Nanometric Surface-selective Regulation Of Au/In₂O₃ Nanofibers As Exhaled H₂S Sensor For Periodontitis Diagnosis

Background:With the development of society and the improvement of people’s living standards,the awkward situation of people in social life due to oral odor is receiving more and more attention.Among them,oral diseases represented by periodontitis is one of the important causes of oral odor.Periodontitis,one of the most prevalent diseases in the world,is a persistent chronic inflammatory state of the gingival structures involving periodontal pathogens,which destroys the supporting tissues around the teeth and gradually affects the patient’s quality of life.However,many patients don’t notice the presence of the disease until the advanced stages of periodontitis.By this time,an irreversible destruction of the patient’s alveolar bone has often occurred,and even loosening and loss of teeth may have also developed.Several studies have recently confirmed the close correlation between volatile sulfide levels and periodontal status,where exhaled H₂S is considered a promising biomarker for prompt and invasive periodontitis screening.Therefore,rapid and accurate knowledge of trace H₂S in the oral environment is significant for early intervention and control of periodontitis.Featuring superior electrochemical properties,promising biocompatibility,remarkably catalytic efficiency and easily miniaturization,nanomaterials gas sensors offer the great possibility for efficient and accurate determination of trace exhaled gas biomarkers in complexes background.Among them,the exhalation sensor based on semiconductor metal oxide（SMO）has been widely studied because of its excellent sensing characteristics.d However,the inherent poor conductivity make it presents the disadvantages of high resistance and high noise,which is a challenge for high resolution detection of low concentration expiratory biomarker.Moreover,the cross-sensitivity resulting from the adsorption and desorption sensing mechanisms of SMO make the sensing material susceptible to interference from gases with similar structure or composition.In general,a single SMO sensor without any modification or adjustment has limited sensitivity and selectivity for trace target gas molecules.Consequently,the high performance H₂S gas sensor with excellent selectivity and sensitivity which is applicable to oral cavity remains technically challenging.Objective:To develop a self-assembled monolayer（SAM）modified highly selective semiconductor oxide sensor for H₂S breath analysis,evaluate the sensing performance of the sensor for trace H₂S under different conditions,and assess the practical performance of the sensor by gas sensitivity testing of exhaled breath from healthy individuals and patients with periodontitis.Methods:1.The 0.1 wt%Au/In₂O₃nanofibers（0.1 wt%Au/In₂O₃NFs）were prepared by electrostatic spinning method and surface modified by hydrothermal method.The manufactured materials were used to fabricate gas-sensitive elements with ceramic tube electrodes.In this experiment,five SAMs with different terminal groups were selected for surface modification for further optimization and analysis of the surface functionalized materials.2.The prepared Au/In₂O₃-SAM NFs materials were characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,high-resolution transmission electron microscopy（HRTEM）,X-ray photoelectron spectroscopy（XPS）,X-ray energy spectroscopy（EDS）and water contact angle（WAC）etc.3.The performance of Au/In₂O₃NFs sensing at different Au contents and different operating temperatures was investigated to determine the optimal material content ratio and operating temperature.4.Several SAM surface-modified Au/In₂O₃NFs were tested and compared for their sensing performance,sensitivity,selectivity,moisture resistance and long-term stability to H₂S at operating temperature.5.The density functional theory（DFT）simulations were performed to analyze the Au/In₂O₃-MPTES NFs with optimal sensing performance and to investigate the mechanism of H₂S detection.6.Breath samples were collected from healthy individuals and patients with periodontitis,and the H₂S content in the breath samples was measured by Au/In₂O₃-MPTES NFs sensors.Results:1.A SAMs-functionalized Au/In₂O₃NFs sensor for H₂S breath analysis was constructed,which allows flexible and effective adjustment of the sensor selectivity.2.Enhanced sensing performance of SAMs-functionalized Au/In₂O₃NFs sensors by systematically tuning the terminal groups and alkyl chains of SAMs to optimize the specific binding ability to H₂S.3.As a result of the strong interaction between the sulfhydryl group at the end of the MPTES molecule and H₂S in the optimal Au/In₂O₃-MPTES NFs sensor,the modification of the MPTES molecule contributes to the significant response enhancement of the Au/In₂O₃NFs.DFT further supports and corroborates our proposed selective sensing by the analysis of the adsorption energy and charge density distribution mechanism.4.The sensor exhibits a superior response to H₂S（1505.3 to 10 ppm）at an operating temperature of 100°C,with a practical detection limit of 10 ppb and a selectivity enhancement of13-145 times.5.The Au/In₂O₃-MPTES sensor allowed to successfully differentiate between the breath of healthy individuals and that of patients with severe periodontitis by detecting H₂S in the breath samples of healthy individuals and patients with periodontitis.Conclusions:In this study,SAM with sulfhydryl terminal group was introduced into conventional SMO sensors to construct highly selective Au/In₂O₃-MPTES NFs sensors for H₂S breath analysis and successfully applied to the detection of trace amounts of H₂S in the oral cavity of periodontal patients.It provides new design insights for the development of highly selective gas sensors,especially for devices used in clinical auxiliary diagnosis and early detection and diagnosis of periodontitis.