Abstract Asymmetrical and symmetrical push‐pull chromophore‐based on triphenylamine (TPA) donors and naphthalenediimide (NDI) acceptors are designed and successfully synthesized via [2+2] cycloaddition‐retroelectrocyclization (CA‐RE) reaction with well‐known electron‐accepting tetracyanoethylene (TCNE) and 7,7,8,8, ‐tetracyanoquinodimethane (TCNQ) groups. The novel series of compounds NDI‐TPA‐1 to NDI‐TPA‐6 were characterized to identify the influence of the TCNE and TCNQ π‐conjugated linkers on the optical, electrochemical, and electronic properties of these molecules. We found that in dichloromethane the NDI‐TPAs 1, 4, 5 , and 6 display absorbance peaks at increasing wavelengths 605, 641, 646, and 645 nm, respectively. We demonstrated that through simple chemical modification we could drop the lowest occupied molecular orbital of NDI‐TPA‐1 to 6 . Furthermore, NDI‐TPA‐1 to 6 were integrated into organic thin‐film transistors (OTFTs) via spin‐coating technique, and charge transfer properties were investigated. We found that the choice of the functional group led to either p‐type, n‐type, or ambipolar characteristics.
Supramolecular self-assembly of an octaphosphonate tetraphenyl porphyrin with three different nucleobases (adenine, cytosine, and thymine) was studied. Porphyrin 1 with 8 and 10 equiv of cytosine produces light-harvesting ring-like structures, that is, architectures similar to those observed in natural light-harvesting antenna. However, porphyrin assembled with adenine or thymine resulted in prisms and microrods, respectively. UV-vis absorption, fluorescence, and dynamic light scattering were used to determine the mode of aggregation in solution. Scanning electron microscopy and X-ray diffraction spectroscopy used to visualize the self-assembled nanostructures and their behavior in the solid state, respectively. Thus, we believe that this study may demonstrate a deeper understanding on how one needs to manipulate donor/acceptor subunits in supramolecular assemblies to construct artificial antenna architectures.
Corrosion of metallic surfaces is prevalent in the environment and is of great concern in many areas, including the military, transport, aviation, building and food industries, amongst others. Polyester and coatings containing both polyester and silica nanoparticles (SiO2NPs) have been widely used to protect steel substrata from corrosion. In this study, we utilized X-ray photoelectron spectroscopy, attenuated total reflection infrared micro-spectroscopy, water contact angle measurements, optical profiling and atomic force microscopy to provide an insight into how exposure to sunlight can cause changes in the micro- and nanoscale integrity of the coatings. No significant change in surface micro-topography was detected using optical profilometry, however, statistically significant nanoscale changes to the surface were detected using atomic force microscopy. Analysis of the X-ray photoelectron spectroscopy and attenuated total reflection infrared micro-spectroscopy data revealed that degradation of the ester groups had occurred through exposure to ultraviolet light to form COO·, -H2C·, -O·, -CO· radicals. During the degradation process, CO and CO2 were also produced.
Irrespective of the technology, we now rely on touch to interact with devices such as smart phones, tablet computers, and control panels. As a result, touch screen technologies are frequently in contact with body grease. Hence, surface deposition arises from localized inhomogeneous finger-derived contaminants adhering to a surface, impairing the visual/optical experience of the user. In this study, we examined the contamination itself in order to understand its static and dynamic behavior with respect to deposition and cleaning. A process for standardized deposition of fingerprints was developed. Artificial sebum was used in this process to enable reproducibility for quantitative analysis. Fingerprint contamination was shown to be hygroscopic and to possess temperature- and shear-dependent properties. These results have implications for the design of easily cleanable surfaces.
Tetrasulfonate-tetraphenylethylene (Su-TPE) is non-emissive in water and upon addition of a good solvent such as THF (fTHF = 95%) it displays strong fluorescence emission with a quantum yield of 6.33%.
Abstract Liquid metal‐based printing techniques are emerging as an exemplary platform for harvesting non‐layered 2D materials with a thickness down to a few nanometres, leading to an ultra‐large surface‐area‐to‐volume ratio that is ideal for sensing applications. In this work, the synthesis of 2D tin dioxide (SnO 2 ) by exfoliating the surface oxide of molten tin is reported which highlights the enhanced sensing capability of the obtained materials to ammonia (NH 3 ) gas is reported. It is demonstrated that amperometric gas sensors based on liquid metal‐derived 2D SnO 2 nanosheets can achieve excellent NH 3 sensing performance at low temperature (150 °C) with and without UV light assistance. Detection over a wide range of NH 3 concentrations (5–500 ppm) is observed, revealing a limit of detection at the parts per billion (ppb) level. The 2D SnO 2 nanosheets also feature excellent cross‐interference performance toward different organic and inorganic gas species, showcasing a high selectivity. Further, ab initio DFT calculations reveal the NH 3 adsorption mechanism is dominated by chemisorption with a charge transfer into 2D SnO 2 nanosheets. In addition, a proof of concept for prototype flexible ammonia sensors is demonstrated by depositing 2D SnO 2 on a polyimide substrate, signifying the high potential of employing liquid metal printed SnO 2 for realizing wearable gas sensors.
pH triggered self-assembly induced enhanced emission of water soluble phosphonic acid–NDI amphiphiles 1 is described. At pH 4.5, the amphiphile self-assembled into interwoven fibres, whilst a ladder-type network was observed at pH 7. At pH 9.5, NDI amphiphile assembled into more complex fractal nanostructures. Interestingly, enhancement of emission was observed under both acidic and basic conditions.
Boron doping of polyimide precursors yields films, that when ion irradiated produces high aspect ratio nanowires of 15–25 nm diameter of B substituted ∼4 nm sp2 C-clusters embedded within polyimide as shown by HRTEM, AFM and electrostatic force EFM. XPS confirmed B substitution within the sp2 structures and also showed that the presence of B during the ion induced thermal transformations enhanced N co-substitution, while the G and D Raman bands indicated a high degree of disorder within these C-nanoclusters which increased with atom substitution. Electron transport properties indicated the semiconducting behaviour of the C-nanowire arrays. Impedance spectroscopy separated electron hopping transport within these nanowires from electron tunnelling between neighbouring nanowires. Nanowires were clearly surrounded by an altered polymer interphase region of increased segmental chain mobility and higher dielectric polarisability allowing control of overall electron transport in device applications. This reactive ion beam irradiation route allows separation of chemical doping and synthesis from the nanostructure fabrication, as a new nanotechnology route.
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