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Conductive wires of sub-micrometer width made from platinum-carbonyl clusters have been fabricated by solution-infilling of microchannels as in microinject molding in capillaries (MIMIC). The process is driven by the liquid surface tension within the micrometric channels followed by the precipitation of the solute. Orientation of supramolecular crystalline domains is imparted by the solution confinement combined with unidirectional flow. The wires exhibit ohmic conductivity with a value of 0.2 S/cm that increases, after thermal decomposition of the platinum-carbonyl cluster precursor to Pt, to 35 S/cm. [ABSTRACT FROM AUTHOR]

Surface photovoltage spectroscopy and spectral photoconductivity measurements have been carried out in the UV spectral region on GaN nanowires to analyze the near band-edge region. The results reveal the presence of tails in the band−band absorption spectra. Surface Photovoltage spectra performed on the as-grown nanowire ensamble show a long band tail of about 0.1 eV. Spectral photoconductivity on singly contacted nanowires shows that the band tail width strictly depends on the wire diameter. These results are explained by the Franz−Keldysh effect due to the internal electric field induced by Fermi level pinning at the nanowire surface. The experimental values of the absorption tail are well in agreement with the results obtained by simulating the electric field in a cylindrical model. [ABSTRACT FROM AUTHOR]

In this letter we report on spectral photoconductivity (PC) on different sections of single MBE-grown GaN nanowhiskers of diameters ranging on the order of 100 nm. The photoconductivity spectra show, besides the band-gap related transition, deep-levels corresponding to the yellow, green, and blue bands. A strong spatial localization of specific photocurrent peaks has been observed, indicating that the defects responsible for such transitions are distributed inhomogeneously along the column growth direction. [ABSTRACT FROM AUTHOR]

We report a new patterning process which takes place as a result of demixing of a binary polymer/solute mixture. An efficient, sustainable approach for ordering nanosized rings of so-called single molecule magnets (SMMs) is thus provided. It exploits the self-organization process in which SMM patterned film evolves to a spatially correlated pattern of nanosized rings. At long time, the anisotropic patterning of the film drives the ring to coalesce, into parallel lines of nanometric width. [ABSTRACT FROM AUTHOR]

Charge transport properties in organic semiconductors depend strongly on molecular order. Here we demonstrate field-effect transistors where drain current flows through a precisely defined array of nanostripes made of crystalline and highly ordered molecules. The molecular stripes are fabricated across the channel of the transistor by a stamp-assisted deposition of the molecular semiconductors from a solution. As the solvent evaporates, the capillary forces drive the solution to form menisci under the stamp protrusions. The solute precipitates only in the regions where the solution is confined by the menisci once the critical concentration is reached and self-organizes into molecularly ordered stripes 100−200 nm wide and a few monolayers high. The charge mobility measured along the stripes is 2 orders of magnitude larger than the values measured for spin-coated thin films. [ABSTRACT FROM AUTHOR]

Controlling materials on multiple length scales is one of the most compelling issues in nanotechnology research today. Here we demonstrate that arrays of nanometer-sized aggregates, each made of a few hundred single-molecule magnets derived from Mn12 complexes, can be patterned on large areas by self-organization assisted by stamps on a surface in a dewetting regime. The large length scale is imposed by the motif of the stamp protrusions, and the smaller length scales, viz., the size and distance of the molecular aggregates, are controlled by deposition and growth phenomena occurring in a volume confined beneath the protrusions by capillary forces. The method is general to a variety of molecular materials and substrates because repulsive, as opposed to specific, interactions are required. Our result hints at the possibility of sustainable patterning of single-molecule magnets for ultra-high-density magnetic storage and quantum computing. [ABSTRACT FROM AUTHOR]

Examines the effect of mechanical interlocking on crystal packing. Intramolecular saturation of the hydrogen bond; Formation of rotaxanes with in-crystal mobility; Movement of the rotaxane building blocks in the solid state.

We present a novel fabrication technique, which we termed lithographically controlled wetting. A stamp is placed in contact with a liquid thin film; in this manner, capillary forces drive the liquid to distribute only under the protrusions of the stamp. As the solvent evaporates, the deposited solute forms a pattern on the surface with the same length scale of the stamp. By carefully choosing the experimental conditions, it is possible to downscale the printed features relative to the size of the stamp features by at least a factor 7, viz., several tens of nanometers-wide nanostructures can be fabricated using a stamp with submicrometer features. The process, which is completely general to a variety of soluble materials, is demonstrated to yield nanosized structures of a relevant molecular material, viz., tris-8-hydroxyquinoline-aluminum(III). [ABSTRACT FROM AUTHOR]

Underpotential (UPD) deposition of sulfur from Na2S solution in 0.1 M NaOH was studied on Ag(100) and Ag(110) using in situ scanning tunneling microscopy (STM). The cyclic voltammogram on Ag(100) presents two broad peaks, whereas three partial overlapping peaks and a sharper one are observed on Ag(110). STM measurements carried out during the whole UPD process show that progressively more compact structures are formed as the applied potential is scanned toward more positive potentials. More precisely, p(2×2), c(2×6), and c(2×2) were found on Ag(100) at E= −1.25, −1.0, and −0.9 V, respectively. Less definite conclusions can be drawn for the structures of S overlayers on Ag(110). However, the experimental findings are consistent with an incomplete p(2×1) at potentials preceding the sharp peak, and with a c(2×2) structure at E= −0.9 V vs Ag/AgCl, KClsat. The coverage values calculated on the basis of the hypothesized structures have been compared with the values obtained from chronocoulometric measurements at the most positive potentials investigated. Thus, the experimental coverage θ = 0.5 coincides with the coverage calculated for the c(2×2) structure found on Ag(110) at E= −0.9 V by STM, whereas the experimental coverage θ = 0.42 suggests that a mixture of structures c(2×6) and c(2×2) is formed on Ag(100). [ABSTRACT FROM AUTHOR]

We show that ultrathin films of a semiconductive discotic liquid crystal, viz. phthalocyanines, can be organized to form a conductive channel tens of microns long between Au electrodes with thickness control over a single monolayer. Our approach exploits the electromigration of the isotropic phase formed starting from the pretransitional region of the columnar-isotropic phase transition. Dewetted isotropic material accumulates to the negative electrode by applying a longitudinal electric field of about 1 V/µm. Dewetting and electromigration expose an ultrathin film, a few monolayers thick, exhibiting columnar liquid crystal order. The layers of this ultrathin film melt progressively above Tc and can be individually exfoliated by electromigration, starting from the ninth down to the first monolayer. The analysis of the current flowing through the junction as a function of the temperature, together with the comparative imaging of the evolution of morphology, yields a detailed picture of the changes in the dimensionality of the conductive phthalocyanine film and allows us to extract the behavior of the order parameter. The phenomenon of electromigration opens interesting questions on the technological control of individual monolayers on device patterns. [ABSTRACT FROM AUTHOR]

In the fight against Glioblastoma Multiforme, recent literature data have highlighted that integrin α5β1 and p53 are part of convergent pathways in the control of glioma apoptosis. This observation prompted us to seek a molecule able to simultaneously modulate both target families. Analyzing the results of a previous virtual screening against murine double minute 2 protein (MDM2), we envisaged that Arg-Gly-Asp (RGD)-mimetic molecules could be inhibitors of MDM2/4. Herein, we present the discovery of compound 7, which inhibits both MDM2/4 and α5β1/αvβ3 integrins. A lead optimization campaign was carried out on 7 with the aim to preserve the activities on integrins while improving those on MDM proteins. Compound 9 turned out to be a potent MDM2/4 and α5β1/αvβ3 blocker. In p53-wild type glioma cells, 9 arrested cell cycle and proliferation and strongly reduced cell invasiveness, emerging as the first molecule of a novel class of integrin/MDM inhibitors, which might be especially useful in subpopulations of patients with glioblastoma expressing a functional p53 concomitantly with a high level of α5β1 integrin. [ABSTRACT FROM AUTHOR]

We investigate the solvatochromic effect of a Fe-based spin-crossover (SCO) compound via ambient pressure soft X-ray absorption spectroscopy (AP-XAS) and atomic force microscopy (AFM). AP-XAS provides the direct evidence of the spin configuration for the Fe(II) 3d states of the SCO material upon in situ exposure to specific gas or vapor mixtures; concurrent changes in nanoscale topography and mechanical characteristics are revealed via AFM imaging and AFM-based force spectroscopy, respectively. We find that exposing the SCO material to gaseous helium promotes an effective decrease of the transition temperature of its surface layers, while the exposure to methanol vapor causes opposite surfacial and bulk solvatochromic effects. Surfacial solvatochromism is accompanied by a dramatic reduction of the surface layers stiffness. We propose a rationalization of the observed effects based on interfacial dehydration and solvation phenomena. [ABSTRACT FROM AUTHOR]

Ferroelectric molecular compounds present great advantages for application in electronics because they combine high polarization values, comparable to those of inorganic materials, with the flexibility and low-cost properties of organic ones. However, some limitations to their applicability are related to the high crystallinity required to deploy ferroelectricity. In this article, highly ordered ferroelectric patterned thin films of diisopropylammonium bromide have been successfully fabricated by a lithographically controlled wetting technique. Confinement favors the self-organization of ferroelectric crystals, avoiding the formation of polymorphs and promoting the long-range orientation of crystallographic axes. Patterned structures present high stability, and the polarization can be switched to be arranged in stable domain pattern for application in devices. [ABSTRACT FROM AUTHOR]

A novel series of 1,2,4-triazolyl 5-azaspiro[2.4]heptanes with high affinity and selectivity at the dopamine (DA) D3 receptor (D3R) is described. Some of these compounds also have high selectivity over the hERG channel and were characterized with respect to their pharmacokinetic properties both in vitro and in vivo during lead identification and early lead optimization phases. A few derivatives with overall favorable developability characteristics were selected for further late lead optimization studies. [ABSTRACT FROM AUTHOR]

This Account aims to describe our experience in the use of patterningtechniques for addressing the self-organization processes of materialsinto spatially confined regions on technologically relevant surfaces.Functional properties of materials depend on their chemical structure,their assembly, and spatial distribution at the solid state; the combinationof these factors determines their properties and their technologicalapplications. In fact, by controlling the assembly processes and thespatial distribution of the resulting structures, functional materialscan be guided to technological and specific applications. We consideredthe principal self-organizing processes, such as crystallization,dewetting and phase segregation. Usually, these phenomena producedefective molecular films, compromising their use in many technologicalapplications. This issue can be overcome by using patterning techniques,which induce molecules to self-organize into well-defined patternedstructures, by means of spatial confinement. In particular, we focusour attention on the confinement effect achieved by stamp-assisteddeposition for controlling size, density, and positions of materialassemblies, giving them new chemical/physical functionalities. Wereview the methods and principles of the stamp-assisted spatial confinementand we discuss how they can be advantageously exploited to controlcrystalline order/orientation, dewetting phenomena, and spontaneousphase segregation. Moreover, we highlight how physical/chemical propertiesof soluble functional materials can be driven in constructive ways,by integrating them into operating technological devices. [ABSTRACT FROM AUTHOR]

We report the firstselective growth of nanographite petals andvarious carbon nanomaterials onto a multipanel electrochemical platform.Different types of nanomaterials can be obtained by fine-tuning thegrowth parameters of the chemical vapor deposition (CVD) process.First, absolute novelty is the catalytic CVD selective growth of differentcarbon nanomaterials only on the working electrodes of the platform.A second novelty is the growth obtained at complementary metal–oxide–semiconductorcompatible temperatures. These novel electrodes have been incorporatedin sensors in which performance characteristics improve with the contentof nanostructures. Unprecedented sensing parameters with respect toboth direct and enzyme-mediated electrochemical biodetection havebeen obtained. [ABSTRACT FROM AUTHOR]

The applications of organic semiconductorsin complex circuitrysuch as printed CMOS-like logic circuits demand miniaturization ofthe active structures to the submicrometric and nanoscale level whileenhancing or at least preserving the charge transport properties uponprocessing. Here, we addressed this issue by using a wet lithographictechnique, which exploits and enhances the molecular order in polymersby spatial confinement, to fabricate ambipolar organic field effecttransistors and inverter circuits based on nanostructured single componentambipolar polymeric semiconductor. In our devices, the current flowsthrough a precisely defined array of nanostripes made of a highlyordered diketopyrrolopyrrole-benzothiadiazole copolymer with highcharge carrier mobility (1.45 cm2V–1s–1for electrons and 0.70 cm2V–1s–1for holes). Finally, we demonstratedthe functionality of the ambipolar nanostripe transistors by assemblingthem into an inverter circuit that exhibits a gain (105) comparableto inverters based on single crystal semiconductors. [ABSTRACT FROM AUTHOR]

We report the first observation of the electronic levelschemein boron (B)- and phosphorus (P)-doped nanowires (NWs). The NWs’morphology dramatically depends on the doping impurity while a fewdeep electronic levels appear in both kinds of nanowires, independentlyof the doping type. We demonstrate that the doping impurities inducethe same shallow levels as in bulk silicon. The presence of two donorlevels in the lower half-bandgap is also revealed. In both kinds ofNWs, B- and P-doped, the donor level (0/) at Ev 0.36 eV of the gold–hydrogen complex is observed.This means that the gold diffusion from the NW tip introduces an electronicallyactive level, which might negatively affects the electrical characteristicsof the NWs. In P-doped NWs, we observed a further donor level at 0.26eV above the valence band due to the phosphorus-vacancy pairs, theE-center, well-known in bulk silicon. These findings seriously questionboth diffusion modeling of impurities in NWs and the technologicalaspects arising from this. [ABSTRACT FROM AUTHOR]

Functional supramolecular architectures for bottom-up organic nano and microtechnology are a high priority research topic. We discovered a new recognition algorithm, resulting from the combination of thioalkyl substituents and head-to-head regiochemistry of substitution, to induce the spontaneous self-assembly of sulfur overrich octathiophenes into supramolecular crystalline fibers combining high charge mobility and intense fluorescence. The fibers were grown on various types of surfaces either as superhelices or straight rods depending on molecular structure. Helical fibers directly grown on a field effect transistor displayed efficient charge mobility and intrinsic `memory effect'. Despite the fact that the oligomers did not have chirality centers, one type of hand-helicity was always predominant in helical fibers, due to the interplay of molecular atropisomerism and supramolecular helicity induced by terminal substituents. Finally, we found that the new sulfur overrich oligothiophenes can easily be prepared in high yields through ultrasound and microwave assistance in green conditions. [ABSTRACT FROM AUTHOR]

Here we describe the synthesis and magnetic characterization of a family of 2D polymetallic oxalate-bridged polymeric networks with general formula [MII(H2O)2]3[MII(ox)3]2(18-crown-6)2 (MII = Cr, Fe; MII= Mn, Fe, Co, Ni; 18-crown-6 = C12H24O6). Depending on the nature of the trivalent metal ion, they exhibit ferro- (Cr3+) or ferrimagnetic (Fe3+) ordering in the 3.6-20 K interval. In contrast with most of the oxalate-bridged CPs reported so far, these complexes do not need any additional templating cation for their assembly and represent the first series of oxalate-based polymeric networks which can be considered intrinsically neutral. As previously observed for other crown ether containing oxalate-based coordination polymers, these compounds are soluble in water, whereas they remain nonsoluble in other organic solvents. Furthermore, when these molecular precursors are subjected to a thermally controlled decomposition process, pure phases of mixed oxides with spinel-like structures can be conveniently generated. Among the resulting materials, the (Mn,Co,Fe)3O4 derivative is particularly remarkable, since it behaves as a magnet at room temperature. Finally, taking advantage of the solubility of these molecular precursors, this room- temperature magnetic oxide has been successfully nanostructured onto a Si(110) substrate via the lithographically controlled wetting (LCW) technique. [ABSTRACT FROM AUTHOR]

We use a “structure director” colloidal composite to fabricate porous titanium oxide films having a hierarchical pore architecture consisting of mesopores regularly distributed in the macropore shell. The colloidal composite consists of polystyrene beads coated with (ammonium lactate)titanium dihydroxide deposited by means of a fluidic technique. The pore properties and interconnections are controlled at different length scales: a macroscale, which is imposed by the polystyrene beads; a mesoscale, which is controlled by the composition and by the thermal history of the composite; a nanometer-scale, controlled by the nanocrystal sintering in air. Our approach can be extended to a wide class of water-soluble metal oxide precursors; therefore, it opens interesting perspectives for “bottom-up” nanotechnology of functional arrays and devices. [ABSTRACT FROM AUTHOR]

We demonstrate field effect transistors based on organic semiconductor molecules dispersed in a self-organized polystyrene (PS) latex bead matrix. An aqueous colloidal composite made of PS and tetrahexylsexithiophene (H4T6) is deposited with a micropipet into the channel of a bottom-contact field effect transistor. The beads self-organize into a network whose characteristic distances are governed by their packing. The semiconductor molecules crystallize in the interstitial voids, leading to the growth of large interconnected domains. Depending on the bead size and the ratio between H4T6 and PS, the fraction of the different phases in the polymorph can be controlled. In the transistors where the H4T6 metastable “red phase” is the largest, the device response and the charge mobility are comparable to those of sexithienyl thin films grown by high-vacuum sublimation. [ABSTRACT FROM AUTHOR]

Two new antibacterial peptides, denominated as Dominulin A and B, have been found on the cuticle and in the venom of females of the social paper wasp Polistes dominulus. The amino acidic sequence of the two peptides, determined by mass spectrometry, is INWKKIAE VGGKIL SSL for Dominulin A (MW = 1854 Da) and INWKKIAEIGKQVL SAL (MW = 1909 Da) for Dominulin B. Their presence on the cuticle was confirmed using MALDI-TOF by means of micro-extractions and direct analyses on body parts. The presence in the venom and the primary structure of the dominulins suggest their classification in the mastoparans, a class of peptides found in the venom of other Aculeate hymenoptera. Their antimicrobial action against Gram+ and Gram− bacteria fits in the range of the best natural antimicrobial peptides. Dominulins can represent an important defense of the colony of Polistes dominulus against microbial pathogens. [Copyright &y& Elsevier]

The self-organization of rotaxane thin films into spatially correlated nanostructures is shown to occur upon a thermal stimulus. The mechanism of formation of nanostructures and their organization has been investigated using atomic force microscopy, bright field transmission electron microscopy, selected area electron diffraction, and molecular mechanics simulations. The evolution of the nanostructures follows a complex pathway, where a rotaxane thin film first dewets from the substrate to form nanosized droplets. Droplets coalesce by ripening, generating spatially correlated motifs. In a later stage, the larger droplets change shape, nucleate, and coalesce to yield crystallites that grow into larger crystals by incorporating the surrounding droplets. The results show the following: (i) the nanostructures represent a metastable state of a crystallization process; (ii) spatial correlations emerge during ripening, but they are destroyed as stable nuclei are formed and crystallization proceeds to completion; iii) crystallization, either on graphite or amorphous carbon films, leads to a precise basal plane, viz. (010), which has minimum surface energy. The inherent degrees of freedom permitted in the rotaxane architecture favors the re-organization and nucleation of the film in the solid state. Low-energy trajectories leading to crystallites with stable surfaces and minimum energy contact plane are found to occur via concerted, small amplitude, internal motions without disruption of packing and intermolecular contacts. [ABSTRACT FROM AUTHOR]

We show that thin films grown by vacuum sublimation, or formed by melted powders, of semiconductor α-quinquethiophene (T5) exhibit a hierarchical self-affinity organization that spans scales from tens of nanometers to hundreds of micrometers. T5 organization was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), and optical microscopy. XRD showed that vacuum-evaporated T5 films were characterized by a preferred orientation of the h00 planes parallel to the glass substrate. Melting of the films followed by rapid quenching to room temperature led to the formation of micrometer-sized, single-crystal-like structures, characterized by uniaxially aligned stripes. XRD proved that the melting-quenching process enhanced molecular ordering and increased the size of domains with the molecule's long axes tilted by about 65° with respect to the substrate plane and piled up side-by-side along parallel columns. AFM measurements on the melt-quenched structures showed that a hierarchical architecture was built by reiteration across multiple length scales of the same recurring motif. Because of the tendency of T5 to form highly crystalline vacuum-evaporated thin films, a field-effect hole mobility comparable to state-of-the-art FET mobility of α-sexithiophene films was reached, without any attempt to optimize deposition conditions. [ABSTRACT FROM AUTHOR]

Investigates the supramolecular organization of sexithiophenes. Composition of sexithiophenes with chiral and achiral penta (ethylene glycol) chain; Analysis on the optical changes from intermolecular processes; Implication of intermediate disorder state of aggregation.