食品中重金属污染的光声光谱检测新技术原理研究

In order to strengthen the determination of trace heavy metal in the field of food contamination, a new photoacoustic spectroscopy technology used for detecting the trace heavy metals such as lead, cadmium was researched. A new idea is proposed to detect the photoacoustic spectroscopy of the heavy metal pollution in foods based on optical-actuated flexible grating in this project. An optical-driving flexible grating will be developed in the project, and the continuous variation of lattice spacing is implemented by controlling the driving source, and the high quality factor of quartz tuning fork (QFT) was used in the program, and the resonance amplitude of QTF was detected by the method of sub-nanometer heterodyne interference to obtain photoacoustic signals. In addition, the quality factor of QTF can be further improved through the transparent vacuum sealed QTF. The environmental interference resistance ability of the system was enhanced in a large extent, and it makes the detection sensitivity of the whole system is higher than the traditional photoacoustic spectroscopy for 3to5 orders of magnitudes. It can realize the photoacoustic spectroscopy detection of trace heavy metals in the open condition. The project dive further into the influencing factors of the new type of photoacoustic spectroscopy detection, and developed the prototype system. It provides a technical guarantee for the industrial application. It is not need to design special photoacoustic pool in the scheme, and the sample preparation process is also leaved out. This method has the advantage of high sensitivity, non-intrusive, low cost and short detection time. A new detection technology is provided for detecting the trace heavy metals pollution, and it has a great significance to ensure food security. The project is in line with the "food safety law implementing regulations of the People's Republic of China" in the "food safety risk monitoring and evaluation".

针对加强食品重金属污染检测的国家需求，研究一种用于铅、镉等痕量重金属元素的光声光谱检测新原理。本项目提出了一种“基于柔性光栅的食品重金属污染光声光谱检测”新思想。将研发出一种光驱动柔性光栅，通过控制驱动光源实现栅距的连续变化,并利用音叉的高品质因子特性，通过亚纳米外差干涉探测音叉的共振振幅，获取光声信号。此外，采用透明真空封装音叉进一步提高音叉的品质因子，增强系统抗干扰能力，使整个系统的检测灵敏度高出传统光声光谱技术3-5个量级，实现开放环境下痕量重金属光声光谱检测。本项目将深入研究影响该方案的因素，并研制出原理样机，为工业应用提供技术保证。该方案无需设计专门的光声池，省去了样品制备过程，具有灵敏度高、非侵入、低成本、检测时间短等优点，为食品痕量重金属污染检测提供一种全新检测技术，对保障食品安全具有重要意义。项目符合“中华人民共和国食品安全法实施条例”中 “食品安全风险监测和评估”的要求。

随着我国工业化的快速发展，工农业废水的肆意排放，使得江河、湖泊、地下水以及土壤大面积污染，造成粮食、肉类、果蔬等食品重金属严重超标，而痕量重金属元素在人体内长期蓄积，则会对人体产生神经错乱、肾损伤、致癌、致畸等毒性作用，危及人体健康。本项目的研究目标是针对食品中痕量重金属污染问题，研究一种基于光驱动柔性光栅的痕量重金属光声光谱检测新技术，通过亚纳米外差干涉技术实现了被测物光声光谱信号的探测。.本项目的主要研究内容包括：（1）利用COMSOL软件实现了不同结构参数下柔性光栅的光驱动数值模拟，得到了在近红外激光照射下光栅栅距的响应规律。(2)设计并加工出光栅掩膜版、硅片，采用MEMS工艺加工聚二甲基硅氧烷(PDMS)/石墨烯(GNP)复合材料,制备出具有光致伸缩特性的柔性光栅。（3）采用斩光盘对经过柔性光栅的光进行光强调制，使其达到光声换能器（石英音叉、压电陶瓷）的共振频率，实现其共振。（4）搭建出了新型光声光谱检测原理样机系统，通过柔性光栅连续改变入射激光的波长，利用亚纳米外差干涉系统探测光声换能器的共振振幅，获得了被测物一氧化碳、硫化氢气体的光声光谱曲线，完成了对被测物的实时在线检测。.课题组根据现有实验条件，搭建出了基于光驱动柔性光栅的食品重金属污染检测原理样机系统，实现了一氧化碳、硫化氢两种不同被测物的实时在线检测，进一步验证了利用该系统实现食品重金属污染的可行性，属于一种原始技术创新，为后续食品重金属污染的进一步定量分析研究鉴定了坚实的科研基础。