A novel sensing material based on pyrene doped polyethersulfone worm-like structured thin film is developed using a facile technique for detection of nitroaromatic explosive vapours. The formation of p-p stacking in the thin fluorescent film allows a highly sensitive fluorescence quenching which is detectable by the naked eye in a response time of a few seconds.Nitroaromatic (NA) explosives are the primary constituents of many unexploded land mines worldwide.1,2 Selective, fast and low-cost detection of NA explosives, such as trinitrotoluene (TNT) and dinitrotoluene (DNT), is crucial for military operations, homeland security, and environmental safety. 3 Various analytical and spectroscopic methods have been developed for sensitive detection of NA compounds. [4][5][6][7] These instrumental techniques are mostly expensive and not portable for use in the field. The detection of NA explosives using fluorescent-based sensors has been extensively studied because of their sensitivity, portability, and short response time. [8][9][10][11][12][13] The most important report in this field was published by Swager' group. 14 They used a conjugated polymer scaffold and improved the detection sensitivity. 14 Trogler and co-workers developed a new class of fluorescent films which were fabricated by spin-coating onto suitable solid substrates for detecting NA explosives both in the air and organic solvents. 15 The underlying explosive detection mechanism of the fluorescent polymer is photo-induced electron transfer (PET) from the polymers to the NA explosives. The key feature of this phenomenon is the presence of the p-p-stacking (excimer) between the polymer chains and chromophore groups.This p-stacked formation can significantly enhance the sensing performance of films.14,15In this report, we have fabricated a novel fluorescent thin film based on the pyrene-doped polyethersulfone (Py-PES) polymer for detection of nitro-explosive vapours using a rapid and facile method. The experimental details of the preparation of this sensing film are given in ESI. † To prepare the fluorescent polymer, we chose pyrene (Py) as the fluorescent dye because of its potential to form highly emissive excited dimers, high fluorescence yield, and known fluorescence quenching sensitivity to NA compounds. 16 The driving force for the quenching mechanism of Py-PES thin films is the formation of p-p Scheme 1 Schematic representation of the quenching mechanism for the Py-PES film by TNT based on photo-electron transfer (PET) process. The main driving force for the PET process is the energy gap between the conduction band of Py-PES films and the LUMO of NA explosives. NA explosives accept the electron from exited state of pyrene due to their low LUMO energies and as a result the fluorescent film is quenched 18 (see details in ESI †).a UNAM-National Nanotechnology Research Center, Bilkent University, 06800 Ankara, Turkey. E-mail: birlik@unam.bilkent.edu.tr b Department of Chemistry, Gazi University, Polatli, 06900, Ankara, Turkey c Institute of Materials Sc...

A large-area superhydrophobic and omnidirectional antireflective nanostructured organically modified silica coating has been designed and prepared. The coating mimics the self-cleaning property of superhydrophobic lotus leaves and omnidirectional broad band antireflectivity of moth compound eyes, simultaneously. Water contact and sliding angles of the coating are around 160°and 10°, respectively. Coating improves the transmittance of the glass substrate around 4%, when coated on a single side of a glass, in visible and near-infrared region at normal incidence angles. At oblique incidence angles (up to 60°) improvement in transmission reaches to around 8%. In addition, coatings are mechanically stable against impact of water droplets from considerable heights. We believe that our inexpensive and durable multifunctional coatings are suitable for stepping out of the laboratory to practical outdoor applications.

Hot electron photovoltaics is emerging as a candidate for low cost and ultra thin solar cells. Plasmonic means can be utilized to significantly boost device efficiency. We separately form the tunneling metal-insulator-metal (MIM) junction for electron collection and the plasmon exciting MIM structure on top of each other, which provides high flexibility in plasmonic design and tunneling MIM design separately. We demonstrate close to one order of magnitude enhancement in the short circuit current at the resonance wavelengths.

separated, there are positive and negative charges generated on coated electrodes depending on the triboelectric polarity of those dielectric materials. Therefore, a perfect design for a triboelectric nanogenerator (TENG) can be achieved by choosing the most distinct materials in terms of triboelectric polarity as well as diminishing of the feature sizes of those materials down to nanometer scale for obtaining maximum contact area. [ 20 ] A list of the triboelectric materials in accordance with their polarity is presented in Table S1, Supporting Information. Working mechanisms of TENG devices are based on two mechanical motion modes, contact and sliding mode. [ 20 ] Recent studies reveal that the sliding mode has a better voltage output. [ 13 ] However, it requires a more complicated device design. The output voltage of TENGs is enhanced above 1 kV by using different material combinations and device geometries. [ 12 ] In this study, we constructed core-shell nanostructures (polyethersulfone (PES) is in the core and As 2 Se 3 is in the shell) for building a 3D TENG device ( Figure 1 a-6,a-7). Aluminum tape was used as a substrate and contact electrode for both polyetherimide (PEI) nanopillars and As 2 Se 3 core-shell nanostructures (Figure 1 a-1,a-5). Detailed information about the fabrication of the As 2 Se 3 core-shell nanostructures and the PEI nanopillars is given in the Supporting Information (see Figure S1). The fl uorination process used in the fabrication of the PEI nanopillars and surface modifi cation of the As 2 Se 3 nanostructures is given in Figure S2 in the Supporting Information. Figure S3 in the Supporting Information illustrates the fabrication process of the nanopillars.Our device can be stimulated by both motion and acoustic waves at different frequencies. We combined fl uorinated As 2 Se 3 kilometer-long core-shell nanostructures, which are produced using an iterative fi ber-drawing technique, with PEI nanopillars, which are produced by a template-based method for the construction of the contact mode TENG in a multilayer fashion. Our device has an output of maximum 1.23 mW direct current (DC) and 0.51 W peak power and can power parallel connected 38 LEDs simultaneously. Our chalcogenide-based TENG has maximum 396 V and 1.6 mA peak-to-peak output voltage and current, respectively. In addition, a fi nite element model is developed to explain contact electrifi cation between core-shell nanostructures and nanopillars using COMSOL Multiphysics. A perfect match between analytically calculated open-circuit voltage (OCV) and OCV measurement for a single layer generator was presented.To enhance the performance of triboelectric devices, there are two important parameters that play a major role in the selection of material combinations: the surface properties and triboelectric polarity. [ 20 ] Since the surface properties can be modifi ed using various techniques, the triboelectric polarity is Scavenging waste energy is an alternative prominent solution, which may play an important role regarding the wor...

A ny surface with water contact angle larger than 150°and sliding angle lower than 5°is generally referred as a superhydrophobic surface. 1 Such extremely water repellent surfaces are attracting a great deal of interest because of their potential applications, including self-cleaning materials, waterproof textiles, and prevention of ice accumulation.2 To obtain a superhydrophobic surface, two conditions must be met; micrometerand/or nanometer-sized roughness and low surface energy. 3Lithographic methods, 4À6 chemical etching, 7À9 or deposition of micrometer-and/or nanometer-sized particles 10À14 have been usually applied for roughening the surfaces, followed by surface modification with low-surface-energy molecules such as hydrocarbons or fluorinated hydrocarbons. However, such multiplestep fabrication of superhydrophobic surface requires sophisticated equipments and is labor-intensive, which make them impractical for large-area fabrication.On the other hand, simple single-step coating from solutions where roughness and low-energy surfaces are obtained simultaneously can be more desirable. For example, phase separation in polymers, 15 electrospinning, 16,17 solÀgel methods, 18,19 and hybrid micro-and nano-particles prepared via co-condensation reactions 20,21 are promising for large-area fabrication of superhydrophobic surfaces. With this insight, we developed a facile single-step method to prepare superhydrophobic surfaces directly applying dispersions of fluorocarbon containing mesoporous silica nanoparticles. Previously, Wang et al. 20 also reported superhydrophobic surfaces from fluorinated silica particles. They prepared the particles via a modified St€ ober method 22 resulting in a nonporous structure. However, mesoporosity of particles can provide extra functionality to the coatings such as antireflection due to low effective refractive indices. Therefore, we used a surfactant template method 23 to obtain mesoporous particles.We prepared the fluorinated mesoporous silica nanoparticles (FMSNs) by respective condensation of tetraethyl orthosilicate (TEOS) and perfluorooctyltriethoxysilane (PFOTS) monomers in a one-pot reaction. Surfactant molecules form self-assembled templates, and silica monomers polymerize around these templates. First, TEOS was polymerized forming mesoporous silica nanoparticles (MSNs). Then, PFOTS molecules were added to form a fluorinated layer around these MSNs; thus enabling selective deposition of PFOTS molecules on the surface of MSNs. As-prepared FMSNs were found to be hydrophobic and formed liquid marbles, which are water droplets enwrapped with hydrophobic particles. 24À26 To prepare a superhydrophobic surface with FMSNs, we dispersed the particles in an organo-modified silica sol (OSS) (prepared by using methyltrimethoxy silane as precursor) which act as a binder and provide mechanical stability. 27 The dispersions of FMSNs and OSS were spin coated on glass substrates and heat treated to cure. The coatings have static water contact angles around 160°and water droplets easil...