High Doping Levels Research Articles

Cerium-Bismuth Oxides/Oxynitrates with Low Toxicity for the Removal and Degradation of Organophosphates and Bisphenols.

Nanoscale cerium-bismuth oxides/oxynitrates were prepared by a scalable low-temperature method at ambient pressure using water as the sole solvent. Solid solutions were formed up to a 1:1 Ce/Bi molar ratio, while at higher doping levels, bismuth oxynitrate photocatalysts with a pronounced layered structure were formed. Bismuth caused significant changes in the structure and surface properties of nanoceria, such as the formation of defects, oxygen-containing surface groups, and Lewis and Brønsted acid sites. The prepared bifunctional adsorbents/photocatalysts were efficient in the removal of toxic organophosphate (methyl paraoxon) from water by reactive adsorption followed by photocatalytic decomposition of the parent compound and its degradation product (p-nitrophenol). Bi-doped ceria also effectively adsorbed and photodegraded the endocrine disruptors bisphenols A and S and outperformed pure ceria and the P25 photocatalyst in terms of efficiency, durability, and long-term stability. The very low toxicity of Bi-nanoceria to mammalian cells, aquatic organisms, and bacteria has been demonstrated by comprehensive in vivo/in vitro testing, which, in addition to its simple "green" synthesis, high activity, and durability, makes Bi-doped ceria promising for safe use in abatement of toxic chemicals.

Entrapped Molecule-Like Europium-Oxide Clusters in Zinc Oxide with Nearly Unaffected Host Structure.

Nanocrystalline ZnO sponges doped with 5 mol% EuO1.5 are obtained by heating metal-salt complex based precursor pastes at 200-900°C for 3min. X-ray diffraction, transmission electron microscopy, and extended X-ray absorption fine structure (EXAFS) show that phase separation into ZnO:Eu and c-Eu2 O3 takes place upon heating at 700°C or higher. The unit cell of the clean oxide made at 600°C shows only ≈0.4% volume increase versus undoped ZnO, and EXAFS shows a ZnO local structure that is little affected by the Eu-doping and an average Eu3+ ion coordination number of ≈5.2. Comparisons of 23 density functional theory-generated structures having differently sized Eu-oxide clusters embedded in ZnO identify three structures with four or eight Eu atoms as the most energetically favorable. These clusters exhibit the smallest volume increase compared to undoped ZnO and Eu coordination numbers of 5.2-5.5, all in excellent agreement with experimental data. ZnO defect states are crucial for efficient Eu3+ excitation, while c-Eu2 O3 phase separation results in loss of the characteristic Eu3+ photoluminescence. The formation of molecule-like Eu-oxide clusters, entrapped in ZnO, proposed here, may help in understanding the nature of the unexpected high doping levels of lanthanide ions in ZnO that occur virtually without significant change in ZnO unit cell dimensions.

Dilution of a polar magnet: Structure and magnetism of Zn-substituted Co2Mo3O8

We report crystal structure, magnetization, and specific heat measurements on single crystals of the hexagonal polar magnet ${\mathrm{Co}}_{2\text{\ensuremath{-}}x}{\mathrm{Zn}}_{x}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$ magnetically diluted by replacing Co by Zn. In contrast to the transformation from the antiferromagnetic to a ferrimagnetic state observed in the isostructural ${\mathrm{Fe}}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$ upon small Zn doping, a robust antiferromagnetic behavior is preserved in Zn-doped ${\mathrm{Co}}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$ up to $x=0.55$. The N\'eel temperature decreases from ${T}_{\mathrm{N}}=40$ K at $x=0$ to 23 K at $x=0.55$, thus extrapolating to $x=1.27$ (36% filling) as the percolation threshold typical for a three-dimensional, highly coordinated network. This indicates strong magnetic couplings beyond the honeycomb planes in ${\mathrm{Co}}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$. A sharp peak in the specific heat and a clear cusp in the susceptibility associated with the onset of magnetic order is observed up to $x=0.55$, whereas at $x=0.66$ these features are broadened due to increased disorder. Interestingly, the in-plane lattice parameter, the Curie-Weiss temperature, and the magnetic entropy vary with $x$ in a concerted but nonmonotonic manner. These observations can be traced back to the observed site-selective Zn substitution. We found that in the low-doping regime ($x<0.2$) ${\mathrm{Zn}}^{2+}$ ions primarily occupy the octahedrally coordinated sites, although they have a clear preference for occupying the tetrahedrally coordinated sites at higher doping levels. Due to the multiple interlayer exchange paths, dependent on the coordination of the ${\mathrm{Co}}^{2+}$ ions, this behavior is reflected in the nonmonotonic variation of the Curie-Weiss temperature and magnetic entropy with substitution.

Peculiarities of erbium incorporation into ZnO microrods at high doping level leading to upconversion and the morphology change. Influence on excitonic as well as shallow donor states

Heavily Er-doped zinc oxide (ZnO) microrods with nominal compositions, ZnO:Er(2, 10, 30%), were prepared by the hydrothermal growth method. The crystallographic phases present in the as grown and annealed materialswere determined. The presence of the hexagonal Wurtzite ZnO phase in the form of the hexagonal shape nanoplatelets and microrods was confirmed. Moreover, the Er2O3phase in the form of nanosheets has been revealed as well. Erbium is partly incorporated into the ZnO hosts. It was thinning upon erbium doping level contributing to erbium oxide. This effect was even more pronounced upon annealing in air. Moreover, the influence of erbium doping and annealing on paramagnetic shallow donor centers has been studied. There were two types of these centers, both affected by the erbium presence. The increase of the neutral zinc vacancies amount upon erbium doping has been proven. Annealing in air moderated the charge distribution between them. Moreover, upconversion processes between the two erbium ions were observed and explained. The surface distribution of excitonic emission centers was studied. The larger the erbium content the weaker the exciton luminescence. The smaller the ZnO microrods the stronger the exciton emission.

Temperature-dependent carrier transport behaviors in phosphorus-doped silicon nanocrystals/silicon carbide multilayers

Size-controllable silicon nanocrystals/silicon carbide multilayers with various phosphorus-doping ratios are fabricated by plasma enhanced chemical vapor deposition system. The carrier concentration of Si NCs with suitable doping levels can be enhanced by six orders of magnitude than that of the un-doped sample and the room temperature conductivity can reach as high as 111 S/cm. The temperature-dependent carrier transport behaviors of the P-doped samples are systematically studied. It is revealed that the carrier transport behaviors are dominated by three different conduction mechanisms in the various temperature range, i.e. Mott variable-range hopping (within 20–80 K), multiple phonon hopping (within 80–300 K) and thermally activation conduction (above 300 K). Meanwhile, the carrier transport mechanism depends on the doping levels. At high doping levels, the localization length is about seven times of the size of dot diameters which may induce the metal-insulator transition.

Decoupling electrochemical parameters of molecular-level-controlled polypyrrole and graphene oxide nanocomposite

A molecular-level-controlled polypyrrole from a predoped two-monomer-connected precursor (TMCP) and graphene oxide (GO) nanocomposite is synthesized for an active electrode. TMCP (Py:NDSA:Py) consists of two pyrrole monomer, in which bifunctional naphthalene disulfonic acid (NDSA) acts as a protonic dopant and connector. Four molecular-level-controlled P(Py:NDSA:Py)/GO-based nanocomposites are formed when Py:NDSA:Py is polymerized on the hydrophilic GO surface with 100, 75, 50, and 25 mol % of NDSA. The resulting P(Py:NDSA100:Py)/GO nanocomposite exhibits excellent electrochemical performance and cycling stability. A systematic investigations of molecular-level-controlled P(Py:NDSA100:Py)/GO nanocomposite shows that various parameters such as relatively high crystallinity (47.2 %), crystalline domain size (24.2 nm), high doping level (35 %), and electrical conductivity (23.6 S/cm) could be well controlled using a 100 mol % of NDSA connector. An optimized P(Py:NDSA100:Py)/GO nanocomposite with 20 wt% GO significantly improves the specific capacitance of 306 F g−1 at a current density of 1 A g−1 and excellent cycling stability of 75 % up to 2000 cycles without using carbon supplement (carbon black). This systematic decoupling of electrochemical parameters of molecular-level-controlled polypyrrole nanocomposites can serve as an approach for rational design with tailored properties of other polymeric nanocomposites for electrochemical applications.

Fabry-Pérot resonant avalanche-mode silicon LEDs for tunable narrow-band emission.

We report on the effect of Fabry-Pérot (FP) resonance on hot-carrier electroluminescence (EL) spectra and the optical power efficiencies of silicon (Si) avalanche-mode (AM) LEDs in the wavelength range from 500 nm to 950 nm. The LEDs, fabricated in a silicon-on-insulator photonics technology, consist of symmetric p-n junctions placed within a 0.21 µm thick Si micro-ring of varying width and radius. We show that the peak wavelength in the EL-spectra can be tuned within a range of 100 nm by varying the ring width from 0.16 µm to 0.30 µm, which is explained by FP resonance. The measured EL-spectra features relatively narrow bands (with a spectral width of ∼50 nm) with high intensities compared to conventional Si AMLEDs. By varying the ring radius and using a high doping level, we obtain a record high optical power efficiency of 3.2×10-5. Our work is a breakthrough in engineering the EL spectrum of Si, foreseen to benefit the performance of Si-integrated optical interconnects and sensors.

A Secondary-Doped Polybenzimidazole Membrane with High Proton Conductivity and Ion Selectivity for Vanadium Redox Flow Batteries

Polybenzimidazole (PBI)-based membranes are one of the most promising proton exchange membranes for vanadium redox flow batteries (VRFBs) due to their excellent ion selectivity. However, the relatively lower proton conductivity limits their application. Herein, a PBI membrane with both high proton conductivity and ion selectivity is prepared through a secondary phosphoric acid-doping method. The secondary-doped PBI membrane has a lower doping level in the surface layer while a higher doping level at the inner layer, forming a significant gradient-doped structure. In this structure, the former ensures an excellent ion selectivity while the latter enables a preferable proton conductivity. As a result, the VRFB with the secondary-doped PBI membrane exhibits an ultrahigh coulombic efficiency (CE) of 99.2% at the operating current density of 200 mA cm−2, which is significantly higher than that of the Nafion 212 membrane (97.7%), signifying an excellent ion selectivity. Meanwhile, the corresponding voltage efficiency (VE) is high up to 87.1%, which is also better than that of the Nafion 212 membrane (84.8%), indicating a high proton conductivity. Therefore, the secondary-doped PBI membrane might be a promising candidate for the highly efficient membrane for VRFB, and the secondary-doping method is simple and facile to realize engineering applications.

Structural-suppressing concentration quenching in dysprosium single-phase white emission and their application in optical thermometric and white light-emitting devices

Single Dy3+ doped material is indispensable to establish single-phase white emission. However, concentration quenching (CQ) and poor stability limit its wider application. Herein, Dy3+-doped Ca3LuAl3B4O15 (CLAB:Dy3+) is reported to be an advanced dual-emitting micro phosphor with promising optical properties making it a promising applicant with potential applications in thermometric and n-WLEDs. The host has a highly disordered crystal structure, suppressing the CQ phenomena of Dy3+, and attains a high doping level. Using the Kubelka–Munk equation, the optical bandgap Calculated for the matrix is 4.66 eV, which is ideal for n-WLEDs. Under 350 nm UV light, the prepared CLAB:Dy3+ displayed emissions at 476 nm and 569 nm with a CIE diagram of (0.382, 0.402) and IQE up to 18.3%. The Blass and Dexter model analyzed the energy migration (EM) mechanism. The dual emissions in CLAB:Dy3+ have distinct thermal reactions caused by thermal quenching. The temperature sensing properties of CLAB:0.08Dy3+ ranging from 300 to 500 K was examined and showed a superb Boltzmann distribution behavior between 455 nm and 476 nm fluorescence intensity ratio (FIR) and the optimum relative sensitivity SR value of 1.46% K−1. Employing the CLAB:Dy3+, a fabricated phosphor-converted white light-emitting diode (pc-WLED) emitted white light with CIE (0.36, 0.39), a color rendering index (CRI = 67.5), and a low color coordinate temperature (CCT = 4624 K). These findings suggest that this incredibly efficient single-phase white-emitting material has great potential for optical thermometric and pc-WLEDs.

Links between defect chemistry, conduction, and lifetime in heavily Nb doped lead zirconate titanate films

Phase pure PbZr0.52Ti0.48O3 (PZT) films with up to 13 mol. % Nb were prepared on Pt-coated Si substrates using chemical solution deposition; charge compensation for Nb was accomplished by reducing the concentration of lead in the film. For high Nb doping levels, (1) superoxidation of the PZT film surface makes the PZT/Pt interface more p-type and, hence reduces electron injection over the Schottky barrier, (2) the bulk charge transport mechanism changes from electron trapping by Ti4+ to hole migration between lead vacancies, and (3) the ionic conductivity due to migration of oxygen vacancies decreases. For ≤6 mol. % Nb, electrical degradation was controlled via field-induced accumulation of oxygen vacancies near the cathode, which, in turn, leads to Schottky barrier lowering and electron trapping by Ti4+. In phase pure 13 mol. % Nb doped PZT films, on the other hand, the increase in the leakage current during electrical degradation was dominated by hole migration between lead vacancies (2[VPb″]∼[h•]). A much lower lifetime and drastic increase in the leakage current upon electrical degradation was observed in mixed phase PNZT films, which was attributed to (1) a more electrically conductive pyrochlore phase and (2) a high concentration of lead vacancies.

Tuning of Morphological, Crystallographic and Optoelectronic Properties in Electrodeposition of CuSCN for Device Applications

Copper(I) thiocyanate (CuSCN) is known as a wide bandgap p-type semiconductor and recently demonstrated its high ability as a hole-transporting material in perovskite solar cells and light emitting diodes. Its thin film is usually fabricated by simple solution coating and drying [1]. In fact, little is known for physical properties of CuSCN, such as bandgap, band positions, optical transparency, carrier density and mobility.We have established methods to electrodeposit well-crystallized CuSCN thin films in various forms. Although the electrochemistry is fairly simple as limited by diffusion of 1 : 1 complex between Cu2+ and SCN- ions ([Cu(SCN)]+), the [Cu2+] : [SCN-] ratio, its absolute concentration and solvent can significantly alter the morphology and crystal orientation of resulting CuSCN [2].These unique features of the electrodeposition technique let us anticipate possibilities to tailor-tune physical properties of CuSCN to match the demands for device applications.In this study, we have carried out electrodeposition of CuSCN to vary its morphology and crystal orientation by tuning the bath composition and studied their band structure to explore the room for tuning its physical properties for thin film diodes and hybrid electroluminescence devices.Morphologies of CuSCN thin films electrodeposited from stoichiometric (REF), Cu-rich and SCN-rich baths are shown in Figs. 1 a-c. While the REF sample has an open structure made of relatively large bulky particles, the Cu-rich sample is dense, made of tiny grains to expose their hexagonally shaped top. On the other hand, the one from the SCN-rich bath show rectangular sides of the grains (Fig. 1 a) and strongly oriented to lay down the c-axis in parallel with the substrate.XRD patterns have found almost parallel orientation for the SCN-rich and a high degree of preference of the Cu rich to orient the c-axis of β-CuSCN perpendicular to the substrate.Although all these films indicate nearly the same energy gap of about 3.6 eV estimated by Tauc plot, significant difference was found for their work function (WF) measured by photoelectron yield spectroscopy (PYS) (Fig. 2). The threshold energy moved downwards from 5.23 to 5.66 eV vs. VAC from Cu-rich to SCN-rich film. The result indicates a high level of p-type doping in the presence of excess SCN-, probably due to increased concentration of Cu2+ as stabilized by SCN- bound to it.Simple devices as ITO / electrodeposited CuSCN / Aluminium were fabricated to examine their diode behaviour. While all of the devices employing the electrodeposited CuSCN thin films showed good rectifications in the J-V curves, the onset voltage determined that to observe 5 mA/cm2 moved from 1.21 to 2.57 V (ITO being positive) from Cu-rich to SCN-rich samples to confirm tunability of the device property by conditions of the electrodeposition. Successful operation of organic light emitting diode was also achieved by employing the electrodeposited CuSCN as a hole-injection layer. The device employing the electrodeposited CuSCN achieved a smaller turn-on voltage than that with spin-coated CuSCN in the I-V-L measurements.[1] Vinod E. Madhavan et al., ACS Energy Lett. 2016, 1, 1112−1117.[2] Lina Sun et al., Physics Procedia, 2011, 14, 12-24. Figure 1

Ho-SiAlON Ceramics as Green Phosphors under Ultra-Violet Excitations.

In most inorganic phosphors, increasing the concentration of activators inevitably causes the concentration quenching effect, resulting in reduced emission intensity at a high level of activator doping and the conventional practice is to limit the activator concentration to avoid the quenching. In contrast, SiAlON ceramics preserve their chemical composition over a very wide range of doping of activator ions, which favors the adjustment and optimization of the luminescence properties avoiding concentration quenching. Here, we investigate the photoluminescence properties of Ho-doped SiAlON (Ho-SiAlON) ceramics phosphors prepared by the hot-press method. Ho-SiAlON ceramics show strong green visible (554 nm) as well as infrared (2046 nm) broadband downshifting emissions under 348 nm excitation. It is shown that there is no concentration quenching, even at a very high level of Ho doping. The emission intensity of the 554 nm band increased two-fold when the Ho concentration is doubled. The results show that the Ho-SiAlON ceramics can be useful for efficient green phosphors.

Significant enhancement in photosensitivity, responsivity, detectivity and quantum efficiency of Co3O4 nanostructured thin film-based photodetectors through Mo doping developed by spray pyrolysis method

Herein, we have developed the high-performance photodetector diodes (p-Co3O4/n-Si and p-Mo@Co3O4/n-Si) by spray pyrolysis route for modern optoelectronic devices. The impact of different molybdenum (Mo) ions concentrations (0, 2, 4, and 6 wt.%) on the structural, morphological, optical and photo-electrical properties of Co3O4 films has been investigated. The X-ray diffraction study confirms the cubic phase of Mo-doped Co3O4 thin films with good crystallinity. From FESEM images, the unevenly sized sphere-like grains were clearly observed which are agglomerated at higher doping levels. UV-VIS spectra confirmed that the thin film owns good absorption and the energy gap varied with Mo doping. The p-Co3O4/n-Si and p-Mo@Co3O4/n-Si (Mo = 2, 4, and 6 wt.%) photodiodes were fabricated. The barrier height of the fabricated diodes was varied in the range of 0.65 to 0.98 eV. The maximum sensitivity of 10382% at 1.2 V has been achieved for 6 wt.% of Mo-doped diodes due to the creation of photo-created charge couples. Also, the quantum efficiency of the diode was enhanced from 39 to 164%. The 6 wt.% of p-Mo@Co3O4/n-Si junction diode exhibited the highest device performance among others and can be used as high performance photodetector.

Molten Salt Self-Template Synthesis Strategy of Oxygen-Rich Porous Carbon Cathodes for Zinc Ion Hybrid Capacitors.

Porous carbon materials are widely used in capacitive energy storage devices because of their chemical stability, low cost, and controllable textures. Molten salt self-template methods are powerful and sustainable synthesis strategies for preparing porous carbons with tunable pore textures and surface chemistries. Herein, we propose a self-template synthesis strategy for preparing oxygen-rich porous carbons (ORC) by directly carbonizing potassium chloroacetate (ClCH2COOK) as the single carbon source. The potassium chloride salts generated in the carbonization play the roles of the template and etchant agent in the pore formation process. The as-prepared ORC samples feature abundant mesopores (average pore sizes of 1.95-2.19 nm and mesopore ratio of 36.4%), high specific surface areas (1410-1886 m2 g-1), and high oxygen doping levels (4.3-8.2 atom %). The zinc ion hybrid capacitors with an ORC cathode exhibited an ultrahigh capacitance of 308 F g-1 at 0.5 A g-1 and a high energy density of 136.5 Wh kg-1 at a power density of 570 W kg-1. Density functional theory demonstrates that oxygen-containing functional groups are conducive to the adsorption of Zn ions. Our work proposes a general synthesis methodology for the synthesis of oxygen-rich porous carbons for a variety of electrochemical energy storage devices.

Effects of Boron Doping on the Bulk and Surface Acoustic Phonons in Single-Crystal Diamond.

We report the results of the investigation of bulk and surface acoustic phonons in the undoped and boron-doped single-crystal diamond films using the Brillouin-Mandelstam light scattering spectroscopy. The evolution of the optical phonons in the same set of samples was monitored with Raman spectroscopy. It was found that the frequency and the group velocity of acoustic phonons decrease nonmonotonically with the increasing boron doping concentration, revealing pronounced phonon softening. The change in the velocity of the shear-horizontal and the high-frequency pseudo-longitudinal acoustic phonons in the degenerately doped diamond, as compared to that in the undoped diamond, was as large as ∼15% and ∼12%, respectively. As a result of boron doping, the velocity of the bulk longitudinal and transverse acoustic phonons decreased correspondingly. The frequency of the optical phonons was unaffected at low boron concentration but experienced a strong decrease at the high doping level. The density-functional-theory calculations of the phonon band structure for the pristine and highly doped samples confirm the phonon softening as a result of boron doping in diamond. The obtained results have important implications for thermal transport in heavily doped diamond, which is a promising material for ultra-wide-band-gap electronics.

Atomic-scale and optical investigation of nanostructured Er disilicates in silica

The optical and structural properties of Er-doped Silicon oxide based thin films elaborated by RF magnetron sputtering were investigated as a function of annealing treatment. Atom Probe Tomography and Transmission electron microscopy were used to analyze the position of rare-earth ions as well as the phase separation occurring in the layer in order to provide a complete picture of the nanostructure. The emission properties of Er3+ ions were investigated using cathodoluminescence (CL) spectroscopy. The high doping level of Er ions in silicon oxide matrix leads to a phase decomposition of pure SiO2 and Er2Si2O7 phases with a nanostructure which is influenced by the annealing treatment. It results on different emission intensities in ultraviolet or infrared ranges. The relationship between the nanostructuration observed and the optical properties is discussed in regards of annealing treatment.

Anomalous Thermal Transport Driven by Electron–Phonon Coupling in 2D Semiconductor h‐BP

AbstractThe electron–phonon coupling (EPC) in semiconductors is typically much weaker than phonon–phonon scattering and its effect on lattice thermal conductivity κl has long been considered negligible. Herein, using first‐principle calculations, it is discovered that the EPC can be significant or even dominant over the intrinsic phonon–phonon scattering via doping in 2D semiconductor hexagonal boron phosphorus (h‐BP). Filling electron pocket till van Hove singularity gradually strengthens the EPC and consequently diminishes the room‐temperature κl by 25% and 80% for monolayer and bilayer h‐BP, respectively. Strikingly, at high doping levels, the EPC drives phonon transport in bilayer h‐BP to an anomalous regime where κl becomes nearly temperature (T) independent deviated from the intrinsic 1/T trend. This distinctive behavior is governed by the joint effects of horizontal mirror symmetry breaking, and weak phonon–phonon scattering stemming from the predominance of normal processes. Further considering electronic contributions, the abnormal T‐independent thermal conductivity is still reserved, thereby facilitating the experimental exploration of EPC effect on κl. This study unveils the exotic thermal transport phenomenon in one‐atom‐thick 2D semiconductors and offers a unique avenue to manipulate heat flow by externally controlling the EPC, which calls for future experimental verification.

Thermometric sensing performance in Erbium modified SrBi2-xNb2ErxO9 ferroelectric ceramic for optoelectronic devices

Er3+ doped ferroelectric ceramic compositions SrBi2-xNb2ErxO9 (x = 0–5 mol %) are prepared by solid-state reaction method and sintered at 1000 °C. The ceramic's structural, ferroelectric, optical, and thermometric sensor properties have been studied. The XRD analysis confirmed the orthorhombic geometry and the A21am phase group of the ceramic. The FTIR studies revealed the typical modes (602 cm−1 and 802 cm−1) of the Aurivillius phases of bismuth layered structure ferroelectrics (BLSFs). The improved hysteresis loops are traced under the electric field < ± 50 kV/cm, and P-E parameters seem to be affected by the insertion of the Er3+ dopant. In upconversion luminescence (UCL) spectra, two intense green bands at 529 nm and 549 nm and a diminished red peak at 670 nm have been identified, corresponding to a 980 nm exciting wavelength. The increase in the lifetime with changing erbium content indicates the efficient energy transfer in Er3+ ions, which results in non-radiative transition at a higher doping level. The optimum dopant concentration is x = 0.03 and is used to measure the pump power dependence on the UCL emission intensity. This study suggests that the two photons are involved in green and red UC emissions. The maximum sensitivity achieved in SrBi2-xNb2ErxO9 ceramic at x = 0.03 is 0.0086 K−1 at 443 K, ranging between temperatures 303 K–443 K, making it a promising non-contact sensor material.

Enhanced oxygen evolution reaction kinetics through biochar-based nickel-iron phosphides nanocages in water electrolysis for hydrogen production

Highly-efficient and stable non-noble metal electrocatalysts for overcoming the sluggish kinetics of oxygen evolution reaction (OER) is urgent for water electrolysis. Biomass-derived biochar has been considered as promising carbon material because of its advantages such as low-cost, renewable, simple preparation, rich structure, and easy to obtain heteroatom by in-situ doping. Herein, Ni2P–Fe2P bimetallic phosphide spherical nanocages encapsulated in N/P-doped pine needles biochar is prepared via a simple two-step pyrolysis method. Benefiting from the maximum synergistic effects of bimetallic phosphide and biochar, high conductivity of biochar encapsulation, highly exposed active sites of Ni2P–Fe2P spherical nanocages, rapid mass transfer in porous channels with large specific surface area, and the promotion in adsorption of reaction intermediates by high-level heteroatom doping, the (Ni0.75Fe0.25)2P@NP/C demonstrates excellent OER activity with an overpotential of 250 mV and a Tafel slope of 48 mV/dec at 10 mA/cm2 in 1 M KOH. Also it exhibits a long-term durability in 10 h electrolysis and its activity even improves during the electrocatalytic process. The present work provides a favorable strategy for the inexpensive synthesis of biochar-based transition metal electrocatalysts toward OER, and improves the water electrolysis for hydrogen production.

Soft‐template assisted preparation of hierarchically porous graphitic carbon nitride layers for high‐performance supercapacitors

AbstractStrong π–π interaction between two‐dimensional graphitic carbon nitride (CN) layers may cause the stacking phenomenon, which leads to the decrease of its surface area and thus the capacitive properties. Hard templates are usually used to avoid the stacking phenomena. However, the use of them needs redundant removing process and may cause environmental pollution. As a result, in this work, P123 was used as the soft template to expand the inter‐layer distance and create more mesopores in the CN sheets. Benefit from the synergistic effect between the unique porous structure and the high nitrogen doping level, the formed graphitic CN (P2‐g‐CN) could exhibit high specific capacitances (520.5 and 176.0 F g−1 at the current density of 0.5 and 50 A g−1), stable cyclic behavior and satisfied energy density. The superior energy storage performances and the facile synthetic approach of P2‐g‐CN indicate its promising application as high‐performance electrode for supercapacitors and other energy storage devices.