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Poly(methyl methacrylate) (PMMA) latices for organic coating systems were prepared via emulsion polymerization using various emulsifying techniques. The dispersion modes have an important effect on the particle size and particle size distribution (PSD) of polymeric latices during the emulsion polymerization process. The different dispersion modes, such as magnetic stirring, ultrasound, and the combination of magnetic stirring and ultrasound, were examined to prepare particle size small and narrow PSD polymer latex. PMMA latex of size less than 20 nm in diameter and narrow PSD was successfully produced using the probe ultrasound method. By modifying the amplitude, temperature, and duration of the ultrasound probe and surfactant/water ratio, the optimal ultrasound conditions for the microemulsion polymerization were determined. This research provides new insights into the relationship between the dispersion modes and the colloidal properties of latex, which may offer more effective and simpler routes to prepare latices with fast polymerization rate and high conversion.

Two-dimensional (2D) semiconductor nanostructures have exhibited great prospect as an efficient photocatalyst for solar-to-fuel application. In this work, a unique 2D tandem heterojunction consisting of ultrathin CdxZn1−xIn2S4 nanosheets coupled with rectangular CdS flakes and defect-rich MoS2 few-layered nanosheets was constructed for the first time. Remarkably, the efficient electron transfer channels present in the CdS/CdxZn1−xIn2S4 and CdxZn1−xIn2S4/MoS2 2D tandem heterojunctions facilitate the spatial separation and directional migration of photo-induced charge carriers effectively. Moreover, such 2D tandem heterojunction CdxZn1−xIn2S4–CdS–MoS2 is provided with excellent light harvesting capacity and abundant HER active sites from the defective MoS2 co-catalyst. These distinct advantages endow the optimized C0.15ZIS–5C–3M hybrid (5 wt% CdS, 3 wt% MoS2) with an exceptional photocatalytic H2 evolution reaction (HER) activity of 27.14 mmol h−1 g−1, approximately 47 times that of pure ZnIn2S4 and it is much superior to that of Pt-decorated C0.15ZIS–5C and most ZnIn2S4-based composites reported previously. A high HER apparent quantum yield (AQY) of 19.97% is achieved at λ = 400 nm. In addition, both the cycling and long-term HER measurements evidence the prominent stability of C0.15ZIS–5C–3M for H2 production. The results indicated here could pave the way for the exploitation of new 2D heterostructures toward highly-efficient solar conversion and utilization.

Development of noble-metal-free photocatalysts for efficient solar-powered water-splitting is of great interest yet still challenging to date. In this work, unique ternary Cd0.85Zn0.15S@WO3/WS2 (CZ0.15S@WO3/WS2) core-shell nanorods consisting of amorphous WO3 and few-layered WS2 nanosheets were synthesized through a two-step solvothermal method for the first time. The composition of WO3/WS2 shell is found to vary with the change of W content, which has a significant impact on the photocatalytic property of CZ0.15S@WO3/WS2 toward H2 evolution reaction (HER). Under visible-light irradiation (λ > 420 nm), the optimized CZ0.15S@WO3/WS2 composite (n (WO3): n (WS2) = 3:1) demonstrates a superior HER activity of 76.33 mmol h−1 g−1 (corresponding to an AQY of 23.9% at 420 nm), which can be further remarkably increased to 157.29 mmol h−1 g−1 when the reaction is driven by full Xe-lamp spectrum. The HER capability of CZ0.15S@WO3/WS2 is much better than that of Pt-decorated CZ0.15S and most CdS-based photocatalysts ever reported, due to the notably enhanced charge transfer and separation via the synergistic cooperation of Z-scheme and type-I charge transfer processes. The findings displayed here could inspire new strategies to optimize the charge separation of multi-component photocatalysts for highly-effective solar conversion and utilization.

Metronidazole(MTZ) is an important antibiotic, which has been widely applied to cure protozoal and bacterial diseases for human beings or animals. Herein, three novel drug supramolecular crystals constructed by MTZ with 2,5-dihydroxy-benzoic acid(2,5-DHBA)(1), 2,6-dihydroxy-benzoic acid(2,6-DHBA)(2) and 3,5-dihydroxy-benzoic acid(3,5-DHBA)(3), respectively, have been discovered. The hydrogen bonds of N—H⋯O(O—H⋯N), C—H⋯O and O—H⋯O play important roles in the 3D supramolecular framework formation for crystals 1–3. Interestingly, due to the vary locations of the substituent groups, the two-dimensional layers in crystals 1 or 2 are constructed via intermolecular hydrogen bonds between MTZ and 2,5-DHBA or 2,6-DHBA, while in crystal 3 water molecules play a significant role except the intermolecular hydrogen bonds between MTZ and 3,5 -DHBA. In addition, five synthons of I R22(8), II R33(9) in crystal 1, III R21(4), IV R22(8) in crystal 2 and V R22(7) in crystal 3 formed through various hydrogen bonds are founded in this work. Systematic studies of syntheses, crystal structures and thermal analysis are reported.

Cancer stem cells (CSCs) are the origin of many malignant tumours, including osteosarcoma that mainly affects adolescents and is accompanied by a poor prognosis. However, little is known about the intrinsic biological information of osteosarcoma stem cells, particularly for the metabolomics features. Hence, an ultra-high performance liquid chromatography coupled with tandem Q-Exactive Orbitrap mass spectrometer (UHPLC-QE-MS)-based metabolomics approach was developed to investigate the metabolism changes in the human osteosarcoma (HOS) cell line in order to understand its possible mechanism. HMDB, METLIN and m/z Cloud databases were used to identify the metabolic markers. Additionally, the compounds were further identified using standards of the metabolites. Comparing HOS-CSCs with non-CSCs, 154 different metabolites were identified in both the positive and negative modes. Based on the clearly distinct metabolites, the changed metabolic pathways were analysed using MetaboAnalyst. The top five altered pathways included alanine, aspartate and glutamate metabolism; arginine and proline metabolism; glutathione metabolism; cysteine and methionine metabolism; and the citrate cycle (TCA cycle). The downregulation of the TCA cycle and elevation of oxidized glutathione levels suggested a decline of mitochondrial metabolism, while most of the amino acid metabolisms were upregulated. Further biological experiments including an analysis of mitochondrial activity confirmed the above hypotheses that were deduced from metabolomics results. These findings not only enhance our understanding of the altered metabolome in osteosarcoma stem cells but also demonstrate the great potential of such a metabolomics method based on UHPLC-QE-MS in large-scale cell studies.

Artificial Z-scheme photocatalytic systems have received considerable attention in recent years because they can achieve wide light-absorption, high charge-separation efficiency, and strong redox ability simultaneously. Nevertheless, it is still challenging to exploit low-cost and stable Z-scheme photocatalysts with highly-efficient H2 evolution from solar water-splitting so far. Herein, we report a novel all-solid-state Z-scheme photocatalyst Cd1− x Zn x S@WO3− x consisting of Cd1− x Zn x S nanorods coated with oxygen-deficient WO3− x amorphous layers. The Cd1− x Zn x S@WO3− x exhibits an outstanding H2 evolution reaction (HER) activity as compared with Pt-loaded Cd1− x Zn x S and most WO3- and CdS-based photocatalysts, due to the generation of stronger reducing electrons through the appropriate Zn-doping in Cd1− x Zn x S and the enhanced charge transfer by introducing oxygen vacancies (W5+/OVs) into the ultrathin WO3− x amorphous coatings. The optimal HER rate of Cd1− x Zn x S@WO3− x is determined to be 21.68 mmol h−1 g−1, which is further raised up to 28.25 mmol h−1 g−1 (about 12 times more than that of Pt/Cd1− x Zn x S) when Cd1− x Zn x S@WO3− x is hybridized by CoO x and NiO x dual cocatalysts (Cd1− x Zn x S@WO3− x /CoO x /NiO x ) through in - situ photo-deposition. Moreover, the corresponding apparent quantum yield (AQY) at 420 nm is significantly increased from 34.6% for Cd1− x Zn x S@WO3− x to 60.8% for Cd1− x Zn x S@WO3− x /CoO x /NiO x . In addition, both Cd1− x Zn x - S@WO3− x and Cd1− x Zn x S@WO3− x /CoO x /NiO x demonstrate good stability towards HER. The results displayed in this work will inspire the rational design and synthesis of high-performance nanostructures for photocatalytic applications.

A monoclinic 0.86 at.% Ho3+:MgWO4 crystal is grown by the Top-Seeded-Solution Growth method. Its spectroscopic properties are studied with polarized light for E || a, b, c. The Ho3+ ion transition probabilities are determined within the modified Judd-Ofelt theory (mJ-O) accounting for the configuration interaction. The intensity parameters are Ω2 = 21.09, Ω4 = 4.42, Ω6 = 2.28 [10–20 cm2] and α = 0.053 [10-4 cm]. The calculated radiative lifetime of the 5I7 state is 6.18 ms. The Stark splitting of the 5I7 and 5I8 multiplets is determined with low-temperature spectroscopy. The absorption, stimulated-emission (SE) and gain cross-sections for the 5I8 ↔ 5I7 transition are derived. Ho3+:MgWO4 features a large Stark splitting of the ground-state (380 cm-1), high maximum σSE of 1.82 × 10–20 cm2 at 2.083 μm, broad gain spectra and high luminescence quantum yield making it suitable for efficient continuous-wave and mode-locked lasers at ∼2.1 μm. First laser operation of Ho3+:MgWO4 crystal is demonstrated at 2.104 μm reaching a slope efficiency of 72%.

Herein, Na2SnO3 is employed as an anode for rechargeable lithium ion battery (LIB). We thoroughly investigated the electrochemical performance of Na2SnO3 in comparison with the most commonly used Sn based oxides, such as SnO2 and Li2SnO3. It is found that Na2SnO3 is greatly superior to SnO2 and Li2SnO3 in terms of capacity, cycling stability and rate capability. Impressively, Na2SnO3 presents favorable specific capacity of 480 mA h g−1 at current density of 200 mA g−1 after 100 cycles and still delivers a capacity of 439 mA h g−1 at extremely large current density of 1000 mA g−1, which are leading the performance in anodes for LIBs. Ex situ SEM analysis of anodes after different cycles revealed the surface microstructure of anodes plays a critical role in determining cycling stability. The SEM results show big cracks on the surface of electrode for SnO2 after less 15 cycles and for Li2SnO3 after more 100 cycles, resulting from their severe volume change during charging-discharging process. However, Na2SnO3 electrode exhibits uniform surface morphology after 100 cycles. It is concluded the “Na2O″ intrinsic matrix of Na2SnO3 combining with “Li2O″ formed from the conversion reaction can act as a mixture buffering matrix that contributes to keeping the electrochemically formed nanoscale Sn particles apart and preventing their agglomeration during Li−Sn alloy formation and decomposition, thus inhibiting the volume expansion and the capacity fading by maintaining the electrode integrity. In addition, the electrochemical reaction mechanism of Na2SnO3 with Li is investigated by ex situ XRD technique. The findings in this study provide a new valuable anode for high-performance LIBs and an insightful viewpoint of developing anode materials with high electrochemical performance by introducing the electrochemical inactive intrinsic matrix.

Controlled integration of metal-based sulfides with phosphides possessing strong coupling effects is a promising way to accelerate electron transfer by modulating the electronic structures of the host species. In this work, a c-doped Ni3S4/Ni2P (C@Ni3S4/Ni2P) hybrid co-catalyst produced by in situ sulfuration and phosphidation of Ni-MOF was decorated on g-C3N4 and subsequently used for photocatalytic H2 evolution under visible-light irradiation. Among the prepared composites tested herein, the optimized g-C3N4/C@Ni3S4/Ni2P-30 composite showed the highest H2 evolution rate (14.49 mmol g−1 h−1) with 1.0 mmol L−1 of Eosin Y (EY)-sensitization, which is 10 times higher than that of pristine g-C3N4 (1.33 mmol g−1 h−1). The enhanced photocatalytic activity of this composite can be attributed to: (i) electronic interactions between Ni2P and Ni3S4 (which synergistically increased the electron transfer rate) and (ii) staggered band alignment of excited-stated EY, g-C3N4, Ni3S4, and Ni2P. This work may provide some perspectives for utilization of MOF-derived hybrid co-catalysts as substitutes of noble metals for effective photocatalytic H2 evolution.

Pipes are the primary structural elements used for transporting fluid in various industries. The most common damage mechanism is corrosion, which occurs in pipes surface of turbine. The corrosive compounds for pipes are inorganic ion (Na+ , Cl- , NH4+ , NO3- , etc.) and grinding oil. For rapid and quantitative detection of inorganic ions on site, more reliable and reproducible analytical methods are demanded. A highly efficient solid-liquid sampling collection system is introduced in this work. Papering on the sample surface, inorganic cations and anions were simultaneously collected and analyzed by capillary electrophoresis with indirect ultraviolet detection. As a result, five cations (Na+ , K+ , NH4+ , Ca2+ , Mg2+ ) and three anions (Cl- , NO3- , SO42- ) were completely separated. The efficiency of the sampling and ability of capillary electrophoresis analysis were presented by the determination of trace-level (mg/m2 ) contaminants. The recoveries of cations and anions on the paper from metal surface were between 86.6 and 107.2%, and the relative standard deviations were less than 12.85%.

[EN]Surface channel waveguides (WGs) based on a half-ring (40–60-µm-diameter) depressed-index cladding (type III) geometry are fabricated in monoclinic Tm3+:MgWO4 by femtosecond (fs) laser writing at a repetition rate of 1 kHz. The WGs are characterized by confocal laser microscopy and 𝜇-Raman spectroscopy. A Tm3+:MgWO4 WG laser generates 320 mW at ∼2.02µm with a slope efficiency of 64.4%. The WG emits a transverse single-mode and linear polarization (𝐸||𝑁𝑚). A remarkable low loss of, Ministerio de Economía y Competitividad (FIS2017-87970-R, MAT2016-75716-C2-1-R (AEI/FEDER, UE)); Agència de Gestió d’Ajuts Universitaris i de Recerca (2017SGR755); Consejería de Educación, Junta de Castilla y León (SA287P18); National Natural Science Foundation of China (51761135115, 61575199, 61850410533, 61875199, 61975208); Ministry of Science and Higher Education of the Russian Federation (Goszadanie 2019-1080); Deutsche Forschungsgemeinschaft (PE 607/14-1).

Tm3+:Na2La4(WO4)7, a disordered tetragonal scheelite-type tungstate crystal, is grown by the Czochralski method. The polarized absorption, stimulated-emission and gain cross-section spectra are determined. The maximum σSE is 1.62 × 10–20 cm2 at 1788.6 nm for σ-polarization. The Judd-Ofelt parameters for Tm3+ are Ω2 = 10.321, Ω4 = 0.183 and Ω6 = 2.122 [10–20 cm2]. The radiative lifetime of the 3F4 state is 1.63 ms. Raman spectroscopy reveals a maximum phonon energy of 923 cm−1. Laser operation under diode-pumping is achieved with both a-cut and c-cut Tm:Na2La4(WO4)7 crystals, reaching a maximum output power for the a-cut of 715 mW at ~ 1937 nm with a slope efficiency of 34%. Microchip laser operation using the c-cut crystal yields a slope efficiency of 41%. The Tm:Na2La4(WO4)7 crystal is promising for mode-locked lasers due to its broadband emission.

Tm3+-doped monoclinic magnesium monotungstate (MgWO4) is a promising material for lasers emitting at above 2 μm. Stark splitting of 3H6 to 1G4 Tm3+ multiplets in MgWO4 is determined using low-temperature spectroscopy, calculated within crystal-field theory modified for the case of an intermediate configuration interaction (ICI) and analyzed in terms of the barycenter plot. Tm3+:MgWO4 features a large Stark splitting of the ground-state (3H6), 633 cm−1, and high transition cross-sections for polarized light due to its low-symmetry structure. A unique feature of Tm3+:MgWO4 to provide a naturally polarized emission at >2 μm, as well as its suitability for broadly tunable and mode-locked lasers in this spectral range are argued. The first tunable and vibronic Tm3+:MgWO4 lasers are demonstrated, yielding a continuous tuning from 1897 to 2062 nm in the former case. A vibronic laser operated at even longer wavelengths up to 2093 nm due to electron-phonon coupling with low-energy phonons of the crystalline host. Moreover, the optical indicatrix axes of high-refractive-index biaxial MgWO4 are assigned.

MOFs are a type of ideal crystalline material with rigid reticular structures whereas microcapsules are usually prepared from soft mater, such as polymers or supramolecules. The synthesis of MOF-based microcapsules with novel nanostructures at the molecular scale remains a great challenge. Herein, we develop a competitive coordination strategy to synthesize MOF-based microcapsules with novel bowl-like structures. During the competitive coordination process, the infinite structures of MOFs are partially broken by the competitive reagents, thus flexibility is introduced into the rigid skeletons and results in the formation of bowl-like microcapsules. Owing to the unique structure and composition of these nano-structures, the microcapsules exhibit excellent performance and stability in adsorbing and removing iodine for both vapor and solution. This work describes new opportunities in designing MOF-based microcapsules with novel structures.

Construction of macro-materials with highly oriented microstructures and well-connected interfaces between building blocks is significant for a variety of applications. However, it is still challenging to confine the desired structures. Thus, well-defined building blocks would be crucial to address this issue. Herein, we present a facile process based on 1.8 nm Pd nanoclusters (NCs) to achieve centimeter-size assemblages with aligned honeycomb structures, where the diameter of a single tubular moiety is ∼4 μm. Layered and disordered porous assemblages were also obtained by modulating the temperature in this system. The reconciled interactions between the NCs were crucial to the assemblages. As a comparison, 14 nm Pd nanoparticles formed only aggregates. This work highlights the approach of confining the size of the building blocks in order to better control the assembly process and improve the stability of the structures. [Figure not available: see fulltext.].

We report a diode-pumped continuous-wave Nd:Gd3Ga5O12 (GGG) laser operating at 1.4 μm spectral region. A dual-wavelength laser at 1423 and 1406 nm is achieved with output power of about 2.59 W at absorbed pump power of 13.4 W. Further increasing the pump power, simultaneous tri-wavelength laser at 1423, 1415 and 1406 nm is also obtained with a maximum output power of 3.96 W at absorbed pump power of 18.9 W. Single-wavelength lasing is also realized at the three emission lines using an intracavity etalon. The laser result is believed to be the highest output power achieved in Nd:GGG crystal, at present, to the best of our knowledge.

Longitudinally diode-pumped continuous-wave dual-wavelength Nd:YAG laser at 1116 and 1123 nm is achieved with maximum output power of 8.18 W and slope efficiency of 42.3%. Using WS 2 as saturable absorber, passive Q-switching of the dual-wavelength laser is also achieved with a maximum average output power of 0.41 W, the shortest pulse width of about 0.64 μs at pulse repetition rate of 100.9 kHz. The present Q-switched laser operation leads to maximum pulse energy of 4.06 μJ and pulse peak power of 6.35 W. A 2-D material WS 2 has been experimentally confirmed to be very promising as Q switcher at 1.1 μm, for the first time to our knowledge.

The development of high-performance non-precious electrocatalysts for both H2 and O2 evolution reactions (HER and OER activities) and overall water splitting is highly desirable but remains a grand challenge. Herein, we report a facile method to synthesize ultrathin, amorphous, porous, oxygen and defect enriched NiCoFe phosphate nanosheets (NSs). Owing to their microporous confinement in a 2D orientation, which can reduce the ion transport resistance during electrochemical processes, and defect enriched structure with higher electrochemically active surface area, these NiCoFe phosphate porous nanosheets supported on nickel foam (NiCoFe phosphate NSs/NF) facilitate the diffusion of gaseous products (H2 and O2) and exhibit remarkable catalytic performance and outstanding stability for both HER, OER and overall water splitting in an alkaline electrolyte (1.0 M KOH). For the OER electrocatalyst, 2D NiCoFe phosphate NSs/NF was oxidized to NiCoFe oxides/hydroxides on the catalyst surface and exhibited remarkable OER activity with a low overpotential of only 240 mV needed to reach a current density of 10 mA cm-2. For HER, 2D NiCoFe phosphate NSs/NF afforded a current density of 10 mA cm-2 at a low overpotential of only -231 mV. Furthermore, employing 2D NiCoFe phosphate NSs/NF as the electrocatalyst for both the anode and the cathode, a water splitting electrolyzer was able to reach 10 mA cm-2 at a cell voltage of 1.52 V with robust durability. Various characterization techniques indicated that the long term stability and the activity for overall water splitting are due to the porosity, the electrochemically active constituents, and synergistic effects. This work could be inspiring in the design of Earth abundant and highly efficient electrocatalysts for overall water splitting, especially for OER.

We report on our latest experimental results concerning laser oscillations at low-gain lines of diode-pumped Nd:YAG crystal lasers on 4F3/2 → 4I13/2 transition and MoS2 -based dual-wavelength passively Q-switched Nd:YAG laser on this transition, for the first time to our knowledge. Using an undoped YAG as etalon to promote the intracavity loss modulation, three new lasing lines of about 1333, 1334, and 1340 nm have been achieved. Especially, the 1334-nm laser can be operated at single wavelength mode with maximum output power of 2.03 W. Dual-wavelength passively Q-switched Nd:YAG laser at 1318 and 1338 nm has also been obtained with maximum average output power of 0.44 W. The shortest pulse width is about 150 ns at pulse repetition rate of 125 kHz, leading to single pulse energy of 3.5 μJ and pulse peak power of 23.4 W.

One of the important objectives in fuel-cell technology is to improve the activity and reduce the loading of Pt for hydrogen-evolution electrocatalysis. Here, an oxidative etching strategy of stacking faults is developed to prepare PtAgCo nanosheets by element-specific anisotropic growth. Sophisticated use of defects in crystal growth allows tailoring the morphology and interfacial polarization to improve catalytic performance of nanosheets for the hydrogen-evolution reaction. Systematic studies reveal that the presence of the stacking faults may be the knob for the formation of nanosheets. In particular, the chemical composition of nanosheets is potentially the key for altering the hydrogen-evolution reaction. As a result, the PtAgCo-II ultrathin nanosheets possess useful HER properties, achieving a current density up to 705 mA cm–2 at a potential of −400 mV.

Metal–organic frameworks (MOFs) are a class of crystalline porous materials with reticular architectures. Precisely tuning pore environment of MOFs has drawn tremendous attention but remains a great challenge. In this work, we demonstrate a competitive coordination approach to synthesize a series of zirconium–metalloporphyrinic MOFs through introducing H2O and monocarboxylic acid as modulating reagents, in which well-ordered mesoporous channels could be observed clearly under conventional transmission electron microscopy. Owing to plenty of unsaturated Lewis acid catalytic sites exposed in the visualized mesoporous channels, these structures exhibit outstanding catalytic activity and excellent stability in the chemical fixation of carbon dioxide to cyclic carbonates. The zirconium-based MOFs with ordered channel structures are expected to pave the way to expand the potential applications of MOFs.

Gas–solid phase reactions between ozone (O3) and three representative solids (alcohols, phenols, and saccharides) were investigated through a heterogeneous chemiluminescence (CL) strategy. When interactions between these two species occurred at the surface of the solid powder, an obvious CL effect was obtained. This performance could be attributed to the evolution of a ROOOH intermediate, which subsequently released emissive 1O2 species. This is the first report analyzing the gas–solid phase CL performance of O3 with alcohols, phenols, and saccharides. It is believed that this strategy can be extended to applications in other gas–solid phase CL analyses utilizing the O3 system. This has also created a novel area of gas–solid CL performance; thus, relevant processes and mechanisms can be deduced and identified.

Graphene-oxide (GO) as saturable absorber (SA) for a 1342 nm passively Q-switched Nd:YVO 4 laser is reported. This system produces laser pulse as narrow as 329 ns with a repetition rate of 214 kHz and the largest output power of 520 mW. Our results demonstrate that GO can be used as an excellent and efficient SA for Nd 3+ -doped lasers at 1.3 μm.

Because of the severe shuttle effect of polysulfides, achieving durable Li-S batteries is still a great challenge, especially under practical operation conditions including the high sulfur content, high loading, and high operation temperature. Herein, for the first time, low-cost, eco-friendly, and hydrophilic cellulose nanocrystals (CNCs) are proposed as a multifunctional polysulfide stopper for Li-S batteries with high performance. CNCs display an intrinsically high aspect ratio and a large surface area and contain a large amount of hydroxyl groups offering a facile platform for chemical interactions. Density functional theory calculations suggest that the electron-rich functional groups on CNCs deliver robust binding energies with polysulfides. In this work, CNCs not only firmly confine sulfur and polysulfides in the cathode as a robust binder, but also further hinder polysulfide shuttling to the Li anode as a polysulfide stopper on a separator. Consequently, the as-prepared Li-S batteries demonstrate outstanding cycling performance even under the conditions of high sulfur content of 90 wt % (63 wt % in the cathode), high loading of 8.5 mg cm-2, and high temperature of 60 °C. These results sufficiently demonstrate that CNCs have significant application potential in Li-S battery technologies.

Monoclinic (wolframite-type) monotungstate crystals are promising for rare-earth doping. We report polarized room- and low-temperature spectroscopy and efficient high-power laser operation of such a Y b 3 + : M g W O 4 crystal featuring high stimulated emission cross section ( σ S E = 6 . 2 × 10 − 20 c m 2 at 1056.7 nm for light polarization E | | N m ), large Stark splitting of the ground state ( 765 c m − 1 ), large gain bandwidth (26.1 nm for E | | N g ), and strong Raman response (most intense mode at 916 c m − 1 ). A diode-pumped Y b 3 + : M g W O 4 laser generated 18.2 W at ∼ 1056 n m with a slope efficiency of ∼ 89 % and a linearly polarized laser output.

We demonstrate sub-100-fs Kerr-lens mode-locking of a T m : M g W O 4 laser emitting at ∼ 2 µ m assisted by a single-walled carbon-nanotube saturable absorber. A maximum average output power of 100 mW is achieved with pulse duration of 89 fs at a pulse repetition rate of ∼ 86 M H z . The shortest pulse duration derived from frequency-resolved optical gating amounts to 76 fs at 2037 nm, corresponding to nearly bandwidth-limited pulses. To the best of our knowledge, these are the shortest pulses generated from any Tm-doped tungstate crystal and the first report on saturable absorber assisted Kerr-lens mode-locking of a Tm laser at ∼ 2 µ m .

We present a sub-50-fs diode-pumped Kerr-lens mode-locked laser employing a novel “mixed” monoclinic Yb:Ca4(Gd,Y)O(BO3)3 (Yb:GdYCOB) crystal as a gain medium. Nearly Fourier-limited pulses as short as 43 fs at 1036.7 nm are generated with an average power of 84 mW corresponding to a pulse repetition rate of ∼70.8 MHz. A higher average power of 300 mW was achieved at the expense of the pulse duration (113 fs) corresponding to an optical-to-optical efficiency of 35.8% representing a record-high value for any Yb-doped borate crystal. Non-phase-matched self-frequency doubling is observed in the mode-locked regime with pronounced strong spectral fringes which originate from two delayed green replicas of the fundamental femtosecond pulses in the time domain.

Exploiting visible-light-responsive photocatalysts for highly-efficient water-splitting is a very promising way to achieve the renewable hydrogen energy. To this end, the rational manipulation on the composition and structure of semiconductor nanomaterials appears extremely necessary. Herein, we construct a unique hybrid consisting of P-doped CZ0.10S-0.5P porous nano-spheres coupled with Ni2P and reduced graphene oxide (rGO) cocatalysts (CZ0.10S-0.5P@Ni2P/rGO), which exhibits an outstanding performance for H2 evolution reaction (HER) under visible-light (λ > 420 nm) irradiation. Noticeably, the CZ0.10S-0.5P@2Ni2P/1.5rGO with 2 wt%-Ni2P and 1.5 wt%-rGO delivers an exceptional HER rate of 616.8 mmol∙h−1∙g−1 (the apparent quantum efficiency reaches 77.0% at 475 nm), outperforming that of Pt-loaded CZ0.10S-0.5P and the great majority of CdS-based composites reported previously. In addition, the CZ0.10S-0.5P@2Ni2P/1.5rGO composite also presents a steady H2 generation activity under prolonged irradiation. The superior photocatalytic property of CZ0.10S-0.5P@Ni2P/rGO could be associated with the abundant active sites provided by Ni2P, excellent visible-light absorption, and effective charge transfer and separation enabled by the Schottky junctions formed between CZ0.10S-0.5P and Ni2P/rGO. The findings indicated here could promote the design and manufacture of advanced semiconductor nanostructures for sustainable energy applications.

Ultrathin nanocrystals generally provide a remarkable catalytic performance due to their high specific surface area and exposure of certain active sites. However, deactivation caused by growth and gathering limits the catalytic application of ultrathin nanocrystals. Here we report Ag nanocrystal-decorated polyoxometalate (Ag-POM) single-walled nanotubes assembled via a concise, surfactant-free soaking method as a new kind of well-defined core-sheath nanoreactor. The diameter of Ag nanocrystals inside polyoxometalate nanotubes can be controlled via simply adjusting the reactant concentration. Ag-POM provided outstanding oxidative desulfurization (ODS) catalytic performance for aromatic sulfocompounds at room temperature. It was suggested that Ag nanocrystals decorated on the inner surface played a key role in adjusting the electronic distribution and enhancing the catalytic activity. The as-prepared Ag-POM nanotubes are promising candidate catalysts with enhanced performance for practical catalytic applications in the gasoline desulfurization industry.

Non-noble metal electrocatalysts have recently received increasing attention for the hydrogen evolution reaction (HER) in acidic electrolytes. However, in alkaline electrolyzers, the slow kinetics of water splitting leads to their poor HER activities. Here, we demonstrate the synthesis of novel hierarchical nanotubes of CoS/MoS2 and Co3S4/MoS2/Ni2P which exhibit prominent and durable HER capabilities in alkaline solution. Particularly, the Co3S4/MoS2/Ni2P nanotubes present an onset overpotential of 60 mV, a Tafel slope of 98 mV dec−1, and a high exchange current density of 0.21 mA cm−2, which are superior to those exhibited by many noble-metal-free electrocatalysts. The enhanced HER properties of the hybrid nanotubes could be related to their open hollow structure, large surface area and active site number, as well as the synergetic cooperation between different components. The results reported here may provide new inspirations for the construction of advanced nanostructures for promising catalytic applications.

A one-pot and template-free strategy for synthesizing hollow TiO2 nanostructures (HTSs) is developed by using titanocene dichloride as a titanium source, acetone as a solvent, and ammonia as a basic source. Transmission electron microscopy (TEM) observations demonstrate that the morphology transformation undergoes solid, yolk–shell and then hollow structures, typical of an Ostwald ripening process. Comparative experiments suggest that the mismatched hydrolysis rate of chloride anion and organic cyclopentadiene in unique titanocene dichloride (Cp2TiCl2) molecules should be responsible for the formation of HTSs. The TiO2 nanostructures exhibit controllable morphologies and tunable sizes by mainly adjusting the amounts of the titanium precursor or ammonia. The HTSs show much improved photocatalytic performance as compared with samples of other morphologies in water splitting application, due to the remarkably increased surface area and active sites, and enhanced mass transfer. Our findings reported herein may offer new perspectives in materials chemistry, and energy- and environment-related applications.

Current laser technology enables table-top high flux XUV sources with photon energies from several tens to several hundreds of eV via high harmonic generation in noble gases. Here we present a compact versatile coupling unit to establish windowless, and thus lossless coupling of such light sources to ultra high vacuum (UHV). The particular coupling unit has been developed to couple a XUV laser source to a heavy ion storage ring. Three-stage differential pumping allows to reduce the input pressure of ~10−6 mbar down to the 10−12 mbar range at the output. The unit particularly reduces the partial pressure of argon, which is used to generate the XUV radiation, by 6 orders of magnitude. Measurements of the pressure distribution inside the different chambers agree well with theoretical simulations. In principle, this unit can also serve for other purposes, where a windowless vacuum coupling is needed, with a transition from High Vacuum (HV) levels to deep UHV, such as coupling to cryogenically cooled detectors, ion traps or to photoelectron emission spectroscopy experiments.

Developing high-performance noble-metal-free photocatalysts for solar water splitting is of great urgency to address the growing energy and environmental crises. However, the current photocatalytic efficiency is unsatisfactory due to the low conversion of solar energy. Herein, we prepared a unique hybrid photocatalyst consisting of twinned CdxZn1-xS solid solutions grown with several layers of defect-rich MoS2 nanosheets (T-CdxZn1-xS/MoS2) to achieve a stable and efficient H2 evolution reaction (HER) activity. Noticeably, the alternating zinc blende/wurtzite (ZB/WZ) homojunctions in T-CdxZn1-xS and intimate heterojunctions formed between T-CdxZn1-xS and MoS2 facilitated the efficient separation and transfer of both bulk and surface charge carriers. Moreover, the good visible-light responses of T-CdxZn1-xS and MoS2 as well as the existence of abundant S22− and Mo5+ active species in defective MoS2 nanosheets also contributed significantly to the activity improvement of T-CdxZn1-xS/MoS2. Benefiting from the above advantages, T-CdxZn1-xS/MoS2 exhibited superior HER rates of 37.22 mmol∙h-1 g-1 in lactic acid solution and 69.25 mmol∙h-1 g-1 in Na2S/Na2SO3 solution, corresponding to the apparent quantum yield (AQY) of 36.3 % and 55.2 % at 420 nm, respectively. The HER capability of T-CdxZn1-xS/MoS2 exceeded that of Pt/T-CdxZn1-xS and most CdS-based photocatalysts reported previously. Our findings will facilitate the exploitation of advanced nanomaterials for sustainable energy conversion and utilization.

Rational design and construction of novel nanostructures with outstanding functions, and investigation on the relationship between their structures and properties have continuously been intriguing but are still challenging now. In this work, 1D TiO2(B) hierarchitectures with epitaxial {100} and {010} high-energy-facetted ultrathin 2D nanosheets that are parallel to the c-axis are demonstrated for the first time. These hierarchitectures show much improved photochemical properties as compared with the nanoparticles and nanowires as well as the physical mixture of nanosheets and nanowires. These include photodegradation of methyl orange and water splitting, due to the remarkably increased surface area and active sites, and enhanced separation and transport of charge carriers. The findings reported here may inspire the engineering of highly active nanostructures for energy and environment related applications.

A channel waveguide (propagation loss: ∼0.1 dB/cm) laser femtosecond-laser-written in monoclinic Tm:MgWO 4 generated up to 320 mW slightly above 2 μm (slope efficiency up to 71%) and vibronic laser emission extending up to ∼2.08 μm.

A novel three-dimensional (3D) superstructure of cobalt hydroxide carbonate assembled from nanoneedles has been synthesized via a facile hydrothermal method. Furthermore, we tested the electrocatalytic oxygen evolution reaction performance, which demonstrated that the superstructure exhibited high catalytic activity, achieving 10 mA cm-2 at a low overpotential of merely 240 mV.

Femtosecond mode-locked lasers near 2 μm based on the Tm3+ ion have been drawing great attention since they are applied in various fields including physics, chemistry and biology [1]. Among the host materials for Tm3+, the monoclinic double tungstate crystals are one of the most promising for ultrashort pulse generation [2]. Recently, we successfully demonstrated efficient laser operation of a new monoclinic divalent metal monotungstate, Tm3+:MgWO 4 , crystal [3]. Due to the low-symmetry structure and the distortion of the rare-earth site caused by the mismatch of the ionic radii of Mg2+ and Tm3+, the absorption and emission bands of Tm:MgWO 4 are rather broad. Motivated by these attractive spectroscopic properties, we study here mode-locked laser operation of Tm:MgWO 4 using a single-walled carbon nanotube (SWCNT) based saturable absorber (SA) in the present work.

The eye-safe Thulium (Tm3+) laser emission at ∼2 μm, based on the 3F4 → 3H 6 transition, is of interest for remote sensing and medicine. Monoclinic double tungstates are known as excellent hosts for Tm + ions allowing for efficient lasers at ∼1.94 μm [1]. However, they suffer irom low thermal conductivity (∼3 W/mK) limiting the power scaling. Recently, another monoclinic tungstate crystal with a wolframite structure, MgWO4 which exhibits much better thermal properties has been proposed for RE3+ doping [2]. In the present work, we report on efficient and compact Tm:MgWO 4 lasers at >2 μm.

Highly active and robust eletcrocatalysts based on earth-abundant elements are desirable to generate hydrogen and oxygen as fuels from water sustainably to replace noble metal materials. Here we report an approach to synthesize porous hybrid nanostructures combining amorphous nickel-cobalt complexes with 1T phase molybdenum disulfide (MoS2) via hydrazine-induced phase transformation for water splitting. The hybrid nanostructures exhibit overpotentials of 70 mV for hydrogen evolution and 235 mV for oxygen evolution at 10 mA cm−2 with long-term stability, which have superior kinetics for hydrogen- and oxygen-evolution with Tafel slope values of 38.1 and 45.7 mV dec−1. Moreover, we achieve 10 mA cm−2 at a low voltage of 1.44 V for 48 h in basic media for overall water splitting. We propose that such performance is likely due to the complete transformation of MoS2 to metallic 1T phase, high porosity and stabilization effect of nickel-cobalt complexes on 1T phase MoS2., Electrocatalysts based on earth-abundant elements have emerged as promising candidates to replace noble metal materials. Here, the authors develop porous hybrid nanostructures combining amorphous Ni-Co complexes with 1T phase MoS2 for enhanced electrocatalytic activity for overall water splitting.

Developing low-cost and high-efficiency photocatalysts for hydrogen production from solar water splitting is intriguing but challenging. In this study, unique one-dimensional (1D) multi-node MoS2/CdS hetero-nanowires (NWs) for efficient visible-light photocatalytic H2 evolution are synthesized via a facile hydrothermal method. Flower-like sheaths are assembled from numerous defect-rich O-incorporated {0001} MoS2 ultrathin nanosheets (NSs), and {112̅0}-facet surrounded CdS NW stems are grown preferentially along the c-axis. Interestingly, the defects in the MoS2 NSs provide additional active S atoms on the exposed edge sites, and the incorporation of O reduces the energy barrier for H2 evolution and increases the electric conductivity of the MoS2 NSs. Moreover, the recombination of photoinduced charge carriers is significantly inhibited by the heterojunction formed between the MoS2 NSs and CdS NWs. Therefore, in the absence of noble metals as co-catalysts, the 1D MoS2 NS/CdS NW hybrids exhibit an excellent H2-generation rate of 10.85 mmol·g–1·h–1 and a quantum yield of 22.0% at λ = 475 nm, which is far better than those of Pt/CdS NWs, pure MoS2 NSs, and CdS NWs as well as their physical mixtures. Our results contribute to the rational construction of highly reactive nanostructures for various catalytic applications. [Figure not available: see fulltext.]

We present a new two-step synthetic route combining the concepts of crystal symmetry, seed ratio and oxidative etching that yields tetrametallic PtAgBiCo nanoplates., Mechanistic control is a powerful means for manufacturing specific shapes of metal nanostructures and optimizing their performance in a variety of applications. Thus, we successfully synthesized multimetallic nanoplates (PtAgBiCo and PtAgBi) by combining the concepts of crystal symmetry, oxidative etching and seed ratio, and tuned their activity, stability and methanol tolerance, as well as Pt utilization, for the oxygen reduction reaction in direct methanol fuel cells. Systematic studies reveal that the formation of PtAgBiCo triangular nanoplates with a high morphological yield (>90%) can be achieved by crystallinity alteration, while electrochemical measurements indicate that the PtAgBiCo nanoplates have superior electrocatalytic activity towards the oxygen reduction reaction. The specific and mass activity of the PtAgBiCo nanoplates are 8 and 5 times greater than that of the commercial Pt/C catalyst, respectively. In addition, the tetrametallic PtAgBiCo nanoplates exhibit a more positive half-wave potential for the oxygen reduction reaction and possess an excellent methanol tolerance limit compared with the commercial Pt/C catalyst.

A synthesis strategy for the preparation of trimetallic PtCoFe alloy nanoparticle superlattices is reported. Trimetallic PtCoFe alloy monolayer array of nanoparticle superlattices with a large density of high index facets and platinum-rich surface are successfully prepared by coreduction of metal precursors in formamide solvent. The concentration of cetyl trimethyl ammonium bromide plays a vital role for the formation of a monolayer array of nanoparticle superlattices, while the size of nanoparticles is determined by NaI. The prepared monolayer array of nanoparticle superlattices is the superior catalyst for oxygen reduction reaction as well as for ethanol oxidation owing to their specific structural and compositional characteristics.

A novel monoclinic magnesium tungstate crystal, Tm:MgWO 4 , was grown and characterized in terms of structure, spectroscopy and laser generation. The output power was 772 mW at 2017–2029 nm with a slope efficiency of 39%.

Monoclinic thulium-doped magnesium monotungstate, Tm3+:MgWO4, is promising for efficient power-scalable continuous-wave (CW) and passively Q-switched lasers at >2 μm. Under diode pumping at 802 nm, a compact CW laser based on Z-cut Tm:MgWO4 generated 3.09 W at 2022–2034 nm with a slope efficiency of 50% which represents the highest output power ever achieved with this type of laser host. Stable passive Q-switching of the Tm:MgWO4 laser is demonstrated for the first time, to the best of our knowledge, using single-walled carbon nanotubes, graphene, and Cr2+:ZnS saturable absorbers. Using the latter, the best performance is achieved with 16.1 μJ/13.6 ns pulses at 2017.8 nm with a maximum average output power of 0.87 W and a peak power of 1.18 kW.

DOI: 10.1364/OE.25.003682 URL: https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-4-3682 Filiació URV: SI Memòria We report on the crystal growth, spectroscopic investigation and laser performance of Tm3+-doped monoclinic magnesium tungstate (Tm:MgWO4), for the first time, to the best of our knowledge. A high-quality crystal has been grown by the top seeded solution growth method. The relevant spectroscopic properties are characterized in terms of absorption, luminescence and Raman spectroscopy. Judd-Ofelt (J-O) analysis is performed to evaluate the spontaneous emission probabilities and the radiative lifetimes. The absorption, stimulated-emission and gain cross-section spectra are determined for the principal light polarizations. The first laser action in the 2 ¿m spectral range is demonstrated in the regime of continuous-wave operation with a maximum output power of 775 mW and a slope efficiency of 39%.

Crystallinity offers countless opportunities for the controlled synthesis of multimetallic 2D and 3D nanomaterials. Herein we have successfully synthesized 2D Pt-Ag ultrathin nanosheets through the oxidative etching of twin seeds and 3D Pt-Ag-Cu tetrapods via altering the crystallinity through the incorporation of copper into the Pt-Ag alloy. A better electrocatalytic activity is obtained for the oxidation of formic acid which is 3.8 times higher than that of a commercial platinum catalyst as the stepped surface atom densities are higher on the nanosheets.

Development of noble-metal-free photocatalysts for highly efficient sunlight-driven water splitting is of great interest. Nevertheless, for the photocatalytic H2 evolution reaction (HER), the integrated regulation study on morphology, electronic band structures, and surface active sites of catalyst is still minimal up to now. Herein, well-defined 1D Cd1-x Znx S@O-MoS2 /NiOx hybrid nanostructures with enhanced activity and stability for photocatalytic HER are prepared. Interestingly, the band alignments, exposure of active sites, and interfacial charge separation of Cd1-x Znx S@O-MoS2 /NiOx are optimized by tuning the Zn-doping content as well as the growth of defect-rich O-MoS2 layer and NiOx nanoparticles, which endow the hybrids with excellent HER performances. Specifically, the visible-light-driven (>420 nm) HER activity of Cd1-x Znx S@O-MoS2 /NiOx with 15% Zn-doping and 0.2 wt% O-MoS2 (CZ0.15 S-0.2M-NiOx ) in lactic acid solution (66.08 mmol h-1 g-1 ) is about 25 times that of Pt loaded CZ0.15 S, which is further increased to 223.17 mmol h-1 g-1 when using Na2 S/Na2 SO3 as the sacrificial agent. Meanwhile, in Na2 S/Na2 SO3 solution, the CZ0.15 S-0.2M-NiOx sample demonstrates an apparent quantum yield of 64.1% at 420 nm and a good stability for HER under long-time illumination. The results presented in this work can be valuable inspirations for the exploitation of advanced materials for energy-related applications.

We report a detailed characterization of the diode-pumping operation of the mixed crystal Yb0.1:Gd0.5Y0.4COB, including cw, tunable and femtosecond laser regimes. This crystal was recently proposed as a promising candidate for high-power as well as femtosecond operation. Our results show that the crystal quality and performance is comparable to the more deeply investigated and closely related calcium yttrium oxoborate and calcium gadolinium oxoborate laser crystals.

We present the first sub-100 fs bulk solid-state laser in the 2-μm spectral range employing the monoclinic Tm3+−dopedMgWO4 crystal as an active medium. By applying a graphene-based saturable absorber and chirped mirrors for dispersion management, stable self-starting mode-locked operation at 2017 nm was achieved. Nearly Fourier-limited pulses as short as 86 fs featuring a bandwidth of 53 nm were generated at a repetition rate of 76 MHz. A pulse energy of 1.1 nJ was achieved at 87 MHz for a pulse duration of 96 fs. The mode-locked Tm3+:MgWO4 laser exhibits excellent stability with a fundamental beat note extinction ratio of 80 dBc above noise level.