Fast synthesis of gold nanoparticles by cold atmospheric pressure plasma jet in the presence of Au^(+) ions and a capping agent

Homogeneous gold nanoparticles were synthesized under atmospheric pressure using a nonthermal helium plasma jet in a single-step process.A current power supply was used to generate the plasma discharge rich in diverse reactive species.These species induce rapid chemical reactions responsible for the reduction of the gold salts upon contact with the liquid solution.In this study,spherical and monodispersed gold nanoparticles were obtained within 5 min of plasma exposure using a solution containing gold(Ⅲ)chloride hydrate(HAuCl_(4))as a precursor and polyvinylpyrrolidone(PVP)as a capping agent to inhibit agglomerations.The formation of these metal nanoparticles was initially perceptible through a visible change in the sample's color,transitioning from light yellow to a red/pink color.This was subsequently corroborated by UVvis spectroscopy,which revealed an optical absorption in the 520-550 nm range for Au NPs,corresponding to the surface plasmon resonance(SPR)band.An investigation into the impact of various parameters,including plasma discharge duration,precursor and capping agent concentrations,was carried out to optimize conditions for the formation of well-separated,spherical gold nanoparticles.Dynamic light scattering(DLS)was used to measure the size of these nanoparticles,transmission electron microscopy(TEM)was used to observe their morphology and X-ray diffraction(XRD)was also employed to determine their crystallographic structure.The results confirm that homogeneous spherical gold nanoparticles with an average diameter of 13 nm can be easily synthesized through a rapid,straightforward,and environmentally friendly approach utilizing a helium atmospheric pressure plasma.

Analysis of extreme ultraviolet spectral profiles of laser-produced Cr plasmas

Radiation from laser-produced plasmas was examined as a potential wavelength calibration source for spectrographs in the extreme ultraviolet(EUV) region.Specifically, the EUV emission of chromium(Cr) plasmas was acquired via spatiotemporally resolved emission spectroscopy.With the aid of Cowan and flexible atomic code(FAC) structure calculations,and a comparative analysis with the simulated spectra, emission peaks in the 6.5–15.0 nm range were identified as 3 p–4 d, 5 d and 3 p–4 s transition lines from Cr5+–Cr10+ions.A normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model were assumed for the spectral simulations, and used to estimate the electron temperature and density in the plasma.The results indicate that several relatively isolated emission lines of highly charged ions would be useful for EUV wavelength calibration.

Spectral and ion emission features of laser-produced Sn and SnO2 plasmas

We have made a detailed comparison of the atomic and ionic debris, as well as the emission features of Sn and SnO2 plasmas under identical experimental conditions. Planar slabs of pure metal Sn and ceramic SnO2 are irradiated with 1.06 μm, 8 ns Nd：YAG laser pulses. Fast photography employing an intensified charge coupled device （ICCD）, optical emission spectroscopy （OES）, and optical time of flight emission spectroscopy are used as diagnostic tools. Our results show that the Sn plasma provides a higher extreme ultraviolet （EUV） conversion efficiency （CE） than the SnO2 plasma. However, the kinetic energies of Sn ions are relatively low compared with those of SnO2. OES studies show that the Sn plasma parameters （electron temperature and density） are lower compared to those of the SnO2 plasma. Furthermore, we also give the effects of the vacuum degree and the laser pulse energy on the plasma parameters.

A Fokker-Planck Code for Laser-Produced Plasmas

A Fokker-Planck code is developed based upon Epperlein＇s scheme to investigate laser-produced plasmas in relevance to inertial confinement fusion. The equations are integrated implicitly by time-splitting method. Three test problems are simulated to show the versatility of the code. The results are in good agreement with the existing simulations.

Measurement and analysis of the extreme ultraviolet emission band of laser-produced antimony plasmas

The temporal evolution of extreme ultraviolet(EUV)emission spectra of laser-produced antimony(Sb)plasmas has been measured in the 7-16 nm wavelength region using spatio?temporally resolved lase-produced plasma spectroscopy technique.The spectral profiles involve an intense quasi-continuous band with superimposed intense characteristic radiation and are different with the increase of delay time.The spectral structures were also analyzed according to Hartree-Fock calculations with configuration interaction effects and contributed from 4d^4/;4d-4p,and 4d-5f unresolved transition arrays of Sb7*-Sb131.A steady-state collisionalradiative model was used to estimate the electron temperature and density range of Sb plasmas.This work would enrich the spectral data of highly-charged ions and provided a possible selection for developing EUV light sources.

Influence of heating effect in Thomson scattering diagnosis of laser-produced plasmas in air

A state diagnosis of laser-produced plasma in air generated by a 1064 nm pulse laser was investigated by the Thomson scattering(TS)method.The evolutions of the electron temperature and electron density were obtained as a function of the time delay which ranged from 300-3200 ns.The heating effect produced by the 532 nm probe beam with different energies on the air plasma at different interaction times was further studied using a time-resolved optical emission spectroscopy technique.The influence of the probe beam on the electron density was found to be negligible,whereas its influence on electron temperature is evident.In addition,the heating effect of the probe beam on the plasma strongly depends on the energy of the probe beam,and gradually weakens with increasing time delay.Our results are helpful for further understanding the TS method and its application in plasma diagnostics.

Analysis of extreme ultraviolet spectra of laser-produced Cd plasmas

In order to provide detailed information about Cd structure and gain more insight regarding ionization degrees and types of transition,as well as the understanding of the temporal evolution behavior of laser produced Cd plasmas,extreme ultraviolet spectra of laser-produced cadmium(Cd)plasmas have been measured in the 8.4-12 nm region using spatiotemporally resolved laser-produced plasma spectroscopy technique.Spectral features were analyzed by the Hartree-Fock(HF)method with relativistic correlations(HFR)using the Cowan code.The results showed that the 4p-5s resonance transition arrays from Cd^9+to Cd^13+merged to form intense lines in this spectral region.A number of new spectral features from Cd^9+and Cd^10+ions are reported in this study.Based on the assumption of a normalized Boltzmann distribution among the excited states associated with a steady-state collisional-radiative model,the plasma parameters were obtained by comparing the experimental and simulated spectra.As a result,we succeeded in reproducing the synthetic spectra for different time delays,which yielded good agreement with the experiments.The temporal evolution behaviors of electron temperature and electron density of plasma were also analyzed.

Time-resolved spectroscopy for 5s^('4)D_(7/2) state transitions undergoing electron–ion recombination in femtosecond laser-produced copper plasma

In the femtosecond laser-produced Cu-plasma, the transient transition dynamics that the excited state 5s4D7/2 via electron-ion recombination transfers to 4p4F9/20 （465.11 nm, Λ1 line） and 4p4D7/20 （529.25 nm, Λ2 line） states are investigated by using the time-resolved spectroscopy. The occupation number and relevant lifetime of the excited state 5s4D7/2, the temporal evolutions of spectral intensities for Λ1 line and Λ2 line emissions are demonstrated to be in direct proportion to the employed laser intensity, which reveals the transient features of transition dynamics clearly differing from that resulted in the traditional collision excitation. Furthermore, some unique characteristics for Λ1 and Λ2 transitions stemming from electron-ion recombination are examined in detail.

Effect of dielectronic recombination on charge-state distribution in laser-produced plasma based on steady-state collisional-radiative models

Armed with four different steady-state collisional-radiative(CR) models,we investigated the effect of dielectronic recombination(DR) on the charge-state distribution in laser-produced silicon plasma. To assess this effect,we performed a series of temporally resolved spectra of highly charged Si ions in the extreme ultraviolet region.Ab initio calculations of the DR rate coefficients were done for Si^(6+)–Si^(4+) ions. We also analyzed the evolution of the collisional ionization, radiative recombination, three-body recombination, photo-ionization, and DR rate coefficients as a function of electron temperature. The electron temperature and electron density for different delay times were obtained by comparing the normalized experimental and simulated spectra. The ion fraction and average charge state from the four different CR models were also obtained. The results indicate that the DR process has a greater influence in the stage of plasma evolution that cannot be neglected in plasma diagnoses.

A laser-produced plasma source based on thin-film Gd targets for next-generation extreme ultraviolet lithography

We have studied laser-produced plasma based on mass-limited thin-film Gd targets for beyond the current extreme ultraviolet(EUV)light source of 13.5 nm wavelength based on tin.The influences of the laser intensity on the emission spectra centered around 6.7 nm from thin-film Gd targets were first investigated.It is found that the conversion efficiency of the produced plasma is saturated when the laser intensity goes beyond 2×10^(11)W cm^(-2).We have systematically compared the emission spectra of the laser-produced plasma with the changes in the thicknesses of the thin-film Gd targets.It is proved that a minimum-mass target with a thickness of 400 nm is sufficient to provide the maximum conversion efficiency,which also implies that this thickness is the ablation depth for the targets.These findings should be helpful in the exploration of next-generation EUV sources,as the thin-film Gd targets will reduce the debris during the plasma generation process compared with the bulk targets.

Study of the 6.x nm short wavelength radiation spectra of laser-produced erbium plasmas for BEUV lithography

Beyond extreme ultraviolet(BEUV)radiation with a wavelength of 6.x nm for lithography is responsible for reducing the source wavelength to enable continued miniaturization of semiconductor devices.In this work,the Required BEUV light at 6.x nm wavelength was generated in dense and hot Nd:YAG laser-produced Er plasmas.The spectral contributions from the 4p–4d and 4d–4f transitions of singly,doubly and triply excited states of Er XXIV–Er XXXII in the BEUV band were calculated using Cowan and the Flexible Atomic Code.It was also found that the radiative transitions between multiply excited states dominate the narrow wavelength window around 6.x nm.Under the assumption of collisional radiative equilibrium of the laser-produced Er plasmas,the relative ion abundance in the experiment was inferred.Using the Boltzmann quantum state energy level distribution and Gram–Charlier fitting function of unresolved transition arrays(UTAs),the synthetic spectrum around 6.x nm was finally obtained and compared with the experimental spectrum.The spatio-temporal distributions of electron density and electron temperature were calculated based on radiation hydrodynamic simulation in order to identify the contributions of various ionic states to the UTAs arising from the Er plasmas near 6.x nm.

Spectral Efficiency of Extreme Ultraviolet Emission from CO_2 Laser-Produced Tin Plasma Using a Grazing Incidence Flat-Field Spectrograph

A grazing incidence flat-field spectrograph using a concave grating was constructed to measure extreme ultraviolet （EUV） emission from a CO 2 laser-produced tin plasma throughout the wavelength region of 5 nm to 20 nm for lithography. Spectral efficiency of the EUV emission around 13.5 nm from plate, cavity, and thin foil tin targets was studied. By translating the focusing lens along the laser axis, the dependence of EUV spectra on the amount of defocus was investigated. The results showed that the spectral efficiency was higher for the cavity target in comparison to the plate or foil target, while it decreased with an increase in the defocus distance. The source＇s spectra and the EUV emission intensity normalized to the incident pulse energy at 45 from the target normal were characterized for the in-band （2% of bandwidth） region as a function of laser energy spanning from 46 mJ to 600 mJ for the pure tin plate target. The energy normalized EUV emission was found to increase with the increasing incident pulse energy. It reached the optimum value for the laser energy of around 343 mJ, after which it dropped rapidly.

Determination of Trace Elements in High Purity Gold by High Resolution Inductively Coupled Plasma Mass Spectrometry

Trace elements were determined in high purity gold by high resolution inductively coupled plasma mass spectrometry （HR-ICP-MS）. Sample were decomposed by aqua regia. To overcome some potentially problematic spectra/ interference, measurements were acquired in both medium and high resolution modes. The matrix effects due to the presence of excessive HCl and Au were evaluated. The optimum conditions for the determination was tested and discussed. The standard addition method was employed for quantitative analysis. The detection limits range from 0.01ug/g to 0.28ug/g depending on the elements. The method is accurate, quick and convenient. It has been applied to the determination of trace elements in high purity gold with satisfactory results.

Visualization of gold nanoparticles formation in DC plasma-liquid systems

Dual argon plasmas ignited by one direct current power source are used to treat an aqueous solution of hydrogen tetrachloroaurate-(Ⅲ)trihydrate(HAuCl_(4)·3H_(2)O)which is contained in an H-type electrochemical cell.The solution contained in one cell acts as a cathode,and in the other as an anode.Experiments are carried out to directly visualize the formation process of gold nanoparticles(Au NPs)in separated cells of the H-type electrochemical reactor.The results and analyzes suggest that hydrogen peroxide and hydrated electrons generated from the plasma-liquid interactions play the roles of reductants in the solutions,respectively.Hydrogen peroxide can be generated in the case of the liquid being a cathode or an anode,while most of hydrated electrons are formed in the case of the liquid being an anode.Therefore,the reduction of the AuCl_(4)−ions is mostly attributed to the hydrogen peroxide as the liquid acts as a cathode,while to the hydrogen peroxide and hydrated electrons as the liquid acts as an anode.Moreover,the p H value of the solution can be used to tune the formation processes and final form of the Au NPs due to its mediation of reductants.

Tamping the movement of the laser absorption cutoff position using gold foam hohlraum

In indirect-driven laser fusion experiments,the movement of the laser absorption layer will distort the radiation uniformity on the capsule.The gold foam has advantages in symmetry control and lowering wall plasma blowoff when used in an inertial confinement fusion(ICF)hohlraum.This work investigates the motion of the laser absorption cutoff position using lowdensity foam gold walls.It is found that the motion of the laser absorption cutoff position can be significantly mitigated through optimal initial low density,tailored to a specific laser shape.For a short square laser pulse,the laser absorption cutoff position remains almost stationary at an initial density of approximately 0.6 g cm^(-3).For a long-shaped laser pulse,the minimal motion of the laser absorption cutoff position is observed at an initial density of about 0.1 g cm^(-3).This approach allows for the adjustment of the symmetry of the hohlraum radiation source.The insights gained from this study serve as a crucial reference for optimizing the hohlraum wall density.

Effective removal of the protective ligands from Au nanoclusters by ambient pressure nonthermal plasma treatment for CO oxidation

We used a dielectric barrier discharge(DBD)plasma technique to eliminate the protective ligand of ZnAl-hydrotalcite-supported gold nanoclusters.We used X-ray powder diffraction,ultraviolet-visible spectrophotometry,thermogravimetric analysis,and high angle annular dark-field-scanning transmission electron microscopy characterization to show that the samples pretreated with/without DBD-plasma displayed different performances in CO oxidation.The enhanced activity was obtained on the plasma-treated samples,implying that the protective ligand was effectively removed via the plasma technique.The crystal structure of the plasma-treated samples changed markedly,suggesting that the plasma treatment could not only break the chemical bond between the gold and the protective agent but could also decompose the interlayer ions over the hydrotalcite support.The particle sizes of the gold after DBD-plasma treatment implied that it was a good way to control the size of the gold nanoparticles under mild conditions.

A simple plasma reduction for synthesis of Au and Pd nanoparticles at room temperature

A simple and fast plasma reduction method is developed for synthesis of Au and Pd metal nanoparticles. The scanning electron microscopy(SEM) analysis indicates a formation of aggregates of Au and Pd nanoparticles with branched structure. The transmission electron microscopy(TEM) image shows that the inclusive nanoparticles are all about 5 nm in size. Compared to conventional hydrogen reduction method, plasma method inhibits the agglomeration of metal particles. The room temperature operation is very helpful to limit the nanoparticle size. Most interestingly, plasma reduction produces more flattened metal particles. This plasma reduction does not require the use of any hazardous reducing chemicals, showing the great potential for the fabrication of noble metal nanoparticles.

Population Diagnostics of a Hot NaBr Plasma by Detailed Simulation of Absorption Spectra

The experimental absorption spectra of a hot NaBr plasma are theoretically studied by using a detailed level accounting model. The sodium and bromine absorption spectra have been well reproduced respectively in the approach of local thermodynamic equilibrium, in which the populations between and within ions are obtained by solving the Saha-Boltzmann equation. The temperature of bromine however is found to be much lower than the one of sodium. Such discrepancy indicates that thermodynamic equilibrium is not reached between the sodium and bromine atoms during the measurement.

Spaced-Resolved Electron Density of Aluminum Plasma Produced by Frequency-Tripled Laser

By using the space-resolved spectrograph, the K-shell emission from laser-produced plasma was investigated. Electron density profiles along the normal direction of the target surface in aluminum laser-plasmas were obtained by two different diagnostic methods and compared with the profiles from the theoretical simulation of hydrodynamics code MULTI1D. The results corroborate the feasibility to obtain the electron density above the critical surface by the diagnostic method based on the Stark-broadened wings in the intermediately coupled plasmas.

Extreme ultraviolet spectral characteristic analysis of highly charged ions in laserproduced Cu plasmas

This paper reports the results of spectral measurements and a theoretical analysis of the temporal and spatial evolution of laser-produced Cu plasma in vacuum in the range of 8–14 nm.The time dependence of the extreme ultraviolet band spectrum at different positions near the target surface was obtained and found to be dominated by three broad-band features.The 3p and 3d excitations of Cu5+–Cu9+ions were calculated using the Hartree–Fock theory with configuration interactions.The characteristics of the spectral line distribution for the 3p–nd and 3d–nf transition arrays were analyzed.Based on the steady-state collisional radiation model and the normalized Boltzmann distribution,the complex spectral structure in the band of 13–14 nm is accurately explained through consistency comparisons and benchmarking between the experimental and theoretical simulation spectra,demonstrating that the structure mainly stems from the overlapping contribution of the 3d–4f and 3p–3d transition arrays for the Cu5+–Cu9+ions.These results may help in studying the radiation characteristics of isoelectronic series highly-charged ions involving the 3d excitation process.