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Nanoparticle enhanced laser ablation and consequent effects on laser induced plasma optical emission
摘要： In this paper the plasmon enhanced ablation for elemental analysis is investigated with several experiments in order to point out the crucial questions concerning the laser matter interaction under the effect of plasmonic coupling between the nanoparticle (NP) system and the laser ablation pulse. The correlation between the electromagnetic field enhancement and the signal enhancement during NP enhanced laser induced breakdown spectroscopy (NELIBS), as well as the laser matter interaction at the nanoscale, is discussed in the case of noble metal NPs deposited on metal samples. The results suggest that, while laser pulse energy is concentrated in the space between the NPs, the NP system is shielded by the field enhancement distribution after the laser pulse interacts with the plasmons of the NP system. Finally the comparison of the laser energy transfer to the sample between NELIBS and conventional LIBS is discussed.
关键词： LIBS,Nanoparticle enhanced laser induced breakdown spectroscopy (NELIBS),laser ablation,plasmonic enhanced ablation,LA-ICP-MS
更新于2025-09-23 15:19:57
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Lasera??Induced Graphene for Electrothermally Controlled, Mechanically Guided, 3D Assembly and Humana??Soft Actuators Interaction
摘要： Mechanically guided, 3D assembly has attracted broad interests, owing to its compatibility with planar fabrication techniques and applicability to a diversity of geometries and length scales. Its further development requires the capability of on-demand reversible shape reconfigurations, desirable for many emerging applications (e.g., responsive metamaterials, soft robotics). Here, the design, fabrication, and modeling of soft electro-thermal actuators based on laser-induced graphene (LIG) are reported and their applications in mechanically guided 3D assembly and human-soft actuators interaction are explored. Over 20 complex 3D architectures are fabricated, including reconfigurable structures that can reshape among three distinct geometries. Also, the structures capable of maintaining 3D shapes at room temperature without the need for any actuation are realized by fabricating LIG actuators at an elevated temperature. Finite element analysis can quantitatively capture key aspects that govern electrothermally controlled shape transformations, thereby providing a reliable tool for rapid design optimization. Furthermore, their applications are explored in human-soft actuators interaction, including elastic metamaterials with human gesture-controlled bandgap behaviors and soft robotic fingers which can measure electrocardiogram from humans in an on-demand fashion. Other demonstrations include artificial muscles, which can lift masses that are about 110 times of their weights and biomimetic frog tongues which can prey insects.
关键词： human-soft actuators interaction,laser-induced graphene,electrothermal actuators,3D assembly
更新于2025-09-23 15:19:57
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Calibration and verification of streaked optical pyrometer system used for laser-induced shock experiments
摘要： Although the streaked optical pyrometer (SOP) system has been widely adopted in shock temperature measurements, its reliability has always been of concern. Here, two calibrated Planckian radiators with different color temperatures were used to calibrate and verify the SOP system by comparing the two calibration standards using both multi-channel and single-channel methods. A high-color-temperature standard lamp and a multi-channel filter were specifically designed for the measurement system. To verify the reliability of the SOP system, the relative deviation between the measured data and the standard value of less than 5% was calibrated out, which demonstrates the reliability of the SOP system. Furthermore, a method to analyze the uncertainty and sensitivity of the SOP system is proposed. A series of laser-induced shock experiments were conducted at the ‘Shenguang-II’ laser facility to verify the reliability of the SOP system for temperature measurements at tens of thousands of kelvin. The measured temperature of the quartz in our experiments agreed fairly well with previous works, which serves as evidence for the reliability of the SOP system.
关键词： shock temperature measurement,laser-induced shock waves,streaked optical pyrometer
更新于2025-09-23 15:19:57
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Laser-Induced Voltage of Oil Shale during Retorting
摘要： In this study, a 248 nm laser was used to analyze oil shale at di?erent pyrolysis temperatures. An induced voltage was obtained when the ultraviolet laser irradiated the oil shale surface. The laser-induced voltage (LIV) peak decreases with temperatures below 200 °C, increases with temperatures in the range 200?400 °C, and then decreases above 400 °C. The critical temperatures of 200 and 400 °C corresponded well with the points conformed using thermogravimetry and di?erential scanning calorimetry (TGA-DSC), gas chromatography and gas chromatography coupled (TG-FTIR-MS), and scanning electron microscopy (SEM). Our research suggested that an LIV method could be applied to the analysis of the oil shale pyrolysis process.
关键词： oil shale,TGA-DSC,TG-FTIR-MS,pyrolysis,laser-induced voltage,SEM
更新于2025-09-23 15:19:57
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Laser induced graphene printing of spatially controlled super-hydrophobic/hydrophilic surfaces
摘要： Spatial control over the wetting properties of graphene surfaces is a desired feature in numerous applications. Traditionally, this is achieved using time consuming chemical treatment processes that lack spatial tuning. Here, we demonstrate the use of laser induced graphene for the direct, spatial printing of surfaces with either superhydrophilic or superhydrophobic character through simple and convenient control over graphene array morphology, and without the need for chemical surface modification. The wetting properties of the graphene surfaces range from superhydrophilic (0°) for sheet-like structures, to superhydrophobic (>150°) for micro-pillar and hemispherical structures. By varying the induction parameters of the CO2 laser, we demonstrate the ability to write patterns with spatially tailored wettability to enable liquid micro-patterning and channeling of flow. Furthermore, we study solid-liquid interactions for such surfaces using viscosity measurements, where a “petal effect” is observed in the graphene material, thus revealing the parahydrophobicity of the surface.
关键词： Superhydrophobic,Superhydrophilic,Petal effect,Laser induced graphene,Wettability
更新于2025-09-23 15:19:57
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Influence of defects on structural colours generated by laser-induced ripples
摘要： The colourisation of metallic surface which appears due to periodic surface patterns induced by ultrashort laser pulses is studied. Ripples due to the sub-micrometer size of their period act as a diffraction grating, generating structural colours. Carefully chosen strategy of the laser spot scanning allows us to mimic the nanostructures responsible for structural colours of some flowers on the metal substrate. We investigate the correlation between the colourising effects and the artificially-induced defects in the ripples structure and show that these defects can make the colours observable in a larger range of viewing angles. Further we address the influence of the processing parameters on the spectral profile of the reflected light.
关键词： structural colours,viewing angles,diffraction grating,defects,laser-induced ripples
更新于2025-09-23 15:19:57
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Evaluation of stress on metal surfaces by laser-induced breakdown spectroscopy
摘要： In this study, we evaluated the feasibility of using laser-induced breakdown spectroscopy (LIBS) to determine the stress generated in metal materials by comparing measured stress levels with those determined by x-ray diffraction (XRD). Magnesium (Mg) alloy specimens underwent impact stress generated under ultrasonic peening. Stainless steel specimens were subjected to bending stress. The reference stress for each specimen was measured using XRD. LIBS measurements were performed to determine the correlation between stress distribution and the ratio of ionic to atomic spectral line intensity. The stress distribution from the surface to the interior of the ultrasonic-peened specimens measured by LIBS showed a similar tendency to that measured by XRD, but there was a difference in the maximum measurable depth. Additionally, the tensile and compressive stress distributions measured by LIBS on bending specimens showed similar trends to those of XRD. From these results, it was possible to measure the correlation between the stress state of the metal matrix and the spectral line strength of LIBS, thus confirming the potential for stress measurement using LIBS.
关键词： laser-induced breakdown spectroscopy,mechanical stress,spectral line
更新于2025-09-23 15:19:57
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Interaction of two counterpropagating laser induced plasmas and shock waves in air
摘要： The interaction of two counterpropagating plasmas and shockwaves due to a 7 ns laser induced breakdown (LIB) of ambient atmospheric air was studied using the 2D emission and shadowgraphic imaging technique. The effect of separation distance (d) between the two plasma sources and their energy ratio on plasma and shockwave evolution is presented. These low density and low temperature plasma sources form a stagnation layer in the interaction zone that showed an interesting dependence on the input energy of the sources. The interaction dynamics of the two counterpropagating plasma plumes and the shock waves in ambient air are compared with that of the respective single plasma source to explicitly bring out the energy exchange during the interaction. The evolution of a plasma jetlet, studied by 2D emission images and shadowgraphic imaging, has shown very good correlation giving valuable insight into the role of a plasma induced shockwave on the expanding plasma. The propagation of the shock front of the high energy source through the plasma of a low energy source is observed to predominantly lead to the formation of a jetlet and its evolution.
关键词： laser induced plasmas,plasma jetlet,plasma interaction,shock waves,counterpropagating,stagnation layer
更新于2025-09-23 15:19:57
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Spectral analysis of Miracle Moringa tree leaves using X-ray photoelectron, laser induced breakdown and inductively coupled plasma -optical emission spectroscopic techniques
摘要： The antioxidant Moringa oleifera (a medicinal plant) leaves (MOLs) containing diverse nutrients are highly beneficial for the human health. The MOLs upon consumption can lower the blood sugar, cure the heart diseases, and reduce the inflammation. In this perception, the “primary nutrients contents” in the dry MOLs (pellet samples) were evaluated for the first time using the XPS, LIBS and ICP-OES techniques. The XPS analysis of the MOLs showed the presence of vital elements like calcium (Ca), magnesium (Mg), manganese (Mn), copper (Cu), phosphorous (P), sulfur (S) and zinc (Zn). The LIBS analyses of the MOLs revealed the atomic and ionic spectral lines corresponding to the essential nutrients such as the Ca, Na, K, Fe, Mg, Mn, Cu, P, S and Zn. The calibration free LIBS algorithm (CF-LIBSA) was developed to quantify the content of each element in the dry MOLs. In addition, the LIBS results were validated by the analysis using ICP-OES standard analytical technique. The elemental contents in the MOLs obtained from the CF-LIBS analyses were counter verified by the ICP-OES results. Present results are highly valuable for the development of a traditional herbal medicine using the miracle MOLs.
关键词： Calibration free LIBS algorithm,Laser induced breakdown spectroscopy,Moringa oleifera leaves,X-ray photoelectron spectroscopy,Inductively coupled plasma atomic emission spectroscopy
更新于2025-09-23 15:19:57
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Rapid qualitative evaluation of velvet antler using laser-induced breakdown spectroscopy (LIBS)
摘要： The aim of this work is to study a rapid analysis method to evaluate velvet antler products qualitatively, using laser-induced breakdown spectroscopy (LIBS). We used principal component analysis to select feature lines of LIBS spectra of velvet antler, and built two partial least squares-discriminant analysis (PLS-DA) classification models to distinguish between inferior and good quality velvet antler by using the intensities of all lines and feature lines as input variables, respectively. The correct classification rates (CCRs) of these two models were both 100%. In order to test the robustness of the models, we used these two models to discriminate the samples not included in the training set to build the model, and the CCRs were 87.5% and 100%, respectively. The results demonstrated that combining LIBS with PLS-DA could evaluate the quality of velvet antler, and the robustness could be improved by using the intensities of feature lines as inputs.
关键词： qualitative evaluation,partial least squares-discriminant analysis (PLS-DA),velvet antler,principal component analysis (PCA),laser-induced breakdown spectroscopy (LIBS)
更新于2025-09-23 15:19:57