A general method for rapid synthesis of refractory carbides by low-pressure carbothermal shock reduction.

Refractory carbides are attractive candidates for support materials in heterogeneous catalysis because of their high thermal, chemical, and mechanical stability. However, the industrial applications of refractory carbides, especially silicon carbide (SiC), are greatly hampered by their low surface area and harsh synthetic conditions, typically have a very limited surface area (<200 m2 g-1), and are prepared in a high-temperature environment (>1,400 °C) that lasts for several or even tens of hours. Based on Le Chatelier's principle, we theoretically proposed and experimentally verified that a low-pressure carbothermal reduction (CR) strategy was capable of synthesizing high-surface area SiC (569.9 m2 g-1) at a lower temperature and a faster rate (∼1,300 °C, 50 Pa, 30 s). Such high-surface area SiC possesses excellent thermal stability and antioxidant capacity since it maintained stability under a water-saturated airflow at 650 °C for 100 h. Furthermore, we demonstrated the feasibility of our strategy for scale-up production of high-surface area SiC (460.6 m2 g-1), with a yield larger than 12 g in one experiment, by virtue of an industrial viable vacuum sintering furnace. Importantly, our strategy is  also applicable to the rapid synthesis of refractory metal carbides (NbC, Mo2C, TaC, WC) and even their emerging high-entropy carbides (VNbMoTaWC5, TiVNbTaWC5). Therefore, our low-pressure CR method provides an alternative strategy, not merely limited to temperature and time items, to regulate the synthesis and facilitate the upcoming industrial applications of carbide-based advanced functional materials.

Drought Alleviates the Negative Effects of Microplastics on Soil Micro-Food Web Complexity and Stability.

Soil ecosystems are under considerable pressure due to anthropogenic factors, including microplastics (MPs) pollution and drought. However, little is known about the interactive effects of MPs and drought on soil organisms, especially soil micro-food web. We conducted a microcosm experiment with MPs pollution (including two types and two sizes of MPs) and drought to investigate their interaction effects on soil microbial, protist, and nematode communities in soil micro-food web. We found that MPs significantly decreased the complexity and stability of soil micro-food web, with greater negative effects of biodegradable and smaller-sized MPs than conventional and larger-sized MPs. Drought had negative effects on soil micro-food web in the non-MPs pollution soils while increasing the complexity and stability of soil micro-food web in the MPs pollution soils. Drought increased the proportion of negative correlations between bacteria and fungi in the biodegradable MPs soils while decreasing the proportion of negative correlations between protists and nematodes in the smaller-sized MPs soils. Our study reveals that drought may alleviate the negative effects of MPs on soil micro-food web by reducing competition among lower trophic levels in the biodegradable MPs pollution soils while reducing competition among higher trophic levels in the smaller-sized MPs pollution soils.

Precise Molecular Engineering of Type I Photosensitizer with Aggregation-Induced Emission for Image-Guided Photodynamic Eradication of Biofilm.

Biofilm-associated infections exert more severe and harmful attacks on human health since they can accelerate the generation and development of the antibiotic resistance of the embedded bacteria. Anti-biofilm materials and techniques that can eliminate biofilms effectively are in urgent demand. Therefore, we designed a type I photosensitizer (TTTDM) with an aggregation-induced emission (AIE) property and used F-127 to encapsulate the TTTDM into nanoparticles (F-127 AIE NPs). The NPs exhibit highly efficient ROS generation by enhancing intramolecular D-A interaction and confining molecular non-radiative transitions. Furthermore, the NPs can sufficiently penetrate the biofilm matrix and then detect and eliminate mature bacterial biofilms upon white light irradiation. This strategy holds great promise for the rapid detection and eradication of bacterial biofilms.

Camouflaged Virus-Like-Nanocarrier with a Transformable Rough Surface for Boosting Drug Delivery.

Due to non-specific strong nano-bio interactions, it is difficult for nanocarriers with permanent rough surface to cross multiple biological barriers to realize efficient drug delivery. Herein, a camouflaged virus-like-nanocarrier with a transformable rough surface is reported, which is composed by an interior virus-like mesoporous SiO2 nanoparticle with a rough surface (vSiO2 ) and an exterior acid-responsive polymer. Under normal physiological pH condition, the spikes on vSiO2 are hidden by the polymer shell, and the non-specific strong nano-bio interactions are effectively inhibited. While in the acidic tumor microenvironment, the nanocarrier sheds the polymer camouflage to re-expose its rough surface. So, the retention ability and endocytosis efficiency of the nanocarrier are great improved. Owing to it's the dynamically variable rough surface, the rationally designed nanocarrier exhibits extended blood-circulation-time and enhanced tumor accumulation.

Enzyme-Based Mesoporous Nanomotors with Near-Infrared Optical Brakes.

As one of the most important parameters of the nanomotors' motion, precise speed control of enzyme-based nanomotors is highly desirable in many bioapplications. However, owing to the stable physiological environment, it is still very difficult to in situ manipulate the motion of the enzyme-based nanomotors. Herein, inspired by the brakes on vehicles, the near-infrared (NIR) "optical brakes" are introduced in the glucose-driven enzyme-based mesoporous nanomotors to realize remote speed regulation for the first time. The novel nanomotors are rationally designed and fabricated based on the Janus mesoporous nanostructure, which consists of the SiO2@Au core@shell nanospheres and the enzymes-modified periodic mesoporous organosilicas (PMOs). The nanomotor can be driven by the biofuel of glucose under the catalysis of enzymes (glucose oxidase/catalase) on the PMO domain. Meanwhile, the Au nanoshell at the SiO2@Au domain enables the generation of the local thermal gradient under the NIR light irradiation, driving the nanomotor by thermophoresis. Taking advantage of the unique Janus nanostructure, the directions of the driving force induced by enzyme catalysis and the thermophoretic force induced by NIR photothermal effect are opposite. Therefore, with the NIR optical speed regulators, the glucose-driven nanomotors can achieve remote speed manipulation from 3.46 to 6.49 µm/s (9.9-18.5 body-length/s) at the fixed glucose concentration, even after covering with a biological tissue. As a proof of concept, the cellar uptake of the such mesoporous nanomotors can be remotely regulated (57.5-109 µg/mg), which offers great potential for designing smart active drug delivery systems based on the mesoporous frameworks of this novel nanomotor.

Constructing Unique Mesoporous Carbon Superstructures via Monomicelle Interface Confined Assembly.

Constructing hierarchical three-dimensional (3D) mesostructures with unique pore structure, controllable morphology, highly accessible surface area, and appealing functionality remains a great challenge in materials science. Here, we report a monomicelle interface confined assembly approach to fabricate an unprecedented type of 3D mesoporous N-doped carbon superstructure for the first time. In this hierarchical structure, a large hollow locates in the center (∼300 nm in diameter), and an ultrathin monolayer of spherical mesopores (∼22 nm) uniformly distributes on the hollow shells. Meanwhile, a small hole (4.0-4.5 nm) is also created on the interior surface of each small spherical mesopore, enabling the superstructure to be totally interconnected. Vitally, such interconnected porous supraparticles exhibit ultrahigh accessible surface area (685 m2 g-1) and good underwater aerophilicity due to the abundant spherical mesopores. Additionally, the number (70-150) of spherical mesopores, particle size (22 and 42 nm), and shell thickness (4.0-26 nm) of the supraparticles can all be accurately manipulated. Besides this spherical morphology, other configurations involving 3D hollow nanovesicles and 2D nanosheets were also obtained. Finally, we manifest the mesoporous carbon superstructure as an advanced electrocatalytic material with a half-wave potential of 0.82 V (vs RHE), equivalent to the value of the commercial Pt/C electrode, and notable durability for oxygen reduction reaction (ORR).

Prevalence and pathology of Cephalopina titillator infestation in Camelus bactrianus from Xinjiang, China.

BACKGROUND: In camels, nasopharyngeal myiasis is caused by the larvae of Cephalopina titillator, which parasitize the tissues of nasal and paranasal sinuses, pharynx, and larynx. C. titillator infestation adversely affects the health of camels and decreases milk and meat production and even death. However, the C. titillator infestation in Bactrian camels has not been widely studied. METHODS: The present study was conducted to determine the prevalence and risk factors of C. titillator in Bactrian camels of northwestern Xinjiang. Suspected larvae recovered from infested camels were evaluated for C. titillator by microscopy and polymerase chain reaction. Nucleotide sequences of the partial mitochondrial cytochrome c oxidase subunit I (COX1) and cytochrome b (CYTB) genes from the C. titillator of camels were aligned from the NCBI database. Furthermore, the gross and histopathological alterations associated with C. titillator infestation were evaluated via pathological examination. RESULTS: Of 1263 camels examined 685 (54.2%) camels were infested with suspected C. titillator larvae. Different larval stages were topically detected in the nasal passages and pharynx of the camel heads. Microscopy analysis of the pharyngeal mucosa tissue revealed necrotic tissue debris and some inflammatory cells. Molecular detection of the larval COX1 and CYTB genes indicated that pathogen collected in Bactrian camels was C. titillator. The epidemiological study demonstrated that the prevalence rate of C.titillator infestation was significantly higher in camels of Bestierek Town Pasture (67.2%) and Karamagai Town Pasture (63.6%) compared to Kitagel Town Pasture (38.7%) and Qibal Town Pasture (35.8%) (P < 0.05). No significant difference was observed between the prevalence rates in male (52.6%) and female (54.6%) camels (P > 0.05). The prevalence was higher in warm (64.2%) than that in cold (48.4%) seasons (P < 0.001). The prevalence in camels with non-nomadic method (67.2%) was significantly higher than in animals with nomadic method (47.5%) (P < 0.001). The prevalence of C.titillator infestation was significantly higher in animals of aged 5-10 (60.1%) and aged > 10 (61.1%) years old compared to those of aged < 5 (31.7%) years old camels (P < 0.001). CONCLUSION: Our results confirm that there is a high prevalence of C. titillator in Bactrian camels from Xinjiang, closely related to age, season, pasture environment, and husbandry methods. Developing prevention, diagnosis, and control programs to prevent transmission is necessary.

Streamlined Mesoporous Silica Nanoparticles with Tunable Curvature from Interfacial Dynamic-Migration Strategy for Nanomotors.

Streamlined architectures with a low fluid-resistance coefficient have been receiving great attention in various fields. However, it is still a great challenge to synthesize streamlined architecture with tunable surface curvature at the nanoscale. Herein, we report a facile interfacial dynamic migration strategy for the synthesis of streamlined mesoporous nanotadpoles with varied architectures. These tadpole-like nanoparticles possess a big streamlined head and a slender tail, which exhibit large inner cavities (75-170 nm), high surface areas (424-488 m2 g-1), and uniform mesopore sizes (2.4-3.2 nm). The head curvature of the streamlined mesoporous nanoparticles can be well-tuned from ∼2.96 × 10-2 to ∼5.56 × 10-2 nm-1, and the tail length can also be regulated from ∼30 to ∼650 nm. By selectively loading the Fe3O4 catalyst in the cavity of the streamlined silica nanotadpoles, the H2O2-driven mesoporous nanomotors were designed. The mesoporous nanomotors with optimized structural parameters exhibit outstanding directionality and a diffusion coefficient of 8.15 µm2 s-1.

Transcriptome analysis identifies putative genes involved in triterpenoid biosynthesis in Platycodon grandiflorus.

MAIN CONCLUSION: Comprehensive transcriptome analysis of different Platycodon grandiflorus tissues discovered genes related to triterpenoid saponin biosynthesis. Platycodon grandiflorus (Jacq.) A. DC. (P. grandiflorus), a traditional Chinese medicine, contains considerable triterpenoid saponins with broad pharmacological activities. Triterpenoid saponins are the major components of P. grandiflorus. Here, single-molecule real-time and next-generation sequencing technologies were combined to comprehensively analyse the transcriptome and identify genes involved in triterpenoid saponin biosynthesis in P. grandiflorus. We quantified four saponins in P. grandiflorus and found that their total content was highest in the roots and lowest in the stems and leaves. A total of 173,354 non-redundant transcripts were generated from the PacBio platform, and three full-length transcripts of ß-amyrin synthase, the key synthase of ß-amyrin, were identified. A total of 132,610 clean reads obtained from the DNBSEQ platform were utilised to explore key genes related to the triterpenoid saponin biosynthetic pathway in P. grandiflorus, and 96 differentially expressed genes were selected as candidates. The expression levels of these genes were verified by quantitative real-time PCR. Our reliable transcriptome data provide valuable information on the related biosynthesis pathway and may provide insights into the molecular mechanisms of triterpenoid saponin biosynthesis in P. grandiflorus.

Molecular cloning and functional characterization of two squalene synthase genes in Atractylodes lancea.

MAIN CONCLUSION: Two squalene synthase genes AlSQS1 and AlSQS2 were isolated from Atractylodes lancea and functionally characterized using in vitro enzymatic reactions. Atractylodes lancea is a traditional herb used for the treatment of rheumatic diseases, gastric disorders, and influenza. Its major active ingredients include sesquiterpenoids and triterpenes. Squalene synthase (SQS; EC 2.5.1.21) catalyzes the first enzymatic step in the central isoprenoid pathway towards sterol and triterpenoid biosynthesis. In this study, we aimed to investigate two SQSs from A. lancea using cloning and in vitro enzymatic characterization. Bioinformatics and phylogenetic analyses revealed that the AlSQSs exhibited high homology with other plant SQSs. Furthermore, AlSQS1 was observed to be localized in both the nucleus and cytoplasm, whereas AlSQS2 was localized in the cytoplasm and endoplasmic reticulum. To obtain soluble recombinant enzymes, AlSQS1 and AlSQS2 were successfully expressed as glutathione S-transferase (GST)-tagged fusion proteins in Escherichia coli Transetta (DE3). Approximately 68 kDa recombinant proteins were obtained using GST-tag affinity chromatography and Western blot analysis. Results of the in vitro enzymatic reactions established that both AlSQS1 and AlSQS2 were functional, which verifies their catalytic ability in converting two farnesyl pyrophosphates to squalene. The expression patterns of AlSQS and selected terpenoid genes were also investigated in two A. lancea chemotypes using available RNA sequencing data. AlSQS1 and AlSQS2, which showed relatively similar expression in the three tissues, were more highly expressed in the stems than in the leaves and rhizomes. Methyl jasmonate (MeJA) was used as an elicitor to analyze the expression profiles of AlSQSs. The results of qRT-PCR analysis revealed that the gene expression of AlSQS1 and AlSQS2 plummeted at lowest value at 12 h and reached its peak at 24 h. This study is the first report on the cloning, characterization, and expression of SQSs in A. lancea. Therefore, our findings contribute novel insights that may be useful for future studies regarding terpenoid biosynthesis in A. lancea.

Nonlinear optical property and application of yttrium oxide in erbium-doped fiber lasers.

Yttrium oxide (Y2O3) has garnered some attention in view of its potential to be integrated into a wide range of high-strength structural components, microelectronic and optoelectronic devices. However, the nonlinear optical research of this promising material has not been implemented yet. In this paper, not only the electronic band structures of Y2O3 are theoretically calculated but also the optical nonlinearity of Y2O3 is validated by using the fiber laser as a platform. Meanwhile, the influence of sample thickness on laser performance is further explored by using Y2O3 saturable absorbers with different thickness. Results indicate that Y2O3 not only has impressive optical nonlinearity but also is beneficial to the investigation of ultrafast photons by adjusting the thickness of Y2O3. Therefore, Y2O3 can be used as a potential saturable absorber candidate for in-depth research and application.

A voltage-pulse-modulated giant magnetoresistance switch with four flexible sensing ranges.

This article introduces an innovative technique for achieving a giant magnetoresistance (GMR) switch with an adjustable sensing field range. A spin-valve (SV) patterned into a strip shape is grown on a specific (110)-cut Pb(Mg1/3Nb2/3)0.7Ti0.3O3(PMN-PT) substrate. In the process of depositing films, a magnetic easy axis of the free layer in the SV is produced along the [001] direction (thex-axis) of the PMN-PT. This PMN-PT can produce a nonvolatile strain by using a positive voltage pulse. Accordingly, the magnetic moment of the free layer can be modulated to they-axis by the strain-mediated magnetoelectric coupling effect produced in the SV/PMN-PT heterostructure. Furthermore, a negative voltage pulse can release the strain and revert the magnetic moment to the initial [001] direction. The effective field along the [1-10] direction produced by the nonvolatile strain can modulate the easy axis of the free layer, changing it from thex-axis to they-axis. Therefore, large and small switching fields are achieved in a bipolar GMR switch. Furthermore, by applying positive and negative voltage pulses at appropriate moments, two asymmetrical switching field ranges are obtained. Thus, a GMR switch with four adjustable switching field ranges can be obtained. The proposed modulating model is flexible and can meet the requirements of specific and different application systems. The proposed design reveals a great potential for the application to the internet of things and the development of low-power and high-efficient magnetoresistive sensors.

[Cloning and prokaryotic expression of 3-ketoacyl-CoA thiolase gene AIKAT from Atractylodes lancea].

In this study, the gene encoding the key enzyme 3-ketoacyl-CoA thiolase(KAT) in the fatty acid ß-oxidation pathway of Atractylodes lancea was cloned. Meanwhile, bioinformatics analysis, prokaryotic expression and gene expression analysis were carried out, which laid a foundation for the study of fatty acid ß-oxidation mechanism of A. lancea. The full-length sequence of the gene was cloned by RT-PCR with the specific primers designed according to the sequence information of KAT gene in the transcriptomic data of A. lancea and designated as AIKAT(GenBank accession number MW665111). The results showed that the open reading frame(ORF) of AIKAT was 1 323 bp, encoding 440 amino acid. The deduced protein had a theoretical molecular weight of 46 344.36 and an isoelectric point of 8.92. AIKAT was predicted to be a stable alkaline protein without transmembrane segment. The secondary structure of AIKAT was predicted to be mainly composed of α-helix. The tertiary structure of AIKAT protein was predicted by homology modeling method. Homologous alignment revealed that AIKAT shared high sequence identity with the KAT proteins(AaKAT2, CcKAT2, RgKAT and AtKAT, respectively) of Artemisia annua, Cynara cardunculus var. scolymus, Rehmannia glutinosa and Arabidopsis thaliana. The phylogenetic analysis showed that AIKAT clustered with CcKAT2, confirming the homology of 3-ketoacyl-CoA thiolase genes in Compositae. The prokaryotic expression vector pET-32 a-AIKAT was constructed and transformed into Escherichia coli BL21(DE3) for protein expression. The target protein was successfully expressed as a soluble protein of about 64 kDa. A real-time quantitative PCR analysis was performed to profile the AIKAT expression in different tissues of A. lancea. The results demonstrated that the expression level of AIKAT was the highest in rhizome, followed by that in leaves and stems. In this study, the full-length cDNA of AIKAT was cloned and expressed in E. coli BL21(DE3), and qRT-PCR showed the differential expression of this gene in different tissues, which laid a foundation for further research on the molecular mechanism of fatty acid ß-oxidation in A. lancea.

Bioremediation by earthworms on soil microbial diversity and partial nitrification processes in oxytetracycline-contaminated soil.

A large proportion (60-90%) of ingested tetracyclines are released to slurry, soils, surface waters and ground water, which has raised extensive concerns and may pose a risk to the soil ecosystem. A 56-day experiment was conducted to study the bioremediation by earthworms on soil microbial diversity and partial nitrification processes in oxytetracycline (OTC)-contaminated soil. The results showed that high OTC concentration significantly decreased the activity of soil bacteria, ammonia-oxidizing bacteria (AOB) and archaea (AOA). Earthworms were found to accelerate the degradation efficiency and rate of OTC, and its main metabolites were 4-epi-oxytetracycline (EOTC) and 2-acetyl-2-decarboxamido-oxytetracycline (ADOTC). Earthworms had an important role in the bioremediation of soil microbial diversity by degrading OTC and its metabolite (EOTC), especially in the high OTC condition. Additionally, the results indicated that the effects of earthworms on the degradation of OTC could remediate the abundances of 16S rRNA and AOB amoA genes and the NO3- content in both low and high OTC-contaminated soils. The structural equation model suggested that earthworms could remediate the microbial diversity, the abundances of 16s rRNA and AOB amoA genes by accelerating the degradation of OTC, which contributed to the bioremediation by earthworms on soil microbial diversity and partial nitrification processes in oxytetracycline-contaminated soil.

Er Miao San, a traditional Chinese herbal formula, attenuates complete Freund's adjuvant-induced arthritis in rats by regulating Th17/Treg cells.

Context: Er Miao San (EMS) is a traditional Chinese medicine composed of Atractylodis Rhizoma and Phellodendri Cortex in a 1:1 weight ratio. EMS has been used to treat rheumatism in China for many years.Objective: To evaluate the anti-arthritic activity of EMS extract on adjuvant-induced arthritis (AA) in Sprague-Dawley rats and to clarify its mechanisms of action.Materials and methods: EMS (0.75, 1.5 and 3 g/kg, once daily) was orally administered from day 18 after immunization to day 31. The effects of EMS on AA rats were evaluated by histopathological examination, paw swelling and polyarthritis index. The proliferation of fibroblast-like synoviocyte (FLS) and T cells was detected by CCK-8. The percentages of Th17 cells and Treg cells in splenocytes were determined by flow cytometry. Levels of cytokines in serum were detected by ELISA.Results: EMS treatment significantly decreased the paw volume (from 1.20 to 0.81), polyarthritis index (from 9.56 to 4.46) and alleviated ankle joint histopathology in AA rats. EMS inhibited the proliferation of FLS and T cells. Furthermore, EMS treatment decreased Th17 cells (from 4.62 to 2.08%) and increased Treg cells (from 2.77 to 4.75%) in splenocytes. The levels of IL-17A, TNF-α and IL-6 were remarkably decreased in the serum of EMS-treated rats, whereas the levels of IL-10 and TGF-ß1 were significantly increased.Conclusions: EMS exhibits anti-arthritic activity in the AA model by regulating the balance of cytokines and the ratio of Th17 and Treg cells. These insights may provide an experimental basis for the clinical treatment of RA.

Nonlytic Recombinant Phage Tail Fiber Protein for Specific Recognition of Pseudomonas aeruginosa.

Rapid and accurate bacterial detection is crucial to an early diagnosis for treating various infectious diseases. A recombinant tail fiber protein (P069) of the Pseudomonas aeruginosa ( P. aeruginosa) phage was expressed in Escherichia coli. After renaturation at a low temperature, the inclusion body of P069 was successfully transformed to an aqueous soluble protein that retained the capacity for recognizing P. aeruginosa. The recombinant P069 did not show lytic activity to P. aeruginosa, which facilitated the capture and manipulation of bacterial whole cells with a high flexibility for downstream identification and detection. Bioluminescent and fluorescent methods using this biorecognition element allowed P. aeruginosa detection with the detection limits of 6.7 × 102 CFU mL-1 and 1.7 × 102 CFU mL-1, respectively. Moreover, the specificity investigations showed that P069 was a species-specific protein. Therefore, it avoided the potential false negative results originating from the excessive high specificity of phage toward a given strain. It has been successfully applied to detect P. aeruginosa in spiked samples with acceptable recovery values ranging from 88% to 98%. The above results demonstrate that P069 is an ideal biorecognition element for the detection of P. aeruginosa in complicated sample matrixes.

Tungsten diselenide for mode-locked erbium-doped fiber lasers with short pulse duration.

In this paper, a WSe2 film prepared by chemical vapor deposition (CVD) is transferred onto a tapered fiber, and a WSe2 saturable absorber (SA) is fabricated. In order to measure the third-order optical nonlinearity of the WSe2, the Z-scan technique is applied. The modulation depth of the WSe2 SA is measured as being 21.89%. Taking advantage of the remarkable nonlinear absorption characteristic of the WSe2 SA, a mode-locked erbium-doped fiber laser is demonstrated at 1557.4 nm with a bandwidth of 25.8 nm and signal to noise ratio of 96 dB. To the best of our knowledge, the pulse duration of 163.5 fs is confirmed to be the shortest compared with previous mode-locked fiber lasers based on transition-metal dichalcogenides SAs. These results indicate that WSe2 is a powerful competitor in the application of ultrashort pulse lasers.

CVD-grown MoSe2 with high modulation depth for ultrafast mode-locked erbium-doped fiber laser.

Two-dimensional materials have been widely used as optical modulator materials in mode-locked fiber lasers. In terms of the performance of the fiber laser, one with an ultrashort pulse and high stability has great commercial value. Herein, the MoSe2 grown by the chemical vapor deposition (CVD) method with high modulation depth, quality lattice structure and uniformity is successfully applied in a mode-locked erbium-doped fiber laser. The pulse duration and signal-to-noise ratio of the laser are 207 fs and 85 dB, respectively. The multifarious performance comparisons indicate that the CVD-based MoSe2 saturable absorber with the tapered fiber structure has unique advantages not only in the generation of ultrashort pulses, but also in the optimization of laser stability.

Simultaneous Synthesis of WO3-x Quantum Dots and Bundle-Like Nanowires Using a One-Pot Template-Free Solvothermal Strategy and Their Versatile Applications.

Tungsten oxide (WO3-x ), a new alternative to conventional semiconductor material, has attracted numerous attentions owning to its widespread potential applications. Various methods have been reported for the synthesis of WO3-x nanostructures such as nanowires or nanodots. However, templates or surfactants are often required for the synthesis, which significantly complicate the process and hinder the broad applications. Herein, one-pot template/surfactant-free solvothermal method is proposed to synthesize the WO3-x nanostructures including fluorescent quantum dots (QDs) and bundle-like nanowires simultaneously. The as-prepared WO3-x QDs can be well dispersed in aqueous medium, exhibit excellent photoluminescent properties, and show an average size of 3.25 ± 0.25 nm as evidenced by transmission electron microscopy. Meanwhile, the diameter of the WO3-x nanowires is found to be about 27.5 nm as manifested by the scanning electron microscope images. The generation mechanism for these two WO3-x nanostructures are systematically studied and proposed. The WO3-x QDs have been successfully applied in efficient fluorescent staining and specific ferric ion detection. Moreover, the WO3-x nanowires can be utilized as effective dielectric materials for electromagnetic wave absorption.

Tungsten disulfide saturable absorbers for 67 fs mode-locked erbium-doped fiber lasers.

In this paper, we demonstrate 67 fs pulse emitting with tungsten disulfide (WS2) in mode-locked erbium-doped fiber (EDF) lasers. Using the pulsed laser deposition method, WS2 is deposited on the surface of the tapered fiber to form the evanescent field. The fiber-taper WS2 saturable absorber (SA) with the large modulation depth is fabricated to support the ultrashort pulse generation. The influences of the WS2 SA are analyzed through contrastive experiments on fiber lasers with or without the WS2 SA. The pulse duration is measured to be 67 fs, which is the shortest pulse duration obtained in the mode-locked fiber lasers with two dimensional (2D) material SAs. Compared to graphene, topological insulator, and other transition metal dichalcogenides (TMDs) SAs, results in this paper indicate that the fiber-taper WS2 SA with large modulation depth is a more promising photonic device in mode-locked fiber lasers with the wide spectrum and ultrashort pulse duration.