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Nonaqueous organic electrolyte was utilized to etch GaN via photo-electrochemical etching technique. From the point of electrochemical window, the organic electrolyte has wider electrochemical window than conventional aqueous etchants. SEM images show that the pore density is up to 1.2 × 107 per square centimeter. The difference of XPS spectra about survey, Ga 3d and N 1s between the non-etched and freshly etched GaN surface can be explained the formation of Ga(BF4)3. The proposed dissolution mechanism can be broadly applied for explaining the etching process of nonaqueous etchants under the assist of electric field and strong light.

Porous gallium nitride (GaN) luminescent materials were fabricated by photoelectrochemical etching using three different 1-ethyl-3-methylimidazolium ([EMIM])-based ionic liquids as the etchants. The as-etched porous GaN presents honeycomb shape, deep gully with some holes in the surroundings, and overlapping hole structure, which are significantly different from the planar GaN. Moreover, photoluminescence (PL) spectra indicates that the porous GaN has more excellent PL performance than the planar GaN. In general, reducing the etching time to 1 min, the PL intensity of porous GaN etched by [EMIM][OTF] is 9.27 times than that of the planar one. These results suggest that porous GaN etched by ionic liquid can be an outstanding substrate in the field of the luminescent material.

Bismuth-modified gallium nitride (Bi/GaN) electrode was fabricated using an in situ plating technique and simultaneously investigated for the detection of Cd2 + by square wave anodic stripping voltammetry (SWASV). Under the optimized conditions, the Bi/GaN electrode showed good linear amperometric responses for Cd2 + in the concentration range from 1 to 150 μg/L. The sensitivity was 0.54418 μA L μg− 1 (i.e., 59.8598 A M− 1) and the limit of detection (LOD) was 0.3 μg/L (i.e., 2.72 nM). Furthermore, the as-prepared Bi/GaN sensor has high repeatability, and retains 95% of its initial stripping peak current after 50 cycles. More importantly, the applicability of the sensor in real samples such as tap water, milk, and fetal bovine serum was researched. The recovery ranges from 92.3 to 106.7%, indicating that the as-fabricated Bi/GaN sensor has potential to monitor Cd2 + in practical environments.

Three-dimensional (3D) metal-semiconductor nanostructures as surface-enhanced Raman scattering (SERS) substrates were designed by in situ electrodeposition of gold nanoparticles (AuNPs) or in situ photodeposition of silver nanoparticles (AgNPs) on gallium nitride (GaN) nanoflowers (NFs) supports fabricated by metal-assisted photochemical etching of single crystalline GaN. 3D AuNPs/GaN NFs and AgNPs/GaN NFs substrates exhibit excellent enhancement effect for Rhodamine 6G (R6G) due to more “hot spots” in the same probing volume compared to 2D GaN based substrates. The enhancement factors of the AuNPs/GaN NFs and AgNPs/GaN NFs substrates are up to 2.1 × 10 7 and 5.9 × 10 7 , respectively, and the corresponding detection limits of R6G are 10 −8 and 10 −10 M, respectively. Moreover, further study reveals both substrates have good reproducibility and long-term stability. The performance of the prepared substrates for biological application was demonstrated by the detection of bovine serum albumin (BSA). A series of characteristic bands of amides suggest BSA can be well adsorbed on the surface of the AuNPs/GaN NFs and AgNPs/GaN NFs substrates, which demonstrates our substrates have good biocompatibility and are promising candidates for SERS biosensors.

In this study, we report for the preparation of nickel phthalocyanine (NiPc) free-standing films on ionic liquid (IL) surface by a physical vapor deposition method. Different from on the solid substrate, the as-obtained film is α phase and with a 2D network structure. In addition, the good transferability of the film make it can be easily transferred onto any substrate for further device applications. The device based on these films shows good photoelectrical property, high stability and high photosensitivity.

Gallium nitride (GaN) nanowires (NWs) were fabricated by metal-assisted photochemical etching (MaPEtch). Gold nanoparticles (AuNPs) as metal catalyst were electrodeposited on the GaN substrate. SEM and HRTEM images show the surface of GaN NWs is smooth and clean without any impurity. SAED and FFT patterns demonstrate GaN NWs have single crystal structure, and the crystallographic orientation of GaN NWs is (0002) face. On the basis of the assumption of localized galvanic cells, combined with the energy levels and electrochemical potentials of reactants in this etching system, the generation, transfer and consumption of electron-hole pairs reveal the whole MaPEtch reaction process. Such easily fabricated GaN NWs have great potential for the assembly of GaN-based single-nanowire nanodevices.

Bismuth nanodendrites (BiNDs) were electrodeposited on planar gallium nitride (GaN) electrode via a differential pulse voltammetric technique to fabricate the non-enzymatic hydrogen peroxide (H2O2) sensor. SEM images revealed that the as-obtained BiNDs had numerous dendrite sub-branches, whose diameters ranged from 136 to 152 nm. The BiNDs/GaN electrode showed linear amperometric responses for H2O2 in the concentration range from 10 µM to 1 mM with the sensitivity of 60.0 μA mM−1 cm−2. Another linear range was from 1 to 10 mM with the sensitivity of 23.3 μA mM−1 cm−2. The limit of detection (LOD) was 5 µM with the signal-to-noise ratio of 3. The applicability of the sensor was investigated to the H2O2 detection in real samples such as fetal bovine serum and milk, and the sensor exhibited excellent anti-interference capacity. The achieved results indicate that the as-prepared BiNDs/GaN sensor with good reproducibility and long-term stability was promising for detecting H2O2 in practical environments.

Gallium nitride (GaN) surface was etched by 0.3 M ethylenediamine tetraacetic acid disodium (EDTA-2Na) via photoelectrochemical etching technique. SEM images reveal the etched GaN surface becomes rough and irregular. The pore density is up to 1.9 × 10 9 per square centimeter after simple acid post-treatment. The difference of XPS spectra of Ga 3d, N 1s and O 1s between the non-etched and freshly etched GaN surfaces can be attributed to the formation of Ga–EDTA complex at the etching interface between GaN and EDTA-2Na. The proposed complexation dissolution mechanism can be broadly applicable to almost all neutral etchants under the prerequisite of strong light and electric field. From the point of view of environment, safety and energy, EDTA-2Na has obvious advantages over conventionally corrosive etchants. Moreover, as the further and deeper study of such nearly neutral etchants, GaN etching technology has better application prospect in photoelectric micro-device fabrication.

Here we report the electrodeposition of gold nanoparticles (AuNPs) onto porous GaN electrode obtained by photoelectrochemical etching planar GaN to fabricate a non-enzymatic hydrogen peroxide (H2O2) sensor. SEM images revealed porous GaN has uniformly high-porosity structure and the diameter of AuNPs is 5–16 nm. The AuNPs/porous GaN electrode exhibited good electrocatalytic activity toward the reduction of H2O2 and performed as amperometric sensor for the detection of H2O2. The AuNPs/porous GaN electrode showed linear amperometric responses for H2O2 in the concentration range from 10 to 100 μM with the sensitivity of 281.5 μA mM−1. The limit of detection (LOD) is 2 μM with a signal-to-noise ratio of 3. In addition, the AuNPs/porous GaN electrode exhibited good repeatability, reproducibility, selectivity and long-term stability for H2O2 detection, in the meanwhile, AuNPs showed excellent adhesive capacity to the porous GaN electrode, which was tested by continually sonicating the AuNPs/porous GaN electrode for 3 h. Above results demonstrated this simply prepared H2O2 sensor has good practicability and is promising to measure the analyte in practical applications.

Here we report an environment-friendly approach to fabricate porous GaN photoelectrode using ionic liquid as the etchant. SEM images revealed photo-assisted electrochemical etching (PECE) has better etching effect than electrochemical etching (ECE). Furthermore, Raman spectra demonstrated porous GaN obtained by PECE has better lattice integrity than that obtained by ECE. The photocurrent of porous GaN prepared by PECE is six times and two times of planar and porous GaN fabricated by ECE, respectively. Above results indicated porous GaN obtained by PECE can be a promising photoelectrode for optoelectronic applications.

By virtue of instability analysis, an index of shear banding susceptibility of metallic glasses (MGs): the critical strain localization factor to initiate an embryonic shear band: χ = γ b / γ m ( γ b shear strain in the embryonic shear band and γ m in the matrix) is derived in analogue to the emergence of geometrically necessary dislocations (GND) in crystals. Physical properties, like Poisson ratio υ , Young's modulus E and the surface energy density ζ , are explicitly incorporated into the formulae of χ with which the origin of the plasticity of MGs are unraveled.

Heterogeneous dynamics in the flow of supercooled metallic liquids are revealed as the oscillated mechanical response in compression and evidenced to be consistent with the range of medium length scales over which structural rearrangements occur detected by small angle X-ray scattering (SAXS) in heating from room temperature to the supercooled liquid region. This range of medium length scales is suggested to be the structural origin of the heterogeneous dynamics of metallic glasses. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Background and Aims Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Aberrant activation of sonic hedgehog (Shh) signaling pathway plays important roles in tumorigenesis and progression of several tumors. Cyclopamine, an important inhibitor of Shh signaling pathway, can induce cell apoptosis. However, the mechanisms underlying cyclopamine-induced apoptosis are not well understood. The aim of this study is to determine the expression of the Shh signaling pathway components in HCC and to investigate the mechanisms underlying cyclopamine-induced apoptosis in HCC cells. Methods Shh signaling components (Shh, Ptch, Smo and Gli-1) expression levels were evaluated by immunohistochemistry on tissue microarrays containing 98 HCCs with paired adjacent noncancerous liver tissues. The relationships between sonic hedgehog signal pathway and clinicopathological factors were analyzed in HCC. Cell viability was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Apoptosis was detected by flow cytometry. mRNA and protein levels were analyzed by RT-PCR and Western blot, respectively. Results Shh, Ptch, Smo and Gli-1 were overexpressed in HCC tissues compared with paired adjacent noncancerous liver tissue. Activated Shh signaling pathway was associated with tumor size, capsular invasion and vascular invasion in HCC. Cyclopamine remarkably decreased cell viability, induced apoptosis and downregulated Bcl-2 expression in HCC cells. Conclusions Shh signaling pathway plays an important role in HCC tumorigenesis and progression, indicating that Shh signaling pathway is a potential therapeutic target for HCC. Cyclopamine induces apoptosis through downregulating Bcl-2 in HCC.

Upon mechanically milling with as-prepared single-walled carbon nanotubes, the dehydriding/rehydriding kinetics of LiBH 4 can be markedly improved, thus rendering the system partial reversibility at reduced temperature/pressure conditions. Based on the property/phase analysis results, as well as the results of the designed experiments, the observed catalytic enhancement was understood as combined effects of metallic Ni, Co, Fe or their borides nanoparticles, and carbon nanotubes.

Quaternary Heusler alloy Ni50Mn8Fe17Ga25 has been synthesized by melt-spinning method. Pole figure examination suggested that the ribbon samples have a strong preferentially orientation in [400] about 5-10degrees tilted from the ribbon normal. The effect of heat treatment on the magnetic and phase transformation properties of Ni50Mn8Fe17Ga25 ribbon has been investigated. Annealing increased the martensitic transformation temperature, Curie temperature and decreased the transformation hysteresis and magnetic hysteresis due to the change of atomic chemical ordering. Thermoelastic transformation strain was decreased from -0.19% to -0.17% after annealing. At the same time, a slighter decrease of transformation strain by adding external bias field was observed in the as-annealed ribbons, which has not been found in the as-spun ribbons. These can be attributed to the relaxation of the internal stress through annealing. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The martensitic transformation and magnetic properties of ferromagnetic shape memory alloy Ni50 + x Fe25 − x Ga25 (x = −1, 0, 1, 2, 3, 4) ribbons have been systematically studied. It has been found that with the increase of Ni concentration, the martensitic transformation temperature increases, but the Curie temperature decreases. Both the two-step thermally induced structural transformation and the one-step transition have been observed in NiFeGa alloys with different compositions. It is found that the two-step transition became the one-step transitio n after the ribbon being heat treated at 873 K or higher. X-ray diffraction patterns show that only L21 → B2 transition occurs in the samples treated at 873 K, while the γ phase will form in the samples treated at higher temperature. Transmission electron microscopy (TEM) studies show that the alloys with martensitic transformation temperature above the room temperature are non-modulated martensite with the large domain size, being different from the stoichiometric Ni2FeGa alloy that is a modulated martensite with small domain size. The influences of Fe substitution for Ni in Ni2FeGa on the saturation magnetization and exchange interaction are also discussed.  2004 Elsevier B.V. All rights reserved.

alpha-MoO3 whiskers were prepared via an oxidation process of a Mo slice in oxygen. MoO3 vapors condensed to form the alpha-MoO3 whiskers with white color. On surfaces of the MoO3 whiskers, the atom ratio of oxygen to molybdenum was 4.4, which was higher than that of bulk MoO3. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The growth behavior and surface morphology of a rough film system, deposited on silicone oil drop surfaces by a r.f. magnetron sputtering method, have been studied. An anomalous film growth relaxation is observed during the deposition process. The relaxation rate is extremely sensitive to the substrate temperature. The surface morphology at the micrometer length scale is very susceptible to the substrate temperature, the incident r.f. capacity, and the nature of the solid substrate on which the oil drop is dripped. A discussion on the physical origins of these phenomena is also presented.