Polyaniline nanofibres can be prepared by a number of methods based on chemical oxidative polymerization and in situ adsorption polymerization. However, the lack of alignment in these nanostructures makes them unsuitable for many applications. Here, we report a simple approach to chemical oxidative polymerization that can control the growth and simultaneous alignment of polyaniline nanofibres grown on a range of conducting and non-conducting substrates in a wide variety of sizes. The diameters of the tips of the nanofibres can be controlled within the range 10-40 nm, and the average length can be controlled within the range 70-360 nm. Moreover, the coatings display a range of properties including superhydrophilicity and superhydrophobicity. Such nanostructured coatings may be useful for applications such as anti-fog coatings, self-cleaning surfaces, DNA manipulation, transparent electrodes for low-voltage electronics, and chemical and biological sensors.

Perovskite light-emitting diodes (LEDs) have recently attracted great research interest for their narrow emissions and solution processability. Remarkable progress has been achieved in green perovskite LEDs in recent years, but not blue or red ones. Here, highly efficient and spectrally stable red perovskite LEDs with quasi-2D perovskite/poly(ethylene oxide) (PEO) composite thin films as the light-emitting layer are reported. By controlling the molar ratios of organic salt (benzylammonium iodide) to inorganic salts (cesium iodide and lead iodide), luminescent quasi-2D perovskite thin films are obtained with tunable emission colors from red to deep red. The perovskite/polymer composite approach enables quasi-2D perovskite/PEO composite thin films to possess much higher photoluminescence quantum efficiencies and smoothness than their neat quasi-2D perovskite counterparts. Electrically driven LEDs with emissions peaked at 638, 664, 680, and 690 nm have been fabricated to exhibit high brightness and external quantum efficiencies (EQEs). For instance, the perovskite LED with an emission peaked at 680 nm exhibits a brightness of 1392 cd m and an EQE of 6.23%. Moreover, exceptional electroluminescence spectral stability under continuous device operation has been achieved for these red perovskite LEDs.

This letter describes the fabrication of three-dimensional particulate-like hydrogel microstructures using a combination of soft lithography and volume expansion induced self-folding. Bilayer structures are produced by solvent casting and photocuring of liquid resins. They curl into three-dimensional (3D) structures upon contacting with water due to differential swelling of the two layers. The curvature can be controlled by adjusting the polymer composition of the primary swelling layer. A simple semiempirical mathematical model is used to predict this self-folding behavior. By designing the two-dimensional (2D) shapes of the bilayers, this technique can lead to complicated 3D microstructures.

Organic metal halide hybrids with zero-dimensional (0D) structure at the molecular level, or single-crystalline bulk assemblies of metal halides, are an emerging class of light-emitting materials with high photoluminescence quantum efficiencies (PLQEs) and color tunability. Here we report the synthesis and characterization of a new single-crystalline bulk assembly of metal halide clusters, (bmpy) 9 [ZnCl 4 ] 2 [Pb 3 Cl 11 ] (bmpy: 1-butyl-1-methylpyrrolidinium), which exhibits green emission peaked at 512 nm with a remarkable near-unity PLQE at room temperature. Detailed structural and photophysical studies suggest that there are two emitting states in [Pb 3 Cl 11 ] 5− clusters, whose populations are strongly dependent on the surrounding molecular environment that controls the excitedstate structural distortion of [Pb 3 Cl 11 ] 5− clusters. High chemical-and photostability have also been demonstrated in this new material.

Highly ordered arrays of stretched DNA molecules were generated over the millimeter scale by using a modified molecular combing method and soft lithography. Topological micropatterning on polydimethyl siloxane stamps was used to mediate the dynamic assembly of DNA molecules into arranged nonostrand arrays. These arrays consisted of either short nanostrands of several micrometers with fixed length and orientation or long nanostrands up to several hundred micrometers in length. The nanostrand arrays were transferred onto flat solid surfaces by contact printing, allowing for the creation of more complex patterns. This technique has potential applications for the construction of next-generation DNA chips and functional circuits of DNA-based 1D nanostructures. molecular combing ͉ soft lithography P atterning DNA molecules at the micrometer scale forms the basis of DNA chips, a widely used technology for genetic analysis and diagnosis (1, 2). At the molecular level, single DNA molecules have been stretched for physical mapping of genes and molecular diagnosis of diseases (3). If stretched DNA molecules can be patterned into a well defined array, large-scale and highly automated analysis may be realized. On the other hand, 1D nanostructures are of great interest for the construction of future devices (4-6). With its high aspect ratio, unique base-pairing ability, designable base sequence, and availability of various techniques for functionalization, DNA is a very attractive material for preparing 1D nanostructures for electronic, magnetic, photonic, and chemical sensing applications (7-13). The ability to position a large number of 1D nanostructures with well defined linear arrangements is a prerequisite for integrating them into functional devices. The lack of this ability is currently hindering the realization of functional devices built on DNAbased 1D nanostructures.Molecular combing is a technique for stretching, aligning, and immobilizing coiled DNA molecules in a solution onto a f lat surface through a dewetting process (3). By creating a pattern of surface structures or properties, combing can be further controlled (14 -18). A number of studies in molecular combing have been reported in the literature, but none are able to demonstrate well defined arrays. For example, a single nanofiber has been combed and placed between two electrodes in a nanojunction (14). But this method cannot control the size of nanofibers and has not demonstrated any ability to pattern nanofiber arrays covering a large area. By f lowing DNA solution through microchannels, stretched DNA molecules confined in the microchannels were obtained. Their orientation and curvature were directed by controlling the geometry of the air-water interface (15). However, the DNA molecules were randomly distributed in the microchannels. In a separate study, polystyrene lines were lithographically patterned on a substrate for end-specific binding of DNA molecules. Combing of the DNA on this substrate created lines of stretched single DNA molecules (16). A li...