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Nanogenerators and self-powered nanosensors have shown the potential to power low-consumption electronics and human-machine interfaces, but their practical implementation requires reliable, environmentally friendly and scalable processes for manufacturing and processing. Furthermore, the emerging flexible and wearable electronics technology demands direct fabrication onto innovative substrates such as paper and plastics typically incompatible with high process temperatures. This article presents a plasma synthesis approach for the fabrication of piezoelectric nanogenerators (PENGs) and self-powered sensors on paper substrates. Polycrystalline ZnO nanocolumnar thin films are deposited by plasma-enhanced chemical vapour deposition on common paper supports using a microwave electron cyclotron resonance reactor working at room temperature yielding high growth rates and low structural and interfacial stresses. Applying Kinetic Monte Carlo simulation, we elucidate the basic shadowing mechanism behind the characteristic microstructure and porosity of the ZnO thin films, relating them to an enhanced piezoelectric response to periodic and random inputs. The piezoelectric devices are assembled by embedding the ZnO films in polymethylmethacrylate (PMMA) and using Au thin layers as electrodes in two different configurations, namely laterally and vertically contacted devices. We present the response of the laterally connected devices as a force sensor for low-frequency events with different answers to the applied force depending on the impedance circuit, i.e. load values range, a behaviour that is theoretically analyzed. The characterization of the vertical devices in cantilever-like mode reaches instantaneous power densities of 80 nW/cm with a mean power output of 20 nW/cm. Besides, we analyze their actual-scenario performance by activation with a fan and handwriting. Overall, this work demonstrates the advantages of implementing plasma deposition for piezoelectric films to dev

Two-dimensional materials present exceptional crystal elasticity and provide an ideal platform to tune electrical and optical properties through the application of strain. Here we extend recent research on strain engineering in monolayer molybdenum disulfide using an adamantane plasma polymer pinning layer to achieve unprecedented crystal strains of 2.8%. Using micro-reflectance spectroscopy, we report maximum strain gauge factors of −99.5 meV/% and −63.5 meV/% for the A and B exciton of monolayer MoS, respectively, with a 50 nm adamantane capping layer. These results are corroborated with photoluminescence and Raman measurements on the same samples. Taken together, our results indicate that adamantane polymer is an exceptional capping layer to transfer substrate-induced strain to a 2D layer and achieve higher levels of crystal strain.

We introduce herein the advanced application of low-pressure plasma procedures for the development of piezo and triboelectric mode I hybrid nanogenerators. Thus, plasma assisted deposition and functionalization methods are presented as key enabling technologies for the nanoscale design of ZnO polycrystalline shells, the formation of conducting metallic cores in core@shell nanowires, and for the solventless surface modification of polymeric coatings and matrixes. We show how the perfluorinated chains grafting of polydimethylsiloxane (PDMS) provides a reliable approach to increase the hydrophobicity and surface charges at the same time that keeping the PDMS mechanical properties. In this way, we produce efficient Ag/ZnO convoluted piezoelectric nanogenerators supported on flexible substrates and embedded in PDMS compatible with a contact–separation triboelectric architecture. Factors like crystalline texture, ZnO thickness, nanowires aspect ratio, and surface chemical modification of the PDMS are explored to optimize the power output of the nanogenerators aimed for harvesting from low-frequency vibrations. Just by manual triggering, the hybrid device can charge a capacitor to switch on an array of color LEDs. Outstandingly, this simple three-layer architecture allows for harvesting vibration energy in a wide bandwidth, thus, we show the performance characteristics for frequencies between 1 Hz and 50 Hz and demonstrate the successful activation of the system up to ca. 800 Hz.

The opto-electronic properties of small-molecules and functional dyes usually differ when incorporated into solid matrices with respect to their isolated form due to an aggregation phenomenon that alters their optical and fluorescent properties. These spectroscopic modifications are studied in the framework of the exciton theory of aggregates, which has been extensively applied in the literature for the study of molecular aggregates of the same type of molecules (homoaggregation). Despite the demonstrated potential of the control of the heteroaggregation process (aggregation of different types of molecules), most of the reported works are devoted to intramolecular aggregates, complex molecules formed by several chromophores attached by organic linkers. The intramolecular aggregates are specifically designed to hold a certain molecular structure that, on the basis of the exciton theory, modifies their optical and fluorescent properties with respect to the isolated chromophores that form the molecule. The present article describes in detail the incorporation of Rhodamine 6G (Rh6G) and 800 (Rh800) into polymeric matrices of poly-(methyl methacrylate), PMMA. The simultaneous incorporation of both dyes results in an enhanced fluorescent emission in the near-infrared (NIR), originating from the formation of ground-state Rh6G-Rh800 intermolecular heteroaggregates. The systematic control of the concentration of both rhodamines provides a model system for the elucidation of the heteroaggregate formation. The efficient energy transfer between Rh6G and Rh800 molecules can be used as wavelength shifters to convert effectively the light from visible to NIR, a very convenient wavelength range for many practical applications which make use of inexpensive commercial detectors and systems.

The large area scalable fabrication of supported porous metal and metal oxide nanomaterials is acknowledged as one of the greatest challenges for their eventual implementation in on-device applications. In this work, we will present a comprehensive revision and the latest results regarding the pioneering use of commercially available metal phthalocyanines and porphyrins as solid precursors for the plasma-assisted deposition of porous metal and metal oxide films and three-dimensional nanostructures (hierarchical nanowires and nanotubes). The most advanced features of this method relay on its ample general character from the point of view of the porous material composition and microstructure, mild deposition and processing temperature and energy constrictions and, finally, its straightforward compatibility with the direct deposition of the porous nanomaterials on processable substrates and device-architectures. Thus, taking advantage of the variety in the composition of commercially available metal porphyrins and phthalocyanines, we present the development of metal and metal oxides layers including Pt, CuO, Fe2O3, TiO2, and ZnO with morphologies ranging from nanoparticles to nanocolumnar films. In addition, we combine this method with the fabrication by low-pressure vapor transport of single-crystalline organic nanowires for the formation of hierarchical hybrid organic@metal/metal-oxide and @metal/metal-oxide nanotubes. We carry out a thorough characterization of the films and nanowires using SEM, TEM, FIB 3D, and electron tomography. The latest two techniques are revealed as critical for the elucidation of the inner porosity of the layers.

The large area scalable fabrication of supported porous metal and metal oxide nanomaterials is acknowledged as one of the greatest challenges for their eventual implementation in on-device applications. In this work, we will present a comprehensive revision and the latest results regarding the pioneering use of commercially available metal phthalocyanines and porphyrins as solid precursors for the plasma-assisted deposition of porous metal and metal oxide films and three-dimensional nanostructures (hierarchical nanowires and nanotubes). The most advanced features of this method relay on its ample general character from the point of view of the porous material composition andmicrostructure,mild deposition and processing temperature and energy constrictions and, finally, its straightforward compatibility with the direct deposition of the porous nanomaterials on processable substrates and device-architectures. Thus, taking advantage of the variety in the composition of commercially available metal porphyrins and phthalocyanines, we present the development of metal and metal oxides layers including Pt, CuO, Fe2O3, TiO2, and ZnO with morphologies ranging from nanoparticles to nanocolumnar films. In addition, we combine this method with the fabrication by low-pressure vapor transport of single-crystalline organic nanowires for the formation of hierarchical hybrid organic@metal/metal-oxide and @metal/metal-oxide nanotubes. We carry out a thorough characterization of the films and nanowires using SEM, TEM, FIB 3D, and electron tomography. The latest two techniques are revealed as critical for the elucidation of the inner porosity of the layers.

Damage-free encapsulation of molecular structures with functional nanolayers is crucial to protect nanodevices from environmental exposure. With nanoscale electronic, optoelectronic, photonic, sensing, and other nanodevices based on atomically thin and fragile organic matter shrinking in size, it becomes increasingly challenging to develop nanoencapsulation that is simultaneously conformal at atomic scale and does not damage fragile molecular networks, while delivering added device functionality. This work presents an effective, plasma-enabled, potentially universal approach to produce highly conformal multifunctional organic films to encapsulate atomically thin graphene layers and metalorganic nanowires, without affecting their molecular structure and atomic bonding. Deposition of adamantane precursor and gentle remote plasma chemical vapor deposition are synergized to assemble molecular fragments and cage-like building blocks and completely encapsulate not only the molecular structures, but also the growth substrates and device elements upon nanowire integration. The films are insulating, transparent, and conformal at sub-nanometer scale even on near-tip high-curvature areas of high-aspect-ratio nanowires. The encapsulated structures are multifunctional and provide effective electric isolation, chemical and environmental protection, and transparency in the near-UV–visible–near-infrared range. This single-step, solvent-free remote-plasma approach preserves and guides molecular building blocks thus opening new avenues for precise, atomically conformal nanofabrication of fragile nanoscale matter with multiple functionalities.

Herein, we present the development of supported organic nanofabrics formed by a conformal polymer-like interconnection of small-molecule organic nanowires and nanotrees. These organic nanostructures are fabricated by a combination of vacuum and plasma-assisted deposition techniques to generate step by step, single-crystalline organic nanowires forming one-dimensional building blocks, organic nanotrees applied as three-dimensional templates, and the polymer-like shell that produces the final fabric. The complete procedure is carried out at low temperatures and is compatible with an ample variety of substrates (polymers, metal, ceramics; either planar or in the form of meshes) yielding flexible and low solid-fraction three-dimensional nanostructures. The systematic investigation of this progressively complex organic nanomaterial delivers key clues relating their wetting, nonwetting, and anti-icing properties with their specific morphology and outer surface composition. Water contact angles higher than 150° are attainable as a function of the nanofabric shell thickness with outstanding freezing-delay times (FDT) longer than 2 h at −5 °C. The role of the extremely low roughness of the shell surface is settled as a critical feature for such an achievement. In addition, the characteristic interconnected microstructure of the nanofabrics is demonstrated as ideal for the fabrication of slippery liquid-infused porous surfaces (SLIPS). We present the straightforward deposition of the nanofabric on laser patterns and the knowledge of how this approach provides SLIPS with FDTs longer than 5 h at −5 °C and 1 h at −15 °C.

A compromise between high power conversion efficiency and long-term stability of hybrid organic–inorganic metal halide perovskite solar cells is necessary for their outdoor photovoltaic application and commercialization. Herein, a method to improve the stability of perovskite solar cells under water and moisture exposure consisting of the encapsulation of the cell with an ultrathin plasma polymer is reported. The deposition of the polymer is carried out at room temperature by the remote plasma vacuum deposition of adamantane powder. This encapsulation method does not affect the photovoltaic performance of the tested devices and is virtually compatible with any device configuration independent of the chemical composition. After 30 days under ambient conditions with a relative humidity (RH) in the range of 35–60%, the absorbance of encapsulated perovskite films remains practically unaltered. The deterioration in the photovoltaic performance of the corresponding encapsulated devices also becomes significantly delayed with respect to devices without encapsulation when vented continuously with very humid air (RH > 85%). More impressively, when encapsulated solar devices were immersed in liquid water, the photovoltaic performance was not affected at least within the first 60 s. In fact, it has been possible to measure the power conversion efficiency of encapsulated devices under operation in water. The proposed method opens up a new promising strategy to develop stable photovoltaic and photocatalytic perovskite devices

This article establishes the bases for a vacuum and plasma supported methodology for the fabrication at mild temperatures of nanostructured platinum in the form of porous layers and nanocolumns using platinum octaethylporphyrin as precursor. In addition, the application of these materials as tunable optical filters and nano-counterelectrodes is proved. On one hand, the transparency in the ultraviolet-visible-near infrared range can be adjusted precisely between 70% and 1% by tuning the deposition and processing conditions, obtaining a high spectral planarity. Deviations of the spectra from an ideal flat filter are below 4%, paving the way to the fabrication of neutral density filters. The transparency limit values yield a sheet resistivity of ¿1350 and 120 ¿ ¿-1, respectively. On the other hand, the catalytic properties of the nanostructures are further demonstrated by their implementation as counterelectrodes of excitonic solar cells surpassing the performance of commercial platinum as counterelectrode in a 20% of the overall cell efficiency due to simultaneous enhancement of short-circuit photocurrent and open-circuit photovoltage. One of the most interesting features of the developed methodology is its straightforward application to other metal porphyrins and phthalocyanines readily sublimable under mild vacuum and temperature conditions.

We present a low-temperature versatile protocol for the fabrication of plasma nanocomposite thin films to act as tunable emitters and optical gain media. The films are obtained by the remote plasma-assisted deposition of a 4-(dicyano-methylene)-2-methyl-6-(4-dimethylamino-styryl)-4H-pyran (DCM) laser dye alongside adamantane. The experimental parameters that determine the concentration of the dye in the films and their optical properties, including light absorption, the refractive index, and luminescence, are evaluated. Amplified spontaneous emission experiments in the DCM/adamantane nanocomposite waveguides show the improvement of the copolymerized nanocomposites’ properties compared to films that were deposited with DCM as the sole precursor. Moreover, one-dimensional distributed feed-back laser emission is demonstrated and characterized in some of the nanocomposite films that are studied. These results open new paths for the optimization of the optical and lasing properties of plasma nanocomposite polymers, which can be straightforwardly integrated as active components in optoelectronic devices.

Oblique angle deposition (OAD) is a powerful technique for the fabrication of porous nanostructured oxide thin films. OAD films typically present a columnar tilted nanostructure due to geometrical shadowing effects during the thin film growth. In this work, we study the fabrication of transparent and conducting indium tin oxide films (ITO) by OAD assisted by a microwave ECR plasma. The objective of assisting the deposition with a plasma discharge is to modify the growth mechanism of the OAD process introducing additional parameters to control the columnar microstructure, composition, porosity of the films. The results indicate the OAD ITO deposition assisted by the plasma discharge is a very effective process to develop in-plane structural anisotropy in the ITO nanocolumnar films what determines their electrical properties.

We report on dye-based photonic sensing systems which are fabricated and packaged at wafer scale. For the first time luminescent organic nanocomposite thin-films deposited by plasma technology are integrated in photonic sensing systems as active sensing elements. The realized dye-based photonic sensors include an environmental NO2 sensor and a sunlight ultraviolet light (UV) A+B sensor. The luminescent signal from the nanocomposite thin-films responds to changes in the environment and is selectively filtered by a photonic structure consisting of a Fabry-Perot cavity. The sensors are fabricated and packaged at wafer-scale, which makes the technology viable for volume manufacturing. Prototype photonic sensor systems have been tested in real-world scenarios. (C) 2016 Elsevier B.V. All rights reserved., QC 20160410

We report on dye-based photonic sensing systems which are fabricated and packaged at wafer scale. For the first time luminescent organic nanocomposite thin-films deposited by plasma technology are integrated in photonic sensing systems as active sensing elements. The realized dye-based photonic sensors include an environmental NO sensor and a sunlight ultraviolet light (UV) A + B sensor. The luminescent signal from the nanocomposite thin-films responds to changes in the environment and is selectively filtered by a photonic structure consisting of a Fabry-Perot cavity. The sensors are fabricated and packaged at wafer-scale, which makes the technology viable for volume manufacturing. Prototype photonic sensor systems have been tested in real-world scenarios.

This study shows the fabrication by a dry approach at mild temperature (<150 °C) of a photoluminescence white light emitting hybrid layer. The white light emitter is obtained by evaporation of two photoluminescent small molecules, a blue (1,3,5-triphenyl-2-pyrazoline (TPP)) and an orange (Rubrene) dye within the porous of an SiO host film fabricated by glancing angle deposition. Fluorescence (Föster) resonant energy transfer between the two organic dyes allows the emission of the combined system upon excitation of the TPP molecule at wavelength of 365 nm. The distribution of the organic molecule within the host layer is analyzed as a function of the substrate temperature and vacuum conditions and the required conditions for the white emission determined by finely controlling the TPP:Rubrene ratio. The full vacuum processing of the hybrid layers provides a straightforward route for the incorporation of the white light emitters as optical defect within 1D Bragg microcavities. As a consequence, directional emission of the system is achieved which allows the development of wide-range in situ tunable photoluminescent devices.

In this paper, we report on the measurement and modeling of enhanced optical refractometric sensors based on whispering gallery modes. The devices under test are optical microresonators made of silicon nitride on silicon oxide, which differ in their sidewall inclination angle. In our approach, these microresonators are vertically coupled to a buried waveguide with the aim of creating integrated and cost-effective devices. Device modeling shows that the optimization of the device is a delicate balance of the resonance quality factor and evanescent field overlap with the surrounding environment to analyze. By numerical simulations, we show that the microdisk thickness is critical to yield a high figure of merit for the sensor and that edge inclination should be kept as high as possible. We also show that bulk-sensing figures of merit as high as 1600 RIU1 (refractive index unit) are feasible.

Transparent nanocolumnar porous ZnO thin films have been prepared by plasma-enhanced chemical vapor deposition. By controlling the H2/O2 ratio in the plasma gas, the deposition conditions were optimized to obtain an intense exciton emission at around 381 nm and virtually no luminescence in the visible region associated with electronic states in the gap. The intensity of the exciton band varied significantly and reversibly with the partial pressure of oxygen in the environment. This behavior and its variations with temperature and water vapor sustain the use of these thin films as photonic sensors of oxygen. Further experiments in liquid water show that fluorescence intensity also varies with the amount of dissolved oxygen even for concentrations lower than 0.02 mg/L where commercial oxygen galvanic sensors show limited sensitivity. These results and the use of ZnO as photonic sensor of oxygen are discussed by assuming a classical mechanism involving the photoactivated adsorption of oxygen when this oxide is irradiated with UV light during its fluorescence interrogation.