Effects Of Molybdenum Disulfide Nanosheets On Growth Traits And Silk Properties Of Silkworm

In recent years,silk has been widely used as a biological material in the fields of medicine,biology,and tissue.In order to obtain silk with mechanical properties and functional enhancement,researchers have done a lot of work,including chemical modification,physical modification,blend modification,feeding method and so on.The feeding method is to obtain a functional silk modification method by feeding a functional material to the silkworm.The method is simple,efficient,and has broad industrial prospects.Studies have shown that feeding silkworms with certain concentrations of graphene,copper,titanium dioxide,and ferroferric oxide can significantly improve the mechanical properties of silk.2D MoS₂ nanomaterial is a typical graphene-like material,which compensates for the lack of band gap of graphene to a certain extent,and is widely used in optoelectronics,biology,energy and other fields,making rapid development in the field of two-dimensional nanomaterials in recent years,but there is no research on the feeding silkworms with2D MoS₂ nanomaterials.Recent studies have found that MoS₂ nanosheets can be prepared by the principle of weathering,and the method is simple without introducing other harmful solvents.Based on this,this experiment used the principle of weathering to prepare MoS₂ nanosheets,and then fed them to silkworm at 6 different concentrations to study the influence of different concentrations of MoS₂ nanosheets on the growth characteristics of silkworm,the mechanical properties of silk and the structure of silk.In addition,the transport process of Mo element in silkworm was studied.The main results are as follows:1.Using the principle of"weathering",Na⁺and OH^-were inserted into the layer of molybdenum disulfide at 30oC,and then the van der Waals force between the MoS₂ layers was overcome by slow crystallization of NaOH,and the MoS₂nanosheets were successfully prepared.Scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and atomic force microscopy?AFM?analysis showed that the prepared samples were uniform in thickness and the thickness was 60-70 nm.At the same time,the samples were characterized by X-ray diffraction and X-ray energy spectroscopy.The results show that the prepared MoS₂nanosheets are hexagonal phase 2H-MoS₂ with high purity and good crystallinity.2.The effects of feeding different concentrations of MoS₂ nanosheets on the growth traits of silkworm were studied by observing the appearance,body weight,tissue section and cocoon weight of silkworm.The results showed that when the feeding concentration of MoS₂ nanosheets was less than 400 mg/group,MoS₂nanosheets had no obvious toxic effect on silkworm.Compared with the control group,when the concentration of MoS₂ nanosheets was 400 mg/group,the body weight and cocoon shell weight of the silkworm decreased slightly,the midgut became shorter,and the silk gland became shorter and thinner,but did not affect spinning cocoons.At the same time,the results of paraffin tissue sections showed that there were no damage in the midgut and silk gland of the silkworm.3.The degumming of silkworm cocoons in each group was carried out to study the effects of different concentrations of MoS₂ nanosheets on the morphology,mechanical properties and structure of degummed silk.The results of scanning electron microscopy?SEM?showed that the drapes on the surface of the silk became more and more obvious with the increase of the concentration of MoS2 nanosheets,indicating that the MoS₂ nanosheets affected the spinning process of silkworm.The mechanical properties test results showed that when the feeding concentration of MoS₂ nanosheets was 10 mg/head,the breaking strength?697.12±84.32 MPa?and elongation at break?35.15±18.25%?of silk were significantly enhanced compared with the control group?breaking strength was 466.17±62.53 MPa?elongation at break was 21.05±11.24%?.The results of synchrotron radiation microscopy infrared spectroscopy?S-FTIR?showed that the secondary structure of degummed silk in the experimental group fed with MoS₂ nanosheets did not change significantly.However,the results of the secondary structures of silk fibers acquired according to the deconvoluted amide I band spectra showed that the content of the secondary structure changed to some extent.Compared with the control group,the random coiling/?-helix content of the degummed silk of the experimental group fed with MoS₂ nanosheets increased to some extent,while the?-sheet content decreased,indicating that MoS₂nanosheets hindered the silk fibroin from random coiling/?-helix transition to?-sheet.The results of wide-angle X-ray scattering spectroscopy?WAXS?showed that the secondary structure of silk did not change significantly.This result was consistent with the results of synchrotron radiation micro-infrared spectroscopy,but the crystallinity of the degummed silk of the experimental group fed with MoS₂nanosheets was lower than that of the control group.And when the feeding concentration is less than 10 mg/head,the crystallinity of the silk decreases as the feeding concentration increases.4.Inductively coupled plasma mass spectrometry?ICP-MS?was used to determine the content of Mo in silkworm midgut,silk gland??middle and posterior??,blood,excrement,cocoon and degummed silk after 24 h feeding of MoS₂ nanosheets to study the transport process of Mo element in silkworm.The results showed that Mo element could be absorbed by silkworm tissues.As the number of feeding materials and feeding concentration increased,the content of Mo in each tissue also increased.The midgut was the first to contact MoS₂ nanosheets,and the Mo content was the highest.Then Mo was absorbed by the blood and silk glands.Finally,most of them were excreted with silkworm excrement,and a small amount entered silk fibroin and sericin.