Highly Selective Gas Sensor Based on Hydrophobic Silica Decorated with Trimethoxyoctadecylsilane

Abstract

Trimethoxyoctadecylsilane (OTMS) was successfully used to decorate mesoporous silica with a self-assembly method to enhance the relative gas selectivity. A quartz crystal microbalance was employed to measure the gas-sensing properties. The content of OTMS was the crucial factor that greatly affected the adsorption capacity (q) of silica, which could be converted to relative selectivity (S) to study the sensing mechanism. With increasing OTMS content, q was far higher for small-molecule gases compared to volatile organic compounds (VOCs), which could be explained by the polarity of the bonding objects, and S reached a maximum value of 45.71%. When exposed to VOCs, S was always greater than 0 among the three alcohols. The sensing mechanisms of undecorated silica and OTMS-decorated silica were quite different; the three-state mechanism was proposed to explain the sensing mechanism of OTMS-decorated silica. When exposed to small-molecule gases, the atoms that bonded with carbon atoms on OTMS greatly influenced q. With increasing OTMS content, the bonding energy of OTMS with CO2 was far less than that with other molecules, resulting in a relative selectivity as high as 38.69%. Furthermore, macroperformance and microproperties were combined in three-dimensional coordinates, which could be applied to predict the sensing performance of silica.

Fabrication of Photostable Siloxane-Coated Quantum Dots for White-Light-Emitting Diodes

“…It was found that core/multishell QDs had bands at 2855 and 2923 cm –1 , which could be assigned to C–H stretching vibration in the original organic ligands (OA), and the carboxyl group symmetric and antisymmetric stretching vibration peaks of OA appeared at 1540 and 1450 cm –1 , respectively. The above peaks weakened or even disappeared after silica coating, and the band that appeared at around 1060 cm –1 was ascribed to the antisymmetric stretching vibration of Si–O–Si and 799 cm –1 was assigned to the symmetrical stretching vibration of Si–O, indicating that silica was successfully coated on the surface of core/multishell QDs . Afterward, the C–H stretching vibration peaks of methylene belonging to the long alkane chain reappeared, attributing to OTMS successfully linked onto the silica surface .…”

“…The above peaks weakened or even disappeared after silica coating, and the band that appeared at around 1060 cm −1 was ascribed to the antisymmetric stretching vibration of Si−O−Si and 799 cm −1 was assigned to the symmetrical stretching vibration of Si−O, indicating that silica was successfully coated on the surface of core/multishell QDs. 36 Afterward, the C−H stretching vibration peaks of methylene belonging to the long alkane chain reappeared, attributing to OTMS successfully linked onto the silica surface. 37 The change of surface functional groups could also affect the hydrophilicity of QDs, the water contact angles of QDs, QDs@SiO 2 , and QDs@SiO 2 -OTMS were measured, and the results are shown in Figure 2e−g.…”

Recent Advances in Quartz Crystal Microbalance Biosensors Based on the Molecular Imprinting Technique for Disease-Related Biomarkers

“…Piezoelectric materials that act as an electromechanical transducers are fitted for use as biosensors and actuators in tools and are good structures [39,40]. The piezoelectric, mass-sensitive, or acoustic wave tools present label-free and quick detection of molecules due to mass, which is the main feature of each molecule.…”

“…Biosensors can be categorized into different transducer groups for the generation of the output signal, including optical, electrochemical, gravimetric, magnetic, and piezoelectric transducers[34][35][36][37]. The selection of a transduction device is primarily based on the natural and physicochemical features of the surface layer, which change when interacting with the target molecule[38].Piezoelectric materials that act as an electromechanical transducers are fitted for use as biosensors and actuators in tools and are good structures[39,40]. The piezoelectric, mass-sensitive, or acoustic wave tools present label-free and quick detection of molecules due to mass, which is the main feature of each molecule.…”

Self-Powered Sensors: New Opportunities and Challenges from Two-Dimensional Nanomaterials

“…Sensors are key ingredients of next-generation electronics in the Internet of Things (IoT) because they contribute to collecting essential signals. The development of various sensors, including photosensors [1][2][3][4], gas sensors [5,6], temperature sensors [7][8][9], and biosensors [10][11][12][13] is extensive, which accelerates innovation in new technologies such as the aforementioned IoT. To realize the desired sensing functions, detection performance, such as high sensitivity, robust immunity to noise, and fast response times, should be comprehensively improved [14][15][16][17].…”