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Comprehensive Summary: The development of efficient and sustainable methods to obtain spirocyclic compounds is of significance as these structures are widely found in pharmaceuticals and agrochemicals. Herein, we disclose an electrochemical dearomative spirocyclization of N‐acyl sulfonamides in a continuous‐flow cell. The reaction is simple and efficient without external catalysts or supporting electrolytes and could be applied in a decagram‐scale synthesis. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The development of efficient and sustainable methods to obtain spirocyclic compounds is of significance as these structures are widely found in pharmaceuticals and agrochemicals. Herein, we disclose an electrochemical dearomative spirocyclization of N‐acyl sulfonamides in a continuous‐flow cell. The reaction is simple and efficient without external catalysts or supporting electrolytes and could be applied in a decagram‐scale synthesis. [ABSTRACT FROM AUTHOR]

An environmentally friendly and efficient electrochemical chlorination of thiophenes has been developed. The monochlorination, dichlorination and trichlorination of thiophenes are selectively achieved. Notably, the reaction has the merits of mild conditions, excellent functional group tolerance, high yields and selectivity, and the capacity for scale‐up, thus providing a synthetically useful alternative to access mono‐ and polychlorinated thiophenes. [ABSTRACT FROM AUTHOR]

Electrochemical dearomative spirocyclization serves as a green and sustainable approach to convert the flat, two‐dimension aromatic feedstock into the value‐added three‐dimension spirocyclic architectures. This review highlights the recent advances, emphasizes mechanistic discussions, and showcases synthetic applications of this emerging versatile and powerful transformation. [ABSTRACT FROM AUTHOR]

Two-dimensional layered metal chalcogenides (LMCs) are widely used in battery anode materials, energy conversion, and semiconductor devices, because of their high energy storage characteristics, high thermoelectric characteristics, and large electron mobility. SnSe2 as a kind of LMC has strong nonlinear optical characteristics. However, its research on dissipative system dynamics as a saturable absorber has not been studied. In this work, we obtained SnSe2 nanosheets using lithium ion intercalation and we reported a passively mode-locked fiber laser with SnSe2 as a saturable absorber to achieve the dissipative soliton in a dissipative system. Due to the high third-order nonlinearity of SnSe2, the evolution of square wave pulses from 2 to 16 ns was obtained in a fiber ring cavity. Through adjusting the polarization state, the evolution phenomenon of soliton rain, the soliton rain phenomenon with a spectrum of dual-wavelengths, and a bound state harmonic phenomenon with a frequency of 313 MHz were obtained. Therefore, the strong nonlinear fiber laser based on SnSe2 provides a good platform for study the pulsation, explosion, rainfall and other phenomena. [ABSTRACT FROM AUTHOR]

As a member of the 2D transition metal chalcogenides (TMCs), 2D Ag2S with large absorption coefficient, broadband optical response, extraordinary metal‐like ductility, high plastic deformation strain, unique layered structure, and very low solubility has offered a platform for achieving tremendous success in various fields. Great achievements have been made in exploring the linear optical, mechanical, and photoelectric properties of 2D Ag2S nanosheets. However, the nonlinear optical properties of 2D Ag2S nanosheets and their applications in ultrafast photonics have not been studied. The saturable absorption property of 2D Ag2S nanosheets is experimentally illustrated at the telecommunication band with a large optical modulation depth of 15.5% and a low saturable intensity of 250.4 MW cm−2. Moreover, the 229th harmonic soliton molecule with repetition rate of 1.1 GHz based on 2D Ag2S saturable absorber is realized at the telecommunication band for the first time to the authors' knowledge. Thankfully, 2D Ag2S nanosheets display excellent nonlinear optical properties suggesting that this may open a new door for advanced photonic devices based on 2D Ag2S nanosheets. [ABSTRACT FROM AUTHOR]

Stannic sulfide (SnS2), a latterly developed two-dimensional (2D) material, has fascinated scientists because it can be widely applied to materials chemistry, biomedicine, photocatalysis, and so on. Especially, SnS2 has the advantages of adjustable band gap and good oxidation resistance, which indicates that this material has promising potential in nonlinear optics. However, the light interaction with SnS2 is rarely investigated. In this study, high-quality SnS2 nanosheets (Ns) developed through a liquid phase exfoliation approach have been applied in ultrafast photonics for nonlinear processes. This fabrication approach can greatly increase the damage threshold of the SnS2 saturable absorber (SA). Furthermore, the SnS2 SA device is applied to an erbium-doped fiber laser (EDFL) to obtain soliton molecules with different orders. Ultimately, eleventh-order soliton molecules, the highest order of soliton molecules through SnS2, are generated with a soliton separation of 8 ps and a spectral modulation period of around 1 nm. The above experimental results indicate that SnS2 has broad application prospects in the fields of mode-locked fiber laser and optical fiber communication. [ABSTRACT FROM AUTHOR]

Laser-sustained plasma (LSP) featured by high radiance in the ultraviolet (UV) spectral range is found to be powerful in high resolution inspection and spectroscopy applications. In this paper, we demonstrate significant enhancement of UV radiance in LSP excited by a high power focused annular laser beam of small F-number. A two-dimensional refractive index distribution in the plasma region is established to obtain the propagation path of the annular beam. Subsequently, the spatial distribution of the annular beam power density is calculated to establish the quantitative relationship between laser power and plasma dimension. Theoretical analysis of a "reservoir" effect constructed by the annular beam is carried out. Abrupt plasma dimension change is observed when the laser power exceeds the "reservoir" boundary. The new model is then validated by experiments. LSP with the highest reported UV radiance to our knowledge has been achieved. This work paves what we believe is a novel way of generating high radiance UV sources by spatial manipulation of excitation laser beam.

Higher brightness UV light sources based on laser-sustained plasma (LSP) finds critical applications in high-resolution optical inspection and measurement. An annular beam focused with a low F-number is proposed for the first time to investigate its effect in realizing high-brightness LSP compared with Gaussian beams. We experimentally verified that the annular laser beam sustained a nearly laterally symmetric plasma with a longitudinal length less than 600 µm plasma length, where the length-width ratio was four times smaller than that driven by a TEM 00 Gaussian beam. Theoretical analysis further explored that the annular beam's transmission path could limit the plasma's longitudinal growth, like a "reservoir". Furthermore, the "reservoir" effect is favorable for effectively increasing the plasma temperature and the effective power ratio of UV from 8% to 15%. This work paves a novel way of generating high-brightness UV sources by spatial manipulation of infrared pumping beam.