Electrokinetic-mechanism of water and furfural oxidation on pulsed laser-interlaced Cu_(2)O and CoO on nickel foam

The electrocatalytic oxidation of biomass-derived furfural(FF)feedstocks into 2-furoic acid(FA)holds immense industrial potential in optics,cosmetics,polymers,and food.Herein,we fabricated Co O/Ni O/nickel foam(NF)and Cu_(2)O/Ni O/NF electrodes via in situ pulsed laser irradiation in liquids(PLIL)for the bifunctional electrocatalysis of oxygen evolution reaction(OER)and furfural oxidation reaction(FOR),respectively.Simultaneous oxidation of NF surface to NiO and deposition of CoO and/or Cu_(2)O on NF during PLIL offer distinct advantages for enhancing both the OER and FOR.CoO/NiO/NF electrocatalyst provides a consistently low overpotential of~359 m V(OER)at 10 m A/cm^(2),achieving the maximum FA yield(~16.37 m M)with 61.5%selectivity,79.5%carbon balance,and a remarkable Faradaic efficiency of~90.1%during 2 h of FOR at 1.43 V(vs.reversible hydrogen electrode).Mechanistic pathway via in situ electrochemical-Raman spectroscopy on CoO/NiO/NF reveals the involvement of phase transition intermediates(NiOOH and CoOOH)as surface-active centers during electrochemical oxidation.The carbonyl carbon in FF is attacked by hydroxyl groups to form unstable hydrates that subsequently undergo further oxidation to yield FA products.This method holds promise for large-scale applications,enabling simultaneous production of renewable building materials and fuel.

Liquid vortexes and flows induced by femtosecond laser ablation in liquid governing formation of circular and crisscross LIPSS

Orientations of laser induced periodic surface structures(LIPSS)are usually considered to be governed by the laser polarization state.In this work,we unveil that fluid dynamics induced by femtosecond(fs)laser ablation in liquid(fs-LAL)can easily break this polarization restriction to produce irregular circular-LIPSS(CLIPPS)and crisscross-LIPSS(CCLIPSS).Fs laser ablation of silicon in water shows formation of diverse LIPSS depending on ablation conditions.At a high power of 700 mW(repetition rate of 100 kHz,pulse duration of 457 fs and wavelength of 1045 nm),single/twin CLIPSS are produced at the bottom of macropores of several microns in diameter due to the formation of strong liquid vortexes and occurrence of the vortex shedding effect.Theoretical simulations validate our speculation about the formation of liquid vortex with an ultrahigh static pressure,which can induce the microstructure trenches and cracks at the sidewalls for fs-LAL of Si and tungsten(W)in water,respectively.At a low power of 50 mW,weak liquid vortexes are produced,which only give birth to curved LIPSS in the valleys of grooves.Consequently,it is deduced that liquid vortex plays a crucial role in the formation of macropores.Mountain-like microstructures induce complex fluid dynamics which can cause the formation of CCLIPSS on them.It is believed that liquid vortexes and fluid dynamics presented in this work open up new possibilities to diversify the morphologies of LIPSS formed by fs-LAL.

Pulsed laser ablation in liquid of sp-carbon chains:Status and recent advances

This review provides a discussion of the current state of research on sp-carbon chains synthesized by pulsed laser ablation in liquid.In recent years,pulsed laser ablation in liquid(PLAL)has been widely employed for polyynes synthesis thanks to its flexibility with varying laser parameters,solvents,and targets.This allows the control of sp-carbon chains properties as yield,length,termination and stability.Although many reviews related to PLAL have been published,a comprehensive work reporting the current status and advances related to the synthesis of sp-carbon chains by PLAL is still missing.Here we first review the principle of PLAL and the mechanisms of formation of sp-carbon chains.Then we discuss the role of laser fluence(i.e.energy density),solvent,and target for sp-carbon chains synthesis.Lastly,we report the progress related to the prolonged stability of sp-carbon chains by PLAL encapsulated in polymeric matrices.This review will be a helpful guide for researchers interested in synthesizing sp-carbon chains by PLAL.

Studies on the Technology and Mechanism of Laser Photoinduced Alignment of Liquid Crystal

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Microstructure evolution and liquid phase separation in Ta-O hypermonotectic melts during laser-cladding

A three-layer Ta_2O_5-containing coating was successfully fabricated by laser cladding on a pure Ta substrate. The maximum thickness of such a coating is about 1.6 mm. The microstructure, phase constitution and elemental distribution in the coating were investigated. Results show that the coating has been metallurgically bonded to the Ta substrate and the microstructure exhibits a graded change along the deposition direction from Ta substrate to the top of coating. In the layers I and II of the graded coating, the microstructure evolution can be confi rmed as a result of hypomonotectic reaction, but in the layer Ⅲ it was formed by hypermonotectic reaction. At the top of coating, the microstructure was still homogeneous although liquid phase separation had occurred, which can be attributed to the fact that the O-rich droplets do not have enough time to fl oat at high cooling rate. The theoretical calculation results show that during laser cladding, the solidifi cation time of the melt pool was less than 0.1 s, which fi ts well with the results from the experiment.

Laser fragmentation in liquid synthesis of novel palladium-sulfur compound nanoparticles as efficient electrocatalysts for hydrogen evolution reaction

One promising way to tune the physicochemical properties of materials and optimize their performance in various potential applications is to engineer material structures at the atomic level.As is well known,the performance of Pd-based catalysts has long been constrained by surface contamination and their single structure.Here,we employed an unadulterated top-down synthesis method,known as laser fragmentation in liquid(LFL),to modify pristine Pd PS crystals and obtained a kind of metastable palladium-sulfur compound nanoparticles(LFL-Pd S NPs)as a highly efficient electrocatalyst for hydrogen evolution reaction(HER).Laser fragmentation of the layered Pd PS crystal led to a structural reorganization at the atomic level and resulted in the formation of uniform metastable LFL-Pd S NPs.Noteworthy,the LFL-Pd S NPs show excellent electrocatalytic HER performance and stability in acidic media,with an overpotential of-66 m V at 10 m A·cm^(-2),the Tafel slope of 42 m V·dec^(-1).The combined catalytic performances of our LFL-Pd S NPs are comparable to the Pt/C catalyst for HER.This work provides a top-down synthesis strategy as a promising approach to design highly active metastable metal composite electrocatalysts for sustainable energy applications.

Onion-structured transition metal dichalcogenide nanoparticles by laser fabrication in liquids and atmospheres

Since the discovery of transition metal dichalcogenide(TMDC)nanoparticles(NPs)with the onion-like structure,many efforts have been made to develop their fabrication methods.Laser fabrication(LF)is one of the most promising methods to prepare onion-structured TMDC(or OS-TMDC)NPs due to its green,flexible,and scalable syntheses.In this mini-review article,we systematically introduce various laser-induced OS-TMDC(especially the OS-MoS_(2))NPs,their formation mechanism,properties,and applications.The preparation routes mainly include laser ablation in liquids and atmospheres,and laser irradiation in liquids.The various formation mechanisms are then introduced based on the different preparation routes,to describe the formations of the corresponding OS-NPs.Finally,some interesting properties and novel applications of these NPs are briefly demonstrated,and a short outlook is also given.This review could help to understand the progress of the laser-induced OS-TMDC NPs and their applications.

Up/down-conversion luminescence of monoclinic Gd_(2)O_(3):Er^(3+)nanoparticles prepared by laser ablation in liquid

Multifunctional luminescent materials are attracting attention nowadays.In this work,monoclinic Gd_(2)O_(3):Er^(3+)nanoparticles,which possess up-conversion luminescence and down-conversion luminescence properties,were successfully synthesized by laser ablation in liquid(LAL)technique.Up-conversion luminescence and down-conversion luminescence of monoclinic Gd_(2)O_(3):Er^(3+)nanoparticles were got under the excitation of 980 nm and 379 nm,respectively.In addition,tunable luminescence was got.Furthermore,the cytotoxicity of the nanoparticles is low and the fluorescence of the nanoparticles in cell is also strong enough.The results indicate that the Gd_(2)O_(3):Er^(3+)nanoparticles synthesized by LAL technique are promising candidates for bio-imaging or other fields that require controllable fluorescence.

Structural deformation of nitro group of nitromethane molecule in liquid phase in an intense femtosecond laser field

The structural deformation of NO2 group induced by an intense femtosecond laser field of liquid nitromethane（NM）molecule is detected by time-and frequency-resolved coherent anti-Stokes Raman spectroscopy（CARS） technique with the intense pump laser. Here, we present the mechanism of molecular alignment and deformation. The CARS spectra and its FFT spectra of liquid NM show that the NO2 torsional mode couples with the CN symmetric stretching mode and that the NO2 group undergoes ultrafast structural deformation with a relaxation time of 195 fs. The frequency of the NO2 torsional mode in liquid NM（50.8±0.3 cm^-1） at room temperature is found. Our results prove the structural deformation of two groups in liquid NM molecule occur simultaneously in the intense laser field.

Different Approaches of Employing Cholesteric Liquid Crystals in Dye Lasers

Two ways of employing cholesteric liquid crystals in tunable dye lasers are considered: the cholesterics as distributed feedback medium and the cholesterics as resonator mirrors. In the dye doped distributed feedback cholesteric liquid crystal lasers the frequency tuning is achieved exploiting light induced effects or using a specially designed cell assembling a chiral dopant concentration gradient in combination with suitable distribution of different dyes. Another approach represents the lasing in a multilayer system consisting of a dye doped isotropic solvent sandwiched between two CLC layers.

Characteristics of droplets ejected from liquid glycerol doped with carbon in laser ablation propulsion

The characteristics of droplets ejected from liquid glycerol doped with carbon are investigated in laser ablation propul- sion. Results show that carbon content has an effect on both the coupling coefficient and the specific impulse. The doped- carbon moves the laser focal position from the glycerol interior to the surface. This results in a less consumed glycerol and a high specific impulse. An optimal propulsion can be realized by varying carbon content in glycerol.

A Hydrogel's Formation Device for Quick Analysis of Liquid Samples Using Laser-Induced Breakdown Spectroscopy

The laser-induced breakdown spectroscopy technique has irreplaceable advantages in the field of detection due to its multi-phase specimen detection ability.The development of the LIBS technique for liquid analysis is obstructed by its inherent drawbacks like the surface ripples and extinction of emitted intensity,which make it unpractical.In this work,an in-situ hydrogel formation sampling device was designed and used the hydrogel as the detection phase of LIBS for Cu,Cr and Al in an aqueous solution.With the measured amount of resin placed in the device,the formed hydrogel could be obtained within 20 s after putting the device into water solution.The formed hydrogel could be directly analyzed by LIBS and reflect the elemental information of the water sample.The prominent performance made this hydrogel＇s formation device especially suitable for quick in-situ environmental liquid analysis using LIBS.

激光轰击金属液面溅射过程的数值模拟

目前,极紫外光被认为是制备特征尺寸小于7 nm芯片所必备的光源,激光轰击液态金属锡靶是其产生的主要方式之一.采用体积分数(volurne of fluid,VOF)方法建立了激光轰击金属锡液面产生溅射的模型,并对液料溅射和雾化的演化过程进行了数值模拟,研究了冠状水花的产生机制以及雾化时的流场变化.在此基础上,进一步研究了金属液态锡在不同的能量、光斑直径和脉宽的激光轰击下溅射产生的冠的宽度和高度随时间演化情况.研究表明:在激光辐照产生的高压等离子体的高速冲击下,液膜经历快速运动、冠状射流和雾化3个阶段,液膜生长主要原因是惯性力作用;液膜上下两端存在较大的速度梯度是射流形状发生变化的主要原因;冠边缘处雾化现象的产生是由Rayleigh-Taylor和Plateau-Rayleigh不稳定性共同作用的结果.在激光轰击下,冠的高度和宽度随激光能量增加而增大,但随着时间推移,冠宽和冠高的增长速率逐渐减小;激光光斑和脉宽对冠宽及冠高的影响较为复杂,在前期影响较小,在后期冠宽及冠高随它们数值增加而减小.

基于液晶偏振光栅的大口径激光光束扫描系统

非机械式激光光束扫描系统具有体积小、重量轻、易集成等优势,在激光雷达、激光武器和激光通信等领域具有较大的应用前景,其通光口径决定着设备的工作距离、扫描精度和目标摧毁能力。基于液晶偏振光栅设计了一种全电控制的大口径激光光束扫描系统。采用液晶偏振光栅和液晶空间光调制器的协同工作方式,实现光束的大角度连续扫描;设计了光束扫描系统,并重点分析了级联液晶偏振光栅组的控制策略,给出了具体控制方法。最后,进行了激光光束的初步扫描实验,实现了70 mm口径光束在−16.575°~16.575°的偏转。该研究结果为激光光束的非机械式扫描控制提供了技术支撑,并在大口径激光扫描系统应用方面进行了初步探索。

液体辅助激光加工织构及表面摩擦特性研究

为了缓解切削加工钛合金等难加工材料过程中存在的刀具磨损等问题,采用激光器分别在空气介质和液体辅助条件下在YG6硬质合金刀具表面加工直线沟槽织构,在UMT直线往复摩擦磨损试验机上测试了不同工艺加工所得织构刀具的摩擦及磨损性能,通过体视显微镜对磨损形貌进行表征分析,采用计算流体力学方法对试验进行模拟仿真,并结合流体动力学分析,探究织构刀具在润滑条件下的减摩机制。结果表明:激光加工工艺显著影响硬质合金刀具表面在切削液润滑条件下的摩擦磨损行为,液体辅助激光加工所得织构表面表现出较好的抗摩擦磨损性能,摩擦因数相对于无织构刀具表面降低了78.2%,主要是由于在摩擦过程中刀具-工件接触区的油膜产生了较好的楔形效应,改善了摩擦过程中的润滑状态,提高了摩擦学性能。

Sustainable Furfural Biomass Feedstocks Electrooxidation toward Value-Added Furoic Acid with Energy-Saving H_(2) Fuel Production Using Pt-Decorated Co_(3)O_(4) Nanospheres

Here,furfural oxidation was performed to replace the kinetically sluggish O_(2)evolution reaction(OER).Pt-Co_(3)O_(4)nanospheres were developed via pulsed laser ablation in liquid(PLAL)in a single step for the paired electrocatalysis of an H_(2)evolution reaction(HER)and furfural oxidation reaction(FOR).The FOR afforded a high furfural conversion(44.2%)with a major product of 2-furoic acid after a 2-h electrolysis at 1.55 V versus reversible hydrogen electrode in a 1.0-M KOH/50-mM furfural electrolyte.The Pt-Co_(3)O_(4)electrode exhibited a small overpotential of 290 mV at 10 mA cm^(-2).As an anode and cathode in an electrolyzer system,the Pt-Co_(3)O_(4)electrocatalyst required only a small applied cell voltage of~1.83 V to deliver 10 mA cm^(-2),compared with that of the pure water electrolyzer(OER||HER,~1.99 V).This study simultaneously realized the integrated production of energy-saving H_(2)fuel at the cathode and 2-furoic acid at the anode.

飞秒激光激发水线产生太赫兹辐射的研究

为了进一步探究飞秒激光激发水线产生太赫兹辐射的影响因素,通过实验研究了激光功率、激光焦点在水线中的位置及水线温度等因素对太赫兹辐射功率的影响。实验结果表明:随着激光功率的升高,太赫兹辐射功率也相应增加,但转换效率却在降低;相较于水线中心,水线边缘的太赫兹波辐射功率更高;同时,随着水线温度的升高,水线中心的太赫兹波辐射功率也随之升高。此外,通过建立水线与邻近空气域的二维平面模型,并对太赫兹电场强度的分布情况进行计算,发现随着太赫兹波频率的增大,辐射至空气中的太赫兹波电场强度也相应增强。

非机械指向空间激光通信接收系统设计与分析

采用非机械指向结构能够极大缩小空间激光通信系统尺寸与重量,由于现有器件性能局限,目前尚未见到成熟的非机械指向空间激光通信接收系统。提出基于正交液晶级联偏振光栅与四象限探测器的空间激光通信接收光学系统,利用了正交液晶级联偏振光栅体积小、口径大、偏转范围大,及四象限探测器接收角度范围大的优势,根据正交液晶级联偏振光栅与四象限探测器的理论与器件性能,设计了光学系统,分析了探测器噪声、背景噪声、系统噪声对于通信与入射角度测量的影响,计算了可实现的通信速率,给出了系统的最大响应角速度。

基于高局域化FBG的液相扩散过程监测方法研究

提出了一种利用高局域化光纤布拉格光栅测量液相扩散过程的方法。采用飞秒激光和相位掩模法在载氢的普通单模光纤中成功制备了一种高局域化光纤布拉格光栅,其折射率变化区域在光束入射方向上高度局域在纤芯中,从而在透射光谱中除了具有纤芯模式对应的损耗峰之外,还具有丰富的包层模式对应的损耗峰,纤芯模式和包层模式对应的损耗峰分别达-17.6 dB和-17.2 dB。实验测得光栅截止模式对液体折射率很敏感,截止模式对应的损耗峰中心波长随液体折射率呈线性变化,折射率灵敏度为531.69 nm/RIU,而纤芯模式几乎不随液体折射率发生改变,可用于折射率测量过程中的温度补偿。将高局域化光纤布拉格光栅布设在两种液体的分界面处时,随着液相扩散过程的进行,光纤周围液体的折射率发生变化,通过监测高局域化光纤布拉格光栅透射光谱中截止模式中心波长的变化,实现了对液相扩散过程的原位实时监测。

基于LC-OPA的空间激光通信技术进展

液晶相控阵既可以在空间激光通信技术建立多点间空间激光通信链路,又能代替压电偏摆镜的精瞄方式。阐述液晶相控阵应用趋势;通过对液晶相控阵中液晶分子电致双折射和多缝衍射光束偏转原理,提出替压电偏摆镜配合终端进行瞄准捕获跟踪的方案;以“一对二”空间激光通信终端为例,提出基于液晶相控阵多点间空间激光通信终端方案和链路工作模式,分析方案优势,并进行未来展望。