Effectively contacted multiwalled carbon nanotube (MWCNT)–titanium dioxide nanocomposites and phosphate-functionalized MWCNT–TiO₂ composites have been successfully synthesized by simple one-pot phase-separated hydrolysis–solvothermal processes. The key to this synthetic strategy is to disperse MWCNTs uniformly in Ti(OBu)₄ in advance and then to put them into the toluene organic phase. The as-prepared nanocomposites between TiO₂ and the correct amount of MWCNT exhibits higher activity in the photocatalytic degradation of rhodamine B than that with the resulting TiO₂, although the activity in the photocatalytic degradation of gas-phase aldehyde and liquid-phase phenol is lower. Interestingly, the functionalization of MWCNTs with an appropriate amount of phosphoric acids prior to the synthesis could greatly improve the activity of the MWCNT–TiO₂ nanocomposites for the degradation of aldehyde and phenol, even superior to that of commercial P25 TiO₂. Based on the measurements of atmosphere-controlled surface photovoltage spectra and O₂ temperature-programmed desorption, it is suggested that MWCNTs are favorable to increase rhodamine B adsorption on the composite to promote the photosensitization oxidation reactions, whereas it is unfavorable for the adsorption of O₂ and responsible for the low photocatalytic activity for the degradation of colorless pollutants. Phosphate functionalization greatly enhances the amount of O₂ adsorbed on the MWCNT, which leads to significant charge separation, and thus, to significant photoactivity for the degradation of colored and colorless pollutants of the nanocomposites.

Pollutant breakdown: As depicted, the photogenerated electrons of TiO₂ transfer to the multiwalled carbon nanotube (MWCNT) and are captured by adsorbed O₂. Phosphate functionalization of MWCNTs promotes O₂ adsorption to improve photogenerated charge separation of the resulting MWCNT–TiO₂ composite.

The alternation of the BN bonds in the central borazine ring of the overcrowded 1,2:3,4:5,6-tris(biphenylylene)borazine (2 a) and its tribromo derivative (2 g) is investigated by computational methods and compared with their experimentally obtained crystal structures. The calculations are performed with a meta-generalized-gradient-approximation (GGA) density functional (Tao–Perdew–Staroverov–Scuseria (TPSS)) without and with dispersion corrections, including Becke–Johnson damping, in conjunction with a polarized triple-ζ basis set. These data show a small bond-length alternation (BLA) of around 0.01 Å in 2 a and 2 g. This outcome is in good agreement with X-ray diffraction data for 2 g, but at variance with earlier X-ray diffraction measurements that gave a BLA of 0.06 Å for 2 a. A re-investigation of the crystal structure of 2 a reveals a positional disorder that precludes a discussion of the BN bond lengths. The synthesis of 2 g is the first example of an electrophilic aromatic substitution of an aryl borazine with elemental bromine. Successful bromination was also demonstrated for hexaphenylborazine.

All things being equal: The electrophilic aromatic bromination of 1,2:3,4:5,6-tris(biphenylylene)borazine yields the tribromo derivative that has only small bond-length alternation (BLA) according to X-ray crystallography and state-of-the art computations (see scheme). A re-investigation of the structure of the parent 1,2:3,4:5,6-tris(biphenylylene)borazine compound by experiment and theory reveals positional disorder of the borazine core.

Invited for this month’s cover is the group of Prof. Shizuaki Murata and Dr. Anatoly Zinchenko from Nagoya University and the group of Prof. Vladimir Sergeyev from Moscow State University. The cover picture shows the accumulation of noble and rare-earth metals by DNA cross-linked hydrogel. Read the full text of the article at 10.1002/cplu.201300047

“… systems containing metal ions inside a polymeric matrix are very promising because they allow various reactions to be performed directly inside the hydrogel.” This and more about the story behind the front cover research can be found on page ██.

A hydrated 5-azotriazolyl salicylic acid of [(H₃ATSA)]⋅2 H₂O (1) and its Cd^II complex of [Cd₂(H₂ATSA)₄]⋅13 H₂O (2) have been synthesized and characterized by single-crystal X-ray diffraction analysis and a neutral trans-Z-enol form of H₃ATSA and another anionic trans-E-enol H₂ATSA⁻ isomer have been found in 1 and 2, respectively. The yellow crystal of 2 can be transformed in situ into red crystals in NaOH solution. The diffuse reflectance and photoluminescent spectra for the crystal powder samples and the aqueous solutions of 1 and 2 have been investigated. The DFT and TDDFT calculations at B3LYP/6–31G* level for 1 and B3LYP/Lanl2dz level for 2 have been used to demonstrate the characteristic absorption spectra and the trans-enol to cis-keto photo- and thermoisomeric reaction for the ATSA³⁻ anion. The onion cell imaging taken by confocal laser scanning microscope was observed with 1 and 2 as fluorescent labels.

No two ways about it: Two photo- and thermoisomeric compounds of [(H₃ATSA)]⋅2 H₂O and [Cd₂(H₂ATSA)₄]⋅13 H₂O have been prepared and their optical properties investigated as well as simulated by DFT and TDDFT calculations (see figure). The multiple chromic properties of these compounds may be exploited to create new photoactive devices.

Fluorescent conjugated polyelectrolytes (CPEs) with a large extinction coefficient, high quantum efficiency, good photostability, and efficient intramolecular/intermolecular exciton migration have recently received great research attention as a new generation of fluorescent probes. Herein, the unique properties of fluorescent conjugated polyelectrolyte and mesoporous silica nanoparticles (MSNs) are combined to prepare a pH-sensitive drug delivery and cellular imaging system using a simple and more general method. To the best of our knowledge, this is the first proof-of-concept investigation on the use of fluorescent conjugated polyelectrolyte as both the capping agent of MSNs and the cellular imaging probe in parallel. Moreover, the bifunctional nanomaterial exhibits low cytotoxicity and good biocompatibility demonstrated by a cytotoxicity assay against HepG2 cells and a hemolysis assay against human red-blood cells. It is a promising candidate for simultaneous diagnostics and therapeutics and can also provide a general strategy to develop novel multifunctional nanomedical systems.

Luminescent cap: The properties of a fluorescent conjugated polyelectrolyte and mesoporous silica nanoparticles have been combined to prepare a pH-controlled drug delivery and cellular imaging system by using a simple and general method (see scheme). The fluorescent conjugated polyelectrolyte was used as both the capping agent and the imaging probe with low cytotoxicity. It is a promising candidate for simultaneous diagnostics and therapeutics.

The introduction of a hydrophobic group at position 7 of 9-fluorenone-2-carboxylic acid generates new tubulin binders, the design of which is suggested by modeling studies. The synthesis is based on the use of 2,7-dibromo-fluorenone as starting material. The antiproliferative activity on two different cell lines, fluorescent microscopy, flow cytometry, and sedimentation assay tests confirmed the supposed mechanism.

Tubulin as the target: The introduction of a hydrophobic group at position 7 of 9-fluorenone-2-carboxylic acid (see structure) generates new tubulin binders, the design of which is suggested by modeling studies. The antiproliferative activity on two different cell lines, fluorescent microscopy, flow cytometry, and sedimentation assay tests confirmed the supposed mechanism.

A facile one-pot synthetic strategy is developed to prepare a class of highly crystalline TiO₂ materials with uniform mesoporous structure and good thermal stability. The synthesis intricately combines the advantages of the Stöber, surfactant-templated, and hydrothermal methods. The mesopore sizes are well controlled by adjusting the ratio of hydrolysis inhibitor to TiO₂ precursor. DSSC testing results highlights the importance of specific surface area and mesopore size to the cell performance. The DSSC based on the optimized mesoporous TiO₂ photoanode reached over 8.3 % power conversion efficiency. It is revealed that electron lifetime is greatly increased because of the confinement effect of the uniform mesoporous structure associated with the photoanode. Electron transport is also accelerated as a result of the highly connected crystalline structure for electron transport. Electron diffusion length on the optimized photoanode is about 2.3 times larger than that in a photoanode of Degussa P25 .

Highly crystalline mesoporous TiO₂ was synthesized by a one-pot strategy that combines advantages of the Stöber, surfactant-templated, and hydrothermal methods (see figure; ACAC=acetyl acetone, IPA=isopropanol, TIP=titanium isopropoxide). The resulting photoanodes showed much higher efficiency because of extended electron lifetime related to the mesoporous structure confinement effect and accelerated electron transport.

Proton-bound [M⋅H⋅G]⁺ diastereomeric complexes between some chiral aromatic amino acids or dipeptides (G) and a chiral multifunctional macrocyclic receptor (M=Chirabite-A) undergo, in the gas phase, highly selective substitution and addition reactions by amines, such as 2-aminobutane and piperidine. All the [M⋅H⋅G]⁺ complexes follow time-dependent monoexponential decays. In some cases, the kinetic curves exhibit a plateau revealing the presence of unreactive [M⋅H⋅G]⁺ structures. In them, the amino acid is accommodated in the macrocycle cavity in the zwitterionic form by sharing its acidic hydrogen atoms with the pyridine nitrogen atoms of the host. The same interactions are structurally inaccessible to G=dipeptides or monofunctional amines, which then can be readily released from [M⋅H⋅G]⁺. When the amino acid interacts with the amidocarbonyl oxygen atoms pointing outside the macrocycle cavity, it saves the canonical structure and can be readily displaced by the amine. The Chirabite-A may act as an efficient template for aromatic amino acids by releasing them or not depending upon the amino acid configuration and the basicity of the amine. These unique properties confer to the gas-phase diastereomeric [M⋅H⋅G]⁺ complexes the features of multi-input multi-output chemo-“logic gates”.

A logical choice: Proton-bound complexes between aromatic amino acids and a chiral multifunctional macrocycle, shown in green in the figure, behave as selective multi-input multi-output devices (“logic gates”) which, in the presence of an amine, may or may not release the amino acid depending on its configuration and basicity of the amine.

The synthesis, structure and electrochemical properties of several silver-containing liquid metal salts have been investigated. These ionic liquids comprise of a silver-containing cation with a silver centre coordinated by two or more alkylamine ligands and a bis(trifluoromethylsulfonyl)imide (Tf₂N) anion. With the monodentate amines tert-butylamine (tBuAm), iso-butylamine (iso-BuAm), sec-butylamine (sec-BuAm), 2-ethylhexylamine (2-EtHexAm), di(2-ethylhexyl)amine and piperidine (pip), compounds with the formula [Ag(L)₂][Tf₂N] are formed, several of which are room-temperature ionic liquids and all melt at or below 100 °C. In the case of [Ag(L)₂][Tf₂N] (L=tBuAm, iso-BuAm and pip), single-crystal X-ray diffraction shows that, in the solid state, the silver centres are two-fold coordinated by two amine ligands and the anion and cation exist as separated ion pairs. With ethylenediamine (en), two different compounds were formed, depending on the silver-to-ligand ratio and their structures were elucidated by X-ray diffraction. [Ag(en)][Tf₂N] has a very high melting point and is polymeric in the solid state, with en ligands coordinated to different silver(I) centres, creating one-dimensional chains. [Ag(en)₂][Tf₂N], on the other hand, is a room-temperature ionic liquid, with four-coordinate silver(I) centres, but is actually polymeric in the solid state. The electrodeposition behaviour of [Ag(2-EtHexAm)₂][Tf₂N] and [Ag(en)₂][Tf₂N] was investigated both at room temperature and at 90 °C and it was possible to achieve very high current densities in unstirred solutions and to electrodeposit closed, crack-free, silver coatings. A crystal of [Ag₂(en)Cl₂] was obtained from a solution of [Ag(en)][Tf₂N] in deuterochloroform and its structure is described.

All that glitters is not gold: Thermally stable liquid metal salts have been synthesised by using readily available organic amine ligands and silver bis(trifluoromethylsulfonyl)imide. These compounds are useful for the electrodeposition of metallic silver with high deposition rates (see picture).

The interactions of various acids, such as hydrochloric, hydrobromic, nitric, perchloric, and tetrafluoroboric acids with 2-(1H-imidazole-2-ylthio)-3-methylnaphthalene-1,4-dione (L) enhance the intensity of the fluorescence emission of L. Exceptionally, the interaction of hydrogen bromide with L not only enhances the emission intensity, but also leads to a sharp characteristic emission at λ=480 nm (λ_ex=350 nm), which is different from the other acids. Bromide-ion recognition by protonated L is explained on the basis of a tautomeric equilibrium. The Stokes shifts were calculated for each case and they were dependent on the anions and, in general, were found at λ>100 nm. Fluorescence lifetimes were measured and it was shown that two independent paths operated for the emission processes in solutions of the salts of L. Various salts of L with the general composition [HL][X] (in which X=Cl⁻ (1), Br⁻ (2), NO₃⁻ (3), ClO₄⁻ (4), and BF₄⁻ (5)) are structurally characterized. The coordination environment of the corresponding anion in these salts in the solid state is guided by electrostatic N⁺H⋅⋅⋅O interactions.

Caught in a bind: A fluorescence emission study on the interactions of various mineral acids reveals that a bromide ion is recognized by the protonated form of 2-(1H-imidazole-2-ylthio)-3-methylnaphthalene-1,4-dione; this is attributed to the formation of the enol form of the corresponding bromide salt in solution (see picture).

In isobutane/2-butene alkylation, chloroaluminate ionic liquid catalysts (CAIL) deactivate fast with time on stream with respect to activity and selectivity. Hence, the effect of anhydrous hydrogen chloride (HCl), which shows co-catalytic behavior, was studied in a batch reactor and its effect on both parameters was investigated. The co-catalyst leads to an increased reaction rate and improves the yield of trimethylpentanes, the primarily desired high-octane compounds of alkylation. Moreover, already deactivated CAIL catalysts are reactivated by gaseous HCl. In addition saturation of the ionic liquid with HCl prior to the reaction effectively suppresses the deactivation of the CAIL catalyst. Thus, the solubility of hydrochloric acid is reported for both the CAIL (IL: [BMIM]Cl/AlCl₃, x=0.64) and organic phase to gain a deeper understanding of the reaction system. Finally conjunct polymers dissolved in the ionic liquid were extracted to study their influence on deactivation.

High-octane action: Isobutane/2-butene alkylation was achieved using an hydrogen chloride gas-promoted, chloroaluminate ionic liquid catalyst in a discontinuous stirred tank reactor. Introducing the HCl additive led to high activity and selectivity in the production of desired trimethylpentanes (TMPs); figure also shows undesired secondary products (C₅-C₇, dimethylhexanes (DMHs), C₉₊). Additionally, deactivation of the ionic liquid catalyst was easily avoided.

A gas-phase radical rearrangement through intramolecular hydrogen-atom transfer (HAT) was studied in the glutathione radical cation, [γ-ECG]^+., which was generated by a homolytic cleavage of the protonated S-nitrosoglutathione. Ion–molecule reactions suggested that the radical migrates from the original sulfur position to one of the α-carbon atoms. Experiments on the radical cations of dipeptides derived from the glutathione sequence, [γ-EC]^+. and [CG]^+., pointed to the glutamic acid α-carbon atom as the most likely site of the radical migration. Infrared multiple-photon dissociation (IRMPD) spectroscopy was employed to generate complementary information. IRMPD of [γ-ECG]^+. in the approximately 1000–1800 cm⁻¹ region was inconclusive owing to the relatively broad, overlapping absorption bands. However, the IRMPD spectrum of [γ-EC]^+. in this region was consistent with the radical migrating from the sulfur to the α-carbon atom of glutamic acid. IRMPD in the 2800–3700 cm⁻¹ region performed on [γ-ECG]^+. is consistent with a mixture of both the original sulfur-based radical and the resulting glutamic acid α-carbon-based species. Comparisons are made with previously published condensed and gas-phase studies on intramolecular HAT in glutathione.

Totally radical: Gas-phase ion–molecule reactions were used to observe a radical rearrangement in the radical cation of glutathione (see scheme). This rearrangement proceeded from sulfur to the glutamic acid α-carbon atom, which was confirmed by infrared multiple photon dissociation (IRMPD) spectroscopy in two different IR regions (1000–1800 and 2800–3700 cm⁻¹) and DFT calculations.

A mesostructured ionic liquid–polyoxometalate (IL-POM) hybrid has been prepared through designing a new dihydroxy-tethered guanidinium-based IL, N′′-(2,3-dihydroxypropyl)-N,N,N′,N′-tetramethylguanidinium chloride, to interact with Keggin-type POM phosphotungstic acid (H₃PW) in a self-assembly process. Scanning electron microscopy and transmission electron microscopy showed its special coral-shaped micromorphology. Nitrogen sorption analysis indicated the formation of a porous structure with a moderate surface area of about 30 m² g⁻¹ and narrowly distributed pore size located in the mesoscale. Assessed in the cis-cyclooctene epoxidation with H₂O₂, the mesostructured hybrid exhibited superior heterogeneous catalytic activity and steady reusability, and the conversion was more than four times that of homogeneous H₃PW itself, and more than 14 times that of the nonporous analogues. On the basis of the experimental results, a unique “substrate–solvent–catalyst” synergistic mechanism is proposed and discussed for understanding the dramatically enhanced catalytic performance.

IL effects: A self-assembled mesoporous polyoxometalate (POM) with coral-shaped morphology was obtained by pairing Keggin POM anions with newly designed dihydroxy-tethered guanidinium cations of an ionic liquid (IL). Enhancement of the heterogeneous catalytic activity in epoxidation is explained by a unique substrate–solvent–catalyst synergistic mechanism (see figure).

Invited for this month’s cover is the collaboration between three different groups at Monash University, Deakin University and the ARC Centre of Excellence for Electromaterials Science. The cover picture shows a photograph of an organic ionic plastic crystal, and the structure of the anti and syn isomers of the ccnm anion. Read the full text of the article at 10.1002/cplu.201300068

“One of the interesting outcomes of our research into the ccnm anion was the idea that the presence of a small amount of a second structural isomer of the anion could enhance the plasticity of a material.” This and more about the story behind the front cover research can be found on p. ██.

Successful attempts have been made to control the synthesis of tubular MnOOH with nanodimensions on high electronic conductivity graphite felt (GF) to be used as a flexible supercapacitor electrode. As a fundamental study, the time-dependent kinetics was investigated to interpret its formation mechanism, which can be depicted as the curling of a two-dimensional precursor into a one-dimensional structure with a hollow interior. As a result of the nanotube structure, the active surface area of MnOOH is completely accessible to electrolyte ions and has a shorter charge-transport length and greater ability to withstand structural deformation. Hence, hollow-structured MnOOH shows great promise as an electrochemical system, which is reflected in its high specific capacitance of 1156 F g⁻¹ at 1 A g⁻¹. Furthermore, the high energy density of 1125 W h kg⁻¹ and power density of 5.05 kW kg⁻¹ reveal the outstanding energy-storage behavior of the MnOOH/GF composites as flexible supercapacitor electrodes.

Nothing on the inside: The unique structural properties of MnOOH nanotubes endow them with excellent electrochemical characteristics in terms of the specific capacitance, energy, and power densities (see figure). Furthermore, hybridizing graphite felt (GF) with MnOOH species using the binder-free concept enables them to be used as flexible supercapacitor electrodes.

Treasure trove: A method for the extraction of noble and rare-earth metals by a DNA cross-linked hydrogel, based on high DNA affinity to these elements, is described (see picture). The hydrogel is promising in applications for metal accumulation and recycling.

A water-soluble ionic palladium(II) nitrogen-containing chelating complex, [palladium(II) 1-(4-N,N′,N′′-trimethylbutylammonium)-4-(2-pyridyl)-1H-1,2,3-triazole dichloride] chloride (3), was prepared through the click reaction of 1-chloro-4-bromobutane, sodium azide, and 2-ethynylpyridine, followed by the quarternization of Me₃N and subsequent reaction with [Pd(cod)Cl₂] (cod=1,5-cyclooctadiene). The catalytic performances of complex 3 were preliminarily evaluated through Suzuki–Miyaura and Hiyama cross-coupling reactions of aryl bromides; excellent catalytic activity in water was observed. TEM analysis revealed that small palladium nanoparticles (NPs) with a narrow size distribution were formed after the catalytic reaction. The NPs were stabilized by the synergetic effect of coordination and electrostatic interactions from the ionic, bidentate, nitrogen-containing ligand; no palladium black was detected after the aqueous solution of palladium NPs was stored in air for months. The use of 3 as a precursor in the formation of palladium NPs was further explored by using NaBH₄ and hydrogen as reductive reagents. The resulting NPs displayed different sizes, surface properties, and catalytic performances in the Suzuki–Miyaura cross-coupling reaction in water.

In complete control: A water-soluble palladium(II) click chelating complex serves as an efficient precursor for the formation of palladium nanoparticles (NPs; see picture). Excellent catalytic performances are achieved in Suzuki–Miyaura and Hiyama cross-coupling reactions in water.

In the search for biocompatible amphiphilic polymers, carborane-substituted poly(ethylene glycol)s (PEGs) have been prepared in either a linear mono- and disubstituted or starlike tetrasubstituted shape. The reaction was performed by UV-initiated radical thiol/ene coupling of para-carborane-1-thiol to the corresponding allyl-terminated PEG, diallyl-terminated PEG, and tetraallyl-terminated starlike PEG. After the optimization of reaction conditions, the products were characterized by standard spectroscopic and chromatographic techniques. It was also demonstrated that it is possible to separate individual species differing in the number of attached carborane moieties by means of HPLC on an (R,S)-hydroxypropyl-modified β-cyclodextrin column. To understand the mechanism in atomistic and energetic detail, this reaction was examined by means of quantum mechanics (QM) calculations. Further, because the carborane cluster is hypothesized to behave as a radical trap, QM calculations of the stability of various radicals derived from all the stable carboranethiol isomers with thiol group attached either to carbon or boron atoms were performed. The newly prepared carborane PEGs have an amphiphilic structure and might therefore be utilized in bio-oriented applications.

Off the PEG: The first example of thiol/ene coupling of carboranes leads to telechelic poly(ethylene glycol)s (PEGs, see figure). The radical stability and the reaction mechanism have been checked by quantum chemical calculations. The raw products are separated by advanced chromatography techniques.

The carbamoylcyano(nitroso)methanide (ccnm) anion has been used for the synthesis of eight new salts, two of which are liquid at room temperature. The ionic liquid containing a large phosphonium cation displays the highest thermal stability, while the imidazolium salt is the most fluid and conductive. Analysis of the crystal structures of four of the new materials, containing pyrrolidinium and small phosphonium cations, reveals notably different anion stacking behaviour depending on the nature of the cation. The solid [ccnm] salts all display good ionic conductivities, above 1 mS cm⁻¹ for the four different pyrrolidinium species. This, and their soft appearance, is hypothesized to be a result of the presence of both the syn and anti conformational isomers of the [ccnm] anion. Finally, solid-state NMR linewidth analysis and second moment calculations have been used to gain further insight into the disorder within one of the pyrrolidinium plastic crystals, revealing significant, quantifiable translational motion of some fraction of the material at temperatures over 0 °C.

Plastic fantastic: The first use of the carbamoylcyano(nitroso)methanide anion for the synthesis of ionic liquids produces crystal structures that depend strongly on the nature of the cation. The organic ionic plastic crystals made using this anion display good solid-state ionic conductivities, consistent with the increasing interest in this type of material as new solid-state electrolytes.

Alkali-metal (Li, Na, K)-doped lanthanum oxysulfide nanoplates were obtained in the hexagonal phase by thermolysis of metal acetylacetonates in organic solvents with high boiling points and sulfurization using sulfur powders. The characterization results showed that the size, shape, crystallinity, composition, and phase stability of the La₂O₂S nanocrystals were affected by the doped alkali metals. Combined with first-principles calculations of the formation energy of anionic defects in the lattices, the ternary phase diagrams for the formation of rare-earth oxysulfides (RE₂O₂S) were calculated. Both the experimental results and the phase diagrams have demonstrated that the doped alkali metals are capable of promoting the formation of RE₂O₂S nanocrystals in the order of K≈Na>Li. With K acting as the doping alkali metal, the phase-formation capability for different RE₂O₂S (e.g., Eu, Gd, Yb, Lu) along the lanthanide series was also explored under the guidance of the hard and soft acid and base (HSAB) theory. Moreover, the as-developed synthetic route could be applied also to the production of K/Eu- and K/Tb-codoped La₂O₂S nanoplates, which displayed intense red and green emissions, respectively, under ultraviolet-light excitations.

Making a difference: The doping alkali metal (Li, Na, K) was demonstrated to affect the size, morphology, composition, crystallinity, and luminescence properties of RE₂O₂S (RE=rare earth) ultrathin nanoplates (see figure) synthesized through thermolysis of metal acetylacetonates in hot surfactant in the presence of sublimed sulfur, as confirmed by both controlled experiments and first-principles calculations.

Nanoparticles are known to self-assemble into large aggregates through interparticle and external forces. Understanding how interparticle interaction forces affect the construction and organization of nanomaterials is of growing importance to the development of the self-assembly technique. Current studies tend to focus on the individual factors and lack the collective effects from multiple forces as virus, lipid, or peptide does. The dual control on the self-assembly process of citrate-capped Au nanoparticles (AuNPs) mediated by the interparticle forces is reported. This self-assembly process is governed by the collective effects of both thiol-containing biomolecules and the ionic strength of dielectric medium. Thiol-containing biomolecules can effectively replace surface citrate molecules on AuNPs forming stable AuS bonds, leading to the lowering of surface potential or charge. Ionic strength of the solution can decrease the ion binding and the screening length of the double-layer repulsion. When these two factors are in play simultaneously, they collectively affect the AuNPs self-assembly process through the interparticle interactions by contributions from both factors, which have been interrogated based on the classical Derjaguin–Landau–Verwey–Overbeek theory. It is interesting to observe the existence of a quasi-stable state existed between two aggregated states, where two factors cancel each other and the AuNPs remain well dispersed, indicating that their concurrent effects are not simply additive. The results provide new insight to the assembly process of metal nanoparticles, and may open up new avenues to manipulate process.

Dual control on the self-assembly process of gold nanoparticles by two factors, thiol-containing biomolecules and ionic strength of dielectric medium, has been developed, resulting in the collective effects and an interesting quasi-stable state (see figure).

Nickel phosphite (Ni₁₁(HPO₃)₈(OH)₆) superstructures assembled by nanotubes are synthesized under mild hydrothermal conditions with the sodium salt of polystyrene sulfonic acid. More importantly, Ni₁₁(HPO₃)₈(OH)₆ superstructures are applied as electrode materials for supercapacitors. Benefitting from their novel superstructures, in a three-electrode system, Ni₁₁(HPO₃)₈(OH)₆ superstructure electrodes show a good specific capacitance (1876 F g⁻¹ at 0.625 A g⁻¹), good rate capability, and excellent cycling properties (95 % of the initial specific capacitance at 6.25 A g⁻¹ after 2000 cycles) in 3.0 M KOH. Additionally, asymmetric Ni₁₁(HPO₃)₈(OH)₆–graphene nanosheet supercapacitors are also designed. The specific energy of a cell in 3.0 M KOH reaches about 28.6 Wh kg⁻¹ at 92.5 W kg⁻¹.

The bigger the better: Nickel phosphite superstructures (see picture) assembled by nanotubes are successfully applied as electrochemical supercapacitors with good specific capacitances (1876 F g⁻¹ at 0.625 A g⁻¹), good rate capabilities, and excellent cycling properties (95 % of the initial specific capacitance at 6.25 A g⁻¹ after 2000 cycles).

A facile soft-template method to synthesize Pd hollow nanospheres (PHNs) through a one-pot route in the presence of rhodamine B (RB) at room temperature is demonstrated. RB-PdCl₄²⁻ complex formed by an electrostatic interaction is used as sacrificial template, which can self-degrade to synthesize metal hollow nanostructures. The PdCl₄²⁻ ions are continually reduced in situ and the hollow nanostructures form gradually. The as-prepared PHNs are characterized by transmission electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical measurements. The as-prepared PHNs exhibit enhanced catalytic activity and durability as electrocatalysts for direct methanol fuel cells and direct formic acid fuel cells.

One for all: Pd hollow nanospheres (PHNs) have been synthesized by a one-pot route using a RB-PdCl₄²⁻ complex (RB=rhodamine B) formed by an electrostatic interaction as sacrificial template (see scheme). The as-prepared materials exhibit enhanced electrocatalytic properties in fuel cells.

Hyper-cross-linked polycyanurate networks (CE-P1 and CE-P2) were synthesized by means of thermal self-cyclotrimerization from two triangular cyanate resin monomers 1,3,5-tri(4-cyanatophenyl)benzene and 1,3,5-tricyanatobenzene, respectively. Interestingly, it was found that CE-P1 exhibited microporous characteristics and a moderately large BET surface area. The two narrow peaks in the nonlocal density functional theory (NLDFT) curve appeared at 0.57 and 1.01 nm. In contrast, the CE-P2 sample had a small surface area and broad pore-size distribution with major pores of around 3.39 nm, which indicated a mesoporous material. The reason for this was interpreted in terms of the geometric configuration, steric hindrance, and reactivity of the cyanate monomers. The adsorptions of CO₂, H₂, benzene, n-hexane, and water vapors were investigated by correlating the data with the porosity parameters, chemical structure, and composition of the two networks. The results showed that the vastly distinct pore properties significantly influenced the adsorptions of gases and vapors. In particular, organic vapors such as benzene and n-hexane tended to be adsorbed on the pore surface owing to their affinity and thereby the adsorption amounts were tightly attached to the surface area of the samples. On the contrary, the hydrophobic nature of polymers made the water molecules preferentially condense within the pores so that the pore size rather than the surface area became the dominant factor influencing the adsorption of water vapor.

Three sides to the story: Microporous and mesoporous polycyanurate networks were synthesized by means of thermal self-cyclotrimerization from two triangular cyanate resin monomers, 1,3,5-tri(4-cyanatophenyl)benzene and 1,3,5-tricyanatobenzene, respectively (see scheme). The adsorptions of CO₂, H₂, benzene, n-hexane, and water vapors were investigated.

Making a stand: By means of in situ reduction and self-assembly at an unconventional liquid–liquid interface, free-standing ultrathin cobalt nanosheets (CoNs) consisting of nanosized Co clusters were successfully synthesized (see figure). The as-prepared CoNs display ferromagnetic behavior and a large thermal irreversibility. This strategy has been used also in the synthesis of Fe and Ni nanosheets.

The cover picture shows a beautiful Indonesian coral reef. The inset is of a millimetre-sized capsule designed to clean up oil spills from environmental waters. Such capsules move as a result of the Marangoni effect. Martin Pumera and co-workers outline cleaning of oil droplets with these self-propelled artificial capsules in their Communication on page 395 ff. They study the influence of different cleaning agents (that is, surfactants) on the removal of oil from a water/air interface.

Invited for this month’s cover is the group of Prof. Martin Pumera from Nanyang Technological University, Singapore. The cover picture shows pristine underwater coral. This image symbolizes the beauty of a clean environment (coral reef in Indonesia), while the inset outlines the mechanism of the motion of the self-propelled cleaning capsule. Read the full text of the article at 10.1002/cplu.201300011

“Fluorine plays an important role in chemistry as well as in material and liefe science.”

This and more about the story behind the front cover can be found on page 280.

Coming clean: Polymer capsules of millimeter dimensions have been loaded with surfactants of negative, positive, or neutral charge, and their influence on the movement of oil droplets at the water/air interface was compared. Release of surfactant molecules from the capsule affects the surface tension γ and pulling force F (see figure) such that an oil droplet moves away from the polymer micromotor.

Strained cages: UV-photoelectron spectroscopy studies of tetrakis(trimethylsilyl)tetrahedrane and its pentafluorophenyl derivative (see figure) demonstrate the effectiveness of the neutral hyperconjugation in the latter, which was initially proposed on the basis of electronic spectra and computational data.

X-ray spectroscopy: Substoichiometric encapsulation of polyoxometalate ions into a metal–organic framework results in a fully functional cation exchanger with accessible porosity. Cu²⁺ cations compensating the charge of [PW₁₂O₄₀]³⁻ in the as-synthesized material can be exchanged with cations such as Na⁺ and Eu³⁺. When exchanged with Eu³⁺, the material appears bright red under UV irradiation (see figure).

In this study, cross-linked enzyme aggregates of tissue-culture-grade trypsin (CLEAs-T) were prepared and introduced to the proteomics analysis instead of the expensive proteomics-grade trypsin, which benefits from the protein purification during the preparation of the CLEAs. Bovine serum albumin, lysozyme, bovine hemoglobin, and α-casein were used as model proteins, and three intensive strategies (high-enzyme-concentration, high-temperature, and ultrasound-assisted digestion) were applied to the rapid and efficient digestion of model proteins by CLEAs-T. The peptide fragments were then identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, which revealed the higher sequence coverage and sharply reduced digestion time of these strategies compared with the conventional in-solution 12 h digestion method. Morphology studies demonstrated that the excellent performance of CLEAs-T in proteomics analysis came from the “scaffoldlike” supermolecular structure, which provided a high resistance to the autolysis and denaturation of trypsin under high-enzyme-concentration, high-temperature, and ultrasound-assisted digestion.

Easy to swallow: Cross-linked enzyme aggregates of tissue-culture-grade trypsin (CLEAs-T) were prepared and introduced to the protein-digestion process in proteomics analysis (see figure). High-analysis throughput was obtained by using CLEAs-T with intensive digestion strategies, such as high enzyme concentration, high temperature, and ultrasound-assisted. The excellent performance of CLEAs-T is attributed to their unique “scaffoldlike” structure.

Three biscyclometalated iridium(III) complexes with three different ancillary ligands have been investigated with respect to the final products of acid-induced transformation in coordinating or non-coordinating solvents. All of these complexes, represented as [Ir(L_C^N)₂L_O^O] and [Ir(L_C^N)₂L_N^O], are susceptible to acid attack, followed by the departure of the ancillary ligand, L_O^O or L_N^O. Depending on the coordinating ability of the solvent molecule and whether or not a coordinating anion exists, the final product will be either a solvento complex or a dichloro-bridged iridium(III) dimer. Although coexistence of the solvento complex and dichloro-bridged iridium(III) dimer was observed under certain conditions, the conversion of the solvento complex into the dichloro-bridged iridium(III) dimer has been proven.

Remaining solvent: Three biscyclometalated iridium(III) complexes with three different ancillary ligands are investigated with respect to the final products of acid-induced transformation in coordinating or non-coordinating solvents (see picture). Although coexistence of the solvento complex and dichloro-bridged iridium(III) dimer is observed under certain conditions, the conversion of the solvento complex into the dichloro-bridged iridium(III) dimer is seen.

The hydrodesulfurization reaction of thiophene has been investigated over graphene-like few-layer MoS₂ as well as over Co- and Ni-nanoparticle-covered few-layer MoS₂. Conversion of thiophene to n-butane over few-layer MoS₂ is superior to that over bulk MoS₂; the percent conversion is approximately 64 % at 450 °C. However, over few-layer MoS₂ covered with Co or Ni nanoparticles the conversion increases to approximately 98 % at around 375 °C as a result of the smaller nanoparticles being more effective.

Less is more: Hydrodesulfurization of thiophene has been carried out using graphene-like few-layer MoS₂ with conversion of approximately 64 %. Further conversion was enhanced to 98 % when Co or Ni nanoparticles covered the surface of MoS₂ (see figure).

We present herein a new single probe, polyethyleneimine (PEI)/MnZnS nanocomposite, for two-color imaging and three-dimensional sensing. The PEI/MnZnS nanocomposite possesses unique, individually excited, two-color, photoluminescence (PL) emissions at λ=495 and 585 nm; this allows two-color imaging of the same space just by changing the excitation wavelength in situ. Moreover, the two PL bands of the nanocomposite are orthogonal, which allows the discrimination of eight proteins just by recording the three-channel optical signals of the single probe. The two PL bands of the PEI/MnZnS composite are capable of distinguishing eight proteins at 0.5 μM, whereas the three-channel signals (two PL bands and light scattering) can discriminate these proteins at no less than 0.25 μM.

Positive discrimination: Polyethyleneimine (PEI)/MnZnS nanocomposites, with two unique individually excited and orthogonal emissions at λ=495 and 585 nm, allow two-color imaging of the same space just by changing the excitation wavelength in situ, and enable the discrimination of eight proteins by recording three-channel optical signals of a single probe (see picture).

Nanoparticle technologies have tremendous potential in clinical medicine. To fully realize this potential, one must further understand how nanoparticles interact with biological systems. Typically, reporters that are conjugated to nanoparticles during synthesis are used to monitor the nanoparticles in biological systems. Unfortunately, conjugating reporters to nanoparticles complicates the synthesis and the reporter itself may alter the nanoparticle properties. To address these challenges, a copper-catalyzed azide–alkyne cycloaddition strategy has been developed to functionalize nanoparticles with fluorescent reporters after they have been delivered to biological systems. Using polyamidoamine dendrimers as model nanoparticles, the utility of this strategy is shown in several biological systems including a cancer cell model, primary immune cells, and a murine model of inflammation. This reporter strategy simplifies the synthesis without sacrificing the ability to monitor the nanoparticle conjugates. It is expected that this bioorthogonal reporter strategy can be used to understand nanoparticle interactions in biological systems, which will facilitate the translation of these technologies to the clinics.

Getting a handle on it: An innovative strategy for tracking multifunctional nanoparticles in biological systems is presented that simplifies the syntheses and can be used to track the nanoparticles in vitro and in vivo. The strategy is based on in situ click chemistry ligation of fluorescent reporters to the nanoparticle scaffold through copper-catalyzed azide–alkyne cycloaddition (see figure).

The acidity of europium(III)-exchanged zeolite L (Eu³⁺/ZL) and its influence on the luminescence performances of encapsulated europium(III) β-diketonate complexes are reported. The results indicate the importance of understanding the acidity of Eu³⁺/ZL in the preparation of luminescent host–guest materials of zeolite L crystals and europium(III) β-diketonate complexes. The acidity of Eu³⁺/ZL was determined roughly by using a dye (thionine) as the probe molecule. The luminescence performances of the host–guest materials, including excitation and emission spectra, lifetime of Eu³⁺ ions, quantum yield, and energy transfer efficiency, have been investigated. The luminescence behavior of the host–guest materials can be tuned by changing the acidity inside the channels of the zeolite L crystals and can potentially be used as a sensor for detecting ammonia.

An acid test: The acidity in channels of Eu³⁺-exchanged zeolite L (ZL) crystals has been investigated and its influence on the luminescence properties of host–guest materials with europium(III) β-diketonate complexes has been studied. Materials containing 2-thenoyltrifluoroacetone (tta) in the channels can be used to detect ammonia (see figure).

Postsynthetic modification of [Cu₂(mand)₂(hmt)] (mand=mandelic acid, hmt=hexamethylenetetramine) with a chiral, dimeric chromium(III)–salen complex led to a robust structure. Characterization of this new material showed that it perfectly preserved the textural and structural properties of the parent metal–organic framework (MOF). Although epoxidation of trans-methyl cinnamate with hydrogen peroxide led to copper leaching of 2–3 %, experiments performed with N-methylmorpholine-N-oxide indicated no leaching, even after 72 h of exposure. The obtained chiral MOF is an effective catalyst for the enantioselective epoxidation of trans-methyl cinnamate and leads to (2R,3S)-phenylglycidate with a high enantiomeric excess at room temperature.

Transformed and ready for action! Postsynthetic modification of [Cu₂(mand)₂(hmt)] (mand=mandelic acid, hmt=hexamethylenetetramine) results in an effective catalyst (see picture) for the enantioselective epoxidation of trans-methyl cinnamate to provide methyl (2R,3S)-phenylglycidate with a high ee value at room temperature.

Laccase from Trametes versicolor 51639 was encapsulated on the nanoscale. The laccase nanogel was prepared by polyacrylamide encapsulation as a result of N-acryloxysuccinimide modification and in situ polymerization. Size-exclusion chromatography, fluorescence resonance energy transfer, dynamic light scattering, and transmission electron microscopy were employed to characterize the laccase nanogel. Higher thermal, pH, and storage stability and organic-solvent tolerance of the laccase nanogel were indicated without activity loss. Moreover, the laccase nanogel was used to synthesize naphthoquinones from hydroquinones with a 10–15 % greater overall yield than that of native laccase.

It′s a wrap: The amino groups of lysine in laccase were modified with N-acryloxysuccinimide (NAS). Acrylamide was then added to the modified laccase molecule through hydrogen bonds to form a modified-laccase molecule–acrylamide assembly, followed by polymerization in situ through addition of ammonium persulfate (APS) and tetramethylethylenediamine (TEMED) to produce a laccase nanogel encapsulated in polyacrylamide (see scheme).

Three new oligomers bearing furan, thiophene, or bithiophene units end-capped by benzofuran moieties were synthesized and studied with respect to their structural, optical, electrochemical, and electrical properties. A comparison of the electronic properties performed by theoretical calculation, absorption and emission spectroscopy, and cyclic voltammetry revealed a strong influence of the spacer unit with a predominant impact on the emission spectra. Although both compounds with thiophene or bithiophene as central units presented relatively low quantum yields of 30 and 17 %, respectively, a maximum yield up to 71 % was measured for the compound based on a central furan core. High-vacuum-evaporated thin films were investigated by X-ray diffraction and AFM, before implementation as p-type semiconducting layers in organic field-effect transistors. Only derivatives with thiophene or bithiophene as central units presented a transistor activity, with mobilities up to approximately 1×10⁻² cm² V⁻¹ s⁻¹.

If the cap fits: A series of three oligomers bearing furan, thiophene, or bithiophene units end-capped by benzofuran moieties have been synthesized and studied with respect to their structural, optical, electrochemical, and electrical properties (see figure). Thin films are used as p-type semiconducting layers in organic field-effect transistors (OFETs).