Enhancement of light output power from LEDs based on monolayer colloidal crystal.

One of the major challenges for the application of GaN-based light emitting diodes (LEDs) in solid-state lighting lies in the low light output power (LOP). Embedding nanostructures in LEDs has attracted considerable interest because they may improve the LOP of GaN-based LEDs efficiently. Recent advances in nanostructures derived from monolayer colloidal crystal (MCC) have made remarkable progress in enhancing the performance of GaN-based LEDs.

Hexagonal crown-capped zinc oxide micro rods: hydrothermal growth and formation mechanism.

Hexagonal crown-capped ZnO micro rods were successfully prepared by a facile low-temperature hydrothermal method. The as-prepared ZnO micro rods are 4.4-5.

Fabrication of volcano-shaped nano-patterned sapphire substrates using colloidal self-assembly and wet chemical etching.

Patterned sapphire substrates (PSS) have been widely used to enhance the light output power in GaN-based light emitting diodes. The shape and feature size of the pattern in a PSS affect its enhancement efficiency to a great degree. In this work we demonstrate the nanoscale fabrication of volcano-shaped PSS using a wet chemical etching approach in combination with a colloidal monolayer templating strategy.

Spin transitions in Fe(II) metallogrids modulated by substituents, counteranions, and solvents.

Two bis(tridentate) Schiff base ligands H2L(x) were used to construct three 2×2 grid-type tetranuclear Fe(II) complexes 1-3 to obtain polynuclear spin-crossover materials. Magnetic susceptibility measurements show that the spin states of the complexes are related to the substituents of H2L(x), and that spin transition occurs only in complexes 1 and 2, which are derived from a bulky ligand, whereas complex 3 is diamagnetic. The transition temperatures of complexes 1 and 2 are close to room temperature and are dependent on counteranions.

Preparation of high-quality colloidal mask for nanosphere lithography by a combination of air/water interface self-assembly and solvent vapor annealing.

Nanosphere lithography (NSL) has been regarded as an inexpensive, inherently parallel, high-throughput, materials-general approach to the fabrication of nanoparticle arrays. However, the order of the resulting nanoparticle array is essentially dependent on the quality of the colloidal monolayer mask. Furthermore, the lateral feature size of the nanoparticles created using NSL is coupled with the diameter of the colloidal spheres, which makes it inconvenient for studying the size-dependent properties of nanoparticles.

Confined Self-Assembly of Asymmetric Diblock Copolymers within Silica Nanobowl Arrays.

The confined self-assembly of asymmetric diblock copolymer polystyrene--poly(methyl methacrylate) (PS--PMMA) within an array of silica nanobowls prepared using a colloidal spheres templating technique is investigated. By manipulation of the nanobowl size, block copolymer (BCP) thickness, and interfacial interaction, a rich variety of ordered BCP nanostructures not accessible in the bulk system or under other confinements are obtained, resulting in hierarchically ordered nanostructures.

Co-self-assembly of binary colloidal crystals at the air-water interface.

A simple, fast, and cost-effective co-self-assembly approach to fabricate large-area two-dimensional (2D) binary colloidal crystals has been developed. By manipulating the size ratio and number ratio of the two monodisperse polystyrene latexes, a variety of binary colloidal crystal monolayers with different structures were successfully prepared. The co-self-assembly mechanism of the 2D binary colloidal crystals at the air-water interface was investigated.

Visual indication of enviromental humidity by using poly(ionic liquid) photonic crystals.

The combination of poly (ionic liquid) and photonic structure affords a new class of self-reporting humidity sensory materials with excellent reversibility, which are able to rapidly, sensitively and visually indicate environmental humidity with colour change from blue to green, orange, and red, covering the whole visible range.

3D-ordered macroporous poly(ionic liquid) films as multifunctional materials.

The integration of 3D-ordered macropores with poly(ionic liquid)s can significantly extend the functions of poly(ionic liquid)s, and afford a new type of material, which can serve as not only tunable photonic crystals and anion-directed molecular gating system, but also as a surface with enhanced tunable wettability and unique stable electro-optic switching.

CdZn2KB2O6F, a new fluoride borate crystal.

During an attempt to grow crystals of the nonlinear optical material Cd(3)Zn(3)B(4)O(12) using a KBF(4) flux, crystals of a new cadmium dizinc potassium borate fluoride compound, CdZn(2)KB(2)O(6)F, were unexpectedly isolated. The structure consists of layers constructed of distorted corner-sharing ZnO(3)F tetrahedra and BO(3) triangles. Both Zn and B reside on threefold rotation axes, while the F(-) anion is located at a site of 3.

LaZnB(5)O(10), the first lanthanum zinc borate.

Lanthanum zinc penta-borate, LaZnB(5)O(10), was synthesized by flux-supported solid-state reaction. It is a member of the LnMB(5)O(10) (Ln = rare earth ion and M = divalent metal ion) structure type. The crystal shows a three-dimensional structure constructed from two-dimensional {[B(5)O(10)](5-)}(n) layers with the lanthanum (coordination number nine) and zinc (coordination number six) ions filling in the inter-layers.

Label-free colorimetric detection of trace atrazine in aqueous solution by using molecularly imprinted photonic polymers.

Based on the combination of colloidal-crystal templating and a molecular imprinting technique, a sensor platform for efficient detection of atrazine in aqueous solution has been developed. The sensor is characterized by a 3D-ordered interconnected macroporous structure in which numerous nanocavities derived from atrazine imprinting are distributed in the thin wall of the formed inverse polymer opal. Owing to the special hierarchical porous structure, the molecularly imprinted polymer opals (or molecularly imprinted photonic polymer; MIPP) allow rapid and ultrasensitive detection of the target analyte.

Degenerated optical parametric chirped-pulse amplification with cesium lithium borate.

A gain amplifier for degenerated optical parametric chirped-pulse amplification (OPCPA) with lithium triborate and cesium lithium borate (CLBO) crystals was demonstrated in a near-collinear configuration. The signal gain of the final energy amplifier with CLBO was approximately 6. After compression, the 123 fs pulse duration was obtained.

Application of the nonlinear crystal SrB4O7 for ultrafast diagnostics converting to wavelengths as short as 125 nm.

We used non-phase-matched second-harmonic generation (SHG) in the highly nonlinear but low-birefringence crystal SrB4O7 for temporal characterization (autocorrelation) of femtosecond UV pulses to convert these pulses to wavelengths as low as 125 nm, close to the transparency limit of SrB4O7. The sensitivity of this method was approximately 1 microJ at the fundamental for a repetition rate of 1 kHz. We also used SHG at longer wavelengths to estimate the three nonlinear coefficients of SrB4O7.

A non-linear optical crystal, Cd(3)Zn(3)(BO(3))(4).

The title compound, tricadmium trizinc tetraborate, Cd(3)Zn(3)(BO(3))(4), is a new non-linear optical (NLO) crystal and its structure has been determined by single-crystal X-ray diffraction. This compound is composed of planar [BO(3)](3-) groups sharing O atoms with CdO(4) or ZnO(4) tetrahedra. The BO(3) triangles are located on threefold axes and are arranged with nearly the same orientation.

Optical parametric properties of ultraviolet-pumped cesium lithium borate crystals.

We report the optical parametric properties of cesium lithium borate (CLBO) crystals pumped by UV radiation of the fourth-harmonic generation at 266 nm and the third-harmonic generation at 355 nm of a picosecond Nd:YAG laser. A special optical design was used to avoid damage to the optical elements by the UV-pumped beam at 266 nm. The optical parametric generator (OPG)/optical parametric amplifier (OPA) of the 266-nm-pumped CLBO covers the tuning range from 347 nm in the UV to 1137 nm in the near IR.