Small Molecule Organic Nanostructures—Fabrication and Properties

Organic materials are of great interest for the development of low cost electronic and optoelectronic devices. Although majority of research on organic materials is concerned with synthesis of novel compounds and organic thin films, organic nanostructures are attracting increasing interest in recent years. We briefly review different growth methods of organic nanostructures, which can be roughly divided into vapor deposition methods and self-assembly techniques in solution. Then we highlight some interesting properties of organic nanostructures, as well as possible applications, includinf field emission, electronic and optoelectronic devices.

Band Edge Emission Improvement by Energy Transfer in HybridⅢ-Nitride/Organic Semiconductor Nanostructure

GaN nanorods are fabricated using inductively coupled plasma etching with Ni nano-island masks. The poly [2- methoxy-5-（2-ethyl）hexoxy-l,4-phenylenevinylene] （MEH-PPV）/GaN-nanorod hybrid structure is fabricated by depositing the MEH-PPV film on the GaN nanorods by using the spin-coating process. In the hybrid structure, the spatial separation is minimized to achieve high-emciency non-radiative resonant energy transfer. Optical properties of a novel device consisting of MEH-PPV/GaN-nanorod hybrid structure is studied by analyzing photoluminescenee （PL） spectra. Compared with the pure GaN nanorods, the PL intensity of the band edge emission of GaN in the MEH-PPV/GaN-nanorods is enhanced as much as three times, and the intensity of the yellow band is suppressed slightly. The obtained results are analyzed by energy transfer between the GaN nanorods and the MEH-PPV. An energy transfer model is proposed to explain the phenomenon.

Progress in organic photocatalysts

Organic materials have advantages of diversity,ease of functionality, self-assembly, etc. The varied mechanistic pathways also make it conceivable to design an appropriate photocatalyst for an identical reaction. From this perspective, organic photocatalysts find wide applications in homogeneous, heterogeneous photocatalysis and photoelectrochemical（PEC） solar cells. In this review, the form of the employed organic photocatalysts ranging from molecules, supported molecules, to nanostructures or thinfilm aggregates will be firstly discussed. Rational design strategies relating to each form are also provided, aiming to enhance the photoenergy conversion efficiency. Finally,the ongoing directions for future improvement of organic materials in high-quality optoelectronic devices are also proposed.

One-step synthesis of organic microwire-disk interconnected structure for miniaturized channel filters

Miniaturized channel filters are in high demand for many applications such as photonic integrated circuits, information-based technology, and platforms for investigation of light–matter interactions.Recently, several photonic schemes have been proposed to achieve nanofilters, which require sophisticated growth techniques. Here, we have fabricated microdisk whispering-gallery-mode（WGM） resonators through controlled assembly of organic materials with an emulsion-solventevaporation method. Based on this emulsion assembly method, the diameters of microdisks can be easily controlled, and more importantly, a microwire-disk interconnected structure is able to be constructed via one-step assembly. This microwire-waveguide-connected microdisk heterostructure can be utilized as a channel drop filter. Our results have demonstrated a facile way to achieve flexible WGM-based photonic components which can be integrated with other functional devices.

Advances in organic micro/nanocrystals with tunable physicochemical properties

Organic micro/nanocrystals based on small organic molecules have drawn extensive attention due to their potential application in organic field-effect transistors,electrochemical sensors,solar cells,etc.Herein,the recent advances for organic micro/nanocrystals from the perspective of molecule aggregation mode,morphology modulation,and optical property modulation are reviewed.The stacking mode and the intermolecular interaction depend on the molecular structure,which eventually determines the morphology of organic micro/nanocrystals.The morphologies of the organic micro/nanocrystals make the aggregates exhibit photon confinement or light-guiding properties as organic miniaturized optoelectronic devices.In this review,we conclude with a summary and put forward our perspective on the current challenges and the future development of morphology and optical tunable direction for the organic micro/nanocrystals.

Preparation of 3D micro/nanostructured CeO2： Influence of organic/inorganic acids

CeO2 is an important porous material with a wide range of applications in the abatement of volatile organic compounds （VOCs）. In this paper, we prepared a series of novel three-dimensional （3D） micro/nanostructured CeO2 materials via a solvothermal method. Organic acid-assisted synthesis and inorganic acid post-treatment were used to adjust the Ce02 microstructures. The size of the 3D micro/nanostructures could be controlled in the range from 180nm to 1.5 μm and the surface morphology changed from rough to smooth with the use of different organic acids. The CeO2 synthesized with acetic acid featured a hierarchical porosity and showed good performance for toluene catalytic combustion： a T50 of 187 ℃ and a T90 of 195 ℃. Moreover, the crystallite size, textural properties, and surface chemical states could be tuned by inorganic acid modification. After treatment with HNO3, the modified CeO2 materials exhibited improved catalytic activity, with a T50 of-175 ℃ and a T90 of -187 ℃. We concluded that the toluene combustion activity is related to the porosity and the amount of surface active oxygen of the CeO2. Both these features can be tuned by the co-work of organic and inorganic acids.

Colored ultrathin hybrid photovoltaics with high quantum efficiency

Most current solar panels are fabricated via complex processes using expensive semiconductor materials,and they are rigid and heavy with a dull,black appearance.As a result of their non-aesthetic appearance and weight,they are primarily installed on rooftops to minimize their negative impact on building appearance.The large surfaces and interiors of modern buildings are not efficiently utilized for potential electric power generation.Here,we introduce dual-function solar cells based on ultrathin dopant-free amorphous silicon embedded in an optical cavity that not only efficiently extract the photogenerated carriers but also display distinctive colors with the desired angle-insensitive appearances.Light-energy-harvesting colored signage is demonstrated.Furthermore,a cascaded photovoltaics scheme based on tunable spectrum splitting can be employed to increase power efficiency by absorbing a broader band of light energy.This study pioneers a new approach to architecturally compatible and decorative thin-film photovoltaics.

Morphology and Photoelectrochemical Characterization of MEH-PPV/PCBM Composite Film Doped with TiO_2 Nanoparticles

Poly[2-methoxy-5-（20-ethylhexyloxy）-io-phenylenevinylene] （MEH-PPV）, [6,6]-phenyl-C61-butyric acid methyl ester （PCBM） and titanium dioxide （TiO2） nanoparticles （n-type） were dissolved, mixed and deposited by physical methods （spin-coating） on indium tin-oxide （ITO） substrate. The incorporation of the titanium dioxide nanoparticles changed the morphology and increased the roughness of polymers film （MEH-PPV/PCBM）, and the photocurrent density of the composite （MEH-PPV/PCBM ＋n-TiO2） was higher than that of single MEH- PPV/PCBM film. The study showed that the presence of n-TiO2 particles in the polymeric film improves the photoelectrochemical properties of M EH-PPV/PCBM composite.

Synthesis and Characterization of ZnO Nanowires and ZnO–CuO Nanoflakes from Sputter-Deposited Brass(Cu_(0.65)–Zn_(0.35)) Film and Their Application in Gas Sensing

A novel method was presented for synthesis of ZnO and ZnO-CuO composites in the form of nanowires, nanorods and nanoflakes on oxidized silicon substrates. Further, the use of the synthesized nanostructures for gas sensing was demonstrated. Pure brass （Cu0.65-Zn0.35） films were deposited on oxidized Si substrate by radio frequency （RF） diode sputtering. Subsequently, these films having thickness in the range of 100-200 nm were oxidized in different oxidizing ambient in the temperature range of 300-550 ℃. The effect of temperature, time and oxidizing ambient on the growth of nanostructures was investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and photoluminescence （PL） techniques. The nanostructures surface was analyzed by X-ray photoelectron spectroscopy （XPS）. The synthesized nanowires had diameter in the range of 60-100 nm and length up to 50 μm. Based on these observations, the growth mechanism has been suggested. For the nanorods, the diameter was observed to be -150 nm. Samples having dense nanowires, nanorods and nanoflakes were used as a gas sensing material. The performance Of the sensor was investigated for different nanostructured materials for various volatile organic compounds （VOCs）, It was observed that ZnO- CuO nanoflakes were more sensitive to VOC sensing compared to ZnO nanowires and nanorods.