Hierarchically Structured Magnetic Nanoconstructs with Enhanced Relaxivity and Cooperative Tumor Accumulation

Iron oxide nanoparticles are formidable multifunctional systems capable of contrast enhancement in magnetic resonance imaging, guidance under remote fields, heat generation, and biodegradation. Yet, this potential is underutilized in that each function manifests at different nanoparticle sizes. Here, sub‐micrometer discoidal magnetic nanoconstructs are realized by confining 5 nm ultra‐small super‐paramagnetic iron oxide nanoparticles (USPIOs) within two different mesoporous structures, made out of silicon and polymers. These nanoconstructs exhibit transversal relaxivities up to ≈10 times (r ₂ ≈ 835 mm ^?1 s^?1) higher than conventional USPIOs and, under external magnetic fields, collectively cooperate to amplify tumor accumulation. The boost in r ₂ relaxivity arises from the formation of mesoscopic USPIO clusters within the porous matrix, inducing a local reduction in water molecule mobility as demonstrated via molecular dynamics simulations. The cooperative accumulation under static magnetic field derives from the large amount of iron that can be loaded per nanoconstuct (up to ≈65 fg) and the consequential generation of significant inter‐particle magnetic dipole interactions. In tumor bearing mice, the silicon‐based nanoconstructs provide MRI contrast enhancement at much smaller doses of iron (≈0.5 mg of Fe kg^?1 animal) as compared to current practice.     

Solution‐Processed High‐Performance Tetrathienothiophene‐Based Small Molecular Blends for Ambipolar Charge Transport

Four soluble dialkylated tetrathienoacene ( TTAR) ‐based small molecular semiconductors featuring the combination of a TTAR central core, π‐conjugated spacers comprising bithiophene ( bT ) or thiophene ( T ), and with/without cyanoacrylate ( CA ) end‐capping moieties are synthesized and characterized. The molecule DbT‐TTAR exhibits a promising hole mobility up to 0.36 cm² V^?1 s^?1 due to the enhanced crystallinity of the microribbon‐like films. Binary blends of the p‐type DbT‐TTAR and the n‐type dicyanomethylene substituted dithienothiophene‐quinoid ( DTTQ‐11 ) are investigated in terms of film morphology, microstructure, and organic field‐effect transistor (OFET) performance. The data indicate that as the DbT‐TTAR content in the blend film increases, the charge transport characteristics vary from unipolar (electron‐only) to ambipolar and then back to unipolar (hole‐only). With a 1:1 weight ratio of DbT‐TTAR DTTQ‐11 in the blend, well‐defined pathways for both charge carriers are achieved and resulted in ambipolar transport with high hole and electron mobilities of 0.83 and 0.37 cm² V^?1 s^?1, respectively. This study provides a viable way for tuning microstructure and charge carrier transport in small molecules and their blends to achieve high‐performance solution‐processable OFETs.     

Harmonic distortion analysis using an improved charge sheet model for PD SOI MOSFETs

This work presents an Improved Charge Sheet compact Model (ICSM) especially valuable for distortion analysis, where precise calculation of derivatives of at least third order is required. A new expression for the charge is used in the calculation of the current. Vertical electric field, mobility and DIBL are represented using previously reported for other purposes more precise expressions. The very good agreement obtained between experimental PD SOI MOSFETs with channel lengths from 0.32 to 10 μm and modeled currents, derivatives and distortion figures is shown.     

Complementary integrated circuits on plastic foil using inkjet printed n- and p-type organic semiconductors: Fabrication,characterization, and circuit analysis

Complementary thin-film transistor circuits composed of 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS–PEN) and a rylene carboxylic diimide derivative for p- and n-channel thin-film transistors (TFTs) were fabricated on flexible foils. The so-called staggered TFT configuration is used, meaning that the semiconductors layers are deposited last. The work-function of the injecting gold electrodes were modified using several self-assembled monolayers (SAMs). For optimized contacts the mobility of the n- and p-channel TFTs was 0.5 cm²/Vs and 0.2 cm²/Vs, respectively. Strongly degraded performance is obtained when the n-channel material was printed on contacts optimized for the p-channel TFT, and vice versa. This illustrates that for CMOS circuits we need careful work-function engineering to allow proper injection for both electrons and holes. We show for the first time that by using a bimolecular mixture for the SAM we can systematically vary the work function, and demonstrate how this affects the performance of discrete n-type and p-type transistors, as well as CMOS inverters and ring oscillators. Under optimal processing conditions we realized complementary 19-stage ring oscillators with 10 μs stage delay operating at 20 V.     

Contact effects in organic thin-film transistor sensors

Contact effects in organic thin-film transistors (OTFTs) sensors are here investigated specifically respect to the gate field-induced sensitivity enhancement of more than three orders of magnitude seen in a DHα6T OTFT sensor exposed to 1-butanol vapors. This study shows that such a sensitivity enhancement effect is largely ascribable to changes occurring to the transistor channel resistance. Effects, such as the changes in contact resistance, are seen to influence the low gate voltage regime where the sensitivity is much lower.     

Behavioural models for distributed Fractal components

This paper presents a formal behavioural specification framework for specifying and verifying the correct behaviour of distributed Fractal components. The first contribution is a parameterised and hierarchical behavioural model called pNets that serves as a low-level semantic framework for expressing the behaviour of various classes of distributed languages and as a common internal format for our tools. Then, we use this model to define the generation of behavioural models for applications ranging from sequential Fractal components, to distributed objects, and finally to distributed components. Our models are able to characterise both functional and non-functional behaviours and the interaction between the two concerns. Finally, this work has resulted in the development of tools allowing the non-expert programmer to specify the behaviour of his components and (semi)automatically verify properties of his application.     

Densification of Oxide Nanoparticle Thin Films by Irradiation with Visible Light

A technique is presented that allows for altering of the physical characteristics of films of TiO₂ nanoparticles by exposure to visible light. In this technique, dye‐sensitized oxide nanoparticles are deposited on a substrate by dip‐coating. Photodissociation of the organic ligand layer leads to cross‐linking of the nanoparticles. Consequently, irradiated films have a decreased porosity, an increased index of refraction and an increased hydrophobicity. Films irradiated with green light are compared to films irradiated with UV light. Within experimental error, visible‐ and UV‐illumination induces the same changes in the films. The mechanism of surfactant elimination in dye‐sensitized oxide particles is discussed, patterning is demonstrated, and prospective applications of the technique are considered.     

Supramolecular Order of Solution‐Processed Perylenediimide Thin Films: High‐Performance Small‐Channel n‐Type Organic Transistors

N,N′‐1H,1H‐perfluorobutyl dicyanoperylenecarboxydiimide (PDIF‐CN₂), a soluble and air stable n‐type molecule, undergoes significant reorganization upon thermal annealing after solution deposition on several substrates with different surface energies. Interestingly, this system exhibits an exceptional edge‐on orientation regardless of the substrate chemistry. This preferential orientation is rationalized in terms of strong intermolecular interactions between the PDIF‐CN₂ molecules. The presence of a pronounced π–π stacking is confirmed by combining near‐edge X‐ray absorption fine structure spectroscopy (NEXAFS), dynamic scanning force microscopy (SFM) and surface energy measurements. The remarkable charge carrier mobility measured in field‐effect transistors, using both bottom‐ and top‐contact (bottom‐gate) configurations, underlines the importance of strong intermolecular interactions for the realization of high performing devices.     

Kitkaite NiTeSe,an Ambient-Stable Layered Dirac Semimetal with Low-Energy Type-II Fermions with Application Capabilities in Spintronics and Optoelectronics

The emergence of Dirac semimetals has stimulated growing attention, owing to the considerable technological potential arising from their peculiar exotic quantum transport related to their nontrivial topological states. Especially, materials showing type-II Dirac fermions afford novel device functionalities enabled by anisotropic optical and magnetotransport properties. Nevertheless, real technological implementation has remained elusive so far. Definitely, in most Dirac semimetals, the Dirac point lies deep below the Fermi level, limiting technological exploitation. Here, it is shown that kitkaite (NiTeSe) represents an ideal platform for type-II Dirac fermiology based on spin-resolved angle-resolved photoemission spectroscopy and density functional theory. Precisely, the existence of type-II bulk Dirac fermions is discovered in NiTeSe around the Fermi level and the presence of topological surface states with strong (≈50%) spin polarization. By means of surface-science experiments in near-ambient pressure conditions, chemical inertness towards ambient gases (oxygen and water) is also demonstrated. Correspondingly, NiTeSe-based devices without encapsulation afford long-term efficiency, as demonstrated by the direct implementation of a NiTeSe-based microwave receiver with a room-temperature photocurrent of 2.8 µA at 28 GHz and more than two orders of magnitude linear dynamic range. The findings are essential to bringing to fruition type-II Dirac fermions in photonics, spintronics, and optoelectronics.     

Fully digital BPSK demodulator for satellite supressed carrier telecommand system

In this paper, we present the design of a fully digital binary phase shift keying demodulator for application in satellite high‐rate suppressed carrier telecommand system. The proposed system digitalizes the received signal in the intermediate frequency stage using bandpass sampling technique, and the resulting baseband signal is used to synchronization of symbol and phase and to bit detection. The design of all functional modules is presented in details. Another innovation presented in this work is the inclusion of a non‐linearity in the phase synchronizer module to permit its operation independent from the signal amplitude. Moreover, aiming the characterization and performance evaluation of the system, we do some original mathematical analyses. Finally, test results show that the demodulator complies all the project requirements, and the prototype implementation loss, in terms of bit energy to noise power density ratio, is less than 0.3 dB. Copyright © 2016 John Wiley & Sons, Ltd.