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Perovskite CH3NH3PbBr3 single crystals were synthesized by ITC method with DMF as solvent. X-ray diffraction was used to determine the structure of as-grown CH3NH3PbBr3 single crystal. The morphology of CH3NH3PbBr3 single crystal was measured by HRTEM and SEAD, and the result shows that the grown CH3NH3PbBr3 crystal is of good crystallinity. Optical properties were investigated by cathodoluminescence (CL) and photoluminescence (PL). The photoelectric performance of a photodetector based on CH3NH3PbBr3 single crystal was studied.The largest responsivity of the device is about 0.67 A/W, and the response time of photocurrent of the detector is 200 ms in the rise time and 250 ms in the fall time. Our results show CH3NH3PbBr3 single crystal has great potential for photoelectric device field.

Ag doped ZnO thin films have potential applications in many electronic and optoelectronic devices. Effective control of the chemical state of Ag is important for adjusting the electrical and optical properties of Ag-doped ZnO materials. So far, the influence of annealing temperature on the physical properties of Ag-doped ZnO thin films prepared by sol-gel method has rarely been reported. In this work, Ag-doped ZnO thin films were prepared by spin-coating technique and the evolution of microstructure, optical properties and conduction type with the rise of annealing temperature were investigated. The experimental results show that with the increase of annealing temperature, the crystalline quality of Ag-doped ZnO thin film is gradually improved and the grains gradually grow up. The ultraviolet emission has been also enhanced step by step. When the annealing temperature exceeds 450 °C, the surface segregation of Ag is directly observed by a field emission scanning electron microscope. In addition, the diffraction peak of metallic Ag is also perceived on the XRD patterns. The X-ray photoelectron spectroscopy shows that the chemical valence of Ag has been changed from +1 to 0. The surface segregation of Ag leads to the conduction type of the ZnO thin film to change from P type to N type. The surface segregation of Ag is caused by the high annealing temperature combined with a rapid cooling treatment.

CH3NH3SnI3 crystals with largest size up to 10 mm × 6 mm × 6 mm were grown in aerobic environment using cooling crystallization method. XRD analysis of the crystal powder shows that the CH3NH3SnI3 crystal grown is of cubic phase with lattice constants a = b = c = 6.2480 A. XRD and EDX results show that the chemical properties of CH3NH3SnI3 crystal are unstable in air, and the oxidation mechanism of CH3NH3SnI3 was analyzed. HRTEM shows that the CH3NH3SnI3 crystal grown is of good crystallinity. FT-IR spectrum of CH3NH3SnI3 crystal was identified. The band gap Eg of the CH3NH3SnI3 crystal is estimated to be 1.33eV according to the absorption spectrum. First-principles calculation shows the band gap of cubic CH3NH3SnI3 crystal is 1.36 eV, which is consistent with the experimental results. The thermal property of CH3NH3SnI3 is analyzed by TG/DTG analysis. Our results show that CH3NH3SnI3 crystal has potential application prospects in the field of solar cells, however its poor chemical stability in air, leading to the formation of SnI4 and SnO would limit its application in photoelectric fields.

In this work, Sn-doped ZnO thin films were deposited by sol-gel method. The structural, morphological and optical properties of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, fluorescence spectroscopy, respectively. The composition of the films was examined by energy dispersive X-ray spectroscopy (EDX). The photocatalytic performance was tested using methylene blue (MB) as a simulated organic pollutant. The results showed that all the ZnO thin films were preferentially oriented along the c-axis direction. The Sn-doping led the grains of the ZnO films to decrease. However, a kind of truncated-cone shaped nanostructures occurred on the surface of ZnO thin films when Sn-doping concentration was above 2 at.%, and both the number and the size of the ZnO truncated-cones increased with the further rise of the Sn-doping concentration. As a result, the surface roughness of the films was largely enhanced and the optical absorption was also improved. The wettability of the films was investigated by the water droplet spreading on the ZnO thin film surfaces. It showed that Sn-doping resulted in a smaller contact angle. The photocatalytic test on MB dyes showed that Sn-doping enhanced photodegradation efficiency of ZnO thin films. The improvement of the degradation efficiency was attributed to three main factors: (1) the formation of truncated-cone nanostructures on the surface of ZnO thin films increased the surface roughness and optical absorption; (2) the recombination of photogenerated electrons and hole was suppressed; (3) Sn-doping enhanced the surface energy of the ZnO thin films.

In this letter, the room-temperature ferromagnetic behavior in the ZnO/CuO nanocomposites has been reported. The composites composed of ZnO and CuO with different ratios were prepared by hydrothermal method. X-ray diffraction (XRD) and selected area electron diffraction (SAED) confirmed that these composites were made up by wurtzite ZnO and monoclinic CuO. X-ray photoelectron spectroscopy (XPS) indicated that Cu ions on the surface of the materials were in a divalent state. Magnetic measurements showed that all ZnO/CuO composites possessed room-temperature ferromagnetism, while pure ZnO was diamagnetic. With the increase of CuO content in the composites, ZnO/CuO composites displayed the coexistence of ferromagnetism and paramagnetism, and paramagnetism was gradually enhanced and dominated later.

Dynamic tuning of the resonance wavelength of subwavelength gratings in the mid-infrared (MIR) region via the permittivity change of phase-change material (PCM) has been demonstrated. A large shift in the peak of reflectance can be obtained by intermediate phase states of the Ge2Sb2Te5 (GST) layer. Fano resonance (FR) can be excited and is verified by the rigorous coupled-wave analysis (RCWA) method. Non-volatile tuning of lattice resonances over a range Δλ of about 1.9 μm (10.9 μm–12.8 μm) is achieved. Significant spectral tuning of FR can also be achieved by changing geometrical parameters as well as the angle of incidence. The wide range of the tunable FR in the technologically important MIR region offers a high resolution filter, which is useful for numerous sensing, imaging, and detection applications.

In this work, novel nanoplate-like Sn-Zn-O thin films were prepared by a sol-gel method and the effect of thermal treatment on the component and morphology was investigated. The photocatalytic activity was evaluated by photodegradation of Methylene blue. The results of X-ray diffraction show that the as-grown sample is a mixture of crystalline zinc hydroxystannate (ZnSn(OH)6) and amorphous ZnO; ZnSn(OH)6 is preferentially oriented along the (2 0 0) plane and has a platy morphology. With the increase of heating temperature, the compact and smooth nanoplates evolve into porous nanoplates, and the ZnSn(OH)6 is transformed into zinc metastannate (ZnSnO3), and the crystallinity of ZnO is gradually improved. For the heat-treated samples, the optical absorption spectra display two absorption edges corresponding to ZnO and ZnSnO3. The photocatalytic performance of Sn-Zn-O films is much higher than that of pure ZnO films and it shows good reproducibility.

An efficient protocol to synthesize substituted benzo[4,5]imidazo[1,2- c]quinazolines starting from N-LG-2-phenylbenzoimidazole and dioxazolones catalyzed by Rh(III) or Ir(III) has been developed. Various substituted benzo[4,5]imidazo[1,2- c]quinazolines could be easily provided in up to 99% yield. A large range of substrates and functional groups are compatible for this transformation. This method features low catalyst loading, acid-free conditions, and low solvent consumption.

A tunable and angle-independent thermal emitter which consists of silicon carbide (SiC) gratings incorporated with Ge2Sb2Te5 (GST) phase change materials (PCMs) in the mid-infrared (MIR) range has been proposed and investigated. The reflectivity under different conditions is simulated by the rigorous coupled wave analysis (RCWA) method. It is shown that a large shift of reflection dip is attainable within the Reststrahlen band of SiC (10.288 μm-12.563 μm) for transverse magnetic (TM) polarization light, when GST is changed between the crystalline and amorphous states. The deep reflection dips appeared for the two states of GST are attributed to the excitation of surface phonon plaritions (SPhPs). In addition, the incident angle independence of wavelength for both states of GST is obtained, which is a major feature of the tunable thermal emitter.

Ag-doped ZnO thin films have potential applications in many optoelectronic devices. In this work, Ag-doped ZnO thin films were prepared by a low-cost sol-gel method and the effect of annealing time on the optical and electrical properties of the samples was studied. The results showed that all the samples were pure ZnO phase with a wurtzite structure. As the annealing time increased, the ZnO grains grew up and the films became denser. In addition, photoluminescence behavior dependent strongly on the annealing time was found. These Ag-doped ZnO films exhibited co-emission of ultraviolet, green, and red light. Considering the results of X-ray photoelectron spectroscopy and other researchers' proposals, the green emission centered at 549 nm was suggested to be related to the zinc vacancy defects, and the red emission centered at 652 nm was probably associated with oxygen interstitials or oxygen species adsorbed on the ZnO surface. Electrical measurement results showed that Ag-doped ZnO films with annealing time longer than 10 min presented P-type conductivity, and as the annealing time increased, the resistivity decreased first and then increased again.

A design consists of low-index contrast grating is proposed to achieve the narrow absorption response for two-dimensional (2D) materials such as a MoS2 monolayer in the visible wavelength regime. High absorption occurs at the wavelength of Fano resonance for both transverse dielectric (TE) and transverse magnetic (TM) polarizations. It is proved that by manipulating related structural parameters and the incident angle, the peak wavelengths of MoS2 absorption can be tuned in a wide range. In addition, an improved structure with MoS2 ribbons is proposed to further boost the light-MoS2 interaction. The relationships between the absorptance and the period and width of MoS2 ribbons are discussed. The proposed optical devices could be efficiently exploited as tunable absorbing structures for optoelectronics and photovoltaic devices in the visible region.

An efficient tandem reaction of imidamides and N-hydroxycarbamates has been developed. Valuable 2-alkylbenzimidazoles could be easily obtained in up to 97% yield for more than 20 examples. The products would further streamline the synthesis of molecules, which are essential building blocks in organic synthesis and drug discovery. This protocol features high regioselectivity, efficiency, good tolerance of functional groups, and mild reaction conditions.

Through the consideration of light trapping theory, a hybrid structure with silicon (Si) photonic crystal slabs and silica (SiO2) spacer layer on gold (Au) substrate has been proposed to enhance the light absorption of monolayer transition-metal dichalcogenides (TMDCs). Complete monolayer TMDCs is utilized without any demand of manufacture process to form periodic patterns, and multiple absorption peaks with near unity absorbance at visible wavelengths can be achieved. Further analysis indicates that the strong confinement of electromagnetic (EM) field through the principle of critical coupling gives rise to the high absorption. The method is a general way to realize the total absorption in any lossy atomically thin two-dimensional (2D) materials. This favorable field enhancement and tunability of absorption not only open up new approaches to accelerate the light-matter interaction in monolayer TMDCs, but also may be of great significance in wavelength-selective photoluminescence and photodetection.

A wavelength tunable perfect absorber with graphene-hexagonal gold (Au) cylinder array on a ground plate is investigated theoretically. The interactions between electromagnetic (EM) waves and monolayer graphene are analyzed through the field distributions and spectral responses in detail. The finite-difference-time-domain (FDTD) method is used to investigate the tunable properties of the absorber. It is demonstrated that in an optimized configuration, monolayer graphene can interact with light via critical coupling, and the absorptance can be greatly enhanced and reach to 100% for both transverse magnetic (TM) and transverse electronic (TE) polarizations. Furthermore, the influence of geometrical parameters of the structure on the response of the hybrid structure is studied. It is expected that the proposed graphene perfect absorbers can be applied for many applications in the visible (VIS) and the near-infrared (NIR) spectral ranges such as wavelength selective infrared photodetectors and plasmonic sensors.

It is a recent hot topic of widespread interest to control the optical properties of metal oxide by noble metal nanoparticles. In this work, ZnO/Ag nanocomposite thin films were prepared by one-step sol-gel method. The crystal phase, morphology of the samples was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The presence of silver nanoparticles was confirmed by transmission electron microscopy (TEM). The distribution and chemical valence state of Ag in the samples was analyzed by elemental mapping images and X-ray photoelectron spectroscopy (XPS), respectively. The optical properties of the samples were studied by UV–visible spectroscopy and photoluminescence. It is found that the thermal treatment temperature has an important effect on the chemical state of silver in ZnO, and the change of chemical state of silver in turn affects the ultraviolet (UV) emission of ZnO. Under an appropriate heating temperature, the doped silver in the ZnO thin film can form silver nanoparticles, and the photoemission transfer of electrons from the silver nanoparticles to ZnO can effectively enhance the UV emission of ZnO thin film. The results show that under the experimental conditions applied in this study, 250°C is an optimum heating temperature, since the ZnO/Ag composite film heated at 250 °C has the strongest UV emission performance.

In this paper, CH3NH3PbI3-xClx crystal was grown by solution cooling method with CH3NH3I and PbCl2 as raw materials. Lead compounds and CH3NH3PbI3-xClx crystal with size about 6 mm × 4 mm × 2 mm were obtained. The chemical reactions with different CH3NH3I/PbCl2 ratios were analyzed. XPS shows the content of chlorine in CH3NH3PbI3-xClx is about 0.91%. PXRD, FT-IR, Raman and absorbance spectra were used to study the structure and optical properties of CH3NH3PbI3-xClx by comparing with CH3NH3PbI3 crystal. The CH3NH3PbI3-xClx crystal grown is of tetragonal structure with the lattice constants a = b = 8.8165 A, c = 12.7920 A and the bandgap value of 1.57 eV.

A multi-band absorber constructed from prism-incorporated one-dimensional photonic crystal (1D-PhC) containing graphene defects is achieved theoretically in the visible and near-infrared (vis-NIR) spectral range. By means of the transfer matrix method (TMM), the effect of structural parameters on the optical response of the structure has been investigated. It is possible to achieve multi-peak and complete optical absorption. The simulations reveal that the light intensity is enhanced at the graphene plane, and the resonant wavelength and the absorption intensity can also be tuned by tilting the incidence angle of the impinging light. In particular, multiple graphene sheets are embedded in the arrays, without any demand of manufacture process to cut them into periodic patterns. The proposed concept can be extended to other two-dimensional (2D) materials and engineered for promising applications, including selective or multiplex filters, multiple channel sensors, and photodetectors.

Since the absorption spectrum of CuO is well matched with the spectrum of the sunlight, it is considered to have potential applications in some optoelectronic devices such as solar cells etc. In order to obtain better performance of CuO-based devices, it is necessary to deeply understand the effect of structural parameters of thin films such as thickness on the physical properties of CuO thin films. In this study, the CuO thin films with different thicknesses were prepared by a facile sol-gel method. The structural, morphological, compositional and optical properties of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis absorption spectra and photoluminescence, respectively. The results show that all samples have a cubic structure regardless of film thickness. However, the photoluminescence behavior that strongly depends on the film thickness is found. When the film thickness is thin, CuO films show a strong violet, green and red co-emission. However, as the thickness increases, the fluorescence of the CuO films is rapidly quenched. It is proposed that the photoluminescence behavior of CuO thin films is closely related to the change of optical bandgap caused by the variation of crystallite size and we gave a tentative explanation for the luminescence changes.

In recent years, Cu-doped ZnO materials have attracted wide attention due to some unique properties, such as p-type conduction, room-temperature ferromagnetism and plentiful luminescence behavior. In this work, Cu-doped ZnO thin films with different doping levels were prepared by sol–gel method. The structural, morphological features and the composition of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX), respectively. The optical properties were analyzed by the UV–visible transmittance spectra and fluorescence spectra. The Cu-doping in a low concentration does not influence the crystal phase of wurtzite ZnO and has a very small impact on c-axis preferred orientation of ZnO thin films. With the increase of Cu-doping concentration, the Cu ions are gradually changed from dominant Cu+ ions to dominant Cu2+ ions. Cu-doping in a low concentration caused strong blue-violet emissions in ZnO thin films. The violet emission is attributed to the transition of electrons from the conduction band to Cu+ acceptor levels, and the blue emission is ascribed to the transition of electrons from Cu2+ donor levels to Cu+ acceptor levels.

In this work, Al-doped, Fe-doped, Mg-doped, Al-Fe and Al-Mg co-doped ZnO thin films were obtained by a spin-coating method. It has been found that Aluminum chloride as a doping source can induce the formation of a high-quality surface layer on the surface of the ZnO films. Here we demonstrated that the presence of Fe and Mg ions does not affect the formation of high-quality surface layer in Al-doped ZnO films, and all samples show strong UV emission properties. In addition, the Al-doping with high concentration can promote the formation of the high-quality surface layer without causing the appearance of impurity phases such as alumina or zinc aluminate. The structure, composition and luminescence behavior of the Al-Fe and Al-Mg co-doped ZnO thin films were characterized by X-ray diffraction, field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy and photoluminescence, respectively. The results show that the ZnO films with high-quality surface layer deposited by sol-gel method have potential applications in short-wavelength light-emitting devices.

Gallium oxide (Ga2O3) thin films were deposited on c-plane sapphire substrates at low temperature (RT) by magnetron sputtering method using Ga2O3 ceramic target and were post annealed at various temperatures ranging from 500 to 900 ℃ . The effect of annealing temperature on the surface morphology, crystalline structure, chemical composition and optical properties of Ga2O3 thin films were investigated. A phase separation is observed at 800 ℃ and α -phase Ga2O3 thin films is obtained at low annealing temperature while β -Ga2O3 at high temperature. With annealing temperature increases, the optical bandgap decreases from 5.47 to 5.00 eV and the surface morphology become more and more smooth. A broad emission band centered at 550 nm is observed for all samples which can be attributed to the donor acceptor pair (DAP) recombination related to the oxygen vacancies.

In recent years, it has attracted much interest to tailor the optical properties of metal oxides by metal nanoparticles. Many studies have found that the presence of Ag nanoparticles is beneficial to improve the ultraviolet (UV) emission of ZnO. In this investigation, Ag/ZnO nanocomposite thin films were prepared by sol-gel method. The effect of the film thickness on the optical properties of the samples was studied. The X-ray photoelectron spectroscopy (XPS) showed that Ag was present in ZnO in the form of simple substance, and Ag nanoparticles were observed by transmission electron microscope (TEM). A strong absorption originating from the surface plasmon resonance of Ag nanoparticles was also seen in the transmittance spectra of the samples. The photoluminescence spectra showed that the UV emission of the Ag/ZnO nanocomposite thin film was first improved with the increase of the film thickness; however, the UV emission was decreased again when the thickness of the film was more than 6 layers. This suggests that the thickness is an important factor which influences the photoluminescnece of the Ag/ZnO nanocomposite films.

A novel Ir-catalyzed annulation of imidamides with sulfonyl azides has been developed. 1,2-Disubstituted benzimidazoles could be easily obtained in up to 99% yield for more than 40 examples. The products further streamline the synthesis of molecules that are important building blocks for organic synthesis and drug discovery. This strategy features high regioselectivity, efficiency, good tolerance of functional groups, and mild reaction conditions.

Pattern assisted ZnO nanorods (NRs) growth are performed using electron beam lithography (EBL) and hydrothermal method. The patterns of lines, circles and squares are prepared on polycrystalline ZnO seed layer using PMMA as photoresist. It is found that the ZnO NRs can only grow on the area with ZnO seed layer, not on the PMMA surface. The TEM results show that the ZnO NRs have single crystal structures with good orientation along the c-axis. The excitation power dependence of photoluminescence (PL) spectra of ZnO NRs shows that with excitation power increasing, the near band edge emission increases rapidly than the defects related visible emissions. The temperature dependence of PL spectra was measured in the temperature range of 13–300 K. The dependence of peak position and peak energy of exciton bound (D0X) emission of ZnO NRs on temperature were analyzed. Two non-radiative recombination channels for the D0X emission are discussed in detail.

Although ZnO as a photocatalyst has attracted wide attention in the word in recent years, it is still a big challenge to develop low-cost, visible-light responsive ZnO based photocatalysts which can be used on a large scale. In this work, the CuO/ZnO nanocomposites have been synthesized by a facile one-step hydrothermal method and the influence of CuO contents on the photocatalytic properties of the nanocomposites has been investigated. The crystalline phase of the CuO/ZnO nanocomposites is determined by X-ray diffraction (XRD); the morphology and microstructures of the samples are analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalytic performance of the samples is tested using methylene blue （MB）dyes as the simulated pollutant under irradiation of a Xe lamp. Compared with pure ZnO, the photocatalytic activity of the CuO/ZnO nanocomposites is largely improved, especially for the sample prepared by the precursor solution with the molar ratio of Zn2+: Cu2+=2:1. The improvement of the photocatalytic activity is attributed to two main factors: (1) the band coupling improves the separation efficiency of photogenerated electrons and holes; (2) the utilization efficiency for solar energy is enhanced in the CuO/ZnO coupling system.

We report Raman lasing and the optical analog of electromagnetically-induced-transparency (EIT) in a whispering-gallery-mode (WGM) microtoroid resonator embedded in a low refractive index polymer matrix together with a tapered fiber coupler. The microtoroid resonator supports both single mode and multimode Raman lasing with low power thresholds. Observations of Fano and EIT-like phenomena in a packaged microresonator will enable high resolution sensors and can be used in networks where slow-light effect is needed. These results will open up new possibilities for portable, robust, and stable WGM microlasers and resonator-based sensors for applications in various environments.

In this work, the multilayered thin films composed of ZnO nanoparticles and SiO x layers were prepared by electron beam evaporation. The evolution behavior of photoluminescent properties of the samples with the increase of ZnO nanolayer thickness and annealing temperature was investigated. The morphology, crystal structures and luminescent properties of the samples were analyzed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and photoluminescence (PL), respectively. The SEM images revealed that the thin films were multilayer-structured with ZnO nanoparticles sandwiched in SiO x layers. The HRTEM disclosed that the SiO x was amorphous and ZnO was crystalline. The componential analyses showed that ZnO nanoparticles contained many oxygen vacancies and the x for SiO x was 1.96. The pure ZnO thin film showed three strong emission bands (namely, near ultraviolet, green and red emission bands) with nearly identical intensity. However, as for the ZnO nanoparticles sandwiched in SiO x layers, their green emission efficiency was greatly improved and the red emission was suppressed. Annealing treatments at 300 and 400 °C further enhanced the green emission. The largely enhanced green emission was attributed to the strong interaction between ZnO and SiO x .

We propose a stratified structure, where the monolayer graphene is sandwiched between two thin film stacks with optimized period number. A band-pass filter based on the stratified structure is realized. The dual-band enhanced optical absorptance of graphene with resonant tunneling in total internal reflection (TIR) regime is investigated theoretically. Both absorptance peaks are enhanced up to almost 100% in the pass-band filter based on resonant tunneling through a graphene sheet over the communication wavelength range due to the strong light field confinement. With the increasing of the bottom mirror layers, the values of the dual-band absorptance peaks improve accordingly while the peak locations are unchanged. The variation of the angle and wavelength can be exploited to realize tunable filters with good rejection.

We propose a new configuration of surface plasmon resonance (SPR) sensor that is based on graphene-MoS2 hybrid structures for ultrasensitive detection of molecules. The present configuration is consisted of chalcogenide glass (2S2G) prism, Ag, coupling layer, guiding layer, graphene-MoS2 heterostructure and analyte. We perform numerical and analytical study of the impact of the thickness and refractive index (RI) of the coupling and guiding layer in a planar sensing structure within the Kretschmann configuration on the resonance properties of the excitation. Results of reflectivity calculations clearly demonstrate the sharp Fano-type resonance appears in the curve of SPR because of the coupling between surface plasmon polariton (SPP) and planar waveguide (PWG) modes. The properties of the Fano resonance (FR) strongly depend on the parameters of the structure. The calculated magnetic field profiles manifest that the hybrid nature of the electromagnetic (EM) modes excited in the present structure. The proposed system displays an enhancement factor of sensitivity by intensity more than 2 × 103-fold when compared to the SPR sensing scheme.

As an important optoelectronic material, ZnO thin film has been used in lots of fields such as antireflection optical coatings, photoluminescence-based sensors, photocatalysts, etc. Many studies have demonstrated that the characteristics of the surface layer of ZnO thin film (such as crystalline state, point defect types, number of point defects, roughness, etc.) dominate its physical properties and thus determine the performance of the optoelectronic or microelectronic device prepared from it, so how to effectively control the characteristics of the surface layer is worthy of in-depth study. In this investigation, we prepared ferric chloride doped ZnO thin films and explored the effect of heat-treatment temperature on the crystalline state and luminescence behavior of the surface layer. The results show that all samples possess a double-layer structure: the bottom layer is a conventional ZnO layer composed of polycrystalline particles, while the top layer is made up of dense pyramid-like nanostructures. These pyramid-like nanostructures have good crystalline quality and high c-axis orientation. The increase of the heat-treatment temperature accelerates the formation of a high-quality optical surface layer in the ZnO thin film, and the formation of this high-quality surface layer in turn greatly improves the ultraviolet emission efficiency of the ZnO thin film.

In this work, nanocrystalline ZnO powders were prepared by a low-temperature hydrothermal method using zinc nitrate and hexamethylenetetramine (HMT) as the Zn and alkaline source, respectively. The influence of the concentration of HMT in the growth solutions on the structural, optical and photocatalytic properties of nanocrystalline ZnO powders was investigated. The results showed that the ZnO powders were composed of lots of ZnO nanoparticles; the different concentration of HMT had almost no influence on the crystalline structure of the ZnO particles. However, with the increase of HMT concentration, the size of the ZnO particles and the ultraviolet emission decreased gradually while the visible emissions gradually enhanced. The photocatalytic tests showed that all the samples exhibited good photocatalytic degradation performance for Rhodamine B (RhB). With the increase of HMT concentration, the photocatalytic activity of the ZnO powders was also enhanced. The enhanced photocatalytic activity was ascribed to the increase of the specific surface area and oxygen vacancies on the surface of the particles.

We demonstrate the excitation of surface phonon polaritons (SPhPs) in the mid-infrared (mid-IR) Reststrahlen band (10.288 μm-12.563 μm) on patterned surfaces with silicon carbide (SiC) substrate and gold (Au) gratings. The very large negative permittivity of Au limits its applications in the mid-IR range, and to couple incident light to SPhPs modes, their momentum mismatch can be compensated by patterning Au grating onto the surface of SiC substrate. Samples were fabricated and characterized experimentally by Fourier transform infrared reflection (FTIR) spectroscopy. The optical properties were also simulated by the rigorous coupled wave analysis (RCWA) method. Reflection dips are observed for light polarized vertical to the grating lines (TM-polarized), which are attributed to the coupling of electromagnetic (EM) waves into the SPhP modes. In addition, we present small-volume index sensing with analyte specificity based on mid-IR SPhPs in the fabricated configuration.

Ultra-narrow linewidth, angle insensitive guide-mode resonance filter (GMRF) has been designed. The aimed performance on the behavior of the filter with respect to the angular divergence of the incident beam was considered. Results show that high reflection (more than 99.9%) can be obtained at the resonance wavelength, the full-width at half maximum (FWHM) of TE- polarized light is only 1.1 × 10−3 μm, and its sideband reflectance from 0.565 to 0.625 μm is less than 1%. In contrast to the ordinary GMRF, where the location of the resonances is incident angle dependent, it is demonstrated that the maximum peaks of the reflected spectrum gradually decreases with respect to the incident angle, but the reflectance peak position does not change.

A planar silicon carbide/dielectric multilayer structure is investigated in Otto geometry, where surface phonon polaritons and planar waveguide mode can be coupled to realize Fano resonances under transverse magnetic polarization. The resonance coupling is analytically demonstrated using the coupled harmonic oscillator model and numerically presented through rigorous coupled-wave analysis calculations, which shows that the coupling strength between different resonances and the resonant wavelength matching condition plays an important role in the bandwidth and position of the Fano resonance (FR); the magnetic field distribution was also shown to explain the origin of FRs qualitatively.

Ir-catalyzed direct C-H sulfamidation of benzaldehydes has been achieved. A series of ortho-amided benzaldehydes were obtained in up to 95% yields for 21 examples with excellent regioselectivity and broad functional group tolerance. This transformation could proceed smoothly with low catalyst loading under external-oxidant-, acid-, or base-free conditions. Molecular nitrogen was released as the sole byproduct, providing an environmentally benign sulfamidation process.

Spectral responses of a novel resonant waveguide grating (WGG) configuration, in which monolayer graphene is prepared on top of the WGG, and the period is composed of two grating ridges with identical width are presented. Fano-like resonance can effectively improve the graphene absorption from 2.3 to 63.2 %. And the absorption width can be tailored without modifying the spectral lineshapes and sideband levels, while the maximum absorption wavelength linearly varies with the increase of period. The situation of oblique incidence is studied as well. Fano-like resonant grating suggests a new opportunity for the design of tunable graphene photonic and optoelectronic devices.

In this work, ZnO thin films were prepared by electron beam evaporation and rapidly annealed at different temperatures. The analysis of X-ray diffraction (XRD) showed that all the ZnO thin films were preferentially oriented along the c-axis. With the increase of annealing temperature, the degree of preferred orientation along the c-axis was enhanced and ZnO crystals also increased gradually. However, the transmittance and optical bandgap of the samples were almost not affected by the rapid annealing treatment. The photoluminescence spectra showed that all the samples exhibited strong UV and visible emissions (mainly green and red emissions). Although the strong UV emission along with strong green emission was often reported previously, the strong co-emission of UV, green and red light was rarely reported. If, as many researchers suggested, the green emission of ZnO was mainly related with oxygen vacancy defects and the red emission was associated with oxygen interstitial defects, thus the strong co-emission of green and red light was hard to happen in theory. The strong co-emission of green and red light or green/red emissions with different wavelengths at the same time implies that there are probably several sources for green or red emissions. Deeply and extensively investigating the luminescence behavior of ZnO materials is favorable for revealing visible emission mechanisms and developing ZnO-based light-emitting devices as possible as soon.

In this work, ZnO and CuO were first prepared by thermal evaporation and direct precipitation, respectively, and then CuO/ZnO composites were obtained by mechanical grinding the mixtures of CuO and ZnO. Scanning electron microscopy, Raman spectroscopy, Raman imaging, UV–vis absorption spectroscopy, and photoluminescence spectroscopy were used to analyze the morphology, structure, and optical properties of CuO/ZnO composites. Raman spectra suggest that the prepared ZnO has a high crystalline quality, while the CuO/ZnO composites have an internal stress. Compared with ZnO, the absorption edge of CuO/ZnO composites shows a red-shift, and the absorption intensity in the visible region is increased greatly. Pure ZnO shows a strong ultraviolet (UV) emission and a weak green emission. As for the CuO/ZnO composites, with the increase of CuO content, the intensity of the UV emission is gradually reduced and the UV peak is gradually moving towards the longer wavelength direction. The decrease in the UV emission intensity should be attributed to interface effects, and the red-shift of UV emission peaks may be caused by unintentional Cu-doping.

ZnO thin film is an important optical material. Therefore, using simple methods or techniques to improve its optical quality is an important research topic. In this study, a sol-gel spin-coating method was used to deposit ZnO thin films co-doped with Fe and Cl on glass substrates and the effect of annealing temperature on their microstructure and optical properties was explored. Field emission scanning electron microscope observes that all samples have a double-layer structure: the upper layer is composed of single-crystal nanocolumns and the lower layer is made up of polycrystalline nanoparticles. The increase of annealing temperature leads to some important changes: (1) the UV emission is gradually enhanced; (2) the absorption edge is gradually red-shifted; (3) cavities are formed in the lower layer of ZnO thin films. As far as we know, there are few reports on cavities in the lower layer of ZnO thin films. The appearance of these cavities, we speculate, is due to the mass transport from the lower layer to the upper layer, that is, the formation of single crystal nanocolumns is the result of sacrificing the polycrystalline nanoparticles in the lower layer of ZnO thin films.

The Zn-Sn-(OH)x thin film was prepared by sol-gel method at low temperature, and its structure, morphology, and photoluminescence properties were studied as a function of annealing temperature. X-ray diffraction patterns showed that the as-grown film contained highly crystalline zinc hydroxystannate. When it was annealed at 300 °C, zinc hydroxystannate was decomposed, and wurtzite-structured ZnO was formed. High-resolution TEM images and selected electron diffraction patterns further confirmed the formation of wurtzite-structured ZnO after annealing. The scanning electron microscope observed that the as-grown Zn-Sn-(OH)x film contained two layers: the upper layer was a crystalline ZnSn(OH)6 thin film, and the underlying layer was an amorphous Zn-Sn-O ternary composite. After it was annealed at 300 °C, some pyramid-like nanostructures appeared on the film surface. As the annealing temperature was further increased, the areal density of the pyramid-shaped nanostructures decreased, but the diameter and height increased. The photoluminescence spectra showed that the ZnSn(OH)6 film exhibited strong violet and blue-green co-emission. After annealing, the visible emission intensity was obviously reduced, while an ultraviolet emission from ZnO was being appeared. We proposed that the violet emission of ZnSn(OH)6 thin film might be related to the zinc interstitials, and the blue-green emission should come from the electronic transitions related to oxygen vacancy levels.