Research On Optical Fiber Sensor For Online Detection Of Mold And Disease Process Parameters On Paper Cultural Relics

As the most important carrier of the inheritance of the splendid history and civilization of the Chinese nation,paper cultural relics have an irreplaceable status and their cultural and historical values are inestimable.However,paper artifacts are rich in cellulose and are susceptible to mold erosion and environmental parameters(light,humidity,and carbon dioxide concentration)that can cause damage to paper artifacts,so preventive protection of paper artefacts is extremely important.In the field of preventive protection of paper relics,online accurate detection of microbial growth process information on the surface of paper relics and disease information on the body of the relics is the basis and key to achieve its preventive protection.However,the current detection of mold and disease process parameters of paper cultural relics mainly relies on offline detection technology,which is difficult to obtain online real-time information on the growth of microorganisms on the surface of cultural relics and the disease information on the body of cultural relics,making it difficult to reveal the mechanism and law of disease on paper relics and to achieve their preventive protection.Based on this,this paper proposes a new method for online non-contact detection of disease process information of paper artifacts by fiber optic spectroscopy.Firstly,a highly sensitive reflective fiber optic sensor was developed for online detection of mold and disease process parameters of paper artifacts;then different species of Aspergillus(Aspergillus niger,Aspergillus flavus,Aspergillus tamarrii,Aspergillus versicolor)were cultured and their morphological characteristics were characterized,and the information of the mold growth process on the surface of paper artifacts was measured qualitatively and quantitatively using the developed sensor;finally,the aging process of paper artifacts was simulated by the disease process parameters(light,humidity,carbon dioxide concentration),and the developed sensor was used to test the paper samples after aging treatment,which provided important support for the investigation of the disease mechanism and law of paper artifacts.Its main research work has the following three points.(1)In this paper,the principle and method of on-line nondestructive detection of mold and disease process parameters on paper cultural relics was proposed,and the structure of the fiber bundle of the sensing probe was studied,and one conical incident fiber and six receiving fibers were selected as the sensor fiber bundle.Established the principle of sensor measurement of paper artifacts,and the detection system was set up,the influence of the diameter and taper angle of the incident fiber,incident and receiving fiber spacing and optical path on the output spectrum and sensitivity of the sensor were respectively investigated,and high-sensitivity reflective optical fiber sensor was prepared and obtained for online nondestructive testing of mold and disease process parameters of paper cultural relics.The experimental results demonstrated that the sensor response sensitivity reached the maximum when the diameter and taper angle of the incident fiber was 1500 μm and 12°,the incident and receiving fiber spacing was 100 μm,and the optical path was 30 mm.(2)Different species of Aspergillus were cultured,camera,optical microscope and field emission scanning electron microscope(FESEM)were used to characterize and measure the distribution of mold,mold height and mold spore size,and then the developed reflective fiber optic sensor was used to detect Aspergillus in different cycles of culture(mold with different heights).The experimental results showed that with the increase of incubation time,the density of mycelium on the surface of paper samples increased,and the height of the mold and the diameter of the spores increased.The spectral information of different molds was obtained by the sensor,and the characteristic absorption peaks of Aspergillus niger,Aspergillus flavus,Aspergillus tamarrii and Aspergillus versicolor were 418 nm,282 nm,275 nm and 350 nm,295 nm and 390 nm,respectively,and the absorbance magnitude corresponding to the absorption peak was linearly related to the height of the mold,and the lower limit of detection of Aspergillus by the sensor reached 10 μm,indicating that the fiber optic sensor studied in this paper can be used to achieve online accurate detection of mold growth process information on the surface of paper artifacts.(3)An experimental system for aging paper samples with disease process parameters(light,humidity,and carbon dioxide concentration)was built,and a tensile tester,thermogravimetric analyzer,Fourier transform infrared spectrometer,and a reflective fiber optic sensor developed in this paper were used to detect the performance of the paper after aging treatment.The experimental study showed that when the light wavelength of LED lamp was 395 nm,humidity was 82% RH,and carbon dioxide concentration was 99.99%,the paper samples showed the lowest tensile strength and the worst thermal stability,and the peak intensity of the Fourier transform infrared spectrum changed significantly and new absorption peak appeared.Meanwhile,the UV-visible absorption spectra obtained from the paper samples detected with the sensor showed characteristic absorption peak,indicating that online accurate detection of the ontological lesion information of paper artifacts can be achieved by using the fiber-optic sensor studied in this paper.