The high-temperature pyrolysis process for preparing M–N–C single-atom catalyst usually results in high heterogeneity in product structure concurrently contains multiscale metal phases from single atoms(SAs),atomic ...The high-temperature pyrolysis process for preparing M–N–C single-atom catalyst usually results in high heterogeneity in product structure concurrently contains multiscale metal phases from single atoms(SAs),atomic clusters to nanoparticles.Therefore,understanding the interactions among these components,especially the synergistic effects between single atomic sites and cluster sites,is crucial for improving the oxygen reduction reaction(ORR)activity of M–N–C catalysts.Accordingly,herein,we constructed a model catalyst composed of both atomically dispersed FeN4 SA sites and adjacent Fe clusters through a site occupation strategy.We found that the Fe clusters can optimize the adsorption strength of oxygen reduction intermediates on FeN4 SA sites by introducing electron-withdrawing–OH ligands and decreasing the d-band center of the Fe center.The as-developed catalyst exhibits encouraging ORR activity with halfwave potentials(E1/2)of 0.831 and 0.905 V in acidic and alkaline media,respectively.Moreover,the catalyst also represents excellent durability exceeding that of Fe–N–C SA catalyst.The practical application of Fe(Cd)–CNx catalyst is further validated by its superior activity and stability in a metalair battery device.Our work exhibits the great potential of synergistic effects between multiphase metal species for improvements of singleatom site catalysts.展开更多
Atomically monolayer 2D material was predicted thermal dynamically unstable,until the ground-breakthrough reports of the isolation of graphene in 2004,which was shortly recognized by the Nobel Prize in 2010.Monoelemen...Atomically monolayer 2D material was predicted thermal dynamically unstable,until the ground-breakthrough reports of the isolation of graphene in 2004,which was shortly recognized by the Nobel Prize in 2010.Monoelemental graphene inherits the merits of simple stoichiometry and crystal structure,which offers the possibilities for basic physics scenarios demonstrations and a great deal of functional devices explorations.展开更多
Black phosphorus(BP), a typical mono-elemental and two-dimensional(2D) material, has gathered significant attention owing to its distinct optoelectronic properties and promising applications, despite its main obstacle...Black phosphorus(BP), a typical mono-elemental and two-dimensional(2D) material, has gathered significant attention owing to its distinct optoelectronic properties and promising applications, despite its main obstacle of long-term stability. Consequently, BP-analog materials with long-term chemical stability show additional potential. In this contribution, tin sulfide(SnS), a novel two-elemental and 2D structural BP-analog monochalcogenide, has been demonstrated to show enhanced stability under ambient conditions. The broadband nonlinear optical properties and carrier dynamics have been systematically investigated via Z-scan and transient absorption approaches. The excellent nonlinear absorption coefficient of 50.5 × 10^-3 cm∕GW, 1 order of magnitude larger than that of BP, endows the promising application of SnS in ultrafast laser generation. Two different decay times of τ1~873 fs and τ2~96.9 ps allow the alteration between pure Q switching and continuous-wave(CW) mode locking in an identical laser resonator. Both mode-locked and Q-switched operations have been experimentally demonstrated using an SnS saturable absorber at the telecommunication window. Femtosecond laser pulses with tunable wavelength and high stability are easily obtained, suggesting the promising potential of SnS as an efficient optical modulator for ultrafast photonics. This primary investigation may be considered an important step towards stable and high-performance BP-analog material-based photonic devices.展开更多
In recent years,multi-wavelength fiber lasers play a significant role in plenty of fields,ranging from optical communications to mechanical processing and laser biomedicine,owing to their high beam quality,low cost,an...In recent years,multi-wavelength fiber lasers play a significant role in plenty of fields,ranging from optical communications to mechanical processing and laser biomedicine,owing to their high beam quality,low cost,and excellent heat dissipation properties.Benefitting from increasing maturity of optical elements,the multi-wavelength fiber laser has made rapid developments.In this review,we summarize and analyze diverse implementation methods covering continuous wave and pulsed fiber lasers at room temperature conditions:inserting an optical filter device and intensity-dependent loss structure in the resonant cavity,and applying ultrafast nonlinear optical response of materials and a dual-cavity structure.Finally,future challenges and perspectives of the multi-wavelength fiber laser are discussed and addressed.展开更多
Owing to its thickness-modulated direct energy band gap, relatively strong light–matter interaction, and unique nonlinear optical response at a long wavelength, few-layer black phosphorus, or phosphorene, becomes ver...Owing to its thickness-modulated direct energy band gap, relatively strong light–matter interaction, and unique nonlinear optical response at a long wavelength, few-layer black phosphorus, or phosphorene, becomes very attractive in ultrafast photonics applications. Herein, we synthesized a graphene/phosphorene nano-heterojunction using a liquid phase-stripping method. Tiny lattice distortions in graphene and phosphorene suggest the formation of a nano-heterojunction between graphene and phosphorene nanosheets. In addition, we systematically investigate their nonlinear optical responses at different wavelength regimes. Our experiments indicate that the combined advantages of ultrafast relaxation, broadband response in graphene, and the strong light–matter interaction in phosphorene can be combined together by nano-heterojunction. We have further fabricated two-dimensional(2D) nano-heterojunction based optical saturable absorbers and integrated them into an erbium-doped fiber laser to demonstrate the generation of a stable ultrashort pulse down to 148 fs. Our results indicate that a graphene/phosphorene nano-heterojunction can operate as a promising saturable absorber for ultrafast laser systems with ultrahigh pulse energy and ultranarrow pulse duration. We believe this work opens up a new approach to designing 2D heterointerfaces for applications in ultrafast photonics and other research.The fabrication of a 2D nano-heterojunction assembled from stacking different 2D materials, via this facile and scalable growth approach, paves the way for the formation and tuning of new 2D materials with desirable photonic properties and applications.展开更多
基金supported by the National Natural Science Foundation of China(22109100,22075203)Guangdong Basic and Applied Basic Research Foundation(2022A1515011677)+1 种基金Shenzhen Science and Technology Project Program(JCYJ2021032409420401)Natural Science Foundation of SZU(000002111605).
文摘The high-temperature pyrolysis process for preparing M–N–C single-atom catalyst usually results in high heterogeneity in product structure concurrently contains multiscale metal phases from single atoms(SAs),atomic clusters to nanoparticles.Therefore,understanding the interactions among these components,especially the synergistic effects between single atomic sites and cluster sites,is crucial for improving the oxygen reduction reaction(ORR)activity of M–N–C catalysts.Accordingly,herein,we constructed a model catalyst composed of both atomically dispersed FeN4 SA sites and adjacent Fe clusters through a site occupation strategy.We found that the Fe clusters can optimize the adsorption strength of oxygen reduction intermediates on FeN4 SA sites by introducing electron-withdrawing–OH ligands and decreasing the d-band center of the Fe center.The as-developed catalyst exhibits encouraging ORR activity with halfwave potentials(E1/2)of 0.831 and 0.905 V in acidic and alkaline media,respectively.Moreover,the catalyst also represents excellent durability exceeding that of Fe–N–C SA catalyst.The practical application of Fe(Cd)–CNx catalyst is further validated by its superior activity and stability in a metalair battery device.Our work exhibits the great potential of synergistic effects between multiphase metal species for improvements of singleatom site catalysts.
文摘Atomically monolayer 2D material was predicted thermal dynamically unstable,until the ground-breakthrough reports of the isolation of graphene in 2004,which was shortly recognized by the Nobel Prize in 2010.Monoelemental graphene inherits the merits of simple stoichiometry and crystal structure,which offers the possibilities for basic physics scenarios demonstrations and a great deal of functional devices explorations.
基金National Natural Science Foundation of China(NSFC)(61435010,61575089)Science and Technology Innovation Commission of Shenzhen(KQTD2015032416270385)+3 种基金China Postdoctoral Science Foundation(2017M612712,2017M612730)Science and Technology Development Fund(STDF)(007/2017/A1)Macao SARChina and the Postgraduate Innovation Development Fund Project of Shenzhen University(PIDFPZR2018004)
文摘Black phosphorus(BP), a typical mono-elemental and two-dimensional(2D) material, has gathered significant attention owing to its distinct optoelectronic properties and promising applications, despite its main obstacle of long-term stability. Consequently, BP-analog materials with long-term chemical stability show additional potential. In this contribution, tin sulfide(SnS), a novel two-elemental and 2D structural BP-analog monochalcogenide, has been demonstrated to show enhanced stability under ambient conditions. The broadband nonlinear optical properties and carrier dynamics have been systematically investigated via Z-scan and transient absorption approaches. The excellent nonlinear absorption coefficient of 50.5 × 10^-3 cm∕GW, 1 order of magnitude larger than that of BP, endows the promising application of SnS in ultrafast laser generation. Two different decay times of τ1~873 fs and τ2~96.9 ps allow the alteration between pure Q switching and continuous-wave(CW) mode locking in an identical laser resonator. Both mode-locked and Q-switched operations have been experimentally demonstrated using an SnS saturable absorber at the telecommunication window. Femtosecond laser pulses with tunable wavelength and high stability are easily obtained, suggesting the promising potential of SnS as an efficient optical modulator for ultrafast photonics. This primary investigation may be considered an important step towards stable and high-performance BP-analog material-based photonic devices.
基金partially supported by the Science and Technology Development Fund,Macao Special Administration Region(SAR)(Nos.007/2017/A1 and 132/2017/A3)National Natural Science Foundation of China(NSFC)(Nos.61875138,61435010,61775142,and 6181101252)+1 种基金Science and Technology Innovation Commission of Shenzhen(Nos.KQTD2015032416270385,JCYJ20150625103619275,and JCYJ20170811093453105)Shenzhen Basic Research Project on Subject Layout(No.JCYJ20170412105812811)。
文摘In recent years,multi-wavelength fiber lasers play a significant role in plenty of fields,ranging from optical communications to mechanical processing and laser biomedicine,owing to their high beam quality,low cost,and excellent heat dissipation properties.Benefitting from increasing maturity of optical elements,the multi-wavelength fiber laser has made rapid developments.In this review,we summarize and analyze diverse implementation methods covering continuous wave and pulsed fiber lasers at room temperature conditions:inserting an optical filter device and intensity-dependent loss structure in the resonant cavity,and applying ultrafast nonlinear optical response of materials and a dual-cavity structure.Finally,future challenges and perspectives of the multi-wavelength fiber laser are discussed and addressed.
基金National Natural Science Foundation of China(NSFC)(61435010,61575089)Shenzhen-Hong Kong Innovation Cooperation Project(SGLH20150205162842428)+3 种基金Science and Technology Innovation Commission of Shenzhen JCYJ20150625103619275,JCYJ20170302153540973,JCYJ20170412111625378,KQTD2015032416270385)Science and Technology Planning Project of Guangdong Province(2016B050501005)Educational Commission ofGuangdong Province 2016KCXTD006)Student Innovation Development Fund of Shenzhen University(PIDFPZR2017002)
文摘Owing to its thickness-modulated direct energy band gap, relatively strong light–matter interaction, and unique nonlinear optical response at a long wavelength, few-layer black phosphorus, or phosphorene, becomes very attractive in ultrafast photonics applications. Herein, we synthesized a graphene/phosphorene nano-heterojunction using a liquid phase-stripping method. Tiny lattice distortions in graphene and phosphorene suggest the formation of a nano-heterojunction between graphene and phosphorene nanosheets. In addition, we systematically investigate their nonlinear optical responses at different wavelength regimes. Our experiments indicate that the combined advantages of ultrafast relaxation, broadband response in graphene, and the strong light–matter interaction in phosphorene can be combined together by nano-heterojunction. We have further fabricated two-dimensional(2D) nano-heterojunction based optical saturable absorbers and integrated them into an erbium-doped fiber laser to demonstrate the generation of a stable ultrashort pulse down to 148 fs. Our results indicate that a graphene/phosphorene nano-heterojunction can operate as a promising saturable absorber for ultrafast laser systems with ultrahigh pulse energy and ultranarrow pulse duration. We believe this work opens up a new approach to designing 2D heterointerfaces for applications in ultrafast photonics and other research.The fabrication of a 2D nano-heterojunction assembled from stacking different 2D materials, via this facile and scalable growth approach, paves the way for the formation and tuning of new 2D materials with desirable photonic properties and applications.
