Study Of Nanoparticle Enhancement On Laser Induced Breakdown Spectroscopy

Laser induced breakdown spectroscopy(LIBS)is a kind of emission spectrum detection technology.By measuring the emission spectrum of high-energy laser induced plasma,the information about element composition and content in the sample can be obtained.LIBS technology has the advantages of rapid response,multi-element analysis,online detection,remote detection,and so on.Therefore,it is widely used in environmental detection,material analysis,food safety,space exploration,mineral metallurgy and other fields.In the paper,the research of nanoparticle enhanced laser induced breakdown spectroscopy(NELIBS)were carried out with Nd:YAG laser,echelle spectrometer,intensified charge coupled device(ICCD)detector and other experimental devices.When comparing with traditional LIBS technology,the emission intensity of NELIBS is significantly enhanced,detection limit is reduced and the detection sensitivity is improved.The main conclusions of this paper are as follows:(1)The coulomb effect of amphiphilic molecules in NELIBS was investigated.It was found that when cationic surfactant hexadecyl trimethyl ammonium bromide(CTAB)and gold nanoparticles were used,k-I lines at wavelength of 766.5 nm and769.9 nm were significantly enhanced,and the detection limit of K reduced to 13ppb from ppm.But LIBS signal was not enhanced for anionic surfactant sodium dodecyl sulfate(SDS)or gold nanoparticles alone.The enhancement mechanism can be attributed to the coulomb attraction between the cationic surfactants and negatively charged gold nanoparticles,and the enhancement of local electric field near the gold nanoparticles due to the localized surface plasmons(LSPs).The new technique provides an effective method for the improvement of the detection sensitivity of LIBS.(2)The effect of halogen anions on NELIBS was also studied.Halogen anions can react with the silver ion on the surface of grey silver colloid,which affects the agglomeration condition of silver nanoparticles,and changs the characteristics of LSPs.Thus it influences the enhancement of LIBS finally.It was found that with the increment of KCl solution concentration in the grey silver colloid,the resonant peak strength of absorption spectrum decreases with nanoparticles aggregating gradually.Mg-I lines of NELIBS for MgSO₄ was enhanced when KCl solution was added,which shows the optimization of chloride ion for NELIBS.(3)We studied the influence of silver nanoclusters coverage on NELIBS.The silver nanoclusters were deposited on the surface of silicone coated PET through magnetron sputtering.It was found that LIBS signal increased when coating time is increasing,then reached a saturated enhancement factor¹5,and finally decreased.With the increment of silver cluster coverage,the local electric field enhances.What's more,the surface plasmon resonance peak shows a red shift,and the absorption cross section increases.When further increasing the coverage,the silver film formed gradually,and the quenching effect appear,which results in the decrease of LIBS.