Influence Of Matrix Temperature On Laser-induced Breakdown Spectroscopic Signal Of Gold And Its Application

Laser-induced breakdown spectroscopy(LIBS)technique is widely used in the analysis of geological samples,but its sensitivity is difficult to achieve the direct detection of gold elements in natural minerals.The study of simple and inexpensive methods to improve the sensitivity of LIBS is of great value for the field analysis of gold minerals.In this paper,the effect of sample matrix temperature on the sensitivity of LIBS detection is investigated,and the combination of LIBS scanning analysis technique and free calibration method is explored for high temperature mineral analysis,which provides an idea for the application of LIBS technology for gold mineral detection and analysis.Firstly,a UV emission spectral acquisition system was built based on the characteristics of the LIBS spectral line distribution of gold elements,a scanning control software based on a three-dimensional motion platform was developed,and a sample heating structure and device were designed.The experimental device is easy to operate and can be heated up to 973 K,which can efficiently heat up the sample and acquire the LIBS spectral signal,laying the foundation for the subsequent study.Secondly,the influence of the LIBS signal on the matrix temperature was investigated for foot gold and artificial specimens with different gold contents.The results showed that the signal intensity and signal repeatability were improved after increasing the substrate temperature compared with the room temperature condition;the actual measured values of ablation were also consistent with the trend of signal intensity,but there were differences with the theoretical calculated values,which may be due to the change of air density inside and outside the device under high temperature conditions and the plasma shielding effect.The experimental results showed that the signal intensity and signal-to-noise ratio of the LIBS signal of the artificial specimen increased after the increase of the substrate temperature compared with the room temperature,and the detection limit was 260%lower than that at room temperature;the calculation of the basic plasma parameters showed that the enhancement of the LIBS signal was due to the increase of the electron density by the increase of the substrate temperature.In order to further establish an in situ quantitative analysis method for geological samples,the paper applies the high-temperature LIBS system combined with scanning technology to natural mineral samples.Both experimental and theoretical analyses can fully demonstrate that elevated matrix temperature has a significant effect on improving the sensitivity of elemental gold LIBS detection,and the research exploration of this paper on matrix temperature enhancement of LIBS system sensitivity and scanning analysis method provides ideas for the subsequent application of LIBS technology in gold geology.