Entropy of the Land Parcel Mosaic as a Measure of the Degree of Urbanization.

Quantifying the urbanization level is an essential yet challenging task in urban studies because of the high complexity of this phenomenon. The urbanization degree has been estimated using a variety of social, economic, and spatial measures. Among the spatial characteristics, the Shannon entropy of the landscape pattern has recently been intensively explored as one of the most effective urbanization indexes.

Azahomofullerenes as New n-Type Acceptor Materials for Efficient and Stable Inverted Planar Perovskite Solar Cells.

Fullerene derivatives with a strong electron-accepting ability play a crucial role in enhancing both the performance and stability of perovskite solar cells (PSCs). However, most of the used fullerene molecules are based on [6,6]-phenyl-C-butyric acid methyl ester (PCBM), which limits the device performance due to difficulties in preparing high-quality and uniform thin films. Herein, solution-processable azahomofullerene (AHF) derivatives (abbreviated as AHF-1 and AHF-2) are reported as novel and effective electron-transport layers (ETLs) in p-i-n planar PSCs.

A Seedless Method for Gold Nanoparticle Growth inside a Silica Matrix: Fabrication of Materials Capable of Third-Harmonic Generation in the Near-Infrared.

A composite in which gold nanoparticles (AuNPs) approximately 10 nm in size are embedded in amorphous transparent silica matrix has been produced. The synthetic protocol uses HAuCl as the Au ion source, tetraethoxysilane (TEOS) as the SiO precursor, and l-ascorbic acid (AA) as the reducing agent. AA is employed before the sol-gel process in an amount sufficient only for reduction of Au ions to Au .

Triggering autocatalytic reaction by host-guest interactions.

The acceleration of a sequential reaction through electrostatic alteration of substrate basicity within a supramolecular host is demonstrated. In the presence of the host, the reaction, which is autocatalytic, starts much sooner and exhibits substrate size selectivity.

Gold-oxoborate nanocomposites and their biomedical applications.

A novel inorganic nanocomposite material, called BOA, which has the form of small building blocks composed of gold nanoparticles embedded in a polyoxoborate matrix, is presented. It is demonstrated that cotton wool decorated with the BOA nanocomposite displays strong antibacterial activity toward both Gram-positive and -negative bacteria strains. Importantly, the modified cotton does not release any toxic substances, and the bacteria are killed upon contact with the fibers coated with the BOA.

Nanoparticles in a capillary trap: dynamic self-assembly at fluid interfaces.

Dynamic self-assembly is an emerging scientific concept aimed to construct artificial systems of adaptative behavior. Here, we present a first nanoscopic system that is able to dynamically self-assemble in two dimensions. This system is composed of charged gold nanoparticles, dispersed at the air-water interface, which self-assemble into a dense monolayer of area of several square centimeters in response to surface tension gradient.

A "wrap-and-wrest" mechanism of fluorescence quenching of CdSe/ZnS quantum dots by surfactant molecules.

We identified a mechanism of fluorescence quenching of CdSe/ZnS quantum dots (QDs) coated with two organic layers, octadecylamine and an amphiphilic polymer containing COOH groups, by nonionic polyoxyethylene-based (C12En) surfactants. The surfactant molecules by themselves do not affect the fluorescence of the QDs. For the quenching to occur, "wrapping" of the QDs by a bilayer of the surfactant molecules is necessary.

A "nano-windmill" driven by a flux of water vapour: a comparison to the rotating ATPase.

We measure the frequency of collective molecular precession as a function of temperature in the ferroelectric liquid crystalline monolayer at the water-air interface. This movement is driven by the unidirectional flux of evaporating water molecules. The collective rotation in the monolayer with angular velocities ω ~ 1 s(-1) (at T = 312 K) to 10(-2) s(-1) (at T = 285.

Close-packed monolayers of charged Janus-type nanoparticles at the air-water interface.

We present a new method to obtain close-packed monolayers composed of noble metal nanoparticles (NP) possessing well-defined permanent charge of either sign. The method is based on the fact that ligands forming the protecting layer exhibit ability to rearrange at the NPs surface. We demonstrate that if the protecting layer is composed of a mixture of hydrophobic and hydrophilic charged ligands in appropriate proportion, the NP exhibits properties of a Janus-type particle with one of the hemispheres hydrophilic and the other hydrophobic.

Autonomous self-assembly of ionic nanoparticles into hexagonally close-packed lattices at a planar oil-water interface.

Let's get charged! Positively charged nanoparticles (NPs) spontaneously self-assemble into hexagonally close-packed lattices at a planar CH(2)Cl(2)-water interface. The self-assembly process is fully autonomous and occurs without any external manipulation.

Gold Micro-Flowers: One-Step Fabrication of Efficient, Highly Reproducible Surface-Enhanced Raman Spectroscopy Platform.

We present a new method enabling simultaneous synthesis and deposition of gold micro-flowers (AuMFs) on solid substrates in a one-pot process that uses two reagents, auric acid and hydroxylamine hydrochloride, in aqueous reaction mixture. The AuMFs deposited onto the substrate form mechanically stable gold layer of expanded nanostructured surface. The morphology of the AuMFs depends on and can be controlled by the composition of the reaction solution as well as by the reaction time.

Aggregation and layering transitions in thin films of X-, T-, and anchor-shaped bolaamphiphiles at the air-water interface.

Aggregation in Langmuir films is usually understood as being a disorderly grouping of molecules turning into chaotic three-dimensional aggregates and is considered an unwanted phenomenon causing irreversible changes. In this work we present the studies of 11 compounds from the group of specific surfactants, known as bolaamphiphiles, that exhibit reversible aggregation and, in many cases, transition to well-defined multilayers, which can be considered as a layering transition. These bolaamphiphiles incorporate rigid π-conjugated aromatics as hydrophobic cores, glycerol-based polar groups and hydrophobic lateral chains.

New one-pot technique to introduce charged nanoparticles into a lyotropic liquid crystal matrix.

We present a new method to incorporate hydrophilic charged nanoparticles into the lyotropic liquid crystal (LLC) template. This method is based on the effect of the polymer-induced phase separation (PIPS) and consists of two steps. In the first step, the nanoparticles are mixed with a surfactant micellar solution.

Evaluation of ligand-selector interaction from effective diffusion coefficient.

We present an analytical technique for determination of ligand-selector equilibrium binding constants. The method is based on the measurements of effective molecular diffusion coefficient of the ligand during Poiseuille flow through a long (approximately 25 m), thin (0.254 mm +/- 0.

Single-walled carbon nanotube/lyotropic liquid crystal hybrid materials fabricated by a phase separation method in the presence of polyelectrolyte.

We present a detailed study on the incorporation of single-walled carbon nanotubes (SWNTs) into lyotropic liquid crystals (LLC) by phase separation in the presence of polyelectrolytes. Two cases were studied in this work: (i) incorporation of SWNTs into the LLC phase formed by an anionic surfactant sodium dodecyl sulfate (SDS) in the presence of an anionic polyelectrolyte poly(sodium styrenesulfonate) (PSS); (ii) incorporation of SWNTs into the LLC phase formed by a cationic surfactant cetyltrimethylammonium bromide (CTAB) in the presence of a cationic polyelectrolyte poly(diallydimethylammonium chloride) (PDADMAC). The SWNTs/LLC composites were characterized by polarized optical microscopy (POM) observations and small-angle X-ray scattering (SAXS) measurements.

From complex structures to complex processes: percolation theory applied to the formation of a city.

We investigate the morphology of the spatial pattern resulting from the division of land into the parcels that is observed in the centers of the cities, by analyzing the distribution function of the parcel areas. A simple model based on a two-dimensional bond percolation is employed to mimic the process of the formation of the city. The model reproduces the empirical distribution of the parcel areas that is found to exhibit the power law with the exponent tau=2.

Polymer-induced ordering and phase separation in ionic surfactants.

We present a new method to induce phase separation in solutions of ionic surfactants. In this method, the phase separation is obtained either by addition of polyelectrolytes or nonionic polymers along with inorganic salt. As a result, the system separates into polyelectrolyte-rich (or nonionic polymer-rich) and surfactant-rich phase.

Mechanism of reactive wetting and direct visual determination of the kinetics of self-assembled monolayer formation.

Reactive wetting (RW) of alkane thiols and disulfides on gold is studied experimentally using the wet stamping technique. Theoretical description based on Langevin dynamics is developed to explain the experimental results and to clarify the physical processes underlying RW. In this description, thermal fluctuations of the three-phase contact line combine with the surface reaction to gradually build a low-energy self-assembled monolayer (SAM) onto which the front propagates.

Late stage of the phase-separation process: coalescence-induced coalescence, gravitational sedimentation, and collective evaporation mechanisms.

We study the separation in the binary and ternary mixtures of the water/surfactant C12E5/polymer PEG system. The phase separation in the mixtures at late stages is governed by two distinct mechanisms: the coalescence-induced coalescence and the droplet evaporation mechanism. We show that when the coalescence-induced coalescence process is globally terminated in the sample consisting of a dense system of domains, another mechanism, which we call the collective droplet evaporation, starts to dominate.

Plastic and moldable metals by self-assembly of sticky nanoparticle aggregates.

Deformable, spherical aggregates of metal nanoparticles connected by long-chain dithiol ligands self-assemble into nanostructured materials of macroscopic dimensions. These materials are plastic and moldable against arbitrarily shaped masters and can be thermally hardened into polycrystalline metal structures of controllable porosity. In addition, in both plastic and hardened states, the assemblies are electrically conductive and exhibit Ohmic characteristics down to approximately 20 volts per meter.

Kinetics of contact electrification between metals and polymers.

Kinetics of charge transfer between metals and polymers was studied using an analytical rolling-sphere tool. The rates of charge transfer were related to the area of contact between contacting surfaces and the tunneling current between them. The derived rate equations accounted for the experimentally observed sigmoidal charging curves.

Electrostatic self-assembly of binary nanoparticle crystals with a diamond-like lattice.

Self-assembly of charged, equally sized metal nanoparticles of two types (gold and silver) leads to the formation of large, sphalerite (diamond-like) crystals, in which each nanoparticle has four oppositely charged neighbors. Formation of these non-close-packed structures is a consequence of electrostatic effects specific to the nanoscale, where the thickness of the screening layer is commensurate with the dimensions of the assembling objects. Because of electrostatic stabilization of larger crystallizing particles by smaller ones, better-quality crystals can be obtained from more polydisperse nanoparticle solutions.

Principles and implementations of dissipative (dynamic) self-assembly.

Dynamic self-assembly (DySA) processes occurring outside of thermodynamic equilibrium underlie many forms of adaptive and intelligent behaviors in natural systems. Relatively little, however, is known about the principles that govern DySA and the ways in which it can be extended to artificial ensembles. This article discusses recent advances in both the theory and the practice of nonequilibrium self-assembly.

Micropatterning chemical oscillations: waves, autofocusing, and symmetry breaking.

Arrays of chemical oscillators are micropatterned by Wet Stamping. The technique is used to demonstrate that chemical waves can be initiated and controlled in oscillatory systems and that such waves can give rise to phenomena not observed in excitable media. Interoscillator coupling and synchronization, kinetic autofocusing, and twist-symmetry breaking are a consequence of the dependence of the oscillation phase on the local concentrations of reagents and on systems' geometry.