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Improving the activity and stability of electrocatalysts for the hydrogen evolution reaction (HER) plays an essential role in the practical application of electrochemical water splitting under alkaline conditions. Here, trace Pd-doped Ru nanoparticles have been achieved using the pulsed laser ablation in liquid technology, which exhibit efficient HER catalytic performance. It is evidenced that the Pd doping amount is maintained at a trace level and increases nonlinearly with the concentration of the Pd precursor. Molecular dynamics simulations demonstrate that the trace doping of Pd is due to the slow thermal decomposition rate of the Pd precursor. This work improves the mechanistic explanation of the metal doping induced by liquid-phase laser ablation, which may promote the fabrication and application of advanced laser-based nanostructures.

After analyzing the pros and cons of existing online education platforms, we find that the disaggregation between multiple supplementary education platforms has many inconveniences for technical course teaching. We propose and design a multiway collaboration model in a heterogeneous data environment to make the multi-platform teaching approach more convenient. This model helps to address the limitations of the multi-platform teaching and learning approach.

Increasing upconversion luminescence (UCL) to overcome the intrinsically low conversion efficiency of upconversion nanoparticles (UCNPs) poses a fundamental challenge. Photonic nanostructures are the efficient approaches for UCL enhancement by tailoring the local electromagnetic fields. Unfortunately, such nanostructures are sensitive to environmental conditions, and the regulation strength is varied in flexible applications. Here, we report giant UCL enhancement from a flexible UCNP-embedded film coupled with a microsphere photonic superlens (MPS), by which the enhancement ratio of UCL is over 10

Surface-enhanced Raman spectroscopy (SERS) has been widely investigated and employed as a powerful optical analytical technique providing fingerprint vibrational information of molecules with high sensitivity and resolution. In addition to metallic nanostructure, dielectric micro-/nano-structures with extraordinary optical manipulation properties have demonstrated capability in enhanced Raman scattering with ultralow energy losses. Here we report a facile cascaded structure composed of a large microsphere (LMS) and a small microsphere array with Ag nanoparticles as a novel hybrid SERS substrate, for the first time. The cascaded microsphere-coupled SERS substrate provides a platform to increase the molecular concentration, boost the intensity of localized excitation light, and direct the far-field emission, for giant Raman enhancement. It demonstrates the maximum enhancement factor of Raman intensity greater than 108 for the limit of detection down to 10−11 M of 4-nitrothiphenol molecules in aqueous solution. The present work inspires a novel strategy to fabricate cascaded dielectric/metallic micro-/nano-structures superior to traditional SERS substrates towards practical applications in cost-effective and ultrahigh-sensitive trace-detection.

Here, we fabricated In2O3(ZnO)m (IZO) superlattice microplates with hexagon morphologies by the substrate-free optical vapor supersaturated precipitation. The IZO microplates possessed a superlattice structure with a large m number, i.e., m = 23, consisting of layered alternating stacks of octahedral InO2− as inversion boundaries and layered InZnmOm+1+ as a zig-zag modulated pattern. The Raman peak at 613 cm−1 confirmed the superlattice of the IZO microplates. The broad asymmetric excitonic photoluminescence (PL) emission with the photon energy of 3.236 eV indicated the heavy doping of indium in the IZO, resulting a redshift of ~ 32 meV from the near-band-edge emission. The unusual negative thermal quenching of PL intensity was also observed. Moreover, the anisotropic electrical properties of the IZO superlattice microplates were manifested, for the first time, where the in-plane conductivity was two orders of magnitude higher than out-plane one. The present work provided new insight into the free-standing IZO superlattice microdevices for future optoelectronic applications.

This paper investigates the effect of porosity and unit cell size variation in topology optimized (TOP) and selective laser melting (SLM) fabricated Ti6Al4V lattice structure on the mechanical properties including compressive strength, failure mechanism and dynamic elastic modulus. Meanwhile, mathematical relations between mechanical properties and geometric parameters are obtained based on Gibson-Ashby model. The results show that both ultimate compressive strength (σ = 23∼498 MPa) and dynamic elastic modulus (E = 3.5∼55.47 GPa) of TOP lattice structures gradually decrease with the increase in porosity and unit cell size. The analysis combining experimental and numerical results indicates that TOP lattice structures are elastic-brittle porous material and have two failure mechanisms. The numerical predicted stress-strain curves are compared with the experimental ones. The numerical models incorporating the Johnson-Cook damage model could predict the slip direction of 45° failure band and ultimate compressive strength. Classical Gibson-Ashby model was used to predict the relation between relative density and mechanical properties of lattice structures. The exponential factors (n) of fitted models are obviously affected by unit cell size, which are determined by the number of unit cells in compressive test and SLM manufacturability in dynamic elastic modulus test. A 3D Modulus-Density-Unit Cell Size model is innovatively proposed, which can provide theoretical basis of tailoring orthopedic implant filled with functional gradient TOP lattice structures.

We presented the experimental and theoretical investigations of the surface plasmon-exciton coupled photoluminescence characteristics of Ga-doped Zinc Oxide (GZO) in Ag/GZO and Au/GZO nanostructures. An eightfold enhancement of the near-band-edge (NBE) emission with suppression of deep levels has been achieved without insertion of a dielectric spacer. The suppression of deep level emission makes these nanostructures useful for visible blind photodetectors. The experimental room temperature photoluminescence consequences pointed that the plasmon-exciton coupling contributed to the enhancement of the radiative recombination rate at the NBE in the metal–semiconductor architecture.

Strain engineering of electrocatalysts provides an effective strategy to improve the intrinsic catalytic activity. Here, the defect-rich crystalline/amorphous Pd nanosheet aerogel with hybrid microstrain and lattice strain is synthesized by combining laser irradiation and phosphorus doping methods. The surface strain exhibited by the microstrain and lattice strain shifts the d-band center of the electrocatalyst, enhancing the adsorption of intermediates in the ethanol oxidation reaction and thus improving the catalytic performances. The measured mass activity, specific activity and C1-path selectivity of the Pd nanosheet aerogel are 4.48, 3.06, and 5.06 times higher than those of commercial Pd/C, respectively. These findings afford a new strategy for the preparation of highl activity and C1 pathway selective catalysts and provide insight into the catalytic mechanism of strain-rich heterojunction materials based on tunable surface strain values.

The controllable catalytic reaction plays a pivotal role in heterogeneous catalysis. Surface-enhanced Raman scattering (SERS) and tip enhanced Raman spectroscopy (TERS) are considered promising techniques for the study of catalytic reactions due to the highly localized sensitivity of SERS and the nanoscale spatial resolution of TERS. Herein, Ag/Au composite films were employed as catalyst for in situ monitoring of the catalytic reaction of 4‑nitrobenzenethiol (4NBT) to p, p'‑dimercaptoazobenzene (DMAB). The catalytic reaction of 4NBT adsorbed on Au film can be manipulated at the nanoscale using TERS by controlling the height between the tip-apex and the sample surface in Ag tip-Au substrate geometry. According to finite difference time domain (FDTD) simulations, the 'hot electron' induced by the localized surface plasmon is sufficient for promoting the catalytic reaction. These findings provide a novel way for controllable graph drawing of molecules at the nanoscale level.

Here a variety of hierarchic nanostructures on the undoped acceptor-rich ZnO (A-ZnO) single-crystal microtube are fabricated by KrF excimer laser irradiation. The effects of process parameters, i.e. laser fluence and number of pulse (NOP), on nanostructure morphology of the A-ZnO microtube are investigated, by which the controllable hierarchic nanostructures are achieved. The mechanism of the nanostructure formation is attributed to self-assembled growth by decomposition and re-nucleation owing to rapid heating and cooling down during laser irradiation near Zn-vacancy-related point defects. The Raman and photoluminescence spectra confirm that the nanostructures possess massive surface defects, e.g. oxygen vacancies (VO) and zinc interstitials (Zni). The electrical resistivity of the nanostructured A-ZnO microtube is down to ∼10−3 Ω cm, about one order of magnitude lower than that of the as-grown A-ZnO microtube. The great ratio of surface area to volume of the nanostructures realizes the improved UV detection and photodegradation performance. The optimal photoresponsivity can be up to 27.08 A/W using the process parameters of 200 mJ/cm2 and 100 pulses. The catalytic degradation rate of the A-ZnO microtube irradiated by 150 mJ/cm2 and 200 pulses with 6-nm Au nanoparticles decoration for methylene blue solution is ∼3.4 times higher than the commercial nanoparticles. The present work paves a new way to design and fabricate a variety of hierarchic nanostructures on undoped A-ZnO microtube for enhanced electrical and photocatalytic performance.

Here we report the contribution of self-absorption to excitonic luminescence in an ultrathin-walled ZnO semiconductor microtube cavity. The trapping structure regulates the X-band and near-band edge emission via various excitation-detection geometries. The self-absorption in the microcavity results in a high concentration of exciton ~3.65 × 1016 cm−3 and boosts the amplified spontaneous emission. The enhancement ratio for the UV band emissions can be up to 40 folds, higher than using localized surface plasmon resonance via Ag nanoparticles. The coefficient of self-absorption by the light-trapping microtube structure is therefore determined to be 6.1. The present work opens up new opportunities to enhance the photons collection and interaction with excitons in wide-band-gap semiconductor for on-chip wavelength-tunable UV-luminescence devices in optoelectronic applications.

Herein, we presented the low-dimensional mechanical-exfoliated growth of hexagonal ZnO nanorods. The structural, morphological and optical properties have been investigated. The hexagonal wurtzite structure has been confirmed via X-ray diffraction graphs showing the (002) preferred orientation. The rod-like hexagonal structure has been revealed in the Field-emission Scanning electron microscopy (FE-SEM) and High-resolution Transmission Electron Microscopy (HR-TEM) analysis. Threefold enhancement in near-band-edge (NBE) emission of photoluminescence spectra has been achieved in low-dimensional ZnO nanorods (NRs) without any doping. This paves new ways for low-dimensional semiconductors in order to fabricate high-efficient luminescence devices.

Here, we report a strategy to regulate the defect level of zinc vacancy ( VZn) in acceptor-rich ZnO (A-ZnO) microtubes by optical vapor supersaturated precipitation (OVSP) combined with the first-principles calculation. The formation energy (FE) of VZn in ZnO is calculated based on the density functional theory, indicating the FE of VZn depending upon the surrounding Zn chemical potential in ZnO. The defect level of VZn is experimentally controlled in the A-ZnO microtubes by regulating the concentration of oxygen during the OVSP process. For the high oxygen concentration, the photoluminescence intensity of VZn-related donor–acceptor pair emission is enhanced by 46%, compared with those grown in oxygen-deficient conditions. Meanwhile, a defective 2LA mode appeared in the Raman spectra of A-ZnO microtubes with the increase in oxygen concentration, confirming the controllability of the generation of VZn. The VZn defects induce the conductive filaments for the resistive switching behavior in the A-ZnO microtubes, by which the on/off ratio can be enhanced by up to ∼103. Moreover, the tunable current-induced thermal tunneling electroluminescence was also realized by the defect-controlled A-ZnO microrods/tubes. This work opens new opportunities for the design of novel optoelectronic devices by defect-engineered wide-bandgap semiconductors in future.

Here we report growth of 〈0 0 0 1〉-oriented ultrathin-walled ZnO single-crystal microtubes with diameter of 75–250 μm and facet wall of

As one of the teaching methods of chemistry in colleges and universities, experimental teaching is the inevitable path of teaching development that is obviously different from traditional teaching, and it is also an indispensable part of constructing and perfecting teaching system and implementing teaching reform. In this case, this paper analyzes and explores in detail the problems existing in inorganic chemistry experiment teaching in colleges and universities, and puts forward relevant methods and measures to provide some valuable references for the optimization of inorganic chemistry experiment methods.

Here we report a novel ZnO microtubular homojunction photodiode (PD) fabricated by optical vapor supersaturated precipitation (OVSP) and sputtering methods. The acceptor-rich ZnO (A-ZnO) microtube grown by OVSP possesses a great UV–visible rejection ratio of ~3.77 and a high external quantum yield of 1.4 × 103%. The formed A-ZnO/n-ZnO homojunction UV-PD realizes an ultrafast photoresponse down to 6 ms (three orders of magnitude faster) and boosts the sensitivity by 2.6-folds with respect to the bare A-ZnO microtube. It is beneficial for weak-signal UV detection down to the threshold of 0.4 mW/cm2 under random excitation conditions, by which the detectivity up to 6.67 × 1012 cmHz1/2/W is achieved. The ZnO microtubular homojunction paves a new way for design of high-performance wide-bandgap semiconductor UV-PDs, promoting their practical applications in future.

Summary Here we demonstrate a novel and robust mechanism, termed as “current-induced Joule heating activated thermal tunneling excitation,” to achieve electroluminescence (EL) by the hot electron-hole-pair recombination in a single highly compensated semiconductor microrod. The radiative luminescence is electrically excited under ambient conditions. The current-induced Joule heating reduces the thermal tunneling excitation threshold of voltage down to 8 V and increases the EL efficiency ~4.4-fold at 723 K. We interpret this novel phenomenon by a thermal tunneling excitation model corrected by electric-induced Joule heating effect. The mechanism is confirmed via theoretical calculation and experimental demonstration, for the first time. The color-tunable EL emission is also achieved by regulation of donor concentration. This work opens up new opportunities for design of novel multi-color light-emitting devices by homogeneous defect-engineered semiconductors in future., Graphical Abstract, Highlights • Current-induced thermal tunneling EL is found in a homogeneous HC-ZnO microrod • The high temperature is beneficial to the current-induced thermal tunneling EL • The tunneling mechanism of Joule-heating-facilitated excitation is revealed • The color-tunable EL emission is demonstrated by regulation of donor concentration, Optical Materials; Devices; Materials Design

ZnO has attracted considerable attention in fundamental studies and practical applications for the past decade due to its outstanding performance in gas sensing, photocatalytic degradation, light harvesting, UV-light emitting/lasing, etc. The large-sized thin-walled ZnO (TW-ZnO) microtube with stable and rich VZn-related acceptors grown by optical vapor supersaturated precipitation (OVSP) is a novel multifunctional optoelectronic material. Unfortunately, the OVSP cannot achieve doping due to the vapor growth process. To obtain doped TW-ZnO microtubes, a solid state method is introduced in this work to achieve thin-walled Al-doping ZnO (TW-ZnO:Al) microtubes with high electrical conductivity. The morphology and microstructures of ZnO:Al microtubes are similar to undoped ones. The Al3+ ions are confirmed to substitute Zn2+ sites and Zn(0/−1) vacancies in the lattice of ZnO by EDS, XRD, Raman and temperature-dependent photoluminescence analyses. The Al dopant acting as a donor level offers massive free electrons to increase the carrier concentrations. The resistivity of the ZnO:Al microtube is reduced down to ∼10−3 Ω·cm, which is one order of magnitude lower than that of the undoped microtube. The present work provides a simple way to achieve doped ZnO tubular components for potential device applications in optoelectronics.

The structural, morphological, and optical characteristics of GZO ultra-thin films were investigated using XRD (X-ray diffraction), FE-SEM (field emission electron microscopy), in situ EDS (Energy Dispersive X-ray) spectroscopy, UV–VIS-IR spectroscopy and photoluminescence spectroscopy (PL) respectively. Morphological analysis reveals the noodle, seed and particle like structure of GZO for GaN, sapphire and Si substrates respectively with average grain size ranging from 5 to 20 nm. An effective mass model (EM-Model) for particle in a cylindrical wave function of e–h pair was correlated with experimental results. The reduction in FWHM value (from 31 nm to 13 nm) of NBE (near-band-edge) emission peak and enhanced NBE intensity have been achieved with small grain size. Blue shift in optical band gap is explained in term of grain radius by EM-model. Improved optical and structural properties were found in relation with quantum confinement effect. The current study states that grain size plays vital role in order to tailor optical properties of GZO thin films.

In this work, high-quality free-standing ZnO single-crystal microtubes with hexagonal cross-section were fabricated by an optical image furnace. Optical vapor supersaturated precipitation (OVSP) and axial photo-thermal-decomposition were proposed to interpret the microrods growth and microtubes formation, respectively. The maximum dimensions of the grown microtube were 5 mm in length, 100 µm in diameter and 1 µm in facet wall thickness. In our previous work, a new room-temperature photoluminescence (PL) peak (~392 nm) of ZnO microtubes was attributed to V Zn -related donor-acceptor-pairs (DAP) transition. This work further confirmed the V Zn -related acceptors widely existing during ZnO microrods/ microtubes growth by OVSP. The effects of major growth parameters ( e.g . lamp power, filament geometry and growth platform shape) on temperature field at the growth platform of precursor rod were studied by a finite element model as well. The lamp power of 65% (1500 W), thick single-filament and appropriate conical growth platform were optimized for a uniform temperature field to achieve consistent finish quality of microtubes and prevent twin-microtubes formation. This work would be beneficial for batch growth of the novel ZnO microtubes/microrods with high quality for a variety of applications.

Optical floating zone (OFZ) is one of the most extensively used techniques to grow a variety of bulk crystals, especially single crystals of metal oxides. Although the growth parameters have been identified to be the nature of feed rod, lamp power, rotation rate, growth atmosphere and gas pressure, etc ., few studies revealed the effects of these parameters on temperature field during crystal growth in image furnaces. It is well known that the temperature gradient is the driving force for float zone crystal growth. Therefore, it is essential to obtain the major growth parameters affecting OFZ temperature field. In this work, a simplified finite element (FE) model was developed for numerical simulation of temperature field during OFZ crystal growth. The effects of major growth parameters ( i.e. lamp power, lamp filament, and molten zone geometry) on temperature field during OFZ crystal growth were hence identified theoretically and validated experimentally. According to the numerical calculation, the growth parameters were optimized and high-quality TiO 2 single crystal was grown in practice. Prospectively, the FE model presented in this work can be applied to optimize growth parameters for other crystals as well as opens up new opportunities to understand the physical process of OFZ crystal growth in a simple and scientific way.

Transparent and blue ZnO:Ga (GZO) single crystals have been grown by the traveling-solvent floating-zone technique using the solvent B2O3 + MoO3 + Nb2O5. The crystals were typically 9–14 mm in diameter and 46–120 mm in length. The largest one was Φ12 mm × 120 mm in size. All GZO crystals were grown along the direction. The growth rate was 0.3–0.5 mm/h, which was far faster than 0.1 mm/day of that grown by the hydrothermal method. The crystalline quality has been characterized by single crystal X-ray diffraction and X-ray rocking curve measurements. Ga substituted on Zn-site and was saturated at about 0.5 wt % of Ga2O3 addition. The GZO crystal doped with 0.5 wt % Ga2O3 has the lowest electrical resistivity of 1.083 × 10–3 Ω·cm and the highest carrier concentration of 1.78 × 1020 cm–3.

Poly(aspartic acid-itaconic acid) copolymers (PAI) is a new scale inhibitor for water treatment. Thus, it is necessary to investigate its biodegradability. The biodegradability of PAI was investigated through CO2 evolution tests under different conditions based on determination of carbon dioxide production. The investigation results showed that the degradation rate of PAI on day 10 and day 28 were respectively 38.7 and 79.5%, indicating that PAI was one kind of easily biodegradable scale inhibitors. With the increase in the content of itaconic acid in copolymerization process, the biodegradability of PAI was significantly reduced. In addition, the high biodegradability might be attributed to the existence of C–N bone-structure and more –COO–. Finally, Cu2+ could decrease the degradation percentage and the enzyme inhibition effect of Cu2+ was not the linear effect, but the “low-dosage effect”.

Here we report a novel hybrid structure composing of microsphere array (MA), Al nanoparticles (Al-NPs), ZnO thin film (luminescence layer), Au nanoparticles (Au-NPs), and substrate (sapphire) for ultraviolet (UV) luminescence enhancement of planar wide bandgap semiconductor film. The plasmonic sandwich structure of Al-NPs/ZnO/Au-NPs boosts the hot electron state density in the conduction band by electron trapping from deep-defect level of ZnO and localized surface plasmon resonances (LSPRs) coupling around dual metallic NPs, enhancing UV emission and suppressing visible emission efficiently. The dielectric microsphere array capping on the plasmonic sandwich structure further increases UV emission intensity via photonic nanojets, optical whispering-gallery modes (WGMs), and directional antenna effect, by which the interaction between photon and exciton is strengthened. The contribution of microsphere cavity coupling with LSPRs to UV luminescence enhancement is therefore revealed. The maximum enhancement ratio of up to two orders of magnitude (~250-fold) is achieved by the optimized 5.06-μm-diameter-MA/Al-NPs/ZnO/Au-NPs/sapphire structure and the UV emission is highly directional with a divergent angle of ~5°. The present work provides a simple and easily-prepared structure incorporating optical WGMs and LSPRs to manipulate UV luminescence of planar wide-bandgap semiconductors for potential optoelectronic applications.

A new and facile procedure for the preparation of 6,6′-diiodo-5,5′-dibromo-3,3′-dimethoxylbiphenyl has been found. From this compound, a general synthetic strategy for the preparation of 1,8-dibromo-9-heterofluorenes will be developed. The Synthesis of 1,8-dibromo-9-heterofluorenes will open the door to new classes of inorganic and organometallic conjugated polymeric materials of polyheterofluorenes.

In this paper, the effect of KrF pulsed excimer laser irradiation on the structural, surface morphology, photoluminescence and electrical properties of ZnO single crystal was investigated. Compared to the as-grown sample, at an irradiation energy density of 257 mJ/cm2, the ZnO single crystal exhibits a series of phenomenon: XRD and Raman results show that the crystallization of ZnO quality change slightly, resistivity is decreased by two orders of magnitude, carrier concentration is increased by one order of magnitude. After laser irradiation, the surface shows some strip lines and no cracks. Formula calculation and simulation results show that the stripes are not caused by surface melting. We speculate that these stripes are caused by the precipitation of ZnO material inside to the surface. Due to the reduction of oxygen vacancies, UV emission has been enhanced and visible emission has been declined after irradiation. After the laser irradiation, the visible light of ZnO surface can be regulated. The experimental results show that KrF laser irradiation could effectively improve the optical and electrical properties of ZnO single crystal, which is important for the application of high performance of emitting optoelectronic devices.

Near-3:2 mullite crystals have been grown successfully with the optical floating zone technique. The growth direction of mullite crystals is along the c axis and growth rate can be reached 10 mm/h. The effect of growth rates on the crystal quality has been studied. The crystalline phase, crystal quality, microstructure, composition distribution of the grown crystals were characterized by powder X-ray diffraction, single crystal X-ray diffraction, scanning electron microscope, electron probe micro-analyzer and Raman spectra, respectively. The grown mullite crystal is formed by peritectic structure with near 3:2 mullite crystal as main face and lamellar or needle-like SiO2-rich aluminosilicate as secondary phase that parallel to the crystal growth direction. The measured dielectric properties show large dielectric anisotropy and good temperature stability in near-3:2 mullite crystals.

Close-packed monolayer silica spheres organized through a self-assembly process have been widely used in micro/nano fabrications. In this study, we present the effects of substrate on the near-field enhancement of microsphere-assisted laser processing. There are significant differences in the surface morphology of sub-micro hole arrays on substrates with different refractive indices, which were fabricated at the same laser fluence by a KrF excimer laser (λ = 248 nm). It is found that the position of the maximum enhancement removes from the exit surface of the silica sphere into the sphere as the refractive index of substrate increased based on the simulation. In addition, the field distribution curve oscillates when there is a substrate under the microsphere, and oscillation spreads deeper into the substrate with a high refractive index. The results contribute toward the optimization of the process conditions of the microsphere-assisted laser micro/nano patterning technique and make the modification profile of the material more controllable.

Three ortho-, meta-, and para-linked polymers derived from 9,9-dioctylfluorene (FO) and dimethoxyl-biphenyl (DMBP) were designed and synthesized via catalyst-transfer Suzuki coupling polymerization with palladium(0) catalyst as initiator. Compared to PFO, the conjugated polymers of PFO-o-DMBP, PFO-m-DMBP, and PFO-p-DMBP displayed a significantly blued-shifted absorption and emission spectra with the change of the connecting site from ortho-, meta- to para-position, and the varying degrees were ascribed to the different types of steric hindrance of ortho-, meta-, and para-linkage, which partly hinder the intermonomer rotation of the polymer backbone, giving rise to molecular configuration from linear, zigzag to intertwined structure, and resulting in shortened conjugation length. The optical bandgap calculated from the onset of absorption spectra of the three polymers in solid film are all wider than that of the PFO, indicating that the incorporating of dimethoxyl-biphenyl increased the chain-twisting hindrance and influenced the molecular conformation of the copolymer. Systematical investigation of electrochemical and photophysical properties of the conjugated polymers suggests that the incorporation of dimethoxyl-biphenyl via ortho-, meta-, and para-linkage is an efficient and economic way to modify the properties of polyfluorenes.

As-Selective Laser Melted (as-SLMed) Ti6Al4V in horizontal direction possess poor ductility because of acicular α ’ martensite and columnar β grains in microstructure. However, traditional ductility improvement methods including high-temperature preheating or heat treatment will decrease not only strength but also the efficiency of SLM fabrication to application. For a satisfactory mechanical property of as-SLMed Ti6Al4V alloy, some special temperature evolution conditions brought about from processing parameters such as layer thickness, hatch spacing, energy density and area ratios between support structure and part, were carried out in the paper. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the microstructure. The microstructure of as-SLMed specimens are found to be different extent decomposing of α ’ martensite. Also, the formation mechanisms of such microstructural variables are proposed based on temperature evolution vs time during SLM process. Moreover, the tensile test presents high elongation (>8%) is achieved for horizontally as-SLMed Ti6Al4V specimens without lowering their strength (the ultimate tensile strength ∼ 1260 ± 30 MPa and yield strength ∼1160 ± 50 MPa), which markedly exceed ASTM standard for castings. The mechanical properties and fracture mechanisms of specimens are obviously affected by the width of α ’ / α martensite and the content of β phase. This work marks an important step forward in the understanding of microstructural tailoring in SLM process for a high-performance Ti6Al4V alloy.

The intrinsic acceptor-rich ZnO (A-ZnO) microtubes fabricated by optical vaporization supersaturated precipitation (OVSP) are compatible to microfluidic channel for on-chip photodegradation. Unfortunately, the micron size and weak charge separation ability in bare A-ZnO microtube limit its degradation rate. Design of heterojunction structure is a feasible way to improve the photocatalytic performance by efficient separation of photogenerated carriers. Here we synthesize p-CuO and n-ZnS nanostructures on A-ZnO microtubes, respectively, achieving various hierarchical heterojunctions. The massive Zn-vacancy-related shallow acceptor carries in A-ZnO as well as the similar bandgap and crystal structure of A-ZnO/n-ZnS achieve the highest photodegradation efficiency up to 0.105 min−1. It is about twice and triple higher than bare A-ZnO microtubes and n-ZnO nanoparticles, respectively. The formed type II heterojunction in A-ZnO/n-ZnS boosts the charge separation superior to other ZnO-based heterojunction. The present work paves a new way to the tubular A-ZnO-based hierarchical heterojunction with n-type wide-bandgap semiconductors for high-performance optoelectronic devices.

Optical and electrical properties of Ga-doped Zinc Oxide (GZO) has been studied in the present article. Density functional theory and Hubbard U (DFT + Ud + Up) based first principle calculations were employed for theoretical estimation whereas Laser ablation method has been used to fabricate GZO thin films on p-GaN, Al2O3 and p-Si substrate for experimental analysis. Single crystal growth of GZO thin films with (002) preferred crystallographic orientation has been shown in X-ray diffraction graphs. The elemental composition of all samples has been studied via EDS (energy dispersive X-ray) spectroscopy, no other unwanted impurity related peaks were found which indicates the impurity-free growth of GZO. Noodle, seed and granular-like structures of GZO/GaN, GZO/Al2O3, and GZO/Si have been revealed via Field-emission scanning electron microscopy micrographs respectively. The morphological analysis suggested GaN substrate as the best candidate for uniform and better quality GZO thin films. Highest carrier mobility (53 cm2/V s) with higher carrier concentration (> 1020 cm−3) has been found with low (1800) laser shots. Fivefold photoluminescence enhancement in the noodle-like structure of GZO/GaN with compared to GZO/Al2O3 and GZO/Si has been recorded. As the noodle-like structure supposed to be a more favorable structure for enhanced optical properties of GZO which points toward shape-driven optical properties. Theoretical (3.539 eV) and experimental (3.43, 3.6 eV) values of band-gap were found quite comparable. Moreover, lowest resistivity (3.5 × 10−4 Ω cm) with 80% transmittance is evident for GZO as a successful alternate of ITO.

A dielectric microsphere-embedded film was developed as a flexible Raman enhancer, which provides a >10-fold enhancement ratio and can be coupled with traditional SERS active substrates for ultrasensitive Raman trace-detection.

Dielectric microspheres with extraordinary microscale optical properties, such as photonic nanojets, optical whispering-gallery modes (WGMs), and directional antennas, have drawn interest in many research fields. Microsphere-enhanced Raman spectroscopy (MERS) is an alternative approach for enhanced Raman detection by dielectric microstructures. Unfortunately, fabrication of microsphere monolayer arrays is the major challenge of MERS for practical applications on various specimen surfaces. Here we report a microsphere-embedded film (MF) by immersing a highly refractive microsphere monolayer array in the poly(dimethylsiloxane) (PDMS) film as a flexible MERS sensing platform for one- to three-dimensional (1D to 3D) specimen surfaces. The directional antennas and wave-guided whispering-gallery modes (WG-WGMs) contribute to the majority of Raman enhancement by the MFs. Moreover, the MF can be coupled with surface-enhanced Raman spectroscopy (SERS) to provide an extra10-fold enhancement. The limit of detection is therefore improved for sensing of crystal violet (CV) and Sudan I molecules in aqueous solutions at concentrations down to 10

Photoluminescent properties from Au/ZnO/sapphire and ZnO/Au/sapphire structures have been investigated. It is found that due to the co-interaction between the incident light and local surface plasmons, the ultraviolet (UV) emissions from the two structures were both enhanced and the visible emissions related to the defects were suppressed. By the means of electromagnetic simulation, it indicates that the enhancement of UV intensity is a result of the enhanced electric field intensity of the 325 nm excitation light, which is induced by localized surface plasmons resonance (LSPR). On the other hand, electron transfer which is induced by the local surface also account for the enhancement of UV emissions. The suppression of the visible emissions might be due to the flowing of electrons in the defect states to the Au, which caused the reduction of the electrons in the defect states.