Advanced Functional Materials

The cover shows controllable underwater oil-adhesion films assembled from nonspherical latex particles. On page 4436, Jingxia Wang, Yanlin Song, and co-workers show how the underwater oil adhesion force of films could be effectively controlled from high adhesion to low adhesion when the films are assembled from latex particles of spherical, cauliflower-like and single-cavity structure, respectively. This offers significant insight for the design and creation of novel underwater anti-fouling materials.

The loading of NiO provides a new strategy to achieve humidity-independent SnO₂ gas sensors. When NiO is loaded to hierarchical SnO₂ nanostructures, the humidity dependence of the gas sensing characteris-tics, such as gas sensitivity, response speed, recovery speed, and resistance in air, are decreased to a negli-gible level. On page 4456, Nicolae Barsan, Jong-Heun Lee, and co-workers confirmed that NiO plays the key role of a strong humidity absorber and protects the SnO₂ from the influence of water-derived species.

Polyfluorenes are widely studied for applications in polymer light-emitting diodes. Unfortunately, blue-light-emitting polyfluorenes suffer from rapid degradation at ambient conditions, resulting in green emission. On page 4502, Paul W. M. Blom and co-workers study the effect of ketone defects on the charge transport and recombination properties of such polyfluorenes. Charge transport is strongly hindered by both electron and hole trap-ping on these ketone defects. Additionally, the green emission is shown to originate from a trap-assisted recombination process.

The structural features of monolithically ordered, hierarchical surface reliefs can be deterministically controlled by localized or co-operative holographic photofluidization of azopolymer. The observations of morphological evolution, presented by Seungwoo Lee, Jung-Ki Park, and co-workers on page 4412, address a long-standing problem: the origin of holography-induced surface relief grating formation onto azopolymer film in terms of azopolymeric photoflows and directional photofluidization.

Directional photofluidization allows a facile fabrication of various large-area, hierarchically ordered monolithic surface-relief gratings (SRGs) with precisely controlled structural features. Furthermore, the use of a micrometer-scale periodic line pattern rather than a flat thin film, which has been generally used in conventional SRG studies, provides a powerful way to quantify the direction of flows of azopolymer during SRG formation.

Molecularly imprinted polymeric nanoparticles (MIPNPs) for atrial natriuretic peptide (ANP) are prepared by precipitation polymerization in the presence of the template, NH₂–SLRRSS–CONH₂, which is a short peptide from ANP. This unique MIPNP contains cavities that can recognize and bind ANP in a cell-culture medium or in human-plasma samples.

A tandem photovoltaic cell based on a MoO₃-modified graphene intermediate layer (IML) is demonstrated. In comparison to a single photovoltaic cell, tandem cells with a MoO₃-modified graphene IML show a nearly doubled V_oc and J_sc in series connection and parallel connection, respectively.

Sticky films: A controllable underwater oil-adhesion interface assembled from nonspherical latex particles is presented. This fabrication of functional films with special oil-adhesion properties will provide new insight for design and creation of novel functional films.

Polymer transistors with high bias-stability comparable to amorphous silicon are realized by optimizing the molecular weight of copolymer semiconductor on dielectric surface. Thermally structural transition from liquid-crystalline to semi-crystalline phases strongly in thin films affects the device performances (charge-carrier mobility and electrical bias-stability) as well as the molecular ordering and the morphological features.

A matrix-free strategy based on pulsed-LDI from nitrocellulose membranes modified with AuNPs is developed for the quantification of Pb²⁺ ions in complicated biofluids with sub-nanomolar sensitivity. This approach provides high sensitivity and selectivity toward Pb²⁺ ions, resulting in clean mass spectra with fewer, weaker signals from AuNP-associated interfering agents, in contrast to noisy spectra obtained using other AuNP-assisted LDI approaches.

The humidity dependenceof the gas-sensing characteristics in a SnO₂-based sensor is reduced to a negligible level by doping with NiO. NiO-doped-SnO₂ hierarchical nanostructures show highly sensitive, ultrafast response and recovery speeds with little dependence on humidity. The NiO plays the roles of a humidity absorber and a catalytic promoter.

ZnO nanowire (NW)-based UV sensors are fabricated in large scale by integrating multiple NWs connected in parallel via the contact printing method. The flexible sensors display a very high photoresponse current of 14.1 mA and on/off current ratio of 120 000.

A novel OA/ionic liquid two-phase system combining the merits of thermal decomposition method, the IL-based strategy, and the two-phase approach is introduced to synthesize high-quality lanthanide-doped NaGdF4 upconversion nanocrystals with different crystal-phases in OA-phase and IL-phase through a one-step controllable reaction. The synthesized lanthanide-doped NaGdF₄ upconversion nanocrystals are effective for dual-mode UCL imaging and X-ray imaging in vivo.

The non-contact dynamic scanning force microscopy image of a solution-processed perylenediimide thin film shows a layer-by-layer structure with closed molecular planes, upon annealing. Antonio Facchetti, Yueh-Lin Loo, Maria A. Loi, and co-workers show, on page 4479, that the strong intermolecular π–π stacking interactions induce long-range supramolecular order, comparable to that of highly crystalline vapor-deposited films. Correlations between molecular orientation and device performance are highlighted in high-performance small-channel n-type organic transistors.

The exceptional supramolecular order of solution-processed perylenediimide thin films is demonstrated. Investigation of their self-assembly on different surfaces upon annealing reveals long-range molecular packing and orientation comparable to those of highly oriented vapor-deposited small molecules. By studying charge transport and injection properties of the resulting field-effect transistors, fundamental correlations between molecular orientation and device performance are highlighted.

A strong nonlinearity is revealed by switching kinetics studies of strontium titanate memristive devices. Based on electrothermal finite element method simulations of the temperature distribution in these devices, thermal enhancement of oxygen vacancies inside a disc region is identified as the dominating factor in this nonlinearity. Design rules for optimized cell design are provided.

First-principle defect calculations reveal that cation anti-sites dominate doping in spinel oxides. Based on their ionization level we found four doping types (DTs). Most of the DT-1 spinels are compensated (c) n- or p- or insulators, while DT-2 are exclusively p-type (p), DT-3 are exclusively n-type (n) and DT-4 are mostly intrinsic (i). A number of compounds belonging to DT-1, DT-2, and DT-4 is presented.

The consequences of ketone defects in poly(9,9-dioctylfluorene) on charge transport and recombination are investigated by analyzing light-emitting diodes, hole-only, and electron-only devices. Charge transport is observed to be strongly hindered by both electron and hole trapping on these ketone defects. The green emission from ketone defects is shown to originate from a trap-assisted recombination process.

Altering the π-system of perylene imide in side-chain homopolymers permits the tuning of electronic character (p-type to n-type semiconductor) and improved optical absorption. The highly soluble polymers PPDB and PPDI exhibit liquid-crystalline mesophases over a broad temperature range. These properties make the two novel compounds interesting for optoelectronic applications and can potentially help with optimization of morphology and device performance of organic photovoltaic cells.

Photoelectric coooperative induced patterned wetting on superhydrophobic aligned-TiO₂/AAO-nanopore array films with a high mechanical strength and excellent controllability for multiple transfer printing is demonstrated. This work is new progress in liquid reprography, and is promising for gearing up the application of photoelectric cooperative liquid reprography.

Better use of sunlight: The performance of polymer:polymer solar cells is improved by doping an electron-accepting polymer with an organosulfonic acid.

A novel electronic spectroscopy instrument to analyze solution processable electrochromic polymer exhibits rapid switching times on the order of 400–700 ms with high transmittance contrasts over 40 Δ%T. The spectrometer detector is capable of rapid data acquisation to track the electrochromic change, with one spectrum collected every 2 ms, in order to elucidate properties of sub-second switching electrochromes.

A new strategy to achieve triple shape memory properties is reported by using side-chain liquid-crystalline (SCLC) type random terpolymer networks that exhibit smectic mesophases. Unique microphase separated morphologies within smectic layers divided into backbone-rich and mesogen-rich domains are exploited and the importance of motional decoupling between these two domains for the resulting shape-memory behavior is highlighted.

Nanolaminates with alternating layers of Cu₅₀Zr₅₀ metallic glasses and nanocrystalline Cu are synthesized and it is found that that samples with an optimal composition of 112-nm-thick metallic-glass layers and 16-nm-thick Cu layers demonstrate a maximum strength of 2.513 GPa. This is 33% greater than that predicted by the rule-of-mixtures and 25% better than that of pure Cu₅₀Zr₅₀ metallic glass.

The tribological behavior of aqueous carbon nanotubes dispersions was studied using a surface forces apparatus and shows promising lubricant additive properties. The friction coefficient is in the range 0.30–0.55. The lateral sliding promotes an accumulation, rather than squeezing out, of nanotubes between the surfaces, that reduces the surface adhesion, and – more importantly – protects the surfaces from becoming damaged (wear).<?br?>

The first example of a turn-on fluorescent sensor for cysteine and logic gates is constructed by exploring the combination of graphene oxide (GO) and DNA metallization. The protocol relies on the large fluorescence enhancement resulting from the cysteine-mediated DNA hybridization and the different binding affinities of GO to single- and double-stranded DNA.

The heating power of metallic iron magnetic nanoparticles with diameters ranging from 5.5 to 28 nm is measured in an alternating applied magnetic field with a frequency of 54 kHz and an amplitude ranging from 8 to 60 mT. The optimal size is visible as a maximum in the curve. Optimized nanoparticles display losses of 8 mJ g⁻¹ at this frequency.

This paper describes the preparation, characterization and high performance of water-based isotropically conductive adhesives (WBICAs) as a novel, green, versatile, ultralow-cost, and printable conductive composite. The WBICA-supported LED and RFID chips are demonstrated. Their unique water-based and room- temperature-curable characters render them superior in mass producing flexible electronic devices on ubiquitous substrates e.g. paper, textile, and wood.

A novel method is established for permittivity enhancement of a silicone matrix for dielectric elastomer actuators by molecular level modifications of the elastomer matrix. A push-pull dipole is synthesized to be compatible with the silicone crosslinking chemistry, allowing direct grafting to the crosslinker molecules, which results in an improvement of actuation strain by a factor of six.