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The development of an effective and selective chemosensor for CN− ions has become the need of the hour due to their hazardous impact on the environment and humans.

Solar energy being a non-depleting energy resource, has attracted scientists' attention to develop efficient solar cells to meet energy demands.

Nonlinear optical (NLO) materials have several uses in many fields such as solid physics, biology, medicine, nuclear physics, and material research. Therefore, a series of nonfullerene-based derivatives (

Photoelectrocatalysts are robust materials for the production of energy through different ways such as water splitting. Narrow optical band gaps and high overpotentials are limiting the development of photoelectrocatalysts. In this study, a series of Co1-(x+y)Fe x Mn y WO4 solid solutions of cobalt tungstate codoped with iron and manganese have been synthesized hydrothermally. The synthesized solid solutions have been characterized by powder XRD, UV-visible spectra, cyclic voltammetry (CV), and linear sweep voltammetry (LSV). They all crystallize in a wolframite-type monoclinic crystal system with space group P2/c. Doping of iron and manganese leads to narrowing of the optical band gap of Co1-(x+y)Fe x Mn y WO4 from 2.60 to 2.04 eV. The electrocatalytic activity toward oxygen evolution reaction of all of the samples has been evaluated through LSV measurements. It is found that the sample named C5, which is codoped with manganese and iron, has the lowest onset potential and needs the lowest overpotential to attain the targeted 5 mA cm-2 and standard 10 mA cm-2 current densities as compared with all other synthesized samples. This study shows that the synthesized tungstates can be good candidates for the photoelectrocatalytic oxygen evolution reaction.

In the present study, three novel fluorinated terphenyl compounds i.e., 2′,4,4′′,5′-tetrafluoro-1,1':4′,1′′-terphenyl (1), 2′,5′-difluoro-1,1':4′,1′′-terphenyl (2) and 2′,5′-difluro-4,4′′-diphenoxy-1,1:4′,1′′-terphenyl (3) have been synthesized by Suzuki Miyaura method. Single crystal XRD study reveals ð-ð stacking stabilization in molecular packing along with F⋯H and F⋯C interactions. This computational quantum chemical exploration was also done by using density functional theory (DFT) methods. The comparison of experimental (SC-XRD) and theoretical (DFT) investigations on structural parameters have been reported which shows reasonable agreements. Hirshfeld surface analysis explores the strength of intermolecular interactions present in the synthesized compounds. A substantial computational analysis of synthesized compounds is done for their optoelectronic and third-order nonlinear optical properties. The third-order NLO study was performed at M06/6-311G* level of theory. A comparative analysis of third-order polarizability of studied compounds is done with that of para-nitroaniline (p-NA) molecule which is often considered as a prototype NLO molecule. The third-order NLO analysis results suggest that all investigated compounds 1, 2 and 3 have significant potential as efficient third-order NLO molecules as compared to p-NA. The studied compounds 1, 2 and 3 possess about 13.7 times, 5.2 times and 5.17 times larger third-order polarizability amplitudes than that of p-NA (25.45 × 10−36 esu) as calculated at same M06/6-311G* levels of theory. Time-dependent density functional theory (TD-DFT) calculations are performed for electronic excitation energies and their oscillator strengths. The studies of frontier molecular orbitals (FMO) analysis, total and partial density of states (DOS) were performed to investigate the intramolecular charge transfer (ICT) process in the entitled compounds.

For environment friendly water splitting, development of highly efficient and stable oxygen evolution reaction (OER) catalyst composed of earth abundant elements is very challenging. Herein, highly efficient OER catalysts TMS@MOF-5 have been prepared by in-situ incorporation of pre-synthesized various transition metal sulfide (TMS = MnS, FeS, CoS, NiS, CuS and ZnS) nanoparticles into MOF-5. Structure, morphology and composition of prepared samples have been analyzed by powder X-ray diffraction, Fourier Transform Infrared Spectroscopy, Raman Spectroscopy, Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, Elemental Mapping and Ultraviolet–Visible Spectroscopy. OER activity of all these samples was determined by coating them on Ni-foam to form TMS@MOF-5/NF as working electrode through cyclic voltammetry. Among all the samples, NiS@MOF-5/NF exhibited excellent stability and OER catalytic activity as it required just 174 mV overpotential to achieve the 10mAcm−2current density, which is better than many other 3d transition metal based and Ni-based OER catalysts. Present study provides new way to design more efficient Ni-based catalysts for electrochemical water splitting applications.

The current research presents the synthesis of novel salicylaldehyde thiosemicarbazones (1–6) and their spectroscopic characterization employing UV–visible, Fourier transform infrared spectroscopy, and NMR techniques. Experimental results are compared and validated with the results obtained theoretically by employing density functional theory at the M06 level with the 6-311G (d,p) basis set. Further, various parameters [natural bond orbital (NBO)], linear and nonlinear optical (NLO) properties, and global reactivity parameters (GRPs) are computationally calculated. The NBO approach has confirmed the stability of compounds on account of charge delocalization and hyper conjugative interaction network. Frontier molecular orbital analysis has explained the charge transfer and chemical reactivity capability, while GRPs have led to the analysis of kinetic stability of the studied molecules. Further, the probability of being NLO-active has been theoretically proved by the HOMO/LUMO energy difference (4.133–4.186 eV) and β values (192.778–501.709 a.u). These findings suggest that the studied compounds possess potential NLO applications as they have shown larger NLO values in comparison with that of the urea molecule, and such distinct properties prove their technological importance.

Materials with nonlinear optical (NLO) properties have significant applications in different fields, including nuclear science, biophysics, medicine, chemical dynamics, solid physics, materials science and surface interface applications. Quinoline and carbazole, owing to their electron-deficient and electron-rich character respectively, play a role in charge transfer applications in optoelectronics. Therefore, an attempt has been made herein to explore quinoline–carbazole based novel materials with highly nonlinear optical properties. Structural tailoring has been made at the donor and acceptor units of two recently synthesized quinoline–carbazole molecules (Q1, Q2) and acceptor–donor–π–acceptor (A–D–π–A) and donor–acceptor–donor–π–acceptor (D–A–D–π–A) type novel molecules Q1D1–Q1D3 and Q2D2–Q2D3 have been quantum chemically designed, respectively. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) computations are performed to process the impact of acceptor and donor units on photophysical, electronic and NLO properties of selected molecules. The λmax values (321 and 319 nm) for Q1 and Q2 in DSMO were in good agreement with the experimental values (326 and 323 nm). The largest shift in absorption maximum is displayed by Q1D2 (436 nm). The designed compounds (Q1D3–Q2D3) express absorption spectra with an increased border and with a reduced band gap compared to the parent compounds (Q1 and Q2). Natural bond orbital (NBO) investigations showed that the extended hyper conjugation and strong intramolecular interaction play significant roles in stabilising these systems. All molecules expressed significant NLO responses. A large value of βtot was elevated in Q1D2 (23 885.90 a.u.). This theoretical framework reveals the NLO response properties of novel quinoline–carbazole derivatives that can be significant for their use in advanced applications.

In the fields of chemical graph theory, topological index is a type of a molecular descriptor that is calculated based on the graph of a chemical compound. Topological indices help us collect information about algebraic graphs and give us mathematical approach to understand the properties of algebraic structures. With the help of topological indices, we can guess the properties of chemical compounds without performing experiments in wet lab. There are more than 148 topological indices in the literature, but none of them completely give all properties of under study compounds. Together, they do it to some extent; hence, there is always room to introduce new indices. In this paper, we present first and second reserve Zagreb indices and first reverse hyper-Zagreb indices, reverse GA index, and reverse atomic bond connectivity index for the crystallographic structure of molecules. We also present first and second reverse Zagreb polynomials and first and second reverse hyper-Zagreb polynomials for the crystallographic structure of molecules.

To switch quadratic nonlinear optical (NLO) effects has become an exciting branch of the NLO material science. However, solid-state molecular crystals showing tunable and switchable NLO behaviors remain scarce. Here, we report an organic picrate-based binary molecular crystal, triethylammonium picrate (TEAP), which undergoes an above-room-temperature phase transition at Tc = 319 K, being solidly confirmed by the thermal and dielectric measurements. A large thermal hysteresis of ∼7 K discloses the first-order feature for its phase transition. More strikingly, the quadratic NLO effects of TEAP can be switched in the vicinity of Tc. That is, TEAP exhibits NLO-active response of ∼1.5 times as large as that of KDP below Tc (i.e., NLO-on state), while its NLO effects totally disappear above Tc (NLO-off state). Structure analyses disclose that the order-disorder transformations of triethylammonium cations and picrate anions collectively contribute to its phase transition, as well as switchable NLO behaviors. This work opens up a new pathway to the designing and assembling of stimuli-responsive materials.

A highly stable and intensely fluorescent composite was assembled by incorporating ruthenium functional unit (Ru unit) into layered double hydroxide matrices. This composite inherits the photoluminescence property of Ru unit but exhibits enhanced photoluminescence with a long lifetime. Importantly, it acts as an excellent chemosensor for sensitive detection on Cr2O72−. Such detection resulted in visible photoluminecence quenching. Furthermore, the composite is remarkably stable in the detection conditions without Ru unit leaking out. Therefore, these results provide us a simple, sensitive, and effective approach to detect Cr2O72−.

A novel molecular phase transition material (PTM), 1-methylpiperidinium perchlorate [18-crown-6] monohydrate (1), has been synthesized, which exhibits reversible switchable dielectric anomalies near room temperature. The phase transition in 1 is from noncentrosymmetric to noncentrosymmetric, displaying non-linear optical (NLO) properties with a second harmonic generation response of ∼0.8 times compared to that of potassium dihydrogen phosphate. Thermal analyses of 1, including differential scanning calorimetry and specific heat measurements, confirm the first-order solid-state phase transition at 260 K. The dielectric constants display temperature-dependent anomalies with the temperature approaching the transition point (Tc), where the evident step-like anomalies demonstrate two distinct states below and above the Tc value, respectively. Variable-temperature single crystal X-ray diffraction discloses that the origin of its phase transition is ascribed to the order–disorder transformation of perchlorate anion, the methyl group of cation and the torsional angular change in crown molecule; that is, all three components contribute to the emergence of this phase transition. This result suggests that 1 could be conceived as a potential switchable dielectric and NLO material, which provides an effective approach to design novel NLO switch materials.

A novel molecular switchable dielectric material N-methylpyrrolidinium hydrogen tartrate (NMPHT) has been synthesized, which undergoes above room temperature phase transition. Thermal measurements, e.g. differential scanning calorimetry and specific heat, confirm the presence of a phase transition around 317.5 K. The dielectric measurement displays a distinct step-like anomaly around Tc, showing two different dielectric states, which reveals that NMPHT is a switchable dielectric material. The single-crystal X-ray diffraction analyses at variable temperatures demonstrate that the phase transition emerges from the severe disordering of the N-methylpyrrolidinium (NMP) cation, and during the transition the symmetry of NMPHT is transformed from higher (C2/c) to lower (P21/n). These findings will provide a new horizon to design smart dielectric structural phase transition materials by incorporating a flexible NMP based scaffold.

A new high-temperature, hybrid, phase-transition material, 1-methylpiperidinium tetrabromozincate (1), that shows a reversible transition at 345 K was synthesized. Differential scanning calorimetry and specific heat capacity measurements confirmed this reversible transformation with a large heat hysteresis of 25 K, which describes a typical first-order phase transition in 1. The dielectric constant exhibited a steplike anomaly and showed high and low dielectric states in the high- and room-temperature phases, respectively, and therefore, this hybrid might be considered as a potential switchable dielectric material. The variable-temperature powder X-ray diffraction patterns displayed remarkable shifts between the experimental patterns at the two different phases. Single-crystal X-ray diffraction analyses at various temperatures revealed that the origin of this transformation could be attributed to disordering of the bromine atoms in the anion and the nitrogen atom of the cation. The cation also assumed a conformational change, which was likely induced by the disordered nitrogen atom. The conformational onset of the transformation of the cation from a planar conformer into a relaxed chair also occurred upon decreasing the temperature below transition point; thus, the combined order-disorder and conformational change induced the structural transformation and the change in symmetry.

A new molecular-ionic phase transition material, N-butyldiethanolammonium picrate monohydrate (BEAPM), which exhibits reversible switchable dielectric performances, has been successfully assembled. This compound undergoes a first-order solid-state phase transition at 160 K (Tc), which is confirmed by the thermal analyses including differential scanning calorimetry (DSC), specific heat (Cp) and dielectric measurements. Variable-temperature single crystal X-ray diffraction reveals that the origin of its phase transition is ascribed to the order–disorder transformation of oxygen atoms of the poly-nitro aromatic system, i.e. the picrate anions. Interestingly, the dielectric constants display clear temperature-dependant anomalies with the temperature approaching to Tc. The evident step-like anomalies of dielectric constants demonstrate two distinct states below and above the Tc, respectively. This result signifies that BEAPM could be conceived as a potential switchable dielectric material. These findings make us believe that BEAPM might be a potential solid–solid dielectric phase transition material.

A novel phase transition has been discovered where the phase transition is primarily accomplished by the order–disorder transformation of metal-coordinated halogen atoms in an organic–inorganic hybrid material [(C6H14)NH2]2·CuBr4 (1). Its phase transition behaviour was verified by specific heat capacity (Cp) and differential scanning calorimetry (DSC) measurements with a thermal hysteresis at 4.8 K. The dielectric measurements of 1 show a distinct step-like anomaly around Tc, demonstrating two states at two different phases, which enlightens that 1 can be conceived as a potential switchable dielectric material. Moreover, temperature-dependent single-crystal X-ray diffraction analyses of 1 disclose that disordering of metal-halides together with reorientations of the cations is the cause of this unique phase-transition material. All these results open a new way to design and assemble novel phase transition materials.

An above-room-temperature new phase transition molecular material, dibutylammonium hydrogen oxalate (1), has been synthesized, which undergoes a reversible phase transition at 321.6 K. Differential scanning calorimetry (DSC) measurements confirm its reversible phase transition with a large heat hysteresis of ∼10 K. The dielectric constants of 1 exhibit an obvious step-like anomaly, showing the high and low dielectric constant states at high and room-temperature phases, respectively, which reveal that 1 might be considered a potential switchable dielectric material. Variable-temperature single crystal X-ray diffraction analyses disclose that the origin of this phase transition is greatly attributed to the coupling of the order–disorder change and reorientation of the dibutylammonium cation; that is, the frozen ordering of ethyl group in butyl moiety triggered by the decreasing temperature forces the reorientation of cation, thus resulting in the structural phase transition.

A new beryllium-free borate Rb3Al3B3O10F has been synthesized and characterized by single-crystal X-ray diffraction. It features a framework structure consisting of alveolate [Al3(BO3)3OF]∞ layers tightly bound via Al-O and Al-F bridged bonds, with the in-layer [BO3](3-) groups in nearly coplanar and aligned arrangement. This compound is transparent down to 200 nm and is phase-matchable with a powder second-harmonic generation efficiency of 1.2 times that of KH2PO4. Remarkably, it exhibits a strong interlayer bonding which is about one order larger than that of the benchmark KBe2BO3F2, thus no layering tendency was observed during the crystal growth. In addition, it is nonhygroscopic and thermally stable up to ∼1462 K. These attributes make Rb3Al3B3O10F a promising nonlinear optical crystal in the deep-ultraviolet region. First-principles calculations, combined with the anionic group theory, were adopted to rationalize the optical properties.

A novel molecular phase transition compound, tri-n-butylammonium trichloroacetate (TBAT), has been successfully synthesized with a reversible phase transition at 196 K. Its phase transition behaviour was confirmed by specific heat capacity and differential scanning calorimetry (DSC) measurements with a 2 K thermal hysteresis, indicating that the phase transition is a first-order one. Dielectric measurements further reveal the reversible nature of the phase transition, which exhibits distinctive step-like anomalies between low and high dielectric states. Moreover, temperature dependent single-crystal X-ray diffraction analyses of TBAT disclose that the order–disorder transformation of the flexible tri-n-butylammonium cations and the haloacetic acids anion together with the torsion in the cations stimulate the structural phase transition. All these results open a new way to design and assemble novel phase transition materials.

Perovskite-type ferroelectrics composed of organometallic halides are emerging as a promising alternative to conventional photovoltaic devices because of their unique photovoltaic effects (PVEs). A new layered perovskite-type photoferroelectric, bis(cyclohexylaminium) tetrabromo lead (1), is presented. The material exhibits an exceptional anisotropy of bulk PVEs. Upon photoexcitation, superior photovoltaic behaviors are created along its inorganic layers, which are composed of corner-sharing PbBr6 octahedra. Semiconducting activity with remarkable photoconductivity is achieved in the vertical direction, showing sizeable on/off current ratios (>10(4) ), which compete with the most active photovoltaic material CH3 NH3 PbI3 . In 1 the temperature-dependence of photovoltage coincides fairly well with that of polarization, confirming the dominant role of ferroelectricity in such highly anisotropic PVEs. This finding sheds light on bulk PVEs in ferroelectric materials, and promotes their application in optoelectronic devices.

A beryllium-free deep-ultraviolet (deep-UV) nonlinear optical (NLO) material K3Ba3Li2Al4B6O20F is developed mainly by the element substitution of Be for Al and Li from Sr2Be2B2O7 that was considered as one of the most promising deep-UV NLO materials. K3Ba3Li2Al4B6O20F preserves the structural merits of Sr2Be2B2O7 and thus exhibits no layering growth tendency and possesses the optical properties required for deep-UV NLO applications, including deep-UV transparency, phase-matchability, and sufficiently large second-harmonic generation (1.5 × KH2PO4). Furthermore, it overcomes the structural instability problem of Sr2Be2B2O7, which is confirmed by the obtainment of large single crystals and phonon dispersion calculations. These attributes make it very attractive for next-generation deep-UV NLO materials. The substitution of Be for Al and Li in beryllium borates provides a new opportunity to design beryllium-free deep-UV NLO materials with good performance.