Femtosecond Laser Combined with Hydrothermal Method to Construct Three-Dimensional Spatially Distributed Wurtzite ZnO Micro/Nanostructures to Enhance Photocatalytic Properties.

Conventional approaches employing nanopowder particles or deposition photocatalytic nanofilm materials encounter challenges such as performance instability, susceptibility to detachment, and recycling complications in practical photocatalytic scenarios. In this study, a novel fabrication strategy is proposed that uses femtosecond laser direct writing of self-sourced metal to prepare a self-supporting microstructure substrate and combines the hydrothermal method to construct a three-dimensional spatially distributed metal oxide micro/nanostructure. The obtained wurtzite ZnO micro/nanostructure has excellent wetting properties while obtaining a larger specific surface area and can achieve effective adsorption of methyl orange molecules. Moreover, the tight integration of ZnO with the surface interface of the self-sourced metal microstructure substrate will facilitate efficient charge transfer. Simultaneously, it improves the efficiency of light utilization (absorption) and the number of active sites in the photocatalytic process, ultimately leading to excellent photodegradation stability. This result provides an innovative technology solution for achieving efficient semiconductor surface-interface photocatalytic performance and stability.

Impact of the geometry of the excitation structure on optical skyrmion.

Optical skyrmions have attracted great attention for the potential applications in novel information storage and communication. It is of great significance to get insight into the generation of optical skyrmions by surface waves. Here, we have paid greater emphasis on the influence of the geometry of the coupling structure on the formation of optical skyrmions. Optical skyrmions are constructed from the superposition of the interfering surface plasmons excited by polygon trenches on Ag film. The results show the field texture of optical skyrmions is mainly determined by the excitation structure, with distinct properties revealed with various closed and non-closed geometries. Moreover, the ratio between the electric field strengths of the optical skyrmions can be larger than 4 between the optimized and unoptimized coupling structures. The pattern of the optical skyrmion shows a strong dependence on the excitation structure, implying the significant role in skyrmion topology it plays.

Directional Drop Rebound on Adhesive-Gradient Micro-Nanostructured Surfaces Formed by a Femtosecond Laser.

The dynamic behavior of droplets hitting a solid surface has received extensive attention due to its broad application prospects. Additionally, controlling the rebound behavior of impacting droplets is an important research topic. Current methods for investigating this behavior focus on the construction of a differentiated wettability surface, which is characterized by contact angle measurements, or a differentiated topography surface, which is represented by geometric height. This information allows one to obtain the nonuniform kinetic energy distribution of rebounding droplets and to realize control of rebounding droplet behavior. In this paper, femtosecond laser processing is proposed for the fabrication of an anisotropic surface with differences in adhesion, which allows for the control of impacting droplet rebound behavior. The experimental results show that the micro-nanostructure of the surface affects its adhesion. By changing the micro-nanostructure of the solid surface, the difference in surface adhesion can be controlled, thereby realizing precise control of impacting droplet rebound behavior. This study demonstrates that the micro-nanostructured surface formed by a femtosecond laser can be used to control a droplet rebound direction and landing site, which is of great significance to the development of liquid transport, microfluidic devices, and other fields.

Effects of Au6 and Au20 Adsorption Sites of Cyromazine-Au Complexes by Raman Spectroscopy and Density Functional Theory.

Cyromazine, when used as an insect growth regulator and low-toxicity insecticide, may degrade into melamine and pose a potential threat to the environment and soil health, which has thus attracted extensive research on eliminating such a harmful effect. In this paper, density functional theory (DFT)/LC-BLYP/6-311G(d,p) is used to optimize the geometric structure and analyze the vibration of cyromazine. The DFT/LC-BLYP/def2-SVP is used for the cyromazine-Au complex optimization and vibration analysis. The molecular electrostatic potential (MEP), frontier molecular orbitals (FMOs), vibration frequency, electrophilicity-based charge transfer (ECT) descriptor, binding energy (BE), polarizability, normal Raman spectroscopy (NRS), and surface-enhanced Raman spectroscopy (SERS) of cyromazine adsorbing on Au6 and Au20 are calculated. The study of the chemical enhancement mechanism of SERS of cyromazine at different adsorption sites of Au6 or Au20 confirms the existence of a charge transfer between cyclopromazine and Au6 and Au20, which can adsorb and form stable cyromazine-Au complexes. The results show that N2, H13, and N4 are the adsorption sites of Au6 and Au20. The Raman spectra of the cyromazine-Au complex can be selectively enhanced with a factor up to 9.07. Compared with those of cyromazine-Au6, the Raman spectra of cyromazine-Au20 are enhanced more significantly.

Density Functional Theory and Raman Spectroscopy Studies of Adsorption Sites of Au Nanoparticles with Alectinib.

Alectinib is an ALK tyrosine kinase inhibitor, which is mainly used in patients with crizotinib-resistant nonsmall cell lung cancer. Alectinib has attracted much clinical attention for its longest progression-free survival time and the best therapeutic effect. The chemical adsorption of Au nanoclusters (AuNPs) with alectinib molecules is studied by density functional theory (DFT) and surface-enhanced Raman scattering spectroscopy (SERS) experiments. DFT/B3LYP-D3/6-311G** was used for optimization and vibration analysis of alectinib-Au6 complexes, as well as molecular electrostatic potential, frontier molecular orbital, and electro-optic-based charge transfer descriptors. Comparing the results of the DFT theory and SERS experiment, alectinib and AuNPs can form Au-N6 bonds primarily through chemical adsorption of N6 atoms, and the experimental results showed that the enhancement factor (EFCHEM) could reach 4.27. The results provide a theoretical basis for exploring the mechanism of chemical enhancement between AuNPs and alectinib.

Coaction effect of radiative and non-radiative damping on the lifetime of localized surface plasmon modes in individual gold nanorods.

Revealing the coaction effect of radiative and non-radiative damping on the lifetime of the localized surface plasmon resonance (LSPR) mode is a prerequisite for the applications of LSPR. Here, we systematically investigated the coaction effect of radiative and non-radiative damping on the lifetime of the super-radiant and sub-radiant LSPR modes of gold nanorods using time-resolved photoemission electron microscopy (TR-PEEM). The results show that the lifetime of the LSPR mode depends on the length of the gold nanorod, and the different variation behavior of an LSPR mode lifetime exists between the super-radiative mode and the sub-radiative one with the increase of nanorod length (volume). Surprisingly, it is found that the lifetime of the super-radiant LSPR mode can be comparable to or even longer than that of the sub-radiant LSPR mode, instead of the usual claim that a sub-radiant LSPR mode has a longer life than the super-radiant mode. Those TR-PEEM experimental results are supported by finite-difference time-domain simulations and are well explained by the coaction effect with the calculation of the radiative and non-radiative damping rate with the increase of the nanorod volume. We believe that this study is beneficial to build a low-threshold nano-laser and ultrasensitive molecular spectroscopy system.

Anisotropic Ice Adhesion of Micro-Nano-Structured Metal Surface by a Femtosecond Laser.

The icephobic materials induced using micro-nano-structured surfaces have aroused great attention for promising applications. Previously, the characterization of ice adhesion of icephobic materials by shear force is usually performed without direction discrimination along the surface whatever the surface is anisotropic or not. In this work, we studied the direction-dependent ice adhesion strength on groove-shaped micro-nano-structured aluminum alloy surfaces formed using a femtosecond laser. It is found that the ice adhesion strength on the surfaces exhibits anisotropy, which corresponds to a smaller ice adhesion strength in the direction parallel to the groove than that orthogonal to the groove. Furthermore, it is found that the ice adhesion strength decreases with the increase in groove width in the orthogonal direction, while it does not change much in the parallel direction. The anisotropic ice adhesion strength is attributed to the change of wettability and morphology in the two directions. The findings in this work suggest that anisotropic ice adhesion should be fully considered when designing an icephobic micro-nano-structured metal structure, which is of great significance to the characterization and application of icephobic materials.

Chemical Enhancement Effect of Icotinib-Au Complex Studied by Combined Density Functional Theory and Surface-Enhanced Raman Scattering.

Icotinib is an epidermal growth factor receptor tyrosine kinase inhibitor used in the treatment of non-small cell lung cancer. The charge transfer effect between gold nanoparticles (AuNPs) and icotinib molecules can be used as a model to study the adsorption mechanism between molecules and metal. The adsorption of icotinib on the AuNP surface was confirmed by UV-vis and transmission electron microscopy (TEM) experiments. To explain the nature of chemisorption between icotinib and AuNPs from a theoretical perspective, the molecular correlation properties of the complex model of icotinib-Au6 were studied by the density functional theory method. By studying the molecular electrostatic potential of an icotinib molecule, four potential binding sites of the icotinib molecule were predicted. The calculation results of binding energy showed that the complex formed by chemisorption of icotinib through acetylene group and Au6 was the most stable one. The molecular frontier orbitals of icotinib and icotinib-Au6 confirmed that the charge transfer effect occurred on the acetylene group, benzene ring, and quinazoline ring of the icotinib molecule. The Herzberg-Teller surface selection rule was used to explain selective enhancement in the theoretically calculated Raman spectra. By comparing the spectra of theory and experiment, the cause of spectral peak shift and broadening that appeared in the surface-enhanced Raman scattering spectrum compared with the normal Raman spectrum was explained as well. This work would contribute to the development and application of the icotinib-Au drug carrier system.

An evolving perspective of endoscopic transnasal optic canal decompression for traumatic optic neuropathy in clinic.

Traumatic optic neuropathy (TON) is a serious complication of craniofacial trauma, which damages the optic nerve indirectly and leads to dysfunction of visual acuity. The clinical intervention for a patient with TON includes optic canal decompression (with or without steroids), treatment with corticosteroids alone, or observation only. Currently, there is a controversy among clinicians as to which treatment is optimal. An increasing number of retrospective studies have unveiled that patients could experience significant improvement in visual acuity after optic canal decompression surgery, particularly endoscopic transnasal/transethmosphenoid optic canal decompression (ETOCD), either with or without corticosteroids. In this review, we discuss the evolving perspective on surgical treatment, specifically ETOCD, for the management of patients with TON and focus mainly on the therapeutic efficacy, safety, and resulting prognosis in the clinic.

Combination analysis on the impact of the initial vision and surgical time for the prognosis of indirect traumatic optic neuropathy after endoscopic transnasal optic canal decompression.

To analyze the impact of the initial vision and surgical time for endoscopic transnasal/transethmosphenoid optic canal decompression (ETOCD) in the treatment of indirect traumatic optic neuropathy (TON). This retrospective case series analysis included 72 patients with indirect TON who underwent ETOCD from August 2017 to May 2019. Visual acuity (VA) was compared before and after surgery to estimate the improvement rate. The overall VA improvement rate of ETOCD was 54.2%. There were 83.3% and 33.3% improvement rate of patients with residual vision and blindness, respectively. VA was improved in 60.9% of patients treated within 3 days, 61.5% treated within 7 days, and 35.0% treated later than 7 days. Of the blindness patients, 50.0%, 37.5%, and 0.0% were treated within 3 days, 3-7 days, and later than 7 days, respectively. Of patients with residual vision, 85.7%, 92.3%, and 70.0% were treated within 3 days, 3-7 days, and later than 7 days, respectively. A statistically significant difference was found between patients with residual vision and those with blindness (P < 0.01), as well as between patients who received ETOCD within 7 days and those who received ETOCD later than 7 days (P = 0.043). The improvement rate of blindness patients managed within 3 days (P = 0.008) and 3-7 days (P = 0.035) was significantly higher than that for patients managed beyond 7 days. Indirect TON patients can directly benefit from ETOCD, and patients with residual vision have better improvement rates. ETOCD should be performed as soon as possible to salvage the patient's VA, especially within the first 7 days. For blindness patients, it is necessary to carry out the surgery within 7 days with increased benefit seen before 3 days.

Manipulation of femtosecond laser filamentation by a gaseous lattice.

Manipulation of femtosecond laser filamentation is essential for many potential applications. We report the simulations of the manipulation of femtosecond laser filamentation by introducing a novel gaseous lattice medium with the alternating positive and negative refractive index distribution at different stages of filamentation. The results show that the filament length has greatly been extended and a multi-filament array can be formed by the gas lattice medium. It has been found that additional focusing and discrete diffraction provided by the gas lattice medium contribute to a new dynamic equilibrium in the filamentation. As a result, a varied cross-section pattern, higher field intensity, and electron density along the filamentation are obtained. Our approach provides a new way to manipulate filamentation for many practical photonic applications.

Distinct spatiotemporal imaging of femtosecond surface plasmon polaritons assisted with the opening of the two-color quantum pathway effect.

Accurately capturing the spatiotemporal information of surface plasmon polaritons (SPPs) is the basis for expanding SPP applications. Here, we report spatio-temporal evolution imaging of femtosecond SPPs launched from a rectangular trench in silver film with a 400-nm light pulse assisted femtosecond laser interferometric time-resolved (ITR) photoemission electron microscopy. It is found that introducing the 400nm light pulse in the spatially separated near-infrared (NIR) laser pump-probe ITR scheme enables distinct spatiotemporal imaging of the femtosecond SPPs with a weak probe pulse in the ITR scheme, which is free from the risk of sample damage due to the required high monochromatic field for a clear photoelectron image as well as the entangled interference fringe (between the SPPs and probe pulse) in the usual spatially overlapped pump-probe ITR scheme. The demonstrated great improvement of the visibility of the SPPs spatiotemporal image with an additional 400nm light pulse scheme facilitates further analysis of the femtosecond SPPs, and carrier wavelength (785nm), group velocity (0.94C) and phase velocity (0.98C) of SPPs are extracted from the distinct spatio-temporal evolution images of SPPs. Furthermore, the modulation of photoemission induced by the quantum pathway interference effect in the 400nm-assisted scheme is proposed to play a major role in the distinct visualization for SPPs. The probabilities of electrons in different quantum pathways are obtained quantitatively through fitting the experimental results with the quantum pathway interference model. The probability that electrons emit through the quantum pathway allows us to quantitatively analyze the contribution to electron emission from the different quantum pathways. These findings pave a way for the spatiotemporal imaging of the near-infrared light-induced SPPs, such as the communication wave band using PEEM.

Polarization manipulated femtosecond localized surface plasmon dephasing time in an individual bowtie structure.

The performance of plasmon in applications is strongly related to plasmon damping, i.e., a dephasing of the optical polarization associated with the electron oscillation. Accurate measurement, manipulation, and, ultimately, prolongation of the dephasing time are prerequisites to the future development of the application of plasmonics. Here, we studied the dephasing time of different plasmonic hotspots in an individual bowtie structure by time-resolved photoemission electron microscopy and proposed an easy-to-operate method for actively and flexibly controlling the mode-dependent plasmon dephasing time by varying the polarization direction of a femtosecond laser. Experimentally, we achieved a large adjustment of the dephasing time ranging from 7 to 17 fs. In addition, a structural defect was found to drastically extend the plasmon dephasing time. Assisted with the finite-difference time-domain simulation, the underlying physics of the dephasing time extension by the structural defect was given.

Analysis of Prognostic Factors for the Indirect Traumatic Optic Neuropathy Underwent Endoscopic Transnasal Optic Canal Decompression.

OBJECTIVE: This study aimed to investigate the clinical outcomes of endoscopic transnasal optic canal decompression (ETOCD) for patients with indirect traumatic optic neuropathy (TON) and identify the relevant prognostic factors. METHODS: Seventy-two indirect TON patients who underwent ETOCD surgery from August 2017 to May 2019 were analyzed retrospectively. The paired t-test was used to compare the visual acuity (VA) before and after ETOCD, and multiple linear regression analysis was used to distinguish the potential prognostic factors. RESULTS: Among the patients analyzed, postoperative VA (-2.87 ±â€Š0.19) was significantly higher than the preoperative VA (-3.92 ±â€Š0.13) (P < 0.05). Multiple linear regression analysis models showed that poor initial VA and longer time to surgery were independent risk factors for VA prognosis (P < 0.05), but surgical time alone was significantly associated with the improvement degree of visual acuity (IDVA) (P < 0.05). Optic canal fracture, orbital fracture, and hemorrhage within the ethmoid and/or sphenoid sinus were not significantly correlated with IDVA and VA prognosis (P > 0.05). CONCLUSIONS: ETOCD surgery could salvage VA impairment in patients with indirect TON. A better initial VA indicates better final VA outcomes after surgery. Additionally, shorter time to surgery implies better VA prognosis and higher IDVA.

Spatial- and energy-resolved photoemission electron from plasmonic nanoparticles in multiphoton regime.

Spatial-resolved photoelectron spectra have been observed from plasmonic metallic nanostructure and flat metal surface by a combination of time-of-flight photoemission electron microscope and femtosecond laser oscillator. The photoemission's main contribution is at localized 'hot spots,' where the plasmonic effect dominates and multiphoton photoemission is confirmed as the responsible mechanism for emission in both samples. Photoelectron spectra from hot spots exponentially decay in high energy regimes, smearing out the Fermi edge in Au flat surface. This phenomenon is explained by the emergence of above threshold photoemission that is induced by plasmonic effect; other competing mechanisms are ruled out. It is the first time that we have observed the emergence of high kinetic energy photoelectron in weak field region around 'hot spot.' We attribute the emergence of high kinetic energy photoelectron to the drifting of the liberated electron from plasmonic hot spot and driven by the gradient of plasmonic field.

Ultrafast switching of photoemission electron through quantum pathways interference in metallic nanostructure.

The localized photoemission electron originating from the plasmonic "hot spots" in a metallic bowtie nanostructure can be separately switched on and off by adjusting the relative time delay between two orthogonally polarized laser pulses. The demonstrated femtosecond timing, nanometric spatial switching of multiphoton photoemission results from the interference of quantum pathways. Energy resolved measurement of the photoemission electrons further shows that the quantum pathway interference mechanism applies to control all the liberated electrons. The experimental results also show that the probability of electron emission through the quantum pathways from a plasmonic hot spot is determined by the localized emission response to the two incident laser pulses. These findings are of importance for controlling photoemission in ultrahigh spatiotemporal resolution in metallic plasmonic nanostructures.

Interference-induced filament array in fused silica.

One- and two-dimensional filament arrays are obtained in fused silica by using two and three interfered femtosecond laser beams, respectively. By modulating the number, cross angle, and azimuth of the beams, the dimension, period, orientation, and geometry of the filament-array can be controlled. The multiple beams interference method provides a convenient and effective method to generate and control the filament array in optical media with multiple degrees of freedom but without any external pulse modulation or focal element.

Out-of-Band Radiation and Spatio-Temporal Characterization of Gd Target Laser Plasma Sources.

In this paper, an Nd∶YAG laser with 10ns pulse width and output wavelength of 1 064 nm was employed to ablate Gd metal target and Gd-doped glass target for plasma generation. The out-of-band (OOB) radiation of extreme ultraviolet sources with the two target configurations was comparatively studied. It has been found that the continuous radiation emitted by the plasma is the main component of the out-of-band radiation. The spectral distribution of the continuum emission matches that of blackbody radiation with a temperature of about 5 eV. And it is also found that the intensity of OOB radiation can be considerably decreased by using Gd-doped glass target. Optical Emission Spectroscopy (OES) has been used to analyze the temporal and spatial behaviors of electron temperature (Te) and density (Ne) of the Gd-doped glass target plasma, and experimental results show that temporal evolution of electron temperature and density of the plasma are found to be decayed exponentially with the increasing of delay time. At 125 ns after laser irradiation, electron temperature and density were 4 eV and 1.2×1018 cm-3 respectively, and then decreased to 1.5 eV and 8×1017 cm-3 with delaying time of 250 ns. On the other hand, spatial evolution of electron temperature and density show that both of them first increase and then decrease in the region of 1~10 mm from the target surface. The electron temperature and electron density achieves the maximum of 2.6 eV and 8.5×1017 cm-3, respectively, when the probe location away from the target surface 6 mm.

[Investigation of Cu Concentration in the CuSO4 Solution by Laser Induced Breakdown Spectroscopy].

In this paper, the concentration of copper element in the CuSO4 solution was measured by Laser Induced Breakdown Spectroscopy with aqueous jets. We used the CuSO4 solution with 7 kinds of concentration and adopted statistical exploratory data analysis method to get calibration curve of Cu, whose linear fitting coefficient R2 was larger than 0.98. The average RSD of LIBS was 6.96%, and the average LOD of Cu was determined to be 12 ppm. The values of relative error by analyzing Cu I 324.75 nm and Cu I 327.40 nm spectral lines were respectively 6.52% and 5.86%, with the method called leave-one-out cross validation. The experimental relative error had a greater value, which was 10.3%, when the concentration of Cu was 10 ppm. However, the relative error decreased to 1.1% for the concentration of 2000 ppm, which indicated that LIBS need to be studied on its accuracy further in detecting lower analytical concentrations. LIBS has the promising application in detecting heavy metal elements in the environmental wastewater pollution.

[Research on the dynamics of ion debris from Sn plasma by use of dual laser pulses].

Extreme ultraviolet lithography is one of the most promising technologies on the next generation of high-capacity integrated circuit manufacturing. However, techniques for ion debris mitigation have to be considered in the application of extreme ultraviolet source for lithography. In our paper the dynamics of ion debris from Sn plasma by using dual ns laser pulses were investigated. The results show that debris from plasma greatly depends on the energy of pre-pulse and the delay time between the two laser pulses. The energy of Sn ions debris was efficiently mitigated from 2. 47 to 0. 40 keV in the case of dual laser pulses, up to 6. 1 times lower than that by using single laser pulse. We also found that Sn ions debris can be mitigated at all angles by using the dual laser pulses method.