Showing papers in "Dalton Transactions in 2014"

A golden future in medicinal inorganic chemistry: the promise of anticancer gold organometallic compounds

Abstract: From wedding rings on fingers to stained glass windows, by way of Olympic medals, gold has been highly prized for millennia. Nowadays, organometallic gold compounds occupy an important place in the field of medicinal inorganic chemistry due to their unique chemical properties with respect to gold coordination compounds. In fact, several studies have proved that they can be used to develop highly efficient metal-based drugs with possible applications in the treatment of cancer. This Perspective summarizes the results obtained for different families of bioactive organometallic gold compounds including cyclometallated gold(III) complexes with C,N-donor ligands, gold(I) and gold(I/III) N-heterocyclic (NHC) carbene complexes, as well as gold(I) alkynyl complexes, with promising anticancer effects. Most importantly, we will focus on recent developments in the field and discuss the potential of this class of organometallic compounds in relation to their versatile chemistry and innovative mechanisms of action.

Luminescent metal-organic frameworks as explosive sensors.

Abstract: Metal organic frameworks (MOFs) are of enormous current interest not only because of their fundamental importance but also due to their great potential for possible applications in gas storage and separation, catalysis, imaging and sensing, to name a few. Recent studies on luminescent MOFs (LMOFs) in both bulk and nanoparticle forms have shown that these materials possess excellent luminescence emission properties that may be utilized to effectively detect high explosive substances. Developing highly sensitive, selective, fast-responding and fully reversible sensors for explosives' detection is in great demand for the homeland security, environmental safety and other humanitarian concerns. In this perspective article, we discuss the development, possible mechanism and future aspects of explosive sensing by LMOF materials.

Metal-organic frameworks MIL-88A hexagonal microrods as a new photocatalyst for efficient decolorization of methylene blue dye

Abstract: Metal–organic frameworks (MOFs) MIL-88A hexagonal microrods as a new photocatalyst show an active performance for methylene blue (MB) dye decolorization using visible light. MB decolorization over the MIL-88A photocatalyst follows first-order kinetics. The addition of a H2O2 electron acceptor can markedly enhance the photocatalytic MB decoloration performance of MIL-88A. Moreover, MIL-88A showed a very stable activity for MB decoloration after four consecutive usages. Owing to the advantages of the visible light response, low cost and abundance in nature, this active MIL-88A MOF photocatalyst would have great potential for environmental purification.

Hybrid photocatalysts using graphitic carbon nitride/cadmium sulfide/reduced graphene oxide (g-C3N4/CdS/RGO) for superior photodegradation of organic pollutants under UV and visible light

Abstract: Graphitic carbon nitride (g-C3N4) was hybridized with CdS nanoparticles and reduced graphene oxide (RGO) sheets using a facile chemical method, for the application of catalytic photodegradation of Rhodamine B and Congo red dyes under irradiation with UV and visible light. Fourier-transform infrared (FTIR) spectroscopy and X-ray photoemission spectroscopy (XPS) analyses confirmed the formation of pure g-C3N4, as well as g-C3N4/CdS, g-C3N4/RGO, and g-C3N4/CdS/RGO composites. The large surface area of the g-C3N4/CdS/RGO composite (70.42 m2 g−1) resulted in rapid dye adsorption onto the surface of the photocatalyst, leading to effective photodegradation of organic pollutants. The addition of CdS and RGO increased the photocatalytic activity of g-C3N4 by a factor of approximately twenty compared with that of the commercially available TiO2 catalyst under visible light, and the g-C3N4/CdS/RGO composite was found to significantly enhance the catalytic effect compared with pure g-C3N4 and with the g-C3N4/CdS and g-C3N4/RGO composites. The superior photocatalytic activity of the g-C3N4/CdS/RGO composite is attributed to enhanced separation of the photogenerated electron–hole pairs, as well as increased visible-light absorption. The improved transport of photoelectrons was consistent with the results of transient photocurrent measurements. Therefore, g-C3N4/CdS/RGO composites using a facile method are applicable to the development of high-efficiency photocatalytic devices for industrial applications.

Crystal chemistry and luminescence properties of red-emitting CsGd1-xEux(MoO4)2 solid-solution phosphors.

Abstract: Scheelite related alkali-metal rare-earth double molybdate compounds with a general formula of ALn(MoO4)2 can find wide application as red phosphors. The crystal chemistry and luminescence properties of red-emitting CsGd1−xEux(MoO4)2 solid-solution phosphors have been evaluated in the present paper. A detailed analysis of the structural properties indicates the formation of isostructural scheelite-type CsGd1−xEux(MoO4)2 solid-solutions over the composition range of 0 ≤ x ≤ 1. The photoluminescence emission (PL) and excitation (PLE) spectra, and the decay curves were measured for this series of compounds. The critical doping concentration of Eu3+ is determined to be x = 0.6 in order to realize the maximum emission intensity. The emission spectra of the as-obtained CsGd(1−x)Eux(MoO4)2 phosphors show narrow high intensity red lines at 592 and 615 nm upon excitation at 394 or 465 nm, revealing great potential for applications in white light-emitting diode devices.

Yb3+ sensitized Er3+ doped La2O3 phosphor in temperature sensors and display devices

Abstract: The frequency upconversion emissions in the Er3+/Er3+–Yb3+ doped/codoped hexagonal shaped La2O3 phosphor characterized by X-ray diffraction (XRD) upon excitation with 980 nm and 800 nm CW lasers have been investigated. The upconversion emissions corresponding to the 2H9/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions peaking at 409 nm, 523 nm, 548 nm and 660 nm have been observed under 980 nm excitation whereas 523 nm, 548 nm and 660 nm upconversion emission bands have been visualized under 808 nm excitation. The upconversion emission intensity of Er3+ ions is enhanced by several times due to the codoping with Yb3+ ions, under 980 nm excitation while there is a reduction in intensity in the codoped sample under 808 nm excitation. The decay curve analysis for the green UC emission band corresponding to the 4S3/2 → 4I15/2 transition in the Er3+/Er3+–Yb3+ doped/codoped La2O3 phosphor upon 980 nm excitation has been done. The colour coordinate of the phosphor sample has been calculated at different pump powers and its value is observed to be almost similar to that of the standard green colour and also independent of the excitation power density. The effect of temperature on the upconversion emission intensity of the green emissions has been determined and noted that the present phosphor material can be used in making temperature sensing device upto 600 K.

Lithium recovery from salt lake brine by H2TiO3

Abstract: The details of the ion exchange properties of layered H2TiO3, derived from the layered Li2TiO3 precursor upon treatment with HCl solution, with lithium ions in the salt lake brine (collected from Salar de Uyuni, Bolivia) are reported. The lithium adsorption rate is slow, requiring 1 d to attain equilibrium at room temperature. The adsorption of lithium ions by H2TiO3 follows the Langmuir model with an adsorptive capacity of 32.6 mg g−1 (4.7 mmol g−1) at pH 6.5 from the brine containing NaHCO3 (NaHCO3 added to control the pH). The total amount of sodium, potassium, magnesium and calcium adsorbed from the brine was <0.30 mmol g−1. The H2TiO3 was found capable of efficiently adsorbing lithium ions from the brine containing competitive cations such as sodium, potassium, magnesium and calcium in extremely large excess. The results indicate that the selectivity order Li+ ≫ Na+, K+, Mg2+, Ca2+ originates from a size effect. The H2TiO3 can be regenerated and reused for lithium exchange in the brine with an exchange capacity very similar to the original H2TiO3.

A new multifunctional Schiff base as a fluorescence sensor for Al3+ and a colorimetric sensor for CN− in aqueous media: an application to bioimaging

Abstract: A multifunctional fluorescent and colorimetric receptor 1 ((E)-N′-((8-hydroxy-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-9-yl)methylene)benzohydrazide) for the detection of both Al3+ and CN− in aqueous solution has been developed. Receptor 1 exhibited an excellent selective fluorescence response toward Al3+. The sensitivity of the fluorescent based assay (0.193 μM) for Al3+ is far below the limit in the World Health Organization (WHO) guidelines for drinking water (7.41 μM). In addition, receptor 1 showed an excellent detection ability in a wide pH range of 4–10 and also in living cells. Moreover, receptor 1 showed a highly selective colorimetric response to CN− by changing its color from colorless to yellow immediately without any interference from other anions.

The energy transfer phenomena and colour tunability in Y2O2S:Eu3+/Dy3+ micro-fibers for white emission in solid state lighting applications

Abstract: This paper reports on the structural, optical and photometric characterization of an Eu3+/Dy3+ doped yttrium oxysulfide phosphor (Y2O2S:Eu3+/Dy3+) for near white emission in solid state lighting. A series of Y2O2S phosphors doped with Eu3+/Dy3+ were prepared by the hydrothermal method. The microstructures of the as-synthesized phosphors were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results reveal that the obtained powder phosphors have a single-phase hexagonal structure and also indicate that the incorporation of the dopants/co-dopants did not affect the crystal structure. The SEM images reveal the morphology of the prepared phosphors as an intense interpenetrating network of interconnected micro-fibers with a diameter of about 0.15 μm. The band gap of the phosphors was calculated from diffuse reflectance spectra using the Kubelka–Munk function. The Eu3+, Dy3+ doped and Eu3+/Dy3+ co-doped phosphors illuminated with ultraviolet light showed characteristic red luminescence corresponding to the 5D0→7FJ transitions of Eu3+ and characteristic blue and yellow luminescence corresponding to the 4F9/2→6H15/2 or 4F9/2→6H13/2 transitions of Dy3+. The luminescence spectra, the energy transfer efficiency and the decay curves of the phosphors indicated that there exists a strong energy transfer from Dy3+ to Eu3+ and this was demonstrated to be a resonant type via a dipole–quadrupole reaction. Furthermore, the critical distance of the Eu3+ and Dy3+ ions have also been calculated. By utilizing the principle of energy transfer it was also demonstrated that with an appropriate tuning of the activator content the Y2O2S:Eu3+/Dy3+ phosphors can exhibit a great potential to act as single-emitting component phosphors for white light emission in solid state lighting technology.

Ag2S/g-C3N4 composite photocatalysts for efficient Pt-free hydrogen production. The co-catalyst function of Ag/Ag2S formed by simultaneous photodeposition

Abstract: Without Pt as cocatalyst, the photocatalytic hydrogen evolution activity of graphitic carbon nitride (g-C3N4) or even its composite is normally rather low (<1 μmol h−1). Exploring Pt-free cocatalysts to substitute precious Pt is of great importance in the photocatalytic field. In the present work, Ag2S-modified g-C3N4 (Ag2S/g-C3N4) composite photocatalysts were prepared via a simple precipitation method. The results demonstrated that the photocatalytic H2-production activity of g-C3N4 can be remarkably increased by the combination of Ag2S. The optimal Ag2S loading was found to be 5 wt%, giving a H2 production of 10 μmol h−1, around 100 times that of pure g-C3N4. The enhanced photocatalytic activity can be mainly attributed to the effective charge transfer between g-C3N4 and Ag/Ag2S, of which the latter is formed by simultaneous photodeposition in the photocatalytic H2 evolution reaction and acts as an efficient co-catalyst for the g-C3N4. This work showed the possibility for utilization of Ag2S or Ag/Ag2S as a substitute for Pt in the photocatalytic production of H2 using g-C3N4.

Facile synthesis of biocompatible cysteine-coated CuS nanoparticles with high photothermal conversion efficiency for cancer therapy.

Abstract: The semiconductor compounds have been proven to be promising candidates as a new type of photothermal therapy agent, but unsatisfactory photothermal conversion efficiencies limit their widespread application in photothermal therapy (PTT). Herein, we synthesized cysteine-coated CuS nanoparticles (Cys-CuS NPs) as highly efficient PTT agents by a simple aqueous solution method. The Cys-CuS NPs have a good biocompatibility owing to their biocompatible cysteine coating and exhibit a strong absorption in the near-infrared region due to the localized surface plasma resonances of valence-band free carriers. The photothermal conversion efficiency of Cys-CuS NPs reaches 38.0%, which is much higher than that of the recently reported Cu9S5 and Cu2−xSe nanocrystals. More importantly, tumor growth can be efficiently inhibited in vivo by the fatal heat arising from the excellent photothermal effect of Cys-CuS NPs at a low concentration under the irradiation of a 980 nm laser with a safe power density of 0.72 W cm−2. Therefore, the Cys-CuS NPs have great potential as ideal photothermal agents for cancer therapy.

Sonication assisted preparation of graphene oxide/graphitic-C3N4 nanosheet hybrid with reinforced photocurrent for photocatalyst applications

Abstract: Graphitic C3N4 (g-C3N4), as an advanced metal free photocatalyst, is known to be poorly exfoliated and dispersed in water from its powder form which has a layered structure, the intrinsic plane structure is not destroyed, and this has largely limited its application. In this work, we report our progress on successful sonication exfoliation of g-C3N4 nanosheets in graphene oxide (GO) aqueous solution. By making use of the substrate character of GO, g-C3N4 nanosheets of unvaried intrinsic structure were exfoliated and anchored on the GO surface, resulting in a GO/g-C3N4 hybrid. Moreover, the photocurrent of the hybrid was largely reinforced at the optimal weight fraction of GO. As a result, the corresponding photocatalytic performance of the hybrid with optimized photocurrent character was largely improved.

Crystallography and spin-crossover. A view of breathing materials.

Abstract: The spin-crossover phenomenon (SCO) is a fascinating field that potentially concerns any material containing a (d4–d7) transition metal complex finding therefore an echo in as diverse research fields as chemistry, physics, biology and geology. Particularly, molecular and coordination-polymers SCO solids are thoroughly investigated since their bistability promises new routes towards a large panel of potential applications including smart pigments, optical switches or memory devices. Notwithstanding these motivating applicative targets, numerous fundamental aspects of SCO are still debated. Among them, the investigation of the structure–property relationships is unfailingly at the heart of the SCO research field. All the facets of the richness of the structural behaviors shown by SCO compounds are only revealed when exploring the whole sample scales – from atomic to macroscopic – all the external stimuli – temperature, pressure, light and any combinations and derived perturbations – and the various forms of the SCO compounds in the solid state – crystalline powders, single-crystals, poorly crystalline or nano-sized particles. Crystallography allows investigating all these aspects of SCO solids. In the past few years, crystallography has certainly been in a significant phase of development pushing the frontiers of investigations, in particular thanks to the progress in X-ray diffraction techniques. The encounter between SCO materials and crystallography is captivating, taking advantages from each other. In this paper, a personal account mainly based on our recent results provides perspectives and new approaches that should be developed in the investigation of SCO materials.

Gold complexes as antimicrobial agents: an overview of different biological activities in relation to the oxidation state of the gold ion and the ligand structure

Abstract: Interest in antimicrobial gold complexes originated from the work of Robert Koch at the end of 19th century, who demonstrated that potassium dicyanidoaurate(I), K[Au(CN)2], showed activity against Mycobacterium tuberculosis, a causative agent of tuberculosis. Subsequently, a large number of gold(I) and gold(III) complexes have been evaluated as possible antimicrobial agents against a broad spectrum of bacteria, fungi and parasites. The first part of the present review article summarizes the results achieved in the field of antibacterial and antifungal activity of gold(I) and gold(III) complexes. The represented gold(I) complexes have been divided into three distinct classes based on the type of coordinated ligand: (i) complexes with phosphine-type ligands, (ii) complexes with N-heterocyclic carbene ligands and (iii) various other gold(I) complexes, while the results related to the antibacterial and antifungal gold(III) complexes have been mainly focused on the organometallic-type of complexes. The second section of this article represents findings obtained from the evaluation of antimalarial activity of gold complexes against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum parasite. Antimalarial gold(I) and gold(III) complexes have been divided into the following classes, based on the nature of the coordinated ligand: (i) complexes with chloroquine and its derivatives, (ii) complexes with N-heterocyclic carbene ligands, (iii) complexes containing functionalised alkynes and (iv) thiosemicarbazonato ligands, as well as (v) other gold(I) and gold(III) complexes. In the last section of the review, gold(I) and gold(III) complexes have been reported to be potential agents against parasites that cause amoebiasis, leishmaniasis and trypanosomiasis. A systematic summary of these results could contribute to the future design of new gold(I) and gold(III) complexes as potential antimicrobial agents.

New ruthenium(II) arene complexes of anthracenyl-appended diazacycloalkanes: effect of ligand intercalation and hydrophobicity on DNA and protein binding and cleavage and cytotoxicity

Abstract: A series of half-sandwich Ru(II) arene complexes of the type [Ru(η6-arene)(L)Cl](PF6) 1–4, where arene is benzene (1, 2) or p-cymene (3, 4) and L is N-methylhomopiperazine (L1) or 1-(anthracen-10-ylmethyl)-4-methylhomopiperazine (L2), has been isolated and characterized by using spectral methods. The X-ray crystal structures of 2, 3 and 4 reveal that the compounds possess a pseudo-octahedral “piano-stool” structure equipped with the arene ligand as the seat and the bidentate ligand and the chloride ion as the legs of the stool. The DNA binding affinity determined using absorption spectral titrations with CT DNA and competitive DNA binding studies varies as 4 > 2 > 3 > 1, depending upon both the arene and diazacycloalkane ligands. Complexes 2 and 4 with higher DNA binding affinities show strong hypochromism (56%) and a large red-shift (2, 10; 4, 11 nm), which reveals that the anthracenyl moiety of the ligand is stacked into the DNA base pairs and that the arene ligand hydrophobicity also dictates the DNA binding affinity. In contrast, the monocationic complexes 1 and 3 are involved in electrostatic binding in the minor groove of DNA. The enhancement in viscosities of CT DNA upon binding to 2 and 4 are higher than those for 1 and 3 supporting the DNA binding modes of interaction inferred. All the complexes cleave DNA effectively even in the absence of an external agent and the cleavage ability is enhanced in the presence of an activator like H2O2. Tryptophan quenching measurements suggest that the protein binding affinity of the complexes varies as 4 > 2 > 3 > 1, which is the same as that for DNA binding and that the fluorescence quenching of BSA occurs through a static mechanism. The positive ΔH0 and ΔS0 values for BSA binding of complexes indicate that the interaction between the complexes and BSA is mainly hydrophobic in nature and the energy transfer efficiency has been analysed according to the Forster non-radiative energy transfer theory. The variation in the ability of complexes to cleave BSA in the presence of H2O2, namely, 4 > 2 > 3 > 1, as revealed from SDS-PAGE is consistent with their strong hydrophobic interaction with the protein. The IC50 values of 1–4 (IC50: 1, 28.1; 2, 23.1; 3, 26.2; 4, 16.8 μM at 24 h; IC50: 1, 19.0; 2, 15.9; 3, 18.1; 4, 9.7 μM at 48 h) obtained for MCF 7 breast cancer cells indicate that they have the potency to kill cancer cells in a time dependent manner, which is similar to cisplatin. The anticancer activity of complexes has been studied by employing various biochemical methods involving different staining agents, AO/EB and Hoechst 33258, which reveal that complexes 1–4 establish a specific mode of cell death in MCF 7 breast cancer cells. The comet assay has been employed to determine the extent of DNA fragmentation in cancer cells.

Na-doped Ni-rich LiNi0.5Co0.2Mn0.3O2 cathode material with both high rate capability and high tap density for lithium ion batteries

Abstract: Na-doped Ni-rich LiNi0.5Co0.2Mn0.3O2 cathode material, Li0.97Na0.03Ni0.5Co0.2Mn0.3O2, is synthesized by a hydroxide co-precipitation route. The structural characterization reveals that the substitution of Na for Li results in a more ordered α-NaFeO2 structure, enlarges Li layer spacing, and reduces the degree of cation mixing. The Li0.97Na0.03Ni0.5Co0.2Mn0.3O2 material has a high tap density of 2.17 g cm−3 that meets the commercial requirement in lithium ion batteries (LIBs). The galvanostatic charge/discharge results show that the electrochemical performance of the Li0.97Na0.03Ni0.5Co0.2Mn0.3O2 is significantly improved. At 0.2, 1, 10, 30 and 50 C, the specific capacities of the Li0.97Na0.03Ni0.5Co0.2Mn0.3O2 are 228.43, 163.12, 121.43, 95.56 and 60.09 mA h g−1, respectively, which are superior to those of the undoped LiNi0.5Co0.2Mn0.3O2 due to the enlargement of Li layer spacing, the decreased degree of cation mixing, and the rapid diffusion of Li-ion in the bulk lattice after the substitution of Na for Li. Therefore, the Na-doped Ni-rich LiNi0.5Co0.2Mn0.3O2 material is a promising cathode candidate for the next generation of LIBs.

Single-phased white-light-emitting NaCaBO3:Ce3+,Tb3+,Mn2+ phosphors for LED applications

Abstract: A series of NaCaBO3:Ce3+,Tb3+,Mn2+ borate phosphors were prepared via a high-temperature solid-state reaction. The obtained phosphors exhibit a strong excitation band between 250 and 400 nm, matching well with the dominant emission band of a NUV light-emitting-diode (LED) chip. The phosphors can generate light from blue to green, and from blue to red by Ce3+→Tb3+ and Ce3+→Mn2+, respectively. Furthermore, a wide-range-tunable white light emission was obtained by precisely controlling the contents of Ce3+, Mn2+, Tb3+. The results show that this phosphor has potential applications as a single-phased phosphor for NUV white LEDs.

State of the art of Lewis acid-containing zeolites: lessons from fine chemistry to new biomass transformation processes

Abstract: The former synthesis of TS-1 opened new catalytic opportunities for zeolites, especially for their application as selective redox catalysts in several fine chemistry processes. Interestingly, isolated Ti species in the framework positions of hydrophobic zeolites, such as high silica zeolites, offer unique Lewis acid sites even in the presence of protic polar solvents (such as water). Following this discovery, other transition metals (such as Sn, Zr, V, Nb, among others) have been introduced in the framework positions of different hydrophobic zeolitic structures, allowing their application in new fine chemistry processes as very active and selective redox catalysts. Recently, these hydrophobic metallozeolites have been successfully applied as efficient catalysts for several biomass-transformation processes in bulk water. The acquired knowledge from the former catalytic descriptions in fine chemistry processes using hydrophobic Lewis acid-containing zeolites has been essential for their application in these novel biomass transformations. In the present review, I will describe the recent advances in the synthesis of new transition metal-containing zeolites presenting Lewis acid character, and their unique catalytic applications in both fine chemistry and novel biomass-transformations.

Role of oxygen vacancy and Fe–O–Fe bond angle in compositional, magnetic, and dielectric relaxation on Eu-substituted BiFeO3 nanoparticles

Abstract: The influence of oxygen vacancies on the dielectric relaxation behavior of pure and Eu-substituted BiFeO3 nanoparticles synthesized by a sol–gel technique has been studied using impedance spectroscopy in the temperature range of 90 °C to 180 °C. The electric relaxation time and activation energy of the oxygen vacancies can be calculated from the Arrhenius equation, and found to be 1.26 eV and 1.76 eV for pure and Eu-substituted BiFeO3, respectively. Substitution induces structural disorder and changes in the Fe–O–Fe bond angle, leading to alteration of the magnetic properties, observed from magnetic studies and evaluated using Rietveld refinement of the XRD patterns. X-ray photoelectron spectroscopy (XPS) confirms the shifting of the binding energy of the Bi 4f orbital, establishing Eu substitution at the Bi site. Calculation of the area under the Fe2+/Fe3+ (2p) and O (1s) XPS spectra gives approximate values of the oxygen vacancies.

p–n junction CuO/BiVO4 heterogeneous nanostructures: synthesis and highly efficient visible-light photocatalytic performance

Abstract: A new strategy via coupling a polyol route with an oxidation process has been developed to successfully synthesize p–n junction CuO/BiVO4 heterogeneous nanostructures. The experimental results reveal that the as-prepared p–n junction CuO/BiVO4 heterogeneous nanostructures exhibit much higher visible-light-driven photocatalytic activity for the degradation of model dye rhodamine B (RhB) than the pure BiVO4 nanocrystals. The photocatalytic degradation rate (C/C0) of the RhB for p–n junction CuO/BiVO4 heterogeneous nanostructures is about two times higher than that of pure BiVO4 nanocrystals. The enhanced photocatalytic efficiency is attributed to a large number of p–n junctions in CuO/BiVO4 heterogeneous nanostructures, which effectively reduces the recombination of electrons and holes by charge transfer from n-type BiVO4 to the attached p-type CuO nanoparticles. This work not only provides an efficient route to enhance the visible-light-driven photocatalytic activity of BiVO4, but also offers a new strategy for fabricating p–n junction heterogeneous nanostructure photocatalysts, which are expected to show considerable potential application in solar-driven wastewater treatment and water splitting.

Fullerene modified C3N4 composites with enhanced photocatalytic activity under visible light irradiation

Abstract: Fullerene modified C3N4 (C60/C3N4) composites with efficient photocatalytic activity under visible light irradiation were fabricated by a simple adsorption approach. The as-prepared C60/C3N4 composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance absorption spectra (DRS), Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectra (PL). The photocatalytic degradation of rhodamine B (RhB) by the C60/C3N4 composites was investigated and optimized, suggesting that the optimal amount of C60 in the composites was 1 wt%. The significantly enhanced photocatalytic activity could be attributed to the efficient separation of photogenerated electrons and holes in the C60/C3N4 composites. A possible mechanism of C60/C3N4 composites as photocatalysts was proposed.

Biogenic synthesis of palladium nanoparticles using Pulicaria glutinosa extract and their catalytic activity towards the Suzuki coupling reaction

Abstract: Green synthesis of nanomaterials finds the edge over chemical methods due to its environmental compatibility. Herein, we report a facile and eco-friendly method for the synthesis of palladium (Pd) nanoparticles (NPs) using an aqueous solution of Pulicaria glutinosa, a plant widely found in a large region of Saudi Arabia, as a bioreductant. The as-prepared Pd NPs were characterized using ultraviolet-visible (UV-vis) spectroscopy, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform-infrared spectroscopy (FT-IR). The hydroxyl groups of the plant extract (PE) molecules were found mainly responsible for the reduction and growth of Pd NPs. FT-IR analysis confirmed the dual role of the PE, both as a bioreductant as well as a capping ligand, which stabilizes the surface of Pd NPs. The crystalline nature of the Pd NPs was identified using XRD analysis which confirmed the formation of a face-centered cubic structure (JCPDS: 87-0641, space group: Fm3m (225)). Furthermore, the as-synthesized Pd NPs demonstrated excellent catalytic activity towards the Suzuki coupling reaction under aqueous and aerobic conditions. Kinetic studies of the catalytic reaction monitored using GC confirmed that the reaction completes in less than 5 minutes.

Blue-shift of Eu2+ emission in (Ba,Sr)3Lu(PO4)3:Eu2+ eulytite solid-solution phosphors resulting from release of neighbouring-cation-induced stress

Abstract: A series of iso-structural eulytite-type (Ba,Sr)3Lu(PO4)3:Eu2+ solid-solution phosphors with different Sr/Ba ratios were synthesized by a solid-state reaction. Crystal structures of (Ba,Sr)3Lu(PO4)3:Eu2+ were resolved by the Rietveld method, which shows an eulytite-type cubic Bi4(SiO4)3 structure with cations disordered in a single C3 site while the oxygen atoms were distributed over two partially occupied sites. The emission peaks of Ba(3−x)SrxLu(PO4)3:Eu2+ (0 ≤ x ≤ 3) phosphors were blue-shifted, from 506 to 479 nm, with increasing Sr/Ba ratio upon the same excitation wavelength of 365 nm, and such interesting luminescence behaviours can also be found in other eulytite-type (Ba,Sr)3Ln(PO4)3:Eu2+ (Ln = Y, Gd) solid-solution phosphors. The blue-shift of the Eu2+ emission with increasing Sr/Ba ratio was ascribed to the variation of the crystal field strength that the 5d orbital of Eu2+ ion experiences, and a new model based on the Eu–O bond length and released neighboring-cation stress in disordered Ba2+/Sr2+/Ln3+ sites is proposed.

Multicycle water vapour stability of microporous breathing MOF aluminium isophthalate CAU-10-H

Abstract: The hydrothermal stability of aluminium hydroxide isophthalate MOF CAU-10-H was proven, under humid multi-cycling conditions. Detailed in situ thermogravimetric measurements and in situ powder X-ray diffraction analysis during water ad-/desorption were used. A reversible structural change during adsorption was detected and thereby exemplified the robustness of breathing-like MOFs over 700 water vapour ad/desorption cycles. In combination with high water adsorption capacity, hydrophilic CAU-10-H is the first breathing-like MOF with a structural change which is a promising candidate for the use in heat transformation processes.

Determination of chemical affinity of graphene oxide nanosheets with radionuclides investigated by macroscopic, spectroscopic and modeling techniques.

Abstract: The chemical affinity of graphene oxide (GO) nanosheets with radionuclides (Eu(III) and U(VI)) was determined by macroscopic, spectroscopic and modeling techniques The macroscopic results showed that the adsorption of Eu(III) and U(VI) on GO nanosheets was independent of ionic strength, indicating that inner-sphere surface complexation predominated their adsorption The maximum adsorption capacities calculated from a Langmuir model at pH 40 and T = 303 K were 20833 mg U(VI) and 2870 mg Eu(III) per gram of GO nanosheets, respectively No hysteresis was observed for both Eu(III) and U(VI) on GO nanosheets when desorption was initiated by lowering solution pH While desorption was induced by replacing the radionuclide supernatant liquid with radionuclide-free electrolyte solution, the adsorption–desorption hysteresis was observed for U(VI) but not for Eu(III), indicating that the chemical affinity of GO nanosheets with U(VI) was stronger than that of GO nanosheets with Eu(III) The adsorption behaviors of Eu(III) and U(VI) on GO nanosheets can be fitted by a double diffuse layer surface complexation model with the mononuclear monodentate >SOM(n−1)+ and >SOMOH(n−2)+ complexes, and larger log K values of U(VI) was observed as compared to those of Eu(III) According to the spectroscopic analysis, the irreversible adsorption of U(VI) on GO nanosheets at variable radionuclide concentrations was attributed to the oxygen-containing functional groups

Layered zeolitic materials: an approach to designing versatile functional solids

Abstract: Relevant layered zeolites have been considered in this perspective article from the point of view of the synthesis methodologies, materials characterization and catalytic implications, considering the unique physico-chemical characteristics of lamellar materials. The potential of layered zeolitic precursors to generate novel lamellar accessible zeolites through swelling, intercalation, pillarization, delamination and/or exfoliation treatments is studied, showing the chemical, functional and structural versatility exhibited by layered zeolites. Recent approaches based on the assembly of zeolitic nanosheets which act as inorganic structural units through the use of dual structural directing agents, the selective modification of germanosilicates and the direct generation of lamellar hybrid organic–inorganic aluminosilicates are also considered to obtain layered solids with well-defined functionalities. The catalytic applications of the layered zeolites are also highlighted, pointing out the high accessibility and reactivity of active sites present in the lamellar framework.

Towards cancer cell-specific phototoxic organometallic rhenium(I) complexes

Abstract: Over the recent years, several Re(I) organometallic compounds have been shown to be toxic to various cancer cell lines. However, these compounds lacked sufficient selectivity towards cancer tissues to be used as novel chemotherapeutic agents. In this study, we probe the potential of two known N,N-bis(quinolinoyl) Re(I) tricarbonyl complex derivatives, namely Re(I) tricarbonyl [N,N-bis(quinolin-2-ylmethyl)amino]-4-butane-1-amine (Re–NH2) and Re(I) tricarbonyl [N,N-bis(quinolin-2-ylmethyl)amino]-5-valeric acid (Re–COOH), as photodynamic therapy (PDT) photosensitizers. Re–NH2 and Re–COOH proved to be excellent singlet oxygen generators in a lipophilic environment with quantum yields of about 75%. Furthermore, we envisaged to improve the selectivity of Re–COOHvia conjugation to two types of peptides, namely a nuclear localization signal (NLS) and a derivative of the neuropeptide bombesin, to form Re–NLS and Re–Bombesin, respectively. Fluorescent microscopy on cervical cancer cells (HeLa) showed that the conjugation of Re–COOH to NLS significantly enhanced the compound's accumulation into the cell nucleus and more specifically into its nucleoli. Importantly, in view of PDT applications, the cytotoxicity of the Re complexes and their bioconjugates increased significantly upon light irradiation. In particular, Re–Bombesin was found to be at least 20-fold more toxic after light irradiation. DNA photo-cleavage studies demonstrated that all compounds damaged DNA via singlet oxygen and, to a minor extent, superoxide production.

Temperature-dependent upconversion luminescence and dynamics of NaYF4:Yb3+/Er3+ nanocrystals: influence of particle size and crystalline phase

Abstract: Oleic acid-capped NaYF4:Yb3+/Er3+ upconversion nanocrystals (UCNCs) with different sizes and crystalline phases were prepared, and their temperature-dependent upconversion luminescence (UCL) and dynamics were studied. It is interesting to observe that the temperature-dependent behavior of UCL for the β-phase (25 nm, 45 nm and bulk) and α-phase (<10 nm) UCNCs is quite different. The UCL intensity of Er3+ ions of the β-phase NaYF4 demonstrates a maximum around 100 K, while the intensity of the α-phase quenches monotonously with elevated temperature (10–400 K). The intensity ratio of 2H11/2–4I15/2 to 4S3/2–4I15/2, RHS, increases solely with temperature for β-phase NaYF4, while for the α-phase sample, it demonstrates a complex and indeterminate variation as a function of temperature. In the β-phase samples, rising processes were observed in the dynamics of Er3+ ions, while in the α-phase sample, no rising process was observed and the decay processes of Er3+ ions were bi-exponential. The rationale for these different temperature-dependent UCL properties was explained carefully.

Synthesis of a nanocomposite composed of reduced graphene oxide and gold nanoparticles

Abstract: We report a seeded-growth process that results in the adhesion of size-controlled gold (Au) nanoparticles (NPs) to the surface of reduced graphene oxide (rGO), leading to the formation of rGO–Au nanocomposites. The synthesis approach involves the utilization of Au molecular precursors (i.e., the seeds) bonded to oxygen functionalities which intrinsically exist on GO. Upon reduction of the Au precursors, surface deposition of Au NPs is ensured. It is found that the size of Au NPs is controlled via the variation of precursor concentration in the growth solution. The redox chemistry between GO and Au precursors causes the reduction of GO to rGO and the generation of Au NPs on the surface of rGO. Microscopic and spectroscopic measurements have been performed to provide evidence for the suggested redox chemistry.

The chemistry and applications of multimetallic salen complexes

Abstract: Multimetallic salen complexes have found utility in a number of fields from materials chemistry to catalysis. The objective of this perspective is to discuss the development of new synthetic strategies to multitopic ligands based on Schiff base chemistry, and the isolation and study of the resulting metal complexes. Developments in catalysis, magnetism, electronic structure, and small-molecule sensing are presented demonstrating the considerable potential of these ligand constructs in facilitating new chemistry.