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Owing to the increasing application of high-performance and multifunctional mid-infrared (MIR) optoelectronic devices, it is important to achieve a high emission efficiency and broadband tunable luminescence. In this study, nanocrystalline units with unique properties were integrated into an amorphous frame with high transmittance and infinite ductility to achieve an enhanced MIR emission. In the single active ion-doped system, owing to the combination of the lower phonon energy of the crystal, the fixed position of the crystal lattice, and the glass transparency, a substantial increase in the infrared fluorescence intensity was achieved. Particularly, an excellent 3 μm luminescence was realized by the stable composite material. In the co-doped system, a bottom-up strategy was adopted to achieve full coverage of the 2 μm MIR atmospheric window, and the results confirmed that the spatial distribution of the optically active nanocrystal units in the glass frame effectively controlled the energy transfer processes.

High-strength-modulus glass fiber is widely used in military, transportation, electronics, chemical industry, environmental protection and other industries. In recent years, with the development of new energy, the research of high-strength-modulus glass fiber which can be applied in the large size fan blade is gradually being paid attention to. It is important to find an excellent glass component for the production of high-strength glass fibers. As is well known, silicate glass has a stable glass-forming region and mature drawing processes into fibers. In this study, to obtain enhanced mechanical properties, glasses with a composition of SiO2-Al2O3-MgO-CaO-B2O3-Fe2O3 were synthesized using TiO2 and CeO2. When the amount of TiO2 and CeO2 is less than 2 wt%, the mechanical properties increase with increases in the TiO2 and CeO2. However, as the amount of TiO2 and CeO2 increases from 2 to 3.5 wt%, the mechanical properties decrease. Co-doping with 1 wt% TiO2 and 1 wt% CeO2 was found to be the optimum approach, with a density, bending strength, compression strength, and compression modulus of 2.626 g/cm3, 108.36 MPa, 240.18 MPa, and 115.03 GPa, respectively. The optical band gap and Raman spectroscopy proved that, as long as the content of oxygen bonds reaches the maximum level, a kind of best structural stability and mechanical properties will be achieved. Hence, this high-strength-modulus silicate glass can be used to make optical fibres for military defence, wind power generation and transportation.

The effect of hydrostatic pressure (HP) on the corrosion behaviour of X80 steel is investigated to assist the development of deep-sea oil and gas resources. The results show that the corrosion curr...

As is well known, a way to obtain a high color resolution and saturation of a liquid crystal display and thereby obtain a higher visual accuracy and comfort in the coming 5G era remains an urgent challenge. In the present study, a new type of phosphor composite material doped with Ln3+ ions provides a promising alternative to the color filters used in White light-emitting diodes (WLEDs), achieving a better performance regarding the realization of a wider color gamut. The advantages of this composite material are illustrated through an abundant phase and morphology analysis along with a discussion regarding the X-ray photoelectron spectroscopy of the valence bond of Ce ions, which maintain the luminescence properties of the phosphor while providing a stable and solid amorphous environment. An improved spectral performance was obtained through color filtering at 580 nm along with the regulating effects of red, green, and blue emissions according to the doped Ln3+ ions. Notably, we fabricated a high-performance WLED based on a Ln3+-doped PiG with a correlated color temperature of 5037 K, color rendering index of 72.8, and high color gamut of 91.97%, providing a new choice for the development of luminescence materials with a high color resolution and saturation.

In this paper, the principle and application of atomic force microscopy (AFM) are reviewed and discussed in detail. Several scientific papers are used to find out data about AFM. The obtained scientific results are summarized to get a better understanding of the method and its application. The application of AFM for corrosion study is discussed in detail, and the possible conclusion is made based on the results of several articles. It is summarized that AFM is an important method to determine the surface phenomena of metal corrosion.

Rattle-structured nanoparticles with movable cores, porous shells and hollow interiors have shown great effectiveness in drug delivery and cancer theranostics. Targeting autophagy and glucose have provided alternative strategies for cancer intervention therapy. Herein, rattle-structured polydopamine@mesoporous silica nanoparticles were prepared for in vivo photoacoustic (PA) imaging and augmented low-temperature photothermal therapy (PTT) via complementary autophagy inhibition and glucose metabolism. Methods: The multifunctional rattle-structured nanoparticles were designed with the nanocore of PDA and the nanoshell of hollow mesoporous silica (PDA@hm) via a four-step process. PDA@hm was then loaded with autophagy inhibitor chloroquine (CQ) and conjugated with glucose consumer glucose oxidase (GOx) (PDA@hm@CQ@GOx), forming a corona-like structure nanoparticle. Results: The CQ and GOx were loaded into the cavity and decorated onto the surface of PDA@hm, respectively. The GOx-mediated tumor starvation strategy would directly suppress the expression of HSP70 and HSP90, resulting in an enhanced low-temperature PTT induced by PDA nanocore. In addition, autophagy inhibition by the released CQ made up for the loss of low-temperature PTT and starvation efficiencies by PTT- and starvation-activated autophagy, realizing augmented therapy efficacy. Furthermore, the PDA nanocore in the PDA@hm@CQ@GOx could be also used for PA imaging. Conclusion: Such a "drugs" loaded rattle-structured nanoparticle could be used for augmented low-temperature PTT through complementarily regulating glucose metabolism and inhibiting autophagy and in vivo photoacoustic imaging.

Phosphor-in-glass (PiG) is a novel fluorescent color conversion material that is an excellent choice for preparing wide-color gamut white LEDs due to its excellent thermal stability, high efficiency and facile preparation process. To the best of our knowledge, this paper is the first to widen the color gamut of the white LED from 77.33% to 92.02% by doping the PiG substrate with two kinds of lanthanide ions: Er3+ and Nd3+. The low sintering temperature and suitable preparation process has ensured the phosphor and glass become compounded independently together while still exhibiting good luminescence performance; this has been demonstrated via X-ray diffraction and field emission scanning electron microscopy. The influence of doping the host glass with Ln3+ ions has been explored, specifically considering the effects on the color gamut, the color coordination, the correlated color temperature and the color rendering index. The results presented herein have demonstrated that the Er3+/Nd3+-doped PiG is a promising candidate as a color filter in the domain of wide-color gamut white LED.

Rare earth doped luminescence glasses have been noteworthy recently in the fields of near-middle-infrared applications. In this work, serious Er3+ doped new kind of germanosilicate-zinc glasses have been investigated aiming to obtain efficient infrared and mid-infrared luminescence performance. The drastically reduced OH− content in present host support the enhanced 2.7 and 1.5 μm emissions corresponding to the 4I11/2 → 4I13/2 and 4I13/2 → 4I15/2 transitions owing to the decreased energy loss between OH− and active ions. Meanwhile, the energy transfer mechanism has been discussed based on both the infrared and visible spectra together with the measured decay curves. Hence, the large absorption and emission cross-sections indicate that this kind of germanosilicate-zinc glasses may provide high gain as a good medium for efficient infrared laser system.

For the first time, hierarchical CoMoO4@Ni(OH)2 core-shell hollow nanotubes were synthesized using hydrothermal and ion-exchange route process. As supercapacitor material, the CoMoO4@Ni(OH)2 core-shell hollow nanotubes exhibited a high specific capacitance of 1246 F g−1 at a current density of 1 A g−1, and 86.7% of the original capacitance was also retained at 5 A g−1, indicating an excellent rate performance. Theoretical analysis showed that the surface capacitance dominated the total capacitance of the CoMoO4@Ni(OH)2 electrode. The asymmetric supercapacitor device based on CoMoO4@Ni(OH)2 and porous carbon exhibited high energy density of 62.5 Wh kg−1. In addition, the overpotential of the as-prepared material was 0.35 V in the oxygen evolution reaction at the scan rate of 10 mV s−1, showing high activity. All these electrochemical properties indicated that the fabricated hierarchical CoMoO4@Ni(OH)2 core-shell nanotubes were promising candidates for highly performed bifunctional supercapacitors and oxygen electrocatalysts.

Manipulating the energy transfer process between the dopants can realize efficient modulation of photoluminescence, which is essential for fabricating optoelectronic devices. This work presents the polarization-assisted energy transfer process between Er3+ and Dy3+ ions in borate glass-ceramics system for the first time. The overall photoluminescence intensities increased gradually as undergoing polarization engineer. The promoted energy transfer process from Er3+ to Dy3+ is obtained by emission spectra and verified by decay dynamics, which can be attributed to the slight tuning of ionic environment around doping ions. Herein, the tunable energy transfer process inspired by polarization may provide guidance for fabricating high-performance optoelectronic devices.

A system of zinc fluoride glasses were synthesized to analyse the sensitization mechanism between doped Ln3+ ions under 808 or 980 nm excitation. Differential scanning calorimetry (DSC) curve and Raman spectra indicate the favourable thermal stability and a low maximum phonon energy of the host. Judd-Ofelt (J-O) theory together with the absorption spectra were utilized to compute the Ωt for predicting radiative features of each sample which coincide with the later measured emission spectra. Broadband emission ranging from 2400 to 3300 nm with a half-width of 361 nm in Er3+/Dy3+ codoped zinc fluoride glasses under 980 nm pumping has been investigated, which may be applicated in mid-infrared fiber amplifier and broadband tunable lasers field. On the other hand, the efficient sensitization effect mechanism between Er3+ and Dy3+ around 3 μm band with an extremely high energy transfer efficiency Ƞ (96.1%) of Er3+:4I13/2→Dy:6H11/2 has been researched under 808 nm excitation. Hence, Er3+ and Dy3+ doped zinc fluoride glasses may be potential optical candidates of great development foreground in the fields of mid-infrared applications.

BaMoO4: Er3+/Yb3+ phosphors with different concentrations have been fabricated by a facile hydrothermal method. The morphology observation shows that the shape and size of BaMoO4 powders change after Er3+/Yb3+ doping. The upconversion luminescence spectra consist of intense green bands centered at 536 and 558 nm and a weak red emission band peaked at 668 nm upon 980 nm excitation. The excitation power and doping concentration have little impacts on the color emitted from the samples. Applying the fluorescence intensity ratio (FIR) technique, the temperature sensing behaviors are investigated based on thermally coupled levels (2H11/2 and 4S3/2) and non-thermally coupled levels (4F9/2 and 4S3/2), respectively. The thermometry is sensitive to the excitation power for 4F9/2 and 4S3/2 levels, leading to large measurement errors caused by the power variation. Such a problem can be solved by using the power-insensitive FIR between 2H11/2 and 4S3/2 levels, which also shows the advantage of high absolute sensitivity with the maximum of 110.7 × 10−4 K−1. So, the developed BaMoO4:Er3+/Yb3+ phosphors can be applied in green light upconverters, display devices and temperature sensors.

With 980 nm laser diode (LD) pumping sources, 2.7 µm emission of Er3+-doped tungsten-tellurite (TWL) glasses were investigated. Absorption spectra were measured and an irregularly increased absorption predicted the phenomena of concentration quenching or clustering at 4 mol% Er2O3 concentration. Emission properties of 2.7 µm, 1.5 µm and visible regions were tested to evaluate the energy transfer process of Er3+ ions. With the increment of Er3+ ions, the excited-state absorption (ESA) from Er3+: 4I13/2 level was becoming more apparent and the lifetime of 1.5 µm emission was decreased. At the same time, the up-conversion emissions at green and red regions were decreased. These phenomena gave the evidence of concentration quenching or clustering. Thus, the best concentration of Er3+ ions in this tungsten-tellurite glass was about 3 mol%. Based on its advantages on high solubility of Er3+ ions, strong emission and good thermal stability, tungsten-tellurite glass is a good candidate for mid-infrared laser matrix.

Efficient NIR–MIR luminescence conversion materials are urgently required for numerous applications in the fields of medicine, remote sensing, and optical communications. The control of the chemica...

We investigated thermal and fluorescence properties of Er3+ doped fluoroaluminate multi-component glasses modified by TeO2 and CaCl2. A better thermal stability with a higher ΔT (98 °C) was obtained for the TeO2 modified sample, which had a high radiative transition probability (Arad) of the Er3+: 4I11/2→4I13/2 transition. In addition, under 980 or 808 nm excitation, the Er3+ 2.7 µm emission intensity of the TeO2 modified sample decreased owing to its increased hydroxyl content induced by TeO2 modifiers. Excellent mid-infrared fluorescence along with a longer lifetime (3.48 ms) were observed in the glass tuned by CaCl2. The CaCl2 modified sample exhibited higher stimulated absorption and emission cross sections, obtained using the Fuchtbauer-Ladenburg and McCumber formulas. Moreover, the strong effect of hydroxyl on the mid-infrared fluorescence properties was systematically analyzed. The oxygen network modifiers in the fluoroaluminate multi-component glass provide improved thermal properties, while the AlF3-based glasses with chlorine network modifiers have larger potentials for applications in the mid-infrared region.

Increasing the number of luminescence emitters without concentration quenching is essential to realize the high doping in silicate glass system, which is favorable for the output of single-frequency fiber lasers. In this work, the concentration quenching threshold of mid-infrared luminescence is enhanced by 60% after macro-scale manipulation of glassy structure. The reason can be attributed to the reduced maximum phonon energy after the increasing of Pb content and the increasing number of emitters due to the looser glassy network. The absorption and emission cross sections after structural engineering can reach to 0.75 × 10–20 cm2 and 1.53 × 10–20 cm2, respectively. These results reveal that the concentration quenching threshold can be effectively enhanced through the structural manipulation in a wide range, and the prepared lead silicate glass after structural engineering can be the ideal candidate for drawing optical fiber and are potential in future optical applications.

In this work, a new optical thermometer relying on highly temperature-dependent 1D2 Pr3+ emission and temperature insensitive Y2Ti2O7 trap emission is reported. Based on the fluorescence intensity ratio (FIR) between them, Pr3+: Y2Ti2O7 with remarkably high absolute and relative sensitivities of ~ 983 × 10−4 K−1 and 5.25% K−1 as well as good signal discriminability is realized. It also exhibits a tunable luminescent color from red to purplish blue with temperature from 289 to 573 K. The strong thermal quenching of 1D2 Pr3+ emission is mainly related to the charge transfer state (CTS). Similarly, Pr3+: Gd2Ti2O7 phosphor also demonstrates a favorable temperature sensing feature, indicating the temperature sensing strategy based on the combination of host trap emission and CTS interfered Pr3+ luminescence is a promising pathway to develop high-performance optical thermometric materials.

Nanostructure is the most important aspect in the development of high performance supercapacitors. In this work, we designed and developed new one-dimensional hierarchical hollow nickel–cobalt layered double hydroxide nanocages assembled on MnO2 nanotubes with uniformly dispersed CoS2 nanoparticles, MnO2@NiCo-LDH/CoS2, using a zeolitic imidazolate skeleton (ZIF-67) as the template via multiple hydrothermal and sulfuration processes. This unique one-dimensional hierarchical nanostructure is characterized by a high specific area and high structural stability. The presence of CoS2 nanoparticles in the nanocage increases the electrical conductivity and enhances the stability of the structure. Electrochemical studies show that MnO2@NiCo-LDH/CoS2 electrode materials have a high specific capacitance of 1547 F g−1 at a current density of 1 A g−1 and 1189 F g−1 at 10 A g−1, exhibiting high rate performance (76.9%) and high stability (82.3%), which is substantially better than the performance of most recently reported similar systems. The asymmetric supercapacitor assembled with MnO2@NiCo-LDH/CoS2 and activated carbon has a maximum energy density of 50 W h kg−1 and a maximum power density of 9658 W kg−1. The unique nanostructure and excellent performance of the asymmetric supercapacitor in the present study demonstrate a new platform for developing highly efficient supercapacitor materials with high energy density and high power density.

Lithium–sulfur batteries are of significant interest because their theoretical energy density exceeds that of Li-ion batteries and they can be fabricated at much lower costs. Although significant efforts have been devoted towards improving sulfur electrodes, the battery requires a “flooded” electrolyte for the dissolution–precipitation chemistry to achieve acceptable energy efficiency (the electrolyte/sulfur ratio, E/S ratio, is typically much higher than 5 : 1 μl mg−1). Herein, we report a complex electrolyte of LiTFSI salt with widely used carbonate solvents (EC and DEC) other than ether (DOL and DME) for use in Li–S batteries based on S8 as the active material. By tuning the electrolyte coordination structure, we demonstrated that the sulfur speciation pathway was fundamentally altered from the conventional dissolution–precipitation category to an akin solid–solid biphasic conversion, leading to low E/S ratios and no shuttle effect. Furthermore, the reduced reactivity of the fully coordinated solvents mitigates Li dendritic formation and related electrolyte consumption. These combined merits allow us to demonstrate that a S8/Ketjenblack electrode can achieve a capacity close to theoretical capacity (1600 mA h g−1) and high coulombic efficiency (above 99%) with a stable cycling performance at an ultralow electrolyte/sulfur ratio (1.5 : 1 μl mg−1); hence, our study defines a new pathway towards the fabrication of highly robust Li–S batteries for high-density energy storage.

Vertically-oriented graphene nanowalls (VGNWs) have been successfully synthesized under different experimental conditions (such as flow rate of argon, growth temperature, plasma power as well as deposition time) on copper foils in the reactive methane and argon environment using a capacitively coupled plasma-enhanced horizontal tube furnace deposition system. It is shown that the morphology and structure of VGNWs can be effectively tailored by experimental conditions. Furthermore, the growth mechanism of VGNWs produced in the plasma-based approach has been investigated. The synthesized VGNWs are used as anode materials in Li-ion batteries and the batteries show outstanding cycle efficiency (~99%). The specific capacity of coin-type cells can be improved by adjusting the experimental parameters and reaches 400 mAh g−1 in the first charge-discharge cycle. This work is particularly important for the development of an advanced process for the synthesis and application of carbon-based nanomaterials.

The temperature dependences of 1.53 μm near infrared and green upconversion (UC) emissions of Er3+ ion have been investigated in Er3+/Yb3+: BaMoO4 powders upon 980 nm excitation. Interestingly, an anomalous enhancement of 1.53 μm luminescence intensity with increasing temperature is observed, which is interpreted based on the phonon-assisted nonradiative process from 4I11/2 to 4I13/2 level. Moreover, the emission intensities from various Stark transitions 4I13/2(Yi)→4I15/2(Zj) show different changing rates with temperature, which is in favor of optical thermometry application based on fluorescence intensity ratio (FIR) technique. The results show that the utilization of FIR-1 (I1504/I1531) from two Stark transitions with the same power-dependence is beneficial to obtain consistent results at different excitation power densities, and avoid measurement error resulted from the power density variation. Besides, when FIR-Green (I533/I557) is used as the thermometric index, a high absolute sensitivity of 115 × 10−4 at 430 K can be obtained. Therefore, Er3+/Yb3+: BaMoO4 is promising for optical thermometry.

Hydrogen permeable V-Cr-Al alloys have been designed based on the lattice matching principle. To elucidate alloying effects of Cr and Al, the hydrogen solubility and hydrogen permeation flux have been characterized at temperatures between 523 and 673 K. V90Cr5Al5 exhibits a highly reduced hydrogen solubility, which contributes to enhanced resistance towards hydrogen embrittlement, at the same time maintaining the high permeability as pure vanadium at 673 K. The stability of the V90Cr5Al5 membrane during hydrogen permeation tests at several temperatures has been characterized: V90Cr5Al5 shows a constant hydrogen permeation flux up to 500 h at 573 K. A small drop in permeation flux (J×d) by 4% was observed at 623 K after 500 h, i.e. from 1.35 × 10−4 to 1.30 × 10−4 mol H2 m−1s−1. Serious degradation in the hydrogen permeation flux during the long-term test was observed at the temperatures above 673 K. This is attributed to the formation of a new barrier layer caused by the interdiffusion between Pd and V90Cr5Al5.

Single-molecule electrical characterization reveals the events occurring at the nanoscale, which provides guidelines for molecular materials and devices. However, data analysis to extract valuable information from the nanoscale measurement data remained as a major challenge. Herein, an unsupervised deep leaning method, a deep auto-encoder K-means (DAK) algorithm, is developed to distinguish different events from single-molecule charge transport measurements. As validated by three single-molecule junction systems, the method applies to the recognition for multiple compounds with various events and offers an effective data analysis method to track reaction kinetics at the single-molecule scale. This work opens the possibility of using deep unsupervised approaches to studying the physical and chemical processes at the single-molecule level.

In this work, we develop a simple customized radio-frequency plasma-enhanced horizontal tube furnace deposition system to directly grow high-quality ZnO nanorod arrays on zinc films and investigate their application as an antireflective layer in n+pp+ monocrystalline silicon (c-Si) solar cells. Field emission scanning electron microscope, X-ray diffractometer, and transmission electron microscope studies reveal that ZnO nanorod arrays feature a perfect crystalline wurtzite structure and grow preferentially along [0001] direction. The antireflective performance of ZnO nanorod arrays is confirmed by Fresnel coefficient matrix method and MATLAB software calculation. Furthermore, PC1D simulation demonstrates that the photovoltaic property for c-Si solar cells of the pyramid-textured front surface using ZnO nanorod arrays as an antireflective layer is much better than that for the other three types of c-Si solar cells (i.e., c-Si solar cells of the pyramid-textured front surface without using any antireflective layer, c-Si solar cells of the planar front surface using ZnO nanorod arrays as an antireflective layer, as well as c-Si solar cells of the planar front surface without using any antireflective layer). In particular, the photovoltaic conversion efficiency of 20.23% has been achieved for c-Si solar cells of the pyramid-textured front surface using ZnO nanorod arrays as an antireflective layer. This work is highly relevant to the development of an advanced process for the realization of high-efficiency, low-cost, and stable solar cells.

Diode-pumped solid-state 2 μm lasers have seen rapid development for their efficient operation, compact size, and stable performance. In this work, doped germanosilicate (SiO2-GeO2-Ga2O3-Lu2O3) glasses with varying Tm3+/Ho3+ concentrations exhibiting excellent physical and optical characteristics were successfully prepared. Thermal and structural properties were analyzed by the measured DSC and Raman spectra. An evident efficient wide absorption band near 770–830 nm demonstrated the feasible energy transfer between Tm3+: 3F4 → 3H6 and Ho3+: 5I7 → 5I8 transitions. Meanwhile, combining with Judd-Ofelt theory, super predicted spontaneous emission probabilities were obtained, which are beneficial to obtain fine laser action for solid-state lasers. This is a first study to demonstrate that a tunable fluorescence peak (1.8–2.05 μm) can be obtained by modulating the combined effects between two luminous activation centers. Therefore, the results indicate a promising rare-earth doped glass host for solid-state 2 μm lasers.

Highly rare earth（RE）ions doped glass laser materials can produce efficient single frequency mid-infrared laser. In this work, a series germanosilicate glasses with various high erbium-doping concentration (up to 4 mol%) and without concentration quenching are fabricated. Spectroscopic properties and energy transfer (ET) mechanism of efficient Er3+:4I11/2 →4I13/2 transition have been investigated in detail upon a conventional 980 nm Laser Diode. The dense structure of silicate glass can be dissolved effectively by the introduction of GeO2, which was analyzed by Raman spectra, so that the compatibility and luminous intensity of RE ions were improved. The high predicted spontaneous transition probability (Arad = 37.65 s−1) based on the Judd-Ofelt theory and large calculated emission cross section (8.8 × 10−21 cm2) are obtained. The above results indicate that these glasses are promising to be the single frequency mid-infrared laser material.

The fluorescence properties in IR region of fluorotellurite glass with high Er3+ concentration up to 13 mol% are investigated and optimum concentration of 2.7 µm emission is 11 mol%, followed by a decrease in fluorescence intensity. The thermal characteristic parameter (ΔT = 98 °C) based on DSC curve shows a good thermal stability. The FWHM corresponding to 1.5 µm broadens as Er3+ increases and reaches a maximum of 110 nm (13 mol%) which shows superior bandwidth properties. The high amplifier gain value(σemi × τmea) of 11.87 × 10–21 cm2 ms, along with longer lifetime (1.72 ms), which benefits from the low phonon energy (612 cm−1) and hydroxyl content (0.03 cm−1), indicates the ideal 2.7 µm laser characteristics. Hopefully, the glass studied here may be find potential applications in the fields of fiber amplifier and MIR microchip lasers.

Although supercapacitors have been extensively investigated due to the good electrochemical performance, the awful energy density, poor cycle stability and low rate performance still remain challenges in applications. In this article, we successfully design and synthesize the hierarchical NiCo2O4@NiCo2S4 core/shell nanowire arrays on Ni foam by a special interface ion-exchange process. As supercapacitor material, it exhibits a high specific capacitance of 3176 F g−1 at a current density of 2 A g−1 and can retain 86.52% at a high current density of 10 A g−1, indicating excellent rate capability. In addition, an asymmetric supercapacitor is assembled with NiCo2O4@NiCo2S4 as the cathode electrode and porous carbon as the anode electrode and KOH solution as the electrolyte, showing a super energy density of 196.8 Wh kg−1 at 752.33 W kg−1 and a high power density of 5625.12 W kg−1 at 162.45 Wh kg−1. After 15000 cyclic voltammetry cycles at a scan rate of 60 mV s−1, 137% of initial capacitance is maintained. Theoretical analysis reveals that the diffusion-controlled reaction is dominant in the total capacitance of NiCo2O4@NiCo2S4 electrode, which may be the reason for the high specific capacitance and excellent rate capability. Thereby, these electrochemical performances demonstrate that the as-fabricated NiCo2O4@NiCo2S4 core/shell nanowire arrays are the promising candidates for high-performance supercapacitors.

The effects of Tm3+ concentration on upconversion emission and temperature-sensing behavior of Tm3+/Yb3+:Y2O3 nanocrystals were investigated. Blue and red emissions were observed under 980 nm excitation. Both upconversion emissions and the blue to red intensity ratio were found to decrease with increasing Tm3+ concentration. The temperature-sensing performances of the samples were studied, the fluorescence intensity ratio of 1G4(a)→3H6 (477 nm) and 1G4(b)→3H6 (490 nm) transitions from Tm3+ ions was chosen as the thermometric index. The results showed that the sensor sensitivity was sensitive to Tm3+ ion concentration. The maximum sensitivity of ~32 × 10-4 K-1 was obtained for 0.1%Tm3+/5%Yb3+:Y2O3 nanocrystals at 344 K. Moreover, a marked optical induced heating effect was also found in the nanocrystals. The prepared Tm3+/Yb3+:Y2O3 nanocrystals could be used in temperature-sensing probes and in optical heaters.

The highly ordered three-dimensional hierarchical NiCo2O4@NiCo2O4 core–shell nanocones arrays on nickel foams are synthesized by stepwise hydrothermal synthesis. The unique nanoarchitectures consist of a layer of NiCo2O4 nanosheets well coated on the surface of NiCo2O4 nanocones. When used in supercapacitors, the NiCo2O4@NiCo2O4 core–shell hierarchical nanostructures exhibit a remarkable capacitance of 2045.2 F g−1 at a current density of 1 A g−1, which are better than that of the individual components of NiCo2O4 nanosheets and NiCo2O4 nanocones. Furthermore, the predominant diffusion-controlled storage is revealed by theoretical analysis. An asymmetric supercapacitor device based on the hierarchical NiCo2O4@NiCo2O4 core–shell nanostructure and activated carbon is fabricated and exhibits a desirable high energy densities with a value of 82.95 Wh kg−1 at power density of 0.35 kW kg−1. These results indicate that the as-prepared NiCo2O4@NiCo2O4 are outstanding candidate for electrochemical supercapacitors.

Fluoride glasses with introduced TeO2 were investigated in present study to develop efficient glass host for Er3+: 2.7 μm laser materials. The physicochemical properties, emission properties, as well as local structure surrounding erbium ions were discussed successively. In spite of little effects on thermal stability and refractive index with the introduced TeO2, it is clear in the emission spectra that 2.7 and 1.5 μm emission intensities were improved with the increase of TeO2 until 4 mol%. According to the XRD data, it can be concluded that there is no crystal phase in these samples. Based on the analysis of XPS spectra, it was found that the introduced oxygen anions participate in the network forming of glass. Thus, the increased 2.7 μm emission can be summarized as the changed symmetrical characteristic surrounding erbium ions. This result indicates that the main factor for 2.7 μm emission is local structure surrounding Er3+ ions, especially the bonds connected with erbium cations (Er―F and Er―O). Based on above analysis, ZBLAN glass with TeO2 (4 mol%) might be a new potential choice for 2.7 μm solid-state laser materials.

Ni doped ZnS nanopowders were synthesized by hydrothermal method. The as-synthesized ZnS nanopowders possessed zinc blende structure with the particle sizes of ∼20 nm, and they display a broad emission band from 400 nm to 700 nm centered at ∼540 nm. The influence of Ni2+ doping and vacuum annealing on the structure, morphology and optical properties was investigated systematically. The results revealed that the emission peaks are blue shifted with Ni2+ doping, and the emission peaks of 0.2, 0.4, 0.6, 0.8 and 1.0 mol% Ni2+ doped ZnS nanopowders are centered at ∼520, ∼ 510, 500, 490 and 470 nm, respectively. While, the zinc blende phase transformed to wurtzite phase when annealing at 600 °C or higher, and the annealed samples exhibited three emission peaks positioned at ∼490, ∼547 and ∼580 nm. The results indicated that the as prepared Ni2+-doped ZnS nanopowders have a potential application in LED as light conversion layer.

Tm3+/Yb3+:Y2O3 nanoparticles (NPs) were prepared by solution combustion method. The prepared NPs are confirmed to be pure cubic Y2O3 phase with the mean size of about 45 nm by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) observation. Under 980 nm excitation, the temperature dependent upconversion (UC) emission spectra of the NPs are obtained. It is found that the NPs show color tunability with a variation in temperature (from blue to almost white) and also a relatively good suppression of temperature quenching (i.e. ∼70.4% of the initial intensity at 473 K). By using the fluorescent intensity ratio (FIR) technique, the temperature sensing behaviors are investigated based on the thermal coupled 1G4(a) (477 nm) and 1G4(b) (490 nm) levels and non-thermal coupled 3F2,3 (684 nm) and 1G4(b) (490 nm) levels from Tm3+ ions, respectively. The results demonstrate that both the absolute sensitivity (Sa) and relative sensitivity (Sr) values based on non-thermal coupled levels of 3F2,3 and 1G4(b) is larger in the experimental temperature range. The maximum Sa and Sr values are obtained to be ∼1170 × 10−4 K−1 at 573 K and ∼1.51%K−1 at 445 K, respectively. Therefore, the studied material is a potential multifunctional composite for optical thermometry and temperature safety sign.

2.85 μm fluorescence of Ho3+ was firstly obtained in Yb3+/Ho3+ co-doped silica-germanate glass. The combination of low OH− concentration and high mid-infrared transmittance were beneficial to the realization of mid-infrared emissions. A large calculated spontaneous radiative transition probability (30.27 s−1) corresponding to the Ho3+:5I6 → 5I7 transition was beneficial for high gain and more opportunity to achieve laser action. Besides, enhanced green (548 nm) and red (662 nm) emissions were obtained due to the energy transfer between Yb3+ and Ho3+. Moreover, the measured lifetime of Ho3+:5I6 reached as high as 283 μs in Yb3+/Ho3+ co-doped silica-germanate glass, which also possesses a large emission cross section (8.05 × 10−21 cm2). All results reveal that Yb3+/Ho3+ co-doped silica-germanate glass might provide a new choice for 2.85 μm laser applications.

The effects of Li+ co-doping concentration on the structure, upconversion luminescence and temperature sensing behavior of Er3+:La2O3 phosphors were investigated. X-ray diffraction and scanning electron microscopy observations reveal that Li+ ion co-doping can change the lattice parameter of La2O3 host and increase the particle size of the samples. The optical investigation shows that co-doping of Li+ ions can enhance the upconversion emission of Er3+ ions in La2O3 matrix effectively. Most importantly, the temperature sensing sensitivity of the samples is found to be dependent on Li+ co-doping concentration, when the emission intensity ratio of the (2H11/2 → 4I15/2) and (4S3/2 → 4I15/2) transitions of Er3+ is chosen as the thermometric index. Both of the optimum upconversion luminescence and temperature sensing sensitivity are obtained for 7 mol% Li+ co-doped sample. When the Li+ concentration is beyond 7 mol%, both the quenching in upconversion intensity and the degradation of temperature sensitivity are observed, which may be due to the serious distortion in local crystal field around Er3+ ions caused by the excess Li+ ions.

Tm 3+ /Ho 3+ doped tellurite glasses with good thermal stability and low phonon energy are prepared. 1.8 µm fluorescence, enhanced near 2 µm fluorescence and a weak 2.3 µm fluorescence are observed in the Tm 3+ /Ho 3+ co-doped glasses. The energy transfer mechanism between Tm 3+ and Ho 3+ has been analyzed according to the absorption spectra, the emission spectra and the level structures of Tm 3+ and Ho 3+ ions. The decay lifetime of 1.8 µm and 2 µm fluorescence in Tm 3+ /Ho 3+ co-doped tellurite glass are 0.38 ms and 2.46 ms, respectively. Moreover, the energy transfer efficiency between Tm 3+ : 3 F 4 and Ho 3+ : 5 I 7 levels is calculated and compared. Additionally, the calculated forward energy transfer coefficient C Tm-Ho is about five times as large as the reverse energy transfer coefficient C Ho-Tm . Results demonstrate that the Tm 3+ /Ho 3+ doped tellurite glass has excellent spectroscopic properties and can be an attractive candidate for 2 µm laser.

A new kind of fluoro-chloride glass was successfully prepared based on fluoroaluminate glass modified by various Cl − . The reductions of phonon density and OH − content revealed by the measured Raman and FTIR spectra show that structural changes caused by the Cl − ions have an effect on the optical properties. With increasing chloride content, the thermal stability factor ΔT showed an increase trend, indicating a better thermal stability of the host. Meanwhile, according to Judd-Ofelt calculation, the intensity parameter Ω 2 increased, which indicates a stronger covalency and local asymmetry of the coordination bonds around the Er 3+ ions after introduction of Cl − . Noticeably, the lifetime (3.48 ms) of Er 3+ : 2.7 μm obtained in the chloride-rich glass (AYF-8Cl) is the longest in reported glass systems, along with obvious enhanced fluorescence intensity. All the results suggested that the fluoro-chloride glasses hint its potential applications in laser materials, especially in 3 μm wavelength.

Non-rare-earth Bi was firstly used as sensitizer on Ho3+: 2.0 μm emission for its mid-infrared applications in successfully prepared germanosilicate glass under 808 nm excitation. Sensitization mechanism has been analyzed theoretically through matched energy transfer processes based on the measured absorption, fluorescence spectra and calculated luminous parameters. Meanwhile, typical broadband near-infrared (NIR) emission band of Bi ions has also been obtained in present germanosilicate glass, which shifts to a longer wavelength with Ho3+ co-doped owing to the different of Bi-related active centers. X-ray Photoelectron Spectroscopy demonstrated that the addition of Ho3+ lead to the part valence conversion among the mixed-valence state of Bi. All results reveal that Bi/Ho co-doped germanosilicate glass might provide a new choice for 2.0 μm laser applications.

Bi can exist in a variety of chemical states (with varying ionic charges) and the microstructure of the glass surrounding the ions can be engineered to manipulate the chemical state. In this work, efficient enhancement of Ho3+ emission is observed with the change in local glass environment around Bi by adding Al2O3 to multi-component germanosilicate glass. In this multi-component glass, Al3+ can form tetrahedral AlO4 by accepting the non-bridging oxygen (NBO) and then, the addition of the AlO4-tetrahedron to the glass network facilitates the diffusion of alkali metals. Hence, Al2O3 decreases the Ba2+-rich domain and is conducive to the existence of Bi ions that are at low valence state. Moreover, the emission spectra indicate high efficiency energy transfer (ET) derived from NIR emission centers (Bi0/Bi+) located in close proximity to the Ho3+ ions. These results indicate that the optimized fluorescence of Ho3+ for optical fiber laser can be achieved by adjusting the local structure of the host glass.

Er 3+ /Yb 3+ /Tm 3+ triply doped Y 2 O 3 nanoparticles have been synthesized by solute combustion method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) demonstrate that the prepared particles are cubic Y 2 O 3 phase with the average size of ∼ 49 nm. The blue (Tm 3+ : 1 G 4 → 3 H 6 ), green (Er 3+ : 2 H 11∕2 , 4 S 3∕2 → 4 I 15∕2 ) and red (Er 3+ : 4 F 9∕2 → 4 I 15∕2 ) upconversion (UC) emissions are observed upon a 980 nm excitation. Applying the fluorescence intensity ratio (FIR) technique, the optical temperature sensing behaviors are studied based on thermally coupled levels ( 2 H 11∕2 and 4 S 3∕2 of Er 3+ ) and non-thermally coupled levels ( 1 G 4(b) (Tm 3+ ) and 2 H 11∕2 (Er 3+ )), respectively. The results show that the absolute sensing sensitivity is much higher in the entire experimental temperature range, when the non-thermally coupled levels with different temperature dependences ( 1 G 4(b) (Tm 3+ ) and 2 H 11∕2 (Er 3+ )) are selected as the thermometric index. The maximum absolute sensitivity is found to be as high as ∼ 1640 × 10 −4 K −1 at 573 K. This demonstrates that an optical temperature sensor with high performance can be designed based on the Er 3+ /Yb 3+ /Tm 3+ :Y 2 O 3 nanoparticles.

The Dy3+/Yb3+ co-doped germanate glasses with good thermal stability have been prepared by the conventional melt quenching method. The J-O intensity parameters and radiative properties such as spontaneous transition probilities (Arad), fluorescence branching ratios (β) and radiative lifetimes (τrad) were investigated according to the absorption spectrum based on Judd-Ofelt theory. An intense emission around ∼3 μm with the FWHM reaching to 322 nm was obtained in present glasses excited by 980 nm LD. The high spontaneous transition probability (63.94 s−1), large emission cross section (6.0 × 10−21 cm2) and superior gain performance corresponding to the Dy3+: 6H13/2 → 6H15/2 transition were obtained. Moreover, the energy transfer mechanism was analyzed qualitatively, and it was found that the energy transfer from Yb3+: 2F5/2 to Dy3+: 6H5/2 level could be quite efficient. Hence, the results indicated that the prepared Dy3+/Yb3+ co-doped germanate glass could be a potential candidate for ∼3 μm mid-infrared solid state lasers.

The mid-infrared emission of low phonon (963 cm−1) lead silicate glass system with Ho3+/Tm3+ co-doped has been investigated. Luminescence at ∼2.1 μm corresponding to 5I7 → 5I8 transition in holmium was obtained by energy transfer between Tm3+ and Ho3+ ions. Energy transfer mechanism between them was analyzed. And the highest value of the luminescence intensity was obtained in glass co-doped with 1Tm2O3/0.3Ho2O3. The full width at half maximum of the (Ho3+/Tm3+) emission reached to 350 nm in 1Tm2O3/0.1Ho2O3 sample. Absorption and emission cross section have also been calculated and analyzed. The maximum emission cross section was 3.9 × 10−21 cm2 around 2.0 μm. And when P > 0.4, a positive gain can be obtained at wavelengths >1941 nm. Results demonstrated that the prepared Ho3+/Tm3+ co-doped lead silicate glasses have excellent spectroscopic properties in mid-infrared wavelengths and can obtain high gain in fiber lasers.

Rigorous temperature measurement employed to characterize physic-chemical state has compelled scientists to explore more novel materials for contactless optical thermometry, which must overcome the drawbacks of low sensitivity and poor signal discriminability. Here, a novel dual-mode optical thermometer La2ZnTiO6: Bi3+/Eu3+ is designed, prepared and characterized via XRD, XPS, EPR, SEM, EDS, PL spectra and decay time. Under 350 nm excitation, the energy transfer process from Bi3+ to Eu3+ allows the samples to demonstrate adjustable multi-color emissions. The temperature-dependent emission spectra display that the luminescence intensity of Bi3+ ions decreases quite faster than that of Eu3+ ions with temperature, leading to a significant chromaticity shift (∆E = 224 ×10−3 in 293–473 K) visible to naked eyes. Based on fluorescence intensity ratio of Eu3+ versus Bi3+ (FIR = IEu/IBi), the sample shows the maximum relative sensitivity (Sr) of ~1.50% K−1 at 293 K and excellent signal discriminability. Meanwhile, the 5D0→7F2 transition of Eu3+ ions shows a thermal-responsive lifetime with the optimal Sr of 1.23% K−1 at 573 K. This work suggests that the La2ZnTiO6: Bi3+/Eu3+ double perovskite phosphor has a great potential for dual-mode optical thermometry, being beneficial to obtain precise, sensitive and reliable temperature detection.

Glass with the composition of SiO2-GeO2-CaCO3-Li2CO3-Nb2O5-BaO-Tm2O3 has been prepared and its characteristic temperatures have been measured. ΔT (155 °C) of the glass indicates it has good thermal stability. A broadband emission spectrum around 2 µm with full-width at half-maximum close to 237 nm has been obtained, which suggests this germanosilicate glass is a competitive candidate for the ultrashort pulse generation as few broadband emission realized by Tm3+ single-doping. The calculated maximum of absorption cross section and emission cross section of the transition Tm3+:3F4→3H6 was 3.31×10−21 cm2 at 1654 nm and 6.88×10−21 cm2 at 1870 nm, respectively. Besides, the energy transfer mechanism of 2 µm fluorescence behaviors was analyzed theoretically and quantitatively. The energy transfer coefficient CD-A of cross relaxation process of Tm3+ ions was 10.9×10−40 cm6/s in SGT glass. These results indicate that the prepared glass may have promising application in 2 µm fluorescence.

The novel Dy 3+ singly doped and Dy 3+ /Nd 3+ co-doped fluoride glasses have been synthesized, and their fluorescence properties have been monitored under 808 nm excitation. The addition of Nd 3+ leads to a higher emission peak, and a longer lifetime of 270 μs for Dy 3+ 2.9 µm emission, benefited by the low OH - content(0.032 cm −1 ) host and effective energy transfer of Nd 3+ : 4 F 5/2 , 2 H 9/2 →Dy 3+ : 6 F 5/2 with a energy transfer coefficient of 3.0×10 –40 cm 6 /s. Radiative and emission parameters were calculated based on the Judd-Ofelt theory, which shows that the Dy 3+ /Nd 3+ co-doped sample possesses a high calculated spontaneous transition probability (38.3 s −1 ) together with a large emission cross section (5.22×10 –21 cm 2 ). The FWHM is as wide as 260 nm, indicating it is suitable for tunable laser medium. These results prove the fluoride glass could be used as a potential candidate for compact and efficient eye safe mid-IR lasers.

International audience; The use of Yb3+ co-doping with Ho3+ to enhance the Ho3+: I-5(6) -> I-5(7) similar to 2.84-mu m emissions is investigated in the tellurite-germanate glasses. An intense similar to 2.84-mu m emission with a full width at half maximum (FWHM) of 132 nm is achieved in the Ho3+/Yb3+ co-doped tellurite-germanate glass upon excitation at 980 nm. The glass not only possesses considerably low OH-absorption coefficient (0.206 cm(-1)), but also exhibits 2.84-mu m large emission cross section (14.6 x 10(-21) cm(2)). Moreover, the measured lifetime of Ho3+: I-5(6) level is as high as 0.283 ms. Results reveal that Ho3+/Yb3+ co-doped Tellurite-germanate glass is an attractive host for developing a mid-infrared 3-mu m solid-state laser.

Tellurite glasses co-doped with Dy 3+ and Dy 3+ /Tm 3+ have been synthesized. Emission around 2.8 μm is successfully obtained in present glass upon excitation of a conventional 808 nm laser diode. Judd-Ofelt intensity parameters and radiative properties of Dy 3+ ions are calculated using the Judd-Ofelt theory. The luminescence characteristics and energy transfer mechanism are investigated and discussed. According to the absorption, fluorescence spectra and lifetime measurements, Tm 3+ ions can effectively absorb excitation and transfer their energy to Dy 3+ ions with high efficiency (up to 86.80%). Hence, the results demonstrate that Dy 3+ /Tm 3+ co-doped tellurite glasses possessing excellent spectroscopic properties is a potential medium for mid-infrared laser.

A kind of novel silicate glasses doped with Tm 3+ sensitized by Yb 3+ were prepared by conventional melt quenching method. The optical properties of the synthesized glasses were theoretically and experimentally investigated. Based on the absorption spectra and the Judd-Ofelt theory, the J-O intensity parameters (Ω t ), radiative transition probability (400.4 s −1 ), fluorescence lifetime (4.99 ms) and absorption and emission cross sections (σ e = 2.51 × 10 −20 cm 2 ) were calculated. According to fluorescence spectra, the 1.8 μm emission of Tm 3+ could be greatly enhanced by adding proper amount of Yb 3+ under the excitation of 980 nm and the optimized concentration ratio of Tm 3+ and Yb 3+ was found to be 1:3 in the present silicate glass system. Besides, the energy transfer mechanism between Yb 3+ and Tm 3+ were thoroughly discussed. With the assistance of Yb 3+ , the lifetime of Tm 3+ from 0.54 ms increased to 1.42 ms. The energy transfer efficiency from Yb 3+ to Tm 3+ could reach 90.94%, and the energy transfer coefficient was 5.43 × 10 −41 cm 6 /s. The content of OH − was measured. The above results showed that Tm 3+ /Yb 3+ co-doping could be expected to a promising way to achieve high efficient 2 μm lasing pumped by a 980 nm LD.

In this work a Tm3+-doped fluoride glass with good thermal stability is prepared. Intensive 1.8 and 2.3 μm emissions are obtained when pumped by an 800 nm laser diode. And the 1.48 μm emission is limited because of the much strong radiation around 1.8 μm. On the basis of absorption spectrum, radiative properties are investigated and discussed according to Judd–Ofelt parameters (Ω2, Ω4, Ω6) calculated by Judd–Ofelt theory. Besides, absorption and emission cross-sections of 3 F 4 → 3 H 6 transition are figured out and analyzed by using McCumber and Beer–Lambert theories. The high gain around 1.8 μm was predicted by the large σemiτrad product (29.8 × 10–21 cm2 ms). The results obtained indicate that the Tm3+-doped fluoride glass can be a promising 2.0 μm laser glass material.

A Tm3+-doped silica-germanate was successfully prepared by high-temperature melting method in this work and compared with traditional silicate and germanate glasses comprehensively. The DSC results indicated a better ability against thermal damage (higher Tg=636 °C) compared with silicate glass together with better thermal stability (ΔT=106 °C and S=3.17) than germanate (ΔT=99 °C and S=2.64) glass. Intense 1.8 μm emission in the silica-germanate glass was also obtained when pumping by an 808 nm laser diode, which possessed larger peak absorption and emission cross section (3.15×10–21 cm2 and 7.08 ×10–21 cm2). Finally, the structure analysis suggested a low phonon energy and high rare earth ions solubility in silica-germanate glass through Raman spectra and X-ray photoelectron spectroscopy. All results indicate that the prepared silica-germanate glass is a promising candidate for 2 μm laser applications.