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Development of multicolor-emitting upconversion nanoparticles (UCNPs) is of significant importance for applications in optical encoding, anti-counterfeiting, display, and bioimaging. However, realizing the orthogonal three-primary color (TPC) upconversion luminescence in a single nanoparticle remains a huge challenge. Herein, we have rationally designed core-multishell-structured NaYF4 UCNPs through regulating the dopant concentration, composition of luminescent layers, and shell position and thickness, which are capable of emitting red, green, and blue luminescence with high color purity in response to ternary near-infrared quadrature excitations (1560/808/980 nm). Moreover, their high color purity is well retained with varying excitation power densities. This orthogonal TPC emissions property of such UCNPs endows them with great promise in the field of security. As a proof-of-concept, we have demonstrated the feasibility of combining such UCNPs with MnO2 nanosheets for information encryption and decryption. This work not only offers a new way to achieve TPC upconversion luminescence at a single nanoparticle level but also broadens the scope of application for security protection.

Optical probes that specifically and sensitively change the optical properties upon contact with targets have become irreplaceable tools in fundamental biology and medicine. Semiconducting polymer dots (Pdots) have emerged as popular optical nanoplatforms because of their excellent characteristics, such as tunable luminescence, high brightness, superior stability and biocompatibility, for biological applications. In particular, facile surface and intra-particle modifications enable Pdots to detect various biological parameters, such as reactive oxygen species (ROS), typical metal ions, pH values, temperature and a variety of biomolecules. In this review, we provide a brief overview of the preparation and bio-functionalization strategies of Pdots. This review focuses on the applications of Pdots as optical probes in biosensors and describes the challenges in this field.

Multifunctional materials have attracted recent attention due to their various applications in many fields. In this work, CaWO4 nanocrystals were prepared by a hydrothermal method. Nanoparticles, nanowires, and micro-sized structures were obtained by controlling the reaction temperature, Ca2+-to-WO42− ratio and type of dopant. The influence of rare earth ions on the morphology and luminescence properties was investigated. Upconversion and downconversion luminescence behaviors showed CaWO4 to be an excellent host for rare earth doping. CaWO4:Er3+ nanowires were also used in dye-sensitized solar cells (DSSCs) to improve device performance. Increased light harvesting caused by improved dye loading capacity and enhanced light scattering led to improved cell efficiency. Moreover, reduced charge recombination due to the additional energy levels of CaWO4:Er3+ was another reason for the improved cell efficiency. Therefore, in this work, we demonstrated the synthesis of CaWO4 nanocrystals and the control of their morphology and luminescence by rare earth doping, which has significant future applications in lighting and display. The applications in DSSCs provide a new strategy to achieve high-performance solar cells by using nanocrystals via increased light harvesting and reduced charge recombination.

Broadband and ultrafast response of plasmonic nanoparticles offer a significant advantage in optical modulation and allow ultrashort pulse generation from visible to mid‐infrared (MIR) region. However, many of the materials exhibit limited saturable absorption bandwidth in MIR spectral region, which limits the MIR pulses generation and the relative applications. Herein, it is shown that solution‐processed silver nanowires (AgNWs) exhibit an ultrabroadband localized surface plasmon resonance (LSPR) from 0.3 to over 25 μm, which contributes to wideband nonlinear optical response in the whole MIR region. Using those AgNWs as saturable absorbers (SA), all‐optical modulation in near infrared and MIR region is demonstrated. Mode‐locked lasers are realized at 1, 1.5, and 2 μm bands with minimal pulse duration down to a few hundreds of femtoseconds, and a Q‐switched laser at 3 μm band is achieved. The results show that AgNWs SA has the potential for constructing pulsed lasers in the MIR or even longer wavelength region.

Semiconducting polymer dots (Pdots) have been applied in various biological fields owing to their tunable fluorescence, high brightness, and facile functionalization. However, most Pdots emit in the visible region, wherein fluorescence imaging would suffer from significant photon scattering and autofluorescence in biological tissues. Furthermore, Pdots typically exhibit a reduced fluorescence compared to the corresponding original polymers in organic solvents as a result of aggregation-caused quenching effect. These drawbacks make it difficult to develop Pdots that exhibit bright emission in the near-infrared (NIR) wavelength range. Herein, based on an aggregation-induced emission (AIE) polymer, we report Pdots exhibiting NIR emission along with high fluorescence quantum yield. After fabricating the AIE polymer into Pdots, the fluorescence intensity was enhanced by 2.5-times, yielding NIR emission with a quantum yield of ∼23%. The Pdots also possess outstanding optical properties and biocompatibility, mak...

Purpose The purpose of this paper is to investigate the mediating effect of information search effort on the relationship between leader narcissism and team creativity in China based on attention theory. The paper also explores participative decision making as a moderator in the relationship between team leader narcissism and information search effort. Design/methodology/approach Through a survey of 667 team members and their team leaders from 96 research and development teams at 23 high-tech enterprises in China with paired samples, cross-time data were collected. Confirmatory factor analysis, hierarchical regression and path analysis were adopted to analyze the data. Findings This paper found that leader narcissism had a positive impact on team information search effort, thereby promoting team creativity, and the effect of leader narcissism on team information search effort is more positive in the context of high participation in decision making. Practical implications Narcissism should be a noteworthy trait in manager selection and promotion especially for the departments and teams which focus on innovation and creation. And companies should pay attention to the team work processes to ensure that team members have the opportunity to participate in decision making for promoting the team leader’s narcissistic “bright” side in the institutional environment and avoiding the “dark” side. Originality/value This paper discusses how and when leader narcissism influences team creativity in Chinese high-technology enterprises based on attention theory. This research expands the application of attention theory at the team level.

In this Letter, we present the mode-locking operation of a 2.87 µm H o 3 + / P r 3 + codoped fluoride fiber laser, helped by the ultrafast nonlinear optical absorption behavior of gold nanowires (GNWs). The mode locker is fabricated by depositing the GNW solution onto a silver mirror. It has a modulation depth of 14.2%, a saturation intensity of 26.2 M W / c m 2 , and a non-saturation loss of 29.9% at 2.87 µm. With an increased pump power, the laser operates in Q -switched mode-locking, fundamental mode-locking, and harmonic mode-locking (HML) states. This represents the first, to our knowledge, mid-infrared mode-locked laser using gold nanomaterials. Additionally, the HML is also the first observation in a laser in this band using material saturable absorbers, implying the capability of GNWs for high repetition rate generation.

It is well known that the upconversion luminescence from lanthanide metal-organic frameworks (Ln-MOFs) is difficult to achieve, and thus, there are few reports on dual luminescence-based MOFs. Here, dual-mode light-emitting Ln-MOFs are synthesized using a low-cost hydrothermal method. Our results show that the obtained Ln-MOFs not only have high thermal stability (up to 420°) but also are stable in deionized water. The dual-mode up- and downconversion luminescence is simultaneously observed from Er-Eu-MOFs. The temperature-dependent fluorescence decay time is calculated to be ranging from 0.46 to 0.36 ms for temperatures from 100 to 300 K. We suggested that this phenomenon was because the number of phonons participating in the MOF matrix increases with temperature during the luminescence process, and the phonons interact with the electrons in the material. The values of the J-O parameters calculated from the emission spectra indicated that the symmetry around Eu3+ ions in Eu-MOF is the highest, which was also higher than that of Er-Eu-MOF. To explore the potential applications of Eu-MOFs in white light-emitting diodes (LEDs), red emission from Eu-MOFs was combined with blue, green, and yellow emissions from metal halide perovskites to achieve white light emission. White light with excellent color quality and vision performance was obtained. These findings demonstrate that Ln-MOFs are potentially successful materials for applications in white LEDs.

To date, no efficacious therapy exists that will prevent or treat the severe osteoporosis in individuals with neurologically motor-complete spinal cord injury (SCI). Recent preclinical studies have demonstrated that sclerostin antibody (Scl-Ab) can prevent sublesional bone loss after acute SCI in rats. However, it remains unknown whether sclerostin inhibition reverses substantial bone loss in the vast majority of the SCI population who have been injured for several years. This preclinical study tested the efficacy of Scl-Ab to reverse the bone loss that has occurred in a rodent model after chronic motor-complete SCI. Male Wistar rats underwent either complete spinal cord transection or only laminectomy. Twelve weeks after SCI, the rats were treated with Scl-Ab at 25 mg/kg/week or vehicle for 8 weeks. In the SCI group that did not receive Scl-Ab, 20 weeks of SCI resulted in a significant reduction of bone mineral density (BMD) and estimated bone strength, and deterioration of bone structure at the distal femoral metaphysis. Treatment with Scl-Ab largely restored BMD, bone structure, and bone mechanical strength. Histomorphometric analysis showed that Scl-Ab increased bone formation in animals with chronic SCI. In ex vivo cultures of bone marrow cells, Scl-Ab inhibited osteoclastogenesis, and promoted osteoblastogenesis accompanied by increased Tcf7, ENC1, and the OPG/RANKL ratio expression, and decreased SOST expression. Our findings demonstrate for the first time that Scl-Ab reverses the sublesional bone loss when therapy is begun after relatively prolonged spinal cord transection. The study suggests that, in addition to being a treatment option to prevent bone loss after acute SCI, sclerostin antagonism may be a valid clinical approach to reverse the severe bone loss that invariably occurs in patients with chronic SCI.

We present the design of fluorotellurite microstructured fibers (FTMFs) with near-zero-flattened dispersion profiles in the wavelength range of 1500–1600 nm for optical frequency comb (OFC) generation. The FTMFs are based on TeO2-BaF2-Y2O3 glass with a zero-dispersion wavelength of ∼2160 nm. The fiber core is surrounded by the two layers of air holes. The addition of large size air holes in the outer layer is to shift the zero-dispersion wavelength of the fiber from ∼2160 nm to the wavelength region of 1500–1600 nm. The addition of small size air holes in the inner layer is to make the dispersion profile of the fiber become flat in the wavelength range of 1500–1600 nm. By optimizing the parameters (the core diameter, the air hole size, the pitch of air holes, etc.) of FTMFs, the fiber with the chromatic dispersion value between −0.5 and 0.3 ps/nm/km in the wavelength range of 1500–1600 nm is achieved. Furthermore, numerical simulations are used to show the potential of the fiber for OFC generation via cascaded four-wave mixing. Flat top OFC extending from 1500 to 1600 nm with tunable mode spacing from 25 to 100 GHz can be generated in a 2-m-long fiber by using a 1550-nm laser with a pulse width of 0.85 ps and a peak power of 49 W as the pump source. The effects of stimulated Brillouin scattering on OFC generation are also investigated.

Optical methods such as absorptiometry, fluorescence, and surface plasmon resonance have long been explored for sensing glucose. However, these schemes have not had the clinical success of electrochemical methods for point-of-care testing because of the limited performance of optical sensors and the bulky instruments they require. Here, we show that an ultrasensitive optical transducer can be used for wireless glucose monitoring via a smartphone. The optical transducer combines oxygen-sensitive polymer dots (Pdots) with glucose oxidase that sensitively detect glucose when oxygen is consumed in the glucose oxidation reaction. By judicious design of the Pdots with ultralong phosphorescence lifetime, the transducer exhibited a significantly enhanced sensitivity by 1 order of magnitude as compared to the one in a previous study. As a result, the optical images of subcutaneous glucose level obtained with the smartphone camera could be utilized to clearly distinguish between euglycemia and hyperglycemia. We further developed an image processing algorithm and a software application that was installed on a smartphone. Real-time dynamic glucose monitoring in live mice was demonstrated with the smartphone and the implanted Pdot transducer.

Ho3+-doped fluoroindate glass fibers (FIGFs) based on InF3-GaF3-ZnF2-BaF2-SrF2-YF3-LiF-PbF2 glasses were fabricated by using a rod-in-tube method. By using a 92-cm-long Ho3+-doped FIGF as the gain medium and a 1120-nm fiber laser as the pump source, lasing at 2875 nm was obtained for a threshold pump power of 278 mW. By further increasing the pump power to 1224 mW, the obtained maximum output power was about 54.5 mW. The corresponding slope efficiency was about 6%. To the best of our knowledge, this is the first time to report lasing at 2875 nm from Ho3+-doped FIGFs.

Optical waveguide amplifiers are essential to improve the performance of integrated communication systems. Previous research has mainly focused on C- and L-bands amplification, but there are few reports on S-band waveguide amplifiers. Here, we introduce a polymer-based waveguide amplifier that uses a NaYF4:Yb3+,Tm3+ nanoparticles–PMMA nanocomposite as gain medium, which can provide loss compensation in the S-band. To obtain the strongest emission luminescence at 1480 nm, we optimized the doping concentration of Yb3+ and Tm3+ to 20% and 1%, respectively. By copolymerizing the nanoparticles and methyl methacrylate monomers, the nanocomposite was synthesized and used as the gain medium to fabricate S-band waveguide amplifiers. A relative gain of 5.6 dB/cm was observed at 1480 nm under the excitation of a 980-nm pump laser. To the best of our knowledge, this is the first time that S-band amplification has been observed in a polymer-based waveguide amplifier. This result is expected to extend the waveband of polymer-based waveguide amplifiers to the S-band.

P r 3 + / Y b 3 + co-doped fluoroindate ( I n F 3 ) glasses were prepared by using a traditional melt-quenching method in dry N 2 atmosphere. Pumped by a 976 or 1570 nm laser diode, efficient emissions at ∼ 4 µ m were obtained from the P r 3 + / Y b 3 + co-doped glasses, which could be ascribed to the transition 3 F 4 → 3 H 6 of P r 3 + ions. The relative stimulated emission cross section was calculated to be ∼ 1.44 × 10 − 24 m 2 at 4 µm, which was ∼ 4.2 times larger than that of transition H o 3 + : 5 I 5 → 5 I 6 ( 3.4 × 10 − 25 m 2 ). In addition, combined with transitions 1 G 4 → 3 F 3 and 1 G 4 → 3 F 4 of P r 3 + ions, ultra-broadband emission ranging from 2.7 to 4.2 µm was also obtained. Our results indicate that P r 3 + / Y b 3 + : I n F 3 glasses could be used to develop efficient ∼ 4 µ m lasers and widely tunable mid-infrared lasers.

All-solid fluorotellurite fibers with near-zero-flattened dispersion profiles in the wavelength range of 1840–2140 nm are designed for mid-infrared optical frequency comb (OFC) generation. The fiber core materials are TeO2-BaF2-Y2O3 (TBY) glasses. The fiber cladding materials are fluoroaluminate and TBY glasses. By controlling the core diameter and the thickness of the thin annular fluoroaluminate or TBY glass, the fiber with the chromatic dispersion value between −0.3 and 0.32 ps nm km−1 in the wavelength range of 1840–2140 nm is achieved. Furthermore, we perform numerical simulations on mid-infrared OFC generation via four-wave mixing in the designed fiber. By using a 1980 nm laser with a pulse width of 1.28 ps and a peak power of 60 W as the pump source, OFC spectrum expanding from 1127 to 4942 nm is obtained in a 2 m long fiber, and the pulse width of the generated OFC is about 25 fs. By varying the repetition rate of the pump source, mid-infrared OFC with tunable mode spacing is generated in the designed fiber.

We investigate coherent broadband mid-infrared supercontinuum generation in all normal dispersion (ANDi) tellurite microstructured fibers through numerical simulations. The proposed tellurite microstructured fibers (PTMFs) have an inverted L-shaped ANDi profile in the wavelength range of < 5.2 μm. By using a 2-μm femtosecond laser as the pump source, the spectral broadening occurs in the PTMF, which is caused by self-phase modulation (SPM) and optical wave breaking. Interestingly, SPM induced spectral broadening is larger on the Stokes side than the antistokes side, since the trailing edge of laser pulse becomes smoother than its leading edge, and the effect of self-steepening (SS) on pulse shape is compensated by the effect of the dispersion in the PTMF. Such a phenomenon is inaccessible in previously reported optical fibers, since the trailing edge of output pulse is steeper than the leading edge of output pulse when SS occurs in previously reported ANDi fibers. As a result, coherent broadband mid-infrared supercontinuum light with long operating wavelength can be generated in the PTMF.

Tm 3+ doped β-NaYbF 4 with different aspect ratios has been synthesized by a facile hydrothermal method. A different morphology and size of β-NaYbF 4 microrods were obtained by changing the NaF/RE (RE = Yb,Tm, 99.5% Yb 3+ , 0.5% Tm 3+ ) molar ratio. The morphology and size of products were explored by SEM, and the influences of the NaF/RE molar ratio on the microrod size were evidenced by XRD. It is shown that the size and morphology of the products can be precisely controlled by modulation of the NaF/RE molar ratio. β-NaYbF 4 microrods with 35 μm in length and 7.5 μm in diameter were prepared when NaF/RE molar ratio is 6. Intense ultraviolet emissions at 290 nm, 345, and 361 nm and visible emissions at 451 and 494 nm were observed in Tm 3+ doped NaYbF 4 microrods with an excitation of a 980 nm diode laser. The effect of NaF/RE ratio on growth rate has been proposed.

Single phase cubic CaF 2 microcrystals co-doped with Eu 3+ and Yb 3+ ions were synthesized through a coprecipitation process followed by annealing at 1200 °C. Under the excitation of 980 nm laser, the intensive emission at ~614 nm ( 5 D 0 → 7 F 2 ) in the red region was observed at room temperature. The color coordinate of CaF 2 :0.1%Yb 3+ /0.1%Eu 3+ was calculated with the Commission Internationale de I’Eclairage (CIE) chromaticity coordinate of ( x=0.572 , y=0.265 ). The excitation of Eu 3+ ions came from the energy transfer of Yb 3+ -dimers through a cooperation sensitization process. Furthermore, not only the emissions from the 5 D i (i=0, 1, 2, 3)→ 7 F j (j=0, 1, 2, 3) transitions but also the rarely reported emission (~398 nm) from the 5 L 6 → 7 F 0 transition was recorded. The cooperation sensitization process was so effective in the Yb 3+ /Eu 3+ co-doped system that all the cooperative luminescence (CL) from Yb 3+ -clusters were quenched and only the red upconversion luminescence of Eu 3+ ions could be seen.

It is a challenge to develop efficient photocatalyst that can be activated by photons with long wavelength. In our previous work, a near infrared (NIR) driven photocatalyst (e.g., NaYF4:Yb,Tm@TiO2) was designed, for which, however, a two-step energy transfer was involved for photocatalysis so that the ultimate photocatalytic capability is low. In this work, we designed and prepared a new type of NIR photocatalyst composed of cooperative luminescence agent CaF2:Yb and semiconductor BiVO4, in which a one-step energy transfer occurs to realize NIR photocatalysis. Steady-state and dynamic fluorescence spectroscopy analysis revealed that cooperative energy transfer of a Yb3+-dimer to BiVO4 leads to the indirect excitation of semiconductor BiVO4 by NIR light. The degradation of methylene blue (MB) compound by CaF2:1%Yb3+@BiVO4 particles upon NIR radiation and its corresponding controlled experiments demonstrated the NIR light responsive photocatalytic capability. It is noteworthy that nearly 80% degradation ratio of MB was achieved with 7 h of NIR light irradiation, indicating a relatively high photocatalytic activity, compared with that of our previously reported system NaYF4:Yb,Tm@TiO2, for which ∼65% of degradation ratio of MB was obtained within 14 h of NIR irradiation. Recycling experiments of photocatalysis indicate that our present CaF2:Yb@BiVO4 composite has good photochemical stability in spite of a long time of NIR irradiation.

In this paper, we demonstrate ∼2 μm lasing in Tm3+-doped fluorotellurite microstructured fibers. The Tm3+-doped fibers are based on TeO2-BaF2-Y2O3 glasses and fabricated by using a rod-in-tube method. Under the pump of a 1570 nm Er3+-doped fiber laser, lasing at 1887 nm is obtained in a ∼42.5 cm long Tm3+-doped fiber with a threshold pump power of 94 mW. As the pump power increases to 780 mW, the obtained maximum unsaturated power reaches up to ∼408 mW with a slop efficiency of ∼58.1%. This result indicates that the Tm3+-doped fluorotellurite fibers are promising gain media for ∼2 μm fiber lasers.

Despite showing great promise in bioapplications, lanthanide-doped upconversion nanoparticles (UCNPs) are still restricted by low upconversion efficiency. In this work, ultra-small, monodisperse and uniform β-NaYbF4:0.5% Tm NPs were successfully prepared through a solvothermal route, and remarkably enhanced ultraviolet upconversion luminescence (UV UCL) had been achieved via Fe3+ doping. The UV UCL enhancement in NaYbF4:0.5% Tm NPs was investigated in detail. It was found that the UCL intensities of the UV and blue emissions of NPs doped with 5 mol% Fe3+ ions were enhanced by 10 and 6 times, respectively, compared to that of the Fe3+-free sample. The enhancement of UV UCL is mainly ascribed to the high population density of excited Yb3+ and the energy transfer from |2F7/2, 4T1g > (Yb3+–Fe3+ dimer) to 3F2,3 (Tm3+) states. Moreover, through dynamic analysis, we further demonstrate the proposed mechanisms of UC processes. The results suggest that ultra-small UCNPs with enhanced UV UCL may have potential applications in the biomedical field.

We demonstrate a passively Q-switched Yb3+/Er3+ co-doped fiber (YEDF) laser using a filmy sodium carboxymethylcellulose (NaCMC)-based Cu1.8S nanocrystals (NCs) saturable absorber (SA). Cu1.8S NCs SA exhibit a broad absorption band from 600 nm to more than 2500 nm. By placing Cu1.8S NCs SA into a YEDF laser cavity, stable passively Q-switched laser with a central wavelength of ∼1567.2 nm was achieved at a threshold pump power of ∼1.4 W. On gradually increasing the pump power from 1.4 W to 5.6 W, the repetition rate of Q-switched laser increases from 16.6 kHz to 51.14 kHz and the pulse duration decreases from 8.7 μs to 2 μs. Particularly, we measure the output power of Q-switched lasers based on two types of plasmonic materials, Cu1.8S NCs and gold nanorods (GNRs). The maximum output power of the Q-switched laser based on Cu1.8S NCs SA is 3–4 times higher than that based on GNRs SA owing to weak photothermal effect of Cu1.8S NCs. These results show that Cu1.8S NCs are promising SAs for constructing high power pulse lasers.

Er3+ doped ZnF2-BaF2-SrF2-YF3 (ZBSY-e) glasses were prepared in a glove box. The absorption coefficient of residual hydroxyl in the glasses was calculated to be ∼0.001 cm−1 at 2.7 μm. Under 978 nm laser diode excitation, intense ∼2.7 μm emissions were observed from the ZBSY-e glasses and the emission intensity was much stronger than that obtained in Er3+-doped fluoroindate, fluorozirconate or fluoroaluminate glasses for a same excitation power density. The efficient ∼2.7 μm emission could be attributed to the relative low phonon energy (420 cm−1) of the ZBSY glass. Our results indicated that the ZBSY-e glass was a potential gain medium for ∼2.7 μm lasers.

STUDY DESIGN: Animal study. OBJECTIVE: This study examined how soon after spinal cord injury (SCI) bone loss occurs, and investigated the underlying molecular mechanism. METHODS: Eight-week-old male Wistar rats underwent complete transection of the thoracic spinal cord at T3–4 or sham operation (n = 10–12 per group). Blood, hindlimb bone samples, and bone marrows were collected at 2 and 7 days after SCI. RESULTS: The neurologically motor-complete SCI causes loss of bone mass and deterioration of trabecular bone microstructure as early as 2 days after injury; these skeletal defects become more evident at 7 days. These changes are associated with a dramatic increase in levels of bone resorption maker CTX in blood. Alternations of gene expression in hindlimb bone tissues and bone marrow cells at the first week after SCI were examined. Gene expressions responsible for both bone resorption and formation are increased at 2 days post-SCI, and the associated bone loss and bone deterioration are likely the result of higher levels of osteoclastic resorption over osteoblastic formation, as may be extrapolated from findings at molecular levels. CONCLUSIONS: Rapid bone loss occurs as early as 2 days after motor-complete SCI and interventions for inhibiting bone resorption and prompting bone formation should start as soon as possible after the injury to prevent bone loss.

In this study, we prepared cubic-phase oleic-acid-coated KMnF3: Yb3+,Er3+ nanoparticles (NPs) and NaYF4:Yb3+,Er3+ NPs, which were about 23 nm. From the down-shifting emissions spectra of the two NPs obtained by 980 nm excitation, we observed the fact that the KMnF3: 18%Yb3+,1%Er3+ NPs were a luminescent material with a broadband near-infrared emission of 1.5 &mu, m, and full-width at half-maximum (FWHM) of 55 cm&minus, 1, which was wider than that of the NaYF4: 18%Yb3+,1% NPs. Therefore, we believe that the oleic-acid-coated KMnF3:Yb3+,Er3+ NPs have great potential in fabricating broadband waveguide amplifiers. Through epitaxial growth of a KMnF3: Yb3+ active-shell on the core NPs, we compounded KMnF3:Yb3+,Er3+@KMnF3:Yb3+ core-active-shell NPs whose 1.5-&mu, m infrared emissions intensity was 3.4 times as strong as that of the core NPs. In addition, we manufactured waveguide amplifiers using KMnF3:18%Yb3+,1%Er3+@KMnF3:2%Yb3+ NPs as the core materials of the waveguide amplifiers. When the input signal power was 0.2 mW and the pump power was 200 mW, we achieved a relative gain of 0.6 dB at 1534 nm in a 10-mm long waveguide.

We demonstrate nonlinear optical modulation by combining mesoporous carbon nanospheres (MCNs) and D-shaped fibers (DFs). The MCNs are prepared by the silica-assisted strategy and the DFs are fabricated through a precision wheel polishing method. When the MCNs are deposited onto the DF as the saturable absorbers (SAs), the SAs possess broadband linear absorption and nonlinear saturable absorption properties. As the DF-MCNs SA is integrated into the laser cavities, ultrafast lasers at 1.56 and 2 μm were realized with minimal pulse duration down to a few hundreds of femtoseconds. Compared with the film and microfiber-based MCNs-SAs, the DF-MCNs SAs exhibit greater robustness and stronger evanescent field, and are more effective at generating femtosecond pulses. Our results verify that DF-MCNs as a kind of cost-effective and easily-prepared SA would be of great importance for stable and high-power femtosecond fiber lasers.

Fluoroindate glass fibers with an E r 3 + doping concentration of ∼ 0.5 m o l % were fabricated by using a rod-in-tube method. Pumped by a 976 nm laser diode, intense emission at ∼ 3.3 µ m was obtained from a 40 cm long E r 3 + -doped fiber, which could be attributed to the transition 4 S 3 / 2 → 4 F 9 / 2 of E r 3 + ions. The calculated emission cross section at ∼ 3.3 µ m was ∼ 3 × 10 − 26 m 2 , which was ∼ 1.5 times larger than that of transitions E r 3 + : 4 F 9 / 2 → 4 I 9 / 2 and D y 3 + : 6 H 13 / 2 → 6 H 15 / 2 . In addition, broad emissions ranging from 3.1 µm to 3.85 µm were obtained in the E r 3 + -doped fiber under a 976 nm/1973 nm dual-wavelength pumping scheme. Our results indicated that E r 3 + -doped fluoroindate glass fibers had the potential for constructing efficient ∼ 3.3 µ m fiber lasers.

Myostatin (MST) is a potent regulator of muscle growth and size. Spinal cord injury (SCI) results in marked atrophy of muscle below the level of injury. Currently, there is no effective pharmaceutical treatment available to prevent sublesional muscle atrophy post-SCI. To determine whether inhibition of MST with a soluble activin IIB receptor (RAP-031) prevents sublesional SCI-induced muscle atrophy, mice were randomly assigned to the following groups: Sham-SCI; SCI+Vehicle group (SCI-VEH); and SCI+RAP-031 (SCI-RAP-031). SCI was induced by complete transection at thoracic level 10. Animals were euthanized at 56 days post-surgery. RAP-031 reduced, but did not prevent, body weight loss post-SCI. RAP-031 increased total lean tissue mass compared to SCI-VEH (14.8%). RAP-031 increased forelimb muscle mass post-SCI by 38% and 19% for biceps and triceps, respectively (p

NaYF4:Yb3+,Tm3+/CdSe nanoheterostructures were synthesized by an improved two-step wet-chemical route. Upon the excitation from a 980-nm near-infrared (NIR) laser, an intense 797 nm NIR emission from Tm3+ ions was observed in the nanoheterostructures while neither ultraviolet (UV) nor blue emissions of Tm3+ ions appeared in the upconversion (UC) spectrum. It indicated that the energy transfer (ET) occurred between NaYF4:Yb3+,Tm3+ and CdSe. Under 980 nm irradiation, the excitation energy absorbed by Yb3+ ions transferred to Tm3+ ions successively, then transferred to CdSe partially from the 1G4 state of Tm3+ ions, and finally the excited CdSe returns the energy back to the 3F2,3 levels of Tm3+ ions. Both the excitation (980 nm) and the emission (797 nm) are located in the NIR spectral range (700–1100 nm) that is referred as the “optical window” of biological tissues. Therefore, the nanoheterostructures could have great potential in applications of biology and biomedicine.

Gain characteristics of polymer waveguide amplifiers based on NaYF4:Yb3+, Er3+ nanocrystals (NCs) at 0.54 μm wavelength were investigated through numerical simulations. NaYF4:18%Yb3+, 10%Er3+ NCs were doped into SU-8 2005 polymer matrix as the core of a polymer waveguide. The absorption spectrum and photoluminescence spectrum of the NCs were recorded and analyzed. The Judd-Ofelt parameters were achieved by means of Judd-Ofelt theory: Ω2 = 6.302×10−20 cm2, Ω4 = 0.69×10−20 cm2, Ω6 = 7.572×10−20 cm2. We simulated the gain characteristics of the waveguide amplifier at 0.54 μm wavelength by combining the atomic rate equations with power propagation equations. The gain curves had the saturation effects. A maximum gain ∼4.3 dB for the 5 cm waveguide with the Er3+ concentration of ∼7.5×1025 m−3 was obtained.

A facile float zone method to grow ZnO microrods with a hexagonal crystal structure is described. It was found that the crystal-growth mechanism was different from the well-known vapor–liquid–solid (VLS) growth mechanism. However, the one-dimensional growth morphologies occurring in the vapor phase are similar to those of ZnO grown using conventional VLS processes. The free-exciton, bound-exciton, acceptor-exciton, two-electron satellite emission, and their phonon replicas, obtained from the 15 K photoluminescence (PL) spectra of the ZnO microrods, were recorded. The PL spectra of the ZnO microrods at temperatures between 15 and 150 K show that the bound-exciton peak dissociates into a free-exciton peak and that the free-exciton emission and its phonon replicas dominate at temperatures above 120 K. Following the approach of Viswanath for measuring the intensity ratio of PL peaks, we found that the strongest bound-exciton peak at 3.3615 eV had a thermal activation energy of 15.9 meV, consistent with the value expected for the exciton-defect binding energy. This bound-exciton peak was not observed at temperatures above 120 K.

The most common materials used to generate near-infrared-driven photocatalysis occur by 980 nm laser excitation of composites that are a combination of a semiconductor and upconverting luminescence particles. The challenge remains to increase the light harvesting efficiency, and thus, it is necessary to extend the absorption spectra of photocatalysts. In this work, NaYF4:Yb,Er/CdSe composites were prepared by depositing CdSe nanocrystals onto the surface of NaYF4:Yb,Er microcrystals. UV and visible emission of light resulted from multiphoton upconverting processes in Er3+ under 1560 nm laser irradiation, which, in turn, activated the CdSe catalyst. The energy transfer between NaYF4:Yb,Er and CdSe was investigated by steady-state and dynamic fluorescence spectroscopy. The photocatalytic performance was investigated by the degradation of methylene blue in aqueous solution. These results show that Er coupled with semiconductor heterojunctions provides a photocatalyst that operates in the extended near-infrared range.

Manganese oxide nanosheets (MnO2 NSs) with two-dimensional formation and typically ultrathin thickness have gained a great deal of attention due to their excellent physical and chemical properties. However, the potential capability of MnO2 NSs in laser application has been rarely explored. Here, we first report the MnO2 NSs as the saturable absorber (SA) for generating Q-switched pulsed laser. The MnO2 NSs–based SA not only shows a broadband absorption, but also possesses nonlinear saturable absorption feature. By integrating the MnO2 NSs-SA into an erbium-doped fiber laser cavity, a stable passively Q-switched operation at central wavelength of ∼1558 nm was realized with a threshold pump power of 220 mW, and 1.26 μs pulse width with a repetition rate of 92.35 kHz was obtained. Our results indicate that the MnO2 NSs can serve as promising candidates for constructing optical pulsed lasers.

We demonstrate passively mode-locked erbium/thulium doped fiber lasers (TDFLs) operating at 1560/1950 nm by using a common gold nanorods (GNRs)/D-shaped fiber as saturable absorber (SA). The SA is prepared by the composite of GNRs with an average aspect ratio of 5.3 and D-shaped fiber, which has broadband absorption from 1000 nm to 3000 nm. By inserting the same SA into an erbium or thulium doped fiber laser cavity, stable passively mode-locked laser at 1560 or 1950 nm is achieved, respectively. A 1560 nm laser with a pulse width of 590 fs and a repetition frequency of 25.72 MHz is obtained for the erbium doped fiber laser (EDFL), and a 1950 nm laser with a pulse width of 373 fs and a repetition rate of 27.66 MHz is also obtained for the TDFL. Our results show that the GNRs/D-shaped fiber SA could be used for constructing broadband femtosecond fiber lasers.

In this Letter, we demonstrate 22.7 W mid-infrared (MIR) supercontinuum (SC) generation in all-solid fluorotellurite fibers. All-solid fluorotellurite fibers based on T e O 2 - B a F 2 - Y 2 O 3 and T e O 2 modified fluoroaluminate glasses are fabricated by using a rod-in-tube method. By using a 0.6 m long fluorotellurite fiber with a core diameter of 11 µm as the nonlinear medium and a high-power 1.93–2.5 µm SC fiber laser as the pump source, we obtain 22.7 W SC generation from 0.93 to 3.95 µm in the fiber for a pump power of 39.7 W. The 10 dB bandwidth is about 1633 nm, and the corresponding spectral range is from 1890 to 3523 nm. The optical-to-optical conversion efficiency is about 57.2%. Our results show that all-solid fluorotellurite fibers are promising nonlinear media for constructing high-power MIR SC light sources.

Polymer-based waveguide amplifiers were the key devices in short-distance optical communication systems. However, the low relative gain of these amplifiers hindered their practical applications. Here, we introduced a kind of waveguide amplifier devices affording higher relative gain, which were using a new nanocomposite as gain media. The nanocomposite was synthesized by copolymerization of the methyl methacrylate (MMA) monomers with the unsaturated organic ligand-modified core-shell rare earth nanoparticles (NPs). Due to the formation of chemical bonds between the NPs and the polymer matrix, the dispersion of NPs and the stability of the nanocomposite were both greatly improved. Therefore, using this nanocomposite as gain media, in a 15 mm long embedded rectangular waveguide, a really high relative gain of 27 dB at 1535 nm with the 980 nm laser pump was observed, which was nearly three times higher than that in our previous work. Owing to its good performance, the nanocomposite could play an important role in the future optical communication technology.

Temporal cavity soliton generation in fiber cavities or microresonators has achieved great breakthroughs and found significant applications in many fields. Despite recent advances in soliton frequency comb generation via external driving or pump light, it remains challenging to identify a versatile approach for driving the cavity coherently, tuning the mode spacing of soliton frequency combs largely, and achieving long-term operation. Here, instead of using external pump light to drive the cavity coherently, intra-cavity pumping is proposed to drive a Kerr-nonlinear optical cavity for generating temporal solitons and soliton frequency combs. By introducing the Brillouin gain into the cavity, the generated intra-cavity Brillouin lasers are used as the pump light to drive the cavity coherently for generating temporal solitons. In contrast to previous works, the soliton pulses form spontaneously via intra-cavity pumping without the need for fine-tuning the external pump light (to match the cavity resonance), which enables the generation of soliton frequency combs via cascaded four-wave mixing between multiple wavelength intra-cavity Brillouin lasers. Furthermore, by varying the frequency separation of multiple wavelength intra-cavity Brillouin lasers, the soliton pulses with a pulse width of hundreds of femtoseconds and a repetition rate of gigahertz (GHz) to terahertz (THz) are achieved via intra-cavity pumping, corresponding to the generation of soliton frequency combs with step tunable mode spacing from GHz to THz.

We demonstrated 10.4 W mid-infrared supercontinuum laser source, and ultrabroadband supercontinuum generation from 600 nm to 5.2 μm in newly-developed all-solid fluorotellurite fibers.

Tunable pulse broadening cancellation via doublet Brillouin gain lines in a silica fiber was theoretically investigated. Minimum broadening factor of 0.96 with time delay of 134.5 ps is achieved by optimizing doublet Brillouin lines for 200 ps Gaussian pulse with pulse distortion. Frequency separation between two gain lines and spectrum bandwidth of single gain line and peak gain values are optimized and considered in the present paper.

Unloading, neural lesions, and hormonal disorders after acute motor-complete spinal cord injury (SCI) cause one of the most severe forms of bone loss, a condition that has been refractory to available interventions tested to date. Thus, these features related to acute SCI provide a unique opportunity to study complex bone problems, potential efficacious interventions, and mechanisms of action that are associated with these dramatic pathological changes. This study was designed to explore the therapeutic potential of sclerostin antibody (Scl-Ab) in a rat model of bone loss after motor-complete SCI, and to investigate mechanisms underlying bone loss and Scl-Ab action. SCI rats were administered Scl-Ab (25 mg/kg/week) or vehicle beginning 7 days after injury then weekly for 7 weeks. SCI resulted in significant decreases in bone mineral density (-25%) and trabecular bone volume (-67%) at the distal femur; Scl-Ab completely prevented these deteriorations of bone in SCI rats, concurrent with markedly increased bone formation. Scanning electron microscopy revealed that SCI reduced numbers of osteocytes and dendrites concomitant with a morphology change from a spindle to round shape; Scl-Ab corrected these abnormalities in osteocytes. In ex vivo cultures of bone marrow cells, Scl-Ab inhibited osteoclastogenesis, and promoted osteoblastogenesis accompanied by increases in mRNA levels of LRP5, osteoprotegerin (OPG), and the OPG/RANKL ratio, and a decrease in DKK1 mRNA. Our findings provide the first evidence that robust bone loss after acute motor-complete SCI can be blocked by Scl-Ab, at least in part, through the preservation of osteocyte morphology and structure and related bone remodeling. Our findings support the inhibition of sclerostin as a promising approach to mitigate the striking bone loss that ensues after acute motor-complete SCI, and perhaps other conditions associated with disuse osteoporosis as a consequence of neurological disorders.

High-order upconversion luminescence (ultraviolet (UV), violet and blue emissions) of rare earth nanocrystals is quite desirable for photodynamic therapy and near-infrared photocatalysis applications. The hexagonal phase NaYF4:Yb3+,Tm3+/x mmol NaYF4 (x = 0, 0.1, 0.5, and 1) crystals were prepared by a hydrothermal method. With the amount of the shell precursor increasing, the crystals shape changed from hexagonal plate to hexagonal prism gradually, with the particles size increased. After coating a homogeneous inert NaYF4 shell, the high-order upconversion luminescence (1I6 and 1D2 radiative transitions) of all core–shell crystals were enhanced by several times compared with core-only crystals. Impressively, when the amount of the shell precursor was 0.1 mmol, the increased ratio of the emissions from 1I6 and 1D2 were 7.44 and 5.63 times, respectively. With further increasing the amount of the shell precursor, the increased ratio displayed a slight decline. The further photoluminescence decay results were consistent with the upconversion luminescence spectra. We demonstrated that the enhancement of high-order upconversion luminescence was attributed to the well-known surface passivation effect of the homogeneous shell.

Semiconductor polymer dots (Pdots) were encapsulated into a SiO2 matrix to form fluorescent nanocomposites using a modified Stober method. Significantly, the photostability and thermal stability of the nanocomposites were greatly improved as compared to those of pure Pdots. The luminescent nanocomposites combined with blue LEDs result in white-light emitting devices with a high color-rendering index.

The demands for multiplexed biological detection have driven the development of fluorescence encoding nanoprobes. We have synthesized water-soluble dual mode emission core–shell rare earth nanoprobes (∼30 nm) for fluorescence encoding. The nanoprobes were composed of ytterbium (Yb), erbium (Er) and/or thulium (Tm) ions co-doped heterogeneous NaYF4/NaLuF4 nanocrystals as cores and amorphous SiO2 embedded with europium (Eu) or terbium (Tb) complexes as shells. Excited by both infrared light and ultraviolet light, the nanoprobes exhibited dual characteristic emissions, which enable a novel spectral encoding strategy. The core nanocrystals exhibited tunable up-conversion emissions through various lanthanide ions doping. Combining these multiple upconversion emissions of core nanocrystals with downconversion emissions of shell containing rare earth complexes, a large amount of distinct fluorescence codes can be generated.

Flying particles with visible fluorescence were observed when a target, ZnF2:Tm3+/Yb3+, was irradiated by using a 953.6 nm pulsed infrared laser. Narrow blue beams showed the ejecting particles with upconversion emissions. The changing brightness along fluorescence traces exhibited the energy transfer from Yb3+ ions to Tm3+ ions and the depopulation of excited Tm3+ ions. Parameters of microexplosions induced by the pulsed laser were estimated by analyzing these flying particles. Compared with the target, these particles have strong infrared-to-ultraviolet upconversion ability. These results not only suggest a way to explore microexplosions induced by pulsed lasers but also provide a feasible scheme for developing ultraviolet upconversion materials.

Organic semiconducting materials have attracted significant attention for use in optoelectronic devices, as they can significantly improve device performance. Herein, a donor–acceptor conjugated polymer (poly(isoindigo-thiopheneylbenzothiadiazole, PID-TBT) was synthesized, which has strong and broad absorption in the visible region (400–800 nm). The band gap of PID-TBT is 1.65 eV. The PID-TBT honeycomb film with a porous structure was easily fabricated by the breath figure method. Compared with the smooth PID-TBT film, the honeycomb film shows significant enhancement in light capture capability and the efficiency of photoelectric conversion. The reflectance of the honeycomb film is reduced by 7% and the photocurrent is tenfold higher than that of the smooth film. Apart from designing new molecules by complex reactions, this work demonstrated that photoelectric conversion can be easily improved by introducing micro or nanostructures into devices.