Graphene, the thinnest two-dimensional material in nature, has abundant distinctive properties, such as ultrahigh carrier mobility, superior thermal conductivity, very high surface-to-volume ratio, anomalous quantum Hall effect, and so on. Laterally confined, thin, and long strips of graphene, namely, graphene nanoribbons (GNRs), can open the bandgap in the semimetal and give it the potential to replace silicon in future electronics. Great efforts are devoted to achieving high-quality GNRs with narrow widths and smooth edges. This minireview reports the latest progress in experimental and theoretical studies on GNR synthesis. Different methods of GNR synthesis-unzipping of carbon nanotubes (CNTs), cutting of graphene, and the direct synthesis of GNRs-are discussed, and their advantages and disadvantages are compared in detail. Current challenges and the prospects in this rapidly developing field are also addressed.

Much effort has been devoted to investigating the unusual properties of the π electrons in Möbius cyclacenes, which are localized in a special region. However, the localized π electrons are a disadvantage for applications in optoelectronics, because intramolecular charge transfer is limited. This raises the question of how the intramolecular charge transfer of a Möbius cyclacene with clearly localized π electrons can be enhanced. To this end,[8]Möbius cyclacene ([8]MC) is used as a conjugated bridge in a donor-π-conjugated bridge-acceptor (D-π-A) system, and NH(2)-6-[8]MC-10-NO(2) exhibits a fascinating spiral charge-transfer transition character that results in a significant difference in dipole moments Δμ between the ground state and the crucial excited state. The Δμ value of 6.832 D for NH(2)-6-[8]MC-10-NO(2) is clearly larger than that of 0.209 D for [8]MC. Correspondingly, the first hyperpolarizability of NH(2)-6-[8]MC-10-NO(2) of 12 467 a.u. is dramatically larger than that of 261 a.u. for [8]MC. Thus, constructing a D-π-A framework is an effective strategy to induce greater spiral intramolecular charge transfer in MC although the π electrons are localized in a special region. This new insight into the properties of π electrons in Möbius cyclacenes may provide valuable information for their applications in optoelectronics.

Natural orbital functional theory (NOFT) is used for the first time in the analysis of different types of chemical bonds. Concretely, the Piris natural orbital functional PNOF5 is used. It provides a localization scheme that yields an orbital picture which agrees very well with the empirical valence shell electron pair repulsion theory (VSEPR) and Bent's rule, as well as with other theoretical pictures provided by valence bond (VB) or linear combination of atomic orbitals-molecular orbital (LCAO-MO) methods. In this context, PNOF5 provides a novel tool for chemical bond analysis. In this work, PNOF5 is applied to selected molecules that have ionic, polar covalent, covalent, multiple (σ and π), 3c-2e, and 3c-4e bonds.

The structural characteristics of fully-hydrogenated carbon and boron nitride mono- and multilayer slabs, together with nanotubes derived from the slabs, are investigated mainly by means of periodic local second-order Møller-Plesset perturbation (LMP2) calculations and the results are compared with Hartree-Fock (HF), density functional theory (DFT), and dispersion function-augmented DFT (DFT-D) obtained ones. The investigated systems are structurally analogous to (111) and (110) slabs of diamond, where the hydrogenated (111) slab of diamond corresponds to the experimentally known graphane. Multilayering of monolayers and nanotubes is energetically favorable at the LMP2 level for both C and BN, while HF and DFT are not able to reproduce this behavior for CH systems. The work highlights the importance of utilizing methods capable of properly describing weak interactions in the investigation of dispersively-bound systems such as the multilayered graphanes and the corresponding nanotubes.

Thermodynamic parameters obtained from studying the micellization of amphiphilic p-sulfonatocalix[n]arenes were correlated with the alkyl chain length and with the number of monomeric units (n) in the calix[n]arene structure. The micellization Gibbs free energy (Δ${G{{{\rm o}\hfill \atop {\rm M}\hfill}}}$) becomes more negative upon increasing the alkyl chain length of the p-sulfonatocalix[4]arene. This is in agreement with the trend generally observed for other surfactants. However, the Δ${G{{{\rm o}\hfill \atop {\rm M}\hfill}}}$ value for transferring one CH(2) group from the bulk aqueous medium to the micelle [Δ${G{{{\rm o}\hfill \atop {\rm M}\hfill}}}$(CH(2))] is lower than the value generally observed for single-chain surfactants, suggesting the existence of intramolecular interactions between the alkyl chains of the free unimers. On the other hand, the critical micelle concentration (cmc; per alkyl chain unit) increased with the increasing number of monomeric units. These results are explained on the basis of the conformation adopted by the calixarene in the bulk solution. The calix[4]arene derivatives are preorganized into the cone conformation, which is favorable for the formation of globular aggregates. The calix[6]arene and calix[8]arene derivatives do not adopt cone conformations. Changing these conformations to the more favorable cone conformer in the aggregates implies an energetic cost that contributes to making Δ${G{{{\rm o}\hfill \atop {\rm M}\hfill}}}$ less efficient. In the case of the calix[6]arene derivative this energetic cost is enthalpic, whereas in the case of the octamer it is both enthalpic and entropic. Both the Δ${G{{{\rm o}\hfill \atop {\rm M}\hfill}}}$(CH(2)) value and the change in heat capacity (ΔC${{\rm p}{{{\rm o}\hfill \atop {\rm M}\hfill}}}$) seem to indicate that for the cone calix[4]arene derivatives all alkyl chains are solvated by the same hydration shell, whereas in the case of the highly flexible calix[8]arene derivative each alkyl chain is individually hydrated.

Magnetic and luminescent bifunctional divalent europium nanocrystals (Eu(2+) NCs) are a promising class of novel advanced materials that have various applications in magneto-optic devices, catalysis, bioimaging, and solar cells. In the past few decades, much work has been carried out to study the synthesis, properties, and applications of Eu(2+) NCs. The aim of this Minireview is to present the progress in preparing Eu(2+) NCs based on the reported research, by describing the advantages and disadvantages of the synthesis methods. The morphologies and size are controlled through adjusting the experimental conditions. Eu(2+) NCs show superior magnetic and luminescence properties simultaneously. Self-assembly and doping with other ions are important routes to improve their magnetic and luminescence properties. Their applications in magneto-optic devices are discussed. Some difficulties and challenges in the fabrication of Eu(2+) NCs are discussed, such as water-soluble Eu(2+) NCs and tunable luminescence in the whole visible region.

A low temperature route to crystalline titania nanostructures in thin films is presented. The synthesis is performed by the combination of sol-gel processes, using a novel precursor for this kind of application, an ethylene glycol-modified titanate (EGMT), and the structure templating by micro-phase separation of a di-block copolymer. Different temperatures around 100 °C are investigated. The nanostructure morphology is examined with scanning electron microscopy, whereas the crystal structure and thin film compositions are examined by scattering methods. Optoelectronic measurements reveal the band-gap energies and sub-band states of the titania films. An optimum titania thin film is created at temperatures not higher than 90 °C, regarding sponge-like morphology with pore sizes of 25-30 nm, porosity of up to 71 % near the sample surface, and crystallinity of titania in the rutile phase. The low temperature during synthesis is of high importance for photovoltaic applications and renders the resulting titania films interesting for future energy solutions.

Camera-based fluorescence correlation spectroscopy (FCS) approaches allow the measurement of thousands of contiguous points yielding excellent statistics and details of sample structure. Imaging total internal reflection FCS (ITIR-FCS) provides these measurements on lipid membranes. Herein, we determine the influence of the point spread function (PSF) of the optical system, the laser power used, and the time resolution of the camera on the accuracy of diffusion coefficient and concentration measurements. We demonstrate that the PSF can be accurately determined by ITIR-FCS and that the laser power and time resolution can be varied over a wide range with limited influence on the measurement of the diffusion coefficient whereas the concentration measurements are sensitive to changes in the measurement parameters. One advantage of ITIR-FCS is that the measurement of the PSF has to be performed only once for a given optical setup, in contrast to confocal FCS in which calibrations have to be performed at least once per measurement day. Using optimized experimental conditions we provide diffusion coefficients for over ten different lipid membranes consisting of one, two and three constituents, measured in over 200000 individual correlation functions. Using software binning and thus the inherent advantage of ITIR-FCS of providing multiple observation areas in a single measurement we test the FCS diffusion law and show how they can be complemented by the local information provided by the difference in cross-correlation functions (ΔCCF). With the determination of the PSF by ITIR-FCS and the optimization of measurement conditions ITIR-FCS becomes a calibration-free method. This allows us to provide measurements of absolute diffusion coefficients for bilayers with different compositions, which were stable over many different bilayer preparations over a time of at least one year, using a single PSF calibration.

Model structures of 1,3,5-triarylbenzenes with a substituted benzene core linked to thienyl or 3,4-ethylenedioxythienyl (EDOT) terminal groups are studied by electrochemical and in situ ESR/UV/Vis/NIR spectroelectrochemical techniques. Oxidative polymerization of the monomers results in CC coupling of the thiophene moieties in the 5-position, forming dimeric structures with bithiophene linkers as the first step. Both the doubly charged protonated dimer and the new dimer formed after proton release are studied in detail for 2,4,6-tris[2-(3,4-ethylenedioxythienyl)]-1-methoxybenzene. Quite high stability of the doubly charged σ dimer formed on oxidation with unusual redox behavior at the electrode is observed. Density functional calculations of the molecular structure as well as spectroscopic and electronic properties of charged states in 1,3,5-triarylbenzene derivatives in the monomeric, dimeric, and oligomeric form are presented. The complex spectroelectrochemical response of a thin solid film formed on the electrode surface upon potentiodynamic polymerization indicates the existence of different charge states of oligomeric structures within the solid matrix.

Fast and fancy: Lithium that was originally disordered within the structure of the perovskite Li(0.18) Sr(0.66) Ti(0.5) Nb(0.5) O(3) can be induced into ordering within the yellow region of the unit cell by low temperatures and treatment with n-butyl-lithium. The fast kinetics of lithium insertion, in connection with a color change, make this nontoxic, air-stable material a suitable candidate for use in electrochromic systems or lithium-storage batteries.

Fullerene peapods have opened the possibility of studying reactions in a confined space that might lead to materials which under other conditions would be impossible to synthesize. Progress has been made, but there are more challenges are ahead.

A theoretical treatment of a Schottky barrier dynamic response is developed on the basis of a general model of a semiconductor with thickness comparable in length to the space charge region width. It is shown that, when the space charge region approaches the metal/semiconductor interface, the electric field at this interface, induced by the charge accumulated on the metal, becomes significant with respect to the electric field induced by the charge accumulated on the semiconductor. Under this condition, the total capacitance of the Schottky barrier becomes independent of the polarization potential and tends to the value ε/L, like in a pure dielectric insulator. The term thin film is intended to be with respect to the screening length, which is a function of the volumetric charge density. In amorphous materials the transition potential at which the semiconducting to insulating behaviour is observed is dependent on the frequency. An approximated analytical solution for the capacitance of the junction is calculated. The model for finite thickness semiconductors is successfully applied to the study of anodic Nb(2) O(5), formed in phosphate buffer 0.5 M aqueous solution up to different formation potentials (namely 5, 10 and 20 V vs. Ag/AgCl). The finite thickness semiconductor model permits extrapolation to a general behaviour of the oxide in a wide range of frequencies, potentials and thicknesses, and identification of the electron transfer between adsorbed surface species and the conduction band of Nb(2) O(5) at potentials near to the flat band value.

Spray-assisted layer-by-layer assembly is applied to the fabrication of functional thin film composites based on colloidal semiconductor nanocrystals. The technique is capable of handling various material combinations, yielding varying functional architectures. Light-emitting devices, including those of all-inorganic design, are generated in order to demonstrate the potential applicability and versatility of this approach.

In recent years, an enormous amount of research has been devoted to the study of photosensitive materials from both fundamental and practical viewpoints, due to their wide applications in photocatalytic([1-3]) and optoelectronic devices,([4, 5]) ultraviolet (UV) photodetectors,([6-9]) photoswitch microdevices,([10, 11]) light-emitting diodes,([12, 13]) photovoltaic devices,([14-16]) and photoelectrochemical cells.([17]) Metal oxides, such as ZnO, TiO(2), SnO(2), and NiO have been the most investigated photosensitive materials.([3, 6-8, 18-21]) To enhance and take full advantage of their photosensitivity, functionalizing their surface with a polymer that has a high light absorption ability has become one of the widely used methods.([1-12, 22-24]) For example, Z. L. Wang et al. reported that the UV photocurrent of a ZnO nanobelt-based sensor was enhanced by close to five orders of magnitude after functionalizing its surface with polystyrene sulfate which has a high UV absorption ability.([25]) T. Sasaki et al. reported the assembly of a TiO(2) nanoparticle film with poly(3,4-ethylenedioxythiophene) and poly(4-styrene sulfonate)(PEDOT-PSS) through layer-by-layer fabrication in the nanometer scale. The electric conductivity of the TiO(2) composite films could be tuned by UV and visible (Vis) light.([22]) Thus, sunlight or photon energy can be used and transformed to electrical energy by UV-photosensitive metal oxides after their surfaces have been functionalized with a dye that has a high Vis absorption ability. To date, most of the dye-sensitized solar cells are based on the surface functionalization of UV-photosensitive metal oxides by dyes.([26-28]) However, to the best of our knowledge, all of the reports on surface functionalization enhanced only the UV photosensitivity of the metal oxide. In other words, this method has been used exclusively to enhance the UV photocurrent in metal oxides that already have UV-photosensitive properties, but not to induce UV photocurrent in metal oxides that have no UV-photosensitive properties. In fact, to the best of our knowledge, there are no surface-functionalizing reports on inducing UV or Vis photocurrent in metal oxides that have no UV- or Vis-photosensitive properties.

This work shows that colloidal stability and aggregation kinetics of hydrophobic polystyrene (PS) nanospheres are extremely sensitive to the nature of the salt used to coagulate them. Three PS latices and four aggregating electrolytes, which all share the same cation (Na(+)) but have various anions located at different positions in the classical Hofmeister series depending on their kosmotropic or chaotropic character, are used. The present study focuses on analyzing different aggregating parameters, such as critical coagulation concentrations (CCC), cluster size distributions (CSD), initial kinetic constants K(11), and fractal dimensions of the aggregates d(f). While aggregation induced by SO(4)(2-) and Cl(-) behaved according to the predictions of the classical Derjaguin-Landau-Verwey-Overbeek theory, important discrepancies are found with NO(3)(-), which become dramatic when using SCN(-). These discrepancies among the anions were far more significant when they acted as counterions rather than as co-ions. While SO(4)(2-) and Cl(-) trigger fast diffusion-limited aggregation, SCN(-) gives rise to a stationary cluster size distribution in a few aggregation times when working with cationic PS particles. Clear differences are found among all analyzed parameters (CCC, CSD, K(11), and d(f)), and the experimental findings show that particles aggregate in potential wells whose depth is controlled by the chaotropic character of the anion. This paper presents new experimental evidence that may help to understand the microscopic origin of Hofmeister effects, as the observations are consistent with appealing theoretical models developed in the last few years.

We report a molecular dynamics study on the EuBr(n)(3-n) complexes (n=0 to 6) formed upon complexation of Br(-) by Eu(3+) in the [BMI][PF(6)],[BMI][Tf(2) N] and [MeBu(3) N][Tf(2) N] ionic liquids (ILs), to compare the effect of the IL anion (PF(6)(-) versus Tf(2) N(-)), the IL cation (BMI(+) versus MeBu(3) N(+)) and the "IL humidity" on their solvation and stability. In "dry" solutions all complexes remain stable and the first coordination shell of Eu(3+) is purely anionic (Br(-) and IL anions), surrounded by IL cations (BMI(+) or MeBu(3) N(+) ions). Long range "onion type" solvation features (up to 20 Å from Eu(3+)), with alternating cation-rich and anion-rich solvent shells, are observed around the different complexes. The comparison of gas phase-optimized structures of EuBr(n)(3-n) complexes (that are unstable for n=5 and 6) with those observed in solution points to the importance of solvation forces on the nature of the complex, with a higher stabilization by imidazolium- than by ammonium-based dry ILs. Adding water to the IL has different effects, depending on the IL. In the highly hygroscopic [BMI][PF(6)] IL, Br(-) ligands are displaced by water, to finally form Eu(H(2) O)(9)(3+). In the less "humid"[BMI][Tf(2) N], the EuBr(n)(3-n) complexes do not dissociate and coordinate at most 1-2 H(2) O molecules. We also calculated the free-energy profiles (Potential of Mean Force calculations) for the stepwise complexation of Br(-), and found significant solvent effects. EuBr(6)(3-) is predicted to form in both [BMI][PF(6)] and [BMI][Tf(2) N], but not in [MeBu(3) N][Tf(2) N], mainly due to weaker interactions with the cationic solvation shell. First steps are found to be more exergonic in the PF(6)(-)- than in the Tf(2) N(-)-based IL. Molecular dynamics (MD) comparisons between ILs and classical solvents (acetonitrile and water) are also reported, affording good agreement with the experimental observations of Br(-) complexation by trivalent lanthanides in these classical solvents.

Large scale for small size: We report a large-scale synthetic method to produce uniform and ultra-small-sized Ag nanoparticles with good productivity. This method is simple and efficient. It produces Ag nanoparticles within 20 min by heating a reaction mixture containing only three chemicals. The size of the nanoparticles is controlled by varying the heating rate.