tunable luminescence from green (529 nm) to yellow (552 nm) and to red (604 nm and 614 nm). It was found that the introduction of N and Br atoms in the assembly units can not only regulate the luminescence range of the cocrystals, but also adjust the luminescence efficiency, which provides a strategy for the development of promising organic luminescent materials. [ABSTRACT FROM AUTHOR]

Metalloviologens, as emerging electron-transfer photochromic compounds, have shown intriguing properties such as radiochromism, photochromism and photoconductance. However, only a limited number of them have been reported so far. Exploration of new metalloviologens is strongly desired. Herein, we report a new solvothermally synthesized metalloviologen complex [CdCl2(ND)2]n (1, ND = 1,5-naphthalenes) that exhibits photochromic and intrinsic white light emission properties. Density functional theory calculation results reveal that the photochromism could be assigned to photoinduced electron transfer from chlorine atoms to ND molecules. The photoinduced charge-separated states are heat/air stable, attributed to the delocalization of ND and strong intermolecular π–π interactions. Besides, complex 1 consistently emits intrinsic white light when excited with 340–370 nm UV light, achieving high color rendering index (CRI) values (82.54–94.04). By adjusting the excitation wavelength, both "warm" and "cold" white light emission can be produced, making it suitable for the application of a white light emitting diode (WLED). Thus, this work demonstrates that the ND-based metalloviologen is not only helpful in producing photochromism, but also beneficial for creating white-light emission. [ABSTRACT FROM AUTHOR]

Four salts of an anionic iron(III) bis-complex, [Fe(L L -thr)2]1−, were synthesized from water or methanol. H2L L -thr is a tridentate ligand derived from the L -threonine amino acid, and the cations used are Li+ (1), Na+ (2), K+ (3), and Ba2+ (4). Single-crystal X-ray diffraction showed that all the complexes are coordination polymers of different dimensionalities. The iron(III) complex binds to cations through its coordinated phenolate and non-coordinated carboxylate oxygen atoms. While Li+ forms a linear chain, all others have a pair of bridged cations intervening the iron(III) complexes. The 3D network of Ba2+ salt has a sizeable solvent-accessible space occupied by aquated chloride ions. The differences in circular dichroism (CD) spectra and significantly lower conductance values in water and methanol support partial retention of the polymeric nature in methanol. The visible spectra of 4 in methanol or water showed an ∼10 nm shift of the charge transfer bands from 3. However, the addition of Al3+ salt to 2 showed a significant colour shift. Further investigation confirmed that the colour shift is due to partial protonation of the complex with protons generated from salt hydrolysis. Most reports on visual aluminium detection consider aluminium's binding as the shift's source. The present results show that protonation due to hydrolysis of aluminium salt can skew the observation. [ABSTRACT FROM AUTHOR]

The urgent need for effective and sustainable electrocatalytic nitrate reduction to mitigate global water contamination and foster fossil-free ammonia generation has driven extensive exploration of bimetallic non-noble metals in electrochemical applications. Herein, we present the development of an electrocatalyst, namely FeCu phosphide (Fe–CuP), which demonstrates high efficiency in the reduction of nitrate. The prepared samples exhibit exceptional catalytic activity in the electrocatalytic reduction of nitrate to NH3 in a neutral electrolyte. It is noteworthy that the Faraday efficiency reaches an impressive 89% at −1.5 V (vs. SCE), with NH3 yield of 0.6 mmol h−1 cm−2, surpassing the performance of the FeCu alloy. This superior performance can be attributed to the distinct surface morphology of the catalyst and its ability to facilitate rapid charge transfer, which is enhanced by the presence of phosphorus. Moreover, the Fe–CuP catalyst also demonstrates remarkable long-term stability making it an excellent candidate for practical applications. Thus, this work not only introduces a novel synthesis method for Fe–CuP but also establishes the efficacy of phosphorus in promoting nitrate reduction to NH3. These findings provide valuable insights into the advancement of electrocatalytic technologies for sustainable water treatment and ammonia synthesis. [ABSTRACT FROM AUTHOR]